South African Journal of Science - Volume 101, Issue 5-6, 2005
Volumes & issues
Volume 101, Issue 5-6, 2005
Author George LindseySource: South African Journal of Science 101, pp 211 –212 (2005)More Less
Academic teaching performance at many South African universities is currently assessed using student feedback of its perceived effectiveness or quality. Such a method does not account for the difficulty of the material presented. This article describes an approach that takes cognizance of the difficulty of the content presented, to distinguish between effective and less effective teaching.
Source: South African Journal of Science 101, pp 213 –215 (2005)More Less
Elephants damage and kill trees. This behaviour often appears to be excessive because their immediate, subsequent consumption of edible parts of these trees is often negligible. Some trees later resprout after snapping and toppling by elephants and thus produce forage at the animals' preferred feeding-height. We argue that this and other 'farming' hypotheses are group-selectionist and are thus not evolutionarily stable strategies. We suggest that excessive damage to trees ismore likely to be due to social or sexual factors. More behavioural analyses and experiments are needed to understand this phenomenon and its implications for conservation.
Source: South African Journal of Science 101, pp 216 –217 (2005)More Less
The development of an effective HIV vaccine is a global health priority. The highest rates of new HIV infections in South Africa occur amongst the youth, and a vaccine will be vital to reduce incidence. Recent debate about the inclusion of adolescents in HIV vaccine trials, both internationally and nationally, is particularly relevant to South Africa, which harbours more HIV-infected people than any other country. To date, no preventative HIV vaccine trials have included adolescents. Vaccine trials in these age groups are constrained by unresolved ethico-legal issues, which are likely to delay licensure for adolescents should a favourable candidate vaccine be identified. There is a moral imperative to resolve these ethical and legal complexities in a broader debate, so that we may develop and test vaccines in a way that both protects and promotes the health of young people.
Technological performance judged by American patents awarded to South African inventors : science policyAuthor Anastassios PourisSource: South African Journal of Science 101, pp 221 –224 (2005)More Less
Patents are accepted internationally as a reflection of a country's inventive and technological achievements and are used for monitoring and assessing national systems of innovation. In South Africa, patents are one of the technological indicators monitored by the Department of Science and Technology. This article reports the results of an assessment of South Africa's technological performance based on the number of utility patents granted to South African inventors by the U.S. Patent and Trademark Office (USPTO). The analysis shows that the country is losing ground in the international technological race. South Africa's shares in the USPTO halved from 0.13% in 1988 to a mere 0.07% in 2001. Finer analysis reveals a small shift towards modern technologies (such as biotechnology, pharmaceuticals, and computers and peripherals) and Science Linkage indicators identify the areas (in particular biotechnology and pharmaceuticals) in which South Africa is producing leading-edge technologies.
Ethical and legal challenges in enrolling adolescents in medical research in South Africa : implications for HIV vaccine trials : science policySource: South African Journal of Science 101, pp 224 –228 (2005)More Less
In this paper we review legal and ethical challenges to the enrolment of children in HIV vaccine trials, and discuss two main Questions : 'When can children participate in research, such as HIV vaccine trials?' and 'Who can consent to child participation in such trials?' In examining the first question, we discuss the constitutional framework for research with children, and in particular the meaning of section 12(2)(c) of the South African Constitution. We submit that while there are no laws specifically prohibiting the enrolment of adolescents (provided that the research protects a child's constitutional rights and 'best interests', and is not against 'public policy'), there are challenges related to the absence of an objective standard in law for acceptable research-related risk for adolescents. We outline some ethical challenges to enrolment; namely, that ethical guidelines regarding what parents may consent to their children participating in are inconsistent, and that some guidelines take a restrictive stance, effectively precluding HIV vaccine trials with children. With regard to who can consent to child participation in such trials, we discuss current law, as well the new National Health Act. We explore possible inconsistencies between the Act and principles found in other children's law, as well as inconsistencies in current ethical guidelines, and the implications this may have for HIV vaccine research. Finally, we make recommendations for future work.
Source: South African Journal of Science 101, pp 229 –232 (2005)More Less
In February 2005, the exotic bark beetle, <I>Scolytus kirschii</I> (Curculionidae: Scolytinae), was detected infesting English elms <I>(Ulmus procera)</I> in Stellenbosch, South Africa. This appears to be the first report of an infestation of <I>Scolytus</I> species in this country. The presence of this beetle is of concern for several reasons. <I>Scolytus kirschii</I> is a serious pest of elms, capable of killing healthy trees, resulting in considerable economic impact. There also exists the possibility that the beetle may undergo a host switch to indigenous trees, with potentially serious ecological consequences. Furthermore, the beetle is capable of being the vector of the pathogens responsible for Dutch elm disease (DED), <I>Ophiostoma ulmi</I> and <I>Ophiostoma novo-ulmi</I>. None of the trees that we inspected in Stellenbosch exhibited symptoms or signs of DED. Isolations from infested host material likewise failed to detect these pathogens. Nonetheless, the damage to the trees by the beetles alone was sufficient to cause tree death. Future directions for research and management of the beetle in its new environment are discussed.
