Scielo RSS <![CDATA[South African Journal of Science]]> vol. 106 num. 11-12 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>How could South Africa produce more PhDs?</b>]]> <![CDATA[<b>Hilary John Deacon</b>: <b>Archaeologist (1936-2010)</b>]]> <![CDATA[<b>Financial diaries of the poor</b>]]> <![CDATA[<b>Can the climate change bandwagon's piccolo player start conducting?</b>]]> <![CDATA[<b>National Research Foundation gets R250 million boost from government while PhD numbers fall</b>]]> <![CDATA[<b>How long does it take to get a PhD?</b>]]> <![CDATA[<b>Concerted intervention needed to escalate PhD numbers</b>: <b>a comment</b>]]> <![CDATA[<b>Balancing science and politics in South African marine biology</b>]]> <![CDATA[<b>Building a knowledge economy in South Africa</b>]]> <![CDATA[<b>The Intergovernmental Panel on Climate Change assessment process is reviewed</b>]]> <![CDATA[<b>An overview of the electricity externality analysis in South Africa within the international context</b>]]> Externalities are an integral part of South Africa's electricity power generation sector as the country is highly dependent on coal as the primary fuel source. While there have been significant efforts to account for the constantly increasing externalities in developed countries, it has not been the case in the developing world. This paper attempts to observe the trend of externalities research in South Africa's power generation sector and to analyse the gaps by placing externality research in context with other studies performed internationally. A statistical analysis adjusted for currency conversions puts into perspective the range of externalities. It also provides an overview of South Africa's energy supply and demand scene, with emphasis on the role of coal in the electricity sector. The paper provides motivation to perform a revised externality analysis along international lines. The aim is to add to the body of literature on externality studies in South Africa by providing an updated comparative analysis. This will enable future research to contextualise studies that were performed during different time periods. <![CDATA[<b>Recent advances in sex identification of human skeletal remains in South Africa</b>]]> We review methods of sex estimation from human skeletal remains in South Africa within the forensic context. Sex is one of the key variables in obtaining a biological profile of the individual or population whose remains are analysed. Sex estimation based on the morphological characteristics of skeletal elements is population specific and thus the establishment of regional criteria is one of the imperatives for modern forensic anthropology. A literature review was carried out wherein the available methods of sex identification (morphological, metrical, geometric morphometrics and molecular) from South African skeletal material were critically examined. The approaches to sex estimation based on bone morphology have a long and productive history in South Africa. A number of approaches providing accurate results on the local populations have been developed. Research in molecular sex determination methods is still in its infancy in South Africa and the first innovative studies appeared only in recent years. While each of the four methods analysed is bounded by a number of constraints, they seem to complement each other and provide the best results when applied in conjunction with each other. <![CDATA[<b>Antibiotic-resistant <i>Staphylococcu</i>s <i>aureu</i>s isolated from milk in the Mafikeng Area, North West province, South Africa</b>]]> The aim of this study was to isolate Staphylococcus aureus from samples of cow's milk obtained from different farm settings and to determine their antibiotic susceptibility patterns. Gram staining, oxidase, catalase, DNase, haemolysis and the MASTASTAPH TM rapid agglutination tests were employed for bacterial identification. A total of 28 milk samples were collected and screened for the presence of S. aureus. All the samples were contaminated with S. aureus. A total of 240 S. aureus isolates were obtained during this study. The levels of contamination with S. aureus were higher in milk obtained from the communal farms in Lokaleng and Mogosane (24.6% and 35.4%, respectively) compared to the commercial farms in Rooigrond and Molelwane (17.9% and 22.1%, respectively). A large percentage of the S. aureus isolates (39%-100%) from both communal farms was resistant to methicillin (MT), ampicillin (AP), penicillin G (PG), sulphamethoxazole (Smx), oxytetracycline (OT), erythromycin (E), nitrofurantoin (NI) and streptomycin (S), but not vancomycin (V). An even higher percentage (64.2% - 100%) of the isolates from both commercial farms was resistant to sulphamethoxazole and nitrofurantoin. A comparably smaller percentage (3.4% - 4.7%) of the isolates from both communal farms was resistant to vancomycin, but all isolates from commercial farm milk were susceptible to this drug. The predominant multiple antibiotic resistant phenotypes for isolates from the commercial farms were AP-Smx-NI and MT-AP-PG-OT-Smx-NI for Rooigrond and Molelwane farms, respectively, while those for isolates from the communal farms were MT-AP-PG-Smx-E-NI-S and MT-AP-PG-OT-Smx-NI-S for Lokaleng and Mogosane, respectively. When comparing the percentage of antibiotic resistance, a significant positive correlation was observed between the isolates from the commercial farms (r = 0.966, p < 0.01). S. aureus is normally resident in humans, therefore, the S. aureus present in the cows may have resulted from transmission between the two species, emphasising the need to improve sanitary conditions in the milking environment. <![CDATA[<b>A socio-structural analysis of crime in the city of Tshwane, South Africa</b>]]> High and rising levels of crime plague post-apartheid South Africa. A common explanation for these high crime rates relates the country's unique socio-political past to a system of ineffective social control