Scielo RSS <![CDATA[South African Journal of Science]]> vol. 113 num. 3-4 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Mathematics and...</b>]]> <![CDATA[<b>Mathematics in mathematics education</b>]]> <![CDATA[<b>Finding synergies between the mathematical and physical sciences</b>]]> <![CDATA[<b>Mathematics and biology</b>]]> <![CDATA[<b>Mathematics and economics: We should expect better models</b>]]> <![CDATA[<b>Mathematical and statistical foundations and challenges of (big) data sciences</b>]]> <![CDATA[<b>Livestock predation in South Africa: The need for and value of a scientific assessment</b>]]> <![CDATA[<b>Let us now praise famous women: Revising South Africa's foundational anthropology narrative</b>]]> <![CDATA[<b>Dragonflies as indicators of aquatic ecosystem health</b>]]> <![CDATA[<b>Showcasing Africa's wonderful and varied geoheritage</b>]]> <![CDATA[<b>Mycotoxigenic <i>Fusarium </i>species associated with grain crops in South Africa - A review</b>]]> Cereal grains include some of the most important crops grown in South Africa and play a major role in the local economy. Maize, wheat and sorghum are extensively consumed by humans and farm animals, and are also utilised in industrial processes. Grain crops that are grown commercially contribute up to 33% of the country's total gross agricultural production, whereas subsistence farmers grow grains mainly to sustain their families. In rural communities an average intake of maize grain of more than 300 g dry weight per person per day is not uncommon. The production of grains is often constrained by pests and diseases that may reduce their yields and quality. In South Africa, 33 mycotoxin-producing Fusarium species have been associated with grain crops. Mycotoxins, such as fumonisins and deoxynivalenol, have been found in levels exceeding the maximum levels imposed by the US Food and Drug Administration and the European Union and therefore pose a serious public health concern. We provide an extensive overview of mycotoxigenic Fusarium species associated with grain crops in South Africa, with particular reference to maize, wheat and sorghum. SIGNIFICANCE: • Mycotoxigenic Fusarium species negatively affect the most important staple food crops grown in South Africa. • Mycotoxin contamination has a direct impact on food safety and security. • The genus Fusarium includes some of the most important mycotoxin-producing species. <![CDATA[<b>A historical assessment of sources and uses of wheat varietal innovations in South Africa</b>]]> We undertook a historical review of wheat varietal improvements in South Africa from 1891 to 2013, thus extending the period of previous analyses. We identified popular wheat varieties, particularly those that form the basis for varietal improvements, and attempted to understand how policy changes in the wheat sector have affected wheat varietal improvements in the country over time. The empirical analysis is based on the critical review of information from policies, the varieties bred and their breeders, the years in which those varieties were bred, and pedigree information gathered from the journal Farming in South Africa, sourced mainly from the National Library of South Africa and the International Maize and Wheat Improvement Center (CIMMYT) database. A database of the sources and uses of wheat varietal innovations in South Africa was developed using information from the above sources. The data, analysed using trend and graphical analysis, indicate that, from the 1800s, wheat varietal improvements in the country focused on adaptability to the production area, yield potential and stability and agronomic characteristics (e.g. tolerance to diseases, pests and aluminium toxicity). An analysis of the sources of wheat varietal improvements during the different periods indicates that wheat breeding was driven initially by individual breeders and agricultural colleges. The current main sources of wheat varietal improvements in South Africa are Sensako, the Agricultural Research Council's Small Grain Institute (ARC-SGI) and Pannar. The structural changes in the agricultural sector, particularly the establishment of the ARC-SGI and the deregulation of the wheat sector, have helped to harness the previously fragmented efforts in terms of wheat breeding. The most popular varieties identified for further analysis of cost attribution and the benefits of wheat varietal improvements were Gariep, Elands and Duzi. SIGNIFICANCE: • These findings form the basis for the next analysis focusing on the attribution of the benefits and costs in terms of investment in wheat breeding in South Africa. <![CDATA[<b>The age of fossil StW573 ('Little Foot'): An alternative interpretation of <sup>26</sup>Al/<sup>10</sup>Be burial data</b>]]> Following the publication (Granger DE et al., Nature 2015;522:85-88) of an 26Al/10Be burial isochron age of 3.67±0.16 Ma for the sediments encasing hominin fossil StW573 ('Little Foot'), we consider data on chert samples presented in that publication to explore alternative age interpretations. 10Be and 26Al concentrations determined on individual chert fragments within the sediments were calculated back in time, and data from one of these fragments point to a maximum age of 2.8 Ma for the sediment package and therefore also for the fossil. An alternative hypothesis is explored, which involves re-deposition and mixing of sediment that had previously collected over time in an upper chamber, which has since been eroded. We show that it is possible for such a scenario to yield ultimately an isochron indicating an apparent age much older than the depositional age of the sediments around the fossil. A possible scenario for deposition of StW573 in Member 2 would involve the formation of an opening between the Silberberg Grotto and an upper chamber. Not only could such an opening have acted as a death trap, but it could also have disturbed the sedimentological balance in the cave, allowing unconsolidated sediment to be washed into the