Scielo RSS <![CDATA[South African Journal of Science]]> vol. 108 num. 9-10 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>How should university research be funded?</b>]]> <![CDATA[<b>Twenty years since the Rio Earth Summit - and now what?</b>]]> <![CDATA[<b>Quantifying South Africa's carbon storage potential using geophysics</b>]]> <![CDATA[<b>Too many actions, too few priorities</b>: <b>commentary on the ministerial review of the STI landscape</b>]]> <![CDATA[<b>The centrality of the language question in post-apartheid South Africa</b>: <b>revisiting a perennial issue</b>]]> <![CDATA[<b>William Bond</b>: <b>excited about the future of South African science</b>]]> <![CDATA[<b>Johann Carl Vogel</b>: <b>chronologist (1932-2012)</b>]]> <![CDATA[<b>Bone microstructure of the forerunners of mammals</b>]]> <![CDATA[<b>The phenomenal, pliable, palatable prickly pear!</b>]]> <![CDATA[<b>Global challenges in the risk assessment of nanomaterials</b>: <b>relevance to South Africa</b>]]> Internationally, there are efforts to develop standardised toxicity testing and risk assessment methods for engineered nanomaterials (ENMs). To this end, health risk assessments need to be conducted on ENMs synthesised in South Africa. Country-specific risk characterisation requires specific exposure assessments for those ENMs for which the likelihood exists for occupational and environmental exposure in that country. A challenge in hazard identification and risk assessment related to ENMs, regardless of country of origin, is that data on toxicity, carcinogenicity, pharmacokinetics, and occupational or environmental exposure are generally not available for most ENMs. Although the mechanisms previously identified as important in the toxicity and carcinogenicity of particles and fibres may be applicable, the possibility exists that the unusual physicochemical properties of ENMs may give rise to unique, and as yet unidentified, adverse effects. Moreover, generalised exposure scenarios that consider the life cycle of the agent have not been developed and are needed for the complete risk characterisation of ENMs. As health risk assessment is both resource and labour intensive, it is imperative to identify the aims of such an exercise prior to embarking on large-scale projects, to ensure that the data most useful for public health decision-making is provided. Identifying priorities in South Africa, in coordination with international efforts, can facilitate the effective use of research efforts for risk assessment and risk management decision-making. <![CDATA[<b>Cooperation and conflict in cancer</b>: <b>an evolutionary perspective</b>]]> Evolutionary approaches to carcinogenesis have gained prominence in the literature and enhanced our understanding of cancer. However, an appreciation of neoplasia in the context of evolutionary transitions, particularly the transition from independent genes to a fully integrated genome, is largely absent. In the gene-genome evolutionary transition, mobile genetic elements (MGEs) can be studied as the extant exemplars of selfish autonomous lower-level units that cooperated to form a higher-level, functionally integrated genome. Here, we discuss levels of selection in cancer cells. In particular, we examine the tension between gene and genome units of selection by examining the expression profiles of MGE domains in an array of human cancers. Overall, across diverse cancers, there is an aberrant expression of several families of mobile elements, including the most common MGE in the human genome, retrotransposon LINE 1. These results indicate an alternative life-history strategy for MGEs in the cancers studied. Whether the aberrant expression is the cause or effect of tumourigenesis is unknown, although some evidence suggests that dysregulation of MGEs can play a role in cancer origin and progression. These data are interpreted in combination with phylostratigraphic reports correlating the origin of cancer genes with multicellularity and other potential increases in complexity in cancer cell populations. Cooperation and conflict between individuals at the gene, genome and cell level provide an evolutionary medicine perspective of cancer that enhances our understanding of disease pathogenesis and treatment. <![CDATA[<b>Darwin as a geologist in Africa - dispelling the myths and unravelling a confused knot</b>]]> Two myths persist concerning the role played by Charles Darwin as a geologist in Africa during his epic voyage around the world (1831-1836). The first myth is that Darwin was a completely self-taught geologist, with no formal training. The second myth is that it was Darwin who finally