Rural livelihood diversification in semi-arid districts of Zimbabwe : an analysis of Muzarabani, Gokwe and Mwenezi districts
- Authors: Musevenzi, Julius
- Date: 2012
- Subjects: Rural development -- Zimbabwe , Rural poor -- Zimbabwe , Zimbabwe -- Rural conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9149 , http://hdl.handle.net/10948/d1018922
- Description: This study focuses on rural livelihood diversification and improvement in dry districts of Zimbabwe during the period from 2000 to 2010. It establishes and documents livelihood activities and interventions in three semi-arid districts in Zimbabwe, analyses evidence for rural livelihood diversification and improvement and related challenges, and analyses institutional and policy issues that determine rural livelihood development in the politically charged period from 2000 to 2010. Rural livelihood diversification and improvement is not a recent phenomenon. For years, rural people have diversified their livelihoods for different economic reasons. Despite several studies on rural livelihoods in Zimbabwe, no similar studies have been done to determine the types of livelihood diversification that occur in a politically charged environment and whether they improve people‟s livelihoods. The study was guided by both the sustainable livelihoods framework and the actor oriented approach. Qualitative methodology was used for the overall data collection. Firstly data was collected „from the top‟ through in-depth interviews with officials from government institutions, non-governmental organisations and community leadership structures. Secondly data was collected „from the bottom up‟ through selected participatory methods in study areas. The overall study findings show that despite having increased livelihood interventions in all semi-arid areas, the politically fraught atmosphere constrained livelihood improvement and poverty remained. Although evidence for livelihood diversification is undisputed in the study, the extent to which it contributed to livelihood improvement was limited. The extended period of political constraint reversed some of the livelihood improvement gains recorded by external interventions. As most of the support was targeted at addressing the immediate food needs of the poor in semi-arid districts, this affected the number of long-term interventions targeted at sustainable livelihood development. The study found that the changing policies and institutional arrangements constrained and limited the potential of some of the livelihood strategies adopted during the period under study and as a result most livelihood activities were limited to survival strategies. The study shows that despite a decline in agricultural production during the period under study, it remained the major livelihood activity. Agricultural activities such as cotton and maize production and livestock rearing experienced a decline, but were partially revived through external support from both the government and nongovernmental organisations. Agriculture as a livelihood activity largely benefited from external interventions that rehabilitated irrigation infrastructure and the provision of agricultural inputs during the period. However, despite the dominance of agriculture as a livelihood activity in semi-arid areas non-farm livelihood activities, both locally initiated and externally fostered, played a significant role in supporting rural livelihoods. Poaching and wild fruit harvesting provided food for immediate consumption, whilst gold and diamond panning, wood carving and the commercialisation of non-timber forest products generated cash income for rural livelihoods. Non-farm external livelihood interventions identified resulted in a number of rural livelihood development models important for future rural development. These models were developed around the commercialisation of non-timber forest products for cash income generation, rural human capital development through vocational skills training and rural small livestock asset development. Human capital resulted in the development of rural industry in the form of community based enterprises. Indirectly it also contributed to migrant labour that sent cash and goods back home. The study shows that it is evident that in a politically charged environment livelihood diversification has a range of positive effects. The re-emergence of the barter exchange economy in rural communities contributed to livelihood diversification although sustainability was limited. It is also possible for both barter exchange and the cash market to co-exist in a politically charged environment. The study also shows that traditional leadership and local authorities in study areas became more politicised and militarised and this diverted them from facilitating and supporting rural development and inhibited rural livelihood development efforts by different rural players. The study found that rural livelihoods are not static, and they adapted as best they could in the face of exogenous trends and shocks. Rural areas underwent deep transformations as a result of political dynamics, local livelihood initiatives and external livelihood support. Rural livelihoods changed as rural people devised combined livelihood strategies that went beyond farming. However, in contrast to the widely accepted argument that diversification plays an important role in poverty alleviation, this was clearly not the case in Zimbabwe‟s politically charged environment. This study contributes to the development debate with a case study on the type and extent of livelihood diversification strategies possible in a politically charged environment. Methodologically the study contributes to the possible application of a dual data collection system where data is collected from the top using different methods from those used to collect data from the bottom. This enriched the data at triangulation phase during analysis. The study also contributes to the understanding of the political economy, the type of rural livelihood development possible in politically charged environments, and to how rural people in Zimbabwe react and behave in an endeavour to survive. There was an increased role played by external interventions in livelihood diversification but the extent of their contribution to positive livelihood outcomes was constrained by the politically charged environment that prompted the interventions in the first place. The normal processes of policy development and implementation changed as the role of politicians in planning and implementation became evident and policy aims shifted from rural development to political party self-preservation.
- Full Text:
- Date Issued: 2012
- Authors: Musevenzi, Julius
- Date: 2012
- Subjects: Rural development -- Zimbabwe , Rural poor -- Zimbabwe , Zimbabwe -- Rural conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9149 , http://hdl.handle.net/10948/d1018922
- Description: This study focuses on rural livelihood diversification and improvement in dry districts of Zimbabwe during the period from 2000 to 2010. It establishes and documents livelihood activities and interventions in three semi-arid districts in Zimbabwe, analyses evidence for rural livelihood diversification and improvement and related challenges, and analyses institutional and policy issues that determine rural livelihood development in the politically charged period from 2000 to 2010. Rural livelihood diversification and improvement is not a recent phenomenon. For years, rural people have diversified their livelihoods for different economic reasons. Despite several studies on rural livelihoods in Zimbabwe, no similar studies have been done to determine the types of livelihood diversification that occur in a politically charged environment and whether they improve people‟s livelihoods. The study was guided by both the sustainable livelihoods framework and the actor oriented approach. Qualitative methodology was used for the overall data collection. Firstly data was collected „from the top‟ through in-depth interviews with officials from government institutions, non-governmental organisations and community leadership structures. Secondly data was collected „from the bottom up‟ through selected participatory methods in study areas. The overall study findings show that despite having increased livelihood interventions in all semi-arid areas, the politically fraught atmosphere constrained livelihood improvement and poverty remained. Although evidence for livelihood diversification is undisputed in the study, the extent to which it contributed to livelihood improvement was limited. The extended period of political constraint reversed some of the livelihood improvement gains recorded by external interventions. As most of the support was targeted at addressing the immediate food needs of the poor in semi-arid districts, this affected the number of long-term interventions targeted at sustainable livelihood development. The study found that the changing policies and institutional arrangements constrained and limited the potential of some of the livelihood strategies adopted during the period under study and as a result most livelihood activities were limited to survival strategies. The study shows that despite a decline in agricultural production during the period under study, it remained the major livelihood activity. Agricultural activities such as cotton and maize production and livestock rearing experienced a decline, but were partially revived through external support from both the government and nongovernmental organisations. Agriculture as a livelihood activity largely benefited from external interventions that rehabilitated irrigation infrastructure and the provision of agricultural inputs during the period. However, despite the dominance of agriculture as a livelihood activity in semi-arid areas non-farm livelihood activities, both locally initiated and externally fostered, played a significant role in supporting rural livelihoods. Poaching and wild fruit harvesting provided food for immediate consumption, whilst gold and diamond panning, wood carving and the commercialisation of non-timber forest products generated cash income for rural livelihoods. Non-farm external livelihood interventions identified resulted in a number of rural livelihood development models important for future rural development. These models were developed around the commercialisation of non-timber forest products for cash income generation, rural human capital development through vocational skills training and rural small livestock asset development. Human capital resulted in the development of rural industry in the form of community based enterprises. Indirectly it also contributed to migrant labour that sent cash and goods back home. The study shows that it is evident that in a politically charged environment livelihood diversification has a range of positive effects. The re-emergence of the barter exchange economy in rural communities contributed to livelihood diversification although sustainability was limited. It is also possible for both barter exchange and the cash market to co-exist in a politically charged environment. The study also shows that traditional leadership and local authorities in study areas became more politicised and militarised and this diverted them from facilitating and supporting rural development and inhibited rural livelihood development efforts by different rural players. The study found that rural livelihoods are not static, and they adapted as best they could in the face of exogenous trends and shocks. Rural areas underwent deep transformations as a result of political dynamics, local livelihood initiatives and external livelihood support. Rural livelihoods changed as rural people devised combined livelihood strategies that went beyond farming. However, in contrast to the widely accepted argument that diversification plays an important role in poverty alleviation, this was clearly not the case in Zimbabwe‟s politically charged environment. This study contributes to the development debate with a case study on the type and extent of livelihood diversification strategies possible in a politically charged environment. Methodologically the study contributes to the possible application of a dual data collection system where data is collected from the top using different methods from those used to collect data from the bottom. This enriched the data at triangulation phase during analysis. The study also contributes to the understanding of the political economy, the type of rural livelihood development possible in politically charged environments, and to how rural people in Zimbabwe react and behave in an endeavour to survive. There was an increased role played by external interventions in livelihood diversification but the extent of their contribution to positive livelihood outcomes was constrained by the politically charged environment that prompted the interventions in the first place. The normal processes of policy development and implementation changed as the role of politicians in planning and implementation became evident and policy aims shifted from rural development to political party self-preservation.
