Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320130001&lang=es vol. 109 num. 1-2 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Education, training and innovation in the National Development Plan 2030</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100001&lng=es&nrm=iso&tlng=es <![CDATA[<b>Arthur Chaskalson (1931-2012)</b>: <b>Former Chief Justice of South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100002&lng=es&nrm=iso&tlng=es <![CDATA[<b>Jakes Gerwel (1946-2012)</b>: <b>Humble intellectual, scholar and leader</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100003&lng=es&nrm=iso&tlng=es <![CDATA[<b>The AIDS conspiracy?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100004&lng=es&nrm=iso&tlng=es <![CDATA[<b>Valuing the humanities</b>: <b>What the reports don't say</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100005&lng=es&nrm=iso&tlng=es <![CDATA[<b>Heritage conservation in Africa</b>: <b>The good, the bad, and the challenges</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100006&lng=es&nrm=iso&tlng=es <![CDATA[<b>Entomology in South Africa</b>: <b>Where do we come from, where are we now and where are we going?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100007&lng=es&nrm=iso&tlng=es <![CDATA[<b>The growth of space science in African countries for Earth observation in the 21st century</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100008&lng=es&nrm=iso&tlng=es <![CDATA[<b>Soft-input iterative channel estimation for bit-interleaved turbo-coded MIMO-OFDM systems</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100009&lng=es&nrm=iso&tlng=es Bit-interleaved coded modulation (BICM) is a robust multiplexing technique for achieving multiplexing gain in multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) systems. However, in order to benefit maximally from the various advantages offered by BICM-based MIMO-OFDM systems, availability of accurate MIMO channel state information (CSI) at the receiver end of the system is essential. Without accurate MIMO CSI, accurate MIMO demapping and coherent detection and decoding of the transmitted message symbols at the system's receiver would be impossible. In such cases, the multiplexing gain offered by the BICM technique, as well as the higher data rate made possible by the MIMO-OFDM system, is not benefitted from in full. In this paper, we propose a soft input based decision-directed channel estimation scheme for the provision of MIMO CSI for coherent detection of signals in MIMO-OFDM systems. The proposed channel estimator works in iterative mode with a MIMO demapper and a turbo decoder, and is based on the fast data projection method (FDPM) and the variable step size normalised least mean square (VSSNLMS) algorithm. Simulation results of the proposed estimator based on the FDPM and VSSNLMS algorithms indicate better performance in comparison with the same estimator employing minimum mean square error criteria and deflated projection approximation subspace tracking algorithms for both slow- and fast-fading channel scenarios. The proposed estimator would be suitable for use at the receiver end of MIMO-OFDM wireless communication systems operating in either slow- or fast-fading channels. <![CDATA[<b>Occurrence of CCA-treated timber in caterers' fuelwood stocks in the Cape Town region</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100010&lng=es&nrm=iso&tlng=es Wood used as fuel under conditions of urban poverty is a source of air pollution. Fuelwood is harvested from peri-urban green areas or sourced as waste from industry or commerce, and used in the informal economy, both by households and by productive activities such as roadside catering. End-of-life timber may have previously been treated for protection, sometimes by impregnation with chromated copper arsenate (CCA). Combustion of CCA-treated timber could magnify the health and environmental risks associated with air pollution, as a result of the release of arsenic and chromium in toxic and carcinogenic forms. Fuelwood supplies of roadside caterers in the urban settlements of Nyanga and Khayelitsha were randomly sampled and 86 collected specimens were prepared for analysis. A further 12 samples were taken, based on their appearance, from households and caterers in settlements near Stellenbosch, Worcester and Paarl. Shavings from the timber specimens were microwave digested using nitric acid and analysed using inductively coupled plasma analysis. All samples collected in the first round showed low concentrations of Cr, Cu and As, believed to be representative of natural backgrounds. Of the 12 peri-urban samples collected in the second round, 8 showed higher levels, typical of treatment to H2-H5 standards. Once it was clear that appearance was a fair indicator of treatment, a further set of 18 suspect pieces from caterers' supplies in Langa, Nyanga, Khayelitsha and Kayamandi were tested, of which at least 1 sample from each area was found to be treated. CCA-treated