Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320070001&lang=en vol. 103 num. 1-2 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Southern African Society for Plant Pathology Conference Papers</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100001&lng=en&nrm=iso&tlng=en <![CDATA[<b>The problematic ratings game in modern science</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100002&lng=en&nrm=iso&tlng=en <![CDATA[<b>A commentary on the intellectual health of the nation</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100003&lng=en&nrm=iso&tlng=en The record of high-quality research at South African universities is not as impressive as we may have thought, according to some international rankings. Whatever we might think of these assessments, we have to take them seriously. We suggest ways in which our universities and other institutions of higher learning might raise the level of their game. <![CDATA[<b>Internationalization of R&D: Where does South Africa stand?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100004&lng=en&nrm=iso&tlng=en Internationalization of trade has extended to services and intangibles such as research and experimental development (R&D). The emergence of knowledge economies with porous borders raises questions concerning the preparedness of countries to manage their systems of innovation in response to these changes. This article draws on the recently completed 2004/5 R&D survey, and other local and international data sources to consider the extent to which South African R&D is positioned to respond to the challenge of the internationalization of R&D. This entails looking at the behaviour of the main role players in the system of innovation, the extent to which they are open to local and global interactions, competitive advantage, and the implications for policy. The evidence suggests that, from an R&D perspective, the emerging South African knowledge economy is still more 'closed' than 'open'. Actions that may contribute to attracting international R&D investment and collaboration include development of skilled people and the further enhancement of direct and indirect R&D incentives. <![CDATA[<b>Atomic force microscopy to determine the surface roughness and surface polarity of cell types of hardwoods commonly used for pulping</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100005&lng=en&nrm=iso&tlng=en Atomic force microscopy can be used to determine the surface roughness and surface polarity of different cell types originating from hardwood species. This analytical method allows images representing the topography and polarity of a surface to be captured simultaneously at a molecular (nanometre) resolution. The distribution of hydrophilic (polar) groups on these cell surfaces influences the subsequent processing of woodpulp in paper manufacture. These surface properties of fibres, vessel elements and parenchyma cells were investigated for Acacia mearnsii, Eucalyptus grandis, E. dunnii and E. macarthurii. A clear distinction was observed between the cell types and the species in terms of polarity and surface roughness. All four species are currently being used for paper manufacture in South Africa,butnot with equal success. This study may help to explain the differences in pulp quality obtained for the various species. <![CDATA[<b>Stereochemistry and vitalism</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100006&lng=en&nrm=iso&tlng=en Atomic force microscopy can be used to determine the surface roughness and surface polarity of different cell types originating from hardwood species. This analytical method allows images representing the topography and polarity of a surface to be captured simultaneously at a molecular (nanometre) resolution. The distribution of hydrophilic (polar) groups on these cell surfaces influences the subsequent processing of woodpulp in paper manufacture. These surface properties of fibres, vessel elements and parenchyma cells were investigated for Acacia mearnsii, Eucalyptus grandis, E. dunnii and E. macarthurii. A clear distinction was observed between the cell types and the species in terms of polarity and surface roughness. All four species are currently being used for paper manufacture in South Africa,butnot with equal success. This study may help to explain the differences in pulp quality obtained for the various species. <![CDATA[<b>Southern African science in the year 1907-100<i>n</i></b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100007&lng=en&nrm=iso&tlng=en Atomic force microscopy can be used to determine the surface roughness and surface polarity of different cell types originating from hardwood species. This analytical method allows images representing the topography and polarity of a surface to be captured simultaneously at a molecular (nanometre) resolution. The distribution of hydrophilic (polar) groups on these cell surfaces influences the subsequent processing of woodpulp in paper manufacture. These surface properties of fibres, vessel elements and parenchyma cells were investigated for Acacia mearnsii, Eucalyptus grandis, E. dunnii and E. macarthurii. A clear distinction was observed between the cell types and the species in terms of polarity and surface roughness. All four species are currently being used for paper manufacture in South Africa,butnot with equal success. This study may help to explain the differences in pulp quality obtained for the various species. <![CDATA[<b>Screening of four <i>Cyclopia </i>(honeybush) species for putative phyto-oestrogenic activity by oestrogen receptor binding assays</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100008&lng=en&nrm=iso&tlng=en Phyto-oestrogens mediate an oestrogenic effect through binding to the oestrogen receptor (ER) subtypes, ERa and ERß. Four commercially available Cyclopia (honeybush) species-C. intermedia, C. subternata, C. genistoides and C. sessiliflora-together with nine commercially obtainable polyphenols present in some or all of the species, were