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The effect of different parameters on the rupture properties of leather in a tensile test

  • Authors: Makhothe, Kelebohile
  • Date: 1998
  • Subjects: Leather -- Testing
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5462 , http://hdl.handle.net/10962/d1005247 , Leather -- Testing
  • Description: This thesis explores the effect of some parameters on the breaking strain, strength and the shape of the stress-strain curve of bovine leather as revealed by uniaxial tensile tests. The parameters explored are fatliquoring, moisture content, strain rate and cyclic stressing. A basic mechanical model of a simple two-dimensional weave is created and used to describe the effect of such a weave on the shape of the stress-strain curve. It is found that fatliquoring lubricates and opens up the fibre structure and thereby makes the weave more extensible. The increase in the extensibility depends on the direction in which samples are cut and therefore the manner in which the fibres are orientated. Patliquoring is observed to increase the degree to which fibres pull out at break. There are indications that the strength of fatliquored leather decreases with time of storage, while the extensibility increases. The effect of the strain rate on the breaking strain, the tensile strength and the shape of the stress-strain curve is not very clear. The stressing and releasing leather decreases the strength of leather when the fibres are orientated preferentially along the direction of the applied stresses, but has an insignificant effect in the transverse direction. It is concluded that the degree of lubrication in a weave and the orientation of the fibre bundles significantly influence the performance of leather in a test. Both moisture and fatliquoring lubricate the weave. In both the cases the degree of fibre adhesions in a weave is decreased. A well lubricated weave allows its constituent fibres to slide and align along the direction of the applied stresses, and this tends to occur before the fibres themselves areextended. Cyclic testing, at low strains, ruptures fibre adhesions and as a result induces permanent set and makes a hide softer. Most of the work done in breaking the fibre adhesion is done in the first cycle.
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  • Date Issued: 1998

The effect of environmental factors and hormone treatments on ovulation rate and spawning success in cardinal tetras, Paracheirodon axelrodi (Pisces: Characidae)

  • Authors: Burton, Simon Mark
  • Date: 1998
  • Subjects: Characidae , Characidae -- Breeding , Tropical fish -- Breeding , Fishes -- Induced spawning , Characidae -- Spawning
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5273 , http://hdl.handle.net/10962/d1005117 , Characidae , Characidae -- Breeding , Tropical fish -- Breeding , Fishes -- Induced spawning , Characidae -- Spawning
  • Description: Cardinal tetras, Paracheirodon axelrodi (Pisces: Characidae), are among the most popular tropical ornamental fish in the world. Millions of cardinal tetras are removed from their natural habitat, the upper tributaries of the Rio Negro in Brazil, each year and exported to North America and Europe where they are abundantly available at low cost. This, combined with the fact that they do not spawn freely in captivity has excluded any incentive to culture this fish on a commercial scale in these areas. However, the demand for cardinal tetras in South Africa is high, but their availability is limited to sporadic imports of wild caught fish which has resulted in an increase in their relative value. Thus, there is an appreciable incentive to investigate methods for inducing this species to reproduce in captivity. Information on methods for inducing spawning would form an integral part of a potential production plan for the culture of this species in South Africa. This study consisted of a number of experiments designed to investigate factors related to the spawning of cardinal tetras in captivity. The first series of experiments investigated the effect of variables such as the water chemistry of the experimental system, the sex ratio of the fish, the effect of conditioning and the effect of different spawning media on spawning success. The second series of experiments tested the effects of various environmental stimuli or hormonal treatments on spawning in cardinal tetras. Environmental stimuli tested included a rise in temperature, a rise in water level and a fresh rain water flush. Hormonal treatments included feeding GnRHa enriched brine shrimps to the fish or the application of hormone injections (hypophysation). Neither environmental stimuli nor brine shrimp enrichment induced cardinals to spawn in a repeatable manner. The same was true for hypophysation, but in this case a low incedence of ovulation of injected females was observed. Oocytes from ovulated and non-ovulated females were examined under a microscope and from this it was determined that cardinal tetras are group synchronous spawners, containing two distinct cohorts of oocytes in the ovary. The effect of a number of environmental stimuli on ovulation rate in cardinal tetras were then tested but did not induce ovulation in any females. A series of three experiments was performed investigating the effect of conditioning the sexes together on ovulation rate and spawning success. Conditioning the sexes together had no effect on spawning success, but a significantly higher ovulation rate was observed in females that vvere conditioned together with males. Male cardinals did not follow this trend and lost condition when conditioned together with females. The next experiment tested if pheromones from red serpae tetras, Hyphessobrycon serpae, could be used to induce ovulation and spawning in cardinal tetras. This was found not to be the case. The final series of experiments tested the effect of Aquaspawn® enriched Artemia on ovulation rates in female cardinal tetras. Aquaspawn® is a water soluble preparation of GnRHa and dopamine. Aquaspawn® enriched Artemia were found to be effective for inducing female cardinal tetras to ovulate. However, the results from this method of enrichment were not entirely reliable and further research is warranted. Finally, a protocol for evaluating spawning in topical, freshwater egg-laying fish was proposed, based on the results from this study. The advantages and disadvantages of such a protocol were discussed.
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  • Date Issued: 1998

The effects of night work and task diversification on efficiency of performance

  • Authors: Munton, Lynne Kerry
  • Date: 1998
  • Subjects: Night work -- Evaluation , Shift systems , Performance
  • Language: English
  • Type: text , Thesis , Masters , MA
  • Identifier: vital:5175 , http://hdl.handle.net/10962/d1018253
  • Description: This study investigated the effects of night work on performance efficiency. Night work is generally acknowledged to impair performance, yet much research has contradicted this assertion. The feasibility of including brief periods of physical activity to stimulate arousal within mentally demanding work shifts was also evaluated. Thirty six postgraduate volunteers were assigned to either the cognitive tasks (CT) or cognitive and motor tasks (CMT) group. All subjects performed three psycho-motor tests, using the Vienna Test System, at midday and midnight. The CMT group performed a short cycling activity before each test. Heart rate responses served as physiological measures, the Perceived Strain Scale was used to quantify individual perceptions of strain and performance efficiency was assessed in terms of speed and accuracy. Although several trends were apparent, no significant differences (p < 0.05) were revealed with respect to the three performance variables between the midday and midnight test sessions, or between the CT and CMT subjects, other than the higher heart rates recorded in the CMT group. In summary, neither time of day nor physical activity were found to affect performance within the controlled environment of this study.
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  • Date Issued: 1998