- Full Text:
- Date Issued: 2012
An analysis of ionospheric response to geomagnetic disturbances over South Africa and Antarctica
- Authors: Ngwira, Chigomezyo Mudala
- Date: 2012
- Subjects: Geomagnetism -- South Africa , Geomagnetism -- Antarctica , Ionospheric storms -- South Africa , Ionospheric storms -- Antarctica
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5534 , http://hdl.handle.net/10962/d1012957
- Description: The ionosphere is of practical importance for satellite-based communication and navigation systems due to its variable refractive nature which affects the propagation of trans-ionospheric radio signals. This thesis reports on the first attempt to investigate the mechanisms responsible for the generation of positive ionospheric storm effects over mid-latitude South Africa. The storm response on 15 May 2005 was associated with equatorward neutral winds and the passage of travelling ionospheric disturbances (TIDs). The two TIDs reported in this thesis propagated with average velocities of ∼438 m/s and ∼515 m/s respectively. The velocity of the first TID (i.e. 438 m/s) is consistent with the velocities calculated in other studies for the same storm event. In a second case study, the positive storm enhancement on both 25 and 27 July 2004 lasted for more than 7 hours, and were classified as long-duration positive ionospheric storm effects. It has been suggested that the long-duration positive storm effects could have been caused by large-scale thermospheric wind circulation and enhanced equatorward neutral winds. These processes were in turn most likely to have been driven by enhanced and sustained energy input in the high-latitude ionosphere due to Joule heating and particle energy injection. This is evident by the prolonged high-level geomagnetic activity on both 25 and 27 July. This thesis also reports on the phase scintillation investigation at the South African Antarctic polar research station during solar minimum conditions. The multi-instrument approach that was used shows that the scintillation events were associated with auroral electron precipitation and that substorms play an essential role in the production of scintillation in the high latitudes. Furthermore, the investigation reveals that external energy injection into the ionosphere is necessary for the development of high-latitude irregularities which produce scintillation. Finally, this thesis highlights inadequate data resources as one of the major shortcomings to be addressed in order to fully understand and distinguish between the various ionospheric storm drivers over the Southern Africa mid-latitude region. The results presented in this thesis on the ionospheric response during geomagnetic storms provide essential information to direct further investigation aimed at developing this emerging field of study in South Africa.
- Full Text:
- Date Issued: 2012
- Authors: Ngwira, Chigomezyo Mudala
- Date: 2012
- Subjects: Geomagnetism -- South Africa , Geomagnetism -- Antarctica , Ionospheric storms -- South Africa , Ionospheric storms -- Antarctica
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5534 , http://hdl.handle.net/10962/d1012957
- Description: The ionosphere is of practical importance for satellite-based communication and navigation systems due to its variable refractive nature which affects the propagation of trans-ionospheric radio signals. This thesis reports on the first attempt to investigate the mechanisms responsible for the generation of positive ionospheric storm effects over mid-latitude South Africa. The storm response on 15 May 2005 was associated with equatorward neutral winds and the passage of travelling ionospheric disturbances (TIDs). The two TIDs reported in this thesis propagated with average velocities of ∼438 m/s and ∼515 m/s respectively. The velocity of the first TID (i.e. 438 m/s) is consistent with the velocities calculated in other studies for the same storm event. In a second case study, the positive storm enhancement on both 25 and 27 July 2004 lasted for more than 7 hours, and were classified as long-duration positive ionospheric storm effects. It has been suggested that the long-duration positive storm effects could have been caused by large-scale thermospheric wind circulation and enhanced equatorward neutral winds. These processes were in turn most likely to have been driven by enhanced and sustained energy input in the high-latitude ionosphere due to Joule heating and particle energy injection. This is evident by the prolonged high-level geomagnetic activity on both 25 and 27 July. This thesis also reports on the phase scintillation investigation at the South African Antarctic polar research station during solar minimum conditions. The multi-instrument approach that was used shows that the scintillation events were associated with auroral electron precipitation and that substorms play an essential role in the production of scintillation in the high latitudes. Furthermore, the investigation reveals that external energy injection into the ionosphere is necessary for the development of high-latitude irregularities which produce scintillation. Finally, this thesis highlights inadequate data resources as one of the major shortcomings to be addressed in order to fully understand and distinguish between the various ionospheric storm drivers over the Southern Africa mid-latitude region. The results presented in this thesis on the ionospheric response during geomagnetic storms provide essential information to direct further investigation aimed at developing this emerging field of study in South Africa.
- Full Text:
- Date Issued: 2012
The feasibility of monetary integration within the SADC region
- Authors: Nindi, Angelique Gugulethu
- Date: 2012
- Subjects: Southern African Development Community Monetary policy -- Africa, Southern Macroeconomics Africa, Southern -- Economic policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1021 , http://hdl.handle.net/10962/d1002756
- Description: The Southern African Development Community (SADC) aims to have a regional central bank by 2016 and a common currency by 2018. The member states are at the early stages of the process of regional economic integration, having launched a free trade area in 2008. Monetary integration is an advanced stage of regional economic integration that requires progressive changes in the participating countries. The purpose of this study is to determine the feasibility of monetary integration within the SADC countries and hence, provide policy recommendations to guide the integration process. To accomplish this, the study analyses the extent to which the member states meet the criteria for an optimum currency area (OCA) as well as the degree to which their economies are converging. The study finds that the main macroeconomic objectives of SADC countries differ due to a difference in the relative importance of monetary policy instruments in member states, which influences each country’s commitment towards achieving the macroeconomic convergence targets and harmonising policies. A more appropriate approach to macroeconomic convergence would be to allow for variable speed, geometry and depth in each country as premature adherence to convergence targets could prevent a harmonisation of the economies in the future and possibly destabilise the union. In addition, the study investigates the importance and similarities of the monetary aggregate channel, the interest rate channel, the exchange rate channel and the credit channel in the transmission of monetary policy using VAR analysis. This is important when considering monetary integration because differences in transmission mechanisms can result in asymmetric behaviour between member states, which in turn will prevent harmonisation of their economies. The results of the analysis suggest that SADC member states display asymmetries in their responses to monetary policy shocks as well as the relative importance of transmission mechanisms. In addition, the results suggest that national monetary policy is generally inefficient in determining economic performance in the member states. Furthermore, the study finds that the failure to meet the OCA criteria implies that the SADC member states will respond asymmetrically to shocks within a monetary union. With no effective alternative adjustment mechanisms in place, the effects of the shocks will endure in union members and possibly widen existing cyclical variation. Hence, monetary integration would not result in harmonisation of the economies of member states. It is therefore, concluded that the SADC countries were not suitable for monetary integration at present.
