Rhodes eResearch Repository
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Repository of the academic and research output of the Rhodes University community.
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1.
Concerning secondary thermoluminescence peaks in ?-Al_2_O_3_:C - Chithambo, M.L.
Thermoluminescence characteristics of two subsidiary glow peaks, one below 100°C and the other above 300°C, have been studied for measurements between 30°C and 500°C in ?-Al_2_O_3_:C. The thermoluminescence intensity of the lower temperature peak decreased with storage with a half-life of about 150 s. In contrast, the intensity of the higher temperature peak increased with storage towards some maximum. The peak-temperature of each of the secondary glow peaks was essentially constant with dose, whereas that of the main peak decreased with irradiation. The dose response for the three peaks was similar except for sublinear growth in the higher temperature peak...
2.
Particle precipitation effects in the daytime E-region in the South Atlantic Anomaly region - Haggard, R.
The behaviour of the normal daytime E-layer over the South Atlantic Anomaly region during 23 days of project ISAAC (29 June to 21 July 1983) has been examined. Enhanced production rates due to precipitated electrons were calculated from the observed data and compared well with the production rates from the mean electron fluxes in the range 0.226 keV observed from the satellite Atmosphere
Explorer-C during 197377, discussed by Gledhill and Hoffman.1 The present study shows that there is evidence of a significant source of extra ionization, in addition to solar ultraviolet and X-radiation, in the South Atlantic Anomaly region.
3.
A bi-directional SOAP/SMS gateway service - Halse, Guy Antony; Terzoli, Alfredo; Wells, George
Many applications need the ability to do real-time notification when events occur. Often the people who need to be kept aware of events are in a remote location.
This paper looks at a bi-directional gateway between networked computers and the GSM short message service. The gateway is implemented as a web service, and uses the Simple Object Access Protocol to facilitate data communication.
The service interacts with a database in order to facilitate retrieval of sent or received messages, as well as provide accounting abilities.
It is intended as a practical proof-of-concept application demonstrating some ofdemonstrating some of the capabilities of the...
4.
XML to facilitate management of multi-vendor networks - Halse, Guy Antony; Wells, George; Terzoli, Alfredo
Many standards aimed at managing networks currently exist, and yet networks remain notoriously difficult to maintain. Template-based management systems go a long way towards solving this problem. By developing an XML based language to describe network elements, as well as the topology of a network, we can create tools that are free from vendor specific idiosyncrasies, and are capable of managing both todays networks and those of the future.
5.
100 years of chemistry at Rhodes University - Brown, Michael Ewart; Eve, D.J.; Kaye, Perry T.; Rivett, D.E.A.; Watkins, G.M.
The history of Grahamstown is well documented and two books deal with the history of Rhodes University. Although the Chemistry Department was one of the founding departments, coverage in the official histories is minimal and sometimes inaccurate or misleading. The Rhodes University Centenary is an appropriate time to look back on some of the achievements of the department and some of its graduates over the past 100 years.
6.
Evidence for Archaean lamprophyre from the Kaapvaal Craton, South Africa - Prevec, Stephen A.; Anhaeusser, Carl R.; Poujol, Marc
A suite of mafic dykes occurs as a late component in a wellcharacterized trondhjemitetonalitedioritegranodiorite assemblage in the Johannesburg Dome of the central Kaapvaal Craton, southern Africa. The dykes have been subdivided into two sets, based on their orientation, and major and trace element geochemistry. Set 1 dykes are characterized by elevated SiO2, Al2O3 and TiO2, and particularly by enriched LILE and HSFE (e.g. Zr > 200 ppm, Nb > 20 ppm, Ba > 300 ppm), higher than in any of the accompanying felsic rocks. REE and trace element values for Set 1 dykes are similar to those for calc-alkaline lamprophyres....
7.
Rare earth element geochemistry of the Insizwa lobe of the Mount Ayliff Complex, Eastern Cape, South Africa - Marsh, J.S.
New rare earth element (REE) data from all lithologies of the Insizwa lobe, Mount Ayliff Complex, are presented. On the basis of size and type of Eu anomaly, the geochemical subdivision of the complex as previously described is sustained and, additionally, the Top Gabbronorite of the Central Zone is shown to have formed from a magma that was compositionally distinct from other Central Zone magmas. The Basal Zone crystallized from magmas with large negative Eu anomalies probably acquired through crustal contamination. Previously recognized compositional heterogeneity in the contact rocks is also a feature of the REE. Overall, the Insizwa magmas...
8.
The kaolinitic clay deposits on Beaconsfield, north of Grahamstown - Jacob, R.E.; Mitha, V.R.; MacPherson, D.
