Scielo RSS <![CDATA[South African Journal of Science]]> http://www.scielo.org.za/rss.php?pid=0038-235320130003&lang=es vol. 109 num. 5-6 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Generation J</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300001&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300002&lng=es&nrm=iso&tlng=es http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300003&lng=es&nrm=iso&tlng=es <![CDATA[<b>An equity index for South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300004&lng=es&nrm=iso&tlng=es We have introduced the concept of an EI to determine the equity profile of an organisation. This index is based on the straightforward Euclidean distance formula. It can be used to gauge the change in equity profile of an organisation over a defined period. Here, we used UKZN staff data for 2009 in order to illustrate the concept. We note that the formula must be used with caution when dealing with small numbers of staff. The need for this caveat was apparent when trying to analyse the profile of UKZN's top and senior management. The EI is best used when the data set is large enough that a small change in actual number causes a small change in percentage. We suggest a threshold of an overall population of 100 be adopted. This formula can be used in a number of different categories to determine the appropriate equity profile. For example, it can be used for student data to determine EIs for enrollment as well as graduation rates. Within an organisation, it can be used to monitor demographic transformation at different levels. In higher education, in particular, one can evaluate the composition of Council, the Institutional Forum, Senate, etc. Indeed, the EI can be used as a national ranking system for all companies, organisations and institutions. We are currently working on an analysis of the higher education sector in order to rank institutions based on their EIs as well as their equity weighted research productivity. We envisage that such an analysis will be quite insightful in interrogating the development of the sector. Similar analyses can be undertaken for other sectors. Finally, we note that the EI can be used as one (important) component to gauge the progress of an organisation's transformation. We acknowledge that transformation is a much broader concept with many nuances. Our EI is the first unbiased measure to determine the progress made with regard to organisational demographic transformation. <![CDATA[<b>Nanoscience and the Scherrer equation versus the 'Scherrer-Gottingen equation'</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300005&lng=es&nrm=iso&tlng=es We have introduced the concept of an EI to determine the equity profile of an organisation. This index is based on the straightforward Euclidean distance formula. It can be used to gauge the change in equity profile of an organisation over a defined period. Here, we used UKZN staff data for 2009 in order to illustrate the concept. We note that the formula must be used with caution when dealing with small numbers of staff. The need for this caveat was apparent when trying to analyse the profile of UKZN's top and senior management. The EI is best used when the data set is large enough that a small change in actual number causes a small change in percentage. We suggest a threshold of an overall population of 100 be adopted. This formula can be used in a number of different categories to determine the appropriate equity profile. For example, it can be used for student data to determine EIs for enrollment as well as graduation rates. Within an organisation, it can be used to monitor demographic transformation at different levels. In higher education, in particular, one can evaluate the composition of Council, the Institutional Forum, Senate, etc. Indeed, the EI can be used as a national ranking system for all companies, organisations and institutions. We are currently working on an analysis of the higher education sector in order to rank institutions based on their EIs as well as their equity weighted research productivity. We envisage that such an analysis will be quite insightful in interrogating the development of the sector. Similar analyses can be undertaken for other sectors. Finally, we note that the EI can be used as one (important) component to gauge the progress of an organisation's transformation. We acknowledge that transformation is a much broader concept with many nuances. Our EI is the first unbiased measure to determine the progress made with regard to organisational demographic transformation. <![CDATA[<b>Cities OPT in while nations COP out</b>: <b>Reflections on COP18</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300006&lng=es&nrm=iso&tlng=es We have introduced the concept of an EI to determine the equity profile of an organisation. This index is based on the straightforward Euclidean distance formula. It can be used to gauge the change in equity profile of an organisation over a defined period. Here, we used UKZN staff data for 2009 in order to illustrate the concept. We note that the formula must be used with caution when dealing with small numbers of staff. The need for this caveat was apparent when trying to analyse the profile of UKZN's top and senior management. The EI is best used when the data set is large