Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320170007&lang=pt vol. 113 num. 11-12 lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Avarice: Signs of threats to credible higher education?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700001&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>A call to halt destructive, illegal mining in Zimbabwe</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700002&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>A cladistic analysis of <i>Graecopithecus</i></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700003&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Critical questions (and some answers) in debates on shale gas</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700004&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>A new look at cheetahs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700005&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Science, stories and scholars</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700006&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Chris Barnard: South Africa's fallible king of hearts</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700007&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Promoting an environment of innovation: A university scientist's view</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700008&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>South African carbon observations: CO<sub>2</sub> measurements for land, atmosphere and ocean</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700009&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Desalination and seawater quality at Green Point, Cape Town: A study on the effects of marine sewage outfalls</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700010&lng=pt&nrm=iso&tlng=pt <![CDATA[<b>Bacterial species from retailed poultry eggs in Tshwane, South Africa: Implication for consumers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700011&lng=pt&nrm=iso&tlng=pt Food safety is an important public health issue and governments across the world are intensifying their efforts to improve the quantity, quality and the safety of national food supplies. Bacteria, especially Salmonella species, present in or on chicken meat and hens' eggs in particular are the most common causes of food poisoning and the major sources of human salmonellosis. Literature reveals little information on the risk factors for salmonellae infection in Africa. The aim of this study was to determine which, if any, bacteria, especially Salmonella species, are present in and on hens' eggs. Representative bacterial colonies were confirmed with Gram staining and then identified using the MALDI-TOF Biotyper assay. The genera identified were Escherichia coli (34%), Enterococcus faecalis (14%), Proteus mirabilis (9%), Klebshiella pneumoniae (7%), Salmonella Typhimurium (6%), Enterobacter cloacae (1%), Stenotrophomonas maltophilia (0.6%), Salmonella Dublin (0.6%) and Salmonella Braenderup (0.2%). Raw hens' eggs and products containing raw hens' eggs may contain pathogenic bacteria, thereby exposing a large number of consumers to the risk of contracting food poisoning when undercooked or uncooked hens' eggs are consumed. SIGNIFICANCE: • Enterobacteriaceae counts are used as an indicator to evaluate the hygienic quality of food. • The presence of Salmonella species and other Enterobacteriaceae in raw hens' eggs poses a health risk to consumers. • Any product in which raw eggs are used must be provided with a conspicuous label stating that it may contain pathogenic bacteria. <![CDATA[<b>Bibliometric analysis of the development of nanoscience research in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700012&lng=pt&nrm=iso&tlng=pt Nanotechnology is a fast-growing scientific research area internationally and is classified as an important emerging research area. In response to this importance, South African researchers and institutions have also increased their efforts in this area. A bibliometric study of articles as indexed in the Web of Science considered the development in this field with respect to the growth in literature, collaboration profile and the research areas that are more within the country's context. We also looked at public institutions that are more active in this arena, including government policy considerations as guided by the National Nanotechnology Strategy launched in 2005. We found that the number of nanotechnology publications have shown a remarkable growth ever since the launch of the strategy. Articles on nanotechnology have been published in numerous journals, with Electrochimica Acta publishing the most, followed by Journal of Nanoscience and Nanotechnology. These publications fall within the traditional domains of chemistry and physics. In terms of the institutional profile and based on publication outputs over the period reviewed, the Council for Scientific and Industrial Research is a leading producer of publications in nanotechnology, followed by the University of the Witwatersrand - institutions that are both based in the Gauteng Province. There is a high level of international collaboration with different countries within this field - the most