Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320110006&lang=en vol. 107 num. 11-12 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Government urgently needs to provide additional bursaries to train talented teachers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600001&lng=en&nrm=iso&tlng=en <![CDATA[<b>The Humanities and Social Sciences in SA</b>: <b>crisis or cause for concern?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600002&lng=en&nrm=iso&tlng=en <![CDATA[<b>Can we improve postgraduate degree throughput rates?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600003&lng=en&nrm=iso&tlng=en <![CDATA[<b>A century of infrastructure service delivery</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600004&lng=en&nrm=iso&tlng=en <![CDATA[<b>On human evolution, <i>Australopithecus sediba</i> and nation building</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600005&lng=en&nrm=iso&tlng=en <![CDATA[<b>A field guide or a handbook?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600006&lng=en&nrm=iso&tlng=en <![CDATA[<b>Decay of eddies at the South-West Indian Ridge</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600007&lng=en&nrm=iso&tlng=en The South-West Indian Ridge in the Indian sector of the Southern Ocean is a region recognised for the creation of particularly intense eddy disturbances in the mean flow of the Antarctic Circumpolar Current. Eddies formed at this ridge have been extensively studied over the past decade using hydrographic, satellite, drifter and float data and it is hypothesised that they could provide a vehicle for localised meridional heat and salt exchange. The effectiveness of this process is dependent on the rate of decay of the eddies. However, in order to investigate eddy decay, logistically difficult hydrographic monitoring is required. This study presents the decay of cold eddies at the South-West Indian Ridge, using outputs from a high-resolution ocean model. The model's representation of the dynamic nature of this region is fully characteristic of observations. On average, 3-4 intense and well-defined cold eddies are generated per year; these eddies have mean longevities of 5.0±2.2 months with average advection speeds of 5±2 km/day. Most simulated eddies reach their peak intensity within 1.5-2.5 months after genesis and have depths of 2000 m - 3000 m. Thereafter they dissipate within approximately 3 months. The decay of eddies is generally characterised by a decrease in their sea surface height signature, a weakening in their rotation rates and a modification in their temperature-salinity characteristics. Subantarctic top predators are suspected to forage preferentially along the edges of eddies. The process of eddy dissipation may thus influence their feeding behaviour. <![CDATA[<b>Patents and economic development in South Africa</b>: <b>managing intellectual property rights</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600008&lng=en&nrm=iso&tlng=en Intellectual property rights systems are important policy instruments in the armoury of governments. They have the potential to have favourable or adverse consequences for the relevant national system of innovation, technology transfer, research and development and, eventually, economic growth. Whilst there is a debate related to optimisation of patent systems in the developed world, there is limited debate related to the approaches used in developing countries like South Africa. This article presents an effort to assess whether the South African non-examining patent system makes a contribution or if it is detrimental to the country's development. We found that the current intellectual property rights regime not only fails to support the objectives of the national innovation system but also that it facilitates exploitation by foreign interests and creates substantial social costs. Policy recommendations are provided. <![CDATA[<b>Effects of an aqueous leaf extract of <i>Sansevieria senegambica</i> Baker on plasma biochemistry and haematological indices of salt-loaded rats</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600009&lng=en&nrm=iso&tlng=en The effects of an aqueous extract of the leaves of Sansevieria senegambica on plasma marker enzymes, plasma chemistry and the haematological profile of salt-loaded rats were studied. The control group received only a commercial feed, whilst the four test groups received a diet consisting of the commercial feed and salt, although the reference treatment group was reverted to the normal feed at the end of 6 weeks. The extract was orally administered daily at 150 mg/kg or 200 mg/kg body weight to two test groups, respectively; whilst the test control, reference and control groups received equivalent volumes of water by the same route. The extract had no negative effects on markers of liver and kidney functions, but it did produce leukocytosis, significantly increased (p < 0.05) plasma calcium and potassium levels and significantly decreased (p < 0.05) plasma sodium and chloride levels in the test animals compared to the test control animals. This result supports the traditional use of Sansevieria senegambica in the