The development of a cultural family business model of good governance for Greek family businesses in South Africa
- Adendorff, Christian Michael
- Authors: Adendorff, Christian Michael
- Date: 2005
- Subjects: Family-owned business enterprises -- South Africa Greeks -- South Africa Greeks -- South Africa -- Social life and customs Corporate governance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1163 , http://hdl.handle.net/10962/d1002779
- Description: Never in the history of the South African nation has the entrepreneurial spirit been more alive. Since the opening of international doors, after the 1994 elections, South Africa has experienced the explosive growth of transnational entrepreneurship. An enduring aspect of the explosion of such economic activity is the need for "good governance" and the need for governance education in South Africa and the rest of the continent has never been greater. The size of the family business component of the South Aftican economy suggests that it is the predominant way of doing business in South Africa. Of importance to this study is the estimate that approximately 95 % of all Greek businesses in South Africa can be classified as family businesses. The sustainability of Greek family businesses requires that they maintain good governance practices that are economically and environmentally acceptable to all stakeholders. It also requires that the next generation of Greek entrepreneurs balance good governance for the businesses as well as for the family. The primary objective of this study was to identify and explore the internal factors that influence and determine good governance to ensure the survival, growth and sustainability of Greek family businesses in South Africa. The secondary research objectives pertained to the underlying dimensions of good governance and required an exploration of the different governance concerns in relation to specific South African Greek behaviour and characteristics. A theoretical model of good governance factors was proposed and tested using Structural Equation Modeling. The study found that perceived good governance in a South African Greek family business context needs to be measured in terms of three factors, namely risk control, the internal regulatory environment and the protection of the stakeholders' interest. The study dealt further with the secondary sources effecting governance for South African businesses and was based on the latest report by the King Commission. An important finding is that the cross cultural aspect of family business governance must now be considered when conducting such research as more and more emphasis is placed on the good governance of all businesses.
- Full Text:
- Date Issued: 2005
- Authors: Adendorff, Christian Michael
- Date: 2005
- Subjects: Family-owned business enterprises -- South Africa Greeks -- South Africa Greeks -- South Africa -- Social life and customs Corporate governance -- South Africa South Africa -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1163 , http://hdl.handle.net/10962/d1002779
- Description: Never in the history of the South African nation has the entrepreneurial spirit been more alive. Since the opening of international doors, after the 1994 elections, South Africa has experienced the explosive growth of transnational entrepreneurship. An enduring aspect of the explosion of such economic activity is the need for "good governance" and the need for governance education in South Africa and the rest of the continent has never been greater. The size of the family business component of the South Aftican economy suggests that it is the predominant way of doing business in South Africa. Of importance to this study is the estimate that approximately 95 % of all Greek businesses in South Africa can be classified as family businesses. The sustainability of Greek family businesses requires that they maintain good governance practices that are economically and environmentally acceptable to all stakeholders. It also requires that the next generation of Greek entrepreneurs balance good governance for the businesses as well as for the family. The primary objective of this study was to identify and explore the internal factors that influence and determine good governance to ensure the survival, growth and sustainability of Greek family businesses in South Africa. The secondary research objectives pertained to the underlying dimensions of good governance and required an exploration of the different governance concerns in relation to specific South African Greek behaviour and characteristics. A theoretical model of good governance factors was proposed and tested using Structural Equation Modeling. The study found that perceived good governance in a South African Greek family business context needs to be measured in terms of three factors, namely risk control, the internal regulatory environment and the protection of the stakeholders' interest. The study dealt further with the secondary sources effecting governance for South African businesses and was based on the latest report by the King Commission. An important finding is that the cross cultural aspect of family business governance must now be considered when conducting such research as more and more emphasis is placed on the good governance of all businesses.
- Full Text:
- Date Issued: 2005
Biology, population dynamics and management of carpenter (Argyrozona argyrozona) an endemic South African reef fish
- Authors: Brouwer, Stephen Leonard
- Date: 2005
- Subjects: Reef fishes -- South Africa Sparidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5241 , http://hdl.handle.net/10962/d1005084
- Description: Carpenter, Argyrozona argyrozona (Valenciennes, 1830), is an endemic South African sparid fish. They form an important component of the commercial linefishery on the South African east coast, where they are the third most important species landed. Recent investigations revealed that the catch per unit effort (cpue) of this species has declined markedly since the early 1900’s. Despite these declines and the importance of this resource, remarkably little biological information on this species exists for providing management advice. This thesis investigates the life history of carpenter, particularly those aspects that are used for management. This includes an investigation into the stock distribution and identification of nursery areas, and an assessment of age, growth, reproduction and movement patterns. Age and growth was assessed using methods based on both otoliths and mark-recapture. Transverse sagittal sections from the Tsitsikamma National Park showed clear opaque and translucent growth increments. Marginal growth zone analysis and mark-recapture of chemically tagged fish (Oxytetracycline) revealed that these were deposited on an annual basis: opaque in summer and translucent in winter. A. argyrozona were found to be long lived (up to 27 years) and slow growing. Within reader (between counts) and between readers average percent error (APE) was 5.3 and 1.8, respectively, showing that readability of carpenter otoliths is high. Comparison between whole and sectioned otoliths showed that the former significantly under-estimated the age of fish older than 10 years (p<0.01). A large proportion (68%) of the individual growth rates derived from mark-recapture data were below those predicted by the otolith based von Bertalanffy growth model (p<0.01). This was attributed to the negative influence of external tags, as hydroids, frequently occurring on the tags of recaptured fish, were observed to cause severe lesions and in some cases, extensive fin damage. This brings into question the use of mark-recapture studies to calculate growth of some species. The effects of sampling design and sample size on age and growth estimation were assessed. The minimum sample size required to accurately estimate growth and mortality, and the effects of using either random or stratified sampling procedures were tested. Decimal and integer ageing both produced similar estimates of von Bertalanffy growth parameters, growth curves, spawner biomass-per-recruit (SB/R) and fishing mortality (F) estimates. Sampling monthly throughout the year and collecting data in a single large sample provided similar growth curves, von Bertalanffy, F and SB/R estimates. The data showed that estimates based on less than 300 random samples were unreliable. However, accurate growth parameter estimates were achievable with less than 200 samples if the sample was stratified with 10 or more samples per 2 cm size class. An investigation into the reproductive biology of A. argyrozona within the Tsitsikamma National Park revealed that they were serial spawning late gonochorists. The size at 50% maturity (L₅₀) was estimated at 292 and 297 mm FL for females and males, respectively. Both monthly gonadosomatic indices and macroscopically determined ovarian stages strongly suggest that A. argyrozona within the Tsitsikamma National Park spawn in the austral summer between November and April. The presence of post-ovulatory follicles (POF's) confirmed the six month spawning season, while monthly proportions of early (0-6 hour old) POF's showed that spawning frequency was highest (once every 1-2 days) from December to March. Although spawning season was more highly correlated to photoperiod (r = 0.859) than temperature (r = -0.161), the daily proportion of spawning fish was strongly correlated (r = 0.93) to ambient temperature over the range 9-22⁰C. Both spawning frequency and season increased with fish length. As a result of the allometric relationship between annual fecundity and fish mass a 3 kg fish was calculated to produce 5 fold more eggs per kilogram of body weight than a fish of 1 kg. In addition to producing more eggs per unit weight each year, larger fish also produce significantly larger eggs. Adult emigration and larval dispersal of A. argyrozona from the Tsitsikamma National Park (TNP), South Africa, were investigated using mark-recapture data and Acoustic Doppler Current Profiler measurements of currents. Tagging data showed that adult carpenter were mainly resident, with a small proportion (7%) leaving the TNP in both easterly and westerly directions. No relationship was found between fish movement patterns and fish size or time-at-liberty. Current patterns suggest that eggs and larvae spawned within the TNP are mainly transported eastwards towards established nursery grounds; the median estimated distance moved was 299 km (range 42-561 km) in 30 days (time to flexion). Given this pattern of ichthyoplankton dispersal together with the fact that adult carpenter within the TNP display a high degree of residency and that they are much more abundant than in adjacent fishing grounds (cpue = 23 times greater), it appears that the TNP protects a viable carpenter spawner population capable of seeding adjacent fishing grounds. Fishery independent biomass surveys and commercial linefish catch returns were used to elucidate the spatial patterns of A. argyrozona distributed along the South African continental shelf. Two distinct areas of abundance were determined, one on the central and the other on the eastern Agulhas Bank. Tagging studies revealed little exchange between them. Two distinct nursery areas were identified. These data suggest that in each area juvenile A. argyrozona settle and move inshore, and then move offshore as they grow. Otolith readability and growth rates varied between regions, with fish from the Eastern Cape having the lowest average percentage error and the slowest growth rates, readability decreased westward. L₅₀ varied between the central and eastern Agulhas Bank as did mass at length. Based on the distribution of carpenter, variability in otolith readability, mass at length, variation in growth and size at maturity, it is concluded that carpenter exist as two separate stocks, one on the central Agulhas Bank and the other on the eastern Agulhas Bank. SB/R, fecundity-per-recruit (Egg/R) and yield-per-recruit (Y/R) models were used to model both South African carpenter stocks. Owing to the allometric relationship between annual fecundity and individual size, Egg/R ratios were between 40 and 74% of SB/R at equivalent F. Egg/R ratios account for allometric increases in fecundity with size/age, and are therefore regarded as more accurate estimates of reproductive potential, and biological reference points for per-recruit analysis should wherever possible be based on this quantum. It is shown that the current length at first capture (lc) (250 mm TL) and F (at M = 0.1) will reduce Egg/R to 6.41% of the pristine value in the Eastern Cape and between 6.06 and 14.15% on the central Agulhas Bank, indicating that both stocks are heavily over exploited. An increase in lc from 250 to 350 mm TL and a 70% reduction in commercial fishing effort is recommended to attain a target reference point of 40% Egg/RF=0. Bag frequency analysis indicates that a reduction in daily bag limit from 10 to 4 fish.person¹.day⁻¹ would effect an equivalent reduction in recreational F. The trawl bycatch of carpenter is only 3% of the reported line catch, consequently restrictions to this fishery are not recommended.
- Full Text:
- Date Issued: 2005
- Authors: Brouwer, Stephen Leonard
- Date: 2005
- Subjects: Reef fishes -- South Africa Sparidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5241 , http://hdl.handle.net/10962/d1005084
- Description: Carpenter, Argyrozona argyrozona (Valenciennes, 1830), is an endemic South African sparid fish. They form an important component of the commercial linefishery on the South African east coast, where they are the third most important species landed. Recent investigations revealed that the catch per unit effort (cpue) of this species has declined markedly since the early 1900’s. Despite these declines and the importance of this resource, remarkably little biological information on this species exists for providing management advice. This thesis investigates the life history of carpenter, particularly those aspects that are used for management. This includes an investigation into the stock distribution and identification of nursery areas, and an assessment of age, growth, reproduction and movement patterns. Age and growth was assessed using methods based on both otoliths and mark-recapture. Transverse sagittal sections from the Tsitsikamma National Park showed clear opaque and translucent growth increments. Marginal growth zone analysis and mark-recapture of chemically tagged fish (Oxytetracycline) revealed that these were deposited on an annual basis: opaque in summer and translucent in winter. A. argyrozona were found to be long lived (up to 27 years) and slow growing. Within reader (between counts) and between readers average percent error (APE) was 5.3 and 1.8, respectively, showing that readability of carpenter otoliths is high. Comparison between whole and sectioned otoliths showed that the former significantly under-estimated the age of fish older than 10 years (p<0.01). A large proportion (68%) of the individual growth rates derived from mark-recapture data were below those predicted by the otolith based von Bertalanffy growth model (p<0.01). This was attributed to the negative influence of external tags, as hydroids, frequently occurring on the tags of recaptured fish, were observed to cause severe lesions and in some cases, extensive fin damage. This brings into question the use of mark-recapture studies to calculate growth of some species. The effects of sampling design and sample size on age and growth estimation were assessed. The minimum sample size required to accurately estimate growth and mortality, and the effects of using either random or stratified sampling procedures were tested. Decimal and integer ageing both produced similar estimates of von Bertalanffy growth parameters, growth curves, spawner biomass-per-recruit (SB/R) and fishing mortality (F) estimates. Sampling monthly throughout the year and collecting data in a single large sample provided similar growth curves, von Bertalanffy, F and SB/R estimates. The data showed that estimates based on less than 300 random samples were unreliable. However, accurate growth parameter estimates were achievable with less than 200 samples if the sample was stratified with 10 or more samples per 2 cm size class. An investigation into the reproductive biology of A. argyrozona within the Tsitsikamma National Park revealed that they were serial spawning late gonochorists. The size at 50% maturity (L₅₀) was estimated at 292 and 297 mm FL for females and males, respectively. Both monthly gonadosomatic indices and macroscopically determined ovarian stages strongly suggest that A. argyrozona within the Tsitsikamma National Park spawn in the austral summer between November and April. The presence of post-ovulatory follicles (POF's) confirmed the six month spawning season, while monthly proportions of early (0-6 hour old) POF's showed that spawning frequency was highest (once every 1-2 days) from December to March. Although spawning season was more highly correlated to photoperiod (r = 0.859) than temperature (r = -0.161), the daily proportion of spawning fish was strongly correlated (r = 0.93) to ambient temperature over the range 9-22⁰C. Both spawning frequency and season increased with fish length. As a result of the allometric relationship between annual fecundity and fish mass a 3 kg fish was calculated to produce 5 fold more eggs per kilogram of body weight than a fish of 1 kg. In addition to producing more eggs per unit weight each year, larger fish also produce significantly larger eggs. Adult emigration and larval dispersal of A. argyrozona from the Tsitsikamma National Park (TNP), South Africa, were investigated using mark-recapture data and Acoustic Doppler Current Profiler measurements of currents. Tagging data showed that adult carpenter were mainly resident, with a small proportion (7%) leaving the TNP in both easterly and westerly directions. No relationship was found between fish movement patterns and fish size or time-at-liberty. Current patterns suggest that eggs and larvae spawned within the TNP are mainly transported eastwards towards established nursery grounds; the median estimated distance moved was 299 km (range 42-561 km) in 30 days (time to flexion). Given this pattern of ichthyoplankton dispersal together with the fact that adult carpenter within the TNP display a high degree of residency and that they are much more abundant than in adjacent fishing grounds (cpue = 23 times greater), it appears that the TNP protects a viable carpenter spawner population capable of seeding adjacent fishing grounds. Fishery independent biomass surveys and commercial linefish catch returns were used to elucidate the spatial patterns of A. argyrozona distributed along the South African continental shelf. Two distinct areas of abundance were determined, one on the central and the other on the eastern Agulhas Bank. Tagging studies revealed little exchange between them. Two distinct nursery areas were identified. These data suggest that in each area juvenile A. argyrozona settle and move inshore, and then move offshore as they grow. Otolith readability and growth rates varied between regions, with fish from the Eastern Cape having the lowest average percentage error and the slowest growth rates, readability decreased westward. L₅₀ varied between the central and eastern Agulhas Bank as did mass at length. Based on the distribution of carpenter, variability in otolith readability, mass at length, variation in growth and size at maturity, it is concluded that carpenter exist as two separate stocks, one on the central Agulhas Bank and the other on the eastern Agulhas Bank. SB/R, fecundity-per-recruit (Egg/R) and yield-per-recruit (Y/R) models were used to model both South African carpenter stocks. Owing to the allometric relationship between annual fecundity and individual size, Egg/R ratios were between 40 and 74% of SB/R at equivalent F. Egg/R ratios account for allometric increases in fecundity with size/age, and are therefore regarded as more accurate estimates of reproductive potential, and biological reference points for per-recruit analysis should wherever possible be based on this quantum. It is shown that the current length at first capture (lc) (250 mm TL) and F (at M = 0.1) will reduce Egg/R to 6.41% of the pristine value in the Eastern Cape and between 6.06 and 14.15% on the central Agulhas Bank, indicating that both stocks are heavily over exploited. An increase in lc from 250 to 350 mm TL and a 70% reduction in commercial fishing effort is recommended to attain a target reference point of 40% Egg/RF=0. Bag frequency analysis indicates that a reduction in daily bag limit from 10 to 4 fish.person¹.day⁻¹ would effect an equivalent reduction in recreational F. The trawl bycatch of carpenter is only 3% of the reported line catch, consequently restrictions to this fishery are not recommended.