productive collaboration is with India, followed by the USA and China, as measured through co-authorship. SIGNIFICANCE: •Nanotechnology as a field of research is experiencing rapid growth and there is a need to understand progress from a South African perspective. <![CDATA[<b>Growth of soil algae and cyanobacteria on gold mine tailings material</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700013&lng=pt&nrm=iso&tlng=pt The goal of revegetation of gold mine tailings storage facilities is to reduce aeolian pollution, nutrient leaching and erosion caused by exposure to wind and water. The establishment of biological soil crusts may prove to be a more cost-effective way to reach the same goal and the aim of this study was therefore to determine if it is possible to establish algae and cyanobacteria on gold mine tailings. Different treatments of Chlamydomonas, Microcoleus and Nostoc were inoculated on gold mine tailings in controlled conditions and algal growth was measured on all of the treatments after 6 weeks. Nostoc treatments had the highest chlorophyll-a concentrations and produced a surface crust, while Chlamydomonas treatments penetrated the tailings material and provided the strongest crust. The results were promising but more research is necessary to determine the best organism, or combination of organisms, to colonise mine tailings and to eventually produce biological crusts. SIGNIFICANCE: •Determination of the best organisms to colonise mine tailings and to produce biological crusts for the revegetation of gold mine tailings storage facilities. <![CDATA[<b>Forecasting winter wheat yields using MODIS NDVI data for the Central Free State region</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700014&lng=pt&nrm=iso&tlng=pt Consumption of wheat is widespread and increasing in South Africa. However, global wheat production is projected to decline. Wheat yield forecasting is therefore crucial for ensuring food security for the country. The objective of this study was to investigate whether the anthesis wheat growth stage is suitable for forecasting dryland wheat yields in the Central Free State region using satellite imagery and linear predictive modelling. A period of 10 years of Normalized Difference Vegetation Index data smoothed with a Savitzky-Golay filter and 10 years of wheat yield data were used for model calibration. Diagnostic plots and statistical procedures were used for model validation and assessment of model adequacy. The period 30 days before harvest during the anthesis stage was established to be the best period during which to use the linear regression model. The calibrated model had a coefficient of determination of 0.73, a p-value of 0.00161 and a root mean squared error of 0.41 tons/ha. Residual plots confirmed that a linear model had a good fit for the data. The quantile-quantile plot provided evidence that the residuals were normally distributed, which means that assumptions of linear regression were fulfilled and the model can be used as a forecasting tool. Model validation showed high levels of accuracy. The evidence indicates that use of Moderate Resolution Imaging Spectroradiometer data during the anthesis growth stage is a reliable, cost-effective and potentially time-saving alternative to ground-based surveys when forecasting dryland wheat yields in the Central Free State. SIGNIFICANCE: •Developing a cost-effective technique based on satellite imagery for wheat yield forecasting is vital for food security planning in South Africa. <![CDATA[<b>The rise and fall of dissolved phosphate in South African rivers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700015&lng=pt&nrm=iso&tlng=pt Eutrophication of water resources following nutrient loading is a global threat to water quality, and has been found to be one of the major threats to water quality in South Africa. Eutrophication is large-scale autotroph growth following nutrient enrichment and has several consequences, including loss of biodiversity, oxygen depletion, taste/odour generation and algal toxin production. Phosphate enrichment is often (but not always) the cause of freshwater eutrophication, and limitation of phosphate is commonly used as a means of controlling eutrophication. This study reports on a survey of trends in nutrient levels in South African freshwater resources. The research reported on here shows a significant decrease in dissolved phosphate levels in recent years, following a long period during which phosphate levels had been increasing with time. While changes in inorganic nitrogen were found, these changes did not match those in phosphate levels. Several potential causes of these changes were assessed, and it is concluded that no one cause can explain the changes observed. While the decrease in freshwater phosphate levels bodes well for water quality management, internal phosphorus cycling and other mechanisms are likely to mask the short-term impact of phosphate decreases. SIGNIFICANCE: • Eutrophication, caused by nutrient loading, is a threat to water quality. • Phosphate levels in South African fresh water have risen steadily with time, but recently have shown a sharp decrease, which cannot easily be attributed to one phosphate source. • The decrease has