- Full Text:
- Date Issued: 2012
- Authors: Nindi, Angelique Gugulethu
- Date: 2012
- Subjects: Southern African Development Community Monetary policy -- Africa, Southern Macroeconomics Africa, Southern -- Economic policy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1021 , http://hdl.handle.net/10962/d1002756
- Description: The Southern African Development Community (SADC) aims to have a regional central bank by 2016 and a common currency by 2018. The member states are at the early stages of the process of regional economic integration, having launched a free trade area in 2008. Monetary integration is an advanced stage of regional economic integration that requires progressive changes in the participating countries. The purpose of this study is to determine the feasibility of monetary integration within the SADC countries and hence, provide policy recommendations to guide the integration process. To accomplish this, the study analyses the extent to which the member states meet the criteria for an optimum currency area (OCA) as well as the degree to which their economies are converging. The study finds that the main macroeconomic objectives of SADC countries differ due to a difference in the relative importance of monetary policy instruments in member states, which influences each country’s commitment towards achieving the macroeconomic convergence targets and harmonising policies. A more appropriate approach to macroeconomic convergence would be to allow for variable speed, geometry and depth in each country as premature adherence to convergence targets could prevent a harmonisation of the economies in the future and possibly destabilise the union. In addition, the study investigates the importance and similarities of the monetary aggregate channel, the interest rate channel, the exchange rate channel and the credit channel in the transmission of monetary policy using VAR analysis. This is important when considering monetary integration because differences in transmission mechanisms can result in asymmetric behaviour between member states, which in turn will prevent harmonisation of their economies. The results of the analysis suggest that SADC member states display asymmetries in their responses to monetary policy shocks as well as the relative importance of transmission mechanisms. In addition, the results suggest that national monetary policy is generally inefficient in determining economic performance in the member states. Furthermore, the study finds that the failure to meet the OCA criteria implies that the SADC member states will respond asymmetrically to shocks within a monetary union. With no effective alternative adjustment mechanisms in place, the effects of the shocks will endure in union members and possibly widen existing cyclical variation. Hence, monetary integration would not result in harmonisation of the economies of member states. It is therefore, concluded that the SADC countries were not suitable for monetary integration at present.
- Full Text:
- Date Issued: 2012
Narrating emergence in the curious terrain of academic development research: a realist perspective
- Authors: Niven, Penelope Mary
- Date: 2012
- Subjects: Education, Higher -- Aims and objectives -- South Africa Universities and colleges -- South Africa Educational change -- South Africa Black people -- Education (Higher) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1675 , http://hdl.handle.net/10962/d1003558
- Description: This dissertation adopts a realist meta-perspective on a body of the scholar's own research papers written between 2005 and 2011, all either published or in press and offered for reference in the Appendices. The six papers represent the point of departure for the thesis; they are the phenomenon for further investigation into 'what must be the case' for the research events to have emerged as they did. One aspect of this study, therefore, is an auto ethnographic account of conducting research in the field of Academic Development within varied settings and over a given time frame. But alongside this personal history it narrates cycles in the Academic Development movement in South Africa over 30 years. Margaret Archer's Social Realist principle of analytical dualism (1995) is used to disaggregate the emergent properties within these histories and to enable an analysis of the underlying mechanisms that generated them. It refers to three social domains. Firstly, it describes the material structures - the institutional environments, policies, roles or professional conditions - in which the projects were conceived. Secondly, it identifies the cultural registers that the profession was drawing on - such as theories, beliefs or discourses. Thirdly, it draws attention to the agency of individuals and communities in the field as they independently activated or mediated these various conditioning structures and registers. So the study is a systematic examination of the parts and the people in research stories, of the complex interrelationship of structural and agential elements, and of how together they have generated particular forms of knowing and kinds of knowledge in Academic Development. Drawing from this 'history-within-a-history', the study makes some claims for 'what must be the case' for substantial knowledge to flourish in a newly emergent, hotly contested and relatively unstable field. It argues that Academic Development has few shared epistemological foundations and boundaries, and its roles and functions are shifting and diverse. It describes the tensions in the field between those who have been inclined to understand it as primarily concerned with redress or equity in the postapartheid state, and yet others who have prioritised Academic Development as an efficiency project within higher education. But there is a third discourse emanating from those in the profession who have consistently argued that neither of these approaches can succeed without drawing on stronger theoretical foundations. This study endorses the view that Academic Developers need to identify more coherent ontological and epistemological frames for their research work. This has important implications for building the kind of substantial knowledge base that could be more influential in addressing the troubled terrain of South African higher education. The study refers extensively to Lewis Carroll's Alice in Wonderland (1865) and Through the Looking-Glass (1871) and to Mervyn Peake's 1946 illustrations of these children's stories, finding in these texts powerful analogies and metaphors for principles in realist philosophy and theory, and for describing a researcher's journey towards a more assured identity in the curious field of Academic Development.
- Full Text:
- Date Issued: 2012
- Authors: Niven, Penelope Mary
- Date: 2012
- Subjects: Education, Higher -- Aims and objectives -- South Africa Universities and colleges -- South Africa Educational change -- South Africa Black people -- Education (Higher) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1675 , http://hdl.handle.net/10962/d1003558
- Description: This dissertation adopts a realist meta-perspective on a body of the scholar's own research papers written between 2005 and 2011, all either published or in press and offered for reference in the Appendices. The six papers represent the point of departure for the thesis; they are the phenomenon for further investigation into 'what must be the case' for the research events to have emerged as they did. One aspect of this study, therefore, is an auto ethnographic account of conducting research in the field of Academic Development within varied settings and over a given time frame. But alongside this personal history it narrates cycles in the Academic Development movement in South Africa over 30 years. Margaret Archer's Social Realist principle of analytical dualism (1995) is used to disaggregate the emergent properties within these histories and to enable an analysis of the underlying mechanisms that generated them. It refers to three social domains. Firstly, it describes the material structures - the institutional environments, policies, roles or professional conditions - in which the projects were conceived. Secondly, it identifies the cultural registers that the profession was drawing on - such as theories, beliefs or discourses. Thirdly, it draws attention to the agency of individuals and communities in the field as they independently activated or mediated these various conditioning structures and registers. So the study is a systematic examination of the parts and the people in research stories, of the complex interrelationship of structural and agential elements, and of how together they have generated particular forms of knowing and kinds of knowledge in Academic Development. Drawing from this 'history-within-a-history', the study makes some claims for 'what must be the case' for substantial knowledge to flourish in a newly emergent, hotly contested and relatively unstable field. It argues that Academic Development has few shared epistemological foundations and boundaries, and its roles and functions are shifting and diverse. It describes the tensions in the field between those who have been inclined to understand it as primarily concerned with redress or equity in the postapartheid state, and yet others who have prioritised Academic Development as an efficiency project within higher education. But there is a third discourse emanating from those in the profession who have consistently argued that neither of these approaches can succeed without drawing on stronger theoretical foundations. This study endorses the view that Academic Developers need to identify more coherent ontological and epistemological frames for their research work. This has important implications for building the kind of substantial knowledge base that could be more influential in addressing the troubled terrain of South African higher education. The study refers extensively to Lewis Carroll's Alice in Wonderland (1865) and Through the Looking-Glass (1871) and to Mervyn Peake's 1946 illustrations of these children's stories, finding in these texts powerful analogies and metaphors for principles in realist philosophy and theory, and for describing a researcher's journey towards a more assured identity in the curious field of Academic Development.
