Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320150002&lang=en vol. 111 num. 3-4 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>A different kind of rising star</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200001&lng=en&nrm=iso&tlng=en <![CDATA[<b>State of green technologies in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200002&lng=en&nrm=iso&tlng=en <![CDATA[<b>Develop energy from shale with local ecosystems in mind</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200003&lng=en&nrm=iso&tlng=en <![CDATA[<b>The writing on the landscape</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200004&lng=en&nrm=iso&tlng=en <![CDATA[<b>Areal and biological approaches in Khoesan linguistics</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200005&lng=en&nrm=iso&tlng=en <![CDATA[<b>The precautionary principle: making managerial decisions on GMOs is difficult</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200006&lng=en&nrm=iso&tlng=en The precautionary approach of the Cartagena Protocol on Biosafety, if incorporated into legislation of countries as a precautionary principle (PP), could cause great difficulty in decision-making on genetically modified organisms. No consensus seems to be possible on the interpretation of the PP, as responsibility often is passed on to political decision-making and, eventually, to court rulings. A case study on the assessment of possible unintended effects of endogenous allergens illustrates the complexity decision-makers may experience. We review the descriptions of the PP and the debate on the interpretation and conclusions that a number of authors have come to, as a step closer to a solution in decision-making. South Africa may have to consider the PP in the broader context of its food security needs, which would require improved communication as an additional step in the process of risk analysis. <![CDATA[<b>Satellite laser ranging measurements in South Africa: contributions to earth system sciences</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200007&lng=en&nrm=iso&tlng=en This contribution reassesses progress in the development of satellite laser ranging (SLR) technology and its scientific and societal applications in South Africa. We first highlight the current global SLR tracking stations within the framework of the International Laser Ranging Service (ILRS) and the artificial satellites currently being tracked by these stations. In particular, the present work focuses on analysing SLR measurements at Hartebeesthoek Radio Astronomy Observatory (HartRAO), South Africa, based on the MOBLAS-6 SLR configuration. Generally, there is a weak geometry of ILRS stations in the southern hemisphere and the SLR tracking station at HartRAO is the only active ILRS station operating on the African continent. The SLR-derived products - such as station positions and velocities, satellite orbits, components of earth's gravity field and their temporal variations, earth orientation parameters - are collected, merged, achieved and distributed by the ILRS under the Crustal Dynamic Data Information System. These products are used in various research fields such as detection and monitoring of tectonic plate motion, crustal deformation, earth rotation, polar motion, and the establishment and monitoring of International Terrestrial Reference Frames, as well as modelling of the spatio-temporal variations of the earth's gravity field. The MOBLAS-6 tracking station is collocated with other geodetic techniques such as very long baseline interferometry and Global Navigation Satellite Systems, thus making this observatory a fiducial geodetic location. Some applications of the SLR data products are described within the context of earth system science. <![CDATA[<b>Assessing the photoprotective effects of red ochre on human skin by in vitro laboratory experiments</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200008&lng=en&nrm=iso&tlng=en Archaeological indicators of cognitive complexity become increasingly prevalent during the African Middle Stone Age, with the habitual exploitation of red ochre widely viewed as a key feature of the emergence of modern human behaviour. Given that some of the uses of ochre remain ambiguous, we present the preliminary results of an ongoing study in which we explore the efficacy of red ochre as a photoprotective device or sunscreen. The capacity of ochre to inhibit the susceptibility of humans to the detrimental effects of ultraviolet radiation was confirmed through the in vitro calculation of the sun protection factor values of samples derived from the Kunene Region in Namibia and the Bokkeveld Group deposits, Western Cape Province, South Africa. Visible spectroscopy was employed to determine colourimetric parameters of samples and assess the correlation between ochre colour and sun protection factor. The possible role of ochre as a sunscreen agent for hominin populations, including modern humans, during the Middle Stone Age in Africa is explored. We conclude that the habitual use of red ochre as a photoprotective agent likely played a role in the ability of prehistoric humans to adapt to novel environmental circumstances. <![CDATA[<b>Use of wood anatomy to identify poisonous plants: charcoal of <i>Spirostachys africana</i></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200009&lng=en&nrm=iso&tlng=en Spirostachys africana Sond. (tamboti/tambotie) is a woodland tree that is often found near water. It has a poisonous and purgative latex. The archaeological site of Sibudu, a rock shelter in KwaZulu-Natal, has evidence, from well-preserved charcoal and seeds, of past environments and wood use from approximately 77-38 thousand years ago (ka). As their uses and environmental indicators are different, it is critical to confidently distinguish among the three anatomically similar woods of the Euphorbiaceae: Spirostachys africana, Sclerocroton