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Studies on dune rehabilitation techniques for mined areas at Richards Bay, Natal

  • Authors: Moll, John Bingham
  • Date: 1993
  • Subjects: Restoration ecology -- South Africa -- KwaZulu-Natal -- Richards Bay , Sand dune ecology -- South Africa -- KwaZulu-Natal -- Richards Bay , Sand dunes -- South Africa -- KwaZulu-Natal -- Richards Bay , Mineral industries -- Environmental aspects -- South Africa -- KwaZulu-Natal -- Richards Bay
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4235 , http://hdl.handle.net/10962/d1003841
  • Description: Rehabilitation is a dynamic process influenced by factors related to more than one field of ecology. It is therefore necessary to consider all these components when assessing the rehabilitation, although in the initial stages the successful revegetation of the disturbed areas is the most important criterion. Richards Bay Minerals, on whose mining site this project was carried out, is dredge mining heavy minerals on the north coast of Natal, where they have rehabilitated mined areas since 1978. This project has been carried out to establish: 1) The success of their dune forest rehabilitation using quantitative techniques. 2) The available seed bank in their rehabilitation stands. 3) The similarities in the succession taking place in rehabilitation stands compared to the revegetated stands in the vicinity of Richards Bay. 4) The best methods for creating alternative vegetation communities, especially grasslands, with a high species diversity on the mined tailings. This study reviews only the success of rehabilitation of the natural vegetation but other studies focusing on the insect, reptile, mammal and bird populations are also being undertaken by other researchers. No particular method of determining the success of vegetation rehabilitation has been chosen by restoration ecologists. Therefore in this study a broad range of quantitative techniques were used to show whether successional changes are occurring in the vegetation and physical environment. The results obtained from sampling the rehabilitated vegetation have shown that both the species richness and diversity are increasing as the returned vegetation matures. Levels of soil properties such as Sodium, Phosphate, Calcium and percentage organic matter have also risen with increasing stand age. Community complexity is also increasing with stand age, and TWINSPAN and DECORANA plots have separated out the differently aged stands based on their differences. A "pilot" study was done on the seed bank present in the rehabilitation stands. This has shown the presence of large amounts of early successional, mostly herbaceous species. Seeds of later successional and woody species were scarce which may be a result of the sampling intensity used. However seeds of late successional ground cover species were found in the older stands. Comparisons between the natural revegetation of disturbed areas in the vicinity of Richards Bay and the rehabilitation stands revealed similarities in both species composition and complexity. Species richness and diversity values are comparatively similar for the younger revegetated and older rehabilitation stands, and lWlNSPAN and DECORANA analysis techniques clustered the samples recorded from these areas in close proximity on their relative plots. The oldest revegetated sites contain a number of species found in the rehabilitated vegetation but as Acacia karroo has thinned-out in these stands many of these other species are now mature individuals. Attempts at rehabilitating an area of grassland at Richards Bay Minerals has not produced satisfactory species diversity and experimental manipulations were used to try and increase the diversity of the existing Eragrostis curvula dominated community. Of the several treatments used for the manipulation, a combination of burning and further topsoiling was the most successful in reducing Eragrostis importance and in increasing the species richness. Grassland topsoil spread directly onto the bare tailings produced an extensive vegetation covering over a short period but species richness was not significantly greater than for the existing Eragrostis dominated grassland, and further treatments and management needs to continue if this technique is to be employed. Only a limited amount of alien infestation of the rehabilitated areas was evident from the sampling undertaken during this research. As the removal of alien plants is an ongoing process and the rehabilitation stands are continuously monitored to identify any new invaders, this is not expected to become a problem. From the results of work done overseas and the rehabilitation carried out in South Africa it appears that it is possible to return natural vegetation communities on mined areas. That this is a lengthy process is to be expected but by manipulating the vegetation and continuously monitoring the process it may be possible to speed up development. Areas in need of further research have been identified based on the findings of this project. This will help to reinforce the undertaking of management proposals that will enhance the vegetation recovery and the success of the rehabilitation programme.
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  • Date Issued: 1993

Tatamkulu Afrika. Dark Rider. Cape Town Snailpress and Mayibuye Books, 1992. Book Review

  • Authors: Klopper, Dirk
  • Date: 1993
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/460836 , vital:76039 , https://journals.co.za/doi/epdf/10.10520/AJA00284459_477
  • Description: New Coin is one of South Africa's most established and influential poetry journals. It publishes poetry, and poetry-related reviews, commentary and interviews. New Coin places a particular emphasis on evolving forms and experimental use of the English language in poetry in the South African context. In this sense it has traced the most exciting trends and currents in contemporary poetry in South Africa for a decade of more. The journal is published twice a year in June and December by the Institute for the Study of English in Africa (ISEA), Rhodes University.
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  • Date Issued: 1993

The biological control of Hakea sericea Schrader by the Hakea seed-moth, Carposina autologa Meyrick, in South Africa