enough that a small change in actual number causes a small change in percentage. We suggest a threshold of an overall population of 100 be adopted. This formula can be used in a number of different categories to determine the appropriate equity profile. For example, it can be used for student data to determine EIs for enrollment as well as graduation rates. Within an organisation, it can be used to monitor demographic transformation at different levels. In higher education, in particular, one can evaluate the composition of Council, the Institutional Forum, Senate, etc. Indeed, the EI can be used as a national ranking system for all companies, organisations and institutions. We are currently working on an analysis of the higher education sector in order to rank institutions based on their EIs as well as their equity weighted research productivity. We envisage that such an analysis will be quite insightful in interrogating the development of the sector. Similar analyses can be undertaken for other sectors. Finally, we note that the EI can be used as one (important) component to gauge the progress of an organisation's transformation. We acknowledge that transformation is a much broader concept with many nuances. Our EI is the first unbiased measure to determine the progress made with regard to organisational demographic transformation. <![CDATA[<b>Scientific collaboration in South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300007&lng=es&nrm=iso&tlng=es We have introduced the concept of an EI to determine the equity profile of an organisation. This index is based on the straightforward Euclidean distance formula. It can be used to gauge the change in equity profile of an organisation over a defined period. Here, we used UKZN staff data for 2009 in order to illustrate the concept. We note that the formula must be used with caution when dealing with small numbers of staff. The need for this caveat was apparent when trying to analyse the profile of UKZN's top and senior management. The EI is best used when the data set is large enough that a small change in actual number causes a small change in percentage. We suggest a threshold of an overall population of 100 be adopted. This formula can be used in a number of different categories to determine the appropriate equity profile. For example, it can be used for student data to determine EIs for enrollment as well as graduation rates. Within an organisation, it can be used to monitor demographic transformation at different levels. In higher education, in particular, one can evaluate the composition of Council, the Institutional Forum, Senate, etc. Indeed, the EI can be used as a national ranking system for all companies, organisations and institutions. We are currently working on an analysis of the higher education sector in order to rank institutions based on their EIs as well as their equity weighted research productivity. We envisage that such an analysis will be quite insightful in interrogating the development of the sector. Similar analyses can be undertaken for other sectors. Finally, we note that the EI can be used as one (important) component to gauge the progress of an organisation's transformation. We acknowledge that transformation is a much broader concept with many nuances. Our EI is the first unbiased measure to determine the progress made with regard to organisational demographic transformation. <![CDATA[<b>What is the ideal ratio of categories of nurses for the South African public health system?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300008&lng=es&nrm=iso&tlng=es We have introduced the concept of an EI to determine the equity profile of an organisation. This index is based on the straightforward Euclidean distance formula. It can be used to gauge the change in equity profile of an organisation over a defined period. Here, we used UKZN staff data for 2009 in order to illustrate the concept. We note that the formula must be used with caution when dealing with small numbers of staff. The need for this caveat was apparent when trying to analyse the profile of UKZN's top and senior management. The EI is best used when the data set is large enough that a small change in actual number causes a small change in percentage. We suggest a threshold of an overall population of 100 be adopted. This formula can be used in a number of different categories to determine the appropriate equity profile. For example, it can be used for student data to determine EIs for enrollment as well as graduation rates. Within an organisation, it can be used to monitor demographic transformation at different levels. In higher education, in particular, one can evaluate the composition of Council, the Institutional Forum, Senate, etc. Indeed, the EI can be used as a national ranking system for all companies, organisations and institutions. We are currently working on an analysis of the higher education sector in order to rank institutions based on their EIs as well as their equity weighted research productivity. We envisage that such an analysis will be quite insightful in interrogating the development of the sector. Similar analyses can be undertaken for other sectors. Finally, we note that the EI can be used as one (important) component to gauge the progress of an organisation's transformation. We acknowledge