mechanisms that suggest high levels of social disorganisation within certain communities. Other explanations emphasise the presence of disaffected youths and deprivation, as well as the rapid immigration of people from neighbouring African countries into South Africa. I examined a number of these socio-structural explanations of crime on contact crime rates in the city of Tshwane, South Africa. The findings are largely consistent with the social disorganisation theory, as well as with what has previously been suggested in local literature. In order to supplement these preliminary findings, the effects of the same socio-structural explanations on contact crime rates were determined for predominantly Black, White, and 'Mixed' (containing a mix of both Black and White residents) suburbs using spatial regression models. Evidence from these analyses suggests that the effects of the various socio-structural explanations do not appear to traverse racial lines. Rather, the findings suggest non-uniformity in terms of the extent to which the various socio-structural factors impact contact crime rates based on race. <![CDATA[<b>Repeat-punctured superorthogonal convolutional turbo codes on AWGN and flat Rayleigh fading channels</b>]]> Repeat-punctured turbo codes, an extension of the conventional turbo-coding scheme, has shown a significant increase in bit-error rate performance at moderate to high signal-to-noise ratios for short frame lengths. Superorthogonal convolutional turbo codes (SCTC) makes use of superorthogonal signals to improve the performance of the conventional turbo codes and a coding scheme that applies the repeat-punctured technique into SCTC has shown to perform better. We investigated two new low-rate coding schemes, repeat-punctured superorthogonal convolutional turbo codes (RPSCTC) and dual-repeat-punctured superorthogonal convolutional turbo codes (DRPSCTC), that make use of superorthogonal signaling, together with repetition and puncturing, to improve the performance of SCTC for reliable and effective communications. Simulation results in the additive white Gaussian noise (AWGN) channel and the frequency non-selective Rayleigh fading channel are presented together with analytical bounds of bit error probabilities, derived from transfer function bounding techniques. From the simulation results and the analytical bounds presented, it is evident that RPSCTC and DRPSCTC offer a more superior performance than SCTC in the AWGN channel, as well as in flat Rayleigh non-line-of-sight fading channels. The distance spectrum is also presented for the new schemes and accounts for the performance improvement rendered in simulations. It is important to note that the improved performance that SCTC, and consequently RPSCTC and DRPSCTC, exhibit is achieved at the expense of bandwidth expansion and complexity and would be ideal for power-limited satellite communication links or interference-limited systems. <![CDATA[<b>Qualitative phase space reconstruction analysis of supply-chain inventory time series</b>]]> The economy systems are usually too complex to be analysed, but some advanced methods have been developed in order to do so, such as system dynamics modelling, multi-agent modelling, complex adaptive system modelling and qualitative modelling. In this paper, we considered a supply-chain (SC) system including several kinds of products. Using historic suppliers' demand data, we firstly applied the phase space analysis method and then used qualitative analysis to improve the complex system's performance. Quantitative methods can forecast the quantitative SC demands, but they cannot indicate the qualitative aspects of SC, so when we apply quantitative methods to a SC system we get only numerous data of demand. By contrast, qualitative methods can show the qualitative change and trend of the SC demand. We therefore used qualitative methods to improve the quantitative forecasting results. Comparing the quantitative only method and the combined method used in this paper, we found that the combined method is far more accurate. Not only is the inventory cost lower, but the forecasting accuracy is also better. <![CDATA[<b>Morphological evaluation of genetic evidence for a Pleistocene extirpation of eastern African impala</b>]]> Palaeontology typically relies on fossil studies, in particular morphological differences, to reconstruct and interpret patterns of vertebrate evolution. However, genetic studies of population histories of extant species provide data about past population events (e.g. local extinctions, recolonisations) which are equally relevant to palaeontological questions. This study used morphological traits to evaluate a hypothesis based on genetic evidence that southern African impala (Aepyceros melampus) are the founder population for all other living African impala populations, after an eastern African extirpation event dating to around 200 000 years ago. Measurements of three horn metrics and the presence or absence of a particular dental trait were compared across four regional impala samples. Eastern African impala possess a unique combination of larger horns and a significantly higher occurrence of entostyles when compared to other impala populations. These traits are likely to have characterised a small group of founding impala which recolonised this region. This pattern appears consistent with the genetic evidence that a subset of the southern African impala gave rise to the eastern African populations. Other species with complex population histories, such as wildebeest, eland, topi and hartebeest may also therefore be expected to express variation in certain morphological traits in the fossil record because of similar patterns of recolonisations. The process of local extinction and subsequent repopulation over shorter timescales (10² - 10³ years) may pass unnoticed in the fossil record, and lineages may appear uninterrupted. Instead, greater morphological variation within a species may