Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320110003&lang=en vol. 107 num. 5-6 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Viable opposition is good for democracy</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300001&lng=en&nrm=iso&tlng=en <![CDATA[<b>The impact of acid mine drainage in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300002&lng=en&nrm=iso&tlng=en <![CDATA[<b>Not all seafood is equal</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300003&lng=en&nrm=iso&tlng=en <![CDATA[<b><i>Tiarajudens</i></b>: <b>a significant mammal-like reptile</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300004&lng=en&nrm=iso&tlng=en <![CDATA[<b>The war for South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300005&lng=en&nrm=iso&tlng=en <![CDATA[<b>Knowledge divides and other tales from social science</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300006&lng=en&nrm=iso&tlng=en <![CDATA[<b>Stephen Watson</b>: <b>poet, scholar and critic (1954-2011)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300007&lng=en&nrm=iso&tlng=en <![CDATA[<b>Biofuels and biodiversity in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300008&lng=en&nrm=iso&tlng=en The South African government, as part of its efforts to mitigate the effects of the ongoing energy crisis, has proposed that biofuels should form an important part of the country's energy supply. The contribution of liquid biofuels to the national fuel supply is expected to be at least 2% by 2013. The Biofuels Industrial Strategy of the Republic of South Africa of 2007 outlines key incentives for reaching this target and promoting the development of a sustainable biofuels industry. This paper discusses issues relating to this strategy as well as key drivers in biofuel processing with reference to potential impacts on South Africa's rich biological heritage. Our understanding of many of the broader aspects of biofuels needs to be enhanced. We identify key areas where challenges exist, such as the link between technology, conversion processes and feedstock selection. The available and proposed processing technologies have important implications for land use and the use of different non-native plant species as desired feedstocks. South Africa has a long history of planting non-native plant species for commercial purposes, notably for commercial forestry. Valuable lessons can be drawn from this experience on mitigation against potential impacts by considering plausible scenarios and the appropriate management framework and policies. We conceptualise key issues embodied in the biofuels strategy, adapting a framework developed for assessing and quantifying impacts of invasive alien species. In so doing, we provide guidelines for minimising the potential impacts of biofuel projects on biodiversity. <![CDATA[<b>Land use and soil organic matter in South Africa 1</b>: <b>a review on spatial variability and the influence of rangeland stock production</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300009&lng=en&nrm=iso&tlng=en Degradation of soil as a consequence of land use poses a threat to sustainable agriculture in South Africa, resulting in the need for a soil protection strategy and policy. Development of such a strategy and policy require cognisance of the extent and impact of soil degradation processes. One of the identified processes is the decline of soil organic matter, which also plays a central role in soil health or quality. The spatial variability of organic matter and the impact of grazing and burning under rangeland stock production are addressed in this first part of the review. Data from uncoordinated studies showed that South African soils have low organic matter levels. About 58% of soils contain less than 0.5% organic carbon and only 4% contain more than 2% organic carbon. Furthermore, there are large differences in organic matter content within and between soil forms, depending on climatic conditions, vegetative cover, topographical position and soil texture. A countrywide baseline study to quantify organic matter contents within and between soil forms is suggested for future reference. Degradation of rangeland because of overgrazing has resulted in significant losses of soil organic matter, mainly as a result of lower biomass production. The use of fire in rangeland management decreases soil organic matter because litter is destroyed by burning. Maintaining or increasing organic matter levels in degraded rangeland soils by preventing overgrazing and restricting burning could contribute to the restoration of degraded rangelands. This restoration is of the utmost importance because stock farming uses the majority of land in South Africa. <![CDATA[<b>Land use and soil organic matter in South Africa 2</b>: <b>a review on the influence of arable crop production</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300010&lng=en&nrm=iso&tlng=en The decline of soil organic matter as a result of agricultural land use was identified for a review with the ultimate aim of developing a soil protection strategy and policy for South Africa. Such a policy is important because organic matter, especially