Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320100005&lang=en vol. 106 num. 9-10 lang. en <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Poverty alleviation versus the redress of inequality?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500001&lng=en&nrm=iso&tlng=en <![CDATA[<b>Who takes responsibility for the 'Reitz four'? Puzzling our way through higher education transformation in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500002&lng=en&nrm=iso&tlng=en <![CDATA[<b>The humble bearded goby is a keystone species in Namibia's marine ecosystem</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500003&lng=en&nrm=iso&tlng=en <![CDATA[<b>First oceanographic survey of the entire continental shelf adjacent to the northern Agulhas Current</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500004&lng=en&nrm=iso&tlng=en <![CDATA[<b>R.O. Dudley</b>: <b>teacher, educator and political dissenter (1924-2009)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500005&lng=en&nrm=iso&tlng=en <![CDATA[<b>Back to basics</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500006&lng=en&nrm=iso&tlng=en <![CDATA[<b>Antibiotic resistance via the food chain</b>: <b>fact or fiction?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500007&lng=en&nrm=iso&tlng=en The mechanisms that bacteria use to acquire additional genetic material, including genes coding for antibiotic resistance, are principally the secondary pathways that have been described as transformation and conjugation pathways. The farming industry often is reported as a hotspot for antibiotic-resistance reservoirs. In this review, we consider the exposure of food animals during the course of their lifespans to preventative, therapeutic or prophylactic treatment with antibiotic agents. In this context, zoonotic bacteria are commonly recognised as a potential threat to human health, with therapeutic treatment of pathogenic organisms on farms increasing the likelihood of selective antibiotic pressure influencing the commensal flora of the intestines. Existing literature indicates, however, that the effective impact on human health of such interventions in the food production process is still subject to debate. <![CDATA[<b>South Africa's diminishing coal reserves</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500008&lng=en&nrm=iso&tlng=en South Africa's coal reserves have been significantly reduced since 2003 and a re-assessment based on the complete statistical history of production from southern Africa has indicated that the present remaining reserve for the entire subcontinent comprises only about 15 billion tonnes or gigatonnes (Gt). South African coal geologists should therefore be mindful of experience in Britain, where reserves were grossly overestimated by conventional techniques and remained a large multiple of future production until very shortly before the effective collapse of the industry in the 1980s. The southern African historical analysis has shown that an impressive leap in coal production occurred between 1975 and 1985, from about 69 million tonnes per year (Mt/yr) to 179 Mt/yr. By 1989, the cumulative production had reached 4 Gt. Despite this doubling since to just over 8 Gt, the underlying pattern has been one of faltering growth. Hubbertarian analysis predicts a peak in production rate of about 284 Mt/yr in 2020, at which stage approximately half (12 Gt) of the total resource (23 Gt) will be exhausted. The Waterberg Coalfield (Ellisras Basin) in South Africa may be a remaining large resource, but structural complexity, finely interbedded coal-shale strata at large depths, low grades, high ash content and water scarcity are likely to inhibit its major development. Given South Africa's heavy dependence on coal for power generation and electricity supply, an anticipated peak production in 2020 will cause problems for future economic growth. <![CDATA[<b>Developing a South African pedestrian environment assessment tool</b>: <b>Tshwane case study</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500009&lng=en&nrm=iso&tlng=en Pedestrians, comprising approximately 60% of the population, are among the most vulnerable road users in South Africa. The roadside environment may be an important factor influencing the nature and frequency of pedestrian fatalities. While there are audit tools for assessing the pedestrian environment in other countries, no such tool exists for South Africa. This study evaluated existing audit tools in relation to South African issues and conditions and developed a South African Pedestrian Environment Assessment Tool (PEAT). PEAT was tested at five sites in the Tshwane Metropolitan Area in Gauteng to assess its applicability. PEAT was simple to use and provided valuable information, however, appropriate measures need to be taken to address fieldworker security, especially for night-time assessments