integerrimus and Shirakiopsis elliptica. A detailed anatomical study of reference and archaeological charcoal shows that xylem vessel width increases proportionally as vessel frequency decreases, from Spirostachys africana, Sclerocroton integerrimus to Shirakiopsis elliptica. Crystals of calcium oxalate are present in ray cells of Spirostachys africana, whereas silica bodies are present in ray cells of Sclerocroton integerrimus and Shirakiopsis elliptica. Using these features, the presence of Spirostachys africana was confirmed amongst hearth charcoal of the Spotty Camel layer, with an age of approximately 58 ka and of the Mottled Deposit occupational layer, with an age of approximately 49 ka. The presence of this charcoal, collected from ancient fireplaces or sieved from surrounding sediments, implies that people at Sibudu understood and used this poisonous tree to their advantage. We are encouraged in this view by the presence of many Cryptocarya woodii leaves found on the surface of 77-ka sedge bedding at Sibudu (Wadley L et al., Science. 2011;334:1388-1391). Cryptocarya woodii has insecticidal and larvacidal properties and members of the Laurel family are well known for their medicinal properties. <![CDATA[<b>Investigating the risk of lightning's pressure blast wave</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200010&lng=en&nrm=iso&tlng=en We investigated the pathology of human trauma associated with lightning's pressure blast wave. Within what range is a human at risk and what are the risks? Two theories for the trauma currently exist: the flash moisture vaporisation theory and the sixth mechanism theory. We performed a simple proof-of-concept experiment in a high-voltage laboratory to determine which theory makes for better predictions. The experiment confirmed the existence of a non-discriminant pressure blast wave around a spark in air. The lightning data were compared with the known medical data. Findings may now help explain some of the more curious lightning injury patterns seen on lightning-strike victims. <![CDATA[<b>An investigation of the nature of a Pc5 pulsation event using SuperDARN and magnetometer data</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200011&lng=en&nrm=iso&tlng=en Pc5 pulsations are global magnetohydrodynamic events in the magnetosphere. We employed an Automated Pulsation Finder program to identify significant Pc5 pulsation events in SuperDARN radar data. The event presented here was visible in the Goose Bay, Saskatoon and Þykkvibaer high-frequency radars, located in the northern polar region. These observations were coordinated with magnetometers within their field of view. These two instrument types - radars and magnetometers - complement each other. These observations represent a significant fraction of the globe in longitude. Pulsation studies of this nature are rare in the literature. Combining these two instrument types, we investigated the nature of the pulsation and determined its qualitative polarisation characteristics. A complex demodulation technique was employed to determine amplitude and phase relationships between field components observed by the radars and magnetometers, which, in turn, afforded resolution of other characteristics of pulsations, such as wave number and phase velocity. The results are discussed in the context of the magnetohydrodynamic theory of magnetic pulsations, speculating on its generation mechanism. Investigation of this mechanism will be the subject of a future publication. <![CDATA[<b>Preliminary laboratory assessments of a lightweight geocomposite material for embankment fill application</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200012&lng=en&nrm=iso&tlng=en The cost of retaining structures used for the lateral support of roadside embankments can be significantly reduced through the use of lightly cemented mixtures of expanded polystyrene (EPS) beads and backfill soils as lightweight roadside embankment material. Four grades of residually derived sandy soils were mixed with EPS beads and the geocomposites were stabilised with 3% cement content, compacted and cured. The textural properties and shear strength parameters of dry and soaked specimens of the cemented geocomposites were determined by direct shear tests. The shear parameters and slope stability charts were used to simulate the slope of typical road embankments. The settlement potentials at different applied normal stresses were also determined. Inclusion of EPS reduced the dry density of the residual soils from an average value of 1790 kg/m³ to 1335 kg/m³. The maximum friction coefficient, tan Ø', mobilised by the geocomposite specimens decreased with an increase in the soil fines content (>0.425 mm). The difference in tan Ø' between the stabilised geocomposites and the natural soil was also dependent on the fines content. For an embankment height of 20 m, slope angles of 38° and 62° were determined for fine sand geocomposites in fully saturated drainage and drained conditions, respectively. Lower slope angles were determined for geocomposites made from silty, coarse and gravelly sands. A limiting embankment height of 50 m was determined for the four geocomposites. Rainfall-induced settlement of geocomposites was dependent on pre-inundation stiffness; for the range of applied stress up to 200 kPa, the settlement exhibited by the fine and silty sand geocomposites was lower than that for the coarse and gravelly sand geocomposites. Fine and silty sands make poor materials for slope embankments because of their poor hydraulic conductivity; however, fine and silty sand geocomposites have a good conductivity and friction angle to support slope embankments. <![CDATA[<b>Distribution and severity of bacterial brown spot on dry beans in South Africa: an update</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200013&lng=en&nrm=iso&tlng=en Bacterial brown spot (BBS) of common