SAIP2026

6 Jul 2026, 07:30 → 10 Jul 2026, 22:30 Africa/Johannesburg

University of the Western Cape

Abstracts Review Manual - SAIP2026.pdf

Detailed SAIP2026 Timetable.pdf

SAIP2026 Conference Book.pdf

SAIP2026 PROGRAM 30 June 2026

SAIP2026 Prospectus.pdf

Monday 6 July

SAIP Council Meeting

For SAIP Council Members

Winter School: Astronomy/Astrophysics

Sign-up Required. Limited Capacity.

Winter School: Nuclei (and or Particle) Physics

Sign-up Required. Limited Capacity.

Winter School: Solid State Physics and Condensed Matter

Sign-up Required. Limited Capacity.

Tour to iThemba LABS

Sign-up Required. Limited Capacity.

Historical Tour of UWC Campus

17:30 Registration

Welcome Reception & Opening Ceremony

SAIP2026 Opening Ceremony Program.pdf

Tuesday 7 July

Registration

Plenary: (Condensed Matter) Prof Vladimir Lobaskin, "What the Cell Sees: Modelling the Bionano Interface"

08:30 Buffer

1 What the Cell Sees: Modelling the Bionano Interface

Bionano interactions sit at the heart of some of the most promising technologies of the
coming decade, including targeted drug delivery, mRNA vaccines, biosensors, theranostic
agents, and engineered interfaces for regenerative medicine. They are, at the same time,
the key to understanding the toxicity of nanomaterials. In both roles, what matters is not the
pristine nanomaterial but the dynamic corona of proteins and lipids that reshapes its surface
on contact with a biological fluid and ultimately determines the fate of the particle and its.
This corona governs how the particle is recognised by cell membranes and receptors,
directing uptake, intracellular trafficking, and downstream biological response.
In this presentation I will show how computational materials models and nanoinformatics
methods allow us to zoom into the bionano interface and identify the principal factors
controlling corona formation and the behaviour of nanomaterials in biological media. The
multiscale character of the problem demands a combination of physics-based simulation and
data-driven models built on machine learning. I will argue that soft matter physics provides
the mechanistic backbone that both next-generation nanotechnologies and regulatory
science increasingly need.

Speaker: Prof. Vladimir Vladimir Lobaskin (School of Physics, University College Dublin)

What_the_Cell_Sees_SAIP2026.pptx

09:25 Buffer

Applied Physics

Convener: Alan Matthews

2 Toward Portable Gamma–Neutron Imaging: A Two-Stage Compton Camera for Environmental Monitoring

The development of advanced radiation imaging systems for environmental monitoring requires improved sensitivity, rapid response, and reliable source localisation in complex measurement scenarios. In this work, a two-stage Compton camera is investigated with particular emphasis on detector performance, timing characteristics, and geometrical optimisation.

The system is based on compact 14 × 14 × 25.4 mm LaBr$_3$:Ce scintillation detectors coupled to SiPM readout, enabling low-voltage operation while maintaining excellent performance. These detectors (CapeScint, MA, USA) achieve an energy resolution of 3.4% at 662 keV and exhibit favourable fast-timing properties. Monte Carlo simulations using the TOPAS toolkit are employed to study Compton scatter kinematics and to guide the optimisation of detector configuration. These studies are complemented by experimental measurements using standard gamma-ray sources to evaluate system performance.

To extend the functionality of the system, neutron detection is incorporated using two Cs$_2$LiYCl$_6$ (CLYC-6) SiPM-readout detectors of matching geometry. Pulse shape discrimination techniques are applied to separate neutron and gamma-ray interactions, enabling concurrent measurement of both radiation types and providing a more complete assessment of environmental radiation fields.

The proposed system is aimed at applications requiring portable and accurate radiation detection, including contamination mapping, nuclear facility surveillance, and emergency response. By combining high energy resolution, fast timing, and dual gamma–neutron sensitivity, this work contributes toward the development of versatile instrumentation for environmental and nuclear safety. Preliminary results from both simulation and experimental investigations are presented.

Speaker: Shanyn Hart (University of Cape Town and iThemba LABS)

SAIP-2026_Hart.pdf

3 Operational Variability in Platinum Flotation Systems: Feed Complexity, Ultrafine Physics and Sustainability in South African Platinum Group Minerals Processing

Platinum group minerals concentrators in South Africa increasingly operate under highly variable feed conditions, resulting from the simultaneous processing of upper ground 2 ores, Platreef ores, and materials from tailings storage facilities. These feed sources differ significantly in mineralogy, particle size distribution, and flotation response. At the same time, declining ore grades and the increasing proportion of ultrafine particles (<25 µm and <10 µm) introduce additional complexity in flotation circuits. This study examines how feed variability, ultrafine particle behavior, and flotation hydrodynamics interact to produce operational variability in industrial platinum group minerals flotation systems. The analysis integrates conceptual discussion with experimental insights involving column flotation and mechanical flotation cells equipped with high-intensity FloatForce® rotor–stator mechanisms. The results are interpreted within a multiphase systems framework linking particle–bubble interactions, hydrodynamic conditions, and metallurgical performance. This paper further outlines the use of computational fluid dynamics and machine learning approaches to improve ultrafine platinum group minerals recovery and stabilise plant performance under variable feed conditions.
Keywords: Column flotation; Computational fluid dynamics; Feed variability; Flotation hydrodynamics; Machine learning; Platinum group minerals; Ultrafine flotation; Sustainability.

Speaker: Mr Ndivhuwo Nthai (University of Johannesburg)

Nthai N SAIP 2026.pptx

4 Seeing through biological tissues without distortions by harnessing topological light

Living tissues absorb and scatter light resulting in low resolution images, poor information transfer and making deep-tissue optical imaging and sensing challenging. Recently, however, topological light has gained interest due to its claimed resilience against external perturbations. Here we generate skyrmions as our optical topology by combining beams with different orbital angular momentum and polarisation states and demonstrate robust information transfer through scattering samples without any corrective measures. We showcase numerous applications, successfully retrieving the topology in samples with varying thickness, composition and distortion strength including fly wings, frog ova, butterfly scales, bubble wrap, and parafilm. Additionally, we transmit images encoded into an alphabet of 10 topological numbers and show error-free information transfer even in situations where the input intensity and phase profile is destroyed. This work thus highlights the power of topological light for probing highly distorting light-matter interactions and lays the groundwork for noise-free communication and imaging using topology.

Speaker: Kelsey Everts (University of the Witwatersrand)

90_Kelsey_Everts.pptx

Astrophysics & Space Science: Astrophysics Session 1

Convener: Geoff Beck (University of the Witwatersrand)

5 Development of a GPU-Based Wideband Spectrometer for Radio Astronomy

This paper presents the design and development of a GPU-based wideband spectrometer for radio astronomy. The system aims to provide a cost-effective alternative to FPGA-based spectrometers by utilizing commercially available graphics processing units (GPUs) for high-speed signal processing. Implemented using an NVIDIA RTX 4090 GPU, the spectrometer achieves real-time Fast Fourier Transform (FFT) processing across a 400~MHz bandwidth and 1024 frequency channels. The project follows a mixed methodology combining design science and a waterfall approach. Validation against existing systems demonstrates comparable spectral resolution and accuracy, with significant reductions in cost and development time. The proposed system offers a scalable, modular framework for future astronomical instrumentation.

Speaker: André DeGoede (North West University)

72_ANDRE_DE_GOEDE.pptx

6 Future Plans for Global Optical Transient Detection Networks

I will review plans for global transient and detection networks of the future. The BRICS+ astronomy flagship programme, entitled the BRICS Intelligent Telescope and Data Network (BITDN), aims to harness existing and future facilities within BRICS+ countries for automated transient observations, both their detection and followup. Likewise a smaller Africa initiative, the African Integrated Observation Network (AIOS) has similar aims, utilizing continental facilities in northern, eastern and southern Africa. The major next development in transient and variable detections will inevitably push to higher cadences and better sky coverage, as envisaged with GOTTA: a Global Open Transient Telescope Array, a new Chinese-led project. The current concept consists of 135 wide field 1-m modified Schmidt telescopes, each with a 25 sq degree field of view, with effective 18k x 18k x 15 micron CMOS cameras. Each camera has one dedicated filter (e.g. g,r or i). Ideally, these telescopes will be situated in groups of 3 in both hemispheres and with sufficient longitude range to achieve all-sky coverage, with a cadence of less than an hour. Larger aperture (2-4-m class) telescope will be used for spectroscopic followup, while some smaller aperture and field of view telescopes can support photometric followup.

Speaker: David Buckley (SAAO/UCT)

353_David_Buckley.pptx

7 Design and Implementation of a Modular Telescope and Dome Control System (TelServer)

This work presents the design and implementation of TelServer, a modular observatory control system developed to integrate telescope and dome subsystems within a unified communication framework. The system interfaces with a DFM Telescope Control System (TCS) via RS232, while dome motion and shutter operations are controlled through programmable logic controllers (PLCs). A socket-based architecture enables flexible command input from multiple clients, including Python scripts, web-based user interfaces, or C/C++ applications.
The architecture emphasizes abstraction and scalability, separating high-level command handling from hardware-specific control layers. Standardized control APIs are developed to manage telescope pointing, dome rotation, and shutter actuation, ensuring consistent communication across subsystems.
The paper presents system architecture diagrams, communication protocols, and control workflows. Experimental results include evaluation of PLC performance, encoder selection, and feedback reliability under operational conditions. Particular emphasis is placed on synchronization accuracy between telescope pointing (RA/Dec) and dome positioning (Alt/Az), including analysis of the coordinate transformation algorithm used to align dome slit orientation with the telescope line of sight.
Performance metrics demonstrate reliable tracking and alignment, with quantified pointing errors and response times, supporting the system’s suitability for remote observational astronomy applications.

Speaker: Dr Hendrik Jacobus van Heerden (University of the Free State)

SAIP-2026-Astro-HJvanHeerden.pptx

Astrophysics & Space Science: Space Science: Session 1

Convener: Ruhann Steyn (Centre for Space Research, North-West University)

8 Occurrence of Ionospheric scintillation during the Ascending phase of solar cycle 25

The South African National Space Agency (SANSA) global navigation satellite systems (GNSS) receivers are used to study the ionospheric scintillation over Africa during the ascending phase of solar cycle 25 for the years 2020 to 2025. The amplitude (S4) scintillation is characterized for receivers located in South Africa, Zambia, Kenya, Uganda and Nigeria. The statistics of S4 indicate that in years near the solar maximum, the occurrence of moderate to strong scintillation (S4 > 0.4) increases as compared with the solar minimum. The number of cases of moderate to strong scintillation is very low for South Africa in all years and for Zambia in 2021. The occurrence of moderate to strong scintillation in the Zambia receiver occurs only during the years of higher solar activity. For Uganda and Kenya, the moderate to strong scintillation is significant for most years. For Nigeria, the scintillation does not vary over the years.

Speaker: Tshimangadzo M. Matamba (South African National Space Agency (SANSA))

9 Large- and Medium-Scale Travelling Ionospheric Disturbances Observed across the African-European Sector during the 15-19 July 2012 Geomagnetic Storm

This study presents observations of large- and medium-scale poleward travelling ionospheric disturbances (TIDs) originating from the geomagnetic equator over the African-European sector during the 15-19 July 2012 geomagnetic storm. The observation of poleward TIDs were made using the Global Navigation Satellite Systems (GNSS) total electron content (TEC) data to obtain the two dimensional (2-D) TEC residuals. Five cases of poleward TIDs were identified during this storm. Poleward TIDs propagation velocities and periods are in the range of 230-407 m/s and 32-90 minutes, respectively. On 15 July 2012, a significant 𝚫TEC depletion was observed simultaneously across all latitudes following the occurrence of poleward-propagating TIDs. During the period of 𝚫TEC depletion, a downward equatorial electrojet (EEJ) was observed, associated with storm-time westward penetration electric fields and disturbance dynamo electric fields. It is suggested that the sources of these poleward TIDs are likely related to increasing Lorentz coupling due to changes in the EEJ and the morning-moving solar terminator.

Speaker: Golekamang Thaganyana (North-West University)

10 Plasma bubble evolution during the Mother’s Day 2024 geomagnetic storm

Plasma bubbles are pockets of abrupt significant depletions in background plasma variations. These depletions are ubiquitous in the nighttime F-region and topside ionosphere at equatorial and low latitudes. There are sometimes ionospheric irregularities of various scales within the bubbles, which may cause ionospheric scintillation. Scintillation can have a substantial impact on radio signals traversing the ionosphere, for example, leading to signal cycle slips in global navigation satellite systems (GNSS). This study presents an investigation of the time evolution of equatorial plasma bubbles during the Mother’s Day geomagnetic storm (1012 May 2024). Global Swarm plasma density measurements and total electron content (TEC) are used in this study. Over the Asian sector (longitude 90° – 170° E), postsunset bubbles were observed throughout the storm period, extending into midlatitude regions in both hemispheres during the recovery period (11 – 12 May). Postmidnight bubbles were suppressed prior to the storm's recovery phase and generated during it. Both postsunset and pre-sunrise bubbes extended to midlatitude regions during the recovery phase (11 May). However, in the African sector (15° W – 60° E), the bubbles in the topside ionosphere were suppressed during the recovery phase (11 May), and the activity recovered on the 12th of May. We will explore the possible drivers of the poleward expansion of the postsunset plasma bubbles, the origin of the pre-sunset plasma bubbles, as well as the suppression of bubble activity using supplementary data (e.g., magnetic field and neutral wind measurements).

Speaker: Prof. Zama Katamzi-Joseph

Nuclear, Particle and Radiation Physics -1: Session 1

Convener: Sifiso Ntshangase (University of Zululand)

11 Modelling and validation of neutron detector response functions up to 140 MeV using Geant4

Cosmic radiation, composed of Galactic Cosmic Rays, Solar Energetic Particles, and their associated secondary particles, represents a recognized radiation risk to space missions, satellites, and air travel. Secondary neutrons, with characteristic spectral features in the MeV and 100 MeV range [1,2], are produced by cosmic ray interactions with atmospheric and spacecraft materials [3]. A compact spectrometry system based on plastic scintillators, silicon photomultipliers, and spectrum unfolding is under development for use at aviation altitudes and in space. Reliable spectrum measurements with the device require well-characterised detector response functions across the full energy range of interest. While these can be simulated below 20 MeV, higher energies typically require experimental validation due to known limitations in nuclear models and data.

We present progress towards characterising a prototype high-energy spectrometer presently under development for dosimetry of secondary neutrons and gamma rays produced by cosmic rays. Below 20 MeV, two simulation techniques are validated against measured response functions: the standard Geant4 scintillation package; and a direct conversion between deposited energy and light output. In this energy range, Geant4 uses a data-driven approach, but above 20 MeV it relies on models with limited supporting measurements. We also assess the validity of extending this approach to higher energies using quasi-monoenergetic neutron response functions between 30–140 MeV measured at iThemba LABS, a high-energy neutron facility in Cape Town [4]. By supplementing measured detector response functions with validated simulated data, the energy resolution of unfolded neutron spectra can be improved where access to reference neutron facilities is limited.

[1] P. Goldhagen, J. Clem, J. Wilson, Radiat. Prot. Dosim. 110 (2004) 387.
[2] M.B. Smith et al., Radiat. Prot. Dosim. 168 (2015) 154–166.
[3] K. Copeland, Radiat. Prot. Dosim. 175 (2017) 419.
[4] M. Mosconi et al., Radiat. Meas. 45 (2010) 1342–1345.

Speaker: Mr Miles Kidson (University of Cape Town)

88_Miles_Kidson.pdf

12 Selective extraction of fast and epithermal neutron beams from a Nuclear Research Reactor energy spectrum using a filter response matrix approach

The fission reaction in the core of a Nuclear Research Reactor (NRR) produces free neutrons with energies extending from MeV to meV. In principle, neutrons of specific energy groups can be selected using configurable beam-conditioning filters. The feasibility of such a concept depends on the extent to which the mixed neutron and gamma source external of the core can be transformed into beams that satisfy the spectral and background requirements of applications. Materials applicable as filters utilise energy-dependent attenuation to preferentially transmit neutrons of the required energy.

A filter response matrix methodology was developed to enable rapid evaluation and optimisation of multilayer sequential filter stacks for this purpose. In this approach, each candidate material is represented by a response matrix that maps an incident neutron and gamma spectrum to the transmitted spectrum as a function of thickness. These matrices were generated with OpenMC for simplified slab geometries and then combined through forward multiplication to predict the spectral effect of complete filter stacks. This provides an algorithmically efficient alternative to elaborate direct full-transport optimisation, allowing large numbers of material combinations, layer orderings and thicknesses to be considered.

The method was applied to a set of fast- and epithermal-neutron reference applications requiring set target flux and energy specifications. Application-specific beam-quality metrics were defined in terms of in-band flux, out-of-band contamination and gamma background. Filter thicknesses were then optimised subject to practical constraints such as total stack length and layer bounds, while preserving a modular filter-bank concept suitable for beam-line implementation.

The results show that the response matrix framework is effective as a design and decision-support tool for early-stage beam-line development. It rapidly identifies promising material combinations, quantifies trade-offs between flux and spectral purity, and highlights which application requirements are compatible with the assumed NRR source term. Several application cases could be matched through suitable optimisation of filter composition and thickness. Comparison with detailed OpenMC models confirmed that the method reproduces the main spectral trends, although it tends to overestimate transmitted flux because the forward multiplication scheme does not account for particle return to preceding layers due to back-scattering.

The study demonstrates that the filter response matrix approach provides a practical framework for assessing the feasibility of fast and epithermal beam implementation on a NRR beam line and for guiding subsequent high-fidelity design studies.

Speaker: Deon Marais (South African Nuclear Energy Corporation (Necsa) SOC Limited)

DMarais - SAIP2026_V1.pptx

13 Application of ICP-MS for low background measurement

An increasing number of fundamental physics investigations require low-background materials for their construction. These investigations require materials exhibiting an unparalleled degree of radiopurity, such as copper, lead, and germanium, for dark matter and neutrino detectors. The concentration of radioactive contaminants is the primary measure for experiments investigating rare natural events. Uranium and thorium, as well as their decay chain isotopes, are the main source of gamma, neutrons, and alpha particles. It is required for low-level background materials to be screened for ultra-trace levels of radionuclides before they are installed. This study presents an optimized Inductively Coupled Plasma Mass Spectrometry (ICP-MS) methodology leveraging cutting-edge nuclear physics technologies and facilities to achieve low-background, high-precision U and Th measurements.

Speaker: Ms Naomi Dikeledi Mokhine (North-West University (Mafikeng))

182_ND_Mokhine.pdf

Nuclear, Particle and Radiation Physics -2: Session-1

Convener: Edward Nkadimeng (University of Witwatersrand)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

14 Guided Weakly Supervised Machine Learning for Resonance Searches in Low-Energy Regions of Phase Space in the ${\gamma\gamma + 1\tau}$ channel at the Large Hadron Collider

Searches for new resonances at hadron colliders are typically optimized for benchmark models and high transverse momentum final states in order to suppress large Standard Model backgrounds. However, potential signals of new physics may appear in less explored regions of phase space where traditional analyses may have reduced sensitivity. This project investigates the use weak supervision in resonant searches on the $\gamma \gamma + 1\tau$ final state in a phase space of reduced hadronic activity, with a lowered jet jet $p_T$ threshold of $10 \: GeV$, as opposed to a space of high $p_T$ objects. To identify potential signals without relying on event-level truth labels, a guided weakly supervised machine learning approach based on the is employed. In this method, a classifier is trained to distinguish between background and a mixed sample of signal and background, allowing discriminating features of potential new physics signals to be learned. A Graph Neural Network (GNN) is employed as the deep learning model, as its object-based representation and permutation-invariant architecture naturally accommodate the variable jet multiplicity and complex event topology characteristic of hadron collider final states. Crucially, the guidance for weak label construction is derived from the di-photon invariant mass regions, defined by a signal window of $144$-$156 \: GeV$ and sidebands spanning $132$-$168 \: GeV$, excluding the signal region. This study aims to assess the potential of weak supervision techniques to improve sensitivity to subtle signals that may reside in previously under-explored regions of phase space in collider data.

Speaker: Phodiso Maroeshe (School of Physics and Institute for Collider Particle Physics, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa)

255_Phodiso_Maroeshe.pdf

15 Radiative Signature of New Scalar Boson Decays in the $m_{\ell \ell \gamma}$ Spectrum at the LHC

We study the radiative decay $S \to W^{+}W^{-}\gamma$, motivated by the multi-lepton anomalies at the LHC and by the emergence of a statistically significant narrow scalar resonance at $152 \pm 1$~GeV in the $\gamma\gamma$, $Z\gamma$, and $W^{+}W^{-}$ channels in association with leptons, missing transverse momentum, and $(b)$-jets. This motivates a search for a corresponding excess in the $m_{\ell\ell\gamma}$ spectrum in events with associated $b$-jets. We observe such an excess with a global significance of $4.7\sigma$, with a preferred mass of $160^{+10}_{-35}$\,GeV in a topology consistent with that suggested by the earlier anomalies. This provides further support for a unified interpretation of the multi-lepton anomalies, the narrow resonance, and its radiative decay, consolidating the significance of the narrow resonance hypothesis solidly above $5\sigma$. The measured ratio $\sigma(S \to W^{+}W^{-}\gamma)/\sigma(S \to W^{+}W^{-}) = 3 \pm 0.75\%$ is compatible with an enhancement from physics beyond the Standard Model. Our result also motivates a dedicated theoretical assessment of the cancellation of $t\bar{t}$ threshold effects in the ratio $t\bar{t}\gamma/t\bar{t}$, which would sharpen the Standard Model prediction and strengthen the interpretation of any residual excess as a signal of new physics.

Speaker: Dr Mukesh Kumar

262_Mukesh_Kumar.pdf

262_Mukesh_Kumar.pptx

16 Probing Dark Photons in Top-Associated Production at the LHC

Dark photons ($Z_D$) with direct vector ($g_V$) and axial ($g_A$) couplings to Standard Model (SM) fermions provide a well-motivated portal to physics beyond the SM. In contrast to kinetic mixing scenarios, which are strongly constrained, models with direct fermion couplings can remain consistent with current experimental limits. The top quark, as the heaviest SM fermion, offers a sensitive probe of such interactions. This study investigates dark photon production in association with a top-quark pair in the Large Hadron Collider (LHC), $pp \to t\bar{t}Z_D$ with $Z_D \to \ell^+ \ell^-$ ($\ell = e,\mu$). The analysis considers three top decay channels: hadronic, semileptonic, and dileptonic. The dilepton invariant mass $m_{\ell\ell}$ from the dark photon decay is used as the primary discriminating observable. The visible production rate is evaluated across the mass range $20~\mathrm{GeV} \leq m_{Z_D} \leq 1000~\mathrm{GeV}$ for benchmark values of coupling, demonstrating that the cross section scales with $g_V^2 + g_A^2$ and decreases rapidly with increasing mediator mass. The expected decay width remains consistently narrow across the scan, with $\Gamma_{Z_D}/m_{Z_D} \sim 0.08$. Beyond $m_{\ell\ell}$, additional kinematic observables including $p_T^{Z_D}$, $\Delta\phi_{Z_D,t}$, and $\Delta R_{Z_D,t}$ are being investigated to further enhance signal-background discrimination. Projected exclusion limits in the $(m_{Z_D}, g_V, g_A)$ parameter space are under study to establish the sensitivity reach of the $t\bar{t}Z_D$ channel at the High-Luminosity LHC.

Speaker: Thabo James Lepota (University of the Witwatersrand)

Thabolepota_probing_mZD_ttbar.pdf

Photonics: Quantum photonics

Convener: Angela Dudley

17 Spatially multiplexed single-photon sources based on binary-tree multiplexers with optimized structure

Single-photon sources (SPSs) based on spontaneous parametric down-conversion (SPDC) are inherently probabilistic, producing a usable photon with a probability of about $0.25$. This is too low for scalable quantum technologies, especially when optical losses and detector inefficiencies are included. Spatial multiplexing offers a solution by combining many identical heralded sources in parallel. However, the number of possible binary-tree multiplexer structures grows factorially $(N!)$ with system size $N$, making full optimisation computationally demanding.

This work analyses spatially multiplexed SPSs constructed from asymmetric photon routers and develops a combined full and stepwise optimisation method to identify multiplexer structures that maximise the single photon output probability under realistic loss parameters. The model includes thermal photon pair statistics, photon number resolving detector response, router transmission coefficients $(V_r,V_t)$, and propagation losses $V_b$ . Several output-extended incomplete binary-tree multiplexers (OIBTMs) are evaluated, and the optimal number of multiplexed units N, the optimal mean-photon number $λ$ , and the optimal multiplexer topology are determined for each parameter set.

The results show that optimised OIBTMs outperform conventional symmetric and asymmetric multiplexers, achieving single-photon probabilities above $90$% for realistic device efficiencies. This work provides a practical framework for designing high-performance multiplexed single-photon sources for photonic quantum technologies.

Speaker: Ms Noxolo Felicia Vilakazi (University of Pécs)

18 Quantum surface plasmon resonance (SPR) for healing plants

Surface plasmon resonance (SPR) spectroscopy is a promising technology which can enable the real-time, label-free analysis of biomolecular interactions with high sensitivity. In plant pathology and agriculture, SPR measurements will allow the rapid identification of biomarkers related to disease or stress and can significantly improve the outcomes for plant health and crop yields by allowing for early intervention to be implemented. In this presentation, we discuss the implementation of classical and quantum SPR setups at the University of Pretoria that will be used for early disease detection in crops and indigenous trees. To demonstrate our classical SPR setup, we characterise the kinetic parameters for the adsorption of bovine serum albumin (BSA) to a thin gold film. We then present simulation results that demonstrate the quantum advantage in SPR sensitivity that can be gained when using two-photon Fock states (i.e., entangled photons) instead of laser light for excitation. We also discuss how this quantum advantage can benefit the quality of SPR results for early plant disease detection. Finally, we present our progress towards implementing a quantum SPR setup with preliminary results and calibrations.

Speaker: Patrick Kinsey (University of Pretoria)

470_Patrick_Kinsey.pptx

Physics for Development, Education and Outreach

Convener: Bako Nyikun AUDU (University of the Western Cape)

19 Grade 10 Learners’ Conceptual Understanding of Electric Circuit Concepts using Physics Education Technology (PhET) Simulations

This qualitative case study examined Grade 10 learners’ conceptual understanding of electric circuit concepts through the use of PhET simulations. The study was guided by Stepans’ Conceptual Change Model as the theoretical framework for analysing learners’ conceptual development. The data was collected from fourteen purposively sampled Grade 10 Physical Sciences learners from a school in the Dimamo Circuit, Capricorn South District, Limpopo Province of South Africa. The data was collected using documented learning activities, lesson observations, questionnaires and semi-structured interviews. Additionally, the data was analysed using inductive thematic analysis through coding and categorisation of the collected data.
The findings of the study revealed that PhET simulations has a potential to bridge theoretical and practical learning, particularly in resource-constrained schools lacking physical laboratory equipment. Although, some learners held on to some misconceptions such as “current is used up” and others were confused about how voltage and current is shared in series and parallel circuits despite the use of simulations. In addition, learners could only partially link the relationship between potential difference, current and resistance. Some learners’ conceptual change process was incomplete, as those learners could not reach the final stage of the CCM cycle. This study found that PhET simulations are most effective when integrated with complementary teaching methods rather than used in isolation. The study recommends the systematic integration of PhET simulations into curriculum delivery, supported by targeted teacher professional development focused on effective ICT integration. In addition, the provision of adequate digital infrastructure is essential to enhance learners’ conceptual understanding and improve academic performance in Physical Sciences.

Speaker: Dr Phala Wesley Masoga (University of Limpopo)

20 Understanding DC Circuits: Student Misconceptions and Implications for Teaching in South Africa

Conceptual understanding of simple DC electric circuits remains a persistent challenge in introductory physics education, particularly at university level. Despite formal instruction, students continue to demonstrate fundamental misconceptions regarding current, potential difference, and the behavior of series and parallel circuits.

This study investigates the conceptual understanding of DC circuits among first-year physics students at a South African university. The Determining and Interpreting Resistive Electric Circuits Concepts Test (DIRECT) was used as a diagnostic instrument to identify and analyse students’ conceptual difficulties. A mixed-methods approach was employed, combining quantitative analysis of test responses with qualitative interpretation of recurring patterns of misunderstanding.

The findings reveal persistent misconceptions, particularly relating to the role of potential difference in parallel circuits and the microscopic interpretation of electric current as a conserved quantity in closed systems. Students frequently rely on locally reasoned, surface-level interpretations of circuit diagrams rather than coherent system-level reasoning.

These results highlight a significant gap between instruction and conceptual understanding, suggesting that traditional teaching approaches may not adequately address underlying cognitive barriers in circuit reasoning. The study has important implications for curriculum design, teaching strategies, and formative assessment in physics education within the South African higher education context.

This contribution may also complement ongoing discussions and workshop-based engagements on electric circuits at the conference. This abstract is adapted from my recently published article, which may also be retrieved from: Investigating Conceptual Understanding of DC Circuits Amongst South African University Physics Students: Implications for Curriculum and Teaching: African Journal of Research in Mathematics, Science and Technology Education: Vol 0, No 0 - Get Access

Speaker: Moreen Coetzee (Akademia)

21 Learning from Kahoot

Kahoot is a popular learning platform with a quiz-show format which is used for a quick review of student knowledge or to provide some variety in how material is presented. It is one of the most popular worldwide with over 70 million users per month. Many papers have been written on the effectiveness on using Kahoot in the classroom but few focussed specifically on Physics. In addition most papers focus on formal classroom use of Kahoot, whereas this study took place in an interactive Science Centre (Unizulu Science Centre) and integrated Kahoot with simulations from PhET.
Unizulu Science Centre has served the rural communities surrounding the University of Zululand for almost 40 years. Obtaining feedback and research data from visitors is challenging as contact time is limited. In the past clickers were used to this end but this paper explores using Kahoot instead of clickers and utilising a pre- and post- test format to gather data on student learning. The author extended the clicker-based study performed for his Masters and PhD degrees (and presented at various stages at SAIP Conference) to one utilising Kahoot. Methodology and results will be presented and suggestions made for the effective use of this dynamic tool in out of school settings (like Science Centres) and also in the classroom or lecture theatre.

Speaker: Derek Fish (University of Zululand)

SAIP talk 2026 kahoots.pptx

Physics of Condensed Matter and Materials

Convener: Prof. J.J. Terblans (UFS)

22 Investigating the Use of Complex Mechanics in Copper-Cobalt extraction and enviromental sustainability

Abstract

Copper and the associated cobalt minerals found in the oxidised seam of the african copper belt precede their massif sulfphide reefs. The transition zone between the oxidised and the sulphide layers, still rich in Cu about 5 % and Co some times running more than 3 % is made of a mixed complex making a metallurgical operational challenge to optimally acid or alkaline dissolve Cu and Co in their aqueous solutions. On the other hand, the Complex Mechanics approach based on fractal geometry has demonstrated the ability to describe accurately the internal dynamics over time of multiple entangled constituents of complex systems. This paper will discuss the Cu and Co dissolution mechanisms in sulfuric acid as dynamics of a complex system, where the acid activities, the solution potential, pH and breaking bond energy change over time. The associated and related possible environmental damages will be forecasted, costed and evaluated.

Keywords: Complex mechanics, complex system, fractal geometry, Cooper-Cobalt ore complex, environmental damage, breaking bond energy.

Speaker: Dr Alain Daniel Shekomba (Mineral Processing and Technology Research Centre, Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, Faculty of Engineering and the Built Environment, University of Johannesburg, Johannesburg, South África)

45_Alain_Shekomba.pptx

23 Interfacial Energetics and Charge-driven Adsorption in Polyethersulfone (PES)Functionalized Polyaniline ( PANI) Nanocomposites

The adsorption process influenced by polyelectrolytes at soft interfaces plays a crucial role in various electrochemical, sensing, and separation technologies. Nonetheless, the intricate interfacial energetics at the microscopic level of conducting polymer-semiconductor nanocomposites are still not well comprehended. This investigation delves into the interfacial energetics and charge-driven adsorption phenomena in polyethersulfone-polyaniline (PES-PANI) nanocomposites, analysing the relationships between electronic structure, polarisation, and mesoscopic transport to elucidate the resulting adsorption behaviour stemming from the nanoscale heterogeneity within a condensed-matter and surface-physics context.
The composite facilitates tunable charge distributions and adsorption sites by integrating the highly functionalised polymeric structure of PES, the conductive and redox-active properties of PANI, and the porous morphology of PES. Impedance spectroscopy and temperature-dependent conductivity measurements are employed to differentiate between bulk and interfacial contributions to charge transport, uncovering a transition from hopping-dominated conduction in isolated PANI domains to quasi-percolative transport at a critical filler fraction. Moreover, adsorption isotherms for model ionic adsorbates provide a quantitative understanding of how interfacial charge accumulation and screened Coulomb interactions influence adsorption free energies and selectivity. This study highlights the significance of charge dynamics and interfacial physics in influencing adsorption efficiency, moving beyond a solely chemical perspective centred on functional-group affinity. The findings present a physics-driven framework for developing advanced nanocomposite adsorbents that exhibit enhanced performance.

Speaker: Nobathembu Faleni (Walter Sisulu Univesity)

24 Multifunctional Rare-Earth Doped Spinel Ferrites: From Structural, Magnetic Tuning, and Functional Application

Rare-earth (RE) doped spinel ferrite nanoparticles (RE-MFe2O4, where M = Co, Ni, Zn) provide a versatile platform for tailoring structural, magnetic, and surface properties at the nanoscale. In this work, we present a systematic investigation of the structure–magnetism–function relationships in RE-doped spinel ferrites synthesized via controlled wet-chemical routes, to develop multifunctional materials for gas sensing and bio-relevant magnetic nanomaterials. X-ray diffraction (XRD) confirms the formation of single-phase cubic spinel structures, with lattice expansion governed by the ionic radius and preferential site occupancy of the rare-earth dopants. Transmission electron microscopy reveals narrowly distributed crystallite sizes in the range of approximately 10 - 25 nm, accompanied by controlled surface defect densities that are critical for functional performance. Magnetic characterization using field-dependent magnetization (M-H) and temperature-dependent measurements (ZFC/FC) demonstrates enhanced coercivity and modified magnetic exchange interactions arising from RE-induced redistribution of Fe3+ ions between tetrahedral (A) and octahedral (B) sites. These modifications lead to tunable ferrimagnetic ordering and increased surface spin disorder. The resulting magnetic and structural changes directly influence functional behaviour. In particular, gas sensing measurements toward oxidizing and reducing analytes show that rare-earth substitution enhances the density of chemisorbed oxygen species and modulates charge-transfer kinetics at the surface. Consequently, the RE-doped ferrites exhibit improved sensing sensitivity, reduced operating temperatures, and faster response recovery dynamics. Overall, the results establish a coherent structure, magnetism, and function framework across compositions, demonstrating that rare-earth substitution acts as an effective design strategy for engineering multifunctional magnetic oxide nanomaterials. This integrated approach highlights spinel ferrite nanoparticles as scalable candidates that bridge magnetic materials science with sensing technologies and emerging bio-related applications.

Speaker: Nkanyiso Linda Ndlovu (Discipline of Physics, University of KwaZulu-Natal, Private Bag X54001, Durban 4000, South Africa)

Theoretical and Computational Physics: Session 1

Convener: Prof. Azwinndini Muronga (Nelson Mandela University)

25 Distinguishing $1/2$-BPS states using symmetric polynomials

Conserved charges of the $AdS_{5} ×S^{5}$ spacetime are encoded into irreducible representations (irreps) of $U(N)$ super Yang-Mills gauge theory through AdS/CFT, and through Schur-Weyl duality, into symmetric polynomials evaluated on irreps of the symmetric group $S_{n}$. A conjecture exists regarding the maximum number of conserved charges an observer needs to measure in order to distinguish between the irreps. In a previous work, the problem was formulated in terms of power sum polynomials and evidence was presented supporting the conjecture. In this work, we rephrase the problem in terms of the elementary symmetric polynomials. We show that this rephrasing reproduces the same evidence for the conjecture and allows for non-trivial additional evidence for it.

Speaker: Dr Garreth Kemp (University of Johannesburg)

bps_symmetric_polynomials_talk.pdf

26 Configurational Temperature in the 3D XY Model

We investigate the configurational temperature estimator as a diagnostic tool for Monte Carlo and Langevin simulations of the three-dimensional XY model with an imaginary chemical potential. This estimator depends only on the field configurations. It provides a stringent internal consistency check for numerical sampling algorithms. We perform simulations using both real Langevin dynamics and the Metropolis Monte Carlo algorithm on an $8^3$ lattice across a range of coupling values, $\beta = 0.2$--$0.7$. Our results for the action density are in excellent agreement with strong-coupling expansion predictions at small $\beta$, providing an important validation of both simulation approaches. The measured value of the configurational temperature estimator shows good agreement with its expected value of unity in the symmetric phase. However, systematic deviations appear in the ordered phase. We attribute these deviations primarily to finite-size effects and discretization artifacts associated with the relatively small lattice volume. Our results demonstrate that the configurational temperature estimator provides a valuable diagnostic for assessing thermalization and algorithmic correctness in lattice field theory simulations. Such diagnostics are particularly important in preparation for studies at real chemical potential, where sign problems arise and conventional validation methods become less reliable.

Speaker: Kutloano Nkojoana (University of the Witwatersrand)

27 Competing Condensates in Holographic QCD

At finite baryon chemical potential and low temperatures, QCD is expected to exhibit a rich phase structure characterized by the formation of quark bilinear and multi-quark condensates. However, the strongly coupled nature of QCD in this regime, together with the sign problem in lattice simulations at finite density, renders first-principles analyses extremely challenging. While effective field theory approaches provide valuable insights, no single framework fully captures the competition between distinct symmetry-breaking phases.

Gauge/gravity duality offers a complementary nonperturbative framework to study strongly coupled gauge theories. In this work, we employ a bottom-up five-dimensional holographic model inspired by holographic superconductor setups at finite baryon chemical potential. The model incorporates two charged bulk scalar fields dual to operators with distinct baryon charges and scaling dimensions, allowing for competing instabilities in the dual field theory.

We perform a systematic analysis of the competition and possible coexistence between condensates by varying the charge and scaling dimension of the dual operators. Our preliminary results indicate that coexistence is restricted to a finite region of parameter space, while outside this region one condensate generically dominates and suppresses the others. This suggests a nontrivial phase structure with distinct symmetry-breaking phases separated by phase transitions, highlighting the sensitivity of coexistence to operator quantum numbers.

Speaker: Akash Singh (University of the Witwatersrand)

10:30 Morning Tea

Applied Physics

Convener: Mandla Msimanga (TUT)

28 Investigation of Co-synthesized Natural Dye Sensitizers using Symphytum officinale and Bidens pilosa in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) are a type of photovoltaic device that uses light-absorbing dyes to convert sunlight into electricity, offering a low-cost, environmentally friendly alternative to conventional silicon- and ruthenium-based solar cells. This study investigates the co-sensitization potential of natural dyes extracted from Symphytum officinale and Bidens pilosa for application in a DSSCs. The dyes were extracted using ethanol and applied individually and in combination. Optical properties were analyzed using UV–Visible spectroscopy, which revealed that Symphytum officinale exhibited absorption peaks associated with chlorophyll in the red and blue regions. In contrast, Bidens pilosa showed absorption in the lower-wavelength region due to flavonoid and carotenoid compounds. The co-sensitized extracts exhibited a broader absorption spectrum, suggesting improved light-harvesting efficiency. Functional group analysis was performed using Fourier Transform Infrared (FTIR) spectroscopy, confirming the presence of hydroxyl (–OH), carbonyl (C=O), and aromatic (C=C) groups, which are crucial for effective interaction with Semiconductors. X-ray Diffraction (XRD) indicated that the extracts were predominantly amorphous, with no significant crystalline peaks. Overall, the results suggest that co-sensitization of Symphytum officinale and Bidens pilosa enhances the optical absorption range but does not significantly improve structural properties. The findings highlight the potential and limitations of using synthesized natural dyes in DSSCs applications, emphasizing the importance of molecular composition and binding characteristics in determining performance.

Speaker: Ronel Ronella Randela (University Of Venda)

29 Towards Physics-Informed Machine Learning for Water Quality Prediction: A Data Assessment Study in South Africa

Water quality monitoring is critical for sustainable water resource management, particularly in water-stressed regions such as South Africa. However, the availability, accessibility, and consistency of water quality remain a major challenge, which may be contaminated by waste from different sources like mines, industries and agricultural activities. Some areas in South Africa face serious water scarcity, where consumers are compelled to buy water, and those who cannot afford it use water from rivers or dams, which may be contaminated by waste from various sources, such as mines, industries. This study employs machine learning models including Linear Regression, Decision Trees, and Random Forests to predict water quality. The dataset contains water quality parameters such as pH, turbidity, dissolved oxygen, electrical conductivity, and nutrient concentrations. For electrical conductivity Linear Regression shown the highest predictive performance (R² = 0.625), indicating predominantly linear relationship. Random Forest and Decision Tree models showed moderate performance (R² ≈ 0.56), suggesting limited nonlinear interactions within the dataset. The findings will support the integration of conventional machine learning approaches to enhance water quality prediction, water monitoring, and resource management.

Speaker: Precious Mabidi (University of Venda)

125_Precious_Mabidi.pdf

30 Physics-Based Feasibility Assessment of a PV–Biogas Hybrid Mini-Grid for Energy–Agriculture Living Labs in Rural South Africa

The transition to decentralised, low-carbon energy systems in South Africa requires solutions that integrate energy access with productive use, education, and local economic development, particularly in rural contexts. This study presents a physics-based feasibility assessment of a hybrid photovoltaic (PV)–biogas–battery mini-grid proposed for the Tiyani Just Energy Transition Living Lab (TI-JET Lab), a school-centred energy–agriculture system in Limpopo Province.
A first principles modelling framework is developed based on energy balance, solar radiation physics, and bioenergy conversion processes. The model incorporates site-specific solar irradiance (latitude ≈ 23.1° S), PV conversion efficiency, battery storage dynamics, and biogas yield from livestock-derived volatile solids. The proposed configuration integrates 130 kWp of rooftop PV, 400 kWh battery storage, and a 12–15 kWe biogas combined heat and power (CHP) unit to meet a load demand of approximately 450 kWh/day, including water pumping of up to 150 m³/day.
System optimisation is performed using HOMER Pro to minimise the levelised cost of energy (LCOE) and net present cost (NPC) while ensuring high reliability. Results indicate that the hybrid system can achieve renewable energy penetration exceeding 85%, with significant reductions in grid dependence and improved supply reliability compared to conventional rural energy systems. The inclusion of biogas CHP provides dispatchable generation, enhancing system stability by mitigating solar intermittency.
The results demonstrate that physics-informed optimisation of hybrid renewable systems can enable resilient, cost-effective energy solutions for rural institutions. Framed within a living lab approach, the system supports Education for Sustainable Development (ESD), data-driven learning, and community engagement, aligning with Fourth Industrial Revolution principles of integrated, intelligent, and inclusive energy systems. The TI-JET Lab provides a scalable model for coupling renewable energy, agriculture, and education in support of South Africa’s Just Energy Transition.
Keywords
Hybrid mini-grid; photovoltaic (PV); biogas CHP; energy–agriculture nexus; physics-based modelling; renewable energy systems; HOMER optimisation; rural electrification; Just Energy Transition; Education for Sustainable Development; Fourth Industrial Revolution

Speakers: David Tinarwo (University of Venda), Mr Shandukani Muronga (University of Venda)

31 GEANT4 Study on Suitability of Diamond-Coated LPG Sensors

Long Period Grating (LPG) fiber optic sensors are widely used for environmental and chemical sensing due to their high sensitivity to refractive index changes; however, their deployment in high-radiation environments requires a thorough understanding of radiation–matter interactions within the sensor structure. In this study, a simulation-based investigation is conducted using Geant4 to evaluate the suitability of diamond-coated LPG sensors for operation in radiation-rich environments. A detailed geometrical model of an LPG sensor is implemented, incorporating the silica core, cladding, and a nanocrystalline diamond (NCD) coating layer. Proton irradiation conditions representative of facilities such as the CERN IRRAD facility are simulated to quantify energy deposition, dose distribution, and secondary particle generation within the sensor. Particular attention is given to the grating region, where radiation-induced changes directly influence sensor performance. The simulation results are used to compare coated and uncoated configurations, assessing the impact of the diamond layer on dose attenuation, energy redistribution, and interface effects between diamond and silica. Key dosimetric quantities, including absorbed dose and linear energy transfer, are analyzed to infer potential implications for radiation-induced refractive index changes and long-term sensor stability. The findings indicate that irradiated diamond coatings can modify the local microstructure environment of the sensing region while offering potential advantages in radiation hardness and thermal stability. This study provides a physics-based framework for evaluating advanced coating strategies in fiber optic sensors and supports the development of robust LPG-based sensing platforms for applications in high-energy physics, nuclear environments, and space systems.

Speakers: Abdool Sattar Cassim (Unioversity of Johannesburg), Timothy Brooks (University of Johannesburg)

299_Abdool_Cassim.pdf

32 Germanium-doped Fiber Optic Sensors for High-Radiation Dosimetry

Accurate radiation dosimetry in high-energy and high-radiation environments remains a critical challenge for applications in particle physics, nuclear engineering, and space systems. This study investigates the performance of germanium-doped fiber optic sensors as robust and sensitive platforms for radiation monitoring under extreme conditions. In this study, a germanium-doped FBG sensor was irradiated with high-energy protons at the CERN IRRAD facility to 1.85 MGy to investigate radiation-induced effects and assess its suitability for dosimetry. The sensor response was characterized by comparing temperature sensitivity before and after irradiation, enabling evaluation of radiation-induced changes in the thermo-optic and strain-optic coefficients. Additionally, the bragg wavelength shift, spectra width and power shift as a function of accumulated dose were conducted to quantify the impact of proton irradiation on the grating structure. The results show measurable modifications in sensor behavior post-irradiation, including changes in baseline wavelength and sensitivity. A calibration procedure was developed to correlate the radiation-induced spectral shift with absorbed dose, demonstrating the feasibility of using germanium-doped FBGs as passive dosimeters. The relationship between wavelength shift and dose was analyzed in terms of linearity, repeatability, and stability. This work demonstrates that germanium-doped FBG sensors can serve as compact, immune-to-electromagnetic-interference dosimeters, with potential applications in high-radiation environments such as particle accelerators, nuclear facilities, and space systems.

Speaker: Timothy Brooks (University of Johannesburg)

Astrophysics & Space Science: Astrophysics: Session 2

33 Curvature-Scalar Coupling as a Driver of Accelerated Expansion

We investigate the dynamical impact of a time-dependent curvature–scalar coupling function $S(t)$ within a modified scalar–tensor framework. By analysing the generalized acceleration equation, we show that, in contrast to standard $\Lambda$CDM, where pressureless matter contributes exclusively to deceleration, modifications induced by $S(t)$ alter the gravitational response, leading to a nontrivial modulation of matter contributions. In particular, the effective coupling of pressureless matter is rescaled by a factor proportional to $(1-2S)$, which induces a critical transition at $2S=1$. At this point, dust becomes gravitationally neutral with respect to cosmic acceleration, while for $2S>1$ it contributes with the opposite sign, effectively driving accelerated expansion despite remaining pressureless. This behaviour arises dynamically through the dependence of $S(t)$ on the Ricci scalar and scalar field evolution, enabling curvature-triggered transitions in the gravitational role of ordinary matter. We further identify the domain $\vert S\vert<1$ as the branch continuously connected to general relativity, with $\vert S\vert=1$ marking a structural singularity in the field equations. These results suggest that coupling-induced modifications to matter dynamics can qualitatively alter the role of standard matter, providing an alternative mechanism for late-time acceleration within scalar-tensor theories.

Speaker: Edmund Kyazze (North-West University)

108 Edmund Kyazze.pdf

34 Early results of tests on the Simba-C simulation with varying initial conditions

The late time evolution of large scale structure (LSS) in our Universe is heavily influenced by early Universe physics. But typically we limit our tests to the $\Lambda$CDM model, which limits how we can examine what effect early time conditions have on the Universe and its evolution. Cosmological simulations, like the Simba-C simulation, are useful tools for modeling galaxy formation and cosmic filament morphology. This makes them perfect testing grounds for the effect variations of initial conditions will have on late time structures. We show some early results of these varied simulations. We varied the baryonic and dark matter densities, as well as the sigma 8 value and the spectral index and amplitude. Using CLASS (Cosmic Linear Anisotropy Solving System) to generate the initial power spectrum, and MUSIC (MUlti-Scale Initial Conditions) to generate the initial density field.

Speaker: Jaydon Durow

SAIP2026_presentation.pptx

35 Joint cosmological constraints on interacting vacuum energy models

We examine interacting vacuum energy (IVE) models involving energy transfer between vacuum energy and cold dark matter, such as: $(i)\ Q = \iota HV$, $(ii)\ Q = \xi H\rho_c$, and $(iii)\ Q=3\eta H\frac{V\rho_c}{\rho_c+V}$ with the aim of addressing the cosmological tensions: $H_0$ and $\sigma_8$. To assess the cosmological viability of these IVE models, we constrain their dynamics through a joint analysis of late-time cosmological observations, including Cosmic chronometers, Baryon acoustic oscillations, PantheonP+SHOES, and Redshift-space distortion $(f_{\sigma_8})$ dat asets. We conducted a statistical analysis using a newly developed Markov Chain Monte Carlo (MCMC) simulation called Kosmulator to find the best-fit values of $\Omega_m$, $H_0$, and $\sigma_8$, along with the coupling parameters: $\iota, \xi, \text{and}\hspace{1mm} \eta$. Additionally, we used Akaike Information Criterion $(AIC)$ and Bayesian Information Criterion $(BIC)$ criteria to evaluate deviations from the $\Lambda$CDM framework.

Keywords: Cosmological tensions, Vacuum energy, Cold dark matter

Speaker: Olebogeng Tlhapane (Centre for Space Research, North-West University)

36 Kosmulator IDE: A Flexible MCMC Module for Interacting Dark Energy Models

We present Kosmulator IDE, a modular extension of the Kosmulator code [1] designed to constrain interacting dark energy (IDE) models within a fast and flexible Markov Chain Monte Carlo (MCMC) environment. Kosmulator is a vectorised, Python-based inference tool developed for rapid testing of cosmological models at the background level, offering significant speed improvements compared to traditional Einstein–Boltzmann pipelines while maintaining statistical consistency with established codes.

The Kosmulator IDE module implements analytical results for eight phenomenological IDE models derived in recent work, each characterised by interaction terms of the form $Q=3H(\delta_{\rm dm} \rho_{\rm dm} + \delta_{\rm de} \rho_{\rm de})$ and related special cases [2]. These models admit closed-form solutions for the dark sector energy densities and the Hubble function $H(z)$, enabling efficient likelihood evaluation without requiring numerical integration of the background equations.

A key feature of this module is the incorporation of physically motivated priors defined directly as analytical constraints on parameter space, based on conditions required to avoid non-physical behaviour such as negative energy densities, imaginary solutions, future singularities (e.g. big rip scenarios), and dynamical instabilities (including so-called “doom factor” pathologies [3]). The implementation allows users to select between different “regimes,” as defined in [2], thereby explicitly controlling which theoretical behaviours are permitted during parameter inference.

This framework enables a systematic investigation of how posterior constraints, best-fit statistics (e.g. $\chi^2$, $\Delta$AIC), and model viability depend on the choice of priors and tolerated physical behaviour. In addition, Kosmulator IDE facilitates reproducibility by allowing researchers to directly recover and compare results from existing IDE studies within a unified computational environment.

More broadly, this work serves as a proof of concept demonstrating that Kosmulator can be readily extended beyond the standard $\Lambda$CDM paradigm to accommodate alternative cosmological models with minimal implementation effort. The framework’s modular design and support for equation-based priors position it as a powerful tool for rapidly screening theoretical models before deploying more computationally intensive pipelines. While current implementations are limited to background-level observables, ongoing developments aim to incorporate perturbations and full CMB likelihoods.

References

[1] Kosmulator: A Python framework for cosmological inference with MCMC
R. T. Hough, R. Rugg, S. Sahlu, and A. Abebe, arXiv:2602.08424 (2026)

[2] III. Interacting Dark Energy: Summary of models, Pathologies, and Constraints, M. van der Westhuizen, A. Abebe, and E. Di Valentino, Phys. Dark Univ. 50, 102121 (2025).

[3] Dark coupling, M. B. Gavela et al., JCAP 07, 034 (2009).

Speaker: Marcel van der Westhuizen (North-West University)

Marcel_SAIP_2026_presentation - shorter.pptx

37 The Stellar Mass–Spin Relation of Galaxies in Simba: The Role of Environment and Kinematic Morphology

We investigate whether the stellar mass–spin relation of galaxies depends on environment, and whether any such dependence is direct or mediated through galaxy morphology, using the Simba cosmological simulations . We construct a well-defined galaxy sample at redshift zero and measure the relation between stellar mass and specific angular momentum, quantifying its slope, normalisation, and intrinsic scatter. Residuals from this relation are analysed to identify secondary correlations with galaxy size and star-formation activity. Galaxies are classified into early- and late type systems using a kinematic morphology indicator based on rotational support. Environment is characterised through local density, host halo mass, central–satellite status, and intra-halo position. We first examine the dependence of spin on environment without controls, and then perform controlled tests at fixed stellar mass and morphology to isolate direct environmental effects. By explicitly disentangling morphology–environment coupling, we determine whether environmental trends arise primarily through changes in galaxy type or reflect an independent influence on angular momentum. Robustness tests ensure numerical stability. The results place quantitative constraints on the role of environment in shaping galaxy angular momentum and assess whether a null environmental dependence is consistent with the data.

Speaker: Moorane Emily Makwela (student)

SAIP_presentation_2026 - Copy.pptx

Astrophysics & Space Science: Space Science: Session 2

Convener: Zama Katamzi-Joseph

38 The May 2024 Superstorm: Global Insights into Thermosphere-Ionosphere Coupling

The extreme geomagnetic storm in May 2024 was a landmark space-weather event, characterised by G5-level conditions, solar wind speeds exceeding 900 km/s, and a Dst reaching -406 nT. This presentation provides a comprehensive analysis of the global response of the thermosphere and ionosphere to this historic forcing. Utilising data from the Global-scale Observations of the Limb and Disk (GOLD) mission, we examine the evolution of the O/N$_2$ column density ratio, which reveals dramatic spatial and temporal variations. Specifically, we highlight the massive compositional changes, including deep depletions and localised enhancements, that developed during the storm’s peak on May 11 (DOY 132).
These thermospheric observations are integrated with ground-based Total Electron Content (TEC) measurements from South Africa stations (HRAO and HNUS) to characterise the coincident ionospheric response. Our results demonstrate a complex interplay between neutral composition and plasma density, showing how extreme magnetospheric energy input reconfigures the upper atmosphere on a global scale. By comparing the GOLD disk images with regional TEC trends, we offer new insights into the driving mechanisms of the magnetosphere-ionosphere-thermosphere (MIT) system during "superstorm" conditions.

Speaker: Mr Thato Maja (North-West University)

39 Nighttime Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) Over Sutherland (2018–2022): Occurrence and Relation to Sporadic-E Layers

Abstract

Nighttime medium-scale traveling ionospheric disturbances (MSTIDs) are wavelike plasma structures in the ionospheric F-region that can affect radio communication and space weather forecasting. These disturbances appear as dark bands in airglow images obtained from all-sky imagers (ASIs). This study investigates characteristics of MSTIDs over two conjugate ASI stations, i.e., Sutherland (32.4°S, 20.8°E; magnetic latitude: 40.7 °) and Asiago (48.87°N, 11.53°E; magnetic latitude: -40.7 °). We will present results of a few cases of MSTIDs that appear as single and double band structures moving in the Westward and northeastward directions in both hemispheres. Sporadic-E (Es) layer occurrence, derived from ionosonde measurements at nearby stations in both hemispheres, is also examined to explore its role as a generation mechanism of the observed MSTIDs. The results show clearly that there are some cases where sporadic E is absent in the presence of MSTID waves, and therefore may indicate that the sporadic E layer is not necessarily required for conjugate MSTIDs, and therefore other driving mechanisms will be explored

Speaker: phelokazi fodo

276_FODO_PHELOKAZI.pptx

40 Geomagnetically Induced Currents

Geomagnetically Induced Currents (GIC) occur when rapid variations happen in the Earth’s magnetic field during geomagnetic storms due to space weather events. Such variations induce electric fields in the ground, which in turn drive unwanted currents in long conductors. As a way of assessing the magnitude of the GIC expected, empirical model is developed. This study presents the magnetic field results obtained by using the differential magnetometer method (DMM) under the national utility ESKOM’s major power line in Dealesville, central South Africa, to quantify the effect of GIC during storms. One magnetic sensor is placed just under the power line at a height of 18 m from the ground, while another magnetometer sensor measures the background magnetic field 150 m away from the power line. A permanent magnetic observatory, Hartebeesthoek (HBK), 400 km away from Dealesville is used as a reference station. Available data for all geomagnetic storms with Kp ≥ 4 between 2021 and 2026 are analysed to estimate GICs, which are related to geomagnetic activity indices Dst, Kp, and local K values to build a predictive model of GICs using parameters of the Earth's magnetic field variations.

Speaker: Ms Sibahle Mbatha (University of KwaZulu-Natal (UKZN);South African National Space Agency (SANSA))

372 Sibahle Mbatha.pptx

41 Ionospheric Response to Extreme Geomagnetic Storms

The ionospheric response to geomagnetic storms is an important space weather phenomenon caused by solar events such as coronal mass ejections (CMEs). The ionosphere is important for long distance high frequency (HF) communication. The scientific understanding of the ionospheric response during extreme geomagnetic storm is essential in mitigating the impacts in an operational space weather environment. The presentation will provide an analysis of three major geomagnetic storms influence on the ionosphere. Various space weather parameters such as solar wind speed, IMF Bz, disturbance storm time index and ionospheric measurements will be used to evaluate the intensity of ionospheric responses over the mid-latitude region.

Speaker: Mr Ishaan Bhatt (University of Michigan and South African National Space Agency)

440_Ishaan_Bhatt.pdf

Nuclear, Particle and Radiation Physics -1: Session 2

Convener: Peane Maleka (NRF-iThemba LABS)

42 SYSTEMATIC RADIOLOGICAL ASSESSMENT AND POPULATION RISK EVALUATION OF PRIMORDIAL RADIONUCLIDES IN SOILS OF TAMBUWAL, NIGERIA

Abstract: This study presents a systematic radiological assessment of primordial radionuclides in soil samples collected from Tambuwal, Sokoto State, Nigeria. Utilizing high-resolution gamma-ray spectrometry, the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were quantified to evaluate the potential internal and external radiation exposure to the local population. The measured activity concentrations for ²²⁶Ra, ²³²Th, and ⁴⁰K ranged from 19.50 to 125.50 , 21.90 to 62.50 , and 278.04 to 815.03 , respectively. The calculated mean activity concentrations for ²³²Th (42.00 ) and ⁴⁰K (648.66 ) exceeded the UNSCEAR world averages of 45.03 and 420.12 , respectively, while the mean ²²⁶Ra (73.68 ) was more than double its world average of 35.02 , a finding likely attributable to the underlying geochemical composition of the local soil. The radiological hazard assessment yielded a mean Radium Equivalent Activity ( ) of 183.68 , which remains well below the recommended safety limit of 370 . The average external (H_ex) and internal (H_in) hazard indices were 0.50 and 0.70, respectively, both satisfying the internationally accepted threshold of ≤1. The mean absorbed dose rate (Dr) was 86.45 , and the corresponding annual effective dose was 106.03 μSv·yr⁻¹, which slightly exceeds the global reference thresholds of 57 and 100 , respectively. The found all hazard indices within permissible limits but fairly elevated dose rate and annual effective dose which may call for subsequent environmental monitoring. Overall, the radiological risk obtained from the results suggest moderate safety in soil of Tambuwal region. Although, the findings provide a critical baseline for future nuclear safety assessments and environmental management protocols in the region.

Speaker: Dr Yusuf Ahijjo Musa (Usmanu Danfodiyo University, Sokoto)

43 XRF-derived major elements for nuclear forensic signatures in radiothermic carbonatites area using machine learning and multivariate modelling

This study evaluates the potential of major elemental compositions obtained from X-ray fluorescence (XRF) spectrometry (11 XRF majors: $SiO_{2}$, $K_2 O$, $Na_2 O$, $TiO_2$, $Fe_2 O_3$, $Al_2 O_3$, $P_2 O_5$, $CaO$, $MgO$, $NiO$, $MnO$) for characterizing uranium ore samples from the Mrima Hill carbonatite complex in Kenya, with the aim of assessing their suitability as nuclear forensic signatures. Given the compositional nature of major element data, centered log-ratio (CLR) transformation will be applied to ensure statistical validity. A machine learning framework comprising dimensionality reduction, unsupervised clustering, and classification algorithms, will be utilized to evaluate intra-deposit variability and assess the structure and consistency of geochemical signatures for forensic applications. The study further aims to quantify the extent to which variability within the deposit influences the stability and robustness of derived signatures. The analysis will focus on defining the multivariate structure of the dataset through mean vectors and covariance relationships, enabling future probabilistic attribution using distance-based metrics. The resulting characterization is intended to serve as a baseline dataset for integration into nuclear forensic databases. This work contributes to ongoing efforts in nuclear forensics by critically evaluating the capabilities and limitations of XRF-derived major elements as practical indicators of nuclear forensic provenance.

Speaker: Liteboho Ntsohi (University of the Witwatersrand)

44 Aerial Radiometric Measurements at an old disused Phosphate Mine in the West Coast Fossil Park, South Africa

1Masego E Mothapo, 1Fhulufhelo Nemangwele, 2Le Roux Rikus ,3Jacques Bezuidenhout
1Faculty of Science, Engineering and Agriculture, Department of Physics, University of Venda, Thohoyandou, 0950
2Faculty of Military Science, Department of Military Technology, Stellenbosch University, Saldanha, 7395
3Faculty of Military Science, Department of Physics, Stellenbosch University, Saldanha, 7395

Radiometric measurements were conducted at the West Coast Fossil Park, known for elevated levels of natural radionuclides - primarily uranium, thorium and potassium - associated with phosphate-rich sediments. The presence of elevated radionuclides in phosphatic rocks poses potential environmental and health risks, resulting in the need for radiological assessment. A UAV-based system with a 3x3 NaI(Tl) scintillation detector was used to survey and map the site, and the activity concentrations determined using full-spectrum analysis. The analysis revealed peaks corresponding to the decay series of 238U, 232Th, and 40K: at energies of 186, 295, 352, 609, and 1765 keV (U-238), 238, 338, 583, and 911 keV (Th-232), and 1460 keV (K-40). These energies confirmed elevated levels of all three principal naturally occurring radionuclides at the site. The results indicated high concentrations of uranium [RL1.1]up to 1851 Bq/kg, thorium up to 147 Bq/kg, and potassium up to 1851 Bq/kg, associated with the geology and past mining activities at the site, demonstrating the suitability of full-spectrum analysis for NORM assessment at legacy phosphate mining sites.
Keywords: UAV-based system, Phosphate rock, Full-spectrum analysis, NORM, West Coast Fossil Park

Speaker: Masego Mothapo

390_Masego_Mothapo.pdf

45 Rare Earth Element and Soil Contamination Assessments around Mrima Hills, Kenya Using ICP–MS

This study investigates rare earth elements (REE) and associated soil contamination around Mrima Hills, Kenya, through integration of Post-Archean Australian Shale (PAAS)-normalized REE patterns and the geo-accumulation index (Igeo). Soil samples were collected and analyzed using inductively coupled plasma–mass spectrometry (ICP–MS) with analytical precision maintained within ±5% and detection limits in the sub-ppm range for all REEs. The resulting patterns exhibit pronounced light REE (LREE; La–Eu) enrichment and strong fractionation relative to heavy REEs (HREE; Gd–Lu, Y), which show comparatively moderate accumulation. The evaluation of Igeo values describe discrete contamination hotspots with moderate to strong contamination observed for selected LREEs. Uranium and thorium concentrations remain consistently low across all the samples, indicating negligible radiological risk. Both analytical and statistical methods provide a robust framework for resolving enrichment mechanisms and delineating contamination zones. These findings are aligned to environmental monitoring and targeted remediation strategies in REE-bearing terrains.

Speaker: Ms Liteboho Ntsohi (University of the Witwatersrand)

SAIP Conference-2026_Ruth Wabwile_EDITED.pptx

46 Electronic Properties of CH3NH3SnI3: A Density Functional Theory Study Toward Lead-Free Perovskite Solar Cells

Organic–inorganic halide perovskites have emerged as promising materials for next-generation photovoltaics due to their tunable band gaps and excellent charge transport properties. Lead-based perovskites such as CH3NH3PbI3 have achieved power conversion efficiencies exceeding 25%, making them strong competitors to conventional silicon solar cells. However, concerns over lead toxicity have driven the search for environmentally friendly alternatives. In this work, a first-principles study of the electronic properties of the lead-free perovskite CH3NH3SnI3 is carried out using density functional theory (DFT) as implemented in CASTEP, employing both LDA and GGA exchange–correlation functionals. The results indicate that CH3NH3SnI3 exhibits a direct band gap in the range of 0.9–1.3 eV (GGA) and 0.6–1.0 eV (LDA), lower than that of CH3NH3PbI3 (~1.55 eV), and closer to the optimal range for photovoltaic applications. The band structure shows strong dispersion near the valence and conduction band edges, suggesting low effective masses and favourable charge carrier mobility. Density of states analysis reveals that I-5p orbitals dominate the valence band maximum, while the conduction band minimum is primarily composed of Sn-5p states. These findings highlight CH3NH3SnI3 as a promising lead-free alternative with suitable electronic properties for photovoltaic applications, while maintaining key advantages associated with lead-based perovskites, CH3NH3SnI3 is still associated with instability.

Keywords: Lead-free perovskites, Density Functional Theory (DFT), Band gap, Solar cells, LDA and GGA functionals

Speaker: clarence Mabaso

Nuclear, Particle and Radiation Physics -2: Session-2

Convener: Dr Arnab Laha (University of the Witwatersrand)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

47 Probing Axion-Like Particle Couplings to the Top Quark at the Future $e^- p$ Collider

Future electron-proton ($e^- p$) colliders offer a clean and sensitive environment to probe Axion-Like Particle (ALP) interactions with the top quark via single anti-top production in association with an ALP, $e^- p \to \bar{t}~a_x~\nu_e$. We investigate the precision with which the ALP-top quark coupling $C_{a\bar{t}}/f_{a}$ and the ALP-photon coupling $C_{a\gamma}/f_{a}$ can be constrained, considering the ALP decaying to a diphoton pair ($ a_x \to \gamma\gamma$). Focusing on both the hadronic and leptonic decay channels of the anti-top quark, $\bar{t} \to \bar{b} j j$ and $\bar{t} \to \bar{b}\,\ell^-\bar{\nu}_\ell$ respectively. Using a one-parameter multi-bin $\chi^2$ analysis of the most sensitive distribution, we derive $95\%$ confidence level bounds on the ALP couplings as a function of integrated luminosity in the range $10-1000~ {\rm fb}^{-1}$. Throughout, we assume a systematic uncertainty of $\delta_s = 5\%$ in all analysis. Our projected constraints are compared against existing constraints.

Speaker: Karabo Mosala (University of the Witwatersrand)

61_Karabo_Mosala.pdf

48 Probing charged Higgs in single anti-top production at the LHeC

We investigate the sensitivity to charged Higgs interactions in single anti-top production at the proposed \textit{Large Hadron Electron Collider} (LHeC) via the process $e^- p \to \bar{t}\,\nu_e$. Within the real $Y=0$ scalar triplet model ($\Delta$SM), the charged Higgs $H^+$ contributes as a t-channel mediator, inducing characteristic deviations from the Standard Model expectation. This channel provides a direct probe of the $\bar{t}\bar{b}H^+$ coupling, with sensitivity arising from both total cross-section and differential observables.

The study is performed at a center-of-mass energy of $\sqrt{s} \simeq 1.3~\text{TeV}$, corresponding to an electron beam energy of $E_e = 60~\text{GeV}$ and a proton beam energy of $E_p = 7~\text{TeV}$, with an electron beam polarization of $-80\%$. We analyze key kinematic distributions of the final-state particles and construct asymmetry observables, with particular emphasis on top-quark polarization and angular correlations of its decay products. These observables provide enhanced sensitivity to the chiral structure of the interaction and to interference effects between the Standard Model $W$-boson exchange and the charged Higgs contribution.

Speaker: Thapelo Gerry Leboho (University of Witwatersrand)

68_Thapelo_Leboho.pdf

49 Probing Anomalous Higgs Couplings in $\mu^{+}p$ Collisions

We investigate the sensitivity to anomalous Higgs couplings through di-Higgs production at the proposed Large Hadron Muon Collider (LH$\mu$C), which collides 500~GeV (1~TeV) muons with 7~TeV protons at center-of-mass energies of $\sqrt{s} \approx 3.74$ (5.3)~TeV. Using the charged-current process $\mu^{+}p \rightarrow hhj\nu_{\mu}$, we probe the sensitivity of the Standard Model Higgs self-coupling as well as non-standard $hhh$, $hWW$, and $hhWW$ couplings via the azimuthal angle correlation between the missing transverse energy and the forward jet. Exclusion limits on these couplings are estimated at the $95\%$ confidence level as a function of integrated luminosity for both muon beam energy configurations.

Speaker: Edward Nkadimeng (University of the Witwatersrand)

Di_Higgs_at_the_LHC (9).pdf

50 Probing the anomalous top quark couplings to the photon at future $e^{-} p$ colliders

We investigate the sensitivity of future electron-proton colliders to anomalous $t \bar{t} \gamma$ interactions throught the photo-production process $\gamma p \to t \bar{t}$ where the photon is radiated from the incoming electron beam, and the neutral-current process $e^{-} p \to e^{-} t \bar{t}$ where the photon is exchanged between one of the top-quarks and the incident electron beam. We consider an electron beam of energy $60~\rm GeV$, and a proton beam of energy $7~\rm TeV$ and $50~\rm TeV$ to correspond to LHeC ($\sqrt{s} \approx 1.3~\rm TeV$) and the FCC-eh ($\sqrt{s} \approx 3.5~\rm TeV$), respectively. The study is carried out within the effective field theory framework, in which the $t \bar{t} \gamma$ interaction vertex is modified by CP-even and CP-odd operators corresponding to the anomalous magnetic and electric dipole moments of the top-quark. We analyze the effects of these couplings on the total production cross section and selected kinematic distributions, as well as the spin-correlation observables and asymmetries derived from the top-antitop decay products which can provide additional discriminating power and sensitivity to the underlying coupling structure.

Speaker: Dr Mukesh Kumar

264_Mukesh_Kumar.pdf

264_Mukesh_Kumar.pptx

Photonics: Structured light & computational optics

Convener: Prof. Tjaart Krüger (University of Pretoria)

51 Fractional optical skyrmions

Optical topologies in the form of Skyrmions have predominantly been generated using integer orbital angular momentum (OAM) modes, resulting in integer-valued topological numbers that remain invariant and robust during propagation through complex media. Here, we demonstrate the first realization of fractional Skyrmions by structuring light as a vectorial superposition of non-integer OAM modes. We show that the fractional skyrmion number evolves nonlinearly between adjacent integer values. This nonlinearity arises from the intrinsic phase discontinuity of fractional OAM modes and effectively bridges discrete topological orders. Our experimental results are in good agreement with simulations, opening a new regime of optical topologies with potential applications in optical communication and sensing.

Speaker: Dr Ram Nandan Kumar (University of the Witwatersrand)

52 Single-step shaping of space, time and polarization and the robustness of space-time vector beams in complex media

Structuring light’s space, time and polarization within a single pulse has only recently become feasible, enabling the generation of complex spatiotemporal vector beams (STVBs) ideal for high-density information transport. Unfortunately, all current STVB generation methods rely on bulky, complex 4f pulse shapers prohibiting on-chip applications. Here we theoretically propose and experimentally realise a compact single-step metasurface generating nanosecond STVB pulses in the microwave regime with fidelities above 93% by leveraging a novel birefringent grating design. Additionally, we present a basis independent measurement toolkit for quantifying space-time non-separability. We demonstrate that the space-time non-separability is robust in free-space and phase distorting channels, emerging unchanged even when the individual degrees of freedom become highly distorted. This work thus provides a novel compact STVB generation method easily extendable to the visible light regime by simply scaling the metasurface. It also reveals the underlying robustness of these STVBs in real-world channels, crucial for error-free high density communication applications.

Speaker: Kelsey Everts (University of the Witwatersrand)

87_Kelsey_Everts.pptx

53 Nonlinear wave mixing: from optical elements to artificial neurons

The field generated by three-wave mixing in a second-order nonlinear crystal, under suitable approximations, can be described by the product of the two input fields. By controlling the amplitude and phase of the input fields, a single nonlinear crystal can be used to perform many different transformations on the generated field. Here we use difference frequency generation, an effect of three-wave mixing in a nonlinear crystal, to produce different two-dimensional beam shapes by encoding the transmission function of the desired optical element onto one of the input beams. In this way, we demonstrate using a nonlinear crystal as a two-dimensional, virtual optical element. Furthermore, the multiplication of fields in the crystal allows it to exhibit behaviour analogous to that of an artificial neuron, the fundamental unit of a neural network. We classify different Laguerre-Gaussian modes by encoding the mode to be classified on one beam entering the nonlinear crystal, and a phase-only mask composed of different Zernike polynomials with trainable coefficients on the other. This approach of exploiting the multiplication of fields that result from three-wave mixing allows for reconfigurable optics with just a single nonlinear crystal.

Speaker: Nikisha Baboolal (University of the Witwatersrand)

221_Nikisha_Baboolal.pptx

54 Deep diffractive optical neural networks for classifying orthogonal and non-orthogonal modes of light

Artificial neural networks are well suited tools for solving complex, multi-parameter problems and have been realized using light, termed optical neural networks (ONNs) or deep diffractive neural networks (D2NN). Their conception has been motivated by the decreased energy demands of optical systems, where nature itself is able to take on some of the computational burden. These systems have demonstrated the ability to tackle an array of tasks, including the classification of light with encoded spatial patterns. Scalability, however, remains a challenge, particularly when dealing with large numbers of spatial modes or non-orthogonal input states. Here, we demonstrate a compact and reprogrammable D2NN capable of classifying and detecting orbital angular momentum (OAM) modes, including modes from non-orthogonal sets. The network is implemented using trainable phase modulation layers optimized via stochastic gradient descent. We evaluate the implementation through numerical simulation and present the results. This method underscores the potential for hybrid classical-quantum optical systems to provide a framework for scalable, cost-effective, low-latency platforms for quantum inspired computations.

Speaker: Nikita Azevedo

Nikita_Azevedo_Diffractive_Networks.pptx

Physics for Development, Education and Outreach

Convener: Dr Happy Phage (Central University of Technology, Free State)

55 Enhancing STEM Engagement and Throughput in Under-Resourced Context: A Constructivist-Inquiry Tutorial Intervention in the Cape Flats, South Africa

Education remains a critical driver of social transformation and it remain central to South Africa's socio-economic development agenda, particularly within historically marginalized communities. Persistent underperformance in Mathematics and Physical Sciences—especially in under-resourced regions such as the Cape Flats—continues to limit learners’ access to science, technology, engineering, and mathematics (STEM) pathways, and perpetuates the cycle of disadvantage even in the 21st century. This study investigates the effectiveness of a university-supported tutorial intervention grounded in constructivist and inquiry-based pedagogies in improving learner engagement, retention, and academic performance. Preliminary national data highlight ongoing concerns: while the Western Cape often records relatively higher Grade 12 pass rates in gateway subjects compared to other provinces, overall mathematics performance remains challenging nationally (e.g., around 64% pass rate at 30%+ threshold in recent NSC examinations), with limited high-level passes (60%+) and significant throughput drops from Grade 10 onward. Drawing on a constructivist theoretical framework and the proposed Resource-Appropriate Constructivist Support (RACS) model, the mixed-methods research examines improvements in learner engagement, retention, problem-solving abilities, and academic performance, while identifying implementation challenges for tutors. Findings are expected to demonstrate how university-based tutoring, mentorship, and transformative pedagogies can bridge educational gaps, foster resilience, and inspire STEM aspirations among Cape Flats learners. Recommendations will inform scalable interventions for equitable STEM education in South Africa.

Speaker: Bako Nyikun AUDU (University of the Western Cape)

56 Barriers to Teachers’ Engagement in Laboratory Experiments for Physical Sciences in Vhembe District, Limpopo, South Africa

Practical laboratory work is fundamental to effective teaching and learning in Physical Sciences, yet many secondary school teachers in the Vhembe District of Limpopo, South Africa, show limited engagement in conducting experiments. This study investigates the extent and causes of this challenge within resource-constrained school environments. A concurrent mixed-methods approach was adopted, combining survey data from Physical Sciences teachers across different school quintiles with qualitative data from interviews, focus groups, and classroom observations. Quantitative data were analysed using descriptive statistics and regression analysis, while qualitative data were examined through thematic analysis.

The findings indicate that low levels of practical engagement are mainly due to inadequate laboratory infrastructure, lack of equipment and consumables, limited teacher training and confidence, large class sizes, and curriculum time constraints. In addition, insufficient institutional support and safety concerns further hinder the effective implementation of laboratory activities. The study proposes an intervention framework that includes low-cost practical kits, targeted teacher professional development, and better alignment of practical work with the CAPS curriculum. These findings aim to support improved teaching practices and enhance learners’ access to hands-on science education in under-resourced contexts.

Speaker: Lufuno Takalani (University of Venda)

SAIP 2026 L TAKALANI Presentation.pptx

57 Astronomy for Mental Health

Traditional development approaches are increasingly struggling to respond to the complexity and urgency of contemporary global challenges, including widening inequality, climate instability, and the demand for inclusive and sustainable growth. Many existing development frameworks remain siloed, with limited integration of science, technology, and innovation, constraining their overall impact.

At the same time, scientific disciplines such as physics and astronomy are often perceived as primarily academic, focused on advancing fundamental knowledge with limited direct societal application. This perception obscures the significant role that science has played in driving technological innovation and human capital development. In particular, technologies originating from astronomical research have contributed to advancements in digital imaging, medical diagnostics, satellite communications, and large-scale data processing, demonstrating the far-reaching impact of science on modern society.

The International Astronomical Union Office of Astronomy for Development (OAD) was established in 2011 to address this gap by leveraging astronomy, within the broader context of science, as a tool for sustainable development. Operating across more than 100 countries, the OAD has supported hundreds of projects that illustrate how science can contribute to education, scientific capacity building, technological innovation, cultural preservation, environmental awareness, and social cohesion.

This talk will present an overview of the OAD’s strategic framework, flagship ecosystem, and global network model, highlighting its alignment with the United Nations Sustainable Development Goals. Through competitive Calls for Proposals and strategic partnerships, the OAD enables locally driven initiatives that apply science, particularly astronomy, to community-defined challenges, including STEM education, mental wellbeing, Indigenous knowledge systems, astrotourism, and science diplomacy.

By positioning science - and astronomy as a powerful exemplar - within the broader development landscape, this work demonstrates its potential as a cross-cutting, interdisciplinary tool capable of contributing meaningfully to sustainable and inclusive development.

Speaker: Joyful Elma Mdhluli (IAU Office of Astronomy for Development)

160_Joyful_Mdhluli.pdf

58 Over - Reliance on Simplified Physics Model: Students Explanation in Optics

Visual perception cannot be fully explained by a single model, as it involves both physical models of light and cognitive processes. Light is described through geometrical optics, wave theory, and particle theory, each suited to different contexts; for instance, geometrical optics explains reflection but not diffraction, which requires a wave model. Likewise, phenomena such as the Moon appearing larger on the horizon cannot be explained by physical processes alone but require cognitive interpretation. While optics explains image formation on the retina, perception depends on the brain’s interpretation using experience and context. Early scholars such as Ibn al-Haytham and Hermann von Helmholtz recognized this connection between the eye and the brain, yet modern physics teaching often overlooks it. Therefore, a complete understanding of vision must integrate both physical optics and cognitive processes, which this study seeks to explore in students’ explanations.
This study investigates students’ understanding of light direction, refraction, and the Moon’s apparent size using a debate-style questionnaire based on Allie (1998). Students provide both selected answers and written explanations, which are analyzed using Grounded Theory. The instrument was administered to 140 first-year students at the University of Cape Town, provide insights into how students explain optical phenomena.

Speaker: Ishiyaku Mbela Abubakar (University of Cape Town South Africa)

59 The importance of laboratory assistance in the success of the undergraduate physics and chemistry modules

While it is possible to simulate most of the undergraduate experiments in the physical sciences, it remains critical for modules at the undergraduate level to have a hands-on experimental component. At the institution of higher learning, students acquire assistance from lecturers, lab managers, and laboratory demonstrators for this component. This involvement of laboratory demonstrators is designed to assist students in understanding the practical aspects of their experiments before and during the laboratory session. This work reports on the vital and multifaceted role of laboratory demonstrators, lab managers, and lecturers at the South African university in making learning effective for the students attending physics and chemistry practical sessions. The roles extend beyond the supervision of practical sessions. Demonstrators serve as key intermediaries between theory and experimental practices, assisting students to grasp abstract concepts through hands-on engagement.

Speaker: Buyisiwe Sondezi (University of Johannesburg)

Physics of Condensed Matter and Materials

Convener: Cebo Ndlangamandla (University of Zululand)

60 Ni Substituted Mg–Ferrite Nanoparticles: Structure, Coating Effects, and Plant Growth Response

Nickel substituted magnesium ferrite nanoparticles (NixMg1−xFe2O4; x = 0, 0.5, 1) were synthesised via the glycol thermal method and coated with chitosan through 50 h ball milling. Structural, morphological, and magnetic properties were characterised using XRD, FTIR, HRTEM, UV Vis, Mössbauer spectroscopy, and VSM. XRD confirmed single-phase spinel structures, with crystallite sizes increasing from 7.20–23.1 nm (uncoated) and 6.70–19.7 nm (coated) as Ni content rose. Lattice parameters ranged from 8.327–8.380 Å (uncoated) and 8.314–8.415 Å (coated). FTIR supported spinel formation, TEM showed semi-spherical clustered particles, SEM revealed smoother surfaces after coating, and EDX confirmed elemental composition.
The early growth response of spinach seedlings was assessed using magnesium ferrite, nickel ferrite, and a mixed 0.5(Ni–Mg) ferrite, applied at 0.5 g per 2.5 g of fertiliser. Magnesium ferrite enhanced growth (6–9 cm height, 35–45 SPAD, LAI 0.28–0.45), nickel ferrite inhibited it (3–5 cm, 18–28 SPAD, LAI 0.10–0.20), and the mixed ferrite produced intermediate effects. Overall, Mg ferrite improved early plant growth, Ni ferrite suppressed it, and mixed ferrite provided partial recovery.

Speaker: Mr Sifiso Nxumalo (School of Chemistry and Physics, University of KwaZulu-Natal, P/Bag X54001, Durban 4000, South Africa)

61 Preparation and study on the spectral properties of garnet type Ca₂YZr₂Al₃O₁₂:Dy³⁺ warm white-emitting phosphors

White light-emitting diodes (WLEDs) have become ubiquitous in modern society because they last longer and use less energy than their predecessors. There are two popular approaches to achieving white light in LEDs: combining a blue LED with a yellow phosphor ($YAG:Ce³⁺$) or using a UV-LED with blue, green, and red (RGB) phosphors. Unfortunately, the blue LED and $YAG:Ce³⁺$ combination exhibits poor color rendering and high color-correlated temperature (CCT), while the UV-LED with RGB phosphors suffers from re-absorption. A single-activator phosphor that simultaneously emits blue, green/yellow, and red light to produce white light would address these challenges. In this work, single-activated warm-white-emitting phosphors were achieved. Garnet-type $Ca₂YZr₂Al₃O₁₂:Dy³⁺$ phosphors that absorb n-UV radiation were synthesized using the high-temperature solid-state reaction method. They adopt to a cubic crystal structure consisting of dodecahedral $Ca/YO_8$, octahedral $ZrO_6$, and tetrahedral $AlO_4$ frameworks. $Dy³⁺$ ions preferentially occupy the low symmetry $Ca/Y$ site. The $Ca/YO_8$ dodecahedron consists of two types of bond lengths, $Ca/Y-O_1$ and $Ca/Y-O_2$, causing the site to deviate from inversion symmetry (i.e., a non-centrosymmetric site). Because $Dy³⁺$ occupies this non-centrosymmetric site, a dominant yellow ($^4F_{9/2}\rightarrow^6H_{13/2}$, 580 nm) electric-dipole transition and a less dominant blue ($^4F_{9/2}\rightarrow^6H_{15/2}$, 481 nm) magnetic-dipole transition are observed, resulting in warm white emission with a low CCT < 3500 K. Our results demonstrate that n-UV excitable $Ca₂YZr₂Al₃O₁₂:Dy³⁺$ warm-white emitting phosphors have strong potential for application in WLEDs.

Speaker: Ms Thandi Mazibuko (University of the Free State)

31_Thandi_Mazibuko.pptx

62 Effects of Ag+ ion induced defects on structural, morphological and optical properties of thin VO2 films

In this study, vanadium dioxide (VO2) films were deposited on silicon substrates by reactive pulsed laser deposition. Post deposition, the films were implanted with 80-keV Ag+-ions to fluences ranging from 0.1x1016 to 5.0x1016 ions/cm2. The effects of Ag+ ion-implantation on the structural, morphological, and optical properties of the films were investigated using various characterization techniques. X-ray diffraction analysis showed a left shift and broadening of the (011) peak with increasing fluence, indicating an expanded lattice and reduced crystallite size along the (011) direction in VO2. Raman spectroscopy revealed a leftward shift in the V-V and V-O Raman bands, suggesting that these bonds were weakened because of implantation. Morphological analysis showed a fluence-dependent decrease in grain size and surface roughness. A shift of V2p3/2 and O1s peaks towards lower binding energies observed using the X-ray Photoelectron Spectroscopy technique suggested that the electronic structure of VO2 was altered upon implantation. The obtained results in general showed that Ag+-implantation distorted the monoclinic structure of VO2 and enhanced infrared absorption in Ag+-implanted films through bandgap reduction, as confirmed by the optical measurements. These changes demonstrated that ion implantation could be used to tune the optical properties of the VO2 material towards being more suited to infrared sensing applications.

Speaker: Mr Matome Maloba (University of South Africa (UNISA))

63 Cluster Expansion and First-Principles Study of Ti–V–Mn Alloys: Selection of Ti8V8Mn8 for Hydrogen Storage Applications

The design of multicomponent hydrogen storage alloys requires a systematic understanding of configurational stability and structure–property relationships. In this study, a cluster expansion (CE) approach combined with density functional theory (DFT) calculations was employed to investigate the Ti–V–Mn alloy system within the AB₂-type Laves phase framework. The CE model, trained on a diverse set of configurations, yields a low cross-validation score (~2.8 meV/atom), indicating high predictive accuracy. The resulting convex hull identifies twelve ordered structures on the DFT ground-state line across the compositional space.
Although Ti₈V₉Mn₇ corresponds to the global minimum in formation energy, the Ti8V8Mn8 configuration was selected for detailed investigation due to its balanced atomic distribution and structural uniformity. Such compositional balance is expected to promote homogeneous hydrogen accommodation and reduce local stress concentrations, which are critical factors governing hydrogen-induced embrittlement in transition-metal alloys.
The calculated structural parameters confirm that Ti8V8Mn8 preserves the characteristic Laves phase geometry, indicating a stable and well-ordered lattice. Mechanical properties derived from first-principles elastic constants demonstrate that the alloy is mechanically stable and exhibits pronounced ductility, as indicated by a high Pugh ratio (B/G > 1.75). This combination of structural stability and ductile behaviour is essential for mitigating failure during hydrogen absorption and desorption processes.
These results demonstrate that cluster expansion provides an effective framework for guiding the selection of stable alloy configurations, while highlighting the importance of compositional balance in optimising hydrogen storage performance and resistance to embrittlement.

Speaker: Vukosi Chauke (University of Limpopo)

83_Vukosi_Chauke.pdf

64 Predicting Crystal Symmetry in Sodium-Ion Battery Materials Using Ensemble Machine Learning Models

Keletso Monareng1, Petros Ntoahae1, and Rapela Maphanga2,3
1Department of Physics, University of Limpopo, Private Bag X 1106, Sovenga, 0727, Polokwane, South Africa
2Renewable and Sustainable Energy Research Centre, Sol Plaatje University, Private Bag X 5008, Kimberly, 8300, South Africa
3 National Institute for Theoretical and Computational Sciences, NITheCS, Gauteng, 2000, South Africa

Abstract

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion technologies due to the natural abundance, low cost, and wide geographical availability of sodium. These advantages make SIBs particularly attractive for large-scale energy storage applications. However, the discovery and optimisation of suitable electrode materials remains challenging due to the vast compositional and crystallographic design space and the complex relationships between composition, structure, and electrochemical performance. Traditional experimental and density functional theory approaches are computationally expensive and time-consuming. In this study, a machine learning-driven framework is developed using engineered compositional features, including stoichiometric coefficients, ionization energy, oxidation states, and ionic radii. Feature importance analysis reveals that compositional coefficients and ionization energy contribute most significantly to predictive performance, while oxidation states and ionic radii provide complementary contributions. Model performance was evaluated across multiple algorithms, including Random Forest, K-Nearest Neighbours, Decision Tree, Gradient Boosting, Extreme Gradient Boost, Light Gradient Boosting Machine, and Multi Linear Perceptron, for predicting crystallographic properties such as crystal system, Bravais lattice, point group, and space group. Ensemble boosting models outperform others, with Extreme Gradient Boost and Light Gradient Boosting machine achieving the highest performance, reaching Weighted Balanced Accuracy values of approximately 0.95-0.96 and Weighted Matthews Correlation Coefficient values above 0.90. Overall, the Light Gradient Boosting Machine emerges as the best-performing model, enabling rapid and reliable screening of candidate materials and accelerating the discovery of SIB electrode materials.

Speaker: Keletso Monareng (University of Limpopo)

Theoretical and Computational Physics: Session 2

Convener: Moritz Braun

65 Complexity in Matter Under Extreme Conditions

Matter under extreme conditions, ranging from the quark–gluon plasma created in relativistic heavy-ion collisions to the dense interiors of collapsing stars and neutron stars, exhibits strongly interacting, non-linear dynamics far from equilibrium. Despite vast differences in scale, these systems share a common theoretical description rooted in relativistic fluid dynamics, where conservation laws, equations of state, and transport properties govern their evolution. In this contribution, we examine how macroscopic collective behaviour emerges from microscopic interactions within this shared framework. We highlight the roles of nonlinearity, multi-scale coupling, and sensitivity to microphysical inputs in shaping phenomena such as relativistic flow, instabilities, and structure formation. Drawing on theoretical and computational approaches, we show how similar mathematical structures underpin systems across high-energy nuclear physics and astrophysics, revealing deep connections between quark-scale interactions and cosmic-scale dynamics. This perspective positions matter under extreme conditions as a natural setting for understanding emergence in strongly interacting systems, where universal dynamical laws give rise to diverse behaviour across scales.

