Academy of Science of South Africa (ASSAf): Open Journal Systems
Not a member yet
8651 research outputs found
Sort by
Improved flood quantile estimation for South Africa
No full textThe performance of the most frequently used flood frequency probability distributions in South Africa (Log-Normal, Log Pearson3 and Generalised Extreme Value) were reviewed and all tend to perform poorly when lower exceedance probability frequency events are estimated, especially where outliers are present in the dataset. This can be attributed to the challenge when analysing very limited ‘samples’ of annual flood peak populations, which are an unknown. At present outliers are inadequately 'managed' by attempting to 'normalise' the flood peak dataset, which conceals the significance of the observed data. Thus, to adequately consider the outliers, this study was undertaken with the aim to improve the current statistical approach by developing a more stable and consistent methodology to estimate flood quantiles. The approach followed in the development of the new methodology, called IPZA, might be considered as unconventional, given that a multiple regression approach was used to accommodate the strongly skewed data, which are often associated with annual flood peak series. The main advantages of IPZA are consistency, the simplicity of application (only one set of frequency factors for every parameter, regardless of the skewness), the integrated handling of outliers and the use of conventional method of moments, thereby eliminating the need to adjust any moments. The performance of IPZA exceeded initial expectations. The results are more consistent and, by taking outliers into account, appear to be more sensible than existing probability distributions. It is recommended that IPZA should be used as a valuable addition to the existing set of decision-making tools for hydrologists/engineers performing flood frequency analyses
Burden of postpartum depression in sub-Saharan Africa: An updated systematic review
No full textPostpartum depression (PPD) is a significant public health concern in resource-constrained sub-Saharan Africa (SSA). Efforts to combat this burden are hampered by the region’s wide variation in reported prevalence. This review aimed to systematically synthesize up-to-date data on PPD in SSA. The review was structured per the Preferred Reporting Item for Systematic Reviews and Meta-analyses. Included in the review were studies that reported the prevalence of PPD in SSA. A search was undertaken of PubMed, Medline, CINAHL, Academic Search Complete, and PsycINFO. A random-effect model was fitted to estimate the pooled burden of postpartum depressive symptoms in SSA. We conducted subgroup analyses to estimate the distribution of postpartum depressive symptoms based on important study characteristics: sample size, the timing of diagnosis, design, study setting/region, instrument, and income/ economy. The prevalence of postpartum depressive symptoms ranged from 3.8% to 69.9%, with a pooled estimate of 22.1% (CI 18.5–26.2; I2 = 98.2; Tau = 0.848; p<0.001). There was a significant variation in postpartum depressive symptoms with sample size (p<0.001). The highest prevalence (25.6% CI 21.5–30.1) was obtained within 12 weeks postpartum. The prevalence estimate was highest (23.3%; CI 20.1–26.8) with the Edinburgh Postnatal Depression Scale (EPDS). South Africa (30.6%; CI 23.6–38.7) and Zimbabwe (29.3%; CI 22.2–37.5) reported the highest prevalence rates, while Tanzania (13.5%; CI 10.1–17.9) reported the lowest prevalence estimates. Upper-middle SSA countries presented the highest prevalence rates (30.6%; CI 23.6–38.7). The prevalence was highest within the period 2010–2015. PPD constitutes a significant health burden in SSA and is fast becoming an epidemic in southern Africa.
Significance:
Given that PPD is a recurring mental health challenge among women in sub-Saharan Africa, there is an urgent need for strategic policy provisions to ameliorate its burden.
An increase in prevalence of PPD from 2005–2010 to 2015–2021 is indicative of the need for national governments to intensify efforts targeted at achieving the UN Sustainable Development Goals 3 and 5 in the region.
In SSA, the prevalence of PPD is highest (approximately 30%) in Southern Africa, precisely South Africa and Zimbabwe, where it is fast becoming an epidemic; hence strategies are needed to curtail its growing trend.
There is a need to characterise and stratify the risk factors of PPD in sub-Saharan to guide policy development of predictive algorithms and implementation strategies
South African research contributions to Lecture Notes in Computer Science, 1973–2022
No full textLecture Notes in Computer Science (LNCS) is a globally recognised publication outlet for the field of Computer Science, including in South Africa. In this study, spanning from 1973 to 2022, we investigated the research participation of South African based authors in LNCS. The publication output and citation impact of these authors were compared to the global Computer Science and LNCS output. The authorship patterns and collaborative behaviour of South African LNCS papers were explored, and a keyword or topic analysis also conducted. Of the total of 518 662 LNCS papers published globally between 1973 and 2022, South African based researchers contributed 1150 papers (0.22%). The LNCS papers from South Africa exhibit a strong collaborative publication culture, with 1043 (91%) co-authored and 107 (9%) single-authored works. Local LNCS researchers prefer institutional collaboration (43%), followed by international (37%) and national collaboration (11%). Europe emerged as the most significant collaboration partner for LNCS researchers in South Africa. Of the 1150 papers, 836 (73%) had received citations, while 314 (27%) had not. On average, papers published by South African based authors received 6.05 citations, compared to the global LNCS average of 9.49 citations per paper. A keyword analysis revealed that the majority of papers by South African authors focus on artificial intelligence. The results indicate that, although LNCS serves as a reputable dissemination platform for Computer Science research output both globally and locally, South African authors should consider publishing more journal articles to build and improve their researcher profiles.
