Scielo RSS <![CDATA[South African Journal of Science]]> vol. 108 num. 7-8 lang. es <![CDATA[SciELO Logo]]> <![CDATA[<b>Square Kilometre Array decision bodes well for South Africa</b>]]> <![CDATA[<b>Science and human rights</b>]]> <![CDATA[<b>The limits of observational epidemiology</b>: <b>hormonal contraception and women's risk of HIV infection</b>]]> <![CDATA[<b>Young scientists reflect on how to effect real change for Rio+40</b>]]> <![CDATA[<b>Success in first-year mathematics</b>: <b>school-leaving examinations and first-year performance</b>]]> <![CDATA[<b>The state of innovation in South Africa</b>: <b>findings from the South African National Innovation Survey</b>]]> <![CDATA[<b>The sustainable use approach could save South Africa's rhinos</b>]]> <![CDATA[<b>Phillip Tobias</b>: <b>anthropologist and mentor (1925-2012)</b>]]> <![CDATA[<b>Convergence and divergence in fire-prone ecosystems</b>]]> <![CDATA[<b>Research Briefs</b>]]> <![CDATA[<b>Radiation biology</b>: <b>an important science for an advanced nuclear nation like South Africa</b>]]> The sustainability of radiation biology (radiobiology) is under threat in South Africa because of underdevelopment in the discipline, despite the fact that South Africa has been a user of radiation since radioactivity and X-rays were discovered. The widespread use of radiation in medicine, nuclear reactors, particle accelerators and other sophisticated nuclear facilities in South Africa makes it imperative that the interaction of radiation with biological systems is understood. For example, radiobiology is critical in radiation oncology and cancer treatment. Radiobiology is a distinctly biological science and its uniqueness and value should be highlighted to provide insight for authorities and other relevant parties. Regrettably, radiobiology has been largely neglected despite the importance of maintaining expertise and competence in this discipline. Many radiation-associated disciplines require radiobiology for their training and practice yet few radiobiologists are available nationally. The scientific community needs to be informed of the predicament of radiobiology in South Africa so that the situation can be addressed. Radiobiology is a scarce skill that needs to be developed to support South Africa's mature radiation infrastructure. The country has too few radiobiologist training programmes and there is a lack of succession planning. Radiobiology is required for training and practice in a number of disciplines that use radiation, but, as a result of a shortage of qualified personnel, teaching of radiobiology has frequently been conducted by non-experts. To reinvigorate radiobiology in South Africa, a collective effort by government, academia, industry and allied professionals is required. <![CDATA[<b>Beyond South Africa's 'indigenous knowledge - science' wars</b>]]> In this paper, the paradoxes and difficulties attending the notion of indigenous knowledge in South Africa are reviewed and an alternative dialogue about intellectual heritage is proposed. Beginning with a survey of debates on 'indigenous knowledge' and sciences in India, Australia and Latin America, the discussion draws attention to differences in regional discussions on the subject of knowledge diversity. Turning to the South African context, the paper foregrounds contradictions in the debate on traditional medicines and the sciences in relation to HIV. The bifurcation of 'indigenous knowledge' and 'science' is argued against. Debates on both indigenous knowledge and science within the critical humanities in South Africa have been characterised by denunciation: an approach which does not facilitate the important discussions needed on intellectual heritage, or on the relationship between sciences and coloniality. In dialogue with current research on the anthropology of knowledge, strategies are proposed to broaden the possibilities for scholarship on knowledge, sciences, and different ways of understanding the world. <![CDATA[<b>Effect of National Senior Certificate maths on the pass rate of first-year Engineering physics</b>]]> There has been much controversy about the mathematics results of the 2008 National Senior Certificate examinations - the first to be written by pupils following the outcomes-based curriculum. This article examines the impact of the new high school mathematics curriculum on the performance in physics by first-year Engineering students at the University of KwaZulu-Natal. The first-year physics results of the Engineering students who wrote the 2008 National Senior Certificate (NSC) examinations were compared with the physics results of the Engineering students of the previous 4 years who wrote the Senior Certificate Examinations (SCE). Analysis of variance was used to compare the average physics marks of the NSC and SCE groups. Correlation analysis was performed to determine the relationship between performance in high school mathematics with performance in first-year physics in Engineering for both the 2008 NSC group and the 2007 SCE group. The results showed a lower physics pass rate for the NSC students compared with that of the SCE students. There was also a significant difference in the average marks obtained in physics between the NSC students and the SCE students. The new high school mathematics curriculum has fallen short in providing essential skills and techniques for students