Serotonin-melatonin interactions in acetaminophen and N,N-dimethylformamide toxicity
- Anoopkumar-Dukie, Shailendra
- Authors: Anoopkumar-Dukie, Shailendra
- Date: 2000
- Subjects: Serotonin , Acetaminophen , Melatonin
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3898 , http://hdl.handle.net/10962/d1003957 , Serotonin , Acetaminophen , Melatonin
- Description: Acetaminophen and N,N-dimethylformamide (DMF) are compounds which are extremely toxic to the liver. Acetaminophen is a drug which is well known for its analgesic and antipyretic properties. However, the abuse potential of this agent as a non-narcotic analgesic in alcoholics is well known. It is also the leading cause of overdose in England. DMF toxicity results mainly from occupational exposure. At present there are no known reports of an antidote for DMF poisoning, while N-acetylcysteine, the antidote for acetaminophen poisoning, is known to produce adverse effects. The present study evaluates the potential of melatonin as an antidote for acetaminophen and DMF poisoning. This study also investigates the mechanism underlying acetaminophen addiction and abuse. Initial studies involved in vitro techniques in an attempt to remove the complexities of organ interactions. The photodegradation studies, using ultraviolet (UV) light, revealed that melatonin accelerates the rate of acetaminophen degradation in the presence of air, and reduces the rate of degradation in the presence of nitrogen. This study also revealed that melatonin is rapidly degraded in the presence of air, following UV irradiation. The effect of DMF on hydroxyl radical generation was also determined. DMF was shown to act as a free radical scavenger, rather that a generator of free radicals. The in vitro studies were followed by lipid peroxidation determination. DMF (0.4ml/kg and 0.8ml/kg) did not produce any significant increases in lipid peroxidation in the liver. Three different doses of acetaminophen (30mg/kg, 100mg/kg, and 500mg/kg) were administered to rats for seven days. Acetaminophen (500mg/kg) was shown to significantly increase (p<0.05) lipid peroxidation in the liver. Melatonin (2.5mg/kg) was not able to significantly reduce the damage. The lower doses of acetaminophen (30mg/kg and 100mg/kg) did not increase lipid peroxidation. Electron microscopy studies showed that DMF adversely affects the liver, and in particular, the endoplasmic reticulum. Co administration of melatonin (2.5mg/kg) was able to reduce the damage. Further experiments need to be performed before an accurate assessment can be made on the ability of melatonin as an antidote for DMF and acetaminophen poisoning. Several experiments were done in an attempt to uncover the biochemical mechanism underlying acetaminophen addiction and abuse. The first experiment targeted the liver enzyme tryptophan-2,3-dioxygenase (TDO). This enzyme is the major determinant of tryptophan levels in vivo. Acetaminophen administration (100mg/kg for three hours) was shown to significantly inhibit (p<0.05) the activity of TDO, indicating increased peripheral levels of tryptophan. This experiment was followed up with determination of brain serotonin and pineal melatonin. Brain serotonin was determined using the ELISA technique. Melatonin was estimated using this technique as well as with pineal organ culture. Acetaminophen administration (100mg/kg for three hours) significantly increased (p<0.05) brain serotonin levels. Using organ culture where exogenous (3H) tryptophan is metabolised to (3H) melatonin, acetaminophen (100mg/kg for three hours) was shown to significantly increase (p<0.05) pineal melatonin concentrations. However, the ELISA technique did not reveal any changes in endogenous pineal melatonin levels. The final experiment was the determination of urinary 5-hydroxyindole acetic acid (5- HIAA), the major metabolite of serotonin, following acetaminophen administration (100mg/kg for three hours). Acetaminophen was shown to significantly reduce 5-HIAA levels (p<0.05) suggesting reduced catabolism of serotonin. The findings of this study indicate that acetaminophen mimics the actions of an antidepressant. This compelling finding has important clinical implications, and needs to be examined further.
- Full Text:
- Authors: Anoopkumar-Dukie, Shailendra
- Date: 2000
- Subjects: Serotonin , Acetaminophen , Melatonin
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3898 , http://hdl.handle.net/10962/d1003957 , Serotonin , Acetaminophen , Melatonin
- Description: Acetaminophen and N,N-dimethylformamide (DMF) are compounds which are extremely toxic to the liver. Acetaminophen is a drug which is well known for its analgesic and antipyretic properties. However, the abuse potential of this agent as a non-narcotic analgesic in alcoholics is well known. It is also the leading cause of overdose in England. DMF toxicity results mainly from occupational exposure. At present there are no known reports of an antidote for DMF poisoning, while N-acetylcysteine, the antidote for acetaminophen poisoning, is known to produce adverse effects. The present study evaluates the potential of melatonin as an antidote for acetaminophen and DMF poisoning. This study also investigates the mechanism underlying acetaminophen addiction and abuse. Initial studies involved in vitro techniques in an attempt to remove the complexities of organ interactions. The photodegradation studies, using ultraviolet (UV) light, revealed that melatonin accelerates the rate of acetaminophen degradation in the presence of air, and reduces the rate of degradation in the presence of nitrogen. This study also revealed that melatonin is rapidly degraded in the presence of air, following UV irradiation. The effect of DMF on hydroxyl radical generation was also determined. DMF was shown to act as a free radical scavenger, rather that a generator of free radicals. The in vitro studies were followed by lipid peroxidation determination. DMF (0.4ml/kg and 0.8ml/kg) did not produce any significant increases in lipid peroxidation in the liver. Three different doses of acetaminophen (30mg/kg, 100mg/kg, and 500mg/kg) were administered to rats for seven days. Acetaminophen (500mg/kg) was shown to significantly increase (p<0.05) lipid peroxidation in the liver. Melatonin (2.5mg/kg) was not able to significantly reduce the damage. The lower doses of acetaminophen (30mg/kg and 100mg/kg) did not increase lipid peroxidation. Electron microscopy studies showed that DMF adversely affects the liver, and in particular, the endoplasmic reticulum. Co administration of melatonin (2.5mg/kg) was able to reduce the damage. Further experiments need to be performed before an accurate assessment can be made on the ability of melatonin as an antidote for DMF and acetaminophen poisoning. Several experiments were done in an attempt to uncover the biochemical mechanism underlying acetaminophen addiction and abuse. The first experiment targeted the liver enzyme tryptophan-2,3-dioxygenase (TDO). This enzyme is the major determinant of tryptophan levels in vivo. Acetaminophen administration (100mg/kg for three hours) was shown to significantly inhibit (p<0.05) the activity of TDO, indicating increased peripheral levels of tryptophan. This experiment was followed up with determination of brain serotonin and pineal melatonin. Brain serotonin was determined using the ELISA technique. Melatonin was estimated using this technique as well as with pineal organ culture. Acetaminophen administration (100mg/kg for three hours) significantly increased (p<0.05) brain serotonin levels. Using organ culture where exogenous (3H) tryptophan is metabolised to (3H) melatonin, acetaminophen (100mg/kg for three hours) was shown to significantly increase (p<0.05) pineal melatonin concentrations. However, the ELISA technique did not reveal any changes in endogenous pineal melatonin levels. The final experiment was the determination of urinary 5-hydroxyindole acetic acid (5- HIAA), the major metabolite of serotonin, following acetaminophen administration (100mg/kg for three hours). Acetaminophen was shown to significantly reduce 5-HIAA levels (p<0.05) suggesting reduced catabolism of serotonin. The findings of this study indicate that acetaminophen mimics the actions of an antidepressant. This compelling finding has important clinical implications, and needs to be examined further.
- Full Text:
Settler women's experiences of fear, illness and isolation, with particular reference to the Eastern Cape Frontier, 1820-1890
- Authors: Dampier, Helen
- Date: 2000
- Subjects: Women -- South Africa -- History , Women -- South Africa -- Eastern Cape -- Social conditions , Women -- South Africa -- Eastern Cape -- History , British settlers of 1820 (South Africa) , Frontier and pioneer life -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2537 , http://hdl.handle.net/10962/d1002389 , Women -- South Africa -- History , Women -- South Africa -- Eastern Cape -- Social conditions , Women -- South Africa -- Eastern Cape -- History , British settlers of 1820 (South Africa) , Frontier and pioneer life -- South Africa
- Description: This thesis is an exploration of diaries and letters written by middle-class English-speaking settler women living on the Eastern Cape frontier between 1820 and 1890. By according primacy to these women’s experiences and perceptions, it aims for a greater understanding of women’s encounters with the frontier, and how these were articulated in their personal writing. An emphasis on the recurrent themes of ill-health, fearfulness and solitude undermines the popular myth of the brave, conquering, invincible pioneers which dominates settler historiography to date. The tensions felt by white women living on the frontier disrupted their identities as middle-class Victorian ‘ladies’, and as a result these women either constantly re-established a sense of self, or absorbed some aspects of the Eastern Cape, and thus redefined themselves. Settler women’s experiences of the frontier changed little during the seventy year period spanned by this study, indicating that frontier life led to a rigidification and reinforcement of old, familiar values and behaviours. Rather than adapting to and embracing their new surroundings, settler women sought to duplicate accepted, conventional Victorian ideals and customs. White Victorian women identified themselves as refined, civilized, moral and respectable, and perceived Africa and Africans as untamed, immoral, uncivilized and threatening. To keep these menacing, destabilizing forces at bay, settler women attempted to recreate ‘home’ in the Eastern Cape; to domesticate the frontier by rendering it as familiar and predictable as possible. The fear, illness and solitariness that characterise settler women’s personal writings manifest their attempts to eliminate alienating difference, and record their refusal to truly engage with the frontier landscape and its inhabitants.
- Full Text:
- Authors: Dampier, Helen
- Date: 2000
- Subjects: Women -- South Africa -- History , Women -- South Africa -- Eastern Cape -- Social conditions , Women -- South Africa -- Eastern Cape -- History , British settlers of 1820 (South Africa) , Frontier and pioneer life -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2537 , http://hdl.handle.net/10962/d1002389 , Women -- South Africa -- History , Women -- South Africa -- Eastern Cape -- Social conditions , Women -- South Africa -- Eastern Cape -- History , British settlers of 1820 (South Africa) , Frontier and pioneer life -- South Africa
- Description: This thesis is an exploration of diaries and letters written by middle-class English-speaking settler women living on the Eastern Cape frontier between 1820 and 1890. By according primacy to these women’s experiences and perceptions, it aims for a greater understanding of women’s encounters with the frontier, and how these were articulated in their personal writing. An emphasis on the recurrent themes of ill-health, fearfulness and solitude undermines the popular myth of the brave, conquering, invincible pioneers which dominates settler historiography to date. The tensions felt by white women living on the frontier disrupted their identities as middle-class Victorian ‘ladies’, and as a result these women either constantly re-established a sense of self, or absorbed some aspects of the Eastern Cape, and thus redefined themselves. Settler women’s experiences of the frontier changed little during the seventy year period spanned by this study, indicating that frontier life led to a rigidification and reinforcement of old, familiar values and behaviours. Rather than adapting to and embracing their new surroundings, settler women sought to duplicate accepted, conventional Victorian ideals and customs. White Victorian women identified themselves as refined, civilized, moral and respectable, and perceived Africa and Africans as untamed, immoral, uncivilized and threatening. To keep these menacing, destabilizing forces at bay, settler women attempted to recreate ‘home’ in the Eastern Cape; to domesticate the frontier by rendering it as familiar and predictable as possible. The fear, illness and solitariness that characterise settler women’s personal writings manifest their attempts to eliminate alienating difference, and record their refusal to truly engage with the frontier landscape and its inhabitants.
- Full Text:
Social change and shifting paradigms: the choice of healer among black South Africans in psychological counselling
- Authors: Johnson, Alexandra Blythe
- Date: 2000
- Subjects: Healers -- South Africa , Psychotherapy Cross-cultural studies , Xhosa (African people) -- Psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2998 , http://hdl.handle.net/10962/d1002507 , Healers -- South Africa , Psychotherapy Cross-cultural studies , Xhosa (African people) -- Psychology
- Description: Social change in South Africa brings to light the multiplicity of world-views operating in our society, which individuals encountering a variety of social contexts are faced with. This raises questions about the choices black South Africans face in response to influences from Western and traditional African culture. This issue was approached through examining helpseeking choices made between different health care sectors that stem from different world-views. This would indicate whether individuals are drawing on a variety of belief systems. The sources of their beliefs are put into context by looking at the communities of practice that influence their local knowledge. Help-seeking is also influenced by the identities the individual may ascribe to, which are derived from the multiple positions held by them in different social contexts. In this research the use of health-care sectors by four black women attending psychotherapy is examined. Their use of these sectors reflects a potential multiplicity of world views. Semistructured interviews were conducted, focusing on participants' prior experience of different help options, and their current perceptions of traditional African healing and psychology. The texts were analysed using a qualitative hermeneutic method, the reading guide. Data was looked at through three main themes, the individual's relationship to the health care sectors, their knowledge of different world views, and the identities they adopted which may be influential in their choice of a healer. It was found that in two participants there was some movement away from traditional beliefs, with one rejecting the traditional healers who did not help her, once she has discovered therapy, and another identifying herself completely with Western medicine. In contrast, one participant illustrated a rediscovery of traditional healing, whilst still attending psychotherapy. This suggests that shifts in knowledge are not necessarily away from traditional beliefs. It was also found that the two participants who had experienced a broader variety of social contexts and identified with multiple belief systems, tended to use a variety of Western and traditional healing sources and selected the healing option they felt was most appropriate to a particular problem. It is argued therefore that having a variety of knowledge and beliefs places individuals in a more powerful position to determine their choice of action than those with a limited range of knowledge.
