Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320110004&lang=en vol. 107 num. 7-8 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Education and training need the involvement of all levels of government</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400001&lng=en&nrm=iso&tlng=en <![CDATA[<b>The great shale debate in the Karoo</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400002&lng=en&nrm=iso&tlng=en <![CDATA[<b>The humanist imperative in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400003&lng=en&nrm=iso&tlng=en <![CDATA[<b>Male philopatry and female dispersal amongst two species of early hominins from the Sterkfontein valley</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400004&lng=en&nrm=iso&tlng=en <![CDATA[<b>Patrick Cullinan (1932-2011)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400005&lng=en&nrm=iso&tlng=en <![CDATA[<b>Bats for Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400006&lng=en&nrm=iso&tlng=en <![CDATA[<b>Funding constrains PhD production</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400007&lng=en&nrm=iso&tlng=en <![CDATA[<b>Predicting the abundance of African horse sickness vectors in South Africa using GIS and artificial neural networks</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400008&lng=en&nrm=iso&tlng=en African horse sickness (AHS) is a disease that is endemic to sub-Saharan Africa and is caused by a virus potentially transmitted by a number of Culicoides species (Diptera: Ceratopogonidae) including Culicoides imicola and Culicoides bolitinos. The strong association between outbreaks of AHS and the occurrence in abundance of these two Culicoides species has enabled researchers to develop models to predict potential outbreaks. A weakness of current models is their inability to determine the relationships that occur amongst the large number of variables potentially influencing the population density of the Culicoides species. It is this limitation that prompted the development of a predictive model with the capacity to make such determinations. The model proposed here combines a geographic information system (GIS) with an artificial neural network (ANN). The overall accuracy of the ANN model is 83%, which is similar to other stand-alone GIS models. Our predictive model is made accessible to a wide range of practitioners by the accompanying C. imicola and C. bolitinos distribution maps, which facilitate the visualisation of the model's predictions. The model also demonstrates how ANN can assist GIS in decision-making, especially where the data sets incorporate uncertainty or if the relationships between the variables are not yet known. <![CDATA[<b>Potential health effects of pesticide use on farmworkers in Lesotho</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400009&lng=en&nrm=iso&tlng=en This study examined the experiences of farmworkers during crop spraying in Lesotho. The main goal of this study was to determine the perceptions and awareness of farmworkers regarding the use of pesticides and the potential effects on their health. The data were obtained from farmworkers using a combination of an open-ended and a close-ended structured questionnaire in July 2006. Of the nine farms serviced by the Ministry of Agriculture and Food Security of Lesotho, Agricultural Research Division, six farms were randomly chosen and 27 farmworkers from these farms were interviewed. The data were analysed using descriptive statistics such as frequency tables. The results showed that farmworkers are relatively poorly educated and that a greater health risk is present when a lack of training and education on the use of pesticides also exists. That is, the majority (85%) of farmworkers did not have secondary education and most (93%) had no training on the use of pesticides, which poses a great health threat to the farmworkers. A lack of education makes it difficult for farmworkers to read and understand the information labels on pesticides and hence it is difficult for them to understand the health hazards of pesticides and the need for personal safety measures. When using and handling pesticides, 52% of farmworkers did not use rubber gloves and 93% did not use goggles or other forms of face cover. This lack of protection puts them at serious risk of skin exposure to pesticides. The farmworkers were quite aware of the harmful effects of pesticides, but were sometimes unable to translate this awareness into their own safety practices because of a lack of knowledge about the adverse effects. Therefore, training, extension services and various awareness programmes should be promoted in Lesotho in order to increase farmworkers' knowledge and awareness of the adverse effects of pesticides on human health and the environment. <![CDATA[<b>Channel and delay estimation for base-station-based cooperative communications in frequency-selective fading channels</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400010&lng=en&nrm=iso&tlng=en A channel and delay estimation algorithm for both positive and negative delay, based on the distributed Alamouti scheme, has been recently discussed for base-station-based asynchronous cooperative systems in frequency-flat fading channels. This paper extends the algorithm, the maximum likelihood estimator, to work in frequency-selective fading channels. The minimum mean square error (MMSE) performance of channel estimation for both packet schemes and normal schemes is discussed in this paper. The symbol error rate (SER) performance of equalisation and detection for both time-reversal space-time block code (STBC) and single-carrier STBC is also discussed in this paper. The MMSE simulation results demonstrated the superior performance of the packet scheme over the normal scheme with an improvement in performance of up to 6 dB when feedback was used in the frequency-selective channel at a