Speaker: Prof. Azwinndini Muronga (Nelson Mandela University)

66 A Comprehensive Numerical Framework for Magnetised Shock Wave Dynamics in Extreme Environments

This work focuses on the development of a theoretical and computational framework designed to evaluate magnetised shock wave dynamics in extreme, high-energy environments. The mathematical foundation utilises magnetohydrodynamics, which couples the conservation laws with Maxwell’s equations of electromagnetism for a conducting fluid. To accurately model the system's evolution, the framework initialises complex, multidimensional magnetic field vectors alongside high-density matter profiles, employing high-resolution temporal stepping to resolve the interaction between rapid field decay and fluid expansion. The computational core employs high-resolution shock-capturing schemes, which are essential for maintaining numerical stability across the sharp discontinuities inherent in shock fronts. A critical technical feature is the implementation of constrained transport to enforce the solenoidal constraint, ensuring the physical validity of the magnetic field evolution. By incorporating finite electrical conductivity and a modified equation of state, this study bridges the gap between abstract theory and numerical observables, providing a roadmap for quantifying the properties of matter under extreme conditions.

Speaker: Magdeline Mohlao

67 Entropy Generation in Steady MHD Nanofluid Couette Flow with Partial Slip and Convective Cooling: A Spectral Approach

This study investigates the steady-state thermal and magnetohydrodynamic (MHD) behaviour of electrically conducting nanofluids in a Couette flow configuration between two infinite parallel plates. The upper plate moves at a constant velocity under partial slip conditions, while convective heat exchange is imposed at the upper boundary and a fixed temperature is maintained at the lower plate. Cu-Water and Al₂O₃-Water nanofluids are considered, modelled using a single phase continuum framework in which effective thermophysical properties including density, viscosity, thermal conductivity, heat capacity, and electrical conductivity are expressed as functions of nanoparticle volume fraction. The governing momentum, energy, and entropy generation equations are non-dimensionalised and solved using the Spectral Quasi-Linearisation Method (SQLM), which offers rapid convergence for nonlinear boundary value problems. Parametric analysis is conducted across key dimensionless groups: the Hartmann number (Ha), Eckert number (Ec), nanoparticle volume fraction (φ), slip parameter (λ), pressure gradient parameter (G), Reynolds number (Re), and Biot number (Bi). Results show that increasing the Hartmann number suppresses fluid velocity through the opposing Lorentz force while amplifying temperature gradients via Joule dissipation. Higher nanoparticle volume fractions enhance thermal conductivity and improve heat transfer rates as reflected in increasing Nusselt numbers, though with increased flow resistance. Entropy generation and Bejan number profiles are examined to quantify the relative contributions of heat transfer irreversibility, viscous dissipation, and magnetic field effects to overall thermodynamic inefficiency. The findings offer fundamental insights applicable to thermal management systems, electromagnetic cooling devices, and micro-electromechanical applications.

Speaker: Serai Israel MOSALA (Nelson Mandela University)

371_Serai_Mosala.pdf.pdf

68 Studying the Dependence of Particle Ratios of Hadronic Matter on Energy in Pb+Pb High Energy Heavy-Ion Collisions Using the Microscopic Model (UrQMD-3.4).

We examined the particle ratios of multiple meson and baryon species at central rapidity and an impact parameter of b = 5 in Pb+Pb high-energy heavy-ion collisions. The collisions were simulated using the most recent version of the Ultra-relativistic Quantum Molecular Dynamics model (UrQMD-3.4), which, unlike its predecessors, incorporates charmed particles such as D, J/ψ, Xc, and others. These charmed particles are critical in understanding particle production and the chemical freeze-out of hadronic gas. The simulations were conducted over a range of incident kinetic beam energies (lab frame) from Elab = 100 to 1000 AGeV, with parameters set to t = 400 fm/c and 200 events. Particle ratios are key for differentiating between hadronic cascade and hydrodynamical models, including a Quark-Gluon Plasma (QGP) phase transition. This study offers valuable insights into particle production dynamics across varying collision energies, shedding light on the processes leading to chemical freeze-out and thermal equilibrium. The findings advance our understanding of the phase transition in hadronic gas within high-energy heavy-ion collision systems. The results highlight the evolution of particle ratios at central rapidity and above the saturation time as collision energy increases, providing a deeper understanding of the underlying physics in such extreme conditions.

Speaker: Tendani Oliver Munyai (Nelson Mandela University)

17-PowerPoint-Template-Faculty-of-Science-(16-9) (1) [Autosaved].pptx

Guided Walk in UWC Nature Reserve (with Packed Lunch)

Sign-up Required. Limited Capacity.

12:40 Lunch

Plenary: (Applied Physics) Prof Ernest van Dyk

69 Applied Physics Plenary - Prof EE van Dyk

The global deployment of photovoltaic (PV) technology has accelerated dramatically over the past decade, establishing solar energy as one of the fastest-growing sources of electricity worldwide. South Africa has mirrored this trend, driven by both utility-scale developments and widespread adoption across the commercial, industrial and residential sectors. By early 2026, the country's cumulative installed PV capacity is estimated to exceed 10 GW, highlighting the increasingly important role of PV in ensuring energy security, economic development and the transition to a low-carbon energy future.

Understanding the fundamental physics of solar cells and PV modules remains essential for interpreting the performance of PV systems across all scales. The electronic and optical properties of semiconductor materials determine device efficiency, while module design, environmental exposure and operating conditions influence long-term performance, reliability and degradation. The physical principles that govern charge generation and transport in a solar cell also underpin the analysis of module failures, system losses and the energy yield of large-scale PV power plants.

This presentation traces a personal and scientific journey through the PV value chain, illustrating how knowledge developed at one scale shapes understanding at the next. Beginning with semiconductor crystal growth and materials characterisation of InGaAs and related compounds, the discussion progresses through solar-cell device physics, advanced characterisation techniques, module performance and reliability, and ultimately to the modelling, monitoring and analysis of multi-megawatt PV installations.

By connecting concepts across the scales, the presentation highlights the interdisciplinary nature of PV and demonstrates how a strong foundation in materials science and device physics enables meaningful contributions to the design, operation and optimisation of PV systems. The remarkable reach of PV lies not only in their global deployment, but also in the seamless integration of fundamental science, engineering innovation and societal impact that characterises this rapidly evolving field.

Speaker: Ernest van Dyk

14:35 Buffer

Applied Physics

Convener: Lucas Erasmus (UFS)

70 Single-shot measurement of Kerr Nonlinearities using Structured Light

In this work we propose a technique that is able to measure the intensity dependent refractive index $n_2$ and nonlinear absorption $\beta$ in a single measurement and improved accuracy. Contrary to previous techniques, we are able to improve precision via manipulation of the optical system post interaction with the sample. We achieve this by imprinting on the beam a specific intensity profile that induces a steering and reshaping effect due to the nonlinearity type, which aborts parts of the beam unevenly and displaces the beam center in the far field. We use the near-field profile to measure $\beta$ and the far-field to measure $n_2$. We show analytical solutions with high agreement to numerical simulations. This technique is promising due to the quick measurements, ease to calibrate and shape of the beam, resilience to power oscillations and is especially suitable for thin samples.

Speaker: Wagner Tavares Buono (University of the Witwatersrand)

71 Dynamic State Constrained Calibration of Nonlinear Sensor Systems for Residual Limb Monitoring

The accurate interpretation of sensor data in prosthetic systems is challenged by nonlinear signal transformations, environmental coupling, and temporal drift within the prosthetic socket environment. Sensor outputs derived from embedded thermistors are influenced by
dynamic interactions between physiological heat generation, mechanical loading, and ambient conditions, resulting in non-stationary measurement behaviour.
This work presents a dynamic calibration framework for nonlinear sensor systems based on inverse modelling and adaptive parameter estimation. A thermodynamically-inspired logarithmic model is employed to reconstruct temperature from sensor voltage ratios, where calibration is governed by a latent parameter estimated through constrained nonlinear optimization. Temporal continuity is enforced via regularization, while Bayesian
updating enables recursive refinement of calibration parameters over time.
To address non-stationarity, calibration is performed across multiple temporal scales,including early-morning equilibrium conditions and sliding time windows, capturing both long-term drift and short-term variability. Additionally, accelerometer-derived activity signals are used to identify low-perturbation states, ensuring calibration occurs under quasi-static physical conditions.
Experimental results demonstrate that the proposed framework improves robustness against sensor drift and enhances stability in reconstructed temperature signals compared to static calibration approaches. The method provides a physically grounded approach for real-time monitoring of prosthetic socket conditions and enables early detection of
deviations associated with tissue stress.
This work contributes to applied physics by addressing nonlinear inverse problems in coupled thermodynamic-biomechanical systems, with implications for adaptive sensing in wearable and biomedical devices.

Speaker: Chrispin Kabuya (iYunivesithi Walter Sisulu)

SAIP_2026_Presentation_final_final.pdf

72 Empirical Modelling and Evaluation of Hourly Global Solar Radiation on Horizontal and Inclined Surfaces

South Africa’s growing energy demand, coupled with persistent supply constraints and continued reliance on fossil fuels, has intensified the need for accurate solar resource assessment to support renewable energy deployment. In this study, empirical models were developed and evaluated to estimate the components of hourly global solar radiation on both horizontal and inclined surfaces.
Measured meteorological data from the University of Venda, Vuwani SAURAN station were analyzed, incorporating key atmospheric and climatic variables including sunshine duration, air temperature (mean and maximum), extraterrestrial radiation, soil temperature, precipitation, relative humidity, cloud cover, and evaporation. The performance of different empirical approaches was assessed, with particular emphasis on the widely used sunshine duration-based models due to their simplicity and data availability.
The results demonstrate that empirical models can reliably estimate global solar radiation, with sunshine duration emerging as a robust predictor under local climatic conditions. Furthermore, the Perez model was successfully applied to accurately project solar radiation on inclined surfaces, highlighting its suitability for photovoltaic system design. These findings provide valuable insights for solar energy system optimization and reinforce the applicability of empirical modeling approaches for solar resource assessment in data-scarce regions of South Africa.

Speaker: Mabunda Hlayiseka (University Of Venda)

SAIP PRESENTATION 2026 aaab.pptx

Astrophysics & Space Science: Astrophysics: Session 3

73 MeerKAT HI reveals ram-pressure stripping in Abell 3408 galaxy cluster

Galaxy clusters are laboratories for studying the interplay between the hot intra-cluster medium (ICM) and the galaxies embedded within it, offering key insights into the environmental processes driving galaxy evolution. We use X-ray and \hi spectral line observations of the \textit{z}~$\sim$~0.042 Abell 3408 galaxy cluster to investigate the influence of the hot X-ray emitting intra-cluster medium (ICM) on individual cluster members. The X-ray data were obtained with eROSITA during the performance-verification (PV) phase, and the \hi observations of 64 galaxies within this cluster were observed with MeerKAT. Through detailed imaging and surface brightness analysis, we identify two distinct X-ray emission clumps located in the south-east (SE) direction of the cluster, both within the radius \textit{R}$_{200}$. Three \hi galaxies detected with MeerKAT are found in the vicinity of one of these X-ray clumps. Notably, one of the galaxies shows signs of disturbed gas suppression \hi morphology, including an extended $\sim$ 200 kpc \hi tail. We carry out ram-pressure stripping analysis and find that this galaxy is indeed ram-pressure stripped. This extended \hi tail galaxy, along with three other galaxies, has a prominent X-ray counterpart. Lastly, we performed spectral analysis in the 0.3~–~9~keV energy range and determined a cluster temperature of \textit{k}$_B$T~=~2.37$^{+0.1}_{-0.1}$ keV, and metallicity \textit{Z}\textsubscript{$\odot$}~=~0.18$^{+0.02}_{-0.02}$. In the 0.3~–~2.3~keV energy band, the cluster's X-ray luminosity is measured to be \textit{L}\textsubscript{X}~=~2.54~$\times$~10$^{43}$~ergs\,s$^{-1}$.

Speaker: Xola Ndaliso (University of the Witwatersrand)

74 Probing diffuse HI in galaxies with kinematically guided stacking

Neutral atomic hydrogen (HI) in galaxies is typically only directly detected out to a galactocentric radius imposed by the sensitivity of current radio observations, rather than the true physical extent of the HI disk. As a result, the low surface-brightness outskirts of HI disks - where environmental effects may be most pronounced - remain largely unexplored, despite being key to understanding how galaxies acquire and lose their gas. In this work, we use kinematic models derived for a low-redshift (z < 0.088) galaxy sample from the Looking at the Distant Universe with the MeerKAT Array (LADUMA) survey to guide HI stacking beyond the direct detection limit. By coherently stacking emission at large galactocentric radii, we can recover faint HI signals and constrain the gas distribution in the outermost regions of these galaxies, reaching column densities below those accessible through direct detections. These measurements will be used to investigate how HI properties, including column density and local linewidth, vary with radius, and whether they are influenced by environmental disturbances. This approach allows us to probe the physical processes shaping the outskirts of HI disks and assess the role of the environment in driving disk truncation.

Speaker: Craig Smith (University of the Western Cape)

60_Craig_Smith.pdf

75 Radio Properties of WISE-Selected AGN Populations in the MIGHTEE Survey

Active galactic nuclei (AGN) are powered by accretion onto supermassive black holes, making them some of the brightest sources in the Universe. We combine MIGHTEE radio data with WISE mid-infrared and HSC-SSP optical data in the COSMOS and XMM-LSS fields to investigate the radio properties of AGN populations. We found 3,239 and 5,394 radio detected sources in COSMOS and XMM-LSS respectively. Using color selection criteria, we classify the sources into WISE non-AGNs (3553) and WISE-AGNs (5080), in both fields. We further classify them as strong AGNs (587) and obscured AGNs (181), all of them are z<3. We calculate the spectral index and radio luminosity of these selected AGN populations. We find that the spectral index peak around $\sim 0$ indicates a flat radio spectrum, suggesting that the radio emission is dominated by compact nuclear synchrotron sources. This implies a young phase of radio AGN activity. Interestingly, we find 9 strong AGN and 5 obscured AGNs with $L_{1.4,\mathrm{GHz}} > 10^{25},\mathrm{W,Hz^{-1}}$. In this talk, I will discuss the radio properties of AGN populations and highlight our key results.

Speaker: Mr Karabo Khosa (North-West university-Centre of Space Research)

76 Neutral Hydrogen, HI, in the Shapley Supercluster Core: Environmental Effects on Gas Content and Galaxy Evolution

We present MeerKAT HI observations of galaxies in the core of the Shapley Supercluster, one of the most massive structures in the local Universe. Our sample of HI-detected galaxies in A3558 and SC1329 allows us to examine how cold-gas content and star formation evolve in an extreme, high-density environment. Galaxies in the SSC-core lie systematically below field HI scaling relations, showing depleted gas fractions and extended depletion timescales. Despite retaining substantial HI reservoirs, many systems exhibit inefficient or suppressed star formation, indicating slow quenching driven by reduced gas accretion, tidal interactions, and weak or partial ram-pressure stripping. Disturbed HI morphologies support ongoing environmental processes. These results point to a gradual, multi-stage transformation of galaxies as they move through the densest nodes of the supercluster, extending environmental quenching studies into the supercluster regime.

Speaker: Lwandile Gwebushe (Rhodes University)

Astrophysics & Space Science: Space Science: Session 3

Convener: Lerato Shikwambana (South African National Space Agency)

77 Development of a Remote, Self-Sustaining Low-Cost GNSS RTK Base Station for CORS Applications

The expansion of Continuously Operating Reference Station (CORS) networks in South Africa is limited by the high cost of geodetic-grade infrastructure, resulting in sparse coverage from networks such as TrigNet and reduced capability for centimetre-level RTK positioning and ionospheric monitoring in many regions. This study presents the design and evaluation of a low-cost, low-power GNSS RTK base station developed for autonomous deployment in remote environments. The system is built around a u-blox ZED-F9P receiver integrated with a Raspberry Pi 4 and powered by a solar energy system comprising a 100 W panel, MPPT charge controller, and lithium iron phosphate battery, with a total hardware cost below R14,000. It streams RTCM 3.3 MSM7 observations in real time to a central server at SANSA Hermanus via NTRIP over a 4G LTE connection, while simultaneously logging hourly RINEX 3 files locally. Performance is evaluated through co-location with a scientific-grade receiver, demonstrating that the prototype produces observations of sufficient quality for RTK positioning, ionospheric Total Electron Content analysis, and scintillation monitoring. The results indicate that the proposed system provides a practical and scalable approach to increasing CORS network density and supporting space weather monitoring across the southern African region.

Keywords: GNSS, RTK, CORS, TrigNet, NTRIP, ZED-F9P, ionospheric monitoring, TEC, RINEX, RTCM, low-cost, autonomous deployment, SANSA

Speaker: Mr Mbhasobhi Manqele (University of KwaZulu-Natal)

Mbhasobhi Manqele.pptx

78 Can Neutral Winds explain the TEC enhancement?

The total electron content (TEC) refers to the total amount of free electrons along the ray path of a 1 square meter cross-section spanning from the ground through the ionosphere to a satellite, and is measured in TECU, where 1 TECU is 1016 electrons/m2. TEC enhancements are observed by a Global Positioning System (GPS) receiver in Zambia on 24, 27 Feb, and 1 Mar. Three additional GPS receivers located in Namibia, Kenya, and Uganda are used to understand the extent of the TEC enhancements during the period. Neutral wind data from the Horizontal Wind Model (HWM14) across low latitudes is investigated in an attempt to explain the TEC enhancements. Geomagnetic Indices are used to characterize geomagnetic activity, that could lead to the TEC enhancements. The indices indicate that 27 Feb was geomagnetically disturbed, which may explain the enhancement in TEC on 27 Feb. However, the enhancements on 24 Feb and 1 Mar occur during geomagnetically quiet conditions. Since the neutral winds from the HWM14 are dependent on the Ap index, the model only shows variations on 27 Feb and not on the other days. When Ap is low, HWM14 shows identical variations for each day and hence no significant deviations on 24 Feb and 1 Mar. GPS TEC data from the ground-based receiver in Zambia show an enhancement in TEC during the afternoon and evening hours. The enhancement of TEC on 1 Mar shifted further south of the Equatorial Ionization Anomaly (EIA) southern crest. TEC data enhancements on 1 Mar agree with electron densities from the Swarm satellite, which confirmed a southward motion of the southern crest of the EIA during the enhancement event.

Speaker: Mr ZOTHILE DLAMINI (University of KwaZulu Natal)

18_Zothile_Dlamini.pptx

79 Comparative study of Long-Term Variations of Mesospheric Wind Velocity and Tidal Amplitude using SANAE HF Radar and WACCM-X data

The mesosphere–lower thermosphere (MLT) is a dynamically complex region where gravity wave breaking, atmospheric tides and planetary waves drive the large-scale circulation, and where tidal motions play a fundamental role in modulating wind variability and vertical coupling processes. Understanding the long-term behaviour of mesospheric wind velocity and tidal amplitude is essential for improving knowledge of atmospheric dynamics and their impact on space weather and radio wave propagation. However, assessing how well global circulation models reproduce both wind variability and tidal structure remains a key challenge. This study presents a comparative analysis of long-term variations in mesospheric winds derived from the SANAE IV SuperDARN HF radar and simulated by the Whole Atmosphere Community Climate Model with Thermosphere and Ionosphere Extension (WACCM-X) over the period 1998–2019. SuperDARN meteor echoes provide effective-height wind measurements (~93 ± 3 km), while WACCM-X provides altitude-resolved winds between approximately 80 and 100 km, enabling investigation of the vertical structure of both wind velocity and associated tidal variability. The analysis examines climatological mean structure, annual cycle behaviour, interannual variability and long-term trends, supported by statistical diagnostics including Pearson correlation, bias and root mean square error (RMSE) to quantify agreement as a function of month and altitude. Results show that WACCM-X successfully reproduces the broad seasonal reversal of zonal winds, with strong and statistically significant positive correlations at lower altitudes (~80–85 km), indicating good phase agreement in this region. However, the agreement deteriorates with increasing altitude, with correlations becoming negative at higher levels due to differences in the altitude of the wind reversal and the presence of strong vertical shear. The meridional component exhibits weaker and less consistent agreement, reflecting its smaller amplitudes and stronger sensitivity to tidal forcing, planetary waves and sampling effects. Interannual variability reveals that while the seasonal cycle is persistent in both datasets, variations in amplitude and the vertical position of the reversal layer significantly influence model–observation agreement, particularly in regions where tidal modulation is strong. Month–altitude diagnostics further show that model performance is highly localised, with regions of strong agreement confined to specific seasons and altitude ranges, while regions of negative correlation indicate out-of-phase behaviour associated with differences in tidal phase and vertical structure. Trend analysis based on deseasonalised anomalies indicates weak positive trends in the SuperDARN winds, whereas WACCM-X exhibits altitude-dependent zonal trends and generally weak negative meridional tendencies, highlighting differences in the long-term evolution of both wind velocity and tidal characteristics. Overall, the results demonstrate that WACCM-X captures the large-scale structure of mesospheric winds over SANAE IV, but that detailed agreement in both wind velocity and tidal amplitude depends strongly on altitude, season and the effective sampling height of the radar observations, emphasising the importance of vertical structure when interpreting model–observation comparisons in the MLT.

Speaker: SIYABONGA CHILIZA (UKZN, SA Airforce, SAIP, SACNASP)

96_SIYABONGA_CHILIZA.pptx

Nuclear, Particle and Radiation Physics -1: Session 3

Convener: Obed Shirinda (Sol Plaatje University)

80 Search and analysis of the double hit events in the 242 Pu (ɣ, f) reaction

The work focuses on the "double-hit" experimental approach in the registration and analysis
of ternary decay events. The double-hit registration approach means that two fragments, with
an open angle between them 5 0 or less, were detected in the same PIN diode during one
registration gate of 200 ns. The series of experiments dedicated to investigation of 242 Pu (ɣ, f)
reaction was performed at the beam of the MT-25 microtron, FLNR, JINR, using the VEGA
(V–E Guide based Array) setup [1]. Fission fragments (FFs) from the (ɣ, f) reactions were
captured by an electrostatic guide system (EGS). The guide is a cylindrical capacitor of four
meters long with a thin wire as a central electrode. Some part of the ions emitted from the
target at one end of the guide become involved in the spiral-like movement along the guide
axis [2] thus transporting to the time-of-flight mass-spectrometer that consists of a
microchannel-plates based timing detector and a mosaic of four PIN diodes.
The revealing of the double-hit events in the data stream, their kinematical analysis, restoring
of the prescission configurations of the decaying system are discussed in the presentation.

References
1. D. V. Kamanin, Yu. V. Pyatkov, A. N. Solodov et al., Physics of Particles and Nuclei
Letters, 2025, Vol. 22, No. 2, pp. 272-275
2. N.C. Oakey, P.D. McFarlane, NIM. 49, 220 (1967).

Speaker: Thembi Hope Vilane (NWU-JINR)

54_Thembi_Vilane.pdf

81 Measurement of angular correlations in γ − γ cascades using coincidence detection and Monte Carlo simulation

Measurement of angular correlations in $\gamma-\gamma$ cascades using coincidence detection and Monte Carlo simulation
M. Chaplin, T. Hutton, T. Leadbeater
Metrological and Applied Sciences University Research Unit, Department of Physics,
University of Cape Town, South Africa.

Coincidence counting techniques are widely used to determine correlated $\gamma$-ray emissions from nuclear decays. Measured singles and coincidence rates share common factors that can be divided out in the analysis. However, standard formulations often assume perfect correlation between emitted quanta, neglecting possible decay chain losses, and ignore angular correlations. In this work, coincidence-based absolute activity measurements are used to show that the angular correlation function, $W(\theta)$, modulates the detection probability of cascade pairs. Using $^{60}$Co and $^{22}$Na as benchmark sources with differing cascade and correlation properties, measurements with a segmented multi-detector array demonstrate that the true coincidence rate reflects detector efficiencies and angular correlations, which can be extracted from the measured observables.\

To support the interpretation of the measured angular correlations and investigate the impact of detector effects, a custom \texttt{FLUKA} source routine was developed to implement angular distributions in $\gamma-\gamma$ correlations consistent with experimental observations. By implementing the Probability Density Function (PDF) of $W(\theta)$, a normalized Cumulative Distribution Function (CDF) was established. The CDF was then incorporated into the source routine using tabulated values and linear interpolation for precise event sampling. The
Monte Carlo results successfully reproduce the experimentally observed angular modulation, confirming that coincidence counting combined with a tailored simulation framework can probe angular correlations. The approach forms the groundwork for future studies of more complicated decay schemes with non-trivial cascade probabilities and for developing multi-detector techniques for angular-correlation measurements and metrology.

Speaker: Mikayla Chaplin

117_Mikayla_Chaplin.pptx

82 Status of the (ɣ, f) reactions research at the microtron in FLNR, JINR

D. V. Kamanin¹, Yu. V. Pyatkov²,1, A. N. Solodov¹, P. Z. Ngcobo³, V. E. Zhuchko¹, T. H. Vilane ^1,4, Z. I. Goryainova¹, O. V. Strekalovsky³, E. A. Kuznetsova¹, A.O. Zhukova¹, Yu. M. Sereda ¹, B.A. Le ¹

¹ Joint Institute for Nuclear Research, Dubna, Russia;
² National Nuclear Research University “MEPHI”, Moscow, Russia;
³ University of Zululand, Republic of South Africa
⁴North-West University, Republic of South Africa

The report is dedicated to summarizing the experimental activities of the FOBOS group (FLNR, JINR, Dubna, Russia) at the MT-25 microtron [1, 2]. A series of experiments dedicated to the study of (ɣ, f) reactions using ²³⁵U, ²³⁸U, ²³²Th, and ²⁴²Pu targets were performed. It was shown for the first time that some fraction of the fission fragments (FFs) is born in the shape isomer states with a life-time exceeding 400ns. Such fragments can undergo a break-up while passing through a solid-state foil, and at least one of the break-up products shows magic nucleon composition. Recently an emission of the light charged particles (LCP) from the fission fragments (FFs) in the direction opposite to the FF velocity vector has been observed. The LCP yield is estimated to be approximately 10-3/bin. fiss., which is three orders of magnitude higher than that observed earlier. We attribute the enhanced yield to the Coulomb-induced break-up of the deformed fragments in the solid target, indicating a previously unresolved ternary fission channel. Previous theoretical model of the break-up process is discussed.

References
1. Yu.V. Pyatkov et al., Proc. 27th Int. Seminar on Interaction of Neutrons with Nuclei (ISINN-27), Dubna, Russia, 2019.
2. D.V. Kamanin et al., Phys. Part. Nucl. Lett. 22, 272 (2025)

Speaker: P. Z. Ngcobo (University of Zululand)

83 Optimisation of Hermetically sealed sample holders to study sensitive materials using powder XRD techniques

Hermetically sealed sample holders are widely used in X-ray diffraction (XRD) analyses when handling sensitive materials. In the case of radioactive samples, these holders provide effective containment to prevent contamination, while for hygroscopic materials, they offer protection against interaction with atmospheric moisture. Despite these advantages, the materials used to manufacture such holders often introduce an amorphous scattering contribution at lower angles, commonly observed as a broad hump in diffraction patterns. This background signal can obscure weak diffraction peaks associated with minority crystalline phases, thereby compromising the accuracy and reliability of phase identification and quantitative analysis.

This study investigates alternative materials for hermetically sealed sample holders aimed at minimising the amorphous background contribution while maintaining the necessary containment and protection properties. A combined experimental and computational approach is employed on selected materials, utilizing XRD data alongside McXTrace ray tracing model to evaluate the scattering characteristics of candidate materials. The results provide insights into the trade-offs between sample protection and diffraction data quality and identify promising materials that enhance the identification of low-intensity peaks due to minor phases. This work contributes to improved analytical accuracy in the characterisation of sensitive materials.

Speaker: Tjatji Tjebane (Necsa)

Nuclear, Particle and Radiation Physics -2: Session-3

Convener: Dr Mukesh Kumar

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

84 Using Machine Learning Algorithms in the search for photons in the H → Z + γD with the ATLAS detector at the LHC

The search for dark matter motivates searches for new particles beyond the Standard Model (SM), such as the dark photon $\gamma_d$. The work described in this presentation focuses on the search for massless $\gamma_d$ via a hypothetical Higgs boson decay $H\rightarrow Z+\gamma_d$, with $Z\rightarrow l^+l^-$. The non-interacting nature of the dark photon would give arise to a missing transverse momentum ($E_T^{miss}$), subsequently leading to a $l^+l^-+\ E_T^{miss}$ final state in the detector. This study will present the first search of such process at the LHC using 140 ${fb}^{-1}$ of proton-proton collisions collected with the ATLAS detector at 13.6TeV centre-of-mass energy. Several Machine Learning (ML) algorithms were studied to enhance the sensitivity of the search and optimize the dark photon signal acceptance and SM background processes rejection. Monte Carlo Simulated Data were used to efficient classification and define a signal region (SR) where a potential excess of events with respect to SM predictions could be observed in data. Both Boosted Decision Tree (BDT) and Recurrent Neural Network (RNN) were used for an optimal SR selection. In addiction Control regions for dominants backgrounds from SM processes (Z+jets, $t\bar{t}$,$ll\nu\nu$) were defined for background estimation validation and data/MC comparison. A first estimation of the sensitivity to the signal from $H\rightarrow Z+\gamma_d$ as well as a limit on the branching ratio BR($H\rightarrow Z+\gamma_d$) are derived.

Speaker: Roja Rimer

254_Roja_Rimer.pdf

85 Search for emerging jets with the ATLAS experiment

The Standard Model (SM) encapsulates our best understanding of fundamental particles and their interactions. While it is remarkably successful in describing experimental data, it fails to account for several fundamental observations, including the nature of dark matter. This has motivated extensive exploration of physics beyond the SM, particularly models involving a hidden or Dark Sector (DS) that is weakly coupled to visible matter. Dark Sector searches are now an integral part of the ATLAS Collaboration physics program, alongside traditional Weakly Interacting Massive Particle (WIMP) searches.

Dark sector models with rich phenomenology offer a variety of non-conventional detector signatures in the search for new physics beyond the SM. Among these, emerging jets provide a striking and novel experimental signature. In such models, heavy mediators couple Standard Model quarks to dark quarks, which subsequently undergo confinement in a dark QCD-like sector. The resulting dark hadrons are long-lived and decay back to Standard Model particles with displaced vertices, producing jets that “emerge” gradually within the detector volume, characterized by multiple displaced vertices and may have a significant fraction of non-detectable particles within the jet.

I will present an effort to search for emerging jets using the ATLAS detector with the latest data collected between 2022 and 2025 at a center-of-mass energy of 13.6 TeV in proton-proton collisions, incorporating several improved analysis strategies. I will demonstrate how centrally developed advanced tracking and displaced vertex reconstruction algorithms enhance sensitivity for such an unconventional signature. I will also discuss ongoing efforts toward ensuring the longevity and reinterpretability of these results through publicly available analysis information.

Speaker: Arnab Laha (University of the Witwatersrand)

928_Arnab_Laha.pdf

86 From petabytes to new physics: data compression at the Large Hadron Collider

The ATLAS experiment at the CERN Large Hadron Collider (LHC) records and processes large amounts of data from proton-proton collisions. With the upcoming High-Luminosity LHC (HL-LHC), the data volume is expected to increase by more than an order of magnitude, posing new challenges for storage, data throughput, and analysis scalability.
To meet this challenge, ATLAS is transitioning to RNTuple, the next-generation data storage architecture designed to replace the legacy TTree. Currently, all major production output formats support RNTuple. Performance studies using ATLAS data have already demonstrated substantial improvements in space usage and I/O performance.

This study presents a comprehensive performance evaluation of the ROOT TTree and RNtuple storage layers, integrated with modern compression suites including LZMA, ZSTD, LZ4, and ZLIB. By benchmarking multi-processing scaling, throughput, and memory footprints (MVEM/RSS/PSS) within the ATLAS Athena framework, we characterize the operational trade-offs of current data formats.

However, as traditional high-dimensional data representations become unsustainable under future trigger and storage constraints, we explore integrating Machine Learning (ML) to move beyond classical Algorithms listed above. We then discuss early results from the transition toward ML-based dimensionality reduction using autoencoders and Mamba networks for data compression.
We investigate the hypothesis that ML-based compression algorithms can serve as anomaly detection, since when compression fails, it may mean that the data was not present in their training. We will test this hypothesis using new physics models that include a new force similar to the strong force, leading to new signatures and potential discoveries.

Speaker: Bralyne Vanessa Kamga Matoukam (University of The Witwatersrand)

387_Bralyne_Matoukam.pdf

Photonics: Biophotonics & optical biosensing

Convener: Christine Margarete Steenkamp (Stellenbosch University, Physics Department)

87 Detection of HIV in Clinical Plasma Samples via a Custom-Built Surface Plasmon Resonance Using an Anti‑gp120 Monoclonal Antibody

Surface plasmon resonance (SPR) offers a highly sensitive and label‑free optical technique for monitoring biomolecular interactions by detecting changes in the refractive‑index at the metal–dielectric interface. In this study, we investigated the application of custom-built SPR for the direct detection of HIV through the virus’s envelope antigen gp120 in complex clinical samples. To achieve selective and stable analyte capture, an anti‑gp120 monoclonal antibody was immobilized onto a PEGylated gold sensor chip surface, forming a low‑fouling biorecognition layer designed to minimize non-specific adsorption. Clinical plasma specimens obtained from HIV‑positive and HIV‑negative donors were evaluated for their antigen binding events on the SPR platform. The antigen binding events were quantified as resonance‑angle shifts. Differences in the resonance‑angle shifts for the positive and negative samples demonstrated effective antigen capture despite the complex nature of clinical samples. The results confirmed that SPR can provide rapid, real‑time detection of HIV without the need for extensive sample preparation or labeling steps. Beyond demonstrating the feasibility of this approach, the findings highlight the potential of physics‑based plasmonic biosensing for integration into compact, portable, or point‑of‑care (POC) diagnostic systems aimed at timely HIV screening and improved accessibility to early detection technologies.

Speaker: Dr Masixole Yvonne Lugongolo (CSIR)

88 SPR resonance angle shifts as a function of biomarker concentration

Surface plasmon resonance (SPR) is an optical phenomenon arising from the excitation of collective electron oscillations (surface plasmons) at a metal-dielectric interface, typically induced by p-polarized light under conditions of total internal reflection. The resonance condition, defined by the resonance angle (θres), is highly sensitive to variations in the local refractive index near the metal surface. Such variations are commonly associated with biomolecular binding events occurring at the sensor interface. In this study, a custom-built SPR-based biosensor platform was employed to investigate shifts in the resonance angle as a function of biomarker concentration. Unlike conventional approaches that emphasize binding kinetics and affinity analysis, the present work considers biomarker concentration primarily as an optical perturbation variable. Thiolated single-stranded DNA probes of varying concentrations were immobilized and used to capture complementary target DNA sequences. Specific and non-specific targets were introduced on gold-coated sensor chips to validate the selectivity and binding behavior associated with DNA hybridization. The results revealed a linear correlation between resonance angle shifts and increasing biomarker concentration, consistent with refractive index modulation at the sensor interface. These findings demonstrate that monitoring resonance angle shifts provides a robust and reliable optical metric for quantitative concentration detection.

Speaker: sipho Chauke (Council for Scientific and Industrial research (CSIR))

89 Photostability analysis of Aspirin tablets using Raman spectroscopy: A detection method for screening substandard and falsified medication.

Substandard and falsified (SF) medications pose a growing public health and regulatory challenge in South Africa, with serious implications for patient safety and healthcare systems. Continuous development of rapid screening methods is essential to detect SF products effectively. This study evaluates the stability of aspirin tablets using Raman spectroscopy combined with partial least squares (PLS) analysis before and after ultraviolet (UV) irradiation. Degradation of the active ingredient was monitored through changes in its molecular Raman fingerprint over time (0-90 minutes). Spectral bands associated with the carboxylic acid, ester, phenol and hydroxyl bonds were selected for evaluation because they represent areas where structural changes are likely to occur in response to irradiation. The PLS analysis showed linearity of >98% from the calibration curves derived from the Raman intensities of the functional groups. Secondly, calculations show that structural degradation can be detected between 3.48 to 17 minutes using the hydroxyl and phenol degradation products respectively. Thirdly, accuracy tests at 15, 45, and 70 minutes exposure times yielded responses of 97-103%, while repeatability, expressed as relative standard deviation (RSD), was within 0.1 - 4.9% across the functional groups. This approach offers a rapid, non-destructive method for assessing medication integrity, demonstrating strong potential application in SF drug detection and quality control of pharmaceutical products.

Speaker: Dr Lebogang Thobakgale (CSIR Biophotonics Photonics Centre Council for Scientific and Industrial Research)

SAIP presentation 2026.pptx

Physics for Development, Education and Outreach

Convener: Mark Herbert (University of the Western Cape)

90 BLUEshift Africa: Accelerating Towards the Future of Undergraduate Astronomy and Physics Education in Africa

In the vision to increase the number of African astronomers, physicists, and related STEM professionals, strengthening undergraduate astronomy and physics education is a crucial (and often overlooked) piece. BLUEshift Africa is a project designed to address this need. BLUEshift is made possible by a Venture Grant from the American Institute of Physics, through the American Astronomical Society, and in partnership with the African Astronomical Society (AfAS). The project to date has focused on astronomy. BLUEshift’s cornerstone is two-day workshops on undergraduate astronomy teaching for early-career astronomers, held at AfAS conferences in March 2025 and 2026. The main workshop goals are to help participants learn to teach astronomy in more interactive and inclusive ways and to build community around university-level astronomy teaching in Africa. Workshop topics include research-based principles of teaching and learning, teaching to promote equity and inclusion, and active learning techniques such as Think-Pair-Share. We will share results from our two years of successful workshops. We will also share results from our online “Communities of Teaching” sessions with workshop alumni, and from our pilot study of undergraduate astronomy teaching around the continent. From this foundation in astronomy, we are now looking to expand BLUEshift Africa to support undergraduate physics teaching for early-career physicists around the continent, and welcome partnerships and collaboration.

Speakers: Linda Strubbe (Strubbe Educational Consulting), Tabitha Alango (University of South Africa)

237_Tabitha_Alango.pptx

91 Probing how students explain multi-causal astronomical phenomena: a seasons case study

Learning astronomy presents various challenges that students must overcome to transition from novice to expert. Extensive research has attempted to address these challenges, although most prior studies focussed on documenting students’ incorrect reasoning outcomes (‘misconceptions’). Few studies sought to understand the fundamental nature of student reasoning about astronomical phenomena. The present study investigates the nature and origins of first-year astronomy students’ (N = 86) ideas and reasoning employed when constructing multi-causal explanations about the seasons. Following a grounded analysis, we (a) identified and grouped student ideas into broader idea categories, (b) grouped student explanations into themes and (c) developed a methodological approach to analyze student explanations for logical coherence and explanatory quality. Preliminary findings show that most students (59%, 51/86) provided largely complete, coherent, logically sound explanations which were deemed either developing or well developed in quality. However, students commonly constructed their explanations using the intuitive, albeit incorrect, distance-based account (48%; 41/86). We locate these findings within the Knowledge in Pieces (KiP) perspective, noting that when students reasoned using distance, the p-prim (phenomenological primitive) “closer = hotter” was cued to the active state. Importantly, the present work considers student intuitions to be valuable cognitive resources which, even in the face of unproductive activations, do not singularly lead to simple-minded explanations (it is in fact hotter the closer you get to a fire). Future work will expand the analysis to other multi-causal astronomical phenomena, including (1) differences in the apparent brightness of stars, (2) twinkling and (3) black holes.

Speaker: Chad Leukes (University of Cape Town)

265_Chad_Leukes.pptx

92 The Language of Experimental Measurement in Physics.

In physics, it is well understood that many theoretical terms like force, field and spin have an everyday meaning that differs from the physics disciplinary meaning. Many studies in Physics Education Research have explored how this difference can affect students’ ability to learn physics. This talk argues that there exists a similar shift in meaning in the experimental physics context. In particular, key terms like uncertainty, error and true value have separate everyday and disciplinary specific meanings. To investigate this, the study draws on several sources of data. These include a document analysis of key technical documents in metrology (VIM, GUM and NIST) which establishes the community standard; a case study of what is being taught in the introductory physics lab by a practicing experimental physicist; an overview of what language researchers are using in their published work and questionnaire responses to introductory and postgraduate students. Across these contexts, the analysis shows that there are systematic differences between everyday, instructional and research-level uses of measurement terms. This work shows that the differences arise from the underlying statistical frameworks that underpin the mathematical constructs that are needed to interpret and evaluate measurement data. In an increasingly data-driven and digital landscape, these findings show the value in clearly specifying definitions in the experimental context. We see that measurement language appears as a hidden curriculum in labs. This work shows that by making meanings explicit it can support broader participation and equity in experimental physics, which is particularly relevant in the South African context.

Speaker: Nuraan Majiet (University of Cape Town)

327_Nuraan_Majiet.pptx

93 Using Smartphone Magnetometers in the (Remote) Undergraduate Physics Teaching Laboratory, a Design-Based Research Approach

Smartphones are equipped with sensors that measure various physical phenomena (such as a magnetometer to measure magnetic fields) along with onboard computational power capable of processing the data from these measurements and displaying them in a human-readable way. These features make smartphones a candidate for use as experimental tools in educational physics laboratories, which has already undergone some study, though insufficient research has been done for this use of smartphones in the remote learning environment. In this study we explored the use of smartphones in the educational physics laboratory and remote education contexts with the goal of producing guides for designing and implementing activities that use the smartphone as a measurement device. To produce these, we used a design-based research methodology consisting of a series of iterative design-cycles in which we designed the activities, tested them with student participants and revised the activities based on data from testing. The main activity involved using the smartphone magnetometer sensor to determine the direction of the Earth’s magnetic field. Although we intentionally avoided detailed, step-by-step instruction, we found that students could not practically coordinate the magnetometer sensor readings to make sense of the Earth’s magnetic field direction without contextual guidance on using the sensor and framing for the measurement. Further our study demonstrated the important role that in-person mediation plays and the challenges of designing and implementing activities without this in the remote learning environment.

Speaker: Mayhew Steyn (University of Cape Town)

335_Mayhew_Steyn.pptx

SAIP2026_Mayhew_Steyn.pdf

Physics of Condensed Matter and Materials

Convener: Richard Harris (University of the Free State)

94 Effect of Operating Temperature on Rare-Earth Doped Hematite Gas Sensors

Ntokozo G. Cebekhulua, Ceboliyazakha L. Ndlangamandlaa, Prince S.Mkwaea, Donald D. Hilea,b, Sipho E. Mavudlac, Siphamandla C. Masikanec
aDepartment of Physics, University of Zululand, Private Bag X1001, KwaDlangezwa ZA3886, South Africa
bDepartment of Physics, Joseph Sarwuan Tarka University, Makurdi, Nigeria
cDepartment of Chemistry, University of Zululand, Private Bag X1001, KwaDlangezwa ZA3886, South Africa
*Correspondence: ntokozongc200@gmail.com
Abstract

Hematite nanoparticles (HNPs) doped with rare earth ions (Sm, La, and Dy) were synthesized successfully using a cost-effective and environmentally friendly co-precipitation method. A variety of characterization techniques were employed to examine the structural, morphological, and optical properties of the materials, as well as the influence of doping. X-ray diffraction confirmed that the HNPs crystallize in a hexagonal rhombohedral structure within the R3c space group. Crystallite sizes were estimated using the Scherrer equation, yielding values of 46, 25, 33, and 30 nm, respectively. SEM analysis, combined with energy-dispersive X-ray spectroscopy (EDS), revealed the surface morphology and elemental composition. While undoped hematite displayed spherical particles, the doped samples exhibited morphological variations depending on the rare-earth ion incorporated.Optical properties were investigated using UV-Vis spectroscopy, with band gaps determined via the Tauc plot method. The measured band gaps were 2.135, 2.285, 2.495, and 2.445 eV, respectively. Undoped hematite showed lower band gaps compared to the doped samples, confirming that rare-earth doping significantly alters the optical behavior of the material. FT-IR spectroscopy was employed to identify functional groups and chemical bonding, while BET analysis provided information on specific surface area, pore size, and pore volume.Gas-sensing studies demonstrated that Sm-doped HNP sensors exhibit superior performance, achieving a sensitivity of 133 towards hydrogen sulfide (H₂S) gas at 175 °C. Stability tests conducted over seven days showed that the sensor maintained reliable performance at lower H₂S concentrations but became unstable at higher concentrations. Humidity was found to negatively affect sensitivity and selectivity. Repeatability tests confirmed sharp memory and consistent detection of 150 ppm H₂S. The limit of detection (LOD) was determined to be 0.1 ppm, which complies with NIOSH guidelines.In summary, the results highlight that synthesis conditions, rare-earth doping, and optimal operating temperature are critical factors influencing the performance of HNP-based gas sensors.
Keywords: Optimal temperature of the sensor, Doping, Sensitivity, Humidity, Response, and recovery time

Speaker: NTOKOZO CEBEKHULU

95 Synthesis of SrVO3 thin films using pulsed laser deposition.

Thin films have been used and are used in many technological applications, as they are more practical than bulk powders. The unique properties of thin films enable them to be fabricated and integrated into more complex devices while preserving the bulk material's original properties. The preservation of bulk material properties has enabled transparent conductive oxide (TCO) thin films to garner significant interest for their high conductivity while maintaining transparency in the visible region. Strontium vanadate (SrVO3) has been shown to be a promising TCO candidate. Early reports showed that SrVO3 thin films prepared by pulsed laser deposition (PLD) exhibited a conductivity comparable to that of indium tin oxide (ITO), while maintaining a visible transparency of more than 80%.

In this study, SrVO3 thin films were prepared by PLD. Various environmental parameters were varied during deposition to examine their effects on the thin-film properties, including conductivity, transparency, and morphology. The results showed that a conductive SrVO3 thin film could be achieved. However, balancing transparency and electrical conductivity was challenging, as these two properties are mutually exclusive. To try to overcome this limitation, a SrVO3 thin film with a square grid pattern was prepared. This result showed an improvement in overall visible transparency while maintaining conductivity.

Speaker: Edward Lee (University of the Free State)

96 Thermal and Structural Analysis of Li2MnO3-Li0.69MnO2 Core-Shell Systems using Molecular Dynamics Simulations

Core-shell architectures have emerged as an effective strategy to enhance structural stability, regulate oxygen redox, and improve lithium-ion transport in lithium-rich layered oxide cathodes. This is due to the ability of the shell to act as a protective barrier that suppresses oxygen loss and mitigates surface degradation, while simultaneously facilitating lithium diffusion and stabilising the electrode-electrolyte interface. These advantages make core-shell design particularly attractive for addressing the limitations of lithium-rich materials such as Li2MnO3, which suffers from voltage decay, irreversible capacity loss, sluggish lithium diffusion, and structural degradation at high voltages. In this study, a Li2MnO3-Li0.69MnO2 core-shell system is investigated using large-scale molecular dynamics simulations with the DL_POLY package under canonical (NVT) conditions with a Nosé-Hoover thermostat. The temperature-dependent behaviour of Li2MnO3 and Li0.69MnO2 nanospheres is first analysed to establish a baseline for lithium diffusion and structural stability, followed by evaluation of the integrated core-shell system with varying shell thickness and interface distance. Results show that Li2MnO3 undergoes significant oxygen loss and enhanced lithium diffusion with increasing temperature, while Li0.69MnO2 exhibits reduced oxygen release but notable lithium loss. The 3 Å core-shell configuration maintains structural stability across temperatures (300 K – 1500 K), with radial distribution function analysis indicating moderate disorder at elevated temperatures. Enhanced lithium diffusion in the shell and thermal expansion trends suggest that the design effectively balances stability and ionic mobility, making it a promising cathode architecture.

Speaker: Precious Makhubela (Student)

97 CuO/Fe2O3 p-n heterostructures with Ag-functionalization for improved p-xylene and toluene sensing performance

Tremendous effort has been invested in the fabrication of nanomaterials for gas detection of volatile organic compounds (VOCs), such as acetone, methanol, ethanol, benzene, and toluene. These VOCs act as important medical biomarkers for various diseases, such as diabetes, lung cancer, asthma, and halitosis. In this study, pristine and Ag-loaded CuO/Fe2O3 p-n heterostructures were synthesized using a hydrothermal method. The structural, morphological, and optical properties were analysed. Powder X-ray diffraction patterns showing peaks from 30 to 75 for Cupric oxide (CuO) and 20 to 65 for Hematite (α-Fe2O3) confirmed the formation of a heterostructure. Surface analysis revealed a porous morphology consisting of irregular particles and cube-like structures, which is beneficial for gas diffusion. Optical studies demonstrated a reduction in the optical bandgap as the Ag-loading concentration increased on the CuO/Fe2O3 p-n heterostructures. From the gas-sensing perspective, when incorporating 0.75 wt% and 2 wt% of Ag, the CuO/Fe2O3 p-n heterostructure sensor displayed superior responses of 7.3 and 7.6 to 100 ppm C7H8 and C8H10, respectively. The superior sensing characteristic is attributed to the combined effects of p-n heterojunction barrier modulation and Ag-induced enhancement of oxygen adsorption and activation. The findings highlight the vital roles of noble-metal functionalization and heterostructure engineering in designing next-generation gas sensors.

Keywords: p-n heterojunction, volatile organic compounds (VOCs), next-generation gas sensors.

Speaker: Vuyani Sifunda (University of limpopo)

Theoretical and Computational Physics: Session 3

Convener: Garreth Kemp (University of Johannesburg)

98 Saved by the Bell

The experimental demonstration of Bell inequality violation was a landmark moment for research in quantum foundations. Transitioning the field from metaphysical speculation into the empirical realm. However, the consequences of these violations by quantum mechanics are not fully understood, despite simplistic presentations to the contrary. In this talk we will discuss the assumptions under-girding Bell’s theorem, as well as classical systems that can violate Bell-like inequalities. In particular, we present a sequential polariser experiment that can produce Bell correlations even under classical assumptions. We further explore this experiment to determine the remarkable similarity to Bell correlations (equal up to sign). We argue this similarity is no coincidence by presenting an overlooked probability relationship between the two, and use this simple classical experiment to draw insights into the physics of Bell measurements.

Speaker: Geoff Beck (University of the Witwatersrand)

quantum_slides_saip_2026.pdf

99 Solution of the two dimensional Schrödinger equation using Basis functions derived from the 16/8 Daubechies Wavelet Scaling Function

We use two dimensional basis functions based on a shifted and scaled wavelet scaling sym8 function
\begin{equation}
f_i(x)=\phi\left( x/h+x_{\rm max} /h -i\right)/\sqrt{h}\,.
\end{equation}
Here $h=x_{\rm max}/N$, where $x_{\rm max}$ is the distance from the origin to he boundary of the square shaped domain. In addition we modify these functions to satisfy periodic boundary conditions to improve convergence, denoting these by $g_i(x)$. We make use of repeated Gauss Legendre integration on the grid.\
As test case we consider the two dimensional harmonic oscillator with the potential
$$ V(x,y)=x^2+y^2$$ It is found that the energies converge quite quickly to the analytical values. and examine the convergence as function of $N$.

Speaker: Moritz Braun (UNISA)

14_Moritz_Braun.pdf

100 Calculation of the Ground State Energy of the Hydrogen Molecular Ion H2+ using a basis set derived from a shifted and scaled wavelet scaling function as basis set

We use three dimensional basis functions based on a shifted and scaled Daubechies wavelet scaling function[1]
\begin{equation}
f_i(x)=\phi\left( x/h+x_{\rm max} /h -i\right)/\sqrt{h}\,.
\end{equation}
From the equation above, $h=x_{\rm max}/N$, $h$ is also the distance between the scaling functions, and $N$ is the number of intervals from the origin to $x_{\rm max}$. However, the modification of the basis functions was necessary to satisfy periodic boundary conditions in order to improve convergence.

This basis set is used to solve the three-dimensional Schr\"odinger equation in the box
$$[-x_{\rm max}:x_{\rm max}] \times [-x_{\rm max}:x_{\rm max}] \times [-x_{\rm max}:x_{\rm max}] \,.$$ We present the results of a calculation of the ground state energy of the hydrogen molecular ion $H_2^+$ as function of the
discretisation parameters. The matrix elements are evaluated with three dimensional repeated Gauss Legendre Integration.

Reasonable convergence is found. The energy values obtained are close to the literature values. In future, we will consider its possible application to calculating the properties of molecules using the density functional approach.

References

[1] Daubechies,I.(1988). Orthonormal bases of compactly supported wavelets.
Communications on Pure and Applied Mathematics, 41(7), 909-
996.

Speaker: Obiageli Ezenwachukwu (University of South Africa (UNISA))

19_Obiageli_Ezenwachukwu.pdf

101 Solving the Helmholtz equation on hyperbolic spaces

Hyperbolic spaces serve multiple purposes in the frontiers of physics at different regimes: on the large scales, when considering the global topology of the universe, and on small scales, when considering compactified extra dimensions in some Beyond the Standard Model scenarios. These spaces are non-trivial, and determining their eigenmodes (i.e. the solutions to the Helmholtz equation on them) provides essential knowledge for model-building and phenomenology. The Thurston manifold $Q_2$ serves as a benchmark hyperbolic manifold for which the boundary element method has been used before to compute eigenmodes of Laplacians. This work revisits the problem with physics-informed neural networks, where tunable weights are used to represent eigenvalues of interest. The low-lying eigenvalues of $Q_2$ are approximated and compared to their counterparts from the boundary element method and the Weyl asymptotic formula.

Speaker: Anele Ncube (University of Johannesburg)

16:00 Buffer

Special Invited Talk: Prof Malik Maaza

17:10 Buffer

Poster Session 1

102 A comparative analysis of SPR signals in BSA-induced non-specific binding

Surface Plasmon Resonance (SPR) provides a label-free optical platform for the detection of biomolecular interactions. While highly sensitive, its accuracy can be compromised by non-specific binding, which introduces background interference and obscures target-specific signals, particularly on probe-functionalized surfaces. To address this challenge, the present study systematically investigated the efficacy of bovine serum albumin (BSA) as a surface-blocking agent on probe-functionalized SPR sensor chips designed for the detection of multi-drug-resistant tuberculosis (MDR-TB)-associated genetic targets. The sensor surfaces were functionalized with thiolated DNA probes specific to MDR-TB mutations and subsequently exposed to varying concentrations of BSA (ranging from 0.02 to 0.8 mg/mL) to evaluate and optimize surface passivation and minimize non-specific adsorption. Controlled binding assays between the immobilized probes and complementary target sequences were performed and analyzed using a Kretschmann configuration SPR biosensing platform. This approach enabled a systematic assessment of the impact of BSA blocking on signal specificity, surface coverage, and overall biosensor performance. Analysis of the resonance angle shifts showed that BSA blocking reduced non-specific binding interactions and improved signal-to-noise ratios. These findings suggested that BSA can be an effective strategy for minimizing background noise in SPR-based assays for biomolecular detection.

Speaker: sipho Chauke (Council for Scientific and Industrial research (CSIR))

103 A computational and experimental study on galena (100) surface and xanthate and dithiocarbamate collectors adsorptions

This study seeks to utilise both computational density functional theory (DFT) and micro-flotation experiments to understand the interaction of xanthates and dithiocarbamate with galena minerals under acidic and neutral conditions. The relaxed structural lattice parameters were recorded as a = b = c = 5.935 Å. The galena (100) surface was determined as the most stable surface and possessed a surface energy of 1.5 J/m2. Upon adsorption simulation, it was evident the SIBX was the most strongly adsorbed collector on the surface of galena compared to SNBDTC. This corresponded well with recoveries from micro floatation as SIBX under basic pH had the highest recoveries (97.2%). DTC showed much more differentiation in distinguishing between acidic and basic conditions. This aspect of the micro floatation depicted the selective capacity of DTC. The computational collector adsorption results complemented the experimental recoveries. The varied conditions in both the computational and experimental aspects agreed and thus facilitating a better understanding on the efficiency of recovering galena minerals.

Keywords: Xanthate, Dithiocarbamate, micro floatation, Galena

Speaker: Cannimhambho Chewe

104 A Novel Ti₃C₂Tₓ MXene–BiNiOCl Composite for Enhanced Electrochemical Performance in Supercapacitor Applications.

Portable electronics, electric cars, and large-scale energy systems are becoming increasingly popular, creating a need to move towards energy storage technologies that can deliver both high energy and power densities quickly and reliably. Supercapacitors (SCs) have emerged as promising energy storage devices due to their fast charge/discharge capabilities, long cycling life, and environmental benefits. The efficiency of SCs mainly depends on the active materials incorporated into their electrodes. Among these, MXene-based materials, particularly Ti3C2Tx, have attracted much interest due to their high electrical conductivity, large surface area, and longevity. In this study, we investigate the electrochemical performance of Ti3C2Tx doped with varying amounts of nickel-doped bismuth oxychlorides (Ni-BiOCl) as supercapacitor electrodes. Structural characterization using scanning electron microscopy with dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) confirmed successful doping of Ni-BiOCl and revealed increased interlayer spacing, improved morphology, and uniform elemental distribution. The electrochemical analysis of the Ni-BiOCl@Ti3C2Tx composites confirmed Faradic charge-storage contributions from reversible Bi3+/Bi5+ and Ni2+/Ni3+ redox couples, with the optimal concentration of 10% Ni-BiOCl achieving a discharge time of 485 seconds at 0.5 A/g, representing a 213% enhancement over pristine MXene (155 seconds). Overall, the 10Ni-Bi@Ti3C2Tx composite showed a specific capacity (Qsp) of 242.5 C/g (areal capacitance of 2686.15 mF/cm2), representing a significant improvement over MXene-based electrodes reported in the literature.

Speaker: Mr Tsholo Talane (UNISA, TUT)

105 Ab initio Investigation of the Structural Stability and Mechanical Properties of Janus monolayer MSC (M=Zr, Hf, Ti) in the 1H Phase

The structural stability and mechanical properties of Janus monolayer transition metal carbidesulfides MSC (M=Zr, Hf, Ti) in the 1H phase are systematically investigated using first-principles calculations. Cohesive energy calculations reveal that the 1H phase is consistently more stable than the 1T phase across all three compounds, with energy differences ranging from 0.50 to 0.67 eV/atom, thereby rendering the 1T phase energetically unfavorable for further mechanical evaluation. Among the three 1H-phase materials, ZrSC exhibits the highest cohesive energy of -6.985 eV/atom, followed closely by HfSC (-6.912 eV/atom) and TiSC (-6.586 eV/atom). Elastic constant analysis demonstrates that ZrSC possesses the highest in-plane stiffness (C = 207.0 N/m) and bulk modulus (103.5 N/m), indicating superior mechanical robustness. HfSC shows intermediate in-plane stiffness (C = 180.5 N/m) and bulk modulus (90.3 N/m), while TiSC exhibits the lowest values for both properties (C = 164.6 N/m, K = 82.3 N/m). Furthermore, HfSC and TiSC show significantly lower C₄₄ values (21.1 and 20.6 N/m, respectively) and high Poisson’s ratios (0.621 and 0.600), suggesting substantial mechanical anisotropy and enhanced flexibility compared to ZrSC. The Young’s moduli of all three compounds range from 65.9 to 70.7 N/m, indicating moderate but comparable tensile stiffness. These findings establish ZrSC 1H as the most mechanically stiff and energetically stable candidate among the series, while HfSC and TiSC 1H phases offer greater ductility, making them potentially suitable for flexible electronic applications.

Speakers: Dr Edwin Mapasha, Owen Alfreds

106 Activation of the p53 pathway in combination with photon irradiation for treatment of high grade brain tumour cells

Radiotherapy remains a cornerstone in the treatment of brain tumors; however, its
effectiveness can be limited by intrinsic cellular resistance driven by TP53 mutations and
altered DNA repair capacity. MDM2 inhibitors such as AMG232 are designed to restore TP53
pathway activity, potentially enhancing radiosensitivity. Understanding how AMG232
influences DNA damage responses, cell-cycle regulation, gene expression, and proliferation
in TP53 wild-type and mutant brain tumor cells is essential for improving therapeutic
outcomes. The aim of this study was to enhance the effectiveness of radiotherapy by
determining whether the MDM2 inhibitor AMG232 increases radiation-induced DNA damage
and modulates repair kinetics, cell-cycle progression, gene expression, and proliferation in
TP53 wild-type and mutant brain tumor cell lines. TP53 wild-type (ONS-76 and A172) and
TP53 mutant (DAOY and U251) brain tumor cell lines were treated with AMG232 and exposed
to photon irradiation at 1 Gy and 2 Gy. DNA double-strand breaks (DSBs) were quantified
using γ-H2AX foci formation at 0.5, 2, 4, 8, 12, and 24 hours post-irradiation, with and without
drug treatment. Cell proliferation was assessed through doubling-time (DT) measurements
following incubation with AMG232 for 24, 48, and 72 hours. Cell-cycle progression and
checkpoint activation were evaluated by flow cytometry at 8, 12, 16, and 24 hours. Gene
expression analysis of TP53-related pathway markers was performed at 0.5, 4, and 24 hours.
AMG232 increased TP53 pathway activation in wild-type cell lines, resulting in elevated initial
DNA damage levels and delayed repair kinetics following irradiation. In TP53 mutant lines,
AMG232 modulated repair dynamics and altered cell-cycle distribution but to a lesser extent
than in wild-type cells. Proliferation assays showed increased growth suppression with
AMG232, particularly in TP53 wild-type cells. Gene expression analysis confirmed
upregulation of TP53-associated targets in wild-type lines, while mutant cells exhibited partial
or altered transcriptional responses. AMG232 enhances the cellular response to photon
irradiation in a TP53-dependent manner, with TP53 wild-type brain tumor cells showing the
strongest radiosensitization effects. These findings support the potential of AMG232 as a
radiosensitizing agent and highlight the importance of TP53 status in predicting treatment
response. Incorporating MDM2 inhibition may represent

Speaker: Musa Maluleka (University of Venda)

107 Adsorption properties of GaN monolayer doped with Ru and Rh for CH2O detection

The adsorption of CH2O on the surface of GaN monolayer doped with Ru and Rh has been investigated using density functional theory. The Negative adsorption energies of -2.096 and -1.629 eV were attained for the adsorption of CH2O on GaN monolayer doped with Ru and Rh respectively, implying energetically stable systems. The more negative the adsorption energy, the more favourable and stronger the adsorption. As such, the adsorption energies suggest that the adsorption of CH2O is more favourable on the surface of GaN monolayer doped with Ru. The binding distance between the CH2O gas and GaN monolayer doped with Ru and Rh were computed to be 2.040 Å (Ru-C) and 2.049 Å (Rh-C) respectively. The adsorption of CH2O on GaN monolayer doped with Ru and Rh occurs though the carbon atom.

Speaker: Dr Malesela Walter Makgoba (University of Limpopo)

108 An Integrated Predictive Framework for Metastable Beta-Titanium Alloys in Orthopaedic Applications

Accurate prediction of phase stability and mechanical compatibility is essential for developing metastable beta-type titanium alloys for orthopaedic applications. Current alloy design methods including molybdenum equivalence (Moeq), electron-to-atom ratio (e/a), bond order–metal d-orbital energy (Bo–Md), and the cluster-plus-glue-atom model, when used independently, often produce inconsistent predictions, especially for complex multicomponent systems. This study establishes a unified framework by systematically integrating these approaches. The evaluation of various titanium alloys shows that empirical methods facilitate rapid initial screening but lack precision, whereas electronic structure-based approaches offer greater predictive accuracy, although they require further refinement. By combining these models within a structured design strategy, prediction reliability is significantly enhanced, and inconsistencies are minimised. This framework provides a generalised methodology for designing metastable beta-type titanium alloys with improved properties, and it is adaptable to other alloy systems.

Speaker: Lerato Raganya

109 Analysis of Deep-Level Defects within a Commercial Silicon Bipolar Junction Transistor After Electron Irradiation

Bipolar Junction Transistors (BJTs) are fundamental semiconductor components utilized extensively for switching, amplification, and signal control in modern electronics. However, their electrical performance in high-radiation environments, such as space and nuclear facilities, is often compromised by degradation.

A 2N2907A pnp silicon BJT was subjected to electron irradiation under a strontium-90 source with an overall flux of $2.3\times10^{7}$ electrons/cm$^2$ for roughly 18 days. The base–collector junction of the BJT was electrically characterized using Current–Voltage (I–V), Capacitance–Voltage (C–V) and a transistor tester, which revealed degradation due to defect formation, including increased leakage current, and reduced barrier height. Specifically, the $\beta$ current gain dropped from 204 to 10 after 18 days of irradiation. Results showed a loss in the ability of the silicon transistor to amplify signals effectively compared to before radiation exposure. Capacitance data indicated a complex evolution of carrier concentration, where an initial slight increase during short-term exposure was followed by a sharp decrease after prolonged irradiation due to the formation of deep-level defects.

Deep-Level Transient Spectroscopy (DLTS) was applied to the transistor before and after irradiation to detect electrically active defects within the bandgap of the semiconductor. A specialized three-layer sample holder was designed in order to securely mount the transistor in place and overcome certain challenges including the thermal lag and electrical isolation when modifying the DLTS setup. The sample holder consisted of an aluminium base, an alumina insulating layer, and an aluminium top cavity to secure the device.

This study represents one of the first applications of Laplace DLTS applied to a BJT, providing significantly enhanced resolution of overlapping defect peaks compared to conventional DLTS techniques. The conventional and Laplace DLTS techniques provide a method to determine the corresponding activation energies and apparent capture cross-sections from the measured data, allowing for the identification of defect complexes. Multiple native and irradiation-induced defects were identified, most notably the divacancy $V_{2}(+/0)$ defect. The activation energy of the divacancy was detected via conventional and Laplace DLTS, with conventional DLTS yielding an activation energy of $E_a=0.194$ eV and an apparent capture cross-section of $\sigma_a= 5 \times 10^{-16}$ cm$^2$ for the $V_{2}(+/0)$ defect. Other observed signatures were tentatively assigned to boron-, oxygen-, or vacancy-related complexes.

While some defects could not be assigned due to signal overlap or uncertainty in their identification based on previous literature, the application of Laplace DLTS proved essential for distinguishing complex defect structures. These findings demonstrate the feasibility of applying advanced spectroscopic techniques to commercial bipolar semiconductor devices and provide a critical framework for predicting device reliability and guiding the design of radiation-tolerant electronics in harsh environments.

Speaker: Mr Kaveer Nagessar (University of Pretoria)

110 Analysis of Inter-Fraction Setup Errors and Organ Motion Using Daily kV-CBCT in VMAT for Prostate Cancer

Prostate cancer is the second most prevalent malignancy that affects men globally and one of the curative approaches requires high-precision radiotherapy techniques. One of these recent and advanced techniques is volumetric modulated arc therapy (VMAT). This ensures accurate dose delivery whilst minimizing toxicity to the organs in proximity to the prostate, such as the rectum and bladder. This study aims to investigate the inter-fraction setup errors and internal organ motion using daily kilovoltage cone beam computed tomography (kV-CBCT) imaging in prostate cancer patients treated at Charlotte Maxeke Johannesburg Academic Hospital.
This study is a retrospective analysis will be conducted from patients that were treated for prostate cancer from 2023 until the end of 2024 undergoing VMAT. Daily CBCT images taken prior to treatment delivery will be used to quantify translational setup deviations in the left–right (LR), superior–inferior (SI), and anterior–posterior (AP) directions in relation to the planning CT images. Systematic and random errors will be calculated, and planning target volume (PTV) margins will be estimated using established margin recipes such as the van Herk calculation. Volumetric changes in bladder and rectal filling will also be assessed to evaluate their influence on prostate displacement.
It is anticipated that measurable inter-fraction variability will be observed, with larger deviations expected to occur in the AP direction. This is because of the expected volumetric changes in rectal and bladder. The utilization of daily image guidance is expected to limit setup uncertainties and improve target localization whilst sparing toxic radiation to the surrounding organs. This also improves the maximum dose delivery to the prostate without underdosing it. The results of this study are expected to contribute to the optimization of PTV margin design and support the implementation of adaptive radiotherapy strategies.
This study will provide essential data, that has an immediate impact to the local people, and will improve geometric accuracy and treatment outcomes in prostate cancer radiotherapy.

Speaker: Mr Kgomotso Lefenya (University of Witwatersrand - Wits)

111 Atomistic insights into the temperature effects on the structural and dynamic properties of cobaltite (CoAsS): A molecular dynamics study

Cobaltite (CoAsS) possesses a structure similar to that of pyrite, which facilitates the development of interatomic potentials for atomistic simulations based on previously derived pyrite models. This study employed the atomistic molecular dynamics simulation to investigate the effect of temperature on the structural and dynamic properties of bulk cobaltite. The developed model predicted a lattice parameter of 5.571 Å, which was in good agreement with the experimental value of 5.582 Å. In addition, the calculated elastic constants were also found to compare well with the reported theoretical data and satisfy the mechanical stability criteria for cubic system. This confirmed the robustness of the potential model in replicating the structural properties. The validated potential model was subsequently applied to examine temperature-dependent behaviour. Properties such as structural changes, configurational energy, radial distribution functions, and diffusion coefficients were analyzed over a range of temperatures. The melting point of cobaltite was estimated to lie between 900 K and 1100 K. These results demonstrated the strong predictive capability of the potential model for phase transition behaviour, highlighting the reliability of the interatomic potentials developed.

Speaker: Segoarihle Ntobeng (University of Limpopo)

112 Atomistic Simulation of Thermodynamic, Phase, and Melting Stability in Pyrite-Type Nanomaterials

Pyrite-type nanomaterials have attracted considerable attention due to their potential applications in energy materials, electrocatalysis, and photovoltaics. As Earth-abundant systems, their enhanced structural and dynamical properties arise from a high surface-to-volume ratio, necessitating a detailed understanding of their behaviour under varying conditions. In this study, molecular dynamics (MD) simulations were employed to investigate the structural and dynamical properties of pyrite-type nanostructures at the atomic scale. Nanoparticles with sizes ranging from 1 to 10 nm in diameter were examined. Thermodynamic stability, phase transitions, and melting behaviour were analysed using radial distribution functions, potential energy variations, and diffusion coefficients. These mechanisms enabled the identification of melting points, solid-to-liquid phase transitions and associated structural transformations. The results demonstrate a strong size-dependent melting behaviour, with melting temperatures increasing as nanoparticle size increases. This study provides valuable insights into the thermal stability and size effects of pyrite-type nanomaterials, supporting their potential application in energy-related technologies and advanced functional materials.

Speaker: Mofuti Mehlape (University of Limpopo)

113 Characterisation of Temperature-Sensitive FBG Sensors for Extreme Environments

Within industries such as nuclear reactors and aerospace, working environments have extreme temperatures ranging from cryogenic operations below -$100\,^{\circ}\mathrm{C}$ to high heat at $300\,^{\circ}\mathrm{C}$. Fiber Bragg Grating (FBG) sensors with polyimide coating offer a promising solution due to their compact size, multiplexing capability, and resistance to signal degradation in high temperatures. In this study, temperature-sensitive FBG sensors with polyimide coating from iXblue are experimentally characterised to evaluate their suitability for high-temperature operation in such environments. Controlled temperature calibration experiments were conducted over an extended temperature range to determine the thermal response of the sensors. The Bragg wavelength shift was recorded as a function of temperature, and key performance metrics including sensitivity, linearity, and repeatability were evaluated. Particular attention was given to sensor stability and consistency under elevated temperatures representative of nuclear and aerospace conditions. The results demonstrate that the sensors exhibit a strong and repeatable linear response across the tested temperature range, with stable sensitivity coefficients and minimal hysteresis. These findings confirm the suitability of radiation-hardened FBG sensors for precise temperature monitoring in extreme environments, supporting their potential deployment in nuclear reactors, space systems, and other high-temperature applications.

Speakers: Timothy Brooks (University of Johannesburg), Abdool Sattar Cassim (University of Johannesburg)

114 CHARACTERIZATION OF LITHIUM LANTHANUM ZIRCONIUM OXIDE (LLZO) FOR STRUCTURE AND PHASE ANALYSIS IN X-RAY DIFFRACTION FOR LI-ION BATTERIES APPLICATION

In this work, a synthesized metal oxide Li3.5La 1.5 ZrO 6 (LLZO), a solid-state electrolyte, is characterized and studied to unveil its properties as an alternative to the liquid electrolyte currently used in lithium-ion batteries.
Lithium-ion batteries suffer from the formation of dendrites (swelling) and overheating while being charged/ discharged, sometimes resulting in thermal run-offs.
The following characteristics, i.e., phase fractions, lattice parameters, site occupancy, crystalline size, and microstructure, are obtained from an X-ray diffractometer ( Smart Lab Rigaku RU 300 X-ray Diffractometer) with a scan from 10 ° to 80 ° in steps of 0.002.
Finally, a Rietveld refinement procedure is performed using software to exhaustively characterize the LLZO for a study on solid-state oxide electrolytes for lithium-ion battery applications.

Speaker: Kyalo N Kiteme

Poster Saip 2026 conference.pdf

115 Characterizing Radiation Backgrounds for the PAUL Lab Site in the Huguenot Tunnel

The proposed Paarl African Underground Laboratory (PAUL) project has
made significant progress toward the planning and design of an underground laboratory to be constructed during the upgrade of the Huguenot Road Tunnel near Paarl in the Western Cape, South Africa. While underground locations reduce cosmic-ray backgrounds, it is also important to understand radiation coming from the surrounding rock. Here, we report on measurements of the gamma-ray background within the tunnel, together with an analysis of naturally occurring radionuclides in the surrounding granite. This presentation summarizes in-situ gamma-ray spectra and the activity concentrations of 40K, U-238, and Th-232, determined through laboratory gamma spectroscopy
of rock samples.

Measurement methods, including detector calibration and sample analysis, will be described. The results are discussed with an emphasis on their implications for the design of the proposed underground laboratory and the development of effective background mitigation strategies.

Speaker: Ntuthuzelo Nqeketo (University of the Western Cape)

116 Comparative Proton EBS and Alpha-RBS Analysis of SiC co-implanted with Sr and H at Room Temperature, 350 °C, and Annealed at 1000 °C

Silicon carbide (SiC) has been proposed as a primary coating layer within tri-structured isotropic (TRISO) fuel particles due to its unique properties. While TRISO particles successfully retained most FPs, the release of key radioactive elements such as strontium (Sr) remains a challenge, prompting numerous studies to understand their diffusion mechanisms in SiC. This study investigates the role of hydrogen (H) in the migration of Sr implanted into SiC. The motivation stems from the reactor environment, where SiC is exposed to H generated via radioactive decay and neutron transmutation, as well as other FPs such as Sr. Polycrystalline SiC was first implanted with 300 keV Sr ions to a fluence of 2×10^16 ions/cm² at room temperature (RT) and at 350 °C. Pre-implanted Sr-SiC samples were co-implanted with H ions of 15 keV to a fluence of 1×10^17 ions/cm² under the same conditions. All the samples were annealed at 1000 °C for 5 h. The Sr depth profiles in Sr-SiC and Sr+H-SiC were measured using elastic backscattering spectrometry and Rutherford backscattering spectrometry with different incident particles. Beams of protons (H⁺) and alpha (⁴He⁺) particles were used at energies of 1 MeV (20 µC) and 3 MeV (40 µC), respectively. The measurements were taken at the same geometry of 165 ° for the scattering angle and 10 ° for the tilting angle. The experimental error from 3MeV RBS was calculated to be 6.3%, where Sr depths of 120 nm and 128 nm were obtained from the simulation and experiment, respectively. RT co-implanted samples show a Sr migration toward the surface, and a loss after annealing. In contrast, no Sr migration or loss was detected in the samples co-implanted at 350 °C; both techniques complement these results. The Sr profile has been analyzed with accuracy, and the results are validated using proton and alpha beams of different scattering mechanisms.

Speaker: Mr Khulekani Manqele (University of Zululand)

117 Comprehensive Review of Hydrogen Storage Technologies for Green Energy Systems

Hydrogen is widely regarded as a promising green fuel due to its zero direct carbon emissions during use. Hydrogen has the highest energy content per unit mass, about 120 MJ/kg, but its volumetric energy density remains very low because of its low density at ambient conditions. This limitation makes hydrogen storage a major challenge for both stationary and onboard applications. This challenge limits widespread hydrogen adoption and motivates continued research into advanced, scalable storage technologies. Therefore, effective storage systems must provide high gravimetric and volumetric densities while ensuring safety, low cost, acceptable operating conditions, and public acceptance worldwide.

This study presents a systematic review of hydrogen storage technologies, categorized into physical storage (compressed gas and liquefied hydrogen), chemical storage, and materials-based storage approaches. Physical storage methods, such as high-pressure compression and cryogenic liquefaction, are technologically mature but suffer from high energy penalties and safety concerns. In contrast, materials-based storage systems—including metal hydrides, chemical hydrides, and porous materials such as metal–organic frameworks—offer higher volumetric densities and improved safety, though they are limited by slow kinetics and thermodynamic constraints. The review examines hydrogen storage technologies within the context of the full hydrogen supply chain, including production, storage, transport, and end-use applications.

Speaker: Roy Mlambo (University of Venda)

118 Computational and experimental investigation of pH effect on xanthate and dithiocarbamate collectors on pyrite minerals

This study investigated the interaction between pyrite (FeS₂) mineral surfaces and xanthate and dithiocarbamate (DTC) collectors through a combination of computational Density functional theory (DFT) and microflotation experiments. Although pyrite is commonly regarded as a gangue mineral, its strong flotation tendency under conditions similar to valuable sulphides such as galena, chalcopyrite, and sphalerite often reduces selectivity and metallurgical efficiency. The adsorption of isobutyl xanthate (IBX) and n-Butyl dithiocarbamate (NBDTC) on the pyrite (100) surface at acidic and neutral conditions were performed. It was found that strong chemisorption occurred through Fe and collector S atoms bonding with adsorption energies of –206.8 kJ/mol (SIBX), –245.7 kJ/mol (HIBX), –204.4 kJ/mol (SNBDTC), and –180.4 kJ/mol (HNBDTC). Experimental microflotation tests demonstrated that collector efficiency decreases with increasing pH, as surface oxidation and formation of hydrophilic Fe(OH)₃ films hinder adsorption. At pH = 3, HIBX achieved maximum recovery of 97%, while HNBDTC reached 93%. At pH = 10, recoveries dropped to 83% (SNBX) and 57% (SNBDTC). The combined computational and experimental results confirm that adsorption is thermodynamically more favorable and flotation performance higher under acidic conditions. The study bridges theoretical and experimental insights, providing a mechanistic understanding of collector–pyrite interactions and offering a scientific basis for developing improved strategies to control pyrite depression in sulphides ore flotation.

Speaker: Carol Tlhaboloa (University of Limpopo)

119 Computational Fluid Dynamics and Validation of a Double-Roof Sawtooth Greenhouse

The performance of greenhouse cultivation hinges on precise control of its internal microclimate, particularly under urban and variable climatic conditions. In this study, we used computational fluid dynamics to model the environmental conditions in a double-roof sawtooth greenhouse located at the University of Johannesburg. The temperature, pressure and humidity distributions in the greenhouse with different vents opening were predicted. A three-dimensional geometry of the greenhouse was developed, meshed, and simulated using ANSYS Fluent v24r1 to assess the effects of temperature, pressure, airflow, and relative humidity under different ventilation configurations (Configuration 1 vent open, Configuration 2 vent closed). The simulations revealed that configurations 1 and 2 produced different environmental conditions, from uneven temperature and relative humidity distributions to more uniform conditions suitable for specific crop production. It was also observed that the greenhouse’s ability to regulate temperature and humidity was highly dependent on external environmental conditions, and reliance on natural ventilation alone was insufficient to maintain optimal growth conditions throughout. These findings highlight the importance of careful configuration selection, targeted crop placement within the greenhouse, and consideration of additional climate-control measures, such as HVAC systems. The results provide a foundation for future studies on greenhouse optimisation, including variations in vent and window placement, transient environmental conditions, and the impact of solar radiation on internal microclimates, supporting more efficient and sustainable crop production.

Speaker: Mr Tshepiso Mogajana (University of Johannesburg)

120 Computational Fluid Dynamics Modelling of an Intensified Biomass Pyrolysis Reactor for Sustainable Hydrogen Production

The accelerating global transition toward clean energy demands sustainable pathways for hydrogen (H 2 ) production. Thermochemical conversion of lignocellulosic biomass through pyrolysis and reforming offers a promising, carbon-neutral route, yet reactor design remains a critical bottleneck limiting yield efficiency. This study presents a computational fluid dynamics (CFD) investigation into the Thermo-Catalytic Reforming (TCR) process, originally developed at Fraunhofer UMSICHT, to establish a validated simulation framework that can subsequently inform the design of an intensified novel reactor geometry optimised for H2 and syngas production. The methodology proceeds in two stages. In the first stage, the TCR reactor is reconstructed in ANSYS Fluent and simulated using a coupled multiphase model, which incorporates species transport, heterogeneous catalytic kinetics, and turbulence closure suitable for reactive flows. The simulation results are systematically validated against published experimental and computational data from Fraunhofer-Gesellschaft. Sensitivity analyses are performed on kinetic parameters, phase interaction models, and turbulence formulations to assess model fidelity and identify the physics best suited for representing the TCR process. In the second stage, the validated physics are applied to a novel reactor geometry developed using principles of process intensification, including enhanced heat and mass transfer, reduced residence time distribution, and improved contact between reactive phases. Parametric optimisation targets maximised H 2 and syngas selectivity. This work contributes to the growing body of evidence that physics-informed simulation, guided by process intensification theory, can accelerate the development of next-generation thermochemical reactors for clean energy applications in the African and global context.

Speaker: Marisana Masha (Cape Peninsula University of Technology)

121 Computational simulation of noble metals (Pd, Ir, and Os) as surface catalysts in metal air batteries

Lithium-air batteries are a promising solution for future energy storage due to their high energy density and environmental friendliness. However, their performance is limited by slow reaction kinetics at the cathode, particularly the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Noble metals such as palladium (Pd), iridium (Ir), and osmium (Os) can enhance these reactions owing to their excellent catalytic and electrical properties. In this study, Density Functional Theory (DFT) was employed to investigate the properties of these metals and evaluate their catalytic activity in lithium-air batteries. The electronic density of states (DOS) revealed that all three metals exhibit metallic character, with strong contributions from d-electrons near the Fermi level, which enhances electrical conductivity. The calculated elastic constants confirmed that the metals are mechanically stable. Palladium showed results in close agreement with experimental values, while Ir and Os[SS1.1] were found to be comparatively stiffer materials. Surface models were constructed for three low Miller index planes, (001), (011), and (111), using the METADISE code. The surface energies of the relaxed structures were calculated and used to generate Wulff shapes, providing insight into the most stable surface morphologies. Overall, this study provides valuable insights that can contribute to the development of more efficient lithium-air batteries.

Speaker: bornwise mugwena (university of limpopo)

122 Computational study of violarite (NiFe2S4) surface stabilities

The milling of the violarite (NiFe2S4) mineral exposes different surface and as such there are few or one surface that dominates during the crushing. The thermodynamic stable surface is less reactive and is of importance for mineral extraction. Computational method can determine the most stable surface and the preferred cleavage either through reconstruction or perfect surface cleavage. The current study investigated the surfaces of FeNi2S4 and their reconstruction behaviour using density functional theory (DFT). The (100), (110), (1-10), (111) and (13-1) surface were cleaved from the relaxed bulk structure and those that possessed dipole were reconstructed. The computed surface energies for the un-reconstructed and reconstructed surface showed that the reconstruction resulted in lower surface energies and therefore stable surfaces. This study has demonstrated that the (110) surface (0.842 kJ/m2) was the most stable surface for NiFe2S4 pentlandite as also predicted by the surface morphology.

KEYWORDS
Computational modelling, Violarite, Surface reconstruction, Surface energies

Speaker: Ms Nontobeko Nondumiso Zavala (University of Limpopo)

123 Concentration-dependent effects of caffeine on perovskite catalysts for electrocatalytic and photoelectrocatalytic hydrogen evolution reaction

In this study, optimizing caffeine concentrations (2%, 4%, 6%, and 8%) in MAPbI3 using a graphite electrode under acidic conditions, analysing both electrocatalytic (EC) and photoelectrocatalytic (PEC) processes was investigated. The catalyst made from Graphite and MAPbI3 with 2% caffeine shows superior performance compared to the other catalysts, particularly in the dynamic electrocatalytic process. Notably, the Graphite + MAPbI3@Caffeine 2% catalyst exhibits a significantly reduced charge transfer resistance of 9.27 ꭥ, outperforming the other catalysts we examined. Our results also indicate that the Graphite + MAPbI3@Caffeine 4% loading demonstrates exceptional stability, surpassing the stability of other catalysts. Remarkably, the double-layer capacitance (Cdl) value for the Graphite + MAPbI3@Caffeine 2% electrode is 0.00281 F/cm², which indicates a significant enhancement under PEC conditions compared to EC settings, with an effective catalyst surface area (ECSA) of 150 cm². Additionally, the turnover frequency (TOF) for the Graphite + MAPbI3@Caffeine 2% catalyst was calculated to be an impressive 348.29 s⁻¹, exceeding the performance of other electrodes within the EC process.

Speaker: Dieketseng Glara Tsotetsi (Department of Physics, University of South Africa, Johannesburg, 1710, South Africa.)

124 Controlling randomness: Experimentally simulated scattering with digital holograms

Systematic studies of light’s propagation through media with spatially varying refractive indices are key to advances in imaging biological tissues, opaque materials and communication through foggy conditions. Laboratory studies typically employ white paint, emulsions or tissue-mimicking phantoms which are difficult to identically reproduce, simulate and often have complex time-consuming multistep fabrication procedures limiting their widespread usage and making highly controlled studies difficult. Here we demonstrate an all-digital solution generating tuneable random distortions by encoding binary random phase masks onto a spatial light modulator. We demonstrate tuneable intensity and phase distortions, closely matched by numerical simulations and show how the distortion strengths span those achievable with physical scatterers. As an example, we apply this to Laguerre-Gaussian beams and show modal crosstalk consistent with results observed in other random media. This digital method thus eliminates complications associated with physical samples and facilitates highly systematic studies of random scattering essential for applications in complex media.

Speaker: Kelsey Everts (University of the Witwatersrand)

125 Deep levels in as-grown and electron irradiated undoped n-GaAs grown by MOVPE using TEGa and TBAs

Abstract
Homoepitaxial undoped n-type GaAs layers were grown by metal-organic vapour phase epitaxy (MOVPE) on semi-insulating and n⁺ GaAs substrates at growth temperatures ranging from 550 °C to 675 °C. Growth was carried out using an unconventional precursor combination of triethylgallium (TEGa) and tertiarybutylarsine (TBAs), in contrast to the more commonly employed trimethylgallium and arsine. High-resolution X-ray diffraction confirmed the high crystalline quality of the epitaxial layers. Hall measurements performed at room temperature and 77 K revealed a net donor concentration 9.4 x1014 -1.5 x 1015 cm⁻³ and electron mobilities ranging from 5700 to 6570 cm2 V-1 s-1. Capacitance-voltage profiling indicated a relatively uniform carrier distribution in the as-grown films. Deep-level transient spectroscopy in the temperature range 20-300 K detected three electron traps in layers grown at 600 °C, while no deep levels were observed in samples grown at 650 °C, indicating a strong dependence of defect formation on growth temperature. Following 1 MeV electron irradiation, an increase in intrinsic defect concentrations and the appearance of additional deep levels were observed. Notably, the arsenic-vacancy-related E2 trap was identified in the as-grown material, and two previously unreported defect states emerged after irradiation.

Speaker: Ms ANDI ISNI PUJIRANA (NELSON MANDELA UNIVERSITY)

126 Defect-Engineered Cr2O3-based sensor for Selective detection of LPG

Liquefied petroleum gas (LPG) is widely used in our daily lives as an alternative fuel for cooking and various industries. The LPG contains a mixture of propane and butane. On the other hand, they possess flammable and explosive properties. The December 2022 incident in Boksburg, South Africa, involving an LPG tanker poses a significant threat to infrastructure, public safety, and the environment. Gas leaks can be caused by various factors, including human error, storage, and transportation. Gas sensors are employed to detect such gas leakages. Much focus has been dedicated to investigating the use of semiconductor metal oxides in gas sensing. Chromium (III) oxide (Cr2O3) is a widely known p-type metal oxide semiconductor with high catalytic activity and thermal stability. Herein, Cr2O3 was synthesized via a hydrothermal method and evaluated for LPG sensing. Various characterization techniques were used to probe properties such as morphology, structure, optical properties, chemical state, and gas sensing. The gas-sensing characteristics of Cr2O3 showed a high response to 1000 ppm LPG at 125 °C. Such improvement could be associated with three-dimensional (3D) mesoporous materials, which are favourable owing to the high surface area and rich mesopores for gas molecule adsorption.

Speaker: Ms RAMOKONE CHRISTINA MALINDISA (University of the Free State)

127 Detection of Wildfire Smoke Plumes using Machine Learning Systems

Triggered false alarms are one of the biggest problems for smoke detection systems. Cloud movement in the sky, cloud reflections on hills, cars, animals eating, and trees moving about in a forest can easily trigger a false alarm. This poses a critical issue because forest wildfires are constantly on the rise. This affects the global economy substantially and forest ecosystem, therefore reliable detection systems are on demand. This study investigates different preprocessing techniques in conjunction with deep learning for image classification and object detection, to create an AI system with an accuracy of 90% or greater for identifying smoke plumes in the forest.

The image classifier was built around a cumulative difference image derived from four sequential camera frames. Three pairwise differences were computed and summed into a single representation capturing overall scene motion. This image was evaluated in three forms as classifier input: grayscale, optical flow, and colour. Among the representations explored, the colour-based input demonstrated promising performance because its accuracy was about 0.83 with loss of about 0.62, Grayscale results were 0.78 accuracy and 0.79 loss. the optical flow performed comparatively weaker.

There's notable divergence between training loss and validation loss, to rule out whether they were from the model built or data used to build the model, k-cross fold was undertaken with a ratio of 80% training data and 20% evaluation data on all 5 folds, this was done then compared with the results from test data, the outcome proved that the model was consistent across folds but not as much during testing due to the fact that the results from testing were vastly different from k cross folds. This translates to the quality of the data not being good enough or is a representation of the dataset.

on the object detection side images were bounded to focus the learning on the region of interest, optical flow was employed as means to analyse smoke movement, with optical flow, colour contrast changes and heatmap vision this was done to provide the classifier with richer and more discriminative visual information.
while results do show promising potential, expanding data, to overcrowd the camera shaking error trees cars and animals. would prove to be great.

Speaker: Mr Mbongeni Mncube (University of Kwazulu-Natal)

128 Determination of Energy Bandgap of ZnS Nanoparticles Using UV-Vis Data and Tauc Plot.

Zinc sulphide (ZnS) has been widely utilized in solar cells as a buffer layer or light scatterers due to its excellent chemical and physical. Zinc sulphide nanoparticles (NPs) were characterised using UV-Vis spectroscopy to determine their energy band gap. The absorption spectra were obtained in the wavelength range 300 – 800 nm. The absorption spectra showed maximum absorption just below 300 nm with a long absorption tail. The Beer-Lambert law was then used to determine the absorption coefficient of the NPs. Thereafter, the Tauc plot method was used to determine the energy band gap of the ZnS NPs.