Significance:
The study shows that LNCS is the most frequent publication outlet for Computer Science researchers, globally and in South Africa.
The study offers insight into the publication output, authorship patterns, collaborative behaviour and citation impact of South African based Computer Science researchers.
Open data set: https://doi.org/10.6084/m9.figshare.21397158.v3
Groundwater contaminant fluctuation at a landfill: a case study of the Coastal Park Landfill, Cape Town
No full textRainfall has been shown to be the main cause of elevated nutrient pollution in groundwater beneath landfills. However, groundwater monitoring is often based on predetermined schedules without considering rainfall patterns. This study examined how rainfall patterns affect fluctuations in groundwater quality at the Coastal Park landfill in Cape Town, South Africa, and the relevance of current groundwater sampling schedules. Boreholes upstream and downstream of two large waste cells, one lined and the other unlined, were monitored for 15 weeks during the onset of the rainy season to detect changes in the groundwater level, pH, conductivity, dissolved oxygen, ammonia, nitrate, and phosphate. Rainfall patterns strongly affected the groundwater parameters, with widely varying fluctuation patterns and lag times. Conductivity peaked downstream of the lined cell 10 weeks later than at the unlined cell, with widely different fluctuation patterns (R2 = 0.36). Ammonia peaked downstream of both the unlined and lined cells well before the early rains, with very similar fluctuation patterns (R2 = 0.97), although it peaked 6 times higher in the unlined cell. Nitrate peaked at Weeks 2 to 4 downstream of the unlined and the lined cell, with a weak correlation (R2 = 0.56). A shorter nitrate peak and a net decrease throughout the rainy season were observed downstream of the lined cell. Phosphate showed a brief, multi-fold increase at Week 3 downstream of both the unlined and lined cells, displaying pH-induced mobilisation and a very strong correlation (R2 = 0.99) between these locations. Lag times and fluctuation patterns varied depending on the presence of liners, and rainfall patterns. Therefore, the low frequency sampling required by many South African landfill waste management permits and licences cannot identify pollutant peak concentrations or describe their trends, and high frequency sampling should be considered
Investigation of the effect of variable-sized energy dissipating blocks on sluice gate performance
No full textThe present research used a combination of experimental and numerical methods to investigate energy dissipation blocks of different heights placed downstream of a sluice gate in an open channel flow. Numerical model simulations were performed using a 3D computational fluid dynamics (CFD) technique, using the Reynolds-averaged Navier-Stokes (RANS) equations with the volume of fluid (VOF) and k-ε turbulence models. The accuracy of the numerical model and the grid sensitivity was assessed according to a recommended procedure in the literature. Different hydraulic and geometry conditions were investigated to understand the energy dissipation behaviour of the blocks. The hydrodynamic effects of different block spacings, heights and configurations were analysed by means of CFD simulations. The results show that the variable size blocks have a high energy dissipation efficiency in sluice gate flows, particularly at high Froude numbers. The energy dissipation efficiency of the blocks downstream of a sluice gate can reach up to 55% for high discharges (Q = 35 L/s). Interestingly, the energy dissipation performance of small gate openings exceeds that of large gate openings, reaching a peak efficiency of 40% for the same discharge. In addition, the block spacing has a minimal effect on the energy dissipation, while smaller block spacing results in a smoother water surface profile
New data on an old pest complex: The status of Phlyctinus callosus Schönherr and Phlyctinus xerophilus Haran (Coleoptera: Curculionidae) in South Africa
No full textPhlyctinus is an endemic weevil genus of the Cape Floristic Region that comprises eight to ten species, previously classified under the monotypic P. callosus sensu lato concept. Two species of this genus, Phlyctinus callosus and P. xerophilus, are of economic concern to the deciduous fruit and grapevine industry in the Western Cape province of South Africa, causing primary damages and being of phytosanitary concern at the adult stage. The taxonomic revision conducted in 2020 raised doubts whether one of the two species was a newly emerging pest and/or what species was considered in studies before the clarification of species boundaries. Also unclear is whether these species can be controlled similarly using current control measures. The aim of this study therefore is to review the pest status of the two species over time based on museum records, field collections and historical publications, and to clarify how control measure(s) are impacted. We infer that neither species appear to be emerging pests in the region, both being of agricultural significance for at least 80 years. Phlyctinus callosus is mostly distributed along the southern coast, while P. xerophilus is distributed in inland valleys. The two species show similar biology, physiology and ecology in agro-ecosystems, and can be excluded from the host plant canopy using stem-barriers, adults being flightless. As such, it is shown that the naming of P. xerophilus as a pest is mainly a taxonomical clarification within a pre-existing species complex
THE INTRODUCTION OF “FREE, PRIOR AND INFORMED CONSENT” TO THE LAND REFORM LEGAL LEXICON Baleni v Minister of Mineral Resources 2019 (2) SA 453 (GP)