the humus fraction, influences the characteristics of soil disproportionately to the quantities thereof present. Part 1 of this review dealt with the spatial variability of soil organic matter and the impact of grazing and burning under rangeland stock production. In this second part of the review, the impact of arable crop production on soil organic matter is addressed. A greater number of studies have addressed the degradation of soil organic matter that is associated with arable crop production than the restoration. However, cropping under dryland has been found to result in significant losses of soil organic matter, which is not always the case with cropping under irrigation. Restoration of soil organic matter has been very slow upon the introduction of conservational practices like zero tillage, minimal tillage, or mulch tillage. Reversion of cropland to perennial pasture has also been found to result in discouragingly slow soil organic matter restoration. Although increases or decreases in soil organic matter levels have occurred in the upper 300 mm, in most instances this took place only in the upper 50 mm. The extent of these changes was dependent inter alia on land use, soil form and environmental conditions. Loss of soil organic matter has resulted in lower nitrogen and sulphur reserves, but not necessarily lower phosphorus reserves. Depletion of soil organic matter coincided with changes in the composition of amino sugars, amino acids and lignin. It also resulted in a decline of water stable aggregates which are essential in the prevention of soil erosion. Although much is known about how arable crop production affects changes in soil organic matter, there are still uncertainties about the best management practices to maintain and even restore organic matter in degraded cropland. Coordinated long-term trials on carefully selected ecotopes across the country are therefore recommended to investigate cultivation practices suitable for this purpose. <![CDATA[<b>A review of marine phylogeography in southern Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300011&lng=en&nrm=iso&tlng=en The southern African marine realm is located at the transition zone between the Atlantic and Indo-Pacific biomes. Its biodiversity is particularly rich and comprises faunal and floral elements from the two major oceanic regions, as well as a large number of endemics. Within this realm, strikingly different biota occur in close geographic proximity to each other, and many of the species with distributions spanning two or more of the region's marine biogeographic provinces are divided into evolutionary units that can often only be distinguished on the basis of genetic data. In this review, we describe the state of marine phylogeography in southern Africa, that is, the study of evolutionary relationships at the species level, or amongst closely related species, in relation to the region's marine environment. We focus particularly on coastal phylogeography, where much progress has recently been made in identifying phylogeographic breaks and explaining how they originated and are maintained. We also highlight numerous shortcomings that should be addressed in the near future. These include: the limited data available for commercially important organisms, particularly offshore species; the paucity of oceanographic data for nearshore areas; a dearth of studies based on multilocus data; and the fact that studying the role of diversifying selection in speciation has been limited to physiological approaches to the exclusion of genetics. It is becoming apparent that the southern African marine realm is one of the world's most interesting environments in which to study the evolutionary processes that shape not only regional, but also global patterns of marine biodiversity. <![CDATA[<b>Bibliometric analysis of public health research in Africa</b>: <b>the overall trend and regional comparisons</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300012&lng=en&nrm=iso&tlng=en Many diseases in Africa can be prevented with appropriate public health interventions. This study aimed to assess the bibliometric characteristics of public health related research articles published by researchers in African institutions from 1991 to 2005. Data used in this study were obtained from the online version of the ISI Web of Science: Science Citation Index Expanded (SCI-Expanded). Articles published between 1991 and 2005 that had the phrase 'public health' in the title, author keywords or abstract, and had at least one author whose contact address was in an African country, were selected for analysis. The annual number of public health related articles published by African researchers significantly increased from 28 articles in 1991 to 135 articles in 2005, a 382% increase. International collaboration also increased: from 45% of articles having international collaborators during 1991-1995, to 52% during1996-2000, and to 67% during 2001-2005. Collaborations were mostly with European and North American countries. Keywords, subject categories and collaboration patterns of articles varied across regions, reflecting differences in needs and