solved the problem of the granite-schist contact at the famous Sea Point coastal exposures in Cape Town, after deliberately setting out to prove his predecessors wrong. These myths are challenged by the now ample evidence that Darwin had excellent help in his geological education from the likes of Robert Jameson, John Henslow and Adam Sedgwick. The story of Darwin and his predecessors at the Sea Point granite contact has become confused, and even conflated, with previous descriptions by Basil Hall (1813) and Clark Abel (1818). Here, the historical record is unravelled and set straight, and it is shown from the evidence of his notebooks that Darwin was quite unaware of the outcrops in Cape Town. His erudite account of the contact was a result of the 8 years spent in writing and correspondence after his return to England and not because of his brilliant insights on the outcrop, as the myth would have it. While there has been little to indicate Darwin's landfalls in Africa, a new plaque now explains the geology of the Sea Point Contact, and includes a drawing of Darwin's ship, the Beagle, and quotes from his work. <![CDATA[<b>The national system of innovation concept</b>: <b>an ontological review and critique</b>]]> The construct 'national system of innovation' (NSI) is used to characterise a country's collective efforts towards fostering technological innovation. Since appearing in the 1996 White Paper on Science and Technology, the term has been used widely in South African policy discourses. This study makes a contribution towards an increased understanding of the meaning and implications of the NSI as a policy construct. The preponderant themes that emerge from this analysis underline the importance of fostering quality networks within the NSI. The NSI philosophical framework provides a solid foundation for organising the country's collective efforts in science and technology in a much more integrated and holistic fashion. Innovation policies and plans should aim to bring about synergy within the various elements of the NSI, particularly within small developing economies such as South Africa, in order to build robust innovation-driven economies. <![CDATA[<b>Heavy metal contamination of vegetables cultivated in home gardens in the Eastern Cape</b>]]> The accumulation of some essential (copper, manganese and zinc) and toxic metals (lead and cadmium) in cultivated vegetables - Brassica oleracea (cabbage), Daucus carota (carrot), Allium cepa (onion), Spinacia oleracea (spinach) and Solanum lycopersicum (tomato) - was examined. The vegetables were locally cultivated in home gardens in Alice, a small town in the Eastern Cape Province of South Africa. Samples of these vegetables were randomly collected from residential areas, dried, digested and analysed for the heavy metals using inductively coupled plasma optical emission spectrometry. The concentrations of heavy metals in the vegetables were in the range of 0.01 mg/kg - 1.12 mg/kg dry weight for cadmium, 0.92 mg/kg - 9.29 mg/kg for copper, 0.04 mg/kg - 373.38 mg/kg for manganese and 4.27 mg/kg - 89.88 mg/kg for zinc. Lead was undetectable in all the samples. Results of analysis of soils from the area revealed that cadmium in soil was in the range of 0.01 mg/kg - 0.08 mg/kg, copper levels were 4.95 mg/kg - 7.66 mg/kg, lead levels were 5.15 mg/kg - 14.01 mg/kg and zinc levels were 15.58 mg/kg - 53.01 mg/kg. The concentration of manganese was the highest of all the metals, ranging between 377.61 mg/kg and 499.68 mg/kg, at all three residential sites. Although the concentrations in soils and vegetables of the critical heavy metals, such as lead and cadmium, may not pose a threat (according to FAO/WHO standards), the concentration of manganese was very high in spinach and soils, whilst that of zinc exceeded safe levels in spinach, onions and tomatoes. However, neither the soils nor the vegetables were consistently found to pose a risk to human health. <![CDATA[<b>Is Greulich-Pyle age estimation applicable for determining maturation in male Africans?