that transformation is a much broader concept with many nuances. Our EI is the first unbiased measure to determine the progress made with regard to organisational demographic transformation. <![CDATA[<b>Plant metabolomics</b>: <b>A new frontier in phytochemical analysis</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300009&lng=es&nrm=iso&tlng=es The primary and secondary metabolites found in plant cells are the final recipients of biological information flow. In turn, their levels can influence gene expression and protein stability. Qualitative and quantitative measurements of these metabolites reflect the cellular state under defined conditions, and yield critical insights into the cellular processes that control the biochemical phenotype of the cell, tissue or whole organism. Metabolomics differs from traditional targeted phytochemical analysis in various fundamental aspects; for example, it is a data-driven approach with predictive power that aims to assess all measurable metabolites without any pre-conception or pre-selection. As such, metabolomics is providing new dimensions in the study of systems biology, enabling the in-depth understanding of the intra- and extracellular interactions of plant cells. Metabolomics is also developing into a valuable tool that can be used to monitor and assess gene function, and to characterise post-genomic processes from a broad perspective. Here, we give an overview of the fundamental analytical technologies and subsequent multivariate data analyses involved in plant metabolomics as a research tool to study various aspects of plant biology. <![CDATA[<b>Pleistocene <i>Homo</i> and the updated Stone Age sequence of South Africa</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300010&lng=es&nrm=iso&tlng=es We provide a brief overview of how the rich South African Pleistocene Homo fossil record correlates with the recently revised Stone Age sequence. The overview and correlation of the data is intended to highlight gaps in the record and/or our understanding thereof, and to stimulate interdisciplinary research and debate on the Homo fossil and archaeological records spanning the Pleistocene. As an updated resource we present a complete inventory of known Pleistocene fossil material assigned to the genus Homo, and, where possible, its association with archaeological material. We demonstrate that (1) anatomical changes are not necessarily paralleled by changes in the archaeological sequence currently based on a range of technocomplexes, (2) the early Homo record of South Africa probably differs from that of East Africa, (3) mid-Pleistocene Homo might be associated with the Earlier to Middle Stone Age transitional phase and (4) the fossil record associated with the Middle Stone Age has wide anatomical variation. Also, hiatuses in the fossil record, such as that associated with the appearance of early Khoe-San-like populations, do not show concurrent hiatuses in the archaeological record. Thus, for a broader understanding of the demographic history of South Africa during the Pleistocene, both sources of information should be considered in tandem. <![CDATA[<b>A new national unit for invasive species detection, assessment and eradication planning</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300011&lng=es&nrm=iso&tlng=es Even with no new introductions, the number of biological invasions in South Africa will increase as introduced species naturalise and become invasive. As of 2010 South Africa had ~8750 introduced plant taxa, 660 recorded as naturalised, 198 included in invasive species legislation, but only 64 subject to regular control (i.e. only widespread invaders are managed post-border). There is only one documented example of a successful eradication programme in continental South Africa - against the Mediterranean snail (Otala punctata) in Cape Town. Here we describe the establishment in 2008 of a unit funded by the Working for Water Programme as part of the South African National Biodiversity Institute's Invasive Species Programme (SANBI ISP) designed to (1) detect and document new invasions, (2) provide reliable and transparent post-border risk assessments and (3) provide the cross-institutional coordination needed to successfully implement national eradication plans. As of the end of 2012, the ISP had an annual budget of R36 million, employed 33 staff working across all nine provinces, supported 10 postgraduate students, hosted 35 interns (including those as part of a drive to collect DNA barcodes for all invasive taxa) and created over 50 000 days of work as part of government poverty alleviation programmes. The unit has worked towards full risk assessments for 39 plant taxa and has developed eradication plans for seven species; the unit is now helping implement these plans. By focusing on science-based management and policy, we argue that SANBI ISP can play a leading role in preventing introduced species from becoming widespread invaders. <![CDATA[<b>Effect of selenium on cadmium-induced oxidative stress and esterase activity in rat organs</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300012&lng=es&nrm=iso&tlng=es Metal toxicity is a threat mainly in the industrialised world where industry discharges many toxic metals into the environment. We investigated the effects of two