- Full Text:
- Date Issued: 2005
African mead biotechnology and indigenous knowledge systems in iQhilika process development
- Authors: Cambray, Garth Anton
- Date: 2005
- Subjects: Biotechnology Indigenous peoples -- Africa Ethnoscience -- Africa Mead -- Africa Brewing -- Microbiology Honeybee Honey
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3929 , http://hdl.handle.net/10962/d1003988
- Description: While the production of mead, a fermented honey beverage, has declined in popularity around the world in recent centuries, a substantial mead industry continues to exist in Africa with an estimated annual production of 1 to 1.7 billion litres. This is largely an ‘invisible industry’, and has functioned outside the formal economy due to proscription of indigenous beverages during colonial times. The traditional African mead industry is, however, also now under pressure due to the environmental degradation of scarce natural ingredients, urbanisation and loss of indigenous knowledge systems (IKS) and, with time, the beverage will likely follow the declining trend of mead consumption observed elsewhere. An analysis of early reports of African mead production suggested that the Khoi-San, among the earliest inhabitants of the continent, are the originators of the mead making techniques which use fibrous plant materials derived from specific plant species, to facilitate mead fermentation in some way. The Eastern Cape represents a region with a large body of Khoi-San IKS preserved in their descendants among the Afrikaans and Xhosa populations. A survey to establish a baseline of mead-making technology in the Eastern Cape was undertaken, and involved interviewing traditional mead makers across an area of roughly 100 000 km2, showing that the mead, iQhilika(Xhosa) Kari (Khoi-San/Afrikaans), is produced using a very similar process throughout the region. This involves the roots of a Trichodiadema sp. plant (imoela – Xhosa, karimoer – Afrikaans/Khoi-San), honey, extract of brood and/or pollen and water. Various other fruit sugar sources were also found to be added at times producing seasonal beverages with unique organoleptic properties. A model traditional iQhilika production operation was investigated in order to describe the main features of the process. Biomass immobilised on Trichodiadema root segments was found to be distributed evenly through the profile of the bioreactor resulting in a well mixed fermentation and a productivity of 0.74 g EtOH/l/h. In the initial stages of fermentation, the ethanol yield was highest in the mid-regions of the bioreactor, but with time the regions closer to the surface, which had atmospheric contact had a higher yield. This phenomenon was attributed to aerobic fatty acid synthesis which allowed the yeast close to the surface to function more efficiently despite rising ethanol concentrations. The mead contained 44.25 g/l (7 % volume) ethanol produced in a fermentation time of 43.5 h. Yeast biomass in the traditional process was either immobilised in the form of flocs or attached to the Trichodiadema intonsum support. Electron microscopy revealed that the cells were covered in a layer of extra-cellular polymeric substance apparently assisting the immobilization, and which was populated by a consortium of yeasts and bacteria. Yeasts isolated from iQhilika brewed in two regions separated by 350 km were found to be very closely related Saccharomyces cerevisiae strains as determined by molecular genetic analysis. The traditional beverage was found to contain populations of Lactic acid bacteria (LAB), which are known spoilage organisms in other beverages. Spoilage characteristics of these organisms matched descriptions of spoilage provided by the IKS survey. Other possibly beneficial LAB, which may contribute useful flavour compounds, were also found to be present in the system. The basic functional aspects of the traditional process were used to design a continuous bench-scale tower bioreactor and process development was based on the IKS survey. This consisted of a packed bed bioreactor, consisting of 2 mm3 T. intonsum root segments, immobilising a novel Saccharomyces cerevisiae strain isolated from a traditional batch of iQhilika. The bioreactor performed well with a yield of close to the theoretical maximum and an ethanol productivity of 3.45 g EtOH/l/h. The parameters of the 5.6 l/d bench-scale bioreactor were used to design a full-scale production bioreactor with a planned maximum output of 330 l/d. This bioreactor had a productivity of 0.19 g EtOH/l/h. The organoleptic properties of the product produced were considered by a taste panel to be better than those of the product of the bench-scale tower bioreactor. This research was based on the development of IKS which imposed a number of constraints and obligations on the project to ensure environmental, and social, in addition to financial viability of the scale-up operation. Makana Meadery was established in partnership with Rhodes University as an empowerment company which, in addition to undertaking the commercialisation of the iQhilika process, would also develop methods for the production of scarce ingredients traditionally unsustainably sourced from fragile ecosystems, provide beekeeping training and the manufacture of beehives.
- Full Text:
- Date Issued: 2005
- Authors: Cambray, Garth Anton
- Date: 2005
- Subjects: Biotechnology Indigenous peoples -- Africa Ethnoscience -- Africa Mead -- Africa Brewing -- Microbiology Honeybee Honey
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3929 , http://hdl.handle.net/10962/d1003988
- Description: While the production of mead, a fermented honey beverage, has declined in popularity around the world in recent centuries, a substantial mead industry continues to exist in Africa with an estimated annual production of 1 to 1.7 billion litres. This is largely an ‘invisible industry’, and has functioned outside the formal economy due to proscription of indigenous beverages during colonial times. The traditional African mead industry is, however, also now under pressure due to the environmental degradation of scarce natural ingredients, urbanisation and loss of indigenous knowledge systems (IKS) and, with time, the beverage will likely follow the declining trend of mead consumption observed elsewhere. An analysis of early reports of African mead production suggested that the Khoi-San, among the earliest inhabitants of the continent, are the originators of the mead making techniques which use fibrous plant materials derived from specific plant species, to facilitate mead fermentation in some way. The Eastern Cape represents a region with a large body of Khoi-San IKS preserved in their descendants among the Afrikaans and Xhosa populations. A survey to establish a baseline of mead-making technology in the Eastern Cape was undertaken, and involved interviewing traditional mead makers across an area of roughly 100 000 km2, showing that the mead, iQhilika(Xhosa) Kari (Khoi-San/Afrikaans), is produced using a very similar process throughout the region. This involves the roots of a Trichodiadema sp. plant (imoela – Xhosa, karimoer – Afrikaans/Khoi-San), honey, extract of brood and/or pollen and water. Various other fruit sugar sources were also found to be added at times producing seasonal beverages with unique organoleptic properties. A model traditional iQhilika production operation was investigated in order to describe the main features of the process. Biomass immobilised on Trichodiadema root segments was found to be distributed evenly through the profile of the bioreactor resulting in a well mixed fermentation and a productivity of 0.74 g EtOH/l/h. In the initial stages of fermentation, the ethanol yield was highest in the mid-regions of the bioreactor, but with time the regions closer to the surface, which had atmospheric contact had a higher yield. This phenomenon was attributed to aerobic fatty acid synthesis which allowed the yeast close to the surface to function more efficiently despite rising ethanol concentrations. The mead contained 44.25 g/l (7 % volume) ethanol produced in a fermentation time of 43.5 h. Yeast biomass in the traditional process was either immobilised in the form of flocs or attached to the Trichodiadema intonsum support. Electron microscopy revealed that the cells were covered in a layer of extra-cellular polymeric substance apparently assisting the immobilization, and which was populated by a consortium of yeasts and bacteria. Yeasts isolated from iQhilika brewed in two regions separated by 350 km were found to be very closely related Saccharomyces cerevisiae strains as determined by molecular genetic analysis. The traditional beverage was found to contain populations of Lactic acid bacteria (LAB), which are known spoilage organisms in other beverages. Spoilage characteristics of these organisms matched descriptions of spoilage provided by the IKS survey. Other possibly beneficial LAB, which may contribute useful flavour compounds, were also found to be present in the system. The basic functional aspects of the traditional process were used to design a continuous bench-scale tower bioreactor and process development was based on the IKS survey. This consisted of a packed bed bioreactor, consisting of 2 mm3 T. intonsum root segments, immobilising a novel Saccharomyces cerevisiae strain isolated from a traditional batch of iQhilika. The bioreactor performed well with a yield of close to the theoretical maximum and an ethanol productivity of 3.45 g EtOH/l/h. The parameters of the 5.6 l/d bench-scale bioreactor were used to design a full-scale production bioreactor with a planned maximum output of 330 l/d. This bioreactor had a productivity of 0.19 g EtOH/l/h. The organoleptic properties of the product produced were considered by a taste panel to be better than those of the product of the bench-scale tower bioreactor. This research was based on the development of IKS which imposed a number of constraints and obligations on the project to ensure environmental, and social, in addition to financial viability of the scale-up operation. Makana Meadery was established in partnership with Rhodes University as an empowerment company which, in addition to undertaking the commercialisation of the iQhilika process, would also develop methods for the production of scarce ingredients traditionally unsustainably sourced from fragile ecosystems, provide beekeeping training and the manufacture of beehives.
- Full Text:
- Date Issued: 2005
The development of motivational strategies for public sector workers in Kenya
- Authors: Chepkilot, Ronald Kiprop
- Date: 2005
- Subjects: Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9380 , http://hdl.handle.net/10948/161 , Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Description: The purpose of this study was to develop motivational strategies for motivating public sector workers in Kenya. To achieve this objective the following procedure was followed: • An examination of the public service was undertaken and the following factors were considered: The history of the public service; Past government reform programmes; The problem of corruption; Future government reform programmes; and The motivational climate in the service. iv • A literature survey was conducted on the approaches used by organisations in motivating employees. The findings were used to develop a motivational strategy model. On the basis of the strategies in the model, a questionnaire was developed for the empirical research study. • The empirical study was undertaken to examine the level of motivation in the public service and to identify the motivational strategies currently used in the public service in Kenya. The study also sought to determine the extent to which public sector managers agreed or disagreed that the motivational strategies developed by the study would be effective in motivating employees in their organisations. The results of the empirical study were incorporated into the integrated motivational strategy model presented in chapter six. The study established that the level of motivation among the public sector workers was extremely low. According to the research findings, 87 per cent of the respondents indicated that the level of motivation of employees in their organisation was low while 13 per cent indicated that it was high. It was also established that the climate in the public service was not conducive for motivating employees: the indicators were lack of job security; very low salaries; limited training and development opportunities; lack of career development programmes and lack of adequate working tools and equipment. It was further established that the government could no longer afford to make any substantial increases in salaries to the workers because the wage bill was extremely high at the level of 9.6 per cent of the GDP. It was observed that any further increases in salaries would v have a negative impact on the economy of the country. In view of the above, this study becomes extremely relevant as it suggests ways of enhancing the levels of motivation in the public service to improve service delivery in the public sector without allocation of vast financial resources. The study strongly recommends the application of the integrated motivational strategy model in its entirety; to enhance the level of employee’s motivation and work performance and achieve efficiency and effectiveness in service delivery. The study also recommends that further research be carried out to determine the effects of corruption on employee motivation and ways of eliminating the vice in the public service.
- Full Text:
- Date Issued: 2005
- Authors: Chepkilot, Ronald Kiprop
- Date: 2005
- Subjects: Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9380 , http://hdl.handle.net/10948/161 , Public administration -- Kenya , Employee motivation , Civil service -- Kenya -- Personnel management
- Description: The purpose of this study was to develop motivational strategies for motivating public sector workers in Kenya. To achieve this objective the following procedure was followed: • An examination of the public service was undertaken and the following factors were considered: The history of the public service; Past government reform programmes; The problem of corruption; Future government reform programmes; and The motivational climate in the service. iv • A literature survey was conducted on the approaches used by organisations in motivating employees. The findings were used to develop a motivational strategy model. On the basis of the strategies in the model, a questionnaire was developed for the empirical research study. • The empirical study was undertaken to examine the level of motivation in the public service and to identify the motivational strategies currently used in the public service in Kenya. The study also sought to determine the extent to which public sector managers agreed or disagreed that the motivational strategies developed by the study would be effective in motivating employees in their organisations. The results of the empirical study were incorporated into the integrated motivational strategy model presented in chapter six. The study established that the level of motivation among the public sector workers was extremely low. According to the research findings, 87 per cent of the respondents indicated that the level of motivation of employees in their organisation was low while 13 per cent indicated that it was high. It was also established that the climate in the public service was not conducive for motivating employees: the indicators were lack of job security; very low salaries; limited training and development opportunities; lack of career development programmes and lack of adequate working tools and equipment. It was further established that the government could no longer afford to make any substantial increases in salaries to the workers because the wage bill was extremely high at the level of 9.6 per cent of the GDP. It was observed that any further increases in salaries would v have a negative impact on the economy of the country. In view of the above, this study becomes extremely relevant as it suggests ways of enhancing the levels of motivation in the public service to improve service delivery in the public sector without allocation of vast financial resources. The study strongly recommends the application of the integrated motivational strategy model in its entirety; to enhance the level of employee’s motivation and work performance and achieve efficiency and effectiveness in service delivery. The study also recommends that further research be carried out to determine the effects of corruption on employee motivation and ways of eliminating the vice in the public service.