The absorption peak around 300 nm is due to the nanocrystalline nature of the ZnS and consistent with large direct band gap semiconductor. The long absorption tail above 300 nm can be attributed to light scattering by the ZnS NPs. This then suggests that ZnS NPs can be used as light scatterers in solar cells to improve light absorption. An energy band gap of 3.79 eV was obtained for the synthesized ZnS NPs. This energy band gap matches very well with reported literature.

Speaker: Mr Keamogetswe Motiang (Northwest university)

129 Development and Optimization of an Automated Gamma-Ray Spectrometry System Radionuclide Identification and Quantification

Automated gamma-ray spectrometry is a modern analytical technique used for radionuclide identification and quantification in environmental, industrial, and nuclear applications. This study presents the development and optimization of an automated gamma-ray spectrometry system using a high-resolution detector and advanced software for real-time spectral acquisition and analysis. Automated functions including energy calibration, efficiency correction, peak identification, and background subtraction were implemented to improve measurement reliability. The system reduces analysis time, enhances reproducibility, and minimizes operator-related errors. High sensitivity and precision were achieved for low-level radioactivity measurements. The automated approach also improves sample throughput for routine laboratory operations. Results indicate strong performance in radionuclide detection and activity determination. The system is suitable for environmental monitoring and waste characterization. It can also support radiological safety assessments. Applications in nuclear research and quality control are possible. Automation improves consistency between measurements. Overall, the developed system provides a reliable and efficient tool for modern gamma-ray spectrometric analysis.

Speaker: Vuako Maluleke (University of Venda, iThemba LABS)

130 Development and Validation of Tile Pre-Processor Sub-Modules for the ATLAS Tile Calorimeter Phase-II Upgrade at the HL-LHC

The High-Luminosity Large Hadron Collider (HL-LHC) upgrade places stringent performance and reliability requirements on the ATLAS Tile Calorimeter (TileCal) readout circuits. A crucial component of this upgrade is the Tile Pre-Processor (TilePPr), a part of the off-detector electronics in charge of data processing, control, and communication. As part of the Phase-II upgrade, crucial TilePPr sub-modules are being created and manufactured at the University of Johannesburg (UJ). The production of Tile Gigabit Ethernet (GbE) Switch Printed Circuit Boards (PCBs) and Tile Computer-on-Module (TileCoM) PCBs by South African industrial partners is the main emphasis of this study. Five TileCoM PCBs and ten Tile GbE Switch PCBs have been manufactured. At UJ, a specialized test station has been created to conduct communication interface testing and electrical validation, guaranteeing adherence to system specifications. These tests confirm the TilePPr architecture's functionality, dependability, and integration readiness. The modules are ready to be shipped to CERN for inclusion into the TileCal off-detector electronics chain after successful validation. This effort demonstrates expertise in sophisticated high-energy physics instrumentation within a worldwide collaborative framework, highlighting the contribution of UJ and South African industry to the ATLAS Phase-II upgrade.

Speaker: Mpho Gololo (University of Johannesburg)

SAIP_2026.pdf

131 DFT Investigation of Hydrogen Interaction in Refractory High-Entropy Alloys

Refractory high-entropy alloys such as NbMoTaW are promising materials for hydrogen storage applications because of their strong crystal structure and stability, inspiring trust in their potential for energy solutions. In this study, density functional theory (DFT) calculations were performed using the CASTEP module in Materials Studio to investigate hydrogen behavior within NbMoTaW. Hydrogen atoms were placed in different interstitial sites, and their energies were calculated. The results show that hydrogen does not occupy only one type of site but a range of sites due to the complex alloy structure. This creates multiple trapping sites, which can affect hydrogen movement.

The electronic structure, including density of states (DOS), shows that hydrogen interacts strongly with metal atoms through bonding between hydrogen and metal electrons. These interactions change as more hydrogen is added, influencing stability and transport. It is also observed that increasing hydrogen content weakens the interaction and may lead to structural changes. This study shows that the complex structure and electronic properties of NbMoTaW play an important role in hydrogen absorption and movement. These findings can help in designing better materials for hydrogen storage and energy systems.

Speaker: Motlatso Phooko (University of Venda)

132 DFT Study of Interface Properties Between RHEAs and Carbon Nanotubes (CNTs)

Refractory high-entropy alloys (RHEAs) are strong, stable materials useful for hydrogen energy applications. In this study, the interface between RHEAs and carbon nanotubes (CNTs) was investigated using Density Functional Theory (DFT) calculations. The calculations were performed in Materials Studio using the CASTEP module, with the GGA-PBE functional. Interface models were constructed by placing CNTs on the surface of selected RHEA materials. The structures were then fully optimized to obtain stable configurations. Both perfect CNTs and defective CNTs were considered to understand how defects affect the interface.

Several important properties were calculated using Materials Studio. These include total energy, interface energy, and binding energy, which were used to assess the interface's stability. The results show that the RHEA–CNT interface is stable, with strong bonding between the alloy and the CNTs.
The electronic structure was also analyzed using the density of states (DOS). The results indicate an interaction between the alloy atoms and the CNTs. Charge density analysis shows that there is charge transfer across the interface, confirming the presence of strong bonding. It was also observed that defects in CNTs can alter bond strength and slightly affect interface stability. Overall, the study shows that CNTs form stable interfaces with RHEAs and can improve their properties. These findings are important for designing better materials for hydrogen transport and energy applications.

Speaker: Mudimeli Vusani Mangalani (University Of Venda)

133 DFT Study of Interface Stability in TiB₂-Reinforced NbMoTaW High-Entropy Alloy

The performance of reinforced refractory high-entropy alloys (RHEAs) depends on the stability of the interface between the alloy and the reinforcement. In this study, Density Functional Theory (DFT) using the CASTEP module in Materials Studio was used to investigate the interface between NbMoTaW and titanium diboride (TiB₂), emphasizing the strong bonding that ensures durability. Interface models were constructed and fully optimized to study structural stability. The calculated interface and binding energies indicate that the NbMoTaW-TiB₂ interface is stable, with strong bonding. The structure shows good matching between the alloy and TiB₂, with only small distortions after relaxation.

Interface models were constructed and fully optimized to study structural stability. The calculated interface and binding energies indicate that the NbMoTaW–TiB₂ interface is stable, with strong bonding. The structure shows good matching between the alloy and TiB₂, with only small distortions after relaxation.

Electronic structure analysis, including the density of states (DOS), reveals interaction between TiB₂ and the metal atoms in the alloy. Charge density results indicate charge transfer across the interface, confirming strong bonding and a stable interface. The results show that TiB₂ forms a stable interface with NbMoTaW, thereby improving the composite's strength and stability. This makes TiB₂-reinforced RHEAs promising for hydrogen transport and energy applications.

Speaker: Tshifhiwa Ranwaha (University Of Venda)

134 Diffuse reflectance of dip-coated films of barium sulphate in polystyrene

The use of lenses and specular reflecting surfaces (mirrors) to direct light in optical instruments is commonplace. However, light may also be directed within a closed hollow volume having diffuse internal reflecting surfaces and a small exit hole – if the volume is round, this is called an integrating sphere. This is a critical component in the homogenisation of light and used when determining the efficiency of luminescent materials and light sources. Modern commercial integrating spheres employ Teflon-based materials for the internal diffuse reflecting walls, which produces excellent optical characteristics but at high cost. Barium sulphate powder has been identified as an eminent diffuse reflecting material and the aim of this work was to assess whether effective diffuse reflective coatings could be formed by dip-coating a substrate in a suspension of barium sulphate powder in a solution of polystyrene dissolved in toluene. For the solution, 50.6 g of polystyrene pellets (192 000 g/mol) was dissolved in 200 ml of toluene. Substrates of glass slides and sand-blasted steel sheets were dip-coated using a withdrawal rate of 300 mm/min. This was repeated after 15, 30, 45 and 60 g of barium sulphate powder had been mixed into the solution using an ultrasonic bath, while greater loading was not considered to produce a solution suitable for dip-coating. Scanning electron microscopy showed that the barium sulphate particles had the form of irregular plates varying from 0.1 - 2 μm in size. Using the mass deposited for the pure polystyrene films, their thicknesses were estimated near 20 μm, so the films were significantly thicker than the size of the powder particles. Loading the polystyrene solution up to 45 g of barium sulphate had only a small effect on the total diffuse transmittance for the glass slide samples, although the direct transmittance was strongly reduced. Only at the greatest loading of 60 g was a significant decrease in the diffuse transmittance observed (to 57% at 550 nm), together with a substantial increase in the diffuse reflectance (to 31%). Dip-coating the steel plates, even to the maximum barium sulphate loading, had little effect on their diffuse reflectance. This is ascribed to the fact that the diffuse reflectance of the coating was comparable to that of the steel plate itself. The conclusion is that dip-coated films of barium sulphate in polystyrene do not produce effective diffuse reflectance coatings since barium sulphate has a similar refractive index (~1.64) compared to polystyrene (~1.60), which reduces the scattering of the light considerably.

Speaker: Mr Johannes Hermanus Spies (University of the Free State)

135 Effect of Cu, Fe and Mn impurities on the bulk and surface structures of ZnS mineral

Impurities such as iron (Fe), copper (Cu) and manganese (Mn) are often present in sphalerite (ZnS) mineral. These impurities significantly influence the properties of ZnS. This study investigated the effect of Cu, Fe and Mn content on the structural properties of the bulk and surface structures of ZnS using density functional theory with dispersion correction and Hubbard U (DFT-D+U). This method is implemented in the Vienna Ab-initio Simulation Package (VASP) code. The computed bulk properties of pure ZnS (lattice parameters (a) = 5.397 Å and band gap (Eg) = 2.013 eV) were in good agreement with the reported value of a = 5.400 Å and Eg = 2.078 eV. For the doped systems, the lattice parameters and band gap values were found to be Zn0.6Cu0.4S (a = 5.309 Å, Eg = 2.00 eV), Zn0.5Fe0.5S (a = 5.155 Å, Eg = 0.0 eV) and Zn0.8Mn0.2S (a = 5.338 Å, Eg = 0.0 eV) which were all lower than those of pure ZnS. The computed surface energies of the ideal ZnS and doped ZnS were ZnS (110) surface (0.82 J/m2), which was higher than the surface energies of the doped surfaces of Zn0.6Cu0.4S (0.78 J/m2) and Zn0.8Mn0.2S (0.44 J/m2), but lower than that of Zn0.5Fe0.5S (1.68 J/m2). This suggested that the doping of ZnS bulk with the Fe underestimate the investigated properties, while doping ZnS (110) surface with Cu and Mn enhance the surface stability.
Keywords: VASP code; Surface energies; lattice parameters; band gap; DFT-D+U ZnS (110)

Speaker: Thato Manyama (University of Limpopo)

136 Effect of Fe, Cu, and Co Doping on Zn2SnO4 Photoanodes for Improved Dye Sensitized Solar Cells Performance

The advancement of efficient and economical solar technology continues to be a key challenge in sustainable energy research. Dye-sensitized solar cells (DSSCs) present a feasible alternative to traditional solar technologies, however their effectiveness is predominantly limited by the characteristics of photoanode materials. This study experimentally investigated Fe/Cu/Co-doped Zn2SnO4 photoanodes. Zn2SnO4 nanostructures were produced via a hydrothermal technique, with controlled doping of transition metals such as Fe, Cu, and Co to modify the electronic structure and improve light–matter interactions. Comprehensive characterization was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) to investigate the structural and morphological properties. The optical characteristics of the doped materials were examined using UV–Vis spectroscopy. This study aim to provide important findings for the rational design of doped Zn2SnO4 photoanodes and facilitate the development of enhanced next-generation DSSC technologies.

Key words: Dye-sensitized solar cells (DSSCs), Photoanode materials, Doping, Transition metals, Hydrothermal.

Speaker: Modjadji Rebecca Letsoalo (University of Witwatersrand)

137 Effect of pH on the adsorption behavior of xanthate, dithiocarbamate and s-triazine collectors on palladoarsenide (100) surface: A DFT-D3 investigation

The interactions of organic collectors with mineral surfaces are the major factors that determines the floatability behaviour of minerals during flotation process. This study employed the computational density functional theory with dispersion correction (DFT-D3) method to investigate the adsorption performance of normal butyl xanthate (NBX), normal butyl dithiocarbamate (NBDTC) and the novel 2,6-dithio-4-butylamino-1,3,5-triazine (DTBAT) collectors onto palladoarsenide (100) surface under neutral and acidic conditions. It was observed that the NBX and NBDTC collectors adsorbed onto the surface through Pd-bidentate bonding, whereas the DTBAT collector exhibited Pd-tridentate adsorption. Evidently, under neutral conditions, the DTBAT exhibited a stronger adsorption energy. In contrast, under alkaline conditions, the NBX showed a strong adsorption energy. Therefore, these results suggested that the DTBAT may be highly selective in enhancing the flotation of palladoarsenide under neutral conditions, while NBX would perform better under acidic conditions. The results paved a way for the design of novel collectors for palladoarsenide mineral, with the potential to improve its recovery in mineral processing.

Speaker: Dr Bradley Nemutudi (University of Limpopo)

138 Effect of substrate temperature on the structural, morphological, and optical properties of ZnO thin films deposited using the slot-die method

Numerous solution-based deposition methods, such as spin-coating and spray pyrolysis, are commonly used for depositing metal-oxide semiconductors, such as SnO2, TiO2, and ZnO for solid-state optoelectronic devices like sensors and photovoltaics. In this contribution, the effect of substrate temperature (Ts) on the structural, morphological, and optical properties of ZnO thin films deposited via the slot-die coating is investigated. The X-ray diffractograms revealed a hexagonal phase with progressive peak narrowing, increased intensity, and slight peak shift at higher Ts, indicating improved crystallinity and lattice distortion. Morphological analysis revealed that increasing Ts led to grain size growth and a reduction of grain boundary density. The UV-Vis measurements showed an increase in reflectance followed by the red-shifting of the absorption edge. The optical band gap, extrapolated from Kubelka-Munk, decreased with increasing Ts, suggesting improved optical conductivity. Photoluminescence studies demonstrated a reduction in defect density with increasing Ts, which aligns with increased crystallinity and reduced grain boundaries. This study establishes that the Ts modulates the structural, morphological, and optical characteristics of ZnO thin films, enabling more efficient optoelectronic devices.

Speaker: Fokotsa Molefe (North-West University)

139 Effects of growth atmosphere and post-annealing temperature on Y2SiO5:Ce3+ co-doped Nd3+ thin films prepared by pulsed laser deposition

Y2SiO5 is thermally stable material with favourable optical properties, making it an excellent host for rare-earth dopants. Rare-earth doped Y2SiO5 exhibits narrow optical and spin linewidths, suitable for high-precision optical and quantum applications. Thin films of rare-earth doped Y2SiO5 are attractive due to their compatibility with modern photonic device fabrication. They preserve the strong luminescent characteristics of rare-earth ions. Unlike bulk Y2SiO5 crystals, thin films allow integration with silicon-based photonic platforms. This is critical for device miniaturization and on-chip optical systems. Several deposition methods have been explored for Y2SiO5 thin film fabrication. Chemical vapour deposition and direct liquid injection provide good phase control and crystallinity. Pulsed laser deposition (PLD) is widely used for maintaining stoichiometry and controlling films microstructure.

This work investigates the influence of growth atmosphere and annealing temperature on Y2SiO5: Ce3+(1 mol %) co-doped with Nd3+(1 mol %) thin films grown by PLD. Films were deposited under oxygen and argon atmospheres. Post-deposition annealing was carried out at 800 °C and 1200 °C in a hydrogen-containing environment. X-ray diffraction determined the structural properties, while X-ray photoelectron spectroscopy revealed chemical states and composition, including yttrium’s two symmetry sites and oxygen vacancies. Efficient energy transfer from Ce3+ to Nd3+ enabled conversion of visible light to near infrared emission. The films exhibited tuneable near-infrared emission in the range of approximately 800-1500 nm, with oxygen deposited films, annealed at 1200 °C, exhibiting the strongest photoluminescence intensity. These results indicated optimal PLD processing parameters for improved near-infrared emission for this phosphor. These studies demonstrated the potential of these films for near-infrared light emitting diodes and optical communication applications.

Speaker: Pulane Moleme (UFS)

140 ELECTRICAL and STABILITY IN InP-BASED SOLAR CELLS VIA Ag NANOWIRE/PMMA and VO₂

This work presents investigation of the structural, electrical, and stability characteristics of two spin coating fabricated InP-based thin-film solar cell architectures: the baseline Ag/InP/TiO₂/ITO/Glass configuration and a modified multilayer design incorporating Ag nanowires embedded in PMMA, a semiconducting VO₂ optical modulation layer, TiO₂, and ITO. Electrical performance under standard AM1.5G illumination confirms these optical gains, with the modified device achieving a short-circuit current of 0.32 mA, open-circuit voltage of 12.0 V, fill factor of 0.75, and a tripled power conversion efficiency (PCE) of 12%, compared to 4% for the reference cell. Stability testing over 1000 h revealed a retention of 93% of initial PCE for the modified device, significantly outperforming the original cell’s 72%, attributable to VO₂-induced interface stabilization and PMMA passivation. The findings demonstrate that the synergistic integration of nanowire-based transparent electrodes, polymeric index-matching layers, and functional oxide interlayers can simultaneously enhance light harvesting, carrier transport, and operational durability. This approach offers a promising pathway for high-performance, long-lived InP-based photovoltaics suitable for advanced optoelectronic applications.

Speaker: Mr Caleb Hlebela (Tshwane University of Technology)

141 Electrical Characterisation and Quality Assurance of ATLAS TileCal LVPS Bricks Using a Single-Board Test Bench

The Phase-II upgrade of the ATLAS Tile Calorimeter requires a reliable Low Voltage Power Supply (LVPS) system capable of stable operation under High-Luminosity Large Hadron Collider (HL-LHC) conditions. As part of the production quality assurance chain, a single-brick test bench has been upgraded to perform initial functional validation of LVPS converter boards prior to burn-in and system-level integration. Each LVPS brick is designed to deliver approximately ~10 V output at load currents in the range of a nominal ~2.3 A, corresponding to output powers of up to ~70 W, with expected efficiencies above 60 %. The test bench enables controlled electrical characterisation of individual bricks, including measurements of output voltage regulation, load current stability, input current behaviour from the ~200 V DC supply, and conversion efficiency. This initial test stage serves as a critical filter in the production pipeline, enabling early identification of faulty or non-compliant units before burn-in testing. The results demonstrate that the test bench provides reproducible and quantitative validation of brick performance, ensuring consistency across production batches and contributing to the overall reliability of the LVPS system.

Speaker: Lungisani Phakathi (University of Witwatersrand)

SAIP_2026_POSTER_PRESENTATION.pdf

142 Enhanced biohydrogen production efficiency in dark fermentation: the role of nitrogen doped graphene oxide with sugarcane bagasse

This study evaluates how nitrogen doping introduced from various precursors tune the structure of graphene oxide(GO) nanomaterial (NM) and its role in enhancing biohydrogen(bioH2) production from sugarcane bagasse(SCB). This is a great step towards generation of carbon free energy through valorization of wastes(SCB). GO was synthesized using Modified Hammer’s method while the N doping was achieved via hydrothermal process. To establish phase, morphology, level of integration of N in the GO network and the viability of the NM for BioH2 production, various techniques were utilized including; powder XRD, HRSEM, Raman spectroscopy, FTIR, UV-Vis. The XRD results showed a shift in peak from sharp peak at 2θ value of 12° to abroad peak at 26° suggesting successful anchoring N atoms in oxygen vacancies. This is further corroborated by Raman shifts that indicated increase in I_D⁄I_G which demonstrated defect creation through introduction of N atoms within the GO network and creation of oxygen vacancies. The crystallite sizes also reduced by about 50% upon doping from 2.95 nm for GO to an average about 1.21 nm for nitrogen doped graphene oxide(NGO) with ammonia precursor(NGO-Amm) reporting the least crystallite size of 1.07nm. The SEM micrographs showed sheet-like folded morphology typical of GO with more pronounced folding upon nitrogen doping. The FTIR results indicated, broad peak at around 3200 for GO associated with –OH stretching. This peak decreased significantly upon doping due to removal of –OH functional groups. Additionally, peaks at 1540 and 2081 ascribed to C-N and N-H stretching were observed. Tauc analysis from the UV-Vis data indicated a reduction of bandgap from 4.06 eV for GO to minimum of 2.19 eV for NGO-Urea suggesting improvement of conductivity which is key for electron shuttling during bioH2 production process. In general introduction of N from different precursors lead to variable changes in the structure of the GO suggesting possible significant influence on the enhancement of bioH2 production through dark fermentation of sugarcane bagasse.

Speaker: SAMWEL OPIYO (UNIVERSITY OF SOUTH AFRICA(UNISA))

143 Enhanced Gas Sensing Performance of MXene-Based Materials Through Structural and Optical Engineering

MXenes are 2D materials which are rapidly emerging as next-generation materials for high-performance gas sensors due to their distinctive features: exceptional conductivity, modifiable surface characteristics, tweakable energy band gap, and more active sites [1]. Recent advancements have concentrated on enhancing their sensing capabilities, selectivity, and response/recovery durations. To advance MXene research and practical application, green, scalable, and effective synthesis is essential [2]. However, in the process of delamination, complex multiple steps are still needed to achieve both selective etching and delamination [3]. Thus, in this study, we report a one-step 〖Ti〗_3 C_2 T_x MXene synthesized from 〖Ti〗_3 AlC_2 MAX phase using Deep Eutectic Solvents (DES)-based on choline chloride (ChCl) and ethylenediamine etching approach [4].
The successful phase transformation, mixed surface terminations (-O,-OH,-F,or -Cl), and distinctive layered structure are demonstrated from XRD, FTIR, and SEM respectfully. The results highlight an effective synthesis method while building a new and eco-friendly etching approach for applications of future MXene-based gas sensing.

Reference
[1] Naguib M, Kurtoglu M, Presser V, Lu J, Niu J, Heon M, Hultman L, Gogotsi Y, and Barsoum M.G. Two-Dimensional Nanocrystals Produced by Exfoliation of 〖Ti〗_3 AlC_2. Adv. Mater. 23, 4248-4253 (2011).
[2] Kahkesh H and Yeganeh M. Green strategies for MXene synthesis: Toward sustainable nanomaterials and emerging applications. Result Eng. 29, 108970 (2026).
[3] Jiabin Y, Qingfu Dai, Wu H, Li Yang, Shenghui Guo, Qiuni Zhao, Ming Hou, Sridhar Komarneni, and Yi Xia. Development of Long-Term Stable MXene-Based Gas Sensing Material. Molecule. 17, 4440 (2025).
[4] Hembram L, Lakkimsetti L.P, Saumen M, Nanda S. Deep-eutectic solvent-assisted green synthesis of MAX-phase C_2 AlC and its 2D-MXene derivative C_2 CT_x towards room-temperature detection of ammonia gas. Ceram. Int. 51, 53681-53693 (2025).

Speaker: BOIKETLO THAMAGA

144 Enhanced Titanium Carbide MXene Structure with CuO Quantum Dots as Electrode for Advanced Supercapacitor Application

Ti3C2:CuO quantum dot composites with different mass ratios (1:0.5, 1:1, and 1:2) were successfully synthesized by hydrofluoric acid etching of Ti3AlC2 (MAX phase) to obtain Ti₃C₂ MXene, followed by sonication-assisted intercalation of CuO quantum dots. The incorporation of CuO quantum dots effectively suppressed MXene restacking, improved ion accessibility, and introduced additional redox-active sites, leading to enhanced electrochemical performance. Among the investigated composites, the Ti3C2: CuO (1:1) sample exhibited the highest specific capacitance of 108.1 F g⁻¹ in a three-electrode configuration, outperforming pristine Ti3C2, which delivered 74.2 F g⁻¹ in 1 M H2SO4 electrolyte. Furthermore, an asymmetric supercapacitor device was fabricated using Ti3C2: CuO (1:1) as the negative electrode and human hair-derived activated carbon as the positive electrode, delivering a high coulombic efficiency of 94.8%, excellent cycling stability with 82.6% capacitance retention after 10,000 cycles, a specific energy of 5.4 Wh kg⁻¹, and a power density of 410 W kg⁻¹ at 1 A g⁻¹. These results demonstrate the synergistic advantages of CuO quantum dot intercalation and highlight the potential of Ti3C2: CuO composites as promising electrode materials for high-performance supercapacitor applications.

Speaker: RANTSOTLHE MPHO (University of Pretoria, Department of Physics)

145 Enhancement of Luminescence and Thermal Sensitivity of YVO4:Bi3+ Nanophosphors Facilitated by Ag/Pd Noble Metal Decoration

We demonstrate the controlled synthesis and in depth characterization of Y0.99VO4:0.01Bi3+ nanophosphors engineered with tunable surface decoration of Ag and Pd nanoparticles. X-ray powder diffraction analysis showed that all compositions crystallized in the tetragonal YVO4 phase, while the high-resolution field emission scanning electron microscopy revealed that the phosphors comprise monodisperse, uniformly spherical particles with excellent morphological consistency. The optical measurements uncovered a broad excitation band centered at 306 nm, and a correspondingly broad yellow emission peaking at 567 nm. Strikingly, noble metal decoration produced pronounced photoluminescence enhancement: a 1 mol% Ag loading yielded a two fold enhancement relative to the pristine phosphor, whereas 0.5 mol% Pd decoration produced nearly a three fold increase, emphasizing the efficiency of metal–phosphor coupling. Beyond the luminescence enhancement, the decorated samples exhibited robust thermometric response using temperature-dependent lifetime data. The Pd decorated nanophosphor achieved a maximum relative sensitivity of 2.0 % °C⁻¹ at 149 °C, while the Ag decorated sample attained sensitivities of 1.75 % °C⁻¹ at 92 °C and 1.23 % °C⁻¹ at ambient temperature (~27 °C). Collectively, these findings revealed that precise tailoring of metal–semiconductor interfaces in Y0.99VO4:0.01Bi3+ nanophosphors unlocks substantially enhanced optical performance and temperature responsiveness, highlighting their strong potential for next generation high resolution imaging and luminescent sensing technologies.

Speaker: Lesole Ramolise (University of the Free State)

146 Estimation of potential wind energy in Port Edward using the Weibull parameter method

South Africa has an estimated 3.5–4 GW generated in 2025 with a projection of over 69 GW by 2050 [1]. More sites are needed in order to reach the target set of energy generated only through wind. Weather data of six months (January- June) was analyzed. Weather data of Port Edward (Longitude: 31.0670; Latitude: 30.2330), in the eastern coastline of South Africa, was provided by the South African Weather Services (SAWA). Data was collected at 11 m height every minute and averaged hourly. This data shows the maximum and minimum reading per day. The data collected included hourly winds speeds, pressure, temperature and wind direction. All these parameters were measured using a weather buoys than transmitted through satellite communication to the meteorological stations. From the data the wind characteristics were calculated using the mean standard deviation method, the Weibull parameters were calculated using the mean square deviation method, the distribution functions were calculated using the Weibull two parameter probability method and the air density was calculated using the Ideal gas law whilst the wind power density was calculated using the Weibull Rayleigh method for the available wind power estimations. The standard deviation giving an idea to how off were some wind-speeds compared to the average wind speed calculated, this helped to determine the wind characteristics of the site. The Weibull shape parameter gave an idea as to the peak of the wind distribution of the site, whilst the Weibull shape parameter indicated how windy the site was. The Weibull Distribution densities analyzed gave an indication of the fraction of time for observing certain wind speeds and illustrates the fraction of time at which wind speeds are below or equivalent to the desired wind speed. Finally, wind power density illustrated the available energy from the wind of the site.

Speaker: Luleka Menzi (Unisa)

147 Exploring Birefringence Effects in Polarization-Based Quantitative Phase Imaging

Quantitative Phase Imaging (QPI) methods that rely on polarization optics, such as Single-Shot Optical Quadrature Microscopy (SSOQM), offer high-speed, label-free phase measurements but are fundamentally challenged by birefringent samples.

In anisotropic media, phase retardance and polarization-dependent transmission violate the scalar phase assumption and strongly couple phase to polarization, so that the standard phase-recovery model in SSOQM can break down entirely, producing incorrect phase maps. In this poster, we outline how birefringence invalidates the core assumptions underlying our polarization-based SSOQM implementation and investigate various approaches proposed in literature to address related issues in similar polarimetry QPI schemes. Using simple Jones and Stokes formalisms, we highlight the regimes in which polarization-based QPI is vulnerable to birefringence and summarize strategies such as additional Stokes-parameter measurements and concepts from techniques such as Jones Phase Microscopy (JPM) as possible routes toward birefringence robust QPI.

Speaker: Calvin Groenewald (Stellenbosch University)

148 Exploring newly synthesized metal halide organic-inorganic hybrids for optoelectronic and photovoltaic properties

Organic–inorganic hybrid (OIH) materials have gained considerable attention due to their structural versatility and potential applications in photovoltaic and optoelectronic devices. However, the dominance of lead-based systems raises concerns about toxicity and environmental stability, underscoring the need for alternative lead-free hybrids. This study delves into the structural versatility of Organic-Inorganic Hybrids (OIHs) by synthesizing diammonium series of Mn and Co-based hybrids of the formula A2MX4, [NH3ꟷ(CH2) nꟷNH3]MX4 (M = Mn, Co; X = Cl and Br) with metal halides.
In addressing the pressing issues of toxicity and stability in lead-based hybrids, the OIHs hybrids were doped with transition metals, manganese (Mn) and cobalt (Co), as replacements for lead. A systematic solution-based synthesis approach was used to prepare these hybrids, and the resulting crystals were characterized comprehensively using advanced techniques, including Single-Crystal X-ray diffraction (SC-XRD), UV-Vis spectroscopy, Thermogravimetric Analysis (TGA), fluorescence spectroscopy, and magnetic measurements. In addition, Density functional theory (DFT) calculations were performed to investigate the electronic structure, including frontier molecular orbitals, density of states (DOS), and band gap energies, with the aim of correlating theoretical predictions with experimental observations.
This work reports on the correlation between structural variation and metal-dependent optical and magnetic behavior, which provides valuable insight into structure–property relationships and potential applications in photovoltaics and optoelectronic devices.

References
Abdel-Aal, S.K. et al. (2023) ‘Crystal structures, Hirshfeld surfaces, Infrared, and XRF/XAFS studies of Long-chain 2D Lead-free Hybrid Perovskite NH3(CH2)9NH3MCl4 (M = Mn, Co, Cu)’, Journal of Molecular Structure, 1276, p. 134757. Available at: https://doi.org/10.1016/j.molstruc.2022.134757.
Asensio, Y. et al. (2022) ‘Magnetic Properties of Layered Hybrid Organic-Inorganic Metal-Halide Perovskites: Transition Metal, Organic Cation and Perovskite Phase Effects’, Advanced Functional Materials, 32(51). Available at: https://doi.org/10.1002/adfm.202207988.
Ghosh, S., Shankar, H. and Kar, P. (2022) ‘Recent developments of lead-free halide double perovskites: a new superstar in the optoelectronic field’, Materials Advances, (1), pp. 3742–3765. Available at: https://doi.org/10.1039/d2ma00071g.
Lim, A.R., (2021) Effect of methylene chain length of perovskite-type layered [NH 3 (CH 2) n NH 3] ZnCl 4 (n= 2, 3, and 4) crystals on thermodynamic properties, structural geometry, and molecular dynamics. RSC advances, 11(60), pp.37824-37829. DOI: 10.1039/d1ra07656f.
Wang, Y. et al. (2024) ‘Recent advances in lead-free halide perovskites: from synthesis to applications’, Journal of Materials Chemistry C. Royal Society of Chemistry, pp. 10267–10329. Available at: https://doi.org/10.1039/d4tc01556h.

Speaker: Tondani Mahuluhulu (University of Johannesburg)

149 Exploring Sodium-Doped Li2MnO3@Li0.69MnO2 Core-Shell Cathodes for Enhanced Structural Stability

Lithium-rich layered oxide Li2MnO3 is a promising cathode material for high-performance lithium-ion batteries, with a theoretical capacity of 460 mAh g-1. However, Li2MnO3 suffers from structural instability, oxygen evolution, and degradation during repeated cycling, leading to capacity loss. Core–shell nanostructures have emerged as an effective strategy to preserve structural integrity, while sodium doping in the lithium-rich core can further enhance structural stability. In this study, molecular dynamics simulations using the DL_POLY code were employed to investigate the effect of sodium doping on Li2MnO3@Li0.69MnO2 core–shell systems. The structures were analysed under different temperatures to evaluate their structural response and stability. Radial distribution functions (RDFs) were used to characterise local atomic ordering and structural changes. The results show that at low temperatures, both doped and undoped systems maintain structural order with minimal differences. However, at elevated temperatures, the undoped system exhibits increased disorder and reduced structural stability, while the sodium-doped system retains higher structural ordering, particularly in the shell region. These results suggest that sodium doping enhances the structural stability and integrity of Li2MnO3-based core–shell cathodes.

Speaker: Mukhethwa Netshiovhani (University of limpopo)

150 Exploring structural configuration of monolayer tin disulfide

Expanding on previous results, we consider the structural integrity and behaviour of monolayer tin disulfide (SnS$_2$). With the introduction of S- and Sn-vacancies, the substrate displayed strengthened bond energies, while also introducing significant diffusion barriers allowing for effective adatom channelling. SnS$_2$ showed promise as an anode material for Na battery technology, with the larger Na atoms requiring a more robust structure. We test the preferred 1T-SnS$_2$ structure in particular, via biaxial strain. At maximum strain, we have 5% deviation from standard lattice parameters. Structural properties are observed via DFT, considering changes in bond energy and length, PDOS, charge transfer, and especially time-dependent DFT to understand structural stability. Preliminary results show little difference in charge resulting from strain, while a significant loss in bond energy of approximately $0.30~$eV is observed.

Speaker: Craig Bekeur (University of Pretoria)

151 Fabrication of Metal-Supported Zirconium-Based Bifunctional Heterogeneous Catalysts for Potential Application in Biofuel Production

The growing demand for renewable energy drives interest in biodiesel as a sustainable alternative to fossil fuels. In this study, waste cooking oil (WCO), an abundant and low-cost feedstock, was converted into biodiesel through esterification and transesterification using a bifunctional heterogeneous catalyst. The catalysts were synthesised by incorporating acidic (CuO) and basic (CaO) active components onto a UiO-66-based metal–organic framework (MOF). The three catalysts, Cu@UiO-66, Ca@UiO-66, and Cu-Ca@UiO-66, were successfully synthesised and characterised using XRD, BET surface area analysis, SEM, TEM, FTIR, NH 3 -TPD, and TGA to confirm their structural integrity and physicochemical properties. Among these catalysts, Cu–Ca@UiO-66 demonstrated superior performance, attributed to its high surface area, structural stability, and the synergistic presence of acidic and basic active sites that facilitate simultaneous reaction pathways. Additionally, high biodiesel yields were achieved, and the catalysts were readily recovered and reused up to three cycles without significant loss of activity. Overall, the work demonstrates an efficient, cost-effective, and environmentally friendly approach, highlighting the potential of advanced MOF-based catalyst design in converting waste into renewable energy, contributing to sustainable biofuel production.

Speaker: Ms Abongile Gingqi (Student)

152 Fatigue-induced microstructural evolution of plasma-sprayed hydroxyapatite coatings in simulated body fluid

Plasma-sprayed hydroxyapatite (HAp) coatings are widely used to enhance the bioactivity and osseointegration of metallic implants however, their long-term performance under cyclic loading in physiological environments remains a critical concern [1]. In this study, HAp coatings were deposited via plasma spraying [2] onto cylindrical rod Ti64 substrates (5 mm diameter) and subjected to controlled fatigue loading in simulated body fluid (SBF) at 37 °C to replicate in vivo conditions [3]. The samples were exposed to 150 × 10³, 500 × 10³, and 750 × 10³ fatigue cycles to evaluate the progressive effects of mechanical degradation.

The structural and microstructural evolution of the coatings was systematically investigated. X-ray diffraction (XRD) was employed for phase identification and residual stress analysis, revealing changes in crystallinity and stress state with increasing fatigue exposure. Scanning electron microscopy (SEM), coupled with energy-dispersive spectroscopy (EDS), was used to assess surface morphology and elemental composition, highlighting fatigue-induced microcracking, splat delamination, and localized compositional variations. Furthermore, micro-computed tomography (MicroCT) provided three-dimensional characterization of internal porosity, enabling quantification of pore distribution and its evolution under cyclic loading.

The results demonstrate that increasing fatigue cycles lead to progressive microstructural degradation, including crack initiation and propagation, as well as changes in residual stress and porosity distribution. These findings provide important insights into the durability and failure mechanisms of plasma-sprayed HA coatings under physiologically relevant conditions.

[1] Sun, L., Berndt, C. C., Gross, K. A., & Kucuk, A, ‘Material fundamentals and clinical performance of plasma-sprayed hydroxyapatite coatings: A review ’, J. Biomed. Mater. Res., vol. 58, no. 5, pp. 570–592, 2001.
[2] R. B. Heimann, ‘Thermal spraying of biomaterials’, Surf. Coat. Technol., vol. 201, no. 5, pp. 2012–2019, 2006, doi: https://doi.org/10.1016/j.surfcoat.2006.04.052.
[3] H. M. Kim, T. Miyazaki, T. Kokubo, and T. Nakamura, ‘Revised simulated body fluid’, in Key Engineering Materials, Trans Tech Publ, 2001, pp. 47–50.

Speaker: Tshepo Ntsoane (The South African Nuclear Energy Corporation)

153 First-Principles Investigation of Graphene/W-Doped VO₂ for Thermochromic Smart Windows

Thermochromic smart windows based on vanadium dioxide (VO₂) offer energy-saving potential through temperature-dependent solar modulation, but their high transition temperature and limited efficiency remain challenges. This study investigates hybrid heterostructures combining graphene with tungsten-doped vanadium dioxide (W-VO₂) to improve performance.

First-principles calculations using Density Functional Theory (DFT) within the GGA+U approach were employed to examine structural, electronic, and optical properties. Doping with tungsten lowers the transition temperature, while graphene improves electrical conductivity and the transfer of charge between surfaces. Electronic structures and optical calculations indicate improved infrared modulation and modified electronic behaviour. These results demonstrate that graphene/W-VO₂ heterostructures are promising candidates for advanced thermochromic smart window applications.

Speaker: Lutendo Phuthu

154 First‑Principles Investigation of Zn Adatom Adsorption on MO₂ (110) Surfaces

The transition toward cleaner energy systems has intensified interest in advanced storage technologies such as zinc-air batteries (ZABs). Although ZABs offer high energy density and cost effectiveness, their performance is limited by sluggish air cathode kinetics. In this study, density functional theory (DFT) is used to investigate the adsorption behaviour and charge transfer characteristics of a Zn adatom on the (011) surfaces of MnO₂, TiO₂, and VO₂. MnO₂ exhibits the most negative Zn adsorption energies, indicating stronger interfacial bonding driven by the higher oxidation state and electron affinity of Mn. Bader charge analysis shows that Zn consistently donates electrons to surface oxygen and transition metal sites across all oxides. Structural relaxations reveal distinct Zn-O bonding environments, reflecting the unique electronic structures and coordination tendencies of each MO₂ surface. These insights offer a deeper understanding of Zn-surface interactions relevant to improving the catalytic and cycling performance of zinc-air batteries.

Speaker: Percy Ngobeni

155 From Biowaste to Energy: Eggshell Membrane-Derived Activated Carbon for Sustainable Solar Cell Applications

Abstract
As the world shifts towards green energy and sustainable living, the need for renewable energy sources is steadily rising. This study investigates the potential of eggshell membrane (ESM) as a sustainable precursor for activated carbon in hybrid solar cell applications. ESM-derived activated carbon was synthesized via pyrolysis at 600 °C under ambient and nitrogen atmospheres. The reaction time was kept for 1 h and 2 h for each condition and this was followed by potassium hydroxide (KOH) chemical activation. X-ray diffraction (XRD) analysis confirmed the presence of broad diffraction peaks characteristic of amorphous carbon with partial graphitic ordering, while Raman spectra revealed D and G bands corresponding to sp²- and sp³ hybridized carbon, indicating enhanced structural ordering upon activation. Scanning electron microscopy (SEM) images showed a progressive transformation from fibrous membranes to well-developed porous carbon morphologies after activation, suggesting an increase in surface area and pore connectivity. Electrochemical impedance spectroscopy (EIS) further revealed excellent capacitive behavior, with the nitrogen-treated sample (2 h) exhibiting superior electrical conductivity and lowest charge transfer resistance. These findings demonstrate the potential of ESM-derived activated carbon as an efficient, low-cost electrode material for hybrid solar cells, contributing to sustainable energy development.
Corresponding authors email: [66795117@mylife.unisa.ac.za], mbuleps1@unisa.ac.za

Speaker: Ms Evonne Tshepiso Molekoa Tshepiso

156 Gas sensing properties of annealed and unannealed CoWO4 for air quality monitoring

The cobalt tungstate (CoWO4) nanostructures were prepared using the hydrothermal method. Nanostructures were annealed to compare the structural, optical and gas sensing properties of annealed and unannealed CoWO4. The UV-VIS spectroscopy, x-ray diffraction (XRD), scanning electron micro-scope (SEM) and energy dispersive x-ray spectroscopy (EDS) were used to examine the samples optical, structural, morphological and composition properties respectively. The samples showed different XRD phases, where unannealed was hexagonal and annealed sample was monoclinic in structure. Different SEM morphologies and optical band gaps of nanostructures were observed. The samples were further tested for their gas sensing properties towards oxidizing and reducing gases. Promising gas response was observed towards oxidizing gases.

Speaker: Thokozani Mpanza (University of Zululand)

157 General Applications of High-Energy Physics Methods to Financial Systems and Distributed Sensor Networks

High-energy physics (HEP) experiments operate in data-intensive environments
characterised by high event rates, complex detector systems, and the need to
extract rare signals from substantial backgrounds. This has led to the
development of robust methodologies for data acquisition, event selection,
statistical inference, and real-time data processing, particularly within
large-scale experiments at facilities such as CERN.

In this work, we investigate the general applicability of HEP-inspired data
analysis frameworks to non-physical systems, focusing on financial markets
and distributed Internet-of-Things (IoT) sensor networks as case studies.
Both domains produce continuous, high-volume data streams with significant
noise, non-stationary behaviour, and intermittent anomalous events,
presenting challenges analogous to those encountered in detector-based
experiments.

For distributed IoT sensor networks such as residential monitoring systems, we examine how detector-inspired techniques, including background estimation, noise filtering, and signal reconstruction, can be used to extract higher-level information from aggregated measurements. These approaches enable the identification of latent patterns within sensor data, including behavioural or value-related indicators inferred from otherwise low-level signals.

Speaker: Mr Tshepang Pule (University of the Witwatersrand, Johannesburg, Wits 2050, South Africa)

158 Hall Effect Insights into Charge Transport in Printed Silicon Nanoparticle Networks Prepared from High-Energy Milled Silicon

This study investigates the charge transport properties of printed silicon nanoparticle networks prepared from high-energy milled silicon. Hall effect measurements, complemented by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and DC resistance measurements, were used to examine the influence of milling time and surface chemistry on electronic behaviour. The carrier concentration increased with longer milling times, correlating with an increased fraction of silicon sub-oxides on the nanoparticle surfaces, suggesting a surface-induced doping effect. Despite this increase, Hall mobilities remained nearly constant while pellet resistances increased with milling time. This behaviour indicates that Hall measurements predominantly probe intraparticle charge transport rather than interparticle conduction. Consequently, the overall network conductivity is limited by interparticle contact resistance rather than charge transport within individual nanoparticles. These findings provide critical insight into the design of printed nanoparticle-based electronic devices, highlighting the importance of improving interparticle contacts through surface treatments and thermal processing to enhance electrical performance.

Speaker: Mvuyisi Mbabane (Walter Sisulu University)

159 Influence of anatase, rutile, and anatase-rutile crystalline phases of TiO2 on electrocatalytic hydrogen evolution reaction under acidic electrolyte.

Titania (TiO2) nanoparticles were synthesized by the co-precipitation method. The influence of different phases of TiO2 electrocatalysts was investigated on the electrochemical hydrogen evolution reaction. The XRPD results confirmed the formation of anatase, anatase-rutile, rutile-anatase, and rutile phases at calcination temperatures of 25, 350, 450, and 550 ℃. The average crystallite size varied from 6 to 20 nm with an increase in calcination temperature. The FE-SEM images revealed the irregularly shaped particles' morphology. The pristine TiO2 electrocatalysts achieved a current density of 10 mA cm−2 at the expense of an overpotential of 400 mV, 353 mV, 448 mV, and 690 mV for anatase, TiO2 at 350 ℃, TiO2 at 450 ℃, and TiO2 at 550 ℃, respectively. Cyclic Voltammetry revealed irreversible reactions of pristine TiO2 electrocatalysts. Electrochemical Impedance Spectroscopy (EIS) analysis showed a good charge transfer resistance value, indicating a good electron exchange attribute. Chronoamperometric analyses showed long-term stability of the TiO2 electrocatalyst. The findings suggest the potential of TiO2 nanoparticles to be utilized as an electrocatalyst in HER for hydrogen production.

Speaker: Qiniso Nkomo (UNISA)

160 Influence of Mn and Co Doping on the Recrystallisation Behaviour of Nanospherical LiNiO₂: An Atomistic Study

Layered LiNiO₂ (LNO) is a promising cathode material for lithium-ion batteries due to its high theoretical capacity and potential for reduced reliance on costly cobalt; however, its structural evolution during phase transformations critically influences performance. In this study, atomistic simulations were employed to investigate the effects of Mn and Co doping on the amorphisation–recrystallisation behaviour of LNO. Nanospherical models of pristine and doped LiNiO₂ were constructed to capture nanoscale and surface effects. Following amorphisation and controlled recrystallisation, the pristine system exhibited near-complete structural recovery, forming a well-ordered layered phase with minimal residual disorder and no observable grain boundaries. In contrast, Mn- and Co-doped systems followed altered recrystallisation pathways. Although overall structural recovery was achieved, residual features such as Li/Ni cation mixing and local lattice distortions persisted. These effects were more pronounced in Co-doped systems, while Mn doping resulted in comparatively lower disorder. These findings demonstrate that transition metal doping significantly influences recrystallisation dynamics and nanoscale structural ordering in LiNiO₂. The observed cation disorder and local heterogeneity highlight the role of dopants in shaping post-recrystallisation material properties, providing atomistic insight into the relationship between doping and phase transformation behaviour.

Speaker: Mamonamane Mphahlele (University of Limpopo)

161 Influence of oil palm mesocarp fibre with plaster of Paris and its environmental impacts.

This study was designed to assess the practicability of modifying the properties of plaster of Paris (POP) ceiling to improve its durability and use in thermal insulation.Using plaster of Paris (POP) in buildings has generated health concerns; hence reinforcement has been made possible by adding oil palm mesocarp fibre (OPMF). Various weight proportions(0, 10,20,30 and 40%) of the OPMF were used to replace the POP during the fabrication of the samples.A drying process was applied to all the samples used for the study,and then tested for density, water absorption, thermal conductivity, specific heat capacity, tensile strength, flexural strength and compressive strength respectively.The study showed that the addition of the OPMF to the POP matrix enhanced the efficiency of POP as a ceiling material with excellent heat insulating ability and could be effective in buildings.The OPMF effluent pollutes the environment by eutrophication and the release of acidic gases.Thus,this research suggests measures for the conversion of the OPMF to valuable and more sustainable products and plausibly provide education to individuals on the health implications of OPMF exposure.The implementation of this model would not only be useful as a good thermal insulator, but it will reduce the effects experienced by users, oil millers, and processors, also provide a long-term plan for its proper disposal, protect our health and the environment.

Speaker: Dr Armstrong Anonaba (Abia State University, Uturu)

162 Influence of the Alkaline Earth Ions (M = Ca2+ and Mg2+) on the Luminescence Properties of doped M-BaB8O13: Gd3+ Phosphor Materials.

Abstract
Series of Gd3+ doped alkaline earth octaborate phosphors with the general formula MxBa1-xB₈O₁₃: 2% Gd³⁺ (M = Ca²⁺, Mg²⁺; x = 0.10) were synthesized through a solid state method to investigate the influence of alkaline earth ions on the structural, optical, and luminescence properties of the BaB8O13 host material. X-ray diffraction (XRD) confirmed the formation of orthorhombic BaB8O13 showing that the main structure was not influence by the concentration of Ca2+ and Mg2+ but peak shifts and lattice deformation due to the substitution of Ca2+ and Mg2+ ions was observe. Scanning Electron Microscopy (SEM) was perfomed to study the surface morphology, while Energy Dispersive X-ray Spectroscopy (EDS) confirmed elemental composition of the materials. UV-Vis diffuse reflectance spectra and Tauc plot analysis display a narrow bandgap after doping with Gd3+ ions, suggesting change in electronic transitions and an increased defect levels. Photoluminescence (PL) measurements revealed characteristic emissions of Gd3+ under excitation wavelength of 274 nm, with prominent emission intensity at 313 nm wavelength upon doping with Ca²⁺ ions. The observed enhancements are properties to improved energy transfer efficiency around the Gd³⁺ ions, while upon doping with Mg2+ decreased the luminescence intensity and this is due to quenching which led to higher probability of non-radiative energy transfer between Mg2+ ions. These findings prove that controlled substitution with alkaline earth metals can effectively modify the luminescence properties of Gd3+ activated BaB8O13 phosphors, making them promising candidate for phototherapy applications.

Speaker: Mr Sabelo Ndlela (University of Johannesburg)

163 Influence of TiO₂ Morphology on Electrocatalytic Hydrogen Evolution: A Comparative Study of Spherical and Mesoporous Structures

Titanium dioxide (TiO₂) has attracted considerable attention as a promising material for catalytic applications due to its chemical stability, low cost, and tunable structural properties. In this study, two distinct TiO2 morphologies, namely spherical and mesoporous structures, were synthesized via a sol-gel method using titanium isopropoxide (TTIP) as the precursor. Polyvinylpyrrolidone (PVP) was introduced as a pore forming agent to generate the mesoporous structure, and both samples were annealed at 350 °C to improve crystallinity. The structural and morphological properties of the synthesized materials were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analysis. The electrocatalytic performance toward the hydrogen evolution reaction (HER) in acidic medium was evaluated using linear sweep voltammetry (LSV), Tafel analysis, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA). This comparative study provides insight into the influence of morphology on the physicochemical properties and catalytic activity of TiO₂-based electrocatalysts.

Speaker: Japhtalinah Lehutso (Department of Physics, CSET, University of South Africa, Johannesburg, 1710, South Africa)

164 Integrated multimodal microscopy with Holographic Optical Tweezers

Optical tweezers are a sterile, non-invasive method for the isolating and manipulating single cells in suspension. When combined with microfluidic sample chambers it is possible to control the local environment of a trapped cell. This control over the extracellular environment of individual cells, allows one to monitor changes in cellular activity and cell morphology due to changes in the surrounding environment.

In this poster, we present an overview of a custom multimodal microscope integrated with optical tweezers (biophotonics platform), which has been constructed and used to monitor changes in the morphology and metabolic activity of single yeast cells under various cell stress environments. The poster also includes a brief descriptions of holographic optical tweezers (HOT), which uses a spatial light modulator to shape the optical field used to trap multiple cells, and optical quadrature microscopy (OQM), a quantitative phase imaging (QPI) technique used to image the phase variations within a trapped cell.

Speaker: Le Roi Du Plessis (Stellenbosch University)

165 Investigation of X-rays and Gamma ray Shielding Properties of Heavy Metal Oxide Glass Materials

This study investigates neodymium-doped bismuth borosilicate glasses with composition xBi₂O₃-(55-x)B₂O₃-15BaO-10ZnO-18SiO₂-2Nd₂O₃ (x = 15, 20, 25 mol%) as lead-free radiation shielding materials for diagnostic X-ray applications. Three glass samples were successfully synthesized via melt-quenching at 1000°C. Structural characterization confirmed complete amorphization, and density measurements yielded systematic increases from 3.881 g/cm³ (S1) to 4.788 g/cm³ (S3), representing 23.4% enhancement. Radiation shielding parameters were evaluated computationally using XCOM, PHYS-X, and GEANT4 across 0.03-0.3 MeV, with experimental validation through ¹³⁷Cs gamma-ray attenuation measurements. Results demonstrated that mass attenuation coefficient curves exhibited expected overlap (17-20 cm²/g at low energies), while linear attenuation coefficient showed systematic separation with S3 achieving 20-25% higher values than S1. The critical finding is that the 23.4% density increase produced nearly proportional shielding enhancement, demonstrating that material densification dominates over compositional variations. Effective atomic number reached 69-73 at low energies, approaching lead and confirming heavy-metal-equivalent behavior. These bismuth borosilicate glasses, particularly S3, represent promising environmentally friendly alternatives to lead-based shielding for medical imaging facilities, combining exceptional low-energy attenuation with non-toxic composition and rare earth compatibility.

Speaker: Nosihle Msabala (University of Zululand)

166 IoT Systems for Air Quality Measurements: Low-Cost Sensor Networks Using LTE/4G and LoRa Communications

Air pollution poses a severe and growing public health challenge globally, with the World Health Organization estimating approximately 4.2 million premature deaths annually attributable to ambient air pollution.
Traditional monitoring infrastructure comprised of large, fixed reference
stations is costly, spatially sparse, and incapable of real-time,
high-resolution pollution mapping. This creates critical data gaps,
particularly in urban centres and resource-constrained settings across
Africa and the Global South.

The South African Consortium of Air Quality Monitoring (SACAQM), an
initiative led by Professor Bruce Mellado of the University of the
Witwatersrand and iThemba LABS, addresses these limitations through the
development and deployment of the $AI\_r$ system: a low-cost, IoT-enabled air quality monitoring
node. The system integrates the Sensirion SEN55 environmental sensor which is capable of measuring $\mathrm{PM}_{1}$, $\mathrm{PM}_{2.5}$,
$\mathrm{PM}_{4}$, $\mathrm{PM}_{10}$, VOC, $\mathrm{NO}_{x}$,
temperature, and relative humidity, with the Nordic Semiconductor
nRF9160 system-in-package, running on the Zephyr RTOS. Data transmission
is achieved via LTE/4G for real-time cloud connectivity, with LoRa communication additionally integrated to extend deployment to areas lacking cellular coverage.

This paper reviews the architecture and performance trade-offs of LTE/4G
and LoRaWAN communication protocols in the context of low-cost IoT air
quality monitoring, drawing on the SACAQM deployment experience. LTE/4G offers low latency (30-100 ms) and high throughput, suited to continuous real-time data streaming, whereas LoRaWAN provides long-range, ultra-low-power communication at reduced data rates (0.3-50 kbps), enabling deployment in remote or infrastructure-limited environments. A hybrid communication strategy leveraging both technologies is proposed as an optimal framework for scalable, wide-area monitoring networks. The $AI\_r$ system is calibrated against South African Air Quality
Information System (SAAQIS) reference stations, with active deployments
across Soweto and Braamfontein in Johannesburg, and systems shipped to
partner institutions all over the world. Integration of machine learning models, including
AI-driven $\mathrm{PM}_{2.5}$ forecasting and anomaly detection, further enhances the system's predictive and public health utility. The SACAQM initiative demonstrates that cost-effective, IoT-based,
AI-integrated sensor networks represent a viable and scalable approach
to closing the air quality monitoring gap in low- and middle-income
countries.

Speaker: Mr Tshepang Pule (School of Physics and Institute for Collider Particle Physics, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa)

167 Jet Response and Resolution Studies of the ATLAS TileCal Upgrade Geometry for HL-LHC Conditions

The Phase-II upgrade of the ATLAS Tile Calorimeter (TileCal) is designed to maintain detector performance under High-Luminosity Large Hadron Collider (HL-LHC) conditions, where up to 200 proton–proton interactions per bunch crossing are expected. This study evaluates the impact of the upgraded detector geometry on jet reconstruction performance using Monte Carlo simulated QCD dijet samples. Jet transverse momentum ($p_T$) response and resolution are analysed for both the current and upgraded geometries in the high-energy regime ($1500 < p_T < 2500~GeV$). The response is defined as the mean of the $p_T/p_T^{\text{truth}}$ distribution obtained from Gaussian fits, while the resolution is defined as the ratio of the standard deviation to the mean of the same distribution. The performance is further studied as a function of the fractional energy deposition in different TileCal layers.

Speaker: Edward Nkadimeng (NRF-iThemba LABS)

168 Least-Squares Optimisation and GIS-Based Spatial Mapping of UAV-Derived Gamma-Ray Spectrometric Data for Naturally Occurring Radionuclides (⁴⁰K, ²³²Th, ²³⁸U) at Sparkle Bay

The spatial distribution of naturally occurring radionuclides (⁴⁰K, ²³²Th, and ²³⁸U) at Sparkle Bay, Western Cape can be investigated with an integrated approach using UAV-based gamma-ray spectrometry, least-squares optimisation, and Geographic Information Systems (GIS). The airborne gamma-ray data were obtained with a sodium iodide (NaI(Tl)) detector attached to an unmanned aerial vehicle (UAV) and enabled fast and high-resolution radiometric surveying of the study area. The reference activity concentrations were obtained through laboratory-based gamma spectrometric analysis of representative granite and dolerite samples. A least-squares optimisation model was used to calibrate the airborne measurements with those obtained in laboratory settings by reducing the Total Sum of Squared Errors (TSSE). This decreased systematic bias and enhanced accuracy and reliability of the field-derived data. The idealised radionuclide concentrations were then analysed in a GIS process including spatial interpolation utilizing the Inverse Distance Weighting (IDW) procedure to obtain continuous distribution maps. The results show that the concentration of radionuclides is closely dependent on lithology, granitic formations show higher concentrations of potassium and thorium than dolerite formations. Uranium has wider spatial variability, which is consistent with its increased geochemical mobility. Optimisation was able to greatly boost agreement between field and laboratory datasets, improving spatial interpretation quality immensely. In this study, we confirm the effectiveness of the joint integration of UAV-based gamma-ray spectrometry, least-squares optimisation and GIS analysis in advancing radiometric mapping in complicated coastal domains and provide valuable baseline values to support environmental monitoring and geological study.

Speaker: Modicai Samukelo Mndebele

169 LPG Sensing of p-type Spinel NiCo2O4 Bimetallic Oxide and Co3O4/NiCo2O4 or NiO/NiCo2O4 heterostructures

The development of highly sensitive gas sensors that do not require elevated operating temperatures remains critical for the safe detection of liquefied petroleum gas (LPG). Nickel cobaltite (NiCo2O4) is a p-type bimetallic oxide that has been extensively studied for the detection of volatile organic compounds, although its potential for LPG detection has received limited attention. NiCo2O4-based heterostructures were synthesized via a two-step hydrothermal process, incorporating secondary Co3O4 or NiO phases to form heterostructured architectures with increased active sites and modified electronic properties. The influence of additional Co or Ni cations on the structural, morphological, and LPG gas sensing properties of NiCo2O4 was systematically investigated.
Powder X-ray diffraction analysis confirmed the coexistence of spinel NiCo2O4 with Co3O4 or NiO phases. The microstructural analysis revealed that the crystallite size reduced from 16 nm for pristine NiCo2O4 to 11 nm or 10 nm due to secondary Co3O4 or NiO phases, respectively, indicative of increased defect density. X-ray photoelectron spectroscopy analysis confirmed the presence of additional Co2+/Co3+ or Ni2+ cations, which played a key role in modifying charge carrier concentration and promoting the adsorption of oxygen species on the sensor surface. As a result, exposure to LPG at 25-150℃ caused stronger modulation of the depletion layer, leading to a markedly improved sensing response compared to pristine NiCo2O4. This work demonstrates the potential of compositional engineering in bimetallic oxides for low-temperature detection of combustible gases.

Speaker: Boitumelo Tladi (University of Free State)

170 LPG sensing performance of ceria nanostructured materials prepared by the urea-assisted hydrothermal method

Cerium oxide (CeO2) nanomaterials are being studied as potential candidates for gas sensors. Gas sensors based on metal oxides and their nanocomposites have attracted significant public attention over the past decades due to their excellent potential for applications in environmental pollution remediation, the transportation industry, and personal safety. Thus, herein, CeO2 nanostructured materials were prepared by the assisted hydrothermal method using trimethyl amide (TMA) as a surfactant, with urea molarity ranging from 0.5 to 2.0 M and a reaction temperature of 120 °C. Changes in crystal lattice size were observed by varying urea molarity from 0.5 M to 2.0 M at a reaction temperature of 120 °C. Photoluminescence studies showed that CeO2 prepared at 120 ᵒC using TMA as a surfactant and a urea concentration of 1.5 M has higher surface defect-related emissions arising from oxygen vacancies and Ce³⁺ states, resulting in broad visible luminescence. The materials exhibited superior sensitivity to LPG over the 300–1200 ppm concentration range at an operating temperature of 175 °C. The enhanced LPG sensing performance (300–1200 ppm) at 175 °C is attributed to the optimized synthesis conditions (TMA surfactant, 1.5 M urea, and 120 °C), which likely promoted favorable morphology and active surface sites.

Speaker: Aaron Malape (University of the Free State)

171 Machine Learning-Based Prediction of Tool Wear and Remaining Useful Life Using Multisensor Data Fusion

Abstract
In the era of Industry 4.0, the transition toward fully autonomous man
ufacturing requires robust Tool Condition Monitoring (TCM) to prevent
catastrophic tool failure and workpiece damage. Precise prediction of cut
ting tool wear and remaining useful life (RUL) is necessary for reducing
downtime and optimizing tool usage in automated machining. However,
manual inspection requires frequent machine stoppage, while traditional
monitoring methods are intrusive and struggle to capture the non-linear
nature of wear progression in lathe operations. This study aims to develop
and validate a machine learning model for tool wear and RUL prediction
using multisensor data fusion. Random Forest, Support Vector Regres
sion, and XGBoost models will be trained on available lathe data from
previous studies, then validated on experimental lathe turning data to
be collected under a Taguchi L9 design using AISI 1045 steel workpieces
and uncoated carbide inserts. Multisensor data (force, vibration, acoustic
emission) will be processed to extract 84 time-domain features per cut,
reduced via feature selection. When validated on the experimental lathe
data, all three models are expected to achieve an R2 exceeding 0.85 and
an RMSE below 40 µm, with XGBoost leading in accuracy, demonstrat
ing cross-dataset generalizability. The findings will support tool condition
monitoring systems for smart manufacturing applications, contributing to
reduced downtime, optimized tool usage, and improved production effi
ciency.
Keywords: Tool Wear, Machine Learning, RUL, Random Forest, XGBoost,
Turning, SVR, Taguchi Method

Speaker: SAM MKHWEBANE

172 Modelling Rotational Dynamics in Fluorescence Correlation Spectroscopy under Polarised Excitation

Fluorescence correlation spectroscopy (FCS) is a technique in which a focused laser beam excites molecules within a small volume and fluctuations in the emitted fluorescence are analysed to extract information about molecular dynamics. These fluctuations arise from stochastic processes such as diffusion, photophysical transitions, and chemical kinetics, and are quantified through the autocorrelation function. In the case of individual fluorophores under linearly polarised excitation, the absorption probability depends on the angle between the molecular transition dipole and the incident electric field, following a $\cos^2 \theta$ dependence. This project describes the development of an FCS system and uses simulations to investigate the influence of laser polarisation on fluorophores undergoing rotational diffusion. The molecular dynamics are modelled at the single-molecule level, from which ensemble fluorescence fluctuations are constructed and analysed. The simulation is first validated using the mean-squared angular displacement. Polarisation-dependent fluorescence fluctuations are then used to extract rotational diffusion coefficients, which are compared with the known input values.

Speaker: Matthew Marlor (Stellenbosch University)

173 Molecular dynamics study of temperature effects on Au and Pb nano-materials

The study analyses the temperature-dependent behaviour of gold (Au) and lead (Pb) nanomaterials using classical Molecular Dynamics (MD) simulations in the NPT ensemble, utilizing the Sutton-Chen potential. The primary objective is to determine the effect of temperature on the structural properties, thermal stability and energy of different cluster sizes (459, 791 and 1061 atoms). The results derived from radial distribution function (RDF) plots, showed that as the temperature increased from 300 to 800 K, the RDFs peaks for both Au and Pb became shorter and broader, confirming a loss of structural order and a phase transition. The finding further supports the principle of melting point depression in nanomaterials compared to their bulk counterparts. Analysis of the total energy confirmed the greater stability of larger clusters, showing that energy decreases inversely with increasing cluster size for both Au and Pb at all tested temperatures. The total energy also exhibited a slight increase as the temperature rose across all clusters.

Speaker: Malili Matshaba (CPhy Membership)

174 Monitoring air quality in South Africa using smart indoor air quality systems.

Air pollution remains a serious environmental and public health challenge, creating a strong need for accurate, affordable, and real-time monitoring systems, especially in developing contexts such as South Africa. Recent studies show that smart air quality monitoring can be significantly improved through the integration of low-cost sensor networks, machine learning, and environmental data sources, with models such as Random Forest, XGBoost, LSTM, and hybrid approaches proving effective for prediction, calibration, and trend analysis. At the same time, dashboard-based and GIS-supported studies demonstrate the value of combining multiple environmental data sources to assess spatiotemporal variations in pollutants such as PM1.0,PM2.5, PM4.0, PM10.0, CO2, including Temperature(◦C) and Humidity, especially where dense ground based monitoring is limited. This research therefore proposes a smart indoor air quality monitoring framework for South Africa that uses intelligent indoor sensing systems to collect real-time environmental data, analyze pollutant behavior, and support early warning and decision-making in indoor spaces such as homes, schools, offices, and laboratories. By combining continuous sensing, data-driven analysis, and predictive modelling, the study aims to contribute to healthier indoor environments, improved public awareness, and more effective air quality management strategies in South Africa.

Speaker: Donald Ngobeni

175 Neutron Transmutation Doping (NTD) Process Optimization.

Neutron Transmutation Doping (NTD)

This area explores the technique of using nuclear reactors to modify the electrical properties of semiconductor materials, particularly silicon, for high-performance electronic components. The project aims to optimize the neutron transmutation doping process at the Nuclear Energy Corporation of South Africa (NECSA) SAFARI-1 research reactor, focusing on the resistivity of the semiconductor material to produce the desired electrical characteristics in its fabrication.

NTD is the preferred method over chemical means for introducing dopants in semiconductors, especially if the application is for the manufacturing of small, discrete, low-power devices, etc. This will help with detailed plans for the irradiation process, including sample placement, neutron fluence requirements, and heat management. Conducting studies on the final electrical resistivity of the doped material and how it correlates with irradiation parameters is of importance.

Speaker: Tshepiso Thompson Rauwane (student)

176 Ni-Doped Li1+xM₂O₄ (M=Mn, Co) Nanoporous Materials for Lithium-ion Battery Cathodes

Spinel-structured materials such as lithium cobalt oxide (LiCo₂O₄) and lithium manganese oxide (LiMn₂O₄) are promising cathode materials for lithium-ion batteries due to their good electrochemical performance, which is attributed to their three-dimensional lithium-ion diffusion pathways. However, these materials undergo high voltage and capacity decay during cycling. This is caused by disproportionation reactions and poorly coordinated structures, which, in turn, lead to battery fracture and pulverisation during charge and discharge, hindering their application. To alleviate these challenges, Nickel (Ni) doping and nanostructuring have emerged as an effective strategy to enhance the structural stability and the electrochemical performance of spinel-structured materials.
Herein, molecular dynamics simulation methods using the DL_POLY code are employed to investigate the structural changes of Ni-doped Li1+xM₂O₄ (M=Mn,Co) nanoporous materials during the discharge process. The nanoporous structures have evolved into single and multiple-grained structures during the amorphisation and recrystallisation processes. The pores of the materials disappear with the Ni-dopant during lithiation. Furthermore, the volume of the materials also increases with increasing Li content and Ni concentration. However, the materials retain their structural integrity upon full lithiation because the nanoporous morphology accommodates volume expansion during cycling. Therefore, Ni-doped nanoporous materials can potentially enhance the cycling performance of spinel-structured LiM2O4 cathodes for lithium-ion battery applications.

Speaker: Beauty Shibiri (University of Limpopo)

177 Optimisation of Natural Radionuclide (Th, K and U) Measurements through Comparison of Field Gamma Spectrometry and ICP-MS Analysis

Accurate quantification of naturally occurring radionuclides such as thorium (Th), potassium (K) and uranium (U) is essential for environmental monitoring, mineral exploration and radiological assessment. This study focuses on the optimisation of radionuclide measurement by comparing in situ gamma spectrometry data with laboratory-based inductively coupled plasma mass spectrometry (ICP-MS) results. Field measurements were conducted using a Medusa gamma-ray spectrometer, complemented by drone-based surveys to enhance spatial coverage and accessibility across the study area.

The radiometric data obtained from ground and aerial platforms were processed and calibrated to derive elemental concentrations, which will then systematically compared with ICP-MS analyses of collected samples. Statistical and spatial analyses will be applied to evaluate the level of agreement, identify discrepancies and assess factors influencing measurement variability, including soil heterogeneity, moisture content and instrument sensitivity.

The results are expected to demonstrate the strengths and limitations of each method, highlight the efficiency of field-based techniques for rapid, large-scale assessments, and confirm the higher precision and accuracy of ICP-MS under controlled laboratory conditions. The integration of drone-assisted surveys further will improve data resolution and coverage, offering a valuable tool for terrains that are difficult to access.

This study contributes to the development of an optimised framework for radionuclide assessment in South Africa, supporting more reliable environmental monitoring and resource evaluation through the combined use of field and laboratory methodologies.

Speaker: Mr Thapelo Mafabatho

178 Optimization of bismuth doped strontium borate for application in fibre optics

Fibre optics enables the transmission of light through total internal reflection and underpins modern telecommunication systems. For efficient optical signal amplification over long distances, fibres are usually directly doped with luminescent ions and pumped with laser diodes. While this approach is simple, currently there is a lack of cost-effective and efficient fibre amplifiers operating in the near-infrared range (1150–1500 nm). Bismuth luminescent centers are emerging as promising candidates due to their broadband near-infrared emission. However, directly bismuth-doped fibres are limited by the low concentration of optically active bismuth centers participating in the luminescent process. In this study, a novel approach was investigated by incorporating bismuth into the strontium tetraborate (SrB₄O₇) host material. The effects of bismuth concentration, annealing time, and annealing atmosphere were systematically investigated. Photoluminescence spectroscopy showed emission in the visible region at 590 nm and 660 nm, and in the near-infrared region at 1290 nm. These different emissions were attributed to the different oxidation states of the bismuth ions. As the bismuth concentration increased from 0.5% to 5%, a significant enhancement in infrared emission was observed. Furthermore, shorter annealing treatments resulted in stronger infrared emission compared to extended annealing, indicating a correlation between thermal processing and active center formation. Controlled variation of processing parameters demonstrated the ability to influence the dominant oxidation state within the luminescent material. This study aims to identify the synthesis conditions that enhance the infrared emission of bismuth in SrB₄O₇ and provide deeper insights into the role of the different bismuth oxidation states.

Speaker: Caitlin van Wyk

179 Optimization of Nitrogen in Transition Metal Oxynitrides for Fuel Cell Applications

Titanium oxide is a promising corrosion-resistant catalyst support for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells; however, its low electrical conductivity and wide band-gap limits performance. In this work, titanium oxynitride materials were synthesized via two routes: a sol–gel method followed by thermal nitridation at 650 °C, and a hydrothermal synthesis calcined at 750 °C. Nitrogen incorporation was controlled using varying titanium precursor-to-urea ratios. X-ray diffraction revealed rutile phase for sol–gel and anatase structures for hydrothermal samples. Raman spectroscopy indicated lattice distortion and defect formation, while UV–Vis analysis showed enhanced visible-light absorption due to defect states. EDS showed 10.52% N incorporation while SEM showed highly agglomerated and porous structures. . The composition with 23.93% nitrogen exhibited the most significant structural and electronic modification across both synthesis routes, suggesting an optimal nitridation level. These results demonstrate that controlled nitrogen incorporation can effectively tune TiO₂ properties for improved ORR activity, supporting the development of sustainable fuel cell technologies.

Speaker: Nicholas Onkoba (UNISA)

180 Performance Evaluation of Radiation-Induced Defects in Nanocrystalline Diamond Using Density Functional Theory

Nanocrystalline diamond has attracted significant attention as a protective material for extreme environments due to its exceptional hardness, high thermal conductivity, chemical stability, and radiation resistance. However, exposure to high-energy radiation can induce lattice defects in diamond—such as vacancies, interstitials, and substitutional defects—that may alter its structural and mechanical properties. In this study, density functional theory (DFT) was employed to investigate the influence of radiation-induced defects on the mechanical behavior of crystalline diamond. Key mechanical properties, including Young’s modulus, bulk modulus, shear modulus, and elastic constants, were predicted. Our results show that lattice defects, including vacancies and defect complexes, significantly modulate the mechanical properties of diamond. These findings provide insights into the performance of diamond-based materials in radiation-intensive environments and inform their suitability for advanced sensing technologies and other applications requiring high radiation tolerance.

Speaker: Mr Kelvin Matamela (University of Johannesburg)

181 Plasmonic effect on the photoluminescence of Eu ions doped CaF2 nanomaterials

Nanomaterials have recently attracted increased attention due to their use in many applications, including solar energy conversion, sensors, transparent electrodes, and catalysis. The grain size of these materials plays a crucial role in determining their optical properties. Size-dependent nanomaterials have various potential applications in optoelectronics, color displays, lasers, biological and medical labeling. Metal nanoparticles, however, have emerged as a new strategy for enhancing luminescent properties through their well-studied surface plasmonic resonance behavior. Surface plasmon resonance can generate a strong electromagnetic field at the surface of metal nanoparticles, thereby enhancing the local density of optical states. These properties have been extensively investigated for fluorescence enhancement.
This work investigated the effects of Au nanoparticles on the photoluminescence of Eu ions doped CaF2 nanomaterials. The structural analysis was done using X-ray diffraction. X-ray photoelectron spectroscopy was used to identify the elemental composition of the material and the obtained CaF2:Eu nanomaterials displayed uniform size distributions. The CaF2:Eu nanomaterials showed emission from both Eu2+ and Eu3+ oxidation states under ultraviolet excitation. The Eu2+ emission steadily enhanced with Au concentrations. The luminescence properties suggest that the material has the potential for various applications, including sensors, color display, and optoelectronics.

Speaker: Mubarak Yagoub (University of Johannesburg)

182 Probing the physical and optical properties doped cobalt oxide (Co3O4) nanoparticles with Molybdenum (Mo) for gas sensing applications in the agricultural sector

The agricultural sector is a key component of the global economy. Driven by human demand for quality agricultural products, the use of nitrogen fertilizer (N-fertilizer) grows rapidly due to an increased need for dietary protein, including animal protein. Nitrogen is one of the significant indicators of soil fertility and crop growth conditions. Hence, monitoring the concentration of nitrogen in the soil can improve the sustainability of agricultural production. The current study prepared pristine Mo and Mo-doped Co3O4 nanoparticles using hydrothermal method and further characterized their physical and optical properties to evaluate their suitability in gas sensing applications. The X-ray diffraction (XRD) analyses show that Mo-doped Co3O4 nanoparticles exhibit a cubic spinel structure. The average crystalline size decreased with increasing concentrations of Mo-doping Co3O4 nanoparticle from 55.23 Å to 16.86 Å. Scanning electron microscopy (SEM) reveal that Mo-doped Co3O4 nanoparticles have nanoflakes particles with the combination of cubic and hexagonal shapes. The Brunauer-Emmett-Teller (BET) surface area analyser results indicate that the average particles size decreases with increasing Mo-doping concentration and therefore resulting in an increase for both the surface area and pore volume. Meanwhile, the Fourie transform-infrared (FTIR) spectroscopy confirms the formation of the Co+2 and Co+3 for the prepared Co3O4 nanoparticles. The findings suggest Mo doping can be used to tailor the structural properties of Co3O4 nanoparticles with improved gas sensing performance. These particles can be further used to develop gas sensors that monitors nitrogen in the soil which will contribute to precision agriculture.

Speakers: Mahlatse komape (UNIVERSITY OF LIMPOPO), Dr Thomas Malwela

183 Rational Interface Engineering of 1D Earthworm-like Polypyrrole Anchored on 3D Hierarchical BiOCl Marigold Flower-like Hybrid Platform for Advanced Energy Storage Applications

Bismuth oxychloride (BiOCl) is a promising electrode material for energy storage due to its layered structure and redox activity; however, its low intrinsic electrical conductivity and pronounced potential drop limit practical performance. In this work, a conducting polymer–based modification strategy is anticipated, in which polypyrrole (PPy) is incorporated into BiOCl to enhance charge-transfer kinetics and suppress the potential (IR) drop during electrochemical operation. 3D porous PPy–BiOCl hybrid electrodes with varying PPy contents (5, 7, and 9 wt.%) were prepared via a simple physical blending technique. Field emission scanning electron microscopy analysis confirms a uniformly distributed 3D porous architecture with a large accessible surface area, facilitating efficient ion transport and electrochemical activity. The BP1 electrode (5 wt.% PPy) supported on nickel foam exhibited pronounced redox peaks in 6 M KOH, indicating a dominant battery-type faradaic charge-storage mechanism. Due to enhanced electronic conductivity and an oxygen-vacancy-enriched hybrid structure, the BP1 electrode exhibited a lower potential drop. It delivered a high specific capacity of 659 C.g⁻¹ at 1.0 A.g⁻¹. A BP1//BP1 symmetric supercapacitor achieved an energy density of 24.0 Wh.kg⁻¹ at a power density of 750.0 W.kg⁻¹. Furthermore, two symmetric devices connected in series successfully powered green and red light-emitting diodes, demonstrating the practical viability of PPy-modified BiOCl hybrid electrodes.

Speaker: Yugesh Singh Thakur (Department of Physics, University of the Free State (UFS), Bloemfontein, ZA 9300, South Africa)

184 Revealing quantum entanglement signatures with OAM states

Quantum entanglement remains the fundamental cornerstone of modern quantum
information protocols, including quantum cryptography, computing, and communication.
Despite this, there are very few quantum entanglement setups available in Africa. Here, we
show how to set up a quantum experiment and verify quantum entanglement to estimate the
properties of quantum states using quantum state tomography. We use a spiral bandwidth to
analyze the correlations between the pairs and perform bell’s inequality by calculating the
CHSH (Clauser-Horne-Shimony-Holt) parameter. A violation of the bell inequality
demonstrates the non-local nature of the generated entangled OAM states and effectively
ruling out local hidden-variable theories. We demonstrate how our approach can be
extended to quantum topological signatures.

Speaker: Ms Pashlene Naidoo (University of Witswatersrand)

185 Schottky Barrier Modulation in Pd Sensitized Co3O4/NiTiO3 Heterojunctions for Trace Level NOx Gas Sensing

Nitrogen oxides (NOx) are among the most hazardous air pollutants emitted from combustion processes in mining, industrial, and transportation sectors, posing severe risks to human health and atmospheric quality. The development of semiconductor based gas sensors that combine high sensitivity with low power consumption remains a critical challenge. In this study, Pd-sensitized Co3O4/NiTiO3 nanostructured heterojunctions were synthesized via the microwave-assisted hydrothermal route, followed by wet impregnation with 0.5, 0.75, and 1 wt.% Pd. Structural, surface, and chemical-state analyses confirmed the successful formation of heterojunctions and the uniform dispersion of metallic Pd nanoparticles on the semiconductor surface. Gas‑sensing measurements revealed that the Pd sensitization significantly enhanced NOx sensing performance, with 0.75 wt% Pd demonstrating superior sensitivity and rapid response–recovery characteristics. The enhanced performance is primarily attributed to the metal–semiconductor Schottky junctions, which generate additional depletion regions and modify the local band structure at the interfaces, leading to pronounced resistance modulation during NOx adsorption. Simultaneously, Pd nanoparticles acted as efficient catalytic mediators, facilitating electron exchange via spillover effects and accelerating surface reaction kinetics, thereby enhancing sensitivity, lowering the detection limit, and enabling fast response kinetics. Importantly, the enhanced sensing activity was achieved at reduced operating temperatures, leading to significantly lower power consumption, which is an essential requirement for portable and battery‑powered sensors. These findings underscore the importance of interface engineering and energy‑efficient materials design in advancing sustainable gas‑sensing solutions for environmental and industrial applications.

Speaker: Zamaswazi Tshabalala (University of the Free State)

186 Shaping light with a deformable mirror

Deformable mirrors are a type of optical element with a reflective surface that can change shape, through different mechanisms. These devices allow for adaptive control of reflected wavefronts offering a method for real-time aberration correction. For this reason, deformable mirrors have a wide range of optical applications from correcting for distortions due to atmospheric turbulence in astronomy to improving the quality of biological images. Other than shaping wavefronts by correcting for distortions, deformable mirrors can be used to impose a particular structure onto the reflected wavefront. This is useful because beam shapes different from the standard Gaussian profile of a laser are often desired for industrial applications such as laser materials processing and photolithography. Here we present an overview of the different types of deformable mirrors and their applications. Since deformable mirrors are usually used for aberration correction, some are readily controllable using aberrations characterised by Zernike polynomials. We demonstrate how we can use these aberrations to shape a Gaussian beam into an elongated spot – a beam shape commonly used for applications in industry and microscopy.

Speaker: Nikisha Baboolal (University of the Witwatersrand)

187 Silver Doped Zinc Oxide Nanoparticles for Enhanced Performance of P3HT:PCBM Photovoltaic Cells

Over the past two decades, there has been a significant progress in incorporating inorganic nanofillers into polymer blends, leading to enhanced performance of organic photovoltaic (OPV) devices. In this work, Poly(3-hexylthiophene-2,5-diyl):phenyl-C61-butyric-acid methyl-ester (P3HT:PCBM) photoactive layer blend was doped with 1, 3, and 5 wt% of ZnO:Ag nanoparticles (NPs). The ZnO:Ag NPs were prepared using a simple wet chemistry method. Electrical characteristics such as the open circuit voltage (VOC), short-circuit current density (JSC), fill factor (FF), and power conversion efficiency (PCE) were extracted from current-voltage (J-V) measurements under illumination. The incorporation of the NPs enhanced the PCE of OPVs from 2.56% to an optimum of 3.28% an improvement of more than 28%. The addition of NPs into the photoactive layer enhanced light absorption by the P3HT:PCBM films due to light scattering (LS) and local surface plasmon resonance (LSPR). Increasing the NP concentration to 5 wt% had negative effects on the performance of the photovoltaic devices, reducing the PCE to 2.75%. This decline is attributed to NP overloading, which may have led to increased recombination and short-circuiting within the devices.

Speaker: Mpilo Dlamini (North-West University)

188 Spectroscopy and selective Ionisation of TbF3 and LaF3: Towards efficient isolation of Tb-149 and Ac-225 for medical applications.

Theranostics approach in TRNT (Targeted Radionuclide Therapy) have gained interest as an alternative method to chemotherapy for their effectiveness in combining imaging and treatment for cancer. Theranostics involves using the same targeting molecule with different radioactive isotopes for a well monitored TRNT. Two useful isotopes in TRNT are terbium Tb-149 and actinium Ac-225. This study investigates the potential for laser-based ionisation by studying two stable isotopes terbium Tb-159 and lanthanum La-139, as a stepping stone towards application to the radioactive isotopes. Tb has very low vapor pressure and can pose challenges for accelerator-based production of Tb-149. Formation of TbF3 and LaF3 offers a solution to this problem but no data exists on TbF3 and LaF3. The study presents a comprehensive spectroscopic investigation and feasibility study of laser-based ionisation of TbF3 and LaF3 for improved separation and characterization in production of medical isotopes.

Speaker: Thakgalo Mangena (Mr Thakgalo Mangena, University of Stellenbosch Physics Department)

189 Sputtering effect of CaF2 on Si and graphite substrates

The sputtering behaviour of CaF₂ thin films produced on Si and graphite substrates was studied in this paper. The study seeks to clarify the role of substrate material, specifically conductive versus semiconductive and structurally different surfaces, on the sputtering yield and surface modification of CaF₂. Thin films of CaF₂ were deposited on both substrates using an e-beam deposition method and irradiated at room and low temperatures under high vacuum, using 20 MeV Cu⁵⁺ ions. After-irradiation examination using 2 MeV He²⁺ beam on Rutherford backscattering spectrometry (RBS) was carried out. Atomic force microscopy (AFM) and Raman spectroscopy found significant differences in sputtering yields and morphological alterations. The CaF₂ layer on graphite has a higher effective sputtering yield than on silicon due to differences in electronic stopping power, thermal conductivity, and interfacial bonding. Surface examination revealed preferential fluorine depletion and the formation of nanoscale hillocks and craters on both substrates, with graphite-supported films exhibiting more pronounced surface roughening. The study found that the substrate has a crucial role in the kinetics of ion-beam-induced sputtering in CaF₂. This has potential implications for radiation-resistant coatings and optical devices.

Speaker: Dr Jean Jules Mboukam (Tshwane University of Technology)

190 Structural and Magnetic Properties of Nanostructured CuxMn1-xFe2O4 (0 ≤ x ≤ 0.8) Synthesized via a Glycol-Thermal Route

Nanocrystalline CuxMn1-xFe2O4 (0 ≤ x ≤ 0.8) ferrites with particle sizes in the range of approximately 8-22 nm were synthesized via a low-temperature glycol-thermal route and systematically investigated for their structural and magnetic properties. X-ray diffraction confirmed the formation of a single-phase cubic spinel structure. The lattice parameter decreased monotonically from 8.506 Å to 8.343 Å with increasing Cu content, consistent with Vegard’s law and the substitution of larger Mn²⁺ ions by smaller Cu²⁺ ions. The increase in X-ray density with Cu concentration reflects enhanced atomic packing within the unit cell. Detailed magnetic studies were performed on the impurity-free composition Cu0.3Mn0.7Fe2O4 as a function of measuring temperature. S-shaped magnetization curves with near-zero coercivity at room temperature indicate superparamagnetic behaviour. The saturation magnetization decreased from ~75 emu g⁻¹ at 10 K to ~48 emu g⁻¹ at 400 K due to thermal spin disorder. The enhancement of coercivity at low temperatures is attributed to surface spin-freezing effects. Zero-field-cooled and field-cooled magnetization measurements yielded a blocking temperature of ~120 K, confirming superparamagnetic relaxation with spin-glass-like behaviour at low temperatures.

Speaker: Prince Phathizwe Majozi (UNIZULU)

191 Structural and Optical Properties of R₂Ti₂O₇ (R = Dy and Sm) Pyrochlore Oxides.

Rare-earth titanate pyrochlores of the general formula R₂Ti₂O₇ have attracted considerable interest owing to their flexible structural chemistry and multifunctional physical properties. In this work, dysprosium titanate (Dy₂Ti₂O₇) and samarium titanate (Sm₂Ti₂O₇) were successfully synthesized using the sol-gel method and subsequently calcined at 1000 0C to obtain phase-pure pyrochlore samples. The structural properties were investigated by X-ray powder diffraction (XRD) with Rietveld refinement, confirming the formation of a single-phase cubic pyrochlore structure (space group Fd3̄m) for both samples. Refined lattice parameters were consistent with the expected systematic variation with rare-earth ionic radius, with Dy₂Ti₂O₇ exhibiting a smaller unit cell than Sm₂Ti₂O₇ in accordance with the lanthanide contraction. Additionally, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate the morphology, chemical composition, particle size, and microstructural features of the synthesized powders. SEM analysis revealed agglomerated particles with morphology with no additional element, while TEM confirmed nanoscale crystallite dimensions and provided lattice fringe spacings consistent with the pyrochlore crystal structure. The optical properties were examined using UV-visible diffuse reflectance spectroscopy, from which optical bandgaps were obtained using Tauc plot analysis. Both samples behave as wide-bandgap insulators, with Sm₂Ti₂O₇ exhibiting a comparatively narrower band gap relative to Dy₂Ti₂O₇, attributed to differences in the rare-earth 4f electronic structure and its hybridization with the O 2p valence band. This work reports the systematic insight into the relationship between rare-earth identity, crystal structure, microstructure, and optical response across the R₂Ti₂O₇ pyrochlore group, with a potential relevance to optical device applications.

Speaker: Saheed Omotosho Yissah (University of Johannesburg)

192 Structural Pore Network Modelling of Carbonate Rocks from 2D SEM Images

Carbonate reservoirs account for a substantial share of global hydrocarbon reserves and are increasingly relevant for subsurface energy applications such as carbon capture and storage, geothermal exploitation, and hydrogen storage. Their potential lies in large pore volumes, dual porosity systems, and complex fracture networks that can enhance fluid storage and transmission. However, these same features make carbonate pore systems highly heterogeneous, with variability in geometry, connectivity, and scale that complicates reliable predictions of permeability and storage capacity.
Previous studies using mercury intrusion porosimetry, micro-CT imaging, and lattice-Boltzmann simulations have advanced understanding of carbonate pore systems, but these methods remain costly, sample-intensive, or computationally demanding. To address this gap, the present study develops a structural pore network model (PNM) derived directly from 2D scanning electron microscope (SEM) micrographs of limestone samples.
Image segmentation was applied to identify pores and throats, which were represented as nodes and links in a simplified network. Geometric descriptors and graph-theoretical connectivity measures were used to quantify pore size distributions, throat dimensions, tortuosity, and coordination numbers. The analysis revealed marked heterogeneity across samples, with connectivity indices highlighting structural variability and potential pathways for fluid movement.
The results demonstrate the feasibility of transforming 2D SEM data into computational pore networks, providing a rapid and cost-effective approach to preliminary reservoir assessment. While restricted to structural characterization, this framework establishes a foundation for future studies that may incorporate flow simulations, multiphase transport, and validation against 3D micro-CT datasets to better capture the full heterogeneity of carbonate reservoirs and their role in subsurface energy systems.
Keywords: Carbonate reservoirs, pore network modelling, 2D SEM, structural heterogeneity, connectivity, pore size distribution

Speaker: Chidiebere Ekwomadu (north west university)

193 Structural Properties of Gd4Fe2O9 Intermetallic Compounds

The magnetic behaviour of Gd is amongst those that exhibit the most striking characteristics. It is among the few elements capable of changing its magnetic characteristics from ferromagnetism at ambient temperatures to paramagnetism at a comparatively low temperature, that is, at around 20°C. This capacity to change its magnetic characteristics is crucial for application in magnetic refrigeration technology, a cooling method based on the magnetocaloric effect. Moreover, Gd4Fe2O9, which exhibits interesting optical properties due to the presence of Gd3+ ions, which have well-known sharp optical transitions in the visible and near-infrared regions, making the compound potentially useful in luminescent applications. For this purpose, we successfully synthesized the Gd4Fe2O9 compound using a solid-state technique. The X-ray diffraction confirms that the material forms as a single phase in a monoclinic structure with space group P21/c. The scanning electron microscopy SEM and EDX were performed and confirmed the presence of the elements in stoichiometric amounts in the material. The Mossbauer spectrum confirmed that all the iron in the sample is in one local environment. The magnetic field of 50.6 T indicates a strong magnetic interaction between the nuclear magnetic moment and the magnetic field due to surrounding electrons. This work reports on the initial physical properties results, which open up understanding into the physics of this class of materials.

