Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320100001&lang=en vol. 106 num. 1-2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<B>The <I>South African Journal of Science</I> adopts online publishing</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100001&lng=en&nrm=iso&tlng=en <![CDATA[<B>No deal at Copenhagen</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100002&lng=en&nrm=iso&tlng=en <![CDATA[<B>Ancient DNA from fossil equids</B>: <B>a milestone in palaeogenetics</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100003&lng=en&nrm=iso&tlng=en <![CDATA[<B>Southern African science in the year 1910 -100<I><SUP>n</B></I></SUP>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100004&lng=en&nrm=iso&tlng=en <![CDATA[<B>I braai, therefore I am</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100005&lng=en&nrm=iso&tlng=en <![CDATA[<B>A window onto the spectacular flora of South Africa</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100006&lng=en&nrm=iso&tlng=en <![CDATA[<B>How has South Africa's scientific landscape changed?</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100007&lng=en&nrm=iso&tlng=en <![CDATA[<B>Science in Wonderland</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100008&lng=en&nrm=iso&tlng=en <![CDATA[<B>Breaking tradition with scientific learning</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100009&lng=en&nrm=iso&tlng=en <![CDATA[<B>A review of phytoplankton dynamics in tropical African lakes</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100010&lng=en&nrm=iso&tlng=en This paper provides a synthesis of current knowledge on phytoplankton production, seasonality, and stratification in tropical African lakes and considers the effects of nutrient enrichment and the potential impacts of climate warming on phytoplankton production and composition. Tropical African lakes are especially sensitive to climate warming as they experience wide fluctuations in the thermocline over a narrow range of high water temperatures. Recent climate warming has reduced phytoplankton biomass and production in the lakes. A decline in the production of palatable chlorophytes and an increase in cyanobacteria has led to reduced zooplankton production and a consequent decline in fish stocks, all of which can be associated with the elevated water temperatures. This indicates that even moderate climate warming may destabilise phytoplankton dynamics in tropical African lakes, thereby reducing water quality and food resources for planktivorous fish, with consequent negative impacts on human livelihoods. <![CDATA[<B>Analysis of Ozone (O<SUB>3</SUB>) and Erythemal UV (EUV) measured by TOMS in the equatorial African belt</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100011&lng=en&nrm=iso&tlng=en We presented time series of total ozone column amounts (TOCAs) and erythemal UV (EUV) doses derived from measurements by TOMS (Total Ozone Mapping Spectrometer) instruments on board the Nimbus-7 (N7) and the Earth Probe (EP) satellites for three locations within the equatorial African belt for the period 1979 to 2000. The locations were Dar-es-Salaam (6.8º S, 39.26º E) in Tanzania, Kampala (0.19º N, 32.34º E) in Uganda, and Serrekunda (13.28º N, 16.34º W) in Gambia. Equatorial Africa has high levels of UV radiation, and because ozone shields UV radiation from reaching the Earth's surface, there is a need to monitor TOCAs and EUV doses. In this paper we investigated the trend of TOCAs and EUV doses, the effects of annual and solar cycles on TOCAs, as well as the link between lightning and ozone production in the equatorial African belt. We also compared clear-sky simulated EUV doses with the corresponding EUV doses derived from TOMS measurements. The TOCAs were found to vary in the ranges 243 DU - 289 DU, 231 DU - 286 DU, and 236 DU - 296 DU, with mean values of 266.9 DU, 260.9 DU, and 267.8 DU for Dar-es-Salaam, Kampala and Serrekunda, respectively. Daily TOCA time series indicated that Kampala had the lowest TOCA values, which we attributed to the altitude effect. There were two annual ozone peaks in Dar-es-Salaam and Kampala, and one annual ozone peak in Serrekunda. The yearly TOCA averages showed an oscillation within a five-year period. We also found that the EUV doses were stable at all three locations for the period 1979-2000, and that Kampala and Dar-es-Salaam were mostly cloudy throughout the year, whereas Serrekunda was mostly free from clouds. It was also found that clouds were among the major factors determining the level of EUV reaching the Earth&acute;s surface. Finally, we noted that during rainy seasons, horizontal advection effects augmented by lightning activity may be responsible for enhanced ozone production in the tropics. <![CDATA[<B>Historical mammal distribution data</B>: <B>how reliable are written records?</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100012&lng=en&nrm=iso&tlng=en Written historical records are widely used to estimate the previous distributions of the larger mammals in southern Africa. However, such records have some limitations and the use of those older than 100 years has been questioned. Written historical records, from the broader Eastern Cape, South Africa, were investigated to examine this contention critically. They were classified according to record quality (acceptability of identification and precision of locality) and analysed according to two levels: 'all' species and 'noticeable' versus 'non-noticeable' species. Records that comprise acceptable identification and precise locality information are the most suitable for mapping historical distributions; they form 33% of the records for the 27 mammal species analysed. A further 49% of the records have acceptable identification but imprecise locality information; they can fulfil a useful function when supported by records where both parameters are of good