The effects of whole body immersion in cold water upon subsequent terrestrial aerobic performance : a study in hypothermia

  • Authors: Manley, Elizabeth
  • Date: 1998 , 2013-09-04
  • Subjects: Hypothermia , Cold -- Physiological effect , Temperature -- Physiological effect , Aerobic exercises , Cryobiology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5143 , http://hdl.handle.net/10962/d1007458 , Hypothermia , Cold -- Physiological effect , Temperature -- Physiological effect , Aerobic exercises , Cryobiology
  • Description: This study examined the extent to which physiological and psychological concomitants of aerobic terrestrial performance were affected by body cooling of varying degrees induced by cold water immersion (CWI). Thirteen male and 13 female subjects underwent three randomly assigned 30 min treadmill runs: a control run without prior manipulation of the subjects' thermal status and the same exercise after "central" (core temperature 1°C below pre-immersion) and "peripheral" cooling (skin heat loss 100kcal.m⁻².h⁻¹). During treadmill runs core temperature was measured, together with chest, leg, arm and hand temperatures, from which mean skin temperature (T [subscript]s[subscript]k) and mean body temperature (T[subscript]b) were calculated. Heart rate, oxygen consumption (VO₂,), carbon dioxide production (VCO₂), minute ventilation (V₂ (BTPS)), breathing frequency (f), cadence and ratings of perceived exertion (RPE) and thermal sensation (PTS) were also measured. Both central and peripheral cooling resulted in significantly reduced T[subscript]r[subscript]e (males : control 37.9±0. 3°C; central cooling : 36.8±0.5°C; peripheral cooling: 37.5±0.4°C; females: control: 37.9±0.4°C; central cooling: 37.2±0.5; p<0.05) during subsequent treadmill running, except following peripheral cooling for females (37.9±0.3°C) . For males and females T[subscript]s[subscript]k was lower following peripheral cooling than control values and lowest after central cooling (males: control: 30.0±1.3°C; central cooling: 36.8±0.5°C; peripheral cooling: 37.5±0.4°C; females: control: 30.5±1.2°C; central cooling: 25.9±1.8°C; peripheral cooling: 26.9±1.9°C; p<0.05). Female subjects experienced significantly higher T[subscript]r[subscript]e than males following central and peripheral cooling and a lower T[subscript]s[subscript]k following central cooling. Females experienced less of an increase in heart rate than males during exercise following central and peripheral cooling (control: l57.7±23.7b.min⁻¹; central cooling: 143.5±20.5b.min⁻¹; peripheral cooling 151.7±16.7b.min⁻¹; p<0 .05). Male responses were the same following central cooling but higher for peripheral cooling than control values (control: 139.1±7.3b.min⁻¹; central cooling 134.7±17.5b.min⁻¹; peripheral cooling: 145.0±16.4b.min⁻¹; p<0.05). These data indicate a depression in cardiovascular function for females following peripheral cooling that was not apparent for males. The VO₂ was not different between tests for males; only peripheral cooling resulted in a raised VO₂ of 28.6±3 .3ml.kg⁻¹.min⁻¹ (p<0 .05) for females compared to 27.6±2.6ml.kg⁻¹.min⁻¹ (control). A biphasic response was evident for VO₂ VCO₂ and V[subscript]B (BTPS). For both sexes overall RPE was lower for peripheral cooling (males: 9.4±1.9; females: 8.7±1.3; p<0 .05) than for control and central cooling. Central RPE was only changed for females following peripheral cooling. Changes in cadence and step length together with the effect of low skin and leg temperatures resulted in higher local RPE for females after central cooling (9.6±1.2; p<0.05) than control (9.4±1.9) and peripheral cooling (8.9±1.2 ). Males and females rated the same ambient temperature during the same exercise lower after peripheral cooling (males: 4.6±1.5; females : 5.3±1.3) than control values and lower still after central cooling (males: 3. 8±1.8; females: 2 .7±l. 5) In this study T[subscript]s[subscript]k was the primary determinant of PTS after precooling. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
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  • Date Issued: 1998

The end of apartheid and the organisation of work in manufacturing plants in South Africa's Eastern Cape Province

  • Authors: Smith, M R , Wood, G T
  • Date: 1998
  • Language: English
  • Type: text , Article
  • Identifier: vital:6319 , http://hdl.handle.net/10962/d1011313
  • Description: The election of 1994 radically changed the environment within which management chose its labour control policies. Prior to the change of government in 1994 plant practices were shaped by the fact of substantial protection against foreign competition, widespread illiteracy, and a set of laws and policies that offered few protections for individual workers or organised labour. Since the change in government the political and legal environment has substantially changed. In this paper we report on management practices before and after the political changes in South Africa in a set of plants in a part of the country where many of the current difficulties of the South African economy exist in a fairly extreme form.
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  • Date Issued: 1998

The growth, development and impact of the Grahamstown Festival of the Arts with special reference to music

  • Authors: Silva, Jane Susan
  • Date: 1998
  • Subjects: Standard Bank National Arts Festival -- Grahamstown , Standard Bank National Arts Festival -- Influence , Grahamstown (South Africa) -- Art and music , Music -- South Africa -- Eastern Cape -- Grahamstown
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2656 , http://hdl.handle.net/10962/d1002322 , Standard Bank National Arts Festival -- Grahamstown , Standard Bank National Arts Festival -- Influence , Grahamstown (South Africa) -- Art and music , Music -- South Africa -- Eastern Cape -- Grahamstown
  • Description: The Grahamstown Festival has become a huge and complex annual celebration of the arts, transforming the small Eastern Cape city for ten days every year. However this event had very modest beginnings, as did music and festivals in the city of Grahamstown. From its early days Grahamstown showed strong signs of becoming an important cultural centre, presenting numerous musical concerts from 1812, the festival tradition in the city beginning in 1887. The modern arts festival, initiated in 1971, had a chequered history during the early and mid 1970's, weathering economic recession, petrol restrictions and a repressive and restrictive political atmosphere. However by 1979 the event had become established and popular enough to ensure continued success during the 1980's. The period 1980-89 was one of great growth and development for the festival regarding attendance, and the number and nature of productions presented. Music had always been an integral part of the festival, and for the first time its role in this artistic celebration is being examined. The impact of such an event is varied and far-reaching, and thus difficult to assess, but the thesis ends with an attempt to gauge the Festival's impact.
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  • Date Issued: 1998