screened for phyto-oestrogenic activity, using a competitive whole-cell ER binding assay. Only naringenin, formononetin and luteolin were able significantly to displace ³H-E2 from hERα, whereas luteolin, naringenin, formononetin, eriodictyol, narirutin and eriocitrin displaced ³H-E2 from hERß. Mangiferin, hesperidin and hesperetin did not bind to either receptor subtype. To our knowledge, this is the first time that binding of eriodictyol, eriocitrin and narirutin to the hERß has been shown. Furthermore, both aqueous and methanol extracts from three independent harvestings of each Cyclopia species were screened. The results suggest that C. genistoides and C. subternata display significant phyto-oestrogenic activity and that methanol extracts from 'unfer-mented' (unoxidized) plant material generally display greater activity. Great variation exists within a species, however, with one C. genistoides harvesting displacing ³H-E2 from both ER subtypes, while another harvesting displaced ³H-E2 from only hERß, and a third did not displace ³H-E2 from either receptor subtype. <![CDATA[<b>Impacts of a South African coastal golf estate on shrubland bird communities</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100009&lng=en&nrm=iso&tlng=en Golf courses and estates are one form of development threatening coastal vegetation in South Africa's Cape Floristic Region. They occupy substantial tracts of land, fragmenting indigenous vegetation. This study investigates the effects on bird community structure and function of replacing natural Strandveld vegetation with a 170-ha golf estate in which 46 ha of Strandveld vegetation was retained in conditions ranging from pristine to moderately degraded. Bird assemblages of the remaining Strandveld patches in the golf estate were compared with those of an adjacent Strandveld conservation area. Field work was conducted during the birds' breeding season, in October and November 2005. The golf estate was more species rich overall, but many species were uncommon, several were present only as a consequence of the creation of new habitats, and species were not evenly distributed across the remaining Strandveld fragments. Bird diversity and abundance were significantly higher in the adjacent conservation area. It is estimated that more than 8500 individual birds were displaced by construction of the golf estate and four Strandveld species were not represented at all within the estate. Within the estate, species richness rose with increasing Strandveld patch size and the minimum area of continuous pristine vegetation required to maintain the natural species assemblage was estimated at 51 ha. The golf estate was characterized by a high proportion of generalist and granivorous species, but at the cost of reduced numbers of frugivores and nectarivores. Energy flow through the bird communities in the two areas was thus markedly different, and pollination and fruit dispersal potential within the golf estate were reduced substantially. Golf courses and golf estates inevitably will not substitute for the natural habitats they have replaced, but careful design with input from ecological theory can reduce the adverse effects of fragmentation. <![CDATA[<b>Physical, chemical and optical properties of aerosol particles collected over Cape Town during winter haze episodes</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100010&lng=en&nrm=iso&tlng=en Airborne measurements were conducted in the winter months of July and August 2003 over the metropolitan area of Cape Town to characterize physical, chemical and optical properties of aerosol particles during intense brown haze episodes. Particles were collected on highly temporally and spatially resolved samples and investigated using a high-resolution scanning electron microscope (SEM). From morphology and elemental composition, particles were categorized in terms of seven groups: aggregated soot particles, mineral dust, sulphates (SO²4 ), sea-salt, tar balls/fly ash, rod-shaped particles associated with soot agglomerates, and those that could not be attributed to any of these groups. Refractive indices of aerosols were derived from chemical distributions obtained from SEM analysis and combined with in situ measurements of number-size distributions to determine optical properties of dry particles in the size range 0.1-3.5 pm. Particles exhibited marked spatial and temporal variability in chemical composition. They were externally mixed with highly absorbing soot particles. From number concentrations, light extinction and absorption coefficient ranges were σep= 19-755 Mm-1 and σap= 7-103 Mm-1, respectively (at wavelength λ = 550 nm). Single scattering albedo, ω0, varied from 0.61 to 0.87 with a mean value of 0.72 ± 0.08; this value was much lower than generally reported in the literature, a result that was attributed to high concentrations of highly absorbing soot (fractional number concentrations of up to 46% were observed in the SEM). The haze could be attributed to extinction of light by fine aerosols composed mainly of anthropogenic particles. High extinction coefficients and low single scattering albedo computed here demonstrate quantitatively the contributions of particulate matter to visibility reduction and the brown haze phenomenon in Cape Town. <![CDATA[<b>Fungus gnats and other Diptera in South African forestry nurseries and their possible association with the pitch canker fungus</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100011&lng=en&nrm=iso&tlng=en Fusarium circinatum is the causal agent of a serious disease of seedlings in South African pine nurseries. Insects, especially fungus gnats (Diptera: Sciaridae, Mycetophlidae), are suspected of transmitting this fungus in nurseries. The aim of this study was to ascertain which species of gnats are present in South African pine nurseries, and to consider whether these and other Diptera carry F. circinatum. Dipteran fauna were surveyed in four major forestry nurseries between 2000 and 2001. Fungi were isolated