timber was found infrequently in fuel supplies of urban caterers, and more frequently in peri-urban areas. Further research and interventions to limit health and environmental risks are recommended. <![CDATA[<b>A step-by-step framework to assess benefits of established temperate marine protected areas</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100011&lng=es&nrm=iso&tlng=es Marine protected areas (MPAs) have been advocated as a solution to the challenges of both conservation and modern fishery management, but their application remains controversial, partly because there are only general guidelines for evaluating their effectiveness. We propose a framework to specifically evaluate established MPAs in six steps. We tested the approach by reviewing published research and unpublished information on the Goukamma MPA in the centre of the South African temperate south coast. Information reviewed included effects on the structure of fish populations, catch and abundance indices of fish species, and ecosystem effects. We investigated factors that determine the usefulness of a MPA in fisheries management, including the movement behaviour of adult fishes, larval dispersal and fisher-displacement patterns. We found that differences in the rates of exploitation across the MPA border resulted in differences in abundance, size and condition of the main target species, roman (Chrysoblephus laticeps). The diversity and abundance of non-target fish species, and the composition of the benthic invertebrate community, were affected by the cessation of fishing. The potential for 'spillover' of adult roman might be limited to the vicinity of the MPA by their small home range, but there is potential for self-seeding and dispersal of roman eggs and larvae over wider areas. These theoretical considerations were confirmed by an analysis of catch data from before and after MPA implementation. The framework presented here may help to identify and fill gaps in the knowledge of established MPAs along South Africa's temperate south coast. <![CDATA[<b>Public attitudes to science in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100012&lng=es&nrm=iso&tlng=es In a global environment characterised by the growing role of science and technology in our economic, social, and political lives, an international research agenda has arisen to measure and understand how science and technology are perceived and evaluated by the public. In 2010, the South African Social Attitudes Survey included 20 items to measure public attitudes towards science, knowledge about science, and sources of information about science. This household survey was administered to a representative, stratified, random sample of 3183 participants. The findings were analysed through a bivariate analysis, and here we report on South African attitudes towards science and technology, how these have changed between 1999 and 2010, and where South African science attitudes fit on the canvas of global science attitudes. The data reveal a complex and shifting relationship between attitudes of promise and reservation towards science in South Africa. In the international context, South Africa has a unique 'fingerprint' of public attitudes towards science. The strongest demographic variable impacting on attitude towards science was educational attainment, followed by age. Gender had no impact on science attitude. This broad overview also highlights some directions for further research to meet the growing academic and policy interest in the interface between the institutions of science and the public. <![CDATA[<b>Climate trends in southern Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100013&lng=es&nrm=iso&tlng=es The observed and projected changes in the climate of southern Africa in the period 1900-2100 were analysed. Ten observed, reanalysed and model-simulated climate data sets were explored for changes in surface air temperature, rainfall, air pressure, winds, ocean currents and sea surface height. The analysis of spatial and temporal climate trends from historical observations provided a context to assess two coupled model simulations (IPSL, MIROC) based on the A1B emission scenario. Temperatures in the satellite era exhibited upward trends greater than +0.4 °C/year in the MIROC and IPSL A1B model simulations; between +0.02 °C/year and +0.03 °C/year in NCDC, HADCRU, CFS-R and NCEPe data sets; +0.01 °C/year in NCEPr and GHCN observations; and +0.002 °C/year in the ECMWF data set. Although rainfall trends in the satellite era were minimal in many data sets because of drought in the early 1980s, there was a significant downtrend in the IPSL simulation of -0.013 mm/day per year. When averaging the longer data sets together over the 20th century, the southern African rainfall trend was -0.003 mm/day per year. Other key features of the analyses include a poleward drift of the sub-tropical anticyclones and a +1.5 mm/year rise in sea surface height along the coast. <![CDATA[<b>Sustainable waste management by