Research Articles (University of Pretoria)

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A multivariate stochastic approach to determine long-term success of SA living annuity portfolios
(Actuarial Society of South Africa, 2025) Van Niekerk, Andries Jacobus; Moutzouris, Vasili; Mare, Eben; vanniekerk.dries@tuks.co.za
Success rates of living annuities within the South African retirement landscape are examined through portfolio modelling that includes domestic equities, cash, and international exposure, via the S&P 500 index. We define success rates based on Cooley’s framework, emphasising financial sustainability throughout retirement. Our approach incorporates foreign exposure by converting S&P 500 gains to South African Rand, accounting for stochastic foreign exchange rate fluctuations. Additionally, US and South African inflation rates are integrated to assess success rates in real terms, ensuring the impact of inflation on retirees’ income is accurately captured. This study incorporates stochastic correlation and stochastic volatility modelling to capture dynamic asset relationships under varied market conditions. The S&P 500 and JSE Top 40 equities are modelled with stochastic volatility, calibrated through the Efficient Method of Moments (EMM), enhancing volatility estimation for equity assets. These techniques support the analysis of optimal portfolio compositions and withdrawal strategies to maximise annuity success rates, providing evidence-based insights for retirement planning in South Africa.
Leave-group-out cross-validation for latent Gaussian models
(Institut d'Estadistica de Catalunya, 2025-07-04) Liu, Zhedong; Van Niekerk, Janet; Rue, Håvard
Evaluating the predictive performance of a statistical model is commonly done using cross-validation. Among the various methods, leave-one-out cross-validation (LOOCV) is frequently used. Originally designed for exchangeable observations, LOOCV has since been extended to other cases such as hierarchical models. However, it focuses rimarily on short-range prediction and may not fully capture long-range prediction scenarios. For structured hierarchical models, particularly those involving multiple random effects, the concepts of short- and long-range predictions become less clear, which can complicate the interpretation of LOOCV results. In this paper, we propose a complementary cross-validation framework specifically tailored for longer-range prediction in latent Gaussian models, including those with structured random effects. Our approach differs from LOOCV by excluding a carefully constructed set from the training set, which better emulates longer-range prediction conditions. Furthermore, we achieve computational efficiency by adjusting the full joint posterior for this modified cross-validation, thus eliminating the need for model refitting. This method is implemented in the R-INLA package (www.r-inla.org) and can be adapted to a variety of inferential frameworks.
Crystallisation and petrogenesis of cenozoic alkaline basaltic lavas on the Kapsiki Plateau (Moukoulvi, Far-North Cameroon) : unveiling the mantle's heterogeneity and HIMU signature
(Elsevier, 2025-06) Djamilatou, Diddi Hamadjoda; Dedzo, Merlin Gountie; Lenhardt, Nils; Tsozue, Desire; Nkengmatia, Elvis Asaah Asobo; Ngarena, Moussa Klamadji
The Kapsiki Plateau represents the northernmost extension of the Cameroon Volcanic Line (CVL) in West Africa. Unlike other regions of the CVL, this area is characterised by a higher prevalence of felsic and intermediate rocks compared to basaltic ones. Detailed investigations into the petrogenetic evolution of these rocks are currently limited. For this reason, Cenozoic alkaline basaltic lavas from the Kapsiki Plateau (Moukoulvi) were studied to enhance comprehension of their crystallisation process, genetic evolution of the magma, and insights into its petrogenesis and source mineralogy. The examined lavas are comparable to the mafic lavas that span the whole range of the CVL and demonstrate major and trace element characteristics similar to those seen in ocean island basalts (OIB). The major and trace element compositions suggest fractional crystallisation mainly including olivine, clinopyroxene, and Fe–Ti oxide with evidence of crustal contamination. The multi-element diagrams reveal consistency with those reported from other CVL volcanoes, displaying depletion of heavy rare earth elements (HREE) and enrichment of light rare elements (LREE), indicating an enriched source and the existence of garnet. The studied lavas have high large ion lithophile element (LILE) contents (Sr = 812–1065 ppm, Ba = 394–467 ppm) relative to high field strength elements (HFSE) (Sr/Zr = 3.97–4.94; average OIB = ∼1 Ba/La = 9.42–11.72; average OIB = 9.4). They also have Zr/Sm ratios (26.93–29.88) that are similar to the average OIB (Zr/Sm = 28). Moreover, the studied lavas exhibit elevated levels of incompatible trace