- Full Text:
- Date Issued: 2005
The biophysical dynamics of the Lower Shire River Floodplain fisheries in Malawi
- Authors: Chimatiro, Sloans Kalumba
- Date: 2005
- Subjects: Shire River Valley (Malawi and Mozambique) Fisheries -- Malawi
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5243 , http://hdl.handle.net/10962/d1005086
- Description: Fishes of African floodplains typically comprise populations having short life cycles, relatively few age groups, more generalised feeding behaviour, and which experience spawning success that is strongly influenced by abiotic factors such as hydrological regime of the river, climatic seasonality and habitat characteristics. In addition, African river-floodplain ecosystems do not have appropriate predictive models for estimating yield in these ecosystems. While most predictive models developed to date for floodplain fisheries have taken into account morpho-edaphic factors, they have generally excluded climatic factors as a mega-determinant of the variability of floodplain fisheries. The principle aim of this thesis has been to develop a predictive management model that incorporates data on essential biological aspects of the target species, characteristics of the habitat as well as overall climatic factors, and thus allow for adaptive management of the fisheries in a continuously fluctuating floodplain environment. Lower Shire Floodplain (34 ⁰ 45’ – 35 ⁰ E and 16 ⁰ 00’-17 ⁰ 15’ S) in Malawi, one of the major rivers-floodplains in the Zambezi Basin, was used to test this type of model. The major hypothesis tested in this study was that “the dynamics of the fishery of Lower Shire Floodplain are driven by and adapted to the seasonal, but predictable, hydro-climatic regime of the floodplain”. The specific objectives were: to describe the floodplain’s climate and hydrological pattern; to develop a quantitative characterisation of the major habitats of the Lower Shire Floodplain; to assess the fishery in terms of size, gear utilisation, gear selectivity and yield; to assess the biological parameters of the target species, necessary for the management of the fishery; to analyse how water fluctuation in the floodplain affects the recruitment and life history of the two target species; and to develop of a predictive hydro-climatic model to benefit the management of the fisheries. The climate of the floodplain was characterised by low (765 ± 198 mm) and fairly variable (Cv = 27%) rainfall, which largely occurred between December and January. The area was generally humid (mean RH 68%), with mild to hot (25- 33ºC) and variable monthly mean diurnal (12ºC) temperature. Four quarterly hydro-climatic seasons were identified and comprised: Quarter 1 (Jul-Sep) characterised by hot, dry weather with a low flood regime; Quarter 2 (Oct-Dec) hot, windy, wet weather with low-but-rising flood regime; Quarter 3 (Jan-Mar) hot humid, wet weather with the flood regime at peak; and Quarter 4 (Apr-Jun) humid and cool weather with receding flood regime. The annual hydrograph of the floodplain was represented by four categories of flood regime as: low (Jul-Sept), low-but-rising (Oct-Dec), peak (Jan- Mar), and falling (Apr-Jun). The floodplain experienced a water deficit of 95.1 mm.year⁻¹, and it was hypothesised that ground water recharge maintained water in the floodplain the rest of the year. Three major habitats were identified in the floodplain. The river-floodplain, characterised by deep fast-flowing water, sandy substrate and little emergent vegetation; the permanently connected lagoons, were shallow (≤ 2 m) with sandymud bottom and slow flowing water; and the seasonally connected lagoons had slowflowing stagnant water, with comparatively more emergent and floating vegetation. Physicochemical characteristics of the habitats varied significantly with hydroclimatic seasons (one-way ANOVA, p ≤ 0.05), indicating the influence of flood regime, which joined the habitats in a non-equilibrial spatial distribution. Consequently, during receding and low flood regimes river-floodplain and permanently connected lagoons exhibited similar characteristics while all three habitats had similar characteristics during the rising and peak flood regimes. It was, therefore, concluded that in floodplains, habitats shift horizontally and vertically according to the water level. Gill nets, cast nets, long line, and fish traps accounted for 99% of the total count of gears, and hence considered the major fishing sectors. Two principal species in the floodplain were the catfish Clarias gariepinus and the cichlid Oreochromis mossambicus. Length-at-maximum-selectivity (ø) and length-at-50%-sexual-maturity (Lm₅₀) for each of the two species showed that although they were selected into the four fishing sectors at lengths above maturity, maximum selectivity into the long line occurred at a length before maturity for O. mossambicus. In addition, the width of the gamma selectivity function (σ) indicated that a considerable proportion of juveniles of the two species were also selected. Therefore, it was decided that management for the floodplain be centred on controlling over-fishing and preserving the spawner stock, by banning seine and mosquito nets, and closing river-floodplain and permanently connected lagoons to fishing during the low flood regime. There were significant seasonal variations in CPUE, lowest in the low flood, and highest during the peak flood regime. Sectioned otoliths were used to determine the age and growth of the two principal species in the floodplain. Marginal zone analysis revealed that annulus formation in all the species occurred during the period of low air and water temperatures, high evaporation and receding water levels, hence a high rate of desiccation and negative water budget. For O. mossambicus, maximum age reached was 6 years while in C. gariepinus it was 9 years. The 3-parameter von Bertalanffy growth model adequately described growth as lt = 177.6(1-e⁻·⁴⁴⁽t ⁺ ¹·⁴³⁾) mm TL for O. mossambicus and lt = 502.9(1-e⁻°·³¹⁽t ⁺ ¹·⁹²⁾) mm TL for C. gariepinus. Female O. mossambicus reached 50%-sexual-maturity at 109 mm SL, while males matured at 105 mm, and both male and female C. gariepinus reached Lm₅₀ at 249 mm SL. The breeding seasons of both O. mossambicus and Clarias gariepinus were between September and March, with modal peaks in January and November, respectively. The annual total mortality rates (Z) were 0.62 ± 0.18 yr⁻¹ for O. mossambicus and 0.93 ± 0.47 yr⁻¹ for C. gariepinus. The mean empirical estimates of natural mortality (M) were 0.46 yr⁻¹ for O. mossambicus and 0.50 year⁻¹ for C. gariepinus, and fishing mortality (F) was calculated as 0.16 yr⁻¹ for O. mossambicus and 0.43 yr⁻¹ for C. gariepinus. The overall exploitation level (Z/K) was 1.41 for O. mossambicus and 3.01 for C. gariepinus. Given that the Z/K ratio was >1, it was asserted that both O. mossambicus and C. gariepinus were mortality-dominated and fairly heavily exploited. However, potential for sustainable exploitation existed since both species showed signs of resilience due short longevity and high rate of natural mortality. Given the limitation of simple exponential models of fish mortality and growth under the situation of seasonal fluctuation of water levels, a simple predictive hydroclimatic- fisheries model was developed. The model predicted the life-history and production parameters fairly accurately (0.53 ≤ r² ≥ 0.98, p ≤ 0.05), and showed that environmental and biological events in the floodplain significantly (0.43 ≤ r² ≥ 0.91, p ≤ 0.05) followed the periodic function of time (day-of-the-year), hence, strongly seasonal. In addition, the flood-pulse preceded all the major biological events, with predicted phase lags established at 55.6º for peak flood, 157.2º, 260.1º, 334.6º and 341.4º for condition factor for O. mossambicus, recruitment, spawning period for O. mossambicus and C. gariepinus, respectively. Therefore, it was recommended that water obstruction on the Shire River must ensure sufficient water flow during the peak flood and spawning period to allow flooding and inundation of the floodplain in order to create habitat favourable for spawning and feeding as well as improve recruitment.
- Full Text:
- Date Issued: 2005
- Authors: Chimatiro, Sloans Kalumba
- Date: 2005
- Subjects: Shire River Valley (Malawi and Mozambique) Fisheries -- Malawi
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5243 , http://hdl.handle.net/10962/d1005086
- Description: Fishes of African floodplains typically comprise populations having short life cycles, relatively few age groups, more generalised feeding behaviour, and which experience spawning success that is strongly influenced by abiotic factors such as hydrological regime of the river, climatic seasonality and habitat characteristics. In addition, African river-floodplain ecosystems do not have appropriate predictive models for estimating yield in these ecosystems. While most predictive models developed to date for floodplain fisheries have taken into account morpho-edaphic factors, they have generally excluded climatic factors as a mega-determinant of the variability of floodplain fisheries. The principle aim of this thesis has been to develop a predictive management model that incorporates data on essential biological aspects of the target species, characteristics of the habitat as well as overall climatic factors, and thus allow for adaptive management of the fisheries in a continuously fluctuating floodplain environment. Lower Shire Floodplain (34 ⁰ 45’ – 35 ⁰ E and 16 ⁰ 00’-17 ⁰ 15’ S) in Malawi, one of the major rivers-floodplains in the Zambezi Basin, was used to test this type of model. The major hypothesis tested in this study was that “the dynamics of the fishery of Lower Shire Floodplain are driven by and adapted to the seasonal, but predictable, hydro-climatic regime of the floodplain”. The specific objectives were: to describe the floodplain’s climate and hydrological pattern; to develop a quantitative characterisation of the major habitats of the Lower Shire Floodplain; to assess the fishery in terms of size, gear utilisation, gear selectivity and yield; to assess the biological parameters of the target species, necessary for the management of the fishery; to analyse how water fluctuation in the floodplain affects the recruitment and life history of the two target species; and to develop of a predictive hydro-climatic model to benefit the management of the fisheries. The climate of the floodplain was characterised by low (765 ± 198 mm) and fairly variable (Cv = 27%) rainfall, which largely occurred between December and January. The area was generally humid (mean RH 68%), with mild to hot (25- 33ºC) and variable monthly mean diurnal (12ºC) temperature. Four quarterly hydro-climatic seasons were identified and comprised: Quarter 1 (Jul-Sep) characterised by hot, dry weather with a low flood regime; Quarter 2 (Oct-Dec) hot, windy, wet weather with low-but-rising flood regime; Quarter 3 (Jan-Mar) hot humid, wet weather with the flood regime at peak; and Quarter 4 (Apr-Jun) humid and cool weather with receding flood regime. The annual hydrograph of the floodplain was represented by four categories of flood regime as: low (Jul-Sept), low-but-rising (Oct-Dec), peak (Jan- Mar), and falling (Apr-Jun). The floodplain experienced a water deficit of 95.1 mm.year⁻¹, and it was hypothesised that ground water recharge maintained water in the floodplain the rest of the year. Three major habitats were identified in the floodplain. The river-floodplain, characterised by deep fast-flowing water, sandy substrate and little emergent vegetation; the permanently connected lagoons, were shallow (≤ 2 m) with sandymud bottom and slow flowing water; and the seasonally connected lagoons had slowflowing stagnant water, with comparatively more emergent and floating vegetation. Physicochemical characteristics of the habitats varied significantly with hydroclimatic seasons (one-way ANOVA, p ≤ 0.05), indicating the influence of flood regime, which joined the habitats in a non-equilibrial spatial distribution. Consequently, during receding and low flood regimes river-floodplain and permanently connected lagoons exhibited similar characteristics while all three habitats had similar characteristics during the rising and peak flood regimes. It was, therefore, concluded that in floodplains, habitats shift horizontally and vertically according to the water level. Gill nets, cast nets, long line, and fish traps accounted for 99% of the total count of gears, and hence considered the major fishing sectors. Two principal species in the floodplain were the catfish Clarias gariepinus and the cichlid Oreochromis mossambicus. Length-at-maximum-selectivity (ø) and length-at-50%-sexual-maturity (Lm₅₀) for each of the two species showed that although they were selected into the four fishing sectors at lengths above maturity, maximum selectivity into the long line occurred at a length before maturity for O. mossambicus. In addition, the width of the gamma selectivity function (σ) indicated that a considerable proportion of juveniles of the two species were also selected. Therefore, it was decided that management for the floodplain be centred on controlling over-fishing and preserving the spawner stock, by banning seine and mosquito nets, and closing river-floodplain and permanently connected lagoons to fishing during the low flood regime. There were significant seasonal variations in CPUE, lowest in the low flood, and highest during the peak flood regime. Sectioned otoliths were used to determine the age and growth of the two principal species in the floodplain. Marginal zone analysis revealed that annulus formation in all the species occurred during the period of low air and water temperatures, high evaporation and receding water levels, hence a high rate of desiccation and negative water budget. For O. mossambicus, maximum age reached was 6 years while in C. gariepinus it was 9 years. The 3-parameter von Bertalanffy growth model adequately described growth as lt = 177.6(1-e⁻·⁴⁴⁽t ⁺ ¹·⁴³⁾) mm TL for O. mossambicus and lt = 502.9(1-e⁻°·³¹⁽t ⁺ ¹·⁹²⁾) mm TL for C. gariepinus. Female O. mossambicus reached 50%-sexual-maturity at 109 mm SL, while males matured at 105 mm, and both male and female C. gariepinus reached Lm₅₀ at 249 mm SL. The breeding seasons of both O. mossambicus and Clarias gariepinus were between September and March, with modal peaks in January and November, respectively. The annual total mortality rates (Z) were 0.62 ± 0.18 yr⁻¹ for O. mossambicus and 0.93 ± 0.47 yr⁻¹ for C. gariepinus. The mean empirical estimates of natural mortality (M) were 0.46 yr⁻¹ for O. mossambicus and 0.50 year⁻¹ for C. gariepinus, and fishing mortality (F) was calculated as 0.16 yr⁻¹ for O. mossambicus and 0.43 yr⁻¹ for C. gariepinus. The overall exploitation level (Z/K) was 1.41 for O. mossambicus and 3.01 for C. gariepinus. Given that the Z/K ratio was >1, it was asserted that both O. mossambicus and C. gariepinus were mortality-dominated and fairly heavily exploited. However, potential for sustainable exploitation existed since both species showed signs of resilience due short longevity and high rate of natural mortality. Given the limitation of simple exponential models of fish mortality and growth under the situation of seasonal fluctuation of water levels, a simple predictive hydroclimatic- fisheries model was developed. The model predicted the life-history and production parameters fairly accurately (0.53 ≤ r² ≥ 0.98, p ≤ 0.05), and showed that environmental and biological events in the floodplain significantly (0.43 ≤ r² ≥ 0.91, p ≤ 0.05) followed the periodic function of time (day-of-the-year), hence, strongly seasonal. In addition, the flood-pulse preceded all the major biological events, with predicted phase lags established at 55.6º for peak flood, 157.2º, 260.1º, 334.6º and 341.4º for condition factor for O. mossambicus, recruitment, spawning period for O. mossambicus and C. gariepinus, respectively. Therefore, it was recommended that water obstruction on the Shire River must ensure sufficient water flow during the peak flood and spawning period to allow flooding and inundation of the floodplain in order to create habitat favourable for spawning and feeding as well as improve recruitment.