production of activated carbon from agroforestry residues</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100014&lng=es&nrm=iso&tlng=es Agroforestry waste presents a problem for disposal and negatively impacts on the environment if left to rot or burn. The aim of this study was to reduce environmental problems associated with agroforestry waste by promoting the innovative use of such waste in the production of activated carbons (ACs) using a low-cost production technique, and ultimately delivering more affordable water and effluent treatment adsorbents. Four varieties of ACs from four different agroforestry materials - pine (Pinus contorta) cones (PC), Abies (Abies cilicica) seeds (AS), maple (Acerginnala) seeds (MS) and peach (Prunuspersica) stones (PS) - were prepared by single-step steam pyrolysis and characterised. The raw materials were evaluated for AC yield while the respective ACs were evaluated on the basis of iodine number, phenol specific area, ash content, pH, moisture content and removal of metal ions, nitrates and sulphates from aqueous solution. The AC yields for PS, PC, AS and MS were found to be 23.0%, 18.0%, 17.8% and 14.6%, respectively. The yield for PS (23%) is within the specified commercial limits of 20% to 40%. The phenol specific areas of the ACs ranged between 381 m²/g and 415 m²/g higher than the commercial lower limit (300 m²/g) generally specified. The ACs also showed the capacity to remove heavy metal ions from their aqueous solutions. Removal of both nitrates and sulphates in raw water was greater than 50%. Although no quantitative analysis has been performed to date, it is envisaged that the production of AC from agroforestry wastes can contribute to the sustainable management of environmental pollution by these residues and the concomitant delivery of cheaper adsorbents. <![CDATA[<b>Vegetable oil based liquid nanocomposite dielectric</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100015&lng=es&nrm=iso&tlng=es Physically smaller dielectric materials would improve the optimisation of space for power systems. Development of nanotechnology provides an effective way to improve the performances of insulating oils used in power system applications. In this research study, we focused on the development of nanomodified vegetable oils to be used in power transformers. Higher conduction currents were observed in virgin linseed oil than in virgin castor oil. However, for both virgin linseed and virgin castor oil, the DC conduction current increased approximately linearly with the applied DC voltage. In nanomodified linseed oil, the characteristic curve showed two distinct regions: a linear region (at lower applied voltage) and a saturation region (at slightly higher voltage). Conversely, in nanomodified castor oil, the characteristic curve showed three distinct regions: a linear region (at lower applied voltage), a saturation region (at intermediate applied voltage) and an exponential growth region (at higher applied voltage). The nanomodified linseed oil exhibited a better dielectric performance than the nanomodified castor oil. Overall, the addition of nanodielectrics to vegetable oils decreased the dielectric performance of the vegetable oils. The results of this study contribute to the understanding of the pre-breakdown phenomenon in liquid nanocomposite dielectrics. <![CDATA[<b>Why all those spines?</b>: <b>Anachronistic defences in the Didiereoideae against now extinct lemurs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100016&lng=es&nrm=iso&tlng=es Plants evolve physical defences, such as spines, against browsing herbivores. However, in some cases, these defences may be anachronistic because the principal consumers of protected parts of the plant are extinct. In such cases, there may be few extant species consuming heavily defended resources. Here we examine the spiny defences of Madagascar's endemic Didiereoideae, and ask whether they may be anachronistic. To accomplish this aim, we reviewed the literature to determine which species consume these plants today, and then used stable isotope biogeochemistry to determine who may have exploited Didiereoideae in the recent past. There are four major groups of browsers that are now extinct in Madagascar: giant lemurs, elephant birds (Aepyornis and Mullerornis: Aepyornithidae), pygmy hippopotamuses (Hippopotamus) and giant tortoises (Aldabrachelys: Testudinidae). Each group was evaluated for isotopic evidence of didiereoid plant consumption. Given the structure of members of this plant clade (especially Alluaudia), we predicted that lemurs would be their most important consumers. Three extant lemur species consume Didiereoideae. Several of the extinct lemurs, particularly Hadropithecus stenognathus, may have relied heavily on these spiny plants. None of the non-lemur megafaunal browsers (elephant birds, hippopotamuses and giant tortoises) were important consumers of Didiereoideae. <![CDATA[<b>Effect of toxoplasmosis on personality profiles of