Multivariate morphometric analysis and behaviour of honeybees (Apis Mellifera L.) in the southern regions of Ethiopia
- Authors: Amssalu, Argaw Bezabeh
- Date: 2003
- Subjects: Honeybee -- Ethiopia -- Behavior Honeybee -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5616 , http://hdl.handle.net/10962/d1003130
- Description: Morphometric and behavioural characteristics of honeybees, Apis mellifera were analysed using multivariate and bivariate statistical methods to characterise honeybees of southern Ethiopian region. A total of 33800 morphometric character measurements were taken from 2600 individual worker honeybees of 130 honeybee colonies collected at 26 sampling localities with an average inter-locality distance of 89km to determine the occurrence of morphoclusters. 117 experienced farmer beekeepers and beekeeping experts were interviewed on pre-tested questionnaire to investigate the behavioural characteristics of these honeybees in their respective areas. Morphometric characters associated with pigmentation and body size exhibited a higher discriminant power while forewing venation angles (B4, N23 and 026) lack discriminatory power to segregate honeybees in the southern Ethiopian region. Principal components and discriminant analyses using the most discriminatory morphological characters delineated four statistically distinct morphoclusters in the southern Ethiopian region: the smallest and yellow honeybees, A. m. woyi-gambella which are different from all African honeybees, occur in the western and southern lowlands; the small and yellowiest honeybees, Apis mellifera jemenitica in the eastern escarpment; the largest and darkest honeybees, Apis mellifera bandasii in the central and eastern highlands; and dark honeybees, Apis mellifera scutellata in the wet tropical forests. High intracolonial and intercolonial variances within and between the boundaries of the honeybee groups were detected. The former suggests areas of ecological instability, while the latter areas of transitional or natural hybridisation zones. These areas are characterised by transitional ecological zones having intermediate climate and physiography. Even though honeybees of the southern Ethiopian region are generally dark and small, they show a high tendency to reproductive swarming, migration and aggressiveness, great variation in pigmentation, size and behaviour were observed both within and between the groups. A. m. jemenitica honeybees have a high propensity to migration and less a tendency for reproductive swarming. A. m. bandasii and A. m. scutellata have a high inclination to reproductive swarming and the former has a lesser and the later intermediate propensity to migration. A. m. woyi-gambella honeybees have intermediate swarming and migration tendencies. These results revealed that reproductive swarming and migration are higher in resource-rich and resource-poor areas respectively. Honey plants of the central highlands of Ethiopia are predominantly herbaceous in nature and mainly grow on open and cultivated lands. The bulk of pollen collected came comparatively from few genera. Strong correlation was observed between the intensities of flowering and rainfall. Reproductive swarming and migration occur during high and low intensity of flowering respectively.
- Full Text:
- Date Issued: 2003
- Authors: Amssalu, Argaw Bezabeh
- Date: 2003
- Subjects: Honeybee -- Ethiopia -- Behavior Honeybee -- Ethiopia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5616 , http://hdl.handle.net/10962/d1003130
- Description: Morphometric and behavioural characteristics of honeybees, Apis mellifera were analysed using multivariate and bivariate statistical methods to characterise honeybees of southern Ethiopian region. A total of 33800 morphometric character measurements were taken from 2600 individual worker honeybees of 130 honeybee colonies collected at 26 sampling localities with an average inter-locality distance of 89km to determine the occurrence of morphoclusters. 117 experienced farmer beekeepers and beekeeping experts were interviewed on pre-tested questionnaire to investigate the behavioural characteristics of these honeybees in their respective areas. Morphometric characters associated with pigmentation and body size exhibited a higher discriminant power while forewing venation angles (B4, N23 and 026) lack discriminatory power to segregate honeybees in the southern Ethiopian region. Principal components and discriminant analyses using the most discriminatory morphological characters delineated four statistically distinct morphoclusters in the southern Ethiopian region: the smallest and yellow honeybees, A. m. woyi-gambella which are different from all African honeybees, occur in the western and southern lowlands; the small and yellowiest honeybees, Apis mellifera jemenitica in the eastern escarpment; the largest and darkest honeybees, Apis mellifera bandasii in the central and eastern highlands; and dark honeybees, Apis mellifera scutellata in the wet tropical forests. High intracolonial and intercolonial variances within and between the boundaries of the honeybee groups were detected. The former suggests areas of ecological instability, while the latter areas of transitional or natural hybridisation zones. These areas are characterised by transitional ecological zones having intermediate climate and physiography. Even though honeybees of the southern Ethiopian region are generally dark and small, they show a high tendency to reproductive swarming, migration and aggressiveness, great variation in pigmentation, size and behaviour were observed both within and between the groups. A. m. jemenitica honeybees have a high propensity to migration and less a tendency for reproductive swarming. A. m. bandasii and A. m. scutellata have a high inclination to reproductive swarming and the former has a lesser and the later intermediate propensity to migration. A. m. woyi-gambella honeybees have intermediate swarming and migration tendencies. These results revealed that reproductive swarming and migration are higher in resource-rich and resource-poor areas respectively. Honey plants of the central highlands of Ethiopia are predominantly herbaceous in nature and mainly grow on open and cultivated lands. The bulk of pollen collected came comparatively from few genera. Strong correlation was observed between the intensities of flowering and rainfall. Reproductive swarming and migration occur during high and low intensity of flowering respectively.
- Full Text:
- Date Issued: 2003
Pyrroloiminoquinone metabolites from South African Latrunculid sponges
- Authors: Antunes, Edith Martins
- Date: 2003
- Subjects: Sponges -- South Africa PQQ (Biochemistry) Marine metabolites -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4340 , http://hdl.handle.net/10962/d1005001
- Description: An in depth chemical investigation of the major and minor pyrroloiminoquinone metabolites produced by four species of endemic South African Latrunculid sponges, collected from Algoa Bay and the Tsitsikamma Marine Reserve off the south eastern coast of South Africa, yielded eleven new and twelve known pyrroloiminoquinone metabolites. The structures of the new metabolites were determined using standard spectroscopic techniques. Tsitsikamma pedunculata was shown to contain 7,8-dehydro-3-dihydro-discorhabdin C (2.1), 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C (2.2), discorhabdin S (2.3), 14-bromo-1-hydroxy-discorhabdin S (2.4), 1-bromo-2-hydroxy-4-debromo-discorhabdin S (2.5), and 2,4-debromo-3-dihydro-discorhabdin C (2.6), together with the known compounds 14-bromo-discorhabdin C (1.51), 14-bromo-3-dihydro-discorhabdin C (1.52) and 3-dihydro-discorhabdin C. The metabolites from T. pedunculata were characterised by the presence of a reduced C-3 carbonyl and bromination at C-14. Compounds isolated from a second Latrunculid sponge, Latrunculia lorii, ranged from a substituted bicyclic pyrrolecarboxylic acid, makaluvic acid A (1.47), to the simple tricyclic known pyrroloiminoquinones makaluvamine C (1.33) and damirone B (1.20) and the more complex discorhabdin D type metabolites, discorhabdin M (3.2), 1-amino discorhabdin D (3.3), 1-methoxy discorhabdin D (3.4) and 1-alanyl discorhabdin D (3.5). Discorhabdin G* (3.1) was also isolated and characterised. This is the first reported occurrence of the known compounds 1.20, 1.33 and 1.47 in a Latrunculia sponge. Discorhabdin and bis-pyrroloiminoquinone type compounds predominated in Tsitsikamma favus. Three known, tsitsikammamines A (1.71) and B (1.72), 1.52, and five new pyrroloiminoquinones, tsitsikammamine N-oxime (4.1), tsitsikammamine B N-oxime (4.2), 2.1, 2.4 and 2.6, were isolated from this sponge. A fourth Latrunculid sponge (Strongylodesma sp.) yielded three known compounds, discorhabdins A (1.57), D (1.61) and 1.53, and one new pyrroloiminoquinone 3.3. The dual role of these metabolites as cytotoxic agents and pigments resulted in an attempt to relate the photochemical properties of these metabolites to their cytotoxicity. The pyrroloiminoquinone metabolites studied exhibited moderate singlet oxygen quantum yields, while three compounds (1.57, 4.1 and 4.2) were shown to be capable of producing radicals at a wavelength of 532 nm. The possibility of a correlation between the electrochemical properties and anti-cancer (HCT-116) activity of selected pyrroloiminoquinones was explored. A study of the oesophageal and ovarian cytotoxicities of two pyrroloiminoquinones (1.57 and 1.72), together with an investigation into the intercalation and topoisomerase I inhibitory activity of the bis-pyrroloiminoquinones (1.71, 1.72, 4.1 and 4.2), are presented.
- Full Text:
- Date Issued: 2003
- Authors: Antunes, Edith Martins
- Date: 2003
- Subjects: Sponges -- South Africa PQQ (Biochemistry) Marine metabolites -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4340 , http://hdl.handle.net/10962/d1005001
- Description: An in depth chemical investigation of the major and minor pyrroloiminoquinone metabolites produced by four species of endemic South African Latrunculid sponges, collected from Algoa Bay and the Tsitsikamma Marine Reserve off the south eastern coast of South Africa, yielded eleven new and twelve known pyrroloiminoquinone metabolites. The structures of the new metabolites were determined using standard spectroscopic techniques. Tsitsikamma pedunculata was shown to contain 7,8-dehydro-3-dihydro-discorhabdin C (2.1), 14-bromo-7,8-dehydro-3-dihydro-discorhabdin C (2.2), discorhabdin S (2.3), 14-bromo-1-hydroxy-discorhabdin S (2.4), 1-bromo-2-hydroxy-4-debromo-discorhabdin S (2.5), and 2,4-debromo-3-dihydro-discorhabdin C (2.6), together with the known compounds 14-bromo-discorhabdin C (1.51), 14-bromo-3-dihydro-discorhabdin C (1.52) and 3-dihydro-discorhabdin C. The metabolites from T. pedunculata were characterised by the presence of a reduced C-3 carbonyl and bromination at C-14. Compounds isolated from a second Latrunculid sponge, Latrunculia lorii, ranged from a substituted bicyclic pyrrolecarboxylic acid, makaluvic acid A (1.47), to the simple tricyclic known pyrroloiminoquinones makaluvamine C (1.33) and damirone B (1.20) and the more complex discorhabdin D type metabolites, discorhabdin M (3.2), 1-amino discorhabdin D (3.3), 1-methoxy discorhabdin D (3.4) and 1-alanyl discorhabdin D (3.5). Discorhabdin G* (3.1) was also isolated and characterised. This is the first reported occurrence of the known compounds 1.20, 1.33 and 1.47 in a Latrunculia sponge. Discorhabdin and bis-pyrroloiminoquinone type compounds predominated in Tsitsikamma favus. Three known, tsitsikammamines A (1.71) and B (1.72), 1.52, and five new pyrroloiminoquinones, tsitsikammamine N-oxime (4.1), tsitsikammamine B N-oxime (4.2), 2.1, 2.4 and 2.6, were isolated from this sponge. A fourth Latrunculid sponge (Strongylodesma sp.) yielded three known compounds, discorhabdins A (1.57), D (1.61) and 1.53, and one new pyrroloiminoquinone 3.3. The dual role of these metabolites as cytotoxic agents and pigments resulted in an attempt to relate the photochemical properties of these metabolites to their cytotoxicity. The pyrroloiminoquinone metabolites studied exhibited moderate singlet oxygen quantum yields, while three compounds (1.57, 4.1 and 4.2) were shown to be capable of producing radicals at a wavelength of 532 nm. The possibility of a correlation between the electrochemical properties and anti-cancer (HCT-116) activity of selected pyrroloiminoquinones was explored. A study of the oesophageal and ovarian cytotoxicities of two pyrroloiminoquinones (1.57 and 1.72), together with an investigation into the intercalation and topoisomerase I inhibitory activity of the bis-pyrroloiminoquinones (1.71, 1.72, 4.1 and 4.2), are presented.
- Full Text:
- Date Issued: 2003
Biological control initiatives against Lantana camara L. (Verbenaceae) in South Africa : an assessment of the present status of the programme, and an evaluation of Coelocephalapion camarae Kissinger (Coleoptera: Brentidae) and Falconia intermedia (Distant) (Heteroptera: Miridae), two new candidate natural enemies for release on the weed
- Authors: Baars, Jan-Robert
- Date: 2003
- Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
- Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
- Full Text:
- Date Issued: 2003
- Authors: Baars, Jan-Robert
- Date: 2003
- Subjects: Lantana camara Lantana camera -- South Africa Biological pest control agents -- South Africa Beetles -- South Africa Hemiptera -- South Africa Weeds -- Biological control -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5647 , http://hdl.handle.net/10962/d1005329
- Description: Lantana camara (lantana), a thicket-forming shrub, a number of different varieties of which were introduced into South Africa as ornamental plants but which has become a serious invasive weed. Conventional control measures for lantana are expensive and ineffective and it has therefore been targeted for biological control since 1961. To date, eleven biological control agent species have become established on lantana in South Africa. However, most agents persist at low densities and only occasionally impact plant populations. Three species regularly cause significant damage, but only reach sufficiently high numbers by midsummer after populations crash during the winter. Overall, the impact of the biological control programme on the weed is negligible and this has been ascribed to the poor selection of agents for release, the accumulation of native parasitoids, differences in insect preference for different varieties of the weed and variable climatic conditions over the weed’s range. This study suggests that the importance of varietal preferences has been over-estimated. A predictive bioclimatic modelling technique showed that most of the agents established in South Africa have a wide climatic tolerance and that the redistribution and importation of new climatypes of these agents will not improve the level of control. Additional agents are required to improve the biocontrol in the temperate conditions, and also to increase damage in the sub-tropical areas where most of the agents are established and where the weed retains its leaves year round. New candidate agents that possess biological attributes that favour a high intrinsic rate of increase, a high impact per individual and that improve the synchrony between the weed and the agent in climatic conditions that promote the seasonal leaflessness of plants should receive prior consideration. A survey in Jamaica indicated that additional biological control agents are available in the region of origin but that care should be taken to prioritise the most effective agents. The various selection systems currently available in weed biocontrol produce contradictory results in the priority assigned to candidate agents and a new selection system is proposed. The biology and host range of two new candidate natural enemies, the leaf-galling weevil, Coelocephalapion camarae and the leaf-sucking mirid, Falconia intermedia were investigated for the biocontrol of lantana. The studies indicated that these have considerable biocontrol potential, in that the weevil has a wide climatic tolerance and has the potential to survive the host leaflessness typical of temperate conditions, while the mirid has a high intrinsic rate of increase, and the potential for several generations a year. Both agents caused a high level of damage to the leaves, with the weevil galling the vascular tissue in the leaf-petiole and the mirid causing chlorotic speckling of the leaves. During laboratory trials both agents accepted indigenous species in the genus Lippia. However, under multiple choice conditions these agents showed a significant and strong oviposition preference for lantana. A risk assessment and post release field trials indicated that F. intermedia is likely to attack some Lippia species in the presence of lantana, but the levels of damage are predicted to be relatively low. A possible low incidence of damage to indigenous species was considered a justifiable ‘trade-off’ for the potentially marked impact on L. camara. Preference and performance studies on the two candidate agents suggested that most of the South African lantana varieties are suitable host plants. The mirid preferred certain varieties in multiple choice experiments, but this is unlikely to affect its impact under field conditions. Permission for release was accordingly sought for both species. Finally, the challenges facing the biological control programme and the potential for improving the control of L. camara in South Africa are considered.
