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Recent Submissions

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Nutrient and Salinity Loading Based On The Temporal And Spatial Water Quality Data In The Upper Crocodile River Basin
(University of the Witwatersrand, Johannesburg, 2024-03) Mistry, Nikhil Jayant; Ali, K. Adam; Abiye, Tamiru
The Upper Crocodile River Basin has undergone a drastic change through anthropogenic factors such as rapid urban growth, industrial activities, agriculture and mining in the past thirty-eight years. This has led to an increase in nutrient and salinity loads with decreasing water quality. The Upper Crocodile River Basin wastewater treatment works struggle to maintain loading rates, causing partially treated wastewater to enter the river systems that increased the salinity loads. Water chemistry and discharge data from the DWS were collected, cleaned and processed; data were summated across the necessary river channels in which they are located to determine the nutrient and salinity loads in all rivers in the Upper Crocodile River Basin. The results indicated that the Hennops, Jukskei and Crocodile Rivers are responsible for the largest nutrient and salinity loading rates. Changes in land use activities and climate over the past thirty-eight years, since 1980, have drastically impacted the rate at which nutrient and salinity loads enter into the UCRB. During the early 1980s to 1990s a significant drop was observed in nutrient and salinity loading rates, spiking in the late 1990s and early 2000s, influenced by changes in water management and climatic events like the La Niña and the El Niño phenomena. The inter-basin transfer in the early 2000s and subsequent two decades have led to an overall rise in nutrient and salinity loading rates, posing serious water quality and health risks to people in the UCRB area. Mining activities, poor landfill management and leaking tailing storage facilities have resulted in increased sulphate loading rates into the UCRB. Nitrogen loading has risen due to uncontrolled waste disposal from informal settlements, industrial activities and sewage spills in the Johannesburg region. Phosphorus loading rates have risen due to agricultural fertiliser runoff, with the Jukskei River being the largest contributor to these loads in the Upper Crocodile River Basin. The loads entering the Hartbeespoort dam during summer and winter seasons in the 2016-2018 period for sulphate is 6819.24 kg/hr, 4873.62kg/hr; for nitrogen 4179.24 kg/hr, 4021.55 kg/hr and for phosphorus 40.08 kg/hr, 34.724 kg/hr, respectively. Salinity loads entering the Hartbeespoort dam during summer and winter are 42952.87 kg/hr and 27548.39 kg/hr, respectively. According to the findings, water resource management must act quickly to improve the overall quality of the water; in the upcoming ten years, as loading rates are expected to rise exponentially as a result of increased demand and stressed water use, which will lead to poor water quality. This will pose serious health and economic risks to the people of the Upper Crocodile River Basin and the populace of South Africa.
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Envisioning the Future of Fashion: The Creation And Application Of Diverse Body Pose Datasets for Real-World Virtual Try-On
(University of the Witwatersrand, Johannesburg, 2024-08) Molefe, Molefe Reabetsoe-Phenyo; Klein, Richard
Fashion presents an opportunity for research methods to unite machine learning concepts with e-commerce to meet the growing demands of consumers. A recent development in intelligent fashion research envisions how individuals might appear in different clothes based on their selection, a process known as “virtual try-on”. Our research introduces a novel dataset that ensures multi-view consistency, facilitating the effective warping and synthesis of clothing onto individuals from any given perspective or pose. This addresses a significant shortfall in existing datasets, which struggle to recognise various views, thus limiting the versatility of virtual try-on. By fine-tuning state-of-the-art architectures on our dataset, we expand the utility of virtual try-on, making them more adaptable and robust across a diverse range of scenarios. A noteworthy additional advantage of our dataset is its capacity to facilitate 3D scene reconstruction. This capability arises from utilising a sparse collection of images captured from multiple angles, which, while primarily aimed at enriching 2D virtual try-on, inadvertently supports the simulation of 3D environments. This enhancement not only broadens the practical applications of virtual try-on in the real-world but also advances the field by demonstrating a novel application of deep learning within the fashion industry, enabling more realistic and comprehensive virtual try-on experiences. Therefore, our work heralds a novel dataset and approach for virtually synthesising clothing in an accessible way for real-world scenarios.