elements (e.g., Rb, Pr, U, and Th), as well as higher Ta/Yb and Th/Yb ratios compared to normal OIB values, associated with a notable fluctuation in Nb/Ta and Zr/Hf ratios. The correlations between Th, La, U, and SiO2, coupled with the trend of the samples on Nb/Y vs. Rb/Y diagrams, indicate the influence of crustal contamination on the lavas' composition. The source of these lavas was a heterogeneous source with less than 4 % garnet that underwent partial melting of less than 2 %. The presence of a Pb depletion (Ce/Pb > 30) also implies that these magmas belong to the high μ (HIMU)-OIB type, attributed to lithospheric mantle metasomatism. The formation of these magmas involved partial melting of a mantle source evolving chemically and mineralogically over time with a HIMU composition at very low temperatures. Hydrous minerals, such as phlogopite or amphibole, may indicate modal metasomatism, supported by high Rb/Sr ratios or K2O high levels. Sr/Zr ratios (3.97–4.94) above OIB values (0.8–1.5) suggest Sr and Ba-rich fluid influence. Elevated Zr/Sm ratios (>28) and variations in Nb/Ta and Zr/Hf ratios point to metasomatic fluids or melts altering the mantle's composition. Therefore, the Moukoulvi lavas, like many CVL alkaline lavas, likely erupted from a metasomatized mantle source that was enriched in incompatible trace elements (Rb, Ba, Ce, Nb, and Zr). This enrichment is reflected in the elevated concentrations of these incompatible trace elements, as well as the relative enrichment in HFSE. The absence of temperature anomalies in the upper mantle beneath the CVL suggests that the magmatism originates from the lithospheric mantle source rather than a mantle plume.
The influence of applying a solar dish to parallel-flow configurations of a Brayton cycle
(Elsevier, 2025-03) Cockcroft, C.C.; Le Roux, Willem Gabriel; willem.leroux@up.ac.za
When adding additional pressure loss components to a Brayton cycle, parallel-flow cycles can be a viable alternative for single-shaft and twin-shaft gas turbines. This study seeks to investigate how a solar heat input, captured via a solar dish and open-cavity tubular receiver, influences various simple and recuperated parallel-flow cycle configurations. Two solar receiver placements are considered: before the combustor, and before the power turbine (which is in parallel with the cycle). Various power turbine split-off points are considered: after the compressor, after the recuperator, after the solar receiver and after the combustor. In this work, various novel solar-dish parallel-flow Brayton cycles that make use of combinations of commercial radial turbochargers to form microturbine configurations are therefore investigated. The best-performing main shaft turbocharger, the G25-550 (AR = 0.92), was selected for analysis together with the GBC14-200 or the GBC17-250 as the power turbine. Variable recuperator dimensions were also introduced to obtain maximum fuel-based thermal efficiencies while remaining within, or as close as possible to, the maximum allowable gasifier turbine inlet temperatures. For unrecuperated cycles, the cycle with the solar receiver placed before the combustor and the power turbine split-off point directly after the combustor provided the best fuel-based thermal efficiency of 7 % at a pressure ratio of 2.75 (with 14.5 kW power output). For recuperated cycles, the cycle with a split-off point directly after the compressor, flowing to both the solar receiver and power turbine, achieved the highest fuel-based thermal efficiency of 22 % at a pressure ratio of 1.5 (with 3 kW power output).
An investigation into the feasibility of using virtual environments as an induction method in SHIP® therapy
(South African Computer Society, 2025-06) Malan, Adolf Weich; Bosman, Isak de Villiers; Bothma, T.J.D. (Theodorus Jan Daniel); isak.bosman@up.ac.za
Virtual reality contributes to the successful treatment of patients by assisting those who have difficulty with the process of imagining the required visual images needed during psychotherapy. SHIP® is a form of psychotherapy that suggests that spontaneous healing is a natural tendency that emerges from within a person. It identifies certain activator images as essential pathways for accessing unconscious trauma material that needs healing. The purpose of this study was to examine whether virtual reality can be used as a medium to induce memories through the utilisation of neutral images based on the SHIP® Frame. Two groups of participants were gathered: one group underwent a traditional SHIP® session while the other group underwent the virtual induction with the aid of a head mounted display. A random clinical trial was used to determine the level of induction and identify the helpful aspects that contributed to the induction. The results indicated that virtual reality was able to assist as a cognitive stimulus as well as a cognitive proxy in the overall process of SHIP®.
