No abstract

As an unambiguous indication of complex cognitive capacity, representational art presents explicit evidence for modern and symbolic human behaviour. The only examples of African figurative art dating to the Late Pleistocene comprise seven stone plaques recovered from Apollo 11 Cave in the Huns Mountains, southern Namibia. The plaques derive from a single anthropogenic layer dated by radiocarbon ( 14 C) accelerator mass spectrometry (AMS) and optically simulated luminescence (OSL) methods to c. 30 000 years ago. We present the results of digital (CIE) L*a*b* colourimetric and portable energy dispersive X-ray fluorescence (ED-XRF), Raman spectroscopic and Fourier transform infrared reflectance (FT-IR) analyses of the pigments present on the plaques. These results provide the earliest direct evidence, in Africa, for the preparation of pigment-based paint-like mixtures and their application to create prehistoric art. Our research shows that in the creation of the depictions on the plaques, the artists used black pigments derived from manganese and charcoal, red pigments likely derived from ocherous shale and white pigments possibly derived from ostrich eggshell. Additionally, these plaques provide unique evidence for the combined use of mineral-and carbon-based pigment 'crayons' during the African Middle Stone Age.

Samples of coal were collected from different seams at a South African coal mine and comparative leaching experiments were carried out under various pH conditions and times to investigate the leaching behavior and potential environmental impact of possibly hazardous elements such as As, Cd, Co, Cr, Mn, Ni, Pb, Th and U. The calculated leaching intensities, sequential extraction results and cumulative percentages demonstrate that the leaching behavior of the elements is strongly influenced by the pH, the leaching time and the properties and occurrences of the elements. The leached concentrations of As, Cd, Co, Cr, Mn, Ni and Pb exceeded the maximum concentrations recommended by the Environmental Protection Agency (EPA) for surface water.

This paper brie y reviews the status of distance education and virtual education in the higher-education sector in Africa. The key issues affecting distance education in Sub-Saharan Africa (SSA) are identi ed and discussed. An analysis of the major issues facing distance education in SSA is made. It is noted that the full range of opportunities offered by information and communication technology (ICT) for higher education in Africa is largely underexploited. Factors responsible for this situation are identi ed and a range of strategies is recommended for resolving this situation. Finally, a model of distance education that can potentially enhance the use of ICT in higher education in SSA is proposed.

Over the past few decades, in response to growing concerns about the impact of polycyclic aromatic hydrocarbons (PAHs) on human health, a variety of environmental forensics and geochemical techniques have emerged for studying organic pollutants. These techniques include chemical fingerprinting, receptor modeling, and compound-specific stable isotope analysis (CSIA). Chemical fingerprinting methodology involves the use of diagnostic ratios. Receptor modeling techniques include the chemical mass balance (CMB) model and multivariate statistics. Multivariate techniques include factor analysis with multiple linear regression (FA/MLR), positive matrix factorization (PMF), and UNMIX. This article reviews applications of chemical fingerprinting, receptor modeling, and CSIA; comments on their uses; and contrasts the strengths and weaknesses of each methodology. Receptor modelingReceptor models assess contributions from a number of sources on the basis of observations at sampling sites (the "receptors") [82]. There are two types of receptor models used for source apportion-