- Full Text:
- Date Issued: 2012
Photophysicochemical and photodynamic studies of phthalocyanines conjugated to selected drug delivery agents
- Authors: Nombona, Nolwazi
- Date: 2012
- Subjects: Phthalocyanines Photochemistry Photochemotherapy Drug delivery systems Magnesium Zinc Nanoparticles Staphylococcus aureus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4333 , http://hdl.handle.net/10962/d1004994
- Description: This work reports on the successful synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines. The synthesis of symmetrical phthalocyanines is also reported. A selection of phthalocyanines have been conjugated, covalently linked, encapsulated or mixed with selected of drug delivery agents which include gold or silver nanoparticles, poly-L-lysine, liposomes and folic acid. The influence of delivery agent on the photophysical and photochemical properties of conjugated phthalocyanine is investigated. The studies showed that the Au nanoparticle significantly lowered the fluorescence quantum yield values of the phthalocyanines. The photodynamic activity of Zn phthalocyanine-ε-polylysine conjugates in the presence of nanoparticles towards the inactivation of Staphylococcus aureus showed high photoinactivation in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC₅₀) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The conjugate also showed no dark toxicity when evaluated using the chick choriallantoic membrane (CAM) assay. The efficiency of selected zinc phthalocyanine as photodynamic therapy (PDT) agents was investigated. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizers were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J.cm⁻². The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
- Full Text:
- Date Issued: 2012
- Authors: Nombona, Nolwazi
- Date: 2012
- Subjects: Phthalocyanines Photochemistry Photochemotherapy Drug delivery systems Magnesium Zinc Nanoparticles Staphylococcus aureus
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4333 , http://hdl.handle.net/10962/d1004994
- Description: This work reports on the successful synthesis, characterisation and photophysical properties of new asymmetric metal free, magnesium and zinc phthalocyanines. The synthesis of symmetrical phthalocyanines is also reported. A selection of phthalocyanines have been conjugated, covalently linked, encapsulated or mixed with selected of drug delivery agents which include gold or silver nanoparticles, poly-L-lysine, liposomes and folic acid. The influence of delivery agent on the photophysical and photochemical properties of conjugated phthalocyanine is investigated. The studies showed that the Au nanoparticle significantly lowered the fluorescence quantum yield values of the phthalocyanines. The photodynamic activity of Zn phthalocyanine-ε-polylysine conjugates in the presence of nanoparticles towards the inactivation of Staphylococcus aureus showed high photoinactivation in the presence of silver nanoparticles. The presence of silver nanoparticels from the minimal inhibition concentration (MIC₅₀) studies showed remarkable growth inhibition for the tested conjugates even at low concentrations. The conjugate also showed no dark toxicity when evaluated using the chick choriallantoic membrane (CAM) assay. The efficiency of selected zinc phthalocyanine as photodynamic therapy (PDT) agents was investigated. The production of reactive oxygen species (ROS) and phototoxicity of the photosensitizers were assessed. Healthy fibroblast cells and breast cancer (MCF-7) cells were treated with either free phthalocyanine or phthalocyanine bound to either gold nanoparticles or encapsulated in liposomes. Cell viability studies showed the optimum phototoxic effect on non-malignant cells to be 4.5 J.cm⁻². The PDT effect of the liposome bound phthalocyanine showed extensive damage of the breast cancer cells. Gold nanoparticles only showed a modest improvement in PDT activity.
- Full Text:
- Date Issued: 2012
Mechanistic studies of unusual Miruta-Baylis-Hillman reactions
- Authors: Nyoni, Dubekile
- Date: 2012
- Subjects: Chemical reactions Benzaldehyde Acrylonitrile Methyl acrylate Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4400 , http://hdl.handle.net/10962/d1006692
- Description: This study has focussed on the application of synthetic, kinetic and exploratory theoretical methods in elucidating the reaction mechanisms of four Morita-Baylis-Hillman (MBH) type reactions, viz, i) the reactions of the disulfide 2,2'-dithiodibenzaldehyde with various activated alkenes in the presence of DBU and Ph₃P, ii) the reactions of chromone-3-carbaldehydes with MVK, iii) the reactions of chromone-2-carbaldehydes with acrylonitrile and iv) with methyl acrylate. Attention has also been given to the origin of the observed regioselectivity in Michaelis-Arbuzov reactions of 3-(halomethyl)coumarins. Cleavage of the sulfur-sulfur bond of aryl and heteroaryl disulfides by the nitrogen nucleophile DBU has been demonstrated, and a dramatic increase in the rate of tandem MBH and disulfide cleavage reactions of 2,2'-dithiodibenzaldehyde with the activated alkenes, MVK, EVK, acrylonitrile, methyl acrylate and tert-butyl acrylate has been achieved through the use of the dual organo-catalyst system, DBU-Ph₃P – an improvement accompanied by an increase in the yields of the isolated products. Detailed NMR-based kinetic studies have been conducted on the DBU-catalysed reactions of 2,2'-dithiodibenzaldehyde with MVK and methyl acrylate, and a theoretical kinetic model has been developed and complementary computational studies using Gaussian 03, at the DFT-B3LYP/6-31G(d) level of theory have provided valuable insights into the mechanism of these complex transformations. Reactions of chromone-3-carbaldehydes with MVK to afford chromone dimers and tricyclic products have been repeated, and a novel, intermediate MBH adduct has been isolated. The mechanisms of the competing pathways have been elucidated by DFT calculations and the development of a detailed theoretical kinetic model has ensued. Unusual transformations in MBH-type reactions of chromone-2-carbaldehydes with acrylonitrile and methyl acrylate have been explored and the structures of the unexpected products have been established using 1- and 2-D NMR, HRMS and X-ray crystallographic techniques. Attention has also been given to the synthesis of 3-(halomethyl)coumarins via the MBH reaction, and their subsequent Michaelis-Arbuzov reactions with triethyl phosphite. An exploratory study of the kinetics of the phosphonation reaction has been undertaken and the regio-selectivity of nucleophilic attack at the 4- and 1'-positions in the 3-chloro- and 3-(iodomethyl)coumarins has been investigated by calculating Mulliken charges, LUMO surfaces and Fukui condensed local softness functions.
- Full Text:
- Date Issued: 2012
- Authors: Nyoni, Dubekile
- Date: 2012
- Subjects: Chemical reactions Benzaldehyde Acrylonitrile Methyl acrylate Coumarins
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4400 , http://hdl.handle.net/10962/d1006692
- Description: This study has focussed on the application of synthetic, kinetic and exploratory theoretical methods in elucidating the reaction mechanisms of four Morita-Baylis-Hillman (MBH) type reactions, viz, i) the reactions of the disulfide 2,2'-dithiodibenzaldehyde with various activated alkenes in the presence of DBU and Ph₃P, ii) the reactions of chromone-3-carbaldehydes with MVK, iii) the reactions of chromone-2-carbaldehydes with acrylonitrile and iv) with methyl acrylate. Attention has also been given to the origin of the observed regioselectivity in Michaelis-Arbuzov reactions of 3-(halomethyl)coumarins. Cleavage of the sulfur-sulfur bond of aryl and heteroaryl disulfides by the nitrogen nucleophile DBU has been demonstrated, and a dramatic increase in the rate of tandem MBH and disulfide cleavage reactions of 2,2'-dithiodibenzaldehyde with the activated alkenes, MVK, EVK, acrylonitrile, methyl acrylate and tert-butyl acrylate has been achieved through the use of the dual organo-catalyst system, DBU-Ph₃P – an improvement accompanied by an increase in the yields of the isolated products. Detailed NMR-based kinetic studies have been conducted on the DBU-catalysed reactions of 2,2'-dithiodibenzaldehyde with MVK and methyl acrylate, and a theoretical kinetic model has been developed and complementary computational studies using Gaussian 03, at the DFT-B3LYP/6-31G(d) level of theory have provided valuable insights into the mechanism of these complex transformations. Reactions of chromone-3-carbaldehydes with MVK to afford chromone dimers and tricyclic products have been repeated, and a novel, intermediate MBH adduct has been isolated. The mechanisms of the competing pathways have been elucidated by DFT calculations and the development of a detailed theoretical kinetic model has ensued. Unusual transformations in MBH-type reactions of chromone-2-carbaldehydes with acrylonitrile and methyl acrylate have been explored and the structures of the unexpected products have been established using 1- and 2-D NMR, HRMS and X-ray crystallographic techniques. Attention has also been given to the synthesis of 3-(halomethyl)coumarins via the MBH reaction, and their subsequent Michaelis-Arbuzov reactions with triethyl phosphite. An exploratory study of the kinetics of the phosphonation reaction has been undertaken and the regio-selectivity of nucleophilic attack at the 4- and 1'-positions in the 3-chloro- and 3-(iodomethyl)coumarins has been investigated by calculating Mulliken charges, LUMO surfaces and Fukui condensed local softness functions.
