A social realist analysis of collaborative curriculum development processes in an academic department at a South African university
- Authors: Vorster, Jo-Anne
- Date: 2010
- Subjects: Rhodes University -- Curricula Journalism -- Study and teaching -- South Africa -- Grahamstown Curriculum planning -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3339 , http://hdl.handle.net/10962/d1004314
- Description: This study reports on a social-realist analysis of collaborative curriculum development in a journalism and media studies (JMS) department at a South African university. Archer's social-realist meta-theoretical framework is used to theorise about mechanisms that influence collaborative curriculum development within the context of the JMS Department. The thesis examines the cultural, structural and agential conditions that influenced the process of developing a JMS curriculum that aimed to integrate theory and practice. Bernstein's theories of knowledge recontextualisation and disciplinary knowledge structures are used in the analysis. Bernstein argues that knowledge recontextualisation constitutes a site of struggle. This thesis is an examination of the "struggles" for the epistemic-pedagogic device (Maton's elaboration of Bernstein's epistemic device) during the recontextualisation process that aimed to integrate media studies (MS) and media production (MP) in the JMS curriculum. Traditionally academic work has been an individual endeavour. However, given the growing need to work in disciplinary and inter-disciplinary teams, it is imperative to develop knowledge of the mechanisms that influence such practices. This thesis is a contribution to knowledge of collaborative processes at the level of an academic department in a university. It contributes to knowledge of cultural, structural and agential mechanisms that enable or constrain collaborative curriculum development within a particular kind of context. In addition it contributes to knowledge of the nature of leadership that may be necessary to facilitate productive collaborative relationships and practices in such a context. The curriculum development project reported on in this thesis was initiated in 2003; however, data collection for the study was conducted in 2006 when the curriculum for the fourth year (JMS 4) of the Bachelor of Journalism degree was developed. Since the JMS course prepares students to work as journalists or media workers it is necessary for the curriculum and pedagogy to be oriented both towards the academy and towards the media industries. The aim of the JMS degree is to develop students who will be critically reflexive journalists or media workers. As such the course is both theoretical (MS) and practical (MP). One of the findings of this research project is that the integration of MS and MP is a complex project given that the knowledge of the two disciplines is structured differently. MS is concept-dependent and some aspects of it can be applied to journalism and media practice, while MP is practical and thus context-dependent, though underpinned by theory. A further finding is that both the collaborative work and the integration project required different identity shifts from the lecturers in the JMS Department. Some were more able to make the shifts than others. The thesis shows that the knowledge recontextualisation struggles in the curriculum development processes of the Department of JMS centred around, inter alia, the setting of boundaries between the department and the media and journalism industries, between MS and MP and between MS theory and journalism theory. In addition, existing boundaries between MS and MP lecturers had to be traversed. These boundaries were circumscribed by, amongst other things, unequal power relations emanating from the higher status traditionally accorded to theoretical knowledge by universities, the tensions around the nature of journalism education and training and the differential properties and powers of the various lecturers within the department. The existence of a strong regulative discourse was found to be an important unifying mechanism in a tension-ridden context.
- Full Text:
- Date Issued: 2010
- Authors: Vorster, Jo-Anne
- Date: 2010
- Subjects: Rhodes University -- Curricula Journalism -- Study and teaching -- South Africa -- Grahamstown Curriculum planning -- South Africa -- Grahamstown
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3339 , http://hdl.handle.net/10962/d1004314
- Description: This study reports on a social-realist analysis of collaborative curriculum development in a journalism and media studies (JMS) department at a South African university. Archer's social-realist meta-theoretical framework is used to theorise about mechanisms that influence collaborative curriculum development within the context of the JMS Department. The thesis examines the cultural, structural and agential conditions that influenced the process of developing a JMS curriculum that aimed to integrate theory and practice. Bernstein's theories of knowledge recontextualisation and disciplinary knowledge structures are used in the analysis. Bernstein argues that knowledge recontextualisation constitutes a site of struggle. This thesis is an examination of the "struggles" for the epistemic-pedagogic device (Maton's elaboration of Bernstein's epistemic device) during the recontextualisation process that aimed to integrate media studies (MS) and media production (MP) in the JMS curriculum. Traditionally academic work has been an individual endeavour. However, given the growing need to work in disciplinary and inter-disciplinary teams, it is imperative to develop knowledge of the mechanisms that influence such practices. This thesis is a contribution to knowledge of collaborative processes at the level of an academic department in a university. It contributes to knowledge of cultural, structural and agential mechanisms that enable or constrain collaborative curriculum development within a particular kind of context. In addition it contributes to knowledge of the nature of leadership that may be necessary to facilitate productive collaborative relationships and practices in such a context. The curriculum development project reported on in this thesis was initiated in 2003; however, data collection for the study was conducted in 2006 when the curriculum for the fourth year (JMS 4) of the Bachelor of Journalism degree was developed. Since the JMS course prepares students to work as journalists or media workers it is necessary for the curriculum and pedagogy to be oriented both towards the academy and towards the media industries. The aim of the JMS degree is to develop students who will be critically reflexive journalists or media workers. As such the course is both theoretical (MS) and practical (MP). One of the findings of this research project is that the integration of MS and MP is a complex project given that the knowledge of the two disciplines is structured differently. MS is concept-dependent and some aspects of it can be applied to journalism and media practice, while MP is practical and thus context-dependent, though underpinned by theory. A further finding is that both the collaborative work and the integration project required different identity shifts from the lecturers in the JMS Department. Some were more able to make the shifts than others. The thesis shows that the knowledge recontextualisation struggles in the curriculum development processes of the Department of JMS centred around, inter alia, the setting of boundaries between the department and the media and journalism industries, between MS and MP and between MS theory and journalism theory. In addition, existing boundaries between MS and MP lecturers had to be traversed. These boundaries were circumscribed by, amongst other things, unequal power relations emanating from the higher status traditionally accorded to theoretical knowledge by universities, the tensions around the nature of journalism education and training and the differential properties and powers of the various lecturers within the department. The existence of a strong regulative discourse was found to be an important unifying mechanism in a tension-ridden context.
- Full Text:
- Date Issued: 2010
A preliminary examination of selected biological links between four Eastern Cape estuaries and the inshore marine environment
- Authors: Vorwerk, Paul D
- Date: 2007
- Subjects: Estuaries -- South Africa -- Eastern Cape Marine fishes -- South Africa -- Eastern Cape Marine ecology -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5747 , http://hdl.handle.net/10962/d1005434
- Description: The coastal transition zone (CTZ), which links the terrestrial and marine environments, has been identified as a region of high biological diversity and elevated production. Results of studies conducted in the northern hemisphere indicate that the links between estuaries and the adjacent marine environment is critical to ecological functioning within the CTZ. This study assessed the influence of selected estuaries with different hydrodynamic characteristics on the adjacent marine environment along the south-eastern coastline of southern Africa. Four estuaries were examined, including two permanently open systems, the fresh water deprived Kariega and fresh water dominated Great Fish, and two temporarily open/closed estuaries (TOCE), the Kasouga and East Kleinemonde. Results of the study indicated that outflow of estuarine water from the Great Fish Estuary contributed to a plume of less saline water being evident within the adjacent marine environment. The plume of water was associated with increased zooplankton biomass and particulate organic matter (POM) and chlorophyll-a concentrations. Adjacent to the Kariega Estuary, no evidence of fresh water outflow into the marine environment was observed. However, in the sea directly opposite the mouth of the estuary an increase in zooplankton abundance and biomass was evident. Results of numerical analyses indicated that the increase in zooplankton abundance observed adjacent to the mouth of both permanently open estuaries could not be attributed to the export of zooplankton from the estuary, but rather the accumulation of marine species within the region. The mechanisms responsible for this accumulation were not determined, but it was thought to be associated with increased food availability in the estuarine frontal zone. A similar, but less dramatic biological response was also observed in the marine environment adjacent to the two TOCEs. It is suggested that the increase in biological activity within these regions could be ascribed to seepage of estuarine or ground water through the sand bar that separates these estuaries from the sea. Results of stable carbon isotope analyses indicated that both the Great Fish and Kariega estuaries exported carbon to the nearshore marine environment. The area influenced by estuarine derived carbon was dependent on the volume of estuarine outflow to the marine environment. Adjacent to the fresh water dominated Great Fish Estuary, estuarine derived carbon was recorded up to 12km from the mouth, while adjacent to the fresh water deprived Kariega, estuarine derived carbon was only evident directly opposite the mouth. The recruitment of macrozooplankton (> 2cm) into the fresh water deprived Kariega Estuary was in the range recorded for other permanently open southern African estuaries with higher fresh water flow rates. This indicates that the mechanisms which allow estuarine dependent larvae to locate and enter estuaries are not related to fresh water inflow. In conclusion, this study has demonstrated that despite their small size relative to European and North American systems, South African permanently open and temporarily open/closed estuaries also influence biological activity within the adjacent nearshore marine environment.
- Full Text:
- Date Issued: 2007
- Authors: Vorwerk, Paul D
- Date: 2007
- Subjects: Estuaries -- South Africa -- Eastern Cape Marine fishes -- South Africa -- Eastern Cape Marine ecology -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5747 , http://hdl.handle.net/10962/d1005434
- Description: The coastal transition zone (CTZ), which links the terrestrial and marine environments, has been identified as a region of high biological diversity and elevated production. Results of studies conducted in the northern hemisphere indicate that the links between estuaries and the adjacent marine environment is critical to ecological functioning within the CTZ. This study assessed the influence of selected estuaries with different hydrodynamic characteristics on the adjacent marine environment along the south-eastern coastline of southern Africa. Four estuaries were examined, including two permanently open systems, the fresh water deprived Kariega and fresh water dominated Great Fish, and two temporarily open/closed estuaries (TOCE), the Kasouga and East Kleinemonde. Results of the study indicated that outflow of estuarine water from the Great Fish Estuary contributed to a plume of less saline water being evident within the adjacent marine environment. The plume of water was associated with increased zooplankton biomass and particulate organic matter (POM) and chlorophyll-a concentrations. Adjacent to the Kariega Estuary, no evidence of fresh water outflow into the marine environment was observed. However, in the sea directly opposite the mouth of the estuary an increase in zooplankton abundance and biomass was evident. Results of numerical analyses indicated that the increase in zooplankton abundance observed adjacent to the mouth of both permanently open estuaries could not be attributed to the export of zooplankton from the estuary, but rather the accumulation of marine species within the region. The mechanisms responsible for this accumulation were not determined, but it was thought to be associated with increased food availability in the estuarine frontal zone. A similar, but less dramatic biological response was also observed in the marine environment adjacent to the two TOCEs. It is suggested that the increase in biological activity within these regions could be ascribed to seepage of estuarine or ground water through the sand bar that separates these estuaries from the sea. Results of stable carbon isotope analyses indicated that both the Great Fish and Kariega estuaries exported carbon to the nearshore marine environment. The area influenced by estuarine derived carbon was dependent on the volume of estuarine outflow to the marine environment. Adjacent to the fresh water dominated Great Fish Estuary, estuarine derived carbon was recorded up to 12km from the mouth, while adjacent to the fresh water deprived Kariega, estuarine derived carbon was only evident directly opposite the mouth. The recruitment of macrozooplankton (> 2cm) into the fresh water deprived Kariega Estuary was in the range recorded for other permanently open southern African estuaries with higher fresh water flow rates. This indicates that the mechanisms which allow estuarine dependent larvae to locate and enter estuaries are not related to fresh water inflow. In conclusion, this study has demonstrated that despite their small size relative to European and North American systems, South African permanently open and temporarily open/closed estuaries also influence biological activity within the adjacent nearshore marine environment.
- Full Text:
- Date Issued: 2007
Designing an evaluation instrument for South African intermediate phase school textbooks
- Authors: Vosloo, Barend Jacobus
- Date: 2004
- Subjects: Textbooks -- South Africa -- Evaluation , Curriculum change -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:11014 , http://hdl.handle.net/10948/324 , Textbooks -- South Africa -- Evaluation , Curriculum change -- South Africa -- Evaluation
- Description: No coherent theory about the practice of South African intermediate phase school textbook evaluation has been forthcoming since the advent of a new South African school curriculum in 1998. This deficiency has had an adverse effect on the quality of intermediate phase school textbooks, as well as on the capacity to assess their value. This research project, therefore, had two aims. The first was to articulate a theory about the practice of textbook evaluation. The second was to develop a procedure for evaluating South African intermediate phase school textbooks in terms of the theory. The research method was underpinned by the interpretive research paradigm in terms of which relevant data were analysed and interpreted. The data emanated from a literature review, an analysis of the national Department of Education’s Revised National Curriculum Statement and its draft policy for the evaluation of learning support material, and two surveys. The first survey comprised a sample of intermediate phase teachers and the second a sample of intermediate phase textbook authors. Sufficient evidence was found to conclude that the capabilities of the authoring team, the authors’ rationale and their observance of the process of learning and instruction, the accessibility of the textbook, the availability of teacher support, meeting the requirements of the Revised National Curriculum Statement, and certain key notions about textbook evaluation play a role in articulating a theory about textbook evaluation in order to guide the process of determining the effectiveness of South African intermediate phase school textbooks. Based on the above-mentioned theory, this study proposes a procedure to assist teachers and textbook evaluators to assess the worth of South African intermediate phase school textbooks in a brief, systematic, thorough, rigorous, and practical manner.
