Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320140004&lang=es vol. 110 num. 7-8 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>What's so bad about sound opinions?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400001&lng=es&nrm=iso&tlng=es <![CDATA[<b>The ABCs of an NRF rating</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400002&lng=es&nrm=iso&tlng=es <![CDATA[<b>South Africa - A global player in the battle against alien plant invasions</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400003&lng=es&nrm=iso&tlng=es <![CDATA[<b>The spark of life: Electricity in the human body</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400004&lng=es&nrm=iso&tlng=es <![CDATA[<b>Golden Gate Highlands National Park: Killing the goose laying golden eggs? Comment on Taru et al. (2013)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400005&lng=es&nrm=iso&tlng=es <![CDATA[<b>Invasion science for society: A decade of contributions from the Centre for Invasion Biology</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400006&lng=es&nrm=iso&tlng=es Biological invasions are a growing problem worldwide. In 2004, the South African Department of Science and Technology, through the National Research Foundation, established a Centre of Excellence for Invasion Biology, with the primary goal of providing scientific understanding and building capacity in the field of biological invasions. South Africa is an extraordinary natural laboratory for the study of biological invasions, and the Centre for Invasion Biology (C-I-B) has capitalised on this situation. During its first decade, the C-I-B generated over 800 publications, and produced almost 200 graduates at honours, master's and doctoral levels. The C-I-B has therefore made a considerable contribution to building human capacity in the field of biological invasions. Substantial advances have been made in all aspects of invasion science, which is not limited to biology and ecology, but includes history, sociology, economics and management. The knowledge generated by the C-I-B has been used to inform policy and improve management practices at national and local levels. The C-I-B has emerged as a leading institute in the global field of invasion biology, with several unique features that differentiate it from similar research institutes elsewhere. These features include a broad research focus that embraces environmental, social and economic facets, leading to a diverse research programme that has produced many integrated products; an extensive network of researchers with diverse interests, spread over a wide geographical range; and the production of policy- and management-relevant research products arising from the engaged nature of research conducted by the C-I-B. <![CDATA[<b>A concise review of the applications of NiTi shape-memory alloys in composite materials</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400007&lng=es&nrm=iso&tlng=es Composite materials have increasingly been used in construction and in the aerospace and automotive industries because they are lightweight, strong and corrosion resistant, and because their anisotropic properties can be controlled; maintenance costs are also low. However, there is a growing demand for improved composite materials which have 'smart' capabilities, that is, they are able to sense, actuate and respond to the surrounding environment. Shape-memory alloys (SMAs) possess sensing and actuating functions. Embedding SMAs into composite materials can create smart or intelligent composites. Amongst the commercially available SMAs, NiTi alloys - in the form of wires, ribbons or particles - are the most widely used because of their excellent mechanical properties and shape-memory performance. These materials have found application in broad fields of engineering and science as a result of their superior thermomechanical properties. Here we review the use of NiTi SMAs in applications such as vibration control, shape control, position control and adaptive stiffening. <![CDATA[<b>Opening dialogue and fostering collaboration: Different ways of knowing in fisheries research</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400008&lng=es&nrm=iso&tlng=es We set out to explore some of the impediments which hinder effective communication among fishers, fisheries researchers and managers using detailed ethnographic research amongst commercial handline fishers from two sites- one on the southern Cape coast and the other on the west coast of South Africa. Rather than assuming that the knowledge of fishers and scientists is inherently divergent and incompatible, we discuss an emerging relational approach to working with multiple ways of knowing and suggest that this approach might benefit future collaborative endeavours. Three major themes arising from the ethnographic fieldwork findings are explored: different classifications of species and things; bringing enumerative approaches into dialogue with relational approaches; and the challenge of articulating embodied ways of relating to fish and the sea. Although disconcertments arise when apparently incommensurable approaches are brought into dialogue, we suggest that working with multiple ways of knowing is both productive and indeed necessary in the current South African fisheries research and management contexts. The research findings and discussion on opening