- Full Text:
- Date Issued: 2003
An evaluation of mentoring to develop a strategy for facilitating the objectives of the Employment Equity Act (Act 55 of 1998)
- Authors: Berry, David Michael
- Date: 2003
- Subjects: Mentoring in business , Employees -- Training of -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DTech (Human Resource Management)
- Identifier: vital:10858 , http://hdl.handle.net/10948/127 , Mentoring in business , Employees -- Training of -- Evaluation
- Description: The research problem in this study was to identify what mentoring strategies organisations can use to facilitate the objectives of the Employment Equity Act (Act 55 of 1998). To achieve this objective a nine-phase theoretical model for organisational mentoring was presented. The presentation of the theoretical model consisted of the following three sub-processes: -The first consisted of a survey of literature related to the development of the Employment Equity Act (Act 55 of 1998) and the implications of the Act for organisations: The second comprised surveying the literature dealing specifically with the impact of mentoring programmes on career development, organisational success and career satisfaction, particularly in terms of employees from designated groups; The third surveyed the literature dealing with various mentoring strategies and models used by organisations for facilitating management development. The theoretical model served as a basis for drawing up a survey questionnaire to establish the extent to which individuals at different levels in the organisations agree with the theoretical model developed in the study. The survey questionnaire was sent to a random sample of individuals employed in the automobile industries of the Nelson Mandela Metropolitan Municipality and the Buffalo City Metropole. The empirical results obtained from the survey indicated a strong concurrence with the theoretical organisational mentoring model presented in the study. These results were included in the theoretical model, leading to the development of an integrated model for organisational mentoring. From the survey literature and the study it became evident that if organisations plan to introduce mentoring strategies that will contribute towards facilitating their employment equity objectives, it is necessary to ensure that a transformational culture exists. Many South African organisations are currently experiencing problems in recruiting, training and retaining individuals from designated groups. The introduction of a mentoring programme based on the integrated model for organisational mentoring cannot be considered as the sole strategy for alleviating these problems and for facilitating management development to achieve the objectives of the Employment Equity Act (Act 55 of 1998). However, when this programme is effectively managed and incorporated into the overall development programme of an organisation committed to transformation, the potential to ease these problems and achieve the objectives of the Employment Equity Act (Act 55 of 1998) is greatly enhanced.
- Full Text:
- Date Issued: 2003
- Authors: Berry, David Michael
- Date: 2003
- Subjects: Mentoring in business , Employees -- Training of -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DTech (Human Resource Management)
- Identifier: vital:10858 , http://hdl.handle.net/10948/127 , Mentoring in business , Employees -- Training of -- Evaluation
- Description: The research problem in this study was to identify what mentoring strategies organisations can use to facilitate the objectives of the Employment Equity Act (Act 55 of 1998). To achieve this objective a nine-phase theoretical model for organisational mentoring was presented. The presentation of the theoretical model consisted of the following three sub-processes: -The first consisted of a survey of literature related to the development of the Employment Equity Act (Act 55 of 1998) and the implications of the Act for organisations: The second comprised surveying the literature dealing specifically with the impact of mentoring programmes on career development, organisational success and career satisfaction, particularly in terms of employees from designated groups; The third surveyed the literature dealing with various mentoring strategies and models used by organisations for facilitating management development. The theoretical model served as a basis for drawing up a survey questionnaire to establish the extent to which individuals at different levels in the organisations agree with the theoretical model developed in the study. The survey questionnaire was sent to a random sample of individuals employed in the automobile industries of the Nelson Mandela Metropolitan Municipality and the Buffalo City Metropole. The empirical results obtained from the survey indicated a strong concurrence with the theoretical organisational mentoring model presented in the study. These results were included in the theoretical model, leading to the development of an integrated model for organisational mentoring. From the survey literature and the study it became evident that if organisations plan to introduce mentoring strategies that will contribute towards facilitating their employment equity objectives, it is necessary to ensure that a transformational culture exists. Many South African organisations are currently experiencing problems in recruiting, training and retaining individuals from designated groups. The introduction of a mentoring programme based on the integrated model for organisational mentoring cannot be considered as the sole strategy for alleviating these problems and for facilitating management development to achieve the objectives of the Employment Equity Act (Act 55 of 1998). However, when this programme is effectively managed and incorporated into the overall development programme of an organisation committed to transformation, the potential to ease these problems and achieve the objectives of the Employment Equity Act (Act 55 of 1998) is greatly enhanced.
- Full Text:
- Date Issued: 2003
Correlates and outcomes of emotional intelligence in organisations
- Authors: Bosman, Leon Abraham
- Date: 2003
- Subjects: Leadership , Emotional intelligence , Organizational behavior
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:11006 , http://hdl.handle.net/10948/337 , Leadership , Emotional intelligence , Organizational behavior
- Description: Emotional Intelligence and Leadership are two very important constructs to organizations. Likewise concepts like OCB, conflict handling and intention to quit of employees are equally important constructs to organizations. The primary aim of the present study was to determine how well Organisational Citizenship Behaviour and intention to quit as well as the conflict handling style of subordinates could be predicted by means of leadership style, and the emotional intelligence of leaders. A secondary aim was to determine whether a causal model could be built to represent the relationships among the variables included in the study. Relationships among these constructs were investigated in a South African sample of employees (N=470) working for various organisations. The construct validity and internal consistency of the measuring instruments were investigated. The finally accepted factor structure of not one of the measuring instruments matched the original structure as found by the authors/developers of the measuring instruments. It was therefore decided that in all cases the factor pattern as determined on the responses of the present sample would be used in further analyses of the data. Emotional intelligence of leaders as seen by subordinates and the self - perceived conflict handling styles of subordinates seem to be related in the case of Integrating and Obliging conflict handling styles and both the emotional intelligence sub-scales, i.e. Motivation and Vigilance. The Multiple Regression analysis indicated that the emotional intelligence sub-scales scores played a minor role in the prediction of Organizational Citizenship Behaviour. Models of the relationships among the variables were built by studying the results of v previous as well as the present study. The model, in which emotional intelligence is depicted as a causal variable influencing - through leadership behaviour – organizational citizenship behaviour and the integrating style of handling interpersonal conflict represented a good fit with the data. These results seem to provide some structure for thinking about the relationships among the variables and can possibly serve as frames of reference in future studies.
- Full Text:
- Date Issued: 2003
- Authors: Bosman, Leon Abraham
- Date: 2003
- Subjects: Leadership , Emotional intelligence , Organizational behavior
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:11006 , http://hdl.handle.net/10948/337 , Leadership , Emotional intelligence , Organizational behavior
- Description: Emotional Intelligence and Leadership are two very important constructs to organizations. Likewise concepts like OCB, conflict handling and intention to quit of employees are equally important constructs to organizations. The primary aim of the present study was to determine how well Organisational Citizenship Behaviour and intention to quit as well as the conflict handling style of subordinates could be predicted by means of leadership style, and the emotional intelligence of leaders. A secondary aim was to determine whether a causal model could be built to represent the relationships among the variables included in the study. Relationships among these constructs were investigated in a South African sample of employees (N=470) working for various organisations. The construct validity and internal consistency of the measuring instruments were investigated. The finally accepted factor structure of not one of the measuring instruments matched the original structure as found by the authors/developers of the measuring instruments. It was therefore decided that in all cases the factor pattern as determined on the responses of the present sample would be used in further analyses of the data. Emotional intelligence of leaders as seen by subordinates and the self - perceived conflict handling styles of subordinates seem to be related in the case of Integrating and Obliging conflict handling styles and both the emotional intelligence sub-scales, i.e. Motivation and Vigilance. The Multiple Regression analysis indicated that the emotional intelligence sub-scales scores played a minor role in the prediction of Organizational Citizenship Behaviour. Models of the relationships among the variables were built by studying the results of v previous as well as the present study. The model, in which emotional intelligence is depicted as a causal variable influencing - through leadership behaviour – organizational citizenship behaviour and the integrating style of handling interpersonal conflict represented a good fit with the data. These results seem to provide some structure for thinking about the relationships among the variables and can possibly serve as frames of reference in future studies.
- Full Text:
- Date Issued: 2003
NeGPAIM : a model for the proactive detection of information security intrusions, utilizing fuzzy logic and neural network techniques
- Authors: Botha, Martin
- Date: 2003
- Subjects: Computer security , Fuzzy logic , Neural networks (Computer science)
- Language: English
- Type: Thesis , Doctoral , DTech (Computer Studies)
- Identifier: vital:10792 , http://hdl.handle.net/10948/142 , Computer security , Fuzzy logic , Neural networks (Computer science)
- Description: “Information is the lifeblood of any organisation and everything an organisation does involves using information in some way” (Peppard, 1993, p.5). Therefore, it can be argued that information is an organisation’s most precious asset and as with all other assets, like equipment, money, personnel, and so on, this asset needs to be protected properly at all times (Whitman & Mattord, 2003, pp.1-14). The introduction of modern technologies, such as e-commerce, will not only increase the value of information, but will also increase security requirements of those organizations that are intending to utilize such technologies. Evidence of these requirements can be observed in the 2001 CSI/FBI Computer Crime and Security Survey (Power, 2001). According to this source, the annual financial losses caused through security breaches in 2001 have increased by 277% when compared to the results from 1997. The 2002 and 2003 Computer Crime and Security Survey confirms this by stating that the threat of computer crime and other related information security breaches continues unabated and that the financial toll is mounting (Richardson, 2003). Information is normally protected by means of a process of identifying, implementing, managing and maintaining a set of information security controls, countermeasures or safeguards (GMITS, 1998). In the rest of this thesis, the term security controls will be utilized when referring to information protection mechanisms or procedures. These security controls can be of a physical (for example, door locks), a technical (for example, passwords) and/or a procedural nature (for example, to make back-up copies of critical files)(Pfleeger, 2003, pp.22-23; Stallings, 1995, p.1). The effective identification, implementation, management and maintenance of this set of security controls are usually integrated into an Information Security Management Program, the objective of which is to ensure an acceptable level of information confidentiality, integrity and availability within the organisation at all times (Pfleeger, 2003, pp.10-12; Whitman & Mattord, 2003, pp.1-14; Von Solms, 1993). Once the most effective security controls have been identified and implemented, it is important that this level of security be maintained through a process of continued control. For this reason, it is important that proper change management, measurement, audit, monitoring and detection be implemented (Bruce & Dempsey, 1997). Monitoring and detection are important functions and refer to the ability to identify and detect situations where information security policies have been compromised and/or breached or security violations have taken place (BS 7799, 1999; GMITS, 1998; Von Solms, 1993). The Information Security Officer is usually the person responsible for most of the operational tasks in the control process within an Information Security Management Program (Von Solms, 1993). In practice, these tasks could also be performed by a system administrator, network administrator, etc. In the rest of the thesis the person responsible for these tasks will be referred to as system administrator. These tasks have proved to be very challenging and demanding. The main reason for this is the rapid advancement of technology in the discipline of Information Technology, for example, the modern distributed computing environment, the Internet, the “freedom” of end-users, the introduction of e-commerce, and etc. (Whitman & Mattord, 2003, p.9; Sundaram, 2000, p.1; Moses, 2001, p.6; Allen, 2001, p.1). As a result of the importance of this control process, and especially the monitoring and detection tasks, it is vital that the system administrator has proper tools at his/her disposal to perform this task effectively. Many of the tools that are currently available to the system administrator, utilize technical controls, such as, audit logs and user profiles. Audit logs are normally used to record all events executed on a system. These logs are simply files that record security and non-security related events that take place on a computer system within an organisation. For this reason, these logs can be used by these tools to gain valuable information on security violations, such as intrusions and, therefore, are able to monitor the current actions of each user (Microsoft, 2002; Smith, 1989, pp. 116-117). User profiles are files that contain information about users` desktop operating environments and are used by the operating system to structure each user environment so that it is the same each time a user logs onto the system (Microsoft, 2002; Block, 1994, p.54). Thus, a user profile is used to indicate which actions the user is allowed to perform on the system. Both technical controls (audit logs and user profiles) are frequently available in most computer environments (such as, UNIX, Firewalls, Windows, etc.) (Cooper et al, 1995, p.129). Therefore, seeing that the audit logs record most events taking place on an information system and the user profile indicates the authorized actions of each user, the system administrator could most probably utilise these controls in a more proactive manner.
- Full Text:
- Date Issued: 2003
- Authors: Botha, Martin
- Date: 2003
- Subjects: Computer security , Fuzzy logic , Neural networks (Computer science)
- Language: English
- Type: Thesis , Doctoral , DTech (Computer Studies)
- Identifier: vital:10792 , http://hdl.handle.net/10948/142 , Computer security , Fuzzy logic , Neural networks (Computer science)
- Description: “Information is the lifeblood of any organisation and everything an organisation does involves using information in some way” (Peppard, 1993, p.5). Therefore, it can be argued that information is an organisation’s most precious asset and as with all other assets, like equipment, money, personnel, and so on, this asset needs to be protected properly at all times (Whitman & Mattord, 2003, pp.1-14). The introduction of modern technologies, such as e-commerce, will not only increase the value of information, but will also increase security requirements of those organizations that are intending to utilize such technologies. Evidence of these requirements can be observed in the 2001 CSI/FBI Computer Crime and Security Survey (Power, 2001). According to this source, the annual financial losses caused through security breaches in 2001 have increased by 277% when compared to the results from 1997. The 2002 and 2003 Computer Crime and Security Survey confirms this by stating that the threat of computer crime and other related information security breaches continues unabated and that the financial toll is mounting (Richardson, 2003). Information is normally protected by means of a process of identifying, implementing, managing and maintaining a set of information security controls, countermeasures or safeguards (GMITS, 1998). In the rest of this thesis, the term security controls will be utilized when referring to information protection mechanisms or procedures. These security controls can be of a physical (for example, door locks), a technical (for example, passwords) and/or a procedural nature (for example, to make back-up copies of critical files)(Pfleeger, 2003, pp.22-23; Stallings, 1995, p.1). The effective identification, implementation, management and maintenance of this set of security controls are usually integrated into an Information Security Management Program, the objective of which is to ensure an acceptable level of information confidentiality, integrity and availability within the organisation at all times (Pfleeger, 2003, pp.10-12; Whitman & Mattord, 2003, pp.1-14; Von Solms, 1993). Once the most effective security controls have been identified and implemented, it is important that this level of security be maintained through a process of continued control. For this reason, it is important that proper change management, measurement, audit, monitoring and detection be implemented (Bruce & Dempsey, 1997). Monitoring and detection are important functions and refer to the ability to identify and detect situations where information security policies have been compromised and/or breached or security violations have taken place (BS 7799, 1999; GMITS, 1998; Von Solms, 1993). The Information Security Officer is usually the person responsible for most of the operational tasks in the control process within an Information Security Management Program (Von Solms, 1993). In practice, these tasks could also be performed by a system administrator, network administrator, etc. In the rest of the thesis the person responsible for these tasks will be referred to as system administrator. These tasks have proved to be very challenging and demanding. The main reason for this is the rapid advancement of technology in the discipline of Information Technology, for example, the modern distributed computing environment, the Internet, the “freedom” of end-users, the introduction of e-commerce, and etc. (Whitman & Mattord, 2003, p.9; Sundaram, 2000, p.1; Moses, 2001, p.6; Allen, 2001, p.1). As a result of the importance of this control process, and especially the monitoring and detection tasks, it is vital that the system administrator has proper tools at his/her disposal to perform this task effectively. Many of the tools that are currently available to the system administrator, utilize technical controls, such as, audit logs and user profiles. Audit logs are normally used to record all events executed on a system. These logs are simply files that record security and non-security related events that take place on a computer system within an organisation. For this reason, these logs can be used by these tools to gain valuable information on security violations, such as intrusions and, therefore, are able to monitor the current actions of each user (Microsoft, 2002; Smith, 1989, pp. 116-117). User profiles are files that contain information about users` desktop operating environments and are used by the operating system to structure each user environment so that it is the same each time a user logs onto the system (Microsoft, 2002; Block, 1994, p.54). Thus, a user profile is used to indicate which actions the user is allowed to perform on the system. Both technical controls (audit logs and user profiles) are frequently available in most computer environments (such as, UNIX, Firewalls, Windows, etc.) (Cooper et al, 1995, p.129). Therefore, seeing that the audit logs record most events taking place on an information system and the user profile indicates the authorized actions of each user, the system administrator could most probably utilise these controls in a more proactive manner.
