University of the Witwatersrand
  • Johannesburg, Gauteng, South Africa
Recent publications
Fungi characterized by metabolic properties are believed to efficiently synthesize several metal nanoparticles (NPs), including copper (Cu) NPs. Several studies have reported biomineralization processes for the synthesis of CuNPs. During the synthesis process, proteins play a critical role in the transformation and biologically induced biomineralization of metals by fungus. However, the interaction mechanism between fungus proteins and the NPs is not yet well established. Nonetheless, due to the greener nature of this process, fungal synthesis of CuNPs has attracted much interest in various emerging fields requiring the use of novel biomaterial-synthesized NPs. The process is also facile, cost-effective, and easily scalable as compared to chemical and physical methods. Therefore, this chapter will report on a greener approach based on fungal mechanistic synthesis of CuNPs. Microscopic and spectroscopic determination of CuNPs to understand their physicochemical characteristics is presented. Finally, the cytotoxic effect of these NPs for their application in agri-food, environmental (e.g., water), and medical treatment and sectors is briefly discussed.
Biofouling in membrane distillation (MD) severely impacts the process performance and significantly reduces membrane lifespan. Herein, polyvinylidene fluoride (PVDF) was modified with silver nanoparticles (AgNPs) embedded on cellulose nanocrystals (CNCs), mainly to endow antibacterial properties to the PVDF membrane. The synthesis of CNC-capped AgNPs was conducted via microwave assisted methods, where CNCs acted both as reducing and capping agents of AgNPs. Transmission electron microscopy (TEM) confirmed the successful synthesis of unevenly distributed AgNPs, markedly exhibiting an average diameter of 13.3 ± 3.94 nm. The antibacterial activity of CNC-capped AgNPs was assessed via minimum inhibitory concentration (MIC). Embedment of CNC-capped AgNPs on the PVDF membrane was performed via the phase-inversion technique, where tap water was used as the coagulating agent. Evaluation of the antibacterial activity of pristine PVDF and CNC/AgNP-modified PVDF membrane was assessed via disc diffusion and cell viability. Five different strains of bacteria were tested including Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Staphylococcus epidermis and Staphylococcus saprophyticus. In comparison to the unmodified PVDF membrane, the CNC/AgNP-modified PVDF membrane exhibited strong antibacterial activity, largely because of a decrease in the number of live cells (up to 98%) following contact with the modified membrane. These results indicate the potential application of CNC/AgNP-modified PVDF membrane toward mitigation of biofouling in MD and other membrane-based water purification processes.
Objective This study assessed the sensitivity and specificity of skeletal lesions to accurately diagnose TB in a pre-antibiotic South African skeletal sample. Materials A total of 435 skeletons of individuals who died before 1950 from the Raymond A. Dart Collection of Human Skeletons. 176 died of TB, 109 died of other pulmonary diseases, and 150 died of other causes. Methods The presence / absence of 23 skeletal lesions were assessed for differences in frequency between groups. Sensitivities and specificities were calculated and compared to Dangvard Pedersen et al. (2019). Results Lesions on the ventral surface of thoracic and lumbar vertebral bodies were observed significantly more often in TB and pulmonary cases than in other cause of death group and yielded a 55% probability of a true TB diagnosis, if observed. An association between skeletal lesions and TB was found for rib and vertebral lesions. Conclusions The results suggest that even when not documented to have died of TB, TB-related changes are observed in many individuals in a South African skeletal sample, indicating that they may have been infected with the disease. Significance The study provides information that can assist palaeopathologists in making inferences about the prevalence of TB in past populations. Limitations Sample sizes were small, and the inclusion of a pulmonary disease group may have confounded the results. Suggestions for further research The selection of a control group without any possible contact with TB may improve the results and should be investigated.