- Full Text:
- Date Issued: 2005
A study of the factors influencing the success of internet marketing in small South African tourism businesses
- Authors: Elliott, Roger Michael
- Date: 2005
- Subjects: Tourism -- South Africa -- Management , Small business -- South Africa -- Management , Internet marketing -- South Africa , Strategic planning , Marketing -- Management , Communication in management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1204 , http://hdl.handle.net/10962/d1016252
- Description: The tourism sector has been identified as an industry that has the potential to make a substantial contribution to job creation, economic growth, and redressing past imbalances in South Africa as it has been recognised as an underexploited sector with considerable potential for growth. The majority of tourism enterprises fall within the definition of small businesses, which have been identified as the most appropriate enterprises through which the economic challenges facing South Africa can be addressed. Small businesses differ from their larger counterparts not only in terms of size, but also in regard to access to resources and marketing expertise. Not surprisingly, one of the issues identified as preventing this sector from reaching its full potential is access to markets. The focus of this study is to identify the primary factors driving the success of the use of the Internet for marketing in small businesses operating in the tourism sector in South Africa. If these factors can be identified, this will allow existing and emerging small businesses to access markets and retain customers more easily leading to a proliferation of these enterprises. A theoretical model was formulated from the literature in which the factors influencing the success of Internet marketing were identified. These factors can broadly be divided into generic (marketing or management) factors and Internet specific factors. The technological aspects of the Internet were not ignored, but regarded as a resource to be managed rather than an autonomous source of competitive advantage. This model was tested by making use of a large-scale empirical study. Convenience sampling was used and the data was collected from small tourism businesses (that is businesses with fewer than 100 employees) in the Western Cape, Eastern Cape and KwaZulu-Natal provinces of South Africa. The factors were identified using exploratory factor analysis and the Cronbach alpha coefficients were assessed to confirm the reliability of these scales. Structural equation modelling was used as the principal mode of statistical analysis to measure the relationships amongst the variables in the model proposed in this study. A correlation analysis was used to measure the impact of marketing objectives on the success of Internet marketing. The primary determinants of the success of Internet marketing in small businesses operating in the tow-ism sector in South Africa were identified by the empirical study as: Product champion Links Alliances Owner-manager knowledge Entrepreneurial orientation Owner-manager vision Customer orientation Marketing objectives Interestingly, one factor, Strategic planning, recorded a negative influence on the success of Internet marketing. This is possibly because the owner-manager felt that this was a redundant exercise given the dominant and pervasive influence of the owner-manager in all spheres of the business. Nevertheless, if small tourism firms consider the factors identified in this thesis as essential aspects in the use of the Internet for marketing, this will allow them to overcome one of the biggest hurdles to their prosperity, namely, the access to markets.
- Full Text:
- Date Issued: 2005
- Authors: Elliott, Roger Michael
- Date: 2005
- Subjects: Tourism -- South Africa -- Management , Small business -- South Africa -- Management , Internet marketing -- South Africa , Strategic planning , Marketing -- Management , Communication in management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1204 , http://hdl.handle.net/10962/d1016252
- Description: The tourism sector has been identified as an industry that has the potential to make a substantial contribution to job creation, economic growth, and redressing past imbalances in South Africa as it has been recognised as an underexploited sector with considerable potential for growth. The majority of tourism enterprises fall within the definition of small businesses, which have been identified as the most appropriate enterprises through which the economic challenges facing South Africa can be addressed. Small businesses differ from their larger counterparts not only in terms of size, but also in regard to access to resources and marketing expertise. Not surprisingly, one of the issues identified as preventing this sector from reaching its full potential is access to markets. The focus of this study is to identify the primary factors driving the success of the use of the Internet for marketing in small businesses operating in the tourism sector in South Africa. If these factors can be identified, this will allow existing and emerging small businesses to access markets and retain customers more easily leading to a proliferation of these enterprises. A theoretical model was formulated from the literature in which the factors influencing the success of Internet marketing were identified. These factors can broadly be divided into generic (marketing or management) factors and Internet specific factors. The technological aspects of the Internet were not ignored, but regarded as a resource to be managed rather than an autonomous source of competitive advantage. This model was tested by making use of a large-scale empirical study. Convenience sampling was used and the data was collected from small tourism businesses (that is businesses with fewer than 100 employees) in the Western Cape, Eastern Cape and KwaZulu-Natal provinces of South Africa. The factors were identified using exploratory factor analysis and the Cronbach alpha coefficients were assessed to confirm the reliability of these scales. Structural equation modelling was used as the principal mode of statistical analysis to measure the relationships amongst the variables in the model proposed in this study. A correlation analysis was used to measure the impact of marketing objectives on the success of Internet marketing. The primary determinants of the success of Internet marketing in small businesses operating in the tow-ism sector in South Africa were identified by the empirical study as: Product champion Links Alliances Owner-manager knowledge Entrepreneurial orientation Owner-manager vision Customer orientation Marketing objectives Interestingly, one factor, Strategic planning, recorded a negative influence on the success of Internet marketing. This is possibly because the owner-manager felt that this was a redundant exercise given the dominant and pervasive influence of the owner-manager in all spheres of the business. Nevertheless, if small tourism firms consider the factors identified in this thesis as essential aspects in the use of the Internet for marketing, this will allow them to overcome one of the biggest hurdles to their prosperity, namely, the access to markets.
- Full Text:
- Date Issued: 2005
Material characterisation of laser formed dual phase steel components
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
Intraspecific comparison of Phanerochaete chrysosporium strains peroxidase production, pollutant degradation and mycelial differentiation
- Authors: Fraser, Sheena Janet
- Date: 2005
- Subjects: Phanerochaete Pollutants -- Biodegradation Lignin -- Biodegradation Bioremediation Peroxidase Fungi -- Differentiation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3964 , http://hdl.handle.net/10962/d1004023
- Description: The wood-degrading basidiomycete, Phanerochaete chrysosporium, has been studied as a model organism in elucidating the mechanisms and pathways enabling this white-rot fungus to degrade recalcitrant lignin. These same mechanisms are implicated in the mineralisation of environmentally persistent, toxic phenolic chemicals. For this reason, P. chrysosporium has been exploited in a number of environmentally sound technologies, including the degradation of the indigestible lignin component in agricultural waste for the generation of digestible animal feedstocks or high sugar content raw materials for ethanol production; brightening processes in the pulp and paper industry; the detoxification and decolourisation of industrial effluents; and the bioremediation of hazardous waste sites. The improvement of these technologies is dependant on ongoing research involving strain selection, strain development using genetic engineering approaches and process development. Strain improvement using non-recombinant methods is beneficial in that it does not limit the inherent robustness observed amongst natural variants. In this research, through a breeding programme, ten P.chrysosporium sibling strains were screened for variable ligninase activities and pollutant degradation capabilities in order to further describe previously identified differences between these organisms. A conventional stationary liquid culture technique was effectively miniaturised from 10 ml flask cultures to a 96-well microtitre plate format, for the assessment of multigenic traits amongst sibling strains. Using the 96-well microtitre plate method, the relationships between P. chrysosporium growth kinetics, peroxidase production, pollutant sensitivity and pollutant degradation was explored. Significant correlations were primarily associated with P. chrysosporium growth [P < 0.05]. Percentage p-cresol removal and tannic acid tolerance were both correlated with a shorter lag phase in growth [tannic acid: r = 0.7698, P < 0.05; p-cresol: r = 0.7584, P < 0.05] and lower stationary phase biomass levels [tannic acid: r = 0.8177, P < 0.05; p-cresol: r = 0.7803, P < 0.05]. A significant correlation (linear relationship) was also detected between percentage Poly-R478 decolourisation and time of onset of MnP [r = 0.9689, P < 0.001]. No correlation was observed between dye decolourisation, p-cresol degradation, lignin degradation and lignin peroxidase (LiP) or manganese peroxidase (MnP) activities [P > 0.05]. These results imply that differences in the biosynthetic pathways for biomass accumulation in sibling strains play a significant role in the intraspecific variation observed in pollutant sensitivity, pollutant degradation, and enzyme production. Categorical analysis of intraspecific differences was assessed according to four criterions. These included growth, extracellular peroxidase activities, tolerance to toxic pollutants and the biodegradation of model pollutants. Sibling strains showing the most variable responses in three or more of the selective criterion were recommended for further studies. These strains include P. chrysosporium ME446, BS 2.52, BS 13, BS 17, BS 18, and BS 24. Interestingly, BS 2.52 (a dikaryotic strain generating from the crossing of two haploid progeny) showed significantly lower degradation capabilities than the wildtype parent strain ME446. The inherited variability observed between sibling strains is to be further explored through proteome and transcriptome analysis and genetic linkage studies aimed at describing the mechanisms or pathways conferring tolerance to or degradation of environmental pollutants. In examining fewer organisms at this next level, the number of replicates examined can be increased and thus the power of detection of experimental procedures improved, enabling the detection of multigenic traits amongst genetically related organisms. Growth was shown to play a significant role in the intraspecific differences detected in pollutant sensitivity and degradation between sibling strains. Little is known about the mechanism of growth and differentiation, or the role of differentiation in regulating the lignolytic activity in this organism. The membrane gradostat bioreactor and a unique plug-flow membrane bioreactor were evaluated as novel tools with which to further explore the relationship between secondary metabolism, pollutant degradation and biofilm development in sibling strains. High yield MnP production at levels as high as 1478.8 U.l-1 was achieved using a laboratory scale membrane gradostat bioreactor. Furthermore, extensive mycelial differentiation and tissue formation are reported for P. chrysosporium in both the membrane gradostat bioreactor and plug-flow membrane bioreactor. Intraspecific differences in the extent of this differentiation were observed in strains ME446, BS 13, BS 17 and BS 26 cultured using the membrane gradostat bioreactor, highlighting the potential of these techniques as a platform for future strain improvement strategies.
- Full Text:
- Date Issued: 2005
- Authors: Fraser, Sheena Janet
- Date: 2005
- Subjects: Phanerochaete Pollutants -- Biodegradation Lignin -- Biodegradation Bioremediation Peroxidase Fungi -- Differentiation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3964 , http://hdl.handle.net/10962/d1004023
- Description: The wood-degrading basidiomycete, Phanerochaete chrysosporium, has been studied as a model organism in elucidating the mechanisms and pathways enabling this white-rot fungus to degrade recalcitrant lignin. These same mechanisms are implicated in the mineralisation of environmentally persistent, toxic phenolic chemicals. For this reason, P. chrysosporium has been exploited in a number of environmentally sound technologies, including the degradation of the indigestible lignin component in agricultural waste for the generation of digestible animal feedstocks or high sugar content raw materials for ethanol production; brightening processes in the pulp and paper industry; the detoxification and decolourisation of industrial effluents; and the bioremediation of hazardous waste sites. The improvement of these technologies is dependant on ongoing research involving strain selection, strain development using genetic engineering approaches and process development. Strain improvement using non-recombinant methods is beneficial in that it does not limit the inherent robustness observed amongst natural variants. In this research, through a breeding programme, ten P.chrysosporium sibling strains were screened for variable ligninase activities and pollutant degradation capabilities in order to further describe previously identified differences between these organisms. A conventional stationary liquid culture technique was effectively miniaturised from 10 ml flask cultures to a 96-well microtitre plate format, for the assessment of multigenic traits amongst sibling strains. Using the 96-well microtitre plate method, the relationships between P. chrysosporium growth kinetics, peroxidase production, pollutant sensitivity and pollutant degradation was explored. Significant correlations were primarily associated with P. chrysosporium growth [P < 0.05]. Percentage p-cresol removal and tannic acid tolerance were both correlated with a shorter lag phase in growth [tannic acid: r = 0.7698, P < 0.05; p-cresol: r = 0.7584, P < 0.05] and lower stationary phase biomass levels [tannic acid: r = 0.8177, P < 0.05; p-cresol: r = 0.7803, P < 0.05]. A significant correlation (linear relationship) was also detected between percentage Poly-R478 decolourisation and time of onset of MnP [r = 0.9689, P < 0.001]. No correlation was observed between dye decolourisation, p-cresol degradation, lignin degradation and lignin peroxidase (LiP) or manganese peroxidase (MnP) activities [P > 0.05]. These results imply that differences in the biosynthetic pathways for biomass accumulation in sibling strains play a significant role in the intraspecific variation observed in pollutant sensitivity, pollutant degradation, and enzyme production. Categorical analysis of intraspecific differences was assessed according to four criterions. These included growth, extracellular peroxidase activities, tolerance to toxic pollutants and the biodegradation of model pollutants. Sibling strains showing the most variable responses in three or more of the selective criterion were recommended for further studies. These strains include P. chrysosporium ME446, BS 2.52, BS 13, BS 17, BS 18, and BS 24. Interestingly, BS 2.52 (a dikaryotic strain generating from the crossing of two haploid progeny) showed significantly lower degradation capabilities than the wildtype parent strain ME446. The inherited variability observed between sibling strains is to be further explored through proteome and transcriptome analysis and genetic linkage studies aimed at describing the mechanisms or pathways conferring tolerance to or degradation of environmental pollutants. In examining fewer organisms at this next level, the number of replicates examined can be increased and thus the power of detection of experimental procedures improved, enabling the detection of multigenic traits amongst genetically related organisms. Growth was shown to play a significant role in the intraspecific differences detected in pollutant sensitivity and degradation between sibling strains. Little is known about the mechanism of growth and differentiation, or the role of differentiation in regulating the lignolytic activity in this organism. The membrane gradostat bioreactor and a unique plug-flow membrane bioreactor were evaluated as novel tools with which to further explore the relationship between secondary metabolism, pollutant degradation and biofilm development in sibling strains. High yield MnP production at levels as high as 1478.8 U.l-1 was achieved using a laboratory scale membrane gradostat bioreactor. Furthermore, extensive mycelial differentiation and tissue formation are reported for P. chrysosporium in both the membrane gradostat bioreactor and plug-flow membrane bioreactor. Intraspecific differences in the extent of this differentiation were observed in strains ME446, BS 13, BS 17 and BS 26 cultured using the membrane gradostat bioreactor, highlighting the potential of these techniques as a platform for future strain improvement strategies.
- Full Text:
- Date Issued: 2005
The design and evaluation of a short-term group psychotherapy model for survivors of a first myocardial infarction
- Authors: Frewen, Sharon H
- Date: 2005
- Subjects: Health -- Psychological aspects , Medicine and psychology , Coronary heart disease -- Psychological aspects , Type A behavior , Stress (Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3247 , http://hdl.handle.net/10962/d1015041
- Description: There is extensive evidence that the rehabilitation of individuals with coronary heart disease needs to include psychological components to complement the exercise and dietary recommendations that are normally provided. However, psychological aspects have not been integrated into medical care in South Africa to any significant degree. Psychological interventions overseas have included the modification of the Type A behaviour pattern, stress management, cognitive restructuring, relaxation techniques, improved communication skills, the identification and expression of emotions, and emotional support. The aim of the present study was to design a short-term group intervention which incorporated these aspects and which included an exploration of the mind-body experience post infarct. In addition, the intervention aimed to increase participants' awareness of the compensatory dynamics of the Type A behaviour pattern. The intervention was tailored to South African conditions and was evaluated by means of a multiple case study design. The intervention was delivered to a group of nine coronary heart disease patients which included six survivors of myocardial infarction, the remaining participants having undergone a by-pass operation. Data included weekly feedback sheets evaluating each session, repeated measures on the Profile of Mood States, the Jenkins Activity Survey, a Spouse Rating Scale and extensive qualitative data on each participant including tape recordings of each session and data collected from a series of interviews before, during and after the programme. The feedback sheets and recordings of the sessions were used as a basis for recommendations for revising the content and structure of the programme for future use. Case narratives were written for three of the participants and provided an in-depth look at how and why individual changes did or did not occur in response to the intervention. In addition, the case narratives revealed the role played by the compensatory dynamics of the Type A behaviour pattern in complicating rehabilitation for survivors of myocardial infarction. Two participants were offered a series of individual sessions at 18-month follow-up and the material from these sessions was also used to aid in the interpretation of the data. The content of the 18-month follow-up sessions provided evidence for the importance of conducting a developmental analysis of the origins of low self-esteem and insecurity that maintain and drive the Type A behaviour pattern. In these sessions, this analysis provided the basis for a brief focused psychodynamic psychotherapy that facilitated marked changes that had not been achieved in the 12-week structured group intervention. It is recommended that future research investigate the use of brief psychodynamic psychotherapy on an individual basis as a complement to a group intervention focusing on psycho-education, building social support and management of problematic emotions in everyday situations.