  • Authors: Gordon, Antony John
  • Date: 1993
  • Subjects: Weeds -- Biological control -- South Africa , Moths , Carposinidae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5648 , http://hdl.handle.net/10962/d1005330 , Weeds -- Biological control -- South Africa , Moths , Carposinidae
  • Description: Hakea sericea Schrader was introduced to South Africa from Australia and has become a major problem in nearly all the coastal mountain ranges of the Cape Province. The hakea seed-moth, Carposina autologa Meyrick was released in South Africa for the biological control of H. sericea. The impact of the moth on the canopy-stored seeds of H. sericea was evaluated at two study sites in the south-western Cape over three years. The moth has reduced the accumulated seeds at the two study sites by 59.4% and 42.6%, respectively. The moth has shown a surprising ability to disperse and establish new colonies at low population levels. Factors contributing to the slow colonization of C. autologa in South Africa was investigated. The moths appear to be unable to distinguish between healthy and previously attacked fruits; 42.5% of the eggs were laid on attacked fruits. Only 13.1% of the healthy fruits with eggs yielded mature larvae. The high pre-penetration mortality found in the present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichum gloeosporioides (Penz.) Sacc., on both H. sericea and C. autologa was investigated. H. sericea trees and branches that die as a result of fungus cause the accumulated fruits on the affected trees or branches to dehisce. This seed loss occurs at a crucial stage during C. autologa larval development. Only 42.1% and 33.0% of the trees were found to be healthy at the two study sites, respectively. One seed crop will always be available for regeneration, since recruitment is linked to fires, and wild-fires occur at a stage when the latest seed crop has escaped attack by c. autologa. C. autologa was released at six sites in the south-western Cape by attaching egg-bearing follicles to healthy fruits in the field. Three release sites were evaluated the year following release to determine whether the moth established or not. The role of C. autologa in the H. sericea biological control programme is discussed. Although seed destruction by C. autologa is not severe, it is expected to contribute to the control of H. sericea.
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  • Date Issued: 1993

The biology of a facultative hyperparasitoid, Tetrastichus Howardi Olliff (Hymenoptera : Eulophidae), and its potential as a biocontrol agent of lepidopterous stem borers

  • Authors: Moore, Sean Douglas
  • Date: 1993
  • Subjects: Eulophidae , Hymenoptera , Cephidae -- Biological control , Pests -- Biological control
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5649 , http://hdl.handle.net/10962/d1005331 , Eulophidae , Hymenoptera , Cephidae -- Biological control , Pests -- Biological control
  • Description: The gregarious pupal endoparasitoid, Tetrastichus howardi Olliff (Hymenoptera: Eulophidae), was introduced into South Africa as a biocontrol agent against the maize and the sorghum stem borers, Busseola fusca Fuller and Chilo partellus Swinhoe. Preovipositional behaviour, ovipositional behaviour, development, fertility, sex-ratio, and longevity were studied in the laboratory. A complex courtship behaviour was observed, however 35.3% of females were mated before emergence from the host pupa. Preoviposition period ranged from 100 mins up to 5 days. Host searching time in Petri dishes was shorter for lepidopteran pupae than for their parasitoid pupae, and shortest when T. howardi had previously experienced the host. Duration of oviposition was significantly longer in the lepidopteran pupae than in the smaller tachinid puparia. T. howardi showed no difference in preference for hosts of different ages. The lepidopteran hosts were preferred to their parasitoids. If T. howardi had previously experienced a certain host its pereference for that host tended to increase, but not significantly. When reared on a certain host, the preference for that host did increase. The parasitoid was able to discriminate between parasitzed and unparasitzed pupae although this ability developed only 2 days after the pupa was parasitized. Cotesia sesamiae Cameron, the main indigenous parasitoid of B. fusca and C. partellus, was not attacked by T howardi. The total duration of development from egg deposition to the adult stage ranged from 18 to 26 days at 24°C and 60% RH. Emergence of adults began after first light, mean emergence time in winter being 09h00. Emergence rate of T. howardi from parasitized hosts, and mortality rate of parasitized hosts, was higher for C. partellus and H. armigera than for Eldana saccharina Walker and Palexorista laxa Curran. This decreased for C. partellus and H. armigera when superparasitized. A strong correlation existed between total parasitoids emerging from a host and percentage of females. When a lepidopteran pupa was parasitized by a single T. howardi female, 55 progeny emerged of which 94% were females. Larger females showed greater fertility and also produced a higher percentage of females. Younger hosts were more suitable for development of T. howardi. Females lived for 5.4 to 52.5 days, and males lived for 3.1 to 28.6 days, depending on presence or absence of food, water and hosts. Reasons for releasing T. howardi in the field are discussed. Only 2 recoveries of parasitized C. partellus pupae were made from the field.
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  • Date Issued: 1993

The biology of Palexorista laxa (Curran) (Diptera : Tachinidae) : an internal larval parasitoid of Heliothis armigera (Hübner) Lepidoptera : Noctuidae)

  • Authors: Van Heerden, Desireé
  • Date: 1993
  • Subjects: Tachinidae , Helicoverpa armigera -- Parasites -- Life cycles , Noctuidae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5650 , http://hdl.handle.net/10962/d1005332 , Tachinidae , Helicoverpa armigera -- Parasites -- Life cycles , Noctuidae
  • Description: The Tachinid fly, Palexorista laxa (Curran) is an important parasitoid of Heliothis armigera (Hubner) in Africa and India. The biological characteristics of the parasitoid were studied with an emphasis on its host instar preference, host range, seasonality and percentage parasitism. The developmental stages were also studied and described. A high host mortality (48%-100%) due to parasite attack occurred when small larvae were parasitised (2nd & 3rd instars). A preference for the 4th and 5th host instars was shown by the flies. P. laxa was found to be a non-specific parasitoid and parasitised a number of lepidopterous larvae in the laboratory including Busseola fusca (Fuller), Chilo partellus (Swinhoe) and Eldana saccharina Walker, but preferred Ii. armigera. The percentage parasitism on H. armigera in the field was variable peaking at 48% in 1988/89. Of the various parasitoids recorded from H. armigera on sunflower P. laxa was by far the most abundant. Mating occurred immediately after emergence with the males emerging a day earlier than the females. Males were capable of multiple matings whereas females mated only once in a lifetime. P. laxa females produced incubated macrotype eggs which hatched almost immediately after oviposition. The duration of development of the incubated egg and larval stage was 6,7 days, the pupa 10,4 days for females and 9,4 days for males, and the adult lived up to 50 days at 25°C. A reduction in pupal weight, an increase in the duration of the pupal stage and higher pupal mortality accompanied an increase in density of parasitoids per host. A linear relationship was shown between adult mass and number of ovarioles and eggs in P. laxa females. The oviposition period was 26,9 days with a high variation in daily progeny production. The total fertility per female was 126,3 puparia. "Inexperienced" females deposited incubated eggs on all parts of the host body while "experienced" females confined oviposition to the head and thorax. P. laxa females did not discriminate between previously parasitised and non-parasitised hosts. The effect of temperature on larval and pupal survival and development time was studied at 20°, 22°, 25°, 28°and 30°C. As expected, duration of development decreased with an increase in temperature, and there was a reduction in mortality.
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  • Date Issued: 1993