Wildlife substitution equivalents based on metabolisable energy for calculating stocking densities on Southern African wildlife ranches
(South African Society for Animal Science, 2025-07-23) Shepstone, C.A.; Van Rooyen, N.; Van Rooyen, M.W.; Bothma, J. du.P.; Burroughs, Richard E.J.
This study aims to bridge the gap between the large stock unit method and the grazer and browser unit methods for estimating the stocking densities of wild herbivore ungulates on wildliferanches and reserves using both extensive and intensive production methods. Animal substitution equivalents based on metabolisable energy are calculated to estimate stocking densities; however a n annual up-to -date vegetation evaluation is required to estimate the carrying capacity of the habitat to support wild herbivore ungulates without it being degraded over time. This study provides an applied approach to how refined large stock, wild herbivore, grazer, and browser u nit equivalents can be usedeffectively. The two production methods described differ in their intensity of animal management. In the extensive wild herbivore ungulate production method, the mean animal mass is used to calculate thelarge stock, wild herbivore, grazer, and browser substitution equivalent units, while in the intensive wild herbivore ungulate production method, the mean mass per physiological state, with varying percentages of suckling offspring, is used to do so. These methods are extrapolated from mean linear transformations of the different physiological states and sexes of the different types of herbivores. The extensive wild herbivore ungulate production method is preferred when evaluating wildlife ranches focused on hunting and tourism, as wildlife census data do not incorporate the numbers of males, females, and offspring, whereas the intensive wild herbivore ungulate production method is preferred for intensive breedingsystems in which the numbers of males, females, and offspring are known.
Causes of delayed antenatal care at an urban community health centre in Gauteng, South Africa
(AOSIS, 2025-04-23) Mlambo, Siphesihle P.; Ibeziako, Ozoemena Joan
BACKGROUND : Maternal and perinatal deaths remain significant despite various strategies that have been implemented. Antenatal care (ANC) for pregnant women is crucial in reducing maternal and child mortality. Delayed ANC is associated with several maternal and foetal complications, which can be prevented through timely intervention. Previous studies have identified various factors contributing to the late initiation of ANC, and although recommendations have been made and implemented, there has been no impact. Objectives were to determine and rank the factors contributing to the delayed initiation of ANC among pregnant women attending a community health centre in the Tembisa township and to explore potential strategies for the early initiation of ANC. METHODS : A cross-sectional survey was conducted using a validated questionnaire on pregnant women attending their first ANC after 20 weeks of gestation. RESULTS : Multiple variables affecting the early initiation of ANC were identified, namely healthcare workers’ behaviour, negative attitude, operational management factors and participants’ socio-economic standing. Staff counselling, support and training in holistic maternal healthcare, as well as accurate, uniform and consistent health educational information that recognises and addresses cultural beliefs, could encourage early initiation of ANC. CONCLUSION : Staff empowerment and support for maternal health care through wellness services are crucial. Clinic operational management should adopt best practices to address prolonged time spent accessing services. Relevant health educational information for change should be provided. CONTRIBUTION : The study‘s findings offer insights into the factors that delay the timely initiation of ANC and strategies to mitigate these delays.
Seven years in limbo and counting : pushing for a comprehensive regulation of tobacco and nicotine products amidst industry pushback in South Africa
(BMJ Publishing Group, 2025) Egbe, Catherine O.; Mthembu, Zanele R.S.; Ayo-Yusuf, Olalekan Abdulwahab
No abstract available.
Conventional and unconventional monetary policy rate uncertainty and stock market volatility : a forecasting perspective
(Walter de Gruyter, 2025-09) Liu, Ruipeng; Segnon, Mawuli; Gupta, Rangan; Bouri, Elie
Theory suggests the existence of a bi-directional relationship between stock market volatility and monetary policy rate uncertainty. In light of this, we forecast volatilities of equity markets and shadow short rates (SSR) – a common metric of both conventional and unconventional monetary policy decisions, by applying a bivariate Markov-switching multifractal (MSM) model. Using daily data of eight advanced economies (Australia, Canada, Euro area, Japan, New Zealand, Switzerland, the UK, and the US) over the period of January 1995 to February 2025, we find that the bivariate MSM model outperforms, in a statistically significant manner, not only the benchmark historical volatility and the univariate MSM models, but also the Dynamic Conditional Correlation Generalized Autoregressive Conditional Heteroskedasticity (DCC-GARCH) framework, particularly at longer forecast horizons. Our findings are robust to different out-of-sample periods, and superiority of the bivariate MSM is also confirmed relative to the corresponding Generalized Autoregressive Score (GAS) model. This finding confirms the bi-directional relationship between stock market volatility and uncertainty surrounding conventional and unconventional monetary policies, which in turn has important implications for academics, investors and policymakers.