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Investigating the DNA methylation status of the PXDN and PXDNL promoter regions in OSCC cell lines
(University of the Witwatersrand, Johannesburg, 2024-06) Sebastian, Mistral; Mavri-Damelin, Demetra
Background: Oesophageal squamous cell carcinoma (OSCC) is the most prevalent form of oesophageal cancer in South Africa. Aberrant DNA methylation is a well-established epigenetic mechanism involved in various cancers, including OSCC. This study focuses on the DNA methylation status of the peroxidasin (PXDN) and perodixasin like (PXDNL) promoter regions and the expression of PXDN and PXDNL in OSCC cell lines. PXDN consolidates the basement membrane through collagen IV unit oligomerization, influences epithelial-mesenchymal transition and correlates with poor prognosis in various cancers. PXDNL modulates the extracellular matrix (ECM) by antagonising PXDN. Since PXDNL shares domains with PXDN, that allow PXDN to interact with the ECM, it is speculated that PXDNL may possess other ECM modulation roles that require further elucidation. Dysregulated PXDNL expression also correlates with poor cancer prognosis. To date, within the context of South African derived OSCC cell lines, no studies pertaining to the DNA methylation status of the PXDN and PXDNL promoter regions and the expression of PXDN and PXDNL have been carried out. Aim: The aim of this project was to investigate the DNA methylation status of the PXDN and PXDNL promoter regions and observe PXDN and PXDNL expression in the SNO and WHCO5 OSCC cell lines. Methods: PXDN and PXDNL localisation was observed using immunofluorescence microscopy; expression of PXDN and PXDNL was quantified using western blotting and the DNA methylation status of the PXDN and PXDNL promoters was assessed using methylation specific PCR and bisulfite sequencing, respectively. Results: Immunofluorescence microscopy results indicated that both cell lines show varying degrees of PXDN and PXDNL expression. In addition, these results also showed that PXDN and PXDNL localise in the ECM. The western blotting results established that these cell lines express the canonical version of PXDN and possibly a PXDNL isoform (146kDa). Methylation specific PCR has shown that the promoter region of PXDN is differentially methylated across both cell lines. The sequencing results of the bisulfite converted PXDNL promoter region were unsuccessful. Hence, bisulfite sequencing requires further optimisation before the DNA methylation status of the PXDNL promoter region can be determined. Conclusion: This study is the first to show the novel finding that PXDN and PXDNL are expressed in South African derived OSCC cell lines. Within the context of OSCC, further investigation is warranted in order to elucidate the underlying mechanisms that these proteins play a role in. In addition, further study may determine whether a correlation exists between PXDN and PXDNL promoter methylation, protein expression as well as prognosis and whether these aspects should serve as novel markers for diagnosis and therapy. This may subsequently lead to increased OSCC patient survival rates by contributing to early diagnosis of OSCC and efficacious targeted therapeutic intervention.
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High entropy spinel oxides and iron-cobalt based electrocatalysts for rechargeable zinc-air batteries
(University of the Witwatersrand, Johannesburg, 2024-08) Mongwe, Agnes Monosi; Ozoemena, Kenneth Ikechukwu; Haruna, Aderemi B.