The interaction of melatonin and its precursors with aluminium, cadmium, copper, iron, lead, and zinc

  • Authors: Limson, Janice , Nyokong, Tebello , Daya, Santy
  • Date: 1998
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/293323 , vital:57075 , xlink:href="https://doi.org/10.1111/j.1600-079X.1998.tb00361.x"
  • Description: Melatonin, a pineal secretory product, and its precursors, tryptophan and serotonin, were examined for their metal binding affinities for both essential and toxic metals: aluminium, cadmium, copper, iron, lead, and zinc. An electrochemical technique, adsorptive stripping voltammetry, showed the varying abilities of melatonin and its precursors to bind the metals in situ. The results show that the following metal complexes were formed: aluminium with melatonin, tryptophan, and serotonin; cadmium with melatonin and tryptophan; copper with melatonin and serotonin; iron(III) with melatonin and serotonin; lead with melatonin, tryptophan, and serotonin; and zinc with melatonin and tryptophan. Iron(II) showed the formation of an in situ complex with tryptophan only. These studies suggest a further role for melatonin in the reduction of free radical generation and metal detoxification, and they may explain the accumulation of aluminium in Alzheimer's disease.
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  • Date Issued: 1998

The invertebrates of temporary rivers in the Eastern Cape, South Africa

  • Authors: Uys, Amanda Cloete
  • Date: 1998
  • Subjects: Rivers -- South Africa -- Eastern Cape Stream ecology -- South Africa -- Eastern Cape Freshwater invertebrates -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5628 , http://hdl.handle.net/10962/d1004908
  • Description: Temporary rivers in dryland regions are subject to highly variable and unpredictable rainfall and flow, and are considered unstable systems relative to perennial rivers of temperate zones. Little is known of the ecology of South Africa's temporary rivers, despite their abundance. The research presented focusses on the aquatic invertebrates inhabiting intermittently-flowing rivers in the 'arid corridor' of the Eastern Cape, South Africa. The major aims of the work were: to investigate which invertebrates inhabit these rivers, how the fauna is affected by environmental variability at various spatial and temporal scales, whether or not a characteristic fauna can be associated with these rivers or the hydrological phases which characterise them, and to establish to what extent faunal overlap occurs between different temporary rivers and between natural and modified temporary and perennial rivers. Research results indicate that the fauna of the Eastern Cape temporary rivers shows little structure at the scales of investigation, and that communities are generally non-equilibrial in character. The major forces shaping the biota are considered to be physical rather than biological, and the most important of these are: present and antecedent hydrological conditions and their duration; time of year; and biotope character, extent and heterogeneity. Three groups of fauna were identified as inhabitants of the temporary rivers: 'residents', 'facultative taxa' and 'opportunist colonists'. Taxa were tentatively allocated to these groups. Faunal resemblance was fairly high in Eastern Cape temporary rivers at the level of family, but not at more detailed taxonomic levels. A comparison between faunas of temporary and perennial rivers in different regions of South Africa illustrated the influence of geographical location on diversity. Within regions, however, there was no indication that perennial rivers were more diverse than intermittent rivers. The relatively high diversities in temporary rivers in this study are attributed at least in part to the heterogeneity in surface water conditions over time. A conceptual framework envisioning a continuum between perennial and temporary rivers is proposed as a basis for ongoing research into these rivers. A supporting terminology for the range of river flow types in South Africa is presented.
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  • Date Issued: 1998

The Marinkas Quellen Carbonatite Complex, southern Namibia: carbonatite magmatism with an uncontaminated depleted mantle signature in a continental setting

  • Authors: Smithies, Robert H , Marsh, Julian S
  • Date: 1998
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/149736 , vital:38879 , https://doi.org/10.1016/S0009-2541(98)00029-1
  • Description: The Marinkas Quellen Carbonatite Complex, in southern Namibia, forms part of the ca. 490–550 Ma Kuboos-Bremen Igneous Province, a zone of alkaline igneous rocks that intrude the Mesoproterzoic to Paleoproterozoic Namaqualand Metamorphic Province and Neoproterozoic platform sediments. The carbonatite complex includes Ca-rich, Mg-rich and Fe-rich carbonatites as well as late ferrocarbonatite dykes that show extreme enrichments in Mn, REE and Th. Compared to most carbonatites, those at Marinkas Quellen are generally depleted in most trace elements, particularly Ba and the LREE.
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  • Date Issued: 1998

The motif of initiation in selected works by Joseph Conrad

  • Authors: Doherty, Helen
  • Date: 1998
  • Subjects: Conrad, Joseph, 1857-1924 -- Criticism and interpretation , Initiation rites in literature
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2220 , http://hdl.handle.net/10962/d1002263 , Conrad, Joseph, 1857-1924 -- Criticism and interpretation , Initiation rites in literature
  • Description: This thesis explores the archetypal theme of initiation in selected texts by Joseph Conrad. The Introduction first surveys critical attention to initiatory motifs in Conrad with the objective of demonstrating the need for an approach to the topic informed by a more formal and theorized understanding of initiation. It then offers a prima facie case for the centrality of the idea of initiation in Conrad's oeuvre, based on references culled from a range of the author's writings. Chapter One seeks to contextualise initiation by providing a history of anthropological research into and theorisations of the rite, proceeding to a description of its typical structure and functions. A detailed account is given of the most widely accepted model of initiation, Arnold van Gennep's tripartite schema. Moving on to Conrad's writing, Chapter Two draws on both his fiction and more personal writings in order to provide a provisional account of the writer's own understanding of initiation and its importance, and to offer some explanation of why Conrad should have been prompted to accord the motif such prominence in his work. Conrad's presentation and (impliedly) his understanding of initiation was never entirely consistent and underwent some change in the course of his writing career. The critical assessment of "Typhoon" in Chapter Three depicts Conrad's more optimistic conception of initiation as a rite benefitting both society, by promoting solidarity, and the individual, by advancing self-knowledge. Chapter Four introduces, via analyses of the novellas "Youth" and "The Shadow Line", that variation on the motif of initiation which is more typical of its manifestation in Conrad: the failure of individuals to complete their cycles of initiation. Chapter Five identifies those characteristics of initiation which appear to be determinative in the representations of incomplete initiation in Conrad's work. Initiation seems to play out approximately seven paradoxes; the impact of some of these is examined through analysis of the initiatory ordeals of the main protagonists in The Secret Agent. Integral to this discussion is an attempt to demonstrate the vital role which initiation plays in the healthy maintenance not only of social order but also of faith and life itself. The Conclusion summarises the more important findings of the study and indicates some directions for further, related research.
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  • Date Issued: 1998

