Showing items 81 - 100 of 153

Your selections:

Interspecific interactions of the sea urchin Parechinus angulosus and the effect of variations in microhabitat availability

  • Authors: Farquhar, Michael Robert
  • Date: 1995
  • Subjects: Sea urchins , Niche (Ecology) , Sea urchins -- Habitat
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5720 , http://hdl.handle.net/10962/d1005406 , Sea urchins , Niche (Ecology) , Sea urchins -- Habitat
  • Description: Intertidal populations of the sea urchin Parechinus angulosus were examined at seven sites along the south and east coasts of South Africa. At the five southerly sites, P. angulosus occurred in allopatry, while, at the two northerly sites, it occurred in sympatry with several species of Indopacific sea urchins. At the five southerly sites, there was a significant correlation of number of sea urchins per pool with the surface area of the overhang in that pool. This relationship broke down for P. angulosus at the two northerly sites, where there was a significant correlation between these two factors for Stomopneustes variolaris. The density of populations of P. angulosus at the two northerly sites, although not significantly different from all five southerly sites, were considerably lower. There was a significant difference between the mean size of populations at the seven sites. Although no direct evidence is available, a competitive interaction between these two species is proposed to explain the observed patterns of microhabitat utilization and densities. Two series of manipulative experiments were conducted at Kowie Point, where P. angulosus occurs in sympatry, The first, involved urchin removals from three experimental sites. The percentage cover of four functional algal groups was monitored in three experimental and three unaltered control sites over a three month period in spring (Sept. - Dec.) 1993. Two 100 point 0,25m² random point quadrats were thrown at each of the six sites at approximately monthly intervals over the experimental period. Since initial cover of algae varied at the six sites, ANOVA's of the change in percentage cover of four functional algal groups were used to determine treatment effects. No treatment effects were identified for any of the four functional algal groups. There was a strong negative correlation between the percentage cover of foliose algae and encrusting coralline algae, suggesting the possibility of a competitive relationship between them. The second, involved the experimental manipulation of microhabitat availability. The blocking of overhangs, by means of cement filled bags, resulted in an approximate 50% decrease in the total number of urchins in the two experimental pools, and the two control pools without overhangs. However, in the control pool with overhangs there was a slight increase in the number of urchins over the same period. Clearly, the presence of suitable shelters, is a prerequisite for the maintenance of dense intertidal population of P. angulosus. It is proposed that, due to the exposed nature of the South African coast, intertidal populations of P.angulosus are restricted to inhabiting suitable shelters from which they emerge to feed on passing drift algae. The implications of these findings are discussed in terms of current ecological literature.
  • Full Text:
  • Date Issued: 1995

Kele Magni

Late Devonian charophytes from the Witteberg Group, South Africa

  • Authors: Gess, Robert W , Hiller, Norton
  • Date: 1995
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/72742 , vital:30106 , https://doi.org/10.1016/0034-6667(95)00007-8
  • Description: The first record of Palaeozoic charophytes from southern Africa allows the establishment of two new genera to which are assigned four new species, Octochara crassa, O. gracilis. Hexachara setacea, and H. riniensis. Each species is represented by both vegetative and reproductive structures and suggested reconstructions are presented. Associated plant and animal remains, and the sedimentology and geochemistry of the containing rocks indicate that the charophytes probably grew in the shallow parts of a brackish coastal lagoon.
  • Full Text: false
  • Date Issued: 1995

Letter of support

  • Date: 1995 , 2022-09-23
  • Subjects: Bam, Brigalia
  • Language: English
  • Type: realia
  • Identifier: http://hdl.handle.net/10948/56694 , vital:56881
  • Description: Framed letter of support for Dr. Brigalia Bam from the Anglican Archbishop of Cape Town, Reverend Desmond M. Tutu. Dr. Bam was appointed as General Secretary of the South African Council of Churches in 1995. , Donated/gifted to Nelson Mandela University Archives , Forms part of: Brigalia Bam collection
  • Full Text: false
  • Date Issued: 1995