collaboration networks. Public health related research output, as well as international collaborations, have been increasing in Africa. Regional variation observed in this study may assist policymakers to facilitate the advancement of public health research in different regions of Africa, and could be useful for international organisations in identifying needs and to allocate research funding. Future bibliometric analyses of articles published by African researchers, can consider conducting regional comparisons using standardised methods, as well as describing the overall patterns, in order to provide a more comprehensive view of their bibliometric characteristics. <![CDATA[<b>A comparative analysis of the hominin triquetrum (SKX 3498) from Swartkrans, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300013&lng=en&nrm=iso&tlng=en The SKX 3498 triquetrum from Member 2 at Swartkrans Cave, South Africa is the only hominin triquetrum uncovered (and published) thus far from the early Pleistocene hominin fossil record. Although SKX 3498 was found over two decades ago, its morphology has not been formally described or analysed, apart from the initial description. Furthermore, the taxonomic attribution of this fossil remains ambiguous as both Paranthropus and early Homo have been identified at Swartkrans. This analysis provides the first quantitative analysis of the SKX 3498 triquetrum, in comparison to those of extant hominids (humans and other great apes) and other fossil hominins. Although the initial description of the SKX 3498 triquetrum summarised the morphology as generally human-like, this analysis reveals that quantitatively it is often similar to the triquetra of all hominine taxa and not necessarily humans in particular. Shared hominid-like morphology between SKX 3498 and Neanderthals suggests that both may retain the symplesiomorphic hominin form, but that functional differences compared to modern humans may be subtle. Without knowledge of triquetrum morphology typical of earlier Pliocene hominins, the taxonomic affiliation of SKX 3498 remains unclear. <![CDATA[<b>Investigation of the power coupling of novel wavelength-selective couplers incorporating axially symmetric long-period fibre gratings</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300014&lng=en&nrm=iso&tlng=en Evanescent-field coupling was studied experimentally in novel optical-fibre-based wavelength-selective couplers, using axially symmetric long-period fibre grating (LPFG) structures. The coupling characteristics of a wavelength-selective coupler at the resonant wavelength were investigated for different LPFG offset distances. It was shown that the wavelength-selective couplers effectively transferred light power at the LPFG resonant wavelength from one fibre to another. The performance of the couplers was consistent with simulations performed in MATLAB using coupled-mode theory. <![CDATA[<b>The effect of work accidents on the efficiency of production in the coal sector</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300015&lng=en&nrm=iso&tlng=en In comparison with other sectors, mining is one of the sectors with the highest rates of work accidents. Such accidents negatively affect a country's economy by wasting domestic resources and causing losses of both labour force and working days. What distinguishes mining from other branches of industry is that its working environments change continually and the working conditions are particularly harsh. Because of the practice of labour-intensive underground production methods, which leads to an increase in risk factors in terms of work accidents, and the fact that coal is a leading resource in meeting the ever-increasing demand for energy, this study investigated how work accidents affected the efficiency of production in the Turkish Hard Coal Enterprise (TTK) between 1987 and 2006. Using data envelopment analysis, the overall sources of technical inefficiency in the years examined were determined. The results from this analysis revealed that the overall technical efficiency was as low as 69.7%, particularly as a result of the disaster in 1992; work accidents therefore had a negative effect on production efficiency. The greatest degree of pure technical inefficiency was found to have occurred in the period between 1992 and 2000, when the highest number of work accidents were noted, whilst the greatest degree of scale inefficiency was found to have occurred between 1987 and 1993. Because TTK has a prominent position among institutions and attaches great importance to workers' health and safety, an increase was noted in efficiency scores after 1993. <![CDATA[<b>A method for calculating the variance and confidence intervals for tree biomass estimates obtained from allometric equations</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300016&lng=en&nrm=iso&tlng=en The need for accurate quantification of the amount of carbon stored in the environment has never been greater. Carbon sequestration has become a vital component of the battle against global climate change, and monitoring and quantifying this process are major challenges for policymakers. Plant allometric