management of hypertension, whilst suggesting that the extract may be a potassium-sparing diuretic whose mechanism of antihypertensive action may be achieved through alteration of plasma sodium and potassium balances, or through calcium-mediated changes in vascular muscle tone. <![CDATA[<b>Heat efficiency of a solar trough receiver with a hot mirror compared to a selective coating</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600010&lng=en&nrm=iso&tlng=en In this article, we present a solar trough system in which the receiver pipe is enclosed in a glass cover under vacuum. The dominant radiation losses from the receiver are reduced by the use of a 'hot mirror' on the glass cover instead of a selective coating on the receiver pipe. We present the results for a general heat transfer model and compare the performance of a selective coating with that of a hot mirror, using simulations. We determined that a hot mirror is a viable alternative to a selective coating, and certainly allows higher temperatures of the working fluid. We recommend the use of a hybrid system, in which a selective coating is used in the part of the receiver pipe in the low temperature region, and a hot mirror is used in the high temperature region to reduce radiation losses. <![CDATA[<b>Influence of gas discharge parameters on emissions from a dielectric barrier discharge excited argon excimer lamp</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600011&lng=en&nrm=iso&tlng=en A dielectric barrier discharge excited neutral argon (Ar I) excimer lamp has been developed and characterised. The aim of this study was to develop an excimer lamp operating at atmospheric pressure that can replace mercury lamps and vacuum equipment used in the sterilisation of medical equipment and in the food industry. The effects of discharge gas pressure, flow rate, excitation frequency and pulse width on the intensity of the Ar I vacuum ultraviolet (VUV) emission at 126 nm and near infrared (NIR) lines at 750.4 nm and 811.5 nm have been investigated. These three lines were chosen as they represent emissions resulting from de-excitation of excimer states that emit energetic photons with an energy of 9.8 eV. We observed that the intensity of the VUV Ar2* excimer emission at 126 nm increased with increasing gas pressure, but decreased with increasing excitation pulse frequency and pulse width. In contrast, the intensities of the NIR lines decreased with increasing gas pressure and increased with increasing pulse frequency and pulse width. We have demonstrated that energetic VUV photons of 9.8 eV can be efficiently generated in a dielectric barrier discharge in Ar. <![CDATA[<b>Publicising chemistry in a multicultural society through chemistry outreach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600012&lng=en&nrm=iso&tlng=en Given the emphasis in Higher Education on community engagement in South Africa and the importance of international collaboration, we discuss a joint approach to chemistry outreach in two countries on two continents with widely differing target school audiences. We describe the history of the partnership between the chemistry departments at Rhodes University and the University of Bristol and provide an outline of the chemistry content of their outreach initiatives, the modes of delivery, the advantages to both departments and their students for involvement in various levels of outreach, the challenges they still face and additional opportunities that such work facilitated. The lecture demonstration 'A Pollutant's Tale' was presented to thousands of learners all over the world, including learners at resource-deprived schools in South Africa. Challenges to extend outreach activities in South Africa include long travelling distances, as well as a lack of facilities (such as school halls and electricity) at schools. Outreach activities not only impacted on the target audience of young learners, they also impacted upon the postgraduate and other chemistry students taking part in these initiatives. This collaboration strengthened both institutions and their outreach work and may also lead to chemistry research collaborations between the academics involved. <![CDATA[<b>Single nucleotide and copy number polymorphisms of the SULT1A1 gene in a South African Tswana population group</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600013&lng=en&nrm=iso&tlng=en Previous studies on gene mapping have firmly established variation in segments of the DNA structure amongst different population groups. SULT1A1 is one of four SULT1A genes that maps to the short arm of chromosome 16, and this area has been shown to contain many repetitive sequences and to be highly duplicated. Using the polymerase chain reaction (PCR)-based restriction fragment length polymorphism method, we set out to determine the SULT1A1 genotype and allele frequency distributions in the largest sample studied to date: a homogeneous South African Tswana population of 1867 individuals from the Prospective Urban and Rural Epidemiological (PURE) study, and found the SULT1A1*1 and SULT1A1*2 alleles present at a frequency of 0.68 and 0.32, respectively. This