Scielo RSS <![CDATA[South African Journal of Science]]> vol. 112 num. 1-2 lang. pt <![CDATA[SciELO Logo]]> <![CDATA[<b>ASSAf turns 20: Young enough to be dynamic and old enough to be trusted with its mission</b>]]> <![CDATA[<b>What's new from the PAST?</b>]]> <![CDATA[<b>Out of Africa: From <i>Homo naledi </i>to <i>'Homo cyborg'</i></b>]]> <![CDATA[<b>South Africa debuts world-class Science Forum</b>]]> <![CDATA[<b>Brave old world: Can today's university truly be 'home' to tomorrow's minds?</b>]]> <![CDATA[<b>Casting the nets wide in the quest for ways to 'Africanise' research and teaching</b>]]> <![CDATA[<b>Participatory democracy for our time</b>]]> <![CDATA[<b>What separates them from us?</b>]]> <![CDATA[<b>Whose knowledge? The politics of scholarship in South(ern) Africa: A critical review of <i>Inside African Anthropology</i></b>]]> <![CDATA[<b>Safe spending rates for South African retirees</b>]]> <![CDATA[<b>ASSAf: Promoting scholarly activity through the <i>SAJS</i></b>]]> <![CDATA[<b>Breast cancer: When do you stop reading the literature?</b>]]> <![CDATA[<b>Neutrophil extracellular traps and their role in health and disease</b>]]> The human innate immune system is indispensable for protection against potentially invasive microbial and viral pathogens, either neutralising them or containing their spread until effective mobilisation of the slower, adaptive (specific), immune response. Until fairly recently, it was believed that the human innate immune system possessed minimal discriminatory activity in the setting of a rather limited range of microbicidal or virucidal mechanisms. However, recent discoveries have revealed that the innate immune system possesses an array of novel pathogen recognition mechanisms, as well as a resourceful and effective alternative mechanism of phagocyte (predominantly neutrophil)-mediated, anti-infective activity known as NETosis. The process of NETosis involves an unusual type of programmed, purposeful cell death, resulting in the extracellular release of a web of chromatin heavily impregnated with antimicrobial proteins. These structures, known as neutrophil extracellular traps (NETs), immobilise and contribute to the eradication of microbial pathogens, ensuring that the anti-infective potential of neutrophils is sustained beyond the lifespan of these cells. The current review is focused on the mechanisms of NETosis and the role of this process in host defence. Other topics reviewed include the potential threats to human health posed by poorly controlled, excessive formation of NETs, specifically in relation to development of autoimmune and cardiovascular diseases, as well as exacerbation of acute and chronic inflammatory disorders of the airways. <![CDATA[<b>Urban farming as a possible source of trace metals in human diets</b>]]> Rapid industrialisation and urbanisation have greatly increased the concentrations of trace metals as pollutants in the urban environment. These pollutants (trace metals) are more likely to have an adverse effect on peri-urban agriculture which is now becoming a permanent feature of the landscape of many urban cities in the world. This review reports on the concentrations of trace metals in crops, including leafy vegetables harvested from different urban areas, thus highlighting the presence of trace metals in leafy vegetables. Various pathways of uptake of trace metals by leafy vegetables, such as the foliar and roots, and possible health risks associated with urban faming are discussed and various morphological and physiological impacts of trace metals in leafy vegetables are described. Defensive mechanisms and positive aspects of trace metals in plants are also highlighted. <![CDATA[<b>The botanical content in the South African curriculum: A barren desert or a thriving forest?</b>]]> Botanists who are interested in education have often expressed their dismay at how plant sciences are neglected in Biology curricula, despite the important roles that plants play. While botanists in several overseas countries have studied the ways in which plant sciences are represented in curricula, no research has been done on how botany is neglected in the South African curriculum. Currently, the South African curriculum is known as the Curriculum and Assessment Policy Statements (CAPS) for Grades R-12. In this study, a comparison was made among the content that is generally taught in introductory plant sciences courses, the American Society of Plant Biologists' principles for plant biology education and the relevant CAPS documents. The time spent on plant, animal or human-focused content was established and compared at both phase and grade level. It was found that while the curriculum addresses all the major concepts in the plant sciences, very little time was being allocated to exclusively plant-focused content as compared to animal and human-focused content. This neglect was particularly prevalent in the Foundation Phase. The way in which the content is structured and presented in the curriculum may in all likelihood not be sufficient to provide a strong knowledge and skills foundation in the plant sciences, nor will it encourage the development of positive values towards plants. While consensus regarding the content of a curriculum will be difficult to achieve, awareness of potential gaps in the curriculum should be brought to the attention of the botanical and educational communities. <![CDATA[<b>Spoilage potential of a novel group of bacteria isolated from dairy products</b>]]> Cold-tolerant