- Full Text:
- Date Issued: 2005
- Authors: Frewen, Sharon H
- Date: 2005
- Subjects: Health -- Psychological aspects , Medicine and psychology , Coronary heart disease -- Psychological aspects , Type A behavior , Stress (Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3247 , http://hdl.handle.net/10962/d1015041
- Description: There is extensive evidence that the rehabilitation of individuals with coronary heart disease needs to include psychological components to complement the exercise and dietary recommendations that are normally provided. However, psychological aspects have not been integrated into medical care in South Africa to any significant degree. Psychological interventions overseas have included the modification of the Type A behaviour pattern, stress management, cognitive restructuring, relaxation techniques, improved communication skills, the identification and expression of emotions, and emotional support. The aim of the present study was to design a short-term group intervention which incorporated these aspects and which included an exploration of the mind-body experience post infarct. In addition, the intervention aimed to increase participants' awareness of the compensatory dynamics of the Type A behaviour pattern. The intervention was tailored to South African conditions and was evaluated by means of a multiple case study design. The intervention was delivered to a group of nine coronary heart disease patients which included six survivors of myocardial infarction, the remaining participants having undergone a by-pass operation. Data included weekly feedback sheets evaluating each session, repeated measures on the Profile of Mood States, the Jenkins Activity Survey, a Spouse Rating Scale and extensive qualitative data on each participant including tape recordings of each session and data collected from a series of interviews before, during and after the programme. The feedback sheets and recordings of the sessions were used as a basis for recommendations for revising the content and structure of the programme for future use. Case narratives were written for three of the participants and provided an in-depth look at how and why individual changes did or did not occur in response to the intervention. In addition, the case narratives revealed the role played by the compensatory dynamics of the Type A behaviour pattern in complicating rehabilitation for survivors of myocardial infarction. Two participants were offered a series of individual sessions at 18-month follow-up and the material from these sessions was also used to aid in the interpretation of the data. The content of the 18-month follow-up sessions provided evidence for the importance of conducting a developmental analysis of the origins of low self-esteem and insecurity that maintain and drive the Type A behaviour pattern. In these sessions, this analysis provided the basis for a brief focused psychodynamic psychotherapy that facilitated marked changes that had not been achieved in the 12-week structured group intervention. It is recommended that future research investigate the use of brief psychodynamic psychotherapy on an individual basis as a complement to a group intervention focusing on psycho-education, building social support and management of problematic emotions in everyday situations.
- Full Text:
- Date Issued: 2005
A phenomenological investigation into lecturers' understanding of themselves as assessors at Rhodes University
- Authors: Grant, Rose
- Date: 2005
- Subjects: Curriculum-based assessment -- South Africa Education, Higher -- South Africa -- Evaluation Educational tests and measurements -- South Africa Education, Higher -- Evaluation Case studies Universities and colleges -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1315 , http://hdl.handle.net/10962/d1003948
- Description: This thesis sets out to obtain an understanding of what it means to be an assessor in higher education, more especially within the Rhodes University context. The concept of assessment, a highly contentious and complex issue, is examined against a background of competing understandings of the nature and purpose of higher education, including the striving for excellence versus the call to more equitable ideals associated with a mass higher education and training system. An overview of salient issues is presented in which both traditional and alternative paradigms of measurement and assessment theory are explored with a view to considering foundational principles upon which sound assessment practice should be based. Specific methods and instruments of assessment are examined with the purpose of evaluating their potential for empowering students as active participants in their own learning and in the assessment process. In a field in which much of the literature seeks improved assessment merely through the administration of increasingly sophisticated assessment techniques, a phenomenological investigation offered a unique way of understanding the meaning assessors make of their practice. Making use of in-depth interviews with five lecturers at Rhodes University the researcher, interacting in a personal manner with people not viewed as experimental objects but as human subjects, assisted participants in moving towards non-theoretical descriptions that accurately reflected their experience. Insights contained in the data were synthesised and integrated into a consistent description of the essential nature of the experience, the primary endeavour of the phenomenologist being to transform naïve experience into more explicitly detailed conceptual knowledge. The essence of how these educators understand themselves as assessors at Rhodes University is perhaps best encapsulated by a considerable sense of agency or initiative on their part. While participants make use of a variety of assessment strategies, they are conscious that assessment cannot be viewed in isolation from other aspects of their teaching and the curriculum. Not only do they make use of different assessment methods but, conscious of accommodating the diverse needs of students, understand their responsibility in terms of providing learning opportunities to assist students in meeting the course outcomes and fulfilling their potential. Rather than allowing pressures from within and outside of the academy to dictate, these lecturers, with significant hard work, courage and a capacity for reflective practice, have embraced the challenges associated with higher education in a state of transition.
- Full Text:
- Date Issued: 2005
- Authors: Grant, Rose
- Date: 2005
- Subjects: Curriculum-based assessment -- South Africa Education, Higher -- South Africa -- Evaluation Educational tests and measurements -- South Africa Education, Higher -- Evaluation Case studies Universities and colleges -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1315 , http://hdl.handle.net/10962/d1003948
- Description: This thesis sets out to obtain an understanding of what it means to be an assessor in higher education, more especially within the Rhodes University context. The concept of assessment, a highly contentious and complex issue, is examined against a background of competing understandings of the nature and purpose of higher education, including the striving for excellence versus the call to more equitable ideals associated with a mass higher education and training system. An overview of salient issues is presented in which both traditional and alternative paradigms of measurement and assessment theory are explored with a view to considering foundational principles upon which sound assessment practice should be based. Specific methods and instruments of assessment are examined with the purpose of evaluating their potential for empowering students as active participants in their own learning and in the assessment process. In a field in which much of the literature seeks improved assessment merely through the administration of increasingly sophisticated assessment techniques, a phenomenological investigation offered a unique way of understanding the meaning assessors make of their practice. Making use of in-depth interviews with five lecturers at Rhodes University the researcher, interacting in a personal manner with people not viewed as experimental objects but as human subjects, assisted participants in moving towards non-theoretical descriptions that accurately reflected their experience. Insights contained in the data were synthesised and integrated into a consistent description of the essential nature of the experience, the primary endeavour of the phenomenologist being to transform naïve experience into more explicitly detailed conceptual knowledge. The essence of how these educators understand themselves as assessors at Rhodes University is perhaps best encapsulated by a considerable sense of agency or initiative on their part. While participants make use of a variety of assessment strategies, they are conscious that assessment cannot be viewed in isolation from other aspects of their teaching and the curriculum. Not only do they make use of different assessment methods but, conscious of accommodating the diverse needs of students, understand their responsibility in terms of providing learning opportunities to assist students in meeting the course outcomes and fulfilling their potential. Rather than allowing pressures from within and outside of the academy to dictate, these lecturers, with significant hard work, courage and a capacity for reflective practice, have embraced the challenges associated with higher education in a state of transition.
- Full Text:
- Date Issued: 2005
An intersubjective perspective on the role of personal therapy in being a psychotherapist
- Authors: Haumann, Hester Johanna
- Date: 2005
- Subjects: Psychodynamic psychotherapy Psychotherapy Clinical psychology Psychotherapists -- Psychology Psychoanalysis Countertransference(Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2988 , http://hdl.handle.net/10962/d1002497
- Description: The purpose of this study was to explore how personal therapy influences experienced psychodynamic psychotherapists’ ways of being clinicians, and, by implication, their professional development. A hermeneutic research method, which also drew upon aspects of grounded theory methodology, was therefore devised to explore and examine how personal therapy and professional practice relate to each other and to the therapist’s development, and to deepen this descriptive account into a more differentiated and theoretically viable understanding. In-depth, semi-structured interviews were conducted with eight psychodynamic psychotherapists who were working as clinicians and who were concurrently in therapy. Keeping the research objective in mind, a list of questions was developed from the interview material through which the data was re-read and edited. In accordance with the aims of the study, and as suggested by the results of the initial phase of the textual analysis, intersubjective theory, mainly that of Jessica Benjamin, was used to generate a conceptual framework through which the interview material was further interpreted. This foregrounded the shifting power distributions and the varying processes of identification between the treating therapists and the participants. The Jungian notion of the wounded healer was intersubjectively reconfigured as indicating a therapist whose (often unacknowledged) needs and vulnerabilities engender a proclivity to relate to patients as objects rather than subjects. The participants could all be described as having started out their professional lives as wounded healers. The effects of personal therapy on their clinical work were conceptualised in terms of increased abilities for subject-to-subject relating. These were linked to augmented capacities for reflective and symbolic thinking and an enhanced openness to the implicit, unformulated and opaque aspects of experiences in the therapeutic space. Finally an intersubjective model of personal therapy and development as a therapist was generated. It was concluded that because of the focus on the therapeutic relationship as the vehicle for change in psychodynamic psychotherapy, as well as the current increasing emphasis on the use of the therapist’s subjectivity, the therapist’s capacity to engage in and sustain subject-tosubject relating and, by implication, the therapist’s personal therapy, are of pivotal importance for all therapists doing the work of psychodynamic psychotherapy.
- Full Text:
- Date Issued: 2005
- Authors: Haumann, Hester Johanna
- Date: 2005
- Subjects: Psychodynamic psychotherapy Psychotherapy Clinical psychology Psychotherapists -- Psychology Psychoanalysis Countertransference(Psychology)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2988 , http://hdl.handle.net/10962/d1002497
- Description: The purpose of this study was to explore how personal therapy influences experienced psychodynamic psychotherapists’ ways of being clinicians, and, by implication, their professional development. A hermeneutic research method, which also drew upon aspects of grounded theory methodology, was therefore devised to explore and examine how personal therapy and professional practice relate to each other and to the therapist’s development, and to deepen this descriptive account into a more differentiated and theoretically viable understanding. In-depth, semi-structured interviews were conducted with eight psychodynamic psychotherapists who were working as clinicians and who were concurrently in therapy. Keeping the research objective in mind, a list of questions was developed from the interview material through which the data was re-read and edited. In accordance with the aims of the study, and as suggested by the results of the initial phase of the textual analysis, intersubjective theory, mainly that of Jessica Benjamin, was used to generate a conceptual framework through which the interview material was further interpreted. This foregrounded the shifting power distributions and the varying processes of identification between the treating therapists and the participants. The Jungian notion of the wounded healer was intersubjectively reconfigured as indicating a therapist whose (often unacknowledged) needs and vulnerabilities engender a proclivity to relate to patients as objects rather than subjects. The participants could all be described as having started out their professional lives as wounded healers. The effects of personal therapy on their clinical work were conceptualised in terms of increased abilities for subject-to-subject relating. These were linked to augmented capacities for reflective and symbolic thinking and an enhanced openness to the implicit, unformulated and opaque aspects of experiences in the therapeutic space. Finally an intersubjective model of personal therapy and development as a therapist was generated. It was concluded that because of the focus on the therapeutic relationship as the vehicle for change in psychodynamic psychotherapy, as well as the current increasing emphasis on the use of the therapist’s subjectivity, the therapist’s capacity to engage in and sustain subject-tosubject relating and, by implication, the therapist’s personal therapy, are of pivotal importance for all therapists doing the work of psychodynamic psychotherapy.
- Full Text:
- Date Issued: 2005
Operationally defining sexual orientation : towards the development of a fundamental measure of adolescent sexual responsiveness variations
- Authors: Heath, Lance Julian
- Date: 2005
- Subjects: Sexual orientation Homosexuality Psychometrics Teenagers--Sexual behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1681 , http://hdl.handle.net/10962/d1003564
- Description: Much published work has pointed to the need for the development of a sound operational definition of sexual orientation in order to enable the research in this area to progress. To contribute to this process the current research set out to develop two measures of sexual orientation and examine their psychometric properties. In order to develop relevant tools historical, conceptual and operational definitions of sexual orientation were critically examined and standard questionnaire development techniques applied. The first scale consisted of 32 items and was administered to a total of 835 adolescents, comprising three sub-groups (189 Grade 11 Scholars, 547 First Year and 99 Third Year Psychology Students). A Cronbach alpha coefficient of 0.85 was calculated indicating that this instrument had very good internal consistency reliability. Similar factors emerged in each of the sample sub-groups when factor analyses were performed suggesting that this instrument has good external and construct validities. These factors each had respectable Cronbach alpha coefficients indicating their own internal consistency. The four factors which consistently emerged were Same Sex Responsiveness, Opposite Sex Responsiveness, Previous Month’s Same Sex Responsiveness and Previous Month’s Opposite Sex Responsiveness. The second scale consisted of 16 items and was administered to 646 adolescents, comprising the latter two sub-groups referred to above. A Cronbach alpha coefficient of 0.82 was calculated indicating that this instrument also had very good internal consistency reliability. Once again similar factors with generally good internal consistency emerged in factor analysis suggesting that this too was a valid instrument. The factors that emerged from the second scale were Same Sex Responsiveness, Unattractive Opposite Sex Responsiveness, Attractive Opposite Sex Responsiveness and Attraction. Future developments, adjustments and applications of the instruments as well as implications for the arena of sexual orientation research are discussed. In the light of the dearth of information with regard to the sexual orientations of South African adolescents the current study also briefly explored and presented the sample’s responses in terms of the dimensions of each questionnaire as well as how each emerging factor related to the demographics (education level, gender, sexual orientation self-label and age) of the sample.