The influence of chloride ion concentration on the product layer of Ti microalloy steel under simulated marine atmospheric conditions
(Springer, 2025) Hu, Jie; Wang, Chuang-wei; Siyasiya, Charles Witness; Tang, Zheng-hua
Please read abstract in the article.
Testing exponentiality based on Gini-index characterization
(Springer, 2025-10) Akbari, Mahboubeh; Akbari, Masoumeh; Chen, Ding-Geng (Din); mahboubeh.akbarilakeh@up.ac.za
The exponential distribution possesses several important properties that make it valuable in statistical inference and applications, such as reliability analysis, queueing theory, and survival analysis. Based on a Gini-index characterization for the exponential distribution, we propose different statistics for testing exponentiality under both complete data and right-censored data. Asymptotic results of the proposed test statistics are studied and a large Monte-Carlo simulation study is designed and performed to evaluate the performance of these statistics and to compare them against the best existing tests. Simulation studies indicate that the proposed tests are comparable to the best existing methods for complete data, while offering simple implementation and robust performance across various alternatives–including IFR, DFR, and UFR–and showing particular effectiveness for small sample sizes and under IFR and UFR alternatives in right-censored data. Finally, three real data sets are used to demonstrate the applicability of the proposed tests.
Antibiotic removal in South African water using artificial neural networks and adaptive neuro-fuzzy inference system models : a review
(Elsevier, 2025-10) Keitemoge, Molly Katlo; Onu, Matthew Adah; Sadare, Olawumi Oluwafolakemi; Seedat, Naadhira; Moothi, Kapil
The growing occurrence of antibiotic residues in South African water systems poses serious environmental and public health risks, owing mostly to pharmaceutical discharge, agricultural runoff, and poor waste management. Conventional water treatment procedures frequently fail to properly remove these micropollutants, needing new predictive and analytical approaches. This review critically investigates the implementation of Artificial Neural Networks (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) models to forecast and optimize antibiotic removal from South African water bodies. To the best of our knowledge, little or no research compares the models’ respective performances in the context of the urban water cycle in South Africa. Therefore, this review elaborates on some of the pharmaceuticals (such as diclofenac sodium and tetracycline) that have been studied, as well as the challenges associated with their removal. It also emphasizes studies on modeling and predicting pharmaceutical removal from wastewater using ANN and ANFIS models. Additionally, this review considered the comparisons between ANN and ANFIS models in predicting the removal of emerging contaminants, as well as the challenges and limitations associated with these modeling techniques. The studies established that AI models achieved higher R² and lower error metrics compared to classical statistical or isotherm models.
Drought tolerance assessment of Bambara groundnut (Vigna subterranea L. Verdc) accessions based on morphological and physiological traits
(Elsevier, 2025-09) Kunene, Sithembile; Gerrano, Abe Shegro; Odindo, Alfred O.
Understanding the adaptive responses of Bambara groundnut (Vigna subterranea L. Verdc) under water-limited conditions is vital for improving resilience of this crop in semi-arid agriculture. This study evaluated the growth, yield, physiological, and photochemical responses of 24 Bambara groundnut accessions under drought stress and non-stress conditions. Significant variation (p < 0.05) was observed among accessions for key morphological traits such as leaf length, plant height, and petiole number. Drought stress markedly reduced biomass and seed yield, with Acc 97 and Acc 100 demonstrating superior yield under stress. Physiological responses showed significant declines in photosynthetic rate, stomatal conductance, and chlorophyll fluorescence parameters under drought. However, accessions such as Acc 25, Acc 61, and Acc 87 maintained relatively higher water-use efficiency and photochemical stability, indicating better drought adaptation. Drought indices highlighted Acc 200, Acc 190, and Acc 175 as promising genotypes, combining high yield potential and stress tolerance. Principal component analysis revealed that photosynthetic efficiency and biomass traits predominantly contributed to phenotypic variation under stress. Overall, this study identified genetically diverse and drought-resilient Bambara groundnut accessions with potential for targeted breeding programs aimed at enhancing drought tolerance and securing food production in marginal environments.