bacteria, also known as psychrotrophic bacteria, are notorious contaminants of milk in the refrigerated dairy food chain. These organisms, especially the pseudomonads, may produce heat-resistant enzymes that are responsible for the breakdown of proteins and lipids in milk and dairy products. Such reactions result in a variety of defects in the raw or unprocessed milk that may affect the suitability of such milk for further processing. The enzymes produced may cause defects in long-life dairy products such as cheese, butter and long-life milk. In the present study, a range of 18 yellow pigmented psychrotrophic bacteria, collectively known as flavobacteria, were isolated from local dairy products. One aim of this study was to identify these bacteria to species level using molecular techniques. A second aim was to determine the spoilage potential of these organisms based on profiles generated by the BIOLOG system (that may relate to hydrolytic enzymes produced). Of the 18 isolates, 14 belonged to the genus Chryseobacterium while 4 were identified as Empedobacter isolates. The most active spoilage organisms in this group were shown to be C. bovis, C. shigense and E. brevis. These findings illustrate that enzymatically catalysed defects in dairy products should not be attributed solely to acknowledged psychrotrophic bacteria such as the pseudomonads, but that flavobacterial species may also be actively involved. <![CDATA[<b><i>Australopithecus robustus </i></b><b>societies - one-male or multimale?</b>]]> Determining the sex of individual specimens is important in estimating the degree of sexual dimorphism. Sexual dimorphism, in turn, provides clues for reconstructing the social organisation and mating systems of extinct species. In an article published in Science, Lockwood et al. (Lockwood CA, Menter CG, Moggi-Cecchi J, Keyser AW. Extended male growth in a fossil hominin species. Science. 2007;318:1443-1446.) suggested an uneven sex ratio (in favour of males) for the known individuals of the South African Pleistocene hominid, Australopithecus robustus, and claimed evidence of an extended period of growth (delayed maturity) for the males of this species. They concluded that this finding, combined with estimates of sexual size dimorphism, suggests a polygynous reproductive strategy, and a social system similar to that of silverback gorillas (i.e. one-male harems). On re-examination of these claims, and based on further analysis, I agree with Lockwood et al. that morphologically A. robustus exhibits an increased (almost gorilla-like) level of facial dimorphism, but propose using an alternate (clustering) technique for grouping the specimens of highly dimorphic species into sexes, and argue that their pronouncements regarding a polygynous social structure of these early hominids are inconclusive. I contend instead that the habitat occupied by this species suggests rather that a one-male harem social structure would have been counterproductive. <![CDATA[<b>Indicative hazard profile for strong winds in South Africa</b>]]> While various extreme wind studies have been undertaken for South Africa for the purpose of, amongst others, developing strong wind statistics, disaster models for the built environment and estimations of tornado risk, a general analysis of the strong wind hazard in South Africa according to the requirements of the National Disaster Management Centre is needed. The purpose of the research was to develop a national profile of the wind hazard in the country for eventual input into a national indicative risk and vulnerability profile. An analysis was undertaken with data from the South African Weather Service's long-term weather stations to quantify the wind hazard on a municipal scale, taking into account that there are more than 220 municipalities in South Africa. South Africa is influenced by various strong wind mechanisms occurring at various spatial and temporal scales. This influence is reflected in the results of the analyses which indicated that the wind hazard across South Africa is highly variable, spatially and seasonally. A general result was that the strong wind hazard is highest from the southwestern Cape towards the central and eastern parts of the Northern Cape Province, and the southeastern parts of the coast as well as the eastern interior of the Eastern Cape Province. On a seasonal basis, the southern parts of the country showed similar magnitudes of relative wind hazard throughout the year. However, further north, a strong seasonal component was evident, with lowest risk of strong winds during autumn and winter, and highest risk in spring and summer when convective activity is strongest. <![CDATA[<b>Visitors' views of human origins after visiting the Cradle of Humankind World Heritage Site</b>]]> The Cradle of Humankind World Heritage Site, west of Johannesburg, was designated in 1999 because of its importance as a locality where numerous hominid fossils have been discovered since the 1930s. In this article, responses to questions from a survey of more than 800 adult visitors to the Cradle of Humankind visitor centres are analysed, covering their understanding of the concept of the 'cradle' and their views on human evolution. Findings indicated that 63% of the respondents conceptualised the cradle as the origin or birthplace of humankind, and a similar proportion thought that nowhere else could be called the Cradle of Humankind (77% of people of South African nationality thought this). Nearly 60% of respondents