The biotechnology of effluent-grown Spirulina, and application in aquaculture nutrition

  • Authors: Maart, Brenton Ashley
  • Date: 1993
  • Subjects: Aquaculture , Spirulina , Algae -- Biotechnology , Fishes -- Feeding and feeds
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4050 , http://hdl.handle.net/10962/d1004111 , Aquaculture , Spirulina , Algae -- Biotechnology , Fishes -- Feeding and feeds
  • Description: The biotechnology of production and utilisation of the cyanobacterium Spirulina has been well documented. Research has centred mainly on application in human and animal nutrition, and has been motivated by the high protein, vitamin, fatty acid and growth factor contents. The main obstacle in realising the full potential of this feed source has been the high production costs associated with its mass culture in defined media. The observation of blooms of Spirulina in tannery effluent evaporation ponds in Wellington, South Africa, prompted this investigation into the harvesting, and nutritional and toxicological evaluation of this potentially low-cost production system, with the ultimate aim of using the product in aquaculture rations. An investigation of the chemical gradient along the evaporation cascade showed a positive correlation between the prevailing chemical conditions and the dominant species populations. A standing crop of 9.5 tonnes/ha of Spirulina was found to be present in the latter alkaline ponds, characterised by relatively lower organic and sulphur contents. Initial harvesting of the biomass was achieved by the design, construction and implementation of a small-scale screen harvest, which yielded a 25 kg (dry weight) crop. A scale-up model was then designed, and implemented in a technical scale harvest, yielding a crop of 250 kg (dry weight). Both these harvests utilised the bloom of surface-autoflocculated biomass. Concentrated cell slurries were sun-dried on muslin beds, and milled to a coarse powder. An evaluation of the harvest revealed a chemical content similar to other published reports of defined media cultures, with the exception of the protein and amino acid contents. The observed lower levels of the latter two are almost certainly due to the sun-drying method employed, known to reduce the protein content due to thermal denaturation. Legislation demands the strict toxicological evaluation of new protein sources, and because of the effluent-nature of the growth medium of this source of Spirulina, its viability lies only in the application as an animal feed or supplement. A range of toxicological tests were chosen that were targeted to elucidate the possible toxicological constraints of this effluentgrown source of protein in animal nutrition. The nucleic acid and pesticide contents of the harvested biomass were within the prescribed safety ranges. Atomic absorption showed minimal accumulation of minerals and heavy metals from the effluent. A bioassay with the brine shrimp Anemia salina showed that the biomass contained no toxicologically active water-soluble components. A short term feeding trial with new-born chicks showed that supplementation with Spirulina had no effect on the growth rates and feed conversion ratios of the different feeding groups. Pathological analyses showed that the liver was the only target organ to elicit a change in response to supplementation of the diets with Spirulina. A general decrease in liver weight was noted, with Cu, Ca, Fe and Zn being significantly accumulated. A histopathological examination however, showed no cellular and functional aberration from the control animals. The toxicological analyses gave the preliminary safe go-ahead for the evaluation of effluent-grown Spirulina in aquaculture nutrition. The South African abalone Haliotis midae, and the rainbow trout Oncorhynchus mykiss were chosen as representative species of edible cultured organisms. The technology for the culture of the perlemoen abalone is being established in South Africa, with the main area of research being the development of an artificial diet for high density culture. A 40 day growth trial demonstrated that lower concentrations of Spirulina supplemented to an agar-based fishmeal diet resulted in growth rates and feed conversion ratios similar to the control fishmeal and purified-casein diets, and thus has application potential in the nutrition of this high-cost marine delicacy. The aquaculture technology of freshwater rainbow trout is already well established. An eight week feeding trial with various concentrations of Spirulina showed that this effluent-grown protein source can partially replace fishmeal in semi-purified diets. Fish fed Spirulina did not exhibit decisive manifestations of toxicity, as determined in a histopathological study. In addition, Spirulina supplementation resulted in enhanced colouration of the skin and flesh, which may have implications in the aesthetic marketing of this sought-after table fish. The primary aim of this preliminary investigation thus concerned the determination of the biotechnological potential of this effluent-source of Spirulina. A technology transfer from the economically unfeasible defined-media culture was implemented. This project is ultimately aimed as a contribution towards the treatment of tannery wastewater, by the removal of contaminants from the effluent in the form of organic biomass.
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  • Date Issued: 1993

The characteristics of some Xhosa dramas

  • Authors: Sirayi, Mziwoxolo
  • Date: 1993
  • Subjects: African literature -- Criticism and interpretation , Xhosa drama -- History and criticism
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:3598 , http://hdl.handle.net/10962/d1002173 , African literature -- Criticism and interpretation , Xhosa drama -- History and criticism
  • Description: This study aims at highlighting some crucial aspects of Xhosa drama. These aspects are of great significance for the understanding of Xhosa drama. It also aims to historicize and contextualize examinations of traditional Xhosa drama and modern Xhosa drama.
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  • Date Issued: 1993