Speaker: Redrisse Djoumessi Fobasso (University of Johannesburg)

194 Structural, morphological, and optical properties of Pr3+-doped La2ZnTiO6 nanophosphors prepared via the sol-gel method

Research on phosphor materials has gained prominence due to the prospective applications of rare-earth (RE³⁺) ion-activated phosphors in sensors, displays, and lighting. This study presents the synthesis of novel red light-emitting Pr³⁺-doped La₂ZnTiO₆ nanophosphors using a citric acid-assisted method. This study systematically investigated how varying Pr³⁺ doping concentrations (0 ≤ x ≤ 4.0) influence the material's structural, morphological, and optical properties. X-ray diffraction results indicated that all La₂ZnTiO₆:x%Pr³⁺ (0 ≤ x ≤ 4.0) nanophosphors had monoclinic crystal structures. Field-emission scanning electron microscopy (FE-SEM) revealed predominantly irregular polyhedral morphologies, with particle size varying as the Pr³⁺ concentration increased. Energy-dispersive X-ray spectroscopy (EDX) verified the incorporation of all expected elemental constituents. Fourier-transform infrared spectroscopy (FTIR) indicated minimal variations in vibrational modes, suggesting that Pr³⁺ incorporation does not significantly distort the host lattice's fundamental structure. The UV-Vis spectra showed that the diffuse reflectance was dominated by absorption edge bands at 299 and 378 nm for undoped La₂ZnTiO₆. Upon Pr³⁺ doping, six distinct absorption bands were displayed at 450, 471, 478, 491, 596, and 609 nm, corresponding to the electron transitions of Pr³⁺. After monitoring the excitation at 290 nm, the photoluminescence (PL) spectra showed four emission bands centered at 489, 610, and 704 nm, attributed to the ³P₀→³H₄, ¹D₂→³H₄, and ¹D₂→³H₅ transitions of Pr³⁺ ions, respectively. The International Commission on Illumination (CIE) colour chromaticity diagram confirmed a white colour for the undoped La₂ZnTiO₆. Upon doping with x mol% of Pr³⁺, a red-shifted colour emission was observed. The results indicated that it would be a suitable component for PC-LEDs that emit white or red light.

Speaker: Delicacy Ntshalintshali (University of the Free State - Qwaqwa Campus)

195 Structural, Optical, and Gas Sensing Characteristics of Rare Earth-Doped CuO/ZrO2 Heterostructures for NO2 Detection

Nitrogen dioxide (NO2) is a very hazardous gas to human health that requires specialized detection at low temperatures for environmental monitoring. This study investigated synthesized rare-earth (RE)-doped CuO/ZrO2 p-n heterostructures doped with various concentrations (0.5-1%) of Ho3⁺ and Yb3⁺ ions via a hydrolysis process and their applications for gas sensing. X-ray powder diffraction (XRPD) analysis revealed monoclinic CuO and tetragonal ZrO2 phases, with no secondary impurities, indicating good phase purity. The crystallite size decreased, accompanied by increased lattice strain and dislocation density, indicating the formation of more defect-induced active sites with increasing RE doping. Surface morphology analyses revealed triangular nanoplatelets and prism-like nanostructures. Optical studies demonstrated that the introduction of RE led to increased surface defects, associated with oxygen vacancies and defect-related transitions, suggesting altered charge-carrier dynamics. The sensing analyses demonstrated that among the materials, the 0.5 wt.% Yb-CuO/ZrO2 disclosed improved NO2 detection. The improved sensing performance is due to the formation of the CuO/ZrO2 p-n heterojunction, increased defect density, enhanced surface adsorption, and improved charge transfer resulting from RE doping. These findings showed that RE-doped CuO/ZrO2 heterostructures are a promising candidate for efficient, selective, and low-temperature NO2 gas detection.

Keywords: CuO/ZrO2, p-n heterostructure, rare earth doping, NO2 sensing.

Speaker: Mr Lekgolo Maebana (University of free state)

196 Study of electronic and magnetic properties of double perovskites La2NiRuO6

A theoretical investigation of electronic and magnetic properties of La2NiRuO6 is studied through density functional theory (DFT) using plane augmented wave method and Monte Carlo simulations. Spin-polarized first-principles calculations are carried out within the DFT+U framework to properly account for electronic correlations associated with the Ni-3d and Ru-4d states. The analysis of the electronic band structure shows that this compound is a narrow band gap semiconductor (0.57 eV) exhibiting antiferromagnetic behavior. Magnetic exchange interactions are obtained by mapping total energies onto an effective Heisenberg Hamiltonian using Wannier-based methods. These exchange parameters are then used as input for classical Monte Carlo simulations to investigate the finite-temperature magnetic properties, that is, magnetization and magnetic susceptibility. The simulation revealed that the compound has a low critical temperature, TN = 27.3K. The results obtained are in good agreement with the experimental ones. These results clarify the microscopic mechanisms responsible for magnetic ordering and reveal the competition between different exchange pathways mediated through the Ni–O–Ru superexchange network. This work reports on the overall results of the combined first principles and statistical-mechanics approach, which provides a coherent understanding of the relationship between structure, electronic properties, and magnetism in La2NiRuO6.

Speaker: Mr IRENEE BRICE MOUADJE MOUADJE (University of Johannesburg)

197 Study of Nuclear Reactions Induced by Weakly Bound Projectiles

Weakly bound and halo nuclei, with low binding energies and extended spatial distributions, provide a unique testing ground for nuclear forces and reaction dynamics. Despite lot of studies done on this, unresolved questions remain regarding breakup mechanisms—particularly whether projectiles dissociate on incoming or outgoing trajectories at deep sub-barrier energies ( [1 - 2]). This research employs the Continuum-Discretized Coupled Channels (CDCC) method ([3]; [8]) to investigate breakup and transfer reactions, incorporating microscopic nucleus–nucleus potentials derived from double-folding procedures and energy density functionals ([5]; [7]). These approaches include nuclear structure effects such as pairing and spin–orbit interactions, addressing limitations of phenomenological Woods–Saxon potentials ([4]; [6]). Comparative analysis of breakup observables ([9]; [10]) will clarify the structural role of weakly bound projectiles. The findings have broader implications for astrophysics, nuclear medicine, and advanced nuclear energy technologies.

Speaker: Mr Happy Vilakazi (UNISA)

198 Super-Diffusion as a Crash Precursor: Insights from Detector Track Reconstruction

Financial physics, also known as econophysics, applies concepts from statistical mechanics and complex systems theory to financial markets. This study investigates whether super-diffusive scaling of price trajectories can serve as a quantitative precursor to market crashes, drawing an analogy with charged particle tracking detectors.

In high-energy particle detectors, the mean square displacement of a reconstructed track exhibits a characteristic scaling exponent α defined as the derivative of the mean squared displacement with respect to the logarithm of time (d⟨Δx²⟩/d log t). Under normal conditions, Brownian motion gives α = 1. However, before a large-angle scattering event—analogous to a market crash—the exponent rises above unity (α > 1), indicating super-diffusion and a diverging critical fluctuation.

We test a single hypothesis: in the days preceding a major market crash, the log-price diffusion exponent α should exceed 1.5, matching predictions from self-organized criticality models of financial collapses.

Using 1-minute S&P 500 data from 1987, 2008, and 2010, we compute rolling 5-day windows of the mean square displacement. Results show that during normal trading periods, α = 1.02 ± 0.03, consistent with Brownian motion. In the 5-day window preceding each crash, α rises to 1.48 ± 0.05, a statistically significant deviation (p < 0.001) that returns to unity immediately after the crash.

This single measurable precursor—super-diffusive scaling—provides a direct bridge between particle detector physics and financial market dynamics. The findings support the view that crashes are not random outliers but critical events preceded by predictable changes in the statistical mechanics of price diffusion. This work contributes toward improved systemic risk assessment and early warning systems grounded in physical principles.

Keywords: Econophysics, super-diffusion, market crashes, particle tracking detectors, self-organized criticality, scaling laws.

Speaker: Vuako Maluleke (University of Venda, iThemba LABS)

199 Symmetry Site Engineering in SrGd2O4:Dy3+ Phosphors for Tunable and High-Quality White Light Emission

Single-component white light phosphors with high thermal stability and balanced photometric properties are essential for next-generation solid-state lighting. In this work, Dy3+-activated SrGd2O4 phosphors were successfully synthesized using a hydrothermal method followed by calcination, and the influence of symmetry-driven site engineering on their structural, optical, and luminescent properties was systematically investigated. X-ray powder diffraction confirmed the formation of a pure orthorhombic SrGd2O4 phase, while peak shifts revealed preferential substitution of Dy3+ ions at Sr2+ sites up to 7 mol%, followed by partial occupation of Gd3+ sites at higher concentrations. Ultraviolet–visible (UV-vis) diffuse reflectance spectra showed strong UV absorption, with a gradual reduction in the band gap from 5.05 to 4.87 eV upon Dy3+ incorporation, suggesting modulation of the electronic structure. Photoluminescence studies revealed characteristic Dy3+ emissions at 480 nm (4F9/2 → 6H15/2), 572 nm (4F9/2 → 6H13/2), and 635 nm (4F9/2 → 6H11/2). The asymmetry-ratio analysis confirmed the dominance of electric dipole transitions and revealed symmetry-dependent site occupancy of Dy3+ ions. Lifetime measurements showed millisecond decay dynamics, with efficient Gd3+ → Dy3+ energy transfer and dipole–dipole–mediated concentration quenching. Among all compositions, the optimized SG-7Dy phosphor exhibited balanced white emission with chromaticity coordinates (0.305, 0.324), close to natural daylight, along with low colour purity (~12%), improved colour rendering index, and high luminous efficacy. Temperature-dependent photoluminescence analysis demonstrated stable white light emission with an activation energy of 0.72 eV, confirming strong resistance to thermal quenching. Thermoluminescence studies revealed Dy3+-mediated trap engineering that optimizes shallow and intermediate trap levels, enhancing persistent luminescence behaviour. Thermal analyses (TGA and DSC) confirmed excellent thermal stability with minimal mass loss and no significant phase transitions. Overall, symmetry-engineered SrGd2O4:Dy3+ phosphors enable efficient single-phase white-light emission with excellent thermal stability, making the optimized SG-7Dy composition a promising candidate for advanced white-light-emitting diode (w-LED) applications.

Speaker: Dr sandeep eswaran panchu (university of the free state)

200 Synergistic improvement of Dy and Ag Co-loaded Co3O4/In2O3 p-n heterojunction for the detection of m-xylene and p-xylene vapour

Abstract: The rising emission of aromatic volatile organic compounds (VOCs), particularly xylene, presents serious environmental and health concerns. Xylene is primarily released from petrochemical industries and automobile exhaust, and exposure to it at different periods can cause skin and eye irritation, respiratory problems, neurological impairment, and deterioration of the central nervous system. These risks highlight the urgent need for effective monitoring and detection of these VOCs using semiconductor metal oxide (SMO) sensors. Strategies such as heterojunction formation and surface modification with noble and rare-earth metals have been employed to enhance the sensing performance of SMO-based sensors. On the other hand, metal-organic frameworks (MOFs) offer a promising platform for developing high-performance SMO sensors due to their high surface area, porosity, and tunable architectures. In this work, a MOF-derived Dy and Ag-loaded Co3O4/In2O3 sensor was developed for the detection of xylene vapour. Comprehensive morphological, structural, and optical characterizations confirmed the successful integration of Dy and uniform dispersion of Ag within the Co3O4/In2O3 surface, leading to improved surface defects, active surface area, and accessible adsorption sites. Compared to the pure sample, Co: In, Dy loading significantly reduces the response time, with 0.5 wt% Dy/Co: In showing the fastest response, due to active sites that facilitate gas adsorption and charge transfer. The 0.5 wt% Ag-loaded samples showed an enhanced sensitivity and selectivity towards m-xylene and p-xylene. The enhanced sensitivity and selectivity are attributed to Ag-induced electron sensitization and to the catalytic activation of oxygen and xylene via spill-over effects.

Speaker: Lindokuhle Mabizela (university of the free state)

201 Synergistic properties and sensing performance of In2O3-based binary and ternary heterostructures for acetone detection

The rapid and precise detection of volatile organic compounds (VOCs), particularly acetone (C3H6O), is essential for environmental monitoring, industrial safety, and healthcare diagnostics. Due to the increased morbidity and mortality rates of metabolic diseases (i.e., diabetes), portable advanced n-p and n-p-n SMO-based acetone sensors should be considered for detecting and monitoring low acetone concentrations. This study examines the gas-sensing performance of In2O3-based binary and ternary sensors, focusing on their gas-sensing performance towards low concentrations of C3H6O. The integrated n-p In2O3-Co3O4, In2O3-CuO, In2O3-Mn3O4, and In2O3-NiO binary heterostructures, along with the n-p-n In2O3-Co3O4-CeO2, In2O3-Co3O4-SnO2, In2O3-Co3O4-ZnO, and In2O3-Co3O4-ZrO2 ternary heterostructures, were fabricated using a hydrothermal approach. From a gas-sensing perspective, the n-p In2O3-Co3O4 binary sensor showed impressive performance, detecting 2.3 ppm of C3H6O at 100 °C compared to other binary sensors. As well, the n-p-n In2O3-Co3O4-ZnO ternary sensor presented remarkable sensitivity to the same C3H6O at 150 °C, outperforming other ternary sensors. The n-p In2O3-Co3O4 binary sensor achieved high sensitivity (2.38 ppm-1), a low detection limit (0.142 ppb), and fast response/recovery times (40/43 s) compared to In2O3-CuO, In2O3-Mn3O4, and In2O3-NiO sensors. In contrast, the n-p-n In2O3-Co3O4-ZnO ternary sensor exhibited remarkable sensitivity (0.14 ppm-1), low detection limit (100 ppb), and fast response/recovery times (74/64 s). These exceptional results are attributed to enhanced interfacial synergy, increased oxygen vacancies, and modulation of heterojunction barriers, resulting in improved gas sensing performance. When comparing n-p In2O3-Co3O4 (binary) sensor to the n-p-n In2O3-Co3O4-ZnO (ternary) sensor, the ternary sensor demonstrated improved sensitivity and a lower detection limit. Although operating temperature remains a challenge, these developments have significant improvements in gas-sensing parameters. This highlights the potential for further advancements in ternary sensor technology for real-world applications in air quality monitoring and breath analysis for diabetes detection.

Speaker: Katlego Morulane (University of the Free State)

202 Synthesis of Sustainable Biomass-Derived Porous Biochars as Promising Electrode Materials for Supercapacitor Applications

Abstract:
Supercapacitors (SC) are excellent energy storage solutions for electronics because they offer greater energy and power densities than traditional capacitors and batteries. Developing efficient and sustainable biochar-based electrode materials continues to be a challenge for developing green energy storage devices. In this study, activated carbons (AC) were produced from agricultural wastes (corncob [CC], groundnut shell [GS]) using physico-chemical activation method, which were used as electrode material for SC electrodes. Each AC was characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) analysis. Electrochemical property was evaluated using Cyclic Voltammetry (CV). Thermogravimetric Analysis (TGA) confirmed a suitable carbonization temperature of 300 °C. SEM and BET results showed good porosity and specific surface areas of 514.10 and 950.00 m²/g for CC and GS, respectively. XRD confirmed the transformation of each precursor into amorphous carbon and FTIR analysis revealed significant functional groups required for electrode materials. Electrochemical performance of each AC electrode displayed a strong correlation between capacitance and surface morphology. AC from CC demonstrated superior performance, with a specific capacitance of 178 F/g, compared to 123 F/g for GS. The results suggested that Agricultural waste derived ACs are promising candidates as electrode materials.
Keywords: Activated carbon, biomass, Porous structure, Electrode materials, Supercapacitors.

Speaker: Salahudeen Adamu Gene (Ibrahim Badamasi Babangida University, Lapai, Nigeria)

203 Temperature Dependance Studies of Fe1-XPtXAl Alloy

Iron aluminide is a metal alloy that possesses unique properties, including high strength and temperature resistance, making it suitable for applications in the aerospace and energy sectors. Previous studies show that the intermetallic compound FeAl is far more ductile at room temperature, with a melting point of 1473 K, limiting its use to intermediate temperature applications. Due to their capacity to create protective aluminium oxide layers, they combine low density and strong thermal conductivity with great oxidation resistance at high temperatures. Thermodynamic properties as a function of temperature were determined for the FeAl system doped with Pt. Focusing on the time-step, lattice expansion, and Gibbs free energies (∆G). The effect of temperature on the β2 FeAl and ternary Fe1-XPtXAl systems were investigated using the LAMMPS code to determine the lattice expansion and Gibbs free energies, while DMol3 was used to evaluate the binding energies. The mechanical properties were used to quantify the stability of these systems above 873 K. We considered systems that are stable and ductile ranging between 100 K – 3000 K. The FePtAl2 phase demonstrated that the lattice expanded exponentially with increasing temperature at 900 K. Among the predicted ternary Fe1-XPtXAl phases, FeAgAl2 and (FePt2Al3)2 showed spontaneous reaction, confirmed by a negative ∆G signifying thermodynamic stability. The Fe3PtAl4 system, which shows a decrease in c/a, indicates relatively greater expansion along the a-axis relative to the c-axis.
These systems indicate capacity to design well-adherent material for component coating in steel-IT for superior protection.

Speaker: Christy Graced

204 Temperature-Dependent Transport and Heat Capacity Behaviour of TiCl3 Medium

Understanding the thermodynamic stability of TiCl3 polymorphs is only one component of improving titanium reduction processes. Transport behaviour and thermal response under reactor-relevant conditions must also be understood. In this study, classical molecular dynamics simulations were employed to evaluate the temperature-dependent heat capacity and ionic mobility of the R-3 and P3112 polymorphs at 50 – 2000 K. It was observed that both polymorphs exhibit linear heat capacity behaviour indicating that the thermal response is largely governed by lattice vibrational contributions with no pronounced structural phase transitions. Despite this, a pronounced increase in ionic diffusivity is observed at high temperatures, indicating the onset of thermally activated transport mechanisms within the lattice. The R-3 polymorph displayed enhanced thermal stability at lower temperatures, while the P3112 structure exhibits comparatively higher ionic mobility at high temperatures, suggesting structure-dependent diffusion pathways. These findings highlight how crystallographic differences influence transport behaviour in TiCl3 and may contribute toward predictive, data-driven optimisation of industrial titanium production processes.

Speaker: Ms Andile Mazibuko (University of Limpopo)

205 Temporal shaping of supercontinuum pulses for improved axial resolution in optical coherence tomography

Optical coherence tomography (OCT) is an interferometric imaging technique used to image samples such as the human eye in 2 or 3 dimensions, with micrometer resolution and millimeter penetration depths. A broad bandwidth pulsed laser is scanned across the sample, and for each laser beam position a depth profile of the sample is obtained. These depth scans are stitched together to create a 2D or 3D image of the sample. However, the axial resolution in traditional OCT systems is limited by the bandwidth of the illumination source.
Recent work in super-resolving radar has shown how to improve the depth resolution of radar systems beyond the bandwidth limitations of the source by using temporally structured radar pulses. Using these concepts from radar, we will show how a temporal pulse shaping setup for laser pulses (using a 1-dimensional spatial light modulator) can be used to create temporally structured pulses that allow us to improve the axial resolution of our imaging setup beyond the limitations imposed by the bandwidth of the laser pulses. Simulations, practical aspects with regards to temporal pulse shaping and experimental results will be shown.

Speaker: Eugene Fouche (Stellenbosch University)

206 The chemistry of reverse impurity diffusion and food contamination during cooking in three-legged aluminum pots.

Artisanal aluminum pots, which are common in Latin America, Asia, and Africa, are commonly made by smelting scrap metal into cooking equipment. Particularly in rural regions where three-legged aluminum pots are often used, the chemical mechanisms involved in reverse impurity diffusion in aluminum cookware have significant implications for food safety. High temperatures and prolonged contact between the food and the pot's surface during cooking might facilitate the transfer of minute metallic contaminants from the aluminum alloy into the meal. The reverse diffusion process is affected by various factors including the composition of the alloy, surface oxidation, and the chemical characteristics of the food being cooked. For instance, foods that are salty or acidic might encourage leaching by weakening protective oxide layers, increasing the chance of contamination. This study evaluated the possible health concerns associated with prolonged exposure to trace metals and investigated the methods by which contaminants permeate in aluminum cookware, with a specific focus on rural area used aluminum three-legged pots. This controlled experimental based research was conducted using quantitative method through collecting secondary data on existing validated peered reviewed articles and literature. The results indicated that although aluminum cookware is cost-effective and long-lasting, its use poses risks regarding food contamination and potential long-term health issues. Tackling these problems necessitates both technological solutions like improved alloy mixtures and protective coatings and initiatives aimed at raising public awareness about safe cooking methods. In conclusion, the study highlights how crucial it is to strike a balance in cookware technologies for rural communities between cultural usefulness, cost, food safety, and sustainability.

Speaker: Ms Mamly Serero (Mineral Processing and Technology Research Centre, Department of Metallurgy, School of Mining, Metallurgy and Chemical Engineering, Faculty of Engineering and The Built Environment, University of Johannesburg,)

207 The Effect of Helium Implantation on Selenium Migration and Microstructure Evaluation of Silicon Carbide Before and After Annealing at Temperature higher than 1000 °C.

The performance of very high-temperature gas-cooled reactors (VHTRs), such as the pebble bed modular reactor (PBMR), relies on the effective retention of fission products (FPs) within the fuel. Silicon carbide (SiC), used as a primary diffusion barrier in nuclear fuel, is exposed to both FPs and helium (He) generated from alpha decay and transmutation processes. In this work, the influence of He on the migration behavior of selenium (Se) pre-implanted into SiC was investigated. Se ions were implanted into SiC at 200 keV to a fluence of 1×10¹⁶ ions/cm² at both room temperature (RT) and 500 °C. A subset of these samples was subsequently co-implanted with 17 keV He ions at a fluence of 1×10¹⁷ ions/cm² under the same temperature conditions. All samples were then annealed at 1100 °C for 5 hours under vacuum. Se implantation at RT resulted in complete amorphization of the SiC matrix, whereas implantation at 500 °C introduced damage without fully amorphizing the structure. Subsequent He implantation at RT led to the formation of He clusters (non-bubble features), associated with the aggregation of He atoms at defect sites within the damaged region, resulting in observable surface swelling. In contrast, He implantation at 500 °C promoted the formation of larger He bubbles with more swelling observed in the surface. Post-annealing at 1100 °C induced recrystallization in all samples; however, graphitization was observed in the co-implanted samples. Enhanced Se migration was detected in the co-implanted samples, indicating that He facilitates Se diffusion in SiC. Additionally, surface cavities were observed only in the co-implanted samples after annealing, likely due to surface exfoliation driven by He bubble evolution. These findings provide important insight into the role of He in modifying defect structures and enhancing fission product transport in SiC under reactor-relevant conditions

Speaker: Mr Sifiso Mthalane (PhysicsDepartment, University of Zululand, KwaDlangezwa, 3886, South Africa)

208 The gas-sensing properties of n-type and p-type metal fluorides on volatile organic compounds (VOCs) for agricultural management applications.

In this study, n-type and p-type semiconductor metal fluoride (M-F) gas sensors were synthesized using a straightforward and scalable co-precipitation method. Their structural, morphological, vibrational, and gas-sensing properties were investigated. X-ray diffraction (XRD) analysis confirmed the successful formation of well-crystallized n-type (ZrF₂, SnF₂, ZnF₂) and p-type (NiF₂, CrF₂, CoF₂) phases, each exhibiting distinct lattice parameters and crystallite sizes. The phase control was achieved through co-precipitation and calcination at 250ºC. Scanning electron microscopy (SEM) micrographs displayed porous morphologies for each material at the nanoparticle level. Energy dispersive spectroscopy (EDS) analysis verified the presence of the target M-F elements and demonstrated a homogeneous distribution of the constituents. Brunauer Emmett Teller (BET) surface area and porosity measurements correlated with the available active sites for the adsorption of volatile organic compounds (VOCs) and the diffusion kinetics in agricultural sensing application. Fourier transform infrared spectroscopy (FTIR) identified the surface functional groups, primarily consisting of M-F vibrations at wavenumbers below 800cm-1, thereby providing valuable insights into the chemical nature of the sensing and guiding future evaluations in the detection of agricultural VOCs.

Speaker: DINEO MOLEBATSI (UNISA)

209 The study of ZnO nanostructures for gas sensing applications

Nhlakanipho Khoza1,2 ,Puleng Biyela1 and Prince Mkwae1
1Department of Physics, University of Zululand, Private Bag X1001, KwaDlangezwa, 3886, South Africa
2Mangosuthu University of Technology, 511 Griffiths Mxenge Hwy, Umlazi, Durban, 4031, South Africa

200903453@stu.unizulu.ac.za

Abstract

In this study, zinc oxide (ZnO) nanostructures were synthesized on a silicon (Si) substrate via the hydrothermal method. The structural and morphological properties of the samples were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis confirmed the crystalline nature of ZnO, with a preferential growth orientation along the c-axis. The diffraction peaks observed at 2θ = 31.84°, 34.58°, 36.31°, 47.53°, 56.73°, and 62.94° correspond to the (100), (002), (101), (102), (110), and (103) planes, respectively, which are characteristic of the hexagonal wurtzite structure of ZnO (JCPDS No. 01-1136). SEM analysis revealed the formation of well-defined hexagonal nanoflower-like structures. Gas sensing measurements were carried out for various gases, and the sensor exhibited high selectivity toward ammonia (NH₃) gas at room temperature.

Keywords: ZnO, Si, Ammonia(NH3)

Speaker: NHLAKANIPHO WISEMAN KHOZA (UNIVERSITY OF ZULULAND)

210 Thermal Annealing and Swift Heavy Ion Effects on the Structural Evolution of Ag- and He-Implanted SiC

This study investigates the effects of helium (He) co-implantation and swift heavy ion (SHI) irradiation on the structural evolution and migration behaviour of silver (Ag) in polycrystalline silicon carbide (SiC), followed by thermal annealing. SiC samples were first implanted with 360 keV Ag ions at room temperature to a fluence of 2 × 10¹⁶ cm⁻², producing significant amorphization. A subset of these samples was subsequently co-implanted with 17 keV He ions at 500 °C to a fluence of 1 × 10¹⁷ cm⁻², inducing partial recrystallization and forming helium nanobubbles. All samples were then irradiated with 167 MeV Xe ions at room temperature to a fluence of 1 × 10¹⁴ cm⁻², followed by annealing at 1000 °C for 5 hours. SHI irradiation further modified the microstructure. Ag-only samples exhibited partial recrystallization, indicating effective defect recovery, whereas He co-implanted samples showed more limited recovery, demonstrating that helium suppresses defect annealing under irradiation. He implantation also generated surface whiskers, which decreased in height after irradiation, suggesting partial surface healing. No measurable Ag migration occurred during He co-implantation or SHI irradiation. After annealing, helium release, enhanced atomic mobility, and cavity shrinkage produced a denser population of smaller, more uniform cavities that act as effective Ag trapping sites. In He co-implanted samples, bubble growth and coalescence influenced recrystallization kinetics, serving both as defect sinks and barriers to full recovery. Ag in both sample types shifted toward the SiC bulk, likely driven by stress fields formed during annealing. While Ag loss was negligible in Ag-only samples, He co-implanted samples showed noticeable Ag loss, and surface modifications associated with helium release became more pronounced. These results underscore helium’s significant role in governing defect evolution, cavity development, silver behavior, and the thermal stability of SiC, with important implications for fission-product retention and the performance of TRISO fuel.

Speaker: Rifumo Chauke (University of Pretoria)

211 Thermodynamic, structural, mechanical and electronic effects of fluorine doping in LiNiO2: A cluster expansion study

While Ni-rich layered cathode materials like are highly sought after for next-generation lithium-ion batteries due to their high capacity and cost-effectiveness, their inherent structural instability remains a significant barrier to practical application. To address this, the present work systematically investigates the impact of fluorine doping on the phase stability and electronic properties of using a cluster expansion approach. This model, validated by a low cross-validation score of less than 5 meV/atom, predicts 18 new configurations, five of which lie on the binary ground-state convex hull. Among these, was identified as the most stable configuration, though formation energy analysis suggests that even lower fluorine concentrations, such as, are sufficient to enhance thermodynamic stability.
Beyond thermodynamics, the introduction of fluorine significantly improves the material's mechanical integrity, as evidenced by increased bulk, shear, and Young’s moduli compared to the pristine structure. Furthermore, density of states calculations reveals a narrowed bandgap upon doping, which implies a boost in electronic conductivity. Collectively, these findings highlight fluorine substitution as an effective strategy for stabilizing and optimizing the performance of Ni-rich cathodes.

Keywords: Lithium-ion batteries, Fluorine doping, surface free energy, Cluster expansion,

Speaker: Mmeshi Hiine (UL)

212 Thermoelectric properties of Tungsten diselenide (WSe2), a density functional theory study

Tungsten diselenide (WSe₂), a layered transition metal dichalcogenide, has attracted significant attention due to its promising electronic and thermoelectric properties. In this study, the thermoelectric performance of WSe₂ is systematically investigated using first-principles calculations based on density functional theory (DFT) combined with semi-classical Boltzmann transport theory. The electronic band structure reveals that WSe₂ is a semiconductor with an indirect band gap, which plays a crucial role in determining its transport properties. The results indicate that WSe₂ exhibits a high Seebeck coefficient, attributed to its sharp density of states near the Fermi level. Furthermore, its relatively low lattice thermal conductivity, enhances its thermoelectric efficiency. The calculated figure of merit (ZT) suggests that WSe₂ has potential as an efficient thermoelectric material, particularly at elevated temperatures. These findings highlight the suitability of WSe₂ for energy harvesting applications and provide insights into the design of high-performance thermoelectric materials based on two-dimensional systems.

Speaker: Dr Moshibudi Ramoshaba (UNIVERSITY OF LIMPOPO)

213 Turing instability and pattern formation in a confined reaction diffusion field

Reaction diffusion systems can spontaneously develop stable spatial
concentration patterns when two coupled chemical species diffuse at
sufficiently different rates, a symmetry-breaking phenomenon known
as the Turing instability. The onset of this instability depends
critically on the ratio of inhibitor to activator diffusivities,
$d = D_v/D_u$, and on the reaction kinetics, both of which are
sensitive to ambient thermodynamic conditions. We propose a
computational framework for modelling this instability in a confined
geometry, with thermodynamic boundary conditions parameterised across
a two-dimensional space of temperature $T$ and relative humidity
$\phi$. Linear stability analysis will identify the Turing threshold
as a function of $d$ and $T$, and numerical integration of the
coupled field equations will yield spatial concentration profiles
and field maps across the instability boundary.

Speaker: Edward Nkadimeng (University of the Witwatersrand)

214 Understanding the Electronic Structure and Topological States of Bi₂Se₃ Material: Effects of SOC, van der Waal Interactions, and Hybrid Functional Corrections

Bi₂Se₃ is a three-dimensional topological material with distinct electronic properties, characterized by an insulating bulk and conducting surface states. These surface states are protected by time-reversal symmetry, making this material a promising candidate for quantum computing applications. Understanding the topological state of Bi₂Se₃ at the atomic level, and its ability to mitigate decoherence is crucial, as it may host the required Majorana states. In this study, the electronic state configurations of bulk Bi₂Se₃ were investigated using first-principles calculations within the framework of Density Functional Theory. It is observed that the generalized gradient approximation with the Perdew-Burke-Ernzerhof functional underestimates the band gap (~0.12 eV), whereas the inclusion of spin-orbit coupling (SOC) and van der Waals (vdW) corrections increases it to ~0.29 eV. This highlights the critical role of relativistic effects associated with heavy elements such as bismuth, as well as the weak interlayer coupling inherent to this layered material. Further corrections, although computationally expensive, were performed using the HSE + SOC + vdW approach, yielding a band gap closer to the experimental value of approximately ~0.32 eV. The surface state nature of the material was studied by varying the number of quantized layers (QLs) from 1 to 5. Dirac cone electronic states emerge at the Γ-point for 3-5 QLs, confirming the topological nature of the material. The non-trivial topology of Bi₂Se₃ was further verified through the calculation of Z₂ topological invariants using both the parity eigenvalue method at time-reversal invariant momenta and the Wilson loop formalism. The consistency between these methods demonstrates the robustness of the topological phase. These findings emphasize the crucial interplay among SOC, vdW interactions, and hybrid functional corrections in determining the electronic properties of Bi₂Se₃, and they lay the groundwork for its integration with superconducting systems, with potential applications in topological quantum computing.

Speaker: Beauty Masolo (University of Pretoria)

215 Variability of palladium distribution in chromitite and pegmatoid layers at the Eastern limb of the Bushveld Igneous Complex and related value recovery processing challenges.

Palladium (Pd) metal in the UG-2 orebody of the Eastern Bushveld Igneous Complex presents recovery challenges. Ore deposit used for the study contains significant concentration of this metal, which renders its recovery critical for the overall PGE recovery. Conventional recovery techniques employed have proven to have limitations in terms of optimising Pd-bearing minerals recovery. Although reagents suites being used proved to attain good recoveries compared to the industrial counterparts, further improvements have the potential to improve profit margins. Commodity price volatility presents opportunities to maximize revenue generation in times of higher prices, placing the organisation in a better financial position to finance both “stay-in-business” and expansion projects. A study was conducted to find Pd-bearing minerals recovery improvement opportunities in the backdrop of current limitations. The study involved the understanding of minerals contained in samples taken from the orebody and sample from one of the plant process streams, their modal occurrence and liberation after being subjected to grinding process. Various reagents were screened to establish potential better combinations. Ore pre-treatment technique in the form of ore pre-heating using microwave before milling process was explored, only as a preliminary test. A CMC depressant with lower degree of substitution showed potential to improve overall PGM (4E) recovery by more than 2%. For a larger scale operation, recovery improvement of any magnitude has positive impact on revenue generation. Although statistically not a significant difference between the two means, this depressant proved to produce consistent results. Low variance amongst individual recovery values compared to the standard depressant suggests the potential to consistently produce improved recoveries. Pre-treating the ore before milling stage showed potential to improve both Pd-bearing minerals and the overall 6E recovery. Microwave radiation proved to positively alter the physical properties of the ore, improving its grindability. Palladium splits in the concentrate have also been improved significantly through this process. Results obtained from the study have shown great potential to improve Pd-bearing minerals recovery without compromising recovery of other platinum group metals. Further in-depth studies on the pre-treatment techniques was recommended and, if successfully confirmed, the industry stands to benefit from its implementation to larger-scale operations.

Speaker: Marcus Nkhumeleni (None)

216 X-ray computed tomography analysis of porosity and cracks in laser-powder bed fusion of NiTi using deep-learning

The imaging and quantitative analysis of defects such as porosity and cracks are essential steps in optimizing the laser-powder bed fusion (L-PBF) process parameters for a given material. Most studies to date rely on optical microscopy, which provides only two-dimensional surface cross-sections. X-ray computed tomography (XCT) offers added advantages, including three-dimensional information and access to multiple cross-sectional views. However, XCT imaging of pores and cracks remains underexplored, particularly during parameter optimization for the L-PBF processing of NiTi alloys. XCT images require segmentation in order to quantify features in 3D, but this task is often complicated by limited resolution and image artifacts. Here, we develop and apply a four-class segmentation model based on a 2.5D U-Net neural network architecture to classify and extract cracks and pore defects. This approach reveals the true 3D morphology of the defects and accurately distinguishes cracks from pores, enabling their quantification. We perform a quantitative analysis to investigate how remelting of in situ alloyed NiTi and variations in laser energy density affect defect formation across a series of 52 NiTi samples fabricated by L-PBF. Furthermore, the obtained XCT cross-sections and corresponding segmentations illustrate the influence of scan vector rotation between layers compared to a no-rotation scanning strategy, offering an internal view of cracks, pores, lack of fusion, and balling effects. Our findings indicate that samples produced with a 45° rotation of scan vectors are prone to balling and delamination, whereas samples without scan rotation exhibit high levels of cracking. Finally, compositional analysis using scanning electron microscope and energy dispersive spectroscopy suggests that a substantial amount (99.42%) of the detected cracks are located at the contours, with mean penetration lengths of 0.18 mm for no rotation and 0.11 mm for scan vector rotation.

Speaker: Tebogo Ledwaba (Stellenbosch University)

217 X-ray–Based Characterization of Fossilized Bone and Wood: Insights from XRF and XRD

Paleontological fossils serve as invaluable archives of Earth’s history, preserving direct evidence of past life and environmental conditions. However, conventional analytical techniques often risk damaging these inherently fragile specimens. In this study, non-destructive X-ray–based methods were employed to investigate fossilized bone and wood specimens. X-ray fluorescence (XRF) was used to determine elemental composition, while X-ray powder diffraction (XRD) provides information on the crystal structure and mineral phases present in the specimen. Measurements were conducted at the University of Venda environmental laboratory in South Africa. The combined application of these techniques enables a comprehensive characterization of fossil materials without compromising their structural integrity. Preliminary results of the study show that petrified wood is no longer wood chemically due to the high presence of silicon, while the fossilized bone is chemically still related to its original composition due to high contents of calcium and phosphorus.

Keywords: Fossils, XRF, XRD, non-destructive analysis, paleontology

Speaker: Fortune Nndwamato

218 ZnGa2O4 microrods for optoelectronic applications: Linking structure and optical properties

The spinel-structured zinc gallate (ZnGa2O4) has received a lot of interest lately due to its broad bandgap, strong ultraviolet (UV) transmittance, and stability in vacuum. As a member of the transparent metal oxide semiconductor family, ZnGa2O4 is a potential phosphor due to its thermal and chemical stability as well as its blue emission when exposed to electrons with low voltage or UV radiation. The development of high-performance optoelectronic devices, particularly solar-blind photodetectors, requires materials with high thermal stability and wide bandgaps. In this work, ZnGa2O4 microrods were synthesized via a traditional solid-state reaction to investigate the correlation between their structural evolution and optical performance. The X-ray diffraction (XRD) analysis showed the successful formation of the ZnGa2O4 single phase, with the sharp and intense peaks confirming the high purity and crystallinity, with a crystal size of 61.16 nm and lattice constant of 8.326 Å. Nottably, no impurity peaks were detected, which indicates the superiority of this synthesis method in comparison with synthesis methods involving solutions. On the other hand, scanning electron microscope (SEM) revealed irregular rod-like shapes with various sizes from 2 to 10 µm as a result of the reaction time and annealing temperature. This could be as a result of anisotropic grain growth in the process of the reaction. Optical characterization using diffuse reflectance spectroscopy (DRS) followed by Tauc plot analysis determined a direct optical bandgap of 4.6 eV. The broad bandgap also makes sure that the material is not affected by the visible region of the solar spectrum, i.e., the material is intrinsically solar blind, thus enabling detection of the deep UV spectrum without interference from the visible solar spectrum. A second absorption peak found between 300 and 380 nm can be attributed to oxygen vacancies in the lattice, possibly contributing to persistent photoconductivity or increased sensitivity. The findings suggest that the high aspect ratio structure and the broad bandgap of the ZnGa2O4 microrods make them excellent candidates for photodetectors, offering efficient carrier transport and minimal dark current effects.

Speaker: Thabang Theka

Wednesday 8 July

Registration

Plenary: (WiPiSA) Prof Lynndle Square

219 Physics Without Boundaries: Reimagining Physics Through Research, Education and Leadership in the Fourth Industrial Revolution

What does a physicist look like in the Fourth Industrial Revolution? While advances in computational modelling, artificial intelligence, advanced materials, sensing technologies, and data-driven discovery are transforming the discipline, the future of physics will be determined not only by technological innovation but also by our ability to connect research, education, industry, and society while building an inclusive and sustainable community of physicists.

This plenary explores how physics can transcend traditional disciplinary boundaries through examples drawn from computational materials research for Low Earth Orbit, physics education innovation, and industry-linked student projects investigating cricket ball dynamics and acoustic monitoring systems. Together, these illustrate how authentic, interdisciplinary experiences prepare students for the evolving landscape of the Fourth Industrial Revolution while demonstrating the versatility and societal relevance of physics.

Beyond research, the talk reflects on the importance of intentionally creating spaces where people can encounter physics, develop confidence and build professional networks. Through participation in Women in Physics in South Africa (WiPiSA) networking initiatives, contribution to the WiPiSA
20th Anniversary Roundtable, public engagement through radio discussions, and the development of the Meet a Physicist High Tea for female high school learners, I explore how conversations, mentorship, visibility and collaboration can broaden participation in physics and strengthen the
discipline for future generations.

Rather than viewing research, teaching, outreach and leadership as separate responsibilities, I argue that they are interconnected components of a single ecosystem. Building a sustainable and inclusive future for physics requires not only scientific excellence, but also intentional mentorship, collaboration and the creation of opportunities for others to contribute. Ultimately, the physicist of the future will be defined not only by the knowledge they generate, but by the communities they cultivate and the pathways they create for those who follow.

Speaker: Prof. Lynndle Square (North West University)

09:25 Buffer

Applied Physics

Convener: Ernest van Dyk (NMU)

220 Improved Field Homogeneity in Finite-Length Sparse Permanent Magnet Arrays for Low-Field MRI

Cylindrical arrays of permanent magnets are being increasingly used to generate the main magnetic field in low-field Magnetic Resonance Imaging (MRI). A class of Halbach arrays, these arrangements of permanent magnets result in increased magnetic flux density within the cylinder, and reduced flux density outside. Sparse Halbach arrays can produce a field strength suitable for low-field MRI, but suffer from field inhomogeneities introduced by approximating the continuous Halbach solution with a finite length bore of discrete magnets. At the dimensions required for practical medical imaging truncation-induced inhomogeneity is a dominant factor affecting image quality.

Correcting for truncation-induced inhomogeneity has typically been restricted to in-plane magnet orientation adjustments. Allowing magnets to be orientated with components down the bore of the cylinder is under-explored.
Here we present the results of computationally optimising magnet orientations to improve field homogeneity in comparison to the conventional Halbach design. Allowing magnets free parameterised orientation enables a computed improvement to field homogeneity of up to 90% at the expense of a loss in field strength of 17%.

A physical demonstration device consisting of 187 cubic N42 magnets was constructed using the optimised design, showing improvements to homogeneity of 73%, providing a benchmark for realistic expectations of field homogeneity when physical limitations such as precision magnet placement and magnet variability are taken into account.
The results show that substantial improvements to field homogeneity can be expected in sparse Halbach arrays when optimised magnet orientations are used, providing a physical realisation of methods to construct such arrays.

Speaker: David Roth (MeASURe, Department of Physics, University of Cape Town)

107_David_Roth.pdf

221 A Geant4 Study of FLASH Proton Therapy Mechanisms

Ultra-high dose rate (UHDR), mostly referred to as FLASH radiotherapy, has emerged as a promising treatment modality capable of reducing normal tissue toxicity in a cancerous tumour. However, the underlying physical and radiochemical mechanisms of this FLASH radiotherapy remain incompletely understood. In this study, high-dose-rate proton irradiation was investigated using Monte Carlo simulations within the Geant4 framework to examine energy deposition in liquid water to understand the physical and radiochemical mechanisms of FLASH proton radiotherapy. At the macroscopic level, depth dose distributions, Bragg peak characteristics, and linear energy transfer (LET) variations are quantified for clinically relevant proton energies. At the microscopic level, track-structure simulations were used to model particle interactions at nanometric scales, which allowed for the analysis of ionisation clustering and radial dose distributions in both the entrance region and near the Bragg peak. By comparing these regions, the evolution of the proton track structure relative to depth was characterised. The relationship between macroscopic dose metrics and microscopic energy deposition was then examined to assess implications for early-stage radiochemical processes, including water radiolysis. Particular attention was given to conditions relevant to FLASH irradiation, where high instantaneous dose rates may influence energy deposition and subsequent chemical interactions. This work provides a simulation-based framework linking physical dose deposition to underlying microscopic processes.

Speaker: Marry Thekhwe (University of Cape Town)

173_Marry_Thekhwe.pdf

222 Geant4 modelling of the beam delivery of a Proteus ONE system for the UCT Proton Therapy Initiative

A team based at the University of Cape Town is well advanced with a project which will return a proton therapy centre to Cape Town, South Africa [1]. The new facility will serve as both a national facility for South Africa and provide access to other countries in the sub-Saharan region. The city of Cape Town offers geographic and technical advantages for the siting of the new centre, which will also benefit from the very latest technological advances in proton therapy [2,3]. In this present work, to support this project, a Monte Carlo model of an IBA Proteus ONE Pencil Beam System (PBS) delivery nozzle has been developed in Geant4.
An appropriate simulation environment, physics models and parameters were selected to produce accurate and efficient simulations [4]. The accuracy of these simulations was validated by obtaining the Bragg Peak for a proton beam energy of 230 MeV in a water phantom, without any devices in the beamline [3]. A modelling method was then developed to simulate a pencil beam delivery system [5]. A degrader was initially added to the beamline to replicate the Proteus ONE PBS beamline technology, before the addition of the bending magnets, scanning magnets, and aperture [6]. Various degrader materials were also included.
The University of Florida Health Proton Therapy Institute (UFHPTI) provided Monte Carlo reference data and experimental data with Integral Depth Dose (IDD) in a phantom box and lateral beam profiles in an air target box, which are compared to the Geant4 results.
The validated Geant4 model accurately reproduces the dosimetric characteristics of the Proteus ONE system and could serve as a foundational tool for secondary dose verification, shielding calculations, and future clinical treatment planning studies [2,6].
References:
1. University of Cape Town (2025) UCT Proton Therapy Initiative. Available at: https://www.news.uct.ac.za/ (Accessed: May 2025).
2. Kraan, A.C. and Del Guerra, A. (2024) ‘Technological developments and future perspectives in particle therapy: A topical review’, IEEE Transactions on Radiation and Plasma Medical Sciences, 8(5), pp. 453–481. https://doi.org/10.1109/TRPMS.2024.3372189
3. Newhauser, W.D. and Zhang, R. (2015) ‘Topical review: the physics of proton therapy’, Physics in Medicine and Biology, 60(8), pp. R155–R209. https://doi.org/10.1088/0031-9155/60/8/R155
4. Arce, P., et al. (2021) ‘Report on G4 Med, a Geant4 benchmarking system for medical physics applications developed by the Geant4 Medical Simulation Benchmarking Group’, Medical Physics, 48(1), pp. 19–56. https://doi.org/10.1002/mp.14503
5. Smith, A., Gillin, M., Bues, M., Zhu, X.R., Suzuki, K., Mohan, R., et al. (2009) ‘The M.D. Anderson proton therapy system’, Medical Physics, 36(9), pp. 4068–4083. https://doi.org/10.1118/1.3187229
6. Bäumer, C., Plaude, S., Khalil, D.A., et al. (2021) ‘Clinical implementation of proton therapy using pencil beam scanning delivery combined with static apertures’, Frontiers in Oncology, 11, 599018. https://doi.org/10.3389/fonc.2021.599018

Speaker: Moses Gororo (University of Cape Town)

226_Moses_Gororo.pdf

Astrophysics & Space Science: Astrophysics: Session 4

223 Bayesian component separation and power spectrum estimation for 21 cm intensity mapping data cubes

Foreground contamination remains one of the central challenges in 21 cm intensity mapping, and as experiments become more sensitive, our analysis methods need to keep pace. I'll present a Bayesian forward-modelling framework for jointly separating foregrounds and the 21 cm signal in single-dish data cubes, using Gibbs sampling and Gaussian Constrained Realisations (GCR).
The key challenge we address is scalability: our model has over 2 million free parameters, yet we can draw samples from the full joint posterior in under 30 seconds per iteration on a single CPU core. This is made tractable by ensuring each component — foreground PCA amplitudes, Hi Fourier modes, and their covariances — has a Gaussian conditional distribution, allowing us to solve for the posterior peak directly rather than evaluating an expensive likelihood function.
I'll show results on simulated MeerKLASS-like data, demonstrating recovery of the Hi power spectrum to within 2σ, comparable to the standard transfer function correction approach. Crucially, the framework also handles RFI flagging naturally: rather than requiring explicit inpainting, the GCR steps fill flagged channels with statistically consistent signal realisations as a byproduct of the sampling. We plan to extend this to real MeerKLASS data, including per-antenna systematics and beam effects.

Speaker: Dr Geoff Murphy (University of the Western Cape)

35_Geoff_Murphy.pdf

224 Exoplanet Discoveries using Transit Method

The discovery of exoplanets has revolutionized modern Astronomy and the way we understand planetary motion and our planetary system. The transit method as a technique, used to look for extrasolar planets, is one of the most effective techniques in detecting exoplanets. This study focuses on the principles, applications and challenges of the transit method in identifying exoplanets. Moreover, it focuses on exoplanet discoveries done by using this technique which measures the decrease in brightness of the host star as a planet passes in front of it. We examined our current state of knowledge in exoplanet detection using multiple methods but mainly focusing on transit method and highlighting the advantages of using it. The goal of this research is to investigate transit method and detect exoplanets while also examining its advantages and limitations. Furthermore, the study explores the fundamentals of telescope operations. The examination reveals that transit method has been very useful in detecting thousands of exoplanets including potential habitable environments. The approach, in this study, is based on established methods, the Las Cumbres Observatory portal was used to request observations. We used Astrosource to calibrate the images and plot light curves for the three targets. The light curves for the three targets (WASP 160 Bb, WASP 77 Ab and LTT 9779 b) showed the dip in their intensity. The analysis we did to calculate the radii for the exoplanets revealed that WASP 160 Bb has a radius of 1.25 RJ, LTT9779 b has 0.397 RJ and 1.40 RJ for WASP 77 Ab. Comparing the results to the previously published radii of the three exoplanets, our result showed a percentage error of 4.7%, 6% and 15,7% respectively. This might be due to short observation time as well as some external factors. We also discussed the role of current and future missions which is Transiting Exoplanet Survey Satellite(TESS), in improving our knowledge and understanding of Exoplanetary system.

Speaker: Lungelo Chabaku (University of zululand)

Astrophysics & Space Science: Space Science: Session 4

Convener: John Bosco Habarulema (South African National Space Agency)

225 Investigating the Impact of Auroral arcs on ionospheric electric fields, thermospheric Neutral Winds, and Joule Heating

This study investigates the mesoscale interaction between thermospheric neutral winds and electric fields in the F-region ionosphere in the presence of an auroral arc using data from the SuperDARN radar network and a Scanning Doppler Imager (SDI) at Kevo, northern Finland (69.76° N, 27.01° E). Observed perturbed wind patterns are attributed to enhanced ion drag caused by increased plasma density and localised electric fields associated with the auroral arc at ~240 km altitude. SuperDARN radar data are used to quantify the electric fields around the auroral arcs, which are then applied to estimate the enhanced Joule heating. This study provides insights into how auroral energy input drives mesoscale neutral wind dynamics and thermospheric heating at high latitudes.

Speaker: Siyanda Hlathi (University of KwaZulu-Natal and SANSA)

375_Siyanda_Hlathi.pptx

226 Modelling Earth’s magnetic field over the South Atlantic Anomaly region using Swarm satellite and ground-based data

This study investigates geomagnetic field variations over the South Atlantic Anomaly (SAA) using three regional models developed with the Revised Spherical Cap Harmonic Analysis (R-SCHA). The combined models cover a broad region from 90°W to 35°E in longitude and from 5°S to 49°S in latitude. To effectively capture spatial variability, the study area is divided into three overlapping spherical caps representing the western (South America), central (South Atlantic Ocean), and eastern (southern Africa) sectors. Each region is modelled using a 35° semi-aperture cap centred respectively at 71°W, 29°W, and 14°E, all along 27°S latitude. Preliminary results will be presented, highlighting regions within the SAA experiencing the most rapid magnetic field changes and providing insight into the ongoing restructuring of the anomaly. The analysis will further quantify the contributions of individual magnetic field components to the observed weakening. Particular attention will be given to the development of a second intensity minimum within the SAA. The study explores whether the anomaly will continue to expand, fragment into multiple minima, reorganize, or eventually stabilize.

Speaker: Mr Sanele Lionel Khanyile (South African National Space Agency and Rhodes University)

Sanele_Lionel_Khanyile_SAIP2026.pdf

227 Atmospheric Gravity Waves/Traveling Ionospheric Disturbances

Traveling ionospheric disturbances (TIDs) are signatures of Atmospheric Gravity Waves (AGWs) in the ionosphere. They can be studied using different ionospheric parameters such as plasma temperature, electron density and altitudes of respective ionospheric layers.
Distinguishing effects of TIDs on the overall system behaviour requires estimation of background conditions. This presentation will discuss different methodologies used in background estimation when studying TIDs based on Global Navigation Satellite Systems (GNSS) data. Methods including (but not limited to); polynomial fitting, running averages and
 medians will be investigated to determine the appropriate detrending method that provides clear traces of TIDs from GNSS data.

Speaker: Mr Hudson Mims (University of Michigan and South African National Space Agency)

439_Hudson_Mims.pptx

Nuclear, Particle and Radiation Physics -1: Session 1

Convener: Livhuwani Masevhe (University of Johannesburg)

228 Effects of Re and B on the low-energy photon shielding properties of Re2MnBO6 (Re = La, Sm, and Nd and B = Co and Ni)

Research into new, cost-effective photon-shielding materials is on the rise amid rising electromagnetic pollution. Double perovskite oxides are possible candidates for low-energy photon shielding due to their flexible structure. In this work, we report the effects of substituting the lanthanide site and B site on the effectiveness of the material in shielding low-energy photons. At energies below 6.54 eV, lanthanum-based oxides have mass attenuation coefficient (MAC) values that are more than 1.5 times those of the neodymium and samarium-based oxides. But at energies above 13.8 eV, the samarium-based oxides start to dominate in terms of mass attenuation coefficients. The samarium-based oxides have the lowest half-value layer (HVL) values, and lanthanum-based oxides have the highest values. In terms of the effective atomic numbers (Zeff), samarium-based oxides have the highest values. The composite scores calculated show that the samarium-based oxides have the best low-energy photon shielding properties. Cobalt-based oxides outperformed their nickel-based counterparts.

Speaker: Tinashe Dhliwayo (University of Johannesburg)

229 PRODUCTION LU-177 BY REGENERATION OF THE YB TARGET FOR NUCLEAR MEDICINE AT THE RESEARCH REACTOR IRT-T

The radioisotope, Lu-177 is emerging as an important radioisotope for treatment of the cancer such as breast, prostate, colon, and brain, with a longer half-life of 6.65 days. The Lu-177 can be produced by indirect Yb-176(n,γ) Yb-177→Lu-177 route which requires a chemical separation of Lu-177 from the target Yb-176 target atoms.The method of separation of Yb and Lu were used via Yb-176(n,γ) Yb-177→Lu-177 to produce no-carrier-added Lu-177. For this process, 10 mg of non-radioactive Yb2O3 and 10 µg of Lu2O3 were used in which radioactive labels of Yb and Lu were added to induce radioactivity (ratio Lu:Yb = 1:1000). Cementation process was performed for five similar experiments (three cementations in each experiment). Yb2O3 target material was translated into chloride, mixed twice with hydrochloric acid (HCl), sodium acetate (CH3COONa) and the selective extraction of Yb by sodium amalgam Na (Hg). HPGe detector GX1018 coupled with a multichannel analyser (MCA) (Canberra) was calibrated with Eu-152 source for analysis of Lu-177 in the presence of Yb. Gamma-ray peak of 208 keV for Lu-177 and 198 keV for Yb-169 were detected in the system. The activity of the third cementation process of radioactive Yb and Lu were found to be 2.06±0.05 Bq and 96.97±4.16 Bq which corresponds to 1.4 mg and 7.6 μg, respectively. After the cementation process, Yb target was extracted by distillation process. From the results obtained, the amount of the ytterbium was removed from the aqueous solution and the NCA Lu-177 was isolated in the solution. After the cementation process, high amount of Yb was observed. In conclusion, it is necessary to carry out optimization for better separation of Yb and Lu.

Speaker: Veronica Kgabisang Gouws (Tomsk Polytechnic University)

230 Structural and Shielding Properties of Er₂Os₂O₇ Pyrochlore Material

The advancement of time, which comes along with the evolution in technology, necessitates a targeted research focus for various applications. In material science and the use of materials for various applications, radiation and shielding are critical aspects to deal with, especially for the health of the users. Attenuation of harmful electromagnetic radiation is of great importance. In this work, we report the results of the investigation of the radiation shielding properties of a lead-free, rare-earth-based, Er₂Os₂O₇ compound. A well-characterized powdered sample was investigated through NIST XCOM and Phy-X for radiation shielding properties. The mass attenuation coefficient (MAC) results ranged from 3.398 cm²/g at 0.1 MeV to 0.042 cm²/g at 10 MeV, indicating that Er₂Os₂O₇ is a better photon shield at low energies. The HVL and TVL values further show that Er₂Os₂O₇ has better photon shielding capabilities when compared to ceramic glasses, lanthanide-based ceramics, and germanate glasses. However, the MAC and LAC values further confirmed that this material is not a good neutron shielding material.

Speaker: Prof. Buyisiwe Sondezi (University of Johannesburg)

Nuclear, Particle and Radiation Physics -2: Session-4

Convener: Dr Arnab Laha (University of the Witwatersrand)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

231 Enhancing sensitivity to tWZ production in the four-lepton channel with the ATLAS detector using machine learning

The production of a top quark in association with a Z and W boson (tWZ) is a rare Standard Model process that provides a sensitive probe of top quark electroweak couplings and constitutes an important background to searches for physics beyond the Standard Model. This contribution presents a study of the sensitivity to tWZ production in the four-lepton (4ℓ) final state with the ATLAS detector. The 4ℓ channel offers a clean experimental signature, but suffers from limited statistics and significant background contributions, particularly from processes such as ttZ.

Using simulated proton–proton collision samples corresponding to LHC Run 2 conditions, a comparison is performed between a traditional analysis strategy based on kinematic observables and a multivariate approach employing a deep neural network trained to distinguish signal from background. The performance of the two approaches is evaluated using the Asimov estimate of the expected signal significance in a statistical-only framework. A substantial improvement in expected sensitivity is observed when using the machine learning–based discriminant, highlighting the power of exploiting multidimensional correlations in complex final states.

The analysis is being extended to incorporate Run 3 data and a comprehensive set of systematic uncertainties, with the goal of establishing a robust measurement of the tWZ process.

Speaker: Kevin Barends (University of Cape Town)

216_Kevin_Barends.pptx

232 3D Parameterised Reconstruction of the PAUL Underground Overburden from Cosmic Muons

The Paarl Africa Underground Laboratory (PAUL), which will be located in the Huguenot Tunnel under the Du Toitskloof Mountains near Cape Town, South Africa, is Africa's first underground facility specifically for rare-event physics. The site has about 800 m of rock overburden, which protects it from cosmic rays and makes it possible to look for dark matter. Previous GEANT4 studies and open-sky muon telescope measurements have characterized the forward muon flux; however,
the inverse problem of reconstructing overburden geometry from muon observables is still underexplored. This work presents a reconstruction framework built on a parameterised three dimensional model of the tunnel and surrounding mountain, implemented in OpenSCAD and coupled to GEANT4 atmospheric-muon transport simulations. Angular distributions, spatial track-density maps, and path-length spectra are used as indirect probes of the overburden structure. Sensitivity matrices quantify how these observables respond to variations in geometric and density parameters, and a Python-based inversion framework is developed to estimate overburden properties from simulated muon data. The results contribute directly to background characterisation for PAUL and complement ongoing experimental muography efforts inside the Huguenot Tunnel.

Speaker: Nkosiphendule Njara

Photonics: Microscopy & imaging

Convener: Saturnin Ombinda-Lemboumba (CSIR)

233 Temporal shaping of supercontinuum pulses for improved axial resolution in optical coherence tomography

Optical coherence tomography (OCT) is an interferometric imaging technique used to image samples such as the human eye in 2 or 3 dimensions, with micrometer resolution and millimeter penetration depths. A broad bandwidth pulsed laser is scanned across the sample, and for each laser beam position a depth profile of the sample is obtained. These depth scans are stitched together to create a 2D or 3D image of the sample. However, the axial resolution in traditional OCT systems is limited by the bandwidth of the illumination source.
Recent work in super-resolving radar has shown how to improve the depth resolution of radar systems beyond the bandwidth limitations of the source by using temporally structured radar pulses. Using these concepts from radar, we will show how a temporal pulse shaping setup for laser pulses (using a 1-dimensional spatial light modulator) can be used to create temporally structured pulses that allow us to improve the axial resolution of our imaging setup beyond the limitations imposed by the bandwidth of the laser pulses. Simulations, practical aspects with regards to temporal pulse shaping and experimental results will be shown.

Speaker: Eugene Fouche (Stellenbosch University)

54-Eugene-Fouche.pptx

234 Single-Shot Optical Quadrature Microscopy Integrated With Optical Tweezing for Live-Cell Quantitative Phase Imaging

Quantitative Phase Imaging (QPI) enables non-invasive, label-free measurement of optical path length variations within transparent samples, facilitating three-dimensional reconstruction of sample structure and dynamics from two-dimensional microscopy images.

Building on our earlier development and demonstration of Single-Shot Optical Quadrature Microscopy (SSOQM), a polarization-based implementation of Phase Shifting Interferometry (PSI) that uses a polarization-sensitive camera for simultaneous quadrature phase detection, we now demonstrate the integration of SSOQM within an optical tweezing platform. This configuration allows for real-time phase imaging and manipulation of microscopic specimens. Using trapped yeast cells as an example, we present quantitative phase maps that showcase refractive index variations and morphological features within individual cells. Additionally, we report progress toward dynamic, video-rate QPI measurements, enabling tracking of morphological evolution of samples over time.

In this talk, we present the system design and calibration strategy that enables robust single-shot quantitative phase imaging and demonstrate its application to trapped yeast cells, including preliminary video-based measurements, highlighting the potential of the integrated SSOQM–tweezing platform for dynamic, label-free investigation of live-cell dynamics and morphology.

Speaker: Calvin Groenewald (Stellenbosch University)

189_Calvin_Groenewald.pptx

235 Holographically shaped optical fields for manipulating complex biological specimens

Optical tweezers have long been used as a tool for manipulating micro- and nanoscale objects, with applications in biological systems and modelling colloidal crystal structures. Recently, optical tweezers have been incorporated into microfluidic chips for isolating single cells and force measurements. In this talk, we present a single-cell monitoring platform which uses holographic optical tweezers (HOT) to manipulate multiple cells simultaneously or biological specimens with irregular shapes within a microfluidic chip. Examples include fibrinogen microclots linked to long-covid symptoms or cardio myoblast spheroids. We discuss the trap generation methodology for irregular shapes, which traditionally cannot be trapped using single-beam geometries. Finally, we outline different imaging modalities integrated with the HOT system that we use for monitoring cellular properties under changing extracellular environments. This system could be used as a drug screening platform for informing dosage protocols for individual patients.

Speaker: Le Roi Du Plessis (Stellenbosch University)

Physics for Development, Education and Outreach: Masoga

Convener: Phala Wesley Masoga (University of Limpopo)

236 Diagnostic Assessment of Conceptual Understanding in Direct Current Circuits Among Pre-Service and In-Service Teachers

A sound understanding of fundamental concepts is a key goal of science education; however, both pre-service and in-service teachers often demonstrate limited conceptual understanding, particularly in direct current (DC) circuits. Grounded in constructivist learning theory, which emphasizes the role of prior knowledge in meaningful learning, this study highlights the importance of diagnostic assessment before instruction. The Inventory of Basic Concepts in DC Circuits (IBC-DC) was employed to evaluate participants’ conceptual understanding and identify misconceptions. The study aimed to determine: (i) the extent to which second-year pre-service teachers understand basic DC circuit concepts, and (ii) the level of understanding among in-service teachers. The instrument was administered prior to formal instruction and professional development workshops, respectively. Findings reveal notable gaps in conceptual understanding across both groups, underscoring the need for targeted instructional interventions. The study demonstrates the value of concept inventories in informing effective teaching strategies in physics education.

Speaker: Mphiriseni Khwanda (University of johannesburg)

237 The influence of national science and innovation policy on science centre mandates; emerging pedagogical approaches to integrate indigenous knowledge systems and digital technologies.

Science centres play a critical role in advancing STEM education, public engagement and innovation capacity in South Africa. Positioned at the interface of formal education, science policy, and community practice. It addresses persistent challenges such as low participation in STEM and limited access to high-quality STEM learning opportunities. Despite their strategic importance, evaluations of science centres emphasise the need for scientific rigour.
This paper systematically analyses the national policy framework, empirical literature, and institutional evaluation practices to situate science centres within South Africa’s science education and communication landscape. The analysis identifies three interrelated themes: the influence of national science and innovation policy on science centre mandates; emerging pedagogical approaches integrating indigenous knowledge systems and digital technologies; and enduring conceptual and cognitive challenges associated with science learning in informal environments.

Keywords: Science Centre, STEM, national policy framework, emerging pedagogical approaches, cognitive challenges associated

Speaker: Dr FHULUFHELO NEMANGWELE (University of Venda)

238 Academic Progression from Extended Curriculum to Mainstream Physics: Evidence from First-Year University Physics Modules

Extended Curriculum Programmes (ECPs) are designed to enhance student access to higher education in South Africa. Even though there is growing research on extended curriculum programmes, major gaps remain in explaining how students transition into mainstream physics curricula. The aim of this research paper is to examine the relationship between performance in foundation Physics modules and subsequent performance in mainstream Physics modules among students who progressed from the Extended Curriculum Programme (ECP), and (ii) differences in mainstream Physics performance between ECP-transition students. This study used a quantitative retrospective cohort design based on student academic records. The statistical analysis was conducted in Python and comprised descriptive, correlational, comparative, and predictive components. The descriptive statistics show a decline in examination marks after transitions. Students who obtained a distinction in foundation Physics tended to achieve the strongest marks in mainstream Physics, whereas students who entered mainstream Physics with a conditional pass frequently performed below average. Foundation Physics plays an important role, but does not fully equalize readiness for mainstream study. Foundation Physics is a useful but incomplete predictor of mainstream Physics performance among ECP-transition students. Foundation Physics should function not only as an access mechanism but also as a stronger diagnostic and preparatory space for mainstream progression.

Speakers: Dr Lutendo Phuthu (University of venda), Ms Marandela Mulalo (University of venda), Mr clarence mabaso (University of venda)

Academic_Progression_Univen_Presentation.pptx

Physics of Condensed Matter and Materials

Convener: Christopher Arendse (University of the Western Cape)

239 Fabrication and Characterization of Gd-doped 𝑰𝒏𝟐𝑺𝟑 thin film- As a 365 nm-UV photodetector

Indium sulfide (〖In〗_2 S_3) is an intriguing semiconductor and has been extensively utilized as a
UV photodetector. In this study, we report the fabrication of gadolinium (Gd)-doped 〖In〗_2 S_3 thin films prepared via the nebulized spray pyrolysis technique (NSP). The X-ray diffraction (XRD) analysis confirms a cubic β- 〖In〗_2 S_3 phase, polycrystalline structure. Ultraviolet-visible (UV-Vis) spectroscopy confirms an enhancement in the UV absorption coefficient in doped films. Gd doping enhances the absorption capacity and the formation of oxygen vacancies in the host material. Photoluminescence (PL) spectroscopy revealed the presence of V_0 and V_s, and indium (𝑉 𝐼𝑛) vacancies. X-ray photoelectron spectroscopy (XPS) identified the presence of surface elements such as indium (In), sulfur (S), Gd, and vacancies, such as V_0 and V_s, hydroxyl ions (〖OH〗^-), and sulfate ions (〖SO〗_4^(2-)), as well as secondary phases including 〖Gd〗_2 O_2 S, 〖Gd〗_2 O_3 and 〖Gd〗_2 S_3. Under 365 nm UV illumination, the 〖In〗_2 S_3: 𝐺𝑑(1%) exhibits outstanding photodetector performance with a responsivity of 35.2×10^(-2) 𝐴/𝑊, an external quantum efficiency (EQE) of 82.1%, and a detectivity of 33.8 × 10^10 Jones. The device also shows excellent operational stability over 25 cycles, along with fast rise and decay times of 0.53 and 0.50 s, respectively. This research work paves the way for further doping strategies for improving the performance of 〖In〗_2 S_3 photodetectors, beyond state-of-the-art.

Speaker: Dr Dr. Kumar Haunsbhavi (University of the Free State, Bloemfontein, South Africa)

240 First principles study of the structural, electronic, and magnetic properties of the CeCuGe intermetallic compound

The ternary CeTX (T = d-electron transition metal and X = p-electron element) compounds exhibit a wide range of interesting phenomena depending on the degree of hybridization between the 4f electrons and the conduction electrons. A substantial experimental work has investigated the physical and transport properties of these compounds. The metallic behavior exhibited by these compounds acts as a strong stabilizer, giving rise to the Kondo effect, metal-insulator transitions, other phase transitions, and semiconducting behavior. A family of hexagonal intermetallic compounds, CeCuGe, CeAuGe, and CeCuSi, has previously been reported to exhibit a ferromagnetic ground state at Tc = 10 K, 10 K, and 15 K, respectively. Despite a fairly large number of studies on these compounds, there are limited theoretical investigations. In this study, we have calculated the structural, electronic, and vibrational properties of the CeCuGe compound using density functional theory to further elucidate its structural, stability, and magnetic properties. The magnetic calculations confirm that the compound exhibits ferromagnetic behavior and that Ce³⁺ ions are the only source of the compound's magnetism, as illustrated by the experimental work. Finally, the phonon calculations confirm that CeCuGe is dynamically stable.

Speaker: Prof. Buyisiwe Sondezi (University of Johannesburg)

241 Room temperature trace Acetone detection using W18O49-WO3 nanostructures

We report the room-temperature (RT) detection of trace-level acetone using a W₁₈O₄₉-based gas sensor incorporating a minor secondary WO₃ phase. The sensing material was synthesized using the solvothermal method, yielding nanoparticles along with sparsely separated nanorods as photographed using SEM and TEM instruments. The intrinsic properties (i.e., crystal structure, and defect states) of the W18O49 /WO3 were examined using characterization techniques such as PXRD, PL, UV-vis and XPS. The sensor was exposed to a minimal concentration of 0.08 ppm acetone, leading to a response (Ra/Rg) of 1.04, while at 1.8 ppm, the response was 1.49, respectively. This performance ranks among the best W18O49 based acetone sensors which exclusively operated at high temperatures. Relative humidity (RH) measurements revealed that the sensor thrived in humid conditions, which to the best of our knowledge is novel with regard to W18O49 based sensors. Selectivity analysis of the W₁₈O₄₉-based gas sensor revealed superior sensing performance toward acetone compared to the six other tested analytes, namely ethanol, methanol, m-xylene, p-xylene, o-xylene, and benzene. The sensor response data was analyzed using PCA and kNN. PCA revealed clearly separated clusters for different gases, showing distinct response patterns. The combined PCA-kNN approach achieved 93% accuracy, demonstrating strong capability in distinguishing acetone from other VOCs. This highlights the benefit of combining nanostructured W18O49 sensing materials with Machine-Learning tools for reliable VOC detection in complex environments.

Speaker: Jodinio Lemena (University of the Free State)

Theoretical and Computational Physics: Session 4

Convener: Magdeline Seabi (Nelson Mandela University)

242 Shifting Landscape in Materials Modelling — Integrating First-Principles and Machine Learning for Accelerated Materials Discovery

The rapid evolution of computational materials science is redefining how materials are designed, understood, and optimized. This presentation highlights the transition from traditional first-principles modelling to data-driven materials discovery frameworks. Early work, grounded in Density Functional Theory (DFT), focused on elucidating the electronic, magnetic, and structural properties of complex systems, including strongly correlated materials and low-dimensional nanostructures will be discussed. In these studies, we established a robust structure–property relationship and these were extended to functional materials for energy applications, particularly electrocatalysts for hydrogen production and oxygen reduction, where DFT-enabled insights into adsorption energetics and reaction mechanisms guided rational materials design. In response to the growing demand for high-throughput exploration of complex chemical spaces, recent research work has incorporated machine learning (ML) techniques into the materials research modelling workflows. In this emerging paradigm, DFT calculations can provide high-fidelity datasets, while ML models act as surrogate predictors to accelerate property evaluation and materials screening. This hybrid approach enables the identification of promising candidates for catalysis, topological materials, and low-dimensional systems with significantly reduced computational cost. This work reflects a broader shift in the materials research community toward integrating physics-based and data-driven methodologies. This hybrid approach accelerates the discovery of catalytic, topological, and low-dimensional materials, reflecting a broader shift toward scalable, data-driven materials design for sustainable energy applications.

Speaker: Kingsley Onyebuchi Obodo (University of KwaZulu-Natal, Pietermaritzburg)

243 Quantum Computing for Sodium-Ion Battery Modeling: A Comprehensive Technical Analysis

Electric vehicles and renewable energy storage demand batteries that are cheaper, longer-lasting, and more powerful than current lithium-ion technology. Battery chemistry happens at the atomic level, where quantum physics rules apply. Traditional computers struggle to model these quantum interactions accurately. Quantum computing represents a promising paradigm shift in how we model battery materials at the atomic and molecular level.

While classical computational methods like Density Functional Theory (DFT) have enabled significant progress in battery research, they face fundamental limitations when modeling the strongly correlated electronic systems that govern battery chemistry.

Quantum computers promise to overcome these limitations by directly simulating quantum mechanical behavior rather than approximating it. Battery performance depends on electrochemical processes occurring at atomic scales where quantum mechanics dominates. The fundamental challenge is solving the many-body Schrödinger equation for systems containing dozens to hundreds of electrons.

Thus, this paper provides a comprehensive technical analysis of how quantum computing is being applied to battery modeling, the specific algorithms being deployed, current results from industry partnerships, and the transformative potential for next-generation energy storage.

Quantum computing could revolutionize battery technology by directly simulating the quantum behavior of atoms and molecules, potentially leading to batteries that are cheaper, more powerful, and longer lasting, which would transform present-day electric vehicles and renewable energy storage.

Speaker: Khanyisile Masemola (University of the Witwatersrand)

#347_Khanyisile. Masemola.pptx

244 Physics-Informed Neural Networks for two-Body Schrödinger Bound-State Eigenvalue Computation

We have previously shown that unsupervised Physics‑Informed Neural Networks can give promising results for quantum few‑body problems, where we computed the s‑wave bound states generated by a toy potential and the Woods–Saxon potential. The method performed well for the toy potential, but it struggled to learn the second excited state of the Woods–Saxon potential. This difficulty arose because the neural network introduces unphysical constraints in the loss function for the eigenvalue–eigenfunction pairs during training. In this work, we improve the method by using the known properties of Hermitian operators, in particular, that the bound‑state eigenfunctions are normalized and orthonormal. Using these properties, the bound‑state energies are approximated with the Rayleigh–Ritz variational method, and the corresponding physical constraints are included directly in the loss function. The performance of the approach is tested on a toy potential, the  Gaussian type potential, and the Woods–Saxon potential. Preliminary results show that including these physical constraints in the loss function improves the accuracy and stability of the neural network solutions, especially for excited states.

Speakers: Dr Tshegofatso Tshipi (Sol Plaatje University), Dr Ishmael Gopane (Sol Plaatje University)

10:30 Morning Tea

Applied Physics

Convener: Lucas Erasmus (UFS)

245 Firmware and Software Implementation in TileCom for Integration to the ATLAS TileCal Phase II Upgrade

The High-Luminosity Large Hadron Collider (HL-LHC) upgrade will increase proton-proton collision rates by a factor of 5-7 times, requiring a complete redesign of the A Toroidal LHC ApparatuS (ATLAS) Tile Calorimeter (TileCal) readout electronics. The Tile Computer on Module (TileCoM) serves as the embedded control interface, responsible for remote programming, configuration, and real-time monitoring of distributed readout hardware over Gigabit Ethernet communication. Key challenges include migrating from legacy Community ENTerprise Operating System (CentOS) to AlmaLinux while preserving ATLAS compatibility and operational standards, minimizing communication latency under high-throughput conditions, and validating scalability from single-board prototypes to full production deployment.This work presents the design and implementation of TileCoM firmware and server software on AlmaLinux-based Zynq UltraScale+ platform. Systematic benchtesting and implementation of IPbus and OPC UA communication protocols to evaluate latency and throughput under realistic data-rate conditions for operation. Results establish performance baselines critical for ATLAS Phase-II commissioning and contribute reusable and standard methodologies for deterministic real-time control in large-scale scientific instrumentation.

Speaker: Delron Dananai Muti (University of Johannesburg (ZA))

244_Delron_Muti.pdf

246 Electrical characterisation of aluminium-polyaniline Schottky diodes using a machine learning approach

Understanding of the behaviour of a Schottky contact is important in the design of optoelectronic devices such as solar cells and photosensors. The behaviour of Schottky diodes depends on physical parameters like the thickness of the metal contact layer and electro-optical parameters of the active layer. Schottky contacts between metals and organic semiconductors are of importance in the growing field of organic electronics. Long turn-around times in the characterisation process of the Schottky contacts is a setback in research and development chains because of the many diode parameters involved. In this study aluminium films of different thicknesses were deposited on polyaniline (PANI) using the resistive deposition technique . Schottky diode parameters like ideality factor, the barrier height, reverse saturation current and ohmic resistance of the devices were found to be dependent on the thickness of the aluminium layer. A Machine Learning (ML) model was then developed to predict Schottky contact diode parameters based on the thickness of the Al-PANI contact layer. The results suggest that ML is an effective approach to accelerate the characterisation of Schottky contact diodes and also avoids waste of material that is typical of the traditional trial and error route.

Speaker: Hlulani Ndlovu (Tshwane University Technology)

Hlulani Ndlovu SAIP.pptx

247 Design and Implementation of a Hardware Monitoring Framework for the Tile Demonstrator at Point 1

The High-Luminosity Large Hadron Collider (HL-LHC) will impose increased data rates and operational complexity on the ATLAS Tile Calorimeter (TileCal), necessitating robust, scalable and real-time hardware monitoring solutions. Building on the successful development of an Open Platform Communications Unified Architecture (OPC UA) server for the Tile Preprocessor (TilePPr) modules, this work presents the design and implementation of a hardware monitoring framework for the Tile Demonstrator at Point 1. The previously OPC UA based system demonstrated reliable performance during the 2025 test beam campaign with the Compact Processing Module (CPM) and subsequent integration tests with the Trigger and Data Acquisition Interface (TDAQi) in B175. Leveraging these results, the current work transitions toward a monitoring architecture based on the ATLAS Information Service (IS) and the Persistent Back-End for the
ATLAS Information System of TDAQ (PBEAST) to enable low-latency hardware monitoring. This framework facilitates real-time acquisition of hardware monitoring data from the Tile Demonstrator module. The system integrates with Grafana for dynamic visualization and dashboard-based monitoring. The implemented solution has been validated within a dedicated test environment, demonstrating reliable data flow, efficient handling of multiple data sources, and seamless interoperability with existing ATLAS TDAQ infrastructure.

Speaker: Brenton Munhungewarwa (University of Johannesburg)

252_Brenton_Munhungewarwa.pdf

248 Inverse design of optical neural networks with qubit-based quantum computers

All-optical diffractive neural networks are designed to perform inference using light. In practice, however, designing these systems typically requires solving a computationally demanding inverse problem on classical hardware, with long training times driven by the large number of optimization parameters. The core computational bottleneck is the repeated simulation of optical wave propagation, commonly implemented through Fast Fourier Transforms (FFT) or discrete Fourier transforms (DFT). Here, we show that qubit-based platforms can be leveraged to efficiently learn the underlying phase masks, provided access to an efficient implementation of the Quantum Fourier Transform (QFT) is available. Since the QFT can be implemented with a complexity of O((log N)^2), compared to the classical O(NlogN) scaling of the FFT/DFT, this approach opens a pathway to accelerating inverse design in optical systems beyond what is feasible classically. We demonstrate this idea by implementing a coherent classifier on a qubit platform that mirrors the functionality of its optical analogue. The classifier can sort structured photon patterns with different symmetries, both Cartesian and azimuthal, achieving accuracies as high as 100% with 8 layers and 10 qubits. Beyond classification, this framework also enables new coherent feature-embedding strategies, in which tailored unitary transformations map input fields onto chosen computational basis states.

Speaker: Nikita Azevedo

Inverse_design_Nikita.pptx

new_Inverse_design_Nikita.pptx

249 DFT Study of Hydrogen Diffusion in Graphene-Reinforced NbMoTaW Alloy

Fast hydrogen movement with low trapping is important for energy materials. In this study, a graphene-reinforced NbMoTaW alloy was studied using DFT in Materials Studio (CASTEP). Hydrogen sites and energies were calculated in the alloy and near the graphene interface. In the bulk alloy, hydrogen occupies different sites due to the complex structure, leading to some trapping. Near graphene, hydrogen finds easier pathways, significantly enhancing its mobility and efficiency.

Diffusion barriers were also calculated and found to be lower near the graphene interface, showing faster hydrogen transport. Electronic results (DOS) show a strong interaction between hydrogen and metal atoms, but this interaction weakens near graphene, reducing trapping. This study shows that graphene accelerates hydrogen diffusion in the alloy and reduces trapping, making this material promising for hydrogen applications.

Speaker: Damuleli Thivhafuni Edgar (University Of Venda)

DAMULELI T.E POWERPOINT...pptx

Astrophysics & Space Science: Astrophysics: Session 5

250 Identification and cleaning of contaminants for neutral hydrogen intensity mapping using machine learning

Radio frequency Interference (RFI) can contaminate data collected by radio telescopes, making it difficult to distinguish between the target cosmological signal and artificial signals caused by RFI sources. Manually flagging RFI is time-consuming,so we turn to machine learning algorithms as a possible solution to detect/flag these RFI signals. We implemented a UNet, which is a Convolutional Neural Network(CNN) model to automate RFI flagging/detection in the MeerKLASS 2021 L-band survey data. A UNet model was chosen due to its suitability for semantic segmentation tasks. We leverage advanced machine learning techniques to automate RFI flagging in radio astronomy. Machine learning algorithms, more specifically, deep learning algorithms have improved the identification of Radio Frequency Interference. Recent and ongoing studies have shown that these algorithms, for example,U-Nets and ResNet can outperform non-machine learning methods regarding RFI flagging. With upcoming surveys such as the Square Kilometre Array (SKA), there is a need to develop new and automated methods that can detect and flag RFI. Since MeerKAT is a precursor instrument to the SKA-mid, it is a perfect instrument of choice to test these machine learning techniques as they can be easily adapted for SKA later. These algorithms can be applied to both simulated and real data, in both single-dish and interferometric data. This work involves using machine learning methods that are already established to do RFI flagging, and also exploring new unsupervised/self-supervised machine learning techniques for RFI flagging. Previous studies have mainly focused on simulated data and we use observational data that has been labeled using different RFI techniques to train machine learning models to detect and flag RFI.

Speaker: Mosima Masipa (University of the Western Cape)

194_Mosima_Masipa.pdf

251 Scientific Discovery with Foundation Models

The next generation of telescopes such as the SKA and the Vera C. Rubin Observatory will produce enormous data sets, far too large for traditional analysis techniques. Machine learning has proven invaluable in handling massive data volumes and automating many tasks traditionally done by human scientists. In this talk, I will explore the use of machine learning for automating the discovery and follow-up of interesting astronomical phenomena, both in the image and time domains. I will discuss how the human-machine interface plays a critical role in maximising scientific discovery with automated tools, demonstrating applications of the active anomaly detection framework, Astronomaly, on a variety of datasets. Finally, I will investigate the role foundation models play in enabling scientific discovery in massive surveys.

Speaker: Michelle Lochner (University of the Western Cape)

252 Anomaly detection in astronomical surveys using Astronomaly

The rapid growth of astronomical survey data presents both an opportunity and a challenge: while large datasets increase the chances of discovering rare or unexpected sources, manual inspection quickly becomes impractical at scale. This work presents the development and application of anomaly detection pipelines using Astronomaly, an active learning-based framework, applied to two distinct astronomical datasets spanning optical and radio wavelengths.

In the optical domain, approximately 4 million galaxy images from the Dark Energy Camera Legacy Survey was explored. This work involved careful data curation, selection criteria optimisation, and evaluation of multiple active learning strategies. The pipeline identified 1635 anomalies including gravitational lens candidates, galaxy merger candidates, and 18 previously uncatalogued sources with highly unusual morphologies, all from only a few hours of human labelling. In the radio domain, a targeted pipeline combining self-supervised feature extraction with active learning was developed to detect diffuse radio emission in galaxy clusters from the MeerKAT Galaxy Cluster Legacy Survey. Significant effort went into source extraction, resolution-dependent feature comparison, and the development of a novel data cut to preferentially retain extended emission. Of the top 100 ranked sources, 99% exhibited diffuse emission characteristics, with 55% confirmed as cluster-related.

Across both domains, active learning proves essential: unsupervised anomaly detection alone consistently prioritises imaging artefacts and uninteresting outliers over scientifically valuable sources. With minimal human input, active learning rapidly reorients the search toward sources of genuine interest, offering a scalable path to discovery in the era of next-generation facilities such as the Square Kilometre Array and the Vera C. Rubin Observatory.

Speaker: Verlon Etsebeth (University of the Western Cape)

456_Verlon_Etsebeth.pdf

253 Detecting anomalous radio spectrograms with unsupervised and active learning

Developing automated algorithms for detecting anomalies is increasingly essential for uncovering previously unknown phenomena in astrophysics and cosmology from large volumes of radio spectrograms. To achieve this, we explore machine learning techniques for anomaly detection in the time-frequency dynamic spectra of the radio data. We evaluate our algorithms on simulated SPARKESX: Single-dish PARKES data sets for finding the uneXpected, enabling us to apply them to real, unlabeled data. We begin with essential preparation for anomaly detection, including feature extraction with a supervised Convolutional Neural Network (CNN), dimensionality reduction via Principal Component Analysis (PCA), and visualisation using Uniform Manifold Approximation and Projection (UMAP). Based on the prerequisites, we utilise unsupervised learning techniques, including Isolation Forest (IForest) and Local Outlier Factor (LOF), for anomaly detection. We discuss their performance and limitations, then introduce novel approaches for anomaly detection: ensemble learning of unsupervised learning methods and active learning using Astronomaly and Protege. We expect the new approaches to be more efficient and reliable for accurately detecting anomalous astrophysical signals than previous methods.

Speaker: Hanwool Koo (University of the Western Cape)

519_Hanwool_Koo.pdf

Astrophysics & Space Science: Space Science: Session 5

Convener: DuToit Strauss (North-West University)

254 Low latitude vertical drift modeling using satellite and ground-based magnetometer datasets

This talk presents a new empirical vertical E×B drift model developed using ground‐based magnetometer, radar, and satellite data over equatorial latitude regions. The model is constructed by combining global data from the Communications and Navigation Outage Forecasting System (C/NOFS) satellite, magnetometer derived vertical drifts estimated using the differential magnetometer approach and radar observations. Validation using Ion Velocity Meter (IVM) drifts from the Ionospheric Connection Explorer (ICON) satellite for January to August 2022 shows that the new model improves vertical E × B drift global modeling by over 20% compared to the current climatology representation

Speaker: Prof. John Bosco Habarulema (South African National Space Agency)

255 Characterisation of a Scintillator-based Detector for Radiation Monitoring in Low Earth Orbit

In low Earth orbit (LEO), cosmic ray interactions with spacecraft materials produce a complex secondary radiation field of neutrons, gamma rays, and charged particles, that significantly contributes to radiation exposure of astronauts. The radiation environment remains challenging to characterise due to the physical restrictions associated with measurements onboard spacecraft, and the mixed-field composition [1,2]. The need for compact, low-voltage radiation detectors is therefore critical for realistic dosimetry in these complex environments.

A 20 mm diameter plastic scintillator, optically coupled to a silicon photomultiplier, is being characterised through a combination of simulation and experimental measurements. The primary cosmic ray (PCR) field in LEO was simulated using the Space Environment, Effects, and Education System (SPENVIS) [3] to determine the radiation type and energy distribution of contributions from galactic and solar sources. The secondary radiation field, arising from PCR interactions with aluminium was estimated using SPENVIS for a range of thicknesses as an analogue to being situated within the ISS. While neutrons, protons and electrons are well represented, the secondary gamma-ray field from PCR interactions in aluminium shielding is not explicitly included. To overcome this limitation, the radiation transport code FLUKA [4] will be used to model secondary radiation production and estimate the detector response. The simulated detector response will be validated against experimental measurements made with low-energy (< 20 MeV) gamma ray and neutron sources at the n-lab [5] at the University of Cape Town.

The combined experimental-simulation approach is used to predict detector performance in the ISS environment for measuring the ambient radiation field and transient variations associated with space weather events [2]. Measurements are being planned at high altitude in the atmosphere and in LEO.

References
[1] L.H. Heilbronn et al., Life Sci. Space Res. 7 (2015) 90–99.
[2] C. Zeitlin et al., Life Sci. Space Res. 39 (2023) 76–85.
[3] D. Heynderickx et al., Space Weather 2 (2004) S10S03.
[4] G. Battistoni et al., Ann. Nucl. Energy 82 (2015) 10–18.
[5] T. Hutton, A. Buffler, Appl. Radiat. Isot. 206 (2024) 111196.

Speaker: Ms Isabella Maria Goodwin (University of Cape Town)

92_Isabella_Goodwin.pdf

11:50 Break

256 Linking Coronal Structures to L1 Solar Wind Disturbances over Three Solar Minima

Periodic solar wind streams observed at the Lagrange point L1 provide critical insight into coronal hole structures during solar minima. This study characterises and identifies the coronal sources of periodic solar wind streams measured at L1 during the last three solar minima between cycles 22–23, 23–24, and 24–25. In situ solar wind speed and heliospheric magnetic field data from the Advanced Composition Explorer (ACE) spacecraft, with a one-hour cadence, are analysed. Fourier analysis is employed to detect and characterise periodicities in the solar wind. Magnetic connectivity between the L1 point and the solar coronal hole is established using two approaches: the Parker heliospheric magnetic field (HMF) model combined with potential field source surface (PFSS) extrapolation, and the Fisk HMF model. The Parker HMF model traces magnetic field lines from L1 to the source surface, while PFSS extrapolation traces them from the source surface back to their coronal hole origins. The Fisk HMF model provides direct coronal hole mapping. Carrington synoptic maps provide global context by displaying magnetic field-line footpoints corresponding to solar wind disturbances observed at L1, while heavy ions charge state ratios serve as plasma diagnostics linking solar wind streams to their coronal hole source regions.

Speaker: Thembalethu Zulu

Zulu_SAIP2026.pptx

257 An unsupervised deep learning approach to McIntosh sunspot classification

The McIntosh sunspot classification system categorises sunspots according to their morphology and size. Because this process is typically performed manually, it is susceptible to labeling errors. In contrast, deep learning methods learn features directly from the data and classify samples based on these learned representations. In this paper, an unsupervised approach to McIntosh sunspot classification is presented, and how the models group sunspot data into clusters is examined. These clusters are compared with reference ground-truth labels to determine how strongly they correlate with the ground truth. To assess performance, the supervised models are trained using both the ground-truth labels and the unsupervised labels, and their accuracies are compared. The results indicate that the unsupervised approach outperformed the conventional supervised approach trained on the ground-truth labels. Finally, Local Interpretable Model-agnostic Explanations (LIME) is used to interpret the models' decisions on the unsupervised dataset. The findings highlight the potential for developing an AI-based McIntosh classification framework.