Silberberg Grotto. This two-staged burial model would thus allow a younger age for the fossil, consistent with the sedimentology of the deposit. This alternative age is also not in contradiction to available faunal and palaeomagnetic data. SIGNIFICANCE: • Data on chert samples taken close to StW573 impose a maximum age for the fossil of 2.8 Ma - younger than the 3.67 Ma originally reported. We propose and explore a two-stage burial scenario to resolve the inconsistency and to reopen the discussion on the age of fossil StW573. <![CDATA[<b>Developments in the production of economics PhDs at four research-intensive universities in South Africa</b>]]> There is a national drive to increase PhD production, yet we know little about how this imperative takes shape within different disciplines. We therefore set out to explore recent developments and the current status of the PhD in economics at four South African research-intensive universities. A data set of all economics PhDs produced in these commerce faculties during the period 2008-2014 was analysed to determine whether the departments of economics responded to the call for increased doctoral production, and the role the PhD by publication might have played in the process. How an increase in quantity might influence doctoral education in the respective academic departments was also considered by supplementing the quantitative data with perspectives from heads of department at the four institutions. The notable increase in doctoral production over the time period studied shows that national and international trends have influenced doctoral education in economics departments within South African research-intensive universities. Increased usage of the PhD by publication has implications for policy and pedagogical practice within these departments, especially as there seems to be limited available supervisory capacity. Other changes in departmental practices, such as the entrenchment of a research culture and the promotion of collaborative research amongst students and staff, also contributed to maintain quality in doctoral education. SIGNIFICANCE: • A substantial increase in the quantity of economics PhDs produced was accompanied by an unexpected increase in quality. • The increase in quality related to management changes, including a move to the PhD by publication, increased attention to ensuring the quality of students allowed entry to PhD programmes, facilitation of full-time doctoral studies through funding arrangements, and the appointment of international faculty with a research orientation. <![CDATA[<b>The enduring and spatial nature of the enterprise richness of South African towns</b>]]> Enterprise richness (measured by the number of enterprise types) showed a statistically significant log-log relationship (or power law) with the total number of enterprises in (1) towns in different regions of South Africa and (2) towns in the same region but seven decades apart. Entrepreneurial space in towns develops or disappears in a regular way as towns grow or regress, which is further proof of orderliness in the enterprise dynamics of South African towns. The power laws are very similar to one another, which was powerfully illustrated by the fact that one relationship extracted from seven-decade-old information could accurately predict the enterprise richness of modern towns in South Africa. The enterprise richness power law of towns in South Africa extends over space and time. Recent reviews of research on small towns and local economic development in South Africa have ignored the orderliness detected in their enterprise structures. Islands have provided laboratories for the study of natural evolution and the MacArthur-Wilson Species Equilibrium Model based on island biogeography was a main contributor to progress in ecology. Research on regional economic geography in South Africa should move beyond the merely descriptive/narrative to more quantified research. In considering the lack of employment and poverty in South Africa, the National Development Plan suggests that towns and rural areas are important cogs in efforts to overcome these problems. Development plans that are out of sync with the observed regularities are perhaps bound to fail. SIGNIFICANCE: • Prediction of enterprise composition and dynamics in South African towns. <![CDATA[<b>Emission factors of domestic coal-burning braziers</b>]]> We present experimental results of emission factors from a suite of domestic coal-burning braziers (lab fabricated and field collected) that span the possible range of real-world uses in the Highveld region of South Africa. The conventional bottom-lit updraft (BLUD) method and the top-lit updraft (TLUD) method were evaluated using coal particle sizes between 20 mm and 40 mm. Emission factors of CO2, CO and NOx were in the range of 98-102 g/MJ, 4.1-6.4 g/MJ and 75-195 mg/MJ, respectively. Particulate matter (PM25 and PM10) emissions were in the range 1.3-3.3 g/MJ for the BLUD method and 0.2-0.7 g/MJ for the TLUD method, for both field and lab-designed stoves. When employing the TLUD method, emission factors of PM25/PM10 reduced by up to 80% compared with those when using the BLUD method. Results showed the influence of ventilation rates on emission factors, which reduced by ~50% from low to high ventilation rates. For energy-specific emission rates, the combined (3-h) PM10 emission rates were in the range of 0.0028-0.0120 g/s, while the combined average CO emission rates were in the range of 0.200.26 g/s, with CO2 emission rates in the range of 0.54-0.64 g/s. The reported emission factors from coal braziers provide the first comprehensive, systematic set of emission factors for this source category, and fill a major gap in previous efforts to conduct dispersion modelling of South African Highveld air quality. SIGNIFICANCE: • The study provides the first comprehensive, systematic set of emission factors from coal braziers. • The study fills a major gap in previous efforts to conduct dispersion