The cicada genus Bavea Distant 1905 (Homoptera Tibicinidae) redescription, distribution and phylogenetic affinities

  • Authors: Villet, Martin H
  • Date: 1993
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/453855 , vital:75294 , https://doi.org/10.1080/03946975.1993.10539232
  • Description: The monotypic genus Bavea Distant 1905 and its constituent species are redescribed. The forewing venation, tymbal structure and aedeagal structure are diagnostic. Bavea concolor (Walker 1850) is endemic to the eastern Cape province of South Africa. The closest affinities of the genus appear to lie with the genera Xosopsaltria Kirkaldy 1904 and Tettigomyia Amyot and Serville 1843, and less closely with Stagira Ståi 1861.
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  • Date Issued: 1993

The construction, implementation and evaluation of a transactional analysis stress management course for adolescents

  • Authors: Ritchie, Harriet Anne
  • Date: 1993
  • Subjects: Transactional analysis Stress in adolescence Adolescent psychology Stress management
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1461 , http://hdl.handle.net/10962/d1003342
  • Description: Stress is a problem in today's world and adolescents are not exempt from suffering its ill effects. Currently no stress management courses are offered as part of the formal guidance programme in high schools or in the community. This pilot study is an attempt to construct a stress management course based on the concepts of Transactional Analysis. The course was implemented with a multi-racial, standard eight group of nine boys and girls. The course was evaluated qualitatively and quantitatively. The quantitative measures proved to be inappropriate to this study and did not render any useful information. The study found that the scholars expressed that they had changed in their handling of their daily stressors as a result of the course. Personal growth had also taken place. The findings of this research are discussed in terms of the important implications they have for school guidance programmes.
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  • Date Issued: 1993

The deaths of Cordelia and Lear

  • Authors: Butler, Guy F
  • Date: 1993
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/457881 , vital:75687 , https://hdl.handle.net/10520/AJA1011582X_33
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  • Date Issued: 1993

The domestic worker some considerations for law reform

  • Authors: Meintjes-van der Walt, Lirieka
  • Date: 1993
  • Subjects: Household employees -- Law and legislation -- South Africa , Black people -- Employment -- South Africa , Women -- Employment -- South Africa
  • Language: English
  • Type: Thesis , Masters , LLM
  • Identifier: vital:3683 , http://hdl.handle.net/10962/d1003198 , Household employees -- Law and legislation -- South Africa , Black people -- Employment -- South Africa , Women -- Employment -- South Africa
  • Description: This thesis examines ways in which domestic workers in South Africa could be included within the scope of existing industrial legislation. At present the legal position of a work force of 862 000 is regulated by the common law contract of service. Socio-economic factors form the background of this investigation,which first sets out to determine whether the common-law contract of employment is capable of equitably regulating the employment relationship. The fallacy of the assumption that individuals agree on the terms of exchange in the employment contract on the basis of juridical equality, and the tenuous nature of the common-law employment relationship in the case of domestic workers are revealed. In the absence of any current statutory minima the employment contract is used to deprive domestic workers of what little protection they enjoy at common law. The two ways in which the individual employee's conditions of service can be protected from terms favouring the stronger of the two contracting parties are discussed. These are collective bargaining and statutory regulation. Difficulties experienced by domestic workers in respect of collective bargaining, whether they be included under the Labour Relations Act or not, are indicated. Proposals for including domestic workers under the Basic Conditions of Employment Act are evaluated in the light of legislation in the United States of America, Zimbabwe, Swaziland and Namibia. Ways of minimum-wage fixing are investigated, and it is concluded that the provisions of the Wage Act could be adapted for domestic workers. The 'unfair labour practice'concept is examined and the implications of its application for the domestic labour sector evaluated. It is recommended that the concept 'fairness' in the Labour Relations Act should apply to domestic workers, but that a code of practice be drafted to provide conceptions of 'fairness' as guidelines for employment behaviour. It is suggested that the parties refer disputes to mediation before being granted access to a Small Labour Court established for this purpose. In conclusion a draft code of practice is presented, as a basis for negotiation at a forum representative of the major actors in the domestic labour arena.
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  • Date Issued: 1993

The ecology of the South African citrus thrips, Scirtothrips aurantii Faure and its economic implications