when several roadside factors, such as lighting, should be evaluated. Although it was not the focus of our study, based on our results, we suggest that the lack of pavements, pedestrian crossings and pedestrian lighting are factors that, potentially, could increase pedestrian vulnerability. <![CDATA[<b>Network resources management in a multi-agent system</b>: <b>a simulative approach</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500010&lng=en&nrm=iso&tlng=en Multi-agent systems (i.e. systems comprising many agents) have been proposed for many Internet and distributed applications. The proposed systems have little or no consideration of the effects of this multi-agent approach on network resources. In this paper, we presented a simulation assessment of the effect of multi-agent systems on network resources. The routing scheme of the agents was formulated based on the travelling salesman problem. Lightweight agent (LWA) controller was modelled using a fuzzy logic toolbox in the MATLAB environment. The performance metrics of bandwidth usage, response time and throughput were used to compare the network resources usage by different groups of LWAs (10 LWAs, 40 LWAs, 100 LWAs, 150 LWAs) during their computational task on the network. Java programs were written for the implementation of lightweight agents in the simulation. The inputs to the system were realised by multiplicative pseudorandom number generation during the simulation. The simulation result analysis was carried out based on the performance metrics stated above for the four groups of agents. Increasing the number of LWAs in a simulated multi-agent system decreased the response time but increased the throughput and the bandwidth usage. All these performance measures should be considered for developing countries with bandwidth shortages, because having too many agents in a multi-agent system could result in bandwidth wastages. <![CDATA[<b>Palladium mixed-metal surface-modified AB<sub>5</sub>-type intermetallides enhance hydrogen sorption kinetics</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500011&lng=en&nrm=iso&tlng=en Surface engineering approaches were adopted in the preparation of advanced hydrogen sorption materials, based on 'low-temperature', AB5-type intermetallides. The approaches investigated included micro-encapsulation with palladium and mixed-metal mantles using electroless plating. The influence of micro-encapsulation on the surface morphology and kinetics of hydrogen charging were investigated. It was found that palladium-nickel (Pd-Ni) co-deposition by electroless plating significantly improved the kinetics of hydrogen charging of the AB5-type intermetallides at low hydrogen pressure and temperature, after long-term pre-exposure to air. The improvement in the kinetics of hydrogen charging was credited to a synergistic effect between the palladium and nickel atoms in the catalytic mantle and the formation of an 'interfacial bridge' for hydrogen diffusion by the nickel atoms in the deposited layer. The developed surface-modified materials may find application in highly selective hydrogen extraction, purification, and storage from impure hydrogen feeds. <![CDATA[<b>Isolation and identification of iron ore-solubilising fungus</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500012&lng=en&nrm=iso&tlng=en Potential mineral-solubilising fungi were successfully isolated from the surfaces of iron ore minerals. Four isolates were obtained and identified by molecular and phylogenetic methods as close relatives of three different genera, namely Penicillium (for isolate FO), Alternaria (for isolates SFC2 and KFC1) and Epicoccum (for isolate SFC2B). The use of tricalcium phosphate (Ca3(PO4)2) in phosphate-solubilising experiments confirmed isolate FO as the only phosphate solubiliser among the isolated fungi. The bioleaching capabilities of both the fungus and its spent liquid medium were tested and compared using two types of iron ore materials, conglomerate and shale, from the Sishen Iron Ore Mine as sources of potassium (K) and phosphorus (P). The spent liquid medium removed more K (a maximum of 32.94% removal, from conglomerate), than the fungus (a maximum of 21.36% removal, from shale). However, the fungus removed more P (a maximum of 58.33% removal, from conglomerate) than the spent liquid medium (a maximum of 29.25% removal, from conglomerate). The results also indicated a potential relationship between the removal of K or P and the production of organic acids by the fungus. A high production of gluconic acid could be related to the ability of the fungus to reduce K and P. Acetic, citric and maleic acids were also produced by the fungus, but in lower quantities. In addition, particle size and iron ore type were also shown to have significant effects on the removal of potassium and phosphorus from the iron ore minerals. We therefore