- Full Text:
- Date Issued: 2004
- Authors: Vosloo, Barend Jacobus
- Date: 2004
- Subjects: Textbooks -- South Africa -- Evaluation , Curriculum change -- South Africa -- Evaluation
- Language: English
- Type: Thesis , Doctoral , DEd
- Identifier: vital:11014 , http://hdl.handle.net/10948/324 , Textbooks -- South Africa -- Evaluation , Curriculum change -- South Africa -- Evaluation
- Description: No coherent theory about the practice of South African intermediate phase school textbook evaluation has been forthcoming since the advent of a new South African school curriculum in 1998. This deficiency has had an adverse effect on the quality of intermediate phase school textbooks, as well as on the capacity to assess their value. This research project, therefore, had two aims. The first was to articulate a theory about the practice of textbook evaluation. The second was to develop a procedure for evaluating South African intermediate phase school textbooks in terms of the theory. The research method was underpinned by the interpretive research paradigm in terms of which relevant data were analysed and interpreted. The data emanated from a literature review, an analysis of the national Department of Education’s Revised National Curriculum Statement and its draft policy for the evaluation of learning support material, and two surveys. The first survey comprised a sample of intermediate phase teachers and the second a sample of intermediate phase textbook authors. Sufficient evidence was found to conclude that the capabilities of the authoring team, the authors’ rationale and their observance of the process of learning and instruction, the accessibility of the textbook, the availability of teacher support, meeting the requirements of the Revised National Curriculum Statement, and certain key notions about textbook evaluation play a role in articulating a theory about textbook evaluation in order to guide the process of determining the effectiveness of South African intermediate phase school textbooks. Based on the above-mentioned theory, this study proposes a procedure to assist teachers and textbook evaluators to assess the worth of South African intermediate phase school textbooks in a brief, systematic, thorough, rigorous, and practical manner.
- Full Text:
- Date Issued: 2004
Network analysis of trophic linkages in two sub-tropical estuaries along the South-East coast of South Africa
- Authors: Vosloo, Mathys Christiaan
- Date: 2012
- Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine ecology , Network analysis (Planning)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10708 , http://hdl.handle.net/10948/d1010966 , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology , Network analysis (Planning)
- Description: Estuaries are some of the most productive yet threatened ecosystems in the world. Despite their importance they face significant threats through changes to river flow, eutrophication, rapid population growth long the caost and harvesting of natural resources. A number of international studies have been conducted investigating the structure and functioning of an array of ecosystems using ecological network analysis. Energy flow networks have been contsructed for coastal, lagoonal, intertidial and, most notably, permantently open estuaries. Despite the valualble insights contributed by these and other studies, a lack of information on the majority of estuarine ecosystems exists.
- Full Text:
- Date Issued: 2012
- Authors: Vosloo, Mathys Christiaan
- Date: 2012
- Subjects: Estuaries -- South Africa -- Eastern Cape , Estuarine ecology , Network analysis (Planning)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10708 , http://hdl.handle.net/10948/d1010966 , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology , Network analysis (Planning)
- Description: Estuaries are some of the most productive yet threatened ecosystems in the world. Despite their importance they face significant threats through changes to river flow, eutrophication, rapid population growth long the caost and harvesting of natural resources. A number of international studies have been conducted investigating the structure and functioning of an array of ecosystems using ecological network analysis. Energy flow networks have been contsructed for coastal, lagoonal, intertidial and, most notably, permantently open estuaries. Despite the valualble insights contributed by these and other studies, a lack of information on the majority of estuarine ecosystems exists.
- Full Text:
- Date Issued: 2012
Biotic and abiotic factors promoting the development and proliferation of water hyacinth (eichhornia crassipes (Mart.) Solms-Laub.) in the Wouri Basin (Douala-Cameroon) and environs, with implications for its control
- Voukeng, Sonia Nadege Kenfack
- Authors: Voukeng, Sonia Nadege Kenfack
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7644 , vital:21281
- Description: The Wouri River, situated in the Wouri Basin, is one of the main rivers of the Littoral Region in the city of Douala in Cameroon. It is a source of income and food for the population living around these areas. Since the 1990s, the fishing, transportation, irrigation and sand extraction activities have been impeded by the invasion of aquatic plants, specifically water hyacinth (Eichhornia crassipes [Mart.] Solms-Laubach: Pontederiaceae). Introduced in 1997 to the shore of Lake Chad, water hyacinth has invaded almost 114 ha of the Wouri Basin. Furthermore, Douala, the economic capital of the Cameroon and location for more than 70% of the country’s industries, uses the Wouri River and its tributaries to deposit its effluent and waste, which has worsened the problem of water hyacinth. This thesis examined the ecological and socio-economic impacts of water hyacinth in the Wouri Basin and its possible control. An increase in the nutrients in the water has provided water hyacinth with appropriate conditions for its fast growth during both the rainy and dry seasons. The availability of nutrients in these areas is enhanced by the constant, daily tidal fluctuation of water, providing enough water to the plant for easy nutrient uptake. A survey of the impacts of water hyacinth on aquatic plant communities in the Wouri Basin showed that this plant is able to out-compete native species. Assessment of the impact of water hyacinth on the abundance and diversity of plant communities indicated that at some invaded sites, 65% of the vegetation consisted of water hyacinth. Species found in association with water hyacinth with a high level of abundance-dominance were Pistia stratiotes L. (Araceae) (another invader), Commelina benghalensis L. (Commelinaceae) and Echinochloa pyramidalis (Lam.) Hitchc. & Chase (Poaceae). This component of the study also showed that habitats rich in water hyacinth were poor in diversity, while habitats without water hyacinth were rich in diversity, thus raising awareness of the importance of monitoring invasive aquatic weeds along the Wouri Basin, and of implementing correct control management of all invasive aquatic weeds. Communities living along the invaded rivers are well aware of the range of problems caused by the weed; because as the rivers and water bodies used for fishing, transportation, and sand extraction are progressively invaded by the weed, the riparian population is the first to feel the impact. The impact on people has been noticeable, with an increase in diseases, such as malaria, cholera, diarrhoea, typhoid, filariasis, schistosomiasis, scabies and yellow fever increasing the need for a medicine and hospitalization. Economic losses due to the management of invasive aquatic weeds were recorded, and the Ministry of Environment spent an estimated US$1 200 000 between 2010 and 2015 to manage this scourge. In 2016, an amount of US$160 000 was transferred to these regions to manage invasive aquatic weeds, especially water hyacinth, although manual clearing is still the only method used to control this weed. Isolation of fungi from diseased water hyacinth plants in the Wouri Basin revealed several fungal species, most of which have been isolated from water hyacinth species in water bodies elsewhere, which showed a higher diversity during the dry season than during the rainy season. These fungi included Acremonium zonatum (Sawada). W. Gams (Hypocreaceae), Alternaria eichhorniae Nag Raj & Ponnappa (Pleosporaceae), Chaetomium sp., Colletotrichum sp., Curvularia pallescens Boedjin (Pleosporaceae), Curvalaria sp., Epicoccum nigrum Link (Pleosporaceae), Fusarium sp., Pithomyces chartarum fBerk. & M. A. Curtis) M. B. Ellis (Montagnulaceae), to a lesser extent Myrothecium roridum Tode ex Fr. (Incertae sedis) and Nigrospora sp. Although never released in Cameroon, arthropod biological control agents (Neochetina eichhorniae Warner (Coleoptera, Curculionidae) and N. bruchi Hustache (Coleoptera, Curculionidae)) were present, but their populations were relatively low. The slow spread of the insect population was explained by several factors, among them the tidal fluctuation of water, which has an impact on the population growth of the weevils. Whilst adults may be able to survive tidal fluctuations, larvae are severely impacted by them, contributing to the slow success of biological control. In this study, a significant increase in pathogen-induced disease severity and incidence was noted when Neochetina eichhorniae weevils were present, possibly because larvae tunnelling on the petiole created openings for the penetration of fungal spores. This study highlights the negative impacts of water hyacinth, on the environment, people, and thus economy of Cameroon. The presence of biological control agents and pathogens offers Cameroon the possibility of initiating and properly implementing the biological control option, or an integrated management solution, to manage water hyacinth in the Wouri Basin, and in the rest of Cameroon.
- Full Text:
- Date Issued: 2017
- Authors: Voukeng, Sonia Nadege Kenfack
- Date: 2017
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/7644 , vital:21281
- Description: The Wouri River, situated in the Wouri Basin, is one of the main rivers of the Littoral Region in the city of Douala in Cameroon. It is a source of income and food for the population living around these areas. Since the 1990s, the fishing, transportation, irrigation and sand extraction activities have been impeded by the invasion of aquatic plants, specifically water hyacinth (Eichhornia crassipes [Mart.] Solms-Laubach: Pontederiaceae). Introduced in 1997 to the shore of Lake Chad, water hyacinth has invaded almost 114 ha of the Wouri Basin. Furthermore, Douala, the economic capital of the Cameroon and location for more than 70% of the country’s industries, uses the Wouri River and its tributaries to deposit its effluent and waste, which has worsened the problem of water hyacinth. This thesis examined the ecological and socio-economic impacts of water hyacinth in the Wouri Basin and its possible control. An increase in the nutrients in the water has provided water hyacinth with appropriate conditions for its fast growth during both the rainy and dry seasons. The availability of nutrients in these areas is enhanced by the constant, daily tidal fluctuation of water, providing enough water to the plant for easy nutrient uptake. A survey of the impacts of water hyacinth on aquatic plant communities in the Wouri Basin showed that this plant is able to out-compete native species. Assessment of the impact of water hyacinth on the abundance and diversity of plant communities indicated that at some invaded sites, 65% of the vegetation consisted of water hyacinth. Species found in association with water hyacinth with a high level of abundance-dominance were Pistia stratiotes L. (Araceae) (another invader), Commelina benghalensis L. (Commelinaceae) and Echinochloa pyramidalis (Lam.) Hitchc. & Chase (Poaceae). This component of the study also showed that habitats rich in water hyacinth were poor in diversity, while habitats without water hyacinth were rich in diversity, thus raising awareness of the importance of monitoring invasive aquatic weeds along the Wouri Basin, and of implementing correct control management of all invasive aquatic weeds. Communities living along the invaded rivers are well aware of the range of problems caused by the weed; because as the rivers and water bodies used for fishing, transportation, and sand extraction are progressively invaded by the weed, the riparian population is the first to feel the impact. The impact on people has been noticeable, with an increase in diseases, such as malaria, cholera, diarrhoea, typhoid, filariasis, schistosomiasis, scabies and yellow fever increasing the need for a medicine and hospitalization. Economic losses due to the management of invasive aquatic weeds were recorded, and the Ministry of Environment spent an estimated US$1 200 000 between 2010 and 2015 to manage this scourge. In 2016, an amount of US$160 000 was transferred to these regions to manage invasive aquatic weeds, especially water hyacinth, although manual clearing is still the only method used to control this weed. Isolation of fungi from diseased water hyacinth plants in the Wouri Basin revealed several fungal species, most of which have been isolated from water hyacinth species in water bodies elsewhere, which showed a higher diversity during the dry season than during the rainy season. These fungi included Acremonium zonatum (Sawada). W. Gams (Hypocreaceae), Alternaria eichhorniae Nag Raj & Ponnappa (Pleosporaceae), Chaetomium sp., Colletotrichum sp., Curvularia pallescens Boedjin (Pleosporaceae), Curvalaria sp., Epicoccum nigrum Link (Pleosporaceae), Fusarium sp., Pithomyces chartarum fBerk. & M. A. Curtis) M. B. Ellis (Montagnulaceae), to a lesser extent Myrothecium roridum Tode ex Fr. (Incertae sedis) and Nigrospora sp. Although never released in Cameroon, arthropod biological control agents (Neochetina eichhorniae Warner (Coleoptera, Curculionidae) and N. bruchi Hustache (Coleoptera, Curculionidae)) were present, but their populations were relatively low. The slow spread of the insect population was explained by several factors, among them the tidal fluctuation of water, which has an impact on the population growth of the weevils. Whilst adults may be able to survive tidal fluctuations, larvae are severely impacted by them, contributing to the slow success of biological control. In this study, a significant increase in pathogen-induced disease severity and incidence was noted when Neochetina eichhorniae weevils were present, possibly because larvae tunnelling on the petiole created openings for the penetration of fungal spores. This study highlights the negative impacts of water hyacinth, on the environment, people, and thus economy of Cameroon. The presence of biological control agents and pathogens offers Cameroon the possibility of initiating and properly implementing the biological control option, or an integrated management solution, to manage water hyacinth in the Wouri Basin, and in the rest of Cameroon.
