Scielo RSS <![CDATA[South African Journal of Science]]> vol. 111 num. 9-10 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>What does 'science' mean in the title <i>South African Journal of Science?</i></b>]]> <![CDATA[<b>Mirror, mirror: The science</b>]]> <![CDATA[<b>For the love of insects</b>]]> <![CDATA[<b>An assessment of eight African universities: Contradictory functions, knowledge production and pacts</b>]]> <![CDATA[<b>South African scholars make Thomson Reuters 'Highly Cited Researchers 2014'</b>]]> <![CDATA[<b>A new star rising: Biology and mortuary behaviour of <i>Homo naledi</i></b>]]> <![CDATA[<b>A review of carbon dioxide as a refrigerant in refrigeration technology</b>]]> Tough environmental laws and stringent government policies have revolutionised the refrigeration sector, especially concerning the cycle fluid known as the refrigerant. It has been observed that only natural refrigerants are environmentally benign. When other refrigerant qualities are considered, especially those relating to toxicity and flammability, carbon dioxide emerges as the best among the natural refrigerants. However, carbon dioxide based refrigerants are not without drawbacks. Even though the use of R744 -a carbon dioxide based refrigerant gas - has solved the direct effect of emissions on the environment, studies to investigate the indirect effects of these systems are needed. Improvement in existing technical solutions and the formulation of additional solutions to existing R744 refrigeration problems is paramount if this technology is to be accepted by all, especially in areas with warm climates. National policies geared to green technologies are important to clear the way and provide support for these technologies. It is clear that carbon dioxide is one of the best refrigerants and as environmental regulations become more intense, it will be the ultimate refrigerant of the future. <![CDATA[<b>Review of the stability of biodiesel produced from less common vegetable oils of African origin</b>]]> The stability of biodiesel is dependent on storage conditions such as contact with ambient air and metals, exposure to sunlight and high temperature conditions which accelerate oxidation reactions. In addition, biodiesels are more susceptible to degradation when compared to fossil diesel because of the presence of unsaturated fatty acid chains which are prone to oxidation. The stability of biodiesel is categorised according to oxidation stability, storage stability and thermal stability. Oxidation instability can led to the formation of oxidation products such as aldehydes, alcohols, shorter chain carboxylic acids, insolubles, gums and sediments in the biodiesel. Thermal instability is concerned with the increased rate of oxidation at higher temperature, which in turn increases the weight of oil and fat due to the formation of insolubles. Storage stability is the ability of liquid fuel to resist change to its physical and chemical characteristics brought about by its interaction with its storage environment, such as contamination with metals. These fuel instabilities give rise to the formation of undesirable substances in biodiesel beyond acceptable limits as per global biodiesel standards such as those of the American Society for Testing and Materials (ASTM D6751) and European Standards (EN 14214). When such fuel is used in the engine, it impairs engine performance through fuel filter plugging, injector fouling, and deposit formation in the engine combustion chamber and various components of the fuel system. We review the stability of biodiesel made from less common vegetable oils of African origin and synthetic antioxidants used in improving the stability of produced biodiesels. <![CDATA[<b>Nematode pests threatening soybean production in South Africa, with reference to <i>Meloidogyne</i></b>]]> The area planted to soybean in South Africa has increased by 54% since the 2009 growing season, mainly as a result of the increasing demand for protein-rich food and fodder sources. Moreover, the introduction of advanced technology, namely the availability of genetically modified herbicide tolerant soybean cultivars also contributed towards increased soybean production. The omnipresence of plant-parasitic nematodes in local agricultural soils, however, poses a threat to the sustainable expansion and production of soybean and other rotation crops. Meloidogyne incognita and M. javanica are the predominant nematode pests in local soybean production areas and those where other grain-, legume- and/or vegetable crops are grown. The lack of registered nematicides for soybean locally, crop production systems that are conducive to nematode pest build-ups as well as the limited availability of genetic host plant resistance to root-knot nematode pests, complicate their management. Research aimed at various aspects related to soybean-nematode research, namely, audits of nematode assemblages associated with the crop, identification of genetic host plant resistance in soybean germplasm to M. incognita and M. javanica, the use of molecular markers that are linked to such genetic resistance traits as well as agronomic performance of pre-released cultivars that can be valuable to producers and the industry are accentuated in this review. Evaluation of synthetically-derived as well as biological-control agents are also discussed as complementary management tactics. It is important that lessons learned through extensive research on soybean-nematode interactions in South Africa be shared with researchers and industries in other countries as they might experience or expect similar problems and/or challenges. <![CDATA[<b>Comparative morphometric analysis of the proximal femur of African hominids and felids</b>]]> Size and shape of the mammalian proximal femur and taxon-specific distinctions in the relative proportions