conclude that the spent liquid medium from the fungal isolate FO can potentially be used for biobeneficiation of iron ore minerals. <![CDATA[<b>Bacterial profiling of casing materials for white button mushrooms (<i>Ag</i>a<i>ricus bisporus</i>) using denaturing gradient gel electrophoresis</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500013&lng=en&nrm=iso&tlng=en Commercial producers of white button mushrooms utilise a casing material to cover the spawn run compost, which stimulates the mushrooms' reproductive stage. Certain bacteria in this casing are responsible for this stimulation, which is known as pinning. Bacterial species richness and diversity within peat and peat-based casing mixtures made from industrial waste materials (i.e. those containing coir, wattle bark, bagasse and filter cake) were examined using denaturing gradient gel electrophoresis (DGGE) at three phases of mushroom growth: (1) casing, (2) pinning and (3) harvesting. Results from the DGGE established that higher bacterial species richness occurred at pinning and harvesting than at casing. Increases in bacterial population density at pinning were greater in the peat-based mixtures, which contained industrial waste materials, than in peat alone. Peat mixtures containing these alternative materials are therefore favourable substrates for bacterial growth. The DGGE profiles for pasteurised casing materials reflected their ability to rapidly re-establish the original bacterial community. The bacteria found to be dominant in casing materials during pinning were closely related to Pseudomonas, Flavobacterium, alpha-Proteobacterium, beta-Proteobacterium, gamma-Proteobacterium, delta-Proteobacterium and uncultured species. <![CDATA[<b>Integrating qualitative methodologies into risk assessment</b>: <b>insights from South Durban</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500014&lng=en&nrm=iso&tlng=en In the field of risk management, there is growing recognition that traditional tools of analysis may be limited in their ability to arrive at a textured understanding of risk as it is actually experienced by communities. This paper begins with the premise that risk is socially constructed by lay people, as well as by scientists, and that this recognition has important implications for the development of risk management approaches. Technical risk assessments can be complemented by qualitative methodologies that are designed to reveal lay or local knowledge of risk. Such research tools were employed in working with respondents from residential communities in the highly industrialised South Durban Basin in KwaZulu-Natal. Here, as in other urban industrial contexts, risk is constructed by residents through their own experience and histories, their understanding of science, and their response to technical management tools. The qualitative approach adopted in this research provided new insight into residents' responses to chronic and acute risk, drew attention to a widening gap between people's actual experiences and the claims of science and risk management experts and exposed currently hidden, everyday risk narratives that are not directly related to the dominant environmental hazards connected with industry, but which significantly impact people's living environments. <![CDATA[<b>Cobalt(II) removal from synthetic wastewater by adsorption on South African coal fly ash</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532010000500015&lng=en&nrm=iso&tlng=en Advanced wastewater-treatment techniques such as adsorption are essential in the removal of non-biodegradable toxic wastes from water. In this study, the use of South African coal fly ash, an industrial byproduct, has been investigated as a potential replacement for the current costly adsorbents used for removing heavy metals from wastewater. We utilised coal fly ash for the adsorption of cobalt(II) ions from synthetic petrochemical wastewater and characterised its performance. A two-level three-factor full-factorial design was successfully employed for experimental design and analysis of the results. The combined effects of pH, initial concentration and adsorbent dose on cobalt(II) removal were assessed using response surface methodology. Although the focus was on removal of cobalt(II), the adsorption was carried out in the presence of phenol and other heavy metal ions using the batch technique. The applicability of the Freundlich and Langmuir models to the equilibrium data was tested. Consequently, the equilibrium data was found to conform more favourably to the Freundlich isotherm than to the Langmuir isotherm; in this case, the coal fly ash had a maximum adsorption capacity of 0.401 mg/g for cobalt(II). We conclude that South African coal fly ash, as a natural, abundant and low-cost adsorbent, might be a suitable local alternative for elimination of cobalt(II) from aqueous solutions.