promise for eutrophication management but changes may not occur in the short term. <![CDATA[<b>The contribution of copyright-based industries to the South African economy</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700016&lng=pt&nrm=iso&tlng=pt We report the results of an effort to measure the contribution of copyright-based industries to the South African economy. Following the methodology of the World Intellectual Property Organization, we identify the copyright industry's contribution to GDP, employment, imports and exports in South Africa for the period 1970-2009. It was estimated that the sector contributed 4.1% to GDP - more than the contributions of other sectors such as agriculture and food, beverages and tobacco. Because of this quantified importance of the copyright-based industries, we recommend that relevant South African policy authorities and policymakers should monitor and publicise regularly the performance of the copyright-based industries as well as promote programmes for their development and growth. SIGNIFICANCE: •Copyright-based industries have the potential to play an important role in job creation and economic growth. •Our findings suggest that policymakers should design and promote the implementation of future policies and strategies related to these sectors. <![CDATA[<b>In the footsteps of Einstein, Sagan and Barnard: Identifying South Africa's most visible scientists</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700017&lng=pt&nrm=iso&tlng=pt Highly visible scientists are increasingly recognised as influential leaders with a special role to play in making science part of mainstream society. Through consultation with a panel of 45 experts working at the science-media interface, we sought to identify the most visible scientists currently living and working in South Africa. In total, 211 scientists - less than 1% of the scientific workforce of the country - were identified as visible in the public sphere. The demographic profile and institutional spread of South Africa's visible scientists suggest that more should be done to increase the diversity of scientists who are publicly visible. Although only 8% of South Africans are white, 78% of the group of visible scientists were white, and 63% of the visible scientists were men. Only 17 black women were identified as publicly visible scientists. While visible scientists were identified at 42 different research institutions, more than half of the visible scientists were associated with just four universities. Recent controversies surrounding the two most visible South African scientists identified via this study, and the potential implications for fellow scientists' involvement in public engagement, are briefly discussed. SIGNIFICANCE: •This is the first study to identify highly visible scientists in South Africa. •The study has meaningful policy implications for mobilising scientists towards public science engagement. •It is an important contribution towards the new public engagement framework of the Department of Science and Technology. <![CDATA[<b>South Africa's geothermal energy hotspots inferred from subsurface temperature and geology</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700018&lng=pt&nrm=iso&tlng=pt South Africa intends to mitigate its carbon emissions by developing renewable energy from solar, wind and hydro, and investigating alternative energy sources such as natural gas and nuclear. Low-enthalpy geothermal energy is becoming increasingly popular around the world, largely as a result of technological advances that have enabled energy to be harnessed from relatively low temperature sources. However, geothermal energy does not form part of South Africa's future renewable energy scenario. This omission may be related to insufficient regional analysis of potentially viable geothermal zones across the country. We considered existing subsurface temperature and heat flow measurements and performed solute-based hydrochemical geothermometry to determine potentially anomalous geothermal gradients that could signify underlying low-enthalpy geothermal energy resources. We correlated these findings against hydro/geological and tectonic controls to find prospective target regions for investigating geothermal energy development. Our results show a significant link between tectonic features, including those on-craton, and the development of geothermal potential regions. In addition, potential regions in South Africa share similarities with other locations that have successfully harnessed low-enthalpy geothermal energy. South Africa may therefore have a realistic chance of developing geothermal energy, but will still need additional research and development, including new temperature measurements, and structural, hydrogeological and economic investigations. SIGNIFICANCE: •The regional low-enthalpy geothermal energy potential of South Africa should be further researched for consideration of low-enthalpy geothermal energy as a renewable energy option. <![CDATA[<b>Finding fossils in Malapa breccia - medical CT scanning or micro-CT scanning?