The Grahamstown clay deposits occur below the Grahamstown Formation silcrete, which forms a remnant of an extensive peneplain that developed on the African erosion surface during the CretaceousTertiary period. This paper provides new data on the distribution of the kaolinitic clay deposits in the Beaconsfield area north of Grahamstown. These data include 23 borehole profiles through the deposits, and the chemistry and mineralogy of the clays. Relatively little information is available on this part of the peneplain. It was found that the thickness of the kaolin horizon varies considerably, but reaches 35m in places. It generally occurs under a silcrete...
9.
The Southern Ocean Group at Rhodes University: seventeen years of biological oceanography in the Southern Ocean reviewed - McQuaid, C.D.; Froneman, P.W.
This paper reviews the main findings of the Southern Ocean Group at Rhodes University over the last 17 years. A primary contribution has been the development of conceptual models of the physical-biological driving mechanisms that support enormous seasonal populations of land-based top predators at the Prince Edward Islands. Collectively, these models are referred to as the life-support system of the islands. Near-shore subcomponents of the ecosystem, including inshore feeding predators, are largely supported by autochthonous primary production of kelps and localized diatom blooms. These energy sources feed indirectly into top predator populations via the benthic communities. A crucial link is...
10.
In situ feeding rates of the copepods, Pseudodiaptomus
hessei and Acartia longipatella, in a temperate, temporarily open/closed Eastern Cape estuary - Froneman, P.W.
Size-fractionated chlorophyll-a (chl-a) concentrations and the in situ grazing rates of the copepods, Pseudodiaptomus hessei and Acartia longipatella, were assessed seasonally at the temporarily open/closed Kasouga estuary situated along the southeast coast of southern Africa. Total integrated chl-a concentration ranged between 1.17 and 12.18 mg chl-a m^(3) and was always dominated by small phytoplankton cells (<20 ?m), which comprised up to 86% (range 6486%) of the total pigment. Total zooplankton abundance ranged between 2676 and 62 043 individuals m^(3). These copepods numerically dominated the zooplankton counts, accounting for between 79% and 91% of the total. Gut pigment concentrations of the...
11.
Iris colour in passerine birds: why be bright-eyed? - Craig, A.J.F.K.; Hulley, P.E.
An initial survey of iris coloration in passerine birds (Aves: Passeriformes) showed that a brightly pigmented iris is much more common in southern African and Australian birds than in those from Europe, temperate North America, and Venezuela. However, the only statistical correlation reflected the distribution of particular bird families in these regions. Ten family-level groups considered to represent monophyletic taxa were then selected for a more detailed analysis, comparing iris coloration with distribution, status, taxonomy, plumage patterns, and some biological and behavioural characters for 1143 species. No pattern associating iris colour with particular traits was common to all families, but...
12.
Mechanisms generating biological diversity in the genus Platypleura Amyot & Serville, 1843 (Hemiptera: Cicadidae) in southern Africa: implications of a preliminary molecular phylogeny - Villet, M.H.; Barker, N.P.; Lunt, N.
Truly understanding biological diversity requires a move from descriptive studies to mechanistic interpretations based on comparative biology and a thorough recognition of the natural history of the focal organisms. A useful step in such comparative studies is the generation of a phylogeny, so that one can assess the phylogenetic independence of the focal taxa and trace the evolutionary significance of their characteristics. As a preliminary to such studies on the platypleurine cicada genus Platypleura, we sequenced 498 bases of the cytochrome oxidase I (COI) gene from thirteen African species. To circumvent problems with outgroup selection, we also included sequences from...
13.
Economic feasibility of an experimental octopus fishery in South Africa - Oosthuizen, Ané
Octopus vulgaris was identified as a new marine resource to be commercially exploited through an experimental fishery. A recent policy on developing fisheries in South Africa emphasizes the importance of investigating the economic feasibility of a fishery as part of its management framework. The study reported here generated baseline information necessary in the design of the experimental fishery, giving guidelines as to which vessels, fishing gear and markets would be most feasible. The proposed fishery, gear and vessel type, fishing techniques and expected catch rates are described, the results of market research are outlined, and the cost of fishing is...
14.
Genetic analysis of the Octopus vulgaris population on the coast of South Africa - Oosthuizen, Ané; Jiwaji, Meesbah; Shaw, Paul
This study on Octopus vulgaris focused on the COIII gene region of mitochondrial DNA. Sequences from 21 samples from the Eastern Cape, and 14 samples from the Western Cape, were compared to determine whether different populations exist along the South African coast. A 380-bp segment of the COIII region of mtDNA was amplified using the polymerase chain reaction with specific designed primers. Phylogenetic inference was made using maximum parsimony (MP), maximum likelihood (ML), and distancebased methods. All sequences conformed to a single haplotype. Lack of variation within and between east and west coast samples precluded further population genetic analysis. The...
15.