- Full Text:
- Authors: Johnson, Alexandra Blythe
- Date: 2000
- Subjects: Healers -- South Africa , Psychotherapy Cross-cultural studies , Xhosa (African people) -- Psychology
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2998 , http://hdl.handle.net/10962/d1002507 , Healers -- South Africa , Psychotherapy Cross-cultural studies , Xhosa (African people) -- Psychology
- Description: Social change in South Africa brings to light the multiplicity of world-views operating in our society, which individuals encountering a variety of social contexts are faced with. This raises questions about the choices black South Africans face in response to influences from Western and traditional African culture. This issue was approached through examining helpseeking choices made between different health care sectors that stem from different world-views. This would indicate whether individuals are drawing on a variety of belief systems. The sources of their beliefs are put into context by looking at the communities of practice that influence their local knowledge. Help-seeking is also influenced by the identities the individual may ascribe to, which are derived from the multiple positions held by them in different social contexts. In this research the use of health-care sectors by four black women attending psychotherapy is examined. Their use of these sectors reflects a potential multiplicity of world views. Semistructured interviews were conducted, focusing on participants' prior experience of different help options, and their current perceptions of traditional African healing and psychology. The texts were analysed using a qualitative hermeneutic method, the reading guide. Data was looked at through three main themes, the individual's relationship to the health care sectors, their knowledge of different world views, and the identities they adopted which may be influential in their choice of a healer. It was found that in two participants there was some movement away from traditional beliefs, with one rejecting the traditional healers who did not help her, once she has discovered therapy, and another identifying herself completely with Western medicine. In contrast, one participant illustrated a rediscovery of traditional healing, whilst still attending psychotherapy. This suggests that shifts in knowledge are not necessarily away from traditional beliefs. It was also found that the two participants who had experienced a broader variety of social contexts and identified with multiple belief systems, tended to use a variety of Western and traditional healing sources and selected the healing option they felt was most appropriate to a particular problem. It is argued therefore that having a variety of knowledge and beliefs places individuals in a more powerful position to determine their choice of action than those with a limited range of knowledge.
- Full Text:
South Africa's growth, employment and redistribution strategy in the context of structural adjustment programmes in the South
- Authors: Lehloesa, Thembinkosi L
- Date: 2000
- Subjects: Growth, Employment And Redistribution Programme (South Africa) , South Africa -- Economic policy , South Africa -- Politics and government -- 1989-1994
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2794 , http://hdl.handle.net/10962/d1003004 , Growth, Employment And Redistribution Programme (South Africa) , South Africa -- Economic policy , South Africa -- Politics and government -- 1989-1994
- Description: This study is a contribution to the ongoing debate concerning the future of South Africa’s macro-economic policy known as the Growth, Employment and Redistribution (GEAR) strategy. The study attempts to draw parallels between the GEAR macro-economic policy framework and structural adjustment programmes in the South. By making use of this comparison, the study argues that the outcome of the GEAR will be no different from structural adjustment programmes in that it will fail to reduce poverty and cause government to meet the basic needs of the people. These conclusions are drawn from the fact that the GEAR policy is premised on the faith that the market is capable of redistributing income and wealth, and providing people with their basic needs.
- Full Text:
- Authors: Lehloesa, Thembinkosi L
- Date: 2000
- Subjects: Growth, Employment And Redistribution Programme (South Africa) , South Africa -- Economic policy , South Africa -- Politics and government -- 1989-1994
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2794 , http://hdl.handle.net/10962/d1003004 , Growth, Employment And Redistribution Programme (South Africa) , South Africa -- Economic policy , South Africa -- Politics and government -- 1989-1994
- Description: This study is a contribution to the ongoing debate concerning the future of South Africa’s macro-economic policy known as the Growth, Employment and Redistribution (GEAR) strategy. The study attempts to draw parallels between the GEAR macro-economic policy framework and structural adjustment programmes in the South. By making use of this comparison, the study argues that the outcome of the GEAR will be no different from structural adjustment programmes in that it will fail to reduce poverty and cause government to meet the basic needs of the people. These conclusions are drawn from the fact that the GEAR policy is premised on the faith that the market is capable of redistributing income and wealth, and providing people with their basic needs.
- Full Text:
Southern African Development Community foreign policy behaviour: the case of trade with external actors
- Authors: Tebu, Perminus Waithaka
- Date: 2000
- Subjects: Southern African Development Community , International trade , Africa, Southern -- Foreign relations
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2834 , http://hdl.handle.net/10962/d1003044 , Southern African Development Community , International trade , Africa, Southern -- Foreign relations
- Description: This thesis is structured around two main and interwoven assumptions operating at two levels. On the one level the external dimension of security threat in Southern Africa is assumed to be the most critical factor for regional renewal and stability. It hinges on pertinent regional issues such as negative trade balances, economic dependence, poverty, unemployment, poor economic growth rates and so forth. The corollary of this assumption is that within the operative framework of SADC, Southern African states are assumed capable of effectively integrating their economies through trade and related arrangements with dominant external actors in the highly competitive global economy. The European Union (EU) and the United States (US) are used as the focal points for illumination. A structured interaction between SADC and the EU within a revised North-South framework of interaction is hypothesized and critically examined. On the other hand, SADC-US interactions are assessed within the context of the new US Africa policy. At another level, the assumption is also made that the post-apartheid democratic state possesses both the political will and the wherewithal to provide regiol].al Leadership. This latter assumption is put to test within the framework of South Africa's regional foreign policy. Adopting an explicit regional unit of analysis, the study utilizes international regime theory as the theoretical and conceptual point of departure. The realist conception of the international system and the underlying assumptions usually considered as obstacles to international cooperation are critically examined in the context of the post-Cold War expanded security agenda. Regime theory is used to provide insight on the motivations that lead states to cooperate in situations of mutual dilemma by institutionalizing patterns of interaction at the regional and international systemic levels. Interstate economic relations at these levels are explained as state actions that are influenced by certain norms and that such norm-governed behaviour is wholly consistent with the pursuit of national interest. Application of the theory explains why such foreign policy behaviour of states is particularly relevant in the post-Cold War era. The thesis has argued that SADC states are capable of conducting a coordinated trade foreign policy in which regional positions are elaborated and adopted. It is argued further that a regional capacity to institute trade and economic policies that reflect local circumstances (necessary for effective integration with the world economy) calls for strong regional developmental democracies in the tradition of social market economy. Regional leadership by South Africa is considered indispensable where Sbuth Africa must find a sustainable balance between its national and regional interests.
- Full Text:
- Authors: Tebu, Perminus Waithaka
- Date: 2000
- Subjects: Southern African Development Community , International trade , Africa, Southern -- Foreign relations
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2834 , http://hdl.handle.net/10962/d1003044 , Southern African Development Community , International trade , Africa, Southern -- Foreign relations
- Description: This thesis is structured around two main and interwoven assumptions operating at two levels. On the one level the external dimension of security threat in Southern Africa is assumed to be the most critical factor for regional renewal and stability. It hinges on pertinent regional issues such as negative trade balances, economic dependence, poverty, unemployment, poor economic growth rates and so forth. The corollary of this assumption is that within the operative framework of SADC, Southern African states are assumed capable of effectively integrating their economies through trade and related arrangements with dominant external actors in the highly competitive global economy. The European Union (EU) and the United States (US) are used as the focal points for illumination. A structured interaction between SADC and the EU within a revised North-South framework of interaction is hypothesized and critically examined. On the other hand, SADC-US interactions are assessed within the context of the new US Africa policy. At another level, the assumption is also made that the post-apartheid democratic state possesses both the political will and the wherewithal to provide regiol].al Leadership. This latter assumption is put to test within the framework of South Africa's regional foreign policy. Adopting an explicit regional unit of analysis, the study utilizes international regime theory as the theoretical and conceptual point of departure. The realist conception of the international system and the underlying assumptions usually considered as obstacles to international cooperation are critically examined in the context of the post-Cold War expanded security agenda. Regime theory is used to provide insight on the motivations that lead states to cooperate in situations of mutual dilemma by institutionalizing patterns of interaction at the regional and international systemic levels. Interstate economic relations at these levels are explained as state actions that are influenced by certain norms and that such norm-governed behaviour is wholly consistent with the pursuit of national interest. Application of the theory explains why such foreign policy behaviour of states is particularly relevant in the post-Cold War era. The thesis has argued that SADC states are capable of conducting a coordinated trade foreign policy in which regional positions are elaborated and adopted. It is argued further that a regional capacity to institute trade and economic policies that reflect local circumstances (necessary for effective integration with the world economy) calls for strong regional developmental democracies in the tradition of social market economy. Regional leadership by South Africa is considered indispensable where Sbuth Africa must find a sustainable balance between its national and regional interests.
- Full Text:
Spirulina as a bioremediation agent : interaction with metals and involvement of carbonic anhydrase
- Authors: Payne, Rosemary Anne
- Date: 2000
- Subjects: Spirulina , Bioremediation , Carbonic anhydrase
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3909 , http://hdl.handle.net/10962/d1003968 , Spirulina , Bioremediation , Carbonic anhydrase
- Description: Heavy metal contamination from mining and other industrial operations is becoming an increasing problem with regards to the depleting water resources in South Africa. This study involved the investigation of the use of an algal biomass as a possible alternative to the traditional chemical means of removing these metals. When the toxic effects of metals were investigated, Spirulina was found to have a threshold level of about 30 μM for copper, zinc and lead. Copper and zinc appeared to have a direct effect on the photosynthetic pathway, thereby causing a rapid decline in cell growth. Lead on the other hand seemed to affect surface properties and hence took longer to cause deterioration in growth. Although relatively low concentrations of metal may have a toxic effect on the cyanobacterium, Spirulina may have potential as a precipitation agent. The role of Spirulina in the precipitation of heavy metals appears to be through its ability to maintain a high pH in the surrounding medium, possibly through the enzyme carbonic anhydrase. Subsequent studies therefore focused on the assay and isolation of this enzyme. Two different radiotracer assays, in which carbonic anhydrase converts radiolabelled bicarbonate to carbon dioxide, were investigated, but were found to have several problems. Results were insensitive and could not be reproduced. The standard Wilbur-Anderson method subsequently investigated also proved to be insensitive with a tremendous degree of variability. Although not quantitative, SDS-PAGE proved to be the most reliable method of detection, and was therefore used in subsequent procedures. Chlamydomonas reinhardtii was the subject of initial enzyme isolation studies as these procedures are well documented. Although the published protocols proved unsuccessful, affinity chromatography of a membrane stock solution from Chlamydomonas reinhardtii yielded two relatively pure protein bands. These bands were presumed to represent two subunits of carbonic anhydrase, although Western blot analysis would be required to confirm their identity. Purification of carbonic anhydrase from Spirulina, however, proved unsuccessful and results obtained were very inconclusive. Hence, further analysis of Spirulina is required. The possibility of cloning CA from a genomic library was also considered, but suitable primers could not be designed from the aligned sequences.
- Full Text:
- Authors: Payne, Rosemary Anne
- Date: 2000
- Subjects: Spirulina , Bioremediation , Carbonic anhydrase
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3909 , http://hdl.handle.net/10962/d1003968 , Spirulina , Bioremediation , Carbonic anhydrase
- Description: Heavy metal contamination from mining and other industrial operations is becoming an increasing problem with regards to the depleting water resources in South Africa. This study involved the investigation of the use of an algal biomass as a possible alternative to the traditional chemical means of removing these metals. When the toxic effects of metals were investigated, Spirulina was found to have a threshold level of about 30 μM for copper, zinc and lead. Copper and zinc appeared to have a direct effect on the photosynthetic pathway, thereby causing a rapid decline in cell growth. Lead on the other hand seemed to affect surface properties and hence took longer to cause deterioration in growth. Although relatively low concentrations of metal may have a toxic effect on the cyanobacterium, Spirulina may have potential as a precipitation agent. The role of Spirulina in the precipitation of heavy metals appears to be through its ability to maintain a high pH in the surrounding medium, possibly through the enzyme carbonic anhydrase. Subsequent studies therefore focused on the assay and isolation of this enzyme. Two different radiotracer assays, in which carbonic anhydrase converts radiolabelled bicarbonate to carbon dioxide, were investigated, but were found to have several problems. Results were insensitive and could not be reproduced. The standard Wilbur-Anderson method subsequently investigated also proved to be insensitive with a tremendous degree of variability. Although not quantitative, SDS-PAGE proved to be the most reliable method of detection, and was therefore used in subsequent procedures. Chlamydomonas reinhardtii was the subject of initial enzyme isolation studies as these procedures are well documented. Although the published protocols proved unsuccessful, affinity chromatography of a membrane stock solution from Chlamydomonas reinhardtii yielded two relatively pure protein bands. These bands were presumed to represent two subunits of carbonic anhydrase, although Western blot analysis would be required to confirm their identity. Purification of carbonic anhydrase from Spirulina, however, proved unsuccessful and results obtained were very inconclusive. Hence, further analysis of Spirulina is required. The possibility of cloning CA from a genomic library was also considered, but suitable primers could not be designed from the aligned sequences.
