1. Academic Wits Research Publications (Faculties submissions)
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Item Dopamine Transporter Deficiency Syndrome (DTDS): expanding the clinical phenotype and precision medicine approaches(MDPI, 2023-06) Waddington, Simon N.; Ng, Joanne; Barral, Serena; Kurian, Manju A.Infantile parkinsonism-dystonia due to dopamine transporter deficiency syndrome (DTDS) is an ultrarare childhood movement disorder caused by biallelic loss-of-function mutations in the SLC6A3 gene. Advances in genomic analysis have revealed an evolving spectrum of SLC6A3-related neurological and neuropsychiatric disorders. Since the initial clinical and genetic characterisation of DTDS in 2009, there have been thirty-one published cases with a variety of protein-truncating variants (nonsense variants, splice-site changes, and deletions) and missense changes. Amino acid substitutions result in mutant proteins with impaired dopamine transporter function due to reduced transporter activity, impaired dopamine binding, reduced cell-surface expression, and aberrant posttranslational protein modification with impaired glycosylation. In this review, we provide an overview of the expanding clinical phenotype of DTDS and the precision therapies in development, including pharmacochaperones and gene therapy.Item Adaptive-Mode PAPR Reduction Algorithm for Optical OFDM Systems Leveraging Lexicographical Permutations(MDPI, 2023-06) Niwareeba, Roland; Cox, Mitchell A.; Cheng, LingIn direct current optical orthogonal frequency division multiplexing (DCO-OFDM) systems, the high peak-to-average power ratio (PAPR) has been a significant challenge. Recently, lexicographical symbol position permutation (LSPP) using random permutations has been introduced as an efficient solution to reduce high PAPR. In this paper, we aim to evaluate the effectiveness of LSPP by comparing both adjacent and interleaved lexicographical permutation sequences with random lexicographical permutation sequences. Our findings demonstrate that random permutation yields superior PAPR reduction performance results when compared to adjacent and interleaved permutation. However, in scenarios with a limited number of sub-blocks, the use of adjacent and interleaved permutation becomes more favorable, as they can eliminate the possibility of generating identical permutation sequences, a drawback of random permutation. Additionally, we propose a novel algorithm to determine the optimal number of candidate permutation sequences that can achieve acceptable PAPR reduction performance while adhering to computational complexity constraints defined by the system requirements.Item Advancing HIV Drug Resistance Technologies and Strategies: insights from South Africa’s Experience and Future Directions for Resource-Limited Settings(MDPI, 2023-06) Steegen, Kim; Hans, Lucia; van Zyl, Gert U.; Claassen, Mathilda; Khan, Aabida; Pillay, Melendhran; Govender, Subitha; Bester, Phillip A.; van Straaten, Johanna M.; Kana, Vibha; Cutler, Ewaldé; Kalimashe, Monalisa N.; Lebelo, Ramokone L.; Moloi, Mokopi B. H.Monitoring of HIV drug resistance (HIVDR) remains critical for ensuring countries attain and sustain the global goals for ending HIV as a public health threat by 2030. On an individual patient level, drug resistance results assist in ensuring unnecessary treatment switches are avoided and subsequent regimens are tailored on a case-by-case basis, should resistance be detected. Although there is a disparity in access to HIVDR testing in high-income countries compared to low- and middle-income countries (LMICS), more LMICs have now included HIVDR testing for individual patient management in some groups of patients. In this review, we describe different strategies for surveillance as well as where HIVDR testing can be implemented for individual patient management. In addition, we briefly review available technologies for HIVDR testing in LMICs, including Sanger sequencing, next-generation sequencing, and some point-of-care options. Finally, we describe how South Africa has implemented HIVDR testing in the public sector.Item Laboratory services in the context of prevention of mother‑to‑child transmission of HIV testing requirements in Copperbelt Province, Zambia: a qualitative inquiry(BioMed Central, 2023-07) Mwanza, Jonathan; Doherty, Tanya; Lubeya, Mwansa Ketty; Gray, Glenda E.; Mutale, Wilbroad; Kawonga, MaryIntroduction: Reliable and timely laboratory results are crucial for monitoring the Prevention of the Mother-to-Child Transmission (PMTCT) cascade, particularly to enable early HIV diagnosis and early intervention. We sought to explore whether and how laboratory services have been prepared to absorb new testing requirements following PMTCT Testand-Treat policy changes in three districts of Zambia. Method: We employed in-depth interviews and thematic data analysis, informed by the health system dynamic framework. Twenty-Six health workers were purposively selected and a document review of laboratory services in the context of PMTCT was undertaken. All face-to-face interviews were conducted in three local government areas in the Copperbelt Province (one urban and two rural) between February 2019 and July 2020. We extracted notes and markings from the transcripts for coding. Different codes were sorted into potential themes and the data extracted were put within the identified themes. Trustworthiness was confirmed by keeping records of