Evolution of Labeo victorianus predates the Pleistocene
desiccation of Lake Victoria: evidence from mitochondrial
DNA sequence variation - Rutaisire, Justus; Booth, Anthony J.; Masembe, Charles; Nyakaana, Sylvester; Muwanika, Vincent B.
Geological data show that Lake Victoria dried out some 15 000 years ago. These data suggest that the entire faunal diversity within the lake has evolved since this time. However, mitochondrial DNA sequence diversity in the endemic cyprinid fish, Labeo victorianus, was high (24 haplotypes in 38 individuals; percentage sequence divergence of 0.74%), suggesting that the evolution of this species predates this Late Pleistocene climatological event. This finding is consistent with what has been reported earlier for cichlid fishes in the lake.
16.
One hundred years of botany at Rhodes University - Lubke, Roy; Brink, Estelle
The Botany Department of Rhodes University is located in the historic Schonland Building. An indigenous garden was created in its courtyard, mainly of species of the Eastern Cape province, and its growth in diversity and stature mirrors the changes in the department over the years. Professor Selmar Schonland, the founding father of botany at Rhodes, was also the curator/director of the Albany Museum. Under his leadership, systematics was firmly established as a discipline at Rhodes and research on the flora of the Eastern Cape begun, to be continued to this day. Under professors William Isaac (19491951) and Edgar Twyman (19511973),...
17.
Quantification of the photosynthetic performance of phosphorus-deficient Sorghum by means of chlorophyll-a fluorescence kinetics - Ripley, Bradford Sherman; Redfern, Sally P.; Dames, Joanna F.
Chlorophyll fluorescence induction curves have been used as a sensitive tool for screening the photosynthetic performance of plants. Experimental treatments involving nitrate supply and chilling stress have been shown to affect fluorescence induction curves and other measures of photosynthesis. We have investigated the photosynthetic performance of Sorghum bicolor supplied with Long Ashton growth solution containing standard (20 ?mol mol^(1)) or low (5 ?mol mol^(1)) phosphorus. The JIP-test based on the chlorophyll fluorescence induction curve was used as a non-destructive method to measure the relative proportions of energy dissipated by different processes (termed energy fluxes) in the light reactions. The various...
18.
The microstructure of plasmodesmata in internodal stem tissue of the Saccharum hybrid var. NCo376: evidence for an apoplasmic loading pathway - Botha, C.E.J.; Cross, R.H.M.; Gerber, J.
The distribution, structure and functional state of plasmodesmata were investigated to gain a clearer understanding of the sucrose transport pathway to the storage parenchyma cells in stem tissue in Saccharum officinarum var. NCo376. Evidence from structural studies on sugarcane stems by electron microscopy indicated that there are numerous plasmodesmata from the vascular bundles through to the storage parenchyma cells in mature stem tissue. Our studies, supported by fluorescence microscopy and iontophoresis, indicate that there are functional plasmodesmata in the phloemunloading pathway from transport phloem tissue to the bundle sheath in Saccharum, which could support symplasmic transport; plasmodesmata outside of the...
19.
Pollination biology of Bergeranthus multiceps (Aizoaceae) with preliminary observations of repeated flower opening and closure - Peter, Craig Ingram; Dold, A.P.; Barker, N.P.; Ripley, B.S.
Little is known about pollination of the Aizoaceae (Mesembryanthemaceae). There are sparse reports of generalist pollination in the family by a variety of insects (predominantly bees). Furthermore, most species are self-incompatible in cultivation. In this study, observations were made on two populations of Bergeranthus multiceps (Salm-Dyck) Schwantes growing in the Eastern Cape province of South Africa. Insects visiting the flowers were collected and examined for pollen. While 79 individual insects (in 24 genera representing 14 families and four orders) were collected visiting the flowers, the majority (43 individuals) were female Allodapula variegata bees (Apidae, subfamily Xylocopinae, tribe Allodapini)collecting pollen. All...
20.
A yellowwood by any other name: molecular systematics and the taxonomy of Podocarpus and the Podocarpaceae in southern Africa - Barker, N.P.; Muller, E.M.; Mill, R.R.
We briefly review the taxonomic history of the Podocarpaceae, with an emphasis on the recognition of numerous segregate genera out of Podocarpus sensu lato. Despite some controversy over the recognition of these genera, molecular data (DNA sequences) provide evidence that supports this taxonomy. The implications for African Podocarpaceae are discussed. In particular, molecular data support the recognition of Afrocarpus as distinct from Podocarpus. Additional taxonomic problems concerning the possible segregation of Podocarpus milanjianus from P. latifolius are addressed using DNA sequence data from the nuclear internal transcribed spacer 2 (ITS2) region. Results of this are inconclusive, and suggest that alternative...
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