Objectives This article explores the perceived value, including associated strengths and challenges, of using a context-specified ethics framework to guide deliberative health technology appraisals. Methods The South African Values and Ethics for Universal Health Coverage (SAVE-UHC) approach, piloted in South Africa, consisted of 2 phases: (1) convening a national multistakeholder working group to develop a provisional ethics framework and (2) testing the provisional ethics framework through simulated health technology assessment appraisal committee meetings (SACs). Three SACs each reviewed 2 case studies of sample health interventions using the framework. Participants completed postappraisal questionnaires and engaged in focus group discussions. Results The SACs involved 27 participants across 3 provinces. Findings from the postappraisal questionnaires demonstrated general support for the SAVE-UHC approach and content of the framework, high levels of satisfaction with the recommendations produced, and general sentiment that participants were able to actively contribute to appraisals. Qualitative data showed participants perceived using a context-specified ethics framework in deliberative decision making: (1) supported wider consideration of and deliberation about morally relevant features of the health coverage decisions, thereby contributing to quality of appraisals; (2) could improve transparency; and (3) offered benefits to those directly involved in the priority-setting process. Participants also identified some challenges and concerns associated with the approach. Conclusions The SAVE-UHC approach presents a novel way to develop and pilot a locally contextualized, explicit ethics framework for health priority setting. This work highlights how the combination of a context-specified ethics framework and structured deliberative appraisals can contribute to the quality of health technology appraisals and transparency of health priority setting.
  • N. BhagwanN. Bhagwan
  • M. EvansM. Evans
Industry 4.0 technologies are reconfiguring energy value chains and changing how we understand efficiency in energy production. Using Scopus, this review identifies research gaps in Industry 4.0 technologies in the energy sectors of Germany, China and South Africa, by technology type, effect and impact. Globally, research on the energy sector is skewed toward the Internet of things, Artificial Intelligence, and Big, Real-Time Data. Publications on Machine-Human-Integration and Robotics are limited. China outnumbers Germany in research publications and, South Africa produces the least, leading to the assumption is that such technologies are missing in energy production in South Africa. The literature presents clear content foci: i. using Industry 4.0 technologies to reduce energy intensity through better process-related materials, thereby shrinking the carbon footprint; ii. growing efficiencies through smart energy systems; iii. rethinking energy policy to incentivise research in Industry 4.0 technologies, and iv. managing network securities in within energy systems. Firm-specific, empirical research on South Africa, although valuable, is scarce regarding if, where and how Industry 4.0 technologies affect energy production, increased plant productivity and revenue. The review encourages implementing firm-based, empirical studies, using actual data on Industry 4.0 technologies in energy production in South Africa. Such studies provide improved understanding of a South African energy sector facing a Fourth Industrial Revolution and in crisis, identifying how Industry 4.0 technologies may be leveraged to increase energy productivity and efficiency. Such studies will contribute to evidence-based policy on expanding Industry 4.0 technologies to create an efficient and sustainable South African energy sector.
Let Gn,δ be a collection of all simple, connected, triangle-free graphs of minimum degree δ and order n. For each integer k≥3, we show that there exists a family G of highly connected graphs Gn,δ,k, which are infinite for each δ and are such that the connected domination number γc(Gn,δ,k)≤2nδ−2, that is, the leaf number L(Gn,δ,k)≥δ−2δn+2. Further, we construct a family, F2,3⊂Gn,δ such that each graph in F2,3 has connected domination number at most 2nδ. For triangle-free graphs, the construction strengthens one of the results by Kleitman and West (1991) [13]. With the help of these graphs and some known results in the literature, we conjecture that for a simple, connected, triangle-free graph G, γc(G)≤2nδ−cδ, where 0≤cδ≤2. The aforementioned conjecture gives a guide for further research, and if true, it gives strengthened or improved results to a conjecture by Linial. We consider only simple connected graphs.
This paper demonstrates the application of smartphones as well as spectrophotometers as tools to demystify the mechanism leading to colour variation of 1,5-diphenylcarbazide functionalized gold nanoparticles (DPC-AuNPs) due to chromium addition. Colour Grab 3.6.1 app was used to capture and decode colours from samples containing DPC-AuNPs with different concentrations of hexavalent Chromium [Cr(VI)] standards. The presence of Cr(VI) aggregated DPC-AuNPs resulted in a colour change from pink to blue and a decrease in the peak intensity as accompanied by a red shift of the SPR peak to 670 nm. The R colour coordinates decreased as Cr(VI) concentration was increased to 16 µM then a rapid decrease was noted between 18–25 µM and G and B colour coordinates followed the same trend. Colour difference (∆E) increased significantly as the Cr(VI) concentration increased. A rapid decrease was noticed in the hue angle between 16–25 µM while chroma decreased significantly as the Cr(VI) concentration increased. Molecular dynamics calculation of a gold cluster was used to simulate the aggregation process. The calculated radial distribution [g(r)] from cluster models of the Cr-DPC complex was two-fold more than Cr-AuNPs. This was associated with the aggregation of gold nanoparticles leading to the appearance of the blue colour of AuNPs solution which was also supported by the intensity obtained from colour Grab. This study will potentially be applied in the future for the fabrication of a Lovibond photometer for the detection of metal ions in environmental samples.
From a land-use planning perspective, informal settlements emerge because of dysfunctions in contemporary cities, leading to inequities in living conditions and exclusions of people in spaces outside the formal planned areas of cities. This paper explores how entrepreneurship in informal settlements contributes to the co-production of public services. The paper is based on social entrepreneurship frameworks (concerned with infrastructure, environment, housing and technology) that emerged from the literature review, focusing on strategies to solve challenges in informal settlements. The essence of the review was to ascertain the nature of existing and potential entrepreneurial initiatives and the implications for actors, communities, urban governance systems and research. The Campbell collaboration systematic literature review technique was adapted (in a scoping format) as a methodology to screen relevant studies by following the PRISMA Flow statement. The literature review process involved screening 2835 articles from 109 scientific journals published between 2014 and 2022. The outcome of the literature review indicated that current research in this area differed in focus, methodology, and application of theory. It concluded that research that focuses on the contribution of entrepreneurs to the co-production of public services in informal settlements is limited. Using the knowledge that emerged from the literature review, the current study produced an entrepreneurial framework for co-producing public services in informal settlements. It also provided an overview of theoretical and practical knowledge for further research. Future researchers can use the findings of this study to align their research within the interface between entrepreneurship and land management.
The battery swapping mode (BSM) for an electric vehicle (EV) is an efficient way of replenishing energy. However, there have been perceived operation-related issues related large-scale deployment of the BSM. However, previous reviews have failed to examine the mathematical methods of the operation optimization process, which are highlighted in this work. The paper aims to provide a complete and systematic overview of the operation optimization approaches for EV battery swapping and charging stations. This work addresses the current operation mode of battery swapping networks and examines the optimization objectives, constraints, and mathematical programming methods. The paper highlights the motivations of different ownership models for establishing different objectives and discusses the merits and drawbacks of approaches in previous studies for different application scenarios. For the possible focus of future work, the paper details opportunities and challenges of dynamic service pricing, battery-to-grid scheduling, and behavior scheduling. This review aids future research of battery charging and swapping station operation and vehicle scheduling, and provides a systematic and theoretical reference for model selection.
Enterprise Resource Planning (ERP) systems are a strategic component of most organisations’ information systems and have evolved to become intelligent ERPs. ERP migrations are often marked by huge costs which is a challenge for developing economies. It remains unclear what the determinants for ERP migrations by organisations are for developing economies in the era of digital transformation. The aim of this study was to identify the factors that influence the decisions of ERP customers in developing countries to adopt intelligent ERPs. The Technological-Organisational-Environmental (TOE) and the institutional theory frameworks were used as the foundation upon which these factors were studied. The study focused on adopters and non-adopters of SAP S/4 HANA within a South African context. Guided by the positivist paradigm, a sample of 95 South African based companies was selected where four employees were targeted per company to respond to an electronic survey. Data was collected using an online data collection tool called, QuestionPro. The data was analysed through the IBM SPSS data analysis tool. The findings revealed that ICT infrastructure, availability of cyber-security systems, mimetic forces, and normative pressures are the influencing factors for intelligent ERPs adoption. The contributions of this study are discussed in this paper.
Nutrient alteration as a tool for enhancement of yields and quality of bio-oils produced from thermal conversion of microalgae has not received sufficient attention. To better understand the effect of nutrient stressing on the process, pyrolysis experiments were conducted on unstressed S. obliquus microalgae (N3), nutrient-stressed S. obliquus microalgae (N1) and its residual algae after lipid extraction (R-N1) at different temperatures (400 °C to 700 °C) and the results compared. The biomass characterization results indicated that nutrient stressed conditions altered the microalgae biomass composition and the empirical formula for N1, R-N1, and N3 microalgae biomass were CH2.00N0.07O0.71, CH2.36N0.08O0.75, and CH2.35N0.14O0.71, respectively. The maximum yield of bio-oil for N1 (46.37 wt%) and R-N1 (34.85 wt%) was obtained at 500 °C, while the highest yield of bio-oil for N3 (41.94 wt%) was obtained at 600 °C. Also, the proportion of nitrogen compounds in N3 bio-oil (47.4 %) was significantly higher than that obtained in the nutrient-stressed microalgae biomass (N1) bio-oil (5.92 %) at a pyrolysis temperature of 500 °C. Thus, the nutrient-stressed approach is considered promising to produce good-quality pyrolytic bio-oil from microalgae biomass. A predictive model was developed based on an artificial neural network (ANN) and can serve as a framework for bio-oil yield prediction.
Membrane distillation (MD) is envisaged as a cost-effective alternative technology for water desalination. When operated by low-grade energy, MD surpasses the cost challenges faced by other water desalination technologies. Further,...
Short video games saw explosive growth and due to their rich content and strong communication features have provided a new marketing platform for corporate commercial activities. However, few studies have examined how to implement a gamification strategy on short-form video platforms. Based on Expectation Violation Theory, this study explored the impacts of three aspects of users' gamification interaction expectation violations on negative use behavior. By collecting and analyzing two waves of data with 320 matched samples, this study revealed that reward expectation violation, achievement expectation violation, and competition expectation violation of users' gamified interactions could predict negative use behaviors. Psychological resistance and emotional exhaustion mediated the effects of gamification expectation violations on users' negative use behaviors. Further, moral licensing negatively moderated the influence of gamification expectation violations on psychological resistance, but the moderation effect of moral licensing between gamification expectation violations and emotional exhaustion was not significant.
In 1987, Phillip Tobias published a comprehensive anatomical analysis of the endocasts attributed to Homo habilis, discussing issues dealing with brain size, sulcal patterns, and vascular traces. He suggested that the neuroanatomy of this species evidenced a clear change toward many cerebral traits associated with our genus, mostly when concerning the morphology of the frontal and parietal cortex. After more than 30 years, the fossil record associated with this taxon has not grown that much, but we have much more information on cranial and brain biology, and we are using a larger array of digital methods to investigate the paleoneurological variation observed in the human genus. Brain volume, the size of the frontal lobe, or the gross hemispheric asymmetries are still relevant issues, but they are considered to be less central than before. More attention is instead being paid to the cortical organization, the relationships with the cranial architecture, and the influence of molecular or ecological factors. Although the field of paleoneurology can currently count on a larger range of tools and principles, there is still a general lack of anatomical information on many endocranial traits. This aspect is probably crucial for the agenda of paleoneurology. More importantly, the whole science is undergoing a delicate change, because of the growing influence of the social environment. In this sense, the disciplines working with fossils (and, in particular, with brain evolution) should take particular care to maintain a healthy professional situation, avoiding an excess of speculation and overstatement.
The scarcity of suitable high-resolution archives, such as ancient natural lakes, that span beyond the Holocene, hinders long-term late Quaternary temperature reconstructions in southern Africa. Here we target two cores from Mfabeni Peatland, one of the few long continuous terrestrial archives in South Africa that reaches into the Pleistocene, to generate a composite temperature record spanning the last ∼43 kyr. The Mfabeni Peatland has previously been proven suitable for temperature and hydrological reconstructions based on pollen and geochemical proxies. Here we use branched glycerol dialkyl glycerol tetraethers (brGDGTs) preserved in the Mfabeni peatland to derive a new quantitative air temperature record for south-east Africa. Our temperature record generally follows global trends in temperature and atmospheric CO2 concentrations, but is decoupled at times. Annual air temperatures during Marine Isotope Stage (MIS) 3 were moderately high (c. 20.5 °C), but dropped by c. 5 °C during the Last Glacial Maximum, reaching a minimum at c.16–15 ka. Asynchronous with local insolation, this cooling may have resulted from reduced sea surface temperatures linked to a northward shift in the Southern Hemisphere westerly winds. Concurrent with the southward retreat of the westerlies, and increasing sea surface temperatures offshore, warming from minimum temperatures (c. 15.0 °C) to average Holocene temperatures (c. 20.0 °C) occurred across the deglaciation. This warming was briefly but prominently interrupted by a millennial-scale cooling event of c. 3 °C at c. 2.4 ka, concurrent with a sudden change in hydrological conditions. The average Holocene temperatures of c. 20.0 °C were similar to those reconstructed for MIS 3, but after the 2.4 ka cooling period, air temperatures in the Mfabeni peat recovered and steadily increased towards the present. In summary, our record demonstrates that land temperature in eastern South Africa is highly sensitive to global drivers as well as nearby sea surface temperatures.
Background Community knowledge is a critical input for relevant health programmes and strategies. How community perceptions of risk reflect the burden of mortality is poorly understood. Objective To determine the burden of mortality reflecting community-nominated health risk factors in rural South Africa, where a complex health transition is underway. Methods Three discussion groups (total 48 participants) representing a cross-section of the community nominated health priorities through a Participatory Action Research process. A secondary analysis of Verbal Autopsy (VA) data was performed for deaths in the same community from 1993 to 2015 (n = 14,430). Using population attributable fractions (PAFs) extracted from Global Burden of Disease data for South Africa, deaths were categorised as ‘attributable at least in part’ to community-nominated risk factors if the PAF of the risk factor to the cause of death was >0. We also calculated ‘reducible mortality fractions’ (RMFs), defined as the proportions of each and all community-nominated risk factor(s) relative to all possible risk factors for deaths in the population . Results Three risk factors were nominated as the most important health concerns locally: alcohol abuse, drug abuse, and lack of safe water. Of all causes of deaths 1993–2015, over 77% (n = 11,143) were attributable at least in part to at least one community-nominated risk factor. Causes of attributable deaths, at least in part, to alcohol abuse were most common (52.6%, n = 7,591), followed by drug abuse (29.3%, n = 4,223), and lack of safe water (11.4%, n = 1,652). In terms of the RMF, alcohol use contributed the largest percentage of all possible risk factors leading to death (13.6%), then lack of safe water (7.0%), and drug abuse (1.3%) . Conclusion A substantial proportion of deaths are linked to community-nominated risk factors. Community knowledge is a critical input to understand local health risks.
Background Despite South Africa being an upper middle-income country producing enough food to sustain its population, and having an advanced social welfare system, it has high levels of food insecurity at the household-level. Food insecurity is linked to malnutrition and undernutrition in children. This manuscript addresses gaps in knowledge about food choices and practices of primary caregivers of children in receipt of South Africa’s largest cash transfer programme, the Child Support Grant (CSG). Objective The main objective of the study was to explore CSG caregivers’ foodways and the choices they made about what food to buy, where to buy it and for what reasons, in Langa in the Western Cape and Mt Frere in the Eastern Cape. Methods We conducted a total of 40 in-depth interviews and 5 focus group discussions with primary caregivers of Child Support Grant recipients younger than 5 years in the Eastern and Western Cape provinces. Results Caregivers’ food choices were less influenced by cultural practices and personal preferences, than by financial and physical constraints in terms of what and where to access food. Constraints in food choices were chiefly a consequence of the small amount of the grant, as well as a food environment that only availed foods of a certain quality and type in these low-income communities Conclusions The foodways of recipients of social assistance can only be better aligned with nutrition messaging and policy if there are changes in the monetary value of cash transfers, and the food environments of low-income households which determine access to, availability and affordability of nutritious food. Local informal food enterprises play an important role in the food system of CSG recipients and need to be considered in any strategies that seek to reform the food system of low-income communities in South Africa and similar settings
This study examines the effect of exchange rate shocks on ten (10) sectoral stock returns in Nigeria from January 2007 to December 2018. The autoregressive distributed lag and nonlinear autoregressive distributed lag are employed to examine symmetric and asymmetric relationship between exchange rate and sectoral stock returns. The result shows that only financial service sector moves in an asymmetric fashion in the short and long period without taking account of structural breaks and with structural breaks, none of the sectoral stock returns were asymmetric. The result shows that exchange rate movement affects the sectors differently. Therefore, this study concludes that a single model cannot fit all the sectoral stock returns because all sectors respond differently to exchange rate movements and the information about a particular sector cannot be used to forecast other sectors. These results offer important insights for investors, regulators and policymakers.