- Full Text:
Stability of prochlorperazine in solution and in the solid-state
- Authors: Antunes, Edith Martins
- Date: 2000
- Subjects: Phenothiazine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4536 , http://hdl.handle.net/10962/d1016399
- Description: Prochlorperazine, a member of the piperazine subclass of phenothiazines, widely used as an anti-emetic, is susceptible to oxidation to sulfoxides. These are main metabolites and degradants of all phenothiazines which are found to be inactive at the dopamine receptors. Prochlorperazine causes photosensitivity effects in patients attributed to dechlorination at C2 with the release of HCI (Huang and Sands, 1967; Nejmeh and Pilpel, 1978; Moore and Tamat, 1980). The aim of this study is to investigate the thermal and photostability of prochlorperazine edisylate and mesylate salts in the solid state and in solution. Prochlorperazine is available as a fine chemical and in a variety of dosage forms, including injectables and tablets. According to ICH guidelines, any degradants greater than 0.1 % are required to be isolated and identified. In order to assess the photostability of the two salts, an HPLC method was developed and validated for linearity, accuracy and precision, selectivity, limit of detection, quantitation and ruggedness. Sulfoxides were synthesised for use as standards in the rate studies according to the well-known hydrogen peroxide method (Owens et al., 1989). The rate of prochlorperazine degradation in solution under various light sources (254 nm UV light, diffuse light and sunlight) was studied. The light sources used abovF were quantified using potassium ferrioxalate as a chemical actinometer). The photodegradation rate was found to be greater in ampoules sealed under nitrogen than air, but the thermal degradation was faster in ampoules sealed with air than those purged with nitrogen. Amber ampoules retarded the rate of degradation under all photolytic conditions. This is a vital consideration for the packaging and storage of prochlorperazine in injectables. Degradation was found to occur mainly by first-order kinetics and the degradation rate decreased in the following order: sunlight » UV light 254 nm > fluorescent I diffuse light. Solid state samples, however, were found to be relatively stable to the various light / heat conditions over a 6 month period when compared to prochlorperazine solutions, but still considerably unstable. Thus both storage and packaging is a vital consideration for prochlorperazine injectables. The thermal behaviour of mixtures of prochlorperazine with standard excipients, was assessed for potential interactions, using differential scanning calorimetry. For most of the excipients (magnesium stearate, stearic acid, Explotab®, AC-Di-Sol®, Encompress® and Ludipress®, lactose and Starch 1500®) disappearance or broadening of the melting endotherm of the drug indicated interactions. Lubritab®, however, was the only 'inert' excipient tested. Liquid chromatography - mass spectrometry (LC-MS) was used to determine the nature of the degradation products. The major degradation pathways included dechlorination and demethylation of the parent drug, as well as sulfoxidation and Noxidation. Prochlorperazine underwent dechlorination and sulfoxidation with subsequent photosubstitution to yield the 2-hydroxy derivative. The solid state photostudies showed the formation of dealkylated, oxidised and hydroxylated products, sulfoxides and dimers. Since N-demethylation, N-oxidation, sulfoxidation and aromatic hydroxylation are reported to occur in the in vitro metabolism of perazine derivatives, it does appear that there is some relationship between metabolites and photoproducts (Breyer, 1974). This study has been successful in providing understanding of the photolytic and thermal degradation pathways of prochlorperazine.
- Full Text:
- Authors: Antunes, Edith Martins
- Date: 2000
- Subjects: Phenothiazine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4536 , http://hdl.handle.net/10962/d1016399
- Description: Prochlorperazine, a member of the piperazine subclass of phenothiazines, widely used as an anti-emetic, is susceptible to oxidation to sulfoxides. These are main metabolites and degradants of all phenothiazines which are found to be inactive at the dopamine receptors. Prochlorperazine causes photosensitivity effects in patients attributed to dechlorination at C2 with the release of HCI (Huang and Sands, 1967; Nejmeh and Pilpel, 1978; Moore and Tamat, 1980). The aim of this study is to investigate the thermal and photostability of prochlorperazine edisylate and mesylate salts in the solid state and in solution. Prochlorperazine is available as a fine chemical and in a variety of dosage forms, including injectables and tablets. According to ICH guidelines, any degradants greater than 0.1 % are required to be isolated and identified. In order to assess the photostability of the two salts, an HPLC method was developed and validated for linearity, accuracy and precision, selectivity, limit of detection, quantitation and ruggedness. Sulfoxides were synthesised for use as standards in the rate studies according to the well-known hydrogen peroxide method (Owens et al., 1989). The rate of prochlorperazine degradation in solution under various light sources (254 nm UV light, diffuse light and sunlight) was studied. The light sources used abovF were quantified using potassium ferrioxalate as a chemical actinometer). The photodegradation rate was found to be greater in ampoules sealed under nitrogen than air, but the thermal degradation was faster in ampoules sealed with air than those purged with nitrogen. Amber ampoules retarded the rate of degradation under all photolytic conditions. This is a vital consideration for the packaging and storage of prochlorperazine in injectables. Degradation was found to occur mainly by first-order kinetics and the degradation rate decreased in the following order: sunlight » UV light 254 nm > fluorescent I diffuse light. Solid state samples, however, were found to be relatively stable to the various light / heat conditions over a 6 month period when compared to prochlorperazine solutions, but still considerably unstable. Thus both storage and packaging is a vital consideration for prochlorperazine injectables. The thermal behaviour of mixtures of prochlorperazine with standard excipients, was assessed for potential interactions, using differential scanning calorimetry. For most of the excipients (magnesium stearate, stearic acid, Explotab®, AC-Di-Sol®, Encompress® and Ludipress®, lactose and Starch 1500®) disappearance or broadening of the melting endotherm of the drug indicated interactions. Lubritab®, however, was the only 'inert' excipient tested. Liquid chromatography - mass spectrometry (LC-MS) was used to determine the nature of the degradation products. The major degradation pathways included dechlorination and demethylation of the parent drug, as well as sulfoxidation and Noxidation. Prochlorperazine underwent dechlorination and sulfoxidation with subsequent photosubstitution to yield the 2-hydroxy derivative. The solid state photostudies showed the formation of dealkylated, oxidised and hydroxylated products, sulfoxides and dimers. Since N-demethylation, N-oxidation, sulfoxidation and aromatic hydroxylation are reported to occur in the in vitro metabolism of perazine derivatives, it does appear that there is some relationship between metabolites and photoproducts (Breyer, 1974). This study has been successful in providing understanding of the photolytic and thermal degradation pathways of prochlorperazine.
- Full Text:
Strike comparison of the compositional variations of the lower group and middle group chromitite seams of the critical zone, Western Bushveld complex
- Authors: Doig, Heather Leslie
- Date: 2000
- Subjects: Chromite -- South Africa , Geology -- South Africa , Mineralogy -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5005 , http://hdl.handle.net/10962/d1005618
- Description: The variations in the composition, specifically the Cr20 S content and the Cr:Fe ratio, and the morphology of the Lower Group (LG) and Middle Group (MG) chromitite seams of the Critical Zone (CZ) across the western Bushveld Complex, including the Ruighoek and Brits sections, is investigated by means of whole-rock chemical data, both major and trace elements analysis, XRD and electron microprobe data. As a result ofthe paucity of exposed or developed LG1 - LG5 chromitite seams in the western Bushveld Complex, this study is confined to the investigation of the compositional variations of the LG6 to MG4 chromitite seams. In only one section, the Ruighoek section, was the entire succession of chromitite seams, from the LG1 - MG4, exposed. The silicate host rocks from the LG6 pyroxenite footwall to the collar of the CC2 drillcore (lower uCZ) in the Rustenburg section were sampled. This study reviews the compositional trends of the silicate host rocks, as the compositional variations of the chromitite seams reflect the chemical evolution of the host cumulate environment and, to a lesser degree, the composition onhe interstitial mineral phases in the chromitite seams. The compositional variations of the LG and MG chromitite seams are attributed to the compositional contrast between the replenishing magma and the resident magma. The chemical trends of the LG and MG chromitite layers and the host cumUlate rOCKS do not support the existence of two compositionalfy dissimilar magmas in the CZ, rather the cyclic layering of the CZ and the chemical variations of the chromitite seams are attributed to the mixing of primitive magma with the resident magma, both of which have essentially similar compositions. The compositional variations of the LG and MG chromitite seams along strike away from the supposed feeder site (Union section) to the distal facies (Brits section) are attributed to the advanced compositional contrast between the resident magma and the replenishing primitive magma pulses. The CZ is characterized by reversals in fractionation trends and this is attributed to the compositional evolution of the parental magma and not to the replenishment of the resident magma by influxes of grossly dissimilar magma compositions. The Cr20 S content and the Cr:Fe ratio of the MG chromitite layers increase from the Ruighoek (near proximal) section to the Brits section (distal facies). This is attributed to the advanced compositional contrasts between the resident magma and the replenishing primitive magma. In contrast, the Cr20 3 content and Cr:Fe ratios ofthe LG6 and LG8a chromitite seams decreases eastwards from the Ruighoek section. The average Cr:Fe ratio for the western Bushveld Complex is between 1.5 and\2.0, nonetheless, a progressively lower Cr:Fe ratio is noted from the LG1 chromitite up through to the MG4 chromitite seam in the Ruighoek section. tn the LG2 - LG4 chromitite interval a deviation to higher.lratios is encountered. A progressive substitution of Cr by AT and Fe in the Cr-spinel crystal lattice characterizes the chromitite succession from the LG1 seam up through the chromitite succession to MG4. The petrogeneSiS of the chromitite seams of the CZ is attributed to magma mixing and fractional crystallization of a single magma type.
- Full Text:
- Authors: Doig, Heather Leslie
- Date: 2000
- Subjects: Chromite -- South Africa , Geology -- South Africa , Mineralogy -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5005 , http://hdl.handle.net/10962/d1005618
- Description: The variations in the composition, specifically the Cr20 S content and the Cr:Fe ratio, and the morphology of the Lower Group (LG) and Middle Group (MG) chromitite seams of the Critical Zone (CZ) across the western Bushveld Complex, including the Ruighoek and Brits sections, is investigated by means of whole-rock chemical data, both major and trace elements analysis, XRD and electron microprobe data. As a result ofthe paucity of exposed or developed LG1 - LG5 chromitite seams in the western Bushveld Complex, this study is confined to the investigation of the compositional variations of the LG6 to MG4 chromitite seams. In only one section, the Ruighoek section, was the entire succession of chromitite seams, from the LG1 - MG4, exposed. The silicate host rocks from the LG6 pyroxenite footwall to the collar of the CC2 drillcore (lower uCZ) in the Rustenburg section were sampled. This study reviews the compositional trends of the silicate host rocks, as the compositional variations of the chromitite seams reflect the chemical evolution of the host cumulate environment and, to a lesser degree, the composition onhe interstitial mineral phases in the chromitite seams. The compositional variations of the LG and MG chromitite seams are attributed to the compositional contrast between the replenishing magma and the resident magma. The chemical trends of the LG and MG chromitite layers and the host cumUlate rOCKS do not support the existence of two compositionalfy dissimilar magmas in the CZ, rather the cyclic layering of the CZ and the chemical variations of the chromitite seams are attributed to the mixing of primitive magma with the resident magma, both of which have essentially similar compositions. The compositional variations of the LG and MG chromitite seams along strike away from the supposed feeder site (Union section) to the distal facies (Brits section) are attributed to the advanced compositional contrast between the resident magma and the replenishing primitive magma pulses. The CZ is characterized by reversals in fractionation trends and this is attributed to the compositional evolution of the parental magma and not to the replenishment of the resident magma by influxes of grossly dissimilar magma compositions. The Cr20 S content and the Cr:Fe ratio of the MG chromitite layers increase from the Ruighoek (near proximal) section to the Brits section (distal facies). This is attributed to the advanced compositional contrasts between the resident magma and the replenishing primitive magma. In contrast, the Cr20 3 content and Cr:Fe ratios ofthe LG6 and LG8a chromitite seams decreases eastwards from the Ruighoek section. The average Cr:Fe ratio for the western Bushveld Complex is between 1.5 and\2.0, nonetheless, a progressively lower Cr:Fe ratio is noted from the LG1 chromitite up through to the MG4 chromitite seam in the Ruighoek section. tn the LG2 - LG4 chromitite interval a deviation to higher.lratios is encountered. A progressive substitution of Cr by AT and Fe in the Cr-spinel crystal lattice characterizes the chromitite succession from the LG1 seam up through the chromitite succession to MG4. The petrogeneSiS of the chromitite seams of the CZ is attributed to magma mixing and fractional crystallization of a single magma type.
