Scielo RSS <![CDATA[South African Journal of Science]]> vol. 105 num. 11-12 lang. en <![CDATA[SciELO Logo]]> <![CDATA[<b>South Africa and Copenhagen</b>]]> <![CDATA[<b>A double anniversary</b>]]> <![CDATA[<b>Charles Darwin at the Cape</b>: <b>notes on his sociological observations</b>]]> <![CDATA[<b>Mary Seely, visionary scientist and dedicated teacher, turns 70</b>]]> <![CDATA[<b>'Knowledge in the blood?'</b>: <b>race, consciousness and understanding in South African higher education</b>]]> <![CDATA[<b>From Lord's to the Union</b>: <b>the imperial foundations of South African cricket</b>]]> <![CDATA[<b>Me, mine and yours</b>: <b>mining and imperialism</b>]]> <![CDATA[<b>A tale of an extraordinary prospector</b>]]> <![CDATA[<b>Darwin</b><b>'s legacy in South African evolutionary biology</b>]]> In the two decades after publication of the Origin of Species, Charles Darwin facilitated the publication of numerous scientific papers by settler naturalists in South Africa. This helped to establish the strong tradition of natural history which has characterised evolutionary research in South African museums, herbaria and universities. Significant developments in the early 20th century included the hominid fossil discoveries of Raymond Dart, Robert Broom, and others, but there was otherwise very little South African involvement in the evolutionary synthesis of the 1930s and 1940s. Evolutionary biology developed into a distinct discipline in South Africa during the 1970s and 1980s when it was dominated by mammalian palaeontology and a vigorous debate around species concepts. In the post-apartheid era, the main focus of evolutionary biology has been the construction of phylogenies for African plants and animals using molecular data, and the use of these phylogenies to answer questions about taxonomic classification and trait evolution. South African biologists have also recently contributed important evidence for some of Darwin's ideas about plant-animal coevolution, sexual selection, and the role of natural selection in speciation. A bibliographic analysis shows that South African authors produce 2-3% of the world's publications in the field of evolutionary biology, which is much higher than the value of about 0.5% for publications in all sciences. With its extraordinary biodiversity and well-developed research infrastructure, South Africa is an ideal laboratory from which to advance evolutionary research. <![CDATA[<b>Balinsky's Darwinian roots</b>]]> Boris Ivan Balinsky (1905-1997) was Professor and Head of the Department of Zoology at the University of the Witwatersrand (Wits), Johannesburg, South Africa. He came to Wits in 1949 (via Munich and Edinburgh) from Kiev, where he was Professor of Embryology. As an acclaimed experimental embryologist he was especially famous for inducing a supernumerary limb in a newt when he was a 19-year-old student in Ivan Schmalhausen's laboratory in Kiev 1924. In Johannesburg he wrote his famous textbook of embryology, which influenced generations of students around the world. In addition to pioneering the application of electron microscopy to the study of early development, he tackled a variety of projects of general zoological interest. Lesser known is his latter day work, carried out during his retirement, on variation and hereditability (especially of wing colouration) in the butterfly Acraea horta, on which he published five papers from 1974 to 1986. His butterfly work showing the loose connection between the genotype and phenotype, with the genotype expressing itself in a variable way in the face of a constant physical environment, is of special interest in the current era of evolutionary and ecological developmental biology. His exposure to the stimulating evolutionary ideas of Schmalhausen during his early Kiev years no doubt provided a context for his butterfly work. Some ideas about how the 'loose connection between the genotype and phenotype' may be achieved through behavioral modification or positional information during development are addressed in this paper in the light of recent work. In his eighties Balinsky worked on the classification of microlepidoptera on which he published several papers. He died in September 1997, just short of his 92nd birthday. <![CDATA[<b>Mechanisms by which circadian rhythm disruption may lead to cancer</b>]]> Humans have evolved in a rhythmic environment and display daily (circadian) rhythms in physiology, metabolism and behaviour that are in synchrony with the solar day. Modern lifestyles have compromised the exposure to bright light during the day and dark nights, resulting in the