  • Authors: Gilbert, Martin Jeffray
  • Date: 1993
  • Subjects: Thrips -- Control -- South Africa Citrus -- Diseases and pests -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5673 , http://hdl.handle.net/10962/d1005358
  • Description: The South African Citrus Thrips, Scirtothrips aurantii Faure (Thysanoptera: Thripidae) has been a serious pest of the citrus industry of Southern Africa for over 70 years. It is indigenous to Africa and has no recorded parasitoids and, in most citrus-growing regions, predators are not economically effective. Firstly, in this study, the general ecology of thrips was reviewed along with the recorded history of S. aurantii and its control. Host plant relationships of S. aurantii were then examined and wild hosts were not found to be important in promoting citrus thrips outbreaks in the orchard after flowering. In addition, Scirtothrips dorsalis Hood, which attacks citrus in Asia, was collected for the first time in Africa, but from Castor Oil plant. It is therefore a potential pest of citrus here. Notes on its appearance compared to that of S. aurantii were prepared. Weekly sampling of S. aurantii adults was carried out from June 1984 to May 1990. Population fluctuations were then correlated with phenology of the citrus trees and the direct and indirect effects of weather. Temperature and rainfall were not found to be significantly directly correlated with thrips numbers recorded. However, the indirect effects of rainfall were important in promoting a large winter thrips population in certain years. Relatively high rainfall during March and April compared to that of the previous January and February stimulated atypical flushing of the citrus trees during autumn and the setting of out-of-season fruit. S. aurantii then exploited this unusual food source and high numbers were subsequently recorded in the following winter; as well as in spring. Thus the mild winter climate alone could not suppress thrips numbers at Letaba. Dispersal/Emergence traps, which are used in the U.S.A. for the monitoring of Scirtothrips citri, were evaluated over 24 months, and were effective in recording population peaks of S. aurantii. The emergence rate of adults in relation to second instar larvae trapped was 43.7%. 35.7% of adults caught after emerging from the soil were males and 64.3 were females. In contrast, yellow traps had recorded 59.1% males and 40.9% females over the same period. The yellow traps were subsequently found to be biased towards male catches when young fruit and/or soft flush was present on the citrus trees. Relative inhibition of female flight activity during times of food abundance is known in other thrips species. During times of food scarcity, the bias in the yellow trap results disappeared. At Letaba Estates, availability of food rather than the direct effects of weather was seen to be the most important factor in governing S. aurantii numbers. Because of the importance of soft flush in the promotion of S. aurantii population increase, it is recommended that more attention should be given to the control of thrips on, as well as conducting surveys for, this food source. As the climate at Letaba is so favourable for citrus thrips, even during winter, it is further recommended that trapping for S. aurantii is carried out throughout the year. Furthermore, males and females should be recorded separately in trapping results as the sex ratio gives an indication of the phenological state of the tree.
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  • Date Issued: 1993

The effect of hydrostatic carbon dioxide pressure and extracellular ethanol on the performance of the yeast strain Saccharomyces cerevisiae during fermentation

  • Authors: Longden, Nicholas Guy
  • Date: 1993
  • Subjects: Brewing -- Microbiology , Yeast , Fermentation , Saccharomyces cerevisiae
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4044 , http://hdl.handle.net/10962/d1004105 , Brewing -- Microbiology , Yeast , Fermentation , Saccharomyces cerevisiae
  • Description: The brewing industry constantly experiences problems in trying to maintain the quality of beer produced. Unfavourable conditions during fermentation may alter the performance of the yeast strain Saccharomyces cerevisiae, resulting in a "poor" end-product. It has been established that high concentrations of extracellular ethanol, when added to the fermentation medium inhibit yeast activity. It has been recently suggested that increased carbon dioxide pressure could inactivate the yeast activity adding to further brewing problems. The aim of this study was to investigate the effect of extracellular carbon dioxide pressure and ethanol addition, on yeast performance when added to a fermentation medium, and to establish whether an inhibitory relationship existed between ethanol and carbon dioxide pressure, when combined and added to the fermentation medium. Dissolved C0₂ in the medium, medium pH and substrate utilisation were analysed daily during a fermentation, as were membrane fatty acid composition. These parameters were used to assess the effect of ethanol and carbon dioxide on the yeast performance and consequently the final end-product. Supplementing the medium with extracellular ethanol, even as low as 5%, was shown to inhibit yeast performance during fermentation. This effect was even more marked as the ethanol concentration was increased, with almost total inhibition of yeast activity occuring after the addition of 15% ethanol (v/v). A similar effect was observed when elevated C0₂ pressures were applied to the medium, and although low C0₂ pressures initially induced the synthesis of saturated yeast membrane fatty acids, elevated C0₂ pressures (greater than 1,0 atm.) was shown to follow a similar inhibitory trend, if not as dramatic, as ethanol. A combination of both ethanol and C0₂ pressure showed a further increase in the level of yeast inhibition, although the low C0₂ pressure appeared to initially inhibit the toxicity of ethanol on the yeast. Increasing the levels of the C0₂/ethanol treatment (1,0 atm.), showed a synergistic effect on yeast performance. The results of this study indicate that both extracellular ethanol and carbon dioxide do appear to inhibit yeast performance and affect membrane fatty acid composition of the cells by inhibiting the synthesis of the respective fatty acid. This affect has a significant bearing on the general metabolism of the yeast cell.
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  • Date Issued: 1993

The effect of short chain fatty acids on picornavirus replication

  • Authors: Ismail-Cassim, Nazeem
  • Date: 1993
  • Subjects: Viruses -- Reproduction , Picornaviruses , Antiviral agents -- Research
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4030 , http://hdl.handle.net/10962/d1004090 , Viruses -- Reproduction , Picornaviruses , Antiviral agents -- Research
  • Description: Picornavirus proteins VP1 to VP3 are exposed on the surface of the virus particle whereas VP4 is internal and modified at its amino terminus by the addition of myristic acid (Chow et al., 1987; Paul et al., 1987). Myristic acid occupies a position in the core of mature poliovirus particles; it has been suggested that it may be important for particle integrity or in the localization of the capsid protein precursor on the hydrophobic membranes during virion assembly (Chow et al., 1987). To determine the function of the amino-terminal myristylation of VP4 in picornaviruses, and to establish whether competition for the acylation site is a possible approach to antiviral chemotherapy, the effect of fatty acids on virus replication has been examined. Some fatty acids are able to enter picornavirus-infected cells and compete for the myristylation site on VP4. Unexpectedly, it was found that short chain fatty acids also inhibit an early event in the replication of bovine enterovirus (BEV) at concentrations which have no detectable effect on cellular macromolecular synthesis and cloning. These findings indicate that fatty acids inhibit cell-mediated uncoating. Short chain fatty acids inhibit the replication of bovine enterovirus but are almost ineffective against poliovirus type 1, coxsackievirus B5, encephalomyocarditis virus and human rhinovirus lB. Lauric acid binds to bovine enterovirus, thereby stabilizing the virus particle to heat degradation. Fatty acid-bound virions attach to susceptible cells but fail to undergo cell-mediated uncoating. The inhibitory effect is reversible with chloroform and may result from a hydrophobic interaction between the fatty acid and a specific site on the virus particie.
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  • Date Issued: 1993