The notion of commitment in selected works of Maishe Maponya

  • Authors: Moorosi, Mabitle
  • Date: 1998
  • Subjects: Maponya, Maishe , Commitment (Psychology) in literature
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2142 , http://hdl.handle.net/10962/d1002374 , Maponya, Maishe , Commitment (Psychology) in literature
  • Description: This study is a critical analysis of selected works of the playwright Maishe Maponya namely, The Hungry Earth, Jika and Gangsters. The main thrust of the analysis of the thesis is centred on questions around what 'Commitment' might mean in literature and drama. This concept has appeared in many names and guises. In theatre, it has assumed names like Theatre of Commitment, Theatre of the Dispossessed, Theatre ofthe Oppressed, Theatre of Resistance, as well as Theatre of Radicalization (Bentley 1968; Boal 1974; Mda 1985; Maponya 1992). These names came into existence as a result of a concerted effort to refrain from the use of the traditional conventional theatre, which does not appear to address itself to societal problems - the preoccupation of Theatre of Commitment. Chapter One is principally concerned with the concept of Commitment and its implications in art and literature, more specifically in theatre. Further, the following interacting elements in South African theatre are highlighted: censorship, banning, detention and other restrictions, as well as DET education and religious institutions. Finally, Maponya is introduced, with his political inclinations and his views on art, together with the issue of theatricality in his plays. Chapter two initiates the proposed critical analysis with a focus on The Hungry Earth. The focus is on Theatre of Commitment and the background events that inspired Maponya's response. Chapter three concerns itself with the critical analysis of Jika, "a play about the making of revolutionaries in South Africa ... and serves a political purpose - as a recording of pivotal moment in South African history ... " (Haysom, 1988: 1). An attempt is made to assess the extent to which the playwright has succeeded or failed to strike a chord harmonious with the pronouncements quoted. Chapter four ends the critical analysis with the treatment of Gangsters. Here an observation is made on the fusing of the three personas, namely Rasechaba, Biko and Maponya, into one symbolic whole representing the image of Jesus Christ on the cross - the Saviour who sacrificed His life for the salvation of sinners. Maponya is seen to have sacrificed his time and energy for the liberation of the downtrodden. The conclusion summarizes the study by placing the selected works in their suitable perspective in respect of the notion of Commitment in literature, with particular reference to theatre. Maponya is seen to have played a commendable role in the liberation of his peoples' minds by teaching them the business of organizing revolutions, as well as by championing the liberation struggle.
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  • Date Issued: 1998

The petrology and geochemistry of the lower pyroxenite succession of the Great Dyke in the Mutorashanga area

  • Authors: Mason-Apps, Alexander Dymoke
  • Date: 1998
  • Subjects: Petrology , Geochemistry , Dikes (Geology) , Dikes (Geology) -- Zimbabwe
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4990 , http://hdl.handle.net/10962/d1005602 , Petrology , Geochemistry , Dikes (Geology) , Dikes (Geology) -- Zimbabwe
  • Description: This thesis focuses on the petrology and geochemistry of the lower Pyroxenite Succession of the Great Dyke of Zimbabwe in an area to the south ofMutorashanga. Particular emphasis is placed upon the economically important chromitite C5, and on the pervasive serpentinization of olivinerich rocks. An overview of the Great Dyke, including the Satellite Dykes, the structure and stratigraphy of the Great Dyke, the economic resources of the Great Dyke, and the evolution of the Great Dyke magma, is given. A review of the geodynamic history of the Zimbabwe Archaean craton, which culminated in widespread cratonisation and emplacement of the Great Dyke is also provided. The silicate rocks of the lower Pyroxenite Succession are highly adcumulate dunites and orthopyroxenites, with well-developed granular textures and a restricted mineral assemblage of olivine and pyroxene, with very minor plagioclase and clinopyroxene. Within cyclic units, the silicate rocks commonly display a textural and modal progression from granular dunite through poikilitic harzburgite, granular harzburgite, and olivine orthopyroxenite, to granular orthopyroxenite. Chromitites commonly occur at the base of each cyclic unit, these are thin, massive, coarse-grained layers, and are shown to be modified, texturally and compositionally, by postcumulus annealing processes. The olivine-rich rocks are pervasively serpentinized to a depth of over 300 metres. The serpentites typically display well-developed pseudomorphic mesh textures, with a slight overprint of nonpseudomorphic interpenetrating textures and late-stage cross-cutting veins. X-Ray diffraction studies indicate that chrysotile is the dominant serpentine mineral, and also reveal the presence of a nickeliferous magnesium hydroxide, occurring as an intimate admixture with serpentine, and believed to be a nickel-bearing analogue of brucite. Mineral and whole rock compositions of chromitite and silicate rocks highlight the strongly magnesian nature of the Ultramafic Sequence. Studies ofthe footwall chromites below chromitite C5 are consistant with a model of replenishment of primitive magma into the Great Dyke magma chamber, at the base of each cyclic unit. The magma injection and subsequent mixing with the evolved resident magma gives rise to chromitite fonnation, and a causes a reversal of the fractionation trend, resulting in a return to more primitive compositions in the silicate rocks. The silicates display an overall fractionation trend that reflects the evolving composition of the parental magma.
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  • Date Issued: 1998

The politics of peacekeeping in Southern Africa: a critical assessment of South Africa's engagement in regional peacekeeping initiatives