</b>]]> Skeletal age estimation as a means of assessing development and skeletal maturation in children and adolescents is of great importance for clinical and forensic purposes. The skeletal age of a test population is estimated by comparison with established standards, the most common standards being those in the Radiographic atlas of skeletal development of the hand and wrist published by Greulich and Pyle in 1959. These standards are based on the assumption that skeletal maturity in male individuals is attained by the chronological age of 19 years. Although they have been widely tested, the applicability of these standards to contemporary populations has yet to be tested on a population of African biological origin living in South Africa. We therefore estimated the skeletal age of 131 male Africans aged between 13 and 21 years, using the Greulich-Pyle method which we applied to pre-existing hand-wrist radiographs. Estimated skeletal age was compared to the known chronological age for each radiograph. Skeletal age was on average approximately 6 months younger than chronological age. The Greulich-Pyle method underestimated skeletal age for approximately 74% of the sample and overestimated skeletal age for 26% of the sample. Skeletal maturity as characterised by complete epiphyseal fusion occurred approximately 2.1 years later than Greulich and Pyle's estimate of 19 years. Thus skeletal maturation was still in progress in a large proportion of the 20- and 21-year-old individuals in our study. The Greulich-Pyle method showed high precision but low accuracy and was therefore not directly applicable to African male individuals. Formulation of skeletal age estimation standards specific to South African populations is therefore recommended. <![CDATA[<b>Microbial contamination of herbs marketed to HIV-infected people in Nairobi (Kenya)</b>]]> Herbal products are used by human immunodeficiency virus (HlV)-infected individuals regardless of safety or efficacy concerns. In this study, we examined the microbiological quality of herbal preparations marketed to HIV-infected individuals. A convenience sample (N = 24) of herbal products was obtained from retailers in Nairobi, Kenya in 2007. Petrifilm plate count methods were used to estimate total aerobic bacteria (APC), coliform, Escherichia coli, Staphylococcus aureus and yeast and mould counts. APC counts ranged from an estimated 1.5 x 10¹ colony forming units (CFU)/g to 7.1 x 10(8) CFU/g. Total and faecal coliform counts ranged from an estimated <10 CFU/g to 3 x 10(6) CFU/g. E. coli load ranged from <10 CFU/g to 5 x 10¹ CFU/g and S. aureus counts ranged from an estimated <10 CFU/g to 2.5 vx 10³ CFU/g. Yeast and mould counts ranged from an estimated <10 CFU/ g to 9 x 10(4) CFU/g. An evaluation using the World Health Organization limits for medicinal herbs found a percentage of samples to contain microorganisms above allowable limits: 33% (APC), 50% (coliforms) and 33% (yeast and moulds). A total of 67% of samples contained S. aureus loads above the United States Pharmacopeia standard. We suggest that the introduction of quality-control measures and safe handling practices for the selling of medicinal herbs and botanicals in Kenya would be beneficial in reducing the potential health risks for immunocompromised consumers of these products. <![CDATA[<b>An air quality assessment in the industrialised western Bushveld Igneous Complex, South Africa</b>]]> South Africa has the largest industrialised economy in Africa, with significant mining and metallurgical activities. A large fraction of the South African mineral assets is concentrated in the Bushveld Igneous Complex (BIC), with the western limb being the most exploited. Because the majority of the world's platinum is produced in the BIC, this area is also of international interest. There are some indications that the western BIC should be considered an air pollution hotspot; however, inadequate data exist to substantiate these claims scientifically. To partially address this knowledge gap, a comprehensive air quality monitoring station was operated for more than 2 years in this area. Meteorological parameters, trace gas concentrations and total mass concentration of particulate matter up to 10 μm in size (PM10) were measured. Compared with South African and European ambient air quality standards, SO2, NO2 and CO concentrations were generally acceptable. The major sources of SO2 were identified as high-stack industry emissions, while household combustion from semi-formal and informal settlements was identified as the predominant source of NO2 and CO. In contrast, O3 exceeded the 8-h moving average more than 322 times per year. The main contributing factor was identified to be the influx of regional air masses, with high O3 precursor concentrations. PM10 exceeded the current South African 24-h standard 6.6 times per year, the future (2015) standard 42.3 times per year and the European standard more than 120 times per year. The main source of PM10 was identified as household combustion from semi-formal and informal settlements. The findings clearly indicate that atmospheric O3 and PM10 levels in the western BIC need to be addressed to avoid negative environmental and human health impacts. <![CDATA[<b>A