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The biology of commercially important fish species and a preliminary assessment of the fisheries potential of Katse Dam, Lesotho
- Authors: Nthimo, Mokitinyane Francis
- Date: 2000
- Subjects: Fishes -- Lesotho -- Katse dam , Fishes -- Physiology , Rainbow trout , Barbus aeneus , Labeo , Katse dam (Lesotho) , Fisheries -- Lesotho -- Katse dam , Fishery management -- Lesotho
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5238 , http://hdl.handle.net/10962/d1005081 , Fishes -- Lesotho -- Katse dam , Fishes -- Physiology , Rainbow trout , Barbus aeneus , Labeo , Katse dam (Lesotho) , Fisheries -- Lesotho -- Katse dam , Fishery management -- Lesotho
- Description: The construction of the Katse dam was completed in 1996. The dam started filling in 1995 and reached full capacity in early 1998. It forms part of Phase 1A of the Lesotho Highlands Water Project (LHWP). The main aim of the project is to provide revenue to Lesotho, by transferring water from the catchment of the Senqu (Orange) River in Lesotho to South Africa’s major industrial and population centres. During the implementation of the project, an estimated 130 people were displaced. However, the most serious impact has been the loss of the traditional way of life in the form of arable and grazing land as a consequence of inundation. One of the obligations of the project is to ensure that the standard of living of those affected by the project is not impaired. The Lesotho Highlands Development Authority identified a number of rural development projects, which included fisheries development. This study is an integral part of fisheries development in Lesotho. The aim of this study was to gain an understanding of the biology and the demographics of the fish species in the lake. This information would serve as the basis for the development of a management plan for the sustainable utilisation of the fisheries resources. To achieve this aim, the following specific objectives were addressed: 1. Investigation of the biology of the three principal species. 2. Description of the key population parameters (growth, mortality & recruitment). 3. Investigation of the distribution and relative abundance of the three species. The three principal species in the Katse dam are rainbow trout, Oncorhynchus mykiss, and the two cyprinids, Barbus aeneus and Labeo capensis. Sectioned otoliths were used to age O. mykiss while both otoliths and scales were used to age B. aeneus and L. capensis. Marginal zone analysis revealed that slow growth was experienced in winter for the three species. The maximum-recorded age for both B. aeneus and L. capensis was 12 years while O. mykiss reached 4 years. There was no significant difference in growth rates of the different sexes and growth was best described by the 3 parameter Von-Bertalanfy growth model as Lt = 603[1-e⁻°·¹⁵⁽t ⁺ °·°³⁾] for B. aeneus, Lt = 526[1-e⁻°·²¹⁽t ⁺ °·⁹⁾] for O. mykiss and Lt = 521[1-e⁻°·¹⁷⁽t ⁺ °·²¹⁾] for L.capensis. Male and female O. mykiss attained 50% sexual maturity (Lm₅₀) at 235 and 275mm FL, respectively. There was no difference in Lm₅₀ for male and female B. aeneus and L. capensis. B. aeneus reached sexual maturity at 285mm FL while L. capensis reached sexual maturity at 244mm. Both cyprinid species spawned in summer (November to January) while O. mykiss spawned in winter (May to August). The mean total mortality rate (Z) estimated from catch curves and Butterworth et al (1989) equation was 0.72 yr⁻¹ for B. aeneus, 0.62 yr⁻¹ for L. capensis and 1.32 yr⁻¹ for O. mykiss. The estimate of natural mortality was 0.41 yr⁻¹ for both B. aeneus and L. capensis and 0.81yr⁻¹ for O. mykiss.
- Full Text:
- Authors: Nthimo, Mokitinyane Francis
- Date: 2000
- Subjects: Fishes -- Lesotho -- Katse dam , Fishes -- Physiology , Rainbow trout , Barbus aeneus , Labeo , Katse dam (Lesotho) , Fisheries -- Lesotho -- Katse dam , Fishery management -- Lesotho
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5238 , http://hdl.handle.net/10962/d1005081 , Fishes -- Lesotho -- Katse dam , Fishes -- Physiology , Rainbow trout , Barbus aeneus , Labeo , Katse dam (Lesotho) , Fisheries -- Lesotho -- Katse dam , Fishery management -- Lesotho
- Description: The construction of the Katse dam was completed in 1996. The dam started filling in 1995 and reached full capacity in early 1998. It forms part of Phase 1A of the Lesotho Highlands Water Project (LHWP). The main aim of the project is to provide revenue to Lesotho, by transferring water from the catchment of the Senqu (Orange) River in Lesotho to South Africa’s major industrial and population centres. During the implementation of the project, an estimated 130 people were displaced. However, the most serious impact has been the loss of the traditional way of life in the form of arable and grazing land as a consequence of inundation. One of the obligations of the project is to ensure that the standard of living of those affected by the project is not impaired. The Lesotho Highlands Development Authority identified a number of rural development projects, which included fisheries development. This study is an integral part of fisheries development in Lesotho. The aim of this study was to gain an understanding of the biology and the demographics of the fish species in the lake. This information would serve as the basis for the development of a management plan for the sustainable utilisation of the fisheries resources. To achieve this aim, the following specific objectives were addressed: 1. Investigation of the biology of the three principal species. 2. Description of the key population parameters (growth, mortality & recruitment). 3. Investigation of the distribution and relative abundance of the three species. The three principal species in the Katse dam are rainbow trout, Oncorhynchus mykiss, and the two cyprinids, Barbus aeneus and Labeo capensis. Sectioned otoliths were used to age O. mykiss while both otoliths and scales were used to age B. aeneus and L. capensis. Marginal zone analysis revealed that slow growth was experienced in winter for the three species. The maximum-recorded age for both B. aeneus and L. capensis was 12 years while O. mykiss reached 4 years. There was no significant difference in growth rates of the different sexes and growth was best described by the 3 parameter Von-Bertalanfy growth model as Lt = 603[1-e⁻°·¹⁵⁽t ⁺ °·°³⁾] for B. aeneus, Lt = 526[1-e⁻°·²¹⁽t ⁺ °·⁹⁾] for O. mykiss and Lt = 521[1-e⁻°·¹⁷⁽t ⁺ °·²¹⁾] for L.capensis. Male and female O. mykiss attained 50% sexual maturity (Lm₅₀) at 235 and 275mm FL, respectively. There was no difference in Lm₅₀ for male and female B. aeneus and L. capensis. B. aeneus reached sexual maturity at 285mm FL while L. capensis reached sexual maturity at 244mm. Both cyprinid species spawned in summer (November to January) while O. mykiss spawned in winter (May to August). The mean total mortality rate (Z) estimated from catch curves and Butterworth et al (1989) equation was 0.72 yr⁻¹ for B. aeneus, 0.62 yr⁻¹ for L. capensis and 1.32 yr⁻¹ for O. mykiss. The estimate of natural mortality was 0.41 yr⁻¹ for both B. aeneus and L. capensis and 0.81yr⁻¹ for O. mykiss.
- Full Text:
The development of a geographic information systems based atlas of southern African freshwater fish, and its application to biogeographic analysis
- Scott, Lucy Elizabeth Powell
- Authors: Scott, Lucy Elizabeth Powell
- Date: 2000
- Subjects: Freshwater fishes -- Africa, Southern , Freshwater fishes -- Geographical distribution -- Atlases , Freshwater fishes -- Africa, Southern -- Geographical distribution -- Atlases , Geographic information systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5256 , http://hdl.handle.net/10962/d1005099 , Freshwater fishes -- Africa, Southern , Freshwater fishes -- Geographical distribution -- Atlases , Freshwater fishes -- Africa, Southern -- Geographical distribution -- Atlases , Geographic information systems
- Description: A Geographic Information Systems (GIS) atlas of southern African freshwater fish was developed for the SADC countries from natural history collection specimens, hydrological, topographical and climatological data. The primary purpose of the development of the atlas of freshwater fish was the construction of a practical framework to transform vast amounts of existing biological data for use in research and management of aquatic resources. The database of freshwater fish collection specimens that was incorporated into the atlas, was developed in association with ALCOM (Aquatic Resources Management for Local Community Development Programme). The development of advanced computing and GIS technology has increased the scope of biological atlas projects by facilitating the integration of large amounts of spatial data to produce derived databases for specific applications. The atlas of freshwater fish was constructed using TNTmips GIS software as the most practical system available for managing and analysing biological data with a spatial component. The atlas contains 35 180 comprehensive distribution records of 735 species of fish. It has many applications as an inventory of ichthyofaunal spatial biodiversity, including those of conservation planning, environmental assessment and biogeographic research. Biogeographic studies have traditionally been subjective due to the logistical problems of working with large amounts of distribution data, although some small-scale quantitative research has been carried out in the past. The content of the atlas of freshwater fish is tested with respect to these previous studies, on known patterns of freshwater fish distributions, and the analytical capability of the atlas is tested and demonstrated with some new preliminary approaches to the analysis of freshwater fish distributions in southern Africa.
- Full Text:
- Authors: Scott, Lucy Elizabeth Powell
- Date: 2000
- Subjects: Freshwater fishes -- Africa, Southern , Freshwater fishes -- Geographical distribution -- Atlases , Freshwater fishes -- Africa, Southern -- Geographical distribution -- Atlases , Geographic information systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5256 , http://hdl.handle.net/10962/d1005099 , Freshwater fishes -- Africa, Southern , Freshwater fishes -- Geographical distribution -- Atlases , Freshwater fishes -- Africa, Southern -- Geographical distribution -- Atlases , Geographic information systems
- Description: A Geographic Information Systems (GIS) atlas of southern African freshwater fish was developed for the SADC countries from natural history collection specimens, hydrological, topographical and climatological data. The primary purpose of the development of the atlas of freshwater fish was the construction of a practical framework to transform vast amounts of existing biological data for use in research and management of aquatic resources. The database of freshwater fish collection specimens that was incorporated into the atlas, was developed in association with ALCOM (Aquatic Resources Management for Local Community Development Programme). The development of advanced computing and GIS technology has increased the scope of biological atlas projects by facilitating the integration of large amounts of spatial data to produce derived databases for specific applications. The atlas of freshwater fish was constructed using TNTmips GIS software as the most practical system available for managing and analysing biological data with a spatial component. The atlas contains 35 180 comprehensive distribution records of 735 species of fish. It has many applications as an inventory of ichthyofaunal spatial biodiversity, including those of conservation planning, environmental assessment and biogeographic research. Biogeographic studies have traditionally been subjective due to the logistical problems of working with large amounts of distribution data, although some small-scale quantitative research has been carried out in the past. The content of the atlas of freshwater fish is tested with respect to these previous studies, on known patterns of freshwater fish distributions, and the analytical capability of the atlas is tested and demonstrated with some new preliminary approaches to the analysis of freshwater fish distributions in southern Africa.
- Full Text:
The development of a pro forma document for use in police rape investigations in South Africa
- Authors: Netto, Lauren Joy
- Date: 2000
- Subjects: Interviewing in law enforcement , Criminal investigation , Police questioning -- Forms , Rape -- Investigation -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3031 , http://hdl.handle.net/10962/d1002540 , Interviewing in law enforcement , Criminal investigation , Police questioning -- Forms , Rape -- Investigation -- South Africa
- Description: This research developed a pro forma document for use in police rape investigations in South Africa. The immediate context for the research is the alarmingly high incidence of rape in South Africa. The rape statistics vary to an extent, largely due to the fact that a large proportion of the rapes that occur in South Africa are not reported to the police. These statistics expose the limited success of the South African Police Services (SAPS) in terms of investigating rape cases in this country, as well as the public perception of the effectiveness of the South African Police Services in this regard as evidenced by the non or under-reporting of rape in South Africa. The pro forma document is an investigative tool designed to standardise and systematise rape investigations by providing set guidelines for obtaining the essential information about each rape case. This is a prerequisite for Tender profiling, which involves predicting the relationship between offence and offender variables. Profiling can only be successful if the investigator obtains all the information about a crime. Hence the pro forma document, as an investigative instrument designed to access essential information about a crime, is a key requirement for the development of informed and accurate profiles of offenders. As a standardised form, the document will allow for systematic and thorough rape investigations in South Africa. The researcher employed the qualitative methodology of action research. This entailed involving the participants in all stages of the research process. The data was collected by means of focus group interviews with detectives from the Serious and Violent Crimes Unit and the Child Protection Unit in Grahamstown. Additional sources of data were various investigative documents that originated from a number of different countries. Analysis of the data followed a number of procedural steps specifically suggested for focus group interview research and involved a process of coding. The codes identified during the analysis provided the foundation for the items that were included in the pro forma document. In keeping with the action research approach, the participants were caned upon to evaluate the progress of the research after the initial data collection and analysis were completed, and a draft version of the pro forma document had been compiled. This feedback provided another source of data which contained suggestions for amendments to the pro forma document which the researcher implemented. The research process was hindered to a certain extent by the unpredictable nature of police work which influenced the data gathering procedure. This could point to a possible limitation of the research. Furthermore, the aim of the research was to develop a pro forma document for use in rape investigations in South Africa. This aim did not encompass marketing the document. Herein lies another possible limitation of the research in that the document has not yet been used and tested in real cases. A discussion of the research process includes issues involved in practically implementing the pro forma document in rape investigations.