bean [Phaseolus vulgaris) is a seed-borne bacterial disease caused by Pseudomonas syringae pv. syringae (Pss). Dry bean is an important field crop in South Africa and all commercially available South African dry bean cultivars are susceptible to BBS. The aim of this study was to determine the current distribution and severity of BBS in the dry bean production areas of South Africa. We surveyed 31 locations in five provinces. Disease severity was evaluated on selected plots on a 0-9 scale in four different farming systems: commercial and subsistence farms and strip and national cultivar trials. Leaves with typical BBS symptoms were harvested and transferred to the laboratory. Bacteria were isolated following standard procedure using King's B medium. Identification of pure isolates was done using physiological and biochemical techniques. Incidence and severity values were used to calculate a disease index. BBS was observed in 88% of locations. BBS incidence was recorded in 54% to 100% of all the farming systems surveyed during the 2008/2009 and 2010/2011 seasons combined. BBS was more severe in the strip and national cultivar trials than on subsistence and commercial farms during the 2008/2009 season and more severe on the commercial farm and in national cultivar trials than on subsistence farms and strip trials during the 2010/2011 season. Findings of this study signal the importance of developing BBS-resistant dry bean cultivars for South Africa. <![CDATA[<b>An assessment of South Africa's research journals: impact factors, Eigenfactors and structure of editorial boards</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200014&lng=en&nrm=iso&tlng=en Scientific journals play an important role in academic information exchange and their assessment is of interest to science authorities, editors and researchers. The assessment of journals is of particular interest to South African authorities as the country's universities are partially funded according to the number of publications they produce in accredited journals, such as the Thomson Reuters indexed journals. Scientific publishing in South Africa has experienced a revolution during the last 10 years. Our objective here is to report the performance of the country's journals during 2009 and 2010 according to a number of metrics (i.e. impact factors, Eigenfactors® and the international character of editorial boards); to identify and compare the impact of the South African journals that have been recently added to the Thomson Reuters' Journal Citation Reports®; and to elaborate on issues related to science policy. <![CDATA[<b>Youngest dinocephalian fossils extend the <i>Tapinocephalus Zone, </i>Karoo Basin, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200015&lng=en&nrm=iso&tlng=en The dinocephalians (Synapsida, Therapsida) were one of the dominant tetrapod groups of the Middle Permian (Guadalupian Epoch, ~270-260 million years ago) and are most abundantly recorded in the Tapinocephalus Assemblage Zone (AZ) of the Main Karoo Basin, South Africa. Dinocephalians are thought to have become extinct near the top of the Abrahamskraal Formation of the Beaufort Group and their disappearance is one criterion used to define the base of the overlying Pristerognathus AZ. Because of the abundance of fossils in the Karoo, the Beaufort Group biozones form the biostratigraphic standard for later Permian terrestrial tetrapod ecosystems, so their stratigraphic delineation is of great importance to Permian palaeobiology. We report two new specimens of the rare tapinocephalid dinocephalian Criocephalosaurus from the lowermost Poortjie Member, which makes them the youngest dinocephalians known from the Main Karoo Basin and extends the Tapinocephalus AZ from the Abrahamskraal Formation up into the Teekloof Formation. The extension of the Tapinocephalus AZ relative to the lithostratigraphy potentially affects the biozone or biozones to which a fossil species can be attributed; this extension has implications for biostratigraphic correlations within the Main Karoo Basin as well as with other basins across Gondwana. These discoveries also indicate that a population of herbivorous tapinocephalids survived as rare constituents of the tetrapod fauna after most generic richness within the clade had already been lost. <![CDATA[<b>Can scientific journals be classified based on their 'citation profiles'?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200016&lng=en&nrm=iso&tlng=en Classification of scientific publications is of great importance in biomedical research evaluation. However, accurate classification of research publications is challenging and normally is performed in a rather subjective way. In the present paper, we propose to classify biomedical publications into superfamilies, by analysing their citation profiles, i.e. the location of citations in the structure of citing articles. Such a classification may help authors to find the appropriate biomedical journal for publication, may make journal comparisons more rational, and may even help planners to better track the consequences of their policies on biomedical research. <![CDATA[<b>Erratum</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532015000200017&lng=en&nrm=iso&tlng=en Classification of scientific publications is of great importance in biomedical research evaluation. However, accurate classification of research publications is challenging and normally is performed in a rather subjective way. In the present paper, we propose to classify biomedical publications into superfamilies, by analysing their citation profiles, i.e. the location of citations in the structure of citing articles. Such a classification may help authors to find the appropriate biomedical journal for publication, may make journal comparisons more rational, and may even help planners to better track the consequences of their policies on biomedical research.