Thaumastocoris australicus Kirkaldy (Heteroptera : Thaumastocoridae) : a new insect arrival in South Africa, damaging to Eucalyptustrees : research in actionSource: South African Journal of Science 101, pp 233 –236 (2005)More Less
The insect <I>thaumastocoris australicus</I> Kirkaldy is reported from South Africa, where it probably is a recent arrival from Australia. The species was originally described from Queensland, but in recent years has taken on pest proportions on some local and planted <I>Eucalyptus</I> species in Sydney, New South Wales. In Gauteng province, South Africa, these gregarious, leaf-sucking bugs primarily infest introduced river red gum trees (<I>Eucalyptus camaldulensis</I> Dehnh.), causing, or contributing to, discoloration of the leaves, dieback of branches or mortality of entire trees. Several other <I>Eucalyptus</I> species also serve as hosts for <I>T. australicus</I> and some are heavily infested and severely damaged. There are confirmed reports of their presence in Gauteng, Mpumalanga and North West provinces but they are possibly already widely distributed in South Africa. Their known distribution in Australia and the localities where they already thrive in South Africa suggest that few climatic regions in southern Africa would be unsuitable for the bugs. The mature and immature insects are of nuisance value and are irritating and hard to dislodge when they fall onto people from infested trees. The possible threats to forestry and beekeeping industries have not been evaluated, but are potentially severe. No effective control measures currently exist and no insecticides have been registered for use against the pest.
First observations of sea-level indicators related to glacial maxima at Sodwana Bay, northern KwaZulu-Natal : research in actionSource: South African Journal of Science 101, pp 236 –238 (2005)More Less
Recent observations made from the submersible <I>Jago</I> have shed new light on palaeo-sea levels found off the continental margins of southeastern Africa. The discovery of deep-water caves within the northern KwaZulu-Natal submarine canyon system, and their corresponding intertidal erosional features, indicates three deeper than present sea levels at depths of 106 m, 124 m and 130 m. A clast-supported, cobble conglomerate is associated with caves of 124 m depth. This is interpreted as a beach deposit that formed during the Last Glacial Maximum (LGM) at 18 000 BP. This is the first evidence of the LGM for the east coast, and suggests tectonic stability throughout southern Africa since that time.
Fire behaviour in a semi-arid Baikiaea plurijuga savanna woodland on Kalahari sands in western Zimbabwe : research letterSource: South African Journal of Science 101, pp 239 –244 (2005)More Less
Human-induced fires are a major disturbance in <I>Baikiaea plurijuga</I> woodland savannas that are economically important for timber production. Most fires occur during the late dry season, when they may severely damage woody plants. Prescribed burning during the early dry season is a management strategy to reduce fuel loads and thus the incidence of intense fires during the late dry season. There is, however, little information on fire behaviour characteristics of early dry season fires. We studied the relationship between experimental fuel conditions and fire behaviour by lighting 15 fires during the early dry season in a <I>Baikiaea</I> woodland. Fire intensity ranged from 25 to 1341 kW m-1, while rate of spread of fire varied between 0.01 and 0.35ms-1. Fire intensity and rate of spread were positively related to flame height, leaf-scorch height and proportion of the area burnt. The relationships suggest that fire characteristics can be retrospectively determined using a variable such as scorch height. The grass fuel load, wind speed, relative humidity and to a lesser extent fuel moisture were important predictors of rate of spread, flame height, leaf-scorch height and proportion of the area burnt, with no impact due to the litter fuel load. The grass fuel load and wind speed had a positive effect on rate of spread, whereas relative humidity and fuel moisture had a negative effect. These findings indicate that managers can predict the likely damage to woody plants during an early dry season burn by ssessing the grass fuel load and weather conditions at the time of burning.
Source: South African Journal of Science 101, pp 245 –248 (2005)More Less
We have determined the tooth enamel carbonate _<sup>13</sup>C values of five cercopithecoid taxa from the Plio-Pleistocene deposits of Swartkrans Members 1 and 2 and Sterkfontein Member 4. These data were used to determine the relative proportions of C<sub>3</sub> and C<sub>4</sub> biomass consumed by extinct baboons and contemporary non-human primates. We compared these results with data on modern <I>Papio hamadryas ursinus</I> from different savanna areas in South Africa, as well as with published isotopic data and dietary interpretations based on molar morphology of these taxa. The data reveal little evidence for use of grasses or grass-based foods by modern South African baboons. The fossil papionins <I>Papio hamadryas robinsoni, Papio (Dinopithecus) ingens</I>, and <I>Parapapio spp.</I>, however, utilized more savanna-based C<sub>4</sub> resources than previously predicted (particularly in the case of <I>P.(D.) ingens)</I>. <I>Theropithecus oswaldi</I> had _<sup>13</sup>C values depicting, as expected, a largely grass-based diet, and we confirm earlier conclusions that this species incorporated a wider range of food items into its diet than do modern <I>T. gelada</I>, as reported in the literature. The colobine monkey, <I>Cercopithecoides williamsi</I>, made extensive use of savanna-.based C<sub>4</sub> foods, confirming some degree of terrestrial foraging by the species.