- Full Text:
- Date Issued: 2003
A qualitative analysis of the need-satisfying experiences of the customers of a niche-restaurant
- Authors: Burger, John Michael
- Date: 2003
- Subjects: Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Language: English
- Type: Thesis , Doctoral , DTech (Marketing)
- Identifier: vital:10767 , http://hdl.handle.net/10948/260 , Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Description: Tradition dictates that marketing decision-makers remain accurately aligned with the dynamic and vacillating need structures of the target markets they serve. To comply with this caveat, a time-honoured and largely unchallenged philosophy of customer orientation has been applied. Theory further strongly contends that if such a business stance is vigilantly and diligently applied, any firm is bound to gain a competitive edge in the market place. A weakness in the above marketing mindset is the perception that when a spectrum of business elements are orchestrated and focussed on customers, target audience members will automatically be satisfied and return their patronage. This so-called marketing concept has undergone major reevaluations over the past decades, and it is now becoming ever more prevalent to witness varied permutations of new marketing architecture evolving in literature and practice. The unit of analysis selected for this research study is a niche restaurant that flouts many of the rudimentary traditional rules of marketing and iconoclastically succeeds despite all counter-logic. What such organisations have been practicing, albeit unknown to themselves, is a new way of business - a stance that has only recently been taken seriously by academics, writers and marketing professionals. These intuitive marketers are succeeding in niche businesses, despite going against the tide of the ingrained paradigm mindsets of conventional marketing stalwarts. Such niche business people have discovered is that there is more to satisfying consumer needs than simply honing in and understanding what the basic needs of designated audiences are. A growing band of new age marketers have been challenging orthodox marketing philosophy. Tofler, the visionary futurist, alluded to a host of unarticulated psychic consumer needs that would emerge as society drifted into a clinical and dispassionate ‘new’ millennium. In a world geared to instant gratification, fast-paced living and mechanistic social interactions, jaded consumers seek recognition as individuals (Tofler, 1970). They quest for inclusion rather than exclusion. They need a place to feel safe and find solace. Hence, it is now clear that simply attempting to satisfy the fundamental dimensions of consumers’ needs is no longer sufficient. Consumers rather seek the fulfilment of an holistic band of experience dimensions. Increasingly, phrases such as “winning consumer hearts and minds” are entering the vocabulary of marketers on a regular basis. The present vogue is to isolate and then include a range of intangible elements that are embodied in the process of satisfying customers needs. However, despite a growing awareness of the significance of mental-need satisfiers, in the specific domain of this investigation there is sparse evidence in literature of the mechanics of such novel thinking. The study unit is a second generation restaurant where many of the hollowed cornerstones of conventional marketing are inadvertently flouted. Different sets of rules of engagement seem to apply to their customers, who are also their most ardent advocates. A unique philosophy and business ethos also appears to prevail. In the study, the idiosyncratic characteristics which socially and competitively differentiate such a business were identified, explored and expiated. The constituents were then harmonised in an effort to establish what ‘it’ was that magnetically attracted patrons back despite the owner’s unintentional dismissive predisposition towards fundamental theory. As a result of this in-depth qualitative study, an holistic model encompassing all of the dimensions of a dining out experience at a niche restaurant have been proposed. Consequently the pillars upon which a sustained, enduring, loyal staunch customer base can be bed-rocked have been identified. Further, for the study unit, a typology of its diner corpse has been developed. The owners of the establishment under investigation have succeeded to provide an intimate family haven for their patrons. They, and their diners have collectively given strong, descriptive voice to the psychogenic need satisfying elements that have always existed, but to date have been unarticulated and unrecorded. This thesis brings the milieu of the iconoclast niche restaurant marketing practitioner to life.
- Full Text:
- Date Issued: 2003
- Authors: Burger, John Michael
- Date: 2003
- Subjects: Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Language: English
- Type: Thesis , Doctoral , DTech (Marketing)
- Identifier: vital:10767 , http://hdl.handle.net/10948/260 , Consumer satisfaction , Diners restaurant -- Marketing , Customer loyalty
- Description: Tradition dictates that marketing decision-makers remain accurately aligned with the dynamic and vacillating need structures of the target markets they serve. To comply with this caveat, a time-honoured and largely unchallenged philosophy of customer orientation has been applied. Theory further strongly contends that if such a business stance is vigilantly and diligently applied, any firm is bound to gain a competitive edge in the market place. A weakness in the above marketing mindset is the perception that when a spectrum of business elements are orchestrated and focussed on customers, target audience members will automatically be satisfied and return their patronage. This so-called marketing concept has undergone major reevaluations over the past decades, and it is now becoming ever more prevalent to witness varied permutations of new marketing architecture evolving in literature and practice. The unit of analysis selected for this research study is a niche restaurant that flouts many of the rudimentary traditional rules of marketing and iconoclastically succeeds despite all counter-logic. What such organisations have been practicing, albeit unknown to themselves, is a new way of business - a stance that has only recently been taken seriously by academics, writers and marketing professionals. These intuitive marketers are succeeding in niche businesses, despite going against the tide of the ingrained paradigm mindsets of conventional marketing stalwarts. Such niche business people have discovered is that there is more to satisfying consumer needs than simply honing in and understanding what the basic needs of designated audiences are. A growing band of new age marketers have been challenging orthodox marketing philosophy. Tofler, the visionary futurist, alluded to a host of unarticulated psychic consumer needs that would emerge as society drifted into a clinical and dispassionate ‘new’ millennium. In a world geared to instant gratification, fast-paced living and mechanistic social interactions, jaded consumers seek recognition as individuals (Tofler, 1970). They quest for inclusion rather than exclusion. They need a place to feel safe and find solace. Hence, it is now clear that simply attempting to satisfy the fundamental dimensions of consumers’ needs is no longer sufficient. Consumers rather seek the fulfilment of an holistic band of experience dimensions. Increasingly, phrases such as “winning consumer hearts and minds” are entering the vocabulary of marketers on a regular basis. The present vogue is to isolate and then include a range of intangible elements that are embodied in the process of satisfying customers needs. However, despite a growing awareness of the significance of mental-need satisfiers, in the specific domain of this investigation there is sparse evidence in literature of the mechanics of such novel thinking. The study unit is a second generation restaurant where many of the hollowed cornerstones of conventional marketing are inadvertently flouted. Different sets of rules of engagement seem to apply to their customers, who are also their most ardent advocates. A unique philosophy and business ethos also appears to prevail. In the study, the idiosyncratic characteristics which socially and competitively differentiate such a business were identified, explored and expiated. The constituents were then harmonised in an effort to establish what ‘it’ was that magnetically attracted patrons back despite the owner’s unintentional dismissive predisposition towards fundamental theory. As a result of this in-depth qualitative study, an holistic model encompassing all of the dimensions of a dining out experience at a niche restaurant have been proposed. Consequently the pillars upon which a sustained, enduring, loyal staunch customer base can be bed-rocked have been identified. Further, for the study unit, a typology of its diner corpse has been developed. The owners of the establishment under investigation have succeeded to provide an intimate family haven for their patrons. They, and their diners have collectively given strong, descriptive voice to the psychogenic need satisfying elements that have always existed, but to date have been unarticulated and unrecorded. This thesis brings the milieu of the iconoclast niche restaurant marketing practitioner to life.
- Full Text:
- Date Issued: 2003
Development of integrated algal ponding systems in the treatment of wine distillery wastewaters
- Authors: Dekker, Leendert Gideon
- Date: 2003
- Subjects: Sewage -- Purification -- Anaerobic treatment Wine and wine making -- Waste disposal -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4062 , http://hdl.handle.net/10962/d1004530
- Description: In South Africa, wastewater disposal in the wine and distilling industry is undergoing a profound transformation as a result of fundamental changes in regulations and license requirements. To deal with this problem conventional Waste Stabilisation Ponding systems have been used by the industry together with irrigation and evaporation disposal practises. Although effective in the evaporation and containment disposal functions, these pond systems are generally not properly designed and/or managed, resulting in overloading and, at times, the generation of seriously offensive odour problems. Preliminary studies on the feasibility of utilising the Advanced Integrated Wastewater Ponding System as a core treatment technology in winery wastewater treatment were conducted. Results indicated that specific problems had to be addressed before successful ponding treatment could be achieved. This research programme undertook an investigation of the performance of a demonstration ponding system treating household sewage, which formed the basis of the research due to limited experience reported on ponds treating wine industry wastewaters. Malfunctions identified were in correlation with the preliminary winery waste ponding survey, which included unstable fermentation pit functions and inadequate nutrient removal. Retrofitting the fermentation pit with a nylon net across the rising water column resulted in improved retention of active anaerobic sludge, especially during periods of system start-up and/or organic overloading. An investigation into nutrient removal utilising algal biomass provided a valuable contribution towards development of an independent nutrient removal system. Harvested algal biomass was passively manipulated to release polysaccharides under anoxic conditions, with subsequent use as a carbon source by denitrifying organisms. Following denitrification, the still viable algal cells were introduced into a High Rate Algal Pond raceway for photosynthetically produced alkalinity. This high pH environment resulted in induced calcium phosphate mineral formation and subsequent precipitation, as well as effective ammonia stripping from the water. Based on the novel positive research outcomes a decision was made to proceed to the construction of a pilot-scale integrated ponding system treating wastewater from a wine lees factory. The system linked the Anaerobic Baffle Reactor, for pre-treatment, with the improved Advanced Integrated Wastewater Ponding System. The potential of this system has shown that a Waste Stabilisation Ponding system can be engineered to treat wine industry wastewaters and thereby effectively reduce the organic and nutrient loads, by using low-cost retrofitted upgrading unit operations. Valuable algal biomass may also be recovered as a by-product of the treatment process.
- Full Text:
- Date Issued: 2003
- Authors: Dekker, Leendert Gideon
- Date: 2003
- Subjects: Sewage -- Purification -- Anaerobic treatment Wine and wine making -- Waste disposal -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4062 , http://hdl.handle.net/10962/d1004530
- Description: In South Africa, wastewater disposal in the wine and distilling industry is undergoing a profound transformation as a result of fundamental changes in regulations and license requirements. To deal with this problem conventional Waste Stabilisation Ponding systems have been used by the industry together with irrigation and evaporation disposal practises. Although effective in the evaporation and containment disposal functions, these pond systems are generally not properly designed and/or managed, resulting in overloading and, at times, the generation of seriously offensive odour problems. Preliminary studies on the feasibility of utilising the Advanced Integrated Wastewater Ponding System as a core treatment technology in winery wastewater treatment were conducted. Results indicated that specific problems had to be addressed before successful ponding treatment could be achieved. This research programme undertook an investigation of the performance of a demonstration ponding system treating household sewage, which formed the basis of the research due to limited experience reported on ponds treating wine industry wastewaters. Malfunctions identified were in correlation with the preliminary winery waste ponding survey, which included unstable fermentation pit functions and inadequate nutrient removal. Retrofitting the fermentation pit with a nylon net across the rising water column resulted in improved retention of active anaerobic sludge, especially during periods of system start-up and/or organic overloading. An investigation into nutrient removal utilising algal biomass provided a valuable contribution towards development of an independent nutrient removal system. Harvested algal biomass was passively manipulated to release polysaccharides under anoxic conditions, with subsequent use as a carbon source by denitrifying organisms. Following denitrification, the still viable algal cells were introduced into a High Rate Algal Pond raceway for photosynthetically produced alkalinity. This high pH environment resulted in induced calcium phosphate mineral formation and subsequent precipitation, as well as effective ammonia stripping from the water. Based on the novel positive research outcomes a decision was made to proceed to the construction of a pilot-scale integrated ponding system treating wastewater from a wine lees factory. The system linked the Anaerobic Baffle Reactor, for pre-treatment, with the improved Advanced Integrated Wastewater Ponding System. The potential of this system has shown that a Waste Stabilisation Ponding system can be engineered to treat wine industry wastewaters and thereby effectively reduce the organic and nutrient loads, by using low-cost retrofitted upgrading unit operations. Valuable algal biomass may also be recovered as a by-product of the treatment process.