- Full Text:
- Authors: Netto, Lauren Joy
- Date: 2000
- Subjects: Interviewing in law enforcement , Criminal investigation , Police questioning -- Forms , Rape -- Investigation -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3031 , http://hdl.handle.net/10962/d1002540 , Interviewing in law enforcement , Criminal investigation , Police questioning -- Forms , Rape -- Investigation -- South Africa
- Description: This research developed a pro forma document for use in police rape investigations in South Africa. The immediate context for the research is the alarmingly high incidence of rape in South Africa. The rape statistics vary to an extent, largely due to the fact that a large proportion of the rapes that occur in South Africa are not reported to the police. These statistics expose the limited success of the South African Police Services (SAPS) in terms of investigating rape cases in this country, as well as the public perception of the effectiveness of the South African Police Services in this regard as evidenced by the non or under-reporting of rape in South Africa. The pro forma document is an investigative tool designed to standardise and systematise rape investigations by providing set guidelines for obtaining the essential information about each rape case. This is a prerequisite for Tender profiling, which involves predicting the relationship between offence and offender variables. Profiling can only be successful if the investigator obtains all the information about a crime. Hence the pro forma document, as an investigative instrument designed to access essential information about a crime, is a key requirement for the development of informed and accurate profiles of offenders. As a standardised form, the document will allow for systematic and thorough rape investigations in South Africa. The researcher employed the qualitative methodology of action research. This entailed involving the participants in all stages of the research process. The data was collected by means of focus group interviews with detectives from the Serious and Violent Crimes Unit and the Child Protection Unit in Grahamstown. Additional sources of data were various investigative documents that originated from a number of different countries. Analysis of the data followed a number of procedural steps specifically suggested for focus group interview research and involved a process of coding. The codes identified during the analysis provided the foundation for the items that were included in the pro forma document. In keeping with the action research approach, the participants were caned upon to evaluate the progress of the research after the initial data collection and analysis were completed, and a draft version of the pro forma document had been compiled. This feedback provided another source of data which contained suggestions for amendments to the pro forma document which the researcher implemented. The research process was hindered to a certain extent by the unpredictable nature of police work which influenced the data gathering procedure. This could point to a possible limitation of the research. Furthermore, the aim of the research was to develop a pro forma document for use in rape investigations in South Africa. This aim did not encompass marketing the document. Herein lies another possible limitation of the research in that the document has not yet been used and tested in real cases. A discussion of the research process includes issues involved in practically implementing the pro forma document in rape investigations.
- Full Text:
The development of a WAIS-III short form for use in South Africa
- Authors: Rust, Annegret L
- Date: 2000
- Subjects: Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3047 , http://hdl.handle.net/10962/d1002556 , Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Description: The Wechsler Adult Intelligence Scale - 3rd Edition (WAIS-III) is the newest of the internationally recognised Wechsler family of intelligence tests. It has been improved in terms of its psychometric properties, neuropsychological assessment abilities and its content. This test is in the process of being standardised by the Human Sciences Research Council (HSRC) in South Africa. As the adapted South African version will be available shortly for use in the multicultural circumstances of South Africa, the application of the various aspects of this test needs to be investigated. This test is very comprehensive and thorough, however its one disadvantage is that it takes on average three hours to administer in its entirety. Thus there is a need to find ways in which to abbreviate the test for particular purposes when time is limited, for example in research, brief clinical assessments or neuropsychological screenings. The concept of abbreviating tests, including the earlier Wechsler intelligence test can be traced back to 1917, when it was asked if all the items on the Binet-Simon scale were required to give an accurate assessment of IQ (Levy, 1968). Since then there have been many short form suggestions made, with many different considerations in mind. These can be divided into two main approaches or methods. Firstly, the number of subtests of the scale can be reduced. Thus with the WAIS-III which consists of 14 subtests in total, an option is to use, for example only four of the subtests to get an estimate of a person's IQ. Secondly, the number of items in each subtest can be reduced. Thus only half the items or even only a third of the items on a subtest can be administered to get an estimate of the persons' performance on each subtest and in this way estimate their overall IQ. Both methods have been used on the WAIS and WAIS-R, although the reduction of the subtests is favoured. Both should now be validated and considered for use with the WATS-III in South Africa. Wechsler tests and their constituent subtests have been found to be differentially effected by race, education, language and socio-economic status (Kaufman, McLean & Reynolds, 1988; Nell 1999). These differences have also been found to impact on the short forms which are suggested, as certain subtests are considered to be more biased towards particular groups than others. Vocabulary and Block Design in particular bias testees who are not as westernised or acculturated towards a largely American and European culture (Kaufman, McLean & Reynolds, 1988). These differences, although often ascribed to race, language or socio-economic status can best be understood more broadly in terms of degree of acculturation (i.e. westernisation) (Shuttleworth-Jordan, 1996) and test-wiseness (Nell, 1999). In South Africa in particular, with its extreme cultural diversity these factors need to be carefully considered when developing short forms. In the present study the development of a short form appropriate to South Africa's diverse cultural circumstances will be approached, through a sample which has been stratified according to gender, first language (English vs. African), quality of schooling received (Private/Model C vs. DET) and level of education achieved (Matric vs. Graduate). Both a subtest reduction method and an item reduction method will be considered to arrive at a short form. The subtest reduction method will be considered further in an attempt to clarify which subtests would be more or less appropriate to include in a short form considering group differences. Finally the thesis will develop suggestions as to which short forms would be best for use in South Africa.
- Full Text:
- Authors: Rust, Annegret L
- Date: 2000
- Subjects: Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3047 , http://hdl.handle.net/10962/d1002556 , Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Description: The Wechsler Adult Intelligence Scale - 3rd Edition (WAIS-III) is the newest of the internationally recognised Wechsler family of intelligence tests. It has been improved in terms of its psychometric properties, neuropsychological assessment abilities and its content. This test is in the process of being standardised by the Human Sciences Research Council (HSRC) in South Africa. As the adapted South African version will be available shortly for use in the multicultural circumstances of South Africa, the application of the various aspects of this test needs to be investigated. This test is very comprehensive and thorough, however its one disadvantage is that it takes on average three hours to administer in its entirety. Thus there is a need to find ways in which to abbreviate the test for particular purposes when time is limited, for example in research, brief clinical assessments or neuropsychological screenings. The concept of abbreviating tests, including the earlier Wechsler intelligence test can be traced back to 1917, when it was asked if all the items on the Binet-Simon scale were required to give an accurate assessment of IQ (Levy, 1968). Since then there have been many short form suggestions made, with many different considerations in mind. These can be divided into two main approaches or methods. Firstly, the number of subtests of the scale can be reduced. Thus with the WAIS-III which consists of 14 subtests in total, an option is to use, for example only four of the subtests to get an estimate of a person's IQ. Secondly, the number of items in each subtest can be reduced. Thus only half the items or even only a third of the items on a subtest can be administered to get an estimate of the persons' performance on each subtest and in this way estimate their overall IQ. Both methods have been used on the WAIS and WAIS-R, although the reduction of the subtests is favoured. Both should now be validated and considered for use with the WATS-III in South Africa. Wechsler tests and their constituent subtests have been found to be differentially effected by race, education, language and socio-economic status (Kaufman, McLean & Reynolds, 1988; Nell 1999). These differences have also been found to impact on the short forms which are suggested, as certain subtests are considered to be more biased towards particular groups than others. Vocabulary and Block Design in particular bias testees who are not as westernised or acculturated towards a largely American and European culture (Kaufman, McLean & Reynolds, 1988). These differences, although often ascribed to race, language or socio-economic status can best be understood more broadly in terms of degree of acculturation (i.e. westernisation) (Shuttleworth-Jordan, 1996) and test-wiseness (Nell, 1999). In South Africa in particular, with its extreme cultural diversity these factors need to be carefully considered when developing short forms. In the present study the development of a short form appropriate to South Africa's diverse cultural circumstances will be approached, through a sample which has been stratified according to gender, first language (English vs. African), quality of schooling received (Private/Model C vs. DET) and level of education achieved (Matric vs. Graduate). Both a subtest reduction method and an item reduction method will be considered to arrive at a short form. The subtest reduction method will be considered further in an attempt to clarify which subtests would be more or less appropriate to include in a short form considering group differences. Finally the thesis will develop suggestions as to which short forms would be best for use in South Africa.
- Full Text:
The dynamics of an emerging outcomes-based educational approach in a second language English classroom
- Authors: Westphal, Vivian
- Date: 2000
- Subjects: English language -- Study and teaching -- Foreign speakers -- South Africa Competency-based education -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1502 , http://hdl.handle.net/10962/d1003384
- Description: Curriculum 2005 and outcomes-based education was introduced to South African educators in 1996 by the Minister of Education, Prof. S.M.E. Bengu as an alternative to the racially divided education system prior to the first democratic elections of 1995. The new curriculum was designed to transform the education system into a more equitable system by focussing on creating learners who would become creative thinkers, independent, productive workers and responsible, non-racial citizens. Learners would take a greater role in their own education and teachers would take on new roles as facilitators in the learning process. The new approach was introduced into grade 1 in 1998 and grade 2 in 1999. By using a modified ethnographic approach, this research project studies how one teacher has begun to think about Curriculum 2005 and implement an OBE approach to ESL teaching in a grade 2 classroom. It also focuses on gaining insights into how the teacher has attempted to make sense of the new curriculum in terms of her current practice and the training she has received in OBE. The ethnographic approach of the thesis has allowed the researcher to draw on many forms of data providing a holistic view. Tentative findings show that the teacher is experiencing difficulty in “unpacking” the underlying principles of OBE in terms of her current methods of teaching ESL. She continues to work from tacit knowledge. Because she has received very little training in OBE, she lacks the tools to become a more reflective practitioner. Despite this, her ESL lessons show a positive communicative approach to language teaching by focusing on stories, rhymes and songs as comprehensible input for the learners. The findings of this thesis tentatively suggest that unless teachers are given more adequate training and learning support materials, their classroom practices will remain relatively unchanged.
- Full Text:
- Authors: Westphal, Vivian
- Date: 2000
- Subjects: English language -- Study and teaching -- Foreign speakers -- South Africa Competency-based education -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1502 , http://hdl.handle.net/10962/d1003384
- Description: Curriculum 2005 and outcomes-based education was introduced to South African educators in 1996 by the Minister of Education, Prof. S.M.E. Bengu as an alternative to the racially divided education system prior to the first democratic elections of 1995. The new curriculum was designed to transform the education system into a more equitable system by focussing on creating learners who would become creative thinkers, independent, productive workers and responsible, non-racial citizens. Learners would take a greater role in their own education and teachers would take on new roles as facilitators in the learning process. The new approach was introduced into grade 1 in 1998 and grade 2 in 1999. By using a modified ethnographic approach, this research project studies how one teacher has begun to think about Curriculum 2005 and implement an OBE approach to ESL teaching in a grade 2 classroom. It also focuses on gaining insights into how the teacher has attempted to make sense of the new curriculum in terms of her current practice and the training she has received in OBE. The ethnographic approach of the thesis has allowed the researcher to draw on many forms of data providing a holistic view. Tentative findings show that the teacher is experiencing difficulty in “unpacking” the underlying principles of OBE in terms of her current methods of teaching ESL. She continues to work from tacit knowledge. Because she has received very little training in OBE, she lacks the tools to become a more reflective practitioner. Despite this, her ESL lessons show a positive communicative approach to language teaching by focusing on stories, rhymes and songs as comprehensible input for the learners. The findings of this thesis tentatively suggest that unless teachers are given more adequate training and learning support materials, their classroom practices will remain relatively unchanged.