Investigation of Ximenia afra Sond. var. afra L. as a source of antiplasmodial and trypanocidal phytochemicals through accelerated bioactivity guided isolation
(Elsevier, 2025-11) Rudolph, Wiehan; Webster, Lauren; Graebin, Cedric; Maharaj, Vinesh J.
ETHNOPHARMACOLOGICAL RELEVANCE : Ximenia afra has been shown to be a potential source for antiprotozoal lead compounds based on its tentatively assigned phytochemistry or purely based on ethnomedicinal applications, where infusions of root, stem, and leaf mixtures, are often used for treating a wide range of parasitic ailments, including malaria and human African trypanosomiasis (HAT). Previous phytochemical analyses of extracts from the leaves showed high abundances of flavonoids and proanthocyanidins, and exhibited moderate to good activity against infections of Plasmodium sp. AIM OF THE STUDY : This study was designed to (i) Rapidly determine the bioactivity of the extract and seven corresponding fractions, from the crude extract of X. afra leaves and twigs, against both P. falciparum and Trypanosoma brucei; (ii) isolate and characterise the bioactive compound from these fractions; (iii) confirm the bioactivity of the isolated compound against P. falciparum and T. b. brucei. MATERIALS AND METHODS : An extract and fractions were produced from the mixed stems and leaves of X. afra. A set of seven polarity-based fractions were produced from the extract and evaluated in an in vitro phenotypic screen against single strains of bloodstream form P. falciparum (3D7) and T. b. brucei (Lister strain 427). High resolution mass spectrometry analysis was done on the bioactive fractions, to tentatively identify the constituents. Guided by these phytochemical profiles and the antiprotozoal activity of the fractions, a single compound was selected for targeted isolation. Quercitrin was isolated by semi-preparative high performance liquid chromatography (HPLC) and fully characterised by accurate mass analysis and nuclear magnetic resonance spectroscopy (NMR). Biological assays were done to determine the antiplasmodial and trypanocidal activities of quercitrin. RESULTS : In vitro phenotypic screening of the extract and fractions showed the mid-polar fractions exhibited significant antiplasmodial and trypanocidal activity. Tentative chemical profiling showed one of the highly bioactive fractions contained one major compound, which was then isolated. Accurate mass and NMR analyses confirmed the structure of the isolated compound as quercitrin. It was found to be active against P. falciparum (3D7), with IC50 = 2.76 μM (n = 2). However, the activity of the compound was poor against T. b. brucei (strain 427) (19 % inhibition at 25 μM; n = 1) and showed no inhibitory activity in the P. falciparum lysyl tRNAse synthetase (PfKRS1) assay. CONCLUSION : Further scientific evidence for the effectiveness of X. afra, in the treatment of malaria and HAT, was obtained. Quercitrin, for the first time, was isolated from the leaves and stems of X. afra and its activity against P. falciparum (3D7) was confirmed in vitro by phenotypic assay. Its activity against this strain was, until now, unknown. Although quercitrin alone was not a potent trypanocidal compound, the combination of it with other flavonoids and proanthocyanidins provided good activity (%-inhibition > 80 %).
South African medicinal plants traditionally used to treat gonorrhoea : a comprehensive review
(Elsevier, 2025-10) Tshikalange, Thilivhali Emmanuel; Lawal, Fatimah; Mabuza, J. Mcebisi; Bapela, Mahwahwatse Johanna
Gonorrhoea is the second most common sexually transmitted infection (STI) and a major health issue in South Africa. This review provides a detailed list of South African medicinal plants used to treat gonorrhoea. The study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Researchers used databases like Google Scholar, Scopus, ScienceDirect, and Web of Science. Search terms included “medicinal” plants, “traditional use,” “gonorrhoea,” “venereal diseases,” “sexually transmitted infections,” and “South Africa.” Plant species were verified through the South African National Biodiversity Institute (SANBI) and the New Plants of Southern Africa (NEWPOSA) online databases. A total of 28 plant species from 21 families were identified in South Africa for treating gonorrhoea. The Fabaceae and Maliaceae families, with three plant species each, were the most commonly used for this purpose. However, only 44 % of these species have undergone pharmacological testing against Neisseria gonorrhoeae. The remaining 56 % have not been evaluated for gonococcal activity. Although some phytoconstituents have been isolated, few antigonococcal compounds have been documented. Cytotoxicity tests have mostly been conducted in vitro, with limited evidence from in vivo studies. In vivo evaluations are essential for accurately determining the clinical safety of crude extracts and isolated compounds. Future research should focus on validating the antigonococcal properties of South African medicinal plants, isolating phytoconstituents, and conducting in vivo safety assessments.