- Full Text:
- Date Issued: 2003
An analysis of the impact of democratization on debt-led growth : the Nigerian experience, 1970-2000
- Authors: Dinneya, Godson Eze
- Date: 2013-05-22
- Subjects: Debts, External -- Nigeria Nigeria -- Politics and government -- 1960- Nigeria -- Economic policy Nigeria -- Economic conditions -- 1960-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1074 , http://hdl.handle.net/10962/d1007807
- Description: The debt-for democracy hypothesis is that undemocratic governments were largely responsible for not only the accumulation but also poor management of externally sourced capital resources. External borrowing had therefore failed to lead to growth of the economies of debtor countries under undemocratic political leadership. Despite this explanation of the debt problem conventional empirical analyses of the debt-growth relationship did not include political institutional variables. This study investigates the relationship between democratization and debt-led growth, using Nigeria, a typical debtor country whose politics was dominated by 'undemocratic ' governance, as a case study. Two broad research questions are investigated namely, whether available data support a negative or positive contribution of debt to the growth of the Nigeria economy during the period 1970-2000; and ifso was there any link between the levels of democratization in Nigeria and debt-led growth. Using a census of major political events in Nigeria around four dimensions of democratization, four primary indices of democratization and one composite index were constructed for the period. Using the Taylor (1983) marginal conditions to gauge the contribution of external debt to the growth of the Nigerian economy, the study found that external debt is capable of playing a double edged sword on the performance of the economy. Positive contributions coincided with the periods when Nigeria's oil dominated foreign exchange revenues were robust, and/ or when debt management strategies were better articulated and vice versa. The analyses of the link between democratization and debt-led growth using both correlation and regression techniques, yielded different results in two definitional contexts of debt-led growth. When defined purely in terms of the Taylor marginal conditions for a positive contribution of debt to the economy of a borrowing nation, the results support the pessimist view that democratization impeded growth. On the contrary, when debt-led growth was defined in a broader sense to incorporate variables such as domestic savings and investment, foreign direct investments, public and private consumption and debt burden, there was strong evidence that debt-led growth performed beller at higher levels of democratization than other wise. The result using the narrow definition was found to be a direct consequence of the overriding influence of export performance in the Taylor conditions. With Nigeria's exports almost entirely dominated by extractive industry the result derived using the narrow definition confirmed the theoretical links between natural resource endowment and regime type on the one hand, and external capital and the nature of the host country 's industry on the other. In the first resource dependence allowed the political leadership to be more detached and less accountable to the electorate since they did not need to levy taxes. Secondly foreign investors concerned with security of their sunk investments in the extractive oil induslly in particular favoured continuity of powerfol regimes with less democratic content. In both findings one thing was common: democratization was associated more with those factors whose decreases affect growth positively than with those whose increases improve growth. The conclusion from this is that the impact of democratization is stronger with negative than with positive growth factors. In other words, while democratization may be supportive of growth its greater impact appears to be in limiting the factors that themselves limit growth. To benefit from the favourable impact of democratisation on debt-led growth therefore the study suggests that improvements in the democratisation process in Nigeria is needed It identifies political education as central to this improvement. A model is developed to show how improvements in the political institutional framework may trickle down, through an enabling environment that is capable of engendering growth-enhancing domestic and international responses to lead in the direction of debt-led growth.
- Full Text:
An analysis of the impact of democratization on debt-led growth : the Nigerian experience, 1970-2000
- Authors: Dinneya, Godson Eze
- Date: 2013-05-22
- Subjects: Debts, External -- Nigeria Nigeria -- Politics and government -- 1960- Nigeria -- Economic policy Nigeria -- Economic conditions -- 1960-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1074 , http://hdl.handle.net/10962/d1007807
- Description: The debt-for democracy hypothesis is that undemocratic governments were largely responsible for not only the accumulation but also poor management of externally sourced capital resources. External borrowing had therefore failed to lead to growth of the economies of debtor countries under undemocratic political leadership. Despite this explanation of the debt problem conventional empirical analyses of the debt-growth relationship did not include political institutional variables. This study investigates the relationship between democratization and debt-led growth, using Nigeria, a typical debtor country whose politics was dominated by 'undemocratic ' governance, as a case study. Two broad research questions are investigated namely, whether available data support a negative or positive contribution of debt to the growth of the Nigeria economy during the period 1970-2000; and ifso was there any link between the levels of democratization in Nigeria and debt-led growth. Using a census of major political events in Nigeria around four dimensions of democratization, four primary indices of democratization and one composite index were constructed for the period. Using the Taylor (1983) marginal conditions to gauge the contribution of external debt to the growth of the Nigerian economy, the study found that external debt is capable of playing a double edged sword on the performance of the economy. Positive contributions coincided with the periods when Nigeria's oil dominated foreign exchange revenues were robust, and/ or when debt management strategies were better articulated and vice versa. The analyses of the link between democratization and debt-led growth using both correlation and regression techniques, yielded different results in two definitional contexts of debt-led growth. When defined purely in terms of the Taylor marginal conditions for a positive contribution of debt to the economy of a borrowing nation, the results support the pessimist view that democratization impeded growth. On the contrary, when debt-led growth was defined in a broader sense to incorporate variables such as domestic savings and investment, foreign direct investments, public and private consumption and debt burden, there was strong evidence that debt-led growth performed beller at higher levels of democratization than other wise. The result using the narrow definition was found to be a direct consequence of the overriding influence of export performance in the Taylor conditions. With Nigeria's exports almost entirely dominated by extractive industry the result derived using the narrow definition confirmed the theoretical links between natural resource endowment and regime type on the one hand, and external capital and the nature of the host country 's industry on the other. In the first resource dependence allowed the political leadership to be more detached and less accountable to the electorate since they did not need to levy taxes. Secondly foreign investors concerned with security of their sunk investments in the extractive oil induslly in particular favoured continuity of powerfol regimes with less democratic content. In both findings one thing was common: democratization was associated more with those factors whose decreases affect growth positively than with those whose increases improve growth. The conclusion from this is that the impact of democratization is stronger with negative than with positive growth factors. In other words, while democratization may be supportive of growth its greater impact appears to be in limiting the factors that themselves limit growth. To benefit from the favourable impact of democratisation on debt-led growth therefore the study suggests that improvements in the democratisation process in Nigeria is needed It identifies political education as central to this improvement. A model is developed to show how improvements in the political institutional framework may trickle down, through an enabling environment that is capable of engendering growth-enhancing domestic and international responses to lead in the direction of debt-led growth.
- Full Text:
Isolation of antigenic peptides of Cowdria ruminantium and their encoding genes using a genome-derived phage display library
- Authors: Fehrsen, Jeanni
- Date: 2003
- Subjects: Bacteriophages -- Genetics Ruminants -- Diseases Heartwater
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3920 , http://hdl.handle.net/10962/d1003979
- Description: The development of new and effective vaccines and immunodiagnostic reagents requires the characterisation of antigenically relevant proteins and their interactions with the products of the immune system. Phage display technology was investigated as a means of elucidating some of the antigenic properties of the rickettsial parasite, Cowdria ruminantium (Cowdria). Randomly fragmented gene-derived libraries have been useful in elucidating viral and other epitopes, but only limited work has been done with entire genomes. A phage display library expressing a repertoire of Cowdria peptides was constructed. It was sufficiently large to represent the organism's genome, but lacked phages displaying peptides coded for by genes containing a Pvu II restriction enzyme site, including the one coding for the major antigenic protein 1 (MAP1). This was considered advantageous since MAP1 is immunodominant and has already been well characterised. Affinity selection with antibodies against Cowdria proteins other than MAP1 allowed several antibody-reactive peptides to be isolated. These selected sequences were placed in the context of the genome by screening a lambda bacteriophage library and by comparison with Cowdria DNA sequences. Apart from showing that antigenic mimics were present in the phage display library, six open reading frames encoding putative Cowdria proteins were identified. All had similarities to, or motifs in common with, membrane proteins and are thus likely to be exposed to the host's humoral immune system. Some of the proteins identified were larger than the antigens used to elicit the antibodies used for selection, probably as a result of the presence of cross-reactive epitopes. Despite limitations experienced when extending a fragmented-gene approach for epitope location to genomes, it was possible to identify an antigenic region on MAP1 by comparison with selected mimics. In addition, binding peptide sequences were identified with two monoclonal antibodies that had been raised against non-Cowdria antigens. An epitope on the VP7 protein of bluetongue virus was identified and peptides were found that reacted with a monoclonal antibody directed against malignant catarrhal fever virus. Thus, apart from being able to identify several potentially important Cowdria epitopes and genes, the fragmented-genome library holds promise as a universal reagent for identifying useful mimics.
- Full Text:
- Date Issued: 2003
- Authors: Fehrsen, Jeanni
- Date: 2003
- Subjects: Bacteriophages -- Genetics Ruminants -- Diseases Heartwater
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3920 , http://hdl.handle.net/10962/d1003979
- Description: The development of new and effective vaccines and immunodiagnostic reagents requires the characterisation of antigenically relevant proteins and their interactions with the products of the immune system. Phage display technology was investigated as a means of elucidating some of the antigenic properties of the rickettsial parasite, Cowdria ruminantium (Cowdria). Randomly fragmented gene-derived libraries have been useful in elucidating viral and other epitopes, but only limited work has been done with entire genomes. A phage display library expressing a repertoire of Cowdria peptides was constructed. It was sufficiently large to represent the organism's genome, but lacked phages displaying peptides coded for by genes containing a Pvu II restriction enzyme site, including the one coding for the major antigenic protein 1 (MAP1). This was considered advantageous since MAP1 is immunodominant and has already been well characterised. Affinity selection with antibodies against Cowdria proteins other than MAP1 allowed several antibody-reactive peptides to be isolated. These selected sequences were placed in the context of the genome by screening a lambda bacteriophage library and by comparison with Cowdria DNA sequences. Apart from showing that antigenic mimics were present in the phage display library, six open reading frames encoding putative Cowdria proteins were identified. All had similarities to, or motifs in common with, membrane proteins and are thus likely to be exposed to the host's humoral immune system. Some of the proteins identified were larger than the antigens used to elicit the antibodies used for selection, probably as a result of the presence of cross-reactive epitopes. Despite limitations experienced when extending a fragmented-gene approach for epitope location to genomes, it was possible to identify an antigenic region on MAP1 by comparison with selected mimics. In addition, binding peptide sequences were identified with two monoclonal antibodies that had been raised against non-Cowdria antigens. An epitope on the VP7 protein of bluetongue virus was identified and peptides were found that reacted with a monoclonal antibody directed against malignant catarrhal fever virus. Thus, apart from being able to identify several potentially important Cowdria epitopes and genes, the fragmented-genome library holds promise as a universal reagent for identifying useful mimics.
- Full Text:
- Date Issued: 2003
Versions of confinement: Melville's bodies and the psychology of conquest
- Authors: Goddard, Kevin Graham
- Date: 2003
- Subjects: Melville, Herman, 1819-1891 -- Criticism and interpretation Human body in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2216 , http://hdl.handle.net/10962/d1002259
- Description: This thesis explores aspects of Melville’s presentation of both the whale and the human bodies in Moby-Dick and human bodies in other important novels. It argues that Melville uses his presentation of bodies to explore some of the versions of confinement those bodies experience, and by doing so, analyses the psychology which subtends that confinement. Throughout Melville’s works bodies are confined, both within literal spatial limits and by the psychology which creates and/or accepts these spatial limits. The thesis argues that perhaps the most important version of bodily confinement Melville addresses is the impulse to conquer bodies, both that of the other and one’s own. It adopts a largely psychoanalytic approach to interpreting bodies and their impulse to conquer, so that the body is seen to figure both in its actions and its external appearance the operations of the inner psyche. The figure of the body is equally prevalent in Melville’s exploration of nationalist conquest, where, as with Manifest Destiny and antebellum expansionism, the psychological and physical lack experienced by characters can be read as motivating factors in the ideology of conquest. A final important strand of the thesis is its argument in favour of a gradual shift in Melville’s interpretation of the value and possibility of genuine communion between human beings and between humans and the whale. One may read Typee as an attempt by Melville to explore the possibility of a this-worldly utopia in which human beings can return to a version of primitive interconnectedness. This exploration may be seen to be extended in Moby-Dick, particularly in Ishmael’s attempts to find communion with others and in some moments of encounter with the whales. The thesis uses phenomenology as a theory to interpret what Melville is trying to suggest in these moments of encounter. However, it argues, finally, that such encounter, or ‘intersubjectivity’ is eventually jettisoned, especially in the works after Moby-Dick. By the end of Melville’s life and work, any hope of an intersubjective utopia he may have harboured as a younger man have been removed in favour of a refusal actually to assert any final ‘truth’ about social, political or even religious experience. Billy Budd, his last body, is hanged, and his final word is silence.
- Full Text:
- Date Issued: 2003
- Authors: Goddard, Kevin Graham
- Date: 2003
- Subjects: Melville, Herman, 1819-1891 -- Criticism and interpretation Human body in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2216 , http://hdl.handle.net/10962/d1002259
- Description: This thesis explores aspects of Melville’s presentation of both the whale and the human bodies in Moby-Dick and human bodies in other important novels. It argues that Melville uses his presentation of bodies to explore some of the versions of confinement those bodies experience, and by doing so, analyses the psychology which subtends that confinement. Throughout Melville’s works bodies are confined, both within literal spatial limits and by the psychology which creates and/or accepts these spatial limits. The thesis argues that perhaps the most important version of bodily confinement Melville addresses is the impulse to conquer bodies, both that of the other and one’s own. It adopts a largely psychoanalytic approach to interpreting bodies and their impulse to conquer, so that the body is seen to figure both in its actions and its external appearance the operations of the inner psyche. The figure of the body is equally prevalent in Melville’s exploration of nationalist conquest, where, as with Manifest Destiny and antebellum expansionism, the psychological and physical lack experienced by characters can be read as motivating factors in the ideology of conquest. A final important strand of the thesis is its argument in favour of a gradual shift in Melville’s interpretation of the value and possibility of genuine communion between human beings and between humans and the whale. One may read Typee as an attempt by Melville to explore the possibility of a this-worldly utopia in which human beings can return to a version of primitive interconnectedness. This exploration may be seen to be extended in Moby-Dick, particularly in Ishmael’s attempts to find communion with others and in some moments of encounter with the whales. The thesis uses phenomenology as a theory to interpret what Melville is trying to suggest in these moments of encounter. However, it argues, finally, that such encounter, or ‘intersubjectivity’ is eventually jettisoned, especially in the works after Moby-Dick. By the end of Melville’s life and work, any hope of an intersubjective utopia he may have harboured as a younger man have been removed in favour of a refusal actually to assert any final ‘truth’ about social, political or even religious experience. Billy Budd, his last body, is hanged, and his final word is silence.