Inhibition of glyoxylate conversion to oxalate in cultured human cells by the carbonyl-scavenging drug, aminoguanidine : research letterSource: South African Journal of Science 101, pp 249 –255 (2005)More Less
Calcium oxalate is the most frequent cause of kidney stones, and is responsible for the damage to kidneys and other organs observed in inherited disorders of oxalate metabolism. Most oxalate produced in the body is derived from its metabolic precursor, glyoxylate. Thus, any means of scavenging glyoxylate to a non-toxic product, thereby diverting it away from oxalate synthesis, has considerable therapeutic implications. Here we show that aminoguanidine, a compound with a proven safety record and used for many years to prevent long-term complications of diabetes, binds glyoxylate covalently and reduces its conversion to oxalate by human liver- and lymphocyte-derived cell lines by >90%. We propose that scavenging glyoxylate with aminoguanidine or its congeners may provide a means of reducing oxalate production <I>in vivo</I>, and advocate the tissue culture system described here as a convenient means for testing such agents <I>in vitro</I>. A serendipitous finding to emerge from our study was the abiotic and strongly pH-dependent formation of oxalate from ascorbate, which has implications for the contribution of ascorbate to urine oxalate excretion.
Source: South African Journal of Science 101, pp 255 –257 (2005)More Less
This paper presents the first accurate geo-referenced bathymetric map of the Aliwal Shoal and illustrates its value as an essential tool for a wide range of applications useful to the broader scientific community. The dense coverage of echo-sounding data in the survey area permitted the construction of a detailed bathymetric contour map and 3-D model. It showed that the Aliwal Shoal forms part of a much larger offshore reef complex than was previously realized. Morphologically, the Aliwal Shoal is dominated by three distinct features, namely, the <I>Crown, Spur</I> and <I>Ridge</I>. The highresolution bathymetric map presented here enabled the accurate positioning of the boundaries of the Restricted Zones of the newly proclaimed Aliwal Shoal Marine Protected Area. This georeferenced GIS-compatible map will form the base map for future studies, ranging from the mapping of biological seafloor habitats to ocean current modelling, thereby also performing the function of an environmental planning and management tool.
Source: South African Journal of Science 101, pp 258 –262 (2005)More Less
Computational physics as a university undergraduate programme, or as a choice of specialized modules or laboratories within the mainstream physics programme, has grown considerably over the past several years, but this trend is yet to develop fully in South Africa. This paper provides a motivation for developing computational physics at our universities and suggests how such a programme may be designed. We argue that students develop a more intuitive feel for physics, that they learn useful, transferable skills that make our graduates sought-after by industry and commerce, and that such graduates are better prepared to tackle research problems at the master's and doctoral levels both in theoretical and experimental physics. We also discuss current research topics in computational physics that are of relevance to South Africa.
Author Vincent W. CoulingSource: South African Journal of Science 101, pp 263 –264 (2005)More Less
Current experimental work being undertaken on electro- and magneto-optical phenomena in the School of Physics, University of KwaZulu-Natal, is reviewed to introduce our research activity to the broader scientific community. I examine the Rayleigh-scattering, the Kerr electro-optic and the Cotton-Mouton magneto-optic experiments and show how molecular (hyper)polarizabilities and (hyper)magnetizabilities may be extracted from the measured data.
Evaluation of an optical characterization model for infrared reflectance spectroscopy of GaAs substrates : physics in South AfricaSource: South African Journal of Science 101, pp 265 –266 (2005)More Less
Source: South African Journal of Science 101, pp 267 –271 (2005)More Less
An overview is given of optical second harmonic generation (SHG) using femtosecond laser pulses to analyse technologically important crystalline materials. The principle of SHG is briefly explained and a typical experimental setup for SHG is outlined. The second harmonic (SH) measurements performed in prototype compound semiconductors reveal the crystalline structure and orientation of monocrystalline SiC, polycrystalline ZnO, and the ternary compound, Pb<sub>x</sub>Cd<sub>1-x</sub>Te, showing the segregation of a Pband a Cd-rich phase. Furthermore, SHG can selectively probe the Si/SiO<sub>2</sub> interface and the build-up of its electric field induced by laser-activated charge carrier separation. The examples presented demonstrate that SHG is a versatile technique to probe the structural and electronic properties of crystalline materials and particularly surfaces and interfaces.