The development of effective and stable rechargeable zinc-air batteries (RZABs) using noble-metal free bifunctional electrocatalysts for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) has been a key challenge to its practical applications. This MSc research work strategically investigated some synthetic methods aimed at tuning the physicochemistry and electrochemical properties of two electrocatalysts (i.e., noble-metal free high entropy spinel oxide (HESOx) ((CoCuFeMnNi)3O4) and spinel Fe2CoO4 for rechargeable zinc-air batteries). For HESOx, a simple and reproducible Pechini method was used to synthesize a homogeneous nanosized electrocatalyst HESOx-550. The HESOx-550 was thereafter supported on onion-like carbon (OLC) in (1) an acidic environment to produce HESOx-550/OLCAT (where AT stands for acid-treated) and (2) a nonacidic environment to produce HESOx-550/OLC. The effects of the different synthesis environments on these three samples were thoroughly investigated using different analytical techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, thermogravimetric analysis (TGA) and Nitrogen Gas Adsorption analysis. The Nitrogen Gas Adsorption analysis results show that the HESOx-550/OLCAT has the largest surface area and more volume. The electron paramagnetic resonance (EPR) and O1s XPS data consistently proved that HESOx-550/OLCAT has improved oxygen vacancies which are essential in improving conductivity and offering abundant reaction sites. The HESOx-550/OLCAT shows the best bifunctional ORR and OER electrocatalytic performance with a bifunctionality index (ΔE) of 0.70 V in 1 M KOH. In addition, the RZAB air electrode with HESOx 550/OLCAT exhibits high areal capacity (60 mAh cm-2) and areal energy density (73.2 mWh cm-2) with a long-term cycle stability over 112 h in 6.0 M KOH and 0.2 M zinc acetate. The HESOx-550/OLCAT RZAB shows better electrochemical performance than 10wt.% Pt/C- IrO2 when cycled over 315 h under 27% depth of discharge condition. For Fe2CoO4, iron cobalt-based electrocatalysts on Vulcan carbon support were synthesized using a simple reduction method to produce two composites (FeCo-Fe2CoO4/CAnnealed), and (FeCo Fe2CoO4/CMicrowave). The physicochemical analytical methods such as XRD, XPS, Raman, TGA and Nitrogen Gas Adsorption analysis were used to investigate the samples. The electrochemical analysis showed that the FeCo-Fe2CoO4/CAnn had a very low “bifunctionality index” (ΔE) of 0.76 V and the FeCo-Fe2CoO4/CAnn air cathode RZAB demonstrated good stability for over 50 h under harsh DOD conditions (35.2%). The assembled RZABs have areal energy densities of 48.4 mWhcm-2 and 60.5 mWhcm-2 which are higher than the minimum recommended areal energy density of 35 mWhcm-2 (and better than most electrocatalysts reported in the literature). This study has significant contributions to the progress of practical applications of RZABs.
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Exploring the 95 GeV Excess with Extended Scalar Models
(University of the Witwatersrand, Johannesburg, 2024-10) Mulaudzi, Anza-Tshilidzi; Mellado, Bruce; Kumar, Mukesh
This thesis focuses on three interconnected studies investigating the presence of an additional scalar particle, S, of mass around mS ≈ 95 GeV. In the initial study, we explore the notion that an SU(2)L triplet scalar, characterised by a hypercharge Y = 0, could be the origin of the observed 95 GeV di-photon (γγ) excesses seen at ATLAS and CMS. By thoroughly examining its properties, particularly the neutral component, and considering a small mixing angle with the Standard Model Higgs boson, we uncover that this scalar naturally exhibits a substantial branching ratio to γγ. Additionally, we find that its Drell-Yan production via pp → W∗ → HH± adequately accounts for the observed excess. The second study examines how recent measurements of the W bosons’s mass by experiments such as ATLAS and CDF affect the theoretical predictions of the Two Higgs Doublet Model augmented with a Singlet Scalar (2HDM+S) model. It addresses how this model’s parameter space is further constrained by the inclusion of vector-like leptons, focusing on their impact on the muon g − 2 measurements. The third study involves exploring the potential discovery of the aforementioned scalar at future electron-positron colliders. Employing several methodologies, including the recoil mass method in e + e − collisions (e + e − → ZS, where Z → µ + µ − and S → b ¯ b), we leverage a Deep Neural Network to refine the differentiation between the Standard Model background and the targeted signal. The outcomes not only reinforce the potential for detecting the proposed scalar, but also enhance the scientific argument for the establishment of future electron-positron colliders like CEPC, FCC-ee or ILC. Together, these studies contribute valuable insights into the evolving landscape of particle physics.