- Full Text:
- Date Issued: 2003
Structural and synthetic investigations of diterpenoid natural products from southern African marine invertebrates
- Authors: Gray, Christopher Anthony
- Date: 2003
- Subjects: Ethyl acetoacetate Diterpenes Limpets -- South Africa Natural products -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4349 , http://hdl.handle.net/10962/d1005014
- Description: This thesis is divided into two parts. The first part (Chapter Two) documents a bioassay guided investigation of the ethyl acetate extracts of four marine invertebrates from Mozambique (an Irciniid sponge, a Haliclona sp. sponge, an ascidian tentatively identified as Diplosoma sp., and the soft coral Cladiella kashmani). Eight known compounds [ilimaquinone (2.1), renierone (2.7), N-formyl-1,2-dihydrorenierone (2.8), 1,6-dimethyl-7-methoxy-5,8-dihydroisoquinoline-5,8-dione (2.9), mimosamycin (2.10) 7Z-allylidene-5-hydroxy-7,7a-dihydro-2H-cyclopenta[b]pyran-6-one (2.11), flaccidoxide (2.18) and 11S,12S-epoxycembra-1Z,3E,7E-trien-14S-ol (2.19)] and a new diterpene [13S,14R-diacetoxy-11S,12R-epoxycembra-1Z,3E,7E-triene (2.20)] were isolated and identified using standard spectroscopic techniques. Anomalies in the published spectral data of 2.1 and 2.8 were exposed and corrected, and the absolute stereochemistry of the cembrane diterpenes 2.18 and 2.20 established using the modified Mosher’s method. The comparative activities of the nine natural products against four cancer cell lines (A549, LOX, OVCAR3, SNB19) are reported. The second part of the thesis (Chapter Three – Chapter Six) is concerned with an ecological, structural and synthetic study of diterpenes from the endemic South African pulmonate limpet Trimusculus costatus. Two new labdane diterpenes [6b,7a-diacetoxylabda-8,13E-dien-15-ol (3.10) and 2a,6b,7a-triacetoxylabda-8,13E-dien-15-ol (3.11)] were isolated from T. costatus and evaluated for anti-feeding activity against the common predatory fish Pomadasys commersonnii. A strategy for the semi-synthesis of 3.10 from rhinocerotinoic acid (4.14), a diterpene reportedly present in the ubiquitous South African shrub Elytropappus rhinocerotis, was devised in order to allow further bioactivity tests to be performed and unequivocally assign the unknown absolute stereochemistry of the T. costatus metabolites. Attempts to isolate rhinocerotinoic acid from local specimens of Elytropappus rhinocerotis were unsuccessful, and as the repetition of a published synthesis of 4.14 from (-)-sclareol (4.15) gave rhinocerotinoic acid in unacceptably low yields with poor stereoselectivity, an improved synthesis of 4.14 is presented. Comprehensive studies using hispanone (5.1) as a model compound showed that 6,7-dioxygenated labda-8-enes could be prepared from compounds possessing a 7-oxo-labda-8-ene skeleton with some degree of stereocontrol. In the process, fourteen new hispanone analogues were prepared and most of these were tested for activity in a suite of ten agro-chemical assays. The novel compound 7b-hydroxy-9a-carbonitrile-15,16-epoxylabda-13(16),14-dien-6-one (5.34) exhibited significant activity against the crop fungus Phytophthora infestans and is currently being subjected to further agro-chemical tests. Unfortunately, the results from the oxygenation study performed on the model compound 5.1 could not be directly extrapolated to rhinocerotinoic acid. Attempts to prepare the naturally occurring 3.10 from 4.14 via an alternative route were unsuccessful but yielded an analogue of 3.10 in which the substituents at C-6 and C-7 are in a diequatorial rather than a diaxial configuration.
- Full Text:
- Date Issued: 2003
- Authors: Gray, Christopher Anthony
- Date: 2003
- Subjects: Ethyl acetoacetate Diterpenes Limpets -- South Africa Natural products -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4349 , http://hdl.handle.net/10962/d1005014
- Description: This thesis is divided into two parts. The first part (Chapter Two) documents a bioassay guided investigation of the ethyl acetate extracts of four marine invertebrates from Mozambique (an Irciniid sponge, a Haliclona sp. sponge, an ascidian tentatively identified as Diplosoma sp., and the soft coral Cladiella kashmani). Eight known compounds [ilimaquinone (2.1), renierone (2.7), N-formyl-1,2-dihydrorenierone (2.8), 1,6-dimethyl-7-methoxy-5,8-dihydroisoquinoline-5,8-dione (2.9), mimosamycin (2.10) 7Z-allylidene-5-hydroxy-7,7a-dihydro-2H-cyclopenta[b]pyran-6-one (2.11), flaccidoxide (2.18) and 11S,12S-epoxycembra-1Z,3E,7E-trien-14S-ol (2.19)] and a new diterpene [13S,14R-diacetoxy-11S,12R-epoxycembra-1Z,3E,7E-triene (2.20)] were isolated and identified using standard spectroscopic techniques. Anomalies in the published spectral data of 2.1 and 2.8 were exposed and corrected, and the absolute stereochemistry of the cembrane diterpenes 2.18 and 2.20 established using the modified Mosher’s method. The comparative activities of the nine natural products against four cancer cell lines (A549, LOX, OVCAR3, SNB19) are reported. The second part of the thesis (Chapter Three – Chapter Six) is concerned with an ecological, structural and synthetic study of diterpenes from the endemic South African pulmonate limpet Trimusculus costatus. Two new labdane diterpenes [6b,7a-diacetoxylabda-8,13E-dien-15-ol (3.10) and 2a,6b,7a-triacetoxylabda-8,13E-dien-15-ol (3.11)] were isolated from T. costatus and evaluated for anti-feeding activity against the common predatory fish Pomadasys commersonnii. A strategy for the semi-synthesis of 3.10 from rhinocerotinoic acid (4.14), a diterpene reportedly present in the ubiquitous South African shrub Elytropappus rhinocerotis, was devised in order to allow further bioactivity tests to be performed and unequivocally assign the unknown absolute stereochemistry of the T. costatus metabolites. Attempts to isolate rhinocerotinoic acid from local specimens of Elytropappus rhinocerotis were unsuccessful, and as the repetition of a published synthesis of 4.14 from (-)-sclareol (4.15) gave rhinocerotinoic acid in unacceptably low yields with poor stereoselectivity, an improved synthesis of 4.14 is presented. Comprehensive studies using hispanone (5.1) as a model compound showed that 6,7-dioxygenated labda-8-enes could be prepared from compounds possessing a 7-oxo-labda-8-ene skeleton with some degree of stereocontrol. In the process, fourteen new hispanone analogues were prepared and most of these were tested for activity in a suite of ten agro-chemical assays. The novel compound 7b-hydroxy-9a-carbonitrile-15,16-epoxylabda-13(16),14-dien-6-one (5.34) exhibited significant activity against the crop fungus Phytophthora infestans and is currently being subjected to further agro-chemical tests. Unfortunately, the results from the oxygenation study performed on the model compound 5.1 could not be directly extrapolated to rhinocerotinoic acid. Attempts to prepare the naturally occurring 3.10 from 4.14 via an alternative route were unsuccessful but yielded an analogue of 3.10 in which the substituents at C-6 and C-7 are in a diequatorial rather than a diaxial configuration.
- Full Text:
- Date Issued: 2003
An analysis of selected World Trade Organisation agreements to determine whether they discriminate unfairly against developing economices
- Authors: Grimett, Leticia Anthea
- Date: 2013-07-29
- Subjects: World Trade Organization Foreign trade regulation General Agreement on Tariffs and Trade (Organization) Free trade -- Developing countries Foreign trade regulation -- Developing countries Competition, Unfair -- Developing countries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3718 , http://hdl.handle.net/10962/d1008368
- Description: The focus of this thesis is the question whether or not the WTO discriminates unfairly against developing economies. In the absence of a test of guidelines for detennining unfairness or fairness of WTO provisions or Agreements has been drawn up using welfare economic and constitutional law principles as a foundation. Unfairness is therefore determined by asking whether the provisions of each Agreement are rational, proportional, efficient and whether they prevent the abuse of power amongst states. In addition, the economic effects of the provisions of the selected Agreements have been analysed to determine whether the relevant provisions are welfare enhancing and conclusive to promoting growth and development within developing economies. The Agreements chosed for analysis are the Agreements on Trade-related Investment Measures (TRIMS), Trade-related Intellectual Property (TRIPS), Agriculture and Services (GATS). The dispute settlement and negotiating process, labour standards and the impact of decreasing most-favoured nation rates on developing economy competitiveness is also discussed. Application of the test has shown that the WTO provisions do not reflect the interests of all members. Even though most member states are developing economies, the3 Agreements constantly cater foe developed country concerns and interests. Where provision is made for developing country interests, it is the LDC's who are favoured, with nonnal developing economies being bound by the same provisions as the developed economies. A fonnal, as opposed to a substantive, defmition has been adopted by the WTO, with a result that the process of equality is placed above the outcomes. While concessions have been made to development, members have not gone for enough. A main reason for the imbalance can be attributed to the negotiating process, which is based upon concessionary bargaining and trade-off. Those states with greater economic power are therefore at an advantage as they have the leverage needed to influence the outcomes of negotiations and hence the provisions of the various Agreements. Even with the LDC's, the WTO has been found to discriminate unfairly against developing economies because it does not adequately address developing country concerns. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Authors: Grimett, Leticia Anthea
- Date: 2013-07-29
- Subjects: World Trade Organization Foreign trade regulation General Agreement on Tariffs and Trade (Organization) Free trade -- Developing countries Foreign trade regulation -- Developing countries Competition, Unfair -- Developing countries
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3718 , http://hdl.handle.net/10962/d1008368
- Description: The focus of this thesis is the question whether or not the WTO discriminates unfairly against developing economies. In the absence of a test of guidelines for detennining unfairness or fairness of WTO provisions or Agreements has been drawn up using welfare economic and constitutional law principles as a foundation. Unfairness is therefore determined by asking whether the provisions of each Agreement are rational, proportional, efficient and whether they prevent the abuse of power amongst states. In addition, the economic effects of the provisions of the selected Agreements have been analysed to determine whether the relevant provisions are welfare enhancing and conclusive to promoting growth and development within developing economies. The Agreements chosed for analysis are the Agreements on Trade-related Investment Measures (TRIMS), Trade-related Intellectual Property (TRIPS), Agriculture and Services (GATS). The dispute settlement and negotiating process, labour standards and the impact of decreasing most-favoured nation rates on developing economy competitiveness is also discussed. Application of the test has shown that the WTO provisions do not reflect the interests of all members. Even though most member states are developing economies, the3 Agreements constantly cater foe developed country concerns and interests. Where provision is made for developing country interests, it is the LDC's who are favoured, with nonnal developing economies being bound by the same provisions as the developed economies. A fonnal, as opposed to a substantive, defmition has been adopted by the WTO, with a result that the process of equality is placed above the outcomes. While concessions have been made to development, members have not gone for enough. A main reason for the imbalance can be attributed to the negotiating process, which is based upon concessionary bargaining and trade-off. Those states with greater economic power are therefore at an advantage as they have the leverage needed to influence the outcomes of negotiations and hence the provisions of the various Agreements. Even with the LDC's, the WTO has been found to discriminate unfairly against developing economies because it does not adequately address developing country concerns. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
The geochemistry of ore fluids and control of gold mineralization in banded iron-formation at the Kalahari Goldridge deposit, Kraaipan greenstone belt, South Africa
- Authors: Hammond, Napoleon Quaye
- Date: 2003
- Subjects: Gold ores -- Geology -- South Africa -- North-West Greenstone belts -- South Africa -- North-West Ore deposits -- South Africa -- North-West Geochemistry -- South Africa -- North-West
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5048 , http://hdl.handle.net/10962/d1008370
- Description: The Kalahari Goldridge mine is located within the Archaean Kraaipan Greenstone Belt about 60 km SW of Mafikeng in the Northwestern Province, South Africa. Several gold deposits are located within approximately north - south-striking banded iron-formation (BIF). Current opencast mining operations are focused on the largest of these (D Zone). The orebody is stratabound and hosted primarily in the BIF, which consists of alternating chert and magnetite-chloritestilpnomelane-sulphide-carbonate bands ranging from mm to cm scale. The ore body varies in thickness from 15 to 45 m along a strike length of about 1.5 km. The BlF is sandwiched between a sericite-carbonate-chlorite schist at the immediate footwall and carbonaceous meta-pelites in the hanging-wall. Further west in the footwall, the schists are underlain by mafic meta-volcanic amphibolite. Overlying the hanging-wall carbonaceous metapeiites are schist units and meta-greywackes that become increasingly conglomeratic up the stratigraphy. Stilpnomelane-, chlorite- and minnesotaite-bearing assemblages in the BlFs indicate metamorphic temperatures of 300 - 450°C and pressures of less than 5 kbars. The BIF generally strikes approximately 3400 and dips from 60 to 75°E. Brittle-ductile deformation is evidenced by small-scale isoclinal folds, brecciation, extension fractures and boudinaging of cherty BIF units. Fold axial planes are sub-parallel to the foliation orientation with sub-vertical plunges parallel to prominent rodding and mineral lineation in the footwall. Gold mineralization at the Kalahari Goldridge deposit is associated with two generations of subhorizontal quartz-carbonate veins dips approximately 20 to 40°W. The first generation consists of ladder vein sets (Group lIA) preferentially developed in Fe-rich meso bands, whilst the second generation consists of large quartz-carbonate veins (Group lIB), which crosscut the entire ore body extending into the footwall and hanging-wall in places. Major structures that control the ore body are related to meso-scale isoclinal folds with fold axes subparallel to mineral elongation lineations, which plunge approximately 067°E. These linear structures form orthogonal orientation with the plane of the mineralized shallowdipping veins indicating stretching and development of fluid - focusing conduits. A second-order controlling feature corresponds to the intersection of the mineralized veins and foliation planes of host rock, plunging approximately 008°N and trending 341°. G0ld is closely associated with sulphides, mainly pyrite and pyrrhotite and to a lesser extent with bismuth tellurides, and carbonate gangue. The ore fluid responsible for the gold deposition is in the C-O-H system with increased CH₄ contents attributed to localized hydrolysis reaction between interbedded carbonaceous sediment and ore fluid. The fluid is characterized by significant C0₂ contents and low salinities below 7.0 wt % NaCl equivalent (averages of 3.5 and 3.0 wt % NaCl equivalent for the first and second episodes of the mineralization respectively) . Calculated values of f0₂. ranging from 10⁻²⁹·⁹⁸ to 10⁻³²·⁹⁶ bars, bracket the C0₂-CH₄ and pyrite-pyrrhotite-magnetite buffer boundaries and reveal the reducing nature of the ore fluid at deposition. Calculated total sulphur content in the ore fluid (mΣs), ranges from 0.011 to 0.018M and is consistent with the range (10⁻³·⁵ to 10⁻¹M) reported for subamphibolite facies ore fluids. The close association of sulphides with the Au and nature of the fluid also give credence that the Au was carried in solution by the Au(HS)₂ - complex. Extensive epigenetic replacement of magnetite and chlorite in BIF and other meta-pelitic sediments in the deposit by sulphides and carbonates, both on meso scopic and microscopic scales gives evidence of an interaction by a CO₂- and H₂S-bearing fluid with the Fe-rich host rocks in the deposit. This facilitated Au precipitation due to changes in the physico-chemical conditions of the ore fluid such as a decrease in the mΣs and pH leading to the destabilization of the reduced sulphur complexes. Local gradients in f0₂ may account for gold precipitation in places within carbonaceous sediments. The fineness of the gold grams (1000*Au/(Au + Ag) ranges from 823 to 921. This compares favourably with the fineness reported for some Archaean BIFhosced deposits (851 - 970). Mass balance transfer calculations indicate that major chemical changes associated with the hydrothermal alteration of BIF include enrichment of Au, Ag, Bi, Te, volatiles (S and CO₂), MgO, Ba, K and Rb but significant depletion of SiO₂ and minor losses of Fe₂O₃. In addition, anomalous enrichment of Sc (average, 1247%) suggests its possible use as an exploration tool in the ferruginous sediments in the Kraaipan greenstone terrane. Evidence from light stable isotopes and fluid inclusions suggests that the mineralized veins crystallized from a single homogeneous fluid source during the two episodes of mineralization under the similar physicochemical conditions. Deposition occurred at temperatures rangmg from 350 to 400°C and fluid pressures ranging from 0.7 to 2.0kbars. Stable isotope constraints indicate the following range for the hydrothermal fluid; θ¹⁸H₂O = 6.65 to 10.48%0, 8¹³CΣc = -6.0 to -8.0 %0 and 8³⁴SΣs = + 1.69 to + 4.0%0 . These data do not offer conclusive evidence for the source of fluid associated with the mineralization at the Kalahari Goldridge deposit as they overlap the range prescribed for fluid derived from devolatization of deep-seated volcano-sedimentary piles near the brittle-ductile transition in greenstone belts during prograde metamorphism, and magmatic hydrothermal fluids. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