No full textAlthough decided four years ago, Baleni v Minister of Mineral Resources (2019 (2) SA 453 (GP) (Baleni)) stands out regarding four significant features and it remains surprising that the decision has not attracted more attention in connection with the land-reform programme. The first feature was the interpretation of the Interim Protection of Informal Land Rights Act 31 of 1996 (IPILRA). The second feature was the emphasis on customary law in the interpretation of IPILRA. The third feature was the application of multiple international-law instruments in the interpretation of IPILRA. The fourth feature was the court’s conclusion that these international-law instruments determine that no decisions may be taken regarding the lands of indigenous peoples without the latter’s “free, prior and informed consent” (FPIC). This conclusion has far-reaching implications for the South African land-reform process introduced by section 25 of the Constitution of the Republic of South Africa, 1996 (the Constitution)
PUTATIVE PRIVATE DEFENCE IN CRIMINAL LAW Tuta v The State 2023 (2) BCLR 179 (CC)
No full textIn a country like South Africa, plagued as it is by violent contact crime, it is not surprising that the defences of private defence and putative private defence are often raised by accused in criminal trials. It is trite that, for a conviction in a criminal court, the prosecution is tasked with proving the accused’s liability beyond reasonable doubt. As an element of a crime, unlawfulness does not simply lie in fulfilment of the definitional elements of a crime. There are instances where, notwithstanding fulfilment of the definitional elements of a crime, the conduct is justified or legally regarded as objectively reasonable. These instances are known as grounds of justification and technically serve to exclude unlawfulness. A ground of justification, if successfully raised, is therefore a complete defence to any criminal charge. There is not a numerus clausus of valid grounds of justification in South African criminal law; the test remains whether the accused’s conduct was objectively reasonable in the particular situation. One such ground of justification is private defence. A person acts in private defence, and therefore lawfully, if they use the minimum force necessary to ward off an unlawful human attack that has commenced, or is imminently threatening, upon their or somebody else’s protected legal interests such as life, physical integrity, property, reputation or dignity. The defensive act in private defence must be: necessary to protect the threatened interest; directed at the attacker; reasonably proportionate to the attack; and perpetrated with the knowledge that it is performed in private defence. Unlike private defence, putative private defence is not a ground of justification that excludes unlawfulness. Putative private defence exists where an accused is under the mistaken belief that they are conducting themselves in private defence whereas there is no such ground of justification in the circumstances. If an accused labours under the genuine but erroneous belief in the existence of a ground of justification, their conduct remains unlawful. The accused lacks the knowledge that they are, in reality, acting unlawfully. While the accused’s conduct remains unlawful, the absence of knowledge of unlawfulness results in a lack of intention, since knowledge of unlawfulness is an integral part of intention. The accused’s mistaken belief that they are acting lawfully in private defence must be honest and genuine but need not be rational or reasonable. If, on the facts, there could be no honest and genuine belief on the accused’s part in the lawfulness of their defensive act, putative private defence cannot exist.
It is trite that, for private defence to succeed as a ground of justification, the test is objective in the sense that the attack and the defensive action must meet certain objective requirements. The accused’s subjective belief, whatever it may be, has no impact on the validity of private defence as a ground of justification. The Constitutional Court in Tuta v The State (2023 (2) BCLR 179 (CC)) was recently tasked with making a finding on the correct legal test to be applied to the existence of the defence of putative private defence. In this contribution, the Constitutional Court’s decision is analysed
Environmental life cycle, carbon footprint and comparative economic assessment of rainwater harvesting systems in schools – a South African case study
No full textRainwater harvesting (RWH) provides a unique opportunity for water conservation. This research aimed to assess the performance of two types of RWH systems (gravity and pump-driven) at a local public school in replacing non-potable water for toilet flushing. The volume of harvested water, efficiency to meet demand, expenses involved and associated environmental burdens were key criteria of performance. Economic considerations included capital costs and return periods, while the environmental aspects encompassed simplified life cycle assessments (LCAs) as well as specific carbon footprints. The gravity-fed system supplied 452.5 kL/annum and covered 31.8% of the demand for flushing water for toilets for the school investigated. The pumped system provided 476.8 kL/annum representing 33.5% of the demand. Together they would be able to supply 65.3% of the demand. The catchment area of these two systems differed and there was no overlap. As expected, the gravity-fed system outperformed the pumped system, both economically and environmentally, because no energy for pumping was needed. In terms of costs, the difference was small, and the payback periods of both systems were similar. However, environmentally, the LCA scores for the pumped system were an order of magnitude higher for all 18 impact categories considered. Carbon footprints showed that in the construction stage both systems have similar footprints. For the operation stage, the comparison was extended, as there were higher energy requirements for the pumped system (about 4 times higher than those from the provision of municipal potable water), but in the same range or lower when compared with other alternative sources of water like groundwater abstraction, recycling of municipal water and desalination. The gravity-fed system required no energy for pumping. This study shows how trade-offs in assessing the overall performance of RWH systems can be considered, leading to better decision making