equations allow managers and scientists to quantify the biomass contained in a tree without cutting it down, and therefore can play a pivotal role in measuring carbon sequestration in forests and savannahs. These equations have been available since the beginning of the 20th century, but their usefulness depends on the ability to estimate the error associated with the equations - something which has received scant attention in the past. This paper provides a method based on the theory of linear regression and the lognormal distribution to derive confidence limits for estimates of biomass derived from plant allometric equations. Allometric equations for several southern African savannah species are provided, as well as the parameters and equations required to calculate the confidence intervals. This method was applied to data collected from a sampling campaign carried out in a savannah landscape at the Skukuza flux site, Kruger National Park, South Africa. Here the error was 10% of the total site biomass for the woody biomass and 2% for the leaf biomass. When the data were split into individual plots and used to estimate site biomass (as would occur in most sampling schemes) the error increased to 16% and 12% of the woody and leaf biomasses, respectively, as the sampling errors were added to the errors in the allometric equation. These methods can be used in any discipline that applies allometric equations, such as health sciences and animal physiology. <![CDATA[<b>Anti-inflammatory and antimicrobial profiles of <i>Scilla nervosa</i> (Burch.) Jessop (Hyacinthaceae)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300017&lng=en&nrm=iso&tlng=en Scilla nervosa (Burch.) Jessop (Hyacinthaceae) [=Schizocarphus nervosus (Burch.) Van der Merwe] is a well-known plant in traditional medicine in South Africa, used for conditions associated with pain and inflammation, such as rheumatic fever. However, the topical anti-inflammatory and antimicrobial activities of the plant have not been investigated. A bioassay-guided fractionation approach was implemented to determine the biological activities of different extracts. A crude methanol extract was prepared from the bulbs to investigate the anti-inflammatory properties in a mouse model of acute croton oil-induced auricular contact dermatitis. The non-polar and polar components present in the methanol extract were separated by extraction with dichloromethane and ethanol, respectively; and their antimicrobial activity against the invasive pathogenic microorganisms Staphylococcus aureus, Klebsiellla pneumoniae and Candida albicans was investigated using a microplate method. Oedema induced by application of croton oil was significantly reduced 3 h (~66%) and 6 h (~40%) after treatment with the extracts. Anti-inflammatory activity was ~1.8-fold lower at 6 h, suggesting a potent, short-acting effect. The non-polar extract exhibited greater efficacy and potency against the microorganisms than the polar extract. The non-polar extract was equipotent against S. aureus and K. pneumoniae, but twice as potent against C. albicans as against the bacteria, suggesting little discrimination between Gram-positive and Gram-negative bacteria but specificity for the fungal yeast. The polar extract was the least potent against K. pneumoniae, but 10-fold more potent against C. albicans, suggesting specificity for Gram-positive bacteria and the fungal yeast. S. nervosa contains compounds that are individually, or in combination, potent anti-inflammatory and antimicrobial agents. The anti-inflammatory activity demonstrated here may rationalise the use of the plant in traditional medicine. <![CDATA[<b>DNH 109</b>: <b>A fragmentary hominin near-proximal ulna from Drimolen, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000300018&lng=en&nrm=iso&tlng=en We describe a fragmentary, yet significant, diminutive proximal ulna (DNH 109) from the Lower Pleistocene deposits of Drimolen, Republic of South Africa. On the basis of observable morphology and available comparative metrics, DNH 109 is definitively hominin and is the smallest African Plio-Pleistocene australopith ulna yet recovered. Mediolateral and anteroposterior dimensions of the proximal diaphysis immediately distal to the m. brachialis sulcus in DNH 109 yield an elliptical area (π/4 *m-l*a-p) that is smaller than the A.L. 333-38 Australopithecus afarensis subadult from Hadar. Given the unusually broad mediolateral anteroposterior diaphyseal proportions distal to the brachialis sulcus, the osseous development of the medial and lateral borders of the sulcus, and the overall size of the specimen relative to comparative infant, juvenile, subadult and adult comparative hominid ulnae (Gorilla, Pan and Homo), it is probable that DNH 109 samples an australopith of probable juvenile age at death. As a result of the fragmentary state of preservation and absence of association with taxonomically diagnostic craniodental remains, DNH 109 cannot be provisionally assigned to any particular hominin genus (Paranthropus or Homo) at present. Nonetheless, DNH 109 increases our known sample of available Plio-Pleistocene subadult early hominin postcrania.