finding corresponded with those obtained for the Black, Caucasian, and mixed-race South African groups reported in previous studies. Next, using a quantitative multiplex PCR method to estimate the SULT1A1 gene number of copies in 459 subjects of our population, we discovered between one and five copies: 0.65% of the subjects had a single copy (allele deletion) and 60.14% of the subjects had three or more copies. Our findings correspond with an earlier study on a small African- American group, but differ from those based on two Caucasian groups. Whereas the genotype distribution was comparable to the Caucasian groups, there was a significant difference in the number of copies, which indicated a genetic link between Tswana and African-American populations despite differences in cultural lifestyle associated with their geographical location. <![CDATA[<b>Molecular phylogeny of Duvenhage virus</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600014&lng=en&nrm=iso&tlng=en The Duvenhage virus (DUVV) constitutes one of the 11 species in the Lyssavirus genus and causes fatal rabies encephalitis. The virus is associated with insectivorous bat species and three human cases have been reported, all of which were linked to contact with bats. Few of these isolates have been studied and thus little is known about the phylogeny and epidemiology of this lyssavirus. Until 2007, when an isolate was made from the East African country of Kenya, all isolations of this virus had been from southern Africa. This discovery led to many questions regarding the spread and diversity of this lyssavirus. Phylogenetic analysis indicated that the DUVV isolates constitute two different lineages, in which the southern African isolates group together to form one lineage and the more recent isolate from Kenya constitutes a new, second lineage. We found that the new isolate has a genetic variation that has not yet been seen for DUVV. Not only is our lack of knowledge regarding the geographical distribution of this uniquely African virus emphasised, but we have also demonstrated the potential diversity within this genotype. <![CDATA[<b>3D techniques and fossil identification</b>: <b>an elephant shrew hemi-mandible from the Malapa site</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600015&lng=en&nrm=iso&tlng=en Conventional methods for extracting fossilised bones from calcified clastic sediments, using air drills or chemical preparations, can damage specimens to the point of rendering them unidentifiable. As an alternative, we tested an in silico approach that extended preparation and identification possibilities beyond those realisable using physical methods, ultimately proving to be crucial in identifying a fragile fossil. Image data from a matrix-encased hemi-mandible of a micromammal that was collected from the Plio-Pleistocene site of Malapa, Cradle of Humankind, South Africa, were acquired using microtomography. From the resultant images, a 3D rendering of the fossil was digitally segmented. Diagnostic morphologies were evaluated on the rendering for comparison with extant comparative specimens, positively identifying the specimen as an elephant shrew (Elephantulus sp.). This specimen is the first positively identified micromammal in the Malapa faunal assemblage. Cutting-edge in silico preparation technology provides a novel tool for identifying fossils without endangering bone integrity, as is commonly risked with physical preparation. <![CDATA[<b>Springtail diversity in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000600016&lng=en&nrm=iso&tlng=en Despite their significance in soil ecosystems and their use for investigations of soil ecosystem functioning and in bioindication elsewhere, springtails (Collembola) have not been well investigated in South Africa. Early recognition of their role in soil systems and sporadic systematic work has essentially characterised knowledge of the southern African fauna for some time. The situation is now changing as a consequence of systematic and ecological work on springtails. To date this research has focused mostly on the Cape Floristic Region and has revealed a much more diverse springtail fauna than previously known (136 identifiable species and an estimated 300 species for the Cape Floristic Region in total), including radiations in genera such as the isotomid Cryptopygus. Quantitative ecological work has shown that alpha diversity can be estimated readily and that the group may be useful for demonstrating land use impacts on soil biodiversity. Moreover, this ecological work has revealed that some disturbed sites, such as those dominated by Galenia africana, may be dominated by invasive springtail species. Investigation of the soil fauna involved in decomposition in Renosterveld and Fynbos has also revealed that biological decomposition has likely been underestimated in these vegetation types, and that the role of fire as the presumed predominant source of nutrient return to the soil may have to be re-examined. Ongoing research on the springtails will provide the information necessary for understanding and conserving soils: one of southern Africa's major natural assets.