Assessment of the genetic diversity of the critically endangered aloe peglerae Schonland (Asphodelaceae) by means of inter-simple sequence repeat (ISSR) markers
(Elsevier, 2025-11) Schmidt, Xander; Barker, Nigel; Frisby, Arnold Walter; nigel.barker@up.ac.za
Aloe peglerae Schönland, commonly known as the Red-hot Poker Aloe or Magaliesberg Aloe, is listed as Critically Endangered on the Red List of endangered plant species of South Africa. It is a slow growing succulent, endemic to the Magaliesberg, with a disjunct population near Krugersdorp, within the Gauteng and North West provinces of South Africa. Sharp population declines due to poaching and habitat loss have prompted both reintroduction programmes and associated studies on the genetic variability of the species across its distribution range, all in an attempt to better inform future conservation efforts. This study sampled 12 A. peglerae localities from which the genetic diversity was assessed using Inter Simple Sequence Repeat (ISSR) DNA “fingerprinting”, coupled with automated fragment detection. Three fluorescently labelled ISSR primers were used to amplify ISSR profiles from the 174 samples obtained from the 12 localities. Following rigorous data quality assessment, a final data set of 145 samples was obtained. The use of automated detection of ISSR fragments was extremely sensitive and the data set comprised over 2500 bands obtained from just three primers. Analysis of genetic variation was conducted using four different methods: STRUCTURE analysis, Networks, Phenetic analyses (using both UPGMA and Neighbour Joining (NJ)), and AMOVA. Results from these analyses indicate a gradual genetic transition between eastern and western localities along the Magaliesberg mountain range, representing one large population, as well as a completely distinct population from the Krugersdorp area. While samples from different localities usually possess enough differentiation to be generally identified as separate groups, those in close geographical proximity share sufficient similarities to suggest that conservation translocations can utilise propagules from neighbouring localities to augment and/or reintroduce depleted populations. Both in-situ and ex-situ conservation of the Krugersdorp population is urgently required, and translocations into this habitat should be done using propagules from within this population alone. This study highlights the advantages of using automated detection of ISSR fragments to provide many more data points than conventional agarose gel visualisation. As such, this approach is cost-effective and is recommended for studies assessing the genetic diversity of rare and endangered plant taxa.
Mixture models inspired by the Kolmogorov-Arnold representation theorem
(Elsevier, 2025-10) Focke, Walter Wilhelm; walter.focke@up.ac.za
Physical property models were developed to predict temperature-dependent multicomponent data using only temperature-independent binary parameters and pure component property temperature dependence. The Kolmogorov-Arnold representation theory was used to extend the linear blending rules and the Padé-like expressions describing the variation of physical properties of ideal solutions with composition. The effectiveness of correlating density, viscosity, refractive index and surface tension using this concept was tested. Ten ternary systems at either three or four different temperatures were regressed and compared to an ideal solution case. It was found that the four-parameter Kolmogorov-Arnold (KA) model performed excellently when the data regression included the full datasets. Unfortunately, the KA model may be too flexible, leading to overfitting binary data when applied to predicting ternary data.
Degradation of rhodamine B Dye on BiOIO3/Bi12O17Cl2 heterostructure photocatalyst under visible light activation
(Elsevier, 2025-10) Ogbeifun, Osemeikhian; Tichapondwa, Shepherd Masimba; Chirwa, Evans M.N.
Dye pollution resulting from industrial waste poses a substantial threat to both human health and the environment. Heterostructure composites of BiOIO3 and Bi12O17Cl2 with varying mass ratios (BiOIO3/Bi12O17Cl2-y:x) were fabricated to enhance the degradation abilities of the individual material towards dye contaminants. The rapid recombination of photogenerated electron-hole pairs in Bi12O17Cl2 and the limited photon utilisation of the visible light wavelengths by BiOIO3 were addressed in the heterojunction. The heterojunction formed between the material provides for spatial charge separation and boost of redox power of photogenerated electrons and holes. The degradation rate constant of Rhodamine B dye on BiOIO3/Bi12O17Cl2–1:1, the best performing material, under visible light in 6 h was 0.4 h−1, which is 2.7 and 4.3 times the rate constants for Bi12O17Cl2 (0.149 h−1) and BiOIO3 (0.093 h−1), respectively. The results demonstrate the contribution of heterostructure formation in improving the photocatalytic degradation process. The main species in the degradation step are hydroxyl (•OH) and superioxide (•O2–) radicals. BiOIO3/Bi12O17Cl2–1:1 has good photocatalytic stability, as 96 % efficiency retention is reported after four cycles. Thus, BiOIO3/Bi12O17Cl2–1:1 is a promising material for the degradation of dyes.