dialogue offered in this work suggest a need to rethink contemporary approaches to fisheries research in order to mobilise otherwise stagnant conversations, bringing different ways of knowing into productive conversation. <![CDATA[<b>Arsenic residues in soil at cattle dip tanks in the Vhembe district, Limpopo Province, South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400009&lng=es&nrm=iso&tlng=es Arsenic-based compounds have been used for cattle dipping for about half a century to combat East Coast Fever in cattle in South Africa. The government introduced a compulsory dipping programme in communal areas to eradicate the disease in 1911. Concern has been raised regarding the ecological legacy of the use of arsenic-based compounds in these areas. We investigated the incidence of arsenic residue in soil at 10 dip sites in the Vhembe district of Limpopo Province, South Africa. We found high levels of arsenic contamination at a depth of 300 mm at some sites. Control samples indicated that these high arsenic levels are the result of the application of inorganic arsenic. Variation of arsenic concentrations is attributed to duration of exposure to the chemical, soil properties and distance from the dip tank. Concerns are raised regarding the structural condition of the dip tanks, encroaching villages and possible health threats to the human population in the area. <![CDATA[<b>An outline of possible pre-course diagnostics for differential calculus</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400010&lng=es&nrm=iso&tlng=es There is a view that many first-year students lack the basic knowledge and skills expected of them to study at university level. We examined the expected work habits and pre-course diagnostics for students who choose to take a course on differential calculus. We focused on the lecturer pre-course expectations of a student in the context of work habits, knowledge and technical skills. In particular, we formulated outcomes and then sample diagnostic questions to test whether the identified learning outcomes on expected work habits and learning are in place. If students are made aware of the expected learning outcomes and if they take the diagnostic test, they should be able to achieve greater success in their studies. The validity of this assumption will be the subject of a future paper which will report on the implementation of the learning outcomes and diagnostic questions that we formulated for pre-course diagnostics in differential calculus. <![CDATA[<b>Craniodental continuity and change between Iron Age peoples and their descendants</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400011&lng=es&nrm=iso&tlng=es The appearance of the Iron Age of southern Africa early in the first millennium AD is associated with the migration of Bantu speakers who were broadly ancestral to present-day Bantu speakers. While there is sufficient genetic, physical anthropological and cultural evidence to support general continuity into contemporary populations, the extent to which events since colonialism have affected morphological variation is poorly understood. We used dental anthropological techniques and three-dimensional craniomandibular metrics to examine biological relationships among Iron Age farmers, a historical 19th-century Ndebele sample and 20th-century Bantu speakers. We show that, although Iron Age and modern morphologies are generally similar, there are differences. Moreover, the historical sample falls between the precolonial and modern samples, suggesting increased genetic exchange from the 19th century onwards. These results suggest that recent historical events altered the genetic make-up of Bantu speakers and that, as a result, extrapolations from modern groups to the past should be done with caution as morphological variability is relative to historical context. <![CDATA[<b>Relationships between ecological infrastructure and the economy: The case of a fishery</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400012&lng=es&nrm=iso&tlng=es The Millennium Ecosystem Assessment identified the regulating services as amongst the least understood but potentially most valuable services offered by ecosystems. This lack of understanding of regulating services has been a major reason for the overexploitation and degradation of ecosystems. The value of regulating services is best determined through an economic production function approach, which derives the value of regulating services as intermediate inputs into other economic goods and services. We used existing scientific knowledge and data sourced from existing scientific databases and studies to develop and demonstrate empirical production functions that measure relationships between ecological infrastructure and the economy in fisheries in KwaZulu-Natal, along the east coast of South Africa. We applied econometric analyses - a technique that allows for evidence-based analysis of observed data, based on existing scientific knowledge. Our work demonstrates that existing scientific databases may contain useful evidence of relationships between ecological infrastructure and the economy, and that decisions need not always wait for the results of controlled experiments. <![CDATA[<b>Assessing leaf spectral properties of <i>Phragmites australis</i> impacted by acid mine drainage</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400013&lng=es&nrm=iso&tlng=es