- Authors: Hammond, Napoleon Quaye
- Date: 2003
- Subjects: Gold ores -- Geology -- South Africa -- North-West Greenstone belts -- South Africa -- North-West Ore deposits -- South Africa -- North-West Geochemistry -- South Africa -- North-West
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5048 , http://hdl.handle.net/10962/d1008370
- Description: The Kalahari Goldridge mine is located within the Archaean Kraaipan Greenstone Belt about 60 km SW of Mafikeng in the Northwestern Province, South Africa. Several gold deposits are located within approximately north - south-striking banded iron-formation (BIF). Current opencast mining operations are focused on the largest of these (D Zone). The orebody is stratabound and hosted primarily in the BIF, which consists of alternating chert and magnetite-chloritestilpnomelane-sulphide-carbonate bands ranging from mm to cm scale. The ore body varies in thickness from 15 to 45 m along a strike length of about 1.5 km. The BlF is sandwiched between a sericite-carbonate-chlorite schist at the immediate footwall and carbonaceous meta-pelites in the hanging-wall. Further west in the footwall, the schists are underlain by mafic meta-volcanic amphibolite. Overlying the hanging-wall carbonaceous metapeiites are schist units and meta-greywackes that become increasingly conglomeratic up the stratigraphy. Stilpnomelane-, chlorite- and minnesotaite-bearing assemblages in the BlFs indicate metamorphic temperatures of 300 - 450°C and pressures of less than 5 kbars. The BIF generally strikes approximately 3400 and dips from 60 to 75°E. Brittle-ductile deformation is evidenced by small-scale isoclinal folds, brecciation, extension fractures and boudinaging of cherty BIF units. Fold axial planes are sub-parallel to the foliation orientation with sub-vertical plunges parallel to prominent rodding and mineral lineation in the footwall. Gold mineralization at the Kalahari Goldridge deposit is associated with two generations of subhorizontal quartz-carbonate veins dips approximately 20 to 40°W. The first generation consists of ladder vein sets (Group lIA) preferentially developed in Fe-rich meso bands, whilst the second generation consists of large quartz-carbonate veins (Group lIB), which crosscut the entire ore body extending into the footwall and hanging-wall in places. Major structures that control the ore body are related to meso-scale isoclinal folds with fold axes subparallel to mineral elongation lineations, which plunge approximately 067°E. These linear structures form orthogonal orientation with the plane of the mineralized shallowdipping veins indicating stretching and development of fluid - focusing conduits. A second-order controlling feature corresponds to the intersection of the mineralized veins and foliation planes of host rock, plunging approximately 008°N and trending 341°. G0ld is closely associated with sulphides, mainly pyrite and pyrrhotite and to a lesser extent with bismuth tellurides, and carbonate gangue. The ore fluid responsible for the gold deposition is in the C-O-H system with increased CH₄ contents attributed to localized hydrolysis reaction between interbedded carbonaceous sediment and ore fluid. The fluid is characterized by significant C0₂ contents and low salinities below 7.0 wt % NaCl equivalent (averages of 3.5 and 3.0 wt % NaCl equivalent for the first and second episodes of the mineralization respectively) . Calculated values of f0₂. ranging from 10⁻²⁹·⁹⁸ to 10⁻³²·⁹⁶ bars, bracket the C0₂-CH₄ and pyrite-pyrrhotite-magnetite buffer boundaries and reveal the reducing nature of the ore fluid at deposition. Calculated total sulphur content in the ore fluid (mΣs), ranges from 0.011 to 0.018M and is consistent with the range (10⁻³·⁵ to 10⁻¹M) reported for subamphibolite facies ore fluids. The close association of sulphides with the Au and nature of the fluid also give credence that the Au was carried in solution by the Au(HS)₂ - complex. Extensive epigenetic replacement of magnetite and chlorite in BIF and other meta-pelitic sediments in the deposit by sulphides and carbonates, both on meso scopic and microscopic scales gives evidence of an interaction by a CO₂- and H₂S-bearing fluid with the Fe-rich host rocks in the deposit. This facilitated Au precipitation due to changes in the physico-chemical conditions of the ore fluid such as a decrease in the mΣs and pH leading to the destabilization of the reduced sulphur complexes. Local gradients in f0₂ may account for gold precipitation in places within carbonaceous sediments. The fineness of the gold grams (1000*Au/(Au + Ag) ranges from 823 to 921. This compares favourably with the fineness reported for some Archaean BIFhosced deposits (851 - 970). Mass balance transfer calculations indicate that major chemical changes associated with the hydrothermal alteration of BIF include enrichment of Au, Ag, Bi, Te, volatiles (S and CO₂), MgO, Ba, K and Rb but significant depletion of SiO₂ and minor losses of Fe₂O₃. In addition, anomalous enrichment of Sc (average, 1247%) suggests its possible use as an exploration tool in the ferruginous sediments in the Kraaipan greenstone terrane. Evidence from light stable isotopes and fluid inclusions suggests that the mineralized veins crystallized from a single homogeneous fluid source during the two episodes of mineralization under the similar physicochemical conditions. Deposition occurred at temperatures rangmg from 350 to 400°C and fluid pressures ranging from 0.7 to 2.0kbars. Stable isotope constraints indicate the following range for the hydrothermal fluid; θ¹⁸H₂O = 6.65 to 10.48%0, 8¹³CΣc = -6.0 to -8.0 %0 and 8³⁴SΣs = + 1.69 to + 4.0%0 . These data do not offer conclusive evidence for the source of fluid associated with the mineralization at the Kalahari Goldridge deposit as they overlap the range prescribed for fluid derived from devolatization of deep-seated volcano-sedimentary piles near the brittle-ductile transition in greenstone belts during prograde metamorphism, and magmatic hydrothermal fluids. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2003
Biogeography and community structure of fishes in South African estuaries
- Authors: Harrison, Trevor D
- Date: 2003
- Subjects: Estuarine ecology -- South Africa Estuarine fishes -- South Africa Fish communities -- South Africa Biogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5235 , http://hdl.handle.net/10962/d1005078
- Description: The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
- Full Text:
- Date Issued: 2003
- Authors: Harrison, Trevor D
- Date: 2003
- Subjects: Estuarine ecology -- South Africa Estuarine fishes -- South Africa Fish communities -- South Africa Biogeography -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5235 , http://hdl.handle.net/10962/d1005078
- Description: The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.
- Full Text:
- Date Issued: 2003
Binding and transcriptional activation by Uga3p, a zinc binuclear cluster protein of Saccharomyces cerevisiae redefining the UAS [subscript GABA] and the Uga3p binding site
- Authors: Idicula, Anu Mary
- Date: 2003
- Subjects: Saccharomyces cerevisiae GABA
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3933 , http://hdl.handle.net/10962/d1003992
- Description: Uga3p, a member of the zinc binuclear cluster transcription factor family, is required for [gamma]-aminobutyric acid-dependent transcription of the UGA genes in Saccharomyces cerevisiae. Crystallographic data of some of the protein-DNA complexes of this family reveal that members of this family bind to CGG triplets. A conserved 19-nucleotide activation element in certain UGA gene promoter regions contains a CCG-N4-CGG everted repeat, proposed to be the binding site of Uga3p, UAS[subscript GABA]. The spacer region (N4) between the CGG triplets has been suggested to be the specificity determinant for binding to UAS[subscript GABA]. The data available from the Saccharomyces genome database indicates that there are multiple repeats of -CCG-N4-CGG- regions within the genome. These transcription factors are involved in the activation of specific pathways and the question arises as to how their specificity of binding is determined. The aim of this study was to understand the binding characteristics of Uga3p to UAS[subscript GABA] and to determine the affinity and specificity of this interaction. In this study, full-length (tagged and untagged) and truncated (1-124 a.a.) Uga3p was produced in a heterologous expression system (E. coli). The interaction of Uga3p with UAS[subscript GABA] in Saccharomyces cerevisiae was characterized in terms of binding in vitro and the transcriptional activation of lacZ reporter genes in vivo. The Uga3p was capable of binding to these sites in vitro independent of exogenous GABA. Electrophoretic mobility shift assays (EMSA) of the full-length Uga3p with the wild type UAS[subscript GABA] sequences produced two distinct mobility complexes. The complexes formed in the EMSA of the full-length Uga3p were those specific to the interaction of the Uga3p to UAS[subscript GABA]. The truncated Uga3p(1-124 a.a.), which has the DNA-binding zinc cluster domain, the linker region and the putative coiled-coil domain was not functionally equivalent to the full-length protein with respect to binding in vitro because the EMSAs of the UAS[subscript GABA] with the truncated Uga3p produced indistinct complexes. EMSAs using mutant UAS[subscript GABA] sequences and heterologously-produced full-length Uga3p, demonstrated that UAS[subscript GABA] consists of two, independent Uga3p-binding sites. This work presents evidence that the two Uga3p molecules bound to UAS[subscript GABA] most likely interact with each other. Unlike other zinc cluster binding sites the Uga3p-binding site is an asymmetric site of 5’-SGCGGNWWT-3’ (S= G or C, W = A or T and N = no nucleotide or G or C). UAS[subscript GABA] is a palindrome containing the two asymmetric Uga3p-binding sites. The two-site consensus sequence required for the binding of Uga3p to the UAS[subscript GABA] is present upstream of UGA1 (region -387 to -370) and UGA4 (region -403 to -387). Furthermore, a single Uga3p-binding site was identified in the 5’ untranslated regions of UGA2 (region -219 to -211). GABA-dependent transcriptional activation by UAS[subscript GABA] in vivo could be directly correlated to a high affinity, specific interaction of two Uga3p molecules to this UAS. Binding with high affinity required the conserved sequences flanking the everted repeat. This study provided evidence that the binding pattern of Uga3p is novel compared to other zinc cluster motifs investigated, as the sequences flanking the everted repeat are important regions for recognition by Uga3p. The studies with the truncated Uga3p (1 –124 a.a.), also suggested that the regions C-terminal to the DNA-binding motif and putative coiled-coil area of this protein are important for Uga3p-specific interactions with UAS[subscript GABA]. Investigation of regions C-terminal to the zinc cluster, linker and putative coiledcoil revealed an eight-motif regulatory region similar to that in other zinc cluster proteins. This indicated that the regions C-terminal to these domains are important for the regulation and activity of these proteins. A putative seven repeat WD40-like motif was identified within this region. This putative domain has been speculated to be important for protein-protein interactions. Phosphorylation and dephosphorylation in other proteins of this class have been indicated to be important for the regulation of the activity of these proteins. The bioinformatic analysis of Uga3p revealed two possible cAMP/cGMP-dependent protein kinase phosphorylation sites, four putative protein kinase C phosphorylation motifs and four putative casein kinase II phosphorylation motifs. This study has contributed to the understanding of the nature of interactions between Uga3p and its specific UAS [subscript GABA] and how the regions flanking the everted repeat determine its specificity. The comparison of the nature of the binding of truncated and full-length Uga3p in vitro provided evidence for the role played by the full-length protein in determining this specific interaction. This evidence suggested that the in vitro binding evidence for other proteins of this family, using truncated peptides that carry the DNA-binding domain, might not reflect the true nature of interactions between the proteins of this class and their specific UASs in vivo.
- Full Text:
- Date Issued: 2003
- Authors: Idicula, Anu Mary
- Date: 2003
- Subjects: Saccharomyces cerevisiae GABA
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3933 , http://hdl.handle.net/10962/d1003992
- Description: Uga3p, a member of the zinc binuclear cluster transcription factor family, is required for [gamma]-aminobutyric acid-dependent transcription of the UGA genes in Saccharomyces cerevisiae. Crystallographic data of some of the protein-DNA complexes of this family reveal that members of this family bind to CGG triplets. A conserved 19-nucleotide activation element in certain UGA gene promoter regions contains a CCG-N4-CGG everted repeat, proposed to be the binding site of Uga3p, UAS[subscript GABA]. The spacer region (N4) between the CGG triplets has been suggested to be the specificity determinant for binding to UAS[subscript GABA]. The data available from the Saccharomyces genome database indicates that there are multiple repeats of -CCG-N4-CGG- regions within the genome. These transcription factors are involved in the activation of specific pathways and the question arises as to how their specificity of binding is determined. The aim of this study was to understand the binding characteristics of Uga3p to UAS[subscript GABA] and to determine the affinity and specificity of this interaction. In this study, full-length (tagged and untagged) and truncated (1-124 a.a.) Uga3p was produced in a heterologous expression system (E. coli). The interaction of Uga3p with UAS[subscript GABA] in Saccharomyces cerevisiae was characterized in terms of binding in vitro and the transcriptional activation of lacZ reporter genes in vivo. The Uga3p was capable of binding to these sites in vitro independent of exogenous GABA. Electrophoretic mobility shift assays (EMSA) of the full-length Uga3p with the wild type UAS[subscript GABA] sequences produced two distinct mobility complexes. The complexes formed in the EMSA of the full-length Uga3p were those specific to the interaction of the Uga3p to UAS[subscript GABA]. The truncated Uga3p(1-124 a.a.), which has the DNA-binding zinc cluster domain, the linker region and the putative coiled-coil domain was not functionally equivalent to the full-length protein with respect to binding in vitro because the EMSAs of the UAS[subscript GABA] with the truncated Uga3p produced indistinct complexes. EMSAs using mutant UAS[subscript GABA] sequences and heterologously-produced full-length Uga3p, demonstrated that UAS[subscript GABA] consists of two, independent Uga3p-binding sites. This work presents evidence that the two Uga3p molecules bound to UAS[subscript GABA] most likely interact with each other. Unlike other zinc cluster binding sites the Uga3p-binding site is an asymmetric site of 5’-SGCGGNWWT-3’ (S= G or C, W = A or T and N = no nucleotide or G or C). UAS[subscript GABA] is a palindrome containing the two asymmetric Uga3p-binding sites. The two-site consensus sequence required for the binding of Uga3p to the UAS[subscript GABA] is present upstream of UGA1 (region -387 to -370) and UGA4 (region -403 to -387). Furthermore, a single Uga3p-binding site was identified in the 5’ untranslated regions of UGA2 (region -219 to -211). GABA-dependent transcriptional activation by UAS[subscript GABA] in vivo could be directly correlated to a high affinity, specific interaction of two Uga3p molecules to this UAS. Binding with high affinity required the conserved sequences flanking the everted repeat. This study provided evidence that the binding pattern of Uga3p is novel compared to other zinc cluster motifs investigated, as the sequences flanking the everted repeat are important regions for recognition by Uga3p. The studies with the truncated Uga3p (1 –124 a.a.), also suggested that the regions C-terminal to the DNA-binding motif and putative coiled-coil area of this protein are important for Uga3p-specific interactions with UAS[subscript GABA]. Investigation of regions C-terminal to the zinc cluster, linker and putative coiledcoil revealed an eight-motif regulatory region similar to that in other zinc cluster proteins. This indicated that the regions C-terminal to these domains are important for the regulation and activity of these proteins. A putative seven repeat WD40-like motif was identified within this region. This putative domain has been speculated to be important for protein-protein interactions. Phosphorylation and dephosphorylation in other proteins of this class have been indicated to be important for the regulation of the activity of these proteins. The bioinformatic analysis of Uga3p revealed two possible cAMP/cGMP-dependent protein kinase phosphorylation sites, four putative protein kinase C phosphorylation motifs and four putative casein kinase II phosphorylation motifs. This study has contributed to the understanding of the nature of interactions between Uga3p and its specific UAS [subscript GABA] and how the regions flanking the everted repeat determine its specificity. The comparison of the nature of the binding of truncated and full-length Uga3p in vitro provided evidence for the role played by the full-length protein in determining this specific interaction. This evidence suggested that the in vitro binding evidence for other proteins of this family, using truncated peptides that carry the DNA-binding domain, might not reflect the true nature of interactions between the proteins of this class and their specific UASs in vivo.
