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Evaluating scenario based performance of DSSAT response to soil depth, initial soil water content and choice of Zea mays L. cultivar selection in semi-arid North West Province in South Africa
Rankin, Christopher James; Lumsden, Trevor; Nangombe, Shingirai S.; Landman, Willem Adolf; Beraki, Asmerom Fissehatsion; Mateyisi, Mohau (Wiley, 2026-03)
Process-based crop models are widely used to assess crop responses to climate variability, yet their performance is highly sensitive to assumptions regarding soil properties, initial soil water content and cultivar selection, particularly in spatially heterogeneous, rainfed systems. This study evaluates the performance of the DSSAT-CERES-Maize model across the North West Province of South Africa using a fine-scale, quinary catchment-based framework. Four scenario simulations were developed to examine the influence of soil depth, pre-season soil moisture and cultivar choice on simulated maize yields. Model outputs were evaluated against district-level reported yields for the 1981–1999 period using a comprehensive multi-criteria assessment framework incorporating distributional tests, correlation analysis, weighted regression and multiple performance metrics. Results indicate that DSSAT effectively reproduces inter-annual yield variability across spatial scales, with stronger agreement at the district level than at the provincial scale. Scenario performance was highly sensitive to soil depth and initial soil water assumptions, with the scenario incorporating deeper effective rooting depth and intermediate pre-season soil moisture consistently achieving superior agreement across most evaluation criteria. Cultivar selection influenced yield variability, highlighting the importance of representative genetic parameterisation in regional applications. While simulated and reported yield medians did not differ significantly at the district scale, error magnitudes and efficiency metrics varied spatially, reflecting the dominant influence of climate variability under rainfed conditions. These findings demonstrate that spatially explicit, scenario-based evaluation enhances confidence in crop model applications and provides valuable insights for agrometeorological assessments, climate adaptation planning and decision support in semi-arid, water-limited agricultural systems.
The effects of in utero HIV and antiretroviral therapy exposure on infant T-cell and monocyte activation, function, and regulation of immune-modulatory pathways
Prinsloo, Andrea; Steel, Helen Carolyn; Feucht, Ute Dagmar; Rossouw, Theresa M. (Wiley, 2026-03)
Human immunodeficiency virus (HIV) infection is characterized by chronic, systemic immune activation. It is unclear how this affects the immune system of infants born to mothers living with HIV (MLWH). The current study assessed whether maternal HIV status and in utero antiretroviral therapy (ART) exposure impact infant T-cell and monocyte activation and regulation, as well as monocyte responsiveness to stimulation at birth and early infancy. T-cell and monocyte activation and expression of immune checkpoint molecules were characterized by means of flow cytometry. Pro- and anti-inflammatory cytokine/chemokine profiles were assessed using a suspension bead array assay. Seventy-one pregnant MLWH and 77 mothers not living with HIV (MNLWH) were recruited at 22 weeks’ gestation, and mother-infant pairs were followed until 6 months postpartum. MLWH had higher percentages of CD4+ and CD8+ T-cells expressing programmed cell death protein-1 (PD-1) and a higher percentage of regulatory T-cells (Tregs). HIV-exposed-but-uninfected (HEU) infants displayed disrupted CD4+ T-cell maturation with an increased number of CD8+ T-cells expressing PD-1 at the time of birth and increased T-cell exhaustion at 10 weeks of age. Higher levels of monocyte activation were observed in MLWH with increased numbers of classical (CL) monocytes expressing CCR2 and CD80. An increased percentage of CL monocytes expressing CCR2 and CD80 was noted in HEU infants at the time of birth, which persisted at 10 weeks of age. Significantly higher levels of C-reactive protein (CRP) and non-significantly higher levels of interleukin (IL)-6 and tumor necrosis factor-alpha were observed in MLWH, indicative of hyperactivated innate inflammation. HEU infants had persistently increased levels of IL-8 and transforming growth factor (TGF)-β1, and lower levels of IL-10, IFN-γ, and CRP. The latter might be secondary to cotrimoxazole use in the HEU infants while the altered cytokine levels might be indicative of altered immune programing. In summary, this cohort study showed that maternal HIV status has a transient effect on basal infant T-cell and monocyte activation, regulation, and monocyte responsiveness, which dissipates at 6 months of age, while altered cytokine levels persisted.