  • Authors: Khobotlo, Shadrack Motlalepula
  • Date: 1998
  • Subjects: Conflict management -- Africa, Southern , National security -- Africa, Southern , Political stability -- Africa, Southern , Africa, Southern -- Politics and government
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2787 , http://hdl.handle.net/10962/d1002997 , Conflict management -- Africa, Southern , National security -- Africa, Southern , Political stability -- Africa, Southern , Africa, Southern -- Politics and government
  • Description: International peacekeeping has gained a high profile in international relations and more so, in the post cold war era. The profound increase in the occurrence of civil wars globally and the consequent high demand for the UN to intervene has compelled the world body to delegate its peacekeeping powers to regional organisations. SADC is one of many regional organisations around the world which are faced with the challenge of developing peacekeeping capacities to resolve local conflicts. This thesis endeavours to investigate the prospects of peacekeeping in Southern Africa with specific reference to the involvement of South Africa as a regional power with the wherewithal to play a leadership role in this regard. This is done within the theoretical framework that is provided by the Realist school of thought in international relations. Furthermore, the concept of national interest as defined by Realism will be utilised to explain why countries in Southern Africa in general and South Africa in particular become involved in regional peacekeeping initiatives. The issue of whether the Republic should be involved and how much it should be involved has provoked an intense debate within the country. This debate will therefore be instructive in understanding the dynamics that influence the country's foreign policy behaviour towards the region in relation to playing a leadership role in regional peacekeeping initiatives. The central issue implicit in the debate is the fact that most of the SADC member states that are expected to contribute towards these initiatives have weak economies. This economic weakness in turn leads to the thorny issue of having to seek foreign assistance from western countries from which the region is trying to gain greater independence. This presents the region with a paradox because foreign assistance has serious implications for the SADC countries' sovereignty. It is in this context therefore, that this thesis examines economic development in individual SADC countries and in the region as a whole to establish whether they are in a position to develop a sustainable regional peacekeeping capacity. The contention of the thesis is that economic development is closely related to peacekeeping because without a sound economic base Southern Africa or any other region for that matter, will not be able to develop a viable peacekeeping capacity. On the other hand, keeping the peace in the region is itself important for economic development because it is only in a peaceful environment that economic development can take root.
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  • Date Issued: 1998

The potential role of Lake Malawi National Park sanctuary areas for biological control of schistosomiasis and development of a sustainable fishery

  • Authors: Msukwa, Amulike Victor
  • Date: 1998
  • Subjects: Lake Malawi National Park (Malawi) , Schistosomiasis -- Prevention , Mollusks , Aquatic ecology -- Study and teaching , Fishes -- Breeding
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5313 , http://hdl.handle.net/10962/d1005158 , Lake Malawi National Park (Malawi) , Schistosomiasis -- Prevention , Mollusks , Aquatic ecology -- Study and teaching , Fishes -- Breeding
  • Description: The potential role of sanctuary areas for biological control of Schistosomiasis and development of sustainable fisheries was investigated at Cape Maclear, Lake Malawi National Park (LMNP). There has been a recent increase in the incidence of schistosomiasis infection which is a threat to the local community as well as the tourism industry which is the major source of income to LMNP as well as Chembe Village. At the same place there is increasing fishing pressure due to growing human population and declining fish resource. The increase in the incidence of schistosomiasis transmission was attributed in part to over-fishing of the molluscivorous fish which are believed to control the vector snails for schistosomiasis. Four molluscivorous fish species, Trematocranus placodon; Trematocranus microstoma; Mylochromis sphaerodon and Mylochromis anaphyrmus were reported to account for more than 90% of the fishes (by numerical abundance) which feed on the gastropods above 15 metre depth. The gastropod numbers was reported to be highest at 1.5 to 4.5 metre depth. Of the four molluscivores, T. placodon was proposed as a biological control agent for schistosomiasis based upon the previous observations of its feeding habits in artificial conditions. Captive propagation of T. placodon for reintroduction at Cape Maclear in Lake Malawi has been proposed. The present study aimed at providing baseline data required to test the hypotheses that: 1) Over-fishing of the molluscivorous fish has resulted to the increased incidence of schistosomiasis at Cape Maclear. A sub hypothesis to this was that an extension of the LMNP can act as a sanctuary area for the biological control of schistosomiasis by protecting molluscivorous fish which could control schistosomiasis vector snails. 2) A park initially designed to protect the colourful rock dwelling fish and for promotion of tourism may not effectively protect the food fish. To test the first hypothesis, the biology and ecology of T. placodon were investigated with a view to evaluating the effect this species could have on the schistosomiasis vector snail population and hence the control of bilharzia in the lake. The proportions of various gastropod species at Cape Maclear was compared with those found in T. placodon guts. Comparisons of T. placodon abundance and demographic structure inside and outside LMNP were made. To test the second hypothesis, this study investigated the food fish species that use LMNP 100 m protected zone and some basic ecological factors to appreciate the extent to which the adjacent fishery might benefit from their use of the park waters. T. placodon numerical abundance (number of individuals per unit area) ranged from 5.7 to 40.5 /200 m² and it significantly (P< 0.05) varied between sampling sites. Otter Point and Mitande which are inside the park had the lowest abundance as compared to the other three sites; Nguli inside the park; Fisheries and Nchenga outside the park. Two sites in the park, Otter Point and Mitande, had a greater proportion of mature T. placodon individuals than all other sites. The abundance of T. placodon fluctuated significantly from month to month at Nchenga, Nguli and Fisheries (X² test, P<0.0001 for all the three sites) and insignificantly (P>0.05) at Otter Point and Mitande (X² test). T. placodon densities found in the present study corresponded to the peak density of 30 individuals / 200 m² reported in 1986 but did not correspond to that of 1.0 / 200 m² for 1994. There was no evidence to support the previous reports that T. placodon abundance had decreased tremendously from 1986. The reason suggested to account for the discrepancies of T. placodon abundance reported in the present study and other studies was inadequate sampling in the previous studies which did not take into account spatial and temporal variability in T. placodon abundance. The findings reported in this thesis show that there is no need for captive propagation of T. placodon to be reintroduced into the lake at Cape Maclear and that it may prove to be unsuccessful. However, since juvenile T. placodon dominated in abundance at the three sites along the major beach which is outside the park boundaries, it is suggested that the park boundaries be extended to this area so that T. placodon should be protected to allow individuals to grow to bigger size which would be more effective for gastropod control. T. placodon between 60 mm and 80 mm TL fed on benthic insects, phytoplankton and from detritus material. Individuals between 80 mm and 100 mm fed on a mixture of benthic insects, fish scales and small gastropods and at sizes greater than 100 mm individuals specialized feeding on gastropods. Gastropods of five genera were taken and they were: Melanoides , Bulinus, Gabiella, Lanistes and Bellamya. Of these genera Melanoides fonned the greatest part of T. placodon diet. Bulinus was the second most abundant genus but compared to Melanoides its proportion was very small. Of the three Bulinus species taken by T. placodon, B. globosus, is a confirmed vector for Schistosoma haematobium which is prevalent at Cape Maclear. This species was eaten in the least quantities. A comparison ofthe five gastropod proportions in T. placodon diet and in the habitats they occupy showed that Melanoides were taken in proportionately more quantities than Bulinus at most sites. These findings contrasted the previous reports that T. placodon preferred Bulinus to Melanoides. By applying the optimal foraging theory which predicts that an animal species searching for food will go for the type of prey with the highest profitability, it is concluded that the Bulinus cannot be eliminated completely by molluscivores because if their population size falls below a certain level, the fish will switch to other gastropod types. It is concluded that the increase in schistosomiasis may not be necessarily due to overfishing the molluscivorous fish but could be due to the fact that there has been an increase in the proportion of the B. globosus albeit in small numbers which are infected with schistosomiasis parasites. An integrated approach to schistosomiasis control at Cape Maclear comprising vector control, improved water supply, sanitation and health education is suggested since no method can be effective in isolation. Few food fish species were observed to use the park at various times, varying from one species to another with regards to duration, life history stages and abundance. Only a few fish species taken by the adjacent artisanal and commercial fisheries were represented among those observed in the park. This was attributed to the limited diversity of habitat types covered. Only small population size of some species visited the protected area and only part of the life cycle of some species were observed in the park. The use of the park area was seasonal for some species and the protected zone boundaries can be crossed more than once within a day because 100 m distance is just a few minutes swim by fish. Under such circumstances the park cannot function as an effective sanctuary for food fish. An increase of the park size may be a better option to effectively protect the food fish.
  • Full Text:
  • Date Issued: 1998