Maou Leye Mara

Mastri

NALEDI research report - Missing the target

  • Authors: NALEDI
  • Date: 1995
  • Subjects: NALEDI
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/174032 , vital:42433
  • Description: The Reconstruction and Development Programme (RDP) was developed by the African National Congress (ANC) prior to entering government. The RDP was developed as an integrated and coherent socio-economic policy framework aimed at transforming South African society. Within this framework the ANC, as the majority party in the Government of National Unity (GNU), undertook to develop detailed policy positions and a legislative programme.
  • Full Text:
  • Date Issued: 1995

NEDLAC and the goals of labour

  • Authors: COSATU
  • Date: 1995
  • Subjects: COSATU
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/176145 , vital:42663
  • Description: The launch of NEDLAC offers a unique opportunity to our country - a chance to rebuild the economy and society through a consensus forged among workers, investors, government and the community. The road to that consensus will, no doubt, be stormy and rocky. You cannot bring together Jabu Xulu, earning R200.00 per week, after working for 15 years, with a family of five to feed; and John Smith, the Chief Executive Officer of a major conglomerate, earning R20 000.00 per week, and expect that it will be a calm and easy process.
  • Full Text:
  • Date Issued: 1995

Nedlac Constitution

  • Authors: NEDLAC
  • Date: 1995
  • Subjects: NEDLAC
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/151654 , vital:39157
  • Full Text:
  • Date Issued: 1995

New tricks for the newspaper trade : an old watchdog meets press freedom and the information age : inaugural lecture delivered at Rhodes University

NUM guide to the Labaour relations Act of 1995

  • Authors: NUM
  • Date: 1995
  • Subjects: NUM
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/168140 , vital:41544
  • Full Text:
  • Date Issued: 1995

Parental preferences regarding medium of instruction in primary schools in the Nongoma district of Kwazulu-Natal

  • Authors: Mhlanga, Samkelisiwe Isabel
  • Date: 1995
  • Subjects: Native language and education -- South Africa Language and education -- South Africa Education -- Parent participation -- South Africa Language policy -- South Africa
  • Language: English
  • Type: Thesis , Masters , MEd
  • Identifier: vital:1686 , http://hdl.handle.net/10962/d1003569
  • Description: This thesis looks at what choice of medium of instruction (MOl) parents in a rural village in KwaZulu would make if they had the opportunity to choose. The background to this choice goes back to 1979, when Education and Training Act No. 90 established the mother tongue as MOl from Sub A to Std 2 in Department of Education and Training (DET) primary schools, followed by a sudden transition to English medium of instruction - (EMl) in Std 3. Though by 1990 98% of the schools had opted for EMI, conditions were not favourable for a sudden transition and the policy led to high drop-out rates. The problems encountered by teachers and learners were researched and documented by Macdonald in the Threshold Project Reports (1990). Although the Minister initially ignored the Project's findings, in May 1991 he admitted that his department's language policy was leading to serious educational disadvantages. The explosive situation that culminated in the 1976 school uprisings led to the amendment of the Act. There was concern among people involved in educational language policy that parents had not been given sufficient information to make informed educational choices. They feared that many parents would, largely out of ignorance, opt for straight-for-English, when in fact the conditions in the schools were not conducive to the success of that choice option. The widespread assumption about the parents choosing straight-for-English was based on anecdotal evidence. I decided to investigate this matter in the Nongoma area. My findings pointed to very healthy attitudes towards the mother tongue and there was even a measure of understanding of the place of mother tongue instruction in the beginner classes. But even though the respondents wanted their language to be respected, they also wanted their children to acquire a good education in English, so as to be eligible for jobs in an economy that emphasises the importance of English.
  • Full Text:
  • Date Issued: 1995

Patterns of distribution and conservation status of freshwater fishes in South Africa