who wish to study physics at university. Furthermore, the high school mathematics results of the NSC students are an indication of considerable grade inflation. <![CDATA[<b>Citrus black spot is absent in the Western Cape, Northern Cape and Free State Provinces</b>]]> The South African citrus industry is strongly focused on exports and South Africa is a signatory member of both the World Trade Organisation Agreement on the application of Sanitary and Phytosanitary Measures and the International Plant Protection Convention. Citrus black spot, caused by Guignardia citricarpa, does not occur in all the South African citrus production areas and, therefore, South Africa has a responsibility to provide those trading partners that have identified G. citricarpa as a regulated pest with reliable information about the distribution of citrus black spot within South Africa. Detection surveys were conducted in citrus production areas in the Western Cape, Northern Cape and Free State Provinces and appropriate diagnostic protocols were used to ensure reliable detection of G. citricarpa. Trees in commercial orchards and home gardens on farms and in towns of 17, 9 and 5 magisterial districts in the Western Cape, Northern Cape and Free State Provinces, respectively, were sampled between 1995 and 2010. Fruit samples were taken during June and July, and leaf samples from November to January. None of the 3060 fruit and leaf samples collected during these surveys tested positive for G. citricarpa. Phyllosticta capitalensis, a non-pathogenic, ubiquitous, endophytic species was, however, detected during these surveys. In compliance with relevant International Standards for Phytosanitary Measures and based on the outcome of these official surveys, these three provinces in South Africa can be recognised as citrus black spot pest free areas. <![CDATA[<b>Sensitivity versus polarisation in multilayer optical thin film design</b>]]> The design of a polarised optical filter is more complicated than that of a filter where the polarisation effect does not exist (at a normal angle of incidence). An error in the optical parameters, such as the physical thickness or refractive index of a layer, results in a change in the spectral performance of the multilayer structure. The correlation between error sensitivity and the polarisation effect of light in structures designed at an oblique angle was investigated. To illustrate the correlation, a perpendicular (S) and parallel (P) polarised beam splitter, at 0.9818 ìéôé central wavelength, designed by genetic algorithm, was used. The beam splitter changes its state of polarisation according to the error in thickness simultaneously induced in each of the layers. The error was calculated by optimising the original design. The observation of the change of the state of polarisation as a result of error sensitivity leads to a different method of designing pure S-polarised or P-polarised optical filters. <![CDATA[<b>Science in South Africa</b>: <b>the dawn of a renaissance?</b>]]> This article reports the findings of a scientometric analysis of South Africa's research performance during the period 2000-2010. A multitude of government incentives were introduced during the period and their effects have appeared in the country's research outputs. In contrast to earlier investigations, it was found that South Africa's world share of publications is on the verge of reaching the highest contribution ever. South Africa improved its international ranking by two positions during 2000-2010 and was ranked 33rd in the world during 2010. It is argued that, provided the plan of the Minister of Science and Technology to increase the research and development expenditure in the country materialises, South Africa may be on the verge of a scientific renaissance. <![CDATA[<b>Immobilisation of yeast cells on carbon nanotubes</b>]]> Carbon nanotubes are increasingly finding application in a wide range of industries. The focus of this study was to investigate the immobilisation of yeast cells onto carbon nanotubes, using a flocculation method, for possible use in fermentation processes. Carbon nanotubes, which are long thin cylinders of carbon, were used as artificial agents to induce flocculation of yeast cells. The immobilisation experiments on carbon nanotubes were conducted under different process conditions and compared with control experiments done on free cells. The resultant immobilised cells or flocs were recovered and freeze dried before analysis was performed. The flocculated cells were characterised by scanning electron microscopy to confirm that flocculation had occurred. Conditions that gave optimum flocculation on carbon nanotubes were found to be: a pH between 5.0 and 5.8, a temperature between 25 °C and 30 °C, an agitation speed of about 110 rpm, and a concentration of carbon nanotubes (in powder form) of between 44 mg/mL and 54 mg/mL. The addition of calcium ions and glucose decreased the rate of flocculation and delayed the onset of flocculation. Our study has demonstrated that carbon nanotubes have great potential to improve the flocculation capacity of brewer's yeast. <![CDATA[<b>A first record of biological soil crusts in the Cape Floristic Region</b>]]> To date, the biological soil crusts (BSCs) of southern Africa are thought to be dominated mainly by cyanobacteria, with the exception of the lichen fields of the