- Full Text:
The economic implications of trade policy reform in South Africa for the automotive industry in the Eastern Cape Province
- Authors: Onyango, Donald Otieno
- Date: 2000
- Subjects: Automobile industry and trade -- South Africa -- Eastern Cape , South Africa -- Commercial policy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:936 , http://hdl.handle.net/10962/d1002669 , Automobile industry and trade -- South Africa -- Eastern Cape , South Africa -- Commercial policy
- Description: South Africa is no longer a pariah state and has been fully integrated into the global family of nations. With the country’s accession to multilateral agreements like the World Trade Organization (WTO), there has been pressure on the government to abandon its hitherto protectionist trade regime in favour of free and fair trade. Trade liberalisation has had profound implications for the country’s manufacturing sector in general, and the automotive industry in particular, which has seen tariff protection radically slashed and import restrictions greatly eased. Not only has the market share of domestic producers fallen, but increases in exports have to date not matched those of imports. As a result there has been a deterioration in the sector’s balance of trade and a reduction in employment levels, at a time when the country desperately needs to create new jobs. Recent developments, however, suggest that this scenario may be set to change. The thesis applies orthodox neoclassical and heterodox approaches to trade policy to an assessment of the likely economic impact of trade liberalisation on the automotive industry in the Eastern Cape, and by extension nationally. The thesis argues that reliance on orthodox trade theory to inform the direction of trade policy, especially in a developing country context, is unlikely to bring about an adequate increase in the level of exports and employment. This is because liberalisation of the import regime is likely to increase import levels without necessarily stimulating export levels, a scenario which serves to negate the presupposed benefits of liberalisation. The study uses information from surveys conducted on both motor vehicle assemblers and component manufacturing firms to investigate the effect of trade liberalisation on the sector in the Province and finds that, by and large, the motor assemblers have not fared as badly as expected and have in fact positioned themselves to export more vehicles and components. The components sector has had to contend with increased competition from cheaper imports. The thesis, while acknowledging that, as far as possible, free trade is an optimal position, nonetheless argues that governments still have an important role to play in the promotion of industrialisation. The scope of government intervention should, however, be limited to selective interventions which are aimed at counteracting market failure and facilitating innovation and the diffusion of technological know-how. The thesis argues that institution of supply side measures, such as the encouragement of research and development (R&D), skills development and industrial training, is necessary for sustained growth in the manufacturing sector to be realised. The thesis also finds that, contrary to expectations, the liberalisation of the automotive sector has not had the desired effects. Despite an increase in the value of automotive exports and an overall trend towards reduced net foreign exchange usage, employment levels are on the decline. The thesis also finds that without major export initiatives by both motor vehicle assemblers and component manufacturers, the future of the industry will be placed in jeopardy, especially with reduced protection and incentives.
- Full Text:
- Authors: Onyango, Donald Otieno
- Date: 2000
- Subjects: Automobile industry and trade -- South Africa -- Eastern Cape , South Africa -- Commercial policy
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:936 , http://hdl.handle.net/10962/d1002669 , Automobile industry and trade -- South Africa -- Eastern Cape , South Africa -- Commercial policy
- Description: South Africa is no longer a pariah state and has been fully integrated into the global family of nations. With the country’s accession to multilateral agreements like the World Trade Organization (WTO), there has been pressure on the government to abandon its hitherto protectionist trade regime in favour of free and fair trade. Trade liberalisation has had profound implications for the country’s manufacturing sector in general, and the automotive industry in particular, which has seen tariff protection radically slashed and import restrictions greatly eased. Not only has the market share of domestic producers fallen, but increases in exports have to date not matched those of imports. As a result there has been a deterioration in the sector’s balance of trade and a reduction in employment levels, at a time when the country desperately needs to create new jobs. Recent developments, however, suggest that this scenario may be set to change. The thesis applies orthodox neoclassical and heterodox approaches to trade policy to an assessment of the likely economic impact of trade liberalisation on the automotive industry in the Eastern Cape, and by extension nationally. The thesis argues that reliance on orthodox trade theory to inform the direction of trade policy, especially in a developing country context, is unlikely to bring about an adequate increase in the level of exports and employment. This is because liberalisation of the import regime is likely to increase import levels without necessarily stimulating export levels, a scenario which serves to negate the presupposed benefits of liberalisation. The study uses information from surveys conducted on both motor vehicle assemblers and component manufacturing firms to investigate the effect of trade liberalisation on the sector in the Province and finds that, by and large, the motor assemblers have not fared as badly as expected and have in fact positioned themselves to export more vehicles and components. The components sector has had to contend with increased competition from cheaper imports. The thesis, while acknowledging that, as far as possible, free trade is an optimal position, nonetheless argues that governments still have an important role to play in the promotion of industrialisation. The scope of government intervention should, however, be limited to selective interventions which are aimed at counteracting market failure and facilitating innovation and the diffusion of technological know-how. The thesis argues that institution of supply side measures, such as the encouragement of research and development (R&D), skills development and industrial training, is necessary for sustained growth in the manufacturing sector to be realised. The thesis also finds that, contrary to expectations, the liberalisation of the automotive sector has not had the desired effects. Despite an increase in the value of automotive exports and an overall trend towards reduced net foreign exchange usage, employment levels are on the decline. The thesis also finds that without major export initiatives by both motor vehicle assemblers and component manufacturers, the future of the industry will be placed in jeopardy, especially with reduced protection and incentives.
- Full Text:
The effect of 6-Methoxy-2-Benzoxazolinone (6-MBOA) on indoleamine regulation and its possible role in depression
- Authors: Tanda, Sindiswa Eunice
- Date: 2000
- Subjects: Tryptophan -- Physiological effect , Tryptophan -- Therapeutic use , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3912 , http://hdl.handle.net/10962/d1003971 , Tryptophan -- Physiological effect , Tryptophan -- Therapeutic use , Antidepressants
- Description: Tryptophan is an essential amino acid that is obtained from the diet. Approximately 98 % of ingested tryptophan is metabolized by the enzyme tryptophan 2,3-dioxygenase (TDO). The metabolism of tryptophan by TDO is an important determinant of tryptophan bioavailability to the brain for serotonin (5-HT) biosynthesis, an essential amine in affective disorders such as depression. Studies done on circadian rhythmicity of the enzyme activity have shown that, TDO activity is high during the scoto-phase (dark-phase), which is attributable to the de novo enzyme synthesis that occurs during this phase. 6-Methoxy-2-benzoxazolinontr-(6-MBOA), a structural analogue of melatonin (aMT) was shown to inhibit TDO activity in both the photo-phase (light-phase) and the scoto-phase with greater potency during the light-phase. Further studies were directed at demonstrating the effects of 6-MBOA on the brain tryptophan hydroxylase (TH) activity, which is a rate limiting enzyme in 5-HT biosynthesis and subsequently on 5-HT levels. The findings showed that, 6-MBOA induces TH activity with a concomitant rise in brain 5-HT levels. The blockade of 5-HT re-uptake into the presynaptic neuron leads to an increase in 5-HT available for the stimulatory action of 5-HT receptors. An attempt to establish whether the administration of 6-MBOA would block the binding of 5-HT to receptors on the synaptosomal membrane showed that 6-MBO A only inhibits the binding of 5 -HT at specific concentrations. In view of the positive effects imposed by 6-MBOA on brain 5-HT levels, urinary 5-hydroxyindole acetic acid (5-HIAA) excretion was measured before and after treatment with 6-MBOA. 5-HIAA excretion was found to be significantly increased after 6-MBOA treatment. Extensive research on the biosynthesis of pineal metabolites has been conducted in the past two decades. The pineal metabolites are synthesized from the precursor tryptophan. In order to obtain an overall picture of the effect of6-MBOA on pineal indole metabolism, an organ culture technique was employed. The results obtained showed that although 6-MBOA administration to rats caused a significant increase in aMT production, there was an insignificant increase in NAS production. This is an immediate precursor of aMT. Other pineal indoles were not affected at all by 6-MBOA administration. Furthermore, the production of pineal NAS and aMT showed an inter-individual variation with some animals producing very high, some very low and some produced average levels of these two metabolites in both photo and scoto-phase experiments. A study undertaken to investigate the circadian rhythm in endogenous aMT production using the competitive ELISA technique showed a clear pattern with high levels of aMT produced during the dark-phase and low levels ofaMT produced during the light-phase. Furthermore, the administration of6-MBOA to rats lead to a significant rise in endogenous aMT production.
- Full Text:
- Authors: Tanda, Sindiswa Eunice
- Date: 2000
- Subjects: Tryptophan -- Physiological effect , Tryptophan -- Therapeutic use , Antidepressants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3912 , http://hdl.handle.net/10962/d1003971 , Tryptophan -- Physiological effect , Tryptophan -- Therapeutic use , Antidepressants
- Description: Tryptophan is an essential amino acid that is obtained from the diet. Approximately 98 % of ingested tryptophan is metabolized by the enzyme tryptophan 2,3-dioxygenase (TDO). The metabolism of tryptophan by TDO is an important determinant of tryptophan bioavailability to the brain for serotonin (5-HT) biosynthesis, an essential amine in affective disorders such as depression. Studies done on circadian rhythmicity of the enzyme activity have shown that, TDO activity is high during the scoto-phase (dark-phase), which is attributable to the de novo enzyme synthesis that occurs during this phase. 6-Methoxy-2-benzoxazolinontr-(6-MBOA), a structural analogue of melatonin (aMT) was shown to inhibit TDO activity in both the photo-phase (light-phase) and the scoto-phase with greater potency during the light-phase. Further studies were directed at demonstrating the effects of 6-MBOA on the brain tryptophan hydroxylase (TH) activity, which is a rate limiting enzyme in 5-HT biosynthesis and subsequently on 5-HT levels. The findings showed that, 6-MBOA induces TH activity with a concomitant rise in brain 5-HT levels. The blockade of 5-HT re-uptake into the presynaptic neuron leads to an increase in 5-HT available for the stimulatory action of 5-HT receptors. An attempt to establish whether the administration of 6-MBOA would block the binding of 5-HT to receptors on the synaptosomal membrane showed that 6-MBO A only inhibits the binding of 5 -HT at specific concentrations. In view of the positive effects imposed by 6-MBOA on brain 5-HT levels, urinary 5-hydroxyindole acetic acid (5-HIAA) excretion was measured before and after treatment with 6-MBOA. 5-HIAA excretion was found to be significantly increased after 6-MBOA treatment. Extensive research on the biosynthesis of pineal metabolites has been conducted in the past two decades. The pineal metabolites are synthesized from the precursor tryptophan. In order to obtain an overall picture of the effect of6-MBOA on pineal indole metabolism, an organ culture technique was employed. The results obtained showed that although 6-MBOA administration to rats caused a significant increase in aMT production, there was an insignificant increase in NAS production. This is an immediate precursor of aMT. Other pineal indoles were not affected at all by 6-MBOA administration. Furthermore, the production of pineal NAS and aMT showed an inter-individual variation with some animals producing very high, some very low and some produced average levels of these two metabolites in both photo and scoto-phase experiments. A study undertaken to investigate the circadian rhythm in endogenous aMT production using the competitive ELISA technique showed a clear pattern with high levels of aMT produced during the dark-phase and low levels ofaMT produced during the light-phase. Furthermore, the administration of6-MBOA to rats lead to a significant rise in endogenous aMT production.
- Full Text:
The effect of load carriage on selected metabolic and perceptual responses of military personnel
- Authors: Ramabhai, Leena I
- Date: 2000
- Subjects: Marching -- Physiological aspects , Military art and science , Marching -- Psychological aspects , Lifting and carrying
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5111 , http://hdl.handle.net/10962/d1005189
- Description: Taking a multi-disciplinary, integrated approach, the present study sought to examine selected physiological and psycho-physical parameters related to load carriage involving a 12 km march under military conditions. Military constraints hampered, but did not entirely inhibit the secondary aim of the study which concerned the effectiveness of relativising loads in order to normalise responses for all soldiers, irrespective of morphological diversity. Forty three subjects were measured in six groups using a test-retest experimental protocol. They were involved in a rest-broken 12 km march at 4 km.h⁻¹ under 40.5 kg absolute total load and under a relative load of 37% of body mass. Heart rates, ratings of perceived exertion (RPE) as well as area and intensity of discomfort were monitored for all subjects. Ten subjects were measured more extensively with regard to physiology using the Metamax, a portable ergospirometry system that provides all the data needed for a complete functional analysis of lung, heart, circulation and metabolic activity. Physiological responses (fc; fb; V̇T; V̇E; V̇O₂; EE; V̇CO₂; R; T°) indicated subjects were not severely physically taxed and that the loads imposed constituted a sub-maximal demand. Moreover, there appeared to be a limited cumulative effect over the 3.5 h. Data from the first and third hours were similar, while the significantly higher responses in the second hour reflected the challenge of the undulating terrain encountered during this section of the march. All responses during the Relative load conditions mirrored those of the Absolute load condition but, because the demands were less, the trends occurred at a reduced level. Furthermore, the reduction in inter-individual variability indicates that relativised load carriage tends to stress the soldiers in a more uniform manner. All "local" RPE responses were higher than "central" ratings, suggesting soldiers were in good cardiovascular condition and experienced marginally more strain in the lower limbs. There was increased perceived strain corresponding to the increase in gradient, with little cumulative effect over the three hours. The shoulders and feet were the two regions in which most discomfort was experienced; the shoulders being the worst area in the first hour and the feet being rated the worst after the third hour of marching. This study clearly demonstrates the probability of a significant improvement in mean combat-readiness following loaded marching by showing that, if loads are set at levels commensurate with individual capabilities to carry them without undue strain, unnecessary physical demands experienced by smaller, more gracile soldiers are reduced.