The fishes of Tristan Da Cunha and Gough Island (South Atlantic), and the effects of environmental seasonality on the biology of selected species

  • Authors: Andrew, Timothy Gilbert
  • Date: 1993
  • Subjects: Fishes -- Tristan da Cunha Fishes -- Gough Island Fishes -- Conservation
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5284 , http://hdl.handle.net/10962/d1005128
  • Description: This study focuses on the taxonomy, biogeography and biological aspects of the fishes of Tristan da Cunha and Gough Island in the cental South Atlantic Ocean. Oceanographic measurements were undertaken to determine the position and nature of the Subtropical Convergence (STC) in the vicinity of the islands. The Tristan da Cunha group is thought to be situated on the northern edge of the STC while Gough Island is situated on the southern edge of the front. The seasonal environmental cycle at the islands is characterised by an annual sea surface temperature fluctuation of approximately 5 °C and an annual change in stratification of the water column. It is suggested that this increase in stratification at the STC, brought about in the summer by insolation warming the surface layers of the ocean, enhances primary production. The STC is identified as a unique habitat for fishes and as an important barrier to dispersal of species in the Southern Ocean. The present study has produced 18 new distributional records from the shelf waters of Tristan da Cunha and Gough Island. The fish fauna known from the shelf waters of these islands is reviewed, and a diagnosis, synonymy, and in some cases an illustration are provided. For certain species, brief notes on their biology, relative abundance and seasonal distribution are included. An analysis of the ichthyofaunal relationships between shallow water areas in the vicinity of the STC has resulted in the identification of a characteristic neritic STC ichthyofauna. The circumglobal distribution of many of these species is thought to be a consequence of a dispersive pelagic phase in their life-cycles. Biological processes in fishes at these islands are temporally and spatially affected by seasonal changes in oceanographic conditions. Seasonal sea temperature variation was identified as being an indicator of other oceanographic phenomena that may affect processes such as growth, reproduction and feeding in fishes at the islands. Most species have a summer spawning season and growth rate increased during the summer months. It was hypothesised that enhanced primary production and a related increase in food quality and availability during the summer were the major factors temporally regulating the growth and reproduction of fishes at the islands. Twenty families of neritic fishes have been recorded in the shelf waters of Tristan da Cunhaand Gough Island. Most families are represented by only one species. Because of this a wide range of life-history strategies are apparent in the fauna. Nevertheless, there are a number of common life-history characteristics shared by most of the neritic species. Firstly, the early lifehistory of many species included an extended pelagic phase which might have facilitated colonisation throughout the STC zone in the past, thereby regulating extant species diversity in this region. Secondly, the common occurrence of an extended summer breeding season and iteroparity suggested that these characters also contributed to survival in what is considered to be an unpredictable environment. It would appear that these common characteristics hold the key to the success of many fishes in the STC zone. This study has contributed to our understanding of oceanic island ecosystems and has revealed distributional patterns of fishes that were unknown previously. By focusing on the biological processes of selected species the regulatory role played by local environmental conditions became apparent. The results of this study are also relevant to proposed conservation measures for Tristan da Cunha and Gough Island.
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  • Date Issued: 1993

The formulation of modern power configurations in the Keiskammahoek district of the Ciskei from c.1948 to the present

  • Authors: Westaway, Ashley Frank Hurford
  • Date: 1993
  • Subjects: Keiskammahoek (South Africa) -- Social conditions , Keiskammahoek (South Africa) -- Economic conditions , Power (Social sciences) -- South Africa -- Keiskammahoek
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:2573 , http://hdl.handle.net/10962/d1002426 , Keiskammahoek (South Africa) -- Social conditions , Keiskammahoek (South Africa) -- Economic conditions , Power (Social sciences) -- South Africa -- Keiskammahoek
  • Description: Much of the available documentation, and the multiple oral testimonies collected for this thesis agree that the most important changes that have occurred in Keiskammahoek district over the past half century resulted from the implementation of the government's conservationist policy known as betterment. The work is thus dominated by a wideranging look at betterment in Keiskammahoek The thesis is arranged chronologically, and each of the successive periods designated is analysed in terms of power. The first period considered is c.1920-c.1936; this was the time during which betterment policy was conceived. The key question that is posed here is why the policy was formed. Foucault's idea of power/knowledge features prominently in answering this question. For all of the remaining periods a conspicuously ,important power relation (unequal relationship) is chosen, and the analyses consist of plotting the histories of the various relations. The first of these periods is that which preceded the implementation of betterment in the district, i.e. c.1936-1960. Since multi-form resistance against betterment characterised this period, the power relation considered is that between the state and the various communities of Keiskammahoek. Next, attention is given to the actual implementation of betterment in the district. Because betterment affected locations in which land was held communally so differently from locations in which land was held under title, these two categories of location are analysed separately. In communal locations, a power relation spawned by betterment that has come to dominate life is that between village neighbours. In the other category of location, betterment has often further differentiated the power relation between title-deed holders and non title-deed holders. The thesis is not exclusively devoted to betterment. The 1970s saw many people being forcibly removed to Keiskammahoek. The final section of the work examines these events in relation to the changing economy of South Africa. In this section the power relation that is deemed important is that between the employed and unemployed The overall aim of the thesis then is to give an indication of the variety of forms or configurations of power that run through modernday Keiskammahoek.
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  • Date Issued: 1993