- Full Text:
- Date Issued: 2017
The role of achievement motivation on the interlanguage fossilization of middle-aged English-as-a-second-language learners
- Authors: Vujisic, Zoran
- Date: 2007
- Subjects: Second language acquisition Language and languages -- Study and teaching Fossilization (Linguistics) Interlanguage (Language learning) English language -- Study and teaching -- Foreign speakers Motivation in education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2368 , http://hdl.handle.net/10962/d1003748
- Description: Second language acquisition (SLA) is seldom entirely successful with adult learners. It has been suggested that all second language (L2) learners, in the process of mastering a target language (TL), develop a linguistic system that is self-contained and different from both the learner's native language and the TL. This system is referred to as 'interlanguage' (lL). In the process of SLA, IL evolves into an ever-closer approximation of the TL, and ideally, a learner's IL should continue to advance until it becomes equivalent to the TL. However, it has been observed that somewhere in the L2 learning process, IL may reach one or more plateaus during which the development of the IL is delayed or arrested. A permanent cessation of progress toward the TL is referred to as 'fossilization'. Researchers in SLA agree that motivation is one of the key factors influencing language-learning success and studies suggest that some language learning motivation may be related to the need for achievement. The purpose of this research was to establish if adult ESL learners are aware of fossilization and, to examine if motivation, and more specifically achievement motivation, is a factor in IL fossilization. The participants in this study consisted of 15 ESL learners in Puerto Rico who had at least eight years of formal ESL training. The instrument used to gather information included a questionnaire to obtain demographical and qualifying data, an 'English Language Proficiency Evaluation' to determine levels of IL fossilization, a 'Measure of Achievement Motivation' to ascertain achievement motive, and individual and group interviews in order to ascertain perception(s) regarding the role of motivation on fossilization and perceptions regarding the barriers to achieving TL competency. The research demonstrated that there is a moderate to strong positive relationship between IL fossilization and achievement motivation, i.e., high achievement motive is correlated to TL competency and descending levels of achievement motive are correlated to ascending levels of IL fossilization. The findings have significant implications for both ESL learning and instruction, and suggest that not all IL fossilization may be permanent.
- Full Text:
- Date Issued: 2007
- Authors: Vujisic, Zoran
- Date: 2007
- Subjects: Second language acquisition Language and languages -- Study and teaching Fossilization (Linguistics) Interlanguage (Language learning) English language -- Study and teaching -- Foreign speakers Motivation in education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2368 , http://hdl.handle.net/10962/d1003748
- Description: Second language acquisition (SLA) is seldom entirely successful with adult learners. It has been suggested that all second language (L2) learners, in the process of mastering a target language (TL), develop a linguistic system that is self-contained and different from both the learner's native language and the TL. This system is referred to as 'interlanguage' (lL). In the process of SLA, IL evolves into an ever-closer approximation of the TL, and ideally, a learner's IL should continue to advance until it becomes equivalent to the TL. However, it has been observed that somewhere in the L2 learning process, IL may reach one or more plateaus during which the development of the IL is delayed or arrested. A permanent cessation of progress toward the TL is referred to as 'fossilization'. Researchers in SLA agree that motivation is one of the key factors influencing language-learning success and studies suggest that some language learning motivation may be related to the need for achievement. The purpose of this research was to establish if adult ESL learners are aware of fossilization and, to examine if motivation, and more specifically achievement motivation, is a factor in IL fossilization. The participants in this study consisted of 15 ESL learners in Puerto Rico who had at least eight years of formal ESL training. The instrument used to gather information included a questionnaire to obtain demographical and qualifying data, an 'English Language Proficiency Evaluation' to determine levels of IL fossilization, a 'Measure of Achievement Motivation' to ascertain achievement motive, and individual and group interviews in order to ascertain perception(s) regarding the role of motivation on fossilization and perceptions regarding the barriers to achieving TL competency. The research demonstrated that there is a moderate to strong positive relationship between IL fossilization and achievement motivation, i.e., high achievement motive is correlated to TL competency and descending levels of achievement motive are correlated to ascending levels of IL fossilization. The findings have significant implications for both ESL learning and instruction, and suggest that not all IL fossilization may be permanent.
- Full Text:
- Date Issued: 2007
An investigation into the feasibility of incorporating didanosine into innovative solid lipid nanocarriers
- Authors: Wa Kasongo, Kasongo
- Date: 2010
- Subjects: Antiretroviral agents HIV infections -- Drug testing Didanosine Nanoparticles Drug delivery systems Nanostructured materials Lipids -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3800 , http://hdl.handle.net/10962/d1003278
- Description: The research undertaken in these studies aimed to investigate the feasibility of developing and manufacturing innovative solid lipid carriers, such as solid lipid nanoparticles (SLN) and/or nanostructured lipid carriers (NLC) using a hot high pressure homogenization method, for didanosine(DDI). In addition, studies using in vitro differential protein adsorption were undertaken to establish whether the SLN and/or NLC have the potential to deliver DDI to the central nervous system (CNS). Prior to initiating pre-formulation, formulation development and optimization studies of DDI-Ioaded SLN and/or NLC, it was necessary to develop and validate an analytical method for the in vitro quantitation and analysis of DDI. An accurate, precise and sensitive RP-HPLC method with UV detection set at 248 nm was developed, optimized and validated for the quantitative in vitro analysis of DDI in formulations. Pre-formulation studies were designed to evaluate the thermal stability of DDI and to select and characterize lipid excipients that may be used for the manufacture of the nanocarriers. It was established that DDI is thermostable at temperatures not exceeding 163°C and therefore a hot high pressure homogenization technique could be used to manufacture DDI-loaded SLN and/or NLC. Lipid screening studies revealed that DDI is poorly soluble in both solid and liquid lipids. A combination of Precirol® ATO 5 and Transcutol® HP was found to have the best solubilizing-potential for DDI of all lipids investigated. The inclusion of Transcutol® HP into Precirol® ATO 5 changed the polymorphic form of the solid lipid from the stable 13-modification to a material that exhibited the co-existence between α- and β-polymorphic forms. The relatively high solubility of DDI in Transcutol® HP compared to Precirol® ATO 5 was an indication that a solid lipid matrix prepared from a binary mixture of Precirol® ATO 5 and Transcutol® HP was likely to have a higher loading capacity and encapsulation efficiency for DDI than a matrix consisting of Precirol® ATO 5 alone. Furthermore, the potential for the solid lipid matrix to exist in the α- and/or β-modifications when Transcutol® HP was added to Precirol® ATO 5 suggested that expulsion of DDI from a solid lipid matrix during prolonged storage periods was likely to be minimal. Therefore it was considered logical to investigate the feasibility of incorporating DDI into NLC and not in SLN. However, due to the limited solubility of DDI in lipids, formulation development of DDI-loaded NLC commenced using small quantities of DDI. Formulation development and optimization studies of DDI-loaded NLC were initially aimed at selecting a surfactant system that was capable of stabilizing NLC in an aqueous environment. Solutol® HS alone or a ternary mixture consisting of Solutol® HS, Tween® 80 and Lutrol® F68 was found to stabilize the nanoparticles in terms of particle size and the polydispersity index. The use of the ternary mixture as the surfactant system was preferred to using Solutol® HS alone as Lutrol® F68 and especially Tween® 80 have been successfully used to target the delivery of API to the brain. Aqueous DDI-free and DDI-Ioaded NLC containing increasing amounts of DDI were manufactured using hot high pressure homogenization at 800 bar for three cycles. The NLC formulations were characterized in terms of particle size, polydispersity index, zeta potential, and polymorphism, degree of crystallinity, encapsulation efficiency (EE), shape and surface morphology. The mean particle size for all formulations was below 250 nm with narrow polydispersity indices, indicating that narrow particle size distribution had been achieved. The d99% values for all formulations tested, were generated using laser diffractometry, and were below 400 nm, with span values ranging from 0.84 - 1.19 also suggesting that a narrow particle size distribution had been achieved. The zeta potential values measured in double distilled water with the conductivity adjusted to 50 μS/cm ranged from -18.4 to -11.4 mV. In addition, all the formulations showed a decrease in the degree of crystallinity as compared to the bulk lipid material and WAXS shows that the formulations existed in a single β-modification form. Furthermore DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. These parameters remained unaffected for most formulations following storage for two months at 25°C. In addition these formulations contained a mixture of spherical and non-spherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations. These studies showed that it was feasible to develop and incorporate small amounts of DDI into NLC. However in order to use these delivery systems for oral administration of DDI to paediatric patients, strategies to improve the amount of DDI that could be loaded into the particles and to achieve high encapsulation efficiencies had to be developed. The limited solubility of DDI in lipid media was identified as a major factor that affected the loading capacity and encapsulation efficiency of DDI in the NLC. Therefore, a novel strategy aimed at increasing the saturation solubility of DDI in the lipid by attempting to increase the dissolution velocity of the drug in the lipid using a particle size reduction approach, was designed and investigated. DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid medium was reduced gradually using hot high pressure homogenization and the product obtained from these studies was used to manufacture DDI-loaded NLC using a cold high pressure homogenization procedure. Although the encapsulation efficiency and drug loading following use of this approach was relatively high, the particles were large and showed a tendency to grow in size leading to the formation of microparticles after storage for two months at 25°C. In addition, the degree of crystallinity of the nanoparticles increased rapidly over the same storage period which led to expulsion of DDI nanoparticles for the NLC, despite the DDI loading in NLC being unaffected. It was clearly evident that this new approach of manufacturing solid lipid nanocarriers could be used as a platform not only for enhancing the loading capacity of DDI in solid lipid nanocarriers but also for other hydrophilic drugs. Differential protein adsorption patterns of DDI-loaded NLC were generated in vitro using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in order to establish the potential for these systems to deliver DDI to the CNS. NLC formulations containing small amounts of DDI were used as these formulations showed a better stability profile than the formulation with a higher encapsulation efficiency and drug loading capacity. Furthermore, the encapsulation efficiency and drug loading of DDI were considered sufficient for use in 2-D PAGE studies. Data obtained from 2-D PAGE analysis reveal that DDI-loaded NLC preferentially adsorb proteins in vitro that are responsible for specific brain targeting in vivo. More importantly, these studies reveal that in addition to Tween® 80 that has already been shown to have the potential to target CDDS to the brain, Solutol® HS 15 has the potential to achieve a similar objective. Consequently, DDI-loaded NLC have the potential to deliver DDI to the brain and these results may be used as a platform for conducting in vivo studies to establish whether DDI can cross the blood brain barrier and enter the CNS when administered in NLC which may in turn lead to a major breakthrough in the management of HIV/AIDS and Aids Dementia Complex (ADC).