Namib Desert. Because soil microorganisms can physically modify, maintain or create habitat for other organisms -including soil biota and plants - they have been considered ecosystem engineers. Therefore, the presence of BSCs may be a good indicator of ecosystem resilience. Although BSCs are found throughout the world, recent work has suggested that the absence of BSCs in the fynbos of South Africa may be as a result of the inherent acidity of soils. We surveyed one area within the fynbos biome for the presence of BSCs and determined the relative cover of vegetation and different crust types. We found a widespread presence (up to 80% of surface soil) of BSC communities in fynbos soils. We conclude that soil acidity may not be a constraining factor in the development of BSCs in fynbos soils and that previous reports on the absence of BSCs in fynbos soils may have been based on insufficient field observations. We encourage future studies in this region in order to determine the currently unexplored spatial distribution of soil microbial communities and the taxonomic composition of microorganisms in fynbos soils. <![CDATA[<b>Fumigant activity of <i>Elsholtzia stauntonii</i> extract against <i>Lasioderma serricorne</i></b>]]> The repeated use of phosphine over decades for the control of the cigarette beetle (Lasioderma serricorne), a significant stored-product insect worldwide, has led to serious negative effects, including strong insecticide resistance, disruption of biological control by natural enemies, and environmental and human health concerns. As an environmentally friendly alternative to synthetic pesticides, plant-derived pesticides have been the focus of much research. We investigated the fumigant activity of whole plant extracts of Elsholtzia stauntonii, a Chinese mint shrub, against the adult, larval, pupal and egg stages of L. serricorne. E. stauntonii extracts exhibited strong fumigant toxicity against L. serricorne; larvae and adults were more susceptible to this toxicity than were eggs and pupae. The toxicity significantly increased with increasing dosage. The corrected mortality of larvae, adults, pupae and eggs reached 99.32%, 97.97%, 44.67% and 33.33%, respectively, at a dosage of 40 μΙ^/Τ air after 48 h of exposure. The declining order of susceptibility of different developmental stages of L. serricorne to E. stauntonii extracts, as indicated by the concentration at which 50% of the insects died (LC50), was as follows: larvae (LC50= 8.82 air), adults (LC50= 10.99 air), pupae (LC50= 45.96 air) and eggs (LC50= 84.57 μΙ/L air). The results suggest that E. stauntonii extracts show promise as a fumigant for the control of L. serricorne. <![CDATA[<b>Modern beachrock formation in Durban, KwaZulu-Natal</b>]]> We explored the recent cementation of modern beachrock on the seaward margin of the Durban Bluff, central KwaZulu-Natal. The low latitude and subtropical climatic setting is a unique context compared to the more commonly documented contemporary beachrock formation in the tropics. Geological field mapping was carried out and here we present results based on sedimentary facies of a clastic shoreline and carbonate diagenesis of interstitial cements using transmitted light microscopy. The beachrock was cemented by micrite and aragonite, and iron oxide infilled voids. The presence of human artefacts within the deposit showed evidence for cementation within the last century. The elevation (at Mean Low Water) and correlation to rates of sea level change for the east coast of South Africa showed that the beachrock is less than 72 years in age. In contrast to older local Pleistocene deposits, beachrocks have cemented along this stretch of coast during successive sea level highstands with similar climatic regimes - the last Interglacial, the Holocene High and the present. Here we report the most southerly documentation of modern beachrock in KwaZulu-Natal, which, to our knowledge, represents the youngest deposit reported in southern Africa. <![CDATA[<b>Number One Reef</b>: <b>an overstepped segmented lagoon complex on the KwaZulu-Natal continental shelf</b>]]> This study of the bathymetry of the mid-shelf of the Durban Bight, KwaZulu-Natal revealed a series of previously undocumented seafloor features. These features were mapped using a high-resolution multibeam bathymetric echosounder and a detailed map of the seafloor topography was produced. We recognised several features that closely resemble features of contemporary segmented lagoon and lake systems: semicircular seafloor depressions, arcuate ridges, cuspate spits and prograding submerged barriers. Based on the striking similarity in morphology to Kosi Bay - a segmented lagoon system from the sandy northern KwaZuluNatal coastal plain - a similar evolutionary model is proposed. This model is of an incised valley formed following a sea level lowering to the Last Glacial Maximum at about 18 000 BP. Thereafter, continued transgressive infilling occurred to a point where an extensive lagoon and back-barrier system was established. At this point, sea levels remained static, causing the net segmentation of the system and the slow closure of the tidal basins or circular depressions. This type of seafloor topography is rarely preserved and is the result of fortuitous cementation after deposition and the later removal of sediment that would ordinarily bury such features.