of the proximal articulation, the femoral neck and the proximal femoral diaphysis, are critical determinants in its adaptation to differential biomechanical stresses and observed locomotor habitus in different taxa. The morphometrics of the proximal femur are considered equally critical in the assessment of locomotor habitus of extinct fossil mammals, particularly extinct Miocene anthropoids and Plio-Pleistocene hominins. Analyses of size and shape of k=10 dimensions of the proximal femur were undertaken for a large sample series of two extant mammal families - the Felidae and Hominidae - using conventional multivariate statistical procedures, commonly used size-correction methods, and post-hoc tests of significance. While significant differences in form do exist, there are equally striking convergences in the functional morphology of extant hominid and felid taxa. Multivariate and bivariate allometric analyses confirm that the proximal femur of these two mammalian families share a common underlying structure manifest in a shared first common principal component. Nevertheless, while considerable convergences in general form of the proximal femur of African hominids and large-bodied felids are apparent, there exist equally discreet distinctions which are consistent with the differential structural demands imposed by their distinct locomotor and behavioural habitus. <![CDATA[<b>Determination of a novel size proxy in comparative morphometries</b>]]> Absolute size is a critical determinant of organismal biology, yet there exists no real consensus as to what particular metric of 'size' is empirically valid in assessments of extinct mammalian taxa. The methodological approach of JE Mosimann has found extensive favour in 'size correction' in comparative morphometrics, but not 'size prediction' in palaeontology and palaeobiology. Analyses of five distinct mammalian data sets confirm that a novel size variate (GMSize) derived from K=8 dimensions of the postcranial skeleton effectively satisfies all expectations of the Jolicoeur-Mosimann theorem of univariate and multivariate size. On the basis of strong parametric correlations between the K=8 variates and between scores derived from the first principal component and geometric mean size (GMSize) in all series, this novel size variable has considerable utility in comparative vertebrate morphometrics and palaeobiology as an appropriate descriptor of individual size in extant and extinct taxa. <![CDATA[<b>Plants, people and health: Three disciplines at work in Namaqualand</b>]]> In Paulshoek, Namaqualand, three research projects focusing on medicinal plants were developed concurrently. The projects were based in the disciplines of anthropology, botany and chemistry. In this paper, we explore how these projects related to one another and describe the conversations that occurred in the process of searching for transdisciplinary knowledge. The projects ostensibly shared a common object of knowledge, but it was through working together that the medicinal plants constituted us as a community of scholars. As our insight into our respective disciplinary relationships with the plants grew, so did our understanding of the limitations of our respective disciplinary positions. The process made possible a 'reimagination' of both the object of study and our relationships to it and to one another. The research project, conceptualised in 2009, engaged current debates on indigenous knowledge and its historical erasures, and offered an approach that has potential to produce new knowledges while respecting the integrity of the disciplines. This approach requires a non-competitive attitude to research and one that acknowledges the contributions that can be made by multiple approaches. <![CDATA[<b>Food consumption changes in South Africa since 1994</b>]]> Food consumption patterns in South Africa have changed dramatically over the past decades and likely will continue to change over the coming decades. Various food-related studies conducted over the last few decades indicate that food consumption shifts in South Africa have been towards a more Western-orientated diet, with nutritional consequences contributing to increased obesity and other non-communicable diseases. Several sources of data may be used to examine patterns in food consumption over time. Each of these methods has its own merits depending on the desired outcome, but are difficult to compare as each measures different levels of dietary information. As a result of the lack of regular national or comparable food consumption data in South Africa, the objective of this study was to establish, through the use of databases (FAOSTAT food balance sheets and Euromonitor International© Passport), the broad food and beverage consumption shifts in South Africa since 1994. Our findings indicate that food consumption shifts have been towards an overall increase in daily kilojoules consumed, a diet of sugar-sweetened beverages, an increase in the proportion of processed and packaged food including edible vegetable oils, increased intake of animal source foods, and added caloric sweeteners, and a shift away from vegetables. The largest shifts in food consumption were observed for soft drinks, sauces, dressings and condiments, sweet and savoury snacks, meat, and fats and oils. Convenience, health and nutrition, and indulgence were the main drivers of the increase in consumption of packaged foods and beverages. These shifts in food consumption are concerning as relates to their fat, sugar and salt composition and potential effect on public health. <![CDATA[<b>Revealing the social face of innovation</b>]]> Despite the introduction of social innovation in the 1996 White Paper on Science and Technology, the concept of social innovation has not been actively implemented or even diffused outside of the policy arena in South