- Full Text:
- Authors: Ramabhai, Leena I
- Date: 2000
- Subjects: Marching -- Physiological aspects , Military art and science , Marching -- Psychological aspects , Lifting and carrying
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5111 , http://hdl.handle.net/10962/d1005189
- Description: Taking a multi-disciplinary, integrated approach, the present study sought to examine selected physiological and psycho-physical parameters related to load carriage involving a 12 km march under military conditions. Military constraints hampered, but did not entirely inhibit the secondary aim of the study which concerned the effectiveness of relativising loads in order to normalise responses for all soldiers, irrespective of morphological diversity. Forty three subjects were measured in six groups using a test-retest experimental protocol. They were involved in a rest-broken 12 km march at 4 km.h⁻¹ under 40.5 kg absolute total load and under a relative load of 37% of body mass. Heart rates, ratings of perceived exertion (RPE) as well as area and intensity of discomfort were monitored for all subjects. Ten subjects were measured more extensively with regard to physiology using the Metamax, a portable ergospirometry system that provides all the data needed for a complete functional analysis of lung, heart, circulation and metabolic activity. Physiological responses (fc; fb; V̇T; V̇E; V̇O₂; EE; V̇CO₂; R; T°) indicated subjects were not severely physically taxed and that the loads imposed constituted a sub-maximal demand. Moreover, there appeared to be a limited cumulative effect over the 3.5 h. Data from the first and third hours were similar, while the significantly higher responses in the second hour reflected the challenge of the undulating terrain encountered during this section of the march. All responses during the Relative load conditions mirrored those of the Absolute load condition but, because the demands were less, the trends occurred at a reduced level. Furthermore, the reduction in inter-individual variability indicates that relativised load carriage tends to stress the soldiers in a more uniform manner. All "local" RPE responses were higher than "central" ratings, suggesting soldiers were in good cardiovascular condition and experienced marginally more strain in the lower limbs. There was increased perceived strain corresponding to the increase in gradient, with little cumulative effect over the three hours. The shoulders and feet were the two regions in which most discomfort was experienced; the shoulders being the worst area in the first hour and the feet being rated the worst after the third hour of marching. This study clearly demonstrates the probability of a significant improvement in mean combat-readiness following loaded marching by showing that, if loads are set at levels commensurate with individual capabilities to carry them without undue strain, unnecessary physical demands experienced by smaller, more gracile soldiers are reduced.
- Full Text:
The evolution of the Brosterlea Volcanic Complex, Eastern Cape, South Africa
- Authors: Surtees, Grant Bradley
- Date: 2000
- Subjects: Volcanism , Geology -- South Africa -- Eastern Cape -- Brosterlea Volcanic Complex , Geology -- South Africa -- Eastern Cape , Flood basalts , Geology, Structural -- South Africa , Formations (Geology) -- South Africa , Geology, Structural -- Maps , Geological mapping
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4944 , http://hdl.handle.net/10962/d1005556 , Volcanism , Geology -- South Africa -- Eastern Cape -- Brosterlea Volcanic Complex , Geology -- South Africa -- Eastern Cape , Flood basalts , Geology, Structural -- South Africa , Formations (Geology) -- South Africa , Geology, Structural -- Maps , Geological mapping
- Description: Detailed field mapping (Map, Appendix B) has been conducted in and around the boundaries of a 14x18km, volcanic complex 35km northeast of Molteno in the Eastern Cape Province, South Africa. The structure is interpreted as a subsidence structure, and is filled with two volcaniclastic breccias, numerous lava flows, a number of sedimentary facies, and lies on a base of Clarens Formation overlying Elliot Formation rocks. This is an important study because 'widespread, voluminous fields of basaltic breccias are very rare (see Hanson and Elliot, 1996) and this is the first time that this type of volcanic complex and its deposits have been described. Detailed analyses of the two volcaniclastic breccias revealed changes in colour, clast types, clast sizes, and degree of alteration over relatively short distances both vertically and laterally within a single breccia unit. The variation in clast sizes implies a lack of sorting of the breccias. The lower of the two volcaniclastic breccias fills the subsidence structure, and outcrops between the Stormberg sedimentary sequence and the overlying Drakensberg basalts and was produced from phreatomagmatic eruptions signalling the start of the break-up of Gondwanaland in the mid-Jurassic. The upper volcaniclastic breccia is interbedded with the flood basalts and is separated from the lower breccia by up to 100m of lava flows in places, it is finer-grained than the lower volcaniclastic breccia, and it extends over 10km south, and over 100km north from the volcanic complex. The upper breccia is inferred to have been transported from outside the study area, from a source presumably similar to the subsidence structure in the volcanic complex. The pyroclastic material forming the upper breccia was transported to the subsidence structure as a laharic debris flow, based on its poorly sorted, unwelded and matrix-supported appearance. However, both breccias are unlikely to have been derived from epiclastic reworking of lava flows as they contain glass shards which are atypical of those derived from the autoclastic component of lava flows. The breccias are therefore not "secondary" lahars. There is also no evidence of any palaeotopographic highs from which the breccias could have been derived as gravity-driven flows. Based on the occurrence of three, 1m thick lacustrine deposits, localised peperite, fluvial reworking of sandstone and breccia in an outcrop to the south of the subsidence structure, and channel-lags encountered only in the upper units of the Clarens Formation and only within the subsidence structure, the palaeoenvironment inferred for the subsidence structure is one of wet sediment, possibly a shallow lake, in a topographic depression fed by small streams. Magmatic intrusions below the subsidence structure heated the water-laden, partly consolidated Clarens Formation sandstones, causing the circulation of pore fluid which resulted in the precipitation of minerals forming pisoliths in the sandstones. Intruding magma mixed, nonexplosively, with the wet, unconsolidated sediments near the base of the Clarens Formation (at approximately 100m below the surface), forming fluidal peperite by a process of sediment fluidisation where magma replaces wet sediment and cools slowly enough to prevent the magma fracturing brittly. Formation of fluidal peperite may have been a precursor to the development of FCIs (Fuel Coolant Interactions) (Busby-Spera and White, 1987). The breccias may represent the products of FCIs and may be the erupted equivalents of the peperites, suggesting a possible genetic link between the two. The peperites may have given way to FCI eruptions due to a number of factors including the drying out of the sediments and/or an increase in the volume of intruded magma below the subsidence structure which may have resulted in a more explosive interaction between sediment and magma. Phreatic activity fragmented and erupted the Clarens Formation sandstone, and stream flows reworked the angular sandstone fragments, pisoliths and sand grains into channelised deposits. With an increase in magmatic activity below the subsidence structure, phreatic activity became phreatomagmatic. The wet, partly consolidated Clarens Formation, and underlying, fully consolidated Elliot Formation sediments were erupted and fragmented. Clasts and individual grains of these sediments were redeposited with juvenile and non-juvenile basaltic material probably by a combination of back fall, where clasts erupted into the air fell directly back into the structure, and backflow where material was erupted out of the structure, but immediately flowed back in as lahars. This material formed the lower volcaniclastic breccia. A fault plane is identified along the southwestern margin of the subsidence structure, and is believed to continue up the western margin to the northwestern corner. A large dolerite body has intruded along the inferred fault plane on the western margin of the structure, and may be related to the formation of the lower volcaniclastic breccia, either directly through fluidisation of wet sediment during its intrusion, or as a dyke extending upwards from a network of sill-like intrusions below the subsidence structure. Geochemical analysis of the Drakensberg basalt lava flows by Mitchell (1980) and Masokwane (1997) revealed four distinct basalt types; the Moshesh's Ford, the Tafelkop, the Roodehoek, and the Vaalkop basalts. Basalt clasts sampled from the lower volcaniclastic breccia were shown to belong to the Moshesh's Ford basalt type which does not outcrop in situ within the subsidence structure. This implies that the Moshesh's Ford basalts were emplaced prior to the formation of the lower volcaniclastic breccia, and may have acted as a "cap-rock" over the system, allowing pressure from the vaporised fluids, heated by intruding basalt, to build up. The Moshesh's Ford basalt type was erupted prior to the resultant phreatomagmatic events forming the lower volcaniclastic breccia.
- Full Text:
- Authors: Surtees, Grant Bradley
- Date: 2000
- Subjects: Volcanism , Geology -- South Africa -- Eastern Cape -- Brosterlea Volcanic Complex , Geology -- South Africa -- Eastern Cape , Flood basalts , Geology, Structural -- South Africa , Formations (Geology) -- South Africa , Geology, Structural -- Maps , Geological mapping
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4944 , http://hdl.handle.net/10962/d1005556 , Volcanism , Geology -- South Africa -- Eastern Cape -- Brosterlea Volcanic Complex , Geology -- South Africa -- Eastern Cape , Flood basalts , Geology, Structural -- South Africa , Formations (Geology) -- South Africa , Geology, Structural -- Maps , Geological mapping
- Description: Detailed field mapping (Map, Appendix B) has been conducted in and around the boundaries of a 14x18km, volcanic complex 35km northeast of Molteno in the Eastern Cape Province, South Africa. The structure is interpreted as a subsidence structure, and is filled with two volcaniclastic breccias, numerous lava flows, a number of sedimentary facies, and lies on a base of Clarens Formation overlying Elliot Formation rocks. This is an important study because 'widespread, voluminous fields of basaltic breccias are very rare (see Hanson and Elliot, 1996) and this is the first time that this type of volcanic complex and its deposits have been described. Detailed analyses of the two volcaniclastic breccias revealed changes in colour, clast types, clast sizes, and degree of alteration over relatively short distances both vertically and laterally within a single breccia unit. The variation in clast sizes implies a lack of sorting of the breccias. The lower of the two volcaniclastic breccias fills the subsidence structure, and outcrops between the Stormberg sedimentary sequence and the overlying Drakensberg basalts and was produced from phreatomagmatic eruptions signalling the start of the break-up of Gondwanaland in the mid-Jurassic. The upper volcaniclastic breccia is interbedded with the flood basalts and is separated from the lower breccia by up to 100m of lava flows in places, it is finer-grained than the lower volcaniclastic breccia, and it extends over 10km south, and over 100km north from the volcanic complex. The upper breccia is inferred to have been transported from outside the study area, from a source presumably similar to the subsidence structure in the volcanic complex. The pyroclastic material forming the upper breccia was transported to the subsidence structure as a laharic debris flow, based on its poorly sorted, unwelded and matrix-supported appearance. However, both breccias are unlikely to have been derived from epiclastic reworking of lava flows as they contain glass shards which are atypical of those derived from the autoclastic component of lava flows. The breccias are therefore not "secondary" lahars. There is also no evidence of any palaeotopographic highs from which the breccias could have been derived as gravity-driven flows. Based on the occurrence of three, 1m thick lacustrine deposits, localised peperite, fluvial reworking of sandstone and breccia in an outcrop to the south of the subsidence structure, and channel-lags encountered only in the upper units of the Clarens Formation and only within the subsidence structure, the palaeoenvironment inferred for the subsidence structure is one of wet sediment, possibly a shallow lake, in a topographic depression fed by small streams. Magmatic intrusions below the subsidence structure heated the water-laden, partly consolidated Clarens Formation sandstones, causing the circulation of pore fluid which resulted in the precipitation of minerals forming pisoliths in the sandstones. Intruding magma mixed, nonexplosively, with the wet, unconsolidated sediments near the base of the Clarens Formation (at approximately 100m below the surface), forming fluidal peperite by a process of sediment fluidisation where magma replaces wet sediment and cools slowly enough to prevent the magma fracturing brittly. Formation of fluidal peperite may have been a precursor to the development of FCIs (Fuel Coolant Interactions) (Busby-Spera and White, 1987). The breccias may represent the products of FCIs and may be the erupted equivalents of the peperites, suggesting a possible genetic link between the two. The peperites may have given way to FCI eruptions due to a number of factors including the drying out of the sediments and/or an increase in the volume of intruded magma below the subsidence structure which may have resulted in a more explosive interaction between sediment and magma. Phreatic activity fragmented and erupted the Clarens Formation sandstone, and stream flows reworked the angular sandstone fragments, pisoliths and sand grains into channelised deposits. With an increase in magmatic activity below the subsidence structure, phreatic activity became phreatomagmatic. The wet, partly consolidated Clarens Formation, and underlying, fully consolidated Elliot Formation sediments were erupted and fragmented. Clasts and individual grains of these sediments were redeposited with juvenile and non-juvenile basaltic material probably by a combination of back fall, where clasts erupted into the air fell directly back into the structure, and backflow where material was erupted out of the structure, but immediately flowed back in as lahars. This material formed the lower volcaniclastic breccia. A fault plane is identified along the southwestern margin of the subsidence structure, and is believed to continue up the western margin to the northwestern corner. A large dolerite body has intruded along the inferred fault plane on the western margin of the structure, and may be related to the formation of the lower volcaniclastic breccia, either directly through fluidisation of wet sediment during its intrusion, or as a dyke extending upwards from a network of sill-like intrusions below the subsidence structure. Geochemical analysis of the Drakensberg basalt lava flows by Mitchell (1980) and Masokwane (1997) revealed four distinct basalt types; the Moshesh's Ford, the Tafelkop, the Roodehoek, and the Vaalkop basalts. Basalt clasts sampled from the lower volcaniclastic breccia were shown to belong to the Moshesh's Ford basalt type which does not outcrop in situ within the subsidence structure. This implies that the Moshesh's Ford basalts were emplaced prior to the formation of the lower volcaniclastic breccia, and may have acted as a "cap-rock" over the system, allowing pressure from the vaporised fluids, heated by intruding basalt, to build up. The Moshesh's Ford basalt type was erupted prior to the resultant phreatomagmatic events forming the lower volcaniclastic breccia.