- Full Text:
- Date Issued: 2010
- Authors: Wa Kasongo, Kasongo
- Date: 2010
- Subjects: Antiretroviral agents HIV infections -- Drug testing Didanosine Nanoparticles Drug delivery systems Nanostructured materials Lipids -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3800 , http://hdl.handle.net/10962/d1003278
- Description: The research undertaken in these studies aimed to investigate the feasibility of developing and manufacturing innovative solid lipid carriers, such as solid lipid nanoparticles (SLN) and/or nanostructured lipid carriers (NLC) using a hot high pressure homogenization method, for didanosine(DDI). In addition, studies using in vitro differential protein adsorption were undertaken to establish whether the SLN and/or NLC have the potential to deliver DDI to the central nervous system (CNS). Prior to initiating pre-formulation, formulation development and optimization studies of DDI-Ioaded SLN and/or NLC, it was necessary to develop and validate an analytical method for the in vitro quantitation and analysis of DDI. An accurate, precise and sensitive RP-HPLC method with UV detection set at 248 nm was developed, optimized and validated for the quantitative in vitro analysis of DDI in formulations. Pre-formulation studies were designed to evaluate the thermal stability of DDI and to select and characterize lipid excipients that may be used for the manufacture of the nanocarriers. It was established that DDI is thermostable at temperatures not exceeding 163°C and therefore a hot high pressure homogenization technique could be used to manufacture DDI-loaded SLN and/or NLC. Lipid screening studies revealed that DDI is poorly soluble in both solid and liquid lipids. A combination of Precirol® ATO 5 and Transcutol® HP was found to have the best solubilizing-potential for DDI of all lipids investigated. The inclusion of Transcutol® HP into Precirol® ATO 5 changed the polymorphic form of the solid lipid from the stable 13-modification to a material that exhibited the co-existence between α- and β-polymorphic forms. The relatively high solubility of DDI in Transcutol® HP compared to Precirol® ATO 5 was an indication that a solid lipid matrix prepared from a binary mixture of Precirol® ATO 5 and Transcutol® HP was likely to have a higher loading capacity and encapsulation efficiency for DDI than a matrix consisting of Precirol® ATO 5 alone. Furthermore, the potential for the solid lipid matrix to exist in the α- and/or β-modifications when Transcutol® HP was added to Precirol® ATO 5 suggested that expulsion of DDI from a solid lipid matrix during prolonged storage periods was likely to be minimal. Therefore it was considered logical to investigate the feasibility of incorporating DDI into NLC and not in SLN. However, due to the limited solubility of DDI in lipids, formulation development of DDI-loaded NLC commenced using small quantities of DDI. Formulation development and optimization studies of DDI-loaded NLC were initially aimed at selecting a surfactant system that was capable of stabilizing NLC in an aqueous environment. Solutol® HS alone or a ternary mixture consisting of Solutol® HS, Tween® 80 and Lutrol® F68 was found to stabilize the nanoparticles in terms of particle size and the polydispersity index. The use of the ternary mixture as the surfactant system was preferred to using Solutol® HS alone as Lutrol® F68 and especially Tween® 80 have been successfully used to target the delivery of API to the brain. Aqueous DDI-free and DDI-Ioaded NLC containing increasing amounts of DDI were manufactured using hot high pressure homogenization at 800 bar for three cycles. The NLC formulations were characterized in terms of particle size, polydispersity index, zeta potential, and polymorphism, degree of crystallinity, encapsulation efficiency (EE), shape and surface morphology. The mean particle size for all formulations was below 250 nm with narrow polydispersity indices, indicating that narrow particle size distribution had been achieved. The d99% values for all formulations tested, were generated using laser diffractometry, and were below 400 nm, with span values ranging from 0.84 - 1.19 also suggesting that a narrow particle size distribution had been achieved. The zeta potential values measured in double distilled water with the conductivity adjusted to 50 μS/cm ranged from -18.4 to -11.4 mV. In addition, all the formulations showed a decrease in the degree of crystallinity as compared to the bulk lipid material and WAXS shows that the formulations existed in a single β-modification form. Furthermore DDI that had been incorporated into the NLC appeared to be molecularly dispersed in the lipid matrices. These parameters remained unaffected for most formulations following storage for two months at 25°C. In addition these formulations contained a mixture of spherical and non-spherical particles irrespective of the amount of DDI that was added during the manufacture of the formulations. These studies showed that it was feasible to develop and incorporate small amounts of DDI into NLC. However in order to use these delivery systems for oral administration of DDI to paediatric patients, strategies to improve the amount of DDI that could be loaded into the particles and to achieve high encapsulation efficiencies had to be developed. The limited solubility of DDI in lipid media was identified as a major factor that affected the loading capacity and encapsulation efficiency of DDI in the NLC. Therefore, a novel strategy aimed at increasing the saturation solubility of DDI in the lipid by attempting to increase the dissolution velocity of the drug in the lipid using a particle size reduction approach, was designed and investigated. DDI was dispersed in Transcutol® HP and the particle size of DDI in the liquid lipid medium was reduced gradually using hot high pressure homogenization and the product obtained from these studies was used to manufacture DDI-loaded NLC using a cold high pressure homogenization procedure. Although the encapsulation efficiency and drug loading following use of this approach was relatively high, the particles were large and showed a tendency to grow in size leading to the formation of microparticles after storage for two months at 25°C. In addition, the degree of crystallinity of the nanoparticles increased rapidly over the same storage period which led to expulsion of DDI nanoparticles for the NLC, despite the DDI loading in NLC being unaffected. It was clearly evident that this new approach of manufacturing solid lipid nanocarriers could be used as a platform not only for enhancing the loading capacity of DDI in solid lipid nanocarriers but also for other hydrophilic drugs. Differential protein adsorption patterns of DDI-loaded NLC were generated in vitro using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) in order to establish the potential for these systems to deliver DDI to the CNS. NLC formulations containing small amounts of DDI were used as these formulations showed a better stability profile than the formulation with a higher encapsulation efficiency and drug loading capacity. Furthermore, the encapsulation efficiency and drug loading of DDI were considered sufficient for use in 2-D PAGE studies. Data obtained from 2-D PAGE analysis reveal that DDI-loaded NLC preferentially adsorb proteins in vitro that are responsible for specific brain targeting in vivo. More importantly, these studies reveal that in addition to Tween® 80 that has already been shown to have the potential to target CDDS to the brain, Solutol® HS 15 has the potential to achieve a similar objective. Consequently, DDI-loaded NLC have the potential to deliver DDI to the brain and these results may be used as a platform for conducting in vivo studies to establish whether DDI can cross the blood brain barrier and enter the CNS when administered in NLC which may in turn lead to a major breakthrough in the management of HIV/AIDS and Aids Dementia Complex (ADC).
- Full Text:
- Date Issued: 2010
The effects of outsourcing practices conducted by organisations in Nairobi
- Authors: Wachira, Wanjungu
- Date: 2015
- Subjects: Contracting out , Industrial management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/4988 , vital:20775
- Description: The purpose of this study is to investigate the relationship between outsourcing and development in Nairobi. The key research question for this study is what are the impacts of outsourcing practices conducted by organisations in Nairobi? Data were obtained from questionnaires distributed in December 2010. A total of 85 profit-making firms in Nairobi with a sample of 165 management employees were selected for this study. The empirical findings obtained relate to four outsourcing theories. Transaction Cost Analysis (TCA) Theory focuses on the cost savings that result from outsourcing. Agency Outsourcing Theory centres on outsourcing firms hiring agents to achieve productivity. Hiring agents may result in permanent staff being retrenched and additional outsourcing personnel being contracted and job creation and/or job loss results. Expectation Confirmation Theory (ECT) emphasises the importance of an outsourcing provider conforming to quality management principles. Resource Based Theory (RBT) proposes that organisations need a collection of resources and capabilities to execute outsourcing successfully. Findings further suggested that outsourcing can yield positive and/or negative outcomes depending on risks encountered, the business environment, company policies, function/s to be outsourced, and the competence and commitment of an outsourcing vendor. To further enhance the positive impact of outsourcing three improvements need to be executed: formulation of standard policies, price regulations, and commitment of outsourcing firms in adhering to set contract deadlines. It is suggested that the following would allow organisations to gain more from outsourcing in the future: the adoption of international/offshore outsourcing practices, more commitment by outsourcing consultants, the standardisation of charges for outsourcing contracts, and the use of new technology that would improve how outsourcing is conducted. It is concluded that the positive impacts of outsourcing would foster development to some extent while the possible negative impact of outsourcing would impede development.
- Full Text:
- Date Issued: 2015
- Authors: Wachira, Wanjungu
- Date: 2015
- Subjects: Contracting out , Industrial management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/4988 , vital:20775
- Description: The purpose of this study is to investigate the relationship between outsourcing and development in Nairobi. The key research question for this study is what are the impacts of outsourcing practices conducted by organisations in Nairobi? Data were obtained from questionnaires distributed in December 2010. A total of 85 profit-making firms in Nairobi with a sample of 165 management employees were selected for this study. The empirical findings obtained relate to four outsourcing theories. Transaction Cost Analysis (TCA) Theory focuses on the cost savings that result from outsourcing. Agency Outsourcing Theory centres on outsourcing firms hiring agents to achieve productivity. Hiring agents may result in permanent staff being retrenched and additional outsourcing personnel being contracted and job creation and/or job loss results. Expectation Confirmation Theory (ECT) emphasises the importance of an outsourcing provider conforming to quality management principles. Resource Based Theory (RBT) proposes that organisations need a collection of resources and capabilities to execute outsourcing successfully. Findings further suggested that outsourcing can yield positive and/or negative outcomes depending on risks encountered, the business environment, company policies, function/s to be outsourced, and the competence and commitment of an outsourcing vendor. To further enhance the positive impact of outsourcing three improvements need to be executed: formulation of standard policies, price regulations, and commitment of outsourcing firms in adhering to set contract deadlines. It is suggested that the following would allow organisations to gain more from outsourcing in the future: the adoption of international/offshore outsourcing practices, more commitment by outsourcing consultants, the standardisation of charges for outsourcing contracts, and the use of new technology that would improve how outsourcing is conducted. It is concluded that the positive impacts of outsourcing would foster development to some extent while the possible negative impact of outsourcing would impede development.
- Full Text:
- Date Issued: 2015
The development of the hydraulic biotope concept within a catchment based hierarchical geomorphological model
- Authors: Wadeson, R A (Roy A)
- Date: 1996
- Subjects: Stream ecology -- South Africa Stream measurements -- South Africa Hydrology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4826 , http://hdl.handle.net/10962/d1005501
- Description: This thesis develops a technique for the identification, classification and quantification of instream flow environments. These features have been traditionally referred to as 'habitats' by lotic ecologists, in this research they are termed 'hydraulic biotopes'. The hydraulic biotope is the lowest of six nested levels of a hierarchical geomorphological model. This model has been developed as a tool to assist river managers, researchers and conservationists to categorise or classify rivers with respect to their geomorphic characteristics. Each level of the model provides data at a different level of resolution. This ranges from the broad scale catchment data to the site specific 'habitat' or hydraulic biotope data. Although this thesis is primarily concerned with the development of the hydraulic biotope, the interaction of all catchment variables needs to be recognised. Detailed analysis of hydraulic biotope data in the Buffalo River are presented within the broader hierarchical model. Consultation with lotic ecologists, together with a review of ecological literature, emphasised the need for a standardised terminology for the classification of ecologically significant instream flow environments. At present a fairly haphazard 'habitat' classification tends to be carried out by most researchers, this often leads to confusion in the identification and naming of different hydraulic biotopes ('habitats'). This confusion is exaggerated by the sharing of terminology between lotic ecology and fluvial geomorphology, usually for the categorisation of different types of features. A review of the ecological literature emphasises the importance of flow hydraulics within a river to describe the distribution of biota. The hydraulic variables considered to be most significant include velocity and depth. As river morphology directly determines the prevailing distribution of depth, velocity and substratum, it is obvious that there are important links to be made between fluvial geomorphology and lotic ecology. This thesis explores the potential of the hydraulic biotope as a tool to help develop those links. This thesis presents a standardised classification matrix for the identification of hydraulic biotopes. The matrix is simply based on water surface characteristics together with channel bed substratum. The validity of this matrix is tested by statistical analysis of hydraulic variables quantifying flow conditions within the various hydraulic biotope classes. Data is presented from four different river systems, each representing a different sedimentological environment. Where possible the influence of discharge has been considered. Results from more than 3000 data points show that hydraulic biotopes have distinct hydraulic characteristics in terms of velocity-depth ratio, Froude number, Reynolds number, 'roughness' Reynolds number and shear velocity. These hydraulic indices represent flow conditions both as an average within the water column, and near the bed. Statistical analysis shows that the hydraulic characteristics of the various hydraulic biotope classes are relatively consistent both within different fluvial environments and at different stages of flow. Unlike the morphological unit in which the hydraulic biotope is nested, in stream flow environments are shown to be temporally dynamic. Using the classification matrix as a tool for identification, hydraulic biotopes identified at one discharge are shown to be transformed from one class to another as a response to change in stage. The pattern of transformation is shown to be consistent within different sedimentological environments. An examination of the associations between hydraulic biotopes and morphological units demonstrates that, although some hydraulic biotopes are common to all morphological units (backwater pools, pools and runs), some features have specific associations. In this study rapids were found to be prevalent in bedrock pavement, bedrock pool and plane bed morphology, while cascades, chutes and riffles were common to plane bed, step and riffle morphology. Results from this research indicate that the hydraulic biotope, within the hierarchical geomorphological model, has the potential to aid the prediction of channel adjustment and associated 'habitat' (hydraulic biotope) transformation in response to changes in flow and sediment yield. These are likely to become increasingly important issues as South Africa strives to maintain a balance between the development of water resources to meet the needs of the rapidly expanding population, whilst at the same time maintaining the fluvial environment for sustainable use.
- Full Text:
- Date Issued: 1996
- Authors: Wadeson, R A (Roy A)
- Date: 1996
- Subjects: Stream ecology -- South Africa Stream measurements -- South Africa Hydrology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4826 , http://hdl.handle.net/10962/d1005501
- Description: This thesis develops a technique for the identification, classification and quantification of instream flow environments. These features have been traditionally referred to as 'habitats' by lotic ecologists, in this research they are termed 'hydraulic biotopes'. The hydraulic biotope is the lowest of six nested levels of a hierarchical geomorphological model. This model has been developed as a tool to assist river managers, researchers and conservationists to categorise or classify rivers with respect to their geomorphic characteristics. Each level of the model provides data at a different level of resolution. This ranges from the broad scale catchment data to the site specific 'habitat' or hydraulic biotope data. Although this thesis is primarily concerned with the development of the hydraulic biotope, the interaction of all catchment variables needs to be recognised. Detailed analysis of hydraulic biotope data in the Buffalo River are presented within the broader hierarchical model. Consultation with lotic ecologists, together with a review of ecological literature, emphasised the need for a standardised terminology for the classification of ecologically significant instream flow environments. At present a fairly haphazard 'habitat' classification tends to be carried out by most researchers, this often leads to confusion in the identification and naming of different hydraulic biotopes ('habitats'). This confusion is exaggerated by the sharing of terminology between lotic ecology and fluvial geomorphology, usually for the categorisation of different types of features. A review of the ecological literature emphasises the importance of flow hydraulics within a river to describe the distribution of biota. The hydraulic variables considered to be most significant include velocity and depth. As river morphology directly determines the prevailing distribution of depth, velocity and substratum, it is obvious that there are important links to be made between fluvial geomorphology and lotic ecology. This thesis explores the potential of the hydraulic biotope as a tool to help develop those links. This thesis presents a standardised classification matrix for the identification of hydraulic biotopes. The matrix is simply based on water surface characteristics together with channel bed substratum. The validity of this matrix is tested by statistical analysis of hydraulic variables quantifying flow conditions within the various hydraulic biotope classes. Data is presented from four different river systems, each representing a different sedimentological environment. Where possible the influence of discharge has been considered. Results from more than 3000 data points show that hydraulic biotopes have distinct hydraulic characteristics in terms of velocity-depth ratio, Froude number, Reynolds number, 'roughness' Reynolds number and shear velocity. These hydraulic indices represent flow conditions both as an average within the water column, and near the bed. Statistical analysis shows that the hydraulic characteristics of the various hydraulic biotope classes are relatively consistent both within different fluvial environments and at different stages of flow. Unlike the morphological unit in which the hydraulic biotope is nested, in stream flow environments are shown to be temporally dynamic. Using the classification matrix as a tool for identification, hydraulic biotopes identified at one discharge are shown to be transformed from one class to another as a response to change in stage. The pattern of transformation is shown to be consistent within different sedimentological environments. An examination of the associations between hydraulic biotopes and morphological units demonstrates that, although some hydraulic biotopes are common to all morphological units (backwater pools, pools and runs), some features have specific associations. In this study rapids were found to be prevalent in bedrock pavement, bedrock pool and plane bed morphology, while cascades, chutes and riffles were common to plane bed, step and riffle morphology. Results from this research indicate that the hydraulic biotope, within the hierarchical geomorphological model, has the potential to aid the prediction of channel adjustment and associated 'habitat' (hydraulic biotope) transformation in response to changes in flow and sediment yield. These are likely to become increasingly important issues as South Africa strives to maintain a balance between the development of water resources to meet the needs of the rapidly expanding population, whilst at the same time maintaining the fluvial environment for sustainable use.