  • Authors: Skelton, Paul H , Cambray, James A , Lombard A , Benn, G
  • Date: 1995
  • Subjects: To be catalogued
  • Language: English
  • Type: text , article
  • Identifier: http://hdl.handle.net/10962/447318 , vital:74610 , https://hdl.handle.net/10520/AJA00445096_904
  • Description: The combined fish collection databases of the Albany Museum and the J.l.B. Smith Institute of Ichthyology are used to identify hotspots of endemism and threatened fish distributions in South Africa. Hotspots of fish species richness occur in the north-eastern lowveld sectors of South Africa and along the ecotone between the tropical/ subtropical and temperate faunal zones. Hotspots of endemic fish richness occur within both the tropical and temperate faunal regions, notably in the Olifants River system, Western Cape and in areas of high relief such as the Cape Fold Mountains, the Amatola-Winterberg (Eastern Cape), and the Drakensberg Escarpment (Kwazulu/ Natal-Eastern Transvaal). Threatened taxa are concentrated in the hotspots of endemic species richness which coincide largely with areas of major river conservation concern. There is limited scope for fish conservation within the ambit of formal (or informal) declared reserves, and the survival of the fauna depends on the success of river catchment conservation management. The value of museum collections in identifying areas of conservation concern for freshwater fishes is emphasized, and highlights the importance of well-preserved voucher specimens for biodiversity conservation.
  • Full Text:
  • Date Issued: 1995

Petrogenesis of the New Amalfi sheet a highly differentiated Karoo intrusion

  • Authors: Williams, Craig Milton
  • Date: 1995
  • Subjects: Petrogenesis -- South Africa -- Eastern Cape -- Karoo , Geochemistry -- South Africa -- Eastern Cape -- Karoo
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4985 , http://hdl.handle.net/10962/d1005597 , Petrogenesis -- South Africa -- Eastern Cape -- Karoo , Geochemistry -- South Africa -- Eastern Cape -- Karoo
  • Description: The New Amalfi Sheet is a highly differentiated tholeiitic intrusion which is situated between the towns of Matatiele and Swartberg in East Griqualand. It lies within the Central area of the Karoo Igneous Province. Rock types range from dolerites at the base and top through to a highly differentiated granophyre which is found as a 'sandwich horizon' within the top half of the sheet. The most evolved granophyre represents 15.86% of the initial liquid, which was found to be very similar in composition to the average Lesotho-type magma of Marsh and Eales (1984). The paragenetic sequence was found to be chromite → olivine → plagioclase → pigeonite and augite. Cumulus magnetite and ilmenite enter the paragenetic sequence together with immiscible sulphide droplets after 35% crystallization. In the late stages of crystallization, augite changes composition towards ferrohedenbergite. The reappearance of iron-rich olivine coincides with the disappearance of pigeonite and apatite appears as a cumulus phase for the first time after 70% crystallization. Granophyric intergrowth, which contains coarse perthitic Kfeldspar, becomes the most abundant modal entity within the most evolved granophyres. Differentiation was dominated by fractionation of plagioclase and pyroxene, with subordinate olivine and opaque-oxide fractionation. A minor amount of assimilation of country rock occurred within the topmost granophyres. The intrusion has been dated, using the Rb-Sr isochron method, at 178.37 ± 5.52 Ma. Extensive subsolidus deuteric alteration has resulted in the formation of a complete series of hydrothermally altered clinopyroxenes which are enriched in CaO but depleted in TiO₂ compared to the unaltered magmatic clinopyroxenes. It has also resulted in the formation of abundant vermiform ilmenite in the most evolved rocks, recognized by the fact that this phase is enriched in MnO compared to magmatic ilmenites. The very iron-rich orthopyroxene, ferrohypersthene, was found to have crystallized, during cooling of the sheet from the intercumulus liquid. Olivine in the dolerite re-equilibrated with the intercumulus liquid, becoming more iron-rich in composition.
  • Full Text:
  • Date Issued: 1995

Physiological signal transduction from the photosynthetic apparatus in the green alga Dunaliella salina