- Full Text:
- Date Issued: 2012
Ruthenium and palladium assisted silver transport in silicon carbide
- Authors: O'Connell, Jacques Herman
- Date: 2012
- Subjects: Gas cooled reactors , Ruthenium , Palladium , Silicon carbide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10404 , http://hdl.handle.net/10948/d1010960 , Gas cooled reactors , Ruthenium , Palladium , Silicon carbide
- Full Text:
- Date Issued: 2012
- Authors: O'Connell, Jacques Herman
- Date: 2012
- Subjects: Gas cooled reactors , Ruthenium , Palladium , Silicon carbide
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10404 , http://hdl.handle.net/10948/d1010960 , Gas cooled reactors , Ruthenium , Palladium , Silicon carbide
- Full Text:
- Date Issued: 2012
Deciding and doing what's right for people and planet : an investigation of the ethics-oriented learning of novice environmental educators
- Authors: Olvitt, Lausanne Laura
- Date: 2012
- Subjects: Environmental education Environmental ethics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1913 , http://hdl.handle.net/10962/d1007238
- Description: This study probes the ethics-oriented reflexive deliberations of three novice environmental education practitioners in South Africa. Two of the cases examined work in a local government context, and the third in an environmental non-governmental organisation context. All three practitioners are studying a one-year professional development course in environmental education. The research asks how their ethical deliberations ‘come to be what they are’, at the interface of their workplace and course-based learning processes. Working within a relational, social realist ontology, the study takes a sociocultural-historical approach to learning, development and social change. Cultural-historical activity theory (CHAT) provides theoretical tools and a descriptive language to approach the rich, qualitative data derived from workplace and course observations, extensive interviews, and document review. Critical discourse analysis was used as a secondary analytical tool to probe ethical and environmental discourses that were found to be influential in the course and workplace activity systems. Data from the three case studies was analysed in stages. In the first stage, CHAT provided a theoretical perspective and language of description to analyse the interacting activity systems in which each learner-practitioner’s ethics-oriented reflexive deliberations occurred. This provided a platform for the second stage of analysis which was framed by Margaret Archer’s (1995) social realist theory of morphogenesis/ morphostasis, followed by a summative retroductive analysis, to give an account of the interplay of historically-emergent social and cultural structures and individual reflexivity in relation to the ethical dimensions of environmental education practice. The study traces how ethics-oriented reflexive deliberations occur at the untidy, unpredictable intersection of workplace, course and personal contexts, and are strongest when they are situated in authentic contexts that resonate with learner-practitioners’ ‘ultimate concerns’ (after Archer, 2003; 2007). In this study, the learner-practitioners’ ‘ultimate concerns’ included family, personal well-being, social justice, cultural identity and religious commitments. The scope and depth of learner-practitioners’ social-ecological knowledge was also identified as a key factor influencing ethics-oriented reflexive deliberations, although the mediation of such knowledge can be hindered by language and conceptual ii barriers, amongst others. The study also noted how ethical positions circulating in the workplace, course and personal contexts were diverse, uneven and dynamic. Some ethical positions were found to be more explicitly differentiated than others, either resonating with or being overlooked by the learner-practitioners as they deliberated the ethical dimensions of their environmental education practice. In situations where there was limited depth, conceptual clarity and/ or confidence to engage directly with ethical concerns, there was a tendency towards (inadvertent) ethical relativism. Insights derived from the study suggest that these factors have limiting effects on the ethics-oriented reflexive deliberations of novice environmental educators. These insights point to the need for ethical deliberations to be re-personalised in context and underpinned by depth knowledge. A relational and pragmatic approach to environmental ethics (that recognises the validity of judgemental rationality – which can be fallible – and which seeks out practical adequacy) is put forward as appropriate and potentially generative in environmental education and training processes. This would need to be supported by careful attention to the influence of environmental discourses and practices in shaping ethical deliberations, and may also be helpful in developing a much-needed accessible, everyday language of ethical engagement. This study’s contribution to new knowledge in the field of environmental education is through its account of ethics-oriented reflexive deliberations emerging (in the Archerian morphogenetic sense) in complex, indeterminate ways at the interface of sociocultural and social-ecological contexts. The ethics-oriented reflexive deliberations of novice environmental educators occur in relation to their ‘ultimate concerns’ and are advanced or hindered by the historically-emergent practices, discourses and material realities of their workplace, personal and educational contexts. These insights require that the complex interplay of intersecting contexts and concerns that shape ethics-oriented reflexive deliberations be acknowledged and carefully mediated in both workplace-based and coursebased professional development processes.
- Full Text:
- Date Issued: 2012
- Authors: Olvitt, Lausanne Laura
- Date: 2012
- Subjects: Environmental education Environmental ethics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1913 , http://hdl.handle.net/10962/d1007238
- Description: This study probes the ethics-oriented reflexive deliberations of three novice environmental education practitioners in South Africa. Two of the cases examined work in a local government context, and the third in an environmental non-governmental organisation context. All three practitioners are studying a one-year professional development course in environmental education. The research asks how their ethical deliberations ‘come to be what they are’, at the interface of their workplace and course-based learning processes. Working within a relational, social realist ontology, the study takes a sociocultural-historical approach to learning, development and social change. Cultural-historical activity theory (CHAT) provides theoretical tools and a descriptive language to approach the rich, qualitative data derived from workplace and course observations, extensive interviews, and document review. Critical discourse analysis was used as a secondary analytical tool to probe ethical and environmental discourses that were found to be influential in the course and workplace activity systems. Data from the three case studies was analysed in stages. In the first stage, CHAT provided a theoretical perspective and language of description to analyse the interacting activity systems in which each learner-practitioner’s ethics-oriented reflexive deliberations occurred. This provided a platform for the second stage of analysis which was framed by Margaret Archer’s (1995) social realist theory of morphogenesis/ morphostasis, followed by a summative retroductive analysis, to give an account of the interplay of historically-emergent social and cultural structures and individual reflexivity in relation to the ethical dimensions of environmental education practice. The study traces how ethics-oriented reflexive deliberations occur at the untidy, unpredictable intersection of workplace, course and personal contexts, and are strongest when they are situated in authentic contexts that resonate with learner-practitioners’ ‘ultimate concerns’ (after Archer, 2003; 2007). In this study, the learner-practitioners’ ‘ultimate concerns’ included family, personal well-being, social justice, cultural identity and religious commitments. The scope and depth of learner-practitioners’ social-ecological knowledge was also identified as a key factor influencing ethics-oriented reflexive deliberations, although the mediation of such knowledge can be hindered by language and conceptual ii barriers, amongst others. The study also noted how ethical positions circulating in the workplace, course and personal contexts were diverse, uneven and dynamic. Some ethical positions were found to be more explicitly differentiated than others, either resonating with or being overlooked by the learner-practitioners as they deliberated the ethical dimensions of their environmental education practice. In situations where there was limited depth, conceptual clarity and/ or confidence to engage directly with ethical concerns, there was a tendency towards (inadvertent) ethical relativism. Insights derived from the study suggest that these factors have limiting effects on the ethics-oriented reflexive deliberations of novice environmental educators. These insights point to the need for ethical deliberations to be re-personalised in context and underpinned by depth knowledge. A relational and pragmatic approach to environmental ethics (that recognises the validity of judgemental rationality – which can be fallible – and which seeks out practical adequacy) is put forward as appropriate and potentially generative in environmental education and training processes. This would need to be supported by careful attention to the influence of environmental discourses and practices in shaping ethical deliberations, and may also be helpful in developing a much-needed accessible, everyday language of ethical engagement. This study’s contribution to new knowledge in the field of environmental education is through its account of ethics-oriented reflexive deliberations emerging (in the Archerian morphogenetic sense) in complex, indeterminate ways at the interface of sociocultural and social-ecological contexts. The ethics-oriented reflexive deliberations of novice environmental educators occur in relation to their ‘ultimate concerns’ and are advanced or hindered by the historically-emergent practices, discourses and material realities of their workplace, personal and educational contexts. These insights require that the complex interplay of intersecting contexts and concerns that shape ethics-oriented reflexive deliberations be acknowledged and carefully mediated in both workplace-based and coursebased professional development processes.