accepted that humans evolved from an ape-like ancestor, while 25% disagreed. South Africans were less likely to accept human evolution than their international counterparts. The great majority of participants who accepted human evolution based their agreement on various forms of evidence and their knowledge of evolution. A religious foundation was used for their rationale by 60% of those who rejected evolution, with 33% citing evidence for their rejection. The implications of the findings are discussed in the light of public awareness and human origins. <![CDATA[<b>Physicochemical characteristics of Bambara groundnut dietary fibres extracted using wet milling</b>]]> The objectives of this study were to extract soluble and insoluble dietary fibres from four Bambara groundnut (BGN) varieties (black-eye, brown-eye, brown and red) using the wet milling method and evaluate their physicochemical properties. The swelling capacities of brown-eye (6.5 g/mL) and black-eye (6.2 g/mL) fibres were higher (p<0.05) than those of red (6.0 g/mL) and brown (5.5 g/mL) fibres while the water holding capacities of black-eye and brown-eye fibres (2.84 g and 2.83 g water/g sample) were higher (p<0.05) than those of brown and red fibres. The bulk densities of insoluble dietary fibres (IDFs) and soluble dietary fibres (SDFs) ranged between 0.57 g/mL (red) to 0.67 g/mL (brown-eye) and 0.46 g/mL (brown-eye) to 0.57 g/mL (black-eye), respectively. The oil binding capacities (OBCs) of SDFs ranged between 2.78 g oil/g sample (brown) and 4.03 g oil/g sample (brown-eye) while the OBC of all IDFs did not differ (p&gt;0.05), ranging between 1.52 g oil/g sample (brown) and 1.40 g oil/g sample (brown-eye and black-eye). Black-eye and brown-eye dietary fibres had higher phenolic and total sugar content. The findings of this study indicate the potential of BGN fibres in food systems as fat replacers, emulsion stabilisers, water binders, bulking agents, thickeners and nutritional additives. <![CDATA[<b>Radioactive nuclides in phosphogypsum from the lowveld region of South Africa</b>]]> We evaluated the suitability of phosphogypsum from the Lowveld region of South Africa (LSA), for the manufacturing of building materials, with reference to (1) the National Nuclear Regulator Act 47 of 1999 and (2) the radioactivity associated risks as quantified in terms of the external and internal hazard indices, the activity concentration index and the radium equivalent. The distribution of radioactive nuclides in the LSA phosphogypsum was also examined. Analyses of 19 samples of the phosphogypsum show that phosphogypsum contains lower activity concentrations of naturally occurring radioactive nuclides of uranium and thorium and their progeny than the 500 Bg/kg limit set for regulation in South Africa. The potassium-40 (40K) activity concentration was below the minimum detectable amount of 100 Bq/kg. The values obtained for external and internal hazard indices and the activity concentration index were: 2.12 + 0.59, 3.44 + 0.64 and 2.65 + 0.76 respectively. The calculated radium equivalent Ra eq was 513 + 76Bq/kg. The final decision regarding phosphogypsum's suitability for use as a building material should consider scenarios of use. <![CDATA[<b>Responses of African elephants towards a bee threat: Its application in mitigating human-elephant conflict</b>]]> Human settlement expansion into elephant ranges, as well as increasing elephant populations within confined areas has led to heightened levels of human-elephant conflict in southern African communities living near protected areas. Several methods to mitigate this conflict have been suggested including the use of bees as an elephant deterrent. We investigated whether bee auditory and olfactory cues (as surrogates for live bees) could be used to effectively deter elephants. We evaluated the responses of elephants in the southern section of the Kruger National Park to five different treatments: (1) control noise, (2) buzzing bee noise, (3) control noise with honey scent, (4) honey scent, and (5) bee noise with honey scent. Elephants did not respond or displayed less heightened responses to the first four treatments. All elephants exposed to the bee noise with honey scent responded with defensive behaviours and 15 out of 21 individuals also fled. We concluded that buzzing bees or honey scent as isolated treatments (as may be the case with dormant beehives) were not effective elephant deterrents, but rather an active beehive emitting a combination of auditory and olfactory cues was a viable deterrent. However, mismatches in the timing of elephant raids and activity of bees may limit the use of bees in mitigating the prevailing human-elephant conflict. <![CDATA[<b>Publishing patterns at the Cape Peninsula University of Technology</b>]]> We report on the publishing and collaborative patterns of researchers in the applied sciences and engineering disciplines at a technological university in South Africa, Cape Peninsula University of Technology. The study focused on works published over a 10-year period (2005-2014) and was based on citations of peer-reviewed literature from Scopus. The results showed a steady growth in research outputs in science and technology at the university. There has also been a growing trend of international collaboration in certain disciplines. This scoping study serves as a benchmark for similar studies. <![CDATA[<b>Radiological and genetic analysis of a Late Iron Age mummy from the Tuli Block, Botswana</b>]]> Mummified