  • Authors: Logie, Malcolme Ronald Ruxton
  • Date: 1995
  • Subjects: Cellular signal transduction Photosynthesis -- Research Green algae Dunaliella
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4035 , http://hdl.handle.net/10962/d1004095
  • Description: The transduction of stress signals in plants is known to involve complex hysiological responses. In D. salina a range of stresses results in hyperaccumulation of ft-carotene and an understanding of stress responses in this organism has important biotechnological implications. In this thesis an attempt was made to elucidate the physiological components involved and establish a role for pH in response to high light stress. In order to achieve this the effect of high light stress on photosynthesis and cell productivity was measured. Results showed that photosynthetic carbon assimilation, oxygen evolution and cellular productivity was initially inhibited by exposure to high light intensities, but this inhibition was transient and was overcome by a rapid increase in all three parameters. The response of the carbon pool intermediates was also investigated. It was shown that on exposure to high light ft-carotene declined but then showed a rapid increase after about 4 hours of exposure. It was also demonstrated that the initial loss of ft-carotene was due to loss of this pigment from the photosynthetic pigment bed and that the hyper-accumulation of ft-carotene was due to accumulation of ft-carotene in lipoidal globules located in the chloroplast stroma. It was further demonstrated that there was mass movement of carbon in the xanthophyll cycle shortly after exposure to high light. This was characterized by the de-epoxidation of violaxanthin to antheraxanthin with a further de-epoxidation to zeaxanthin, thereby decreasing the epoxidation state of the cycle. Furthermore, it was shown that there was relocation of carbon from violaxanthin to the plant growth regulator abscisic acid. It was also shown for the first time in D. salina that the production of ft-carotene and operation of the epoxidation state of the xanthophyll cycle has a periodicity which is established after exposure to successive cycles of a light regime. Chlorophyll fluorescence was used together with well established ammonia stress responses to acquire a general overview of energy dissipation from the photosynthetic pigment bed. In conjunction with an understanding of xanthophyll cycle operation during exposure to high light stress it has been possible to establish a relationship between chlorophyll florescence, xanthophyll cycle operation and intracellular pH. It was also shown using chlorophyll fluorescence that after 4 hour exposure to high light a maximum fluorescence peak could no longer be induced indicating a transition at about this point from a state of reversibility to commitment of the full stress response. Nuclear magnetic resonance was used to follow intracellular pH fluxes during exposure to high light. A novel technique was developed for studying photosynthetically active organisms in the dark using nuclear magnetic resonance. These results showed that on exposure to high light stress there is rapid acidification of the chloroplast stroma and to a lesser degree of the acidic vacuole. The pH of these compartments is re-established after about 4 hours which is co-incident with the onset of fl-carotene hyper-accumulation and the loss of the induction of the chlorophyll fluorescence peak indicating an intimate relationship for fl-carotene, chlorophyll fluorescence, xanthophyll cycle operation and pH. The results from this study allow for the proposal of a general physiological stress transduction response mechanism for D. salina which is common for a range of different stresses and where intracellular pH plays a central role.
  • Full Text:
  • Date Issued: 1995

Physiological, perceptual and performance responses to competitive stress in individual and team sports among youth sport participants

  • Authors: Swart, Kamilla
  • Date: 1995
  • Subjects: Sports -- Psychological aspects , Competition (Psychology) in adolescence -- Testing , Stress in adolescence -- Testing , Anxiety in adolescence -- Testing
  • Language: English
  • Type: Thesis , Masters , MA
  • Identifier: vital:5169 , http://hdl.handle.net/10962/d1016257
  • Description: Due to limited research in the field testing of youth sport, specifically with regard to females, this project was delimited to the examination of the responses of youth participants in relation to the nature of the sport, when participating under conditions of competitive stress. It further attempted to elucidate gender related differences within these responses. Forty four male and female subjects aged 15 - 19 years volunteered to participate in this study; all pupils were First team members who competed in a variety of team and individual sports. Subjects participated in a battery of psychological, physiological and performance tests before and after competing in a practice session and during competitive league matches. The data were statistically analyzed for the various parameters under investigation. The results of the Sport Competition Anxiety Test indicated that the females, and the male team players had the highest competitive anxiety traits (CTA). The Task and Ego Orientation in Sport Questionnaire scores showed that most subjects have a general dominance of task orientation to sport. The results of the Physical Self-Perception Profile revealed that the females' poorer perception of their physical was not as substantial as their difference in CTA compared to males. Team participants, particularly the males, had a poorer self-image than individual sport counterparts. Elevated heart rate responses were observed prior to performing in a competitive ambience, with significant increases in team, rather than individual, players. The Evaluation of Task Demands revealed that team players, especially the females, perceived the match demands as significantly higher than the individual athletes. No significant differences were observed in the players' Evaluation of Perceived Strain. Neither were any significant differences observed in the players' ratings of their performance. In conclusion, although differences appear to exist between male and female responses within a competitive ambience, the magnitude of difference was far more notable between team and individual responses to competitive stress, particularly for competitive matches as opposed to practice sessions.
  • Full Text:
  • Date Issued: 1995