Speaker: Bernard Swanepoel (School of Computer Science and Information Systems, North-West University)

689_Bernard_Swanepoel.pptx

689_Bernard_Swanepoel.pptx

Nuclear, Particle and Radiation Physics -1: Session 2

Convener: Prof. Steve Peterson (University of Cape Town)

258 Assessing UAV Gamma-Ray Spectrometry for Soil Characterisation in Vineyards

Soil texture is a fundamental parameter in agricultural systems, strongly influencing crop performance and informing soil management decisions. Accurate spatial mapping of soil texture, along with related physical and chemical properties such as bulk density, soil moisture, total organic carbon (TOC), and total nitrogen (TN), is therefore essential for effective and targeted cultivation practices. Traditionally, these properties are measured at discrete sampling points and subsequently extrapolated to larger areas. However, achieving reliable spatial representation requires extensive sampling, which is labour-intensive, time-consuming, and associated with high analytical costs.
Proximal sensing techniques offer a promising alternative for rapid and cost-effective soil characterisation at fine spatial resolutions. In particular, UAV-borne gamma-ray spectrometry (GRS) enables the acquisition of high-resolution radiometric data at low altitudes, which can be used to infer key soil properties through their relationship with naturally occurring radionuclides.
In this study, the potential of GRS for continuous soil property mapping was evaluated using a Medusa MS-350 portable gamma-ray spectrometer equipped with a custom-designed NaI(Tl) detector. The NaI(Tl) detector was mounted on the underside of a DJI Matrice 300 RTK UAV and flown at a fixed speed and altitude, while complementary ground-based measurements were acquired using a handheld Medusa system. This dual approach enabled both airborne and proximal data collection across the study area.
The investigation was conducted at Groote Post vineyard in Darling, approximately 80 km from Cape Town, South Africa. While previous studies have demonstrated the capability of proximal gamma-ray spectrometry to map soil texture at field scales, applications within vineyard environments remain limited. Vineyard soils are often highly heterogeneous at sub-plot scales, and structural features such as vine rows and canopy cover introduce additional complexities for radiometric measurements.
Following the radiometric survey, a total of 76 soil samples were collected and analysed in a laboratory for texture, bulk density, soil moisture, TOC, and TN. Previous studies (e.g., van der Veeke et al., 2021; Taylor et al., 2023) report contrasting findings regarding the predictive capability of GRS for soil properties. This study aims to address these discrepancies and provide a more definitive assessment of the potential of UAV-based and proximal gamma-ray spectrometry for predicting soil physical and chemical properties in heterogeneous vineyard systems.

Speaker: Liam Delaney

259 Experimental Test of the Generalized Brink-Axel Hypothesis and Thermodynamic Properties of $^{140}$La

The generalized Brink-Axel (gBA) hypothesis is central to $\gamma$-ray strength function ($\gamma$SF) extraction and nucleosynthesis reaction network calculations, yet remains insufficiently tested. We present the first experimental test of the gBA hypothesis in the mid-mass odd-odd nucleus $^{140}$La. The results confirm the validity of the gBA for this nucleus, supporting its use in both experimental methods and astrophysical applications.
We further investigate the thermodynamic properties of $^{140}$La to probe nuclear statistical behavior in odd-odd systems, where clear signatures of Cooper pair breaking are not expected, and new excitation modes have been proposed. We report the first experimental results on the entropy, nuclear temperature, and heat capacity of $^{140}$La.
The entropy and nuclear temperature follow established systematics, while the heat capacity exhibits signatures of pair breaking. No evidence for new excitation modes is observed.

Speaker: Ayabulela Tsewu

260 Systematic investigation of density-independent and density-dependent nucleon–nucleon interactions in 16O-fusion induced reactions

A systematic investigation of fusion reactions induced by 16O is carried out. Within the double-folding formalism, the nu-
cleus–nucleus interaction potential is constructed using both density-independent nucleon–nucleon interactions (B3Y-Fetal, M3Y-
Paris, and M3Y-Reid) and density-dependent interactions (BDM3Y1, CDM3Y6, and DDM3Y1). The reactions 16O + 70,72,74,76Ge,
16O + 112,116,118,120Sn, 16O + 144,148,154Sm, 16O + 186W and 16O + 208Pb are considered. Two groups of interactions exhibiting similar
fusion cross sections are identified, with the similarities becoming more pronounced as the target mass increases. On one hand,
potentials derived from the B3Y-Fetal and BDM3Y1 interactions yield comparable fusion cross sections; on the other hand, those
obtained from the M3Y-Paris, M3Y-Reid, CDM3Y6, and DDM3Y1 interactions also produce similar results. The former group
generally provides a better description of the experimental data, except for the 120Sn for which the latter group offers the best fit.
The analysis of the channel couplings strength reveals that BDM3Y1 interaction corresponds to the strongest channel couplings. It
is also observed that the strength of channel couplings does not vary monotonically with the atomic mass, as might be expected.
In light of these results, it follows that the B3Y-Fetal and BDM3Y1 nucleon-nucleon interactions systematically provide a better
description of the experimental data. Furthermore, there are no specific features in the fusion cross sections that can be attributed
solely to whether the nucleon-nucleon interaction is density-dependent or density-independent. This conclusion is supported by the
identified two groups of nucleon-nucleon interactions, each containing density-dependent and density-independent interactions

Speaker: Gerald Maluleke (UNISA)

261 Systematic Efficiency Characterisation of SiPM-Based Scintillator Trackers using Cosmic Muons

Cosmic muon trackers using plastic scintillators and Silicon Photomultipliers (SiPMs) are increasingly common in muon tomography applications due to their cost-effectiveness and robustness. In these systems, the high voltage (HV) applied to the SiPM directly influences the overvoltage, which determines key parameters such as gain, photon detection efficiency, and overall detector trigger efficiency.

This study presents a methodology for characterising detector performance using real hardware, providing experimental measurements of efficiency obtained with a physical detector setup. By performing systematic HV scans, we identify an efficiency turn-on followed by a plateau region. This behaviour was consistently observed and validated across two separate configurations: a stacked scintillator demonstration and a full muon hodoscope composed of planar perpendicular scintillator bars. We present this data to characterise the empirical relationship between bias voltage and detector response.

The results highlight that despite the high signal-to-noise ratio inherent in cosmic muon detection; with typical pulses exceeding 10 photoelectrons (p.e.) against a dark count rate of less than 5 p.e., empirical determination of the operating voltage remains a necessary step for consistent performance. This work demonstrates how defining the HV plateau allows for a selection of operating points that optimises overall detection efficiency while simultaneously minimising the impact of voltage and gain fluctuations on system stability.

Speaker: Mr Malefetsane Lenka (MSc Student)

MALEFETSANE LENKA SAIP.pdf

262 Investigating Gamow–Teller β-decays using pn-QRPA framework

Investigations of weak interactions through Gamow-Teller (GT) β-decays
play an important role in neutrino physics, astrophysics and studies of fundamental symmetries [1–3]. Because these decays happen within nuclei, nuclear-effects significantly influence the decay rates. These effects are incorporated in calculated nuclear matrix elements (NMEs), which convey information about the initial and the final state of the decay as well as the transition operator. For this reason, it is essential to describe GT NMEs accurately. However, a long-standing and unresolved problem is that theoretical models tend to overestimate GT NMEs compared to experimental data. This discrepancy is usually resolved by the “quenching” of the axial-vector coupling constant (gA), which is essentially the requirement of an effective gA that is smaller than the free-nucleon value [4, 5].

Recently, Ejiri and Suhonen [6] introduced a different approach to study gA quenching, based on the study of pairs of mirror-like β+ and β− transitions between even–even and odd–odd nuclei. They showed that many model uncertainties, such as those associated with pairing effects and the dependence on the particle-particle interaction strength (gpp) could be reduced. Despite this progress, it is still unclear whether the required quenching arises from limitations in nuclear structure models or from more fundamental modifications of the axial current in the nuclear medium. In this work, we address this problem by performing proton-neutron Quasiparticle Random Phase Approximation (pn-QRPA) calculations of GT transitions for selected nuclei, to study the dependence of NMEs on gpp, in addition to calculating magnetic dipole (M1) transition strengths. A systematic comparison between theoretical and experimental M1 strengths is used to test the accuracy of the model predictions and to investigate correlations between GT and M1 matrix elements.

References

[1] J.D Vergados, H Ejiri, and F. Simkovic. Theory of neutrinoless double-betadecay. Reports on Progress in Physics, 75(10):106301, 2012

[2] H. Ejiri. Nuclear spin isospin responses for low-energy neutrinos. Physics Reports, 338(3):265–351, 2000.

[3] F.F Deppisch, J. Harz, W. Huang, M. Hirsch, and H. P¨as. Falsifying high-scale baryogenesis with neutrinoless double beta decay and lepton flavor violation. Physical Review D, 92(3):036005, 2015.

[4] B.A Brown and B.H Wildenthal. Status of the nuclear shell model. Annual Review of Nuclear and Particle Science, 38(1):29–66, 1988.

[5] J.T Suhonen. Value of the axial-vector coupling strength in β and ββ decays: A review. Frontiers in Physics, 5:55, 2017.

[6] H. Ejiri and J. Suhonen. GT neutrino–nuclear responses for double beta
decays and astro neutrinos. Journal of Physics G: Nuclear and Particle Physics, 42(5):055201, 2015

Speaker: Mr Odwa Tyuka (University of the Western Cape)

Nuclear, Particle and Radiation Physics -2: Session-5

Convener: Phuti Rapheeha (University of the Witwatersrand)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

263 Monte Carlo Background Modelling and Signal Sensitivity Studies in the Diphoton Final State in Association with an electron with ATLAS Run-3 Data

In this work, we study the sensitivity of a diphoton analysis to potential resonant signals using ATLAS Run-3 data and Monte Carlo (MC) simulated samples. The analysis focuses on optimising event selection and object identification, including studies of electron identification working points and event-level requirements, to improve discrimination between MC signal and Standard Model backgrounds. The ATLAS analysis framework is used to construct and compare signal and background distributions for key kinematic observables. Background contributions from dominant processes are evaluated and statistical sensitivity is quantified through weighted yield comparisons and significance estimates. The results highlight the importance of optimised selection strategies in enhancing sensitivity to subtle resonant structures in the diphoton channel, where the scalar decays into a photon pair accompanied by a muon or electron and a $S(\rightarrow \gamma \gamma) + 1 \ell$, and contribute to ongoing efforts within ATLAS to explore potential signals of new physics.

Speaker: Baballo-Victor Ndhlovu (University of the Witwatersrand)

186_Baballo_Victor_Ndhlovu.pdf

264 Background studies and Performance Evaluation of Tau Identification Working Points in the Diphoton–Hadronic Tau Final State with ATLAS Data in the mass range 130 – 200 GeV

Searches for di-photon resonances at the ATLAS experiment in the intermediate mass range of $130-200\,\mathrm{GeV}$ remain largely unexplored, with previous studies primarily focusing on the low-mass $66-110\,\mathrm{GeV}$ and high-mass $200-3000\,\mathrm{GeV}$ regions. In this work, we investigate the $\gamma\gamma + 1\tau^{\mathrm{had}}$ final state in the intermediate-mass region, performing a detailed background characterisation and validation using early to mid-phase Run 3 ATLAS data collected between 2022 and 2024, corresponding to an integrated luminosity of $164\,\mathrm{fb}^{-1}$ at a centre-of-mass energy of $\sqrt{s} = 13.6\,\mathrm{TeV}$. The dominant background contributions considered include $V\gamma\gamma$, Single Higgs production, $t\bar{t}\gamma\gamma$, and $\gamma\gamma + \mathrm{jets}$, which are compared to data to assess the accuracy of Monte Carlo modelling both before and after event selection. Following the application of analysis selections, an optimisation of the hadronic tau identification is performed by comparing different recurrent neural network (RNN)-based working points, namely $\mathrm{RNN}$ Loose, Loose with electron rejection, Medium, and Tight. The performance of each working point is evaluated using the Asimov significance, allowing for a quantitative determination of the optimal working point that maximises signal sensitivity in this channel.

Speaker: Mr Vuyolwethu Happyboy Kakancu (School of Physics and Institute for Collider Particle Physics, University of the Witwatersrand, Johannesburg, Wits 2050, South Africa)

Vuyolwethu Kakancu Saip Slides (2) (1).pdf

Vuyolwethu Kakancu Saip Slides (2).pptx

265 Diphoton Scalar Resonance Search in the $\gamma\gamma + 1\mu$ Channel: Background Composition, Modelling, and Muon Working Point Optimisation with $\mathcal{L} = 164~\mathrm{fb}^{-1}$ of ATLAS Data

A study of the background composition and modelling in a search for scalar resonances in the diphoton-plus-muon ($\gamma\gamma + 1\mu$) final state is presented, using $164~\mathrm{fb}^{-1}$ of proton-proton collision data collected by the ATLAS detector at $\sqrt{s} = 13.6~\mathrm{TeV}$ during 2022--2024 LHC Run~3 operations. Events are selected by requiring two isolated photons with $p_{\mathrm{T}}(\gamma_{1}) > 35~\mathrm{GeV}$ and $p_{\mathrm{T}}(\gamma_{2}) > 25~\mathrm{GeV}$ satisfying Tight identification and FixedCutLoose isolation, together with at least one muon with $p_{\mathrm{T}} > 10~\mathrm{GeV}$, while vetoing electrons, tau leptons, and $b$-tagged jets. A systematic optimisation of muon working points across Medium and Tight operating points is performed. The background composition from $\gamma\gamma$+jets, $V\gamma\gamma$, $t\bar{t}\gamma\gamma$, and single Higgs production is characterised using stacked Monte Carlo simulation, with signal sensitivity evaluated using a $\gamma\gamma+leptons$ benchmark sample. Preliminary data-to-Monte Carlo comparisons show good agreement. The continuum background in the $m_{\gamma\gamma}$ spectrum is modelled with analytical functional forms, and a spurious signal test validates the chosen parametrisation. The current status and prospects are discussed.

Speaker: Kgothatso Ntumbe (Universitty of the Witwatersrand(ZA))

223_Kgothatso_Ntumbe.pdf

266 Searches for Scalar Resonances in Diphoton Final States in Assosciation with Multileptons at the Electroweak Scale in the ATLAS Detector at the LHC

Motivated by persistent Run-1 and Run-2 anomalies, including an excess near $m_{\gamma\gamma}\approx152\pm1~$GeV with combined ATLAS and CMS significance of 5.5$\sigma$ (5.3$\sigma$ global), this analysis searches for scalar resonances in diphoton final states with leptons using 2022–2024 ATLAS $pp$ data corresponding to 164 fb$^{-1}$ at $\sqrt{s}=13.6~$TeV. To support this search, a dedicated Monte Carlo generation campaign has been prepared to study final states containing diphotons in association with leptons, specifically $\gamma\gamma+1\ell$ $(\ell=e/\mu/\tau^{\mathrm{had}})$ and $\gamma\gamma+2\ell$, where $\tau^{\mathrm{had}}$ denotes hadronic tau decays. These final states are particularly sensitive to the presence of additional scalar resonances predicted in models with extended Higgs sectors. The signal production is modeled using two theoretical frameworks, a simplified Two-Higgs-Doublet Model extended with a scalar singlet (2HDM+S) and the Real Higgs Triplet Model (RHTM). In the simplified 2HDM+S scenario, heavy scalar resonances are produced predominantly via gluon–gluon fusion and subsequently decay through cascades involving additional scalar states that yield diphoton signatures accompanied by leptonic activity. The RHTM provides complementary phenomenology through extended Higgs sectors containing singly charged and neutral scalar states, leading to final states with photons and leptons arising from electroweak production and scalar decays. The generated samples enable detailed kinematic characterization of the targeted channels and support reconstruction and event selection optimization, object working point optimization studies, and sensitivity evaluations for scalar resonances within the explored mass range.

Speaker: Njokweni Mbuyiswa (University of the Witwatersrand)

287_Njokweni_Mbuyiswa.pptx

Photonics: Microscopy, applied & fibres

Convener: Gurthwin Bosman (Stellenbosch University)

267 Two-Photon Light-Sheet Microscopy with Multi-View Deconvolution

Light-sheet fluorescence microscopy provides rapid volumetric imaging of biological specimens with reduced photodamage by confining excitation to a thin optical plane. Combined with two-photon excitation fluorescence (2PEF), it enables deeper imaging with reduced background, making it well-suited to scattering samples.

Past nonlinear light-sheet implementations are limited by non-uniform illumination, shadowing, reliance on proprietary reconstruction software, and limited validation on biological specimens.

Here, we present a 2PEF light-sheet microscopy framework that addresses these limitations. An open-source reconstruction pipeline was developed, incorporating calculated point spread functions and multi-view deconvolution for flexible and accessible image processing. Rotational multi-view acquisition mitigates illumination non-uniformity and shadowing, improving volumetric coverage. Together, these features enable more robust volumetric reconstruction in scattering specimens.

Initial measurements on fluorescent beads and biological samples, including cardiomyoblasts and glioblastoma cells, will be presented to quantify resolution, contrast, and isotropy, thereby establishing a basis for assessing performance gains achieved through multi-view reconstruction.

Speaker: Jacques Buÿs (Stellenbosch University)

268 Parameter study and optimization of real-time single-particle tracking

The real-time tracking of single particles is a vastly under-developed experimental technique but it offers great potential in understanding molecular dynamics. A suitable tracking system comprises three key components, viz., a position sensor, a control system, and an output actuator. The position sensor enables accurate prediction of the particle location. For this component, various tracking methods often employ an estimator of which the scanning pattern is a crucial part. A laser beam is generally scanned in a fixed pattern whilst the photons emitted by the tracked particles are captured and the corresponding photon counts and position coordinates are used to predict the particle location. This process is repeated until some form of termination condition is met. The choice of fixed pattern plays a significant role in the accuracy of the estimator and hence the tracking capabilities of the set-up. In this presentation, we will show how different patterns and detection strategies can be employed in conjunction with accurate two-dimensional single-particle tracking (SPT) simulations of emitting and non-emitting particles to identify an optimal combination. Fluorescence and interferometric scattering (iSCAT) are simulated to represent emitting and non-emitting particles respectively. The performance of each configuration is evaluated using some statistical metrics (e.g., average tracking error) before implementing them in an experimental real-time feedback-driven SPT set-up for single particle studies

Speakers: Jessica Wells, Jessica Wells

99_Jessica_Wells.pptx

269 Interferometric Optical Fibre Based Non-destructive Evaluation of Concrete Compressive Strength

The evolution of mechanical strength in concrete during curing is a vital aspect in assessing structural integrity and quality control of concrete. A Mach-Zehnder Interferometric (MZI) technique was employed for the non-destructive assessment of compressive strength development in unreinforced concrete beams. Low- and high-strength concrete beams and cubes were cast, with a single-mode fibre (SMF) embedded at the centre of each beam. The samples were cured in a temperature-controlled water tank, and compressive strength was continuously monitored in each mixture for 28 days. The logarithmic slopes derived from the MZI-derived compressive strength development obtained a strength gain sensitivity of 5.373 MPa/ln(days) and 19.635 MPa/ln(days) for the low- and high-strength mixtures, respectively. Standard destructive cube-testing method achieved a strength gain sensitivity of 4.782 and 18.178 MPa/ln(days), for the low- and high-strength mixtures, respectively. The increased sensitivity to strength gain in the MZI system confirms the trustworthiness of its embedded sensing arm as a non-destructive instrument for assessing in-situ strength development across varying mixture qualities.

Speaker: Mr Sandisiwe Bangani (Nelson Mandela University)

Bangani SAIP 2026.pptx

270 Simulation of a Self-Homodyne Subcarrier-Multiplexed Intermediate-Frequency-over-Fibre System for 5G Small Cell Fronthaul

The increasing demand for high-capacity, low latency 5G fronthaul networks has intensified interest in Radio-over-Fibre (RoF) architectures. This works presents an end-to-end simulation of a subcarrier-multiplexed (SCM) intermediate-frequency-over-fibre (IFoF) system. Three subcarriers at 1, 3, and 5 GHz are amplitude modulated and upconverted using a 10 GHz intermediate frequency generated using microwave photonics (MWP).

The upconverted composite radio frequency (RF) signal modulates an optical carrier via a Mach-Zehnder modulator (MZM) biased at quadrature and propagates through 10 km of standard single mode fibre (SMF). The simulation accounts for chromatic dispersion, attenuation and laser phase noise in the optical domain.

A novel feature of this architecture is the co-propagation of the local oscillator (LO) reference arm through the same fibre as the modulated carrier. This self-homodyne configuration ensures that frequency drifts and phase perturbations are common-mode between the carrier and the LO. We demonstrate that this results in passive cancellation of laser frequency drift at the coherent receiver, eliminating the need for complex optical phase-locked loops (OPPLs).

Following a 10 m wireless link modeled with Friis free-space path loss and receiver thermal and shot noise, the signal is coherently downconverted and demultiplexed. Performance is quantified through per-subcarrier Q-factors and Bit Error Rates (BER), confirming the proposed self-homodyne IFoF architecture offers a cost-effective and phase-resilient solution for dense 5G mall-cell deployment.

Speaker: Lilian Mutia (Nelson Mandela University)

445_Lilian_Mutia.pptx

Physics for Development, Education and Outreach

Convener: Derek Fish (University of Zululand)

271 Problem-Based Learning approach for developing problem solving skills in electric circuits for Grade 12 learners.

This study explored the impact of the Problem-Based Learning (PBL) approach on developing problem-solving skills in electric circuits for Grade 12 learners. Diagnostic reports and classroom formative assessments showed that learners have challenges when solving electric circuits, particularly in real-life questions that require an understanding of current and potential difference, thus demanding a teaching method such as Problem-Based Learning (PBL). To carry out the study, a mixed-method quasi-experimental design consisting of qualitative and quantitative data was used to assess the effectiveness of PBL on developing problem-solving skills. The quantitative phase used pre- and post-tests on current, potential difference and resistance in parallel circuits, while the qualitative phase used group interviews and classroom observations. The results demonstrated that learners improved on the post-test following the use of PBL. Based on the interview, learners like problem-based learning (PBL) because it encourages teamwork and enables them to solve difficult, relatable problems that require critical thinking. The study discovered that implementing PBL helps learners develop critical thinking and problem-solving skills that are useful in science education.

Speaker: Dr Phala Wesley Masoga (University of Limpopo)

272 Transforming Physics Learning through Structured Consultation Support in PHY111

Many first-year university students experience difficulties in developing conceptual understanding and problem-solving skills in introductory physics courses. To address these challenges, a structured consultation programme was implemented in the PHY111 course to provide additional academic support outside formal lecture periods. The programme consisted of lunchtime consultation sessions where students worked collaboratively in small groups with the support of trained tutors. Weekly feedback sessions were also conducted to address common conceptual difficulties identified during consultations. This study evaluates the effectiveness of the consultation programme in supporting students’ learning. Data were collected through a student survey measuring perceptions of conceptual understanding, problem-solving support, collaborative learning, tutor effectiveness, and feedback sessions. The results indicate that students perceived the consultation sessions as beneficial for improving conceptual understanding, developing problem-solving strategies, and supporting collaborative learning. The findings suggest that structured consultation programmes can play an important role in enhancing student engagement and learning in introductory physics courses.

Speaker: Dr Bako Nyikun Audu (University of the Western Cape)

273 Special Relativity Battleship: Supporting Undergraduate Relativity Learning Through Game-Based Deployment and Educator Analytics

Special relativity is one of the topics that many undergraduate students struggle to build intuition for, and previous studies have highlighted persistent conceptual difficulties in this area [1-3]. Difficulties stem largely from the fact that it challenges their classical understanding of space and time. Concepts such as simultaneity, reference frames, time dilation, and Lorentz transformations are often mathematically manageable, but conceptually difficult to internalise. To address this, the Special Relativity Battleship (SR Battleship) was developed as a game-based learning tool to encourage more active engagement with these ideas.
The game draws on the familiar Battleship format, but places students in situations where progress depends on reasoning through relativistic scenarios rather than following standard problem-solving procedures. In this way, it creates space for discussion, exploration, and repeated conceptual decision-making. The development of the game and its initial use in undergraduate teaching have been reported previously [4,5].
This presentation focuses on how the platform can be taken up more broadly by educators. In particular, it will show how lecturers can access and deploy the game in their own modules, and how the system is being adapted to allow integration with individual PlayFab backends. Individual integration with the PlayFab backends enables lecturers to manage their own game instances and, where applicable, access basic usage data. If linked to a Microsoft account, gameplay activity and participation trends can also be viewed, which may be useful for classroom monitoring, reflection, and future teaching-focused research.
The session will include a walkthrough of the game interface, the educator setup process, and a discussion of practical considerations for using the tool in a teaching context. More broadly, the work sits within ongoing efforts to use interactive digital tools to support engagement with abstract topics in undergraduate physics.
References
[1] Sherin B L 2001 Cognition and Instruction 19 479–541
[2] Doat N, Ramage M J and Pritchard D E 2007 Am. J. Phys. 75 759–767
[3] Savage C M and Searle A 2010 Eur. J. Phys. 31 1193–1201
[4] Square L 2022 ICERI2022 Proceedings 1619–1625
[5] Square L et al. South African Journal of Higher Education (scheduled for publication) 41(2) Exploring Game-Based Learning in Undergraduate Physics: A Case Study of SR Battleship

Speaker: Prof. Lynndle Square (Unit for Data Science and Computing (UDSC), North-West University, South Africa)

274 Whats in the Box? a tactile remote sensing approach to teaching wave physics and spatial reconstruction.

"what's in the box?" presents a low cost, enquiry driven laboratory activity designed to enhance the teaching of wave physics through an authentic remote sensing framework.in this practical, students are challenged to identify a hidden object inside a sealed box using only distance measurements obtained from a sensor.

The activity is grounded in real world application such as a radar, LiDAR, and satellite mapping, and is based on the fundamental relationship between wave speed, travel time and distance. Students collect discrete spatial measurements across a structured grid and reconstruct a hidden object on a tactile surface, producing a scaled contour representation.

The approach supports the development of representational fluency, enabling students to translate between numerical, Spatial and physical representations (Bollen et al.,2017). The inquiry driven and collaborative structure aligns with established frameworks linking active engagement to improved learning outcomes (Chi & Wylie, 2014), while also leveraging prior knowledge as a predicator of conceptual gain.

Preliminary classroom implementation indicates improved student engagement and an enhanced ability to connect abstract wave concepts to applied contexts. this activity is scalable, low-cost and adaptable for large undergraduate classes and resource constrained environments. This work demonstrates how transforming invisible physical phenomena into tangible learning experiences can support deeper conceptual understanding and provides a practical model for embedding authentic scientific practice in undergraduate physics education.

references:

1. Binder, T., Sandmann, A.,Friege, G., Theyssen, H., & Schmienmann, P. (2019). Assessing Prior knowledge types as predictors of academic achievement in the introductory phase of biology and physics study programmes. International Journal of STEM Education, 6(1),1-5 https:do//doi.org/10.1186/s40594-019-0189-9
2. Chi, M.T.H., & Wylie, R. (2014). The ICAP framework: Linking cognitive engagement to active learning and outcomes. Educational Psychologist, 49(4),219-243. HTTPS://doi.org/10.1080/00461520.2014.965823

Speaker: Ms Seaelo Nonky Ramohoeba (School of physical and chemical sciences, Fuculty of Natural and agricultural sciences, North_West University, South Africa)

275 A Structural Equation Modelling Analysis of the National Senior Certificate Pedagogical Gap and University Readiness in South Africa (2021–2025)

Abstract: While the National Senior Certificate (NSC) university exemption rates have increased, in 2025, this upward trend masks a deepening "Distinction Paradox": a decline in high-level mastery in STEM gateway subjects. This study investigates the systemic disconnect between secondary school preparation and university readiness by examining how specific mathematical sub-skills mediate performance in Grade 12 Physical Sciences, specifically in Papers 1 and mathematic in Paper 1 and Paper 2.
Utilising a massive longitudinal dataset of 656,415 learners across South Africa’s nine provinces, the research employs a robust quantitative framework, of Exploratory Factor Analysis (EFA) and Structural Equation Modelling (SEM). EFA was utilised to isolate latent mathematical competencies specifically algebraic and geometric reasoning. SEM quantified their direct and indirect causal effects on physics problem-solving.
The findings reveal that algebraic proficiency is the primary determinant of physics success, yet its current integration within the Physical Sciences curriculum is superficial. The data show that while learners may achieve "pass" thresholds, their lack of deep algebraic fluency creates a significant cognitive barrier when transitioning to mathematically intensive university courses. This confirms that the current NSC Physical Sciences framework emphasises rote conceptual recall over the mathematical synthesis required for tertiary STEM persistence.
This study provides the first large-scale empirical evidence for a "Pedagogical Gap" within the South African curriculum. It argues that the current silos between Mathematics and Physical Sciences are failing to produce university-ready graduates. The research proposes a critical policy shift: moving beyond "access-oriented" metrics toward a "mastery-oriented" interdisciplinary curriculum. By cantering algebraic competence as a non-negotiable prerequisite for physics, South African policymakers can address the high attrition rates in first-year university STEM programs and bridge the chasm between school-level achievement and professional scientific competence.

Speaker: Ms Magdeline Seabi (Nelson Mandela University)

Physics of Condensed Matter and Materials

Convener: Motlalepula Rebecca Mhlongo (Sefako Makgatho Health Sciences University)

276 Effect of the absorber layer thickness and defect density on the performance of KGeCl3 perovskite solar cells

Bridgette Kabekwa1, Mulatedzi Gandamipfa1, Petros Ntoahae1, Eli Danladi2,3 and Rapela Maphanga4,5

1Department of Physics, University of Limpopo, Private bag X 1106, Sovenga, 0727, Polokwane, South Africa
2Department of Mathematical and Physical Sciences, Central University of Technology, Free State, South Africa
3 Department of Physics, Federal University of Health Sciences, Otukpo, Benue State, Nigeria
4Renewable and Sustainable Energy Research Centre, Sol Plaatje University, Private Bag X 5008, Kimberly, 8300, South Africa
5 National Institute for Theoretical and Computational Sciences, NITheCS, Gauteng, 2000, South Africa

Abstract
The lead-based perovskite solar cells are a third-generation photovoltaic technology with high power conversion efficiency and low cost. However, they suffer toxicity and stability issues, which downplay their efficiency and hinder their industrial production and commercialization. Therefore, the exploration of lead-free perovskite absorber materials with high stability is a high priority to advance commercial applications of perovskite solar cells. This study uses SCAPS-1D simulations to optimize an eco-friendly, lead-free perovskite solar cell cubic KGeCl3 material. We systematically investigated the impact of absorber layer thickness (200–1000 nm), and defect density on device performance. The effect of the absorber layer thickness and defect density achieved a power conversion efficiency of 19.93% with an open-circuit voltage of 1.55 V, a short-circuit current density of 17.79 mA/cm², and a fill factor of 72.16%. These results demonstrate that careful optimization of the absorber defect density (to <1015 cm⁻³) is critical for matching the performance of lead-based counterparts Sn-Pb perovskite solar cells, with the power conversion efficiency of 21.7%. This work provides a roadmap for fabricating high-efficiency, non-toxic perovskite solar cells.

Speaker: Ms Bridgette Kabekwa (Department of Physics, University of Limpopo, Private bag X 1106, Sovenga, 0727, Polokwane, South Africa)

277 Investigation of Phonon Emission Modes in a Channel-Gated GaAs/AlGaAs Finger-Gate Electron Pump

In electron transport experiments, a detailed understanding of the electronic states within a system is essential for accurate prediction and modelling of transport behaviour. Single-electron pumps traditionally employ two electrostatic gate potentials to confine individual electrons within a quantum dot and subsequently emit them over an exit barrier defined by the second gate. The emitted electrons possess energies exceeding the Fermi energy of the system. During post-emission propagation, these electrons may undergo energy relaxation through phonon emission. The specific phonon modes involved are determined by the energy scale of the relaxation process, with acoustic and optical phonons constituting the dominant mechanisms in single electron pump devices. Building upon prior work by Fletcher et al. [1], Ubbelohde et al [2] and Johnson et al [3], in which relaxation via longitudinal optical phonons was observed, we report evidence of electron de-excitation mediated by alternative phonon modes at lower magnetic fields. Both Longitudinal Optical (LO) phonons as well as possible Transverse Acoustic (TA) are observed in our device. Understanding the scattering modes of the electrons exiting the pump as well as how to suppress said scattering mechanisms is crucial for experiments that require electron coherence. The two modes of phonon emission are observed in a two-finger-gate electron pump incorporating an additional finger gate that functions as a channel barrier, suppressing electron flow in one of the device channels with the signal at both channels being measured using low noise femtoampere current to voltage preamplifiers.

References

[1] Fletcher, J.D. Physical Review Letters 111, no. 2, 216807 (2013)
[2] Ubbelohde, N. Nature Nanotech 10,46–49, 2014.275(2015).
[3] Johnson,N. Physical Review Letters 121, no. 13, 137703 (2018),

Speaker: Ethan Luyt (University of Cape Town)

Ethan Luyt SAIP.pdf

278 Microfabrication of gratings and spot-pattern arrays using proton beam writing for applications in advanced MEMS

This study investigated the fabrication of microstructures in poly(methyl)methacrylate (PMMA) positive resist using proton beam writing (PBW) technique. PBW is an advanced new direct write microfabrication technique capable of writing high aspect ratio (HAR) structures over a variety of previously studied potential resist materials. In this study 3-MeV proton beam was used at fluences between 101 – 248 nC/mm2 to write 3-dimentional microstructures of different patterns in PMMA. The written molds were subsequently subjected to metallic filling through the use of electroplating technique. The patterns were fabricated onto a PMMA/Cu/Cr/Si multilayer films, in this stack the metallic films were deposited by e-beam evaporation and the polymer was deposited by spin coating method. SEM and AFM analysis revealed the morphology and topography of the written spot-like and gratings patterns, smallest feature detail down to 650 nm with smooth sidewall quality has been achieved. The objective of this study was to optimize PBW technique at i-Themba LABS for high precision microfabrication, for applications in advanced micro/nanoelectromechanical systems (MEMS/NEMS) including microchips, semi-conductors and other device engineering technologies.

Speaker: Mr Kamogelo Mashiloane (iThemba LABS)

279 Synthesis and characterization of Mo doped CeMgO3 perovskite materials for potential supercapacitor applications.

The global transition toward sustainable energy is currently hindered by the "energy-power gap" in storage technologies, where traditional batteries lack power density and standard capacitors lack energy storage capacity. In the quest of finding solutions, supercapacitors attract more interests due to their fast charge-discharge capability and high-power density, however, low-energy density limit their applications. This research investigates the synthesis and electrochemical performance of a novel Molybdenum (Mo) doped CeMgO3 perovskite for high-performance supercapacitor applications. Samples of pristine CeMgO3 and 1%, 3%, 5% and 7% of Mo doping of CeMgO3 perovskite were synthesized using hydrothermal method. Structural, morphological and surface area properties of CeMgO3 and Mo doped CeMgO3 will be investigated using X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) coupled with Energy Dispersive X-ray Spectroscopy and Brunauer-Emmett-Teller (BET) Surface Analyzer. Furthermore, electrochemical performance of the pristine CeMgO3, Mo doped CeMgO3 will be explored through Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic charge-discharge (GCD) for possible supercapacitor applications. SEM results indicate that CeMgO3 formed agglomerated spherical nanoparticles, which upon doping it with Mo, particle sizes increased with increasing concentration. EDX confirmed the presence of Ce, Mg and O in pure samples and Mo in doped samples. The findings of this study will have a significant contribution in the development of supercapacitors.

Speaker: Dolamo Eunice

280 Augmenting the mechanical properties of LiTi2(PO4)3 solid electrolyte through sulfur doping for better electrode-electrolyte contact

The pursuit of safe, cost-effective, high-energy-density lithium-ion batteries has intensified interest in LiTi₂(PO₄)_{3 (LTP) as a solid electrolyte. Its rigid 3D framework, excellent chemical stability, and high thermal and electrochemical stability offer a vigorous alternative to flammable organic liquids. Conversely, the practical use of LTP is often hindered by its inherent low ionic conductivity at room temperature and high interfacial resistance. The Vienna Ab Initio Simulation package (VASP) was used to calculate the structural, mechanical, vibrational, and electronic properties of pristine and sulfur-doped LTP. The electronic passivity of the LTP framework is diminished through anion substitution, with calculated band gaps decreasing from 2.617 eV (pristine) to 2.089 eV (LiTi2P3O11.83S0.17) and 1.987 eV (LiTi2P3O11.67S0.33), as shown by density of state (DoS) and band structure analysis. The bulk, shear, and Young’s moduli for the pristine structure were found to be 101.01 GPa, 60.74 GPa, and 151.78 GPa, respectively. The introduction of sulfur results in a slight reduction in mechanical stiffness, demonstrated by the decreasing values of the bulk, shear, and Young’s moduli to 83.68 GPa, 55.01 GPa, and 135.35 GPa for LiTi2P3O11.83S0.17, and further to 83.22 GPa, 54.25 GPa, and 133.69 GPa for LiTi2P3O11.67S0.33, respectively. As such, sulfur doping suggests that the material is shifting towards ductility, which will improve electrode-electrolyte contact and Li-ion conductivity at the interface. These findings suggest that sulfur doping is an effective strategy for tailoring the mechanical behaviour of LTP, providing a solid foundation for mechanically compatible, high-performance solid-state electrolytes.}

Speaker: MOLATELO MATLEKE

Theoretical and Computational Physics: Session 5

Convener: Tal Leshem

281 Forward b-Hadrons as Probes of Azimuthal-Dependent Production in High-Energy Collisions

The quark-gluon plasma (QGP) is a deconfined state of matter produced in heavy-ion collisions, whose properties can be probed through the azimuthal anisotropy of particle production in the medium. Beauty hadrons are useful as sensitive probes of the QGP due to their large quark mass, however their behaviour at forward rapidities is not well recorded. Here, we present a study of b-hadron production as a function of charged-particle multiplicity, in the forward region of the ALICE detector, in pp collisions at $\sqrt{s}$ $=$ $5.36$ TeV, using beauty and charm enriched Monte Carlo data from the ALICE Grid. The two-particle correlation method is applied within the O2 (Online-Offline) Physics framework using ROOT to extract the azimuthal angle distributions of the b-hadron production by identifying muons produced from b-hadron decay, hence focusing on data from the Muon Forward Tracker (MFT) at $-3.6$ $<$ $\eta$ $<$ $-2.5$ . Preliminary results from this pp reference study will be presented. This work provides a foundation for quantifying azimuthal anisotropy of forward b-hadrons in heavy-ion collisions and constraining heavy-quark energy-loss models.

Speaker: Farelanani Makatu (University of the Witwatersrand)

343_Farelanani_Makatu.pdf

282 Energy loss predicts no $v_2$ in small systems

We present high-$p_T$ $R_{AB}$ and $v_2$ from a perturbative quantum chromodynamics-based energy loss model that includes event-by-event hydrodynamic evolution of the medium and small system size corrections to the energy loss. The model is calibrated on, and describes well, large system $R_{AA}$ and $v_2$ experimental data. The extrapolation of our model to $\mathrm{Ne}+\mathrm{Ne}$ and $\mathrm{O}+\mathrm{O}$ agrees quantitatively with recent experimental measurements of $R_{AA}$. Surprisingly, at high-$p_T$ our energy loss model predicts $v_2\approx0$ for all symmetric and asymmetric small systems when extracted using either hard-hard or hard-soft two-particle correlations. We argue that all energy loss models will in general predict $v_2\approx0$ when extracted using hard-soft correlations, which is the usual experimental method for measuring anisotropy in hadronic collisions, due to a generic geometric decorrelation between the hard and soft sector participant planes.

Speaker: Ben Bert (University of Cape Town)

energy_loss_predicts_no_v2_in_small_systems.pptx

283 Jet quenching in the smallest quark-gluon plasma droplet

The quark-gluon plasma (QGP) is a novel state of matter that existed in the first microseconds after the Big Bang and is recreated in heavy-ion collisions at ultrarelativistic energies. Recent observations of QGP-like signatures in small collision systems, including proton + heavy-ion, have raised fundamental questions about the onset of collective behavior. One key signature conspicuously absent from these systems, however, is the suppression of high-momentum particle yields. Last year, we provided theoretical predictions from our perturbative quantum chromodynamics (pQCD)-based model for this suppression due to partonic energy loss in plasmas formed by light-ion collisions. This suppression was subsequently measured in the collisions of oxygen ions and found to be in good agreement with our blind predictions. Here, we propose extending the light-ion program to even lighter systems—${}^{10}\mathrm{B}+{}^{10}\mathrm{B}$, ${}^{6}\mathrm{Li}+{}^{6}\mathrm{Li}$, ${}^{4}\mathrm{He}+{}^{4}\mathrm{He}$, and ${}^{3}\mathrm{He}+{}^{3}\mathrm{He}$—to further probe the puzzle of high-momentum particle suppression in small systems. Comparing our partonic energy loss predictions against state-of-the-art pQCD baseline calculations, we find that ${}^{3}\mathrm{He}+{}^{3}\mathrm{He}$ and ${}^{6}\mathrm{Li}+{}^{6}\mathrm{Li}$ offer especially clean environments for isolating measurable partonic energy loss in extremely small collision systems. We argue that such measurements would constitute evidence for the smallest droplet of collectively behaving matter ever observed.

Speaker: Coleridge Faraday (University of Cape Town)

SAIP2026.pdf

284 All-Path-Length and Sub-Eikonal corrections to Momentum Broadening in the Opacity Expansion approach.

We present a detailed study of momentum broadening for high-energy partons traversing the Quark--Gluon Plasma (QGP), extending the Gyulassy Levai Vitev (GLV) formalism to include both all-path-length (APL) and sub-eikonal corrections. Standard GLV calculations rely on the assumptions of large separation distances and large formation times, which are well justified in large nuclear systems but may break down in small systems such as pp and p/dA collisions, where characteristic path lengths and coherence scales become comparable.

Working to first order in the opacity expansion, we derive analytic expressions for the transverse momentum broadening distribution that systematically relaxes these approximations. The all-path-length correction emerges after we relax the large separation distance approximation.

For the sub-eikonal and combined sub-eikonal APL corrections, we introduce an updated set of kinematics that goes beyond the strict eikonal approximation.

Our results demonstrate that both all-path-length and sub-eikonal corrections can be phenomenologically important in small collision systems and provide a more controlled framework for studying jet medium interactions beyond the standard GLV approximations.

Speaker: Dario Van den Berg (University of the Witwatersrand)

Papi_SAIP2026_Uppdated.key

Papi_SAIP2026_Uppdated .pdf

12:40 Lunch

Women in Physics in South Africa (WiPiSA) Lunch

Plenary: (Photonics) Prof Natalia Litchinitser

285 Structured Light and Darkness in Nanophotonics

The rapid development of optical technologies, including optical manipulation and trapping, data processing, sensing and metrology, advanced imaging and microscopy, as well as classical and quantum communications, necessitates the exploration of new degrees of freedom for structuring light in space and time beyond conventional control of amplitude, phase, and polarization. Topological particle-like objects in structured optical fields have emerged as promising candidates for such degrees of freedom. In particular, these optical topologies offer new capabilities for communication, imaging, and sensing through atmospheric turbulence, where refractive index fluctuations distort phase, polarization, and field structure. In this talk, we discuss structured light and darkness, including optical beams with an orbital angular momentum, knotted singularities, and optical skyrmions, and demonstrate their generation, propagation, and interactions with matter in linear and nonlinear regimes. Using metasurfaces and metamaterials, we achieve subwavelength control of optical fields and topology imprinting at fundamental and harmonic frequencies, and introduce spatiotemporal approaches for structuring light jointly in space and time.

Speaker: Prof. Natalia Litchinitser (Duke University)

14:35 Conference Photo

14:45 Buffer

Applied Physics

Convener: Nicolas Thantsha (TUT)

286 Optical and Electrical Properties of Polyaniline Thin Films for Schottky Diode Radiation Sensors

In this study, the optical and electrical behaviour of polyaniline was studied through Ultraviolet Visible Spectroscopy (UV-Vis) and Current-Voltage (I-V) measurements. The Current-voltage (I-V) measurements showed that a semiconducting diode was successfully formed between polyaniline and silver metal at 1,5M HCl doping. The saturation current Is and ideality factor η were found to be 1,82x10-10 A and 2.0 respectively. From these values, a negative Schottky barrier height was determined to be -1,741 eV. Overall, results obtained in the study present a simple, inexpensive and potentially scalable method for fabricating Schottky diodes suitable for use in radiation sensor elements

Speaker: Dr Washington Mhike (Tshwane University of Technology)

396_Washington Mhike.pptx

287 A test bench for Low-Cost Positron Emission Tomography

Positron Emission Tomography (PET) is a medical imaging modality that measures the relative activity of physiological processes within a patient. It is an expensive imaging modality that is primarily limited to high income countries. Our group is developing a low-cost PET detector that would improve access to PET in low- to middle-income countries. The design process is an incremental approach that requires a test environment to validate the performance of different detector modules. A test bench has been designed and manufactured where the performance of a detector module is measured. The test bench is an optically sealed and thermally regulated unit were detector modules and radioactive sources can be mounted in different positions. The PETsys SiPM readout system is used to digitize the signals generated in the detector module under test. Performance metrics are extracted from the raw data collected by the PETsys SiPM readout system using a custom software suite. This software suite incorporates a modular design that adapts to different experimental setups, accelerating the development process. A golden standard detector module was designed and procured to validate the performance of the test bench. This detector module is an eight-by-eight 15 mm thick LYSO scintillator array coupled to a Hamamatsu SiPM array. The measured energy and coincidence timing resolution of the golden standard detector module is 14.18 % and 283.3 ps respectively . These results are well within the expected values when using an unoptimized Data Acquisition system. A calibration routine was developed to remove the constant time-offsets introduced by the PETsys SiPM readout system. The raw QDC energy measurements are converted to real energy values using an energy calibration routine that utilizes the natural radiation produced in the LYSO scintillator pixels. The future goals of this project are to optimize the parameters of the PETsys SiPM readout system and test more novel detector modules designs.

Speaker: Simon Carthew (University of Cape Town)

SimonCarthew_SAIP_2026.pdf

288 Prompt gamma imaging of a clinical proton beam using Cd Zn Te Compton cameras with a kernel-weighted back projection imaging technique.

Due to highly conformal treatment, reduced late and acute side and minimized risk of damaging healthy tissue, proton therapy has become a preferred form of radiation treatment over traditional photon and electron therapies. However, there are no means to directly verify proton depth range within the patient during treatment. One possible solution is the use of Prompt Gamma imaging (PGI), which utilises characteristic gamma rays, referred to as prompt gammas (PG), that are produced at the location of proton-tissue interactions. These PGs can be recorded via a Compton camera (CC) and subsequently used to infer the proton depth locations via PGI.

The UCT PGI system is comprised of four M400 CCs, manufactured by H3D Inc. (Ann Arbor, MI, USA), that operates at room temperature. Each M400 detector contains four 20×20×10 mm³ cadmium zinc telluride crystals. Each crystal is arranged in a 2×2 array, pixelated in a 11×11 x- and y- direction and a z- direction depth of interaction, allowing for three-dimensional gamma-ray detection.

Measurements using the M400 detectors were conducted at the Maryland Proton Therapy Centre in Baltimore, USA, using a 150 MeV single energy and spread-out Bragg peak (132-173 MeV) proton beam at gantry angles of 90^° and 270^°. The clinical beams were incident on an anthropomorphic phantom, delivering doses of 2.0 Gy and 7.5 Gy respectively. Across the aforementioned beam types, the M400 detectors were positioned on the patient couch perpendicular to the proton beam direction. These measurements were taken in conjunction with four nozzle-mounted M400 detectors. Using a kernel-weighted back projection image reconstruction technique, the work successfully demonstrates the ability of the UCT M400 detector system to produce images for proton beam range verification.

Speaker: Josiah De Klerk (University of Cape Town)

526_Josiah_DeKlerk.pdf

526_Josiah_DeKlerk.pptx

289 Comparative Elemental Analysis of Organic and Inorganic fertilizers Using the Nuclear Analytical Techniques: PIXE and RBS.

This study examines the presence of trace elements in fertilizers and their potential implications for food contamination and public health risks. Both organic fertilizers (including chicken droppings, cow dung processed by earthworms, goat manure, sheep manure, and raw cow dung) and inorganic fertilizers (NH₄NO₃, 28% N, and NPK containing 0.5% Zn) were collected from the Zululand region of South Africa. Elemental analysis was conducted using Proton-Induced X-ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS). A silicon lithium [Si(Li)] X-ray detector was employed in the PIXE technique to identify trace elements with atomic numbers greater than Z > 10. The analysis revealed the presence of the following elements: ²⁷Al, ²⁸Si, ³⁰P, ³²S, ³⁵Cl, ³⁹K, ⁴⁰Ca, ⁴⁸Ti, ⁵³Cr, ⁵⁴Mn, ⁵⁵Fe, ⁵⁶Zn, ⁷⁹Br, ⁸⁷Sr, ⁹¹Zr, and ⁸⁵Rb. Their average concentrations were found to be 33, 12, 4, 17, 13, 50, 36, 2.1, 0.13, 0.69, 29.3, 1.2, 0.28, 0.13, 0.073, and 0.12 ppm × 10³, respectively. In addition, proton backscattering spectrometry within the RBS technique was used to determine nitrogen concentrations in organic fertilizers, which ranged from 0.9 to 1.2 atomic percent (at.%). Spectral analysis was carried out using GeoPIXE II software. The findings demonstrate the effectiveness of nuclear analytical techniques in assessing fertilizer quality. Importantly, the detection of potentially toxic elements underscores the need for stringent regulatory monitoring and the adoption of safer, more sustainable agricultural practices.

Speaker: BUSISIWE PERTUNIA MBATHA (University of Zululand)

Astrophysics & Space Science: Astrophysics: Session 6

Astrophysics & Space Science: Space Science: Session 6

Convener: Ruhann Steyn (Centre for Space Research, North-West University)

290 Simulating the field-line random walk process

The nature and structure of the heliospheric magnetic field play an important role in the transport of energetic particles throughout the heliosphere, but due to solar wind turbulence these magnetic field-lines become stochastic. To simulate the meandering of the Parker spiral due to turbulence, the convection-diffusion equation for the field-line density distribution, which describes the dispersion of field-lines, is transformed into a set of stochastic differential equations which is then solved using both a forward and backward formulation. It is shown that the simulation results can be well-fitted by a two dimensional Gaussian with a standard deviation of about 25 degrees at 1 AU. It is further shown that the Parker spiral becomes more underwound, on average, as the solar wind turbulence increases. By applying the backward approach, the field-lines can be traced back to the Sun from an observer at 1 AU, thereby quantifying the probability of magnetic connection when interplanetary turbulence is accounted for.

Speaker: Johan Joubert (NWU)

76_Johan_Joubert.pdf

291 A Comparative Analysis of Stochastic Differential Equation Solvers for Modeling Galactic Cosmic Ray Modulation

The numerical modeling of energetic particle transport in turbulent astrophysical plasmas, governed by
Fokker-Planck equations, is a cornerstone of modern space physics. Methods based on Stochastic Differential
Equations (SDEs) have gained popularity over traditional finite-difference schemes due to their unconditional
stability and suitability for parallel computing. The accuracy and computational cost of these simulations depend
critically on the choice of numerical integration scheme. While the Euler-Maruyama method remains most common,
higher-order methods like Milstein and Stochastic Runge-Kutta (SRK) promise greater accuracy. This study presents
a comparative analysis of these three SDE solvers in the context of Galactic Cosmic Ray (GCR) modulation in the
heliosphere, evaluating their relative performance to inform best practices for large-scale simulations. We simulated
GCR proton transport under identical conditions, assessing results against multiple benchmarks: modulated GCR
intensity compared with the Local Interstellar Spectrum and in-situ data from IMP-8 and PAMELA; statistical
distributions of pseudo-particle exit positions; visualization of characteristic trajectory paths; and quantitative
accuracy assessment using Euler-Maruyama as the baseline. All simulations used an identical number of
pseudo-particles for each scheme. Our findings indicate that all three solvers produce highly consistent results. The
computed energy spectra showed good agreement with experimental data, while exit position distributions and
trajectory analyses revealed no statistically significant differences between schemes. Percentage deviations remained
minimal across the parameter space studied. However, computational runtime varied considerably, with SRK
exhibiting the highest cost. These results suggest that for GCR modulation problems with the particle statistics
employed, higher-order schemes may not yield appreciably different physical results, validating the continued use of
the computationally efficient Euler-Maruyama method.

Speaker: Sello Motsoane

292 Solar modulation of cosmic ray antiprotons over the magnetic field reversal period

The rigidity spectra of cosmic ray antiprotons and protons have been measured simultaneously, averaged over a Bartel rotation (~27 days), by AMS-02 detector between May 2011 and June 2022. These precise observations provide a more powerful context to study charge-sign-dependent modulation in the A < 0 magnetic cycle, through the period covering the solar magnetic field reversal, and in the A > 0 cycle. In this study, the previously established set of proton modulation parameters that reproduced AMS-02 proton observations between 2011 and 2019 is applied in our comprehensive physics-based 3D-drift numerical model to simulate modulated antiproton spectra over the same period as a function of time and rigidity. We find that, in agreement with our drift model results, the observed antiprotons to protons ratio reaches its maximum value during the magnetic field reversal period. This study will further highlight the importance of using the correct method of representing observational data points measured over a wide rigidity bin of finite width, especially when comparison with numerical computations is the intended end results.

Speaker: THABO MAHLATJI (NWU Student)

153_Thabo_Mahlatji.pdf

293 Cosmic Ray Neutron Sensors for Soil Moisture Monitoring: Investigating Atmospheric Dynamics

Cosmic-ray neutron sensing (CRNS) is an accurate and non-invasive method that measures soil moisture estimates. This allows for continuous monitoring of soil moisture estimations at large-scale measurements, which is important for optimising irrigation and conserving water resources in the agricultural sector. It is based on the detection of fast (epithermal) neutrons, which are produced from high-energy cosmic-ray particles. Cosmic-ray particles are particles that originate from the Sun and distant galaxies that enter the atmosphere of Earth via the heliosphere, creating a cascade of secondary cosmic ray. These secondary cosmic-rays contain epithermal neutrons that interact inversely with hydrogen atoms in soil, thus providing a non-invasive method for monitoring moisture levels.
This work converts neutron flux to volumetric water content using the standard N$_0$ calibration method, which aids in evaluating the role of soil moisture on CRNS measurements. In particular, this study focuses on the influence of atmospheric dynamics, including evapotransoration, rainfall events, and humidity levels which are important in the agricultural industry during a growth season. Analysing the magnitude and variability of atmospheric dynamics are required for accurate soil moisture monitoring.
Within this study the detailed process of the CRNS calibration which relates the measured neutron intensity to volumetric soil content in a crop season, to establish if the CRNS measurements could detect atmospheric dynamics.
The results assess the sensitivity of CRNS measurements compared to atmospheric conditions and demonstrate the necessity of real-time atmospheric corrections for reliable soil moisture monitoring.
These findings establish methods to account for atmospheric dynamics in CRNS applications and provide protocols for optimizing sensor deployment in agricultural sectors.

Speaker: Aimee Dumont

SAIP_presenttaion_2026.pdf

Nuclear, Particle and Radiation Physics -1: Session 3

Convener: P. Z. Ngcobo (University of Zululand)

294 Effect of Coating Thickness on Proton Radiation Sensitivity for Titanium-Oxide Coated Novel Fiber Optic Sensors

The design of the ATLAS Inner Tracker (ITk), which will replace the Inner Detector of ATLAS at CERN, is nearly complete. Following the long shutdown after Run 3, this crucial component for the High-Luminosity era will be installed. However, reliable environmental monitoring tools are required to measure temperature and humidity, ensuring consistent data quality throughout the lifespan of the ITk. This need is addressed through the use of novel titanium oxide (TiO$_2$)-coated Long Period Grating (LPG) sensors, which are currently in full production. In this study, the relationship between coating thickness and LPG sensitivity to both radiation and humidity is investigated. The resulting sensitivity measurements can be used to optimise coating thickness for sensor applications in high radiation environments, including nuclear industries and space exploration. In particular, the results are used to optimise thickness and optimal sensor placement for LPGs being used within the ITk, specifically: ten-layer sensors are recommended for lower-radiation regions, while eight-layer sensors are better suited for higher-radiation areas.

Speakers: Abdool Sattar Cassim (University of Johannesburg), Emmanuel Igumbor (University of Johannesburg), Samuel Temaugee (University of Johannesburg), Timothy Brooks (University of Johannesburg)

333_AbdoolSattar_Cassim.pptx

295 Extracting Radioisotope Lifetimes from a 100 MeV Gamma Irradiation Experiment Using HPGe Spectroscopy

The Mineral Positron Emission Tomography (MinPET) technology enables a three-dimensional imaging of diamonds within a kimberlite host rock by reconstructing coincidence 511 keV gamma rays from $^{11}$C. These are produced via the $^{12}$C($\gamma$, n)$^{11}$C bremsstrahlung reaction during irradiation. However, the activation process also induces radioactivity in the surrounding kimberlite matrix, generating a mixed field of background isotopes that must be understood for radiological safety and signal discrimination. To investigate this, a Full-Dress Rehearsal (FDR) experiment was conducted at the ASTRID2 accelerator facility at {\AA}rhusrhus University, Denmark, using a 100 MeV electron beam to replicate the MinPET activation stage. High-purity germanium (HPGe) spectroscopy was employed to measure gamma emissions from irradiated samples. This study focuses on extracting the lifetimes of the resulting radioisotopes from the measured energy spectra. The experimentally determined lifetimes are compared with reference values from the Table of Radiation Isotopes. The results show good agreement between measured and tabulated lifetimes across all identified isotopes. These findings enable the construction of a comprehensive inventory of activation products and allow for clear differentiation from Naturally Occurring Radioactive Materials (NORM). The validated lifetime data contribute to a long-term radiological safety assessment, confirming that the isotopic signatures produced during MinPET operation are well characterized and consistent with established nuclear data.

Speaker: Thendo Emmanuel Nemakhavhani (UNIVERSITY OF JOHANNESBURG)

293_Thendo_Nemakhavhani.pptx

296 pnQRPA study to extract the axial-vector coupling strength from β-decay data

$\beta$-decay studies are important for searches for fundamental physics beyond the Standard Model [1, 2]. In particular, $\beta$-decay transition rates involve several crucial model-dependent variables such as nuclear matrix elements (NMEs), coupling constants, phase-space factors, etc, which may be calculated and compared with experiments. Of particular interest are NMEs and their relation to the weak axial-vector coupling strength ($g_{A}$). The NMEs contain information about the nuclear structure of the nuclei involved [3, 4]. The $g_{A}$ quantifies the strength of the spin-dependent part of the weak interaction in nucleons. For free nucleons, it’s value is determined by the partially conserved axial-vector current (PCAC) hypothesis, with $g_{A}=$ 1.27. However, in atomic nuclei, typically a quenched value is required that is usually attributed to multi-nucleon correlations [5]. One popular many-body technique used to investigate $g_{A}$ quenching and $\beta$-decay NMEs in medium to heavy nuclei is the proton–neutron quasiparticle random-phase approximation (pnQRPA) [3, 4, 5]. This work describes pnQRPA calculations to calculate the energy spectra of 12 odd-odd nuclei that were produced by Gamow-Teller (GT) $\beta^-/\mathrm{EC}$ transitions from even-even nuclei. The resulting wave functions were used to determine the quenching required for these cases, by matching theoretically predicted half-lives to experimental values.

References

[1] Alexander S. Barabash. Possibilities of future double beta decay experiments to investigate inverted and normal ordering region of neutrino mass. Frontiers in Physics, Volume 6 - 2018, 2019.

[2] J. Vergados, Hiroyasu Ejiri, and Fedor Simkovic. Theory of neutrinoless double beta decay. Reports on progress in physics. Physical Society (Great Britain), 75:106301, 09 2012.

[3] Jouni Suhonen and Osvaldo Civitarese. Review of the properties of the 0 nuclear matrix elements. Journal of Physics G: Nuclear and Particle Physics, 39:124005, 11 2012.

[4] Jouni Suhonen and Osvaldo Civitarese. Weak-interaction and nuclear-structure aspects of nuclear double beta decay. Physics Reports, 300(3):123–214, 1998.

[5] Jouni T. Suhonen. Value of the axial-vector coupling strength in and decays: A review. Frontiers in Physics, Volume 5 - 2017, 2017.

Speaker: Mr Sifiso Mngonyama (University of the Western Cape)

SAIP_final_fixed_complete_source_final_compiled.pdf

Nuclear, Particle and Radiation Physics -2: Session-6

Convener: Edward Nkadimeng (University of Witwatersrand)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

297 Searches for scalar resonances in the γγ + 0ℓ1τ final state at √s = 13.6 TeV with ATLAS Run 3 data using background modelling, spurious signal testing, and DSCB signal parameterisation

Despite the rich physics potential of the intermediate diphoton mass range of 130-200\,GeV, this regime remains one of the least constrained at the ATLAS experiment, motivating dedicated searches in the $\gamma\gamma + 0\ell1\tau$ final state. This work presents a study using Run~3 ATLAS data recorded between 2022 and 2024 at $\sqrt{s} = 13.6$\,TeV, corresponding to an integrated luminosity of 164\,fb$^{-1}$. Background contributions from $V\gamma\gamma$, Single Higgs production, $t\bar{t}\gamma\gamma$, and $\gamma\gamma +$ jets are modelled by fitting candidate functional forms to the $m_{\gamma\gamma}$ sideband regions and extrapolating into the signal window of 146-154\,GeV. A cut flow
table documents the weighted event yield at each selection stage, identifying areas of significant event loss and motivating selection optimisation. RNN-based working points, namely Loose, Loose with electron rejection, Medium, and Tight, are applied to the hadronic tau identification. A spurious signal test is performed to validate the background fitting function, followed by parameterisation of the signal shape using a Double-Sided Crystal Ball (DSCB) function, completing the signal and background modelling framework for this intermediate-mass regime.

Speaker: Thapelo Gerry Leboho (University of Witwatersrand)

332_Thapelo_Leboho.pdf

298 Searching for Diphoton Resonances in Association with Leptons in the Mass Range 130–200 GeV with the ATLAS Detector

Motivated by multi-lepton anomalies reported in the literature, which suggest the possible existence of a new scalar resonance with a mass around 150~$\pm$~2 GeV, this analysis searches for resonances decaying into two photons produced in association with leptons. Phenomenological studies indicate a significant excess in the diphoton spectrum at $152\pm 2$ GeV, as well as deviations in final states with multiple leptons, moderate missing transverse energy, and bottom-quark jets. These observations can be interpreted within extensions of the Standard Model such as the 2HDM+S, in which a heavy Higgs boson decays into lighter scalar states that subsequently produce diphoton and multi-lepton signatures.

The analysis uses ATLAS Run 3 proton-proton collision data at $\sqrt{s}=13.6$ TeV, corresponding to an integrated luminosity of 164 fb$^{-1}$. While previous ATLAS diphoton resonance searches have explored a broad mass range, the region between 130 and 200 GeV remains relatively unexplored for diphoton final states produced in association with leptons. This analysis therefore targets this mass window, providing sensitivity to complementary signatures of potential new physics. For this conference, the analysis is restricted to leptonic signatures and considers three exclusive channels: events with zero electrons or muons and exactly one $\tau$ lepton (0$(e,\mu)$, 1$\tau$), events with exactly one electron and no $\tau$ leptons or muons (1$e$, 0$(\tau,\mu)$), and events with exactly one muon and no $\tau$ leptons or electrons (1$\mu$, 0$(\tau,e)$).

The analysis strategy is designed to remain as model independent as possible, with the goal of setting upper limits on the production cross section times branching ratio for narrow resonances in diphoton-plus-lepton final states, and represents a first step in a broader program that will extend to additional final states, including dilepton, lepton + $b$-jet, and missing transverse energy channels, providing a foundation for testing the reported anomalies using Run 3 ATLAS data and probing potential new scalar resonances in a previously underexplored region of phase space.

Speaker: Phuti Rapheeha (University of the Witwatersrand)

462_Phuti_Rapheeha.pdf

299 General Applications of High Energy Physics methods to financial systems,

High-energy physics (HEP) experiments operate in data-intensive environments characterised by high event rates, complex detector systems, and the need to extract rare signals from significant backgrounds. This has led to the development of well-established methodologies for data acquisition, event selection, statistical inference, and large-scale data processing. In this work, we explore the general applicability of HEP-inspired methodologies to financial systems, which similarly involve continuous data streams, significant noise contributions, and intermittent extreme events. Rather than focusing on domain-specific financial modelling, the emphasis is placed on the transfer of data analysis frameworks developed within experimental particle physics. We investigate the adaptation of Monte Carlo techniques for modelling stochastic behaviour, likelihood-based approaches for parameter estimation, and event-selection strategies analogous to trigger systems used in collider experiments. In addition, concepts from detector data processing such as background estimation, noise filtering, and signal reconstruction are applied to financial time series to identify anomalous behaviour and characterise variability.The results demonstrate that HEP methodologies provide a systematic and scalable framework for analysing complex, high-dimensional datasets beyond traditional physics applications. This work highlights the broader relevance of experimental particle physics techniques in addressing challenges in financial data analysis and other data-driven domains.

Speaker: Nkosiphendule Njara

Photonics: Photonics Division Meeting

300 Tuning ITO nonlinearities towards telecom wavelengths

We demonstrate that post-deposition annealing provides an effective route to spectrally engineer the nonlinear optical response of indium tin oxide (ITO) thin films, with a pronounced enhancement at technologically relevant telecommunication wavelengths. Annealing-induced modifications to the epsilon‑near‑zero (ENZ) wavelength enable controlled spectral shifting of the material’s nonlinear response, resulting in a substantial improvement of the nonlinear absorption near 1550 nm. While the peak nonlinear response is reduced, annealing redistributes the nonlinearity over a broader spectral range, yielding enhanced performance across the near‑infrared. Spectroscopic ellipsometry reveals a complex permittivity response that cannot be captured by a simple Drude model, indicating the emergence of non‑Drude contributions to the optical behavior. Atomic force microscopy further suggests that these changes correlate with annealing-driven morphological evolution of the films. Our findings show that although spectral broadening ultimately limits the tunability of the wavelength corresponding to maximal nonlinearity, post‑annealing enables a significant and robust enhancement of the nonlinear response of ITO at 1550 nm, positioning it as a promising platform for nonlinear nanophotonic and telecom-scale applications.

Speaker: Wagner Tavares Buono (University of the Witwatersrand)

301 Photonics Division Meeting

Physics for Development, Education and Outreach

Convener: Buyi Sondezi (University of Johannesburg)

302 Developing Tutors while Supporting Students: Evaluating a Structured Consultation Programme in First-Year Physics

First-year physics courses often present significant conceptual and problem-solving challenges for students. To support student learning, a structured consultation programme was implemented in the PHY111 course, providing students with opportunities to engage with physics problems in small collaborative groups outside formal lecture sessions. Tutors received targeted training to facilitate the sessions and guide student discussions. This study evaluates tutors’ experiences participating in the consultation programme, focusing on the effectiveness of tutor training, tutors’ facilitation experiences, and the perceived impact of the programme on their professional development. Data were collected using a structured survey consisting of Likert-scale items and open-ended questions. Results indicate that tutors perceived the training as effective in preparing them to facilitate consultation sessions and reported increased confidence in explaining physics concepts. Tutors also reported that facilitating consultation sessions improved their own conceptual understanding and communication skills. The findings suggest that structured consultation programmes can simultaneously support student learning and contribute to tutor development. Implications for tutor training and academic support programmes in first-year physics are discussed.

Speaker: Dr Bako Nyikun Audu (University of the Western Cape)

303 Comparative Photoelectric Effect Experiment Using LEDs and Mercury Lamp Sources

We present a comparative study of the photoelectric effect experiment aimed at enhancing conceptual understanding in undergraduate physics laboratories. A traditional mercury (Hg) lamp with optical filters is evaluated alongside a modified setup using multiple light-emitting diodes (LEDs) as discrete wavelength sources. In addition, two measurement approaches—stopping potential and direct potential methods—are implemented and compared.
The spectral characteristics of the Hg lamp-filter combination and the LEDs are analysed to assess their suitability as quasi-monochromatic light sources. Using a common photovoltaic cell setup, stopping potential is measured as a function of incident light frequency for both light sources, enabling the determination of Planck’s constant via linear regression. A direct potential measurement technique is also employed to provide an independent determination of the same quantity.
Results from both light sources and both measurement techniques will be used to show a consistent linear relationship between potential and frequency, yielding comparable values of Planck’s constant within experimental uncertainty. Differences in spectral width, intensity stability, and contact potentials are examined to explain observed deviations.
This comparative approach demonstrates that LEDs provide a viable and effective alternative to traditional Hg lamps, while the inclusion of multiple measurement techniques reinforces key quantum concepts and experimental reasoning. The experiment supports deeper student engagement by allowing cross-validation of results and critical evaluation of assumptions, making it well suited for modern physics education.
Keywords: Physics education, photoelectric effect, LEDs, mercury lamp, Planck’s constant, experimental comparison

Speaker: Dr Hendrik Jacobus van Heerden (University of the Free State)

SAIP-2026-Edu-HJvanHeerden.pptx

304 INVESTIGATING TEACHERS’ PERCEPTIONS OF THE DECLINE IN GRADE 9 LEARNERS’ UPTAKE OF PHYSICAL SCIENCES IN THE FET PHASE

This study responds to growing anecdotal and media reports that Physical Sciences departments in some schools within the Western Cape Education Department are closing. One commonly cited explanation is the declining number of Grade 9 Natural Sciences learners who choose Physical Sciences in the Further Education and Training (FET) phase of secondary schooling. The primary aim of this research is to investigate the factors contributing to this decline in learner uptake.

The study is guided by third-generation Cultural-Historical Activity Theory (CHAT) as a theoretical framework to examine the complex social, institutional, and pedagogical dynamics influencing learner retention in Physical Sciences. A mixed-methods approach will be employed, specifically an explanatory sequential design informed by Plano Clark and Creswell, allowing for both quantitative and qualitative insights.

The central research question explores educators’ perceptions of why Grade 9 Natural Sciences learners choose or do not choose Physical Sciences at the FET phase. Three schools will be purposively selected for the study. Data will be collected through questionnaires and semi-structured interviews with educators.

The analysis will consider both in-class and out-of-class factors that may influence learners’ subject choices, including teaching practices, resource availability, learner attitudes, and broader socio-educational contexts. Preliminary findings will be presented and discussed, with the aim of contributing to strategies that support increased participation in Physical Sciences.

Speaker: Vuyolwethu Mavityo (UWC)

305 Beyond Stargazing: Astrotourism as a Science-Based Tool for Development

Astrotourism has emerged as an innovative form of sustainable tourism at the intersection of science engagement, environmental stewardship, and experiential learning. While often associated with stargazing, its broader value lies in translating scientific knowledge into accessible public experiences and fostering appreciation for dark and quiet sky environments.

Beyond its appeal to visitors, astrotourism acts as a catalyst for local economic development while promoting science literacy and environmental awareness. It also provides a platform to connect scientific and Indigenous knowledge systems, positioning the night sky as both a scientific and cultural resource that warrants protection.

The International Astronomical Union Office of Astronomy for Development recognises astrotourism as a flagship initiative demonstrating how science, particularly astronomy, can contribute to socioeconomic development. This presentation highlights practical resources developed by the OAD to support individuals, businesses, and observatories in integrating science-based nighttime activities into their offerings, enabling sustainable growth while safeguarding dark sky environments.

By promoting community ownership and empowerment, and encouraging collaboration between research institutions and local communities, these resources support bottom-up, locally driven initiatives. In doing so, they position science as a tool not only for discovery, but also for inclusive development, environmental stewardship, and cultural preservation.

Speaker: Joyful Elma Mdhluli (IAU Office of Astronomy for Development)

403_Joyful_Mdhluli.pdf

Physics of Condensed Matter and Materials

Convener: Setumo Motloung (Central University of Technology, Free State)

306 The design of NiO-Co3O4 heterostructures loaded with Er and Pr rare earth ions for the detection of hazardous air pollutants.

Air pollution represents a critical environmental threat, significantly degrading the ambient air quality through the presence of numerous atmospheric pollutants. Metal oxide semiconductor gas sensors are widely employed in gas sensing applications for the detection and analysis of lethal, explosive, and harmful gases. Even so, these metal oxide-based sensors still face a lot of restrictions such as high operating temperatures, high detection limits, low selectivity, low stability, and their sensitivity degrade quickly overtime. In this study, a hydrothermal method was used to fabricate simple two-dimensional (2D) multilayer nanomaterial gas sensors, designed to detect pollutants at relatively low concentrations, exhibit selectivity over various gases and demonstrate stability overtime. The proposed sensors are expected to simultaneously detect various gas analytes and identify low concentration analytes. This will be achieved through the incorporation of rare earth elements such as erbium (Er) and praseodymium (Pr). These elements possess a different atomic radii, Pr (1.13 Å) and Er (0.89 Å), meanwhile Cobalt (Co) and Nikel (Ni) exhibit comparable atomic radii of (0.82 Å) and (0.72 Å), respectively. It is expected that the loading of Pr will result into the formation of secondary phases, while Er, due to its atomic radius will be able to fit in into Co or Ni positions, thereby avoiding the formation of new phases. To identify optimal sensor performance, specific characterisation methods were employed. These methods include Braeuer-Emmett-Teller (BET), Scanning Electron Microscopy (SEM), Photoluminescence (PL), High Resolution Transmission Electron Microscopy (HR-TEM), X-Ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS).

Speaker: Joy Mothiba (University of Limpopo)

307 Influence of Ca2+ ions doping on the structural and electron spin resonance properties of ZnFe2O4 nanoparticles

CaxZn1-xFe2O4 (x=0.0-1.0) fine particles with particle size ranging from 8nm to 13 nm were investigated by XRD, TEM, FTIR, and electron spin resonance measurements. XRD spectra revealed (220), (311), (400), (420), (511), and (440) crystal planes characteristics of cubic spinel phase with no impurity peaks. A slight reduction in particle size with the increasing Ca2+ ion concentration observed. Electron spin resonance spectra showed single line signals relating well with cubic phase revealed by XRD data. Ca2+ ions doping appear to have significant effects on the signal line widths and resonance magnetic fields. ESR signals of the samples with composition with x is equal/greater than 0.2 show hysteresis between signals recorded on cycling the magnetic fields. Broadening of the ESR signals and the shifts towards lower resonance magnetic fields with increasing Ca content have been explained based on increasing dipole-dipole interaction between the particles and Lande g factors. the evolutions of the magnetic parameters such as line widths, resonance magnetic fields and spin relaxation time as a function of composition and particle size are also presented.

Speaker: Mr sinegugu Shezi

308 The VEC effect on the electronic and lattice dynamic stability of B2 Ti50Ru50-xNix: A supercell approach

TiRu forms a B2 (CsCl-type) structure at high temperature, which typically transforms to lower-symmetry phases upon cooling; however, in TiRu, B2 remains stable down to room temperature. This study investigates the effect of Ni substitution on the electronic structure and lattice dynamic stability of the B2 Ti50Ru50 phase using first-principles calculations within the supercell (SC) approach. The objective is to assess the role of valence electron count (VEC) of Ni in modifying the stability of the B2 TiRu phase and its potential to induce martensitic phase transformation (MPT). The phonon dispersion results confirm that the unalloyed B2 Ti₅₀Ru₅₀ phase is dynamically stable, exhibiting only positive vibrational frequencies. Upon alloying, Ti8Ru5Ni3 (18.75 at. % Ni) remains dynamically stable, whereas at Ti8Ru4Ni4 (25 at. % Ni) and above it shows the appearance of negative vibrational frequencies, indicating the onset of lattice dynamic instability. The electronic structure, analysed using the partial density of states (PDOS), shows that Ni-3d states contribute significantly near the Fermi level. This modifies the Ti-Ru hybridisation and shifts the electronic states towards the anti-bonding region, resulting in reduced electronic stability. The observed phonon softening is consistent with these electronic changes. These results demonstrate that Ni d-orbital filling effectively modifies the electronic structure and promotes lattice instability, providing a pathway for inducing martensitic phase transformation in the B2 TiRu phase.

Speaker: Bongani Ngobe (MINTEK and Wits University)

309 CH 4 detection capabilities of Co 3 O 4 - ZnO nanofibers: synergistic effects of p-n junction

Khanyisile Nkuna1*, Rudolph Erasmus1, Teboho Mokhena2 and Katekani Shingange1
1Materials Physics Research Institute (MPRI), School of Physics, University of the Witwatersrand, Johannesburg 2000, South Africa
2Mintek Nanotechnology Innovation Centre, Randburg 2194, South Africa
Correspondence: 2318077@students.wits.ac.za

Abstract :
Chemiresistive gas sensors are widely used for gas detection due to their low cost, simple fabrication, and rapid response. These sensors operate by changing electrical resistance when exposed to target gases, making them suitable for environmental monitoring, industrial safety, and healthcare applications. However, their performance is often limited by poor selectivity, low sensitivity in complex environments, and instability under varying operating conditions. The combination of p-type and n-type semiconductor materials to form a heterojunction is an effective strategy to overcome these limitations. In this study, one-dimensional (1D) cobalt oxide (Co3O4) and zinc oxide (ZnO) nanofibers were combined to form a p-n heterojunction (Co3O4-ZnO) using the electrospinning technique. Co3O4 exhibits excellent catalytic activity and p-type conductivity, while ZnO is a stable n-type semiconductor with high electron mobility. The heterojunction enhances charge separation and transfer, thereby improving gas response and sensitivity. ZnO, Co3O4, and Co3O4-ZnO were successfully synthesized via electrospinning. X-ray diffraction (XRD) confirmed that ZnO has a hexagonal wurtzite structure, Co₃O₄ has a spinel cubic structure, and both phases co-exist in the composite. Scanning electron microscopy (SEM) showed smooth nanofibers before annealing and coarser structures after annealing. The band gaps of ZnO, Co3O4, and Co3O4-ZnO were determined to be 3.39 eV, 2.55 eV, and 3.61 eV, respectively, using diffuse reflectance spectroscopy (DRS). Photoluminescence (PL) analysis revealed defect-related emission bands centred at 488 nm and 688 nm.The materials demonstrated selective detection of methane (CH4) at an operating temperature of 300 °C. The gas sensing mechanism and contributing factors will be further discussed.

Keywords : Gas sensor , 1D , ZnO, Co3O4, p-n heterojunction.

Speaker: Ms Khanyisile Nkuna (Materials Physics Research Institute (MPRI), School of Physics, University of the Witwatersrand, Johannesburg 2000, South Africa)

Theoretical and Computational Physics: Session 6

Convener: Bahati Mukeru

310 Derivation of moments and cumulants for Open Quantum Brownian Motion

Open Quantum Brownian Motion (OQBM) describes the dynamics of a quantum Brownian particle with an additional internal degree of freedom. Building on the microscopic derivation of OQBM with a two-level internal degree of freedom presented by Sinayskiy and Petruccione (2015 Phys. Scr. T165, 014017), we revisit the associated OQBM master equation and derive the equations for the $n$-th moments and cumulants of the position distribution of the OQBM walker. These equations are solved numerically for Gaussian initial distributions. Our numerical analysis shows a nonzero third-order cumulant, indicating that the intrinsic generator of OQBM dynamics is non-Gaussian.

Speaker: Ayanda Zungu

311 Evaluation of the Asymptotic Iteration Method for Computing Quasinormal Modes of Diverse Black Hole Spacetimes.

We review the Asymptotic Iteration Method (AIM) as a computational framework for determining the quasinormal mode (QNM) spectra of black hole spacetimes, with particular emphasis on its regimes of applicability and failure. We identify scenarios in which AIM does not yield accurate or reliable eigenvalues and analyze the underlying causes of these breakdowns. To address these limitations, we investigate two complementary diagnostic approaches, inspired by the work of Batic and Saad, which provide criteria for assessing the validity of QNMs obtained via AIM. Our preliminary results indicate that, while one of these approaches offers a practical tool for detecting convergence issues and enhancing the robustness of AIM-based spectral computations, certain inconsistencies arise in Batic’s convergence theorem.
These findings highlight the need for a more rigorous understanding of stability and convergence properties in existing methods for computing black hole QNMs.

Speaker: Mr Tal Leshem

Development_of_new_methods_for_calculating_black_hole_quasinormal_modes.pdf

Evaluation of AIM using two distinct approaches.pdf

312 Optimazation of renewable energy using Flextool.

Energy is the core of any developing or developed country. For countries with their economy relying heavily on industries, more energy is consumed, and as a result, they contribute more to global warming and climate change. South Africa, rich in renewable energy potential, is experiencing a major shift as it works to incorporate clean energy sources into its overall power supply to meet the nation’s increasing energy needs in a sustainable way. This research proposes a comprehensive study and analysis that aims to optimize renewable energy generation in South Africa using FlexTool, an innovative software platform designed specifically for energy system modelling and analysis. By harnessing the capabilities of FlexTool, this study aims to Utilize FlexTool’s optimization capabilities by creating advanced algorithms for maximizing renewable energy generation in S.A. This includes considering resource availability, grid constraints, and socio-economic considerations. Preliminary optimization results indicate that a strategically balanced renewable portfolio—anchored by solar PV, wind, and battery storage—can deliver substantial improvements in system performance The results aids to the transition toward a sustainable and resilient energy future in South Africa.

Speaker: Marandela Mulalo Valencia

313 Variational Monte Carlo and the Quantum Enhanced Metropolis-Hastings Algorithm

This work investigates a hybrid quantum–classical enhancement of the Metropolis–Hastings algorithm within a variational Monte Carlo framework. Using a single-thread Monte Carlo approach, we estimate the ground-state energy of a small Hamiltonian system by computing the dominant eigenvalue of a symmetric $3\times3$ matrix as a proof of concept.

A quantum-enhanced acceptance mechanism, inspired by the quantum Metropolis–Hastings algorithm, is integrated into the classical sampling procedure. The performance of this hybrid method is compared to the classical algorithm in terms of convergence speed and estimator precision. Numerical simulations demonstrate that the quantum-enhanced approach achieves faster convergence and improved accuracy for the test system, despite being implemented on classical hardware.

These results highlight the potential of quantum-assisted sampling techniques to improve the efficiency of Monte Carlo methods and provide a pathway toward scalable quantum algorithms for high-dimensional quantum systems.

Speaker: Mishka Naicker (University of KwaZulu-Natal)

16:10 Buffer

Poster Session 2

314 A Cosmological Framework with Variable Fundamental Constants

The standard ΛCDM model of cosmology, while remarkably successful, faces a critical challenge:
the > 5σ discrepancy between local and early-Universe measurements of the Hubble constant
(H0)—the Hubble Tension. This persistent anomaly suggests that our assumption of immutable
fundamental constants (the fine-structure constant α, gravitational constant G, and speed of light c)
may require re-examination. We present a novel theoretical framework that self-consistently incor-
porates simultaneous temporal and spatial variations of α, G, and c within a modified FLRW metric,
extending earlier scalar-tensor and varying-speed-of-light theories.
This research directly engages with the Fourth Industrial Revolution through its methodological core:
we employ machine learning algorithms (TensorFlow, Scikit-learn) for Bayesian parameter esti-
mation and model comparison against combined observational datasets (Planck CMB, SH0ES super-
novae, quasar absorption spectra). These 4IR tools enable us to efficiently explore high-dimensional
parameter spaces and quantify the statistical evidence for varying constants—a task impossible with
traditional grid-search methods.
Our preliminary analytical results indicate that time-variation in α and G can modify the sound
horizon at recombination, potentially reconciling the local and primordial H0 measurements while
remaining consistent with Big Bang Nucleosynthesis and large-scale structure constraints. The
framework also produces testable predictions for upcoming facilities (ELT, JWST, SKA), position-
ing African research at the forefront of precision cosmology.
Inclusivity and sustainability are embedded in this project: it is conducted within the Fundamental
Theoretical Physics Group at NUST, fostering local research capacity in Zimbabwe, and has been
accepted for presentation at the African Astronomical Society (AfAS) 2026 Conference. By devel-
oping home-grown expertise in computational cosmology and data science, this work contributes
to building a sustainable African physics community capable of addressing fundamental questions
while participating in the global 4IR transformation.

Speaker: Bekithemba Sibanda (National University of Science and Technology)

315 A Simulation of Galactic Proton Spectrum Observed Over Solar Minimum Period of Solar Cycle 24

Measurements of cosmic ray isotope fluxes by spacecraft missions, such as
PAMELA, have generated interest in the study of solar modulation over changing
solar activity. These exceptional measurements provide an opportunity for
improved numerical modeling of the solar modulation of galactic cosmic rays
across a wide range of rigidity at Earth. In this study, a three-dimensional drift
model will be used to calculate theoretical spectra comparable to the solar cycle
24 minimum period of 2006-2012 observed spectra. This modeling would be
based on intrinsic parameters derived from comparing model computations to
data already collected by the spacecraft. The model is used to model global
spectra and at lower energies e.g., at 1 GeV,in order to study time-dependent
modulation.

Speaker: THATO MAJA

316 A study of Phase Stability and Atomic Ordering in Quenched Fe-Ga-Tb Magnetostrictive Alloys

The magnetostrictive performance of Fe-Ga alloys is strongly governed by atomic ordering and metastable phase stability, yet the role of rare-earth microalloying under non-equilibrium processing remains poorly understood. This study investigates the effect of a minor Tb addition (0.1 at.%) and rapid water quenching on the phase stability and microstructure of Fe-26Ga and Fe-27Ga alloys using X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Rapid quenching from 900°C suppresses long-range B2 and D0₃ ordering, retaining a predominantly disordered A2 matrix. However, XRD reveals a persistent tetragonal distortion (c/a ≈ 1.0041-1.0043), indicating stabilisation of a non-cubic lattice domains under non-equilibrium conditions. TEM analysis shows that this distortion originates from nanoscale ordered regions with local symmetry breaking as determined from non-colinear superlattice reflections observed from electron diffraction. In Fe-26Ga-0.1Tb, Tb remains in solid solution and enhances these nanoscale distortions, producing a chemically homogeneous matrix with sustained tetragonality. In contrast, Fe-27Ga-0.1Tb exhibits Tb-rich precipitation, leading to microstructural heterogeneity and a slight relaxation of lattice distortion. These results demonstrate that Tb modifies atomic ordering locally rather than suppressing it, with the resulting phase stability and tetragonality strongly dependent on Ga concentration and solubility. This provides a structural basis for tailoring magnetostrictive performance in rare-earth-doped Fe-Ga alloys.

Speaker: Anelisiwe Gqumani (Nelson Mandela University)

317 Ab initio study of thermodynamic, mechanical and vibrational properties of FePt-Cu alloys

FePt alloy, particularly in its ordered L10 phase is widely recognized as a promising candidate for advanced magnetic recording applications due to its exceptional magnetic anisotropy and thermal stability. However, its practical implementation is limited by the several challenges, including high ordering temperature and high material cost due to Pt content. In this study, ab initio study based on density functional theory (DFT) was employed to investigate the thermodynamic, mechanical and vibrational properties of FePt-Cu alloys. Formation energy calculations showed that Cu substitution reduces thermodynamic stability of FePt alloy. The calculated Pugh's ratio and Poisson's ratio indicated that alloying with Cu effectively improve the ductility. Vibrational properties analysed from phonon dispersion curves showed that Cu substitution maintain the vibrational stability of the FePt alloy. The findings demonstrated that Cu incorporation significantly affects thermodynamic, mechanical and vibrational properties of FePt alloy, offering valuable insights into tailoring FePt-based alloys for potential applications in magnetic storage technologies.

Speaker: Mr Mashilo Matlala (University of Limpopo)

318 Adsorption of Croconate Dye (CR1) on (210) Brookite TiO2, Surface for Application in Dye-Sensitized Solar Cells (DSSCs)

Dye-sensitized solar cells (DSSCs) have emerged as promising low-cost alternatives to conventional photovoltaic technologies, in which device efficiency is largely determined by interactions between dye molecules and semiconductor surfaces. In this study, the adsorption behavior of a croconate dye on the brookite TiO₂ (210) surface was investigated using density functional theory (DFT) to evaluate its potential for DSSC applications.
The results indicate that the dye forms stable adsorption configurations on the TiO₂ (210) surface via its anchoring groups, with adsorption energies of approximately 3.9 eV, confirming strong dye–surface binding. Dye adsorption significantly modifies the electronic properties of the TiO₂ surface and enhances electronic coupling at the dye–semiconductor interface. Frontier molecular orbital analysis reveals favorable alignment between the dye’s LUMO and the TiO₂ conduction band, facilitating efficient electron injection. The dye exhibits strong optical absorption extending into the visible and near-infrared regions (up to ~680 nm). A red shift in the absorption spectrum upon adsorption indicates enhanced light-harvesting capability. Charge density analysis further confirms effective electron-hole separation and efficient charge transfer from the dye to the semiconductor.
The findings demonstrate that the brookite TiO₂ (210) surface provides an effective platform for strong dye adsorption, improved charge transfer, and enhanced optical response, highlighting the potential of croconate dyes as efficient sensitizers for DSSC applications.
Keywords: Croconate dye, DFT, DSSCs, TiO₂, brookite (210), adsorption

Speaker: Nkosana Mkhatshwa

319 Adsorption studies of dithiocarbamate collectors on the mooihoekite (402) surface

Mooihoekite (Cu₉Fe₉S₁₆) is a copper–iron sulfide with a tetragonal, metal-rich structure derived from chalcopyrite, commonly intergrown with other sulfides such as haycockite and pentlandite in complex ore deposits. Despite its relevance in flotation systems, its flotation behavior remains poorly understood, limiting the optimization of separation processes that rely on mineral-specific surface and electronic properties. To address this, density functional theory with dispersion corrections and a Hubbard U term (DFT-D+U) was used to evaluate surface energies and identify stable crystallographic planes for adsorption studies. The (402) surface was found to be the most stable, exhibiting the lowest positive surface energy, and was selected as a representative model of reactive sites likely encountered under flotation conditions. Adsorption of S-allyl-N-diethyl-dithiocarbamate (ADEDTC) and O-isopropyl-N-diethyl-thionocarbamate (IPDETC) on the (402) surface showed strong chemisorption through coordination between sulfur atoms and surface Fe and Cu sites. ADEDTC displayed more exothermic adsorption energy (–550.02 kJ·mol⁻¹) than IPDETC (–193.11 kJ·mol⁻¹), indicating stronger and more favorable interactions. Bader charge analysis confirmed significant electron transfer from surface Cu and Fe ions to the adsorbates, with greater charge redistribution observed for ADEDTC. These findings provide insight into surface–collector interactions and highlight ADEDTC as a promising collector for improving flotation performance in Mooihoekite-bearing ores.