The geology of the Welkom Goldfield with special reference to the "A", "B" and Beatrix Reefs

  • Authors: Dwyer, Gordon Bransby
  • Date: 1993
  • Subjects: Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4963 , http://hdl.handle.net/10962/d1005575 , Gold mines and mining -- South Africa -- Free State , Gold ores -- Geology -- South Africa
  • Description: The first Witwatersrand gold deposits in the Orange Free State were discovered under younger cover rocks in the 1930's with the aid of drilling and geophysics. The Welkom gold deposits are found in the sedimentary rock sequences of the Central Rand Group, which represent unconformity bounded genetic packages. The structural configuration of the goldfield is one of a north to south trending synform that is split near it's axis by the De Bron and Homestead faults. The "B" Reef is a highly variable, erratically mineralised reef that lies on an unconformity at the base of the Spes Bona Formation. The "A" Reef Zone consists of several placers 1 including the "Reworked BPM" 1 the Witpan, the Uitsig, the Hanging Wall Grits and the Upper "A" Reef. The Beatrix Reef lies at the base of the Eldorado Formation on an unconformity surface overlying the Virginia Formation in the southern part of the Welkom Goldfield. The origin of gold in the Witwatersrand basin can be classified into the modified placer theory, the syngenetic theory and the epigenetic theory. From the distribution of basin edge unconformities it can be deduced that the Welkom fan depository was tectonically active on the western, southern and eastern margins during sedimentation. Palaeocurrent studies indicate that sediment was transported predominantly from the south and west. It is thought that the "B", "A" and Beatrix Reefs were all deposited in a braided stream environment. A multidisciplinary approach to ore evaluation of Witwatersrand deposits is considered to be the best method, where sedimentology, geostatistics and structural geology are used.
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  • Date Issued: 1993

The influence of contrasting freshwater inflows on the feeding ecology and food resources of zooplankton in two eastern Cape estuaries, South Africa

  • Authors: Grange, Neil
  • Date: 1993
  • Subjects: Freshwater zooplankton -- Ecology -- South Africa Aquatic ecology -- Research -- South Africa
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:5714 , http://hdl.handle.net/10962/d1005400
  • Description: The trophodynamic implications of reduced freshwater inflow on the zooplankton of eastern Cape estuaries was investigated by a comparison of the community composition and standing stocks, grazing rates and food resources of zooplankton in two systems, the Kariega and the Great Fish estuaries, which are subject to contrasting freshwater inflow. The climate of South Africa is semi-arid, and the low rainfall, coupled with high evaporative loss, result in the region having one of the lowest conversions of rainfall to run-off in the world. In addition, many of the major rivers are extensively impounded, consequently, estuaries often experience prolonged periods of zero or reduced freshwater inflow. The amount of freshwater available for estuarine management in the future is expected to decline as the demand for domestic, agricultural and industrial use increases. The influence of climate, tidal amplitude and wave action are essentially constant, consequently, the individual characteristics of an estuary are determined largely by the indirect influences of catchment size and regulation. Estuaries along the eastern Cape coast range from negative hypersaline systems, to positive systems in which a salinity gradient is well established. The Kariega estuary is a homogeneous marine estuary as a result of minimal freshwater inflow, whereas the Great Fish estuary receives sustained freshwater inflow and is partially-stratified. The quality and quantity of particulate food resources for suspension-feeders depended to a large extent on the allochthonous import of material associated with freshwater inflow. Nutrients, rather than light penetration of the watercolumn are the major factor limiting phytoplankton standing stocks. In the Kariega estuary, phytoplankton standing stocks were low (up to 1.0 μg l⁻¹) and the estuary is classified as oligotrophic. Correlation analyses indicated that lower quality detritus, originating from fringing macrophytes, may contribute substantially to suspended particulate organic material. Phytoplankton food resources were considerably higher in the Great Fish estuary (up to 21.8 μg ⁻¹) which is classified as mesotrophic/eutrophic, and correlation analyses indicated that phytoplankton comprised the dominant fraction of the particulate organic material. Although this suggested that the organic material was of a higher quality, the seston was "masked" by a higher suspended inorganic load. Consequently, the organic fraction comprised between 13 and 22% of total particulate material in the Great Fish estuary, compared with between 20 and 39% in the Kariega estuary. Food resources demonstrated a fairly uniform distribution along the length of the Kariega estuary and exhibited a slight seasonal increase during warmer months. By contrast, the point source influence of freshwater inflow resulted in a spatial gradient of food resources in the Great Fish estuary with higher values recorded towards the upper reaches. There was evidence that higher concentrations of particulate material in the upper reaches are also a consequence of hydrodynamic trapping. There was no marked seasonal pattern in the availability of food resources which were generally elevated in response to sporadic pulses of freshwater inflow. Tidal currents were responsible for elevating suspended food resources by re-suspension of material from the sediments. This effect was probably of greater importance in the Kariega estuary where food resources were generally limiting. In the Kariega estuary, the zooplankton community was dominated by calanoid copepods of the genera Acartia and Pseudodiaptomus. However, in the Great Fish estuary, the community was dominated by the mysid Mesopodopsis siabberi, and the calanoid P. hessei. Community biomass generally reflected the trophic status of the estuary. The mean seasonal biomass recorded in the Kariega estuary was 38 mg m⁻³ compared with 1597 mg m⁻³ in the Great Fish estuary. Greater spatial variability in community biomass was evident in the Great Fish estuary, partly in response to the food resource gradient, but also due to the inability of the mysid shrimps, which dominated the community biomass, to penetrate the lower salinity water of the upper reaches. Zooplankton in the Kariega estuary demonstrated a seasonal pattern of abundance whereas in the Great Fish estuary, community biomass was elevated in response to sporadic pulses of freshwater inflow. Grazing rates, measured in situ using a modified Gliwicz-Haney chamber, indicated that the zooplankton communities were capable of "clearing" substantial proportions of the watercolumn at certain times of the year. The pattern of grazing pressure over a diel cycle was examined in relation to the diel vertical migration movements of the zooplankton. Higher nighttime grazing rates were generally associated with the greater abundance of zooplankton resulting from the movement of zooplankton into the watercolumn after dusk, and their return to the sediments at dawn. Seasonal estimates of diel grazing pressure, extrapolated from daytime and nighttime feeding rates, indicated that the zooplankton "cleared" up to 40% of the watercolumn in a day in the Kariega estuary, and up to 120% d⁻¹ in the Great Fish estuary. However, values of around 25% d⁻¹ in the Kariega estuary, and 50 to 80% d⁻¹ in the Great Fish estuary, were not uncommon. Multiple regression analyses were used in an attempt to explain the influence of environmental factors on the variation in in situ grazing rates. These attempts were largely unsuccessful and the possible reasons, as well as recommended improvements to the methods used, are discussed. Seston concentration in the estuaries was highly variable as a result of the effects of tidal re-suspension and freshwater inflow. Consequently, further laboratory-based experiments were carried out to examine the influence of seston concentration on the filtration rates of the dominant calanoid copepods. Results indicated that some of the unexplained variability in the community filtration rates may be attributed to differences in species-specific response to changes in seston concentration.
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  • Date Issued: 1993