- Full Text:
- Date Issued: 2012
Studies on existing and new isolates of Cryptophlebia leucotreta granulovirus (CrleGV) on Thaumatotibia leucotreta populations from a range of geographic regions in South Africa
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2012
- Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- South Africa Cryptophlebia leucotreta -- Biological control Cryptophlebia leucotreta -- Life cycles Baculoviruses Lepidoptera -- Biological control Tortricidae -- Biological control Microbial insecticides Pests -- Integrated control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5778 , http://hdl.handle.net/10962/d1005466
- Description: Baculoviruses are arthropod-specific DNA viruses that are highly virulent to most lepidopteran insects. Their host specificity and compatibility with IPM programmes has enabled their usage as safe microbial insecticides (biopesticides). Two baculovirus-based biopesticides, Cryptogran and Cryptex, which have been formulated with Cryptophlebia leucotreta granulovirus (CrleGV) have been registered for the control of false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa and have been successfully incorporated into IPM programmes. However, several studies have indicated that insects can develop resistance to baculovirus-based biopesticide as was shown with field populations of codling moth (CM), Cydia pomonella (L.), which developed resistance to the biopesticide Cydia pomonella granulovirus (CpGV-M) in Europe. Other studies have shown that, under laboratory conditions, FCM populations differ in their susceptibility to Cryptogran and Cryptex. In order to investigate difference in susceptibility as well as protect against any future resistance by FCM to Cryptogran and Cryptex, a search for novel CrleGV-SA isolates from diseased insects from different geographic regions in South Africa was performed. Six geographic populations (Addo, Citrusdal, Marble Hall, Nelspruit, Baths and Mixed colonies) of FCM were established and maintained in the laboratory. Studies on the comparative biological performance based on pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and duration of life cycle of the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies revealed a low biological performance for the Citrusdal colony. This was attributed to the fact that FCM populations found in the Citrusdal area are not indigenous and may have been introduced from a very limited gene pool from another region. When insects from five colonies, excluding the Baths colony, were subjected to stress by overcrowding , a latent baculovirus resident in the Addo, Nelspruit, Citrusdal, Marble Hall and Mixed colonies was brought into an overt lethal state. Transmission electron micrographs revealed the presence of GV occlusion bodies (OBs) in diseased insects. DNA profiles obtained by single restriction endonuclease analysis of viral genomic DNA using BamH 1, Sa/1, Xba1 , Pst1, Xh01 , Kpn1, Hindlll and EcoR1 revealed five CrleGV-SA isolates latent within the insect populations. The new isolates were named CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl, CrleGVSA Nels and CrleGV-SA Mix isolates. The novelty of the five CrleGV-SA isolates was confirmed by the presence of unique submolar bands, indicating that each isolate was genetically different. PCR amplification and sequencing of the granulin and egt genes from the five isolates revealed several single nucleotide polymorph isms (SNPs) which, in some cases, resulted in amino acid substitutions. DNA profiles from RFLPs, as well as phylogenetic analysis based on granulin and egt sequencing showed the presence of two CrleGV-SA genome types for the CrleGV-SA isolate. Cryptex and CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl and CrleGV-SA Mix were placed as members of Group one CrleGV-SA, and Cryptogran and CrleGV-SA Nels isolate were placed into Group two CrleGV-SA. In droplet feeding bioassays, the median survival time (STso) for neonate larvae inoculated with Group one and two CrleGV-SA were determined to range from 80 - 88 hours (3.33 - 3.67 days), for all five colonies. LDso values for Group one and two CrleGV-SA against neonates from the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies varied between some populations and ranged from 0.80 - 3.12 OBs per larva, indicating some level of variation in host susceptibility. This is the first study reporting the existence of genetically distinct CrleGV baculovirus isolates infecting FCM in different geographical areas of South Africa. The results of this study have broad-ranging implications for our understanding of baculovirus-host interactions and for the application of baculovirus basedbiopesticides.
- Full Text:
- Date Issued: 2012
- Authors: Opoku-Debrah, John Kwadwo
- Date: 2012
- Subjects: Cryptophlebia leucotreta Cryptophlebia leucotreta -- South Africa Cryptophlebia leucotreta -- Biological control Cryptophlebia leucotreta -- Life cycles Baculoviruses Lepidoptera -- Biological control Tortricidae -- Biological control Microbial insecticides Pests -- Integrated control
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5778 , http://hdl.handle.net/10962/d1005466
- Description: Baculoviruses are arthropod-specific DNA viruses that are highly virulent to most lepidopteran insects. Their host specificity and compatibility with IPM programmes has enabled their usage as safe microbial insecticides (biopesticides). Two baculovirus-based biopesticides, Cryptogran and Cryptex, which have been formulated with Cryptophlebia leucotreta granulovirus (CrleGV) have been registered for the control of false codling moth (FCM), Thaumatotibia (=Cryptophlebia) leucotreta (Meyrick) (Lepidoptera: Tortricidae) in South Africa and have been successfully incorporated into IPM programmes. However, several studies have indicated that insects can develop resistance to baculovirus-based biopesticide as was shown with field populations of codling moth (CM), Cydia pomonella (L.), which developed resistance to the biopesticide Cydia pomonella granulovirus (CpGV-M) in Europe. Other studies have shown that, under laboratory conditions, FCM populations differ in their susceptibility to Cryptogran and Cryptex. In order to investigate difference in susceptibility as well as protect against any future resistance by FCM to Cryptogran and Cryptex, a search for novel CrleGV-SA isolates from diseased insects from different geographic regions in South Africa was performed. Six geographic populations (Addo, Citrusdal, Marble Hall, Nelspruit, Baths and Mixed colonies) of FCM were established and maintained in the laboratory. Studies on the comparative biological performance based on pupal mass, female fecundity, egg hatch, pupal survival, adult eclosion and duration of life cycle of the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies revealed a low biological performance for the Citrusdal colony. This was attributed to the fact that FCM populations found in the Citrusdal area are not indigenous and may have been introduced from a very limited gene pool from another region. When insects from five colonies, excluding the Baths colony, were subjected to stress by overcrowding , a latent baculovirus resident in the Addo, Nelspruit, Citrusdal, Marble Hall and Mixed colonies was brought into an overt lethal state. Transmission electron micrographs revealed the presence of GV occlusion bodies (OBs) in diseased insects. DNA profiles obtained by single restriction endonuclease analysis of viral genomic DNA using BamH 1, Sa/1, Xba1 , Pst1, Xh01 , Kpn1, Hindlll and EcoR1 revealed five CrleGV-SA isolates latent within the insect populations. The new isolates were named CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl, CrleGVSA Nels and CrleGV-SA Mix isolates. The novelty of the five CrleGV-SA isolates was confirmed by the presence of unique submolar bands, indicating that each isolate was genetically different. PCR amplification and sequencing of the granulin and egt genes from the five isolates revealed several single nucleotide polymorph isms (SNPs) which, in some cases, resulted in amino acid substitutions. DNA profiles from RFLPs, as well as phylogenetic analysis based on granulin and egt sequencing showed the presence of two CrleGV-SA genome types for the CrleGV-SA isolate. Cryptex and CrleGV-SA Ado, CrleGV-SA Cit, CrleGV-SA Mbl and CrleGV-SA Mix were placed as members of Group one CrleGV-SA, and Cryptogran and CrleGV-SA Nels isolate were placed into Group two CrleGV-SA. In droplet feeding bioassays, the median survival time (STso) for neonate larvae inoculated with Group one and two CrleGV-SA were determined to range from 80 - 88 hours (3.33 - 3.67 days), for all five colonies. LDso values for Group one and two CrleGV-SA against neonates from the Addo, Citrusdal, Marble Hall, Nelspruit and Mixed colonies varied between some populations and ranged from 0.80 - 3.12 OBs per larva, indicating some level of variation in host susceptibility. This is the first study reporting the existence of genetically distinct CrleGV baculovirus isolates infecting FCM in different geographical areas of South Africa. The results of this study have broad-ranging implications for our understanding of baculovirus-host interactions and for the application of baculovirus basedbiopesticides.