- Full Text:
- Date Issued: 2005
- Authors: Heath, Lance Julian
- Date: 2005
- Subjects: Sexual orientation Homosexuality Psychometrics Teenagers--Sexual behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1681 , http://hdl.handle.net/10962/d1003564
- Description: Much published work has pointed to the need for the development of a sound operational definition of sexual orientation in order to enable the research in this area to progress. To contribute to this process the current research set out to develop two measures of sexual orientation and examine their psychometric properties. In order to develop relevant tools historical, conceptual and operational definitions of sexual orientation were critically examined and standard questionnaire development techniques applied. The first scale consisted of 32 items and was administered to a total of 835 adolescents, comprising three sub-groups (189 Grade 11 Scholars, 547 First Year and 99 Third Year Psychology Students). A Cronbach alpha coefficient of 0.85 was calculated indicating that this instrument had very good internal consistency reliability. Similar factors emerged in each of the sample sub-groups when factor analyses were performed suggesting that this instrument has good external and construct validities. These factors each had respectable Cronbach alpha coefficients indicating their own internal consistency. The four factors which consistently emerged were Same Sex Responsiveness, Opposite Sex Responsiveness, Previous Month’s Same Sex Responsiveness and Previous Month’s Opposite Sex Responsiveness. The second scale consisted of 16 items and was administered to 646 adolescents, comprising the latter two sub-groups referred to above. A Cronbach alpha coefficient of 0.82 was calculated indicating that this instrument also had very good internal consistency reliability. Once again similar factors with generally good internal consistency emerged in factor analysis suggesting that this too was a valid instrument. The factors that emerged from the second scale were Same Sex Responsiveness, Unattractive Opposite Sex Responsiveness, Attractive Opposite Sex Responsiveness and Attraction. Future developments, adjustments and applications of the instruments as well as implications for the arena of sexual orientation research are discussed. In the light of the dearth of information with regard to the sexual orientations of South African adolescents the current study also briefly explored and presented the sample’s responses in terms of the dimensions of each questionnaire as well as how each emerging factor related to the demographics (education level, gender, sexual orientation self-label and age) of the sample.
- Full Text:
- Date Issued: 2005
The oxidative coupling of phenols using stoichiometric metal oxidants
- Authors: Hoffmann, Eric
- Date: 2005
- Subjects: Phenols , Oxidation , Stoichiometry
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10977 , http://hdl.handle.net/10948/180 , Phenols , Oxidation , Stoichiometry
- Description: The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
- Full Text:
- Date Issued: 2005
- Authors: Hoffmann, Eric
- Date: 2005
- Subjects: Phenols , Oxidation , Stoichiometry
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10977 , http://hdl.handle.net/10948/180 , Phenols , Oxidation , Stoichiometry
- Description: The oxidative coupling of 2,6-di-t-butylphenol under mild reaction conditions is well documented and the subject of many patents. However, the coupling of other monoand di- substituted phenols is not as well documented and thus there is scope for further investigation for providing a convenient, environmentally friendly and economically viable method for the oxidative coupling of these phenols. In this study, the oxidative coupling of a variety of alkylated phenolic substrates, 2-tbutylphenol, 2,6-di-t-butylphenol, 2,4 -di-t-butylphenol and ,4-dimethylphenol, using a range of different oxidizing agents, were investigated by means of experimental and/or theoretical means. The dibutylated aromatics provided the highest selectivities to their respective coupled products, with results obtained with the dimethyl analogue being only satisfactory, and that for 2 -t-butylphenol being totally inefficient. PM3 Molecular orbital (MO) calculations were used to predict the possible modes of coupling for the substrates 2,6 -di-t-butylphenol and 2,4-di-t-butylphenol, and these results were then compared with those obtained experimentally in the laboratory. Preliminarily, the coupling of unsubstituted phenolics was also assessed by means of MO calculations. Much emphasis was placed on Ce(IV) as the oxidant, and the reaction conditions under which it was used and the results that were obtained have not been reported before and are therefore novel. The oxidation of 2,4-di-t-butylphenol using Ce(IV) in the presence of methanesulphonic acid was optimized to afford high yields and selectivities to the desired ortho C-ortho C coupled product under mild reaction conditions. Various reaction parameters were also investigated in this case, such as varying the MeSO3H concentration, the solvent, the reaction temperature, the reaction time, the substrate loading, the rate of oxidant addition and the substrate to oxidant ratio. Ce(IV) also gave a high selectivity to the para C-para C coupled product when IX using 2,6-di-t-butylphenol as the substrate. However, it was not as effective with 2,4- dimethylphenol, and even less so with 2-t-butylphenol. The oxidation reactions of 2-t-butylphenol and 2,4-dimethylphenol with various coupling agents were also investigated with the intention of obtaining high selectivities to the respective desired coupled products. In these studies, 2-t-butylphenol afforded a large number of products, irrespective of the oxidant used. The dimethyl analogue was more selective, but results were not optimal. It was clear that the number of substituents on the phenol ring, their nature and their position with regards to the hydroxyl moiety was of great importance and made a significant impact on the preferred coupling mode of the substrate. It was observed that steric effects also played a major role in the outcome of these reactions: 2,6-di-t-butylphenol never afforded any C-O coupled products whereas 2-t-butylphenol, 2,4-di-t-butylphenol and 2,4-dimethylphenol all appeared to undergo some C-O coupling. Finally, reaction mechanisms were provided for both the K3Fe(CN)6 and Ce(IV) work, these reacting in basic and acidic media, respectively. It was proposed that both of these mechanisms operate through the initial formation of the phenoxyl radical.
- Full Text:
- Date Issued: 2005
An investigation into the pharmacological properties of propolis
- Authors: Hu, Fuliang
- Date: 2005
- Subjects: Propolis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5831 , http://hdl.handle.net/10962/d1007955
- Description: Propolis is a traditional value-added product from beekeeping, and has been widely used in medicine and the chemical industry because of its extensive biological activities. In this dissertation some pharmacological properties of propolis extracted by ethanol (EEP) and water (WSP) were studied by means of modem pharmacological methods. The results of the experiments show the following: 1. Both EEP and WSD led to decreased levels of fasting blood glucose (FBG), glycosylated haemoglobin (HBA1c), Fructosamine (FRU), blood urea nitrogen (BUN), uric acid (UA), malonaldehyde (MDA), nitric oxide (NO), nitric oxide synthetase (NOS), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and very-low density lipoprotein cholesterol (VLDL-C) in the serum of fasting rats; and, to increased serum levels of high-density lipoprotein cholesterol (HDL-C) and superoxide dismutase (SOD) in rats with diabetes mellitus. This suggests that propolis can control blood glucose and modulate the metabolism of glucose, blood lipid and protein, leading to decreased outputs of lipid peroxidation and scavenging free radicals in rats with diabetes mellitus. 2. Both EEP and WSD showed inhibitory effects on swelling induced by Freund's complete adjuvant and decreased the degree of local inflammatory responses; significantly inhibited the increase of interleukin-6 (lL-6) in inflamed tissues, but had no significant effect on levels of interleukin-2 (IL-2) and interferon-y (IFN-y). The results are consistent with the interpretation that EEP and WSD may exert these effects by inhibiting the activation and differentiation of mononuclear macrophages. 3. Both EEP and WSD exhibited significant anti-inflammatory effects in animal models with respect to thoracic capillary vessel leakage in mice, Carrageenan-induced oedema, Carrageen-aninduced pleurisy and acute lung damage in rats. The mechanisms for the anti-inflammatory effects probably involve decreasing prostaglandin and NO levels. 4. Both EEP and WSD had an inhibitory effect on the level of TG, TC, LDL-C, glutamic-pyruvic transaminase (GPT) and glutamic-oxalacetic transaminase (GOT) in serum, and TC, TG and MDA in liver of hyperlipidemic SD rats; but were without effects on HDL-C, MDA, SOD and NO in serum. EEP also reduced body weight, liver weight and liver index, but WSD did not reduce those indexes. The results showed that the two extracts contribute to the improvement of lipid metabolism in hyperlipidemic rats and provide them with the required anti-oxidative activity. 5. The 80% ethanol extracts of propolis had the highest flavonoid content. The flavone content of water extracts of propolis were obtained with a natural surface-active agent, under ultrasonic perturbation at 80°C, for 12 h and was 6.7 times greater than that of propolis extracted with water at room temperature. Compared to EEP, WSD has the same or a greater anti-tumor or anti-inflammation effect at the same dosage, and shows considerable pharmacological potential especially because of its low side effects and ease of preparation.
- Full Text:
- Date Issued: 2005
- Authors: Hu, Fuliang
- Date: 2005
- Subjects: Propolis
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5831 , http://hdl.handle.net/10962/d1007955
- Description: Propolis is a traditional value-added product from beekeeping, and has been widely used in medicine and the chemical industry because of its extensive biological activities. In this dissertation some pharmacological properties of propolis extracted by ethanol (EEP) and water (WSP) were studied by means of modem pharmacological methods. The results of the experiments show the following: 1. Both EEP and WSD led to decreased levels of fasting blood glucose (FBG), glycosylated haemoglobin (HBA1c), Fructosamine (FRU), blood urea nitrogen (BUN), uric acid (UA), malonaldehyde (MDA), nitric oxide (NO), nitric oxide synthetase (NOS), total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and very-low density lipoprotein cholesterol (VLDL-C) in the serum of fasting rats; and, to increased serum levels of high-density lipoprotein cholesterol (HDL-C) and superoxide dismutase (SOD) in rats with diabetes mellitus. This suggests that propolis can control blood glucose and modulate the metabolism of glucose, blood lipid and protein, leading to decreased outputs of lipid peroxidation and scavenging free radicals in rats with diabetes mellitus. 2. Both EEP and WSD showed inhibitory effects on swelling induced by Freund's complete adjuvant and decreased the degree of local inflammatory responses; significantly inhibited the increase of interleukin-6 (lL-6) in inflamed tissues, but had no significant effect on levels of interleukin-2 (IL-2) and interferon-y (IFN-y). The results are consistent with the interpretation that EEP and WSD may exert these effects by inhibiting the activation and differentiation of mononuclear macrophages. 3. Both EEP and WSD exhibited significant anti-inflammatory effects in animal models with respect to thoracic capillary vessel leakage in mice, Carrageenan-induced oedema, Carrageen-aninduced pleurisy and acute lung damage in rats. The mechanisms for the anti-inflammatory effects probably involve decreasing prostaglandin and NO levels. 4. Both EEP and WSD had an inhibitory effect on the level of TG, TC, LDL-C, glutamic-pyruvic transaminase (GPT) and glutamic-oxalacetic transaminase (GOT) in serum, and TC, TG and MDA in liver of hyperlipidemic SD rats; but were without effects on HDL-C, MDA, SOD and NO in serum. EEP also reduced body weight, liver weight and liver index, but WSD did not reduce those indexes. The results showed that the two extracts contribute to the improvement of lipid metabolism in hyperlipidemic rats and provide them with the required anti-oxidative activity. 5. The 80% ethanol extracts of propolis had the highest flavonoid content. The flavone content of water extracts of propolis were obtained with a natural surface-active agent, under ultrasonic perturbation at 80°C, for 12 h and was 6.7 times greater than that of propolis extracted with water at room temperature. Compared to EEP, WSD has the same or a greater anti-tumor or anti-inflammation effect at the same dosage, and shows considerable pharmacological potential especially because of its low side effects and ease of preparation.
- Full Text:
- Date Issued: 2005
On the growth and characterisation of AIGaN alloys for optoelectronic applications
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
Isolation and characterization of a novel thermostable and catalytically efficient laccase from Peniophora sp. strain UD4
- Authors: Jordaan, Justin
- Date: 2005
- Subjects: Enzymes Enzymes -- Industrial applications Peniophora Laccase
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3970 , http://hdl.handle.net/10962/d1004029
- Description: Enzymes are becoming an effective tool in industrial processes, from crude applications such as bioremediation to fine processes such as chirally selective biocatalysis. The ligninolytic enzymes have recently received considerable attention for industrial application due to both their broad substrate range and their ability to degrade the most recalcitrant natural polymer, lignin. This group of enzymes was therefore identified as the target group for this study. Improved enzyme properties are constantly being sought to enhance the range of applications for enzymes. Biodiversity provides a wide variety of enzymes. Several researchers have concentrated on extremophiles as their primary source of superior enzymes, consequently neglecting temperate environments in their search for these enzymes. The relatively neglected fungal biodiversity of South Africa provided an opportunity to test the hypothesis that potentially important industrial enzymes with unusual properties could be isolated from mesophilic basidiomycetous fungi. Subsequent screening of Eastern Cape biodiversity for thermostable ligninolytic enzymes from basidiomycetes resulted in the isolation of a novel laccase enzyme from a basidiomycetous species. This fungus was identified as Peniophora sp. UD4 by phylogenetic analysis of rDNA ITS sequences. Initial studies indicated a superior optimum temperature of 70°C and thermostability, indicated by no loss in activity at 60°C over nine hours. Further characterization of the laccase revealed a broader than usual substrate range through its unusual ability to oxidatively couple DMAB and MBTH. The laccase also exhibited a broad pH oxidation range for ABTS (pH 2 – 6.8), and a relatively high affinity (K_m_ = 0.0123 mM) and catalytic efficiency (63 252 mM^(-1)^s^(-1)^) for ABTS as a substrate. The laccase activity from Peniophora sp. UD4 was shown to be comprised of three isozymes with a molecular weight of 62 kDa and pI’s of 6.33, 6.45 and 6.50. Investigation of the nutrient and physical factors affecting ligninolytic enzyme production and growth of Peniophora sp. UD4 indicated that the wild-type organism was unsuitable for large scale production of the thermostable laccase due to the low levels of laccase production. The thermostable laccase was applied to defouling of ultrafiltration membranes, bioremediation of industrial waste streams, biocatalysis, and biosensor technology as potential applications. Application of the Peniophora sp. UD4 laccase to defouling of membranes used for ultrafiltration of brown water showed large flux recoveries of 31, 21 and 21% after the first three defouling recycles respectively, compared to 3% for the control without immobilized enzyme. The novel laccase showed potential for the bioremediation of industrial waste streams, the most successful being that of bleach plant effluent, where a reduction of 66% of the phenolic load was achieved. Application of the novel laccase to biocatalytic oxidation of ferulic acid and (±)-α-pinene showed higher product yield as compared to oxidation of these compounds by Trametes versicolor laccase in mediated and non-mediated systems. The major products of (±)-α-pinene oxidation were identified as verbenol and trans-sorberol. The Peniophora sp. UD4 laccase was successfully applied to biosensor technology, which benchmarked significantly better than Trametes versicolor laccase for the detection of 4-chlorophenol. The biosensor developed with laccase from UD4 by covalent binding to a glassy carbon electrode exhibited the best combination of sensitivity and stability. This thesis shows that a laccase with superior properties was obtained from a mesophilic South African basidiomycete. The catalytic properties displayed by the novel laccase from Peniophora sp. UD4 all contribute to the increased industrial applicability of laccases, and may be the most industrially feasible enzyme of its class isolated to date.