The decanting of acid mine drainage (AMD) from the Western Basin on the Witwatersrand in late 2010 raised concerns about AMD risks in other gold, coal and copper mining areas of South Africa. Field spectroscopy and the use of vegetation indices could offer an affordable and easy means of monitoring the impact of mine water and/or AMD on vegetation. The impact of raw and treated mine water or contaminated soil on wetland vegetation often manifests in growth inhibition and reduction of foliar pigments and nutrient levels. Surveying the impact on wetland vegetation or underlying soils can be difficult and expensive considering the cost of laboratory analysis of samples. The potential of field spectroscopy for detecting the impact of mine water on wetland vegetation was examined by assessing (1) whether there was a significant difference in leaf spectra between sites receiving mine water and a non-impacted control site and (2) whether there was a gradation of vegetation condition downstream from the decanting site. Two vegetation indices were derived from portable field spectrometer-measured spectra of five green leaves of Phragmites australis - the chlorophyll red edge position (REP) and the normalised difference vegetation index (NDVI) - for two dormant (winter) and peak growth (summer) seasons in 2011-2012. Mean REP and NDVI values were significantly (p<0.05) lower for affected sites compared to the control site for both seasons and years. The range of REP values for young green leaves in winter for affected sites was 695-720 nm compared to the narrower range of 705-721 nm for the control site. The mean REP values for young green leaves in winter was 708 nm for the affected sites compared to 716 nm for the control site. The downstream gradation, however, fluctuated for REP and NDVI over the study period. We conclude that field spectroscopy shows potential to serve as a relatively quick and affordable means to assess the condition and health of vegetation affected by AMD. <![CDATA[<b>Observed and modelled trends in rainfall and temperature for South Africa: 1960-2010</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400014&lng=es&nrm=iso&tlng=es Observed trends in seasonal and annual total rainfall, number of rain days and daily maximum and minimum temperature were calculated for a number of stations in South Africa for the period 1960-2010. Statistically significant decreases in rainfall and the number of rain days are shown over the central and northeastern parts of the country in the autumn months and significant increases in the number of rain days around the southern Drakensberg are evident in spring and summer. Maximum temperatures have increased significantly throughout the country for all seasons and increases in minimum temperatures are shown for most of the country. A notable exception is the central interior, where minimum temperatures have decreased significantly. Regionally aggregated trends for six water management zones covering the entire country are not evident for total rainfall, but there are some significant trends for the number of rain days. Temperature in these zones has increased significantly for most seasons, with the exception of the central interior. Comparison of the observed trends with statistically downscaled global climate model simulations reveals that the models do not represent the observed rainfall changes nor the cooling trend of minimum temperature in the central interior. Although this result does not rule out the possibility of attributing observed local changes in rainfall to anthropogenically forced global change, it does have major implications for attribution studies. It also raises the question of whether an alternative statistical downscaling method or dynamical downscaling through the use of a regional climate model might better represent regional and local climatic processes and their links to global change. <![CDATA[<b>Policy required for entry of DNA profiles onto the National Forensic DNA Database of South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400015&lng=es&nrm=iso&tlng=es The recent Criminal Law (Forensic Procedures) Amendment Act (2013) provides a definition for forensic DNA profiles and, in so doing, states that medical information about an individual may not be revealed through a forensic DNA profile. Yet chromosomal abnormalities can exhibit as tri-allelic patterns on DNA profiles and such information can expose medical conditions such as Down syndrome. This short report highlights this concern and suggests a policy be created for the entering of such DNA profiles onto the National Forensic DNA database of South Africa. <![CDATA[<b>Climate and the mfecane</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532014000400016&lng=es&nrm=iso&tlng=es The recent Criminal Law (Forensic Procedures) Amendment Act (2013) provides a definition for forensic DNA profiles and, in so doing, states that medical information about an individual may not be revealed through a forensic DNA profile. Yet chromosomal abnormalities can exhibit as tri-allelic patterns on DNA profiles and such information can expose medical conditions such as Down syndrome. This short report highlights this concern and suggests a policy be created for the entering of such DNA profiles onto the National Forensic DNA database of South Africa.