Developing a contextually relevant ECD milestone guide for South African practitioners
(AOSIS, 2025-07-17) Charge, Keren; Du Toit, Linette; Du Plessis, Danielle; Köstlin, Tabea; Wagner, Julia; Eccles, Renata; Van der Linde, Jeannie; Du Toit, Maria; maria.dutoit@up.ac.za
BACKGROUND : Two hundred and fifty million children under five in low- and middle-income countries are at risk of not achieving their developmental potential. High-quality milestone guides can help mitigate these risks but are often not contextually appropriate for countries like South Africa, because of unavailable resources and its inappropriateness in multilingual group contexts. AIM : This study aimed to develop and pilot a contextually relevant ECD milestone guide for practitioners working with preschool children (3–5 years 11 months) in low-resourced South African communities. SETTING : This study focused on ECD practitioners within low-resourced South African communities. METHODS : Data collection involved four phases: (1) An initial questionnaire and an abridged milestone guide were reviewed by an expert panel, who suggested contextual adaptations and activities, (2) The Delphi method was used to rank suggestions, (3) Virtual focus group addressed six milestones that required further consensus, (4) a pilot of the language and communication domain was conducted where six practitioners provided feedback on its usability. RESULTS : Practitioners found the milestone guide valuable and usable, supporting their work with young children in low-resourced communities. Feedback informed further refinements to improve usability and contextual relevance. CONCLUSION : The adapted milestone guide equipped practitioners in low-resourced ECD classrooms with tools to promote age-appropriate development and identify developmental delays early. By addressing these delays, the guide helps break cycles of disadvantage, enabling children to thrive and reach their full potential. CONTRIBUTION : This study offers a framework for developing contextually relevant milestone guides to support ECD practitioners in low-resourced settings.
Developmental outcomes of small infants at a high-risk clinic : a short-term longitudinal study
(AOSIS, 2025-08-14) Macaskill, Tayla-Ann; Du Toit, Maria; Eccles, Renata; Graham, Marien A.; Van der Linde, Jeannie; maria.dutoit@up.ac.za
BACKGROUND : Small infants face more developmental risks than their full-term peers, necessitating early intervention and long-term monitoring. OBJECTIVES : This study examined the longitudinal developmental and hearing outcomes of small infants attending a high-risk clinic in a South African low-income community setting. METHOD : A Short-term longitudinal within-subject descriptive study design was employed, where 28 participants underwent hearing and developmental screenings and assessments at two follow-up appointments (T1 and T2), at 6- and 12-month corrected age. Developmental outcomes, such as communication, motor and daily living skills, were evaluated using developmental screening tools (Parents Evaluation of Developmental Status [PEDS]), hearing screening (ABR MB11) and developmental assessments (Vineland-3). RESULTS : All participants underwent hearing screening, with four (14.3%) failing twice (T1 and T2) and being referred for diagnostic evaluation. Developmental screening at T1 identified concerns in communication, gross motor and social-emotional skills (28.5%). Concerns persisted across T1 and T2 in the PEDS tool, with fine motor skills emerging as a key issue at T2. Vineland-3 assessments showed improvement from T1 to T2; initial concerns in daily living (M = 104.12; standard deviation [s.d.] = 38.99) and motor skills (M = 88.82; s.d. = 45.26) were no longer present at T2, where all participants had age-appropriate developmental scores. CONCLUSION : The findings highlight the need for comprehensive, routine developmental monitoring and early intervention to address delays in small infants. Continued follow-up care and support from birth to 12 months corrected age can improve outcomes and caregiver developmental literacy. CONTRIBUTION : This study provides valuable insights for caregivers, healthcare policymakers and early intervention professionals by emphasising the importance of early screening, continuous monitoring and caregiver education in optimising developmental outcomes for small infants.

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