human remains are valuable sources of information on past populations. Here we report on the radiological and molecular findings of a partially mummified individual found in northern Botswana. This desiccated mummy from the Tuli region is the first to have been reported from this region. The remains were those of an older male adult of African origin. He was interred in a tightly flexed position and wrapped in an animal skin. Computerised tomography (CT) scanning revealed that none of the internal organs was preserved. Multiple post-mortem alterations are seen, but apart from some degenerative changes of the lower vertebral column, the axial skeleton has remained intact. The advanced osteophytosis suggests an older age than what was previously estimated. The aDNA analysis confirms Sotho-Tswana and possibly Khoesan genetic relatedness, as could be expected from individuals from that region. These results represent one of the first CT scans of a mummified individual from southern Africa, and also the first successful aDNA extraction from such remains. <![CDATA[<b>Investigating atmospheric photochemistry in the Johannesburg-Pretoria megacity using a box model</b>]]> Urban air pollution has become a major concern over the past decades. One of the largest conurbations in Sub-Saharan Africa is developed around the cities of Johannesburg and Pretoria (Jhb-Pta megacity). In this study, a photochemical box model with a detailed representation of ozone (O3) formation chemistry was used to investigate the state of current air quality and photochemical processes in the Jhb-Pta megacity, as well as scenarios that could possibly mitigate air pollution. Results indicated that the Jhb-Pta megacity is within a VOC-limited (or NOx-saturated) regime. Major sources of NOx include transport from the Mpumalanga Highveld and local traffic emissions. O3 levels in the Jhb-Pta megacity will be more effectively reduced if VOC (volatile organic compound) emissions are decreased. A reduction of NOx emissions leads to an increase in O3 because of a decrease in titration through the reaction with NO. The same effect was observed in various cities worldwide where O3 levels increased when NOx emissions were reduced during emission control strategies. The effect of reducing vehicular emissions in the Jhb-Pta megacity on the production of O3 was also investigated. A significant increase of approximately 23 ppb O3 was observed when emissions of VOCs, NOx and CO were reduced by changing from Euro-0 to Euro-3 vehicles. It is therefore recommended that VOC emissions are decreased together with the implementation of Euro-3 and cleaner vehicles in the future. <![CDATA[<b>Evidence for aeolian origins of <i>heuweltjies </i>from buried gravel layers</b>]]> Although heuweltjies (19-32 m diameter) dominate the surface of much of the southwestern Cape of South Africa, their origins, distribution and age remain controversial. Current hypotheses are that the heuweltjies are (1) constructed by the excavation and mounding habits of burrowing animals; (2) the result of erosion by water of areas between patches protected from fluvial action by denser vegetation or (3) the product of localised aeolian sediment accumulation beneath denser vegetation associated with termitaria. At a site where quartz-containing gravels occur on the soil surface in areas between heuweltjies, these gravels were found to extend as a relatively intact layer of uniform concentration from the inter-mound area into the mound at the same plane as the surrounding soil surface. This buried layer suggests that heuweltjies were either built-up by deposition on a previous soil surface layer or eroded from sediment accumulated above the buried gravel layer. Mounds contain a relatively large proportion of silt consistent with sediment deposition. Mound sediment elemental composition was strongly correlated with that of local shale, indicating a local source of sediment. Pedogenesis was considerably more advanced off- than on-mound. There was no evidence of extensive regional aeolian sediment mantling over the vast area in which the heuweltjies occur. These findings and observations support the aeolian deposition hypothesis of heuweltjie origins combined with a degree of erosion, rather than a termite bioturbation hypothesis or a predominantly erosion-based hypothesis. <![CDATA[<b>High-speed detection of emergent market clustering via an unsupervised parallel genetic algorithm</b>]]> We implement a master-slave parallel genetic algorithm with a bespoke log-likelihood fitness function to identify emergent clusters within price evolutions. We use graphics processing units (GPUs) to implement a parallel genetic algorithm and visualise the results using disjoint minimal spanning trees. We demonstrate that our GPU parallel genetic algorithm, implemented on a commercially available general purpose GPU, is able to recover stock clusters in sub-second speed, based on a subset of stocks in the South African market. This approach represents a pragmatic choice for low-cost, scalable parallel computing and is significantly faster than a prototype serial implementation in an optimised C-based fourth-generation programming language, although the results are not directly comparable because of compiler differences. Combined with fast online intraday correlation matrix estimation from high frequency data for cluster identification, the proposed implementation offers cost-effective, near-real-time risk assessment for financial practitioners.