be observed, which may be misinterpreted as reflecting a speciation event, or ecophenotypic variation. Combining data from genetic studies and palaeontology may provide further clues as to how faunal dispersals within Africa shaped the morphological variation in the fossil record, and how to best interpret such differences. <![CDATA[<b>Characterisation of <i>Shigella</i> species isolated from river catchments in the North West province of South Africa</b>]]> The occurrence and distribution of Shigella species in water from the five river catchments in the North West province of South Africa were investigated. Shigella is a Gram-negative, non-motile, facultative anaerobic bacillus that causes shigellosis, an important cause of morbidity and mortality in high-risk populations (such as children, the elderly and immuno-compromised individuals) that depend on river water. A total of 54 water samples collected in winter (April 2007 to July 2007) and summer (December 2007 to March 2008) were cultured on Salmonella-Shigella agar by the spread-plate method. Suspected Shigella isolates obtained were characterised by primary biochemical (Triple Sugar Iron agar and agglutination) and molecular (polymerase chain reactions, PCR) tests. Amplification of the invasion plasmid gene (ipaH) by PCR was done to confirm the presence of Shigella spp. in water. In total, 214 Shigella boydii, 15 Shigella dysenteriae, 11 Shigella flexneri and 2 Shigella sonnei were confirmed by serotyping in both winter and summer samples. The ipaH gene (606 bp) was present in 176 and 49 of the winter and summer isolates, respectively. The presence of Shigella spp. in water was confirmed with over 90% specificity. The need for more effective management of these river catchments and the provision of potable water and sanitation facilities is needed to minimise the occurrence and transmission of water-borne diseases caused by these and other pathogenic bacteria. <![CDATA[<b>Turbidity removal</b>: <b>gravel and charcoal as roughing filtration media</b>]]> Roughing filtration is an important pre-treatment process for wastewater, because it efficiently separates fine solid particles over prolonged periods, without the addition of chemicals. For this study, a pilot plant was designed at Delmas Coal Mine in the Mpumalanga province of South Africa. The design and sizing of the pilot plant was guided by Wegelin's design criteria. Gravel was used as a control medium because it is one of the most commonly used roughing filter media and because it was used in developing the criteria. We compared the performance of gravel as a filter medium to that of another locally available material, charcoal, for the removal of turbidity in wastewater. The pilot plant was monitored continuously for 90 days from commissioning until the end of the project. The overall performance of the roughing filter in turbidity removal, using gravel or charcoal, was considered efficient for the pre-treatment of waste water. Charcoal performed slightly better than gravel as a filter medium for the removal of turbidity, possibly because charcoal has a slightly higher specific surface area and porosity than gravel, which could enhance sedimentation and other filtration processes, such as adsorption, respectively. <![CDATA[<b>Comparative analysis of some search engines</b>]]> We compared the information retrieval performances of some popular search engines (namely, Google, Yahoo, AlltheWeb, Gigablast, Zworks and AltaVista and Bing/MSN) in response to a list of ten queries, varying in complexity. These queries were run on each search engine and the precision and response time of the retrieved results were recorded. The first ten documents on each retrieval output were evaluated as being 'relevant' or 'non-relevant' for evaluation of the search engine's precision. To evaluate response time, normalised recall ratios were calculated at various cut-off points for each query and search engine. This study shows that Google appears to be the best search engine in terms of both average precision (70%) and average response time (2 s). Gigablast and AlltheWeb performed the worst overall in this study. <![CDATA[<b>The influence of deposition temperature on vanadium dioxide thin films microstructure and physical properties</b>]]> Vanadium dioxide thin films were successfully prepared on soda lime glass substrates using the optimised conditions for r.f-inverted cylindrical magnetron sputtering. The optimised deposition parameters were fixed and then a systematic study of the effect of deposition temperature, ranging from 450 ºC to 550 ºC, on the microstructure of thermochromic thin films was carried out. The deposited films were found to be well crystallised, showing strong texture corresponding to the (011) plane, indicating the presence of vanadium dioxide. <![CDATA[<b>Hybrid wildebeest (Artiodactyla: Bovidae) provide further evidence for shared signatures of admixture in mammalian crania</b>]]> The genus Connochaetes, Lichtenstein, 1814, contains two extant species, the blue wildebeest (C. taurinus, Burchell, 1823) and the black wildebeest (C. gnou, Zimmermann, 1780). In recent years, forced sympatry in confined areas within South Africa has led to interbreeding between these taxa and to fertile hybrid offspring. Here we report on a series of cranial characteristics of a hybrid wildebeest population culled at Spioenkop Dam Nature Reserve, KwaZulu-Natal, South Africa. Dental, sutural and horn morphological anomalies occur at high frequency within these animals. Similar cranial morphological anomalies have been shown in other mammalian hybrids and this study provides further evidence that such anomalies may characterise hybridisation more broadly across phylogenetically divergent mammalian groups, although the anomalies appear to differ in their expression across taxa. An increased ability to identify hybrids may also have important applications in the conservation of the endemic black wildebeest.