- Full Text:
- Date Issued: 2005
- Authors: Jordaan, Justin
- Date: 2005
- Subjects: Enzymes Enzymes -- Industrial applications Peniophora Laccase
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3970 , http://hdl.handle.net/10962/d1004029
- Description: Enzymes are becoming an effective tool in industrial processes, from crude applications such as bioremediation to fine processes such as chirally selective biocatalysis. The ligninolytic enzymes have recently received considerable attention for industrial application due to both their broad substrate range and their ability to degrade the most recalcitrant natural polymer, lignin. This group of enzymes was therefore identified as the target group for this study. Improved enzyme properties are constantly being sought to enhance the range of applications for enzymes. Biodiversity provides a wide variety of enzymes. Several researchers have concentrated on extremophiles as their primary source of superior enzymes, consequently neglecting temperate environments in their search for these enzymes. The relatively neglected fungal biodiversity of South Africa provided an opportunity to test the hypothesis that potentially important industrial enzymes with unusual properties could be isolated from mesophilic basidiomycetous fungi. Subsequent screening of Eastern Cape biodiversity for thermostable ligninolytic enzymes from basidiomycetes resulted in the isolation of a novel laccase enzyme from a basidiomycetous species. This fungus was identified as Peniophora sp. UD4 by phylogenetic analysis of rDNA ITS sequences. Initial studies indicated a superior optimum temperature of 70°C and thermostability, indicated by no loss in activity at 60°C over nine hours. Further characterization of the laccase revealed a broader than usual substrate range through its unusual ability to oxidatively couple DMAB and MBTH. The laccase also exhibited a broad pH oxidation range for ABTS (pH 2 – 6.8), and a relatively high affinity (K_m_ = 0.0123 mM) and catalytic efficiency (63 252 mM^(-1)^s^(-1)^) for ABTS as a substrate. The laccase activity from Peniophora sp. UD4 was shown to be comprised of three isozymes with a molecular weight of 62 kDa and pI’s of 6.33, 6.45 and 6.50. Investigation of the nutrient and physical factors affecting ligninolytic enzyme production and growth of Peniophora sp. UD4 indicated that the wild-type organism was unsuitable for large scale production of the thermostable laccase due to the low levels of laccase production. The thermostable laccase was applied to defouling of ultrafiltration membranes, bioremediation of industrial waste streams, biocatalysis, and biosensor technology as potential applications. Application of the Peniophora sp. UD4 laccase to defouling of membranes used for ultrafiltration of brown water showed large flux recoveries of 31, 21 and 21% after the first three defouling recycles respectively, compared to 3% for the control without immobilized enzyme. The novel laccase showed potential for the bioremediation of industrial waste streams, the most successful being that of bleach plant effluent, where a reduction of 66% of the phenolic load was achieved. Application of the novel laccase to biocatalytic oxidation of ferulic acid and (±)-α-pinene showed higher product yield as compared to oxidation of these compounds by Trametes versicolor laccase in mediated and non-mediated systems. The major products of (±)-α-pinene oxidation were identified as verbenol and trans-sorberol. The Peniophora sp. UD4 laccase was successfully applied to biosensor technology, which benchmarked significantly better than Trametes versicolor laccase for the detection of 4-chlorophenol. The biosensor developed with laccase from UD4 by covalent binding to a glassy carbon electrode exhibited the best combination of sensitivity and stability. This thesis shows that a laccase with superior properties was obtained from a mesophilic South African basidiomycete. The catalytic properties displayed by the novel laccase from Peniophora sp. UD4 all contribute to the increased industrial applicability of laccases, and may be the most industrially feasible enzyme of its class isolated to date.
- Full Text:
- Date Issued: 2005
Fractured solidarities: labour regulation, workplace restructuring, and employment 'flexibility' in Namibia
- Authors: Klerck, Gilton
- Date: 2005
- Subjects: Industrial relations -- Namibia Labor -- Namibia Labor unions -- Namibia Organizational change -- Namibia Labor laws and legislation -- Namibia Casual labor -- Namibia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3343 , http://hdl.handle.net/10962/d1004898
- Description: A central concern of this thesis is the expansion, distribution and control of 'non-standard' employment in Namibia since independence. The employment relationship has assumed various historical forms under capitalism, each of which corresponds to a specific mode of regulation with distinct structural dynamics. An attempt is made to extend the regulation approach 'downwards' to account for the problem of order in the workplace and to place the employment relationship within its own regulatory framework. The point of departure in this study of the dynamics of labour regulation is the contradictory nature of labour's incorporation, allocation, control and reproduction within the labour market. The employment relationship is never only an economic exchange, but is also mediated through an institutional framework that connects the processes of production and social reproduction, and regulates conflicting interests inside and outside the workplace. This relationship, as critical realists have pointed out, is a product of the indeterminate intersection of several generative structures. The roots of these generative structures can be traced to three sets of social processes: the processes of production and the structuring of labour demand; the processes of social reproduction and the structuring of labour supply; and the forces of regulation. Non-standard employment is viewed as a particular social and spatio-temporal 'fix' for the various regulatory dilemmas generated by the standard employment relationship. This conception underscores the fact that a national system of labour regulation decisively shapes the conditions under which employers are able to casualise a part of their workforce. The differential experience across national boundaries suggests that analytical space needs to be provided for systems of labour market regulation which may either accentuate or moderate pressures for casualisation. Segmentation on the demand side of the labour market is explored through an analysis of the types of non-standard jobs created in different economic sectors. The various forms of employment 'flexibility' tend to vary in importance according to the specific manner in which a firm chooses to compete. Consequently, non-standard employees are distributed in a complex and uneven manner across industrial sectors and the occupational hierarchy, and face a diverse range of possibilities and liabilities that shape their levels and forms of participation in the labour market. By counteracting the homogenisation effects of labour law and collective bargaining, the mobilisation of cheap and disposable labour through non-standard employment contracts allows employers much greater discretion in constructing the wage-effort bargain. With non-standard employment, social and statutory regulation is weak or underdeveloped and hence managerial control is autocratic, with a significant contractual component. Although the changing social composition of the workforce associated with employment 'flexibility' poses serious challenges to the modes of organisation that have long served the labour movement, trade unions in Namibia and elsewhere have been slow to respond to the threats of casualisation. Of concern here, is the extent to which attempts to promote the security of existing union members is compatible with attempts to organise non-standard employees. This thesis shows that the unions have developed a complex amalgam of strategies in their efforts to regulate non-standard employment relationships.
- Full Text:
- Date Issued: 2005
- Authors: Klerck, Gilton
- Date: 2005
- Subjects: Industrial relations -- Namibia Labor -- Namibia Labor unions -- Namibia Organizational change -- Namibia Labor laws and legislation -- Namibia Casual labor -- Namibia
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3343 , http://hdl.handle.net/10962/d1004898
- Description: A central concern of this thesis is the expansion, distribution and control of 'non-standard' employment in Namibia since independence. The employment relationship has assumed various historical forms under capitalism, each of which corresponds to a specific mode of regulation with distinct structural dynamics. An attempt is made to extend the regulation approach 'downwards' to account for the problem of order in the workplace and to place the employment relationship within its own regulatory framework. The point of departure in this study of the dynamics of labour regulation is the contradictory nature of labour's incorporation, allocation, control and reproduction within the labour market. The employment relationship is never only an economic exchange, but is also mediated through an institutional framework that connects the processes of production and social reproduction, and regulates conflicting interests inside and outside the workplace. This relationship, as critical realists have pointed out, is a product of the indeterminate intersection of several generative structures. The roots of these generative structures can be traced to three sets of social processes: the processes of production and the structuring of labour demand; the processes of social reproduction and the structuring of labour supply; and the forces of regulation. Non-standard employment is viewed as a particular social and spatio-temporal 'fix' for the various regulatory dilemmas generated by the standard employment relationship. This conception underscores the fact that a national system of labour regulation decisively shapes the conditions under which employers are able to casualise a part of their workforce. The differential experience across national boundaries suggests that analytical space needs to be provided for systems of labour market regulation which may either accentuate or moderate pressures for casualisation. Segmentation on the demand side of the labour market is explored through an analysis of the types of non-standard jobs created in different economic sectors. The various forms of employment 'flexibility' tend to vary in importance according to the specific manner in which a firm chooses to compete. Consequently, non-standard employees are distributed in a complex and uneven manner across industrial sectors and the occupational hierarchy, and face a diverse range of possibilities and liabilities that shape their levels and forms of participation in the labour market. By counteracting the homogenisation effects of labour law and collective bargaining, the mobilisation of cheap and disposable labour through non-standard employment contracts allows employers much greater discretion in constructing the wage-effort bargain. With non-standard employment, social and statutory regulation is weak or underdeveloped and hence managerial control is autocratic, with a significant contractual component. Although the changing social composition of the workforce associated with employment 'flexibility' poses serious challenges to the modes of organisation that have long served the labour movement, trade unions in Namibia and elsewhere have been slow to respond to the threats of casualisation. Of concern here, is the extent to which attempts to promote the security of existing union members is compatible with attempts to organise non-standard employees. This thesis shows that the unions have developed a complex amalgam of strategies in their efforts to regulate non-standard employment relationships.
- Full Text:
- Date Issued: 2005
An investigation into the neuroprotective properties of acetylsalicylic acid and acetaminophen
- Authors: Maharaj, Himant
- Date: 2005
- Subjects: Aspirin Acetaminophen Analgesics Alzheimer's disease -- Treatment Parkinson's disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3769 , http://hdl.handle.net/10962/d1003247
- Description: The potent analgesic property of acetylsalicylic acid and acetaminophen makes these the most commonly used analgesics in the world. Easy accessibility and cost effectiveness of these agents are attractive to patients seeking pain relief. However, the abuse of nonnarcotic analgesics such as acetaminophen and acetylsalicylic acid by alcoholics and patients seeking to relieve dysphoric moods is well documented. These agents therefore impact on the brain neurotransmitter levels and therefore all processes involved in the synthesis and metabolism of neurotransmitters may be affected. The use of non-narcotic analgesics has been reported to reduce the incidence of neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). The mode of action by which acetylsalicylic acid and acetaminophen elicit neuroprotection is however unclear as many mechanisms of action have been inconclusively postulated. The first part of this study aims to elucidate the various mechanisms by which acetylsalicylic acid and acetaminophen affect the enzymes responsible for the catabolism of tryptophan, which is a precursor for the mood elevating neurotransmitter serotonin, as well as to investigate whether these agents alter the interplay between serotonin and pineal indole metabolism. The second part of this study focuses on the neuroprotective properties of acetylsalicylic acid and acetaminophen utilizing the neurotoxic metabolite of the kynurenine pathway, quinolinic acid and the potent Parkinsonian neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). The ability of acetylsalicylic acid and acetaminophen to alter TRP metabolism was determined by investigating the effects of these agents on the primary enzymes of the kynurenine pathway i.e. tryptophan 2, 3-dioxygenase and indoleamine 2,3-dioxygenase as well as to investigate whether these agents would have any effects on 3-hydroxyanthranilic acid oxygenase. 3-Hydroxyanthranilic acid oxygenase is the enzyme responsible for the synthesis of quinolinic acid. Acetylsalicylic acid and acetaminophen alter tryptophan metabolism by inhibiting tryptophan 2, 3-dioxygenase and indoleamine 2,3-dioxygenase thus increasing the availability of tryptophan for the production of serotonin. Acetylsalicylic acid and acetaminophen also inhibit 3-hydroxyanthranilic acid oxygenase thus implying that these agents could reduce quinolinic acid production. Acetaminophen administration in rats induces a rise in serotonin and norepinephrine in the forebrain. Acetylsalicylic acid curtails the acetaminophen-induced rise in brain norepinephrine levels as well as enhances serotonin metabolism, indicating that analgesic preparations containing both agents would be advantageous, as this would prevent acetaminophen-induced mood elevation. The results from the pineal indole metabolism study show that acetylsalicylic acid enhances pineal metabolism of serotonin whereas acetaminophen induces an increase in melatonin levels in the pineal gland. Neuronal damage due to oxidative stress has been implicated in several neurodegenerative disorders such as AD and PD. The second part of the study aims to elucidate and characterize the mechanism by which acetylsalicylic acid and acetaminophen afford neuroprotection. The hippocampus is an important region of the brain responsible for memory. Agents such as quinolinic acid that are known to induce stress in this area have detrimental effects and could lead to various types of dementia. The striatum is also a vulnerable region to oxidative stress and hence (MPP+), which is toxic for this particular region of the brain, was also used as a neurotoxin. The results show that ASA and acetaminophen alone and in combination, are potent superoxide anion scavengers. In addition, the results imply that these agents offer protection against oxidative stress and lipid peroxidation induced by several neurotoxins in rat brain particularly, the hippocampus and striatum. Histological studies, using Nissl staining and Acid fuchsin, show that acetylsalicylic acid and acetaminophen are able to protect hippocampal neurons against quinolinic acidinduced necrotic cell death. Immunohistochemical investigations show that QA induces apoptotic cell death in the hippocampus, which is inhibited by ASA and acetaminophen. In addition, ASA and acetaminophen inhibited MPP+ induced apoptotic cell death in the rat striatum. The study also sought to elucidate possible mechanisms by which ASA and acetaminophen exert neuroprotective effects in the presence of MPP+ as these agents are shown to prevent the MPP+-induced reduction in dopamine levels. The results show that acetylsalicylic acid and acetaminophen inhibit the action of this neurotoxin on the mitochondrial electron transport chain, a common source of free radicals in the cell. In addition, these agents were shown to block the neurotoxic effects of MPP+ on the enzymatic defence system of the brain i.e. superoxide dismutase, glutathione peroxidase and catalase. The reduction in glutathione levels induced by MPP+ is significantly inhibited by acetylsalicylic acid and acetaminophen. The results imply that these agents are capable of not only scavenging free radicals but also enhance the cell defence mechanism against toxicity in the presence of MPP+. These agents also block the MPP+-induced inhibition of dopamine uptake into the cell. This would therefore reduce auto-oxidation of dopamine thus implying another mechanism by which these agents exert a neuroprotective role in MPP+-induced neurotoxicity. The discovery of neuroprotective properties of acetylsalicylic acid and acetaminophen is important considering the high usage of these agents and the increased incidence in neurological disorders. The findings of this thesis point to the need for clinical studies to be conducted as the results show acetylsalicylic acid and acetaminophen to have a definite role to play as antioxidants. This study therefore provides novel information regarding the neuroprotective effects of these agents and favours the use of these agents in the treatment of neurodegenerative disorders, such as AD and PD, in which oxidative stress is implicated.