The Precambrian metallogeny of Kwazulu-Natal

  • Authors: Hira, Hethendra Gangaram
  • Date: 1998
  • Subjects: Metallogeny -- South Africa , Metallogeny -- South Africa -- KwaZulu-Natal , Geology, Stratigraphic -- Precambrian
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4993 , http://hdl.handle.net/10962/d1005605 , Metallogeny -- South Africa , Metallogeny -- South Africa -- KwaZulu-Natal , Geology, Stratigraphic -- Precambrian
  • Description: The Precambrian rocks of KwaZulu-Natal comprise the Archaean granite-greenstone remnants of . the Kaapvaal craton and Late Archaean volcanics and sediments of the supracratonic Pongola Supergroup. These Archaean rocks have been intruded by numerous mafic/ultramafic complexes and voluminous granitoid intrusives of various ages. To the south, the basement rocks are represented by the Mid- to Late-Proterozoic Natal Metamorphic Province (NMP). The NMP comprises three discontinuity-bound tectonostratigraphic terranes. These are, from north to south, the Tugela, Mzumbe and Margate Terranes. The Tugela Terrane has been interpreted as an ophiolite suite that was thrust northwards onto the stable Archaean craton as four nappe structures. Continued thrusting resulted in the two southern terranes being thrust northwards over each other, resulting in numerous sinistral transcurrent shear zones and mylonite belts. The greenschist facies Tugela terrane has been intruded by mafic-ultramafic complexes, alpine serpentinites, plagiogranites and a number of alkaline to peralkaline granitoids. The Mzumbe and Margate Terranes comprise arc-related, felsic to mafic supracrustal gneisses and metasediments that were intruded by syn-, late- and post-tectonic granitoids. Mineralisation in the granite-greenstones consists of structurally-hosted lode-gold deposits. These deposits have many characteristics in common with lode-gold deposits found in other granitegreenstone terranes throughout the world. The Nondweni greenstones also contain volcanogenicrelated massive sulphide deposits. The Pongola Supergroup is host to lode-gold mineralisation and placer gold mineralisation. These placer deposits have been correlated with deposits found in the similarly-aged Witwatersrand Basin in an adjacent part of the craton. The metallogeny of the NMP can be described in relation to the various stages in the tectonic evolution of the belt. The initial, rifting and extension-related stage was characterised by arcrelated magmatism and volcanic arc activity. Alkali basalt magmatism due to hot-spot activity in the oceanic basin in which the Tugela Terrane initially accumulated, produced magmatic segregation deposits, while volcanic-arc activity is responsible for the submarine-exhalative massive sulphide mineralisation. All the mineralisation within the NMP is structurally-related. These thrusts and shear zones were developed during obduction and thrusting during the NMP event, and created the paths necessary for the migration of mineralising fluids. Alpine-type ophiolite deposits were also emplaced along these zones. Epigenetic, shear zone-hosted gold mineralisation occurs in the Tugela and Mzumbe Terranes. Mineralisation occurs within quartz veins and is also disseminated within the sheared host-rocks. The Mzumbe Terrane also contains small showings of massive sulphide deposits that were related to volcanogenic exhalative processes during the formation of this terrane. Potential for finding further mineralisation of this type appears to be good. The massive sulphide deposits formed early in the evolution of the belt, and were deformed and metamorphosed during the later accretionary processes. The southernmost Margate Terrane is characterised by a lack of metalliferous mineralisation, but hosts the extensive, and economically important, limestone deposits of the Marble Delta. The recently discovered spodumene-rich pegmatite deposits of this terrane may also be considered for exploitation. Post-collisional magmatism and metamorphism resulted in extensive rapakivi-type granite/charnockite plutons
  • Full Text:
  • Date Issued: 1998

The removal and recovery of toxic and valuable metals from aqueous solutions by the yeast Saccharomyces cerevisiae