- Full Text:
- Date Issued: 2012
Exploiting the adaptability of recent information and communication technology to improve the site management process
- Ozumba, Aghaegbuna Obinna Uche
- Authors: Ozumba, Aghaegbuna Obinna Uche
- Date: 2012
- Subjects: Construction industry -- Information technology , Construction industry -- Materials management , Information technology -- Management.
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9705 , http://hdl.handle.net/10948/d1019811
- Description: Construction is a big role player in every economy, and the Site Management Process (SMP) occupies a strategic position in the construction process. Despite existence of appreciable research, technology diffusion in the construction industry is slow. Information and Communication Technology (ICT) implementation processes and products have not adequately and beneficially exploited ICT for improvement of the SMP. This is especially true in developing countries. Without increase in utilisation of ICT, potential benefits for the SMP remain untapped. The aim of the thesis was to ascertain the levels of utilisation of recent ICT developments for the SMP, and thereby gauge the benefits or lack thereof. The theoretical concept of the research is based on the technology transfer sub-concept of adaptation. A fundamentally positivistic view, with principles of objectivist approach was used for the enquiry. The approach included an extensive literature review, and a multi-stage investigation strategy, set in South Africa. Theory reviewed was in the main disciplines of construction science and technology, computer science and technology, and management science. Investigations involved case studies of construction sites, a global ICT survey, a national practitioner survey, and analysis of ICT products. Findings from literature assert the appreciable potential utility in recent ICT, thereby substantiating the adaptability of recent ICT. In addition ICT adoption in the SMP is inadequate and inexpedient, falling short of potential benefits for construction, both generally and in the local context. Furthermore there are challenges to ICT adoption, which could vary according to context. Field research results also point to underutilisation of innovations located in recent ICT. The main challenges in this regard include inadequate knowledge of potential utility of recent ICT, and lack of relevant support and effective approaches to technology integration, in the SMP. Moreover exploitation of the adaptability of recent ICT in the local SMP does not go beyond basic adoption. As such most diffusion occurs only for items requiring an adaptation of usage context or area of application. The results strongly indicate minimal innovativeness in this regard. Frameworks for possible adaptations of existing technologies were also derived, while propositions are made for approaches to improve the utility of recent ICT in the SMP. Through a customised approach, the thesis establishes foundational understanding towards a generic framework for adapting potential utility in ICT to uses in construction, especially in the SMP. Thus the research contributes strategic information to the fledgling CICT body of knowledge, especially in the local context.
- Full Text:
- Date Issued: 2012
- Authors: Ozumba, Aghaegbuna Obinna Uche
- Date: 2012
- Subjects: Construction industry -- Information technology , Construction industry -- Materials management , Information technology -- Management.
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9705 , http://hdl.handle.net/10948/d1019811
- Description: Construction is a big role player in every economy, and the Site Management Process (SMP) occupies a strategic position in the construction process. Despite existence of appreciable research, technology diffusion in the construction industry is slow. Information and Communication Technology (ICT) implementation processes and products have not adequately and beneficially exploited ICT for improvement of the SMP. This is especially true in developing countries. Without increase in utilisation of ICT, potential benefits for the SMP remain untapped. The aim of the thesis was to ascertain the levels of utilisation of recent ICT developments for the SMP, and thereby gauge the benefits or lack thereof. The theoretical concept of the research is based on the technology transfer sub-concept of adaptation. A fundamentally positivistic view, with principles of objectivist approach was used for the enquiry. The approach included an extensive literature review, and a multi-stage investigation strategy, set in South Africa. Theory reviewed was in the main disciplines of construction science and technology, computer science and technology, and management science. Investigations involved case studies of construction sites, a global ICT survey, a national practitioner survey, and analysis of ICT products. Findings from literature assert the appreciable potential utility in recent ICT, thereby substantiating the adaptability of recent ICT. In addition ICT adoption in the SMP is inadequate and inexpedient, falling short of potential benefits for construction, both generally and in the local context. Furthermore there are challenges to ICT adoption, which could vary according to context. Field research results also point to underutilisation of innovations located in recent ICT. The main challenges in this regard include inadequate knowledge of potential utility of recent ICT, and lack of relevant support and effective approaches to technology integration, in the SMP. Moreover exploitation of the adaptability of recent ICT in the local SMP does not go beyond basic adoption. As such most diffusion occurs only for items requiring an adaptation of usage context or area of application. The results strongly indicate minimal innovativeness in this regard. Frameworks for possible adaptations of existing technologies were also derived, while propositions are made for approaches to improve the utility of recent ICT in the SMP. Through a customised approach, the thesis establishes foundational understanding towards a generic framework for adapting potential utility in ICT to uses in construction, especially in the SMP. Thus the research contributes strategic information to the fledgling CICT body of knowledge, especially in the local context.