Policy Memo - Renegotiating the SACU agreement

  • Authors: NALEDI
  • Date: 1995
  • Subjects: NALEDI
  • Language: English
  • Type: text
  • Identifier: http://hdl.handle.net/10962/151381 , vital:39062
  • Description: South Africa is in the process of renegotiating the Southern African Customs Union Agreement with Botswana, Lesotho, Namibia and Swaziland. The origins of the Agreement date back to 1889 making this one of the world’s oldest customs union agreements. The present version of the Act dates back to 1969. Since that time various conflicts have arisen between member countries regarding the objectives and operations of the agreement. Given the new political situation and the changing international trade climate, a decision has been made to renegotiate the agreement entirely. Discussions are now underway and these are being co-ordinated through the Customs Union Task Team which comprises representatives of the various countries. The South African government, through the Department of Trade and Industry recently held a workshop in order to brief interested parties. Parties have been invited to comment on the process and the Department has agreed to involve the Nedlac Trade and Industry chamber in any decision about the future of SACU.
  • Full Text:
  • Date Issued: 1995

Progestin receptor heterogeneity in a breast cancer cell line

  • Authors: Levy, Anita Rochelle
  • Date: 1995
  • Subjects: Breast -- Cancer , Hormone receptors , Cancer cells -- Growth -- Regulation , Progesterone -- Receptors , Cellular control mechanisms
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4039 , http://hdl.handle.net/10962/d1004100 , Breast -- Cancer , Hormone receptors , Cancer cells -- Growth -- Regulation , Progesterone -- Receptors , Cellular control mechanisms
  • Description: Anti-oestrogens act via the oestrogen receptor whether they compete with the hormone for binding to the receptor and therefore interfere with DNA binding or inhibit transcriptional activity. These receptors exist as a large 85 complex and/or a small 45 form on sucrose density gradients. High performance ion-exchange chromatography has confirmed that the oestrogen and progestin complex is present in various isoforms. Progestin receptor heterogeneity could be influenced by the presence of oestrogens and anti-oestrogens in the culture media of hormone-dependent neoplastic cells. Cell culture methods offer the opportunity to test effects of specified components in repeated experiments on a homogeneous population of cells. MCF-7 and T47-D human breast cancer cell lines were conditioned to grow in a serum-free environment. There was no difference in cell proliferation rates, nor in their oestrogen or progestin receptor levels when compared to the same cells grown in conventional media. Receptors were present mainly in the large molecular 85 form. Both the MCF-7 and T47-D breast cancer cells showed an increase in proliferation rate with the addition of oestrogen or diethylstilbestrol. There was a corresponding loss of progestin receptor levels and an alteration in the high performance ion-exchange isoforms. Flow cytometry confirmed differences in the S-phase components of the cells following exposure to oestrogens. The proliferation rates of the cell lines as well as their progestin receptor levels decreased when treated with tamoxifen or the hydroxylated tamoxifen. There were marked changes on high performance ion-exchange chromatography profiles. DNA ploidy and S-phase showed signs of toxicity and there was an increase in cellular debris. The MCF-7 and T47-D human breast cancer cell line retained response to antioestrogen saturation.
  • Full Text:
  • Date Issued: 1995