all data field notes, transcripts, and reflexive journals. Results: The findings revealed that the health system inputs (infrastructure and supplies, human resources, knowledge, and information and finance) and service delivery were unequal between the rural and urban sites, and this affected the ability of health facilities to apply the new testing requirements, especially, in the rural-based health facilities. The major barriers identified include gaps in the capacity of the existing laboratory system to perform crucial PMTCT clinical and surveillance functions in a coordinated manner and insufficient skilled human resources to absorb the increased testing demands. The centralized laboratory system for HIV testing of mothers and exposed neonates meant facilities had to send specimens to other facilities and districts which resulted in high turnaround time and hence delayed HIV diagnosis. Conclusion: New guidelines implemented without sufficient capacitation of health system laboratory capacity severely limited the effectiveness of PMTCT program implementation. This study documented the areas relating to health system inputs and laboratory service delivery where greater support to enable the absorption of the new testing requirements is needed.Item Feeding through the ages: revisiting the diet of meerkats(Elsevier, 2025-02) Jubber, Walter R.; Manser, Marta B.; Fuller, AndreaWe investigated the diet and foraging behaviour of a social carnivore, the meerkat (Suricata suricatta), living in stochastic dryland, and examined seasonal, as well as age-related variation in diet. Insecta constituted the highest percentage of prey eaten (88.4%), followed by Arachnida (5.7%), Diplopoda (4.3%), and Reptilia (1.1%). Within Insecta, Coleoptera (70.4%) was the most dominant prey order in the diet, followed by Lepidoptera and Hymenoptera. There was seasonal variation in the diet of meerkats, with the three main Coleoptera families eaten year-round, but higher consumption of Coleoptera adults in the wet season than in the dry season. We found that old adult meerkats (>24 months) consumed the most large-sized prey, while sub-adults (6–10 months) had the highest prey count of small adult Carabidae beetles. Yearlings (15–24 months) ate the highest percentage of Hepialidae caterpillars. Whether the high representation of Coleoptera in the meerkat diet reflects dietary opportunism associated with the relatively high abundance of Coleoptera, or specialisation in the diet regardless of abundance, remains to be determined.Item Analysing the disciplinary power of proactive monitoring bodies(Emerald, 2025-07) Flowers, Kevin; van Zijl, Wayne; Ram, Jaywant; Warren MarounPurpose – The important role of regulatory monitoring bodies in enhancing financial statement quality is increasingly being studied. Prior research focuses on developed economies and often adopts a relatively unproblematic regulatory perspective to explain how these bodies foster compliance. This paper adopts a more critical approach by investigating the forces and processes at work by utilising a Foucauldian disciplinary power perspective on the proactive monitoring unit (PMU) regulating South African listed companies on the Johannesburg Stock Exchange. Design/methodology/approach – Seventeen semi-structured, open-ended interviews were conducted with expert financial statement preparers, auditors, regulators and academics. Open, axial and selective coding were used to analyse the interview data. Findings – The PMU isindicative of an enclosure mechanism that monitors and controlsthe financial reporting space of listed companies. Consequently, preparers and auditors resemble well-trained individuals who follow the PMU’s guidance without question. The PMU’s constant gaze, combined with the negative reputational impact of an adverse review for individual preparers and auditors, results in them presenting their financial statements in conformity with the PMU’sinterpretation. However, complete panoptic control is not achieved, as there is some resistance. Originality/value – This is one of the first studies to examine how an external monitoring body, the PMU, functions in a real-world setting. There is a limited understanding of what drives companies to comply with monitoring bodies that do not enjoy the direct force of law. This paper makes use of the novel Foucauldian framework to contribute towards understanding the disciplinary power that may be applied by the PMU.Item Testing the suitability of portable X-Ray Fluorescence (pXRF) analysis of dried herbarium specimens to detect Ni hyperaccumulators in South Africa(Elsevier, 2023-07) Balkwill, Kevin; Samojedny Jr. Thomas J.; Rajakaruna, Nishanta; Siebert, Stefan J.Metal hyperaccumulators accumulate particular metals or metalloids in their leaves to concentrations hundreds or thousands of times greater than is normal for most plants. Globally, Ni is the most often hyperaccumulated metal, with 532 hyperaccumulator species documented to date. Hyperaccumulators have attracted much attention as potential candidates for green technologies, including phytoremediation and agromining. In South Africa, six serpentinite-associated plants in the genera Berkheya and Senecio hyperaccumulate Ni (to > 0.1% of leaf tissue dry weight). It is surprising that only six of about 70 Berkheya and 290 Senecio species native to South Africa hyperaccumulate Ni, given about ∼10–20% of taxa from each genus occur on