Africa. Perceptions about what the concept of social innovation should encompass are contested and range from ideas of social welfare outcomes, public goods and a primary focus on the poor. More recently, the emphasis has been on inclusive development that embraces and supports the poor as innovators and which incorporates elements of social and economic development. While contestation in terminology persists, evidence from South Africa's rural areas suggests that although there may be limited state intervention, hampered by structural constraints, and limited understanding of contemporary ideas about innovation and social innovation, local actors practise a variety of forms of social innovation. In most instances, the purpose is to improve social and economic well-being of the poor. Such innovation activities occur almost as widely and as often as strictly commercially oriented innovation activities. However, it is unclear from observed social innovation practices who should benefit from these practices (the poor or everyone), how (directly or indirectly) and when (immediately or gradually). It is suggested that extensive use of the actor-oriented sociological approach to understanding social dynamics in both science and development can provide a means of understanding the subtleties involved in innovation practices and its use should be adopted to address structural challenges within the National System of Innovation that mediate against the contribution of innovations to the poor for inclusive development. <![CDATA[<b>Sectoral electricity elasticities in South Africa: Before and after the supply crisis of 2008</b>]]> In this paper, we estimate the price elasticity of electricity for various industrial sectors of the South African economy from 2002 to 2011. The data used include sectoral electricity consumption data and electricity tariff data, both courtesy of Eskom as well as output data based on national statistics. The most important contribution this paper makes is that it includes the period after the sharp rises in electricity tariffs in 2007/2008 following a period of load-shedding and insecurity in electricity supply. Previous studies have included data only until 2007 and, for the most part, have found statistically insignificant, positive elasticities. However, for the period post-2007, we found statistically significant and negative elasticities for 9 of the 11 sectors considered. Our results show that the majority of industrial sectors have become much more sensitive to changes in the price of electricity following 2007/2008, indicating to policymakers that tariff restructuring might influence consumer behaviour significantly. <![CDATA[<b>The time to degree or dropout amongst full-time master's students at University of KwaZulu-Natal</b>]]> Universities around the world are grappling with strategies to increase throughput and minimise dropout rates of postgraduate students. This study focuses on students at the University of KwaZulu-Natal and we attempt to estimate the time that it takes for these students to successfully complete or drop out from a master's programme. We used survival analysis to identify the factors which affect this. The results of this analysis showed that having some form of financial aid and/or being a student in the Faculties of Humanities or Management, all significantly shortened the length of time that it took to eventually drop out from a master's programme. For students who successfully completed a master's degree, having some form of financial aid, being of international origin and/or being registered in the Faculties of Health, Humanities, Law or Management, all helped to significantly shorten the length of time it took to successfully complete a master's programme. Students in the Faculty of Medicine, however, took longer to successfully complete their studies. Black Africans took less time to complete their master's degrees when compared with otherwise identical students from the other race groups. <![CDATA[<b>Testing and implementation of a transportable and robust radio-element mapping system</b>]]> Gamma ray spectroscopy has been successfully applied as a survey tool in the fields of morphology, geology and mineral exploration. Gamma ray surveys are regularly done at ground level, which frequently requires transecting remote and unforgiving environments. Thus a need for the development of a transportable, robust and portable gamma ray detection system was identified. In addition to collecting radiation data, such a system was required to also provide the geographic position of the data and allow for various analyses tools to be utilised in the field. These functions were achieved by integrating a USB-driven scintillation detector with a field tablet and creating software to control acquisition and analyses of radiation data, as well as logging position. The system was tested in different geographical locations under different modes of transport. The instrument was tested by employing several different methods of data analysis in order to extract natural nuclide condensations. The consistency in the obtained data demonstrated the reliability of the instrument in the different environments. The system also successfully replicated previous radio-element survey findings and provided information on several geographical phenomena, including information on the geology, paved road structure and beach sediment characteristics. <![CDATA[<b>An LC-MS/MS based survey of contaminants of emerging concern in drinking water in South Africa</b>]]> Advances in many analytical techniques allow the detection of compounds in water at very low concentrations (ng/L), which has facilitated the identification of many compounds in drinking water that went previously undetected. Some of these compounds are contaminants of emerging concern (CECs), which is