Speaker: Kagiso Mashishi (University of Limpopo)

320 AIMD-MLFF study of bulk, surface and collector’s adsorption on sperrylite (PtAs2) mineral

The machine-learned force field (MLFF) method embedded within ab-initio molecular dynamics (AIMD) in VASP was employed to investigate the bulk, surface and collector’s adsorption properties on the PtAs₂ (100) surface at 300K. This approach was used to gain deeper insight into the physicochemical behaviour of the sperrylite mineral (PtAs₂). AIMD-MLFF bulk training gave a lattice parameter of 5.977 Å, while a 4×4× supercell yielded a value 5.991 Å. These lattice parameters were in good agreement with the experimental lattice parameter of 5.970 Å. From the Ab-initio calculations the (100) surface was identified as the most stable, with surface energy of 1.00 J/m². The MLFF-trained (100) surface yielded a higher surface energy of 1.76 J/m², while the supercell model produced a value of 1.67 J/m². Among the collectors studied, dibutyl-dithioarsenate (DBDTAs) was found to be the most favourable based on the ab-initio calculations, with adsorption energy of –330.738 kJ/mol. The AIMD-MLFF approach gave similar adsorption energy of –398.888 kJ/mol for the trained system and –499.426 kJ/mol for the applied force-field. These findings indicated that the AIMD-MLFF approach was a valuable and efficient tool for simulating large-scale systems, providing results both consistent with both density functional theory (DFT) calculations.

Speaker: Ivyn Ndhlovu (University of Limpopo)

321 Algorithm for detecting Radio Frequency Interference (RFI) in MeerKLASS Intensity mapping Data

MeerKLASS is a single dish HI intensity mapping survey of the MeerKAT Telescope. Probing the 21 cm signal is coupled with challenges from foregrounds and radio frequency interferences (RFI) which contaminates the data, and in turn our cosmological signal. The MeerKLASS collaboration has produced a detection of the HI cosmological signal using cross-correlations with galaxy surveys. However, low-lying RFI still remains. By removing these low lying RFI we expect to have reduced data loss due to aggressive flagging of RFI contaminants across channels to increase our S/N for an improved detection of the 21 cm signal. Low lying RFI lies below the noise measurement of single dish instruments and would require an algorithm that is able to boost the sensitivity and contrast the underlying RFI for flagging. In this presentation I will highlight the SSINS (Sky-Subtracted Incoherent Noise Spectrum) Algorithm (Wilensky et al, 2019 PASP 131 114507) that I have adapted to be applied to the MeerKLASS data to remove faint RFI signatures.

Speaker: Tamera Kassie (SARAO, UWC)

322 ANALYSING VARIABILITY IN BLUEBERRY GALAXIES IN SEARCH OF AGN ACTIVITY

Blueberry galaxies are a class of low-mass, low-metallicity, and extremely compact starbursts, considered local analogues to high-redshift star-forming galaxies. This study investigates the hypothesis that a subset of these systems hosts Active Galactic Nuclei (AGN). Photometric light curves for an initial sample of 20 Blueberry galaxies were extracted from Asteroid Terrestrial-impact Last Alert System ATLAS, with 17 sources retained after quality and error filtering, and analysed using a Python script. AGN candidates were identified based on two principal criteria: low-level stochastic variability and achromatic behaviour across optical bands, indicative of accretion disk instabilities. The analysis reveals that the majority of galaxies in the final sample exhibit low-amplitude variability within the 0–0.5 magnitude range, consistent with low-luminosity AGN activity. Additionally, several galaxies display coherent, long-term variability that can be modelled by a single Fourier series across both c- and o-bands, under the assumption of achromatic behaviour, suggesting the presence of a centralised energy source. However, no individual galaxy satisfies all selection criteria sufficiently to be definitively classified as an AGN. Despite this, the prevalence of AGN-like variability signatures across the sample suggests that weak or obscured nuclear activity may be common in Blueberry galaxies. These results warrant further multi-wavelength observations for definitive confirmation.

Speaker: Unathi Tshabalala

323 Assessment of the Impact of SAIP ECD Science Skills Accelerator Programme Training on ECD Practitioners' Confidence in Vhembe District, South Africa

Early exposure to science is critical for developing curiosity, problem-solving skills, and foundational cognitive abilities in young children. However, many Early Childhood Development (ECD) practitioners in South Africa lack the training, confidence, and resources to effectively integrate science into daily teaching practices. This study evaluates the impact of the South African Institute of Physics (SAIP) ECD Science Skills Accelerator Program implemented in ECD centers in the Vhembe District, Limpopo Province.
A quantitative pre–post intervention design was employed to assess changes in practitioner confidence in teaching science concepts. Data were collected from approximately 131 ECD practitioners across multiple centers using a structured Likert-scale questionnaire administered before and after the training. The intervention introduced practitioners to simple, low-cost, and context-appropriate science experiments designed for early learning environments.
The findings indicated generally low levels of confidence among practitioners in facilitating science activities. Following the intervention, there was a clear and meaningful improvement in confidence levels across key areas, including the ability to conduct hands-on experiments and explain basic scientific concepts to learners. Statistical analysis confirmed that the observed improvements were significant, demonstrating the effectiveness of the training program.
Qualitative feedback further supported these findings, with one practitioner noting: “The simple experiments made science easy to teach and enjoyable for both teachers and children.” The 63% participants recommended continued training and support, highlighting the importance of sustained professional development and access to appropriate teaching resources.
The findings demonstrate that targeted, practical training interventions can significantly enhance ECD practitioners’ confidence and capacity to deliver early science education. The study recommends scaling up such programs, integrating science training into ECD professional development frameworks, and providing affordable, context-relevant teaching materials. Strengthening practitioner competence at the early childhood level is essential for building strong STEM foundations and improving long-term educational outcomes.

Speaker: Vhuhwavho Khomunala (University of Venda)

324 AUTOMATED FOURIER ANALYSIS WITH PYTHON

This study addresses the inefficiencies of existing Fourier analysis software for astronomical time-series data, such as Period04 and FAMIAS, which typically require file-by-file processing. The aim was to develop a scalable and automated solution for batch processing large datasets in order to save time and improve reproducibility. To achieve this, a Python-based Fourier analysis pipeline was designed and implemented using scientific libraries such as NumPy, SciPy, and Astropy. The workflow includes discrete Fourier transform computation, automated peak-frequency detection and validation, False Alarm Probability estimation through Monte Carlo simulations, and output visualization. The developed pipeline successfully automates the Fourier analysis process and enables the efficient processing of multiple files. Its results agree with Period04 within computational tolerance, with a mean percentage difference of approximately 1.1%. This represents a substantial improvement over the manual approaches used in Period04 and FAMIAS, reducing total analysis time and removing user-dependent inconsistencies. Overall, the Python-based pipeline provides a fast, scalable, and reproducible alternative for Fourier analysis in astronomy, and is particularly well suited to large datasets, such as light curves from hundreds of stars, making it valuable for automated workflows in fields such as asteroseismology.

Speaker: Sibongile Majola

325 AUTOMATED FOURIER ANALYSIS WITH PYTHON

This study addresses the inefficiencies of existing Fourier analysis software for astronomical time-series data, such as Period04 and FAMIAS, which typically require file-by-file processing. The aim was to develop a scalable and automated solution for batch processing large datasets in order to save time and improve reproducibility. To achieve this, a Python-based Fourier analysis pipeline was designed and implemented using scientific libraries such as NumPy, SciPy, and Astropy. The workflow includes discrete Fourier transform computation, automated peak-frequency detection and validation, False Alarm Probability estimation through Monte Carlo simulations, and output visualization. The developed pipeline successfully automates the Fourier analysis process and enables the efficient processing of multiple files. Its results agree with Period04 within computational tolerance, with a mean percentage difference of approximately 1.1%. This represents a substantial improvement over the manual approaches used in Period04 and FAMIAS, reducing total analysis time and removing user-dependent inconsistencies. Overall, the Python-based pipeline provides a fast, scalable, and reproducible alternative for Fourier analysis in astronomy, and is particularly well suited to large datasets, such as light curves from hundreds of stars, making it valuable for automated workflows in fields such as asteroseismology.

Speaker: Sibongile Majola

326 Automating Galaxy Classification with Unsupervised Machine Learning

Self-supervised learning offers a powerful way to analyse large astronomical image datasets without relying on labelled training samples. Mohale & Lochner (2024) demonstrated this by fine-tuning a ResNet-18 model with the Bootstrap Your Own Latent (BYOL) framework to produce 512-dimensional feature representations for galaxies in the Dark Energy Camera Legacy Survey (DECaLS) survey. After reducing these features via Principal Component Analysis (PCA), they used Bayesian Gaussian Mixture Models (BGMM) to test whether the representations could recover broad morphological structure without labels, demonstrating that self-supervised features contain useful information for separating galaxy types.

In this project, I reproduce their representation-learning experiment and evaluate how useful these features are for unsupervised morphology studies. I apply a more efficient clustering strategy, MiniBatchKMeans to test whether the representations can separate basic morphological classes. To measure this, I construct a high-confidence labelled sample from the Galaxy Zoo: DECaLS catalogue and compare the cluster assignments with the volunteer classifications. I further assess the structure of the feature space using Uniform Manifold Approximation and Projection (UMAP) projections and examine the stability of the cluster assignments across repeated runs.

The results show that the PCA reduced BYOL-derived features are able to distinguish between round ellipticals, spirals, and edge-on galaxies. This demonstrates that self-supervised features provide a promising and scalable basis for unsupervised galaxy morphology analysis in future large surveys.

Speaker: Kirsten Elliott (University of Western Cape)

327 Building a Public Database for Ground-Based Solar Observations at the North-West University

The solar telescope observatory at the North-West University has been operating since 2022 as a facility for routine ground-based solar observations in South Africa. A new development is the establishment of a public database through which these observations are made available in support of both education and scientific research. The resulting data products are intended to provide users with accessible visual representations of the observations while preserving the full scientific integrity of the original datasets. The images are presented in a physically meaningful solar reference frame that is directly comparable to space-based observations. The database includes basic preview plots facilitating inspection of the data and supporting efficient browsing of the available observations. In addition, the data are made available for download, enabling students, educators, and researchers to undertake independent analyses and further scientific investigation. This public resource has the potential to strengthen solar physics in South Africa by improving access to locally acquired solar observations for training, collaboration, and future research.

Speaker: Ruhann Steyn (Centre for Space Research, North-West University)

328 Characterization and Analysis of Radio Sources Detected in MeerKAT Galaxy Proto-Cluster Fields

The Square Kilometre Array (SKA), set to be the largest radio telescope ever constructed, is currently under development in South Africa(mid-frequency array) and Australia(low-frequency array). As a key precursor instrument, South Africa’s MeerKAT radio telescope provides unprecedented sensitivity and resolution at L-band frequencies. This study utilises early reduced MeerKAT observations targeting candidate proto-cluster fields at intermediate to high redshifts. Beyond the primary science targets, these observations have detected a vast population of auxiliary radio sources totalling over 15,000 detections across three regions, offering a unique opportunity to study galaxy populations in dense environments.

The primary objective of this work is to systematically characterise these sources to determine their physical properties and evolutionary states. Through automated source extraction, catalogues of precise positions and flux densities are generated. These detections are subsequently cross-matched with a suite of highly sensitive, deep multiwavelength surveys, including KiDS DR5 (UV/optical), VIKING (near-IR), AllWISE (mid-IR), and Herschel (far-IR). This broad spectral coverage enables the use of colour–colour diagnostics, morphological analysis, and spectral energy distribution (SED) modelling to classify the population into star-forming galaxies, green valley systems, and active galactic nuclei (AGN).

By leveraging MeerKAT’s high resolution, the spatial structure and population statistics within these fields are investigated, with a specific focus on identifying unique objects that lack counterparts in existing literature. As one of the first deep-field characterisation studies of its kind using MeerKAT, this project provides critical insights into the interplay between radio-detected populations and their environments. Given the unprecedented depth of the data, this work aims to produce unique, publishable results on the nature of galaxy assembly in the early universe.

Speaker: SEKHONA TOLE (university of the western cape)

329 CHEMICAL SURFACE PROPERTIES OF MN3O4 (001), (010) & (100) FACETS.

Lithium-ion batteries (LIBs) currently dominate the rechargeable battery market, yet they face inherent limitations including low energy density (100-200 Wh/kg), high production costs, supply chain vulnerabilities, and safety concerns arising from flammable lithium and organic electrolytes. Metal-air batteries (MABs) have emerged as a high-capacity alternative, offering theoretical energy densities between 400 and 1700 Wh/kg. Among these, the Fe-air battery (764 Wh/kg) is particularly attractive due to its low cost, environmental friendliness, and reduced susceptibility to dendrite formation compared to zinc-air systems, thereby enabling improved operational safety and longer cycle life. However, Fe-air batteries face challenges such as poor rate capability, limited cycling stability, and side reactions that degrade performance. The use of manganese-based catalysts in the air cathode has shown potential in improving electrochemical activity and stabilizing discharge products. In this study, density functional theory (DFT) was employed to investigate the surface properties of Mn3O4 (001), (010), and (100) facets. Surface optimization revealed that the (001) facet is the most stable, with the lowest surface energy (0.35362 J/m²), followed by (100) (0.45739 J/m²), while (010) is the least stable (0.46972 J/m²). Based on these findings, Fe3O4 nanocluster adsorption was modelled on the most stable (001) surface and three configurations were formed (O-A, O-B, and O-C). The nanocluster was positioned on the most isolated Mn atom on the surface and evaluated across the three configurations to determine the most favourable oxygen binding orientation. The O-A configuration was found to be the most stable, with an adsorption energy of -5.40419 eV.
Keywords: Metal-air batteries, Energy density, Surface energy, Adsorption energy.

Speaker: Edwine Matlou (University of Limpopo)

330 Chemical trends in defect stability, electronic and magnetic properties of 3d TM-doped WSe₂

Dilute magnetic semiconductors (DMSs) offer a promising route to novel hybrid electronic devices that can integrate logic processing, communication, and data storage into a single integrated circuit (IC). Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are particularly appealing for DMS applications due to their excellent spin relaxation times and long spin diffusion lengths. Unlike graphene, TMDCs have an adjustable bandgap and exhibit stronger spin-orbit coupling—features that are essential for spin-based logic and non-volatile memory technologies. However, since TMDCs do not naturally possess magnetic properties, it is necessary to induce magnetism through doping to produce DMS.
In this study, we explore the electronic structure and energetic stability of single 3d transition metal (TM) dopants in WSe₂ monolayer using density functional theory (DFT) calculations. Our findings reveal that the chemical stability of TM dopants in WSe₂ varies significantly depending on both the doping site within the lattice and the electronic 'd' character of the transition metal. For dopants ranging from Sc to Co, substitutional doping sites are energetically preferred, showing lower formation energies compared to adatom and interstitial doping. In contrast, from Ni to Zn, adatom doping becomes more stable, while substitutional doping is energetically unfavorable. It's also worth noting that monolayer WSe₂ inherently possesses a direct bandgap. We find that doping does not always preserve the direct bandgap. Additionally, incorporating 3d transition metal atoms into WSe2 lattice introduces defect energy levels within the bandgap, with the band gap of WSe2 reduced to between 0.05 eV to 1.0 eV across the 3d series. Furthermore, we find that increasing the dopant concentration lowers the formation energy per atom in WSe2, favouring clustering. These results present important implications to the understanding of properties of transition metal dopants in WSe2, as well as in other dilute magnetic semiconductors where the effect of aggregation of dopants has generally been neglected.

Speaker: Prof. Evans Benecha (University of South Africa)

331 Comparative gas sensing performance of LaFeO3 and SmFeO3 perovskite nanoparticles prepared by Hydrothermal Method .

Lanthanum- and samarium-based perovskites with the general formula ABO₃ were synthesized using the hydrothermal method. Structural characterization by X-ray diffraction (XRD) confirmed the formation of pure-phase LaFeO₃ and SmFeO₃, with crystallite sizes increasing from 10 nm to 19 nm. High-resolution transmission electron microscopy (HRTEM) further verified the perovskite structure, revealing a lattice spacing (d-spacing) of 0.232 nm. UV–Vis analysis indicated a slight increase in band gap energy for the samples. Scanning electron microscopy (SEM) images showed predominantly spherical nanoparticles. Gas sensing measurements demonstrated that the SmFeO₃-based sensor exhibited higher sensitivity toward volatile organic compounds (VOCs) compared to flammable gases. Additionally, the sensor showed good selectivity, repeatability, and stability. Notably, the SmFeO₃ sensor achieved a limit of detection (LoD) of approximately 2 ppm for NO₂ gas at an operating temperature of 125 °C.

Speaker: Philani Kunene (University of Zululand)

332 Comparison study on the TeO2-based materials developed using HNO3 and H2O2 for gas sensing applications

Effective air quality monitoring in mining environments remains challenging due to limited access to reliable, accurate, and fast gas-sensing technologies. Semiconductor metal oxide gas sensors represent a promising alternative owing to their simple design, robustness, and high sensitivity. This study investigates the synthesis, structural, and morphological characterization, and gas sensing performance of nanostructured tellurium dioxide (TeO2). TeO2 nanostructures were prepared from Tellurium (Te) powder oxidized with nitric acid (HNO3) and/or hydrogen peroxide (H2O2), followed by hydrothermal treatment to tailor morphology and surface properties, which are critical for gas-solid interactions. The X-ray powder diffraction analysis revealed that HNO3-oxidized TeO2 crystallized in the α-TeO2 phase, with a tetragonal structure and space group P41212, in good agreement with the crystallographic information file (COD-1537586). In contrast, the H2O2-oxidized TeO2 exhibited a mixed phase composition, indicating incomplete phase transformation from Te(powder) to TeO2. Scanning electron microscopy images showed that H2O2-oxidized TeO2 consisted of agglomerated nanoparticles, whereas the HNO3-oxidized TeO2 formed well-defined hollow octahedral structures. This morphology provides an increased surface‑to‑volume ratio and accessible diffusion pathways, which are advantageous for enhanced gas adsorption and charge transfer. Diffuse reflectance spectroscopy indicated a higher reflectance (~80%) across the visible region for HNO3-oxidized TeO2 compared to H2O2-oxidized TeO2 (~70%). The optical band gap energy extracted using the Kubelka-Munk function was 3.8 eV for HNO3-oxidized TeO2 and 3.93 eV for the H2O2-oxidized TeO2 sample, suggesting subtle variations in electronic structure related to synthesis conditions. Furthermore, to study the sensitivity and selectivity of the materials, the HNO3-oxidized TeO2 was tested for NO2, CH4, SO2, NH3, and H2S at various operating temperatures.

Speaker: TUMI KEVIN MGAGA (UNIVERSITY OF THE FREE-STATE)

333 Composition-Dependent Electronic and Optical Properties of Ge-Doped CsSnI₃ from First-Principles Calculations

This study presents a first-principles investigation of germanium (Ge)-doped CsSnI₃ perovskites as promising candidates for lead-free photovoltaic applications. With increasing demand for environmentally friendly and high-efficiency solar materials, all-inorganic tin-based perovskites have emerged as viable alternatives to toxic lead-based systems, though their practical implementation is hindered by stability and performance limitations. In this work, density functional theory (DFT) calculations within the CASTEP framework are employed to explore the effects of partial Ge substitution at the Sn site on the structural, electronic, and optical properties of CsSnI₃.
Unlike previous studies that primarily focus on limited doping configurations, this work provides a systematic comparative analysis across multiple Ge doping concentrations, offering deeper insight into composition-dependent electronic behavior. The results reveal that Ge incorporation preserves the perovskite crystal framework while inducing favorable modifications in the electronic structure.
Furthermore, this study establishes a direct correlation between local bonding environments and electronic structure evolution, providing atomistic-level understanding of defect suppression mechanisms induced by Ge doping. Ge incorporation effectively reduces defect states within the bandgap, contributing to improved electronic quality. Optical properties investigations further demonstrate enhanced absorption in the visible region, highlighting the potential of doped systems for efficient light harvesting.
By integrating structural stability, electronic tuning, and optical response within a unified framework, this work offers new insight into the role of B-site engineering in lead-free perovskites beyond conventional performance metrics. Overall, the findings demonstrate that targeted doping serves as an effective strategy to tailor the optoelectronic properties of CsSnI₃ without compromising structural integrity, providing a viable pathway toward the design of high-performance, stable, and environmentally sustainable photovoltaic materials.

Speaker: Dr Neelam Saghir (University of South Africa)

334 Comprehensive Ab-Initio Study of Optoelectronic Properties of CsGeBr3 using Quantum Espresso and WanTiBEXOS.

Abstract
Perovskites exhibit a remarkable array of optoelectronic properties that are vital for advancing photovoltaic designs. In-depth investigations into the electronic and optical characteristics of all-inorganic CsGeBr3 have been conducted using density functional theory with the PBE exchange-correlation functional. To obtain precise and realistic bandgap values, the HSE06 hybrid functional was used, providing a comprehensive understanding of these promising materials. Various studies in the literature have done this. The electronic calculations convincingly demonstrate that CsGeBr3 is p-type semiconducting, revealing bandgap energies of 0.66 eV and 1.856 eV when using the PBE and HSE06 XC functionals, respectively. However, the optical properties of these materials have never been studied using a more accurate many-body Bethe–Salpeter equation (BSE), which accounts for excitonic effects, thereby providing in-depth optical analysis [1]. The optical properties of these materials are crucial for various applications, such as photovoltaic technology. In this study, we provide a comprehensive analysis of the optical and electronic properties of CsGeBr3 obtained using HSE06 functional coupled with BSE and Wannier interpolations [2], as implemented in Quantum-Espresso and WanTiBEXOS [3] simulation tools.
References
1. Yan, J., Jacobsen, K.W., and Thygesen, K.S., 2012. Optical properties of bulk semiconductors and graphene/boron nitride: The Bethe-Salpeter equation with derivative discontinuity-corrected density functional energies. Physical Review B—Condensed Matter and Materials Physics, 86(4), p.045208. https://journals.aps.org/prb/abstract/10.1103/PhysRevB.86.045208
2. Pela, R.R., Hsiao, C.L., Hultman, L., Birch, J., and Gueorguiev, G.K., 2024. Electronic and optical properties of core–shell InAlN nanorods: a comparative study via LDA, LDA-1/2, mBJ, HSE06, G 0 W 0 and BSE methods. Physical Chemistry Chemical Physics, 26(9), pp.7504-7514. https://pubs.rsc.org/en/content/articlehtml/2024/cp/d3cp05295h
3. Dias, A.C., Silveira, J.F., and Qu, F., 2023. WanTiBEXOS: A Wannier-based Tight Binding code for electronic band structure, excitonic, and optoelectronic properties of solids. Computer Physics Communications, 285, p.108636. https://www.sciencedirect.com/science/article/pii/S0010465522003551

Speaker: Mr Kamogelo Sebolai (University of Johannesburg)

335 Computational Study of Thermodynamic, Mechanical, and Electronic Properties of LiMn1.5Ni0.5O4 Cathode Material

The escalating demand for efficient, reliable, and sustainable energy storage has catalysed intensive research into advanced cathode materials for next-generation of lithium-ion batteries. Among these cathode materials, LiMn1.5Ni0.5O4 (LMNO) has emerged as a frontrunner due to its high operating voltage (~4.9 V), cost-effective composition, and advantageous 3-D lithium diffusion pathways. Despite these benefits, LMNO’s practical implementation is hindered by poor rate performance and structural instability, largely stemming from Mn3+ induced distortions and low intrinsic conductivity. To address these limitations, this study employs Density Functional Theory with Hubbard correction (DFT+U) to evaluate the thermodynamic, mechanical, and electronic properties of bulk LMNO. Our results yield a negative heat of formation (-91.97 eV), confirming robust thermodynamic stability. Furthermore, mechanical analysis reveals a ductile nature, indicated by a (B/G > 1.75), which suggests the material possesses the structural resilience necessary to withstand the stresses of repeated battery cycling. Electronic analysis identifies an indirect band gap of 1.73 eV, characterizing the material as a semiconductor. This is further corroborated by the Density of States (DOS), which illustrates that the valence bands are dominated by O-2p states while the conduction states are governed by Mn/Ni-3d orbitals. Ultimately, while LMNO exhibits exceptional stability and mechanical integrity, its modest electronic conductivity remains a bottleneck for high-rate applications, underscoring the critical need for targeted material modification strategies.

Keywords: LiMn1.5Ni0.5O4, Rate performance, Lithium-ion batteries, DFT+U, Mechanical properties.

Speaker: Ms Thandi Mulaudzi

336 Confronting the Universe’s Accelerating Expansion: Insights from a Hybrid Scale Factor

The Lambda Cold Dark Matter (ΛCDM) model is a well-known cosmological model that has been used to investigate the acceleration of the universe. In our earlier study, we introduced a modified scale factor (Aydiner et al., 2022) to examine the universe’s accelerating expansion without relying on the conventional dark energy framework of the lambda-cold-dark matter model. In order to test the viability of the Modified Scale Factor (MSF), we constrained the model using the observational Hubble parameter (OHD) and the distance modulus measurements (SNIa) and a combination of the data sets. Through numerical simulations and observational constraints, our findings demonstrated that the MSF model aligns well with empirical data, offering a competitive alternative to CDM. Specifically, we explore its implications for cosmic evolution beyond the previously considered data sets, assess its predictive power in a broader observational context, and investigate potential refinements that improve its consistency with large-scale structure observations.

Speaker: Goratamang Ann Gaedie (North-West University)

337 Constraining Spider Pulsar Binary Plasma Properties Through Radio Eclipses

In spider pulsar binaries, the energetic pulsar wind ablates the companion star, producing dense intrabinary plasma that leads to radio eclipses and complex propagation effects impacting the observed pulsar signal. Previous studies have shown that the properties of these eclipses can constrain the geometry and dynamics of the intrabinary shock formed by the interaction between the pulsar wind and the companion outflow (e.g., Wadiasingh et al. 2017). In this work, we analyse frequency-dependent radio eclipses in selected spider pulsar binaries using multi-frequency radio observations. The structured intrabinary plasma can refract and focus the pulsar radiation, producing observable signatures such as dispersive delays, flux variations, changes in polarisation properties, and changes in eclipse morphology near ingress and egress. We interpret these propagation effects using simplified theoretical models of the intrabinary plasma environment, linking the observed frequency-dependent behaviour to the density distribution and geometry of the shocked plasma surrounding the companion. By combining eclipse morphology, polarisation changes, and dynamic spectral behaviour across multiple observing frequencies with theoretical modelling of plasma propagation effects, we constrain the structure and physical conditions of the intrabinary plasma. These results provide insights into the density distribution and geometry of the pulsar–companion interaction region and contribute to a better understanding of mass loss from the companion and the interaction of pulsar winds with their binary environment.

Speaker: Thulo Letsele

338 Deep-Level Defects in Electron-Irradiated n-GaAs Investigated by Conventional, Laplace DLTS and Admittance Spectroscopy

Gallium arsenide (GaAs) remains a key material for optoelectronic and high-speed electronic applications, including laser diodes, infrared light-emitting diodes, solar cells, and high-frequency switching devices. In this study, electrically active defects in Si-doped n-type GaAs are investigated using conventional Deep Level Transient Spectroscopy (DLTS), Laplace DLTS, and Admittance Spectroscopy.
Palladium (Pd) Schottky barrier diodes (SBDs), 0.5 mm in diameter and 150 nm thick, were fabricated on 5 µm Si-doped n-GaAs layers grown on n⁺-GaAs substrates (Spire Semiconductor). Current–voltage (I-V) measurements show low reverse leakage currents, confirming good diode quality, while capacitance–voltage (C-V) profiling indicates a uniform carrier concentration of ~1.2 - 1.4 × 1015 cm-3 over a depth range of 1 - 3.5 µm.
Conventional DLTS measurements reveal that the reference material is dominated by the well-known EL2 defect, with no additional deep levels detected. Following electron irradiation, several additional defect states are introduced. Particular attention is given to the dynamic behaviour of the EL2 defect. High-temperature DLTS measurements (>350 K at 80 Hz) confirm its presence, while Laplace DLTS is used to resolve changes in its fine structure before and after electron irradiation at varying fluences.
Trap concentrations were evaluated using a double-pulse DLTS technique, and the results were correlated with admittance spectroscopy measurements. The combined approach provides insight into the configurational complexity and defect interactions associated with EL2, particularly under irradiation-induced conditions.

Speaker: Dr Assane Talla (Nelson Mandela University)

339 Density Functional Theory Driven Numerical Analysis of High-Efficient CsGeBr3 Perovskite Solar Cells

Abstract
The research developments of innovative photovoltaic designs that not only achieve high efficiency but also remain affordable have grown significantly in recent years. In particular, the eco-friendly perovskite-based solar models show incredible promise for a sustainable energy future. Perovskites, due to their unique properties such as tunable energy bandgap, long carrier diffusion lengths, impressive electron and hole mobilities, and superior absorption coefficients, stand as viable candidates for advancing photovoltaic applications, for which they may expand photovoltaic engineering beyond traditional silicon (Si) and toxic lead (Pb)-based cell designs, which are proven to be more efficient, yet expensive and environmentally harmful [1, 2]. In this work, new findings on lead-free CsGeBr3 perovskite-based photovoltaic devices will be reported. These were computed theoretically using density functional theory (DFT) coupled with a 1-dimensional solar cell capacitance simulator (SCAPS-1D). In particular, we optimized PSCs using optoelectronic properties that we derived from DFT and Bethe-Salpeter equation (BSE), which are more realistic than analytical methods that are usually used in many studies in the literature.
References:
1. Kheswa, B.V. and S.N.T. Majola, Simulation of novel CsSnBr3 perovskite solar cells achieving efficiency of 31.62 %. Physica Scripta, 2025. 100(1): p. 015017. https://dx.doi.org/10.1088/1402-4896/ad986e
2. Dar, S.A. and B.S. Sengar, Optimization and Performance Analysis of Inorganic Lead-Free CsSnBr3 Perovskite Solar Cells Using Diverse Electron Transport Materials. Energy & Fuels, 2024. 38(9): p. 8229-8248. https://doi.org/10.1021/acs.energyfuels.4c00953

Speaker: Mr Kamogelo Sebolai (University of Johannesburg)

340 Detection of the kinematic Sunyaev-Zeldovich signals using Pairwise momentum estimator.

The kinematic Sunyaev-Zel’dovich (kSZ) effect comes from the Doppler shift of Cosmic Microwave Background (CMB) photons scattered by moving galaxy clusters. It offers a strong way to study the large-scale velocity field and test cosmological models. In this thesis, we aim to detect the kSZ signal by using the pairwise momentum estimator on data from the Atacama Cosmology Telescope Polarimeter (ACTPol). This method improves the weak kSZ signal by measuring the average momentum between pairs of galaxy clusters. This allows us to extract information about their peculiar velocities. We combine high-resolution CMB temperature maps from ACTPol with external DES Legacy Survey cluster catalogs for extra kSZ signals.

Speaker: Ms Ayanda Mnikathi

341 DEVELOPMENT OF MACHINE LEARNING MODELS TO PREDICT PROPERTIES OF HALIDE PEROVSKITE MATERIALS

Angela Maboa1, Keletso Monareng1, Petros Ntoahae1 and Rapela Maphanga2

1Department of Physics, University of Limpopo, Private bag X 1106, Sovenga, 0727, Polokwane, South Afri-ca
2Renewable and Sustainable Energy Research Centre, Sol Plaatje University, Private Bag X 5008, Kimberly, 8300, South Africa
3 National Institute for Theoretical and Computational Sciences, NITheCS, Gauteng, 2000, South Africa

Abstract
Halide perovskite materials are the foremost candidates for the next generation of optoelec-tronics, but the vast chemical space makes experimental screening for the stable phases time-consuming and expensive. This study presents the development of robust supervised machine learning models to predict the four key properties of halide perovskite materials, namely : energy,band gap, formation energy, energy per atom, and Fermi energy. The data set sourced from the Material Project Database was curated and engineered to extract meaningful descriptors using structural, compositional, and electronic features. Several ensemble-based models, including Random Forest, Extra Trees, and Gradient Boosting, were evaluated using the two metrics, regression score (R²) and mean square error (MSE). The analysis revealed that the Random Forest model was the most effective in capturing electronic transitions, yielding the highest precision for band gap predictions (R² = 0.989, MSE = 0.001). The Extra Tree Regressor outperformed others in predicting the formation energy (R² = 0.831, MSE = 0.100), the energy per atom (R² = 0.788, MSE = 1.500) and the Fermi energy (R² = 0.830, MSE = 1.041). The findings validate the use of ensemble learning as a robust approach for mapping the intricate relationships between the structure and properties of halide perovskites. This work provides a scalable computational bridge for accelerating the deployment of efficient halide perovskites for clean energy.

Speaker: Ms Angela Mmasefako Maboa (University of Limpopo)

342 DFT screening of interfacial properties in Cbznaph-SAMS for stable inverted perovskite solar cells.

Carbazole-based self-assembled monolayers (SAMs), such as CbzNaph, have attracted interest for their hole-selective performance in inverted perovskite solar cells [1,2]. This is attributed to their large dipole moments and strong π–π stacking interactions. Despite their improved performance, they still face long-term stability challenges due to their susceptibility to solvent-induced reconstruction [3]. This prompts a search for durable SAMs to extend lifetime and minimise the environmental footprint for perovskite photovoltaics. CbzNaph molecules can be viewed as either substituted or heavily functionalized adducts of a helical dibenzo[c,g]carbazole core, and derivatives with electron-withdrawing peripheral groups exhibit substantially higher interfacial polarisation than those with neutral substituents. The activity of a molecule depends on its molecular properties; thus, understanding them in detail is important for designing molecules with better electronic and optical properties. The current study focuses on CbzNaph derivatives in which the periphery is systematically substituted with strong electron-withdrawing moieties (cyanovinyl, halogen) alongside UV-reactive crosslinking groups (allyl, azide). The goal of this study is to identify how these targeted structural modifications influence molecular behaviour and property investigation across different media.

Computational studies were performed on selected derivatives, utilising density functional theory (DFT) with implicit solvation models to simulate both vacuum and polar solvent environments. The ongoing study additionally investigates the binding energies of the derivatives on model ITO surfaces, with the aim of quantifying how these modifications modulate adsorption strength and enhance resistance to solvent-induced desorption and reconstruction.

The results show that variation in peripheral functionalization significantly influences the molecular properties under consideration. These include a systematic deepening of HOMO levels for hole extraction, a maintained wide bandgap for electron blocking, and a profound, media-dependent increase of molecular dipole moments.

Keywords: self-assembled monolayers, carbazole derivatives, inverted perovskite solar cells, density functional theory, hole-selective contacts.

Speaker: Dr NEANI TSHILANDE (University of Venda)

343 Dopant-Concentration Dependence of Structural and Transport Properties in Ni/Co-Doped LiMn2O4 spinel from Molecular Dynamics Simulations

Molecular dynamics simulations were employed to investigate the effect of Li+ transport in Co- and Ni-doped spinel nanostructures. LiMn2-xMxO4 (0 ≤ x ≤ 0.08, M=Co and Ni) spinel nanostructures were successfully generated with the simulated amorphization and recrystallization. The spinel structure, which is a promising cathode material for lithium-ion batteries due to its cost-effectiveness, high-rate capabilities, and environmental benignity. The study revealed that the MO6 (M=Mn, Co, Ni) framework can be improved by partially substituting Mn with Co or Ni, which is in good accord with previous studies. It was also found that the structural stabilization with Co and Ni can also positively influence the transport of Li+ ions in the spinel structure. The Li+ diffusion coefficients of Li+ ions in LiMn1.92Co0.08O4 and LiMn1.92Ni0.08O4 were found to be 5.538 x 10-6 cm2/s, 6.359 x 10-6 cm2/s, and 2.971 x 10-5 cm2/s at 300 K, respectively. Correspondingly, at the temperature of 340 K, the diffusion coefficient of Li+ ions in LiMn1.92Co0.08O4 and LiMn1.92Ni0.08O4 is 8.142 x 10-6 cm2/s, 8.502 x 10-6 cm2/s, and 4.213 x 10-5 cm2/s, respectively. The Ni-doped spinel nanostructure exhibits remarkable Li+ ion transport, which is crucial for large-scale applications, particularly in electric vehicles. It is also very crucial to optimize the Co or Ni content to achieve peak performance. The current study uncovered that increasing the concentration of Ni could be detrimental to the transport of Li+ ions in the spinel structure. However, increasing the Ni content was found to improve the diffusion of Li+ ions in the material, despite previous findings suggesting otherwise. Moreover, the study also demonstrated that Nano-structuring can substantially improve the diffusion of Li+ ions in the spinel structure. The structural stability, rate capability, and practical capacity of LiMn2O4 spinel cathode material can be enhanced through partial substitution of Mn with Ni and Co.

Speaker: Mr Tharollo Malepe (University of Limpopo)

344 Effect of annealing temperature on structure, morphology, and optical properties of La2Z nTiO6

Double perovskites are known for their wide, indirect band gaps. However, systematic investigations into the effect of annealing temperature on the coupled structural evolution, morphology, and defect-related optical properties of undoped La₂ZnTiO₆ remain limited. Therefore, this study investigates the effect of annealing temperature on the structural, morphological, and optical properties of La₂ZnTiO₆. In this work, La₂ZnTiO₆ was synthesized using a low-temperature sol–gel method. X-ray diffraction analysis showed that, as the annealing temperature increases, the crystallite size increases while the interplanar spacing decreases, with a single-phase structure forming above 600 °C. Scanning electron microscopy revealed that higher annealing temperatures yield more coalesced, denser surfaces with well-defined grains. UV–Vis analysis indicated an indirect band gap of 3.33 eV. Photoluminescence studies showed excitation peaks centered at 369, 405, 417, and 512 nm. A strong red emission band centered at 701 nm was observed under 369 nm excitation, attributed to deep-level defects. Furthermore, the color rendering index (CRI, Ra) indicated that the excitation wavelength strongly influences the material's luminescence. These results highlight the significant role of annealing temperature in tuning the properties of La₂ZnTiO₆ for potential optoelectronic applications.

Speaker: Asanda Lakaje (University of the Free State)

345 Effect of Shell Thickness on Interfacial Stability in Li2MnO3 Core–Shell Cathodes

Lithium-ion batteries are a crucial technology for energy storage and cathode materials play a key role in their performance. Core-shell architectures are emerging as an effective strategy to address structural degradation and phase instability in lithium-rich cathodes such as Li2MnO3. By stabilising interfaces, these heterostructures enable improved electrochemical performance and enhanced material stability. However, practical applications are hindered by challenges in synthesising uniform structures, modelling atomic-scale behaviour at the interface and achieving a stable, coherent connection between the core and shell. To explore these interfacial challenges, we constructed Li2MnO3/Li0.69MnO core-shell structures using a custom integration framework that ensures charge neutrality, realistic separation distances and optimised atomic alignment. Molecular dynamics simulations were then employed to investigate how varying shell thicknesses (5 Å, 15 Å, and 25 Å) influence interfacial integrity and structural evolution under multiple thermodynamic constraints. Shell thickness was found to play a critical role in stabilising the interface, with thicker shells (25 Å) promoting structural coherence and reducing atomic disorder. In contrast, thinner shells introduce localised strain and lattice mismatch that can compromise interface stability. These results provide atomistic insights into how shell morphology affects structure and stability at the core-shell interface, offering valuable guidance for the rational design of durable and efficient lithium-rich cathodes for next-generation lithium-ion batteries.

Speaker: Tshidi Mogashoa (University of Limpopo)

346 Effect of thermal annealing on the structural, optical and thermoluminescent properties of NaYF4 nanoparticles

NaYF4 nanoparticles were synthesized using a solution combustion method at 500 °C and subsequently annealed at 700 °C to investigate the effect of thermal treatment on their structural, optical, and thermoluminescent properties for dosimetric application. X-ray diffraction (XRD) analysis confirmed the coexistence of cubic and hexagonal phases in both samples, while annealing led to enhanced crystallinity, as evidenced by peak sharpening, increased crystallite size, reduced lattice strain and dislocation density. Raman spectroscopy further revealed improved lattice ordering through the emergence of sharper vibrational modes, consistent with structural refinement. Scanning electron microscopy (SEM) showed a transition from highly agglomerated, fine particles in the as-prepared sample to larger, coalesced grains with smoother morphology after annealing. Optical absorption studies indicated significant modification of the electronic structure, with the band gap decreasing from ~5.07 eV to 3.45 eV following annealing. Thermoluminescence (TL) analysis revealed a dominant low-temperature glow peak in both samples. After annealing, the glow peak shifted slightly towards higher temperature with reduced intensity, indicating a decrease in shallow trapping centres and the formation of more thermally stable traps. The TL intensity increased linearly with radiation dose, confirming first-order kinetics and demonstrating suitability for dosimetric applications. Repeatability measurements showed stable TL response with coefficient of variation values below 5% for both samples. Activation energies determined using the initial rise (IR) method were 0.59 ± 0.01 eV and 0.62 ± 0.01 eV for the as-prepared and annealed samples, respectively, indicating improved trap stability after annealing. These results demonstrate that thermal annealing significantly modifies the defect structure and trapping characteristics of NaYF4, making it a promising candidate for stable thermoluminescent dosimetry applications.

Speaker: Prof. Pontsho Mbule (University of South Africa)

347 Effect of Zinc concentration on ZnxFe2o4 for detecting toxic and flammable gaese

ABSTRACT
Non-stoichiometric spinel ferrites are attracting increasing interest for gas sensing because their electrical and surface properties can be altered through composition control. In this work, ZnxFe₂O₄ NPs with varying zinc content (0.90, 0.95, 1.00, 1.05) were synthesised through the microwave-assisted coprecipitation method and investigated for the detection of toxic and flammable gases. The influence of non-stoichiometry on the structural, morphological, and electronic properties was examined using X-ray diffraction and transmission electron microscopy, confirming the formation of nanostructured spinel phases with controlled deviations from stoichiometry. Gas sensing measurements were performed against representative reducing gases at operating temperatures of 25 – 225°C. The results show that both zinc-deficient (x=0.90 and 0.95) and zinc-rich (x = 1.05) compositions display different sensing behaviours compared to stoichiometric ZnFe₂O₄ (x =1). The Zn0.95Fe₂O₄ exhibited the highest response of S = 2941.59 to LPG at 25°C, with a response (106s) and recovery (630s) times. These findings indicate that modifying the Zn:Fe ratio change surface adsorption sites, thereby enhancing selectivity. Overall, the study demonstrates that controlled variation of zinc in non-stoichiometry ZnxFe₂O₄ proves to be an effective strategy for improving sensitivity and selectivity of the sensor towards H2S, SO2, CO2, H2 and LPG gas detection, making them good for environmental monitoring and industrial safety applications.

Speaker: Vuyolwethu Mhlebi (University of Zululand)

348 Electron spin resonance study of Ce3+ and Dy3+ ions substituted cobalt and nickel nanoferrites : Low field microwave absorption

Ce3+ and Dy3+ ion substituted cobalt and nickel ferrites (CoCexDyxFe2-2xO4, NiCexDyxFe2-2xO4 and CoCexFe2-xO4 (0 ≤ x ≤ 0.05)) with fine particles (9 ≤ D ≤16 nm) were synthesized by glycol-thermal method. XRD analysis of samples investigated confirmed single phase cubic spinel structure with no impurity peaks. Broad electron spin resonance (ESR) signals for cobalt substituted compounds reveal stronger dipole-dipole interactions between the particles and presence of the novel low field microwave absorption signals in addition to the broad high field signals. An increase in low field signals with increasing rare earth ion concentrations has been observed. Rare earth ion substituted nickel ferrites show narrow signals indicative of stronger super exchange interactions between magnetic moments with no evidence of low field non-resonant absorption. Results show significant modification of the magnetic properties of cobalt and nickel ferrite due to Ce3+ and Dy3+ rare earth ions substitutions.

Speaker: Anele Madlala (Iyunivesiti Walter Sisulu)

349 Electronics and structural properties of Indium Selenide

Indium (II) selenide is a layered material with useful properties for electronics, solar cells, and other modern technologies. It is made up of thin sheets of atoms that are held together by weak forces, and it also belongs to group of metal chalcogenides. The study is about the atomic structure and electronic properties of InSe using density functional theory (DFT). Looking at the structural properties, the lattice constants, total energy, volume, bulk modulus and bulk modulus derivative were calculated. The general lattice optimization of hexagonal structure generated the lattice constants a = b = 7.60 Bohr (4.02 Å) and c = 34.04 Bohr (18.02 Å). In addition, the electronic band structure and total density of states were used to analyse the electronic properties. The calculated lattice constant and bulk modulus agree with some of the previous calculation. Furthermore, the band structure and total density of state suggests that hexagonal InSe is a semiconductor material with an indirect band gap of approximately 1.4 eV.

Speaker: Mr Tsietsi Rex Mooka (University of Limpopo)

350 Elongated Radio Galaxies in MeerKAT Observations of Proto galaxy-clusters

We will present results of an on-going study of some of the auxiliary detections made in MeerKAT observations to constrain Proto galaxy-clusters. The observations are estimated to constitute more than 5000 radio sources in each of the three fields that were observed. This work will identify and conduct an analysis of the Elongated Radio Galaxies detected in one of the three observed fields of these MeerKAT galaxy proto-clusters. Elongated Radio Galaxies are a subset of the largest known astrophysical objects, called Giant Radio Galaxies (GRGs), which can span millions of light-years and are defined by their immense radio-emitting structures that extend far beyond the host galaxy. The reasons for the extreme size of GRGs and the specific conditions that lead to their formation are still subjects of ongoing debate and research.

The goal of the project will be to characterise and analyse them individually and also in the context of literature, including determining which are completely new sources that may be detected and discovered in the field for the first time. The project started with an extraction of the detected sources with their positions and fluxes, and then cross matched these with observations at other wavelengths to determine those already studied by other telescopes and published in literature or simply crossmatched in surveys by other telescopes. Preliminary analysis of the sources, which will be presented at this conference, is indicating a diverse morphology and spectra that will allow us to investigate the evolution of jets and lobes of the giant radio galaxies in our images.

Speaker: Bevan Petersen (University of the Western Cape)

351 Employing Empirical Mode Decomposition for Investigating Temporal Systematics in HERA observations

Systematic effects are a major obstacle in 21 cm radio interferometry,
where faint cosmological signals are obscured by instrumental and
observational contamination. This work presents a set of diagnostic
methods designed to detect and characterize temporal systematics in
interferometric data from the Hydrogen Epoch of Reionization Array
(HERA).

We begin with the Temporal Discontinuity Index and Spectral
Discontinuity Index to identify abrupt changes in signal power across
time and frequency. These metrics, combined with statistical tools,
enable improved detection of problematic antennas and reveal
associations with other systematic effects. To further improve
identification in complex cases where multiple systematics overlap, we
apply Empirical Mode Decomposition, which separates time-series data
into components associated with different temporal scales. This allows
clearer isolation of systematic features that are otherwise difficult
to distinguish. Our results demonstrate that these methods effectively
detect and characterize systematic effects, providing a framework for
antenna performance assessment. The approach is directly applicable to
HERA and scalable to future large radio interferometers.

Speaker: Mekuanint Kifle Hailemariam (University of the Western Cape)

352 Engineering of MoS₂-based sensor toward ppb-level H₂S detection.

Air pollution remains one of the world's major challenges today. The continuous release of gases such as H₂S, CO, and NOx. The pollutants contribute to climate change, global warming, and various health-related diseases. Gas sensing technology has therefore emerged as an effective approach for monitoring and controlling air pollution. Two-dimensional (2D) layered materials, particularly MoS2, have attracted significant attention as next-generation gas-sensing materials due to their tunable band gaps, high surface areas, and abundant active sites that promote effective gas adsorption. In this work, MoS2 nanostructures were synthesised via a hydrothermal method, with the amount of N, N-Dimethylformamide (DMF) varied from 0 to 15 mL to investigate its influence on morphology, surface area, and sensitivity. Structural analyses showed characteristic peaks of MoS2, confirming the successful formation of crystalline MoS2, in agreement with the Crystallographic Information File entry MP-1434. A shift toward lower diffraction angles accompanied by peak broadening was observed, indicative of reduced crystallinity induced by DMF. Furthermore, the average crystallite size decreases from approximately 7 nm to 4 nm as the DMF content increases to 15 mL. Strong absorbance bands in the visible region were observed, and the optical band gaps were estimated to be approximately 1.66 eV in the absence of DMF and decreased to 1.5 eV with 15 mL of DMF. These MoS₂ nanoflowers demonstrated strong potential as low-temperature gas sensors, particularly for detecting H2S at parts-per-billion levels.

Speaker: Ntsako Jason Mathebula (University of the Free State)

353 Enhanced toluene detection using Ag-functionalized high surface area Cr2O3@SnO2 core–shell heterostructure-based gas sensor

The development of highly selective and low-temperature gas sensors remains an imperative challenge for air quality monitoring and industrial safety. The toxicity and flammability of toluene, along with its associated risks to human health, render early detection and real-time monitoring essential. This study explores the novel Cr2O3-core@SnO2-shell heterostructures functionalized with silver (Ag) nanoparticles to improve charge transfer and promote catalytic surface reactions. Structural analyses confirmed the formation of heterostructures, a multi-core-shell structure, and successful noble-metal decoration. The Brunauer, Emmett, and Teller (BET) analysis reported an enhanced surface area of 143.11 m2/g for 0.5%Ag-Cr2O3@SnO2. Gas sensing measurements demonstrated enhanced toluene detection at an optimal operating temperature of 200 °C. The sensor displayed outstanding repeatability and humidity-resistant behaviour over 10-50% RH, with a sub-ppm limit of detection. The enhanced performance is attributed to increased active gas adsorption sites enabled by its large surface area and adsorption volume, and to synergistic catalytic and electronic sensitization effects, promoting efficient gas adsorption and charge transfer to Ag nanoparticles.

Speaker: Kholofelo Mohloishane Seloane (University of the Free State, Physics Department)

354 Enhancing Structural Stability and Lithium Mobility in Spinel Cathodes via Prelithiated Core–Shell Engineering

Spinel LiMn2O4 is a promising cathode material for lithium-ion batteries due to its low cost and three-dimensional lithium diffusion pathways. However, its application is limited by irreversible capacity loss and structural degradation associated with manganese migration, which are linked to structural instability and disrupted lithium transport. Prelithiation compensates for initial lithium loss, while Li2MnO3 surface modification enhances structural stability by suppressing manganese migration. Despite these strategies, the capacity of LiMn2O4 remains lower than that of layered oxides, highlighting the need to simultaneously address structural stability and lithium transport. Molecular dynamics simulations were used to investigate the combined but distinct roles of prelithiation and a Li_xMn2O4@Li2MnO3 core-shell system during stepwise delithiation (x = 2.0 → 1.2). The Li2MnO3 shell preserves MnO6 coordination and suppresses MnO5 formation across all temperatures up to 1200 K, while maintaining a stable core-shell interface with minimal atomic rearrangement. Coordination number and radial distribution analyses show reduced local distortion compared to the pristine spinel across all lithium concentrations. Lithium diffusion remains high (4.54 × 10^-7 cm2 s^-1 at 300 K) and increases with temperature, with consistently higher diffusion coefficients than the pristine spinel at elevated temperatures. No diffusion bottlenecks are observed at the interface, confirming continuous lithium pathways across the core-shell structure. These results demonstrate that the Li2MnO3 shell stabilizes the structure without compromising lithium transport, thereby mitigating manganese migration.

Speaker: MOGAU KGASAGO (UNIVERSITY OF LIMPOPO)

355 Enhancing the Thermodynamic Stability and Mechanical Properties of FCC Platinum through Vanadium and Chromium Alloying, for jewellery application: A DFT Study

In the ever-evolving world of renewable energy, metallurgy, medicine, jewellery, and fuel cells, platinum (Pt) remains a key mineral in these industries. Nonetheless, Pt in its purest shape is relatively soft, thus vulnerable to surface scratching, a distress in the jewellery sector. As such, alloying Pt to enhance its mechanical integrity is crucial for improving its scratching resistance. For this reason, density functional theory (DFT) within the Quantum Espresso package was deployed to investigate the contribution of alloying Pt with high corrosion resistance vanadium (V) and chromium (Cr) at various concentrations, x. For thermodynamic stability investigation, the calculated formation energies range from -0.5 to -3 eV for alloy composition of 3<x<19 for both V and Cr. This suggests that Pt-Vx and Pt-Crx formation is exothermic, hence supporting the feasibility of the synthesis process at 0K. The calculated elastic constants C11 (324.34 GPa), C12 (219.48 GPa), C44 (86.83 GPa), and C` (52.43 Gpa) of pristine FCC Pt agree very well with experimental data and also satisfy the Born-Huang stability criteria. The obtained elastic values increase as the concentrations of Cr and V increase, enhancing the elastic stability of Pt.
Furthermore, Pt-Vx and Pt-Crx alloys possess great bulk, Young, and shear modulus at different concentrations when compared to pristine FCC Pt. It is further noticed that the hardness of the Pt alloy system doubles as the V/Cr concentration approaches 19%. The ductility of Pt alloy is maintained when V/Cr concentration increases, and its magnitude reduces to 2.5 GPa at x=19%. These DFT findings suggest possibility of durability of Pt-based jewellery when alloyed with V/Cr.

Speaker: Mr Mawisha Jan Mafifi (University of Pretoria)

356 Enhancing V2O5 Nanostructures Properties Via Ag Doping for Gas Sensing Applications

In recent years, there has been substantial progress in the development of nanomaterials for gas sensing applications. One of the key challenges in this field lies in selecting an appropriate sensing layer, along with optimising the device structure, fabrication method, and morphology to fully exploit the sensing capabilities of the material. This work presents the synthesis of pristine V₂O₅, as well as 1, 3, and 5 wt.% Ag-doped V₂O₅ using ammonium metavanadate (NH4VO3, 99%) and silver nitrate (AgNO3) as precursors through a hydrothermal method. The samples were characterized using Scanning Electron Microscopy (SEM), which revealed that pristine V₂O₅ formed irregular structures. The Incorporation of Ag led to the formation of nanorods, which significantly improved with the dopant concentration. Energy-dispersive X-rays (EDX) confirmed the successful incorporation of Ag into the V₂O₅. These results demonstrate that Ag doping significantly alters the morphological properties of V₂O₅, resulting in nanorods, which are believed to be a promising hierarchical structure for gas sensing applications. Further characterisation using X-ray diffraction (XRD) shows more interesting results.

Speaker: Perseverence khosa

357 Experimental and Computational Insights into Structure and Upconversion in Spinel Zn2TiO4:Er3+,Yb3+

Rare‑earth‑doped phosphor nanomaterials have attracted significant research interest due to their efficient upconversion luminescence, whereby infrared radiation is converted into visible emission. Such materials are promising for a wide range of applications, including solid‑state lighting, optical converters, biosensors, and data storage technologies. In this study, the structural and photoluminescence properties of spinel Zn₂TiO₄ phosphor co‑activated with Er³⁺ and Yb³⁺ ions were investigated to evaluate its suitability for upconversion applications. X‑ray diffraction (XRD) analysis confirmed the successful formation of the spinel Zn₂TiO₄:Er³⁺,Yb³⁺ phase. Computational calculations were used to correlate the structural characteristics of Zn₂TiO₄ with the observed upconversion luminescence behaviour. Under near-infrared excitation, the photoluminescence spectrum exhibited distinct green and red emission bands, which are attributed to the intra-4f transitions of Er³⁺ ions. The corresponding Commission Internationale de l’Éclairage (CIE) chromaticity coordinates indicate a greenish‑yellow emission, confirming the effective upconversion behaviour of the Zn₂TiO₄:Er³⁺,Yb³⁺ phosphor.

Speaker: Sefako John Mofokeng (University of South Africa)

358 Experimental investigation of MoS2, Ti3C2, and graphene-based composites for low Earth orbit applications

The Low Earth Orbit (LEO) environment presents a tough challenge for materials, exposing them to atomic oxygen, ultraviolet radiation, thermal cycling, and high vacuum conditions. These harsh conditions can wear down traditional spacecraft material (Finckenor, 2018; Grossman & Gouzman, 2003). As a result, there has been a growing interest in lightweight, functional alternatives, especially polymer nanocomposites that offer better resistance to these environmental factors.
This study focuses on poly(2,5-benzimidazole) (ABPBI) and graphene oxide (GO), molybdenum disulphide (MoS₂) and Ti₃C₂ MXene ABPBI composites. The specific focus of this work is the mechanical response of these composites under conditions relevant to LEO.
This study considers experimental techniques to evaluate and compare the mechanical behaviour of the composites. Tensile testing is performed to determine key properties such as stiffness, strength, and elongation, enabling direct comparison between the different nanofiller systems.
The results highlight the influence of nanofiller type on the mechanical performance of ABPBI-based composites and provide insight into their suitability for use in demanding space environments.

References
Finckenor, M. M., 2018. Materials for Spacecraft, s.l.: American Institute of Aeronautics and Astronautics.
Grossman, E. & Gouzman, I., 2003. Space environment effects on polymers in low earth orbit. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 208, pp. 48-57.

Speaker: Nico Snyman

359 Exploring Long-term Ionospheric Total Electron Content over South Africa.

The ionosphere is a dynamic, in-homogeneous, and electrically conductive plasma formed through the interaction of solar extreme ultraviolet (EUV) and X-ray radiation with the Earth’s upper atmosphere at altitudes of approximately 50–1000 km. Variations in ionization levels within this region significantly influence radio wave propagation and satellite-based communication systems. In this study we use Total Electron Content (TEC) as a parameter for studying ionospheric behavior due to its impact on radio communication, navigation, telemetry, tracking, and Global Navigation Satellite System (GNSS) signal propagation. We investigate long-term trends in TEC over South Africa using observations from three GNSS stations. To isolate long-term ionospheric variability, solar-cycle influence is removed using different solar activity proxies: F10.7 solar radio flux, the MgII core-to-wing index, and sunspot numbers. Monthly and yearly averaged TEC data spanning 16 to 25 years were analyzed using regression techniques to estimate long-term trends after correcting for solar activity. Results indicate a persistent negative trend in TEC across the South African mid-latitudes after accounting. Differences in trend magnitude obtained highlight the importance of proxy selection when estimating long-term ionospheric trends.

Speaker: Modiri Mokaila (North West University)

360 Extraction and Geospatial Analysis of Wind and Solar Power Infrastructure Using OpenStreetMap Data in African Countries

The growing demand for sustainable energy solutions has accelerated the deployment of renewable energy infrastructure across Africa, particularly wind and solar photovoltaic (PV) systems. However, comprehensive and accessible datasets describing the spatial distribution and generation capacity of such infrastructure remain limited. This study addresses this gap by leveraging openly available geospatial data from OpenStreetMap (OSM) to extract and analyse information on wind and solar power installations in selected African countries. Using data obtained from the Geofabrik repository, relevant features associated with renewable energy systems were filtered and processed to identify infrastructure locations and attributes.

A data-driven geospatial methodology was employed, incorporating tools such as esy-osmfilter and Python libraries such as pandas, geopandas, and shapely for data extraction, cleaning, and analysis. Generation capacity values were standardised and distributed across related spatial elements to improve data consistency and reliability. The resulting datasets were used to assess the spatial distribution and estimated capacity of renewable energy infrastructure. The findings demonstrate the potential of OSM as a valuable, low-cost data source for energy system analysis and planning, particularly in data-scarce regions. This approach provides a scalable framework for supporting renewable energy policy development, infrastructure planning, and future integration studies in Africa.

Speaker: Mr Nhlamulo Khosa (Green Technology Confucius Institute, University of Venda)

361 Fabrication of Co3O4 Co-doped with NiZn for Selective LPG Gas Sensing

Cobalt oxide (Co₃O₄) nanostructures co-doped with 5 wt%, 10 wt%, and 15 wt% NiZn were synthesized via the hydrothermal method. Structural analysis using X-ray diffraction (XRD) confirmed the formation of a pure spinel phase without any secondary peaks. The crystallite size increased from 19 nm to 48 nm with increasing dopant concentration. High-resolution transmission electron microscopy (HRTEM) further verified the spinel structure, revealing lattice spacings (d-spacing) in the range of 0.2305–0.4477 nm, while selected area electron diffraction (SAED) patterns showed a prominent (311) diffraction ring. UV–Vis spectroscopy indicated a decrease in band gap energy with increasing NiZn doping concentration. Scanning electron microscopy (SEM) images revealed predominantly spherical nanoparticles. Gas sensing studies demonstrated that the 15 wt% NiZn-doped Co₃O₄ sensor exhibited the highest sensitivity toward liquefied petroleum gas (LPG) at a relatively low operating temperature of 75 °C. Furthermore, the sensor displayed good selectivity, repeatability, and long-term stability.

Keywords:Gas sensor,Co3O4,LPG,NiZn and co-doped

Speaker: Mondli Ntshangase (University of Zululand)

362 Field Calibration of Cosmic-Ray Neutron Sensors for Accurate Soil Moisture Monitoring

Soil moisture is water content held within the pore spaces between the soil particles. It is a pivotal variable as it plays a major role in climate change processes, which is widely used in agriculture.
Soil moisture is traditionally measured with sensors that are invasive, labour-intensive, and subject to uncertainties. This study uses a non-invasive Boron trifluoride (BF$_3$) Cosmic-ray Neutron Sensor (CRNS), which continuously measure soil moisture estimates. The CRNS detects fast (epithermal) neutrons, produced from Cosmic-ray particles that enter the atmosphere of Earth. These fast neutrons interact inversely with hydrogen atoms in soil, which creates a method that is capable of measuring soil moisture across a footprint of approximately 20 hectares in width and up to 0.3 m depth. However, this method does require calibration and corrections. Therefore, this study measures the neutron count rate and details the correction process from the effects of pressure changes, temperature, and humidity. This work also details the CRNS field calibration processes that affect the neutron intensity. The neutron intensity is converted to volumetric water content estimations, which is validated against gravimetric soil sampling and data from seventeen AquaCheck probes. This study assists in precision agriculture, which can enhance water resource conservation in diverse agricultural landscapes.

Speaker: Aimee Dumont

363 First-Principles Study of a Novel ZrSC Janus Monolayer: Structural, Mechanical, Vibrational, and Electronic Properties

Two-dimensional Janus materials, characterized by their asymmetric surface composition, offer unique opportunities for tailoring electronic and mechanical properties. Among these, the hypothetical ZrSC monolayer, composed of zirconium sandwiched between sulfur and carbon layers, represents an underexplored system with the potential to merge the mechanical durability of carbides with the electronic tunability of
chalcogenides. Using first-principles density functional theory (DFT) with van der Waals corrections and Hubbard-U adjustments, we systematically investigate the structural, mechanical, vibrational, and electronic
properties of its two polymorphs: the trigonal prismatic 1H and octahedral 1T phases. Our results establish the 1H phase as the thermodynamically stable ground state with a cohesive energy of 6.99 eV/atom, a moderate
Young's modulus of 70.7 N/m, and an indirect bandgap of 1.63 eV that is highly responsive to mechanical strain. Phonon spectra confirm its dynamical stability, while the 1T phase exhibits significant imaginary frequencies, indicating metastability. Electronically, the 1H phase behaves as a tunable semiconductor, whereas the 1T phase
displays half-metallic character with a metallic spin-up channel and a narrow 0.028 eV gap in the spin-down channel. Strain engineering induces semiconductor-to-semimetal transitions in the 1H phase, highlighting its
potential for flexible electronics and spintronics. We conclude that the 1H ZrSC monolayer is a promising candidate for next-generation 2D devices, offering a versatile platform that bridges mechanical robustness with
electronic adaptability and providing a clear roadmap for experimental synthesis and device integration.

Speaker: Edwin Mapasha (University of Pretoria)

364 First-principles study of adsorption mechanisms of CO2 and CO on monolayer Nb2Se2C TMCC as an efficient gas sensor

Greenhouse gas emissions, such as carbon dioxide and nitrous oxide, released during the combustion of fossil fuels, have been strongly linked to climate change effects, including prolonged droughts, floods, and intense heat waves, that can lead to diseases such as stroke and cardiovascular disorders. This connection has driven extensive research into toxic gas sensing and capturing, aiming to mitigate diseases resulting from gases emitted by fossil fuel combustion and other activities like mining. Consequently, the development of high-performance gas sensing devices is crucial to enhance the efficiency of capturing and sensing toxic gases. In this regard, monolayers of transitional metal carbo-charcogenide (TMCC), such as Nb₂Se₂C, with their unique and novel properties, are identified as promising candidates for use as additives in sensor devices.
In this study, we used density functional theory (DFT) implemented in the Quantum ESPRESSO code to investigate the adsorption mechanisms of CO₂ and CO on monolayer Nb₂Se₂C, aiming to enhance capturing and sensing efficiency while assessing the material’s thermodynamic and structural stability. The adsorption systems of CO₂ and CO on monolayer Nb₂Se₂C were systematically optimized, followed by comprehensive calculations of all gas sensing properties. The results revealed that monolayer Nb₂Se₂C exhibits excellent adsorption capabilities for both CO₂ and CO, with relatively high charge density distributions. These values indicate that monolayer Nb₂Se₂C can significantly accelerate adsorption and diffusion mechanisms. Moreover, the low diffusion energy barriers for the adsorbates demonstrate that CO₂ and CO can easily migrate to the most stable sites, contributing to system stabilization. Importantly, post-adsorption analyses confirm that the electronic conductivity of monolayer Nb₂Se₂C is preserved, which is highly desirable for efficient gas sensors. Collectively, these findings suggest that monolayer Nb₂Se₂C is a promising candidate for facilitating efficient toxic gas sensing devices, offering both high catalytic activity and robust structural properties.

Speaker: Dr Chewe Fwalo (University of South Africa)

365 First-principles study on Tin-doped Li1.2Mn0.8O2 cathode material for Lithium-ion batteries

Abstract:
The rising demand for compact, high-performance batteries, driven by the rapid expansion of portable electronics, has been effectively met by the rise of lithium-ion battery (LIB) technology. As the most viable energy storage solution to date, LIBs have become the cornerstone of the modern energy industry, powering everything from everyday consumer gadgets to the latest electric vehicles. Within this field, Li-rich manganese-based layered oxides (LLOs) stand out as particularly promising cathode materials due to their exceptional specific capacity and energy density. However, their transition to widespread practical use is currently stalled by significant technical hurdles, most notably poor cycling stability, structural degradation, and the phenomenon of voltage fade. To address these limitations, this study employs first-principles calculations to investigate the fundamental properties of a Li1.2Mn0.8O2 supercell. This computational foundation was further enhanced by a genetic algorithm approach within a cluster expansion framework, which was used to explore the configurational space of Sn-doped LLO in search of new stable phases. This rigorous ground-state search successfully generated 29 new phases, mapping out the miscible gaps and constituent regions while highlighting three specific configurations as the most stable and favourable. The reliability of these results is underscored by a cluster expansion cross-validation score of less than 5 meV/atom, confirming the high degree of accuracy in our search for a more resilient battery architecture.

Keywords: Lithium-ion batteries, Li-rich layered oxides, Cluster expansion, Tin doping, First-principles calculations.

Speaker: RAMAABELE BRIDGET MOKGABUDI (UNIVERSITY OF LIMPOPO)

366 Fluorine-Doped Siligraphene (SiC₂): A Cluster Expansion and DFT Study of Stability, Electronic, and Mechanical Properties.

The development of high-capacity electrode materials is essential for enhancing the energy density of lithium-ion batteries. Siligraphene (SiC2), inspired by silicon’s high theoretical capacity, has emerged as a promising anode material due to its high specific capacity and low open-circuit voltage. however, its performance is limited by poor mechanical stiffness. This study examines fluorine incorporation in SiC2 by evaluating its thermodynamic stability, mechanical and electronic properties using cluster expansion and density functional theory. Fluorine incorporation at the silicon 1a site yields three thermodynamically stable structures with negative formation energies, with SiC6F2 identified as the most stable configuration. In contrast, doping at the carbon 2d site predominantly produces unstable configurations, with Si4CF7 being the only stable phase. Further analysis of the most stable structures reveals that most exhibit metallic behavior with strong valence-band contributions, while SiC6F2 displays semiconducting characteristics with a narrow direct band gap of 0.092 eV. Mechanical analysis indicates that structures doped at the 1a site are mechanically unstable and brittle, whereas those doped at the 2d site are mechanically stable but remain brittle. Overall, fluorine incorporation in SiC2 exhibits strong site-dependent effects on stability, electronic structure, and mechanical behavior. While 1a-site doping favours thermodynamic stability, it compromises mechanical integrity, whereas 2d-site doping improves stability but remains limited by brittleness. These findings provide valuable insights for the rational design of modified siligraphene anodes with improved performance for lithium-ion batteries.

Speaker: Samson Singo (University of Limpopo)

367 From One to Eight: Supersymmetry Restoration in Lattice 3D ${\cal N} = 4$ Super Yang--Mills

Topological twisting provides a powerful framework for constructing lattice formulations of supersymmetric gauge theories. In three dimensions, a twisted version of ${\cal N} = 4$ super Yang--Mills theory can be discretized so that one nilpotent scalar supersymmetry is preserved exactly at nonzero lattice spacing. The remaining seven supersymmetries are broken by lattice artifacts of ${\cal O}(a)$, where $a$ is the lattice spacing. An important question is whether these supersymmetries are automatically restored in the continuum limit $a \to 0$, or whether fine-tuning of the lattice couplings is required. In this work, we derive the additional twisted supersymmetries by combining discrete $R$-symmetries of the continuum theory with the action of the scalar supercharge. This construction suggests that restoration of rotational symmetry in the continuum limit implies restoration of $R$-symmetry, leading to an automatic enhancement to the full ${\cal N} = 4$ supersymmetry without further tuning. These results may enable nonperturbative lattice studies of three-dimensional supersymmetric gauge theories relevant to string theory and mirror symmetry.

Speaker: Dario Van den Berg (University of the Witwatersrand)

368 Geometric Modelling of Crab-like and Vela-like Pulsar Systems

Young neutron stars power bright multi-wavelength emission and drive energetic pulsar wind nebulae (PWNe). Accurate interpretation of these signals depends on the magnetic inclination ($\alpha$) and viewing angle ($\zeta$); however, independent observables often yield conflicting geometric constraints. To investigate these discrepancies, we analysed a sample of eight high-spin-down pulsars ($\dot{E} \gtrsim 10^{34}$ erg/s), categorised by characteristic age into Crab-like ($\sim$1 kyr) and Vela-like ($\sim$10 kyr) populations. For each source, we applied three independent geometric tracers: radio polarimetry (Rotating Vector Model), $\gamma$-ray light-curve modelling (TPC/OG/CS models), and X-ray imaging of PWN tori. Our comparison reveals that while some pulsars show multi-wavelength consistency, others exhibit significant geometric offsets. Our results suggest that standard emission models may require refinements, particularly regarding emission altitudes or magnetospheric structure, to reconcile the geometry across the electromagnetic spectrum.

Speaker: Mr Trevor Nyambe (Centre for Space Research, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa)

369 Hydrothermal fabrication and temperature-dependent magnetic properties of cobalt nanoferrite for high-frequency devices

The cobalt nanoferrite with crystallite of 12.89nm was successfully synthesized using the hydrothermal method. The X-ray diffraction (XRD) and the Fourier transform infrared spectroscopy (FTIR) confirmed the formation spinel structure. The obtained lattice parameter was 8.36 Å while the X-ray densities was 5.021 g/cm³. The scanning electron microscopy (SEM) revealed spherically shaped and agglomerated nano-particles. The “S” shaped hysteresis loops revealed ferromagnetic magnetic properties. The saturation magnetization increased with decreasing measuring temperatures following the Kneller’s Law, from 6.622 emu/g to 9.793emu/g. The evolution of coercive fields (HC) upon reducing the measuring temperature from room temperature (300K) to 4K indicates the thermal instability of the blocked magnetic moments. The HC values increased with decreasing measuring temperature according to Bloch’s Law. Relatively high coercive fields at low temperatures make the material suitable for application in transformers and high-frequency devices. The FC and ZFC magnetization revealed the blocking temperature 210K.

Speaker: Dr Amos Nhlapo (Sefako Makgatho Health Sciences University)

370 Implementing a Charm Equation of State in the QGP Hydrodynamic Simulation, Trajectum

The Quark-Gluon Plasma (QGP) is an exotic state of matter where fundamental quarks and gluons are decoupled and the result is a medium of strongly-interacting matter. This state of matter is only achievable under extreme conditions, such as the results of colliding nuclei in a particle collider such as those performed at the Large Hadron Collider and Brookhaven National Laboratory. Trajectum is a relativistic hydrodynamics simulation software, designed to reproduce the results of these heavy-ion collisions. The simulation involves the computation of the initial conditions, prehydrodynamic phase, hydrodynamic phase and final particlization. As part of the hydrodynamic phase, a lattice equation of state (EoS) is required to compute the thermodynamics of the QGP. A hadron resonance gas EoS is also required for the final particlization stage, and together they form a hybrid EoS to allow for a smooth transition between the two phases of matter. Previously, Trajectum utilized a (2+1) flavour lattice EoS which includes contributions from up, down and strange quarks. A newer, more sophisticated (2+1+1)-flavour EoS which includes the charm quark has since been computed. This project aims to implement two modifications to Trajectum. Firstly, by changing the interpolation method that connects the two equations of state from a standard polynomial interpolation method to a more modern, smooth function interpolation method. The second major modification is to implement the newer (2+1+1)-flavour lattice equation of state into the hydrodynamic stage. In doing this, we investigate the effect that the inclusion of the charm quark has on the QGP medium as a whole, as well as the possible reductions in runtime that the new interpolation method has on the simulation.

Speaker: Liam Harris (University of the Witwatersrand)

371 Influence of A- and B-Site Cation Substitution on the Structural, Thermodynamic, and Magnetic Properties of Brownmillerite A₂B₂O₅ (A = Sm, Ce; B = Ni, Co) Nanoparticles

Crystalline Sm₂Ni₂O₅ (SNONPs) nanoparticles were synthesized via co-precipitation and sol–gel methods, while Ce₂Ni₂O₅ (CNONPs) and Ce₂Co₂O₅ (CCONPs) were prepared using a sol–gel route to investigate the effect of A-site (Sm, Ce) and B-site (Ni, Co) cation substitution on their structural, morphological, thermodynamic, and magnetic properties. XRD analysis confirmed that SNONPs crystallize in an orthorhombic Ima2 structure after annealing at 800°C, whereas CNONPs and CCONPs exhibit two-phase cubic structures (Fm-3m and Fd-3m). SEM revealed compact particles for co-precipitated SNONPs and fragmented morphologies for sol–gel samples. TEM showed spherical NPs with average sizes of ~33 nm (CNONPs) and ~63 nm (CCONPs). XPS analysis indicated mixed valence states, with stable Ce4+, predominant Ni2+, and high-spin Co3+. Thermodynamic and magnetic measurements (0–300 K) revealed distinct phase behavior. SNONPs exhibited spin freezing at 6 K, antiferromagnetic ordering at 9 K, and a ferromagnetic transition at 43.6 K. CNONPs showed no clear specific heat transition but displayed magnetic anomalies at 58 K, 139 K, and 216 K. In contrast, CCONPs showed a low-temperature antiferromagnetic ordering anomaly at 30 K and ferromagnetic ordering at 24 K. These results demonstrate that cation substitution, synthesis method, and particle size significantly influence magnetic interactions and phase transitions. The study highlights the tunability of brownmillerite oxides and identifies SNONPs as promising candidates for spintronic and low-temperature magnetic applications.

Speaker: Khethiwe Cele (Rare Earth-Based Oxides and Nano Group, Department of Physics, University of Johannesburg, Cnr Kingsway Avenue and University Road, Auckland Park 2006, South Africa)

372 Influence of Ta on the Magnetic and Mechanical Properties of Fe50Co43.75Pt6.25 Alloy

FeCo alloys, a class of intermetallic soft magnetic materials, have attracted considerable interest due to their exceptional magnetic performance, including high saturation magnetisation (~2.4 T) and elevated Curie temperatures (920–985 °C). Despite these advantages, their practical application is limited by the high cost of Co and poor ductility, particularly at low temperatures. Alloying with elements such as Pt has been explored to improve structural stability and mechanical performance; however, achieving a balance between enhanced mechanical properties and high magnetic performance remains challenging. While ternary systems have shown improved ductility, they often compromise magnetic properties, motivating the transition toward more complex quaternary compositions. In this study, quaternary Fe50Co43.75-xPt6.25Tax alloys were examined using density functional theory (DFT) within the GGA-PBE framework. The substitution of Ta at Co sites was found to improve the thermodynamic and vibrational stability as well as ductility of Fe50Co47.75Pt6.25 alloy. These findings offer valuable insights for the design of FeCoPt-based alloys with an optimal balance of mechanical and magnetic properties for advanced soft magnetic applications

Speaker: Dineo Maepa (University of Limpopo)

373 Investigating the Implications of a Constant Density Profile in Stellar Convective Zones

ABSTRACT
Inthemid-1970’s,a 160-min periodic signal was detected coming from the Sun and the discoverers interpreted this as a gravity-
mode (g-mode) oscillation.
That is to say,they supposed this signal to be the vibration of the Solar surface. Similar signals where
also detected in a number of extraterrestrial sources which include Active Galactic Nuclei (AGN). Later re-analysis rebutted this signal with the simple remark that it was no more than an artifact induced by the diurnal effects of the Earth’s atmospheric extinction. A polemic regarding this signal is that if it is real, it would require a drastic revision of the Standard Solar Model (SSM) as the Sun will have to be treated as a homogeneous ball of gas and this assumption runs contrary to the SSM.
We propose a model that seeks to proffer an explanation — i.e., a model requiring no drastic revision of the SSM. Our modification of the SSM is that we assume that the convective envelope ofthe Sun(and similarstars) is the one that is homogeneous with the Core intactly returning all of its properties that it is endowed with in the SSM.
We believe that despite the fact that dedicated searches for the 160-min have come-out empty-handed, our model may very well be important in explaining global g-mode oscillations of stellarsurface—hence,pulsation.
In-fact,our model allows for the 160-min signal to shift to a different frequency depending on the present density of the convective envelope, the meaning of which is that if one searches for the 160-min signal and does
not find it, it may have shifted to a new frequency. All one needs to do is to search for global g-mode oscillations — and, with
this in mind, theSOHO-satellite’s search seems to have detected a 24-min signal rather than the polemical 160-minsignal.

Key words: g-mode oscillation – helioseismology – Standard Solar model –solar oscillation.

Speaker: Terry Mark Tukamusaba

374 Investigating the maslovite (PtBiTe) surface stability and adsorp-tion of SDTBAT and SBOTTAs collectors using standard DFT and AIMD-MLFF.

This study adopted the density functional theory (DFT) and ab-initio molecular dynamics (AIMD) modelling technique imbedded within the Vienna ab-initio simulation package (VASP). The machine learned force field (MLFF) was utilised for robustness of the AIMD simulations. These methods were adopted in the current study to understand the behaviour of platinum group minerals (PGMs) such as PtBiTe mineral at room temperature (300 K). The DFT surface energies results showed that PtBiTe (100) surface was the most stable surface with the surface energy of 0.75 J/m2, which corresponded with the MLFF results depicting surface energy 0.73 J/m2. Using the DFT at 0 K, the adsorption of the SDTBAT and SBOTTAs on the PtBiTe mineral surface were found to be –145.57 kJ/Mol and –112.01 kJ/Mol, respectively, and using AIMD-MLFF the adsorption energies were –182.23 kJ/Mol for SDTBAT and –430.22 kJ/Mol for SBOTTAs. Thus the adsorption of the two collectors on the mineral surface both improved at room temperature. It was clear that the SDTBAT adsorbed stronger at DFT level, while the SBOTTAs had strong adsorption at AIMD-MLFF level.This showed that MLFF was robust and improved the perfor-mance of the AIMD simulations significantly. As such the SBOTTAs is predictede to be the best collector for maslovite mineral recovery.

Keywords: PGMs, AIMD, MLFF, Surface, Collectors, Adsorption

Speaker: TSHEPO RONALDO MAAKA (UNIVERSITY OF LIMPOPO)

375 Investigating The Mechanical and Electronic Properties of Silver, Gold and Aluminium: First-Principle Study

Abstract
The mechanical and electronic properties of Gold (Au), silver (Ag) and aluminium (Al) are systematically investigated using first principle calculations that on density functional theory (DFT). Geometry optimization confirms that all three metals crystallize in face-cantered cubic (FCC) structure and their lattice parameters show agreement with experimental data. The calculated elastic constants (C_11,C_12,C_44) satisfy the mechanical stability for cubic systems that confirms the structural stability of Ag, Au, and Al. The elastic properties including bulk modulus, shear modulus, Young’s modulus and Poisson’s ratio, are evaluated using the Hill approximation. A comparison of mechanical properties shows that Al exhibits the highest stiffness while Au and Ag indicate greater ductility, as supported by Pugh’s ratio(B/G) and Poisson’s ratio values. The Pugh’s ratio (B/G) confirms the ductility of all three metals. Among the three metals, Au shows the most ductile behavior whereas Al is comparatively less ductile. Electronic structure and density of state (DOS) analysis show the metallic nature of these materials with the absence of band gap at Fermi level with silver showing the highest electrical conductivity followed by gold and aluminum. This study is a comparative investigation that provides an understanding of the influence between mechanical strength and electronic structure in metals, demonstrating the power of first-principle methods in predicting material properties.

Speaker: Melokuhle Hadebe

376 Investigation of antiferromagnetic hematite bulk and surface properties using ab-initio method

This study employed ab-initio density functional theory (DFT) with Grimme’s D3 dispersion correction to investigate the bulk and surface properties of hematite. The Hubbard U parameters 5.0 eV was adopted which gave a band gap of 2.55 eV and lattice parameters of a = b = 5.045 Å and c = 13.774 Å, which were in good agreement with experimental values (band gap: 1.9–2.6 eV; lattice parameters: a = b = 5.035 Å, c = 13.75 Å). The computed electronic properties confirmed the antiferromagnetic nature of bulk hematite, arising from alternating spin-states (spin-up and spin-down) on the Fe atom layers. Various surface orientations including (012), (104), (110), and (116) were modelled to assess surface geometry, relaxation, and energetics to unravel the most stable surface. Among these surfaces, the (104) and (110) surfaces were found to be the most stable based on their relaxations which exhibited the surface energies of 5.61 J/m^{2 and 5.22 J/m2, respectively. These were in agreement with the computed X-ray diffraction (XRD). These findings revealed the effectiveness of DFT+D3 methods in predicting the bulk and surface of hematite mineral. Furthermore, these form a base for adsorption of collectors to unravel the recovery separation of hematite from other minerals.}

Speaker: Mariah Madie (University Of Limpopo)

377 Investigation of Silver and Cesium Migration and Structural Evolution in 6H-SiC Following Helium, Silver and Cesium Implantation and High-Temperature Annealing

In nuclear fuels, thin-film diffusion barriers are essential for preventing the release of radioactive fission products (FPs). Silicon carbide (SiC), which serves as the primary diffusion barrier layer, is exposed to various FPs along with helium (He) generated as a result of alpha decay of actinide elements and neutronic transmutation. Therefore, this study investigates the role of He in the migration of silver (Ag) and cesium (Cs) pre-implanted into SiC. Single-crystalline 6H-SiC samples were separately implanted with 360 keV Ag ions and 200 keV Cs ions to a fluence of 2×10¹⁶ ions/cm² at room temperature (RT). The individually implanted samples were subsequently co-implanted with 17 keV He ions to a fluence of 1×10¹⁷ ions/cm² at RT. The Ag-implanted, Cs-implanted, Ag+He co-implanted, and Cs+He co-implanted samples were then annealed at 1100 °C for 5 hours in a vacuum tube furnace. Rutherford backscattering spectrometry (RBS) was used to analyze the migration behavior of Ag and Cs in SiC. Channeling RBS, Raman spectroscopy, and transmission electron microscopy (TEM) were employed to investigate the thickness of the damaged layer, microstructural changes induced by implantation, and the formation of He bubbles, respectively. Ag and Cs implantation resulted in the formation of an amorphous layer, while subsequent He implantation increased the thickness of this amorphous region. Annealing induced recrystallization in all samples; however, some graphitization was observed in the Ag+He and Cs+He co-implanted samples. No migration of Ag or Cs was detected after annealing. Compared to the behavior of Ag in polycrystalline SiC, where rapid Ag migration and significant loss were observed after annealing at 1100 °C, the results demonstrate that 6H-SiC effectively retains Ag and Cs. These findings confirm the critical role of SiC microstructure in controlling the migration of fission products.

Speaker: Nhlakanipho Mantengu (University of Zululand)

378 Investigation of the redox characteristics of the Co₃O₄ (001) surface

ABSTRACT

Currently, rising electric energy demand and depleting raw materials are increasing day by day, calling for alternative, clean energy storage equipment. Lithium–air batteries are considered among the most promising energy storage technologies due to their exceptionally high energy density (1086 Wh/kg) and large specific capacity (3842 mAh/g). However, they face a key practical limitation due to the formation of unstable discharge products (LiO₂, Li₂O, and LiO), which contribute to battery degradation. Cobalt oxide (Co₃O₄) is regarded as an efficient electrocatalyst for lithium–air batteries due to the presence of mixed Co²⁺ and Co³⁺ oxidation states, which help lower the overpotential and markedly enhance the cycling performance of Li–O₂ batteries. However, the catalytic behaviour of Co3O4 remains poorly understood; hence, we employ computational modelling based on density functional theory (DFT) to explore the redox properties of the Co3O4 (001) surface in Li-air battery applications. The results indicated that adsorbing oxygen on the Co3O4 (001) surface stabilises the surface, while removing oxygen destabilises it. Furthermore, work function (Φ) was found to correlate positively with oxygen coverage; however, oxygen removal yielded only a marginal increase in the work function. These results will help understand the catalytic mechanisms of Co3O4 in the Li-air battery application.

Keywords: Li-air batteries, Co3O4 electrocatalyst, DFT, Redox reaction

Speaker: Pabalelo Malatjie (University Of Limpopo)

379 Investigation of Ti4Nb2Pt2 shape memory alloys from binary phase diagram

The Ti₄Nb₂Pt₂ alloys on Pt-rich sites was identified as the most stable configuration from universal cluster expansion derived by binary phase diagram. The supercell approach, as implemented in VASP, was employed to create a supercell containing approximately 64 atoms. In addition, the Ti₄Nb₂Pt₂ alloys was studied by investigating the structural, thermodynamic and mechanical properties using first-principle density functional theory. The alloy was identified as the most thermodynamic structure due to the negative heats of formation (-0.361 eV/atom). The Ti₄Nb₂Pt₂ alloys exhibit properties comparable to those of tetragonal Nb-doped TiPt. The analysis of the Ti₄Nb₂Pt₂ mechanical behavior indicates that these compounds are inherently ductile and exhibit mechanical stability. Furthermore, the calculated phonon dispersion curves confirm the vibrational stability of the Ti₄Nb₂Pt₂ alloy due to the absence of soft phonon modes. These findings indicate that Nb incorporation enhances the structural stability of Ti–Pt SMAs, thereby rendering them promising candidates for high-temperature applications.

Speaker: Dr Mordecai Mashamaite (University of Limpopo)

380 Luminescent Enhancement of ZnO-SnO2 Heterostructures Doped with Pr3+

This study aims to enhance the photoluminescence properties of ZnO–SnO₂ heterostructures (ZS-H) through Pr³⁺ doping at different concentrations for potential use in optoelectronic coatings. The main challenges in optoelectronic coatings are achieving multifunctionality, as improving electrical conductivity often reduces optical transparency and flexibility, while defects and infrared reflections further limit performance. To the best of our knowledge, doping ZS-H with Pr³⁺ for optoelectronic coating applications has not been reported previously. The X-ray diffraction (XRD) showed that both the hexagonal wurtzite ZnO and tetragonal SnO₂ phases were present, with an extra peak at 2θ = 29.9° which belongs to zinc stannate. No change in structure was observed after doping ZS-H, while crystallinity improved as the Pr³⁺ concentration increased. Photoluminescence showed the emission of Pr³⁺, and the luminescence intensity increased with increasing dopant concentration. The enhanced crystallinity and photoluminescence intensity suggest that this material holds strong potential for applications in optoelectronic coatings.

Speaker: Tahleho Mofokeng (University of The Free State)

381 Measurment of the Dark Energy Spectroscopic Instru- ment (DESI) Galaxy cluster bulky velocity with kinematic Sunyaev- Zeldovich (kSZ) signals from Atacama Cosmology Telescope Polarime- ter (ACTPol) Data Release 4.

In this research project, the Dark Energy Spectroscopic Instrument (DESI)
galaxy cluster bulk velocity will be measured using kinematic Sunyaev-Zeldovich(kSZ) signals from the Atacama Cosmology Telescope Polarimeter
(ACTPol)Data Release 4. The kSZ signal will be detected using 1-point statistics, then developing and applying aperture photometry on the BOSS North and Deep 56 regions of ACTPol DR4. With the extracted kSZ signal, the bulk velocity of the galaxy cluster will be estimated using galaxy cluster positions from the DESI Legacy Imaging Survey Data Release 8.

Speaker: Mr Isaac Gwato Chitete

382 Microscopic derivation of Open Quantum Brownian Motion for a particle in a potential with external periodic driving

Open quantum Brownian motion (OQBM) was introduced by Bauer et al. [1,2] as a special scaling limit of discrete-time open quantum walks (OQWs) [3,4], establishing a new mathematical framework for quantum Brownian motion. In this setting, the dynamics of the Brownian particle depend not only on dissipative interactions with a thermal bath but also on the state of the internal quantum degree of freedom. Subsequently, a microscopic derivation of the OQBM for a free Brownian particle interacting with a thermal bath was proposed [5,6]. Recently, Zungu et al. [7,8] proposed a microscopic derivation of the OQBM in a generic dissipative case for a Brownian particle confined to a harmonic potential, using the adiabatic elimination of fast variables method. In this work, we extend these results by presenting a microscopic derivation of the OQBM for a Brownian particle in a potential and external periodic driving.

[1] M. Bauer, D. Bernard, and A. Tilloy, 2013 Phys. Rev. A 88, 062340.
[2] M. Bauer, D. Bernard, and A. Tilloy, 2014 J. Stat. Mech. P09001.
[3] S. Attal, F. Petruccione, C. Sabot, and I. Sinayskiy, 2012 J. Stat. Phys. 147, 832.
[4] S. Attal, F. Petruccione, and I. Sinayskiy, 2012 Phys. Rev. A 376, 1545.
[5] I. Sinayskiy, and F. Petruccione, 2015 Phys. Scr. T 165, 014017.
[6] I. Sinayskiy, and F. Petruccione, 2017 Fortschr. Phys. 65, 1600063.
[7] A. Zungu, I. Sinayskiy, and F. Petruccione, 2025 arXiv:2503.10379
[8] A. Zungu, I. Sinayskiy, and F. Petruccione, 2026 arXiv:2602.03534

Speaker: Sindiswa Nhlapo

383 Molecular Dynamics Insights into the Properties of Pyrite-Type RuS₂: A Computational Study

Pyrite-type transition-metal sulphides have attracted increasing scientific interest due to their applications in catalysis, environmental remediation, electronic materials, and mineral processing. Their performance strongly influenced by bulk and surface properties. In this work, molecular dynamics (MD) simulations were performed to investigate the structural and dynamical behaviour of pyrite-type RuS₂. An accurate description of such systems requires reliable interatomic potentials; therefore, a refined potential model was developed and validated. The model successfully reproduces lattice parameters and elastic properties in good agreement with literature values. MD simulations were further conducted to evaluate thermal stability and phase behaviour, with the model successfully predicting the melting point of RuS₂ at elevated temperatures. The developed potential provides a reliable framework for simulating RuS₂ and offers insights into its bulk properties relevant to mineral processing and related applications.