desynchronisation of endogenously generated circadian rhythms from the external environment and loss of coordination between rhythms within the body. This has detrimental effects on physical and mental health, due to the misregulation and uncoupling of important cellular and physiological processes. Long-term shift workers who are exposed to bright light at night experience the greatest disruption of their circadian rhythms. Studies have shown an association between exposure to light at night, circadian rhythm disruption and an increased risk of cancer. Previous reviews have explored the relevance of light and melatonin in cancer, but here we explore the correlation of circadian rhythm disruption and cancer in terms of molecular mechanisms affecting circadian gene expression and melatonin secretion. <![CDATA[<b>Experimental measurement and computational fluid dynamics simulation of mixing in a stirred tank</b>: <b>a review</b>]]> Stirred tanks are typically used in many reactions. The quality of mixing generated by the impellers can be determined using either experimental and simulation methods, or both methods. The experimental techniques have evolved from traditional approaches, such as the application of hot-wire anemometry, to more modern ones like laser Doppler velocimetry (LDV). Similarly, computational fluid dynamics (CFD) simulation techniques have attracted a lot of attention in recent years in the study of the hydrodynamics in stirred tanks, compared to the empirical modelling approach. Studies have shown that the LDV technique can provide very detailed information on the spatio-temporal variations in a tank, but the method is costly. For this reason, CFD simulation techniques may be employed to provide such data at a lower cost. In recent years, both integrated experimental and CFD approaches have been used to determine flow field and to design various systems. Both CFD and LDV data reveal the existence of flow maldistribution caused by system design features, and these in turn show that the configurations that have, over the years, been regarded as standard may not provide the optimal operating conditions with regards to the system homogeneity and power consumption. The current trends in CFD studies point towards an increasing application of more refined grids, such as in large eddy simulation, to capture turbulent structures at microscales. This trend will further improve the quality of the simulation results for processes such as precipitation, in which micromixing and reaction kinetics are important. <![CDATA[<b>The ongoing evolution of humanness</b>: <b>perspectives from Darwin to de Chardin</b>]]> The nature of humanness is discussed from observations made by Aristotle in 4th-century Greece, through to those of Charles Darwin, Teilhard de Chardin and William Shakespeare. Attempts to define humanness upon a narrow range of criteria, as some have tried, is argued as flawed, for humanness is more elusive than a single or a few demonstrated phenomena. The path that Darwin pursued in determining the place of humans in nature in his book The Descent of Man, and Selection in Relation to Sex is assessed from a 19thcentury perspective; the difficulties he faced, both personally and with the broader public, are reviewed and then evaluated in a modern context. Darwin's thesis adheres to scientific principles, and is debated, defended and later verified on these principles. This is somewhat at variance to the approach adopted by the priest-scientist de Chardin a century later in his major work, The Phenomenon of Man-in which an attempt is made to reconcile a deep Christian faith with science. De Chardin scores well from a theological viewpoint, but fails on scientific grounds as his thesis moves beyond the realms of empiricism into mysticism. Surprisingly, de Chardin's predicament of a future wherein human evolution enters a new stage of consciousness through the noosphere (an invisible layer of thought encompassing the globe) has been partially realised through the worldwide web, although the nature of the web is almost certainly not what de Chardin might have anticipated, or desired. Science too fails to answer all, particularly the nature of God. Darwin considered the Creator in several of his works and does not dismiss the concept of a farseeing deity, although we are left with the notion that he died agnostic. Humanness is derived from an elevated moral code and this is reflected in our arts, particularly literature, wherein we may temporally reflect upon quintessential human traits such as mercy. However, expression of the arts is only achievable by the