Numerical simulations of sunspots

The origin, structure and evolution of sunspots are investigated using a numerical model. The compressible MHD equations are solved with physical parameter values that approximate the top layer of the solar convection zone. A three dimensional (3D) numerical code is used to solve the set of equations in cylindrical geometry, with the numerical domain in the form of a wedge. The linear evolution of the 3D solution is studied by perturbing an axisymmetric solution in the azimuthal direction. Steady and oscillating linear modes are obtained

Microcystis aeruginosa: source of toxic microcystins in drinking water

Cyanobacteria are one of the earth's most ancient life forms. Evidence of their existence on earth, derived from fossil records, encompasses a period of some 3.5 billion years in the late Precambrian era. Cyanobacteria are the dominant phytoplanton group in eutrophic freshwater bodies worldwide. They have caused animal poisoning in many parts of the world and may present risks to human health through drinking and recreational activity. Cyanobacteria produce two main groups of toxin namely neurotoxins and peptide hepatotoxins. They were first characterized from the unicellular species, Microcystis aeruginosa, which is the most common toxic cyanobacterium in eutrophic freshwater. The association of environmental parameters with cyanobacterial blooms and the toxicity of microcystin are discussed. Also, the synthesis of the microcystins, as well as the mode of action, control and analysis methods for quantitation of the toxin is reviewed. Key Words: Cyanobacteria, microcystins, mcyB gene, PCR-RFLP. African Journal of Biotechnology Vol.3(3) 2004: 159-16

Linking climate change and progressive eutrophication to incidents of clustered animal mortalities in different geographical regions of South Africa

Cyanobacterial blooms have become an increasing problem in South African freshwater bodies. Since certain species of cyanobacteria are well-known for biosynthesis of potent hepatic and neurotoxins, such blooms can pose a significant threat to the health of animals and humans. The massiveproliferation of these organisms in rivers and lakes is largely due to progressive eutrophication. However, a warming trend in the Southern hemisphere, indicated by a threefold increase in the minimum temperature compared to maximum temperature between 1950 and 1990, is likely the cause of the increasing occurrence of toxic cyanobacterial bloom forming species, previously hampered by low water temperatures in different geographical regions of South Africa

Relational experiences of community members participating in a rural health initiative with interprofessional students

Background. A South African faculty of health sciences created a forum for the community to voice their relational experiences with interprofessional students through visual projections. No other studies that explore such experiences using the Mmogo method could be located. Objective. To gain an understanding of the relational experiences of community members participating in Lifestyle-groups as part of a rural health initiative with interprofessional student groups. Methods. The Mmogo method is a qualitative, structured, observation technique. Participants constructed visual projections representing specific relationships. Thereafter, during a group discussion, participants explained the meaning of their projections. The visual data were analysed according to their literal presentation and subjective, symbolic meaning. A thematic analysis was used for the transcribed data. Results. Thirteen of the 24 visual projections were of a quality that allowed visual analysis; all 24 members participated in the discussions. Light was identified as an overarching theme to represent the community-student interaction. Sub-themes and categories associated with light were healthier lifestyles (knowledge sharing, lifestyle transformation, improved health outcomes), solidarity (reciprocity, collaboration, person centredness, multidimensional approach) and affirmation (gratitude and acceptance). Conclusion. Though some statements by participants related to health education as opposed to health dialogue highlighted areas requiring improvement, the findings correlated with the outcomes prescribed for students by this rural health initiative. Emotional connections in relational experiences could facilitate higher levels of self-efficacy in communities. The question is whether a stronger emphasis on health dialogue can be a catalyst for improved self-efficacy

Molecular analysis of fruit ripening: The identification of differentially expressed sequences in Vitis vinifera using cDNA-AFLP technology

Differential gene expression patterns were studied during the ripening process of grape berries (Vitis vinifera cv. Chardonnay). Thirty PstI + MseI primer combinations were used to generate 213 fragments that appeared to be differentially expressed of which 94 % were successfully re-amplified. Reverse northern dot-blot analysis indicated that 35 % of the fragments had similar gene expression profiles to cDNA-AFLPs regarding developmental-stage specificity. Northern blot analyses confirmed the tissue and/or developmental stage specific expression of three of these cDNA fragments. This work illustrates that developmentally regulated sequences can be identified from grape berry tissue using cDNA-AFLP technology

Monetary value of the impacts of filamentous green algae on commercial agriculture: Results from two geographically different case studies

This paper presents estimates of the monetary value of the impact of eutrophication (algae) on commercial agriculture in two different catchments in South Africa. A production function approach is applied to estimate the monetary value of the impact of filamentous green algae on commercial agriculture in the Dwars River, Western Cape and the Loskop irrigation area, Groblersdal, in South Africa. The main emphasis was on the impacts of algal growth on farm profitability, which relied on detailed information on the impact, and the extent of the impact, of algae on farming practice. The paper presents the study areas, methodological approach, surveyed pollution impacts and the calculated monetary value of the impacts of such pollution. A short conclusion discusses some potential applications of the results. Initial results point towards a value of R1 887 per hectare per year for the Dwars River area and R2 890 per hectare per year for the Loskop irrigation area. The information can not only be used to compare different eutrophication mitigation strategies within the study areas and, to a lesser extent, similar areas outside these areas, but can also inform a process focusing on assessing the market potential for tradable pollution permits as a mitigation practice to manage water pollution in both catchments.Keywords: water quality, filamentous algae, economic impact, farmin

First report on the colony-forming freshwater ciliate Ophrydium versatile in an African river

Ophrydium versatile (Müller 1786) Ehrenberg 1830 – a symbiotic ciliate that forms gelatinous colonies – is widely distributed in temperate lakes in Europe and America, but has not previously been recorded from rivers. In this paper we report the first record of O. versatile in an African river, based on an identity confirmed by molecular taxonomic identification. The limnological conditions within the Lephalala River during the sampling period were characterised as oligotrophic with low DOC concentrations, similar to the conditions observed in temperate northern hemisphere lakes where these organisms have been recorded previously. The majority of O. versatile colonies occurred in areas where thin orange-coloured films containing high concentrations of iron (> 60% Fe) covered the substrate and bedrock of the river; this may be related to the abundant picophytoplankton that were associated with these films and oligotrophic conditions. The planktonic diatom Gomphonema venusta Passy was dominant in the water column throughout the study period and acted as an environmental indicator of low electrical conductivity (EC) conditions in the habitat where O. versatile colonies were recorded. Keywords: Lapalala River, oligotrophic indicator, water qualit