broadly defined as any chemical or microorganism that is not currently being routinely monitored but has recently been identified as being present in the environment, and that may pose health or ecological risks. CECs can include pharmaceuticals, personal health care products and pesticides. Some CECs can act as endocrine disruptors, interfering with the normal functioning of the human endocrine system, potentially influencing foetal and child development. Although the level of many of these compounds are orders of magnitude below known acute toxicity levels, the health impact of long term exposure at low levels is mostly unknown. In this study, we present the results of a national survey over four seasons of potential CECs in the drinking water of major South African cities. The contaminants most often detected were the related herbicides atrazine and terbuthylazine, and the anticonvulsant and mood-stabilising drug, carbamazepine. The levels of these CECs were well below maximum levels proposed by the World Health Organization and the US Environmental Protection Agency. However, the range of CECs detected in drinking water, and seasonal and geographic variability in CECs levels, warrant a more frequent screening programme. <![CDATA[<b>Estimation and monitoring of aboveground carbon stocks using spatial technology</b>]]> Monitoring temporal changes of aboveground carbon (AGC) stocks distribution in subtropical thicket is key to understanding the role of vegetation in carbon sequestration. The main objectives of this research paper were to model and quantify the temporal changes of AGC stocks between 1972 and 2010 in the Great Fish River Nature Reserve and its environs, Eastern Cape Province, South Africa. We used a method based on the integration of remote sensing and geographical information systems to estimate AGC stocks in a time series framework. A non-linear regression model was developed using Normalised Difference Vegetation Index values generated from SPOT 5 High Resolution Geometric satellite imagery of 2010 as an independent variable and AGC stock estimates from field plots as the dependent variable. The regression model was used to estimate AGC stocks from satellite imagery for 1972 (Landsat TM), 1982 (Landsat 4 TM), 1992 (Landsat 7 ETM), 2002 (Landsat ETM+) and 2010 (SPOT 5) satellite imagery. AGC stocks for the respective years were compared by means of change detection analysis at the subtropical thicket class level. The results showed a decline of AGC stocks in all the classes from 1972 to 2010. Degraded and transformed thicket classes had the highest AGC stock losses. The decline of AGC stocks was attributed to thicket transformation and degradation, which were attributed to anthropogenic activities. <![CDATA[<b>Digital terrain model height estimation using support vector machine regression</b>]]> Digital terrain model interpolation is intrinsically a surface fitting problem, in which unknown heights H are estimated from known X-Y coordinates. Notable methods of digital terrain model interpolation include inverse distance to power, local polynomial, minimum curvature, modified Shepard's method, nearest neighbour and polynomial regression. We investigated the support vector machine regression (SVMR) as a new alternative method to these models. SVMR is a contemporary machine learning algorithm that has been applied to several real-world problems aside from digital terrain modelling. The SVMR results were compared with those from notable parametric (the nearest neighbour) and non-parametric (the artificial neural network) techniques. Four categories of error analysis were used to assess the accuracy of the modelling: minimum error, maximum error, means error and standard error. The results indicate that SVMR furnished the lowest error, followed by the artificial neural network model. The SVMR also produced the smoothest surface followed by the artificial neural network model. The high accuracy furnished by SVMR in this experiment attests that SVMR is a promising model for digital terrain model interpolation. <![CDATA[<b>Modelling of extreme minimum rainfall using generalised extreme value distribution for Zimbabwe</b>]]> We modelled the mean annual rainfall for data recorded in Zimbabwe from 1901 to 2009. Extreme value theory was used to estimate the probabilities of meteorological droughts. Droughts can be viewed as extreme events which go beyond and/or below normal rainfall occurrences, such as exceptionally low mean annual rainfall. The duality between the distribution of the minima and maxima was exploited and used to fit the generalised extreme value distribution (GEVD) to the data and hence find probabilities of extreme low levels of mean annual rainfall. The augmented Dickey Fuller test confirmed that rainfall data were stationary, while the normal quantile-quantile plot indicated that rainfall data deviated from the normality assumption at both ends of the tails of the distribution. The maximum likelihood estimation method and the Bayesian approach were used to find the parameters of the GEVD. The Kolmogorov-Smirnov and Anderson-Darling goodness-of-fit tests showed that the Weibull class of distributions was a good fit to the minima mean annual rainfall using the maximum likelihood estimation method. The mean return period estimate of a meteorological drought using the threshold value of mean annual rainfall of 473 mm was 8 years. This implies that if in the year there is a meteorological drought then another drought of the same intensity or greater is expected after 8 years. It is expected that the use of Bayesian inference may better quantify the level of uncertainty associated with the GEVD parameter estimates than with the maximum likelihood estimation method. The Markov chain Monte Carlo algorithm for the GEVD was applied to construct the model parameter