individual being part of a greater whole: the human community, the essence of which is distilled in the Bantu concept of ubuntu, wherein humanness is best realised through the act of living in harmony. <![CDATA[<b>Charles Darwin and John Herschel</b>]]> The influence of John Herschel on the philosophical thoughts of Charles Darwin, both through the former's book, Natural Philosophy, and through their meeting in 1836 at the Cape of Good Hope, is discussed. With Herschel having himself speculated on evolution just a few months before he met Darwin, it is probable that he stimulated at least the beginnings of the latter's lifelong work on the subject. <![CDATA[<b>Solid-state compound phase formation of TiSi<sub>2 </sub>thin films under stress</b>]]> Different stress situations were created on an Si(100) wafer by depositing either Si3N4 or SiO2 thin films on the back side. Si3N4 has a different thermal expansion coefficient from that of SiO2. A thin Ti film was then deposited on the front side of the Si wafer. The structures were then annealed at various high temperatures for different periods of time. Real-time Rutherford backscattering spectrometry, as well as sample curvature measurements, were used to characterise the samples. Different reaction rates were found between Si3N4-deposited samples and SiO2-deposited samples. <![CDATA[<b>Minerals, trace elements and antioxidant phytochemicals in wild African dark-green leafy vegetables (<i>morogo</i>)</b>]]> Wild African dark-green leafy vegetables (morogo) are an important constituent of the traditional starch-based African diet. Three wild morogo types were sampled from different geographical regions in South Africa to determine their mineral, total polyphenol, total carotenoid and beta-carotene contents. Mineral and trace element compositions were determined using inductively coupled argon plasma mass spectrometry (ICP-MS). Concentrations of total carotenoids and total phenolics were measured by spectrophotometry and beta-carotene concentrations by high performance liquid chromatography (HPLC). In comparison with values reported for commercial spinach and swiss chard, results from the present study indicate relatively high calcium and magnesium concentrations in the wild morogo. Total carotenoid concentrations in the three morogo types were comparable with that of spinach. Beta-carotene concentrations were highest in Amaranthus hybridus, but this value was lower than those reported for other morogo species grown commercially. Concentrations of total phenolics were in the same range as those reported for conventional and commercially-grown non-conventional dark-green leafy vegetables. Results from the present study suggest that readily accessible wild morogo varieties represent inexpensive sources of dietary minerals, trace elements and antioxidant phytochemicals. <![CDATA[<b>CSIR South Africa mobile LIDAR-First scientific results</b>: <b>comparison with satellite, sun photometer and model simulations</b>]]> We present the first scientific results from the Council for Scientific and Industrial Research-National Laser Centre (CSIR-NLC) mobile LIght Detection And Ranging (LIDAR) and its validation and comparison with other ground-based and space-borne measurements. The LIDAR results are compared with aerosol extinction measurements from the Stratosphere Aerosol Gas Experiment (SAGE) II, optical depth derived from sun photometers employed under the AErosol RObotic NETwork (AERONET) and backscatter coefficients simulated from weather balloon humidity measurements. <![CDATA[<b>System description of the mobile LIDAR of the CSIR, South Africa</b>]]> South Africa's first mobile LIDAR (LIght Detection And Ranging) system is being developed at the National Laser Centre (NLC) of the Council for Scientific and Industrial Research (CSIR) in Pretoria (25°45'S; 28°17'E). The system is designed primarily for remote sensing of the atmosphere. At present, the system is being optimised for measuring vertical atmospheric backscatter profiles of aerosols and clouds. In this paper, we describe the complete LIDAR system, including laser transmission, telescope configuration, data acquisition, data archival and post-processing. <![CDATA[<b>Chimpanzee subspecies and 'robust' australopithecine holotypes, in the context of comments by Darwin</b>]]> On the basis of comparative anatomy (including chimpanzees, gorillas and other primates), Darwin¹ suggested that Africa was the continent from which 'progenitors' of humankind evolved. Hominin fossils from this continent proved him correct. We present the results of morphometric analyses based on