Iranian men and women</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100017&lng=es&nrm=iso&tlng=es There is evidence to suggest that the protozoan Toxoplasma gondii, which causes toxoplasmosis, changes the personality of people who are infected with it. The aim of this study was to compare the personality characteristics of Iranian students with and without latent toxoplasmosis. A total of 237 students (111 men and 126 women) of Jundishapur University of Medical Sciences (Ahvaz, Iran) were tested for the presence of anti-Toxoplasma antibodies and completed demographic questionnaires and Cattell's 16 Personality Factor Questionnaire. Data were analysed using multiple univariate analyses of variance. Women with latent toxoplasmosis had a significantly different personality profile from women without toxoplasmosis, namely higher O (apprehension), N (privateness) and Q4 (tension) scores, and lower Q1 (openness to change) scores. Infected men had significantly higher L (vigilance, mistrust) scores compared to non-infected men. Factors E (dominance) and Q1 (openness to change) tended to be higher in infected men than non-infected men but the difference was not quite statistically significant. Our findings have, for the first time, independently confirmed that personality profile is affected by latent toxoplasmosis. <![CDATA[<b>Mid-latitude ionospheric signature of a weak solar flare in winter</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100018&lng=es&nrm=iso&tlng=es Measurements of the amplitude and phase of very low frequency transmitter signals were used to evaluate the effects on the ionosphere of a moderate intensity solar flare that occurred on 13 December 2007. These measurements were compared to modelled results from the Long Wave Propagation Capability code. The ionospheric effects were found to be delayed by ~1 min with respect to the 0.1-0.8 nm solar X-ray flux. <![CDATA[<b>Comparison of two personal ultraviolet index monitors for sun awareness in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100019&lng=es&nrm=iso&tlng=es Exposure to solar ultraviolet (UV) radiation is known to have both adverse and beneficial consequences for human health. Sunburn and skin cancer are probably the most well-known acute and chronic adverse health impacts. These themes have recently been discussed in the media for the general public; consequently interest in sun protection is growing. The promotion of the use of practical personal strategies to reduce adverse health risks, such as healthy sun behaviour, sun protection mechanisms and solar ultraviolet radiation awareness tools, is increasing. One such tool is the personal UV index (UVI) monitor, promoted commercially as a viable tool for sun awareness; however, such instruments have not been scientifically evaluated in a South African context. Here, two different types of personal UVI monitors, commercially available in South Africa, were compared with a research-grade UVB biometer for a continuous 7-h period on 02 March 2012 in Pretoria. One of the two personal UVI monitors showed reasonable agreement with the UVB biometer, whereas the other monitor overestimated UVI by up to 4 UVI units. When comparing two identical products manufactured by the same company, one monitor overestimated UVI twofold, suggesting inter-instrument variability may be a concern. Commercially available, personal UVI monitors should be used with caution as a public health tool for sun awareness in South Africa. <![CDATA[<b>Erratum</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000100020&lng=es&nrm=iso&tlng=es Exposure to solar ultraviolet (UV) radiation is known to have both adverse and beneficial consequences for human health. Sunburn and skin cancer are probably the most well-known acute and chronic adverse health impacts. These themes have recently been discussed in the media for the general public; consequently interest in sun protection is growing. The promotion of the use of practical personal strategies to reduce adverse health risks, such as healthy sun behaviour, sun protection mechanisms and solar ultraviolet radiation awareness tools, is increasing. One such tool is the personal UV index (UVI) monitor, promoted commercially as a viable tool for sun awareness; however, such instruments have not been scientifically evaluated in a South African context. Here, two different types of personal UVI monitors, commercially available in South Africa, were compared with a research-grade UVB biometer for a continuous 7-h period on 02 March 2012 in Pretoria. One of the two personal UVI monitors showed reasonable agreement with the UVB biometer, whereas the other monitor overestimated UVI by up to 4 UVI units. When comparing two identical products manufactured by the same company, one monitor overestimated UVI twofold, suggesting inter-instrument variability may be a concern. Commercially available, personal UVI monitors should be used with caution as a public health tool for sun awareness in South Africa.