- Full Text:
- Date Issued: 1996
A history of the Thembu and their relationship with the Cape, 1850-1900
- Authors: Wagenaar, E J C
- Date: 1989
- Subjects: Tembu (African people) -- History Missions -- South Africa -- Cape of Good Hope South Africa -- History -- Frontier Wars, 1811-1878 Cape of Good Hope (South Africa) -- Politics and government Land tenure -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2569 , http://hdl.handle.net/10962/d1002422
- Description: Present day Thembuland is situated roughly between the Mthatha and Kei rivers. It lies within the south-western portion of the political unit which has been known since 1976 as the Republic of Transkei. It comprises the territories formerly known as Emigrant Thembuland (now the districts of Cala and Cofimvaba) and Thembuland Proper, i.e. the districts of Mqanduli, Umtata, Engcobo and Bomvanaland. We have evidence that Thembu people had already settled in Thembu land Proper, at the Mbashe river, by the beginning of the 17th century. Pioneering clans many have entered the territory at a much earlier date. In the 1830's some clans broke away from the Mbashe settlement, and moved to the region of present day Queenstown. In 1853 their lands were included in the so-called Tambookie Location, which in 1871 became the district of Glen Grey. Emigrant Thembuland came into existence in 1865 when four chiefs from Glen Grey accepted Sir Philip Wodehouse's offer to settle on the lands across the White Kei whence the Xhosa chief Sarhili had been expelled in 1857. This thesis deals with the history of the people who lived in these territories between 1850 and 1900.
- Full Text:
- Date Issued: 1989
- Authors: Wagenaar, E J C
- Date: 1989
- Subjects: Tembu (African people) -- History Missions -- South Africa -- Cape of Good Hope South Africa -- History -- Frontier Wars, 1811-1878 Cape of Good Hope (South Africa) -- Politics and government Land tenure -- South Africa -- Cape of Good Hope
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2569 , http://hdl.handle.net/10962/d1002422
- Description: Present day Thembuland is situated roughly between the Mthatha and Kei rivers. It lies within the south-western portion of the political unit which has been known since 1976 as the Republic of Transkei. It comprises the territories formerly known as Emigrant Thembuland (now the districts of Cala and Cofimvaba) and Thembuland Proper, i.e. the districts of Mqanduli, Umtata, Engcobo and Bomvanaland. We have evidence that Thembu people had already settled in Thembu land Proper, at the Mbashe river, by the beginning of the 17th century. Pioneering clans many have entered the territory at a much earlier date. In the 1830's some clans broke away from the Mbashe settlement, and moved to the region of present day Queenstown. In 1853 their lands were included in the so-called Tambookie Location, which in 1871 became the district of Glen Grey. Emigrant Thembuland came into existence in 1865 when four chiefs from Glen Grey accepted Sir Philip Wodehouse's offer to settle on the lands across the White Kei whence the Xhosa chief Sarhili had been expelled in 1857. This thesis deals with the history of the people who lived in these territories between 1850 and 1900.
- Full Text:
- Date Issued: 1989
Environmental education : a strategy for primary teacher education
- Authors: Wagiet, Razeena
- Date: 1997
- Subjects: Environmental education -- Study and teaching (Elementary) Environmental education -- Study and teaching (Elementary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1512 , http://hdl.handle.net/10962/d1003394
- Description: This research focuses on environmental education in initial teacher education, and is grounded in three interlinked and widely recognised assumptions. First, that education for sustainable living can assist in resolving some environmental problems that are contributing to the environmental crises of sustainability currently facing South Africa and the rest of the world. Second, that education for sustainable living can assist in the establishment of a new environmental ethic that will foster a sustainable way of living. Third, that teacher education is a vital process for the attainment of both. These assumptions inform the aim of this research, which is to explore the potential for the implementation of education for sustainable living, and to identify a strategy for this, for initial teacher education, for senior primary school student teachers in the Western Cape. The strategy is derived following the grounded theory approach, developed through the case study method. In the process of identifying the strategy, this study establishes that there are challenges at macro, meso and micro levels that are obstructing the changes necessary for education for sustainable living. Change theory provides the basis for explaining these shortcomings, by helping to identify the barriers that might obstruct the realisation of the changes that are necessary for education for sustainable living. These challenges need to be perceived in the light of overcoming three sets of barriers in the way of the potential implementation of education for sustainable living in teacher education. First are those that can be ascribed to the formal education system that, while clinging to Western, Eurocentric values on the one hand, bave also failed to secure a policy for environmental education on the other. Second are the barriers ascribed to the teacher educators themselves, with the whole notion of their powerlessness at its core. Finally, there are the logistical barriers, which encompass, for example, time and financial constraints. With these barriers as a backdrop, to facilitate the incorporation of environmental education into initial teacher education, the study identifies a need for the development of a strategy to secure that education for sustainable living assumes its rightful place in the curriculum for initial teacher education. This framework emerges from the theory grounded in the interviewees' responses during the research, and from the theory grounded in the literature. Central to this framework is for education for sustainable living to contribute to the realisation of real change, change that would further the transformation of our conflict-riddled and inequitable society towards a more democratic and just one. This thesis demonstrates that the realisation of the changes necessary for education for sustainable living demand a reconstruction of current teacher education in order to secure and to sustain an appropriate and sound education ethic to form the basis of a trans formative teacher education curriculum for sustainable living within initial teacher education. Except formal policy, but central to overcoming these barriers, is the need for professional development programmes for teacher educators. A strategy in this regard, is outlined.
- Full Text:
- Date Issued: 1997
- Authors: Wagiet, Razeena
- Date: 1997
- Subjects: Environmental education -- Study and teaching (Elementary) Environmental education -- Study and teaching (Elementary) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1512 , http://hdl.handle.net/10962/d1003394
- Description: This research focuses on environmental education in initial teacher education, and is grounded in three interlinked and widely recognised assumptions. First, that education for sustainable living can assist in resolving some environmental problems that are contributing to the environmental crises of sustainability currently facing South Africa and the rest of the world. Second, that education for sustainable living can assist in the establishment of a new environmental ethic that will foster a sustainable way of living. Third, that teacher education is a vital process for the attainment of both. These assumptions inform the aim of this research, which is to explore the potential for the implementation of education for sustainable living, and to identify a strategy for this, for initial teacher education, for senior primary school student teachers in the Western Cape. The strategy is derived following the grounded theory approach, developed through the case study method. In the process of identifying the strategy, this study establishes that there are challenges at macro, meso and micro levels that are obstructing the changes necessary for education for sustainable living. Change theory provides the basis for explaining these shortcomings, by helping to identify the barriers that might obstruct the realisation of the changes that are necessary for education for sustainable living. These challenges need to be perceived in the light of overcoming three sets of barriers in the way of the potential implementation of education for sustainable living in teacher education. First are those that can be ascribed to the formal education system that, while clinging to Western, Eurocentric values on the one hand, bave also failed to secure a policy for environmental education on the other. Second are the barriers ascribed to the teacher educators themselves, with the whole notion of their powerlessness at its core. Finally, there are the logistical barriers, which encompass, for example, time and financial constraints. With these barriers as a backdrop, to facilitate the incorporation of environmental education into initial teacher education, the study identifies a need for the development of a strategy to secure that education for sustainable living assumes its rightful place in the curriculum for initial teacher education. This framework emerges from the theory grounded in the interviewees' responses during the research, and from the theory grounded in the literature. Central to this framework is for education for sustainable living to contribute to the realisation of real change, change that would further the transformation of our conflict-riddled and inequitable society towards a more democratic and just one. This thesis demonstrates that the realisation of the changes necessary for education for sustainable living demand a reconstruction of current teacher education in order to secure and to sustain an appropriate and sound education ethic to form the basis of a trans formative teacher education curriculum for sustainable living within initial teacher education. Except formal policy, but central to overcoming these barriers, is the need for professional development programmes for teacher educators. A strategy in this regard, is outlined.
- Full Text:
- Date Issued: 1997
The identification of criteria to be utilised in mathematical diagnostic tests
- Authors: Wagner-Welsh, Shirley Joy
- Date: 2008
- Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
- Full Text:
- Date Issued: 2008
- Authors: Wagner-Welsh, Shirley Joy
- Date: 2008
- Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
- Full Text:
- Date Issued: 2008
Resource utilization and reproduction of the hermit crab Clibanarius virescens (Crustacea: Decapoda : Anomura)
- Authors: Wait, Michelle
- Subjects: Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10599 , http://hdl.handle.net/10948/1553 , Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Description: Clibanarius virescens (Krauss) is a common and abundant hermit crab along the East coast of South Africa. Despite this, its biology is poorly known, both in South Africa and throughout the rest of its range in the West Indo-Pacific region. This study focuses on the descriptive analysis of the shell resource used by C. virescens and of the effects of this resource on crab populations. The underlying hypothesis of the study is that biogeographically imposed gradients in the morphology of intertidal gastropod shells used by hermit crabs affect hermit crab population parameters. The gradient of potential change in the shell resource was captured by sampling at 12 localities, encompassing the range of C. virescens in South Africa. Seasonal changes in shell use, population structure and reproduction at a single locality (Cape Recife) were recorded over a period of 13 months. The breeding season of C. virescens at the southern extreme of its range extended from December to June. The population structure shows some seasonal change, but no clear trends emerge. The shell resource changed substantially in nature over the region studied. Based on shell use, localities clustered into separate southern and northern groups with a break occurring between Dwesa and Coffee Bay. Southern localities were characterised by use of Burnupena cincta, B. lagenaria and B. pubescens. Northern localities were characterised by the use of Morula granulata, M. nodosa and Peristernia forskalii. Intertidal shells used by C. virescens show fewer adaptations to predation in southern localities than shells from northern localities. Southern shells ii are relatively large, light and have wider apertures than those from northern localities which are generally smaller, heavier and have decreased aperture widths. Shell parameters affect population size-distributions as southern crabs were larger and heavier than northern crabs. C. virescens show sexual size dimorphism in which male crabs uniformly dominate the larger size classes at all localities. Differences in the sex ratio between males and females show more variable patterns. Most southern localities show no difference in the number of male and female crabs, but most northern localities show a skewed sex ratio in favour of females. Shell use and population size distributions of females affect reproductive output. Southern females produced significantly larger clutches than northern females. Reproductive output was related to crab mass and shell volume. Shell use patterns conform to the biogeographical regions in the range of the study and have a clear effect on both the population size distributions and reproductive output of Clibanarius virescens.
- Full Text:
- Authors: Wait, Michelle
- Subjects: Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10599 , http://hdl.handle.net/10948/1553 , Hermit crabs -- South Africa , Hermit crabs -- South Africa -- Reproduction
- Description: Clibanarius virescens (Krauss) is a common and abundant hermit crab along the East coast of South Africa. Despite this, its biology is poorly known, both in South Africa and throughout the rest of its range in the West Indo-Pacific region. This study focuses on the descriptive analysis of the shell resource used by C. virescens and of the effects of this resource on crab populations. The underlying hypothesis of the study is that biogeographically imposed gradients in the morphology of intertidal gastropod shells used by hermit crabs affect hermit crab population parameters. The gradient of potential change in the shell resource was captured by sampling at 12 localities, encompassing the range of C. virescens in South Africa. Seasonal changes in shell use, population structure and reproduction at a single locality (Cape Recife) were recorded over a period of 13 months. The breeding season of C. virescens at the southern extreme of its range extended from December to June. The population structure shows some seasonal change, but no clear trends emerge. The shell resource changed substantially in nature over the region studied. Based on shell use, localities clustered into separate southern and northern groups with a break occurring between Dwesa and Coffee Bay. Southern localities were characterised by use of Burnupena cincta, B. lagenaria and B. pubescens. Northern localities were characterised by the use of Morula granulata, M. nodosa and Peristernia forskalii. Intertidal shells used by C. virescens show fewer adaptations to predation in southern localities than shells from northern localities. Southern shells ii are relatively large, light and have wider apertures than those from northern localities which are generally smaller, heavier and have decreased aperture widths. Shell parameters affect population size-distributions as southern crabs were larger and heavier than northern crabs. C. virescens show sexual size dimorphism in which male crabs uniformly dominate the larger size classes at all localities. Differences in the sex ratio between males and females show more variable patterns. Most southern localities show no difference in the number of male and female crabs, but most northern localities show a skewed sex ratio in favour of females. Shell use and population size distributions of females affect reproductive output. Southern females produced significantly larger clutches than northern females. Reproductive output was related to crab mass and shell volume. Shell use patterns conform to the biogeographical regions in the range of the study and have a clear effect on both the population size distributions and reproductive output of Clibanarius virescens.