  • Authors: Wilhelmi, Brendan Shane
  • Date: 1998
  • Subjects: Saccharomyces cerevisiae , Yeast fungi -- Biotechnology , Sewage -- Purification -- Heavy metals removal
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4002 , http://hdl.handle.net/10962/d1004062 , Saccharomyces cerevisiae , Yeast fungi -- Biotechnology , Sewage -- Purification -- Heavy metals removal
  • Description: This project considered the use of the yeast Saccharomyces cerevisiae as a biosorbent for the removal and recovery of a range of metals from contaminated waters. S. cerevisiae, as a biosorbent, has the potential to provide a cost effective, selective and highly efficient purification system. Initial studies focused on metal accumulation by an immobilized baker's S. cerevisiae biosorbent. The parameters affecting metal uptake were investigated, these included metal concentration, time and solution pH. Metal uptake was rapid. Gold and cobalt reached saturation within 5 min of contact with the biosorbent in batch reactors. Copper, zinc, nickel, cadmium and chromium reached saturation within 30 min of contact. Metal accumulation was pH dependent and was generally unaffected at a solution pH ≥ 4, and was substantially decreased at pH ≤ 2. The exception was gold which was preferentially accumulated at a solution pH of 2. The immobilized baker's yeast accumulated metals with maximum binding capacities in the order of gold > cadmium > cobalt > zinc > copper > chromium > nickel. A rapid method to assess metal recovery was developed. Bioaccumulated metal was efficiently recovered using dilute mineral acids. Copper recovery of ≥ 80 % was achieved by decreasing the solution pH of the reaction mixture to 2 with the addition of nominal quantities of HCl, H₂SO₄ or RNO₃. Adsorption-desorption over 8 cycles had no apparent adverse effect on metal uptake or recovery in batch reactors. Transmission electron microscopy showed no evidence of damage to cells used in copper adsorption-desorption investigations. Biosorption columns were investigated as bioreactors due to their application potential. The metals investigated were effectively removed from solution. At a saturation threshold, metal uptake declined rapidly. Most metals investigated were desorbed from the columns by eluting with 0.1 M HCl. Initially recoveries of copper, cobalt and cadmium were as high as 100%. Desorbed copper, zinc, cadmium, nickel and cobalt were concentrated in 10 to 15 ml of eluent, representing up to a 40 fold decrease in solution volume. Cadmium, nickel and zinc uptake increased with the second application to the columns. Initial accumulation of gold and chromium was 42.2 μmol/g and 28.6 μmol/g, however, due to the low recoveries of these two metals, a second application was not investigated. Copper was applied to a single column for 8 consecutive adsorption-desorption cycles. Uptake increased from an initial 31.3 μmol/g to 47.8 μmol/g at cycle 7. The potential for selective metal recovery was demonstrated using two biosorption columns in series. Copper was accumulated and recovered most efficiently. Zinc, cobalt and cadmium were displaced to the second column. Copper bound preferentially to zinc at a ratio of 6:1. Copper bound preferentially to cobalt at a ratio of 4:1. Cadmium was only displaced at a ratio of 2:1. The successful transfer of the bioremediation technology from the laboratory to an industrial application has yet to be realized. Bioremediation of a Plaatjiesvlei Black Mountain mine effluent, which contained copper, zinc, lead and iron, was investigated in this project. The removal of the metals was most effective at pH 4. A combined strategy of pH adjustment and bioremediation using immobilized S. cerevisiae decreased the copper concentration by 92.5%, lead was decreased by 90% and zinc was decreased by 60%. Iron was mostly precipitated from solution at pH ≥ 4. An ageing pond at the mine with conditions such as; pH, water volume and metal concentration, which were more conducive to biological treatment was subsequently identified. The investigation indicated a possible application of the biomass as a supplement to chemical remediation. The metal removal capability of a waste brewer's yeast was subsequently investigated. A yeast conditioning step increased metal uptake up to 100% and enhanced reproducibility. Metal removal from solution was rapid and pH dependent. The metals were efficiently removed from solution at pH ≥ 4. Uptake was substantially inhibited at pH ≤ 3. The waste brewer's yeast accumulated metals with maximum binding capacities in the order of copper (25.4 μmol/g) > lead (19.4 μmol/g) > iron (15.6 μmol/g) > zinc (12.5 μmol/g). No correlation between cell physiology and metal uptake was observed. Uptake of the four metals was confirmed by energy dispersive X-ray microanalysis. The interference of lead, zinc and iron on copper uptake by the waste brewer's yeast, and the interference of copper on the uptake of lead, zinc and iron was investigated. Maximum copper uptake was not decreased in the presence of lead. The Bmax remained constant at approximately 25 μmol/g. The dissociation constants increased with increasing lead concentrations. Lead bioaccumulation was significantly decreased in the presence of copper. The type of inhibition was dependent on the initial copper concentrations. Zinc had a slight synergistic effect on copper uptake. The copper Bmax increased from 30.8 μmol/g in a single-ion system to 34.5 μmol/g in the presence of 200 μmol/l of zinc. Zinc uptake was severely inhibited in the presence of copper. The maximum uptake and dissociation constant values were decreased in the presence of copper, which suggested an uncompetitive inhibition. The affinity of copper was substantially higher than zinc. The presence of higher levels of copper than zinc in the yeast cells was confirmed by energy dispersive microanalysis. Copper uptake was decreased in the presence of iron, with the copper Bmax being decreased from 25.4 μmol/g in a single-ion system to 20.1 μmol/g in the presence of 200 μmol/l iron. Iron Bmax values remained constant at 16.0 μmol/g. Combined biosorption and EDXA results suggested the iron bound at a higher affinity than copper to the cell wall. Total copper removal was higher as larger quantities of copper were deposited in the cell cytoplasm. Metal removal from the Plaatjiesvlei effluent by free cell suspensions of the waste brewer's yeast was satisfactory. Copper levels were decreased by 96%, iron by 42%, lead 25% and zinc 2%. Waste brewer's yeast is a cheap source of biomass in South Africa, and could potentially provide the basis for the development of an innovative purification system for metal-contaminated waters.
  • Full Text:
  • Date Issued: 1998