quality. Thus, the majority (82%) of written historical records from the study area are useful for compiling historical distribution maps and the quality of these records is consistent back to 1750 for this data set. The number and quality of written historical records varies between species. Historical distribution data should be evaluated for reliability (quality) and degree of usefulness, rather than simply discarded a priori. <![CDATA[<B>Henry Selby Hele-Shaw LLD, DSc, EngD, FRS, WhSch (1854-1941)</B>: <B>engineer, inventor and educationist</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100013&lng=en&nrm=iso&tlng=en H.S. Hele-Shaw (1854-1941) was one of the most outstanding engineering scientists of his generation and an eminent figure in engineering education during the late-19th and early-20th centuries. His work in hydrodynamics (the Hele-Shaw cell and Hele-Shaw pump) and his important contribution to the successful development of high-speed aircraft (his variable pitch airscrew), continues to be relevant today. In 1922, as President of the Institution of Mechanical Engineers, he introduced the National Certificate scheme in Britain. It is not well known that Hele-Shaw spent two years in South Africa (1904-1905) attached to the Transvaal Technical Institute, a forerunner of the University of the Witwatersrand. One of only three Fellows of the Royal Society of London in southern Africa in 1905, he was a founder Council member of the Royal Society of South Africa and one of the hosts of the 1905 visit to southern Africa by the British Association for the Advancement of Science. The purpose of this paper is to highlight the time he spent in South Africa and to contextualise it within the larger perspective of his engineering career. <![CDATA[<B>One or two species?</B><B> </B><B>A morphometric comparison between robust australopithecines from Kromdraai and Swartkrans</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100014&lng=en&nrm=iso&tlng=en The type specimen of Paranthropus robustus (TM 1517, including a partial cranium) was discovered at Kromdraai near Sterkfontein in 1938 and described by Robert Broom as a new species. Subsequently, more robust australopithecines were discovered at the nearby site of Swartkrans. These Swartkrans hominins were described by Broom as Paranthropus crassidens. Many palaeoanthropologists currently regard the robust australopithecines from Kromdraai and Swartkrans as one species, but consensus has not been reached on this issue. A morphometric analysis has been undertaken to assess the probability that specimens attributed to P. crassidens represent the same species as that which is represented by TM 1517, the holotype of P. robustus. Our results failed to reject the null hypothesis that both sites sample the same, single species of robust australopithecine. <![CDATA[<B>Antibiotic resistance profiles of <I>Escherichia coli</I> isolated from different water sources in the Mmabatho locality, north-west province, South Africa</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100015&lng=en&nrm=iso&tlng=en The antibiotic resistance profiles of Escherichia coli (E. coli), isolated from different water sources in the Mmabatho locality were evaluated. Water samples were collected from the local wastewater- and water-treatment plants, the Modimola Dam and homes in the area, and then analysed for the presence of E. coli, using standard methods. Presumptive isolates obtained were confirmed by the analytical profile index test. Antibiotic susceptibility testing was performed by the disc diffusion method. Of the 230 E. coli isolates tested, marked antibiotic resistances (over 70%) were observed for erythromycin, tetracycline, ampicillin, chloramphenicol and norfloxacin. Multiple antibiotic resistance patterns were also compiled. Overall, the phenotype T-Ap-E was frequent for E. coli isolated from the local wastewater and water-treatment plants, Modimola Dam and tap water. Cluster analysis performed showed a unique antibiotic resistance pattern which suggested a link between isolates from all sampling points. The findings indicated that improper wastewater treatment may have a potential impact on the dissemination and survival of E. coli, as well as other pathogenic bacteria in water for human and animal consumption. This may result in water- and food-borne disease outbreaks with a negative effect on antibiotic therapy. <![CDATA[<B>Forecasting electricity demand in South Africa</B>: <B>a critique of Eskom's projections</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100016&lng=en&nrm=iso&tlng=en Within a short period, Eskom has applied to the National Energy Regulator of South Africa (NERSA) for the third time since the 2008 electricity crisis, proposing a multiyear price determination for the periods 2010-2011 and 2012-2013. The new application, submitted at the end of September 2009, motivated for the debate of strategies with which the consequences of the proposed price hikes could be predicted, measured and controlled. In his presentation to Parliament in February 2009, Eskom's then CEO, Mr Jacob Maroga presented the current energy situation in the country, the reasons for the crisis in 2007-2008, as well as the challenges of the future. The purpose of this paper is to contribute some new ideas and perspectives to Eskom's existing arguments regarding the demand for electricity. The most important issue is the fact that Eskom does not sufficiently take into account the impact of the electricity prices in their electricity demand forecast. This study proposed that prices have a high impact on the demand for electricity (price elasticity of -0.5). Employing similar assumptions for the country's economic growth as Eskom, the results of the forecasting exercise indicated a substantial decrease in demand (scenario 1: -31% in 2025 and scenario 2:-18% in 2025). This