WIReDSpace

Welcome to WIReDSpace (Wits Institutional Repository on DSpace)

For queries relating to content and technical issues, please contact IR specialists via this email address : openscholarship.library@wits.ac.za,
Tel: 011 717 4652 or 011 717 1954

Photo by @inspiredimages

Communities in WIReDSpace

Select a community to browse its collections.

Now showing 1 - 5 of 20

Recent Submissions

  • Thumbnail Image
    Item type:Item,
    The influence of El Niño Southern Oscillation (ENSO) on rainfall over the mega-dam region of South Africa
    (University of the Witwatersrand, Johannesburg, 2025-08) Abubakar, Mohamed; Steinkopf, Jessica; Engelbrecht, Francois
    This dissertation investigates the impact of the El Niño Southern Oscillation (ENSO) on rainfall variability over the eastern escarpment of South Africa, a key water source for surrounding regions. Using observational rainfall data from the Climate Research Unit (CRU) and ERA5 reanalysis, this study analyses annual and seasonal patterns in response to different ENSO phases, namely El Niño, La Niña, and neutral conditions, from 1981 to 2023. The results show that there is significant regional variability, particularly in the eastern escarpment which tends to record higher annual rainfall compared to other parts of the country. Seasonal analysis of CRU data identifies the December-February (DJF) and September-November (SON) seasons as the wettest periods, whereas the June-August (JJA) season experiences the least rainfall. The results show a strong correlation between ENSO and rainfall variability, particularly during DJF, when El Niño events suppress rainfall, and La Niña phases enhance rainfall. Notably, the severe El Niño events of 1982/83 and 2015/16 led to severe drought conditions. ERA5 data is found to closely align with CRU observations, successfully capturing seasonal rainfall patterns and interannual rainfall variability, though ERA5 data does slightly overestimate rainfall. Composite maps highlight spatial differences in rainfall anomalies associated with ENSO events, clearly identifying the eastern escarpment as one of the regions most impacted by ENSO. Rainfall anomalies are particularly pronounced over the eastern escarpment study site, when compared to the country as a whole, especially during DJF, with El Niño phases significantly rainfall, and La Niña phases enhancing it. This study underscores the importance of understanding how ENSO shapes rainfall variability, with implications for water resource management, agricultural planning, and drought mitigation in South Africa. Improved forecasting of ENSO events could help reduce economic losses and societal impacts linked to extreme weather climates.
  • Thumbnail Image
    Item type:Item,
    Vulnerability of affordable housing to global warming in South Africa: case study of a Masonry House in Johannesburg
    (MDPI, 2023-06) Bradley, Ryan
    Global warming is expected to lead to longer and more intense heatwaves, which will have negative environmental and socioeconomic impacts around the world. South Africa is projected to experience significant warming, with surface temperatures possibly increasing by up to 3 ◦C by mid-century. This warming trend has implications for architecture, as the demand for cooling in buildings could rise dramatically. However, socioeconomic conditions in developing countries may limit the use of air conditioning to mitigate indoor overheating. In South Africa, research has shown that government provided low-cost housing structures are thermally inefficient, with temperatures occasionally exceeding outdoor levels. Residents often rely on natural ventilation and personal actions to cope with heat. However, the effects of climate change may render these strategies insufficient if energy poverty and housing improvement are not addressed. This study aims to examine the impact of global warming on a high mass, naturally ventilated, affordable housing structure in Johannesburg, South Africa. Measured operative temperature data from a long-term experimental study, alongside adaptive temperature limits to evaluate overheating, highlight the vulnerability of indoor spaces without adequate insulation and/or thermal mass. The results underscore concerns about the performance of low-cost and affordable housing in warmer future climates in the South African interior
  • Thumbnail Image
    Item type:Item,
    Understanding the female athlete: molecular mechanisms underpinning menstrual phase differences in exercise metabolism
    (Springer, 2023) Oosthuyse, Tanja; Strauss, Juliette A.; Hackney, Anthony C.
    Research should equitably reflect responses in men and women. Including women in research, however, necessitates an understanding of the ovarian hormones and menstrual phase variations in both cellular and systems physiology. This review outlines recent advances in the multiplicity of ovarian hormone molecular signaling that elucidates the mechanisms for menstrual phase variability in exercise metabolism. The prominent endogenous estrogen, 17-β-estradiol (E2), molecular structure is bioactive in stabilizing plasma membranes and quenching free radicals and both E2 and progesterone (P4) promote the expression of antioxidant enzymes attenuating exercise-induced muscle damage in the late follicular (LF) and mid-luteal (ML) phases. E2 and P4 bind nuclear hormone receptors and membrane-bound receptors to regulate gene expression directly or indirectly, which importantly includes cross-regulated expression of their own receptors. Activation of membrane-bound receptors also regulates kinases causing rapid cellular responses. Careful analysis of these signaling pathways explains menstrual phase-specific differences. Namely, E2-promoted plasma glucose uptake during exercise, via GLUT4 expression and kinases, is nullified by E2-dominant suppression of gluconeogenic gene expression in LF and ML phases, ameliorated by carbohydrate ingestion. E2 signaling maximizes fat oxidation capacity in LF and ML phases, pending low-moderate exercise intensities, restricted nutrient availability, and high E2:P4 ratios. P4 increases protein catabolism during the luteal phase by indeterminate mechanisms. Satellite cell function supported by E2-targeted gene expression is countered by P4, explaining greater muscle strengthening from follicular phase-based training. In totality, this integrative review provides causative effects, supported by meta-analyses for quantitative actuality, highlighting research opportunities and evidence-based relevance for female athletes.
  • Thumbnail Image
    Item type:Item,
    Elastic constants of titanium carbide films using surface Brillouin scattering
    (Elsevier, 2023) Sumanya, C.; Wamwangi, D. M.; Jakata, K.; Comins, J. D.
    Surface Brillouin scattering (SBS) from surface phonons has been used for determining the dispersion curves of guided acoustic modes propagating along titanium carbide (TiC) films. Dispersion curves have been obtained by varying both the layer thickness and the angle of incidence. Elastic stiffnesses for the TiC on silicon and TiC on silicon carbide systems were determined from a least-squares fitting procedure of the velocity dispersion curves and used to simulate the respective SBS spectra. For each system there is good agreement between measured and calculated SBS spectra.
  • Thumbnail Image
    Item type:Item,