from these flies and the resulting Fusarium species were identified. Bradysia difformis was the only fungus gnat species found and it occurred in all nurseries. Other Dipteran families collected included Agromyzidae, Cecidomyiidae, Chironomidae, Ephydridae, Muscidae, Simulidae and Tachinidae. This is the first report of B. difformis in South Africa. Fusarium circinatum was not isolated from any of the Diptera collected. Fusarium oxysporum and F. stil-boides were isolated from Chironomidae, but these fungi are not considered important pathogens in the nurseries surveyed. <![CDATA[<b>Temporal variation in Plio-Pleistocene <i>Antidorcas </i>(Mammalia: Bovidae) horncores: The case from Bolt's Farm and why size matters</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100012&lng=en&nrm=iso&tlng=en Morphological differences in samples of fossil (Antidorcas recki) and modern (A. marsupialis) springbok horncores suggest that the ancestral species shows less sexual dimorphism than is observed in the horn dimensions of modern springbok. This pattern may prove useful when evaluating fossil springbok specimens in South African Plio-Pleistocene faunal assemblages. Undated Antidorcas craniodental specimens from Pit 3, Bolt's Farm (Cradle of Humankind, Gauteng, South Africa) have previously been referred to A. recki by Cooke.¹ However, comparison with numerous other springbok samples suggests that these specimens are more likely to represent male and female fossils of the extant species, A. marsupialis. This re-evaluation adds weight to the fossil evidence implying that the modern form of springbok is a southern African endemic species which first appeared around 1.5-1.0 million years ago in Swartkrans Member 1.2,3 Bolt's Farm Pit 3 fossils are inferred to be of a similar age. <![CDATA[<b>A double-tusked dicynodont and its biostratigraphic significance</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100013&lng=en&nrm=iso&tlng=en A new specimen of Eodicynodon oosthuizeni, discovered near Prince Albert Road in the Western Cape province of South Africa, has a double distinction. Of stratigraphic importance is the fact that it is the only specimen of Eodicynodon known from above the first maroon mudrocks of the Beaufort Group, a feature which has important implications for understanding the development of the earliest terrestrial environments of Gondwana during the middle Permian. Of anatomical significance is the presence of two canines on the left maxilla. This rare condition, known in only three dicynodonts, is here considered to be pathological and not the result of tooth replacement. <![CDATA[<b>Extended procolophonoid reptile survivorship after the end-Permian extinction</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100014&lng=en&nrm=iso&tlng=en The end-Permian extinction event is regarded as the most severe of the five major extinction events in the history of life. Recent work in the Karoo Basin of South Africa suggests that the extinctions at the Permo-Triassic boundary (PTB) may have been followed by a second pulse of extinctions, one that claimed the few species that crossed the PTB and thus survived the first extinction pulse. We report here a new specimen of the procolophonoid reptile, Sauropareion anoplus, which was known heretofore only from a single specimen from Lower Triassic strata of the Palingkloof Member, Balfour Formation. The new specimen comes from the lower part of the overlying Katberg Formation and serves as the last appearance datum for the stratigraphic range of S. anoplus. It indicates that S. anoplus survived the second pulse of PTB extinctions and reinforces the hypothesis that procolophonoid evolution was not seriously perturbed by extinctions that mark the beginning of the Triassic Period. <![CDATA[<b>A climate-based model for malaria prediction in southeastern Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100015&lng=en&nrm=iso&tlng=en Malaria is a major health problem in southeastern Africa. In this study, we explore relationships between malaria and regional climate. Malaria incidence data from the eastern border of South Africa and Swaziland over a 33-year period were de-trended and used to identify epidemics. Composite weather maps were then constructed for seasons with high and low malaria incidence and evaluated. Surface-air temperature rose over the east coast during malaria epidemics and rainfall doubled over a large area including Swaziland, Zimbabwe and southern Mozambique. Remote climatic signals that anticipated malaria epidemics were found in composite analyses, and a statistical model was developed for prediction. Upper-level winds over the Western Pacific were found to predict 57% of malaria variance at a lead time of 6 months. <![CDATA[<b>Surface drift at the western edge of the Agulhas Bank</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532007000100016&lng=en&nrm=iso&tlng=en The Agulhas Bank is a wide continental shelf that forms the southern tip of the African continent. On the eastern side of this shelf the flow of water is dominated by the adjacent Agulhas Current. On its western border, the movement is more complex. It is influenced by the Benguela Current, by the occasional presence of products from the Agulhas Current such as Agulhas rings, Agulhas filaments and by lee eddies. Understanding the flow on this western side of the Agulhas Bank is of considerable ecological importance because it has been assumed that a shelf edge jet carries immotile or weakly motile fish larvae and eggs from the spawning region on the bank to the biologically productive regions of the Benguela upwelling regime. We have used the tracks of a set of surface drifters to study the movement at the western edge of the bank, and show that on average the movement is indeed equatorward along this shelf edge, but that this movement is not persistent in direction or magnitude. Instead, this movement appears to be driven entirely by mesoscale turbulence created at the termination of the Agulhas Current.