metals - cadmium and selenium - on the cytosolic antioxidant enzymes and esterases in the liver, kidneys and testes of rats. Male Sprague-Dawley rats( N =28) were divided equally into four groups: control, cadmium, selenium and cadmium/selenium. Salts of the metals were administered intraperitoneally for 15 days. In the liver, cadmium treatment (1.67 mg/kg per day) resulted in a decrease in catalase activity and an increase superoxide dismutase (SOD) activity. Selenium treatment (0.23 mg/kg per day) resulted in increases in glutathione s-transferase, catalase and DT-diaphorase activities. Treatment with both cadmium and selenium resulted in an increase in glutathione peroxidase (GPx) activity. Esterase activities were significantly lower in the presence of cadmium. In the kidney, cadmium treatment caused a decrease in catalase, DT-diaphorase, and SOD activities and selenium supplementation reversed the cadmium-induced decrease in these enzyme activities. Selenium treatment increased catalase and SOD activities in the kidney. In the testis, cadmium treatment decreased GPx and SOD activities, but at the same time increased catalase and DT-diaphorase activities. Esterase activities increased in the presence of selenium in both the kidney and testis. These results suggest that selenium might be toxic to the liver while at the same time play a protective role against cadmium-induced oxidative stress and toxicity in the kidney and testis. <![CDATA[<b>Numerical investigation into the existence of limit cycles in two-dimensional predator-prey systems</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300013&lng=es&nrm=iso&tlng=es There has been a surge of interest in developing and analysing models of interacting species in ecosystems, with specific interest in investigating the existence of limit cycles in systems describing the dynamics of these species. The original Lotka-Volterra model does not possess any limit cycles. In recent years this model has been modified to take disturbances into consideration and allow populations to return to their original numbers. By introducing logistic growth and a Holling Type II functional response to the traditional Lotka-Volterra-type models, it has been proven analytically that a unique, stable limit cycle exists. These proofs make use of Dulac functions, Liénard equations and invariant regions, relying on theory developed by Poincaré, Poincaré-Bendixson, Dulac and Liénard, and are generally perceived as difficult. Computer algebra systems are ideally suited to apply numerical methods to confirm or refute the analytical findings with respect to the existence of limit cycles in non-linear systems. In this paper a class of predator-prey models of a Gause type is used as the vehicle to illustrate the use of a simple, yet novel numerical algorithm. This algorithm confirms graphically the existence of at least one limit cycle that has analytically been proven to exist. Furthermore, adapted versions of the proposed algorithm may be applied to dynamic systems where it is difficult, if not impossible, to prove analytically the existence of limit cycles. <![CDATA[<b>Hypercarnivory, durophagy or generalised carnivory in the Mio-Pliocene hyaenids of South Africa?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300014&lng=es&nrm=iso&tlng=es Carnivorans, the members of the order Carnívora, exhibit wide dietary diversity - from overwhelmingly herbivorous species (like the giant and red pandas) to species that specialise in the consumption of flesh (like the hypercarnivorous felids). Throughout the evolution of this order, many craniodental forms have emerged and gone extinct - notably the sabretooth felids that existed until the late Pleistocene. However, one carnivoran lineage, remarkable for its extreme masticatory adaptations, persists - the bone-cracking hyaenids. Three of the four extant members of this family (Crocuta crocuta, Hyaena hyaena and Parahyaena brunnea) are among the most durophagous mammals to have ever lived. The fourth extant hyaenid - the aardwolf (Proteles cristatus) - also exhibits impressive, although wholly different, masticatory adaptations as one of the most derived mammalian insectivores. How and when did the level of durophagy evident in extant bone-cracking hyenas evolve, and how do Mio-Pliocene hyenas compare to the extant members of the order in terms of their own dietary specialisations? An examination of the premolars of the Mio-Pliocene hyaenids from Langebaanweg, South Africa suggests that modern levels of durophagy appeared relatively recently. Results from an analysis of dental radii-of-curvature and premolar intercuspid notches suggest that these hyenas were neither bone crackers nor flesh specialists, but were dietary generalists. <![CDATA[<b>Pathogenicity associated genes in <i>Fusarium oxysporum</i> f. sp. <i>cubense</i> race 4</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300015&lng=es&nrm=iso&tlng=es Fusarium oxysporum f. sp. cúbense (Foc) is a fungus that infects banana roots and causes a destructive plant disease called Fusarium wilt. Foc consists of three pathogenic races (Foc races 1, 2 and 4), classified according to their selective impairment of banana cultivars. Foc race 4 is economically important as it comprises strains that infect Cavendish bananas, which are the most widely planted variety of bananas in the world, in both the tropics (Foc TR4) and subtropics (Foc STR4). The aim of this study was to investigate which genes are potentially involved in fungal pathogenicity by comparing transcript-derived cDNA fragments (TDFs) from Foc STR4 and TR4 to those from non-pathogenic F. oxysporum using cDNA-AFLP analysis. This comparison resulted in the identification of 229 unique gene fragments which include the putative pathogenicity-related TDFs encoding chitinase class V (chsV), GTPase activating protein, Major Facilitator Superfamily (MFS) multidrug transporter and serine/threonine protein kinase (ste12) genes. Quantitative analysis of transcript abundance showed a significant increase in expression of chsV, MFS multidrug transporter and ste12 genes in Foc STR4 and TR4 compared with the non-pathogenic F. oxysporum. These genes play a role in escaping host defence responses and in cell wall degradation. In addition, pathogenicity-related genes from other formae speciales of F. oxysporum, such as the sucrose non-fermenting, cytochrome P450 and F-box protein required for pathogenicity genes, were significantly up-regulated in Foc STR4 and TR4 but not in F. oxysporum isolates non-pathogenic to banana. This study provides the first in vitro comparative analysis of TDFs expressed in pathogenic Foc race 4 isolates and non-pathogenic F. oxysporum isolates from banana. <![CDATA[<b>Beyond just species: Is Africa the most taxonomically diverse bird continent?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300016&lng=es&nrm=iso&tlng=es We analysed avian diversity in 8 similar-sized regions of Africa, and in an additional 16 regions spread across the world; half of these 24 regions were tropical and the other half were temperate. For each region, counts of species, genus, family and order were recorded rather than only a species count. We assert that this approach gives more accurate insights into diversity patterns, as we show that in relatively species-rich parts of the world species are on average taxonomically more similar to each other than in species-poor areas. Northwestern South America is the world's most species-rich region for birds, but we show that sub-Saharan Africa has greater diversity at higher taxonomic levels and is thus arguably the richest corner of the world for birds: the Mozambique-Zimbabwe region displays the highest diversity at the order level (with 30 orders), with all other sub-Saharan regions having between 27 and 29 orders each. Northern India is also extremely diverse (surprisingly so for a marginally temperate region) at all taxonomic levels below that of order. We hope that our study might generate further analyses of avian diversity beyond the species level. <![CDATA[<b>Is the southern Benguela a significant regional sink of CO<sub>2</sub>?</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300017&lng=es&nrm=iso&tlng=es This study was undertaken to characterise the seasonal cycle of air-sea fluxes of carbon dioxide (CO2) in the southern Benguela upwelling system off the South African west coast. Samples were collected from six monthly cross-shelf cruises in the St. Helena Bay region during 2010. CO2 fluxes were calculated from pCO2 derived from total alkalinity and dissolved inorganic carbon and scatterometer-based winds. Notwithstanding that it is one of the most biologically productive eastern boundary upwelling systems in the global ocean, the southern Benguela was found to be a very small net annual CO2 sink of -1.4 ± 0.6 mol C/m² per year (1.7 Mt C/year). Regional primary productivity was offset by nearly equal rates of sediment and sub-thermocline remineralisation flux of CO2, which is recirculated to surface waters by upwelling. The juxtaposition of the strong, narrow near-shore out-gassing region and the larger, weaker offshore sink resulted in the shelf area being a weak CO2 sink in all seasons but autumn (-5.8, 1.4 and -3.4 mmol C/m² per day for summer, autumn and winter, respectively). <![CDATA[<b>A first report on meteor-generated seismic signals as detected by the SANSN</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-23532013000300018&lng=es&nrm=iso&tlng=es A bright meteor with an apparent magnitude of -18 was seen over large parts of southern Africa at ~23:00 South African Standard Time on 21 November 2009. Here we discuss the eye-witness accounts related to the meteor as well as the seismic signals generated by the meteor's passage through the atmosphere as detected by the Mussina seismograph station forming part of the South African National Seismograph Network. Two signals were identified on the seismogram; the first arrival is interpreted as a precursor coupled seismic wave and the second, which arrived ~138 s after the first, as a directly coupled airwave. The meteor is thought to have entered the atmosphere close to Mussina shortly before 22:55.06 local time, from where it proceeded in a westerly to northwesterly direction with an elevation angle not exceeding 43°. Our results presented here dispel the beliefs of many observers who thought that the meteor must have made landfall very close to their localities. In addition, this contribution documents the first instance of meteor-related seismic signals recorded by the South African National Seismograph Network.