cranial data obtained from chimpanzee taxa currently recognised as distinct subspecies, namely Pan troglodytes troglodytes and Pan troglodytes schweinfurthii, as well as Pan paniscus (bonobo). Our objective was to use a morphometric technique² to quantify the degree of similarity between pairs of specimens, in the context of a statistical (probabilistic) definition of a species.3-5 Results obtained from great apes, including two subspecies of chimpanzee, were assessed in relation to same-scale comparisons between the holotypes of 'robust' australopithecine (Plio-Pleistocene hominin) taxa which have traditionally been distinguished at a species level, notably Paranthropus robustus from South Africa, and Paranthropus (Australopithecus/Zinjanthropus) boisei from East Africa. The question arises as to whether the holotypes of these two taxa, TM 1517 from Kromdraai6 and OH 5 from Olduvai,7 respectively, are different at the subspecies rather than at the species level. <![CDATA[<b>Facial-based ethnic recognition</b>: <b>insights from two closely related but ethnically distinct groups</b>]]> Previous studies on facial recognition have considered widely separated populations, both geographically and culturally, making it hard to disentangle effects of familiarity with an ability to identify ethnic groups per se. We used data from a highly intermixed population of African peoples from South Africa to test whether individuals from nine different ethnic groups could correctly differentiate between facial images of two of these, the Tswana and Pedi. Individuals could not assign ethnicity better than expected by chance, and there was no significant difference between genders in accuracy of assignment. Interestingly, we observed a trend that individuals of mixed ethnic origin were better at assigning ethnicity to Pedi and Tswanas, than individuals from less mixed backgrounds. This result supports the hypothesis that ethnic recognition is based on the visual expertise gained with exposure to different ethnic groups. <![CDATA[<b>Were Malagasy <i>Uncarina </i>fruits dispersed by the extinct elephant bird?</b>]]> We hypothesise that the spiny fruits of the endemic Madagascar genus Uncarina (Pedaliaceae) are trample burrs that evolved to be dispersed on the feet of the extinct elephant bird (Aepyornis). Our evidence is: i) the morphology of the fruit with its large grapple hooks is more likely to attach to a foot than to adhere to fur and ii) the presentation of mature fruits on the ground rather than in the canopy. These differences to adhesive burrs make lemurs unlikely dispersers. We argue, given the absence of other large terrestrial mammals in Madagascar, that the most likely dispersers of Uncarina fruits were the extinct large birds. If correct, our hypothesis has implications for conservation of Uncarina, the biogeography of the elephant birds and dispersal biology. For example, we predict that the demography of Uncarina will be skewed towards adult plants, and that the dispersal mutualism could possibly be rescued by domestic animals. <![CDATA[<b>Anti-inflammatory and antibacterial profiles of selected compounds found in South African propolis</b>]]> Propolis is a complex resinous substance manufactured by honey bees to scaffold and protect the hive against pathogens. Although it has been widely used for its medicinal properties, it is unknown whether the activity depends on the concentrations of specific constituents or on potentiation between these. This study describes (1) the individual topical anti-inflammatory activities of selected flavonoids commonly found in propolis, and (2) their antibacterial activities, alone or in combination with the non-flavonoid caffeic acid phenethyl ester (CAPE). For the anti-inflammatory activities, the reduction in croton oil-induced oedema in a mouse model, after topical application of quercetin and galangin for 3 h, was more than 50%, while after6hof treatment the reduction was less then 50%. By contrast, the suppressive activity of luteolin was about 30% and 50%, for treatments of 3 h and 6 h, respectively. The maximum inhibition of the growth of Staphylococcus aureus by each of CAPE, eriodictyol and quercetin was about 20%, while luteolin was inactive. When combined with CAPE, potentiation of the antibacterial effect was observed in the case of luteolin, but antagonism was observed when combined with either eriodictyol or quercetin. The propolis flavonoids each appear to have significant anti-inflammatory activity while their antibacterial activities are somewhat weaker and significant only when luteolin was combined with CAPE.