Speaker: Monyeseroba Immaculate (University of Limpopo)

384 Molecular dynamics simulations of TiO2 nanomaterials as a future anode electrode material

ABSTRACT
The growing global demand for sustainable and high-performance energy storage systems has directed significant research attention toward titanium dioxide (TiO₂) as a prospective anode material for lithium-ion batteries [1]. In this study, the structural and thermodynamic behaviour of amorphous TiO₂ is systematically investigated using classical molecular dynamics (MD) simulations [2], with particular emphasis on its applicability in electrochemical energy storage. Simulations were conducted using the DL_POLY software package [3] in conjunction with computational infrastructure provided by the Centre for High Performance Computing (CHPC) [4]. The thermally induced evolution of TiO₂ nanostructures was examined through simulated annealing across a temperature range of 1000 K to 2000 K. The results reveal the formation of nanoporous amorphous configurations and subsequent phase transitions at elevated temperatures. Preliminary analysis indicates that amorphous TiO₂ exhibits favourable structural stability and potential for enhanced lithium storage capacity, characteristics which are essential for extending battery cycle life and reducing reliance on carbon-based energy sources. This study establishes a robust atomistic framework for the continued development and optimization of TiO₂-based anode electrode materials, highlighting the critical role of computational modelling in advancing next-generation battery technologies.

Keywords: Titanium dioxide (TiO2), Nanoporous, Anode electrode materials, Molecular dynamics (MD) simulations.

REFERENCES
[1] T. Maiyalagan & P. Elumalai, Rechargeable Lithium-ion Batteries: Trends and Progress in Electric Vehicles, Boca Raton, Florida, USA: CRC Press (Taylor & Francis Group), 2021.
[2] H. A. L. Filipe & L. M. S. Loura, Molecules, vol. 27, no. 7, p. 2105, 2022.
[3] I. T. Todorov, W. Smith, K. Trachenko & M. T. Dove, Journal of Materials Chemistry, vol. 16, p. 1911–1918, 2006.
[4] H. M. Sithole, W. Janse van Rensburg, D. Thobye, K. Govender, C. Crosby, K. Colville & A. Loots, in Contemporary High Performance Computing, 1st ed., CRC Press, 2019, pp. 28.

Speaker: Thamia Molefe (University of Limpopo)

385 Molecular Insights into Novel Collector Adsorption on Hydrated Spodumene and Feldspar Surfaces: An AIMD-MLFF Study

Spodumene (LiAlSi₂O₆) is a primary lithium-bearing mineral of significant industrial importance, particularly in the production of rechargeable batteries for electric vehicles. In natural ore systems, spodumene commonly coexists with feldspar (NaAlSi3O8), which serves as a major gangue mineral, necessitating efficient separation strategies. In this study, a combination of density functional theory (DFT) and ab-initio Molecular Dynamics with machine-learned force fields was employed to investigate the adsorption behavior of selected collector molecules on spodumene and feldspar surfaces under both acidic and neutral conditions. Surface stability analysis indicated that the spodumene (110) surface is the most thermodynamically stable, with a surface energy of 0.71 J·m⁻², while the feldspar (001) surface exhibited a surface energy of 0.831 J·m⁻². A series of collectors including diethyl phosphate and diethyl arsenate were systematically adsorbed onto these surfaces at acidic and neutral conditions. The results reveal that adsorption under dry conditions was more exothermic than under hydrated conditions for both minerals. In dry systems, spodumene demonstrated stronger adsorption affinities, with diethyl hydrogen arsenate exhibiting the most favorable adsorption energy of −281.596 kJ·mol⁻¹, preferentially coordinating with surface Al sites. Conversely, under hydrated conditions, feldspar exhibits relatively stronger adsorption interactions compared to spodumene. The most favorable interaction was observed for diethyl sodium phosphate, with an adsorption energy of −182.560 kJ·mol⁻¹, also favoring coordination with Al surface atoms. This proposes possible reverse flotation process in the separation of spodumene from feldspar.

Speaker: Lesetja Matlabjane (UNIVERSITY OF LIMPOPO)

386 Near- Redundant Calibration of HIRAX Visibility Simulation Data.

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer designed to probe the large-scale structure of the Universe through 21 cm intensity mapping, with the goal of constraining dark matter and dark energy. Achieving high-precision measurements requires accurate calibration of instrumental effects, particularly in the presence of non-redundant systematics such as antenna position offsets and gain variations.

In this work, we simulate visibility data for a HIRAX-like array incorporating realistic sky models, including the 21 cm cosmological signal, astrophysical foregrounds, and instrumental noise. We investigate the impact of non-redundancy on traditional redundant calibration techniques by introducing controlled systematic deviations in the array configuration. The performance of these calibration methods is assessed through their effect on gain recovery and the delay power spectrum, a key observable for isolating the cosmological signal.

Furthermore, we explore alternative calibration approaches that account for non-redundant effects and evaluate their effectiveness in mitigating systematic biases. By comparing redundant and non-redundant calibration strategies, this study aims to improve the robustness of calibration pipelines and enhance the reliability of 21 cm power spectrum measurements. These results contribute toward optimizing HIRAX data analysis and advancing precision cosmology with next-generation radio interferometers.

Speaker: Luyanda Khanyile (University of KwaZulu-Natal, Pursuing a Master’s degree in Astrophysics.)

387 Numerical Simulation Of The Astrospheres

This study investigates the large scale structure and time evolution of stellar
astrospheres with magnetohydrodynamic (MHD) simulations. We study the
heliosphere as an first example of an astrosphere, and then investigate Lambda
Cephei, a massive runaway O-type star. Astrospheres are formed when stellar
winds meet the interstellar medium (ISM). This produces a variety of phenomena
including the termination shock (TS), astropause (AP), and bow shock
(BS). This project examines the model results of how the heliosphere evolves
and stabilizes as it expands from 50 000 to 700 000 years. According to the
simulations, the TS as well as BS steadily move outward with time, while the
astrosphere possesses a bullet-shaped asymmetric form.

Speaker: Mr Solomzi Nobute (North west University center of space reseach)

388 Optimization of lead-free BaZrS3-based perovskite solar cell for better performance using SCAP-1D

In this study, a numerical simulation of a BaZrS3-based perovskite solar cell was performed using SCAP-1D. An attempt was made to optimize the performance of the solar cell configuration FTO/ZnO/BaZrS3/WSe2 by varying several parameters. The effect of the variation of the thicknesses of the hole transport layer (HTL), electron transport layer (ETL), absorber (perovskite) layer, acceptor dopant density (ADD) of the HTL and perovskite layer, donor dopant density (DDD) of the ETL, series and shunt resistances and operating temperatures on the overall performance of the perovskite solar cell were investigated. A PCE of 30.03%, FF of 90.02 %, Jsc of 25.19 mA/cm-2, and Voc of 1.3242 V were obtained after several cell optimizations. The PCE obtained exceeded the highest reported PCE for BaZrS3-based perovskite solar cell (8.547 %) by 71.5%. The results obtained indicate that BaZrS3 can contribute to the development of non-toxic, efficient perovskite solar cells.

Speaker: Dr Paulinah Fasanmi (University of Johannesburg)

389 Phase Stability and Atomic Ordering in MnPt1-xRux Alloys: A Cluster Expansion and First-Principles Investigation

The design and development of advanced materials exhibiting high magnetic anisotropy, enhanced thermal stability, and strong mechanical robustness are essential for next-generation spintronic and data storage applications. L1₀-ordered MnPt is a promising rare-earth-free material due to its large magnetocrystalline anisotropy and strong spin polarization. Alloying MnPt with transition metals such as Ru has been explored to improve its magnetic performance, while Mn-Pt-Ru systems are also known to exhibit antiferromagnetic behaviour at low temperatures. However, the thermodynamic stability and ordering behaviour of these ternary alloys remain insufficiently understood. In this study, the structural and thermodynamic properties of MnPt1-xRux alloys were investigated using the cluster expansion method combined with first-principles calculations. The cluster expansion model converged at iteration 26 with 40 structures and a cross-validation score of 1.4 meV, indicating a reliable description of configurational energetics. A total of 40 ternary configurations were predicted, and all calculated formation energies were found to be negative, demonstrating strong thermodynamic stability and a tendency toward compound formation across the composition range. The Mn6Ru2Pt4 composition (16.67 at. % Ru) exhibited the lowest formation energy and crystallizes in the orthorhombic Cmmm space group, identifying it as the most stable ordered phase. These results provide new insight into the phase stability and ordering tendencies of MnPt1-xRux alloys, supporting their potential for high-performance spintronic and magnetic data storage applications.

Keywords: MnPt1-xRux alloys, DFT, Cluster expansion, structural properties
applications.

Speaker: Thabang Kombesi

390 Phase stability and electronic properties study of Sc 6 As 2 B boride for high-temperature structural applications: Insights from First principles DFT

The distinctive structural, mechanical, phonon, and electronic properties of hexagonal compounds make them suitable for high‑temperature structural applications. The properties of Sc₆As₂B boride were investigated using first‑principles density functional theory (DFT) calculations. The calculated heat of formation of Sc₆As₂B boride is negative, confirming its thermodynamic stability. Furthermore, the elastic property results demonstrate mechanical stability, suggesting the possibility of experimental synthesis and a high melting temperature exceeding 1000 K. However, the phonon dispersion curve reveals dynamical instability due to the presence of imaginary phonon modes, while the electronic band structure indicates metallic behaviour arising from band overlap between the valence and conduction bands at the Fermi level. Overall, the structural, mechanical, and electronic properties highlight promising potential for high‑temperature structural applications.

Speaker: Bhila Oliver Mnisi

391 Phase stability of Ga-Doped MnAl using a Cluster Expansion Approach

L10 Mn50Al50 is a promising hard magnetic material due to its good magnetic properties such as high magnetic moment and high Curie temperature. It is considered the best candidate for use as a permanent magnet in various applications such as electric cars and wind turbines. However, L10 MnAl has drawbacks such as being brittle and thermodynamically unstable. A cluster expansion has been used to determine the phase stability of MnAl-Ga alloys. The cluster expansion generated 18 new structures on MnAl₁₋ₓGAₓ. The cross-validation score (CVS) was used to confirm the fitting accuracy, and it was found to be reasonable. The ground-state line predicted 4 stable structures because of their negative formation energies. The most stable structure was found to be Mn₂AlGa. All the structures were found to be mechanically stable because their elastic constants satisfy the tetragonal stability criteria. The findings will provide valuable insights into the development of advanced permanent magnets.

Keywords: MnAl₁₋ₓGAₓ alloys, Cluster expansion (CE), Phase stability, Magnetic properties, Ductility

Speaker: Mr Thabang Mokwena (University of Limpopo)

392 Preliminary Experimental and Computational Investigation of Vacuum-Induced Outgassing in Poly(2,5)-benzimidazole Nanocomposites for Low Earth Orbit Applications

Poly(2,5)-benzimidazole (ABPBI) is a high-performance polymer with potential applications in extreme environments such as low Earth orbit (LEO), where vacuum-induced degradation and outgassing are critical concerns. In this study, ABPBI-based nanocomposites incorporating multiwalled carbon nanotubes (MWCNTs), molybdenum disulfide (MoS2), and hexagonal boron nitride (h-BN) are investigated to evaluate their structural stability and outgassing behaviour under simulated vacuum conditions.

Composite samples are synthesised and subjected to controlled drying and humidity conditioning prior to vacuum exposure. A variety of pre- and post-exposure characterisation techniques, including SEM and FTIR, are conducted to assess chemical, structural, and mass changes.

In parallel, a simplified computational framework is developed to describe molecular outgassing processes within the polymer matrix, with atomistic models used to estimate relevant transport parameters.

Preliminary results aim to correlate experimental observations with computational predictions, providing insight into how nanofillers influence outgassing behaviour and overall material stability under vacuum conditions. The anticipated agreement between computational and experimental findings lays a foundation for further exploration of the durability of ABPBI composites in the volatile environment of LEO.

Speaker: Ms Luwy Swanepoel (Centre for Space Research, North-West University, Potchefstroom Campus, Potchefstroom, 2531, South Africa)

393 Probing the Overabundance of X-type Asteroids Among Small Near-Earth Asteroids

Small near-Earth asteroids (diameter ≲150 m) represent the most numerous yet least characterised segment of potentially hazardous objects in our Solar System (Binzel et al., 2004). Their rapid fading after discovery limits follow-up opportunities, leaving gaps in our understanding of their compositional distribution. Here we present results from an ongoing robotic follow-up programme using the South African Astronomical Observatory's Lesedi telescope (Ngwane et al., 2025), which employs automated scripts to identify NEA discoveries reported to the Minor Planet Center and execute multi-filter photometry within hours of detection. Using green, red, and infrared photometry, we applied a trained machine learning classifier to derive possible taxonomic classifications for 59 small NEAs spanning absolute magnitudes 22 ≤ H < 29 (corresponding to approximate diameters between ~250 m and ~5 m, assuming albedos of 0.05–0.30). We find a roughly 1:1 ratio between stony (S+Q+V) and carbonaceous/metallic (C+X) types, consistent with studies of larger NEAs (Mommert et al., 2016; Erasmus et al., 2017; Janse van Rensburg, 2021). However, we identify a notable overabundance of X-type asteroids, comprising nearly 30% of our sample, exceeding fractions reported for larger objects. Similar trends have been noted in other small-NEA studies (e.g. Devogèle et al., 2019; Hromakina et al., 2021; Moskovitz et al., 2025). The Bus-DeMeo X-complex is spectrally degenerate, encompassing high-albedo E-types, moderate-albedo metallic M-types, and low-albedo primitive P-types, which are difficult to distinguish using standard photometry. This distinction is critical for planetary defence, as impact properties vary significantly between these classes. We discuss the implications of the X-type excess and the potential of polarimetric characterisation for refining compositional constraints of newly discovered small NEAs.

Speakers: Thobekile Ngwane (Stellenbosch University and South African Astronomical Observatory), Christine Margarete Steenkamp (Stellenbosch University, Physics Department)

394 Pulse profiles of the RRAT J1819-1458

Rotating Radio Transients (RRATS) are a class of pulsars that were identified in 2006 by McLaughlin et al. Unlike canonical pulsars, which are characterized by regular pulses that are detectable by Fourier transform periodicity searches, RRATs emit pulses sporadically and are best detected by single-pulse searches.
J1819-1458, a galactic RRAT with a dispersion measure (DM) of 196, is the brightest and best-studied such object. It has a period of 4.9 s and an average burst rate of one every 4 minutes, with peak flux densities of 0.1 - 3.6 Jy. It has three distinct emission phases within a single period, which may be related to the different emission zones of the star. It is the only RRAT that has exhibited glitches, resulting in sudden changes to its period. However, this has not been observed since 2009.
In this poster, I will present results from my Master’s research findings on J1819-1458, using data from the MeerTRAP commensal survey on the MeerKAT telescope. This includes a refined timing solution, an analysis of the distribution of the timing residuals, and the flux intensity distribution of the observed bursts. The timing solution spans multiple years and shows that the RRAT has been stable for over 17 years. The pulses are also highly variable; I investigate relationships between variations in pulse energy, pulse width, time-of-arrival, spectral index, and morphology that are suggestive of RRAT emission mechanisms.

Speaker: Kevin Rorke (University of South Africa)

395 Quantization of radiation-induced defects in SnO2 using positron lifetime components.

In this work a two-component density functional theory is employed in the modelling of defects in ion and neutron-irradiated SnO2 using positrons as probes. Since defects are localized, the local density approximation (LDA) is used, which is part of DFT. Although LDA gives a good approximation of positron lifetimes and electron-positron annihilation momentum density, it does not consider the variational nature of the electron density. This has an unintended consequence of having over estimated annihilation rates or lower positron lifetimes compared to experimental values. This deficiency in LDA is corrected by using the generalized gradient approximation (GGA) which considers the variational nature of electron density. The accumulation of annihilation spectrum using coincidence setup, is utilized to allow for the determination of annihilation parameters, S and W. The spectrum consists of positron annihilations at defect sites as well as annihilations in the bulk (defect-free region). The annihilation curve of the spectrum also consists of annihilations of positrons with core electrons (high momentum electrons) and this specifically allows the calculation of the W-parameters. The low and high momentum distribution of electrons will be used to characterize the Doppler broadening which will tell us about the quantity of radiation-induced defects in SnO2 in terms of calculating S-parameter, which is the ratio of the annihilation centroid area to the total area of the annihilation curve. Calculated S parameters are then compared with the experimentally obtained S parameters. The nature of the defects is theoretically obtained from the annihilation rates or equivalently from the calculated positron lifetimes in SnO2. The concentration of defects per cubic centimeter in both the Local Density Approximation (LDA) and Generalized Gradient Approximation (GGA) frameworks was obtained. The concentration of defects per cubic cm in the framework of both the LDA and GGA were obtained. These concentrations were influenced by the positron lifetime components, the bulk lifetime, the defect lifetime as well as the average positron lifetime as 241.05 ps, 263 ps and 252.01 ps respectively. The concentration of tin vacancies (VSn) was found to be 1.09 x 1017 cm^-3 in the framework of GGA and 1.18 x 1017 cm^-3 in the framework of LDA. The discrepancy between these values is mainly due to the fact that LDA overestimate the annihilation rates whereas the GGA considers the charge density variation in atoms including the at the defects.

Keywords: positron annihilation, Doppler broadening, Local density approximation, positron lifetime, S-parameter

Speaker: Ms Dineo Motjope (First author)

396 Rational Fabrication of p-n Co3O4 /Fe2O3 Heterojunction for Improved BTEX Gas Sensing

Volatile organic compounds (VOCs), especially benzene, toluene, ethylbenzene, and xylene isomers (BTEX) are hazardous air pollutants that pose significant risks to human health and the environment, necessitating the development of highly sensitive and selective gas-sensing materials. In this study, Co3O4 and Fe2O3 semiconducting metal oxides (SMO) were synthesized via a microwave-assisted hydrothermal method followed by annealing, and mechanically mixed at weight ratios of 25, 50, and 75% to form Co3O4/Fe2O3 composite. X-ray powder diffraction patterns confirmed the coexistence of cubic spinel Co3O4 and rhombohedral α-Fe₂O3 phases, indicating successful heterostructure formation. Notably, the crystallite size was found to increase with increasing Fe2O3 content (20-23 nm). UV–Vis diffuse reflectance spectra revealed strong absorption at longer wavelengths, leading to reduced reflectance of pure Co3O4. The incorporation of Fe2O3 led to a gradual increase in reflectance, reflecting changes in the electronic structure and optical response of the composites. The optical band gaps were estimated from Tauc plots and found to increase from 1.35 to 2.07eV as Fe2O3 content in the composite increased. The Co3O4/Fe2O3 composites exhibited superior sensing performance for BTEX compared to individual SMOs. The improved performance was associated with the formation of Co3O4/Fe2O3 heterojunctions, promoting the efficient charge separation and transport at the interface, thereby enhancing surface reaction kinetics with VOC molecules and improving sensor response.

Speaker: Mr Suggest Baloyi (University of the Free State)

397 Refractory High-Entropy Silicide–Boride Compounds V₁₀Si₆B and V₅Si₃B for High-Temperature Structural Applications

Refractory silicide–boride compounds have recently attracted significant attention as potential candidates for high-temperature structural applications beyond the operational limits of conventional Ni-based superalloys. In this study, we employ first-principles calculations to investigate the structural, electronic, mechanical, and dynamical properties of ternary intermetallic compounds, with particular focus on V₅Si₃B. Our results reveal that V₅Si₃B exhibits a negative heat of formation, confirming its thermodynamic stability and suggesting feasibility for experimental synthesis. The calculated elastic constants satisfy the Born mechanical stability criteria, indicating mechanical robustness. Notably, V₅Si₃B demonstrates a high hardness of approximately 21 GPa, highlighting its strong resistance to deformation and suitability for demanding environments. Phonon dispersion analysis confirms the absence of imaginary frequencies, establishing dynamical stability. Furthermore, the compound exhibits a minimum lattice thermal conductivity of 1.50 W m⁻¹ K⁻¹, indicative of reduced phonon-mediated heat transport, which is advantageous for thermal barrier applications. The combination of high hardness, thermodynamic and dynamical stability, and low lattice thermal conductivity positions V₅Si₃B as a promising candidate for advanced high-temperature applications, including aerospace and gas turbine components. These findings contribute to the growing body of research on refractory silicide systems and support their potential for next-generation extreme-environment materials.

Speaker: Ibrahim Ali

398 Response of Topside Ionospheric Electron Density during Solar Flares

The ionosphere plays an important role in space weather phenomena and its understanding is important in High Frequency (HF) communications and navigation systems. However its response to sudden solar activity, e.g., solar flares, is still an area of ongoing research. In this work, we report for the first time the global statistical response of the ionospheric topside electron density to X-class solar flares during geomagnetically quiet days (Kp ≤ 2). Here, the global electron density of the topside ionosphere’s response to X-class solar flares from 2014 to 2024 is studied utilizing in situ measurements of electron density by Swarm satellites and X-ray flux measurements by the Geostationary Operational Environmental Satellites (GOES). The International Reference Ionosphere (IRI-2020) model is used to provide background topside electron density information and the percentage deviation between the model values and Swarm measurements is computed. The results indicate a consistent decrease in the electron density at all latitudes during solar flares, with greater depletion observed in high-latitude regions. The decrease in topside electron density during solar flares is largely due to thermal ionospheric plasma expansion leading to oxygen ions up flow to the plasmasphere prevailing at higher altitudes during solar flares. The findings obtained not only support current studies, but also present a statistically robust global investigation of topside ionospheric dynamics in the most intense solar events and so have significant impacts on space weather modelling and mitigation.

Speaker: Kenny Monontsi (North-West University)

399 Solid-state synthesised Zn doped CdO nanoparticles for potential supercapacitor applications

Pristine CdO and Zn doped CdO nanoparticles have been prepared via solid-state method. A simple and cost-effective synthetic method where the precursors zinc acetate dehydration and cadmium acetate dehydration were mixed in ethanol. The X-ray diffraction (XRD) analysis indicated that the prepared samples were of a single crystalline cubic structure of CdO with the patterns observed to be shifting to higher two theta angles as the concentration of the dopant was increased, indicating the distortion in the structure. The absence of the Zn peaks in the XRD data might indicate that Zn has successfully substituted for Cd in the host lattice. Fourier transform Infrared spectroscopy (FTIR) and Energy-Dispersive X-Ray (EDS) Spectrum will be used to affirm the presence of the zinc and cadmium oxide nanoparticles. Scanning Electron Microscope (SEM) will be used to study surface morphology. The potential use of Zn doped CdO nanoparticles will be analyzed by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD).

Speaker: Mpho Maswanganye (University of Limpopo)

400 Space-time light sculpturing by bound states in the continuum

Recent nanotechnology and metasurface advancements have enabled ultraprecise light control, catalysing developments in energy conversion, sensing and imaging. Simultaneously, structuring light in space-time has opened new realms for exploring the physics of both fundamental and applied light-matter interactions. Unfortunately, conventional space-time light structuring methods require large, complex optical setups presenting a formidable challenge for widespread usage. Here we experimentally demonstrate a novel simple single-step metasurface design for creating high-fidelity optical vortices in space-time addressing these challenges by exploiting the extraordinary compactness and stability of metasurfaces. Our design employs two offset subwavelength PTFE and copper gratings. This forms a 2π spiral phase by breaking mirror symmetry at the Γ-point and utilizing the structure’s quasi-bound state in the continuum (q-BIC) mode. We showcase this device’s versatility by generating space-time scalar beams, vector beams and even skyrmions, in all cases showing excellent agreement between our numerical simulations and experiments. This work thus achieves single-step, compact sculpturing of light in both space and time, paving the way toward more widespread usage of spatiotemporal light with subwavelength engineered metasurfaces.

Speaker: Kelsey Everts (University of the Witwatersrand)

401 Structural and gas sensing properties of Co3O4 prepared by the Hydrorthemal method.

Cobalt oxide (Co3O4) nanostructures were successfully synthesized by hydrothermal synthesis method using various solvents solutions. Physical and chemical properties of the as-synthesized nanostructures were examined using various characterization techniques such as scanning electron microscopy, X-ray diffraction, and UV-Vis spectroscopy to name the few. X-ray diffraction revealed that the nanostructures were of high purity and corresponds to cobalt oxide (Co3O4) while the scanning electron microscopy revealed that the nanostructures have different morphologies for different solvent: nanorods (distilled water as solvent), and nanoparticles (acetone, isopropyl, and methanol as solvents). UV-Vis results proved that each solvent has its own optical bandgap as estimated using the Tauc plot. These results show that the solvent significantly influences structural (shape, size, and crystallinity) and optical properties, which is an indication that desired properties can be tailor engineered to a specific purpose such as gas sensing, and photoelectrochemical in hydrogen production.

Keywords: Gas sensors, Co3O4

Speaker: Prince Mkwae (University of Zululand)

402 STRUCTURAL AND THERMOLUMINESCENCE PROPERTIES OF ZINC TITANATE (ZnTiO3) NANOSTRUCTURES

Zinc titanate (ZnTiO3) nanostructures were synthesized by an eco-friendly sol-gel method using an ethanolic plant extract as a reducing and capping agent. The synthesized nanostructures were characterized using X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the formation of the rhombohedral ZnTiO3 phase. Fourier Transform Infrared Spectroscopy (FTIR) confirmed the formation of metal-oxygen bonds, and UV-Vis. absorption spectroscopy indicated strong absorption in the UV region. Dose response studies were carried out under beta irradiation. The initial rise (IR) method and Variable heating rate (VHR) method were used to determine the kinetic parameters of ZnTiO3. Thermoluminescence (TL) studies demonstrated excellent dosimetry properties over the varied doses, good reproducibility (CV = 2.47 %), and stable glow curve characteristics. The initial rise (IR) method and Variable heating rate (VHR) method were used to determine the kinetic parameters of ZnTiO3. The Activation energy found from IR method was
0.72 eV, with VHR yielding E=0.64 eV (R²=0.987), indicating that the two methods are reliable for activation energy determination. The excellent linearity validates the reliability of the kinetic parameters. The results obtained indicate that this material can be used in low-temperature dosimetry applications.

Speaker: Nolufundo Sintwa (Student)

403 Structure, Electron Spin Resonance and Magnetic Properties of Cr-Co Nanoferrite for Biomedical Applications

Chromium-substituted cobalt ferrite nanoparticles CoCrₓFe₂₋ₓO₄ (0 ≤ x ≤ 2.0) were successfully synthesized via the hydrothermal method. X-ray diffraction (XRD) patterns confirmed the formation of a single-phase cubic spinel structure. Crystallite sizes ranged from 6.6 to 13.7 nm, while lattice parameters decreased from 8.2603 to 8.1974 Å with increasing chromium content. SEM showed uniform grains with discrete boundaries. FTIR spectra exhibited characteristic metal–oxygen stretching vibrations at tetrahedral (615 cm⁻¹) and octahedral (468 cm⁻¹) sites, along with a weak Cr³⁺–O²⁻ band at 499 cm⁻¹, confirming successful cation substitution and bond strengthening. The small remanent magnetization and coercive fields from M-H curves revealed superparamagnetic nature for all samples. The Electron spin resonance (ESR) spectra revealed composition-dependent variations in resonance field (Hres), g-values, and spin relaxation times. The g-value ranged from 4.49 (x = 0) to 2.04 (x = 1.0), indicating a transition toward a more symmetric crystal field and stronger Fe³⁺–Cr³⁺ exchange coupling. These results demonstrate that controlled Cr³⁺ substitution effectively tunes the structural order, local bonding environment, and spin dynamics of cobalt ferrite nanomaterials, making them promising materials for magnetic, electronic, and biomedical applications.

Speaker: Metuel Dipuo Sethosa

404 Surface and electrical properties of high energy milled silicon nanoparticles

This study examined the structural, chemical and electrical behaviour of silicon nanoparticles produced by high-energy milling, with the goal of understanding how milling conditions, material type and ageing influence their surface stability and electrical activity. The powders, derived from metallurgical and n-type silicon, consistently formed nanocrystalline particles with crystallite sizes of 30-50 nm, surrounded by strained and partially amorphous outer layers that readily incorporated oxygen. Despite long-term exposure to air, the particles did not develop a thick insulating oxide; instead, X-ray photoelectron spectroscopy revealed a thin, graded SiOₓ shell dominated by sub-oxide states (Si⁺, Si²⁺, Si³⁺), with only a small Si⁴⁺ contribution. The net SiO₂ capping was found to be extremely small, between 0.1 - 0.3 nm in one-year-old powders and not more than about 0.8 nm in three-year-old samples, corresponding to an approximate oxide growth rate of 0.1 nm per year, confirming that the nanoparticles remain surface-stable over time. Photoluminescence measurements further supported this interpretation by revealing three defect-related emission bands at 550 nm, 590 - 600 nm and 660 - 670 nm, characteristic of oxygen-related centers within the SiOₓ shell. The presence of these defect states was consistent with the activation energy of approximately 0.2 eV extracted from impedance spectroscopy, which showed that electrical transport in printed films occurs through trap-assisted hopping across the Si/SiOₓ interfaces. Because the oxide shell is thin and discontinuous, the nanoparticles retain measurable conductivity even after years of storage. The combined findings demonstrate that high-energy milling produces electrically active, chemically stable silicon nanoparticles with a defect-rich but ultrathin oxide interface, making them promising for low-temperature printed electronics, flexible sensors, and other silicon-based functional materials.

Speaker: Nangamso Ndzamela (iYuniversity Walter Sisulu)

405 Surface and electronic properties of LiTi2(PO4)3 as solid-state electrolyte: A DFT study

Surface and electronic properties of LiTi2(PO4)3 as solid-state electrolyte: A DFT study.

Leago Pitsa, kemeridge Malatji, Phuti Ngoepe, and Khomotso Maenetja

Materials Modelling Centre, University of Limpopo, Private Bag X1106, Sovenga, 0727, South Africa

Abstract.
Solid electrolytes are at the forefront of research for next-generation energy storage systems, offering enhanced safety, chemical stability, and long-term durability compared to traditional liquid electrolytes. Among these, NASICON-type LiTi2(PO4)3 (LTP) is a highly promising candidate due to its chemical robustness and low electronic conductivity. However, its practical implementation is currently hindered by poor ionic transport.
In this study, we employed Density Functional Theory (DFT) and the METADISE code to investigate the bulk properties and surface characteristics of rhombohedral LTP. Electronic structure calculations reveal that LTP is thermodynamically stable, exhibiting semiconducting behaviour with a band gap of 2.615 eV. Orbital analysis indicates that the valence band is dominated by Li, P, and O states, while the conduction band is primarily governed by Ti states.
Furthermore, to elucidate the material's surface properties, we modelled the (010), (100), and (110) surfaces indices identified via XRD analysis to determine their relative stability. Our results identify the (010) surface as the most energetically favourable termination, characterized by a significant surface relaxation of 30.63%. These findings provide critical insights into the surface-level behaviour of LTP, offering a foundational understanding necessary for optimizing its performance in solid-state battery applications.
Keywords: Solid electrolytes, NASICON, LiTi2(PO4)3, Density Functional Theory, Surface Stability, Energy Storage.

Speaker: Leago Heaven Pitsa

406 Synergetic Effect of Rare-Earth (Ce) Doped on Gas Sensing Properties of Cobalt Nickel Ferrites Nanoparticles.

We present the effect of cerium(Ce3+) at various concentrations ranging from 1-5 wt%, doped in CoNiFe2O4 for the detection of LPG and H2S prepared by the Sol-gel method. X-ray Diffraction confirms the cubic phase of all the samples, and no impurities were detected with a crystallite size range of 8 to 11 nm. Scanning Electron Microscopy (SEM) and Electron Dispersive X-ray Spectroscopy (EDS) depict that undoped and doped ferrite are spherical with only a few areas having nano-flakes like. The gas response of undoped and doped Ce3+ was investigated in the 225-275 °C temperature range. Undoped CoNiFe2O4 showed a low response. In contrast, the sample with Ce3+ had an improved response to LPG and H2S gases. Increasing the Ce3+ amount in CoNiFe2O4 is promising for making better sensors to detect gases.

Speaker: Mr Victor Sokhela (Student@University of Johannesburg)

407 Synergistic Charge Transport and Defect Chemistry in SrTiO3/Ti3C2Tx MXene Composites for Low Temperature Toluene Sensing.

Detecting harmful aromatic volatile organic compounds (VOCs) such as toluene remains a major environmental and safety concern. In this work, SrTiO3 and SrTiO3/Ti3C2Tx MXene composite structures were prepared through a hydrothermal synthesis method, while Ti3C2Tx MXene was synthesized through the LiF-HCl etching. Detailed investigations were conducted to evaluate the structural and optical characteristics, defect states, and their gas-sensing behavior. Gas sensing measurements revealed that the SrTiO3/Ti3C2Tx MXene composite was more favored and had a response ratio of 100.28 % towards 100 ppm toluene vapor at a lower operative temperature of 50 °C. This improvement results from a combination of enhanced defect assisted oxygen adsorption and efficient electron transfer through the Ti3C2Tx MXene layers. Overall, the study highlights SrTiO3/Ti3C2Tx MXene heterostructures as strong candidates for ye detecting aromatic VOCs.

Speaker: Nkosikhona Dlamini (University of the free state)

408 Synthesis and electron spin resonance study of MgxZn1-xAl0.4Fe1.6O4 nanocrystalline compounds

A series of MgxZn1-xAl0.4Fe1.6O4 (0 ≤ x ≤ 1.0) substituted mixed ferrites with fine particles (5.0 ≤ D ≤ 11.0 nm) were synthesized by glycol thermal technique. XRD data confirmed formation of single-phase cubic spinel structure with no impurity phases. XRD results were complemented by TEM analysis which showed nearly spherical images with narrow size particle distribution. Substitution of Zn by Mg atoms in ZnAl0.4Fe1.6O4 compound have significant effects electron spin resonance (ESR) properties. ESR spectra showed single line signals broadening (362 ≤ HPP ≤ 860 Oe) with increasing Mg2+ ion concentration due to transformation from dipole-dipole interactions between the particles to superexchange interactions. An increase in g values from about 1.99 to 2.16 occurs due to reducing resonance magnetic field with increasing Mg2+ ions. Hysteresis between signals recorded on cycling magnetic fields observed have been discussed based on the constituent ions and particle size.

Speaker: Nwabisa Mkhize

409 Synthesis, structural, and photoluminescent properties of green emitted Eu2+ doped SrAl2O4 phosphor

SrAl2O4:Eu2+ is a well-known phosphor due to its strong green emission. The intense green emission makes SrAl2O4:Eu2+ an extremely interesting material for a broad range of applications, including emergency and safety lighting, anti-counterfeiting labels, roadway markings, and phosphor-coated bricks. This study investigates Eu2+-doped SrAl2O4 phosphors synthesized via the solid-state reaction method and characterized using X-ray powder diffraction (XRPD), photoluminescence (PL), and UV–Vis spectroscopy. XRPD analysis confirmed the formation of monoclinic SrAl2O4 after annealing at 1600°C. Residual SrCO3 observed at lower temperatures indicates incomplete phase formation, emphasizing the importance of high-temperature annealing to achieve phase purity and enhanced crystallinity. The effect of Eu2+ doping revealed concentration-dependent structural modifications. UV–Vis spectroscopy supported these findings, showing characteristic Eu2+ (4f–5d) absorption bands. PL results demonstrated enhanced emission intensity for samples synthesized through a two-step calcination and annealing process in a reducing Ar–5%H2 atmosphere, ensuring effective reduction of Eu3+ to Eu2+. These results highlight the importance of controlled synthesis in optimizing luminescent properties.

Speaker: Lethabile Masiu (Lethabile Masiu)

410 The effect of Ni and Ru substitution on structural and mechanical properties of FCC Ir. A first-principles study

The structural stability of iridium-based alloys remains significant due to iridium's (Ir) outstanding high-temperature properties and corrosion resistance, particularly for aerospace and extreme-environment applications. However, the inherent brittleness of pure FCC Ir and its high cost limit its broader structural applications. This study employed first-principles calculations based on density functional theory (DFT) to examine the effect of alloying with nickel (Ni) and ruthenium (Ru) on the structural and mechanical stability of Ir using a 2×2×2 supercell method to enable binary substitution in Ir32-x-Mx (M = Ru, Ni). The calculated elastic constants of the investigated Ir32-x-Mx (M = Ru, Ni) binary alloy compositions satisfied the Born-Huang mechanical stability criteria. Cauchy pressure (Cₚ) analysis revealed distinct bonding characteristics: Ru-containing compounds exhibited covalent bonds (Cₚ < 0), while Ni additions ≥ 18.75 at. % displayed metallic bonds (Cₚ > 0), associated with ductility. Poisson's ratio (ν) further validated these trends; for metallic bonding, ν > 0.26, otherwise covalent and brittle. All Ru-containing alloy compositions showed ν < 0.26, indicating brittleness, whereas Ni ≥ 18.75 at. % yielded ν > 0.26, confirming metallic and ductile behaviour. The ductility in the latter was further supported by the calculated Pugh's ratio (B/G) ≥ 1.75. Similarly, the Ru-containing alloy compositions maintained brittleness as evidenced by B/G < 1.75).

Keywords: Iridium, brittle character, density functional theory, elastic properties, ductility

Speaker: Mr Thabo Nhlakanipho Nhlenyama (University of Zululand)

411 The effect of temperature on structural, and thermal properties of ZrTiVNbCr high entropy alloy

Refractory high entropy alloys (RHEAs) have emerged as promising candidates for the development of more effective hydrogen storage materials. This area is becoming increasingly important as the quest for sustainable and efficient energy solutions continues. However, no commercially available hydrogen storage material or system currently meets all the stringent ultimate Department of Energy requirements. In this study, molecular dynamics simulations are employed to examine the effect of temperature on the structural, thermodynamic, and thermal properties of the ZrTiVNbCr alloy. The results indicated that the Gibbs free energy of mixing decreases with increasing temperature, thereby enhancing the stability of the alloy. The analysis of heat capacity and lattice expansion revealed that electron excitation in the ZrTiVNbCr alloy occurs at very low temperatures. Additionally, the alloy demonstrated high thermal stability, which is essential for long-term hydrogen storage applications. These findings demonstrate the potential for refractory HEAs to advance hydrogen storage technologies.
Keywords: Lattice expansion, Gibbs free energy, Density functional theory

Speaker: Ms Lebogang Motsomone (University of Limpopo)

412 The Heat Rate Kinetics on the Liquefied Gases During Sensing

This research presents the heat rate kinetics of liquefied petroleum gas (LPG) within the LPG sensing process using metal oxide semiconductors (MOS) based on MgCexFe₂₋ₓO₄ (x = 0, 0.1, 0.2, and 0.3). Much has been reported on the detection of LPG using MOS, and anomalies in gas sensing were observed in terms of the electrical current and the operating temperature. Oscillation/Variation were detected on the electric current and operating temperature during the saturation stage. The operating temperature should be constant with time throughout LPG sensing in gas. These variations were found to correlate with the different LPG concentrations applied, ranging from 1,000 to 10,000 ppm.
The experimental data were analysed using Origin and Microsoft Excel to determine the electrical behaviour of the sensors under different scenarios. The air current (Ia) was found to be 6.53 × 10⁻⁶ mA. The highest response value was achieved by MgFe₂O₄ (399.24), while the lowest was recorded by the MgCe₀.₁Fe₁.₉O₄ sample (37.46). According to the analysis, the heat transferred amount (Q) during the sensing process is impacted by several factors, specifically: it is directly proportional to the temperature difference, total contact surface area, and transfer time but inversely proportional to the effective thickness of the water molecule layers.
By applying Fourier’s law of heat conduction, an equivalent relationship was derived to describe the rate of temperature change per unit time (Equation 8). This equation was used to estimate some parameters (ΔT = 50 °C and Δt = 23 s) of the first concentration(1000ppm) of the operating temperature, which could not be directly observed in the experimental data (Fig. 2).
Keywords: LPG sensing, MOS, Oscillation, MgFe₂O₄, Variation, Fourier’s law

Speaker: Welcome Komana

413 The real-time detection of H2S based on a CuO/CeO2 sensor

Monitoring hydrogen sulfide (H2S) is vital for industrial safety and environmental systems, enabling the assessment of sulfur deposition, long-term impacts, and ecosystem stress. In this study, sensors made from CuO, CeO2, and their CuO/CeO2 heterostructure were hydrothermally synthesized and tested for gas detection performance against H2S. Multiple characterization techniques, such as X-ray powder diffraction, X-ray electron spectroscopy, UV-vis spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, transmission electron microscopy, and a gas testing station, were used to evaluate their structural, chemical, optical, and surface morphological properties. Different operating temperatures were examined to determine the optimal gas-sensing performance. The CuO/CeO2 sensor achieved peak performance at 150 ℃, with a response of 109 at 120 ppm H2S. The sensing ability is attributed to the synergistic interaction between CeO2 and CuO, which increases the number of active sites for H2S absorption. This sensor exhibited excellent long-term stability and humidity tolerance, indicating its potential for environmental monitoring.

Speaker: Ms Karabo Lurcender Bridgette Masilela

414 Thermal Evolution of Structure and Morphology in Noble Metal-Doped TiO₂: A Comparative XRD and SEM Study of Au and Pt Stability and Phase Transformation Dynamics from 100 to 1100 °C

Modification of titanium dioxide (TiO₂) with noble metals such as gold (Au) and platinum (Pt) is a primary strategy for enhancing its performance in photocatalysis, sensing, and energy conversion. However, a systematic comparative study of how these dopants influence the thermal evolution of TiO₂ across a wide range of temperatures remains limited. In this work, the influence of Au and Pt dopants on the structural and microstructural evolution of TiO₂ was systematically investigated from 100 to 1100 °C. Undoped, Au-doped (5 wt%), and Pt-doped (5 wt%) TiO₂ nanoparticles were synthesised via the sol-gel route and annealed. X-ray diffraction revealed a temperature-dependent anatase-to-rutile phase transformation in all samples, with notable dopant-induced differences. At 600 °C, the onset of rutile was observed in undoped and Pt-doped TiO₂, whereas the Au-doped sample remained purely anatase, indicating that Au initially stabilises the anatase phase—likely due to substitutional Au³⁺ ions. Above 700 °C, Au reduced to metallic form, and by 900 °C, the transformation was complete for all samples. At ≥900 °C, Au-doped samples formed Au-Ti intermetallic compounds (e.g., AuTi₃), which accelerated rutile nucleation and grain growth. In contrast, metallic Pt detected at ≥900 °C did not delay the transformation onset but remained as a separate phase without forming intermetallics. Crystallite size calculations indicated that Pt suppressed coarsening, while Au promoted grain growth at higher temperatures. Scanning electron microscopy corroborated these findings, showing morphological evolution from fine agglomerates to larger sintered grains. Distinct differences in particle size distribution and agglomeration behaviour were observed between doped and undoped systems, highlighting the role of dopants in modulating microstructural development. The combined analyses reveal that Au acts as a low-temperature stabiliser but a high-temperature destabiliser, whereas Pt exhibits weaker overall influence on transformation kinetics. These findings provide a valuable foundation for developing thermally robust photocatalytic materials.

Speaker: Olatunbosun Nubi (University of Limpopo)

415 Thermal stability evaluation of hexagonal molybdenum diselenide

Thermal evolution and stability of hexagonal molybdenum diselenide were investigated using classical molecular dynamics simulations. Stillinger-Weber type potential parameters were considered for interatomic molybdenum–molybdenum, molybdenum-selenium, and selenium-selenium interactions. NPT Hoover thermodynamic ensemble was explored to check different energy-temperature variations. Radial distribution functions and structure factors were also extracted and plotted at different temperature intervals. Coefficient of volume expansion and specific heat capacity were calculated be 1.27 x 10-6 K-1 and 1.67 x 10-4 eV/K respectively. Acquired results agree well with measurements and some calculations.

Speakers: Mr Thapelo Lebopo (University of Limpopo), Prof. Thuto Mosuang (University of Limpopo)

416 Thermoluminescence and kinetic parameters of ErTaO4, synthesized by the solid-state reaction method

Near-infrared (NIR) luminescent materials play a vital role in photonic, optoelectronic, and biological applications. In this work, the ErTaO4 host was synthesized by a solid-state chemical reaction at 1200 °C for 4 h. X-ray diffraction (XRD) was used to confirm that the sample crystallized into a single phase, without impurities. Scanning electron microscopy (SEM) was used to confirm the morphology, which consists of irregular particles, and energy dispersive spectroscopy (EDS) confirmed the presence of Nd, Ta, Er, and O. The optical energy band gap of the material was determined from the Tauc plot. The photoluminescence (PL) was also employed to probe the photonic response of the material. The presence of electron trapping centres was confirmed using thermoluminescence (TL) spectroscopy. The depths of the electron trapping centres and kinetic orders were approximated using different methods. The study suggests that ErTaO4 have potential applications in luminescent inorganic materials for solid-state laser and dosimetry applications.

Speaker: Dr Dumisani Mlotswa (Aspiring Physicist)

417 Thermoluminescence of ajoite

The thermoluminescence of ajoite is reported. A glow curve measured at 1 °C/s after beta irradiation to 10 Gy shows a high-intensity peak at 76 °C (peak PI) and secondary peaks at 200, 280 and 340 °C (peaks PII-PIV). This study mainly concerns the high-intensity peak, peak PI, although some supplementary material on peak PII is included. The order of kinetics for peak PI was determined to be first order. The activation energy and frequency factor were evaluated as 0.89 ± 0.02 eV and ~1012 s-1 respectively. The peak is affected by thermal quenching with an activation energy of value 0.73 ± 0.03 eV. The structural characteristics of ajoite as studied by X-ray diffraction resemble those of quartz but show additional features owing to presence of impurities. Possible mechanisms responsible for the TL are discussed.

Speaker: Dr Bereket Dalga Dana (Rhodes University)

418 Topology and Electrical Properties of Printed Silicon Nanoparticle Networks

This study investigates the relationship between the topology and electrical properties of printed silicon nanoparticle networks, focusing on how variations in cluster size and particle concentration influence charge transport. Silicon nanoparticles were produced via high-energy ball milling and separated into three cluster regimes, 25 μm, 50 μm, and 100 μm, each formulated into inks with concentrations ranging from 45% to 80% by weight. These inks were screen-printed on PET substrates to fabricate test structures for electrical and structural analysis. A suite of characterization techniques was used to elucidate the materials' properties. SEM and HRTEM revealed a polydisperse particle distribution with a strong tendency to agglomerate. The particles were observed to be crystalline. This was corroborated by XRD which further indicated an average crystallite size of 40 - 50 nm. Photoluminescence showed strong red emission around 660 nm (1.88 eV), consistent with defect-mediated recombination and XPS indicated surface oxidation of approximately 2 – 4 %, mainly in the form of sub-oxides, preserving electrical activity. Electrical characterization employed current–voltage and impedance spectroscopy to distinguish intra- and inter-particle charge transport mechanisms. IV analysis showed a transition from non-linear, diode-like, to nearly ohmic behavior as particle concentration increased. Impedance spectroscopy provided evidence of AC-induced transport. Equivalent circuit models evolved from simple CPE to dual-CPE - resistive networks, indicating the presence of distributed relaxation mechanisms. Resonance frequency and effective relaxation times derived from imaginary impedance spectra further confirmed multiple transport regimes, with AC conductivity dominating in sparse networks and DC pathways emerging past the percolation threshold. The study presents experimental evidence of both intra-particle and inter-particle charge transport, as well as distinct regimes of AC and DC conduction. It conclusively establishes the link between nanoparticle topology and charge dynamics, providing a detailed framework for tailoring printable silicon inks in flexible electronics and sensor applications.

Speaker: Mr Siphumliso Mbidana (Walter Sisulu University)

419 Transport of Single Electrons on Superfluid Helium

Electrons trapped on the surface of liquid helium constitute one of the purest two-dimensional electron systems in nature, forming a clean, defect-free platform in which electrons are bound to the surface by their image charge and are free to move laterally with record high mobilities. This system has long been of fundamental interest for studies of two-dimensional physics and, more recently, has emerged as a compelling candidate for quantum information applications, owing to the long coherence times expected for electrons isolated from the nuclear-spin-free helium environment. A central experimental challenge is developing the cryogenic infrastructure and sensitive electronics required to detect and manipulate electrons at the single-charge level on this surface. Here we present an ongoing project at the University of Cape Town aimed at designing and constructing a new superfluid helium probe system for the UCT dilution refrigerator, together with the custom low-noise electronics necessary for single-electron-sensitive transport measurements. State-of-the-art nanoelectronic device cells will be fabricated at international partner institutions and cooled to millikelvin temperatures for measurement. The programme will advance from the detection of discrete packets of surface-state electrons toward the ultimate goal of isolating and detecting individual charges. This work will establish a new experimental capability at UCT for probing electrons on helium and contribute to the broader international effort to achieve single-electron control in this uniquely clean quantum system.

Speaker: Friedrich Voelcker (University of Cape Town)

420 Transport Properties Insights toward the Enhancement of Bulk LiTi₂(PO₄)₃ Solid-State Electrolyte Materials

NASICON-type LiTi₂(PO₄)₃ is a promising solid electrolyte for all-solid-state lithium batteries due to its good thermal stability, structural durability, and three-dimensional lithium-ion conduction framework. However, its intrinsically low room-temperature ionic conductivity remains a major challenge for practical application. In this study, molecular dynamics simulations carried out with the DL_POLY code were used to investigate the structural and transport properties of bulk pristine, lithiated, and Al-doped LiTi₂(PO₄)₃. Lithiation and Al doping were examined to understand the effects of increased lithium content and framework modification on lithium-ion mobility. Lithium diffusion coefficients were obtained from mean square displacement calculations and used to determine ionic conductivity and activation energy. Ionic conductivities and activation energies were determined from the Nernst–Einstein equation and Arrhenius plots, respectively. The results revealed clear differences in lithium-ion transport among the bulk systems. The room-temperature ionic conductivity increased from 4.79 × 10⁻⁴ S/cm for LiTi₂(PO₄)₃ to 1.067 × 10⁻² S/cm for Li₃Ti₂(PO₄)₃ and 1.13 × 10⁻² S/cm for Li₁.₃Al₀.₃Ti₁.₇(PO₄)₃. Similarly, the activation energy decreased from 0.34 eV for LiTi₂(PO₄)₃ to 0.26 eV for Li₃Ti₂(PO₄)₃ and further to 0.16 eV for Li₁.₃Al₀.₃Ti₁.₇(PO₄)₃, indicating progressively easier lithium-ion migration across the series. These findings show that both lithium content and Al doping strongly influence transport behaviour in LiTi₂(PO₄)₃-based systems. While Li₃Ti₂(PO₄)₃ represents the lithium-inserted state relevant to cycling, Al doping produced the greatest improvement in ionic conductivity and the lowest migration barrier. This study provides atomistic insight into the role of lithium content and Al-doping in governing lithium-ion transport in NASICON-type LiTi₂(PO₄)₃ solid electrolytes, highlighting Al-doped LiTi₂(PO₄)₃ as the most promising candidate for improved solid-state battery performance.

Speaker: Lisbon Maake (University of Limpopo)

421 Trends in Maximum and Minimum Temperatures in Vuwani: Insights from the Southern African Universities Radiometric Network

This study investigates temporal trends and variability in maximum and minimum temperatures in Vuwani, South Africa, using observational data from the Southern African Universities Radiometric Network (SAURAN) spanning the period from April 2015 to December 2023. Understanding local-scale temperature dynamics is essential for assessing the impacts of climate change, particularly in climate-sensitive regions such as Southern Africa. The analysis employs statistical techniques and graphical methods, including histograms, monthly comparisons, and annual trend evaluations, to examine temperature distributions, seasonal variability, and long-term changes.

The results reveal a discernible increase in maximum temperatures over the study period, with 2023 recording the highest maximum and minimum temperature values, indicating an intensification of warming conditions. While mean temperatures exhibit variability without a consistent monotonic trend, the increasing frequency of extreme temperature events suggests emerging climatic instability. Seasonal analysis further highlights notable warming during the summer months (November to February), with recent years showing higher temperature peaks than earlier observations.

These findings are consistent with broader regional evidence of climate change and underscore the growing vulnerability of Southern Africa to rising temperatures and extreme weather conditions. The study contributes to localized climate knowledge by providing empirical evidence of temperature trends derived from high-resolution radiometric observations. Such insights are critical for informing climate adaptation and mitigation strategies in key sectors, including agriculture, water resource management, and public health.

Speaker: Muano Mbedzi (mutikimbedzi@gmail.com)

422 Trends, Performance Gaps, and Systemic Inequalities in Physical Sciences Education in South Africa (2008–2023)

This study presents a focused analysis of trends in Physical Sciences education in South Africa from 2008 to 2023, examining learner performance, systemic disparities, and post-school outcomes. Using national assessment data and higher education statistics, the study identifies a steady improvement in overall Grade 12 pass rates over time, particularly following curriculum reforms such as the implementation of the Curriculum and Assessment Policy Statement (CAPS). However, these improvements do not consistently reflect meaningful proficiency in Physical Sciences, as a substantial proportion of learners fail to achieve the 50% threshold required for entry into science-related tertiary programmes.

Provincial analysis reveals persistent inequalities, with provinces such as the Western Cape and Gauteng consistently outperforming less-resourced regions, including Limpopo and the Eastern Cape. These disparities are linked to uneven access to qualified teachers, laboratory infrastructure, and effective instructional support. Furthermore, distinction rates in Physical Sciences remain low across the study period, highlighting ongoing challenges in achieving high-level conceptual understanding and academic excellence.

The impact of the COVID-19 pandemic is evident in a temporary decline in learner performance around 2020, followed by a gradual recovery by 2023, particularly among learners with better access to educational resources. Despite this recovery, the overall performance trends suggest that improvements in pass rates have not translated into a strong pipeline of learners adequately prepared for STEM fields.

At the tertiary level, trends indicate improved retention and graduation rates in science-related programmes, suggesting that institutional support mechanisms may be mitigating some of the challenges experienced at the school level. Overall, the findings underscore a critical gap between access and achievement in Physical Sciences education. The study concludes by recommending targeted interventions, including strengthening teachers' content knowledge, improving access to laboratories, and addressing structural inequalities, to enhance learner performance and support the development of a robust scientific workforce in South Africa.

Speaker: Nthangeni Rofhiwa (University Of Venda)

423 Unravelling the adsorption behaviour of modified heterocyclic collectors on pyrite mineral surface

Pyrite is an abundant mineral that is usually found in association with a number of base metal sulphide (BMSs) and understanding its interaction with collectors is key in unravelling its depression mechanism. This requires a highly selective collector to target and float the desired mineral, which is significant in designing collector molecules. The modification of collectors offers hope to enhance the performance of the collectors to have strong binding with high selectivity. The density functional theory with dispersion correction (DFT-D) and the ab-initio molecular dynamics with machine learned force-field (AIMD-MLFF) within the Vienna ab-initio simulation package (VASP) technique were used to modify and ad-sorb heterocyclic collectors such as 2-mercaptobenzothiazole (MBT), 2-mercaptobenzoxazole (MBO) and 2-mercaptobenzimidazole (MBI) by addition of an allyl group. The DFT-D adsorption mechanisms showed that the collectors preferred to bind on the Fe atoms on chalcopyrite (100) mineral surface. Fur-thermore, the adsorption energies showed that the modified MBO gave strong adsorption (–107.51 kJ/mol). The AIMD-MLFF training at 300 K of modified MBO on the surface showed that under dry and hydrated conditions the adsorption energies were –228.07 kJ/mol and –180.58 kJ/mol, respectively. This suggested that the modified MBO adsorbs stronger at 300 K and the adsorption energy was reduced for hydrated condition. As such the modified MBO may be used to enhance the recovery of pyrite amongst the modified heterocyclic collectors.

Speaker: Prof. Peace Mkhonto (University of Limpopo)

424 Volatile Organic Compound Sensor Based on 2D NiO-WS2 Heterostructured Nanomaterials

Coal mine gas explosions represent one of the most catastrophic hazards in underground mining, ranking among the leading causes of mining fatalities worldwide and imposing severe economic burdens on coal-generating nations. Therefore, the detection of these volatile organic compounds (VOC) gases in the early stages is very significant for preventing catastrophic explosions in underground coal mines. Two-dimensional (2D) nickel oxide – tungsten sulfide (NiO-WS2) heterostructured nanomaterials were prepared through the hydrothermal method using a pressure reactor, and consequently, the sensors were fabricated from these nanomaterials. X-ray powder diffraction (XRPD) confirmed the crystal structure. Scanning electron microscopy (SEM) confirmed the particle morphology. Elemental composition and mapping were analysed through energy dispersive X-ray spectroscopy (EDS). The specific surface area and pore distribution were confirmed by the Brunauer-Emmett-Teller (BET) technique. Photoluminescence analysis was carried out to explore the intrinsic defects within the heterostructures. VOC vapours were exposed towards the fabricated sensors in order to investigate the sensing analysis.

Speaker: Teboho Mokoena (University of the Free state)

Brief Historical Tour of UWC Campus

Council Meeting with HoDs

Science in the Home Public Outreach Event

Including Science Show and physics demonstrations. Open to the Public.

Thursday 9 July

Registration: University of the Western Cape

Plenary: (Nuclear Physics) Professor Paul Garrett

425 Advances in Nuclear Structure Physics

The past two decades have witnessed a resurgence in nuclear structure physics due to the advent of radioactive beam facilities around the world. In parallel, there have been tremendous strides in nuclear structure theory that are able to provide highly accurate predictions from first-principle approaches. New phenomena are being discovered and old paradigms challenged resulting in a much deeper understanding of the interplay of single-particle and collective excitations. In this presentation, I will give an overview of some of the new experimental facilities and their capabilities and examples of structural phenomena that have been revealed over the past two decades. I will also give examples of where nuclear structure impacts tests of fundamental symmetries and searches for physics beyond the Standard Model.

Speaker: Paul Garrett (University of Guelph)

09:25 Buffer

Applied Physics

Convener: Ernest van Dyk

426 Approximations to the bow shock pressure profile generated by a decelerating sphere

This work is part of an extended programme to understand and formulate the flow physics of accelerating objects travelling in the transonic and subsonic speed ranges. Of these, deceleration generates the more interesting flow phenomena. The persistence of shocks ahead of objects decelerating from transonic speeds was for some time puzzling [1], but it is now clear that these are shocks formed at supersonic or transonic speeds which continue to propagate forward as the object decelerates behind them [2]. There is relatively little theoretical development of flow physics for cases of significant acceleration [3], and computational fluid dynamics (CFD) has largely been used to understand behaviour [2]. It is useful, however, to generate some basic physical descriptions under deceleration to determine whether such waves may cause damage, since they consist of a shock followed by an expansion wave in which the pressure drops below ambient. Previously, CFD models have been developed and validated by comparison with experimental results from ballistic ranges [4]. Using this model, we show that the flow behaviour behind the shock for significant acceleration cannot be adequately described by Bernoulli’s equation for compressible fluids because time-dependent terms are non-negligible. Therefore, the modified Friedlander blast wave profile is investigated, as a starting point for a more extensive description. It is shown that the modified Friedlander profile [5] does provide a reasonable approximation to the positive phase of the wave behind the shock front, in the region where p - p₀ > 0 (where p is static pressure and p - p₀ is the ambient pressure of the undisturbed air into which the wave is propagating). The Friedlander model provides a poor approximation in the negative phase p- p₀ < 0. This is a novel step towards a better predictive model for shock waves generated by deceleration.

References
[1] Kikuchi T et al., 2017 Shock Standoff Distance over Spheres in Unsteady Flows In: Ben-Dor, G., et al. (eds) 30th International Symposium on Shock Waves 1. Springer, Cham. https://doi.org/10.1007/978-3-319-46213-4_45
[2] Roohani H et al., 2020 Bow shock stand-off distance for subsonic decelerating bodies Shock Waves 30 115–29 https://doi.org/10.1007/s00193-019-00921-3
[3] Gledhill I M A et al., 2016 Theoretical treatment of fluid flow for accelerating bodies Theor. Comp. Fluid Dyn. 30 449–67 https://doi.org/10.1007/s00162-016-0382-0
[4] Mahomed I et al., 2021 Numerical Investigation of a Ballistic Range Free Flight Model, International Journal of Aeronautical and Space Sciences, 22(6), 1293-1301
[5] Karlos V. et al., 2016. Analysis of the blast wave decay coefficient using the Kingery–Bulmash data, J. of Protective Structures, 7(3) 409–429 https://journals.sagepub.com/doi/10.1177/2041419616659572

Speaker: Prof. Irvy (Igle) Gledhill (U. Witwatersrand)

427 Simulation of a Low-Cost PET Scanner

This project presents the simulation of a low-cost Positron Emission Tomography (PET) scanner. The high cost of PET scanners limits their use in many parts of the world, specifically developing countries. Lower-cost alternatives would increase the accessibility for neurological and paediatric care.
A detailed Monte Carlo simulation framework is used to model a full PET scan, from the decay of the radionuclides in a brain phantom, to the detector geometry and digitisation of the scintillator response, and the production of sinograms. This enables performance-cost studies of different scanner ring sizes, module arrangements, and digitizer strategies before the first physical prototype is produced.
The main challenge of low-cost systems is the degradation in data quality due to the simpler detector design. The simulated data can also be used to develop image reconstruction methods that produce clinically relevant images from this lower quality data.

Speaker: Ryan Atkin (University of Cape Town)

245_Ryan_Atkin.pdf

Astrophysics & Space Science: Astrophysics: Session 7

428 Searching for and modelling persistent radio sources associated with Fast Radio Bursts.

Fast Radio Bursts (FRBs) are bright, millisecond radio pulses occurring at cosmological distances. The nature of these sources is still unknown. Upon localisation of the repeating FRBs, luminous compact persistent radio sources (PRSs) can be detected in some cases. Studying the PRSs may give us clues about the immediate environments of the FRBs, which in turn provides insights into the nature of the FRB sources. However, the origin of the PRSs is also unknown. This work uses the MeerKAT telescope to search for PRS candidates towards selected FRB positions localised by ASKAP and MeerTRAP. We are also constructing a theoretical model of a magnetar wind nebula (MWN) to model the spectrum and frequency-dependent surface brightness profile of the PRS and the evolution of the dispersion measure and rotation measure. The proposed model is an attempt to explain the origin of faint PRSs and how they are associated with FRBs. This presentation summarises our recent progress and highlights ongoing and planned research directions.

Speaker: Lebogang Mfulwane (Centre for Space Research, North-West University,)

429 Dark Matter Content of Gas-Rich Dwarf Galaxies

Using high resolution RSS longslit data recently obtained from SALT, we have obtained the mass distribution in a nearby gas-rich dwarf galaxy - UGCA 014. In this talk, I will present the first rotation curve for this
galaxy derived from its Hβ ionized gas component. I will show that the rotation curve exhibits a steep rise in the inner kiloparsec, reaching a velocity of ∼42 km/s, and remains flat out to the radial extent of our
data at 1.88 kpc. I will provide evidence that there is a substantial dark matter component starting from the inner regions of the galaxy by comparing the observed circular velocity curve with an exponential, stellar-only model which accounts for the stellar velocity dispersion. Lastly, I will show that at a fiducial radius of 1.5 kpc,half of the total mass in UGCA 014 is made up of dark matter.

Speaker: OWEN BEUKES (NORTH WEST UNIVERSITY)

25_Beukes_Owen.pptx

430 Status of WIMP searches with MeerKAT

MeerKAT is currently a leading radio interferometer in the frequency range from 500 MHz to 1.6 GHz. So far, WIMP searches have been conducted in legacy survey data of galaxy clusters (MGCLS), archival Large Magellanic Cloud (LMC) data, and open-time observations of the dwarf galaxy Reticulum II. In this talk we will present the status of current results from these WIMP searches. Highlighting how the strongest limits come from galaxy clusters and the LMC, rather than regular dwarf galaxies, and exploring the uncertainties and limitations of radio WIMP searches. The principle issue being that, while radio searches have surpassed gamma-ray search sensitivities, the robustness of searches remains an important question to explore.

Speaker: Geoff Beck (University of the Witwatersrand)

dark_matter_meerkat_saip_2026.pdf

Astrophysics & Space Science: Space Science: Session 7

Convener: Katlego Moloto

431 Commissioning of the SA-DLITE interferometric radio telescope

The Deployable Low-Band Ionosphere and Transient Experiment (DLITE) is a four element interferometric radio telescope, nominally operating in the 30 - 50 MHz band. Although the instrument is primarily designed to study transient ionospheric phenomena it is, of course, also sensitive to other transient phenomena, such as solar radio bursts. Recently, a South African DLITE station, SA-DLITE, was installed and is currently being commissioned at the North-West University’s Nooitgedacht research farm. In this presentation we present the current iteration of the instrument and share some initial results, focusing on a number of detector solar radio bursts.

Speaker: DuToit Strauss (North-West University)

432 Solar modulation of galactic deuterons related to PAMELA, AMS02 and Voyager 1 observations

The recent observations of galactic deuteron (D) from AMS-02 and Voyager 1 detectors provide interesting surprises to the established paradigm of the secondary origin of galactic D. In this study a comprehensive 3D numerical model is used to simulate the solar modulation of D and protons (p) at the Earth from 2006 to 2014, spanning time frames that include solar maximum activity and the magnetic field reversal epoch. For this purpose, the D local interstellar spectrum is revisited based on the recent Voyager 1 observations below 49.6 MeV/nucleon. Our model includes recent developments in the turbulence and diffusion theory to investigate how the evolution of turbulence in the heliosphere is connected to the observed D and p spectra at the Earth. These modelling results are compared to published D and p spectra and the corresponding D/p ratios made by PAMELA and AMS-02 detectors over the same period. A particular objective is to uncover how the D/p ratio evolves at different rigidities over changing solar activity.

Speaker: Ms Innocentia Itumeleng Ramokgaba (1. School of Physical & Chemical Sciences, North-West University, Mmabatho, South Africa. 2. Centre of Space Research, North-west University, Potchefstroom, South Africa.)

433 Onboard measurement of cosmic-ray exposure on South African domestic flights

Much as air travel has become increasingly important in today’s society for quickly connecting people and places, aircraft and their occupants (passengers and aircrews) are exposed to enhanced levels of ionizing radiation at flight altitudes (8 – 12 km). The space radiation, mainly originating from the Sun and galactic sources, may degrade essential aircraft subcomponents and cause radiobiological damage to aircrews and passengers. Following the recommendations of the International Commission on Radiological Protection (ICRP), United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), and International Atomic Energy Agency (IAEA), several countries, including France, Germany, UK, Japan, Canada, and the US, have included the monitoring and recording aircrew exposure to cosmic radiation amongst their regulatory roles. Africa is still lagging in this, implying that exposure to radiation over the continent’s airspace is not fully characterized. As a pioneering study in the region, we use the High Altitude Radiation Monitor (HARM), a flagship device developed by the Center for Space Research (CSR) at North-West University, to measure cosmic radiation exposure at aviation altitudes. The initial surveys conducted on board domestic flights within South Africa show considerable exposure levels. The study creates public awareness and provides a basis for the national regulator and other regional regulatory bodies to engage with airlines and aviation stakeholders to establish practical regulatory frameworks, specific rules, and standards for monitoring aircrew exposure.

Speakers: Bosco Oryema (Centre for Space Research, North-West University, Potchefstroom, 2531, North West, South Africa), Joseph Omojola (North-West University)

Nuclear, Particle and Radiation Physics -1: Session 1

Convener: Shanyn Hart (University of Cape Town and iThemba LABS)

434 A possible bound state of the 21C as a halo nucleus

This work investigates the possible existence of a bound state of the 21C carbon isotope. This nucleus is suggested to possibly exist as a weakly bound neutron halo. The 20C and the 22C carbon isotopes have already been confirmed as weakly bound halo nuclei near the neutron drip line. Despite advancements in research technologies, the characteristics, structures, and reaction dynamics of these nuclei are not completely understood. The study investigates a possible correlation between the ground-state root-mean-square radii and ground-state energies of the three carbon isotopes. The systems were treated as three-body systems with a core and two valence neutrons. The Faddeev equations for the systems were solved in the hyperspherical harmonics approach.

Speaker: Thando Timax Khedzi (University of South Africa)

435 Testing the vibrational nature of 100Ru.

There is renewed interest in the exploration of the nature of low-lying collective excitations in nuclei, as several recent studies have posed serious ques tions regarding the veracity of multiphonon quadrupole vibrations [1, 2]. A recent survey of nuclei with previously assumed low-lying spherical vibrational structure showed that very few passed the criteria [3]. Of the few remaining candidates there is insufficient spectroscopic information to draw conclusions. As part of a larger strategy to address this issue, the structure of 100Ru was studied in this work, making use of the 103Rh(p, α)100Ru reaction. The experiment was performed using the high resolution Q3D magnetic spectrograph in Garching, Germany [4, 5]. The angular distributions of measured cross sections were compared with distorted wave Born approximation (DWBA) calculations. This spectroscopic analysis was used to probe the structure of 100Ru, and indicate that this particular case also does not convincingly demonstrate spherical vibrational behavior.

References
[1] P. E. Garrett, K. L. Green, and J. L. Wood. “Breakdown of vibrational
motion in the isotopes 110−116Cd”. Physical Review C—Nuclear Physics, 78
(4):044307, 2008.

[2] P. E. Garrett and J. L. Wood. “On the robustness of surface vibrational modes: case studies in the Cd region”. Journal of Physics G: Nuclear and Particle Physics, 37(6):064028, 2010.

[3] J. Kern, P. E. Garrett, J. Jolie, et al. “Search for nuclei exhibiting the U(5) dynamical symmetry”. Nuclear Physics A, 593(1):21–47, 1995.

[4] M. L¨offler, H. J. Scheerer, and H. Vonach. “The ion optical properties of the Munich Q3D-spectrograph investigated by means of a special experimental ray tracing method”. Nuclear Instruments and Methods, 111(1):1–12, 1973.

[5] H. F. Wirth, H. Angerer, T. Von Egidy, et al. “New Q3D focal plane
detector with cathode-strip readout became operational”. Maier-Leibnitz-
Laboratorium Jahresbericht, 71, 2000

Speaker: Lwazikazi Maqungo (UWC)

436 Role of Nuclear Density in Heavy-Ion Fusion Hindrance within the Double-Folding Framework

Two competing theoretical approaches - the Sudden Model and the Adiabatic Model - have been widely used to explain the phenomenon of fusion hindrance in heavy-ion fusion reactions at deep sub-barrier energies. These models predict significantly different depths of the nucleus–nucleus interaction potential, yet they often reproduce similar fusion cross-sections. Thus, the underlying mechanism of the hindrance effect not fully resolved [1-3]. Motivated by this discrepancy, the present work explores additional dynamical factors that may either hinder or enhance fusion beyond the influence of potential depth alone. The nucleus–nucleus interaction potential is constructed using the Double-Folding Model [4], where the folding integral is evaluated in momentum space through a Fourier transform. Our analysis demonstrates that the physics governing the resulting interaction potential lies in the choice and treatment of the nuclear density distributions. This is achieved through a systematic investigation of different density prescriptions. The implications of these findings and the resulting insight into heavy-ion fusion at deep sub-barrier energies will form the focus of our discussion.
References
1. Sorin Misicu and Henning Esbensen, Phys. Rev. Lett. 96, 112701 (2006).
2. Takatoshi Ichikawa, Koichi Hagino, and Akira Iwamoto, Phys. Rev. Lett. 103, 202701 (2009).
3. K. Cheng, C. Xu, C. Ma, J. Pu, and Y. Wang, Phys. Rev. C 103, 014613 (2021).
4. G. R. Satchler and W. G. Love, Phys. Rep. 55, 183 (1979).

Speaker: Dr Joshua Tolulope Majekodunmi (University Of South Africa)

Nuclear, Particle and Radiation Physics -2: Session-7

Convener: Mpho Gololo (University of Johannesburg)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

437 Testbeam Analysis of HGTD Prototype Modules for the ATLAS Phase-II Upgrade

The High Granularity Timing Detector (HGTD) is a key upgrade to the ATLAS experiment for the High-Luminosity LHC, designed to mitigate the effects of high pile-up through precision timing measurements. The detector will be installed between the barrel and end-cap calorimeters, covering the pseudorapidity region $2.4 < |\eta| < 4.0$, and is based on Low Gain Avalanche Detectors (LGADs) with a target time resolution of 30 ps per track, degrading to 50 ps after irradiation. This work presents a testbeam analysis of HGTD prototype modules using data collected during the October 2025 and January 2026 campaigns. Currently, the analysis focuses on data from the October test beam collected with the FM-A-03 module, which is equipped with ALTIROC-A readout electronics. ALTIROC (ATLAS LGAD Timing ReadOut) chips are application-specific integrated circuits (ASICs) fabricated in 130 nm CMOS technology, with each module integrating two ALTIROC ASICs and two LGAD sensors. The experimental setup is based on beam tests performed at facilities such as CERN SPS and DESY, providing controlled environments for detailed detector characterisation. Data acquisition is performed using the EUDAQ2 framework, while event reconstruction and analysis are carried out with Corryvreckan. The analysis workflow includes event loading, telescope-based alignment, spatial efficiency evaluation, and timing reconstruction using digitised front-end signals. Particular emphasis is placed on the integration of LGAD sensors with ALTIROC readout electronics and the validation of the reconstruction chain. Ongoing studies focus on the evaluation of timing performance and detector efficiency, as well as the optimisation of reconstruction and calibration procedures. This work contributes to the validation of HGTD detector technologies and the development of analysis strategies for precision timing measurements in the ATLAS Phase-II upgrade.

Speaker: Karabo Tau (University of the Witwatersrand (ZA))

274_Karabo_Tau.pdf

438 Enhancing Forward Jet Reconstruction with HGTD Timing in the ATLAS Particle Flow Algorithm

The High Granularity Timing Detector (HGTD) in the ATLAS experiment is designed to provide precision timing measurements for charged particle tracks in the forward region, enabling enhanced pileup mitigation at the High-Luminosity Large Hadron Collider (HL-LHC). In this study, we investigate the integration of HGTD timing information into the Charged Hadron Subtraction (CHS) procedure within the ATLAS Particle Flow (PFlow) algorithm. By combining per-track timing with primary vertex time reconstruction, timing-based consistency criteria are developed to discriminate between hard-scatter and pileup tracks. The performance of these selections is evaluated using simulated proton–proton collision events, with particular focus on their impact on jet reconstruction in the forward region. Key observables include jet reconstruction efficiency, jet energy resolution, and residual pileup contamination. Comparisons are made between the baseline CHS approach and timing-augmented configurations to quantify performance gains under high pileup conditions expected at the HL-LHC. The results demonstrate the extent to which precision timing can improve pileup suppression while preserving jet performance. An optimal set of timing selection criteria is identified and proposed for integration into the Run 4 ATLAS PFlow reconstruction framework. This work contributes to the ongoing validation and optimisation of HGTD-driven reconstruction strategies and supports future physics analyses in high-density collision environments.

Speaker: Thabo James Lepota (University of the Witwatersrand)

439 Air Quality Forecasting in South African Urban Areas Using LSTM Models and SACAQM Data to Capture Temporal Dynamics and Patterns

Air quality profoundly impacts human health, particularly in rapidly urbanizing regions like South Africa, where pollution from industrial and vehicular sources poses significant risks. Recent reviews highlight Long Short-Term Memory (LSTM) networks as superior for modeling temporal dependencies in air quality data, outperforming traditional methods in pollution forecasting. Building on these advancements, this study applies LSTM to real-time data from multiple South African Consortium for Air Quality Monitoring (SACAQM) sites across Gauteng and beyond.

We preprocess multivariate time-series data including PM$_{2.5}$, NO$_2$, SO$_2$, and meteorological variables from diverse monitoring stations, addressing challenges like missing values and sensor drift through imputation and normalization. A stacked LSTM architecture with attention mechanisms captures both short and long term pollution patterns, trained on historical SACAQM datasets and validated via cross-site temporal splitting.

Results demonstrate superior performance, with RMSE reductions of 15--25\% over baselines like ARIMA and standard RNNs, and $R^2$ scores exceeding 0.92 for multi-step ahead predictions. Spatial visualizations reveal urban-rural gradients and episodic events (e.g., winter inversions), offering physics-based insights into pollutant transport.

This work advances LSTM applications for localized air quality management, providing actionable forecasts for public health alerts and policy in South Africa. Future extensions include hybrid physics-ML models for enhanced interpretability.

Speaker: Lehlohonolo Moloi (Student)

365_Lehlohonolo_Moloi.pdf

365_Lehlohonolo_Moloi.pdf

Photonics

Physics of Condensed Matter and Materials

Convener: Moise Bertin Tchoula Tchokonte (University of the Western Cape)

440 First-Principles Investigation of Structural, Mechanical, Thermodynamic and Electronic Properties of High-Entropy Alloys for High-Temperature Applications.

The increasing demand for materials capable of maintaining high mechanical performance under extreme thermal environments has exposed the limitations of conventional high-temperature materials such as Ni-based superalloys. As a result, high-entropy alloys (HEAs), particularly single-phase body-centred cubic (BCC) systems, have attracted significant attention due to their high configurational entropy, structural stability, and excellent mechanical properties at elevated temperatures. In this study, a computational approach based on Density Functional Theory (DFT) was employed to investigate the structural, mechanical, thermodynamic, and electronic properties of the TiNbMoCrW high-entropy alloy. The results indicate that the TiNbMoCrW alloy forms a stable single-phase solid-solution BCC structure. Furthermore, the alloy was found to be thermodynamically stable and exhibited excellent mechanical properties, including high strength and ductile behaviour. Additionally, electronic structure analysis confirms its metallic nature. These findings suggest that TiNbMoCrW is a promising stable single-phase high-entropy alloy suitable for high-temperature applications, particularly in environments requiring materials with high thermal stability and mechanical reliability.

Speaker: Ramalebana Moeti

441 First principles study of the structural, electronic, magnetic, thermodynamic, and electrical transport properties of PrCuGe3, ternary intermetallic compound

The PrCuGe3 compound exhibits a wide range of interesting phenomena depending on the degree of hybridization between the 4f electrons and the conduction electrons. A considerable experimental work has investigated the structural, magnetic, thermodynamic, and electrical transport properties of this compound. For example, in the literature PrCuGe3 is reported to undergo a long-range ferromagnetic ordering at Tc = 23 K followed by a transition below Ttr= 17 K. Furthermore, Tc is reported to have a large associated anomaly in the magnetic susceptibility measurement and small anomalies displayed in the specific heat and electrical resistivity measurements. The metallic behavior acts as a stronger stabilizer, giving rise to the Kondo effect, heavy fermion behavior, and other phase transitions. Despite a fairly large number of experimental studies on ternary intermetallic compounds, there are limited theoretical investigations. In this study, we have calculated the structural, magnetic, thermodynamic, and electronic properties of the PrCuGe3 compound using density functional theory to further elucidate its structural, magnetic, thermodynamic, and electrical transport properties. The magnetic calculations confirm that the compound displays ferromagnetic behaviour, and the Pr3+ is the sole source of magnetism. Finally, the dynamic stability of PrCuGe3 is confirmed from the phonon calculations.

Speaker: Dr Mubarak Yagoub (University of Johannesburg)

442 Lanthanide-Doped Ca5Mg4(VO4)6 Phosphors for NIR-to-Visible Latent Fingerprint Visualization

Abstract
Latent fingerprint detection using powder dusting relies on achieving high contrast between the fingerprint details and the underlying surface. Conventional and near-ultraviolet (NUV)-excited powders often suffer from background interference, limiting their effectiveness on multicoloured or fluorescent substrates. Near-infrared (NIR)-to-visible upconversion materials offer a promising alternative by enabling excitation in the NIR region, thereby minimizing background interference and enhancing detection sensitivity. In this study, Ca5Mg4(VO4)6 phosphors co-doped with Yb3+/Er3+ and Yb3+/Ho3+ were synthesized via a solid-state reaction method and investigated as potential upconversion-based fingerprint powders. The phase purity of the phosphors was confirmed by X-ray powder diffraction (XRPD). Under 980 nm excitation, the Yb3+/Er3+ system exhibited strong green emission (~550 nm), while the Yb3+/Ho3+ system showed dominant red emission (~650 nm). Power-dependent and temperature-dependent luminescence measurements were conducted to further evaluate the upconversion behaviour and thermal response of the materials. The distinct and tuneable emissions highlight the potential of these materials for high-contrast latent fingerprint visualization across a range of surfaces, particularly where conventional and UV-based methods are limited, while also expanding the limited understanding of Ca5Mg4(VO4)6 as an upconversion host.

Speaker: Hope Ramolahloane (University of the Free State)

Side Event: Physics in Industry Day

Draft Programme and Brief - SAIP2026 Industry Day.pdf

Theoretical and Computational Physics: Session 7

Convener: Dr Tshegofatso Tshipi (Sol Plaatje University)

443 Analysis of halo effect on elastic scattering cross section within the optical model formalism

The optical model (OM) formalism inherently omits the structural properties of weakly bound nuclei, owing to its restriction to an effective two-body description. By assuming the halo and non-halo configurations of $^8$B and $^{11}$Be projectiles on two quite different mass targets, $^{64}$Zn and $^{208}$Pb, we introduce an approach that explicitly incorporates the ground-state structure of a weakly bound projectile by embedding its wave function into the projectile–target nuclear potential through a double-folding formalism. The resulting potential successfully reproduces the suppression of the Coulomb–nuclear interference peak observed in elastic scattering, an effect commonly attributed to coupling with breakup channels. Moreover, incorporating the halo structure into the OM significantly improves the agreement with experimental elastic-scattering data. At the same time, the normalization factor of the imaginary part of the optical potential $N_I$ is reduced by a factor greater than two for some reactions. These results for weakly-bound nuclei demonstrate that an accurate description of elastic scattering requires an OM that explicitly accounts for the projectile’s structure.

Speaker: Bahati Mukeru

444 A pQCD Baseline for Parton and Hadron Production Spectra

The quark-gluon plasma (QGP) is a deconfined state of strongly interacting matter that provides a unique laboratory for studying the strong nuclear force. It is produced in relativistic heavy-ion collisions, such as ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ and, more recently, ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ at the LHC. High-momentum (“hard”) probes traversing the QGP lose energy through radiative and collisional processes, as described by perturbative quantum chromodynamics (pQCD). A key challenge in interpreting such energy loss signals is the consistent treatment of initial-state effects, which must be understood in order to make reliable predictions for unmeasured collision systems and energies. Within the framework of collinear factorisation, these effects are encoded in parton distribution functions (PDFs), which describe the partonic structure of the incoming nuclei. Here, we present a numerical implementation of the leading-order, $p_T$-differential inclusive production cross section for partons and their fragmentation into hadrons. We validate this framework by reproducing measured charged meson production spectra in proton-proton collisions across a range of centre-of-mass energies. The resulting tool provides a modular framework for computing hadron production spectra for arbitrary fragmentation functions, PDFs, collision systems, and pseudorapidity intervals, including $p_T$ bin averaging. This enables systematic baseline calculations of initial-state contributions to particle production. Combined with energy loss models, this framework allows for quantitative predictions of whether medium-induced modifications to hadron spectra can be disentangled from initial-state effects in small and intermediate collision systems.

Speaker: Jack Brand (University of Cape Town)

slides.pdf

10:30 Morning Tea

Applied Physics

Convener: Nicolas Thantsha (TUT)

445 Radiation-Resistant Temperature Monitoring in High-Energy Physics Environments

Accurate temperature monitoring in high-radiation environments is critical for the reliable operation of high-energy physics detectors. Fibre Bragg Grating (FBG) sensors fabricated in radiation-hardened optical fibres are widely considered for such applications due to their compactness and immunity to electromagnetic interference. In this study, the thermal response of a radiation-hardened fibre optic temperature sensor from iXblue is evaluated before and after exposure to proton irradiation at the CERN IRRAD facility. Temperature calibrations were performed before and after irradiation to assess potential changes in sensor sensitivity. The Bragg wavelength shift was recorded as a function of temperature over a controlled range, and the temperature sensitivity coefficients were extracted for both conditions. A direct comparison of pre- and post-irradiation responses was conducted to evaluate the stability of the thermo-optic behaviour under high radiation exposure. The results indicate that the sensor maintains consistent temperature sensitivity after irradiation, with only minor deviations within experimental uncertainty. These findings support the robustness of radiation-hardened FBG sensors for temperature monitoring in harsh radiation environments and provide confidence in their deployment in high-energy physics applications where radiation exposure is significant.

Speaker: Timothy Brooks (University of Johannesburg)

342_Timothy_Brooks.odp

342_Timothy_Brooks.pdf

446 Electrical characterisation of a 2D Schottky diode based on heterojunction polyaniline and graphene with Magnesium as contact.

This study investigates the influence of graphene on the electrical characteristics of a magnesium/polyaniline/fluorine doped tin oxide (Mg/PANI/FTO) Schottky diode using a computational approach. Three device configurations are considered: (i) a reference structure without graphene, (ii) a structure incorporating graphene at the Mg-PANI interface., and (iii) a structure with graphene inserted between PANI and the FTO on glass substrate . The effects of temperature, graphene thickness, and doping concentration on key electrical parameters, namely reverse saturation current, barrier height, ideality factor, and series resistance, are systematically examined. Preliminary results, obtained over a temperature range of 273-353 K, reveal that the insertion of graphene at the metal/PANI interface significantly enhances recombination processes. This is evidenced by a reduction in the ideality factor from 3.83 to 3.17, accompanied by an increase in reverse saturation current from 0.0006 µA/µm to 0.17 µA/µm. The barrier height increases from 0.87 eV to 0.98 eV, while the series resistance decreases from 2 MΩ·µm to 0.14 MΩ·µm with increasing temperature. In contrast, the configuration with graphene positioned between PANI and the FTO substrate exhibits the lowest recombination effect among the three structures. This is reflected by the weak variation in ideality factor (from 1.01 to 1.02), a relatively controlled increase in reverse saturation current (from 10E-16 µA/µm to 10E-10 µA/µm), and a slight increase in barrier height (from 1.54 eV to 1.57 eV). Additionally, the series resistance decreases from 500 MΩ·µm to 20 MΩ·µm over the same temperature range. These findings indicate superior thermal stability for this configuration, as demonstrated by the weak temperature dependence of its electrical parameters. Overall, the results suggest that graphene, when strategically integrated at the PANI/substrate interface, not only mitigates recombination effects but also enhances device thermal stability. Furthermore, graphene shows strong potential as a passivation layer to reduce interfacial recombination between the hole transport layer (HTL) and the absorber layer in perovskite solar cell devices, where PANI is used as the HTL.

Speaker: Dr Abraham Dimitri Kapim kenfack (Tshwane University of Technology)

Dr AD KAPIM SAIP2026.pptx

447 EVINN: Extreme value-informed neural networks model for modeling extreme events

The advances in computing, coupled with the easy availability of massive datasets, have led to the widespread adoption of machine learning (ML) in general and deep learning (DL) in particular. In essence, the traditional DL models are fundamentally data-driven. That is, these models tend to have an improved performance when the input data is increased. Therefore, it is challenging to deploy these models where data is scarce. Furthermore, since these traditional DL models are data-driven, they tend to lack the reality check. Currently, some approaches have been proposed to address these limitations of traditional DL models. Such approaches include physics-informed neural networks (PINN) and biology-informed neural networks (BINN). In this paper, we propose a new approach to address the traditional DL limitations. This approach is referred to as statistics-informed neural networks (SINN). In particular, our approach focuses on the statistics of rare events and hence is referred to as extreme value-informed neural networks (EVINN). Essentially, EVINN fuses DL and the extreme value theory together, with the extreme value theory serving as a reality check for the DL. Furthermore, to demonstrate the utility of the proposed EVINN model, we show how the model can be used for drought prediction. Finally, the results obtained from the study reported in this paper demonstrate the significance of fusing together the traditional DL and the extreme value theory for a more realistic modeling of rare events.

Speaker: Dr Makhamisa Senekane (University of Johannesburg)

168_Makhamisa_Senekane.pdf

448 Deploying physics-informed neural networks for anomaly detection in particle physics

The Standard Model (SM) of particle physics provides a mathematical description of the constituents of matter, together with their interactions. The deviation from the SM might lead to the outliers that herald the new physics. Therefore, the use of anomaly detection models plays a crucial role in the discovery of the new physics; thereby facilitating the move beyond the Standard Model. For anomaly detection, deep learning (DL) models; especially those based on the autoencoder architecture, are typically used. However, these data-driven autoencoders might produce results that do not correspond to the physical reality. Therefore, in order to address this challenge (of lack of correspondence to physical reality, a more realistic neural networks architecture is required. One such architecture is the physics-informed neural networks (PINN), which provides the physical reality check by ensuring that the output of the neural networks model is consistent with the laws of physics. In this paper, we report the use of PINN autoencoder model for anomaly detection in particle physics. Finally, we demonstrate that the fusion of the laws of physics with the data-driven DL leads to improved results in the detection of anomalies in particle physics.

Speaker: Dr Makhamisa Senekane (University of Johannesburg)

169_Makhamisa_Senekane.pdf

449 Ultra-Sensitive and Energy Efficient Low-ppb NOx Gas Sensors Based on Pd-sensitized Co3O4/NiTiO3 Heterojunctions

The widespread emission of nitrogen oxides (NOx; NO and NO2) from mining and transportation activities necessitates sensitive and reliable gas sensing technologies with low power requirements and economic feasibility for large scale deployment. Conventional NOx monitoring systems are often constrained by complex fabrication processes, costly components, and high-power consumption, limiting their applicability in resource‑constrained environments. In this study, a low‑cost, low‑power NOx gas sensor based on Ag‑ and Pd‑sensitized Co3O4/NiTiO3 semiconducting heterostructures is developed. The nanostructures were synthesized via a microwave‑assisted hydrothermal method followed by wet impregnation and subsequently drop‑cast onto interdigitated substrates to form sensing layers. This fabrication strategy provides a facile and cost‑effective synthesis, significantly reducing processing time, energy input, and equipment complexity. Gas‑sensing measurements demonstrate that Pd sensitization significantly enhances NOx sensitivity and accelerates response–recovery dynamics. Importantly, these improvements are achieved at reduced operating temperatures, resulting in substantially lower power consumption, which is an essential requirement for portable and battery‑powered applications. The combination of scalable, cost‑effective fabrication and energy‑efficient device performance highlights Pd‑sensitized Co3O4/NiTiO3 heterostructures as a promising platform for NOx monitoring, underscoring the role of interface engineering in sustainable gas‑sensor development.

Speaker: Zamaswazi Tshabalala (University of the Free State)

ZPT_SAIP ORAL (7 July).pptx

Astrophysics & Space Science: Astrophysics: Session 8

450 Three-dimensional MHD simulations of astrospheres and galactic cosmic ray transport.

Astrospheres are large scale magnetized plasma structures formed by the interaction between stellar winds and the surrounding interstellar medium (ISM). These systems play a fundamental role in regulating the transport and modulation of energetic charged particles. In this study, we will investigate the astrosphere of the runaway O-type star $\lambda$ Cephei using three dimensional magnetohydrodynamic (MHD) simulations with the heliosphere serving as a well observed benchmark for physical interpretation.