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The experience of multi-cultural communication within a South African organization
- Authors: Lesch, Anthea M
- Date: 2000
- Subjects: Intercultural communication -- South Africa , Communication in management -- South Africa , Communication in personnel management -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:3008 , http://hdl.handle.net/10962/d1002517 , Intercultural communication -- South Africa , Communication in management -- South Africa , Communication in personnel management -- South Africa
- Description: This research study was conducted in an attempt to explore the experience of multicultural communication within a South African organization. To this end employees, representing both Black and White culture, within a South African organization in the throes of transformation, were accessed. A model of managing diversity, focussing on the personal, interpersonal and organizational levels, was utilized in an attempt to uncover the nature of the experience of multi-cultural communication within Company X. A qualitative research design, and more specifically the case study method was employed in this study. Consistent with the case study approach a number of data sources were accessed. The primary data source consisted of a 3-stage interview process. Other data sources included documentary sources and company publications. By accessing multiple data sources, the researcher attempted to gain a holistic understanding of the experience of multi-cultural communication. It was found that the societal context of our post-Apartheid society exercises a profound influence on multi-cultural communication. Under Apartheid cultural separation was promoted. Diverse peoples thus have little common basis for interaction and view each other with skepticism and distrust. This exercises an effect on the personal and organizational levels of the managing diversity model. Influences at the personal level relate to the cultural paradigms of the individuals which provide the rules governing interactions and affect judgements of acceptable and unacceptable behaviours. Issues at the organizational level relate to its structures and policies which are still based on the “white is right ideology”. These issues, in turn, affect the interpersonal level of managing diversity, i.e., where the interactions occur, causing “communication short circuits” within the process of multi-cultural communication. In order to deal with failed multi-cultural communication, the individuals have developed a number of coping strategies. The results of the study indicate that both the organization and its employees share a responsibility for creating an environment that will facilitate effective multi-cultural communication.
- Full Text:
- Authors: Lesch, Anthea M
- Date: 2000
- Subjects: Intercultural communication -- South Africa , Communication in management -- South Africa , Communication in personnel management -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:3008 , http://hdl.handle.net/10962/d1002517 , Intercultural communication -- South Africa , Communication in management -- South Africa , Communication in personnel management -- South Africa
- Description: This research study was conducted in an attempt to explore the experience of multicultural communication within a South African organization. To this end employees, representing both Black and White culture, within a South African organization in the throes of transformation, were accessed. A model of managing diversity, focussing on the personal, interpersonal and organizational levels, was utilized in an attempt to uncover the nature of the experience of multi-cultural communication within Company X. A qualitative research design, and more specifically the case study method was employed in this study. Consistent with the case study approach a number of data sources were accessed. The primary data source consisted of a 3-stage interview process. Other data sources included documentary sources and company publications. By accessing multiple data sources, the researcher attempted to gain a holistic understanding of the experience of multi-cultural communication. It was found that the societal context of our post-Apartheid society exercises a profound influence on multi-cultural communication. Under Apartheid cultural separation was promoted. Diverse peoples thus have little common basis for interaction and view each other with skepticism and distrust. This exercises an effect on the personal and organizational levels of the managing diversity model. Influences at the personal level relate to the cultural paradigms of the individuals which provide the rules governing interactions and affect judgements of acceptable and unacceptable behaviours. Issues at the organizational level relate to its structures and policies which are still based on the “white is right ideology”. These issues, in turn, affect the interpersonal level of managing diversity, i.e., where the interactions occur, causing “communication short circuits” within the process of multi-cultural communication. In order to deal with failed multi-cultural communication, the individuals have developed a number of coping strategies. The results of the study indicate that both the organization and its employees share a responsibility for creating an environment that will facilitate effective multi-cultural communication.
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The geomorphological impacts of impoundments, with particular reference to tributary bar development on the Keiskamma River, Eastern Cape
- Authors: McGregor, Gillian Kathleen
- Date: 2000
- Subjects: Rivers--South Africa--Regulation , Rivers--South Africa--Regulation--Environmental aspects , Rivers--South Africa--Eastern Cape , Geomorphology--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4835 , http://hdl.handle.net/10962/d1005510 , Rivers--South Africa--Regulation , Rivers--South Africa--Regulation--Environmental aspects , Rivers--South Africa--Eastern Cape , Geomorphology--South Africa--Eastern Cape
- Description: The primary aim of this research was to develop and test a conceptual model of the geomorphological impacts of river regulation, based on a review of relevant international literature. It was motivated by the fact that there is very little local information on the topic, and it was intended that the model might provide a starting point for assessing the impact of impoundments on South African river systems. At present most research in South Africa on the impact of impoundments is undertaken from an ecological perspective. In order to manage our water resources sustainably it is necessary to have a better understanding of our river systems. South Africa is characterised by a variable climatic regime and, in order to supply water to the various user sectors of the nation, dams have to be larger than elsewhere in the world, to trap most of the mean annual runoff and provide a reliable water store (Alexander, 1985). South African dams have been designed to reduce the variability of a naturally variable regime. The impact of flow regulation in dryland rivers has been described as 'ecologically catastrophic at every level.' It is therefore hardly surprising that the impact of these dams on the natural functioning of rivers is substantial. The conceptual model showed that there are many responses to river impoundment, which are varied and complex, both in time and space. Responses or secondary impacts depended on the nature and degree of the primary impact or process alteration, on the sediment and flow regime of the river. High flows were affected in all cases and low flows were affected in most cases. The simplest form of change was Petts' (1979) concept of 'accommodation' of the regulated flow within the existing channel form. More complex responses occUrred where the channel perimeter was unstable, or where tributaries introduced fresh sediment loads. The river could adjust its long profile, cross sectional area and substrate composition by aggradation or degradation. The conceptual model was used in the Building Block Methodology to predict impoundment impacts at Instream Flow Requirement workshops on the Berg, Komati and Bivane rivers. It was also used in assessing the impact of the Sandile Dam on the Keiskamma river. Tributary junctions were identified as likely sites of change, and the morphology of bars at these junctions was investigated. Due to the number of variables affecting the sediment and flow regime in the system, and due to the fact that the primary impacts were not substantial, it was not possible to come to any decisive conclusions. It would seem that the dam is well located in the catchment, and, because the water is not heavily utilised, the secondary impacts are not great. The conceptual model was found to be a useful basic tool which might contribute to a better understanding of our river systems, and ultimately to improved sustainable resource management.
- Full Text:
- Authors: McGregor, Gillian Kathleen
- Date: 2000
- Subjects: Rivers--South Africa--Regulation , Rivers--South Africa--Regulation--Environmental aspects , Rivers--South Africa--Eastern Cape , Geomorphology--South Africa--Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4835 , http://hdl.handle.net/10962/d1005510 , Rivers--South Africa--Regulation , Rivers--South Africa--Regulation--Environmental aspects , Rivers--South Africa--Eastern Cape , Geomorphology--South Africa--Eastern Cape
- Description: The primary aim of this research was to develop and test a conceptual model of the geomorphological impacts of river regulation, based on a review of relevant international literature. It was motivated by the fact that there is very little local information on the topic, and it was intended that the model might provide a starting point for assessing the impact of impoundments on South African river systems. At present most research in South Africa on the impact of impoundments is undertaken from an ecological perspective. In order to manage our water resources sustainably it is necessary to have a better understanding of our river systems. South Africa is characterised by a variable climatic regime and, in order to supply water to the various user sectors of the nation, dams have to be larger than elsewhere in the world, to trap most of the mean annual runoff and provide a reliable water store (Alexander, 1985). South African dams have been designed to reduce the variability of a naturally variable regime. The impact of flow regulation in dryland rivers has been described as 'ecologically catastrophic at every level.' It is therefore hardly surprising that the impact of these dams on the natural functioning of rivers is substantial. The conceptual model showed that there are many responses to river impoundment, which are varied and complex, both in time and space. Responses or secondary impacts depended on the nature and degree of the primary impact or process alteration, on the sediment and flow regime of the river. High flows were affected in all cases and low flows were affected in most cases. The simplest form of change was Petts' (1979) concept of 'accommodation' of the regulated flow within the existing channel form. More complex responses occUrred where the channel perimeter was unstable, or where tributaries introduced fresh sediment loads. The river could adjust its long profile, cross sectional area and substrate composition by aggradation or degradation. The conceptual model was used in the Building Block Methodology to predict impoundment impacts at Instream Flow Requirement workshops on the Berg, Komati and Bivane rivers. It was also used in assessing the impact of the Sandile Dam on the Keiskamma river. Tributary junctions were identified as likely sites of change, and the morphology of bars at these junctions was investigated. Due to the number of variables affecting the sediment and flow regime in the system, and due to the fact that the primary impacts were not substantial, it was not possible to come to any decisive conclusions. It would seem that the dam is well located in the catchment, and, because the water is not heavily utilised, the secondary impacts are not great. The conceptual model was found to be a useful basic tool which might contribute to a better understanding of our river systems, and ultimately to improved sustainable resource management.
- Full Text:
The implementation of a core architecture for geophysical data acquisition
- Authors: Heasman, Ray Edward
- Date: 2000
- Subjects: Geophysics -- Data processing , Computer software -- Development , Seismometers , Computer input-output equipment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5471 , http://hdl.handle.net/10962/d1005256 , Geophysics -- Data processing , Computer software -- Development , Seismometers , Computer input-output equipment
- Description: This thesis describes the design, development and implementation of the core hardware and software of a modular data acquisition system for geophysical data collection. The primary application for this system is the acquisition and realtime processing of seismic data captured in mines. This system will be used by a commercial supplier of seismic instrumentation, ISS International, as a base architecture for the development of future products. The hardware and software has been designed to be extendable and support distributed processing. The IEEE-1394 High Performance Serial Bus is used to communicate with other CPU modules or peripherals. The software includes a pre-emptive multitasking microkernel, an asynchronous mailbox-based message passing communications system, and a functional IEEE-1394 protocol stack. The reasons for the end design and implementation decisions are given, and the problems encountered in the development of this system are described. A critical assessment of the match between the requirements for the project and the functionality of the implementation is made.
- Full Text:
- Authors: Heasman, Ray Edward
- Date: 2000
- Subjects: Geophysics -- Data processing , Computer software -- Development , Seismometers , Computer input-output equipment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5471 , http://hdl.handle.net/10962/d1005256 , Geophysics -- Data processing , Computer software -- Development , Seismometers , Computer input-output equipment
- Description: This thesis describes the design, development and implementation of the core hardware and software of a modular data acquisition system for geophysical data collection. The primary application for this system is the acquisition and realtime processing of seismic data captured in mines. This system will be used by a commercial supplier of seismic instrumentation, ISS International, as a base architecture for the development of future products. The hardware and software has been designed to be extendable and support distributed processing. The IEEE-1394 High Performance Serial Bus is used to communicate with other CPU modules or peripherals. The software includes a pre-emptive multitasking microkernel, an asynchronous mailbox-based message passing communications system, and a functional IEEE-1394 protocol stack. The reasons for the end design and implementation decisions are given, and the problems encountered in the development of this system are described. A critical assessment of the match between the requirements for the project and the functionality of the implementation is made.
- Full Text: