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Event in honour of Doctor Sir Michael Edwardes

  • Authors: Henderson, Derek Scott
  • Date: 1980
  • Language: English
  • Type: Text
  • Identifier: vital:7420 , http://hdl.handle.net/10962/d1018297
  • Full Text:
  • Date Issued: 1980

Event in honour of Reverend Bill Burnett

  • Authors: Henderson, Derek Scott
  • Date: 1980
  • Language: English
  • Type: Text
  • Identifier: vital:7419 , http://hdl.handle.net/10962/d1018296
  • Full Text:
  • Date Issued: 1980

Exit Hymn

Exit Hymn

Exit Hymn from the Missa Zimbabwe

Exit hymn from the Missa Zimbabwe

Exit hymn from the Missa Zimbabwe transcribed into Venda

Fence with sign (Oxton-manor)

First H F Doppler soundings of the ionosphere at SANAE

  • Authors: De Kock, Errol James
  • Date: 1980
  • Subjects: Ionosphere
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5500 , http://hdl.handle.net/10962/d1006869 , Ionosphere
  • Full Text:
  • Date Issued: 1980

Four rural houses near fence and the start of a hill with rocks

Gamas = Immigrants

Genetic studies and physiological responses to ultraviolet radiation in the Bacteroides fragilis group

  • Authors: Jones, David Todman
  • Date: 1980
  • Subjects: Bacteroides Ultraviolet radiation
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4072 , http://hdl.handle.net/10962/d1007047
  • Description: The contents of this thesis have been divided into 2 parts . The first part deals with genetic studies carried out on 36 strains belonging to the Bacteroides fragilis group. A number of mutants were isolated from several of the strains. A notable feature of the methods used was the low yield of mutants obtained and the marked sensitivity of these organisms to the mutagenic agents. Variations in colonial morphology was found to be a common feature amongst these organisms. In a few strains this phenomenon was clearly visible, in the remainder it was much weaker, and often could only be seen with the aid of a microscope . Colonial variation was found to be due to the ability of a proporti on of the cells to pruduce capsules or slime layers. The variants were found to segregate at high frequency and different growth conditions were found to have little effect on the segregation frequency or capsule formation . A number of phages specific for B. fragilis and B. t hetaiotaomicron were isol ated. All these phages were virulent and attempts to induce lysogenic phages were unsuccesful . The use of these phages in attempts to obtain transduction proved unsuccessful. A phage carrier state was found to occur in the majority of the phage-host cell systems, which seemed to be due to the presence of phage-resistant encapsulated cells in the population. Bacteriocins were produced by about half the strains, these inhibited the growth of a high proportion of the 36 strains tested. The bacteriocins were released into the growth media at the end of the growth period in the 2 bacteriocins tested. A link between the mode of action of one bacteriocin and rifampicin-resistance was investigated. All the bacter iocins tested were found to be inactive against some rifampicin-resistant mutants of a susceptible strain, suggesting a common mode of action. The presence of capsules in some cells appeared to confer bacteriocin-resistance on these variants. The second part of the thesis deals with a study of the physiological responses of a single strain of B.fragilis to ultraviolet radiation. This strain was found to be more sensitive to ultraviolet radiation under aerobic conditions. The amount of pyrimidine dimers formed after irradiation under anaerobic and aerobic conditions, was not found to differ significantly, indicating that the increase in sensitivity under aerobic conditions was not due to an increase in DNA damage. The use of repair inhibitors and the survival characteristics indicate that this difference was due to decreased repair capabilities under aerobic conditions. Liquid holding recovery in B.fragiZis was found to occur under aerobic conditions . This process was brought about by excision repair and appeared to be due to a decrease in repair efficiency under aerobic conditions. Under anaerobic conditions, where full repair capabilities were present, liquid holding recovery was inhibited. Both minimal medium recovery and fluence dependent filament formation were found to occur in irradiated B.fragiZis cells. The survival kinetics of a number of irradiated B.fragiZis phages were determined and a number of phage reactivation processes were investigated. Little or no host cell reactivation appeared to occur in the strains investigated, however, some ultraviolet reactivation and multiplicity reactivation was found to occur, but only under anaerobic conditions. Photoreactivation was found to be absent in this organism, but an excision repair system was present . The excision repair system was partially characterized and was found to resemble short patch excision repair in E.coli. Evidence was found which suggested that a second mode of repair which was sensitive to oxygen, also occurred in this strain. This repair system which appeared to be responsible for error-prone repair, and the systems which were responsible for ultraviolet reactivation and multiplicity reactivation, seemed to be dependent on a recombination function' which was inhibited by oxygen. The significance of this finding for future genetic studies was discussed.
  • Full Text:
  • Date Issued: 1980

Geochemical and mineralogical aspects of the Molteno Formation, South Africa

  • Authors: Reynolds, Adrian J
  • Date: 1980
  • Subjects: Sediments (Geology) -- South Africa , Mineralogy -- South Africa , Petrology -- South Africa , Geochemistry -- South Africa , Molteno Formation (South Africa)
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4901 , http://hdl.handle.net/10962/d1001561
  • Description: The Triassic Molteno Formation is a clastic sedimentary sequence consisting of a series of cycles, dominated lithologically by coarse grained sandstones. Aspects of the petrography have been examined using the conventional petrographic microscope as well as the scanning electron microscope. Both solution and overgrowth features are present not only on the quartz grains but also on certain of the heavy mineral species present. Intrastratal solution of garnet would appear to be a significant feature in the Molteno Formation. Mineralogical examination of the laterally persistent Indwe Sandstone Member indicates no significant variation in heavy mineral content. Evidence from a study of zircon elongation ratios shows the presence of two distinct zircon populations indicating two provenance areas. X-ray diffraction and electron microprobe analysis has identified mineral species characteristic of granites, pegmatitic granite and metamorphic rocks, especially amphibolites. Palaeocurrent data indicates that this source area lay to the south-east; to the south the source area consisted mainly of the Cape Supergroup sediments. Analysis for Nb, Zr, Y, Sr, Rb, Zn, Mn, Ba, Cu, Ni, Co, Cr, V and Ti for 22 samples from the Molteno Formation, indicates, as expected for a highly arenaceous sequence, a substantial depletion in these trace elements. No consistent variation of trace element concentration occurs with height in the sequence so trace element content may not be used for purposes of stratigraphic correlation. There are indications of trace element variation with geographical position, no doubt a reflection of the contribution of 2 source areas of different compositions. Factor analysis of the interelement correlations has identified 3 factors which influence the trace element content of the Molteno Formation these are a "heavy mineral" factor, a "pH-Eh" factor and a "clay mineral" factor. These trace factors are ultimately an expression of the source rock composition, the prevailing climate and a combination of the two. Comparison with the more argillaceous overlying Elliot Formation, indicates that factors influencing geochemical variation in this sequence were far more complex than for the Molteno Formation
  • Full Text:
  • Date Issued: 1980

Geological and economic factors affecting ore reserve estimation and grade control in porphyry type deposits

  • Authors: Reichhard-Barends, E O
  • Date: 1980
  • Subjects: Porphyry , Geology, Economic , Ore deposits , Copper mines and mining
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4921 , http://hdl.handle.net/10962/d1004466
  • Description: From introduction: The mining of porphyry type deposits accounts for about 50% of the world's present copper (Figs.I,2) and molybdenum production and resources. Mining organizations therefore invest substantial amounts of time, money and skills in the location and delineation of these types of deposit. The optimization of this investment effort is based on complex inter-relationships between geological, economic and political factors. The object of this dissertation is to review the geological and some of the economic aspects involved in the exploration and evaluation of porphyry deposits . These may hopefully provide some practical guidelines for decision making during the exploration and evaluation of such deposits. For the purpose of this dissertation, the exploration-evaluation of porphyry deposits, has been divided into three main stages:- Stage 1 : Geological mapping, interpretation of exploration drilling results and other geological factors which may help in understanding the shape and nature of the deposit. A knowledge of existing geological models for porphyry deposits will be essential in understanding the geological factors affecting tonnage and grade of these deposits Stage 2 Stage 3 (see Part I). Determination of grade-tonnage relationships. This is important in order to establish the different tonnage-grade alternatives for the deposit. Based on this, reserve estimations are calculated for different possible scales of mining. Drilling and sampling techniques, as well as statistical and preliminary economic evaluation methods are applied during this stage (see Part 2). Mine development and feasibility studies involve factors that influence type and scale of mining, and factors affecting mineral processing and extraction in relation to tonnage- grade alternatives. These factors are reviewed in Part 3.
  • Full Text:
  • Date Issued: 1980

Geological factors in the evaluation of vein deposits

  • Authors: Neuhoff, Larry E.
  • Date: 1980 , 2013-04-02
  • Subjects: Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5029 , http://hdl.handle.net/10962/d1006911 , Veins (Geology) , Hydrothermal deposits , Mineralogy , Geology, Economic
  • Description: From introduction: Vein-type mineralization, particularly gold, copper, tin and tungsten has provided a source of metal to man for over 2000 years. These deposits are usually small but in some cases are of very high grade. Prior to 1940 veins were extremely important sources of metals because of their relatively high-grades. However, with improved mining, smelting and concentrating methods, much lower grade material became economic, hence these smaller deposits could no longer hold their dominance. Recently the energy crisis and escalating costs of capital for large projects has made smaller deposits attractive once more (Temblay and Descarreaux, 1978) . At the present time gold, tin and tungsten command high prices on world markets. It is for these reasons that a study of the evaluation techniques pertaining to these deposits has been undertaken. In this review the geological factors which influence the evaluation are stressed. In particular, emphasis is placed on the emplacement of vein deposits, and the subsequent chemical and structural modifications of these deposits. The latter part of the review concentrates on the limitations of the sampling and ore reserve techniques that can be applied to the evaluation of mineralized veins. In the conclusion those techniques that are most applicable are stressed, and an evaluation model is outlined.
  • Full Text:
  • Date Issued: 1980

Gezani sithi siyotshela makolwa

Gloria

Gloria

Gloria

Gloria

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