correlation for predicting the abrasive water jet cutting depth for natural stones</b>]]> The abrasive water jet (AWJ) cutting method has been used widely for the cutting and processing of materials because of its cool, damage-free, and precise cutting technique. Nowadays, the use of AWJ cutting in the natural stone industry is increasing. However, the effectiveness of AWJ cutting of natural stones is dependent on the rock properties and machine operating parameters. In this study, injection-type AWJ cutting was applied to 42 different types of natural stones to investigate the effects of rock properties and operating parameters on the cutting depth. Shore hardness, Bohme surface abrasion resistance and the density of the rocks were the most significant rock properties affecting the cutting depth. The working pump pressure and traverse velocity were the most significant operating parameters affecting cutting, as has been shown previously. The relationships between the rock properties or operating parameters and the cutting depth were evaluated using multiple linear and nonlinear regression analyses, and estimation models were developed. Some of the models included only rock properties under fixed operating conditions, and others included both rock properties and operating parameters to predict cutting depth. The models allow for the preselection of particular operating parameters for the cutting of specific rocks types. The prediction of cutting depth is a valuable tool for the controlled surface machining of rock materials. <![CDATA[<b>Equal channel angular pressing technique for the formation of ultra-fine grained structures</b>]]> Equal channel angular pressing is one of the techniques in metal forming processes in which an ultra-large plastic strain is imposed on a bulk material in order to make ultra-fine grained and nanocrystalline metals and alloys. The technique is a viable forming procedure to extrude materials by use of specially designed channel dies without substantially changing the geometry by imposing severe plastic deformation. This technique has the potential for high strain rate superplasticity by effective grain refinement to the level of the submicronscale or nanoscale. We review recent work on new trends in equal channel angular pressing techniques and the manufacturing of die-sets used for the processing of metals and alloys. We also experimented on a copper alloy using the equal channel angular pressing technique to examine the microstructural, mechanical and hardness properties of the ultra-fine grained and nanocrystalline materials produced. After deformation, all samples were subjected to a hardness test and the results showed improved mechanical behaviour of the ultra-fine grained copper alloy that was developed. This research provides an opportunity to examine the significance of the equal channel angular pressing process for metals and alloys. That is, these ultra-fine grained materials can be used in the manufacturing of semi-finished products used in the power, aerospace, medical and automotive industries. <![CDATA[<b>Oldest 'earthquake' in South Africa (Robben Island, 07 April 1620) discredited</b>]]> The oldest recorded earthquake in South Africa is widely accepted (in several seismic catalogues) to have occurred on 07 April 1620. This earthquake was regarded as having a Modified Mercalli Scale intensity of II-IV, corresponding to a Richter Scale Magnitude of ~4. An examination of the original sources on which the record of this earthquake rests, reveals that it was based on a description of 'two startling thunderclaps like cannon shots while ship was becalmed near Robben Island' by Augustin de Beaulieu, who was the head of a fleet of three ships which put in Table Bay in March-April 1620. A full excerpt of Beaulieu's account reveals that the thunderclaps took place in a short period of calm during an extended period of stormy weather, and that the observations were made on board ship, so that no seismic ground vibration was felt. The Western Cape has a much lower incidence of lightning than the interior of South Africa, and the fact that the thunderclaps were not accompanied by lightning is not unusual. Thus the simplest explanation of the thunderclaps is that they were the result of atmospheric phenomena, and not a result of seismic activity, as interpreted by J.N. Theron in 1974. The events of 07 April 1620 should thus be removed from the catalogues of historical seismicity in South Africa, making the slight shock felt in Cape Town in 1690, with a Modified Mercalli Scale intensity of III, the oldest recorded seismic tremor in the history of South Africa.