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700019&lng=pt&nrm=iso&tlng=pt Computed tomography (CT) imaging of fossils has revolutionised the field of palaeontology, allowing researchers to gain a better understanding of fossil anatomy, preservation and conservation. Micro focus X-ray computed tomography (µXCT) has been far more extensively used for these purposes than medical CT (XCT) - mostly because of the exquisite detail that the µXCT scanning modality, using slices of micron thicknesses, can produce. High energy X-rays can potentially penetrate breccia more effectively than lower energy beams. This study demonstrates that lower energy beams produce superior images for prioritising breccia for preparation. Additionally, XCT scanners are numerous, accessible, fast and relatively cost-effective when compared to µXCT scanners - the latter are not freely available, scanning times are much longer and there are significant limitations on the size and weight of scannable objects. Breccia blocks from Malapa were scanned at high and lower energy and images were analysed for image quality, artifact and certainty of diagnosis. Results show that lower energy images are deemed superior to higher energy images for this particular application. This finding, taken together with the limitations associated with the use of µXCT for the imaging of the large breccia from Malapa, shows that XCT is the better modality for this specific application. The ability to choose fossil-bearing breccia, ahead of manual mechanical preparation by laboratory technicians, would allow for the optimal use of limited resources, manual preparatory skills as well as the curtailment of costs. SIGNIFICANCE: •'Blind' manual preparation of fossil-bearing breccia is a costly and time-consuming exercise - and often results in a low yield. •The ability to triage fossil-bearing breccia ahead of manual preparation would allow for the optimal use of limited resources. •Medical CT is better than micro-CT to triage breccia to allow for prioritisation of rocks for manual preparation. <![CDATA[<b>Direct environmental impacts of solar power in two arid biomes: An initial investigation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700020&lng=pt&nrm=iso&tlng=pt According to recent national energy plans and policy documents, the number of renewable energy developments is expected to increase in South Africa, thus contributing to the diversification of the country's energy system. Consequently, numerous solar power developments are being deployed in the sunny arid interior - areas generally represented by the Nama-Karoo and Savanna Biomes. These developments come with a range of novel environmental impacts, providing opportunities for multidimensional exploratory research. Here, a mixed-method approach was used to identify and investigate possible environmental impacts associated with two types of solar power plants: concentrating solar power and photovoltaic. Structured interviews conducted with experts and experienced professionals, together with observations from site visits generated complementary findings. In addition to the risk of cumulative ecological impacts associated with individual solar plant developments, landscape impacts of multiple power plants and the direct impact on avifauna were found to be the most significant environmental impacts. These direct impacts appear to be most significant during the construction stage, which represents an intensive 10% of the total power plant lifespan. This investigation provides an early, broad and informative perspective on the experienced and expected impacts of solar power in South African arid regions as well as insights to possible future research areas. SIGNIFICANCE: •Solar power represents a large component of the needed diversification of South Africa's electricity system. •Research on the environmental impacts of solar power developments in the arid biomes of South Africa still is relatively scarce. •Increased energy developments in the arid biomes will require knowledge of the associated impacts for conservation planning. •Identification of environmental impacts throughout solar power lifespans enables informed management. <![CDATA[<b>Student throughput variables and properties: Varying cohort sizes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700021&lng=pt&nrm=iso&tlng=pt A recent research paper described how student throughput variables and properties combine to explain the behaviour of stationary or simplified throughput systems. Such behaviour can be understood in terms of the locus of a point in the triangular admissible region of the H-S plane, where H represents headcounts and S successful credits, each depending on the system properties at that point. The efficiency of the student throughput process is given by the ratio S/H. Simplified throughput systems are characterised by stationary graduation and dropout patterns of students as well as by annual intakes of student cohorts of equal size. The effect of varying the size of the annual intakes of student cohorts is reported on here. The observations made lead to the establishment of a more generalised student throughput theory which includes the simplified theory as a special case. The generalised theory still retains the notion of a triangular admissible region in the H-S plane but with the size and shape of the triangle depending on the size