study's findings contrasted significantly with Eskom's projection, which has extensive implications as far as policy is concerned. <![CDATA[<B>The effects of <I>Sutherlandia frutescens</I> extracts in cultured renal proximal and distal tubule epithelial cells</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100017&lng=en&nrm=iso&tlng=en Sutherlandia frutescens (SF), a medicinal plant indigenous to South Africa, is traditionally used to treat a diverse range of illnesses, including cancer and viral infections. The biologically active compounds of SF are polar, thus renal elimination increases susceptibility to toxicity in that organ. This study investigated the antioxidant potential, lipid peroxidation, mitochondrial membrane potential and apoptotic induction by SF extracts on proximal and distal tubule epithelial cells. Cell viability was determined using the MTT assay. Mitochondrial membrane potential was determined using a flow cytometric JC-1 Mitoscreen assay. Cellular glutathione and apoptosis were measured using the GSH-GloTM Glutathione assay and Caspase-Glo® 3/7 assay, respectively. The IC50 values from the cell viability results for LLC-PK1 and MDBK were 15 mg/mL and 7 mg/mL, respectively. SF extracts significantly decreased intracellular glutathione in LLC-PK1 (p < 0.0001) and MDBK (p < 0.0001) cells, while lipid peroxidation increased in treated LLC-PK1 (p < 0.0001) and MDBK (p < 0.0001) cells. JC-1 analysis showed that SF extracts promoted mitochondrial membrane depolarization in both LLC-PK1 and MDBK cells by up to 80% (p < 0.0001). The activity of caspase 3/7 increased in both LLC-PK1 (11.9-fold; p < 0.0001) and MDBK (2.2-fold; p < 0.0001) cells. SF extracts at high concentrations appear to increase oxidative stress, to alter mitochondrial membrane integrity, and to promote apoptosis in renal tubule epithelia. <![CDATA[<B>Characterisation of the arsenic resistance genes in <I>Bacillus</I> sp. UWC isolated from maturing fly ash acid mine drainage neutralised solids</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100018&lng=en&nrm=iso&tlng=en An arsenic resistant Bacillus sp. UWC was isolated from fly ash acid mine drainage (FA-AMD) neutralised solids. A genomic library was prepared and screened in an arsenic sensitive mutant Escherichia coli strain for the presence of arsenic resistance (ars) genes. Sequence analysis of a clone conferring resistance to both sodium arsenite and sodium arsenate revealed homologues to the arsR (regulatory repressor), arsB (membrane located arsenite pump), arsC (arsenate reductase), arsD (second regulatory repressor and a metallochaperone) and arsA (ATPase) genes from known arsenic resistance operons. The Bacillus sp. UWC arsRBCDA genes were shown to be arranged in an unusual manner with the arsDA genes immediately downstream of arsC. <![CDATA[<B>Apoptosis-promoting effects of <I>Sutherlandia frutescens</I> extracts on normal human lymphocytes <I>in vitro</B></I>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100019&lng=en&nrm=iso&tlng=en Sutherlandia frutescens (SF), an indigenous medicinal plant to South Africa, is traditionally used to treat a diverse range of illnesses. More specifically, the immune-enhancing potential of SF has been recognised to the extent that SF extracts have been recommended as an adjuvant in HIV/AIDS treatment by the South African Ministry of Health, despite a lack of knowledge of its mechanism of action or potential immune toxicity. As yet, unsubstantiated data support the notion of immunostimulatory effects of SF extracts in HIV-infected patients. This was suggested by post-treatment recovery of CD4+ cells brought about by the reduction of the impact of virus-induced apoptosis. This study investigated the apoptotic effects of SF extracts on normal human lymphocytes in vitro. Initially, an acute cytotoxic profile of SF extract was formulated, from which an IC50 of 7.5 mg/mL was calculated and administered for 3 h, 6 h and 12 h to cell populations. At 12 h, SF caused a significant increase in apoptosis in the total lymphocyte population and CD4+ cells as evidenced by increased phosphatidylserine (PS) translocation, caspase-3/7 activity, and decreased ATP content. After 12 h, the SF extract initiated lymphocyte activation in both total lymphocyte and CD4+ subpopulations, indicated by a doubling of the number of cells expressing the CD69 activation marker. The apoptosis observed may thus be the result of activation-induced lymphocyte cell death (AICD). Our results are in conflict with preliminary clinical evidence which has suggested SF extracts are possibly beneficial in the treatment of HIV infection. More extensive evaluations of the effects of SF extracts on the immune system in such subjects are urgently needed. <![CDATA[<B>Competence of Science Foundation students in basic intellectual skills</B>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000100020&lng=en&nrm=iso&tlng=en The competence of Science Foundation students at the Mafikeng Campus of North-West University in some basic intellectual skills was studied, over a period of three years, utilising carefully designed questions. The skills tested included language, mathematical, graphical, three-dimensional visualisation, information processing and reasoning skills. The results showed that their competence in the basic intellectual skills needed to study science effectively was far below standard. This lack of competence could be expected to be detrimental to self-confidence and may also be an important reason for the high failure rate of students in their science courses. We concluded with the suggestion that much greater emphasis should be placed on the systematic and sustained training of students in intellectual skills and strategies of various types and that such training should be integrated, throughout the courses, with the teaching of subject content.