- Full Text:
- Date Issued: 2003
Studies of the environmental and endocrine control of reproduction in the four striped field mouse, Rhabdomys pumilio
- Authors: Jackson, Claire
- Date: 2003
- Subjects: Microtus Microtus -- South Africa -- Reproduction Mice -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5777 , http://hdl.handle.net/10962/d1005465
- Description: Previous studies of the control of reproduction in Rhabdomys pumilio have shown that day length alone does not inhibit spermatogenesis, that a reduction in food availability and ambient temperature results in an inhibition of gametogenesis, that females are more susceptible to inhibition than are males, and that mice that are able to maintain a body fat store in the face of an energetic challenge, are less likely to show reproductive inhibition than those that lose their fat store. In the present study, field and laboratory experiments were conducted to examine the effects of winter food supplementation on reproduction and population dynamics, and the effects of exogenous GnRH, leptin and mercaptoacetate (MA) on reproductive activity of Rhabdomys pumilio exposed to an energetic challenge. In the field food supplementation experiments in Thomas Baines Nature Reserve (2000, 2001), there was no winter inhibition of reproduction and provision of supplementary food had little effect. While at Mountain Zebra National Park (2002) winter was harsher, females became reproductively inactive, spermatogenesis continued and the provision of extra food resulted in higher rates of individual growth and larger reproductive organs. Treatment of mice that had been exposed to a prolonged energetic challenge, with exogenous GnRH (1µg/mouse/treatment) resulted in an increase in the masses of the testes and epididymides, and in the activity of the reproductive organs. Treatment with exogenous leptin (40µg/mouse/treatment), concurrently with an energetic challenge, countered the negative effects of the energetic challenge, and treated males had larger reproductive organs. MA (600µmol/kg body mass), given concurrently with an energetic challenge, did not inhibit fat metabolism, although the high-fat diet countered the effects of the energetic challenge. Results suggest that the first response of male Rhabdomys pumilio to an energetic challenge is a reduction in the size of the reproductive organs, without an inhibition of spermatogenesis. It is likely that this effect is mediated via white fat and leptin, and leptin’s influence on the hypothalamic-pituitary-gonad axis. Results of the study support the suggestion that females are more sensitive to reproductive inhibition than males and that reproduction in Rhabdomys pumilio is truly opportunistic.
- Full Text:
- Date Issued: 2003
- Authors: Jackson, Claire
- Date: 2003
- Subjects: Microtus Microtus -- South Africa -- Reproduction Mice -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5777 , http://hdl.handle.net/10962/d1005465
- Description: Previous studies of the control of reproduction in Rhabdomys pumilio have shown that day length alone does not inhibit spermatogenesis, that a reduction in food availability and ambient temperature results in an inhibition of gametogenesis, that females are more susceptible to inhibition than are males, and that mice that are able to maintain a body fat store in the face of an energetic challenge, are less likely to show reproductive inhibition than those that lose their fat store. In the present study, field and laboratory experiments were conducted to examine the effects of winter food supplementation on reproduction and population dynamics, and the effects of exogenous GnRH, leptin and mercaptoacetate (MA) on reproductive activity of Rhabdomys pumilio exposed to an energetic challenge. In the field food supplementation experiments in Thomas Baines Nature Reserve (2000, 2001), there was no winter inhibition of reproduction and provision of supplementary food had little effect. While at Mountain Zebra National Park (2002) winter was harsher, females became reproductively inactive, spermatogenesis continued and the provision of extra food resulted in higher rates of individual growth and larger reproductive organs. Treatment of mice that had been exposed to a prolonged energetic challenge, with exogenous GnRH (1µg/mouse/treatment) resulted in an increase in the masses of the testes and epididymides, and in the activity of the reproductive organs. Treatment with exogenous leptin (40µg/mouse/treatment), concurrently with an energetic challenge, countered the negative effects of the energetic challenge, and treated males had larger reproductive organs. MA (600µmol/kg body mass), given concurrently with an energetic challenge, did not inhibit fat metabolism, although the high-fat diet countered the effects of the energetic challenge. Results suggest that the first response of male Rhabdomys pumilio to an energetic challenge is a reduction in the size of the reproductive organs, without an inhibition of spermatogenesis. It is likely that this effect is mediated via white fat and leptin, and leptin’s influence on the hypothalamic-pituitary-gonad axis. Results of the study support the suggestion that females are more sensitive to reproductive inhibition than males and that reproduction in Rhabdomys pumilio is truly opportunistic.
- Full Text:
- Date Issued: 2003
Intercohort cannibalism and parturition-associated behaviour of captive-bred swordtail, Xiphophorus helleri (Pisces: Poeciliidae)
- Jones, Clifford Louis Wilshire
- Authors: Jones, Clifford Louis Wilshire
- Date: 2003
- Subjects: Poeciliidae -- Behavior Xiphophorus helleri Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5351 , http://hdl.handle.net/10962/d1007812
- Description: Adult fish that belong to the family Poeciliidae cannibalise juveniles, both in the wild and under captive conditions, but this behaviour has only been partly investigated in the Poeciliidae in some of the commercially valuable species. The objective of the research is to develop an understanding of intercohort cannibalism and parturition-associated behaviour in captive-bred swordtail (Xiphophorus helleri), with applications to industry and future research of other poeciliids. Experiments investigating the effect of adult stocking density and sex ratio on the production of juveniles were used to determine if cannibalism occurs under culture conditions. The average rate of intercohort cannibalism ranged from (5.5 to 53.9%), and was positively density dependent and independent of sex ratio, indicating that males and females were probably equally cannibalistic. The highest number of juveniles (1725.7±141.4) produced per tank over 70 days was obtained from two males and eight females. To develop a better understanding of adult and juvenile behaviour during parturition, fish were observed under controlled laboratory conditions using video and behaviours such as attack (burst of speed by an adult in the direction of a juvenile), escape (avoidance of cannibalism after attack) and cannibalism (predation of a live juvenile by an adult), for example, were identified. Under laboratory conditions most young escaped in downward direction after attack (49%) and most utilised the refuge made that was made available. Furthermore, most attacks (62-65%) and cannibalism (57-84%) occurred at the bottom. Since the presence of refuge significantly increased the rate of juvenile survival under culture conditions, it was hypothesised that the rate of cannibalism could be reduced under farming conditions if juveniles were protected when they escaped downwards. This hypothesis was accepted as it was found that refuge at the bottom of the water column or the inclusion of a false-bottom reduced the rate of cannibalism by 49% and 72%, respectively. Similarly, the hypothesise that the rate of cannibalism could be reduced if juveniles where given protection when escaping sideways (32% of juveniles escaped sideways in the laboratory) was also accepted when tested under farm-scale conditions because a false-side reduced the rate of cannibalism by an average of 45%. Since males and females were equally responsible for cannibalising juveniles in the laboratory, it was hypothesised that the rate of cannibalism would decrease proportionately with the removal of males (Le. 20% of the cannibals) from the population; the removal of males under farming conditions resulted in a 19.5% reduction in the rate of cannibalism. Since older juveniles were better able to escape cannibalism than neonates and since adults habituate to stimuli that previously resulted in attack behaviour, it was hypothesised that the rate of cannibalism would remain unaffected by the length of time that juveniles were exposed to adults in the breeding tanks. This hypothesis was also accepted when tested under farm conditions. However, some hypotheses based on laboratory observations were not accepted. For example, a constant low light intensity did not appear to decrease the rate of cannibalism under farm conditions; also, the occurrence of dead and deformed juveniles went unnoticed in the laboratory, and under farm conditions, where adults did not have access to the bottom of the tank, 10% of the harvest consisted of dead and deformed juveniles. It is concluded that technologies, such as bottom-refuge or a false-side, that increase the size of the liveharvest and allow for the removal of potentially less viable offspring are recommended for the commercial production of poeciliids. The overall similarity of X. helleri behaviour between the laboratory experiments and the farm-scale trials suggests that the post-partum behaviour of X. helleri remains consistent under these different conditions; thus, behaviour under one set of conditions may be used to predict behaviour under other conditions. The application and significance of extrapolations to industry and future research of X. helleri and possibly other poeciliids were discussed and the most applicable laboratory observations with the highest extrapolation capacity were proposed. Furthermore, techniques were developed to aid industry and future researchers in making predictions relating to behaviour of X. helleri under different conditions based on laboratory observations. The results were used to develop a model indicating that selection pressures against cannibalism are not likely to exist at the rate of cannibalism observed here since the potential genetic gain through kin survival and inclusive fitness was shown to be greater than any potential genetiC loss experienced by a victim of cannibalism. The model was successfully tested under a range of social conditions. Other possible explanations for cannibalism in poeciliids, such as parental manipulation, nutritional advantages, opportunistic predation and the recovery of energy are discussed. It is suggested that the most likely proximate cause of cannibalism under captive conditions is opportunistic predation. The theory that cannibalism ensures that only viable genes of the victim are expressed, through inclusive fitness, is a possible ultimate cause of cannibalism, which may have been inherited from feral ancestors of captive-bred X. helleri.
- Full Text:
- Date Issued: 2003
- Authors: Jones, Clifford Louis Wilshire
- Date: 2003
- Subjects: Poeciliidae -- Behavior Xiphophorus helleri Fish culture
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5351 , http://hdl.handle.net/10962/d1007812
- Description: Adult fish that belong to the family Poeciliidae cannibalise juveniles, both in the wild and under captive conditions, but this behaviour has only been partly investigated in the Poeciliidae in some of the commercially valuable species. The objective of the research is to develop an understanding of intercohort cannibalism and parturition-associated behaviour in captive-bred swordtail (Xiphophorus helleri), with applications to industry and future research of other poeciliids. Experiments investigating the effect of adult stocking density and sex ratio on the production of juveniles were used to determine if cannibalism occurs under culture conditions. The average rate of intercohort cannibalism ranged from (5.5 to 53.9%), and was positively density dependent and independent of sex ratio, indicating that males and females were probably equally cannibalistic. The highest number of juveniles (1725.7±141.4) produced per tank over 70 days was obtained from two males and eight females. To develop a better understanding of adult and juvenile behaviour during parturition, fish were observed under controlled laboratory conditions using video and behaviours such as attack (burst of speed by an adult in the direction of a juvenile), escape (avoidance of cannibalism after attack) and cannibalism (predation of a live juvenile by an adult), for example, were identified. Under laboratory conditions most young escaped in downward direction after attack (49%) and most utilised the refuge made that was made available. Furthermore, most attacks (62-65%) and cannibalism (57-84%) occurred at the bottom. Since the presence of refuge significantly increased the rate of juvenile survival under culture conditions, it was hypothesised that the rate of cannibalism could be reduced under farming conditions if juveniles were protected when they escaped downwards. This hypothesis was accepted as it was found that refuge at the bottom of the water column or the inclusion of a false-bottom reduced the rate of cannibalism by 49% and 72%, respectively. Similarly, the hypothesise that the rate of cannibalism could be reduced if juveniles where given protection when escaping sideways (32% of juveniles escaped sideways in the laboratory) was also accepted when tested under farm-scale conditions because a false-side reduced the rate of cannibalism by an average of 45%. Since males and females were equally responsible for cannibalising juveniles in the laboratory, it was hypothesised that the rate of cannibalism would decrease proportionately with the removal of males (Le. 20% of the cannibals) from the population; the removal of males under farming conditions resulted in a 19.5% reduction in the rate of cannibalism. Since older juveniles were better able to escape cannibalism than neonates and since adults habituate to stimuli that previously resulted in attack behaviour, it was hypothesised that the rate of cannibalism would remain unaffected by the length of time that juveniles were exposed to adults in the breeding tanks. This hypothesis was also accepted when tested under farm conditions. However, some hypotheses based on laboratory observations were not accepted. For example, a constant low light intensity did not appear to decrease the rate of cannibalism under farm conditions; also, the occurrence of dead and deformed juveniles went unnoticed in the laboratory, and under farm conditions, where adults did not have access to the bottom of the tank, 10% of the harvest consisted of dead and deformed juveniles. It is concluded that technologies, such as bottom-refuge or a false-side, that increase the size of the liveharvest and allow for the removal of potentially less viable offspring are recommended for the commercial production of poeciliids. The overall similarity of X. helleri behaviour between the laboratory experiments and the farm-scale trials suggests that the post-partum behaviour of X. helleri remains consistent under these different conditions; thus, behaviour under one set of conditions may be used to predict behaviour under other conditions. The application and significance of extrapolations to industry and future research of X. helleri and possibly other poeciliids were discussed and the most applicable laboratory observations with the highest extrapolation capacity were proposed. Furthermore, techniques were developed to aid industry and future researchers in making predictions relating to behaviour of X. helleri under different conditions based on laboratory observations. The results were used to develop a model indicating that selection pressures against cannibalism are not likely to exist at the rate of cannibalism observed here since the potential genetic gain through kin survival and inclusive fitness was shown to be greater than any potential genetiC loss experienced by a victim of cannibalism. The model was successfully tested under a range of social conditions. Other possible explanations for cannibalism in poeciliids, such as parental manipulation, nutritional advantages, opportunistic predation and the recovery of energy are discussed. It is suggested that the most likely proximate cause of cannibalism under captive conditions is opportunistic predation. The theory that cannibalism ensures that only viable genes of the victim are expressed, through inclusive fitness, is a possible ultimate cause of cannibalism, which may have been inherited from feral ancestors of captive-bred X. helleri.