Prosocial behaviour in South African students a qualitative enquiry

  • Authors: Cholerton, Steven M
  • Date: 1995
  • Subjects: Helping behavior , Interpersonal relations , Altruism , Social ethics , College students -- South Africa -- Attitudes
  • Language: English
  • Type: Thesis , Masters , MCom
  • Identifier: vital:2948 , http://hdl.handle.net/10962/d1002457 , Helping behavior , Interpersonal relations , Altruism , Social ethics , College students -- South Africa -- Attitudes
  • Description: The central aim of this study was to conduct a qualitative exploration of the prosocial inclinations possessed by young South African students. The literature review argues that traditional approaches to moral responding separate the individual from the social. An alternative approach that reinstates language and ideology is delineated. It is argued that such a paradigm is most appropriate to a study of prosocial responding during a period of social change. Hypothetical moral dilemmas were administered to twenty-nine students. Six students were selected and each was interviewed on two separate occasions. In this way six case studies were developed. The methodological traditions of phenomenology and hermeneutics were employed to analyze the protocols and subsequent interviews. Seven themes descriptive of a moral response were identified. These consisted of moral reasoning, empathy, mood, guilt, alienation, a sense of group-identity, and ambiguity regarding the relative interests of self versus other. These themes are fully discussed in terms of the literature. It is concluded that moral reasoning may be insufficient to motivate prosocial behaviour. Conventional moral narratives may be appropriated in order to make sense of conflicting emotions. Empathy was identified as a necessary but not sufficient condition for a prosocial response. Empathy might translate into either sympathy or personal distress. Mood was found to largely dictate attentional focus. Alienation was found to be a defensive formulation that inhibits the emergence of sympathy. Guilt might precipitate an alienated posture. It was found that guilt might be attributed to group-identity and thereby denied. Tension between a self- and other-oriented response, or between blame and sympathy, was common. It is suggested that this ambiguity reflects ideological contradictions that have been internalized. It is postulated that during periods of social change such contradictions are accentuated.
  • Full Text:
  • Date Issued: 1995

Reactions of iron- and zinc-fuelled pyrotechnic systems

  • Authors: Tribelhorn, Michael John
  • Date: 1995
  • Subjects: Detonators Peroxides Chemistry, Analytic
  • Language: English
  • Type: Thesis , Doctoral , PhD
  • Identifier: vital:4341 , http://hdl.handle.net/10962/d1005003
  • Description: A major industrial use of pyrotechnic compositions is as delay fuses in electric detonators. Suitable delay times may be achieved through (i) choice of chemical components (ii) adjustment of composition of the system chosen and, finally, (iii) adjustment of the length of fuse used. This study forms part of a survey of binary fuel/oxidant combinations in an attempt to provide some fundamental information on the first step above: (i) choice of chemical components. The complete survey has included studies of a single fuel in combination with one of a variety of oxidants, and studies of the oxidation of one of several different fuels separately by barium peroxide and strontium peroxide. This study is part of this second approach and the fuels chosen were iron and zinc powders, mainly for chemical reasons (including the potential for use of thermomagnetometry on the iron systems), but also for possible environmental advantages. The mixed oxide products of pyrotechnic combustion could also have some scientific and/or commercial value. The techniques used included thermal analyses of mixtures and their individual components, and measurements of temperature-time profiles during combustion. Thermodynamic and kinetic information was obtained under a variety of conditions and scanning electron microscopy and X-ray diffraction and microprobe analyses provided additional information. Possible mechanisms of reactions are discussed in detail. The practical conclusions were that any potential use which the Fe/peroxide systems may have as delay compositions, with burning-rates of from 3-30 mm s⁻¹, is offset by the susceptibility of the oxidants to reaction with water and CO₂ in the atmosphere. The Zn/BaO₂ and Zn/SrO₂ systems did not burn under compaction, and combustion of uncompacted powders was erratic. Zinc liquid (and probably zinc vapour) take part in the reaction and the gaseous nature of the combustion makes zinc-fuelled pyrotechnic systems unsuitable for delay applications. All the techniques used showed the heterogeneity of the solid residues of combustion. If these residues were to be of any value, they would need further conventional treatment involving grinding of the residue, possible adjustment of compositions, and calcining to produce uniform materials.
  • Full Text:
  • Date Issued: 1995
  • Disclaimer
  • Privacy
  • Copyright
  • Contact