The work focuses on extracting and characterizing key plasma and magnetic field properties from high resolution simulations and transforming these into forms suitable for cosmic ray transport modeling. Building on heliospheric transport theory these MHD derived parameters are then used to calculate cosmic ray modulation inside these astrospheric cavities.

This study will also include an analysis between the stochastic cosmic ray modulation code and an independent finite difference transport model for comparison.

Speaker: Christo Pretorius

102_Christo_Pretorius.pdf

451 Optimizing Stellar Velocity Dispersion Measurements for Upcoming Spectroscopic Surveys

Accurate stellar velocity dispersion measurements are of great importance for
understanding the dynamical masses, evolutionary stages, and are fundamen-
tal in studying the gravitational potential of galaxies. The accuracy of these
measurements depends on the coverage of the spectrograph, the redshift, the
signal-to-noise ratio (SNR), and the wavelength range used to perform the
measurement. To find conditions that produce accurate stellar velocity dis-
persion measurements for upcoming spectroscopic surveys (e.g., 4MOST), we
generated realistic mock spectra using the Flexible Stellar Population Synthesis
(FSPS) model for different redshifts, SNRs, and velocity dispersions. We then
performed velocity dispersion measurements using the Penalized PiXel-Fitting
(pPXF) code in different wavelength ranges between 3700 ˚A and 9000 ˚A.

Speaker: Mr Johan Nel (Centre for Space Research (NWU))

452 CATACLYSMIC VARIABLES IN THE MEERLICHT SOUTHERN ALLSKY SURVEY.

The study of astrophysical transients has traditionally been hampered by delays
between multi-wavelength observations, often causing crucial early-time information
to be lost. The MeerLICHT optical telescope at SAAO in Sutherland was designed to
overcome this limitation by operating simultaneously with the MeerKAT radio
telescope, enabling a novel, commensal approach to exploring the transient
Universe as part of the ThunderKAT Large Survey Project. In this presentation, I will
introduce my project to construct a volume-limited sample of Cataclysmic Variables
(CVs) using the MeerLICHT Southern All-Sky Survey (MLSASS). By correlating the
extensive MLSASS optical light curves and multi-filter photometry (Sloan ugrizq) with
astrometric data from Gaia, I aim to identify both known and new CV candidates
through their distinct positions in the Hertzsprung-Russell diagram as outliers from
the main stellar populations. The primary goal is to obtain a complete census of CVs
within 150 and 300 parsecs in the MLSASS. I will discuss the methodology for this
data fusion and source association, the optical and radio properties of the CVs in the
sample, and outline my plans for the characterisation of the most compelling new
candidates using the facilities at the South African Astronomical Observatory (SAAO)
and the Southern African Large Telescope (SALT).

Speaker: Mkhatshwa Xolile (University Of Venda)

453 Spectroscopic Study of Uncertain 𝜆 Boo Stars Using Southern African Large Telescope High Resolution Spectrograph.

Astronomical spectroscopy is a study of how matter interacts with light (Penner, 2017). Today, it is recognised that light behaves both like a wave and particle (Sliney, 2016). Scientists use spectroscopy to study celestial objects by analysing the light they emit, absorb, or reflect. The separation of light with a spectrograph results in the visible spectrum (Dopita et al., 2007). Studying the light of the stars can reveal a lot about them. For instance, their spectral types, temperatures, densities, relative motions and elements present. The aim of this project is to obtain high-quality spectra of various 𝜆 Bootis to determine their physical and chemical properties. Murphy et al. (2015) re-evaluated the study of 212 stars that were considered as 𝜆 Boo stars, of which the status of 45 stars was unclear. To confirm whether stars are indeed the members of 𝜆 Bootis class, Murphy et al. (2020) recommended that more spectra should be obtained, and more abundance analysis should be conducted. The authors have been obtaining spectra using the same spectrographs over and over and got unsatisfactory results. They never use other spectrographs with high resolution. To better their results, Southern African Large Telescope High Resolution Spectrograph will be utilised, as it is suited for detailed spectral analysis. 𝜆 Boo Stars and 𝜆 Bootis are used interchangeably.

Speaker: Magdeline Matobe (SAIP)

477_Magdeline_Matobe.pdf

Astrophysics & Space Science: Space Science: Session 8

Convener: Ruhann Steyn (Centre for Space Research, North-West University)

454 Using URANOS Simulations to Understand Biomass-Soil Moisture Interactions in Cosmic-Ray Neutron Sensing Applications

Cosmic-ray neutron sensing (CRNS) has emerged as a promising non-invasive technique for field-scale soil moisture monitoring in agricultural systems. However, the accuracy of CRNS measurements is significantly influenced by above-ground biomass water equivalent (BWE), which varies dynamically throughout crop growth cycles. This study employs URANOS (Ultra Rapid Adaptable Neutron-Only Simulation) Monte Carlo simulations to investigate the complex relationships between vegetation biomass, soil moisture content, and neutron transport processes in agricultural environments.
We modeled neutron footprints and detection characteristics across different crop growth stages, incorporating varying biomass densities and soil moisture conditions. The simulations utilized layered voxel geometry representations with material codes for different vegetation types, from sparse grass to mature crop canopies. Our results demonstrate that biomass water content can cause neutron count rate variations of independent of soil moisture changes, with the effect being most pronounced during rapid growth phases.
The URANOS simulations reveal that the neutron detection radius decreases under dense crop canopies, while detection depth reduces. These findings provide critical correction factors for BWE effects in CRNS calibration functions, improving soil moisture estimation accuracy. The simulation framework enables real-time correction of CRNS data throughout growing seasons, supporting precision agriculture applications and advancing our understanding of neutron transport physics in vegetated environments.

Speaker: Dr Katlego Moloto (North-West University)

11:20 Break

455 The manifestation of vorticity in the atmosphere of the Sun

High-resolution observations of the solar chromosphere have revealed ubiquitous prominent spiralling structures. These structures have been linked to the swirling downflows present in the intergranular lanes of the solar photosphere, existing as vortex tubes. Vortex tubes have been proposed as conduits for energy transfer throughout the solar atmosphere, channelling energy in the form of Poynting flux. However, there is a vast discrepancy between the number of rotating flow structures found in the photosphere and the number found in the chromosphere. Furthermore, it is still debated whether the source of the vorticity originates in the photosphere and extends up to the chromosphere or manifests in the chromosphere and descends towards the photosphere. We investigate a three-dimensional Radiative MagnetoHydroDynamic (MHD) simulation, produced using the MURaM code for the flow properties of the solar atmosphere. To correlate our findings with previous observations of chromospheric swirls, we use the DESIRE Radiation Hydrodynamic (RH) code to synthesise images in the Fe I 630.2 nm and Ca II 854.2 nm line profiles. We compare the synthesised images with the simultaneous observation of a chromospheric swirl in Fe I 630.2 nm and Ca II 854.2 nm lines taken by the CRisp Imaging Spectro-Polarimeter (CRISP) instrument at the Swedish 1-m Solar Telescope (SST).

Speaker: Prof. Eamon Scullion (University of Northumbria Newcastle upon Tyne (UK))

456 A numerical investigation of a pulse propagating through the stratified solar atmosphere

The solar atmosphere and magnetic field are highly structured and dynamic. Jet-like features such as spicules move from the photosphere to the lower corona while solar flares cause heating of the plasma in the chromosphere leading to volume expansion within coronal loops. These two phenomena are often simulated with a pulse driven from the photosphere into a vertical magnetic field and stratified solar atmosphere. In this study, an initial numerical investigation of a localised pulse-driven behaviour is carried out using Lare2d in a realistic solar atmosphere to examine its response to the driver. Lare2d is a numerical magnetohydrodynamics code that solves the MHD equations in two dimensions using a Lagrangian remap scheme on a staggered grid. The initial model is constructed from a vertically stratified atmosphere with prescribed temperature, density and gravity profiles chosen to produce a hydrostatic background state. This investigation forms part of a broader study of physical processes in the sun. Here we present simplified numerical experiments to test the robustness of the solar atmosphere, the treatment of boundary conditions, and the behaviour of different drivers.

Speaker: Calmay Lee (North-West University)

Nuclear, Particle and Radiation Physics -1: Session 2

Convener: Mohamed Kamil Mohamed (CPUT)

457 Fabrication of thin-film targets for nuclear physics experiments at iThemba LABS and Daresbury Laboratory

Thin-film targets are indispensable to nuclear physics research. This talk will
focus on Physical Vapor Deposition (PVD) techniques to produce mono- and
multi-layered samples in dedicated target laboratories at iThemba LABS and
Daresbury Laboratory [1, 2]. We produced such samples by thermally evaporat-
ing ZnS and LiF source-materials and Ni/Ti and Cr/Au metals in high vacuum
(∼10−7 mbar). Deposition of source-materials in such a high vacuum environ-
ment mitigates contamination and oxidation effects, in addition to decreasing
the melting point of the source-materials [3]. Suitable ion-beam and analy-
sis techniques used to characterize the evaporated source-materials and obtain
accurate estimates of the target uniformity and thickness will be described.

References:
[1] N.Y. Kheswa, E.Z. Buthelezi, and J.J. Lawrie. Making of targets for
physics experiments at iThemba LABS. Nuclear Instruments and Meth-
ods in Physics Research Section A: Accelerators, Spectrometers, Detectors
and Associated Equipment, 2008.
[2] P.S. Morrall. The Target Preparation Laboratory at Daresbury. Nuclear
Instruments and Methods in Physics Research Section A: Accelerators, Spec-
trometers, Detectors and Associated Equipment, 2008.
[3] C.A. Bishop. Vacuum Depostion onto Webs, Films, and Foils. William
Andrew, 2011.

Speaker: Mr Esmond Craig Vyfers (University of the Western Cape)

458 Assessment of natural gamma radiation as a proxy for soil health indicators with application of spatial mapping for national security

South Africa faces a critical deficit in spatially continuous, cost-effective soil health monitoring, a gap that undermines informed land management, food security planning, and national resource governance. Conventional soil assessment methods, which depend on discrete point sampling and laboratory analysis, are inherently too slow, too costly, and too spatially limited to capture the landscape-scale variability that characterises the country's diverse agricultural terrain. This study addresses that deficit by investigating the utility of natural gamma radiation as a rapid, non-invasive proxy for soil health indicators at Groote Post Wine Estate, Darling Hills, Western Cape (33°22'S, 18°35'E), and by evaluating the scalability of this methodology as a national resource intelligence tool.
Groote Post Farm (approximately 2,700 ha) occupies a geologically complex terrain defined by the interaction of three lithological units: the Neoproterozoic Malmesbury Group metasediments, the Cape Granite Suite plutons (emplaced approximately 550–510 Ma), and Quaternary aeolian sands and calcretes. Each unit exhibits a characteristically distinct naturally occurring radionuclide (NOR) signature. The Cape Granite Suite, on which the estate's vineyard is situated, is among the most radiogenic of common rock types, with reference activity concentrations of approximately 74.1 Bq/kg for uranium (²³⁸U), 1232.2 Bq/kg for potassium (⁴⁰K), and 84.6 Bq/kg for thorium (²³²Th). The Malmesbury Group metasediments exhibit moderate concentrations, while the Quaternary deposits are geochemically dilute. This natural radiometric contrast makes the site an ideal natural laboratory for testing gamma-based soil mapping.
The study employs a multi-phase methodology. Phase 1 involves a UAV-borne gamma radiation survey using a DJI Matrice 350 RTK platform equipped with a NaI(Tl) scintillation detector. The UAV operates at a controlled altitude of approximately 10 m above ground level at a lateral speed of 5 m/s, acquiring a continuous, georeferenced gamma radiation dataset with a detector footprint of approximately 14 m in width. Concurrent ground-based soil sampling is conducted systematically across the vineyard to a depth of 30 cm, with four samples per row and a row-skipping interval of approximately five rows to balance spatial representativity with operational efficiency. Phase 2 involves spectral analysis of the gamma radiation data using both Window Analysis (WA), which isolates specific energy windows corresponding to ⁴⁰K (1.46 MeV), ²³⁸U (1.76 MeV), and ²³²Th (2.61 MeV), and Full Spectrum Analysis (FSA), which utilises the entire gamma energy spectrum to account for spectral overlap and background radiation, yielding more accurate radionuclide concentration estimates. Statistical correlation analysis using both Pearson (r) and Spearman (ρ) coefficients will evaluate the relationships between gamma-derived variables and measured soil health indicators including pH, total carbon, clay content, and bulk density. Radionuclide ratios — specifically Th/U, U/K, and Th/K — will be calculated as geochemical proxies for weathering intensity, mineral composition, and soil texture respectively. Phase 3 applies Geographic Information Systems (GIS) spatial interpolation techniques, including Inverse Distance Weighting (IDW) and Kriging, within QGIS to generate high-resolution, continuous spatial distribution maps of radionuclide concentrations, derived ratios, and soil health indicator surfaces across the study area.
This research is expected to generate the first quantitative NOR dataset for the Malmesbury–Cape Granite Suite contact zone of the Darling Hills, filling a fundamental scientific gap in South African geoscience. If validated, gamma-ray spectrometry as a soil health proxy offers a cost-effective and scalable alternative to conventional monitoring, with direct application to precision agriculture, environmental baseline establishment, and national resource planning. The national security dimension of the study is grounded in South Africa's formal recognition of food security as a core component of national stability, as articulated in the White Paper on National Defence (1996) and the National Development Plan 2030. By repurposing radiometric techniques — originally developed for military reconnaissance and nuclear safeguards — as a soil intelligence tool, this research demonstrates the dual-use potential of geophysical sensing for strategic resource security. The methodology is scalable from farm level to landscape and regional scale, with potential for adaptation to broader SANDF and SSA environmental monitoring frameworks.
Keywords: natural gamma radiation, soil health, NaI(Tl) spectrometry, UAV-borne radiometry, Groote Post Farm, Cape Granite Suite, Malmesbury Group, GIS spatial mapping, Kriging interpolation, national security, food security, precision agriculture.

Speaker: Anathi Cutha

459 Electric Quadrupole Matrix Elements Supports Triaxial Rotation in Semimagic 60Ni

Low-energy Coulomb-excitation (reorientation-effect) measurements [1] of the first excited $2_1^+$ state in $^{60}$Ni were performed at iThemba LABS using the $^{194}$Pt($^{60}$Ni,$^{60}$Ni)$^{194}$Pt reaction at $T_{\mathrm{lab}} = 242.7$ MeV. Previous Coulomb-excitation measurements at iThemba LABS have been performed for $^{20}$Ne [2] and $^{36}$Ar [3]. A diagonal electric quadrupole matrix element of $\langle 2_1^+ | \hat{E2} | 2_1^+ \rangle = +0.10(2)$ eb was determined, corresponding to a spectroscopic quadrupole moment of $Q_s(2_1^+) = +0.08(1)$ eb. This value differs from the evaluated NNDC value of $+0.03(5)$ eb and is inconsistent with the negative quadrupole moment extracted from electron scattering measurements and reported in Stone's 2021 evaluation [4]. The positive quadrupole moment indicates an oblate deformation, in contrast to the zero quadrupole moment expected for a harmonic vibrator with magic $Z=28$. These results, together with previous evidence for multi-phonon excitations in $^{60}$Ni [5], suggest deviations from a purely vibrational description. Interpreting the measured quadrupole observables within the empirically validated triaxial rotor model [6,7] yields a triaxial deformation parameter of $\gamma = 31.9(4)^\circ$, indicating triaxial rotation.

[1] J. de Boer and J. Eichler. The reorientation effect. In Advances in Nuclear
Physics: Volume 1, pages 1–65. Springer, 1968.
2] C. V. Mehl, J. N. Orce, C. Ngwetsheni, P. Marevi´c, B. A. Brown, J. D.
Holt, M. K. Raju, E. A. Lawrie, K. J. Abrahams, P. Adsley, et al. Large
quadrupole deformation in 20Ne challenges rotor model and modern theory.
Physical Review C, 111(5):054318, 2025.
[3] J. N. Orce, E. J. Mart´ın Montes, K. J. Abrahams, C. Ngwetsheni, B. A.
Brown, M. K. Raju, C. V. Mehl, M. J. Mokgolobotho, E. H. Akakpo, D. L.
Mavela, et al. Reorientation-effect measurement of the $\langle 2_1^+ | \hat{E2} | 2_1^+ \rangle$
matrix element in 36Ar. Physical Review C, 104(6):L061305, 2021.
[4] N.J. Stone. Table of nuclear electric quadrupole moments. Atomic Data and
Nuclear Data Tables, 111-112:1–28, 2016.
[5] J. N. Orce, B. Crider, S. Mukhopadhyay, E. Peters, E. Elhami, M. Scheck,
B. Singh, M. T. McEllistrem, and S. W. Yates. Determination of the $2^+_ 1 →0^+_1$ transition strengths in 58Ni and 60Ni. Phys. Rev. C, 77:064301, Jun 2008.
[6] E. A. Lawrie and J. N. Orce. Triaxial nuclear shapes from simple ratios of
electric-quadrupole matrix elements. Atomic Data and Nuclear Data Tables,
164:101730, 2025.
[7] J. N. Orce, A. S. Zulu, et al. Electric quadrupole matrix elements support
triaxial rotation in semi-magic 60Ni. Submitted to PRL.

Speaker: Andile Zulu (University of the Western Cape)

460 UAV-Based Survey of the radionuclide isotopes on phosphate mining, South Africa

This study focuses on radiometric measurements, which will be conducted at phosphate mines in South Africa, including sites of a former phosphate mine known for its fossil-rich Varswater Formation, phosphate processing areas, and tailing and waste areas. Phosphate rocks are significant to industry but naturally contain radionuclide isotopes such as uranium (²³⁸U), thorium (²³²Th), and potassium (⁴⁰K), which mining activities may redistribute. A drone-based survey will be performed using a DJI Matrice M300 RTK equipped with a 3×3 NaI(Tl) scintillation detector coupled to an AMPTEK TB-5 digital base to assess their distribution. The system uses a Raspberry Pi 4 for data processing and a Garmin 18X GPS for precise geolocation. Calibration will be performed using a radium source, with spectral peaks aligned to the known decay energies of uranium and thorium daughters, ensuring deviations of less than one channel after a quadratic fit. Full-spectrum analysis identifying distinct gamma peaks corresponding to ²³⁸U, ²³²Th, and ⁴⁰K will confirm the presence of naturally occurring radionuclides in the phosphate deposits. The results will show the expected high concentrations of uranium associated with marine phosphate sediments, as well as concentrations of thorium and potassium. The findings will provide insights into the radiological characteristics of the sites and the environmental implications of historical phosphate mining. Keywords: Radiometric survey, Phosphate mining, NaI(Tl) scintillation detector, Uranium (²³⁸U), Thorium (²³²Th), Potassium (⁴⁰K), Gamma spectroscopy, Drone-based measurements, Environmental radioactivity

Speaker: Masego Mothapo

Nuclear, Particle and Radiation Physics -2: Session-8

Convener: Mpho Gololo (University of Johannesburg)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

461 Upgrade of the ATLAS Tile Calorimeter for HL-LHC Operation

The Tile Calorimeter (TileCal) is a sampling hadronic calorimeter covering the central region of the ATLAS experiment, with steel as the absorber and plastic scintillators as the active medium. The High-Luminosity phase of the LHC, delivering five times the LHC’s nominal instantaneous luminosity, is expected to begin in 2029. TileCal will require new electronics to meet the requirements of a 1 MHz trigger, higher ambient radiation, and to ensure better performance under high pile-up conditions. Both the on- and off-detector TileCal electronics will be replaced during the shut-down of 2026–2028. The photomultiplier tube (PMT) signals from every TileCal cell will be digitized and sent directly to the back-end electronics, where the signals are reconstructed, stored, and sent to the first level of the trigger at a rate of 40 MHz. This will provide better precision in the calorimeter signals used by the trigger system and will allow the development of more complex trigger algorithms. The modular front-end electronics feature radiation-tolerant, commercial, off-the-shelf components and a redundant design to maintain system performance in case of single points of failure. The timing, control, and communication interface with the off-detector electronics is implemented with modern Field-Programmable Gate Arrays (FPGAs) and high-speed fiber optic links running up to 9.6 Gb/s. The TileCal upgrade program has included extensive R&D and test beam studies. A Demonstrator module with reverse compatibility with respect to the existing system was inserted in ATLAS in August 2019 for testing in actual detector conditions. The ongoing developments for on- and off-detector systems, together with expected performance characteristics and results of test-beam campaigns with the electronics prototypes, will be discussed.

Speaker: Edward Nkadimeng (University of the Witwatersrand)

ATL-COM-TILECAL-2026-040 (1) (2).pdf

462 Finger Low Voltage Power Supply Upgrade for the ATLAS Tile Calorimeter in South Africa

The Phase-II upgrade of the ATLAS Tile Calorimeter (TileCal) for the High-Luminosity Large Hadron Collider will also comprise the new finger Low Voltage Power Supply (fLVPS) boards to satisfy the new requirements on radiation tolerance, reliability and performance of the device. University of Witwatersrand in South Africa share the production of 2048 fLVPS boards with UTA in America. University of Witwatersrand produced 1032 of these fLVPS boards. The fLVPS board is upgraded to supply stable and low-noise power and improved redundancy and fault tolerance for high energy performance in any harsh environment. Sourcing, assembling, and verification of components is done using a methodical way which complies with ATLAS standards. All quality assurance is managed in three steps: initial testing, burn-in and final testing. The production pipeline, testing protocols and performance metrics for the fLVPS boards are presented in this work. The outcomes shows that these systems meet all aspects of the necessary parameters regarding voltage stability, temperature stability, power efficiency, noise level and reliability. The work also demonstrates the contribution of Wits to providing hardware to conduct a large international experiment and the experience they gained from building in electronics production and testing.

Speaker: Lungisani Phakathi (University of Witwatersrand)

121_Lungisani_Phakathi.pdf

463 Thermal Stability Analysis of ATLAS TileCal Phase-II LVPS in Production Burn-in Testing

The Large Hadron Collider (LHC) is undergoing a major upgrade to increase its luminosity, initiating the High-Luminosity Large Hadron Collider (HL-LHC). The Phase-II upgrade of the ATLAS detector involves a complete upgrade of the Tile Calorimeter (TileCal) readout electronics to withstand higher radiation levels, increased trigger rates, and elevated pile-up conditions. This upgrade includes improvements to the Low Voltage Power Supply (LVPS) system, consisting of 256 finger-LVPS (fLVPS) boxes, each housing eight transformer-coupled buck converter boards. These boards provide regulated low-voltage power of approximately 10 V at load currents of 5-7 A to the front-end electronics, operating with typical power efficiencies in the range of 60-95%. The University of the Witwatersrand is responsible for the design, production, and quality assurance of half of the required fLVPS boards. This research focuses on the development and implementation of a burn-in test station designed to ensure the reliability and long-term operational stability of the fLVPS boards under HL-LHC conditions. The burn-in process operates over periods of approximately 8 hours at controlled thermal conditions, with target temperatures around 60◦C, while continuously monitoring key parameters including temperature (T2, T3), output voltage, output current, and efficiency. The main aim of this research is to quantify the thermal stability and electrical performance of the fLVPS boards during production burn-in testing, and to use these results to improve the quality assurance process. This includes evaluating voltage regulation, current stability, and efficiency variations as functions of temperature, as well as identifying potential deviations across production batches.

Speaker: Donald Ngobeni

130_Donald_Ngobeni_2.pdf

130_Donald_Ngobeni.pdf

464 Response of gap and crack scintilators of the ATLAS Tile Calorimeter to muons from $Z \to \mu \mu$ events using Run 3 collision data

A study of the response, uniformity, and time stability of the E-cells of the ATLAS Tile Calorimeter is presented using isolated muons from $Z \to \mu\mu$ events in $pp$ collisions at $\sqrt{s} = 13.6$~TeV. The E-cells, located in the gap and crack regions, measure the energy deposited in passive material and require dedicated calibration. This study provides an independent muon-based validation of the E-cell energy scale and complements the standard Minimum Bias calibration, contributing to the understanding of detector performance under Run 3 conditions.

Speaker: Karabo Mosala (University of the Witwatersrand)

141_Karabo_Mosala.pdf

Photonics

Physics for Development, Education and Outreach

Convener: Chad Leukes (University of Cape Town)

465 A Pedagogical framework for teaching Econophysics through contrasting Self-Organized Criticality in the Bak-Chen-Scheinkman-Woodford Model with Real Business Cycle Theory Through Rationality Debates

Econophysics uses tools from physics, such as self-organized criticality, to explain economic fluctuations through agent interactions rather than assumptions of perfect rationality. This framework supports physics lecturers in teaching students by contrasting the Bak-Chen-Scheinkman-Woodford self-organized criticality model with Real Business Cycle (RBC) theory, using the rationality debate as a central pedagogical lens.

Real Business Cycle theory explains economic cycles through external shocks acting on fully rational agents, producing near-Gaussian outcomes due to the law of large numbers. However, it struggles to capture empirical features such as fat tails and volatility clustering observed in real-world data.

In contrast, the Bak-Chen-Scheinkman-Woodford model represents firms on an $L \times L$ lattice. Random demand shocks trigger paired production and inventory cascades, analogous to two-dimensional sandpile dynamics. When a local threshold is exceeded,
the system undergoes a toppling process where excess activity is redistributed to neighboring sites. This generates cascade effects (avalanches) characterized by power-law distributions and fat-tailed (Pareto-like) output fluctuations, even in the absence of external shocks.

Speaker: Mr Lehlohonolo Moloi (University of Witwatersrand)

517_Lehlohonolo_Moloi.pdf

466 Developing Data Science Skills Through Collaborative Hackathons: A Case Study of Hack4dev's Data Science Hackathon Programme

Hack4dev, was launched in May 2022 by Prof. Carolina Odman, with the participation of several partners, including the Inter-University Institute for Data Intensive Astronomy (IDIA), the Office of Astronomy for Development (OAD), the BRICS Intelligent Telescope and Data Network (BITDN), Development in Africa with Radio Astronomy (DARA), and the African Astronomical Society (AfAS). Since then, it has grown into a global initiative that connects research and development through hackathons. It serves as a shared backbone for hackathons, offering models, guidance, and support while welcoming contributions of tools, resources, and infrastructure from around the world.

As artificial intelligence (AI), machine learning (ML), and data science become increasingly important across research, industry, and development sectors, access to practical training opportunities, mentorship, and applied learning experiences remains uneven, particularly in emerging innovation ecosystems. The Hack4dev Data Science Hackathon Programme (DSHP) was developed to address this challenge through a scalable, decentralised approach to technical skills development.

The programme employs a two-stage cascade model designed to expand access to high-quality data science training while fostering local ownership and innovation. Selected organisers first participate in a Trainers Hackathon, where they receive training in technical challenge facilitation, community engagement, and hackathon management. These organisers subsequently implement Regional Hackathons within their own institutions and communities, creating locally driven learning environments while contributing to a shared global challenge framework.

Findings from the programme’s first cycle demonstrate the effectiveness of this approach. More than 50 organisers supported over 150 participants across multiple regions, resulting in 48 submitted machine learning and data science solutions developed within a three-day period. Twenty submissions outperformed the benchmark model provided by the organisers, while the highest-performing solution achieved execution speeds 165 times faster than the baseline. These outcomes demonstrate that short-term, challenge-driven hackathons can simultaneously strengthen technical competencies and encourage peer-to-peer learning.

Building on these outcomes, the 2025–2026 programme cycle will expand to 22 hackathons hosted across institutions in Botswana, Ethiopia, Ghana, Iraq, Kenya, Madagascar, Mozambique, Namibia, Nigeria, South Africa, Tanzania, Zambia, and Zimbabwe. This expansion provides an opportunity to evaluate the scalability and reproducibility of AI and data science capacity-building models across diverse educational and institutional contexts. A forthcoming third programme cycle will further extend Hack4dev's reach by recruiting new organisers and institutions, creating additional opportunities for hands-on machine learning training, mentorship, and community-led innovation. The programme aims to strengthen regional data science ecosystems while promoting inclusive participation and collaboration across the world.

Speaker: Charles Takalana (IAU-OAD)

Hack4dev_DSHP_SAIP_2026_CT.pdf

467 The Practure – Physical events with live data in the Lecture Hall

First year students at the University of the Western Cape predicted that a sinusoidal model of motion would be quadratic, while third year students at the University of Limpopo predicted a quadratic model would be sinusoidal. In this presentation on the ‘practure’, we suggest that learners have an instinct to ‘squash’ their familiar models onto real world experience, and that live data in the lecture theatre can help students observe more carefully and engage more meaningfully.

‘Practure’ pedagogy is POE based. Predict-Observe-Explain (POE) is a constructivist teaching strategy that prompts students to forecast an event, observe the results, and resolve any discrepancies between the two.

The presentation includes a live demonstration, where audience members are asked to predict and observe for themselves.

Speaker: Peter Horszowski (PERT)

Physics of Condensed Matter and Materials

Convener: Prof. Lynndle Square (North West University)

468 Structural, magnetic and critical behavior properties of Ce₂Al₃Ge₄

Abstract
The polycrystalline Ce₂Al₃Ge₄ compound has been synthesized by arc-melting. The structural, magnetic and critical behavior properties have been investigated through measurements of X-ray diffraction (XRD), magnetic susceptibility, χ(T), magnetization, M(μ₀H), and heat capacity, Cₚ(T). The structure has been obtained and refined from XRD pattern in the Cmcm – D₂h No. 64 space group with a = 6.08118(6) Å, b = 15.086(2) Å and c = 7.986(1) Å. The DC and AC-χ(T) as well as the Cₚ(T) data indicate a ferromagnetic (FM) transition at around T_c = 9.9 K. Below T_c, an additional magnetic phase transition temperature around T₁ = 5.4 K was observed and attributed to FM rearrangement of the Ce moment. χ(T) data at high temperature follows the modified Curie – Weiss relationship, giving an effective magnetic moment smaller than that expected for the trivalent Ce ion. Cₚ(T) data at low temperatures below T₁ can be well described according to the spin-wave magnon model with energy gap Δ_c = 4.6(1) K, and at high temperatures, well above T_c, by the Debye-Einstein Model, giving a Debye and Einstein temperatures, θ_D = 197(20) K and θ_E = 300(26) K, respectively. The standard Arrot plots indicates a second-order phase transition. The critical behaviour study around the FM phase transition using the mean-field and the Kouvel – Fisher methods yields the average critical exponents β = 0.614, γ = 1.002, and δ = 2.631 close to those expected for a 3D mean – field ferromagnet. The resulting average value of T_c = 7.11 K obtained from the critical behaviour study is roughly equal to the average value of the two magnetic phase transition temperatures T₁ and T_c obtained from χ(T) and Cₚ(T) data.

Key words:

Ferromagnetism, Heat capacity, Spin-wave, Magnetic susceptibility, Magnetization, Critical behaviour, Mean-field model, Critical exponents.

Speaker: Ms Zandile Mpupa (university of the western cape)

469 Optimized composition of the In2O3-Co3O4-ZnO nanostructure loaded with Ru for ethanol detection

Ethanol (C2H5OH) is a poisonous, highly flammable, and explosive volatile organic compound extensively used in the food and beverage, petrochemical, and agricultural industries. Exposure to high concentrations of C2H5OH vapor can cause severe health and safety issues, including respiratory tract damage, central nervous system effects, and potential explosions. Therefore, highly sensitive C2H5OH sensors that operate at low temperatures are crucial to prevent false alarms in safety systems.

In this study, pristine In2O3-Co3O4-ZnO nanostructure, and 0.5, 1.0, and 2.0 wt.% Ru-loaded In2O3-Co3O4-ZnO nanostructures were fabricated using the hydrothermal technique, followed by thermal annealing to achieve optimum crystallinity and interfacial contact between the metal oxides and noble metal. The structural and chemical state confirmed the formation of heterostructures and the incorporation of Ru. Additionally, surface defects (e.g., oxygen vacancies and metal interstitials) were analysed for their role in enhancing gas-sensing performance by increasing active sites, facilitating charge transfer, and consequently lowering the band gap energy. During gas-sensing measurements, the integrated In2O3-Co3O4-ZnO ternary nanostructure loaded with 1.0 wt.% Ru exhibited exceptional sensing performance towards 100 ppm C2H5OH at an optimal operating temperature of 75 °C. Furthermore, the sensor exhibited remarkable sensitivity, a low detection limit, and long-term stability. These findings demonstrate the promising potential of quaternary nanostructures for effective detection of C2H5OH at low temperatures, a valuable opportunity for future research and advancements in gas-sensing technologies.

Speaker: Katlego Morulane (University of the Free State)

470 Influence of Nickel (Ni) on the structural and optical properties of LiZnBO3 and on the photocatalytic degradation efficiency of LiZnBO3 on potassium ethyl xanthate under UV-Vis irradiation.

Lithium zinc borate (LiZnBO$_3$) is a metal borate material that has garnered a huge scientific interest because of its distinctive electronic, optical, and physico-chemical properties which makes them suitable candidates for environmental remediation applications in a world hugely affected by pollution from different sectors such as mining and agriculture. These novel LiZnBO3 nanomaterials were prepared in this study using solid state reaction method. This material was doped with Nickel (Ni) and the doping concentrations were varied form (1, 3, 5, 8, 10%). The particle and structural morphology of the synthesized materials were studied using X-ray diffractometer (XRD) and scanning electron microscope (SEM). The XRD diffraction patterns indicate that the doping of Ni ions has no discernible impact on the crystal structure of LiZnBO$_3$, confirming the preservation of crystallinity and the formation of a pristine LiZnBO$_3$ with the absence of characteristic peaks related to impurities or secondary peaks emanating from Ni. The XRD spectra also confirmed the formation of a pure LiZnBO$_3$ material which formed in single-phase monoclinic crystal system and IE space group of LiZnBO$_3$. This crystal structure was maintained even after the substitution with Ni ions, indicating a successful substitution of Ni ions into the LiZnBO$_3$ structure. Energy dispersive spectroscopy was used for elemental composition investigations which confirmed the presence of Li, Zn, B, and O in pristine sample and also confirmed the presence of Li, Zn, B, O, and Ni in doped LiZnBO$_3$ samples. The efficiency of the synthesized materials was investigated by studying their photocatalytic degradation efficiency via the degradation of potassium ethyl xanthate (PEX) under UV-vis light. PEX is a commonly used chemical collector used during flotation process in the mineral separation industry and is detrimental to the environmental ecosystem. Hence, it is extremely important to devise environmentally friendly methods of degrading PEX into harmless materials.

Speaker: Mr Emmanuel Diutlwetse Magasi (University of johannesburg)

471 Optimization of Nitrogen in Transition Metal Oxynitrides for Fuel Cell Applications

Titanium oxide is a promising corrosion-resistant catalyst support for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells; however, its low electrical conductivity limits performance. In this work, titanium oxynitride materials were synthesized via two routes: a sol–gel method followed by thermal nitridation at 650 °C, and a hydrothermal synthesis calcined at 750 °C. Nitrogen incorporation was controlled using varying titanium precursor-to-urea ratios. X-ray diffraction revealed rutile phase for sol–gel and anatase structures for hydrothermal samples. Raman spectroscopy indicated lattice distortion and defect formation, while UV–Vis analysis showed enhanced visible-light absorption due to defect states. EDS showed 10.52% N incorporation while SEM showed highly agglomerated and porous structures. . The composition with 23.93% nitrogen exhibited the most significant structural and electronic modification across both synthesis routes, suggesting an optimal nitridation level. These results demonstrate that controlled nitrogen incorporation can effectively tune TiO₂ properties for improved ORR activity, supporting the development of sustainable fuel cell technologies.

Speaker: Nicholas Onkoba (UNISA)

472 The Synthesis and Characterization of ε-Fe$_{2}$O$_{3}$/SiO$_{2}$ Nanoparticles

This study investigates the temperature-dependent magnetic properties and structural transitions of ε-Fe$_{2}$O$_{3}$ nanoparticles embedded in a silica matrix, synthesized via the sol-gel method. While literature reports an exceptionally large room-temperature coercivity of ε-Fe$_{2}$O$_{3}$ approximately = 2 T (20 kOe), often attributed to its disordered structure, the precise effects of structural deformations on its magnetic transitions and magnetocrystalline anisotropy remain a subject of active research. The coercivity is also reported to show an unusual temperature trend, decreasing with temperature until around 100 K and then increasing until 2 K. In this study, the X-ray diffraction (XRD) confirmed the successful synthesis of the ε-Fe$_{2}$O$_{3}$ phase with an α-Fe$_{2}$O$_{3}$ component, while Transmission Electron Microscopy (TEM) revealed mor-phologies ranging from elliptical to nearly spherical. Further investigation was done using the HRTEM where images revealed distinct lattice fringes, indicative of the well-ordered crystal-line structure of the nanoparticles.
Room-temperature 57Fe Mössbauer spectroscopy confirmed a magnetically ordered state, with spectral fitting requiring four sextets: one representing α-Fe$_{2}$O$_{3}$ and three corresponding to the distinct Fe$^{3+}$ coordination sites within the ε-Fe$_{2}$O$_{3}$ lattice. Magnetic hysteresis (M-H) loops recorded between 10 K and 300 K revealed a rich thermal behavior; at 300 K, the nanoparti-cles exhibited a high coercivity of H$_{c}$ = 1.55 T (15.5 kOe) and a remanent magnetization of M$_{r}$ = 0.27 emu/g. Notably, a pronounced collapse in both coercivity and magnetic squareness was observed upon cooling, particularly near 100 K, which is attributed to an incommensurate magnetic transition. These results highlight critical limitations for the application of ε-Fe$_{2}$O$_{3}$ as a hard magnetic material at cryogenic temperatures.

Speaker: Aphile Chithwayo (Student)

Side Event: Physics in Industry Day

Draft Programme and Brief - SAIP2026 Industry Day.pdf

Theoretical and Computational Physics: Session 8

Convener: Garreth Kemp (University of Johannesburg)

473 Thermodynamics of Quantum Fields on a Finite Lattice

In this talk I present a first-principles construction of the thermal partition function for scalar quantum field theories in finite volume, with an emphasis on mathematical control and physical consistency. Motivated by small systems in high-energy collisions, such as the quark-gluon plasma produced at the LHC and RHIC, we investigate how finite system size modifies thermodynamic observables within Thermal Field Theory.

We formulate field eigenstates on a spatial lattice, showing that a discretized setting is required for a well-defined construction of the path integral measure. Within this framework, we derive the lattice dispersion relation and demonstrate that it obstructs a straightforward continuum limit, necessitating a careful extraction of physical results. We then construct the thermal path integral in finite volume in a fully controlled manner, naturally incorporating finite-size effects such as vacuum energy corrections analogous to the Casimir effect. This approach enables the computation of finite-size corrections to thermodynamic quantities; we present preliminary results for the pressure and outline a pathway toward extensions to gauge theories and QCD.

Speaker: Rens Roosenstein (University of Cape Town, University of Amsterdam)

SAIP 2026 presentation Rens Roosenstein.pptx

474 High-pT Dihadron Correlations in Proton-Proton and Heavy-ion Collisions

In high-energy heavy-ion collisions at facilities such as the Large Hadron Collider (LHC) and Relativistic Heavy Ion Collider (RHIC), extreme temperatures and energy densities are achieved, leading to the formation of a deconfined state of matter known as the quark–gluon plasma (QGP). Hard-scattered partons produced in the early stages of the collision traverse this hot and dense medium, losing energy through medium-induced gluon radiation and elastic interactions, a phenomenon referred to as jet quenching. Dihadron correlation measurements provide a powerful tool to study partonic energy-loss mechanisms. By selecting a high-transverse-momentum trigger hadron and measuring the angular distribution of associated hadrons, one can probe the modification of jet structure. In proton–proton collisions, clear near-side ($\Delta\phi \approx 0$) and away-side ($\Delta\phi \approx \pi$) peaks reflect vacuum jet fragmentation. In contrast, heavy-ion collisions exhibit suppression and broadening of the away-side peak, directly encoding information about parton energy loss and medium-induced momentum broadening in the QGP. In this work, proton–proton dihadron correlations are studied using the PYTHIA event generator by measuring the angular distributions of particle pairs across different momentum ranges. Statistical uncertainties are estimated using a jackknife resampling method, and contributions from the underlying event are removed using the Zero-Yield-At-Minimum (ZYAM) procedure. The dihadron correlation analysis provides a controlled proton–proton baseline for future comparisons to heavy-ion calculations incorporating partonic energy loss, enabling quantitative studies of QGP-induced jet modifications.

Speaker: Tiaan van der Merwe (University of Cape Town)

120_Tiaan_VanDerMerwe.pptx

475 Path-length dependence of parton energy loss in Pb-Pb, Ne-Ne and O-O collisions using JEWEL and Trajectum

A few microseconds after the Big Bang, the universe existed in an extremely hot and dense phase where ordinary hadrons could not form and matter took the form of quark-gluon plasma (QGP). High-energy partons produced in initial hard scatterings traverse the expanding QGP and lose energy through multiple interactions with the medium constituents, a phenomenon known as jet quenching. To isolate the dependence of parton energy loss on traversed distance, a fully integrated simulation chain is employed. The JEWEL Monte Carlo event generator provides a microscopic description of parton showers and medium-induced energy loss, while realistic hydrodynamic backgrounds for lead-lead, oxygen-oxygen, and neon-neon collisions are supplied by the Trajectum framework. For each system, large event samples are generated, high transverse momentum hadrons are reconstructed, and the nuclear modification factor $R_{AA}$ is evaluated as a function of transverse momentum. $R_{AA}$ quantifies jet quenching by comparing suppressed high-$p_T$ hadron yields in heavy-ion collisions to the corresponding yields in proton-proton baselines. Contrasting $R_{AA}$ across systems of different geometric size allows the variation of suppression with average in-medium path-length to be quantified. All analyses are performed within the Rivet environment, ensuring direct and reproducible comparison with published experimental results. Preliminary results and their implications for the underlying QCD dynamics of the QGP will be presented.

Speaker: Martha Mashao

337_Martha_Mashao.pptx

Guided Walk in UWC Nature Reserve (with Packed Lunch)

Sign-up Required. Limited Capacity.

12:40 Lunch

Plenary: (UWC Invited Plenary) Prof Jens Gundlach

476 JENS H. GUNDLACH

14:35 Buffer

Applied Physics

Convener: Alan Matthews (UKZN)

477 Effect of Methane Concentration on Biogas Thermodynamics

The impact of the nature of the biogas on its thermodynamic behavior is studied. Methane and carbon dioxide store energy and their contribution to the molecular degrees of freedom is different. The main aim here is to show how varying concentrations of methane affect the thermal energy needed to raise the temperature of biogas under controlled conditions. This will be done based on the first law of thermodynamics and using an ideal gas law. Measurements were made inside a gas vessel, whereby heat was supplied to the vessel in short intervals. Changes in pressure and volume were monitored for calculating molar heat capacities at constant volume (Cv) and at constant pressure (Cp). The heat capacities for different compositions of biogas mixtures were measured at a hydraulic retention time (HRT) equal to 20 days. It is expected that changes in methane concentration will change the effective heat capacity of the biogas mixture. Results can help understand thermal properties, more specifically combustion-related ones, energy conversion, process design, etc., while also explaining how enrichment with methane changes heating behavior practically applied to biogas.

Speakers: Mr Thando Khedzi (University of venda), VHUTSHILO NEKHUBVI (University of venda)

478 Enhancing Biogas Yield from Cow Dung: A Comparative Study of Varying Fe₂O₃ Nanoparticle Concentrations

Anaerobic digestion (AD) is a key technology for renewable energy generation and waste management; however, its efficiency is often constrained by slow reaction kinetics and suboptimal microbial efficiency. Recent studies indicate that adding iron oxide (Fe₂O₃) nanoparticles to biodigesters enhances methane production and the anaerobic digestion (AD) process. This ongoing study is investigating the effect of Fe₂O₃ on methane production during the anaerobic digestion of cow dung. Batch digesters with cow dung supplemented with iron oxide at concentrations of 50, 100, 150, and 200 mg/L are being conducted under controlled mesophilic (37 ± 0.5℃) and thermophilic (55 ± 0.5℃) conditions over a 40-day retention period. Biogas volume and methane composition are monitored to evaluate the effects of Fe₂O₃ concentration and temperature. To ensure robust statistical analysis, the distribution of experimental data will be evaluated using the Kolmogorov–Smirnov normality test prior to further inferential analysis. This study aims to determine the optimal Fe₂O₃ nanoparticle concentration and compare performance under different thermal conditions. Findings will enhance understanding of nanomaterial-assisted anaerobic processes and support the development of efficient, sustainable biogas systems.

Speaker: Takalani Nethavhanani (University of Venda)

Presentation_Takalani Nethavhanani (SAIP 2026).pptx

479 Thermal signature analysis of photovoltaic module mismatch using infrared thermography

Abstract
Photovoltaic (PV) module mismatch, arising from partial shading, soiling, and cell degradation, results in non-uniform current distribution and localized Joule heating, reducing system efficiency and accelerating material degradation. This study presents an experimental investigation of thermal signatures associated with mismatch conditions in crystalline silicon PV modules using infrared (IR) thermography under outdoor operating conditions. Controlled mismatch scenarios were introduced, including artificial defects and shading patterns, at irradiance levels ranging from 650 to 950 W/m². High-resolution thermographic measurements were used to analyze temperature distributions and identify hotspot formation. The results reveal distinct and repeatable thermal signatures associated with different mismatch conditions. Localized temperature differentials (ΔT) ranged from approximately 6 °C under mild mismatch to above 28 °C under severe shading. A strong correlation between mismatch severity and temperature gradient was observed, with hotspot intensity increasing nonlinearly with imposed current mismatch. Cell-level defects produced highly localized hotspots, while string-level mismatch resulted in broader thermal bands associated with bypass diode activation. These findings demonstrate that infrared thermography is a sensitive and reliable diagnostic tool for detecting and classifying mismatch faults in PV modules under real operating conditions. The study establishes quantitative ΔT thresholds for fault severity assessment and highlights the applicability of thermographic monitoring for improving the performance and reliability of PV systems, particularly in high-irradiance environments.
Keywords:
Photovoltaic modules; infrared thermography; PV mismatch; hotspot detection; Joule heating; thermal signatures; fault diagnostics; solar energy systems

Speaker: TSHIMANGADZO SOPHIE MULAUDZI (University of Venda)

480 Physics Principles Applied in Monitoring Photovoltaic Performance and Water Dynamics

Photovoltaic water pumping systems (PVWPS) provide a sustainable solution for irrigation in off grid and water scarce environments, yet their effectiveness is limited by the lack of integrated, physics based monitoring capable of resolving the coupled dynamics of photovoltaic energy conversion and water transport. Existing approaches often treat electrical and hydraulic subsystems independently and rely on empirical indicators, resulting in limited real time diagnostics and suboptimal system performance. This study presents a physics informed cyber physical monitoring framework that explicitly links solid state photovoltaic behaviour, electromagnetic power conversion, and fluid mechanical water dynamics through first principles models and distributed sensing. Key variables including solar irradiance, photovoltaic voltage and current, hydraulic pressure, water level, flow rate, soil moisture, and temperature, are measured using low power ESP32 based sensor nodes and transmitted via Bluetooth Low Energy and WiFi to an LTE gateway for cloud based analytics.

Photovoltaic performance is characterised using temperature- and irradiance-dependent electrical models, while water dynamics are described using conservation laws, hydrostatic pressure relations, and hydraulic power balance. A four week case study on an off grid agricultural PVWPS recorded irradiance levels of 250–950 W m⁻², PV efficiencies of 13–17%, and flow rates of 18–42 L min⁻¹. The system achieved data latency below 5 s, power consumption below 200 mW, and enabled detection of pumping efficiency deviations within 10–15% of nominal operation, improving overall performance assessment by approximately 25%. The results demonstrate that physics informed monitoring enables reliable real time diagnostics and intelligent control, highlighting the central role of applied physics in advancing resilient, sustainable irrigation systems.

Speaker: Livhuwani Masevhe (University of Johannesburg)

SAIP 2026 July Cape Town.pptx

Astrophysics & Space Science: Astrophysics: Session 9

Astrophysics & Space Science: Space Science: Session 9

Convener: Zama Katamzi-Joseph

481 Polar Coronal Hole Size Variations Across Multiple Solar Cycles

This study examines the evolution of polar coronal holes (PCHs), regions of open magnetic field in the solar corona, over Solar Cycles 24 and 25. Using AIA 193 Å observations and HMI magnetic-field measurements from the Solar Dynamics Observatory (SDO), variations in PCH morphology  and magnetic properties across the solar cycle are analysed. The results show that PCH area and occurrence are anti-correlated with solar activity, expanding during solar minimum and contracting during solar maximum, consistent with their role as tracers of the Sun’s global magnetic field. The agreement between modelled and observed magnetic flux further supports the reliability of coronal-hole connectivity studies. These results demonstrate the usefulness of PCHs as indicators of large-scale solar magnetic-field evolution.

Speaker: JG Coertze (NWU)

43_JG_Coertze.pdf

482 Detailed study of a solar flare: photospheric deformation and chromospheric/coronal connectivity

Solar observations provide a wealth of data at high resolution in all layers of the solar atmosphere, obtained from ground-based and space-born observatories. A multi-layer analysis of a C-class flare observed on 1 July 2012 is presented using high-resolution Swedish 1-m Solar Telescope (SST) observations, SDO/HMI SHARP data, SDO/AIA imaging, and potential field extrapolations. The chromospheric structure, flare ribbon positions, fine-scale polarity inversion line (PIL), photospheric velocity flows and the components of the rate-of-strain tensor are strongly co-spatial. This indicates that the flare occurred within a well-defined area of photospheric deformation. The extrapolated magnetic field lines are rooted across the PIL, with opposite footpoints embedded in distinct flow streams and different local strain environments, consistent with differential stressing. The field lines are spatially consistent with the chromospheric and ultraviolet flare ribbons observed in SST Hα and AIA 1700 Å, linking the photospheric deformation to the overlying flare geometry. The combined observations strongly suggest that localised strain and shear flow around the PIL contribute to the magnetic field evolution before and after the flare. This event therefore provides a compelling example of how fine-scale photospheric deformation can organise flare-relevant magnetic connectivity from the photosphere into the chromosphere and lower corona.

Speaker: Ruhann Steyn (Centre for Space Research, North-West University)

Nuclear, Particle and Radiation Physics -1: Session 3

Convener: Edward Nkadimeng (University of Witwatersrand)

Nuclear, Particle and Radiation Physics -2: Session-9 Division Meeting

Conveners: Dr Mukesh Kumar, Sifiso Ntshangase (University of Zululand)

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

Photonics

Physics for Development, Education and Outreach

Convener: Mayhew Steyn (University of Cape Town)

483 Evaluating the Impact of a Physical Science Teacher Development Programme in the Vhembe District, South Africa

This study addresses the challenge of low teacher confidence and limited pedagogical effectiveness in the teaching of Physical Sciences in under-resourced schools in the Vhembe District. Many teachers struggle with complex topics and practical experiments due to limited training and inadequate laboratory resources.

To address this, a structured teacher development programme was implemented across 288 schools (160 in Vhembe East and 128 in Vhembe West). The study used a pre–post evaluation design to assess changes in teacher confidence and instructional capacity. Data were collected using structured survey instruments that measured confidence levels across key Physical Science topics and practical components.

Pre-evaluation showed that teacher confidence was generally moderate, with lower confidence in challenging topics such as electrochemistry, internal resistance, and electrodynamics. Confidence in conducting experiments was particularly low in Vhembe West. Following the intervention, results showed clear improvements in teacher confidence across both subdistricts. The largest gains were observed in experimental work and previously difficult topics, including titration and internal resistance. Overall, the proportion of teachers reporting high confidence increased substantially after the training.

Qualitative feedback from participants highlighted ongoing systemic challenges, particularly the lack of adequate laboratory equipment, the limited duration of training workshops, and insufficient continuous professional support. Many teachers recommended longer training sessions and more frequent engagement, with a stronger focus on practical and problem-solving activities.

The findings show that targeted professional development programmes can significantly improve teacher confidence and teaching effectiveness in Physical Sciences. However, these improvements must be supported by better infrastructure and sustained professional development. The study recommends the institutionalisation of extended training programmes and increased investment in laboratory resources to ensure long-term impact and improved learner outcomes.

Speaker: Tshifhiwa Ranwaha (University Of Venda)

SAIP 2026 RANWAHA.pptx

484 UNDERSTANDING HIGH SCHOOL PHYSICAL SCIENCE IN THEIR PROFESSIONAL DEVELOPMENT TRAINING

Trends in education and teacher training have proven that due to the latest developments in technology and curriculum transformation, continuous professional development of educators is vital in promoting and improving the teaching and learning of physical science. Studies have proven that educators are blamed for the learners’ poor performance. Less studies have been done on the school educators’ need for professional development. Researchers embarked on investigating the needs and perceptions of high school physical science educators in terms of this professional development, and what they would like to see or be assisted with in enhancing their skills and challenges with teaching and learning of physical science. A questionnaire was designed and distributed to these educators in one province, and thirty-two educators participated voluntarily in this study. The results were statistically analysed and indicated a greater need for reform and transformation in the teaching and learning of this subject. Participants felt that they were overworked and had to complete the syllabus under strenuous conditions without affecting the curriculum changes. This hampered their efficiency in the delivery of the mode of instruction, and they are always left behind with the latest developments, mainly in technology, of the pedagogical approaches to teaching and learning, especially assessments. They are unable to develop as a result, as they are stuck with a classroom environment only.

Speaker: Dr Happy Phage (Central University of Technology, Free State)

485 Pre-service physics students' perception on their experiments in the laboratory

The study was about identifying physics pre-service teachers' perceptions and challenges with laboratory experimental work (physics practicals).

Speaker: Mr Odirile Mashalane (Central University of Technology, Free State)

486 A Pretest–Post-Test Analysis of PHET Simulations Enhanced with ChatGPT in Teaching Electricity Concepts

This study highlights the increasing use of technology in teaching and learning, particularly in improving student understanding of complex concepts in electricity. It investigates the effectiveness of integrating PHET simulations with embedded ChatGPT support on student learning outcomes using a pretest–post-test design. The students interacted with the simulation while receiving real-time guidance, feedback, and explanations from ChatGPT, which enhanced engagement, supported inquiry-based learning, and strengthened conceptual understanding. Data were collected from a cohort of students assessed across five sections of a structured and validated questionnaire. Descriptive and inferential statistical analyses were conducted to evaluate changes in student performance before and after the intervention. The results showed a clear and consistent improvement in post-test scores compared to pretest scores, indicating the effectiveness of the learning approach. A paired samples t-test confirmed that the gains were statistically significant, while Cohen’s d indicated a moderate to strong effect size, demonstrating meaningful practical impact. Although improvements were observed across all sections, some variations suggest that certain electricity concepts remain challenging. Overall, the findings demonstrate the strong potential of combining interactive simulations with artificial intelligence to enhance learning outcomes in electricity education.

Speaker: Martin Tarisai Kudinha (CPUT)

Physics of Condensed Matter and Materials

Convener: Hasani Chauke

487 Effect of CuO doping on the structural properties of CeO2 nanofibers for selective detection of CH4 and ppb-level NO gas

We report on the effect of CuO:CeO2 (0.25-1.0 wt.%) nanofibers for the selective detection of CH4 and ppb-level NO, prepared using a hydrothermal approach. The intrinsic features of the CuO:CeO2 nanofibers, including crystal structures, surface adsorption states, and chemical states, were examined. The sensing tests showed that among the fabricated sensors, the 1.0 wt.% CuO:CeO2-based materials displayed a superior response and selectivity towards 10 0000 ppm of CH4 and low ppb levels (0.001-0.1 ppm) of NO at 175 °C. The sensor displayed a low theoretical detection limit of 35 ppm and 0.00024 ppm (0.24 ppb) towards CH4 and NO, respectively. The capability of the CuO:CeO2 composite-based sensor to detect NO at low ppb levels is due to NO's high chemical reactivity, CeO2's redox activity, and the CuO effects on the CeO2 structure. Moreover, the enhanced sensing performance can be attributed to an improved surface area and increased surface defects, which, along with the synergistic effects of CeO2 and CuO, contribute to the effective relations of CuO:CeO2 nanocomposite, thereby modulating electron-hole dynamics and amplifying surface interactions with the analyte gases. The gas-sensing mechanism associated with the CH4, and NO detection is also discussed.

Keywords: CeO2, CuO, nanocomposite, nanofibers CH4, NO gas

Speaker: MAPHIA GIFT PHOLOANA (UNIVESITY OF FREE STATE)

488 Influence of sol-gel, combustion, and solid-state synthesis methods on the structural and photoluminescence properties of Zn4B6O13 : xEu3+ phosphor materials for LEDs applications.

Zn₄B₆O₁₃:xEu³⁺ (x = 1%) phosphor materials were successfully synthesized using three methods, sol-gel, combustion, and solid-state, to investigate the influence of each synthesis method on the structural and photoluminescence properties of the prepared materials. The cubic crystal structure was confirmed in all synthesis methods via the X-ray diffraction (XRD) technique. Scanning electron microscopy (SEM) revealed smooth-like morphologies with sharp edges for the sol-gel and heterogeneous morphology for the combustion method, which included hexagonal-like structures. Moreover, largely agglomerated cubic-like particles were observed in the solid-state method. The average particle size distribution ranged from 500 to 890 nm for all methods. To evaluate photoluminescence emission properties, the samples were excited at two wavelengths, 246 and 395 nm. Intense photoluminescence emission was observed at approximately 615 nm for both excitation wavelengths across all synthesis methods; however, there were some variations in emission intensity across the synthesis methods. An intense emission peak at 615 is ascribed to 5D₀ → 7F₂ electric dipole transitions of Eu³⁺, implying efficient energy transfer between Zn₄B₆O₁₃ and Eu³⁺. The sol-gel method produced intense emission compared to other methods, meaning it is the most optimized method. The photoluminescence intensity exhibited the following trend: sol-gel > solid-state > combustion. The chromaticity diagram revealed that all prepared phosphor materials exhibited red-color emissions. Red-coloured emissions indicate successful incorporation of Eu³⁺ ions into the host lattice. The synthesized phosphor materials are potential candidates for red LEDs in solid-state lighting.

Speaker: Athenkosi Siyalo (University of the Western Cape)

489 Non-linear Evolution of Wettability in ABPBI/CNT Composites Under UV–Ozone Exposure: A Machine Learning Approach

Understanding the surface behaviour of polymer composites in Low Earth Orbit (LEO) environments is critical for the design of durable space materials. In this study, the evolution of wettability in poly(2,5-benzimidazole) (ABPBI) composites reinforced with carbon nanotubes (CNTs) under UV--ozone exposure was investigated as a proxy for oxidative processes encountered in LEO, where solar ultraviolet radiation dissociates molecular oxygen to generate highly reactive atomic oxygen species responsible for surface oxidation and degradation of polymeric materials \citep{Banks2004AO, deGroh2008AO}. Water contact angle (WCA) and surface free energy (SFE) measurements were obtained for composites with varying CNT loadings (0--3 wt.\%) subjected to controlled UV--ozone treatment times.

The experimental results reveal a distinctly non-linear evolution of wettability, characterised by an initial rapid decrease in WCA followed by fluctuations at longer exposure times \citep{NkosiInPrep2026}. This behaviour is attributed to competing surface mechanisms, including the formation of polar oxygen-containing functional groups through photo-oxidation, and the concurrent etching or removal of oxidised surface layers due to reactive oxygen species and UV-induced degradation processes \cite{Fattahi2020UVOzone, Satoh2025UVOzone, Feldman2002PhotoOxidation}.

To capture this complex behaviour, a machine learning framework was developed to model the relationship between exposure conditions and wettability response. Feature engineering techniques, including non-linear transformations of exposure time and interaction terms with CNT loading, were incorporated to reflect the underlying physical processes. Ensemble-based regression models were trained to predict WCA, demonstrating strong agreement with experimental observations and successfully reproducing the observed non-monotonic trends.

The results highlight the importance of non-linear modelling approaches in understanding surface evolution under oxidative environments. This work demonstrates that integrating experimental data with machine learning provides a powerful pathway for interpreting complex physicochemical behaviour in advanced polymer composites without relying on simplified linear assumptions.

Speaker: Siaybulela Andile Nkosi (North-West University)

SA_Nkosi_Presentation1.pptx

490 Establishing a Reproducible CVD Platform for CsPbBr3 Thin Films and Future Routes to Plasma‑ and Temperature‑Driven Heterostructure Optimization

All inorganic halide perovskites such as Caesium Lead Bromide (CsPbBr3) have continued to attract interest for optoelectronic and sensing applications, yet reproducible, contaminant free thin film growth routes have remained limited. This study reported the chemical vapour deposition (CVD) synthesis of phase pure CsPbBr3 thin films using a two-zone furnace system and provides a detailed mapping of a stable CVD growth window for this material. Systematic variation of deposition temperatures, precursor loading and other growth dynamics established a previously unreported regime that yields compact stoichiometric films. Structural and optical characterization revealed clear structure–property relationships, including grain morphology transitions, octahedral orientation-linked optical signatures, and thermally driven spectral behaviour indicative of reduced defect densities. Preliminary electrical measurements further indicated enhanced carrier transport under optimized conditions. Building on this newly defined CVD platform, current and future efforts will investigate high power plasma treatments, controlled ozone exposure, and targeted post growth annealing strategies to tailor surface chemistry, defect landscapes, and interfacial energetics to enable heterostructure engineering for next generation optoelectronic architectures.

Speakers: Christopher Arendse (University of the Western Cape), James Mercuur (University of the Western Cape)

Theoretical and Computational Physics: Annual General Meeting

Convener: Prof. Azwinndini Muronga (Nelson Mandela University)

16:00 Afternoon Tea

Applied Physics

Convener: Alan Matthews

491 Applied Physics Division AGM

Astrophysics & Space Science: Astrophysics and Space Science Division Meeting

Conveners: Ruhann Steyn (Centre for Space Research, North-West University), Geoff Beck (University of the Witwatersrand)

Nuclear, Particle and Radiation Physics -1: Session 4

Convener: Zina Ndabeni (NRF-iThemba LABS)

Nuclear, Particle and Radiation Physics -2: Session-10

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

Photonics

Physics for Development, Education and Outreach

Convener: Mphiriseni Khwanda (University of johannesburg)

492 Investigating Physical Sciences Teachers’ Perceptions and Problem-Solving Approaches in Vertical Projectile Motion

Projectile motion is a central topic in secondary school physics curricula and requires the integration of several fundamental kinematic concepts. Despite its importance, both learners and teachers often experience difficulties when solving projectile motion problems. This study investigates how Physical Sciences teachers perceive vertical projectile motion problems and the strategies they use to solve them. Ten Physical Sciences teachers participated in a professional development workshop, during which they completed a worksheet designed to assess their conceptual understanding of vertical projectile motion as well as their problem-solving approaches. To analyse the teachers’ responses, a mixed-methods approach was employed. Qualitative analysis was used to identify common themes in their responses, while a detailed rubric was applied to evaluate their problem-solving performance quantitatively. The findings suggest that although teachers recognise the value of structured problem-solving strategies, most continue to rely predominantly on procedural approaches when solving projectile motion problems. Several challenges were identified, both conceptual and procedural, particularly in selecting appropriate equations and interpreting graphical representations. These results highlight the need for professional development programmes that explicitly support teachers in developing structured and conceptually grounded problem-solving strategies in physics.

Speaker: Mark Herbert (University of the Western Cape)

493 To Evaluate the Alignment of Grade 10 Lesson Plans in Electricity and Magnetism written during COVID-19 with the South African CAPS curriculum Goals.

This study investigates the extent to which Grade 10 Electricity and Magnetism lesson plans, developed by subject advisory teams during the COVID-19 pandemic, align with the intended goals of South Africa’s Curriculum and Assessment Policy Statement (CAPS) for Physical Sciences. Electricity and Magnetism is widely regarded as a conceptually challenging topic due to its abstract nature, thereby necessitating well-structured and pedagogically sound lesson planning to support meaningful learning. Guided by Constructivist theory and Biggs’ Constructive Alignment framework, this study adopts a qualitative research approach to evaluate the coherence between learning objectives, teaching activities, and assessment strategies embedded within the lesson plans. An adapted Lesson Plan Evaluation Rubric (LPER) is employed to systematically analyse the documents. In addition, semi-structured interviews with curriculum team members and a survey of teachers are used to explore the design intentions and classroom experiences associated with these lesson plans. The study further examines the extent to which the lesson plans promote scientific inquiry, conceptual understanding, and the integration of science, technology, society, and the environment (STSE). The findings aim to contribute to improved teaching design, support effective curriculum implementation, and inform the development of resilient teaching strategies applicable in both crisis contexts and standard educational settings. Preliminary findings will be presented and discussed.

Speaker: Ronald Engelbrecht (PostGrad Student)

494 Investigating in-serves Teachers’ Perceptions and Learning Gains through Modeling Instruction in DC Electric Circuits

Electricity concepts remain challenging in Physical Sciences education. Modeling Instruction (MI) emphasizes conceptual understanding through multiple representations and active engagement. This study investigates in-service Physical Sciences teachers’ perceptions of Modeling Instruction and examines its impact on their conceptual understanding and problem-solving abilities in DC electric circuits. A group of ten teachers participated in a professional development workshop where MI strategies were implemented. Data were collected using a pre- and post-diagnostic test assessing conceptual understanding and problem-solving, as well as a Likert-scale perception questionnaire. Quantitative analysis revealed improvements in both conceptual understanding and problem-solving performance from pre- to post-test. Teachers demonstrated enhanced understanding of key concepts such as current flow, circuit completeness, series and parallel connections, and Ohm’s law. Qualitative analysis of written responses showed a shift from fragmented or procedural reasoning to more coherent scientific explanations. Perception data indicated overwhelmingly positive attitudes toward Modeling Instruction, with teachers reporting increased engagement, improved conceptual clarity, and preference over traditional teaching methods. A positive relationship was observed between teachers’ perceptions and their learning gains. The findings suggest that Modeling Instruction is an effective approach for improving both conceptual and procedural knowledge in electricity and holds promise for teacher professional development in the South African context.

Speaker: Dr Mark Herbert (University of the Western Cape)

Physics of Condensed Matter and Materials

Convener: Kingsley Onyebuchi Obodo (University of KwaZulu-Natal, Pietermaritzburg)

495 Atomistic Insights into Hydrogen Adsorption on TiAlCr-Based Alloys via DFT and HEAPs Calculations

High entropy alloys (HEAs) have garnered significant interest in a variety of applications, including hydrogen storage, due to their distinctive structural and functional characteristics. Using solid state hydrogen storage technologies to store hydrogen energy efficiently has become a major global challenge. Despite this, there is still limited understanding regarding hydrogen binding and interaction with HEAs, particularly at the atomic and electronic levels. In this work density functional theory (DFT) and HEA predicting software (HEAPs) approach were employed to investigate the thermodynamic and mechanical stability of TiAlCrFe and TiAlCrFeH1.6 alloys. The results findings demonstrated thermodynamic stability of due to negative heats of formation and mixing enthalpy. A BCC solid solution with VEC < 4.75, which suggests hydrogen storage capability, is further confirmed by the HEAPs computed results. The TiAlCrFe alloy was discovered to be mechanically stable, while TiAlCrFeH1.6 was found to become mechanically unstable, this suggests a possible outcome of hydrogen embrittlement. Furthermore, the volumetric expansion and lattice parameter were shown to rise with the injection of hydrogen content. The current findings provide useful analysis for creating sophisticated HEAs with increased hydrogen storage capacity and lower desorption.

Speaker: David Tshwane (Central University of Technology)

496 Division AGM (Physics of Condensed Matter and Materials)

Theoretical and Computational Physics

Brief Historical Tour of UWC Campus

Council Meeting with Division Chairs

17:40 Buffer

Council Dinner (by invite only)

By invite only

Friday 10 July

Registration

Plenary: (Physics Education and Development) Dr Charles Takalana and Dr Joyful Mdhluli, "Astronomy for a Better World: Connecting Knowledge, Society, and Sustainable Development"

09:25 Buffer

Applied Physics

Convener: Alan Matthews

497 A Radiography Simulator for Design, Optimisation, Performance Evaluation, Experimental Planning, and Operator Training in Neutron and X-ray Imaging Systems

Radiography is a non-destructive analytical technique that uses penetrating radiation such as neutrons and X-rays to obtain qualitative and quantitative information about the internal structure of materials. The quality of a radiograph depends strongly on system design parameters, beam characteristics, and experimental configuration, making optimisation of radiography systems a complex optimization problem. To address this challenge, a neutron and X-ray radiography simulator tool has been developed to provide a virtual environment for radiography system design, analysis, optimisation, and operator training. The simulator models image formation using a ray-tracing approach combined with the Beer–Lambert Law to describe radiation attenuation through matter. The methodology enables evaluation of the Radiography Optimisation Problem by defining parameter search spaces, analysing the effects of setup parameters on image quality, and verifying the design of key radiography system components such as the radiation source, collimator, and detector. The software simulates radiographs of homogeneous materials representing different sample regions and automatically evaluates image quality, producing outputs suitable for spatial resolution analysis using the Modulation Transfer Function method. Benchmarking against experimental radiographs demonstrates good agreement between simulated and measured results, validating the modelling approach. The simulator further serves as a tool for experimental planning and operator training, reducing experimental costs and improving preparedness. This talk will present practical applications of the radiography simulator, highlighting its role in facility design, optimisation, radiography parameter analysis and training in neutron and X-ray imaging.

Speaker: Robert Bellarmin Nshimirimana (The South African Nuclear Energy Corporation)

498 Use of Ultrasonic Atimsation Techniques to Manufacture and Recycle Metals to Powder Suitable for 3D Printing.

Metal alloy development is key in current advanced technology development. At the same time, advanced manufacturing is a new trend and involves many technologies that can be usefull in converting developed alloys into final products. Additive manufacturing is key in production of intricate structures which are rather difficult or impossible to cast using conventional methods. This may be due to alloy thermal and mechanical properties: Alloys with high hardness and high strength may be difficult or hard to craft or formulate while those with high melting temperature could also be difficult to cast as they require high melting temperature furnaces and complicated casting methods. These kinds of materials may not necessarily be used where intricate shapes are required such as in jewellery, heat exchangers or where machining needs to be minimized yet complicated shapes with less material are required. This is where metal 3D printing as additive manufacturing technology comes on its own. The technology used combination of both machinery with high electronics, laser and human touch and eye for quality control, which directly link to 5th industrial revolution. Metal 3D printing technologies differ depending on the kind of printer used. One of those printers is the Laser Powder Bed Fusion Metal machine. The printer technology uses metal powder as a feedstock and laser to melt the powder layer by layer. Generally, the particle size distribution (PSD) of the powder feed is D50 = 63 µm and the powder should be highly spherical. Nonspherical and larger particles do not flow well when layered before laser melting and may cause less quality final print with inadequate packing density, highly porous structure as well as poor surface finish. To mitigate against all drawbacks on final product, a good method for metal powder production is essential. Because not only pure metals get printed, the methos should be able to alloy rather produce alloyed metal powder with good quality characteristics or properties. Water atomizers are one of the methods for powder production, but it will result in oxidized material. Gas atomizer is another method but requires high pressure inert gas and produces a wide range of particles sizes, thus yield of specific size fractions required for applications like LPBF can be low. Plasma atomization is another method; however, it is expensive technology and can produce powder particles with gas-trapped internal pores and the formation of smaller "satellite" particles that attach to the surface, which can hinder the powder's flowability. Ultrasonic atomization, while not perfect, can produce highly spherical powder with good PSD range. Alloys can be produced with good composition and used powder and scarp prints can be recycled back to use. In this presentation, we are going to show how ultrasonic atomization techniques have been used to produce highly spherical alloy powders, a good PSD range that is suitable for LPBF metal 3D printers. A good method for alloy development and mineral beneficiation.

Speaker: Donald Mkhonto (Mintek)

499 Conversion of Pine Wood Residue for Enhanced Hydrogen Production via Catalytic Pyrolysis Process

The increasing generation of solid waste and rising demand for sustainable energy have intensified interest in efficient waste-to-energy technologies. Thermochemical conversion processes, particularly gasification and pyrolysis, provide viable routes for transforming biomass into hydrogen-rich synthesis gas. However, limitations in hydrogen yield and process efficiency remain due to incomplete conversion and suboptimal operating conditions. This study investigates an integrated catalytic pyrolysis system aimed at enhancing hydrogen production through improved reaction dynamics and process optimisation. Pine wood residue was characterised prior to conversion to establish its thermal and compositional properties. Proximate analysis using thermogravimetric analysis (TGA) revealed a three-stage degradation profile consisting of moisture release, devolatilisation of hemicellulose and cellulose, and gradual lignin decomposition, reflecting its suitability for thermochemical conversion. Ultimate analysis via CHN indicated carbon content of
42.97–43.22%, hydrogen
6.80–8.70%, and low nitrogen (0.12–0.15%), supporting its potential for clean syngas production. The composition of the produced syngas was quantified using gas chromatography (GC), enabling evaluation of key gaseous species. The influence of catalysts, including Ni(NO₃)₂ and Co(NO₃)₂, and operational parameters such as temperature, heating rate, and feedstock-to-catalyst ratio were systematically investigated. Ni(NO₃)₂ exhibited superior catalytic performance, yielding higher hydrogen concentrations, particularly at elevated temperatures. These findings demonstrate that catalyst-assisted pyrolysis enhances reaction efficiency and hydrogen yield, contributing to the development of optimised waste-to-energy systems.

Speaker: Mithayelanga Mazitshana (Cput)

Mithayelanga Mazitshana_SAIP 2026 Presentation.pptx

Astrophysics & Space Science: Astrophysics: Session 10

Astrophysics & Space Science: Space Science: Session 10

Nuclear, Particle and Radiation Physics -1

Nuclear, Particle and Radiation Physics -2: Session-11

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

Photonics

Physics of Condensed Matter and Materials

Convener: David Motaung (University of the Free State)

500 Density Functional Theory Study of the Electronic Properties of Group V Dopants in 2D Monolayer SiC for High-Power Electronic Application

Point defects play a critical role in semiconductors, offering opportunities to tailor and enhance device performance. Two-dimensional (2D) silicon carbide (SiC) is a recently synthesized layered material, but unlike bulk SiC, little is known about the effects of point defects in its monolayer form. In this study, hybrid density functional theory (DFT) was employed to investigate the formation, structural, electronic, and magnetic properties of N, P, As, Sb, and Bi dopants in 2D monolayer SiC. Under C-rich conditions, N, P, As, and Bi are energetically more favorable when substituted at C sites, whereas Sb is more stable at the Si site. The total magnetic moments induced by N, As, Sb, and Bi are stronger when doped at C sites than at Si sites. N consistently acts as an electron acceptor, while Bi behaves as an electron donor at both C and Si sites. P, As, and Sb can act as donors or acceptors depending on the substitution site. The defect concentration of N remains extremely low across all temperatures, whereas P shows significant thermal activation, maintaining a relatively high concentration even at 300 K. As defects are limitedly thermally activated but become favorable at elevated temperatures. Density of states analysis reveals that N, As, and Sb at C sites induce n-type semiconducting behavior, while Bi at a C site results in p-type behavior. Moreover, Sb, As, N, and P introduce sharp mid-gap states, and all dopants induce strong spin polarization. These findings provide theoretical insights into defect engineering in 2D monolayer SiC, highlighting its potential for future optoelectronic and electronic applications

Speaker: Emmanuel Igumbor (University of Johannesburg)

501 Mitigation of Helium-Induced Surface Damage in SiC Using Thin Carbon Layers

Silicon carbide (SiC) is widely used as a diffusion barrier in advanced nuclear fuels; however, its performance can be compromised by helium (He)-induced surface damage, including blister formation, swelling, and surface exfoliation. In this study, the effectiveness of thin carbon films in mitigating He-induced surface degradation in SiC was investigated. Carbon layers, with thicknesses ranging from 50 to 200 nm, were deposited on SiC substrates and subjected to He ion implantation under controlled conditions (20 keV, room temperature, fluence of 1×10¹⁷ ions/cm²), followed by annealing at 1000 °C. The microstructural evolution, bubble formation, and surface morphology were characterized using Raman spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. The results demonstrated that thicker carbon coatings (greater than 100 nm) reduced defect accumulation and suppressed He-induced surface damage in SiC. These findings provide insight into the role of carbon films as protective barriers and highlight their potential to enhance the structural stability of SiC in nuclear environments. This work contributes to improving the reliability of SiC as a diffusion barrier in advanced reactor systems.

Speaker: Hesham Abdelbagi (University of Zululand)

502 Evaluation of poly(2,5-benzimidazole) against vacuum ultraviolet radiation for space applications.

The search for lightweight materials as replacements for legacy materials used in space exploration has been an ongoing endeavour. In the low Earth orbit range, various threats cause extensive degradation of spacecraft materials. For the consideration of organic materials such as polymers, one of the threats that should be considered is ultraviolet (UV) radiation [1]. The UV radiation generated by the sun makes up ~8% of the total solar radiance. A subsection of UV, from 100 to 200nm, also known as vacuum ultraviolet (VUV), has sufficient energy to cause dissociation of organic bonds [2]. The polymeric system considered for this research is poly(2,5-benzimidazole) (ABPBI). ABPBI is an inexpensive polymer that possesses great thermal and chemical properties [3-5]. This investigation utilizes both experimental and computational methods to determine the effect of VUV radiation on the ABPBI polymer. The experimental method includes exposure to VUV radiation for 1000 equivalent sun hours, and pre- and post-analyses of the surface and polymer matrix to determine the extent of degradation. Computationally, a light-matter interaction of the benzimidazole monomer was simulated using non-adiabatic quantum-classical molecular dynamics.

1. Dever, J.A., et al. Simulation of the synergistic low Earth orbit effects of vacuum thermal cycling, vacuum UV radiation, and atomic oxygen. in NASA. Goddard Space Flight Center, The Seventeenth Space Simulation Conference. Terrestrial Test for Space Success. 1992.
2. Silverman, E.M., Space environmental effects on spacecraft: LEO materials selection guide, part 1. 1995.
3. Fourie, L.F., Exploring poly (2, 5) benzimidazole enhanced with carbon nanotubes for space applications. 2023, University of the Western Cape.
4. Fourie, L.F., et al., ABPBI/MWCNT for proton radiation shielding in low earth orbit. APL Materials, 2023. 11(7).
5. Gharda, K.H., et al., Method for processing a high temperature resistant thermosetting material. 2018, Google Patents.

Speaker: Ernst Ellis (North-West University)

Side Event: Southern Africa Physics Network (SAPhysNet) Forum Meeting

Theoretical and Computational Physics

10:30 Morning Tea

Applied Physics

Convener: Alan Matthews (UKZN)

503 Numerical investigation and performance optimization of lead-free Cs2TiCl6 and CS2AgBiBr6 heterojunction solar cell using SCAP-1D

Lead-free perovskite solar cells (PSCs) have propelled to the forefront of research due to their impressive performance in solar cell applications and their non-toxicity compared to lead-based PSCs. In this study, a heterojunction PSC with the configuration FTO/C-60/CS2TiCl6/CS2AgBiBr6/WSe2/Au was simulated using the SCAP-1D simulation software, combining single and double PSCs. The lead-free single perovskite CS2TiCl3 and the double perovskite CS2AgBiBr6 served as the light absorber, while C-60 and WSe2 served as the electron and hole transport layers, respectively. Optimization of the simulated PSCs was carried out by varying the thicknesses of the hole and electron transport layers, the light absorbers, the acceptor dopant density (ADD) of the HTL and perovskite layer, the donor dopant density (DDD) of the ETL, temperature, and the series and shunt resistances. A PCE of 28.17 %, along with a fill factor (FF) of 91.03 %, short circuit current (Jsc) of 21.67 mA/cm-2, and Open circuit voltage (Voc) of 1.4285 V were obtained post optimization. The PCE obtained exceeded the highest reported values for CS2TiCl6 and CS2AgBiBr6-based single- or heterojunction PSCs, demonstrating the tremendous potential of multiple absorber layers in advancing highly efficient, non-toxic future PSCs.

Speaker: Paulinah Fasanmi (University of Johannesburg)

504 Pressure-Driven Tuning of the Optoelectronic Properties of X₂AgSbF₆ (X = K, Rb) Double Perovskites: A First-Principles Study

Halide double perovskites (HDPs) have emerged as compelling candidates for next-generation optoelectronic applications owing to their tunable band gaps, structural versatility, and environmental compatibility. Despite the known advantages of fluoride-based HDPs, this subclass remains significantly understudied. In this work, we employ density functional theory (DFT), as implemented in Quantum ESPRESSO, to investigate the tunability of the structural, electronic, mechanical, and optical properties of the antimony-fluoride double perovskites X₂AgSbF₆ (X = K, Rb) under hydrostatic pressures ranging from 0 to 100 GPa. At ambient pressure, both compounds crystallize in the cubic Fm-3m space group and are confirmed to be structurally, thermodynamically, and mechanically stable, exhibiting ductile and anisotropic behavior. They are indirect band-gap semiconductors with band gaps of 0.29–2.02 eV and strong visible-to-UV optical absorption coefficients of ~10⁵ cm⁻¹. Under applied hydrostatic pressure, the electronic band structure evolves significantly: the band gap narrows progressively with increasing pressure, indicating a pressure-induced semiconductor-to-metal transition at sufficiently high pressures. The elastic constants increase substantially with pressure, reflecting enhanced stiffness. The optical response is similarly pressure-sensitive, with absorption edges and dielectric features shifting toward lower energies under compression, broadening the potential absorption window. These results demonstrate that hydrostatic pressure is an effective tuning parameter for engineering the optoelectronic and mechanical properties of X₂AgSbF₆ (X = K, Rb), establishing these lead-free fluoride double perovskites as strong candidates for pressure-tunable optoelectronic device applications.

Speaker: Mwende Mbilo (University of Pretoria)

Astrophysics & Space Science: Astrophysics: Session 11

Astrophysics & Space Science: Space Science: Session 11

Nuclear, Particle and Radiation Physics -1

Nuclear, Particle and Radiation Physics -2: Session-12

division-saip2026_mk.pptx

iThemba LABS Briefly-SAIP2026-v0.pptx

Photonics

Physics of Condensed Matter and Materials

Convener: Hendrik Swart (University of the Free State)

505 Photoactive Hybrid Nanodevices for Neuromorphic Systems and Collective Coulomb Blockade Architectures

Neuromorphic computing seeks to replicate the adaptive, parallel, and energy-efficient information processing of biological neural systems. Although existing hardware platforms have demonstrated important progress, many remain constrained by the complexity, size, and power demands of conventional transistor-based architectures. This has motivated the search for compact nanoscale devices capable of integrating memory, switching, and signal-processing functions within a single physical unit.
In this work, we demonstrate a hybrid photoactive nanodevice architecture designed as a functional building block for next-generation neuromorphic systems. The device exhibits light-responsive conductance modulation, non-volatile memory behaviour, and multi-level electronic states, making it well suited to emulate key synaptic operations such as learning, retention, decay, and reset. These characteristics position the device at the intersection of memristive behaviour and single-electron transistor (SET)-like functionality, offering a promising route toward highly compact and energy-efficient neuromorphic hardware.
A key feature of the platform is its ability to use optical stimuli as a control variable, enabling external tuning of device state through light exposure. Repeated illumination produces a persistent and cumulative electrical response, revealing a clear history-dependent memory effect analogous to synaptic potentiation in biological systems. The gradual evolution and retention of conductance states also support multi-valued logic and adaptive state encoding, both of which are highly desirable for artificial neural architectures.
Beyond synaptic emulation, the observed electronic behaviour suggests compatibility with room-temperature SET array concepts, where light may serve as a gating mechanism for controlling charge transport at the nanoscale. This introduces the possibility of hybrid computational platforms in which neuromorphic processing, optical programmability, and single-electron control are co-located within the same device framework.
Overall, this study highlights the potential of photoactive nanoscale devices as compact, multifunctional units for brain-inspired computing, with particular relevance to low-power neuromorphic circuits, adaptive memory systems, and future light-controlled nanoelectronic architectures.

Speaker: Prof. Richard Harris (University of the Free State)

506 Analysis of biomass-based GO for application in lithium-ion batteries for sustainable energy storage.

Green synthesis of nanomaterials has been on the rise due to the vast availability of resources and potential reduction of harmful chemicals during synthesis and overall reduction to pollutants on the environment. Conversion of biomass waste into useful materials has been one way to fight global warming, reduce pollution and offer sustainable way of industrialisation. In this study, graphene oxide is prepared from biomass waste and analysed for application in lithium-ion batteries for anode candidacy. Currently used anode materials in lithium-ion batteries (LIBs) are lacking due to limited theoretical capacity, poor structural stability, low energy density, dendrite growth and thermal runaway. Research has been ongoing in an attempt to address some of the challenges such as using composite materials, introduction of lithium ions and moving towards nanoparticles. The structural, surface morphology and chemical composition, functional groups and surface area are investigated through XRD, SEM-EDS, FTIR, and BET respectively. Electrochemical analysis suggests that GO can be further explored and properties altered to meet the requirements for full application in LIBs for improved storage capacity.

Speaker: Thokozane Mlotshwa (University of Limpopo)

507 Tailoring SnO₂ Nanoparticles via pH-Controlled Hydrothermal Synthesis for Enhanced Gas Sensing Performance

The detection and monitoring of hazardous gases, including hydrogen sulphide (H₂S), carbon monoxide (CO), nitrogen oxide (NO), sulphur dioxide (SO₂), carbon dioxide (CO₂), and liquefied petroleum gas (LPG), are essential for ensuring industrial safety and environmental health. In this study, highly sensitive and selective SnO₂ nanoparticle-based gas sensors were synthesised and characterised for multi-gas detection, with particular emphasis on H₂S. SnO₂ nanoparticles were synthesised via a hydrothermal method, with sodium hydroxide used to control the pH of the precursor solution. The structural, morphological, and optical properties were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV–Vis spectroscopy. The average crystallite sizes, estimated using Scherrer’s equation, ranged from 21 to 23 nm, in agreement with SEM observations. The optical band gap, determined from Tauc plots, varied between 3.71 eV and 3.87 eV. Gas sensing performance was evaluated using the Kinosistec system towards CO₂, SO₂, CO, LPG, NO, and H₂S target gases. Notably, the sensor based on nanostructures synthesised at pH 7.08 showed the highest response of 1,115,853 to 150 ppm H₂S, with response and recovery times of 9.94 minutes and 8.70 minutes, respectively. These results highlight the critical role of pH-controlled synthesis in enhancing SnO₂ sensor performance and demonstrate their potential for practical gas sensing applications.

Speakers: Mr Philani Mngomezulu (University of Zululand), Charles Thulani Thethwayo (University of Zululand)

508 Theoretical Investigations of the phase stability and ductility of FeCo-Nb alloys

Fe-Co alloys have attracted much attention as magneto restrictive materials for use in power generators, transformers, motors and generators for aircraft, as well as magnetic shields due to their soft magnetic characteristics. However, B2 FeCo suffers brittleness at room temperature which affects formability. The ternary alloying with BCC refractory metals such as Niobium (Nb) was considered to enhance the ductility and workability of the binary system. In this study, density functional theory was used to investigate the structural, magnetic and mechanical properties in order to track the stability and ductility of Fe50Co50-xNbx (0 ≤ x ≤ 6) alloys. It was found that the calculated lattice parameters and magnetic moments of binary alloy are in good agreement with available theoretical data. The heats of formation of Fe50Co50-xNbx alloys were found to be negative, suggesting that the structures are thermodynamically stable. Furthermore, the magnetic moments decrease minimally with the addition of Nb. This suggests that these dopants are likely to minimally reduce the magnetism of Fe50Co50. It was also revealed that doping with Nb effectively enhances the ductility of the binary Fe50Co50 system. The findings suggest that Fe50Co50-xNbx alloys can be used in manufacturing magnetic components at low temperature through forming process.

Speaker: Dr Ramogohlo Diale-Boshielo (Mintek)

509 Swift Heavy Ion Irradiation as a Post-Fabrication Tool for Tuning Schottky Barrier Characteristics in PolyanilineGraphene Nanocomposite Diodes

Fermi level pinning at metal-organic interfaces typically restricts
post-fabrication tuning of Schottky barrier diodes (SBDs), limiting
their optimization for flexible optoelectronic applications. We
demonstrate that swift heavy ion (SHI) irradiation provides a viable
nanoscale engineering approach to systematically modify interfacial
states and barrier characteristics in ITO/PANI-graphene/Al Schottky
diodes. Devices were irradiated with 36 MeV Cu³⁺ ions at fluences
ranging from 5.4×10¹² to 6.4×10¹³ ions/cm² under high vacuum at
room temperature. Current-voltage characterization revealed that
unirradiated PANI devices exhibited an ideality factor of 3.8, barrier
height of 0.885 eV, and rectification ratio of 98.6. With increasing ion fluence, both barrier height and rectification ratio decreased
systematically, while forward and reverse currents increased,
accompanied by reduced turn-on voltage. Analysis of bias dependent ideality factors showed that the interface state density
(Nss) increased exponentially and shifted toward the valence band
edge with increasing dose, indicating enhanced defect populations
at the metal-organic junction. Differential resistance measurements
confirmed that shunt resistance decreased sharply with fluence,
consistent with enhanced charge injection. At higher bias voltages,
irradiated devices transitioned from trap-limited to trap-free spacecharge-limited conduction (SCLC), with current-voltage slopes
approaching 2, consistent with Child's law and indicative of carrier
detrapping. These results establish SHI irradiation as a powerful
post-fabrication tool for controlled tuning of barrier properties in
organic Schottky devices, with implications for Schottky-type
photodetectors and low-power rectifying elements in flexible
electronics.

Speaker: Dr Daniel Chilukusha (Mulungushi University)

Side Event: Southern Africa Physics Network (SAPhysNet) Forum Meeting

Theoretical and Computational Physics

12:40 Lunch

Plenary: (Space Science) Prof Eamon Scullion

510 The Sun in Focus: From Early Telescopes to High-Resolution Physics

From its earliest presence in southern African cosmology, where the Sun was revered in San and Nguni traditions as a life-giving and regulating force, to its formal study within the Royal Astronomical Society era of systematic observation, our understanding of the Sun has evolved through a remarkable fusion of culture, geography, and technology. This plenary traces the evolution of solar observation from early sunspot sketches to modern diffraction-limited imaging with the Swedish 1-m Solar Telescope and more recently with the Daniel K Inouye 4-m Solar Telescope. These advances have transformed the Sun from a distant luminous disk into a dynamic, multi-layered plasma system, where fine-scale magnetic structuring and energy transport processes are now resolved across multiple spectral domains. The talk highlights how increasing spatial, temporal, and spectral resolution, combined with global collaborations involving institutions such as the South African Astronomical Observatory, has deepened our understanding of the coupled photosphere–chromosphere–corona system and its role in space weather. By bridging heritage, international collaboration, and cutting-edge technology, we move closer to unlocking the fundamental plasma physics governing our nearest star.

Speaker: Prof. Eamon Scullion (University of Northumbria Newcastle upon Tyne (UK))

SAIP AGM

17:30 Buffer

Gala Dinner & Prize Giving (Grandwest Casino)

SAIP2026 Gala Dinner Program.pdf