- Full Text:
- Date Issued: 2005
- Authors: Maharaj, Himant
- Date: 2005
- Subjects: Aspirin Acetaminophen Analgesics Alzheimer's disease -- Treatment Parkinson's disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3769 , http://hdl.handle.net/10962/d1003247
- Description: The potent analgesic property of acetylsalicylic acid and acetaminophen makes these the most commonly used analgesics in the world. Easy accessibility and cost effectiveness of these agents are attractive to patients seeking pain relief. However, the abuse of nonnarcotic analgesics such as acetaminophen and acetylsalicylic acid by alcoholics and patients seeking to relieve dysphoric moods is well documented. These agents therefore impact on the brain neurotransmitter levels and therefore all processes involved in the synthesis and metabolism of neurotransmitters may be affected. The use of non-narcotic analgesics has been reported to reduce the incidence of neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). The mode of action by which acetylsalicylic acid and acetaminophen elicit neuroprotection is however unclear as many mechanisms of action have been inconclusively postulated. The first part of this study aims to elucidate the various mechanisms by which acetylsalicylic acid and acetaminophen affect the enzymes responsible for the catabolism of tryptophan, which is a precursor for the mood elevating neurotransmitter serotonin, as well as to investigate whether these agents alter the interplay between serotonin and pineal indole metabolism. The second part of this study focuses on the neuroprotective properties of acetylsalicylic acid and acetaminophen utilizing the neurotoxic metabolite of the kynurenine pathway, quinolinic acid and the potent Parkinsonian neurotoxin, 1-methyl-4-phenylpyridinium (MPP+). The ability of acetylsalicylic acid and acetaminophen to alter TRP metabolism was determined by investigating the effects of these agents on the primary enzymes of the kynurenine pathway i.e. tryptophan 2, 3-dioxygenase and indoleamine 2,3-dioxygenase as well as to investigate whether these agents would have any effects on 3-hydroxyanthranilic acid oxygenase. 3-Hydroxyanthranilic acid oxygenase is the enzyme responsible for the synthesis of quinolinic acid. Acetylsalicylic acid and acetaminophen alter tryptophan metabolism by inhibiting tryptophan 2, 3-dioxygenase and indoleamine 2,3-dioxygenase thus increasing the availability of tryptophan for the production of serotonin. Acetylsalicylic acid and acetaminophen also inhibit 3-hydroxyanthranilic acid oxygenase thus implying that these agents could reduce quinolinic acid production. Acetaminophen administration in rats induces a rise in serotonin and norepinephrine in the forebrain. Acetylsalicylic acid curtails the acetaminophen-induced rise in brain norepinephrine levels as well as enhances serotonin metabolism, indicating that analgesic preparations containing both agents would be advantageous, as this would prevent acetaminophen-induced mood elevation. The results from the pineal indole metabolism study show that acetylsalicylic acid enhances pineal metabolism of serotonin whereas acetaminophen induces an increase in melatonin levels in the pineal gland. Neuronal damage due to oxidative stress has been implicated in several neurodegenerative disorders such as AD and PD. The second part of the study aims to elucidate and characterize the mechanism by which acetylsalicylic acid and acetaminophen afford neuroprotection. The hippocampus is an important region of the brain responsible for memory. Agents such as quinolinic acid that are known to induce stress in this area have detrimental effects and could lead to various types of dementia. The striatum is also a vulnerable region to oxidative stress and hence (MPP+), which is toxic for this particular region of the brain, was also used as a neurotoxin. The results show that ASA and acetaminophen alone and in combination, are potent superoxide anion scavengers. In addition, the results imply that these agents offer protection against oxidative stress and lipid peroxidation induced by several neurotoxins in rat brain particularly, the hippocampus and striatum. Histological studies, using Nissl staining and Acid fuchsin, show that acetylsalicylic acid and acetaminophen are able to protect hippocampal neurons against quinolinic acidinduced necrotic cell death. Immunohistochemical investigations show that QA induces apoptotic cell death in the hippocampus, which is inhibited by ASA and acetaminophen. In addition, ASA and acetaminophen inhibited MPP+ induced apoptotic cell death in the rat striatum. The study also sought to elucidate possible mechanisms by which ASA and acetaminophen exert neuroprotective effects in the presence of MPP+ as these agents are shown to prevent the MPP+-induced reduction in dopamine levels. The results show that acetylsalicylic acid and acetaminophen inhibit the action of this neurotoxin on the mitochondrial electron transport chain, a common source of free radicals in the cell. In addition, these agents were shown to block the neurotoxic effects of MPP+ on the enzymatic defence system of the brain i.e. superoxide dismutase, glutathione peroxidase and catalase. The reduction in glutathione levels induced by MPP+ is significantly inhibited by acetylsalicylic acid and acetaminophen. The results imply that these agents are capable of not only scavenging free radicals but also enhance the cell defence mechanism against toxicity in the presence of MPP+. These agents also block the MPP+-induced inhibition of dopamine uptake into the cell. This would therefore reduce auto-oxidation of dopamine thus implying another mechanism by which these agents exert a neuroprotective role in MPP+-induced neurotoxicity. The discovery of neuroprotective properties of acetylsalicylic acid and acetaminophen is important considering the high usage of these agents and the increased incidence in neurological disorders. The findings of this thesis point to the need for clinical studies to be conducted as the results show acetylsalicylic acid and acetaminophen to have a definite role to play as antioxidants. This study therefore provides novel information regarding the neuroprotective effects of these agents and favours the use of these agents in the treatment of neurodegenerative disorders, such as AD and PD, in which oxidative stress is implicated.
- Full Text:
- Date Issued: 2005
Characterization of the hydantoin-hydrolysing system of Pseudomonas putida RU-KM3s
- Authors: Matcher, Gwynneth Felicity
- Date: 2005
- Subjects: Hydantoin Hydrolysis Pseudomonas Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3939 , http://hdl.handle.net/10962/d1003998
- Description: The biocatalytic conversion of 5-monosubstituted hydantoin derivatives to optically pure amino acids involves two reaction steps: the hydrolysis of hydantoin to N-carbamylamino acid by an hydantoinase or dihydropyrimidinase enzyme, followed by conversion of the Ncarbamylamino acid to the corresponding amino acid by an N-carbamoylase enzyme. This biocatalytic process has been successfully applied in several industrial processes for the production of enantiomerically pure amino acids used in the synthesis of pharmaceuticals, insecticides, hormones, and food additives. P. putida RU-KM3S was selected for study based on inherent high levels of hydantoinase and N-carbamoylase activity. Subsequent biocatalytic analysis of the enzyme activity within this strain revealed unique properties thus prompting further characterization. The main focus of this research was the isolation of the genes encoding the hydantoin-hydrolysing pathway in RU-KM3S. A genomic library was constructed and screened for heterologous expression of the hydantoin-hydrolysing enzymes. However, this approach was unsuccessful prompting the use of transposon mutagenesis in order to circumvent the drawbacks associated with complementation studies. The enzymes responsible for hydantoin-hydrolysis were identified by insertional inactivation as a dihydropyrimidinase and b-ureidopropionase encoded by dhp and bup respectively. A third open reading frame, encoding a putative transport protein, was identified between the dhp and bup genes and appeared to share a promoter with bup. Analysis of the amino acid sequence deduced from bup and dhp substantiated the distinctive properties and potential industrial application of the L-enantioselective b-ureidopropionase and provided targets for potential optimisation of the substrate-selectivity and activity of the dihydropyrimidinase by site directed mutagenesis. Several transposon-generated mutants with an altered phenotype for growth on minimal medium with hydantoin as the sole source of nitrogen were also isolated. Analysis of the insertion events in these mutants revealed disruptions of genes encoding key elements of the Ntr global regulatory pathway. However, inactivation of these genes had no effect on the dihydropyrimidinase and b-ureidopropionase activity levels. An additional mutant in which the gene coding for the dihydrolipoamide succinyltransferase, which is involved in the TCA cycle, was isolated with reduced levels of both dihydropyrimidinase and b-ureidopropionase activities. These results indicated that the hydantoin-hydrolysis pathway in RU-KM3S is regulated by carbon rather than nitrogen catabolite repression. This was confirmed by the reduction of hydantoin-hydrolysis in cells grown in excess carbon as opposed to nitrogen. Identification of a putative CRP-binding site within the promoter region of these enzymes further supported the regulatory role of carbon catabolite repression (CCR). As CCR in Pseudomonads is poorly understood, elucidation of the mechanism by which the hydantoinhydrolysing pathway in RU-KM3S is regulated would provide valuable insight into this complex process.
- Full Text:
- Date Issued: 2005
- Authors: Matcher, Gwynneth Felicity
- Date: 2005
- Subjects: Hydantoin Hydrolysis Pseudomonas Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3939 , http://hdl.handle.net/10962/d1003998
- Description: The biocatalytic conversion of 5-monosubstituted hydantoin derivatives to optically pure amino acids involves two reaction steps: the hydrolysis of hydantoin to N-carbamylamino acid by an hydantoinase or dihydropyrimidinase enzyme, followed by conversion of the Ncarbamylamino acid to the corresponding amino acid by an N-carbamoylase enzyme. This biocatalytic process has been successfully applied in several industrial processes for the production of enantiomerically pure amino acids used in the synthesis of pharmaceuticals, insecticides, hormones, and food additives. P. putida RU-KM3S was selected for study based on inherent high levels of hydantoinase and N-carbamoylase activity. Subsequent biocatalytic analysis of the enzyme activity within this strain revealed unique properties thus prompting further characterization. The main focus of this research was the isolation of the genes encoding the hydantoin-hydrolysing pathway in RU-KM3S. A genomic library was constructed and screened for heterologous expression of the hydantoin-hydrolysing enzymes. However, this approach was unsuccessful prompting the use of transposon mutagenesis in order to circumvent the drawbacks associated with complementation studies. The enzymes responsible for hydantoin-hydrolysis were identified by insertional inactivation as a dihydropyrimidinase and b-ureidopropionase encoded by dhp and bup respectively. A third open reading frame, encoding a putative transport protein, was identified between the dhp and bup genes and appeared to share a promoter with bup. Analysis of the amino acid sequence deduced from bup and dhp substantiated the distinctive properties and potential industrial application of the L-enantioselective b-ureidopropionase and provided targets for potential optimisation of the substrate-selectivity and activity of the dihydropyrimidinase by site directed mutagenesis. Several transposon-generated mutants with an altered phenotype for growth on minimal medium with hydantoin as the sole source of nitrogen were also isolated. Analysis of the insertion events in these mutants revealed disruptions of genes encoding key elements of the Ntr global regulatory pathway. However, inactivation of these genes had no effect on the dihydropyrimidinase and b-ureidopropionase activity levels. An additional mutant in which the gene coding for the dihydrolipoamide succinyltransferase, which is involved in the TCA cycle, was isolated with reduced levels of both dihydropyrimidinase and b-ureidopropionase activities. These results indicated that the hydantoin-hydrolysis pathway in RU-KM3S is regulated by carbon rather than nitrogen catabolite repression. This was confirmed by the reduction of hydantoin-hydrolysis in cells grown in excess carbon as opposed to nitrogen. Identification of a putative CRP-binding site within the promoter region of these enzymes further supported the regulatory role of carbon catabolite repression (CCR). As CCR in Pseudomonads is poorly understood, elucidation of the mechanism by which the hydantoinhydrolysing pathway in RU-KM3S is regulated would provide valuable insight into this complex process.
- Full Text:
- Date Issued: 2005
Fishing rights, redistribution and policy : the South African commercial T.A.C. fisheries
- Authors: Mather, Diarmid John
- Date: 2005
- Subjects: Fisheries -- South Africa Fish trade -- South Africa Fishery law and legislation -- South Africa Fishery policy -- South Africa Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1061 , http://hdl.handle.net/10962/d1007531
- Description: The main objective of this thesis is to provide an analysis of the economic logic behind fisheries policy and redistribution in South African. An examination of the institutional and organizational evolution reveals that South African fisheries policy followed the world trend in the movement toward quota management systems. However, it is argued that due to the peculiarities of the Apartheid political system, South Africa developed a unique and persistent structure of individual fishing rights that resulted in a transfer of power from the fisher to monopsonistic, and subsequently vertically integrated, fish processing companies. Problems, however, arose with the need to redistribute fishing rights to previously repressed racial groups. It is proposed that, within a specific form (TAC), the structure of individual fishing rights can be decomposed into four operational rules, namely, the right of participation, asset size, tradability and duration of term. Policy design is restricted to a feasible set of rules that impact on the flexibility of the system, the incentives facing private fishing companies and fishers, the efficiency of the fisheries management plan and finally the effect it has on a redistribution strategy. Within this analytical framework, South Africa's policy yields a very flexible system favourable to monopsonistic industrial organisation. However, by adding a redistribution constraint, this structure has a number of important effects. First, as new quota holders are added the information costs for effective fisheries management increase exponentially. Second, the transaction costs to private fishing companies are increased. Third, only the resource rent is redistributed (weak redistribution). Next, the micro to small vessel fisheries, the medium vessel fisheries and the large vessel fisheries are examined separately. The major aim is to determine, within the available data, the effect that a weak redistribution policy (redistribution of the resource rent), has on strong redistribution (redistribution of fishing capital and skills). The evidence definitely supports the analytical framework and suggests that fundamentally the structure of individual fishing rights, which evolved in response to a monopsonistic industrial organisation during the apartheid era in South Africa, works against strong redistribution. Also, that different fisheries face different constraints and that these should in certain instances be treated separately.
- Full Text:
- Date Issued: 2005
- Authors: Mather, Diarmid John
- Date: 2005
- Subjects: Fisheries -- South Africa Fish trade -- South Africa Fishery law and legislation -- South Africa Fishery policy -- South Africa Fishery management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1061 , http://hdl.handle.net/10962/d1007531
- Description: The main objective of this thesis is to provide an analysis of the economic logic behind fisheries policy and redistribution in South African. An examination of the institutional and organizational evolution reveals that South African fisheries policy followed the world trend in the movement toward quota management systems. However, it is argued that due to the peculiarities of the Apartheid political system, South Africa developed a unique and persistent structure of individual fishing rights that resulted in a transfer of power from the fisher to monopsonistic, and subsequently vertically integrated, fish processing companies. Problems, however, arose with the need to redistribute fishing rights to previously repressed racial groups. It is proposed that, within a specific form (TAC), the structure of individual fishing rights can be decomposed into four operational rules, namely, the right of participation, asset size, tradability and duration of term. Policy design is restricted to a feasible set of rules that impact on the flexibility of the system, the incentives facing private fishing companies and fishers, the efficiency of the fisheries management plan and finally the effect it has on a redistribution strategy. Within this analytical framework, South Africa's policy yields a very flexible system favourable to monopsonistic industrial organisation. However, by adding a redistribution constraint, this structure has a number of important effects. First, as new quota holders are added the information costs for effective fisheries management increase exponentially. Second, the transaction costs to private fishing companies are increased. Third, only the resource rent is redistributed (weak redistribution). Next, the micro to small vessel fisheries, the medium vessel fisheries and the large vessel fisheries are examined separately. The major aim is to determine, within the available data, the effect that a weak redistribution policy (redistribution of the resource rent), has on strong redistribution (redistribution of fishing capital and skills). The evidence definitely supports the analytical framework and suggests that fundamentally the structure of individual fishing rights, which evolved in response to a monopsonistic industrial organisation during the apartheid era in South Africa, works against strong redistribution. Also, that different fisheries face different constraints and that these should in certain instances be treated separately.
- Full Text:
- Date Issued: 2005