- Full Text:
HPLC analysis and pharmacokinetics of cyclizine
- Authors: Walker, Roderick Bryan
- Date: 1995
- Subjects: High performance liquid chromatography Piperazine Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3801 , http://hdl.handle.net/10962/d1003279
- Description: The investigations detailed in this dissertation have been conducted to address the paucity of pharmacokinetic information, in published literature, pertaining to cyclizine. The areas of investigation have included the selective quantitation of both cyclizine and its demethylated metabolite, norcyclizine in serum and urine, assessment of stability of both compounds in stored biological samples, dosage form analysis, dissolution rate testing of tablets, and bioavailability and pharmacokinetics following administration of an intravenous solution, and tablets to humans. High-performance liquid chromatography (HPLC) was used as the main analytical technique throughout these studies. An original HPLC method employing ultraviolet detection with a limit of quantitation of 5μg/ℓ was developed for the determination of cyclizine in serum and both cyclizine and norcyclizine in urine, Solid-phase extraction using extraction columns packed with reversed-phase C18 material, and followed by a simple phase-separation step proved successful for the accurate and precise isolation of the compounds. The validated method was applied to the analysis of serum and urine samples from a pilot study in which a single volunteer was administered 50mg of cyclizine hydrochloride. Several samples collected during the pilot study revealed the presence of both drug and metabolite in concentrations below the limit of detection. In order to improve the selectivity and sensitivity of the analytical method an HPLC method with electrochemical detection operating in the "oxidative-screen" mode was developed. The solid-phase extraction procedure was modified slightly and the method found to be precise, accurate, selective and highly sensitive with a limit of quantitation of Iμg/g/l for both cyclizine and norcyclizine in both serum and urine. This method was applied to the determination of both compounds after intravenous and oral administration of cyclizine to humans. HPLC with electrochemical detection was used for the analysis of samples collected during dissolution studies on the batch of tablets used for pharmacokinetic studies. In addition, this method was used to assess content uniformity of the tablets and of samples from the batch of intravenous ampoules of cyclizine lactate. Dissolution studies showed that all tablets tested passed the compendial specifications for cyclizine. Content uniformity assessment revealed that within-batch uniformity existed for both the tablets and ampoules and, therefore, variations in pharmacokinetic parameters for the drug would more than likely be as a result of inter- and intra-individual variability within the subject population. Pharmacokinetic information for cyclizine was obtained following administration of an intravenous bolus dose of cyclizine lactate as a solution, oral administration of cyclizine hydrochloride as a single dose of 50mg and as fixed multiple doses of 50mg every 8 hours for five days. Further information was acquired following administration of single doses of 100mg and 150mg cyclizine hydrochloride. Data collected from these studies were evaluated using both compartmental and non-compartmental techniques. Cyclizine was rapidly absorbed following oral administration with mean kₐ = 1.54 hr⁻¹ and was found to have an absolute bioavailability (F) of 0.47. The presence of norcyclizine in serum following oral and not intravenous dosing suggests cyclizine is susceptible to "first-pass" metabolism in either the gut wall or the I iver. Mean ClTOT determined following the intravenous dose was 0.865 ℓ/hr/kg. The mean ClTOT of 0.823 ℓ/hr/kg calculated following oral dosing, using a unique value of F for each subject compared favourahly with that obtained following intravenous dosing. Renal clearance of cyclizine is negligihle indicating that non-renal routes of elimination account for the majority of removal of cyclizine form the body. Cyclizine is extensively distributed and the mean Vz following an intravenous dose was 16.70 ℓ/kg. This value is lower than that calculated from all oral studies from which the mean Vz was determined to be 25.74 ℓ/kg. Cyclizine is eliminated slowly with a mean elimination t½ = 20.11 hours. Cyclizine dose not appear to follow dosedependent kinetics and therefore, inability to predict steady state levels are more than likely due to accumulation as a result of frequent dosing rather than saturation of elimination mechanisms. Modelling of intravenous data to one-compartment (lBCM), two-compartment (2BCM) and threecompartment models indicated that the pharmacokinetics of cyclizine can be adequately described by a 3BCM. The drug is rapidly distributed into a "shallow" peripheral compartment (α = 9.44 hr⁻¹ , and k₂₁ = 2.09 hr⁻¹ ), and slowly distributed to the "deep" peripheral compartment (β = 0.451 hr⁻¹ and k₃₁ = 0.120 hr⁻¹ ). Modelling of all oral data indicated that a 2BCM best described the pharmacokinetics of the drug, however, distribution to the peripheral compartment is not as rapid as to the "shallow" peripheral compartment following the intravenous dose. Mean distribution parameters were α = 0.64 hr⁻¹1 and, k₂₁ = 0.39 hr⁻¹. Mean CITOT following intravenous dosing of 0.70 ℓ/hr/kg was similar to the mean CIToT of 0.73 ℓ/hr/kg determined after oral dosing. The mean distribution volume at steady state determined following intravenous dosing (17.78 ℓ/kg) was lower than that obtained from the oral studies (25.52 ℓ/kg). The mean terminal elimination half-lives calculated for cyclizine following fitting of intravenous and oral data was 25.09 hours. In general, mean pharmacokinetic parameters calculated following titting of data to a 2BCM after oral administration correlate closely with those calculated using non-compartmental techniques. However, the pharmacokinetics following intravenous dosing are better described by a 3BCM and a close correlation between parameters estimated using noncompartmental techniques and compartmental techniques is evident when a 3BCM model is used.
- Full Text:
- Date Issued: 1995
- Authors: Walker, Roderick Bryan
- Date: 1995
- Subjects: High performance liquid chromatography Piperazine Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3801 , http://hdl.handle.net/10962/d1003279
- Description: The investigations detailed in this dissertation have been conducted to address the paucity of pharmacokinetic information, in published literature, pertaining to cyclizine. The areas of investigation have included the selective quantitation of both cyclizine and its demethylated metabolite, norcyclizine in serum and urine, assessment of stability of both compounds in stored biological samples, dosage form analysis, dissolution rate testing of tablets, and bioavailability and pharmacokinetics following administration of an intravenous solution, and tablets to humans. High-performance liquid chromatography (HPLC) was used as the main analytical technique throughout these studies. An original HPLC method employing ultraviolet detection with a limit of quantitation of 5μg/ℓ was developed for the determination of cyclizine in serum and both cyclizine and norcyclizine in urine, Solid-phase extraction using extraction columns packed with reversed-phase C18 material, and followed by a simple phase-separation step proved successful for the accurate and precise isolation of the compounds. The validated method was applied to the analysis of serum and urine samples from a pilot study in which a single volunteer was administered 50mg of cyclizine hydrochloride. Several samples collected during the pilot study revealed the presence of both drug and metabolite in concentrations below the limit of detection. In order to improve the selectivity and sensitivity of the analytical method an HPLC method with electrochemical detection operating in the "oxidative-screen" mode was developed. The solid-phase extraction procedure was modified slightly and the method found to be precise, accurate, selective and highly sensitive with a limit of quantitation of Iμg/g/l for both cyclizine and norcyclizine in both serum and urine. This method was applied to the determination of both compounds after intravenous and oral administration of cyclizine to humans. HPLC with electrochemical detection was used for the analysis of samples collected during dissolution studies on the batch of tablets used for pharmacokinetic studies. In addition, this method was used to assess content uniformity of the tablets and of samples from the batch of intravenous ampoules of cyclizine lactate. Dissolution studies showed that all tablets tested passed the compendial specifications for cyclizine. Content uniformity assessment revealed that within-batch uniformity existed for both the tablets and ampoules and, therefore, variations in pharmacokinetic parameters for the drug would more than likely be as a result of inter- and intra-individual variability within the subject population. Pharmacokinetic information for cyclizine was obtained following administration of an intravenous bolus dose of cyclizine lactate as a solution, oral administration of cyclizine hydrochloride as a single dose of 50mg and as fixed multiple doses of 50mg every 8 hours for five days. Further information was acquired following administration of single doses of 100mg and 150mg cyclizine hydrochloride. Data collected from these studies were evaluated using both compartmental and non-compartmental techniques. Cyclizine was rapidly absorbed following oral administration with mean kₐ = 1.54 hr⁻¹ and was found to have an absolute bioavailability (F) of 0.47. The presence of norcyclizine in serum following oral and not intravenous dosing suggests cyclizine is susceptible to "first-pass" metabolism in either the gut wall or the I iver. Mean ClTOT determined following the intravenous dose was 0.865 ℓ/hr/kg. The mean ClTOT of 0.823 ℓ/hr/kg calculated following oral dosing, using a unique value of F for each subject compared favourahly with that obtained following intravenous dosing. Renal clearance of cyclizine is negligihle indicating that non-renal routes of elimination account for the majority of removal of cyclizine form the body. Cyclizine is extensively distributed and the mean Vz following an intravenous dose was 16.70 ℓ/kg. This value is lower than that calculated from all oral studies from which the mean Vz was determined to be 25.74 ℓ/kg. Cyclizine is eliminated slowly with a mean elimination t½ = 20.11 hours. Cyclizine dose not appear to follow dosedependent kinetics and therefore, inability to predict steady state levels are more than likely due to accumulation as a result of frequent dosing rather than saturation of elimination mechanisms. Modelling of intravenous data to one-compartment (lBCM), two-compartment (2BCM) and threecompartment models indicated that the pharmacokinetics of cyclizine can be adequately described by a 3BCM. The drug is rapidly distributed into a "shallow" peripheral compartment (α = 9.44 hr⁻¹ , and k₂₁ = 2.09 hr⁻¹ ), and slowly distributed to the "deep" peripheral compartment (β = 0.451 hr⁻¹ and k₃₁ = 0.120 hr⁻¹ ). Modelling of all oral data indicated that a 2BCM best described the pharmacokinetics of the drug, however, distribution to the peripheral compartment is not as rapid as to the "shallow" peripheral compartment following the intravenous dose. Mean distribution parameters were α = 0.64 hr⁻¹1 and, k₂₁ = 0.39 hr⁻¹. Mean CITOT following intravenous dosing of 0.70 ℓ/hr/kg was similar to the mean CIToT of 0.73 ℓ/hr/kg determined after oral dosing. The mean distribution volume at steady state determined following intravenous dosing (17.78 ℓ/kg) was lower than that obtained from the oral studies (25.52 ℓ/kg). The mean terminal elimination half-lives calculated for cyclizine following fitting of intravenous and oral data was 25.09 hours. In general, mean pharmacokinetic parameters calculated following titting of data to a 2BCM after oral administration correlate closely with those calculated using non-compartmental techniques. However, the pharmacokinetics following intravenous dosing are better described by a 3BCM and a close correlation between parameters estimated using noncompartmental techniques and compartmental techniques is evident when a 3BCM model is used.
- Full Text:
- Date Issued: 1995
Public utility pricing and industrial decentralization in South Africa
- Authors: Wallis, Joseph Lyall
- Date: 1984
- Subjects: Industrial management -- South Africa Public utilities -- South Africa Pricing -- South Africa Decentralization in management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1030 , http://hdl.handle.net/10962/d1003747
- Description: From Introduction: 1. Background to the thesis: During the 1950' sand 1960' s it would appear that the explicit objectives of economic policy in South Africa were full employment and economic growth with some occasional emphasis on the pursuit of relative price stability. Other goals such as efficiency in resource allocation and the pursuit of an "acceptable" income distribution were at best implicit and subordinate to these objectives. This is exemplified by the fact that a number of key prices which were controlled by the authorities such as the exchange rate, interest rates and public utility tariffs were generally set at levels which were either over- or under-priced relative to factor scarcities throughout this period.
- Full Text:
- Date Issued: 1984
- Authors: Wallis, Joseph Lyall
- Date: 1984
- Subjects: Industrial management -- South Africa Public utilities -- South Africa Pricing -- South Africa Decentralization in management -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1030 , http://hdl.handle.net/10962/d1003747
- Description: From Introduction: 1. Background to the thesis: During the 1950' sand 1960' s it would appear that the explicit objectives of economic policy in South Africa were full employment and economic growth with some occasional emphasis on the pursuit of relative price stability. Other goals such as efficiency in resource allocation and the pursuit of an "acceptable" income distribution were at best implicit and subordinate to these objectives. This is exemplified by the fact that a number of key prices which were controlled by the authorities such as the exchange rate, interest rates and public utility tariffs were generally set at levels which were either over- or under-priced relative to factor scarcities throughout this period.