The requirements for accurate analysis of pharmaceutical research at South African Universities

  • Authors: Haigh, John M , Smith, Eric W
  • Date: 1998
  • Language: English
  • Type: text , Article
  • Identifier: vital:6367 , http://hdl.handle.net/10962/d1006067
  • Description: International Pharmaceutical Abstracts is a valuable database for pharmaceutical research, although the multisiciplinary nature of this field implies that the database should only be the starting point of a search. This database is totally inappropriate for comparing outputs of individual pharmacy teaching institutions.
  • Full Text:
  • Date Issued: 1998

The shuttle effect : the development of a model for the prediction of variability in cognitive test performance across the adult life span

  • Authors: Jordan, Ann B
  • Date: 1998
  • Subjects: Cognition -- Age factors Aging -- Psychological aspects Cognition in old age Human information processing -- Age factors Older people -- Psychology
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:3191 , http://hdl.handle.net/10962/d1008556
  • Description: The aim of this thesis was to investigate inter-individual variability on cognitive task performance in normal older adults. In a review of the cognitive aging literature, the implications of a differential perspective were drawn out in order to establish a theoretical and methodological basis for an investigation into variability. A number of regularly occurring patterns, identified on the basis of available reports in the literature, were used to develop a model of variability (the shuttle model). The empirically-based model was located broadly within a neuropsychological framework, and derived explanatory power from the tenets of brain reserve capacity (BRC) theory. It served to describe the bulge in interindividual variability due to aging (the shuttle bulge), and the shifting occurrence of the bulge in relation to the age axis due to cohort and task-related influences (the shuttle shift). A two phase research study was conducted in order to test hypotheses derived from the model. Phase 1 comprised between-groups analyses of normative data covering a broad range of neuropsychological tests in the domains of attention, memory, language, visual and hand motor skills, in order to examine the progression of variability effects across the adult age range. Phase 2 constituted between and within-groups analyses of normative data from a more limited number of neuropsychological tests. It included the examination of raw score distributions and the characteristics of outliers, and was undertaken to explore more closely the nature of the variability phenomena detected in the first phase of the analysis. Taken together, the results of both phases of the investigation revealed statistically significant variability effects in support of the shuttle model. There was a consistent pattern of increased variability in association with older age regardless of functional modality; frequently, in association with later old age, there was also a subsequent decrease in variability (the shuttle bulge). The age of onset of the initial increase in variability occurred earlier or later (the shuttle shift) as a function of four factors: education, gender, task challenge and age-sensitivity of task. The finding of an earlier onset of variability effects for low education, male gender, high task challenge and high age-sensitivity of task was interpreted in terms of BRC threshold theory. The clinical and social implications of the outcome were discussed with special emphasis on the need for a differential perspective on aging, as a complement to the prevailing normative tradition. It was concluded that the shuttle model has considerable heuristic value. It presents an integrative framework for understanding existing variability data and provides clear indications for future research.
  • Full Text:
  • Date Issued: 1998

The theoretical and empirical analysis of trade integration among unequal partners : implications for the Southern African Development Community

  • Authors: Cattaneo, Nicolette Sylvie
  • Date: 1998
  • Subjects: Southern African Development Community , Customs unions , Africa, Southern -- Foreign economic relations , Africa, Southern -- Economic integration
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:1008 , http://hdl.handle.net/10962/d1002743 , Southern African Development Community , Customs unions , Africa, Southern -- Foreign economic relations , Africa, Southern -- Economic integration
  • Description: The re-acceptance of South Africa into the international community has cleared the path for the closer integration of South Africa with its neighbours in a broader southern African regional union. In particular, the countries of the Southern African Development Community {SADC), which South Africa joined in August 1994, have committed themselves to the formation of a free trade area (FTA) over an eight-year period. The most likely impediment to this process is the perception of a highly unequal distribution of the economic gains and losses of such an arrangement. This reflects the particular context of SADC: one of a comparatively undeveloped region, dominated by a relatively large, more industrially advanced country, which is itself small by international standards. The essential question with which this study is concerned, therefore, is whether, despite the existing inequalities in the region, a FTA among SADC members could be mutually beneficial to South Africa and its partners. The thesis applies orthodox and new trade theory to the analysis of economic integration among unequal partners. Using the theoretical analysis, and with reference to empirical studies of such experience elsewhere in the world, it attempts to provide an assessment of the existing body of literature on the possible effects of a SADC FTA. In the light of this discussion, and from its own preliminary empirical analysis of the possible pattern of inter-sectoral versus intra-sectoral specialisation which may result on union, the study suggests ways in which a fuller evaluation of the welfare implications of a southern African FTA may be achieved. The thesis argues that the orthodox theory based on perfect competition provides an insufficient framework for the analysis of the likely effects of a SADC FT A. It finds that, firstly, in an alternative analytical framework which retains the assumption of perfect competition, there may be other criteria for judging the success of a regional union that are neglected by orthodoxy, particularly in the case of developing countries. Secondly, the new trade theory based on imperfect competition and product differentiation provides useful insights into the possible effects of a regional union among countries at unequal levels of development. The formal extension of this body of literature to the theory of economic integration is clearly called for. It is found, however, that neither orthodox customs union theory, nor its suggested alternatives and extensions, enable one to conclude, a priori, that the formation of a FTA in the southern African region could not be beneficial to both South Africa and its smaller partners. Further, the present empirical studies on SADC do not take account of the full range of factors necessary for a complete welfare assessment of the possible effects. Since the outcome of integration depends on the empirical circumstances of the particular case, and since the information necessary for a comprehensive welfare evaluation is not currently available, the study concludes that the countries of the region have committed themselves to a FTA without any definite knowledge of its likely effects.
  • Full Text:
  • Date Issued: 1998

The third Marion Island oceanographic study (MIOS III) conducted during April and May 1998

  • Authors: Froneman, Pierre William , Ansorge, Isabelle J
  • Date: 1998
  • Language: English
  • Type: Article
  • Identifier: vital:6937 , http://hdl.handle.net/10962/d1011959
  • Description: Focuses on the third Marion Island Oceanographic Study (MIOS III). Objectives of the study; Details on the results; Conclusions.
  • Full Text: false
  • Date Issued: 1998
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