- Full Text:
- Date Issued: 2003
Language and value : the place of evaluation in linguistic theory
- Authors: Kilpert, Diana Mary
- Date: 2003
- Subjects: Linguistics -- Philosophy Systemic grammar Discourse analysis English language -- Standardization Linguistic analysis (Linguistics) Functionalism (Linguistics) Halliday, M. A. K. (Michael Alexander Kirkwood), 1925- Chomsky, Noam Labov, William Pinker, Steven, 1954- Harris, Roy, 1931-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2353 , http://hdl.handle.net/10962/d1002635
- Description: It is a central claim of modern linguistic theory that linguists do not prescribe, but describe language as it is, without pronouncing on correctness or judging one variety better than another. This attempt to exclude evaluation is motivated by a desire to be ' politically correct', which hinders objective analysis of language, and by an ill-advised imitation of the natural sciences, which obstructs the discipline's progress towards becoming a science in its own right. It involves linguists, as users of a valued variety, in self-deception and disingenuousness, distances them from the concerns of the ordinary language user, and betrays a failure to understand the involvement of social values in language, the nature of language itself, and the limits of linguistic science. On a wider scale, linguistics reflects society's devaluing and mechanisation of language. Despite growing concern expressed in the literature, and the incoherence that becomes apparent when linguists attempt to address social problems using a theory that regards language as an autonomous object, newcomers to the discipline continue to be taught that anti-prescriptivism is the natural corollary of a scientific approach to language. This thesis suggests that the way out of these difficulties is to rethink the meaning of ' theory' in linguistics. If we take the reflexivity of language seriously, building on M.A.K. Halliday's notion of 'linguistics as metaphor', we are reminded that a linguistic theory is made of language. Metalanguage must use the experiential and interpersonal meaning-making resources of everyday language. It follows that a linguistic theory cannot escape being evaluative, because evaluation is an inherent part of interpersonal meaning. If we fail to notice our own metalinguistic evaluation, this is because language disguises its evaluative meanings, or perhaps we are just not used to thinking of them as part of the grammar. To achieve clarity about the involvement of value in language, we need to turn our metalanguage back on itself - 'using the grammar to think with about the grammar' . Some ways of doing this are demonstrated here, turning the resources of systemic functional linguistics on linguists' own language. The circularity of this process should be seen not as a drawback but as a salutary reminder that linguistics is an interpretive rather than a discovery process. This knowledge should help us revalue language and make a place for evaluation in linguistic theory, paving the way for a socially responsible and productive linguistics.
- Full Text:
- Date Issued: 2003
- Authors: Kilpert, Diana Mary
- Date: 2003
- Subjects: Linguistics -- Philosophy Systemic grammar Discourse analysis English language -- Standardization Linguistic analysis (Linguistics) Functionalism (Linguistics) Halliday, M. A. K. (Michael Alexander Kirkwood), 1925- Chomsky, Noam Labov, William Pinker, Steven, 1954- Harris, Roy, 1931-
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2353 , http://hdl.handle.net/10962/d1002635
- Description: It is a central claim of modern linguistic theory that linguists do not prescribe, but describe language as it is, without pronouncing on correctness or judging one variety better than another. This attempt to exclude evaluation is motivated by a desire to be ' politically correct', which hinders objective analysis of language, and by an ill-advised imitation of the natural sciences, which obstructs the discipline's progress towards becoming a science in its own right. It involves linguists, as users of a valued variety, in self-deception and disingenuousness, distances them from the concerns of the ordinary language user, and betrays a failure to understand the involvement of social values in language, the nature of language itself, and the limits of linguistic science. On a wider scale, linguistics reflects society's devaluing and mechanisation of language. Despite growing concern expressed in the literature, and the incoherence that becomes apparent when linguists attempt to address social problems using a theory that regards language as an autonomous object, newcomers to the discipline continue to be taught that anti-prescriptivism is the natural corollary of a scientific approach to language. This thesis suggests that the way out of these difficulties is to rethink the meaning of ' theory' in linguistics. If we take the reflexivity of language seriously, building on M.A.K. Halliday's notion of 'linguistics as metaphor', we are reminded that a linguistic theory is made of language. Metalanguage must use the experiential and interpersonal meaning-making resources of everyday language. It follows that a linguistic theory cannot escape being evaluative, because evaluation is an inherent part of interpersonal meaning. If we fail to notice our own metalinguistic evaluation, this is because language disguises its evaluative meanings, or perhaps we are just not used to thinking of them as part of the grammar. To achieve clarity about the involvement of value in language, we need to turn our metalanguage back on itself - 'using the grammar to think with about the grammar' . Some ways of doing this are demonstrated here, turning the resources of systemic functional linguistics on linguists' own language. The circularity of this process should be seen not as a drawback but as a salutary reminder that linguistics is an interpretive rather than a discovery process. This knowledge should help us revalue language and make a place for evaluation in linguistic theory, paving the way for a socially responsible and productive linguistics.
- Full Text:
- Date Issued: 2003
An investigation of the isolation, characterisation and application of hydantoinases for the industrial production of amino acids
- Authors: Kirchmann, Shaun
- Date: 2003
- Subjects: Hydantoin Amino acids Hydrolysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3969 , http://hdl.handle.net/10962/d1004028
- Description: This thesis describes a series of investigations into the hydantoin-hydrolysing activity of bacterial strains RU-KM1 and RU-OR, which were previously isolated for their ability to hydrolyse hydantoins to amino acids. The main aim of the study was to develop biotransformations with potential application in the production of enantiomerically pure amino acids using a bioreactor based system utilising the hydantoin hydrolysing enzymes of the two isolated microorganisms. Different substituted hydantoins may be used as substrates by these enzymes for the production of a variety of amino acids. These are not only important for amino acid production, but they may be used for production of other industrially important compounds, such as semisynthetic penicillin/ampicillin, L-aspartame (sweetener), Fluvalinate (insecticide), Enalapril (ACE inhibitor). Thus, the ability of the above-mentioned strains to hydrolyse these substrates was investigated, with the view to utilizing the maximum potential of these biocatalysts. Hydantoin conversion involves a two-step hydrolysis reaction which yields, initially, an N-carbamylamino acid intermediate, and subsequently, an amino acid. The hydantoin-hydrolysing enzymes of a Pseudomonas sp. RU-KM1, and an Agrobacterium sp. RU-OR were characterised as whole cells and in a crude extract preparation, and reaction conditions for its biocatalytic application were optimised. The optimum conditions for conversion of hydantoin to glycine were found to be 1 hour at 40 °C, with conversion yields greater than 30 % achieved. The enzymes of RU-KM1 demonstrated considerable stability, retaining 80 % of their activity after storage for 2 weeks at 4 °C. The activities of the enzymes were increased by the addition of a detergent to the extraction medium, suggesting that the enzymes might be membrane-bound. The results of the determination of the metal-dependence of the hydantoinase and N-carbamoylase of RU-KM1 suggested that these enzymes required metal ions for activity, with metal ions such as Cu[superscript (2+)], Fe[superscript (2+)], and Co[superscript (2+)] resulting in no significant change in enzyme activity, however there was an activation of the enzymes when Mn[superscript (2+)] was added to the enzymes. The stereoselectivity of the enzymes was investigated, and the results suggested that the hydantoinase was D-selective, whereas the N-carbamoylase was shown to be L-selective by other researchers. The hydantoin substrate selectivity of RU-KM1 and RU-OR was investigated, and the organisms were shown to be able to hydrolyse all of the seven substrates tested. However, there was a difference in activity levels between crude extract preparations and whole cells, with crude extracts generally showing slightly lower activity than whole cells in RU-KM1, and the whole cells or RU-OR showing the lower activity than its crude extract. Some difference was also observed in the order of preference of substrates between whole cells and crude extracts. The preferred substrate for RU-KM1 whole cells was isopropylhydantoin, whereas the crude extract preparation preferentially hydrolysed p-hydroxyphenylhydantoin, achieving 57 % and 52 % conversions respectively. RU-OR whole cells preferred methylhydantoin where as the crude extract preferred isopropylhydantoin, and showed 49 % and 51 % conversions respectively. The enzymes were characterised in terms of their temperature and pH optima, inducer requirements, and product inhibition studies. The hydantoinase of RU-KM1 was shown to be inducible with low levels of hydantoin, and thermostable upto 75 °C with its optima between 60 and 70 °C. The N-carbamoylase was shown to have its optima at 50 °C. The addition of ATP (0.5 mM), DTT (1 mM) and a protease inhibitor (2 mg.mL[superscript (-1)]) all increased the hydantoinase activity of RU-KM1 crude extract, however they had very little effect on the N-carbamoylase activity. The hydantoinase enzyme from extracts of RU-KM1 was partially purified by development of cell disruption methods using mechanical and lysing enzymes, followed by precipitation and chromatographic resolution. The results obtained showed a hydantoinase enzyme of between 48 and 66 kDa. RU-KM1 was grown under fermentation conditions using different minimal media. The activity and yields under these conditions were low. Previous attempt to grow the organism in a rich medium had resulted in an increase in biomass but no hydantoinase activity. A rich medium was developed by carbon and nitrogen optimisation and yielded biomass up to 30 g.L[superscript (-1)] dry cell weight. The hydantoinase activity was restored by nitrogen starvation in stationary phase. This resulted in high biomass with increased activity. This data is currently in press. Crude extract and whole cells were immobilised on flat sheet membranes, hollow fibre membranes and in alginate beads. Low hydantoinase activity was measured in bioreactors using membranes in different configurations. A significant increase in hydantoinase activity was measured when the crude extract was immobilised in sodium alginate, as a result of stabilisation of the N-carbamoylase. Temperature and pH optima were unaffected by the immobilisation procedure, however the durability of the enzymes increased 2-fold. Different configurations of the bioreactor were investigated, as well as a hydroxyphenylhydantoin as an alternative substrate in this study. The bioreactors showed a near 95 % conversion of the hydantoin to glycine, and a 99 % conversion using HPG. In conclusion, the hydantoin-hydrolysing enzymes of RU-KM1 have been shown to be possibly membrane associated, which is a novel finding. This study has shown that the hydantoinase of RU-KM1 is D-stereoselective, with high temperature stability. A growth medium was developed for the rapid production of active biomass. A bioreactor was developed using a single and a dual biocatalyst configuration, which was capable of hydrolysing hydantoin and monosubstituted hydantoins to produce amino acids. To our knowledge this system is the first such dual biocatalyst system reported for the production of amino acids.
- Full Text:
- Date Issued: 2003
- Authors: Kirchmann, Shaun
- Date: 2003
- Subjects: Hydantoin Amino acids Hydrolysis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3969 , http://hdl.handle.net/10962/d1004028
- Description: This thesis describes a series of investigations into the hydantoin-hydrolysing activity of bacterial strains RU-KM1 and RU-OR, which were previously isolated for their ability to hydrolyse hydantoins to amino acids. The main aim of the study was to develop biotransformations with potential application in the production of enantiomerically pure amino acids using a bioreactor based system utilising the hydantoin hydrolysing enzymes of the two isolated microorganisms. Different substituted hydantoins may be used as substrates by these enzymes for the production of a variety of amino acids. These are not only important for amino acid production, but they may be used for production of other industrially important compounds, such as semisynthetic penicillin/ampicillin, L-aspartame (sweetener), Fluvalinate (insecticide), Enalapril (ACE inhibitor). Thus, the ability of the above-mentioned strains to hydrolyse these substrates was investigated, with the view to utilizing the maximum potential of these biocatalysts. Hydantoin conversion involves a two-step hydrolysis reaction which yields, initially, an N-carbamylamino acid intermediate, and subsequently, an amino acid. The hydantoin-hydrolysing enzymes of a Pseudomonas sp. RU-KM1, and an Agrobacterium sp. RU-OR were characterised as whole cells and in a crude extract preparation, and reaction conditions for its biocatalytic application were optimised. The optimum conditions for conversion of hydantoin to glycine were found to be 1 hour at 40 °C, with conversion yields greater than 30 % achieved. The enzymes of RU-KM1 demonstrated considerable stability, retaining 80 % of their activity after storage for 2 weeks at 4 °C. The activities of the enzymes were increased by the addition of a detergent to the extraction medium, suggesting that the enzymes might be membrane-bound. The results of the determination of the metal-dependence of the hydantoinase and N-carbamoylase of RU-KM1 suggested that these enzymes required metal ions for activity, with metal ions such as Cu[superscript (2+)], Fe[superscript (2+)], and Co[superscript (2+)] resulting in no significant change in enzyme activity, however there was an activation of the enzymes when Mn[superscript (2+)] was added to the enzymes. The stereoselectivity of the enzymes was investigated, and the results suggested that the hydantoinase was D-selective, whereas the N-carbamoylase was shown to be L-selective by other researchers. The hydantoin substrate selectivity of RU-KM1 and RU-OR was investigated, and the organisms were shown to be able to hydrolyse all of the seven substrates tested. However, there was a difference in activity levels between crude extract preparations and whole cells, with crude extracts generally showing slightly lower activity than whole cells in RU-KM1, and the whole cells or RU-OR showing the lower activity than its crude extract. Some difference was also observed in the order of preference of substrates between whole cells and crude extracts. The preferred substrate for RU-KM1 whole cells was isopropylhydantoin, whereas the crude extract preparation preferentially hydrolysed p-hydroxyphenylhydantoin, achieving 57 % and 52 % conversions respectively. RU-OR whole cells preferred methylhydantoin where as the crude extract preferred isopropylhydantoin, and showed 49 % and 51 % conversions respectively. The enzymes were characterised in terms of their temperature and pH optima, inducer requirements, and product inhibition studies. The hydantoinase of RU-KM1 was shown to be inducible with low levels of hydantoin, and thermostable upto 75 °C with its optima between 60 and 70 °C. The N-carbamoylase was shown to have its optima at 50 °C. The addition of ATP (0.5 mM), DTT (1 mM) and a protease inhibitor (2 mg.mL[superscript (-1)]) all increased the hydantoinase activity of RU-KM1 crude extract, however they had very little effect on the N-carbamoylase activity. The hydantoinase enzyme from extracts of RU-KM1 was partially purified by development of cell disruption methods using mechanical and lysing enzymes, followed by precipitation and chromatographic resolution. The results obtained showed a hydantoinase enzyme of between 48 and 66 kDa. RU-KM1 was grown under fermentation conditions using different minimal media. The activity and yields under these conditions were low. Previous attempt to grow the organism in a rich medium had resulted in an increase in biomass but no hydantoinase activity. A rich medium was developed by carbon and nitrogen optimisation and yielded biomass up to 30 g.L[superscript (-1)] dry cell weight. The hydantoinase activity was restored by nitrogen starvation in stationary phase. This resulted in high biomass with increased activity. This data is currently in press. Crude extract and whole cells were immobilised on flat sheet membranes, hollow fibre membranes and in alginate beads. Low hydantoinase activity was measured in bioreactors using membranes in different configurations. A significant increase in hydantoinase activity was measured when the crude extract was immobilised in sodium alginate, as a result of stabilisation of the N-carbamoylase. Temperature and pH optima were unaffected by the immobilisation procedure, however the durability of the enzymes increased 2-fold. Different configurations of the bioreactor were investigated, as well as a hydroxyphenylhydantoin as an alternative substrate in this study. The bioreactors showed a near 95 % conversion of the hydantoin to glycine, and a 99 % conversion using HPG. In conclusion, the hydantoin-hydrolysing enzymes of RU-KM1 have been shown to be possibly membrane associated, which is a novel finding. This study has shown that the hydantoinase of RU-KM1 is D-stereoselective, with high temperature stability. A growth medium was developed for the rapid production of active biomass. A bioreactor was developed using a single and a dual biocatalyst configuration, which was capable of hydrolysing hydantoin and monosubstituted hydantoins to produce amino acids. To our knowledge this system is the first such dual biocatalyst system reported for the production of amino acids.
- Full Text:
- Date Issued: 2003