- Full Text:
- Date Issued: 1984
An investigation into the antidiabetic and catalytic properties of oxovanadium(IV) complexes
- Authors: Walmsley, Ryan Steven
- Date: 2012
- Subjects: Hypoglycemic agents Ligands (Biochemistry) Complex compounds Potentiometry Proton transfer reactions Stability Imidazoles Vanadium catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4320 , http://hdl.handle.net/10962/d1004978
- Description: In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.
- Full Text:
- Date Issued: 2012
- Authors: Walmsley, Ryan Steven
- Date: 2012
- Subjects: Hypoglycemic agents Ligands (Biochemistry) Complex compounds Potentiometry Proton transfer reactions Stability Imidazoles Vanadium catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4320 , http://hdl.handle.net/10962/d1004978
- Description: In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.
- Full Text:
- Date Issued: 2012
The assessment and management of bycatch and discards in the South African demersal trawl fishery
- Authors: Walmsley, Sarah Ann
- Date: 2005
- Subjects: Bycatches (Fisheries) Fishery management -- South Africa Fisheries -- South Africa Trawls and trawling -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5228 , http://hdl.handle.net/10962/d1005071
- Description: Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.
- Full Text:
- Date Issued: 2005
- Authors: Walmsley, Sarah Ann
- Date: 2005
- Subjects: Bycatches (Fisheries) Fishery management -- South Africa Fisheries -- South Africa Trawls and trawling -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5228 , http://hdl.handle.net/10962/d1005071
- Description: Over the past few decades it has become recognised that an ecosystem approach is required to manage world fisheries. Management strategies must ensure that non-target (bycatch) as well as target catches are sustainable. To achieve this, detailed commercial catch and biological information is required. The composition of catches made by trawlers operating off the south and west coasts of South Africa was investigated. Distinct fishing areas were identified on each coast, based on target species and fishing depth. Catch composition differed markedly among the areas defined. Although hake Merluccius sp. dominated South Coast catches, a large proportion of the catch was composed of bycatch. On the West Coast, hake dominated catches and this domination increased with increasing depth. On both coasts approximately 90% of the observed nominal catch was processed and landed. Estimates of annual discards suggested that the fishery discarded 38 thousand tons of fish per annum (16% of the nominal trawl catch). The data also indicated that hake discarding, the capture of linefish and the increased targeting of high value species might be cause for concern. Spatial analysis indicated that a variety of factors such as trawling position, catch size and catch composition affects bycatch dynamics. The monkfish Lophius vomerinus is a common bycatch species that has been increasingly targeted by demersal trawlers. This study showed that L. vomerinus is a slow-growing, long-lived species (West Coast males L∞ = 68.50cm TL, t₀ = -1.69yr, K = 0.10yr⁻¹; West Coast females L∞ = 110.23cm TL, t₀ = -1.54yr, K = 0.05yr⁻¹; South Coast sexes combined L∞ = 70.12cm TL, t₀ = - 0.80yr, K = 0.11yr⁻¹), that matures at approximately 6 years of age. These traits could have serious management implications for the species. Per-recruit analysis suggested that the stock might be overexploited, although further investigation is required to confirm this. Solutions were suggested for each of the concerns raised, taking cognisance of the differences observed between the South and West Coasts and the economic dependence of South Coast companies on bycatch. The needs of future research were considered.
- Full Text:
- Date Issued: 2005
An investigation into the bacterial diversity associated with South African latrunculid sponges that produce bioactive secondary metabolites
- Authors: Walmsley, Tara Aisling
- Date: 2014
- Subjects: Sponges -- South Africa -- Algoa Bay , Sponges -- Classification , Metabolites -- South Africa -- Algoa Bay , Marine metabolites -- South Africa -- Algoa Bay , PQQ (Biochemistry) , Bacterial diversity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4109 , http://hdl.handle.net/10962/d1012943
- Description: Algoa Bay Latrunculid sponges are well known for their production of cytotoxic pyrroloiminoquinones with speculation that these secondary metabolites may have a microbial origin. This study describes a thorough investigation into the bacterial community associated with Tsitsikamma favus, Tsitsikamma scurra a newly described Latrunculia sp. and a yellow encrusting sponge associated with T. scurra. Molecular and chemical characterisation were used in conjunction with traditional taxonomy in identification of the sponge specimens. The 28S rRNA and COX1 analysis confirmed the traditional taxonomy with T. favus and T. scurra being very closely related. Chemical analysis revealed that T. favus and T. scurra shared the discorhabdins 2,4-debromo-3-dihydrodiscorhabdin C, 7,8-dehydro-3-dihydrodiscorhabdin C and 14-bromo-1-hydroxy-discorhabdin V in common with each other and Tsitsikamma pedunculata indicating that these pyrroloiminoquinones are common to Tsitsikamma sponges in general. The bacterial community associated with T. favus was explored using 16S rRNA molecular techniques including DGGE, clonal libraries of full length 16S rRNA genes, as well as 454 pyrosequencing. DGGE analysis revealed that the bacterial community associated with T. favus appeared to be highly conserved, which was confirmed by both the clone library and 454 pyrosequencing, with the Betaproteobacteria as the most dominant class. Further exploration into T. favus, as well as T. scurra, Latrunculia sp. and the yellow encrusting sponge indicated that the bacterial populations associated with each of these sponge species were conserved and species specific. OTU analysis to the species level revealed that T. favus and T. scurra shared an abundant Spirochaete species in common while the most abundant species in the Latrunculia sp. and the yellow encrusting sponge belonged to the class Betaproteobacteria. The exclusivity of the tsitsikammamines to T. favus precipitated attempts to culture the T. favus associated bacteria, with a focus on the dominant betaproteobacterium as indicated by the 16S rRNA clone library. Actinobacteria associated with the Algoa Bay sponge specimens were also cultured and the actinobacterial isolates were sent for screening against Mycobacterium aurum with two Kocuria kristinae isolates and a Streptomyces albdioflavus isolate showing good antimycobacterial activity.
- Full Text:
- Date Issued: 2014
- Authors: Walmsley, Tara Aisling
- Date: 2014
- Subjects: Sponges -- South Africa -- Algoa Bay , Sponges -- Classification , Metabolites -- South Africa -- Algoa Bay , Marine metabolites -- South Africa -- Algoa Bay , PQQ (Biochemistry) , Bacterial diversity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4109 , http://hdl.handle.net/10962/d1012943
- Description: Algoa Bay Latrunculid sponges are well known for their production of cytotoxic pyrroloiminoquinones with speculation that these secondary metabolites may have a microbial origin. This study describes a thorough investigation into the bacterial community associated with Tsitsikamma favus, Tsitsikamma scurra a newly described Latrunculia sp. and a yellow encrusting sponge associated with T. scurra. Molecular and chemical characterisation were used in conjunction with traditional taxonomy in identification of the sponge specimens. The 28S rRNA and COX1 analysis confirmed the traditional taxonomy with T. favus and T. scurra being very closely related. Chemical analysis revealed that T. favus and T. scurra shared the discorhabdins 2,4-debromo-3-dihydrodiscorhabdin C, 7,8-dehydro-3-dihydrodiscorhabdin C and 14-bromo-1-hydroxy-discorhabdin V in common with each other and Tsitsikamma pedunculata indicating that these pyrroloiminoquinones are common to Tsitsikamma sponges in general. The bacterial community associated with T. favus was explored using 16S rRNA molecular techniques including DGGE, clonal libraries of full length 16S rRNA genes, as well as 454 pyrosequencing. DGGE analysis revealed that the bacterial community associated with T. favus appeared to be highly conserved, which was confirmed by both the clone library and 454 pyrosequencing, with the Betaproteobacteria as the most dominant class. Further exploration into T. favus, as well as T. scurra, Latrunculia sp. and the yellow encrusting sponge indicated that the bacterial populations associated with each of these sponge species were conserved and species specific. OTU analysis to the species level revealed that T. favus and T. scurra shared an abundant Spirochaete species in common while the most abundant species in the Latrunculia sp. and the yellow encrusting sponge belonged to the class Betaproteobacteria. The exclusivity of the tsitsikammamines to T. favus precipitated attempts to culture the T. favus associated bacteria, with a focus on the dominant betaproteobacterium as indicated by the 16S rRNA clone library. Actinobacteria associated with the Algoa Bay sponge specimens were also cultured and the actinobacterial isolates were sent for screening against Mycobacterium aurum with two Kocuria kristinae isolates and a Streptomyces albdioflavus isolate showing good antimycobacterial activity.
- Full Text:
- Date Issued: 2014
Regulation of tryptophan-2,3-dioxygenase and pineal indoleamines by selected tryptophan derivatives and antidepressants
- Authors: Walsh, Harold Archibold
- Date: 1997
- Subjects: Antidepressants Tryptophan -- Physiological effect Tryptophan -- Therapeutic use Depression, Mental -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4017 , http://hdl.handle.net/10962/d1004077
- Description: The regulation of tryptophan-2,3-dioxygenase (TDO) (EC 1.13.1.12) and, to a lesser extent, pineal indoleamines, both in vitro and in vivo, is examined in this study. Rat liver TDO is a cytosolic enzyme which plays a crucial role in the regulation of circulating tryptophan (TRP) levels. Stimulation of this enzyme by heme enhances the catabolism of TRP, making less TRP available for uptake into the brain and other tissues, and for protein synthesis. At pH 7, the enzyme has an approximate Km of 100μM, is subject to substrate inhibition immediately beyond Sopt([S] at Vmax), and response of the enzyme is cooperative in both uninhibited and inhibited regions. Hill analysis of the uninhibited region reveals a biphasic plot and two classes of binding sites. Negative cooperativity is brought about through deprotonation of the enzyme. Substrate iphibition also occurs at both acidic and basic pH values with concomitant shifts in Sopt. The results obtained indicate that substrate inhibition could be an additional mechanism whereby the flux through the TRP-kynurenine pathway is regulated. TDO is subject to a diurnal rhythm, with peak activity during the pre-dark period and the loweSt activity towards the end of the dark period. It is possible that the enzyme controls the synthesis of the neurotransmitter serotonin (5-HT), and that the circadian rhythm in TDO activity is due to the endogenous rhythm of melatonin (aMT) production by the pineal gland. In the present study, aMT displaces TRP from bovine serum albumin (BSA) in vitro, and it is therefore possible for the indoleamine to regulate the availability of TRP for uptake into the brain for conversion to its derivatives. Chronic intraperitoneal administration of aMT affects physiological hepatic parameters in rats, such as TDO activity and stromal fatty acid composition, whilst no observable effect is demonstrable with respect to protein synthesis, nucleic acid metabolism, membrane fatty acid composition and pineal indole biosynthesis. On the other hand, chronic treatment of rats with antidepressants, the tricyclic desmethylimipramine (DMI) and the selective serotonin reuptake inhibitor (SSRI), fluoxetine, reveals significant negative alterations in TDO concentrations and pineal indole amine synthesis. Combining aMT with any of these two drugs normalises the activity of the hepatic enzyme. DMI is found to be an effective inhibitor of TDO in the micromolar range in vitro, and also affects total enzyme concentrations in vivo. Fluoxetine has no effect on TDO in vitro, but in vivo also reduces total enzyme levels in the liver. However, the SSRI does not affect conjugation between apo- and holoenzyme. Instead, it decreases extant holoenzyme levels. Indoleamine synthesis by the pineal gland, in organ culture, is altered by both antidepressants, although in different ways. DMI increases N-acetylserotonin levels and reduces the output of methoxyindole acetic acid and meth6xytryptophol. Fluoxetine treatment markedly reduces aMT concentrations and also brings about high levels of the 5-HT catabolites, 5-hydroxytryptophol and 5-hydroxyindole acetic acid. Insulin also lowers aMT synthesis significantly in pineal organ cultures, via a mechamsm that involves inhibition of the enzyme, N-acetyl transferase, that regulates aMT synthesis. The effects of insulin on pineal indole metabolism are due to the observation that a carbohydrate rich diet which induces insulin release elevates plasma TRP and brain 5-HT, but has no effect on pineal TRP and indole amine synthesis. It could thus be possible for insulin to have an effect on the pineal, since the latter is outside the blood brain barrier. The finilings of this study support the biogenic amine deficiency hypothesis, implicating some of the major biogenic amines such as noradrenaline (NA), 5-HT and aMT in depression. There is believed to be a deficiency of NA and 5-HT at their respective synapses in the depressed state. The drug DMI could act, firstly, by inhibiting TDO and thus increasing plasma TRP levels, and could, secondly, stimulate NA release and inhibit NA reuptake at the pineal membrane. The combined effect would be to enhance aMT synthesis, with eventual remission. Fluoxetine, on the other hand, appears to utilize a slightly different mode of action to DMI, which seems to focus on the preservation of 5-HT. The fact that aMT counteracts the effects of both antidepressants, and restores the activity of TDO to that of the controls, is also consistent with the observation that the therapeutic action of drugs such as these coincides willi the restoration of normal plasma levels of the neurohormone in depressives. In view of the biogenic amine deficiency hypothesis of depression and the contentious claim that TDO is the major peripheral determinant of brain TRP, brain 5-HT and ultimately aMT, the regulation of TDO is investigated and discussed. The study concludes that TDO activity is regulated by a number of endogenous compounds which are mainly derivatives of TRP, such as aMT and oxidized nicotinamide adenine dinucleotide and exogenous substances, of which DMI and fluoxetine are but two. In addition, modulation of IDO activity in depression appears to be an important aspect of antidepressant action. aMT, the product of the pineal gland, also has the potential to increase plasma TRP and hence forebrain TRP levels, and ultimately 5-HT concentrations, firstly by displacing TRP from serum albumin and secondly by inhibiting TDO.
