Rhodes University
  • Grahamstown, South Africa
Recent publications
This chapter examines the determinants of personal wellbeing among South Africans aged 60 years and older, using representative data from the South African Social Attitudes Survey (SASAS) covering 2009–2023. Wellbeing increased from 2009 to 2013 but declined steadily from 2016 to 2021, with a slight recovery in 2021–2023. Religion, personal relationships, and community belonging were highly rated domains. However, concerns about health, safety, and financial security remained, especially among the most vulnerable. Significant disparities in wellbeing exist among older persons, linked to education, employment, and subjective poverty. Higher education levels and employment status correlated with increased life satisfaction, while self-rated poverty significantly reduced wellbeing. Marital status also influenced satisfaction levels. Racial and geographic disparities were evident, with Black African and rural-based older adults displaying lower wellbeing. The analysis also highlights the growing impact of digital technology, with Internet usage enhancing wellbeing, though a digital divide persists. In the context of widespread poverty and socio-economic challenges, the analysis underscores the need for comprehensive social policies focused on elder care, social assistance, healthcare, and digital inclusion to reduce inequalities and improve the quality of life of older South Africans.
Killer whales (Orcinus orca) have been documented to prey on white sharks (Carcharodon carcharias), in some cases causing localised shark displacement and triggering ecological cascades. Notably, a series of such predation events have been reported from South Africa over the last decade, with killer whales specifically targeting sharks' liver. However, observations of these interactions are rare, and knowledge of their frequency across the world's oceans remains limited. In October 2023, a 4.7 m (total length) white shark carcass washed ashore in southeastern Australia, coinciding with reports from citizen scientists of killer whales hunting a large, unidentified prey item in the area. Visual inspection of the carcass revealed that the liver, digestive, and reproductive organs were missing, and the presence of four distinctive bite wounds, one of which was characteristic of killer whale liver extraction as seen in South Africa. Genomic analyses performed on swabs taken from the bite wounds confirmed the presence of killer whale DNA in the major bite area, while the other bites were embedded with genetic material from the scavenging broadnose sevengill shark (Notorynchus cepedianus). These results provide confirmed evidence of killer whale predation on white sharks in Australia and the likely selective consumption of the liver, suggesting predations of this nature are more globally prevalent than currently assumed.
Microplastics (MPs) have been characterised in South African rivers, lakes, and the marine environment, yet we know less about MPs in subterranean environments. In this study, we assessed MP pollution in the sediment, subsurface water, and resident freshwater amphipod, Sternophysinx species across six South African subterranean cave systems. We hypothesised that MP pollution will increase with human visitations and activities in and around selected subterranean caves. We found MPs in sediments, subsurface waters, and amphipod species ranging from 4.9 ± 1.2 to 25.0 ± 6.9 particles/kg–1, 2.7 ± 0.7 to 15.0 ± 1.7 particles/L–1 and 2.1 ± 0 to 9.8 ± 3.1 particles/dry mass, respectively, with polypropylene being the most abundant polymer according to FTIR analysis. White fibres were dominant in sediments and water samples, whereas blue fibres were dominant in amphipods. Our results supported the hypothesis that MPs densities were correlated with human visitation and activities in and around the caves. The presence of MPs in subterranean caves presents a biodiversity and conservation threat to endemic and understudied cave-dwelling aquatic invertebrates, due to MPs ability to be transferable between trophic levels causing physiological constraints.
Macroplastic pollution remains a growing global environmental concern, and our understanding of its interaction with aquatic organisms is underdeveloped. It is also less clear how hydraulic biotopes influence macroinvertebrates colonisation of macroplastic relative to natural substrates. We investigated temporal and spatial patterns of macroinvertebrate colonisation on macroplastic litters in contrasting stream hydraulic biotopes (riffle, pool, and run) in minimally impacted headwater streams of Eastern Cape, South Africa. Plastic substrates of different proportions of natural and plastic litter were deployed across four sites. The Substrate group included 100% natural substrates (NS), 50% natural material and 50% plastic litters (NP), and 100% plastic (PD) litters. Each substrate group was deployed in riffle, pool, and run habitats for six months at each site. Across hydraulic biotopes, macroinvertebrate colonised substrate groups equally (PERMANOVA, p > 0.05). Macroinvertebrate diversity indices were statistically different across substrate groups in pools but not in other hydraulic habitats (PERMANOVA, p < 0.05). We observed that NS had significantly higher macroinvertebrate Margalef’s richness, Shannon, and Simpson diversity values than macroplastic substrates in pools. This difference suggests that specific-hydraulic biotope characteristics, such as sediment accretion and stream discharge, influence macroinvertebrate diversities. However, the dominant taxa had a marked presence in all substrate groups within hydraulic biotopes throughout the study, resulting in temporal variance that was not significant. Our findings highlight the importance of hydraulic biotope influence on macroinvertebrate colonisation of macroplastic substrates. It also provides a baseline for further research involving riverine macroplastic pollution.
Hybrid nanofluids are designed to improve conventional nanofluids' stability and other thermal properties. The present work investigates the flow of combined convective transport and the influence of radiation on the studied flow. A hybrid nanofluid ( Cu Al O  2 3 /water) flows through a vertically inclined stretching/shrinking sheet. To simplify the governing equations, the deterministic two-variable differential equations (PDEs) are systematically transformed into a system of one-variable differential equations by using appropriate similarity transformations. The bvp4c function of the MATLAB program is also used to solve the simplified mathematical model. The present study investigates and presents in tabular and graphical form the effects of stretching/shrinking surfaces, suction, and volume fraction of the nanoparticles on the velocity and temperature profiles as well as on the engineering quantities. The present results are first validated and confirmed as acceptable before the full calculations are performed. Overall, the results of this study show that the investigated parameters influence the flow characteristics, which can serve as a controlling factor for heat transfer.
This paper examines how dominant discourses celebrating the Bulawayo Ecobank robbery on the ‘ 4 Million Heist updates’ WhatsApp group are an expression of vicarious dissent. It draws on Eric Hobsbawm’s Social Banditry framework and the concept of vicarious dissent to reveal how the endorsement and support for the robbers underscores citizens’ anger and frustration over the state’s complicity in the prevailing social, political and economic hardships. These are punctuated by low salaries, the cash crisis, weak institutions and state-enabled corruption. This form of digital protest signals a broader demand for justice and the government’s accountability in addressing hardships facing Zimbabwe.
In this article we investigate the transparency of language in learning place value in either a Southern African indigenous language (isiXhosa, Setswana, Oshiwambo or Emakhuwa) or a European-based language (Afrikaans, English, German or Portuguese). Since language is a key mediator in developing place value understanding, it is important to investigate the ways in which the transparency of various languages may impact place value learning. A review of pertinent literature and an analysis of literal translations of number words (to thousands) of our eight languages lead us to the conclusion that Southern African indigenous languages are more accessible in their meaning, in relation to place value, than the four European-based languages spoken in Southern Africa, which we analysed. We identified two key advantages in the indigenous languages: (i) there was transparency of the ‘places’ in how numbers are named; and (ii) there was logical alignment between the spoken and symbolic representation of numbers. Despite this, many Southern African learners learn mathematics in English, Afrikaans or Portuguese even though this is not their home language (L1). This means that many learners are denied access to the transparency of the place value concepts that exist in their L1 and must manage learning place value, not only in a yet to be learned ‘foreign’ language, but also in one where they must learn to decode the idiosyncratic ‘irregularities’ of the way those languages name numbers. We conclude this article by discussing the implications of these findings for the teaching of place value in Southern African classrooms, in which indigenous learners are often learning in a European-based language that is not their L1.
n this in memoriam we want to ask your help for the one thing he didn’t accomplish: securing a stable future for his World Database of Happiness (Veenhoven 2024a), so that it will be updated regularly with new empirical findings on happiness. Veenhoven regarded the World Database of Happiness (WDH) as his life’s work. He and a team of volunteers and coworkers compiled nearly 50,000 standardized descriptions of empirical findings on happiness as subjective appreciation of life. He believed that the WDH was a solution to an ever-growing stream of research findings on happiness, which was increasingly difficult to oversee. ‘As a result, capitalization on earlier research investment is declining, and the accumulation of knowledge is stagnating’ (Veenhoven 2023, p. 7861) The field needs a place where one can quickly scan the correlates of happiness.
Forest Fruits Organic Honey Vinegar (FFOHV) is a spontaneously fermented (yeast) and acetified (Acetic Acid Bacteria—AAB) Miombo Woodland honey vinegar developed in Zambia. Live vinegars containing live microbial cultures are marketed for their probiotic health benefits. The correlation between a well‐developed gut microbiome and human health is well studied and fermented products such as live vinegar containing AAB contribute to a healthy gut microbiome. This study details a metagenomic analysis of stable, bottled FFOHV (Zambia) alongside two commercially available live vinegar products: Bragg Organic Apple Cider Vinegar (BOACV) and Nature's Source Apple Cider Vinegar (NSACV). FFOHV contained representatives of five bacterial and nine fungal genera, compared to BOACV with two bacterial and five fungal, and NSACV containing no bacterial and six fungal genera. FFOHV and BOACV showed a dominance of Komagataeibacter bacterial species. The dominant yeast was Vanrija humicola present in all three vinegar samples. FFOHV contained greater diversity of genera, with the notable species Monascus purpureus—a microbe that produces several health‐enhancing compounds. The analysis showed that FFOHV is a microbially diverse product containing several potentially health‐enhancing microbes. Graphical Abstract Text: This study presents a metagenomic analysis of Forest Fruits Organic Honey Vinegar (FFOHV) from Zambia, compared with two commercial live cider vinegars: Bragg Organic Apple Cider Vinegar (BOACV) and Nature's Source Apple Cider Vinegar (NSACV). FFOHV exhibited a richer microbial diversity, containing five bacterial and nine fungal genera, including the health‐promoting species Monascus purpureus. Both FFOHV and BOACV were dominated by Komagataeibacter species, with Vanrija humicola as the prevalent yeast across all samples. This confirmed FFOHV's unique potential probiotic benefits.
We detail the REACH radiometric system designed to enable measurements of the 21-cm neutral hydrogen line. Included is the radiometer architecture and end-to-end system simulations as well as a discussion of the challenges intrinsic to highly-calibratable system development. Following this, we share laboratory results based on the calculation of noise wave parameters utilising an over-constrained least squares approach. For five hours of integration on a custom-made source with comparable impedance to that of the antenna used in the field, we demonstrate a calibration RMSE of 80 mK. This paper therefore documents the state of the calibrator and data analysis in December 2022 in Cambridge before shipping to South Africa.
Health misinformation has long impacted public health, influencing behaviours and adherence to guidelines. Young people are one of the social groups at the centre of health communication in the digital age; they are digital ‘informavores’, meaning they actively seek out, gather, consume and share information to meet various needs. This study examines how young adults (aged 18–30) in urban locations in Nigeria navigated COVID-19 misinformation and the underlying interdependencies this implicates. Drawing on social cognitive theory, the study takes a qualitative approach, collecting data using focus groups and individual semi-structured interviews. Findings from the critical thematic analysis confirm the severity, virality and velocity with which false information about the novel coronavirus spread in parts of the country. Besides, the results reveal that the drivers of misinformation included the government, politicians, bloggers, social media influencers and citizen journalists. Young adults utilized unique verification and correction strategies, such as deliberate scepticism and curiosity, social listening and eavesdropping, personal experience and peer or citizen fact-checking. A chain of ‘interdependencies’ were fundamental to these experiences, including (inter)personal and cultural intermediaries, religion, politics, socioeconomic status, affect and emotions, among others. Young adults advocated for a proactive government, media collaboration, ethics of care and media and information literacy interventions to combat health misinformation. The findings align with the World Health Organization's public health research agenda for managing health misinformation from a sociological point of view, with the aim to foster evidence-based intervention.
This survey emphasizes the significance of Explainable AI (XAI) techniques in detecting hateful speech and misinformation/Fake news. It explores recent trends in detecting these phenomena, highlighting current research that reveals a synergistic relationship between them. Additionally, it presents recent trends in the use of XAI methods to mitigate the occurrences of hateful land Fake contents in conversations. The survey reviews state-of-the-art XAI approaches, algorithms, modeling datasets, as well as the evaluation metrics leveraged for assessing model interpretability, and thus provides a comprehensive summary table of the literature surveyed and relevant datasets. It concludes with an overview of key observations, offering insights into the prominent model explainability methods used in hate speech and misinformation detection. The research strengths, limitations are also presented, as well as perspectives and suggestions for future directions in this research domain.
Type 2 diabetes mellitus (T2DM) is a prevalent metabolic disorder with global cases expected to increase significantly in the coming decades. Existing treatments include sulphonylureas and thiazolidinediones (TZDs), which target insulin secretion and sensitivity. Hence, in this study, we have virtually designed a new hybrid of 2,4‐thiazolidinedione‐sulphonylureas 6a‐r by utilizing molecular hybridization of sulphonylurea and TZD moieties to enhance and improve their antidiabetic efficacy and bioavailability while eliminating their side effects. Furthermore, we have used computational techniques to evaluate the antidiabetic and pharmacokinetic properties of hybrids 6a‐r. The docking study of hybrids 6a‐r was assessed against five key proteins: α‐glucosidase, α‐amylase, PPAR‐γ, DPPIV, and SGLT2. The SwissADME and PkCSM results revealed the favorable pharmacokinetic profiles and acceptable toxicity. Amongst the 2,4‐thiazolidinedione‐sulphonylurea hybrids 6a‐r investigated, glitazone 6c and rhodanine 6k emerged as the best inhibitors of DPPIV and SGLT2 with binding free energies of −38.76 kcal/mol and −36.45 kcal/mol respectively, as well as corresponding docking scores of −8.78 and −6.28 kcal/mol. Furthermore, molecular dynamics simulations confirmed the stability of these binding to the enzymes' active sites. These findings suggest that glitazone and rhodanine hybrids can act as DPPIV and SGLT2 inhibitors, thus assisting in the drug discovery of new potential antidiabetic agents.
We introduce a new combined repair process to describe repairs that are initially better-than-minimal, then become minimal, before finally becoming worse-than-minimal. The extended generalized Polya process (EGPP), non-homogeneous Poisson process (NHPP), and generalized Polya process (GPP) are used to describe this repair pattern, respectively. Several useful properties are derived for the combined process under two settings: change in repair type after a specified time and change in repair type after a specified number of failures/repairs. As an application, the optimal age replacement problem is defined and its optimal solution is analyzed. Detailed numerical examples support our findings.
Pollinators are thought to play a key role in driving incipient speciation within the angiosperms. However, the mechanisms underlying floral divergence in plants with generalist pollination systems, remains understudied. Brunsvigia gregaria displays significant geographical variation in floral traits and are visited by diverse pollinator communities. Because pollinators are often shared between populations, we investigated whether specific pollinators are responsible for driving floral divergence between them. Three distinct ecotypes were identified, each dominated by three different pollinators: bees, swallowtail butterflies, and long‐proboscid flies. Across seven populations, we found a pattern of association between style length and the morphology of pollinators that visit the flowers most frequently and contact the reproductive parts most often. Furthermore, we found significant linear, quadratic and correlational selection on flower number, tepal length and style length within the butterfly‐ and bee‐dominated populations. We also found partial evidence for divergent selection on these traits between experimental sites. Our findings suggest that a handful of key pollinators that vary in their importance have the potential to drive population‐level divergence in floral traits, which may lead to pollination ecotype formation.
Along their lengths, stems experience different functional demands. Because bark and wood traits are usually studied at single points on stems, it remains unclear how carbon allocation changes along tip‐to‐base trajectories across species. We examined bark vs wood allocation by measuring cross‐sectional areas of outer and inner bark (OB and IB), IB regions (secondary phloem, cortex, and phelloderm), and wood from stem tips to bases of 35 woody angiosperm species of diverse phylogenetic lineages, climates, fire regimes, and bark morphologies. We examined how varied bark vs wood allocation was and how it was affected by precipitation, temperature, soil fertility, leaf habit, and fire regime. Allocation to phloem (relative to wood) varied little across species, whereas allocation to other tissues, strongly affected by the environment or shed in ontogeny, varied widely. Allocation to parenchyma‐rich cortex and phloem was higher at drier sites, suggesting storage. Higher allocation to phloem and cortex also occurred on infertile soils, and to phloem in drought‐deciduous vs cold‐deciduous and evergreen species. Allocation to OB was highest at sites with frequent fires and decreased with fire frequency. Our approach contextualizes inferences from across‐species studies, allows testing functional hypotheses, and contributes to disentangling the functional roles of poorly understood bark tissues.
Fundamentals of heat and fluid flow in green energy system is found as an alternative transition technique to achieving a sustainable energy system (combat climate change, energy conversion, renewable energy). Dissipation being an integral part of heat generation and energy transfer in flow medium received no or little attention on conjugate mixed convection model. Considerable attention of this Ethylene Glycol-based hybrid nanofluid is vested on the examination of the Joule and viscous dissipation effects for enhancing nuclear reactor and automotive radiator coolants in mechanical systems. The Tiwari-Das model is employed to incorporate the effects of nanoparticles in the deterministic model. This model provides a comprehensive framework for understanding how the presence of nanoparticles influences the system’s behaviour. As such, the model incorporates the dynamics of Joule heating, electric current density, Darcy, and viscous dissipation for Al2O3{\textrm{Al}}_{2}{\textrm{O}}_{3} and Cu nanoparticles in the energy conservation equation. The bivariate spectral local linearization method (BSLLM) is employed to solve the conjugate mixed convection model of Ethylene Glycol fluid suspending Al2O3{\textrm{Al}}_{2}{\textrm{O}}_{3} and Cu nanoparticles, since the governing differential equation is of the two unknown variables. During numerical and graphical simulations, results show that for cooling mechanism, the hybridized nanofluid (Ethylene Glycol + Al2O3{\textrm{Al}}_{2}{\textrm{O}}_{3} + Cu) outperformed the usual Ethylene Glycol, Ethylene Glycol + Al2O3{\textrm{Al}}_{2}{\textrm{O}}_{3} nanofluid throughout the cases considered. The results indicate that in the absence of the Eckert number, the Nusselt number decreases by 0.205%0.205\% for the nanofluid, while increasing by 4.639%4.639\% for the hybrid nanofluid. Additionally, when excluding the effects of conjugate heat transfer, the Nusselt number decreases by 11.833%11.833\% for the nanofluid and by 21.438%21.438\% for the hybrid nanofluid. Lastly, when the electric field effect is removed, the Nusselt number decreases by 9.056%9.056\% for the nanofluid and by 15.156%15.156\% for the hybrid nanofluid.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
5,170 members
Gavin Cecil Fraser
  • Department of Economics
Brett Pletschke
  • Department of Biochemistry and Microbiology
George Wells
  • Department of Computer Science
Anton Robert Krueger
  • Department of Literary Studies in English
Information
Address
Grahamstown, South Africa
Head of institution
Lex Mpati