modelling of South African Highveld air quality. • Results have implications for stove design and lay the groundwork for improvements in the design of existing coal braziers. • Results have implications for understanding the potential health impacts of condensed matter emissions from coal braziers. <![CDATA[<b>Co-infection with <i>Schistosoma haematobium </i>and soil-transmitted helminths in rural South Africa</b>]]> Schistosomiasis and soil-transmitted helminthiasis are among the most prevalent neglected tropical diseases and may lead to severe consequences. We assessed the extent of co-infection between Schistosoma haematobium and the soil-transmitted helminths (STHs) Ascaris lumbricoides and Trichuris trichiura in schoolgirls in the rural areas of KwaZulu-Natal, South Africa. We also explored if S. haematobium can serve as a predictor for soil-transmitted helminths in this area. From 15 selected schools, 726 primary schoolgirls aged 10-12 years provided both urine and stool samples. The samples were examined for the presence of eggs using the urine sedimentation technique for S. haematobium and the Kato Katz technique for STHs. Pearson's chi-square test was used to calculate the association and Spearman's rank correlation was used for the correlation analysis. There was a highly significant correlation between S. haematobium and STHs at a school level (Spearman's correlation coefficient =0.93; p<0.001). The prevalences were found to be 36.9% and 38.8% for S. haematobium and STHs, respectively. A significant association was found between S. haematobium and STHs (odds ratio =2.05; confidence interval =1.58-2.93; p<0.001). Indirect indicators of urogenital schistosomiasis (e.g. water contact and haematuria) were significantly associated with A. lumbricoides and T. trichiura infection. We have demonstrated a highly significant correlation and overall association between urogenital schistosomiasis and A. lumbricoides and T. trichiura. We cautiously suggest that all S. haematobium endemic areas should be treated for STH infections. SIGNIFICANCE: • The prevalences of urogenital schistosomiasis and soil-transmitted helminth infections were highly significantly correlated. • More than half (60%) of the investigated schools are in need of annual treatment for S. haematobium infection. • Almost half of the infected schoolgirls had a heavy intensity of S. haematobium infection. • Nearly all the schools investigated require treatment for soil-transmitted helminthiasis once or even twice per year. • This study can contribute to the epidemiological planning process of the deworming programme. <![CDATA[<b>Characterisation of <i>vumba </i>and <i>ubumba </i>clays used for cosmetic purposes</b>]]> Two traditional cosmetic clays bear similar names in different local South African languages: vumba (Tshivenda) and ubumba (isiZulu). The wet clays are applied topically for cosmetic purposes by the respective indigenous peoples. Six samples from two South African provinces were characterised using X-ray diffraction, X-ray fluorescence spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis and scanning electron microscopy. It was found that the samples differed widely with respect to mineralogy and chemical composition. This finding raises the possibility that texture characteristics during application on the skin override composition effects. Of concern is the high levels of quartz found in all the samples as it might pose a health hazard; the lowest value for quartz was 11 wt% for vumba, while values for ubumba ranged from 26 wt% to 85 wt%. All samples contained varying amounts of silicates in the form of smectite, kaolin, chlorite and plagioclase. Minor amounts of anatase and rutile were present in some samples. Three samples also contained goethite. All samples were essentially free from the toxic elements As, Pb, Hg, Cd, Se and Sb. However, they did contain low levels of chromium and heavy metals such as Cu, Zn and Ni. The pH values of ubumba slurries were slightly basic, while those of a vumba slurry were slightly acidic. SIGNIFICANCE: • Wide ranges of composition appear to be acceptable. • The clays do not contain highly toxic or radioactive elements. • The high levels of quartz present may pose a human health risk. <![CDATA[<b>Potential for identifying plant-based toxins on San hunter-gatherer arrowheads</b>]]> The antiquity of the use of hunting poisons has received much attention in recent years. In this paper we present the results of a pilot study designed to detect the presence of organic compounds, typically of less than 1200 Da, from poisonous plants that may have been used as hunting poisons in the past. We used ultra-performance liquid chromatography connected to a Synapt G2 high-resolution MS-QTOF mass spectrometer (UPLC-QTOF-MS) to provisionally identify plant-based toxins present in (1) extracts of fresh plant material, (2) a blind control recipe consisting of three plant ingredients and (3) a Hei||om arrow poison of unknown ingredients. Although not all expected toxic compounds were identified, those that were identified compared favourably with those reported in the literature and confirmed through databases, specifically the Dictionary of Natural Products and ChemSpider. MS/MS fragmentation patterns and accurate mass were used for tentative identification of compounds because archaeological residues usually contain insufficient material for unambiguous identification using nuclear magnetic resonance. We highlight the potential of this method for accurately identifying plant-based toxins present on archaeological artefacts and unique (albeit non-toxic) chemical markers that may allow one to infer the presence of toxic plant ingredients in arrow poisons. Any chemical study of archaeological material should consider the unique environmental degradative factors and be sensitive to the oxidative byproducts of toxic compounds. SIGNIFICANCE: • Methodology is presented for the identification of ancient plant-based arrow poisons.