serpentinite. While it is costly and time consuming to field collect and chemically analyze leaves of all species in these genera, a novel method (portable X-Ray Fluorescence or pXRF analysis of herbarium specimens) allows for rapid (100 s of specimens/day) and non-destructive measurement of Ni in dry herbarium specimens. We tested the accuracy of this approach on known Ni hyperaccumulators vouchered at two South African herbaria (C.E. Moss Herbarium (J) of the University of the Witwatersrand and A.P. Goossens Herbarium (PUC) from North-West University). While the absolute concentrations of Ni determined by ICP-MS and pXRF were not always directly in agreement, we had 100% success in confirming those that were known to hyperaccumulate Ni with those that did not. We propose pXRF as a cheap, effective, and efficient approach to rapidly screen herbarium specimens across South Africa to discover additional metal hyperaccumulators for much-needed remediation purposes.Item Debating South Africa's approach to a lower inflation target(University of the Witwatersrand, Joahnnesburg, 2025) Willcox, OwenThis policy brief argues against lowering of the inflation target. A lower inflation target will worsen South Africa’s fiscal dynamics, leading to deeper and longer fiscal austerity, which will result in lower economic growth and employment. The arguments of the South African Reserve Bank (SARB) for a lower target are cogent but ignore the impact on government debt, and hence the negative impact on the macroeconomy at large.Item The valorisation of platinum group metals from flotation tailings: A review of challenges and opportunities(Elsevier, 2023-06) Gibson, Borbor A.K.K.; Nwaila, Glen; Manzi, Musa; Ndlovu, Sehliselo; Ghorbani, Yousef; Petersen, JochenFlotation tailings from South Africa’s platinum group minerals (PGM) represent complex polymetallic orebodies comprising a low-grade platinum group elements (PGE) content and complex mineralogical composition. Nevertheless, given the valuable mineral potential in the tailings, it is understandable that the substantial historic tailings deposits and sizeable annual production volume from primary processes represent a potential secondary resource. For several decades, valorising the PGM tailing materials received very little interest due to limitations associated with extractive metallurgical technology to achieve economically viable PGE extraction. The early 21st century saw the coming online of technologies, including but not limited to ultrafine grinding, suitable to meet challenges in primary metallurgical treatment processes to recover valuable minerals from ultrafine particle fractions, which could not otherwise be recovered. More so, such processes were critical in improving the liberation of partially liberated particles without compromising additional ultrafine generation. These technologies led to the development of re-treatment pilot tests and subsequent industrial re-treatment recovery processes. The current industrial re-treatment approach – via tertiary scavenging flotation circuits – renders profit in small increments up to 1 ~ 2% additional recovery relative to the primary plant head grade. These small increments relate to about ~12–30% PGE recovery of the feed grade to the re-treatment circuit, thereby enhancing the primary plant’s overall economics as well as aiding the supply of critical metals to meet global demands. With a focus on South Africa, this review provides an overview of (a) the current and future drivers of the precious metals global demand; (b) proffers discussion on the PGM characteristic mineralogy and the metallurgical value chain; (c) relates the parent orebodies (“reefs”) mineral characteristics to the inherent processed tailings; (d) estimates the economic potential these massive processed waste materials contain, (e) provides an overview of existing technologies that are industrially used in tailing re-treatment plants; and (f) outlines a comprehensive understanding of the nature of value minerals rejection to tailings.Item The impact of diferences in plasma glucose between glucose oxidase and hexokinase methods on estimated gestational diabetes mellitus prevalence(Nature Research, 2019-05) Dickson, Lynnsay M.; Buchmann, Eckhart J.; Janse Van Rensburg, Charl; Norris, Shane A.We evaluated the extent of measurement discordance between glucose oxidase and hexokinase laboratory methods and the efect of this on estimated gestational diabetes mellitus (GDM) prevalence in a routine clinical setting. 592 consecutive urban African women were screened for GDM. Paired venous specimens were submitted to two independent calibrated laboratories that used either method to measure plasma glucose concentrations. World Health Organisation diagnostic criteria were applied. GDM prevalence determined by the glucose oxidase and hexokinase methods was 6.9% and 5.1% respectively. The overall GDM prevalence was 9%. Only 34% of GDM positive diagnoses were common to both laboratory methods. Bland Altman plots identifed a bias of 0.2mmol/l between laboratory methods. Plasma glucose concentrations measured by the glucose oxidase method were more platykurtic in distribution. Low diagnostic agreement between laboratory methods was further indicated by a Cohen’s kappa of 0.48 (p<0.001). Reports of GDM prevalence using either the glucose oxidase or hexokinase laboratory methods may not be truly interchangeable or directly comparable.