The influence of geological, genetic and economic factors on the ore reserve estimation of Kwaggashoek east iron ore deposit

  • Authors: Latorre-Muzzio, Gina
  • Date: 1993
  • Subjects: Iron ores -- Geology -- South Africa , Geology -- South Africa -- Transvaal
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4972 , http://hdl.handle.net/10962/d1005584 , Iron ores -- Geology -- South Africa , Geology -- South Africa -- Transvaal
  • Description: Tectonics plays an important role in the genesis and subsequent mlnlng development of the Kwaggashoek East ore body. Lithological key units control the effectiveness of the ore forming processes, affecting the in situ ore reserve, The Kwaggashoek East deposit is the product of primary and secondary processes. A genetic model focussed on the source, migration and deposition of iron suggests a possible original source of iron as the product of very dilute hydrothermal input into deep ocean waters, with subsequent migration through structural conduits. Supergene processes account for the upgrading of the ore and the phosphorus redistribution. A good correlation between samples in a preliminary geostatistical study reflects the effectiveness of this process in the high grade ore zone. A broad overview of the economic issues which affect the commercialization of iron, indicates a balanced supply-demand situation for the five next years. The reserve estimation procedure requires accurate scientific terminology and appropriate methodology. Documentation is essential and should be detailed enough to allow for future reassessment. The results of three estimation methods in Kwaggashoek East differ by less than 5%. The accuracy of the final results depends more on geological interpretation and assumptions than on the method applied. Although optimization of grade and tonnage in the Kwaggashoek East deposit seems to be met with the actual cut-off grade used in the Thabazimbi mine district, the grade-quality concept introduced in this thesis indicates a decrease in the estimated reserves for the deposit
  • Full Text:
  • Date Issued: 1993

The integration of academic skills/support programmes into university department structures: a case study in the sociology of education

  • Authors: Drewett, Michael
  • Date: 1993
  • Subjects: Education, Higher -- South Africa , Compensatory education -- South Africa , Education, Higher , Education -- Philosophy , Rhodes University. Academic Development Programme
  • Language: English
  • Type: Thesis , Masters , MSocSc
  • Identifier: vital:3327 , http://hdl.handle.net/10962/d1003115
  • Description: This research focuses on the extent to which the Rhodes University Academic Skills Programme (ASP), now known as the Academic Development Programme, is able to act as an agent of progressive change within Rhodes University. In so doing it concentrates on the potential of the strategy of integrated academic development for dealing with the academic needs of university students within the context of South Africa as a society in transition. The candidate considers the inability of structuralist educational theory to account for the potential of human agency at the site of formal education. It is shown that structuralist theories provide deterministic and pessimistic accounts of the role of institutions of formal education. In support of this contention this study explores the history of ASP at Rhodes University, demonstrating that significant change in student academic development has already taken place. ASP has contributed to change within the said University through challenging traditional notions of academic development. This thesis suggests that the non-structuralist critical theory of Jurgen Habermas provides a more holistic account of ASP than do structuralist theories of formal education. Through the incorporation of Habermas's theory of communicative action a process of critical integration is explored, showing that a strategy of integrated academic development has the potential to involve all those who have an interest in university education through a process of rational discourse. This potential is strengthened by the fact that many students and staff have expressed an awareness of the need for an integrated academic development strategy. This thesis subsequently explores the possibility of there being a process of democratic and rational discourse which could lead to a progressive integration programme in the Rhodes University Department of Sociology and Industrial Sociology. This thesis stresses the contested nature of the integration process within departments. It is indicated that Habermas's critical theory is able to account for the changes which have taken place in the past and which are presently under way. It is argued that it not possible to predict future outcomes, but that if ASP pursues a process of rational discourse, it will indeed be able to stimulate a critical integrative approach to academic development in the Rhodes University Department of Sociology and Industrial Sociology.
  • Full Text:
  • Date Issued: 1993
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