of the student cohorts. The ratio S/H again emerges as the process efficiency measure for throughput systems in general with unchanged roles assigned to important system properties. This theory provides for a more fundamental understanding of student throughput systems encountered in real life. SIGNIFICANCE: •A generalised stationary student throughput theory through varying cohort sizes allows for a far better understanding of real student throughput systems. <![CDATA[<b>The influence of collaboration in research priorities: The SADC Case</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700022&lng=pt&nrm=iso&tlng=pt This study was aimed at providing evidence of the effects of collaboration among unequal partners on their research priorities. Co-authorship patterns were investigated among South African authors publishing with authors of other countries in the region, with and without other non-African co-authors. It was identified that the non-African collaborators have a high impact on the quantity of co-authored publications and on the research disciplines in which co-authored research is undertaken. The findings raise a number of policy questions. SIGNIFICANCE: • The findings make profound that African countries should prioritise and engage their limited resources in areas of national priorities. <![CDATA[<b>Dispersal of semi-fleshy fruits to rock crevices by a rock-restricted rodent</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700023&lng=pt&nrm=iso&tlng=pt Seed dispersal allows successive generations of plants to be mobile in space and time. Heeria argentea's unusual fruit and its ubiquity in extremely rocky habitats, suggests that this tree requires a specialist disperser. We therefore investigated the dispersal ecology of H. argentea and Hartogiella schinoides. We found M. namaquensis rapidly removed H. argentea and H. schinoides fruits, moving them short distances within and between rock outcrops, and consumed only the pericarps. Birds were observed consuming H. schinoides, but not H. argentea fruits, suggesting M. namaquensis is its sole, specialist disperser. Most H. argentea seeds (65%) with removed pericarps germinated successfully, while intact fruits did not. We show rock outcrops represent fire refugia, allowing H. argentea trees to grow to large sizes, with small stems and a co-occurring, wind-dispersed tree, Widdringtonia nodiflora found away from these sites. This rodent-tree mutualism is perhaps the clearest global example of directed dispersal and shows that these endemic trees are highly adapted for survival in the southwestern Cape habitat and are not tropical relicts. SIGNIFICANCE: •The fruits of rock-restricted Cape trees are directly dispersed by rock rats to rock outcrops. This is the first description of rodent dispersal of fleshy fruits in South Africa. •This species-specific interaction allows for rapid germination of seeds and protection from frequent fires for adults. This rodent-tree mutualism is perhaps the clearest global example of directed seed dispersal. <![CDATA[<b>Revisiting the peroneal trochlea of the StW 352 calcaneus</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532017000700024&lng=pt&nrm=iso&tlng=pt StW 352, from Sterkfontein Member 4 (South Africa), is a partial calcaneus attributed to Australopithecus africanus and is dated to ~2.0-2.6 Ma. The unusual robusticity of the peroneal trochlea (PT) of StW 352 has been commented on by several authors. The size of hominin PTs has been hypothesised to be positively correlated with the degree of recruitment of peroneus longus during bipedal locomotion and/or climbing. Given the potential functional relevance of an enlarged PT for reconstructing hominin activity patterns, we present the following previously unrecognised structural details of the reconstructed StW 352 that affect current interpretations of its functional morphology: (1) we estimate that the PT has been reattached to the body of the calcaneus ~5 mm dorso-distally from its original anatomical position; and (2) the presence of intrusive matrix has artificially misshaped the PT by expanding it laterally and proximodistally. Future studies of this specimen that apply geometric morphometrics, or other shape analysis tools, should compensate for these inaccuracies before undertaking comparisons between it and other calcanei. Additionally, given that the PT is likely smaller than previously reported for StW 352, caution should be exercised when using it to infer muscle function and extrapolate activity patterns of this individual, and thus by extension, within Australopithecus africanus in general. Lastly, these findings highlight the importance of not only the production of accurate reconstructions, but also the critical evaluation of the accuracy of existing reconstructions when working with damaged fossil material. SIGNIFICANCE: •This work epitomises the value of critically evaluating original fossil reconstructions, especially of postcranial elements. •New technologies (e.g. microCT) offer non-destructive opportunities for evaluating/improving the accuracy of fossil reconstructions. •Re-assessing StW 352 suggests peroneal muscles may have factored less prominently in A. africanus locomotion than previously thought.