Constructing mathematical models from small data sets : cell-viability model of melanoma under inhibition by MAZ-51
Anguelov, Roumen; Basson, Charlise; Bipath, Priyesh; Hlophe, Yvette Nkondo; Nadasen, Carolyn Courtney; Phiri, Avulundiah Edwin; Serem, June Cheptoo (EDP Sciences, 2026-01)
The synthetic indolinone derivative MAZ-51 is a selective inhibitor of vascular endothelial growth factor receptor 3 (VEGFR-3), a tyrosine kinase receptor essential for lymphangiogenesis and tumor progression. By competing with adenosine triphosphate (ATP) for VEGFR-3 binding, MAZ-51 blocks VEGF-C activity, thereby suppressing melanoma cell proliferation and promoting apoptosis. In this study, we employ mathematical modelling to quantify the inhibitory effects of MAZ-51 on the growth of B16-F10 melanoma cells. Cell viability is modeled as a function of both treatment duration and inhibitor concentration, providing a dynamic framework for assessing therapeutic efficacy. Our approach addresses a central challenge in mathematical biology: developing models that remain interpretable and predictive despite limited and variable data. By integrating biological insight with experimental data, we derive a parsimonious model that avoids overparameterization and yields biologically meaningful parameters. The model allows straightforward computation of pharmacological measures such as the half-maximal inhibitory concentration (IC50) and provides deeper insight into the growth rate reduction of melanoma cells under VEGFR-3 inhibition. This work highlights the utility of mathematical modelling in elucidating drug action mechanisms and in quantitatively evaluating targeted cancer therapies.
From golden age to renewal : South Africa’s Science, Technology and Innovation policy trajectory, 1994–2025
Pouris, Anastassios (Academy of Science of South Africa, 2026-05)
South Africa’s post-apartheid transformation of its science and innovation system represents one of the most ambitious undertakings in the Global South. Over the past three decades, the country has developed a National System of Innovation (NSI) aimed at promoting excellence, equity and developmental relevance. This article presents a comprehensive retrospective of the NSI’s evolution, grounded in National Innovation Systems theory, and identifies the period between 2005 and 2015 as a ‘golden age’ for research and development (R&D). It examines the influence of strategic incentives, institutional reforms and funding trajectories, while also analysing the consequences of recent fiscal retrenchment and political ambivalence. A central critique is the persistent failure to establish an independent Science, Technology and Innovation (STI) Observatory – an omission that has constrained the NSI’s capacity to inform political decision-making and secure sustained investment. The article concludes with an assessment of recent policy responses in 2025 and offers strategic recommendations for revitalising South Africa’s science and innovation landscape. SIGNIFICANCE : This article provides a critical retrospective on South Africa’s evolving National System of Innovation (NSI), situating its trajectory within global debates on science and development. By identifying the 2005–2015 period as a ‘golden age’ of R&D, it highlights the enabling role of incentives, institutional reforms and funding. Equally, it underscores the risks posed by fiscal retrenchment and policy ambivalence, particularly the absence of an independent STI Observatory. The analysis offers timely insights, presenting evidence-based recommendations to strengthen governance, secure investment and re-energise South Africa’s science and innovation system for developmental impact and global competitiveness. By explicitly situating the analysis within National Innovation Systems theory and comparative policy frameworks, the article contributes to both scholarly debates and practical policymaking.
The life and legacy of Professor Roseanne Denise Diab (1949–2026) : environmental scientist, institution builder and champion of women in science
Soodyall, Himla; Gevers, Wieland; Crewe, Robin M.; Wright, Caradee Yael (Academy of Science of South Africa, 2026-05)
It was with a sense of profound shock that the scientific community learned of the passing of Professor Roseanne Diab in January 2026. At the time of her death, she was the Vice-President of the Academy of Science of South Africa (ASSAf), and was working in the field of air quality and human health on a South African Medical Research Council contract. Roseanne’s career was divided into two parts: the first being her contributions as a university teacher and scholar in environmental science and the second being her leadership roles in higher education and in international science policy. Her contributions in both of these contexts were exemplary.