Background Overweight and obesity are major risk factors for noncommunicable diseases. This presents a major burden to health systems and to society in South Africa. Collectively, these conditions are overwhelming public healthcare. This is happening when the country has embarked on a journey to universal health coverage, hence the need to estimate the cost of overweight and obesity. Objective Our objective was to estimate the healthcare cost associated with treatment of weight-related conditions from the perspective of the South African public sector payer. Methods Using a bottom-up gross costing approach, this study draws data from multiple sources to estimate the direct healthcare cost of overweight and obesity in South Africa. Population Attributable Fractions (PAF) were calculated and multiplied by each disease’s total treatment cost to apportion costs to overweight and obesity. Annual costs were estimated for 2020. Results The total cost of overweight and obesity is estimated to be ZAR33,194 million in 2020. This represents 15.38% of government health expenditure and is equivalent to 0.67% of GDP. Annual per person cost of overweight and obesity is ZAR2,769. The overweight and obesity cost is disaggregated as follows: cancers (ZAR352 million), cardiovascular diseases (ZAR8,874 million), diabetes (ZAR19,861 million), musculoskeletal disorders (ZAR3,353 million), respiratory diseases (ZAR360 million) and digestive diseases (ZAR395 million). Sensitivity analyses show that the total overweight and obesity cost is between ZAR30,369 million and ZAR36,207 million. Conclusion This analysis has demonstrated that overweight and obesity impose a huge financial burden on the public health care system in South Africa. It suggests an urgent need for preventive, population-level interventions to reduce overweight and obesity rates. The reduction will lower the incidence, prevalence, and healthcare spending on noncommunicable diseases.
Women’s perceptions of respectful maternity care (RMC) are critical to its definition and measurement globally. We evaluated these in relation to globally defined RMC norms. We conducted a descriptive study involving eight focus group discussions with 50 pregnant women attending antenatal clinic at one primary and one secondary health facility each in the North-west and South-west local government areas of Ibadan Metropolis, Nigeria. One focus group each with primigravidae and multiparas were held per facility between 21 and 25 October 2019. Shakibazadeh et al’s 12 domains of RMC served as the thematic framework for data analysis. The women’s perceptions of RMC resonated well with seven of its domains, emphasising provider-client inter-personal relationships, preserving their dignity, effective communication, and non-abandonment of care, but with mixed perceptions for two domains. However, their perceptions deviated for four domains, namely maintaining privacy and confidentiality; ensuring continuous access to family support such as birth companions; obtaining informed consent; and respecting women’s choices about mobility during labour, food and fluid intake, and birth position. The physical environment was not mentioned as contributing to an experience of RMC. Whilst the perceptions of the Nigerian women studied about RMC were similar to those accepted internationally, there were significant deviations which may be related to cultural differences and societal disparities. Different interpretations of RMC may influence women’s demand for such care in different settings and challenge strategies for promoting a universal standard of care.
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Ananyo Choudhury
  • Sydney Brenner Institute of Molecular Bioscience
Andrew Patrick Macphail
  • Department of Internal Medicine
Lesedi Masisi
  • School of Electrical and Information Engineering
Clarence S Yah
  • School of Health Sciences
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Professor Adam Habib
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