- Full Text:
- Date Issued: 1997
- Authors: Walsh, Harold Archibold
- Date: 1997
- Subjects: Antidepressants Tryptophan -- Physiological effect Tryptophan -- Therapeutic use Depression, Mental -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4017 , http://hdl.handle.net/10962/d1004077
- Description: The regulation of tryptophan-2,3-dioxygenase (TDO) (EC 1.13.1.12) and, to a lesser extent, pineal indoleamines, both in vitro and in vivo, is examined in this study. Rat liver TDO is a cytosolic enzyme which plays a crucial role in the regulation of circulating tryptophan (TRP) levels. Stimulation of this enzyme by heme enhances the catabolism of TRP, making less TRP available for uptake into the brain and other tissues, and for protein synthesis. At pH 7, the enzyme has an approximate Km of 100μM, is subject to substrate inhibition immediately beyond Sopt([S] at Vmax), and response of the enzyme is cooperative in both uninhibited and inhibited regions. Hill analysis of the uninhibited region reveals a biphasic plot and two classes of binding sites. Negative cooperativity is brought about through deprotonation of the enzyme. Substrate iphibition also occurs at both acidic and basic pH values with concomitant shifts in Sopt. The results obtained indicate that substrate inhibition could be an additional mechanism whereby the flux through the TRP-kynurenine pathway is regulated. TDO is subject to a diurnal rhythm, with peak activity during the pre-dark period and the loweSt activity towards the end of the dark period. It is possible that the enzyme controls the synthesis of the neurotransmitter serotonin (5-HT), and that the circadian rhythm in TDO activity is due to the endogenous rhythm of melatonin (aMT) production by the pineal gland. In the present study, aMT displaces TRP from bovine serum albumin (BSA) in vitro, and it is therefore possible for the indoleamine to regulate the availability of TRP for uptake into the brain for conversion to its derivatives. Chronic intraperitoneal administration of aMT affects physiological hepatic parameters in rats, such as TDO activity and stromal fatty acid composition, whilst no observable effect is demonstrable with respect to protein synthesis, nucleic acid metabolism, membrane fatty acid composition and pineal indole biosynthesis. On the other hand, chronic treatment of rats with antidepressants, the tricyclic desmethylimipramine (DMI) and the selective serotonin reuptake inhibitor (SSRI), fluoxetine, reveals significant negative alterations in TDO concentrations and pineal indole amine synthesis. Combining aMT with any of these two drugs normalises the activity of the hepatic enzyme. DMI is found to be an effective inhibitor of TDO in the micromolar range in vitro, and also affects total enzyme concentrations in vivo. Fluoxetine has no effect on TDO in vitro, but in vivo also reduces total enzyme levels in the liver. However, the SSRI does not affect conjugation between apo- and holoenzyme. Instead, it decreases extant holoenzyme levels. Indoleamine synthesis by the pineal gland, in organ culture, is altered by both antidepressants, although in different ways. DMI increases N-acetylserotonin levels and reduces the output of methoxyindole acetic acid and meth6xytryptophol. Fluoxetine treatment markedly reduces aMT concentrations and also brings about high levels of the 5-HT catabolites, 5-hydroxytryptophol and 5-hydroxyindole acetic acid. Insulin also lowers aMT synthesis significantly in pineal organ cultures, via a mechamsm that involves inhibition of the enzyme, N-acetyl transferase, that regulates aMT synthesis. The effects of insulin on pineal indole metabolism are due to the observation that a carbohydrate rich diet which induces insulin release elevates plasma TRP and brain 5-HT, but has no effect on pineal TRP and indole amine synthesis. It could thus be possible for insulin to have an effect on the pineal, since the latter is outside the blood brain barrier. The finilings of this study support the biogenic amine deficiency hypothesis, implicating some of the major biogenic amines such as noradrenaline (NA), 5-HT and aMT in depression. There is believed to be a deficiency of NA and 5-HT at their respective synapses in the depressed state. The drug DMI could act, firstly, by inhibiting TDO and thus increasing plasma TRP levels, and could, secondly, stimulate NA release and inhibit NA reuptake at the pineal membrane. The combined effect would be to enhance aMT synthesis, with eventual remission. Fluoxetine, on the other hand, appears to utilize a slightly different mode of action to DMI, which seems to focus on the preservation of 5-HT. The fact that aMT counteracts the effects of both antidepressants, and restores the activity of TDO to that of the controls, is also consistent with the observation that the therapeutic action of drugs such as these coincides willi the restoration of normal plasma levels of the neurohormone in depressives. In view of the biogenic amine deficiency hypothesis of depression and the contentious claim that TDO is the major peripheral determinant of brain TRP, brain 5-HT and ultimately aMT, the regulation of TDO is investigated and discussed. The study concludes that TDO activity is regulated by a number of endogenous compounds which are mainly derivatives of TRP, such as aMT and oxidized nicotinamide adenine dinucleotide and exogenous substances, of which DMI and fluoxetine are but two. In addition, modulation of IDO activity in depression appears to be an important aspect of antidepressant action. aMT, the product of the pineal gland, also has the potential to increase plasma TRP and hence forebrain TRP levels, and ultimately 5-HT concentrations, firstly by displacing TRP from serum albumin and secondly by inhibiting TDO.
- Full Text:
- Date Issued: 1997
Plaatje's African romance: the translation of tragedy in Mhudi and other writings
- Authors: Walter, Brian Ernest
- Date: 2001
- Subjects: Plaatje, Sol. T. (Solomon Tshekisho), 1876-1932. Mhudi Race in literature Politics in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2188 , http://hdl.handle.net/10962/d1002230
- Description: This study brings together Plaatje’s politicaland literary visions, arguing that the one informs the other. Plaatje’s literary work is used as a starting point for the discussion, and the first chapter explores the relationship of his political and artistic visions. Mhudi is his definitive romance text, and it is argued that Plaatje’s romance visionin this text is reflected in his political thinking, and in turn reflected by it. His romance work was part of a literary romance tradition which Plaatje both drew upon and transformed, and thus the basic features of romance are explored in Chapter Two. Plaatje’s work is situated between two influential romance models, therefore Chapter Two also discusses the romances of Shakespeare, whomPlaatje read as reflectinga non-racial humanism that was translatable into the African context, in terms of political vision and of literary text. His other models were the colonial romances of Haggard. It is argued that, while Plaatje could glean many elements fromHaggardthat suited his purposes as an African, specifically a SouthAfrican, writer, he nevertheless—despite his own pro-British leanings, qualified though they might have been by the complexities of his colonial context—would not have represented Africa and Africans in terms of the exotic other in the way Haggard clearly did. Thus Plaatje, in terms of his romance vision, may have usedmanyofthe themesand techniques of Haggardianromance, but consistently qualified these colonial works by using the more classically shaped Shakespearean romance structure at the deep level of his work. The third chapter examines Haggard’s romance, but differentiates between two Haggardian types, the completed or resolved romance, whichis more classical in its form, and evokes an image of a completed quest, as well as the necessity of the quester entering the world again. Haggard’s “completed” African romance, it is argued, is resolved only in terms of a colonial vision. Chapter Four, by contrast, examines examples of his unresolved African romance, in which African ideals implode, and show themselves to be inneed of foreign intervention. It is argued that Haggard’s image of Africa was based on the unresolved or incomplete romance. His vision of Africa was such that it could not in itself provide the materialfor completed romance. This vision saw intervention as the only option for South Africa. While Plaatje uses elements of Haggard’s “incomplete” romance models when writing Mhudi, he handles both his narrative and politicalcommentaryin this text in terms of his own politicalthought. This non-racial politicalvisionis guided by his belief that virtue and vice are not the monopoly of any colour, a non-racialism he associates with Shakespeare. However, within the context of the South Africa of his fictionand of his life, this non-racial ideal is constantly under threat. It is partly threatened by political forces, but also challenged by moral changes within individuals and societies. In Chapter Five the examination of Plaatje’s work begins withhis Boer War Diary, inwhicha romance structure is sought beneath his diurnal observations and political optimismduring a time of warfare and siege. The discussion of this text is followed by a reading of Native Life in South Africa in which it is argued that Plaatje looks, in the midst of personal and social suffering, for that which can translate a tragic situation into romance resolution. “Translation” is used in a broad sense, echoing Plaatje’s view of the importance of translation for cross-cultural understanding and harmony. The arguments of Chapter Five are extended into Chapter Six, where a reading of Mhudi places emphasis on the possibilities of change implied in romance. Plaatje’s non-racial humanism recognizes the great potential for injustice and human suffering within the context of South African racism, but constantly seeks to translate such suffering into the triumph of romance. While the narrative of Mhudi concludes on a romance peak, tensions between the tragic and romance possibilities alert the reader to the sense that, despite its romance resolution, something has been lost in the translation of the potential tragedy into romance.
- Full Text:
- Date Issued: 2001
- Authors: Walter, Brian Ernest
- Date: 2001
- Subjects: Plaatje, Sol. T. (Solomon Tshekisho), 1876-1932. Mhudi Race in literature Politics in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2188 , http://hdl.handle.net/10962/d1002230
- Description: This study brings together Plaatje’s politicaland literary visions, arguing that the one informs the other. Plaatje’s literary work is used as a starting point for the discussion, and the first chapter explores the relationship of his political and artistic visions. Mhudi is his definitive romance text, and it is argued that Plaatje’s romance visionin this text is reflected in his political thinking, and in turn reflected by it. His romance work was part of a literary romance tradition which Plaatje both drew upon and transformed, and thus the basic features of romance are explored in Chapter Two. Plaatje’s work is situated between two influential romance models, therefore Chapter Two also discusses the romances of Shakespeare, whomPlaatje read as reflectinga non-racial humanism that was translatable into the African context, in terms of political vision and of literary text. His other models were the colonial romances of Haggard. It is argued that, while Plaatje could glean many elements fromHaggardthat suited his purposes as an African, specifically a SouthAfrican, writer, he nevertheless—despite his own pro-British leanings, qualified though they might have been by the complexities of his colonial context—would not have represented Africa and Africans in terms of the exotic other in the way Haggard clearly did. Thus Plaatje, in terms of his romance vision, may have usedmanyofthe themesand techniques of Haggardianromance, but consistently qualified these colonial works by using the more classically shaped Shakespearean romance structure at the deep level of his work. The third chapter examines Haggard’s romance, but differentiates between two Haggardian types, the completed or resolved romance, whichis more classical in its form, and evokes an image of a completed quest, as well as the necessity of the quester entering the world again. Haggard’s “completed” African romance, it is argued, is resolved only in terms of a colonial vision. Chapter Four, by contrast, examines examples of his unresolved African romance, in which African ideals implode, and show themselves to be inneed of foreign intervention. It is argued that Haggard’s image of Africa was based on the unresolved or incomplete romance. His vision of Africa was such that it could not in itself provide the materialfor completed romance. This vision saw intervention as the only option for South Africa. While Plaatje uses elements of Haggard’s “incomplete” romance models when writing Mhudi, he handles both his narrative and politicalcommentaryin this text in terms of his own politicalthought. This non-racial politicalvisionis guided by his belief that virtue and vice are not the monopoly of any colour, a non-racialism he associates with Shakespeare. However, within the context of the South Africa of his fictionand of his life, this non-racial ideal is constantly under threat. It is partly threatened by political forces, but also challenged by moral changes within individuals and societies. In Chapter Five the examination of Plaatje’s work begins withhis Boer War Diary, inwhicha romance structure is sought beneath his diurnal observations and political optimismduring a time of warfare and siege. The discussion of this text is followed by a reading of Native Life in South Africa in which it is argued that Plaatje looks, in the midst of personal and social suffering, for that which can translate a tragic situation into romance resolution. “Translation” is used in a broad sense, echoing Plaatje’s view of the importance of translation for cross-cultural understanding and harmony. The arguments of Chapter Five are extended into Chapter Six, where a reading of Mhudi places emphasis on the possibilities of change implied in romance. Plaatje’s non-racial humanism recognizes the great potential for injustice and human suffering within the context of South African racism, but constantly seeks to translate such suffering into the triumph of romance. While the narrative of Mhudi concludes on a romance peak, tensions between the tragic and romance possibilities alert the reader to the sense that, despite its romance resolution, something has been lost in the translation of the potential tragedy into romance.
- Full Text:
- Date Issued: 2001