MSE of 3 x 10-2. The SER simulation results showed that, although both the normal and packet schemes achieved similar diversity orders, the packet scheme demonstrated a 1 dB coding gain over the normal scheme at a SER of 10-5. Finally, the SER simulations showed that the frequency-selective fading system outperformed the frequency-flat fading system. <![CDATA[<b>Antidiabetic effects of <i>Aloe ferox</i> and <i>Aloe greatheadii</i> var. <i>davyana</i> leaf gel extracts in a low-dose streptozotocin diabetes rat model</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400011&lng=en&nrm=iso&tlng=en The medicinal use and commercialisation of the plants Aloe ferox and Aloe greatheadii are primarily based on research done on Aloe vera and Aloe arborescens. Consequently, in this study we investigated the possible antidiabetic effects of ethanol extracts of A. ferox and A. greatheadii var. davyana leaf gel in a streptozotocin (STZ)-induced type 2 diabetes rat model. Fifty male Wistar rats, weighing 200 g - 250 g, were randomly divided into five groups of n = 10: normal control rats, diabetic control rats, diabetic rats receiving A. ferox leaf gel extract (300 mg/kg), diabetic rats receiving A. greatheadii leaf gel extract (300 mg/kg), and diabetic rats receiving glibenclamide (600 Mug/kg). Diabetes was induced by a single intraperitoneal injection of STZ (40 mg/kg). Rats were sacrificed 5 weeks after injection, following a 12-hour fast, and blood and tissue samples were collected. Compared to the normal control group, STZ significantly increased relative liver and kidney weights, end-point plasma glucose, fructosamine, oxidative stress, liver enzymes, total cholesterol (TC), triglycerides, very low density lipoprotein-cholesterol and TC: high density lipoprotein-cholesterol (HDL-C) values and reduced serum insulin levels. Treatment with A. greatheadii moderately increased serum insulin and HDL-C levels and moderately reduced end-point plasma glucose and liver alkaline phosphatase (ALP) and significantly decreased TC:HDL-C ratios. A. ferox supplementation similarly resulted in moderately increased serum insulin, accompanied by slight corrections in ALP and HDL-C, without any change to end-point plasma glucose values. A. greatheadii and, to a lesser extent, A. ferox, resulted in a clinically relevant improved diabetic state (indicated by moderate to high effect sizes), suggesting that these Aloe species may show promise for treating diabetes. <![CDATA[<b>Vertebrate distributions indicate a greater Maputaland-Pondoland-Albany region of endemism</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400012&lng=en&nrm=iso&tlng=en The Maputaland-Pondoland-Albany (MPA) biodiversity hotspot (~274 316 kmĀ²) was primarily recognised based on its high plant endemism. Here we present the results of a qualitative biogeographical study of the endemic vertebrate fauna of south-eastern Africa, in an exercise that (1) refines the delimitation of the MPA hotspot, (2) defines zoogeographical units and (3) identifies areas of vertebrate endemism. Initially we listed 62 vertebrate species endemic and 60 near endemic to the MPA hotspot, updating previous checklists. Then the distributions of 495 vertebrate taxa endemic to south-eastern Africa were reviewed and 23 endemic vertebrate distributions (EVDs: distribution ranges congruent across several endemic vertebrate taxa) were recognised, amongst which the most frequently encountered were located in the Eastern Escarpment, central KwaZulu-Natal, Drakensberg and Maputaland. The geographical patterns illustrated by the EVDs suggest that an expansion of the hotspot to incorporate sections of the Great Escarpment from the Amatola-Winterberg-Sneeuberg Mountains through the Drakensberg to the Soutpansberg would be justified. This redefinition gives rise to a Greater Maputaland-Pondoland-Albany (GMPA) region of vertebrate endemism adding 135% more endemics with an increase of only 73% in surface area to the MPA hotspot. The GMPA region has a more natural boundary in terms of EVDs as well as vegetation units. An accurate delimitation of this hotspot, as well as a better understanding of biogeography in the region, would greatly benefit conservation planning and implementation. Towards these aims, we used EVDs to delimit non-overlapping zoogeographical units (including 14 areas of vertebrate endemism), facilitating numerical biogeographical analyses. More importantly, this study opens up possibilities of refining hotspot delimitation and identifying local conservation priorities in regions of the world where data do not allow numerical analyses. <![CDATA[<b>Examination of the Florisbad microvertebrates</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532011000400013&lng=en&nrm=iso&tlng=en Florisbad is a Middle Stone Age locality in the Free State Province, South Africa, well known for an archaic Homo sapiens cranium discovered there in 1932. Whilst substantial work has been accomplished on the materials excavated from this site, there is still more to be learned about the palaeoenvironment from the microvertebrates. In broader terms, the make-up and distribution of the Plio-Pleistocene small animal fauna of the Free State Province is underrepresented relative to other provinces, which negatively impacts our understanding of geographic and temporal ranges of many Plio-Pleistocene taxa. Much of the Florisbad small vertebrate material is fragmentary, with diagnostic elements primarily limited to isolated molars. Analysis of this material found a small but diverse assemblage including springhares, rabbits, rodents and reptiles. The small mammal fauna is dominated by springhares, lagomorphs and otomyine and gerbilline rodents. In agreement with previous research on sediments and large mammal fauna, the small animal fauna described here is consistent with an open, treeless grassland.