estimates using the Bayesian approach. These findings are significant because results based on non-informative priors (Bayesian method) and the maximum likelihood method approach are expected to be similar. <![CDATA[<b>Studies on CO variation and trends over South Africa and the Indian Ocean using TES satellite data</b>]]> In this study, we used measurements from the tropospheric emission spectrometer aboard the Earth Observing System's Aura satellite over South Africa, Madagascar and Reunion Island to investigate variations and trends in tropospheric carbon monoxide (CO) over 5 years, from 2005 to 2009, and at 47 pressure levels from 1000 hPa to 10 hPa. We believe that the study is the first of its kind to address the use of space-borne data for CO distribution over southern Africa. Maximum CO was recorded during spring and minimum during summer. Positive anomalies were identified in 2005 and 2007 during the spring and negative anomalies in the beginning of the year (especially in 2006, 2008 and 2009). The estimated trends based on a linear regression method on inter-annual distribution predicted a decreasing rate of 2.1% per year over South Africa, 1.8% per year over Madagascar and 1.7% per year over Reunion Island. The surface CO measurements made at Cape Point station (34.35°S, 18.48°E) showed an average decline of 0.1 ppb per month, which corresponded to 2.4% of the average annual mean for the studied period. The observed decrease in CO was linked to the La Nina event which occurred in 2006 and 2008 and a declining rate of biomass burning activity in the southern hemisphere over the observation period. TES measurements are in agreement with ground-based measurements and can be used with confidence to complement CO measurements for future analyses over the southern tropics and middle latitude. <![CDATA[<b>Systematic land-cover change in KwaZulu-Natal, South Africa: Implications for biodiversity</b>]]> Land-cover change and habitat loss are widely recognised as the major drivers of biodiversity loss in the world. Land-cover maps derived from satellite imagery provide useful tools for monitoring land-use and land-cover change. KwaZulu-Natal, a populous yet biodiversity-rich province in South Africa, is one of the first provinces to produce a set of three directly comparable land-cover maps (2005, 2008 and 2011). These maps were used to investigate systematic land-cover changes occurring in the province with a focus on biodiversity conservation. The Intensity Analysis framework was used for the analysis as this quantitative hierarchical method addresses shortcomings of other established land-cover change analyses. In only 6 years (2005-2011), a massive 7.6% of the natural habitat of the province was lost to anthropogenic transformation of the landscape. The major drivers of habitat loss were agriculture, timber plantations, the built environment, dams and mines. Categorical swapping formed a significant part of landscape change, including a return from anthropogenic categories to secondary vegetation, which we suggest should be tracked in analyses. Longer-term rates of habitat loss were determined using additional land-cover maps (1994, 2000). An average of 1.2% of the natural landscape has been transformed per annum since 1994. Apart from the direct loss of natural habitat, the anthropogenically transformed land covers all pose additional negative impacts for biodiversity remaining in these or surrounding areas. A target of no more than 50% of habitat loss should be adopted to adequately conserve biodiversity in the province. Our analysis provides the first provincial assessment of the rate of loss of natural habitat and may be used to fulfil incomplete criteria used in the identification of Threatened Terrestrial Ecosystems, and to report on the Convention on Biological Diversity targets on rates of natural habitat loss. <![CDATA[<b>The qualification of coal degradation with the aid of micro-focus computed tomography</b>]]> The production of unwanted coal fines during the handling and utilisation of coal is a serious problem in processes that rely on large or closely sized particles. Coal degradation occurs at many different steps within the beneficiation or utilisation processes and through many different mechanisms, none of which are understood thoroughly. In an effort to describe the degradation mechanisms, the changes within a number of coal particles were tracked using micro-focus X-ray computed tomography (μ-CT). The observed changes were caused by impact loading, compressive loading and thermal shock. The resolution of the μ-CT tomograms enabled the identification and tracking of changes in the coal microstructure. A comparison of the tomograms taken before, during and after breakage and fracture showed that the microstructure of coal had an influence on the breakage characteristics. For impact- and compressive loading as well as during thermal treatment, the biggest structural contributor was shown to be the network of pre-existing cracks and cleats within a particle. Lower density macerals contributed more to breakage than the higher density macerals and any structure (pre-existing cracks, lithotypes boundaries and mineral boundaries) present within the particles had the potential to either act as a crack initiation site, change the direction of a propagating crack or arrest crack propagation. The direction of the applied loads during compressive- and impact loading was the biggest contributor to the directionality of newly formed cracks. For thermal treatment, the vitrinite rich microlithotypes showed more new crack formation compared to the other microlithotypes present. The particles also showed no evidence of devolatilisation (an increase in the porosity of the particle) but did show evidence of thermal drying (new cracks formed perpendicular to existing cracks).