- Full Text:
- Date Issued: 2012
A critical realist exploration of the implementation of a new curriculum in Swaziland
- Authors: Pereira, Liphie
- Date: 2012
- Subjects: Critical realism Education -- Philosophy Critical pedagogy -- Swaziland Curriculum change -- Swaziland Education -- Swaziland Education and state -- Swaziland Education -- Aims and objectives -- Swaziland Critical discourse analysis International General Certificate of Secondary Education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1484 , http://hdl.handle.net/10962/d1003365
- Description: This study offers an in-depth exploration of the conditions from which the implementation of a curriculum called the International General Certificate of Secondary Education (IGCSE), later localised into Swaziland General Certificate of Secondary Education (SGCSE), emerged and the constraining and enabling conditions for the implementation of the new I/SGCSE curriculum. It derives its theoretical foundation from Roy Bhaskar’s critical realism and Margaret Archer’s concept of analytical separability. The study therefore offers explanations about the curriculum change and its implementation that are based on how structural, cultural, and agential mechanisms operating at a deeper level of reality (the intransitive layer of reality or the domain of the real) and existing independently of what we see, know or believe of them (the transitive layer of reality or domains of the actual and empirical) interacted to condition the emergence of I/SGCSE and the way it is implemented. I conduct a critical discourse analysis of relevant literature, I/SGCSE documents and interview data in order to identify those mechanisms that were cultural and also those that were structural and agential. Bernstein’s concepts of classification and framing are used to analyse observation data in order to explore the influence of these mechanisms on the teaching practices of the teachers who took part in the study. Analysis of the data suggests that the change from General Certificate of Education Ordinary Level (GCE O-level) to I/SGCSE was conditioned by inconsistencies between the cultural and structural mechanisms of the Swazi context. Many of the cultural elements of the Swazi context such as the discourses of good citizens, of competitive advantage, and of quality education draw from global discourses which view relations between people from a postmodernist position and therefore support weakly classified and framed pedagogic practices. In contrast, the discourse of morality and many of the structural elements of the Swazi context, such as the pre2006 education system and the Tinkhundla government system, all view reality from a modernist position, therefore supporting strong relations of power and control. The cultural system therefore exerted more influence in conditioning the change from the strongly classified and framed GCE O-level curriculum to the weakly classified and framed I/SGCSE curriculum. Furthermore, the analysis of interview and observation data suggests that inconsistencies between the global discourses and the discourses and structures that teachers confront in their day-to-day lives, together with the decisions teachers made in response to structural constraints, created constraining conditions for the change from GCE O-level to I/SGCSE. The study adds to knowledge on curriculum change and implementation through insights into the enabling and constraining effects of mechanisms operating at a deeper level of reality on curriculum-change decisions and on the ability of teachers to implement curriculum changes. The focus on the deeper level of reality may therefore contribute towards emancipatory knowledge which could be used not only by the Ministry of Education and Training and teachers in Swaziland but also elsewhere to inform future planning, decision making, and practice in relation to curriculum change and implementation.
- Full Text:
- Date Issued: 2012
- Authors: Pereira, Liphie
- Date: 2012
- Subjects: Critical realism Education -- Philosophy Critical pedagogy -- Swaziland Curriculum change -- Swaziland Education -- Swaziland Education and state -- Swaziland Education -- Aims and objectives -- Swaziland Critical discourse analysis International General Certificate of Secondary Education
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1484 , http://hdl.handle.net/10962/d1003365
- Description: This study offers an in-depth exploration of the conditions from which the implementation of a curriculum called the International General Certificate of Secondary Education (IGCSE), later localised into Swaziland General Certificate of Secondary Education (SGCSE), emerged and the constraining and enabling conditions for the implementation of the new I/SGCSE curriculum. It derives its theoretical foundation from Roy Bhaskar’s critical realism and Margaret Archer’s concept of analytical separability. The study therefore offers explanations about the curriculum change and its implementation that are based on how structural, cultural, and agential mechanisms operating at a deeper level of reality (the intransitive layer of reality or the domain of the real) and existing independently of what we see, know or believe of them (the transitive layer of reality or domains of the actual and empirical) interacted to condition the emergence of I/SGCSE and the way it is implemented. I conduct a critical discourse analysis of relevant literature, I/SGCSE documents and interview data in order to identify those mechanisms that were cultural and also those that were structural and agential. Bernstein’s concepts of classification and framing are used to analyse observation data in order to explore the influence of these mechanisms on the teaching practices of the teachers who took part in the study. Analysis of the data suggests that the change from General Certificate of Education Ordinary Level (GCE O-level) to I/SGCSE was conditioned by inconsistencies between the cultural and structural mechanisms of the Swazi context. Many of the cultural elements of the Swazi context such as the discourses of good citizens, of competitive advantage, and of quality education draw from global discourses which view relations between people from a postmodernist position and therefore support weakly classified and framed pedagogic practices. In contrast, the discourse of morality and many of the structural elements of the Swazi context, such as the pre2006 education system and the Tinkhundla government system, all view reality from a modernist position, therefore supporting strong relations of power and control. The cultural system therefore exerted more influence in conditioning the change from the strongly classified and framed GCE O-level curriculum to the weakly classified and framed I/SGCSE curriculum. Furthermore, the analysis of interview and observation data suggests that inconsistencies between the global discourses and the discourses and structures that teachers confront in their day-to-day lives, together with the decisions teachers made in response to structural constraints, created constraining conditions for the change from GCE O-level to I/SGCSE. The study adds to knowledge on curriculum change and implementation through insights into the enabling and constraining effects of mechanisms operating at a deeper level of reality on curriculum-change decisions and on the ability of teachers to implement curriculum changes. The focus on the deeper level of reality may therefore contribute towards emancipatory knowledge which could be used not only by the Ministry of Education and Training and teachers in Swaziland but also elsewhere to inform future planning, decision making, and practice in relation to curriculum change and implementation.
- Full Text:
- Date Issued: 2012
Rhenium complexes with multidentate benzazoles and related N,X-donor (X = N, O, S) ligands
- Authors: Potgieter, Kim Carey
- Date: 2012
- Subjects: Rhenium , Benzimidazoles , Ligands (Biochemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10438 , http://hdl.handle.net/10948/d1020773
- Description: The coordination behaviour of 4-aminoantipyrine (H2pap) and its Schiff base derivatives with the oxorhenium(V) and tricarbonyl rhenium(I) cores are reported. The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with H2pap were studied, and the complexes cis-[ReX2(pap)(H2pap)(PPh3)](ReO4) were isolated. The ligand pap is coordinated monodentately through the doubly deprotonated amino nitrogen as an imide, and H2pap acts as a neutral bidentate chelate, with coordination through the neutral amino nitrogen and the ketonic oxygen. The reactions of trans-[ReOBr3(PPh3)2] and cis-[ReO2I(PPh3)2] with -(2-aminobenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (H2nap) and 4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (Hoap) are also reported. The complexes cis-[Re(nap)Br2(PPh3)]Br, [ReO(OEt)(Hnap)(PPh3)]I and [ReO(OMe)(oap)(PPh3)]I were isolated and structurally characterized. The reactions of the Schiff base derivatives 1,2-(diimino-4’-antipyrinyl)ethane (dae) and 2,6-bis(4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one)pyridine (bap) with [Re(CO)5X] (X = Br or Cl) produced fac-[Re(CO)3(dae)Cl] and fac-[Re(CO)3(bap)Br] respectively. A series of rhenium(I) tricarbonyl complexes containing bidentate derivatives of aniline was synthesized and structurally characterized. With 1,2-diaminobenzene (Hpda) the ‘2+1’ complex salt fac-[Re(CO)3(κ1-Hpda)(κ2-Hpda)]Br was isolated, but with 2-mercaptophenol (Hspo) the bridged dimer [Re2(CO)7(spo)2] was found. The neutral complex [Re(CO)3(ons)(Hno)] was isolated from the reaction of [Re(CO)5Br] with 2-[(2-methylthio)benzylideneimino]phenol (Hons; Hno = 2-aminophenol), with ons coordinated as a bidentate chelate with a free SCH3 group. In the complex [Re(CO)3(Htpn)Br] (Htpn = N-(2-(methylthio)benzylidene)benzene-1,2-diamine) the potentially tridentate ligand Htpn is coordinated via the methylthiol sulfur and imino nitrogen atoms only, with a free amino group. These rhenium(I) complexes, with the exception of [Re2(CO)7(spo)2], revealed broad emissions centred around 535 nm. The reactions of the rhenium(V) complex cis-[ReO2I(PPh3)2] with 2-aminothiophenol (H2atp), benzene-1,2-dithiol (H2tdt) and 2-hydroxybenzenethiol (H2otp) led to the formation of the rhenium(III) compounds [Re(Hatp)(ibsq)2].OPPh3, [Re(sbsq)3].OPPh3 and [Re(obsq)3].OPPh3 (ibsq = 2-iminothiobenzosemiquinonate, sbsq = 1,2-dithiobenzosemiquinonate, obsq = 2-hydroxothiobenzosemiquinonate) respectively. The complexes adopt a trigonal prismatic geometry around the rhenium centre with average twists angles between 3.20-26.10˚. The E1/2 values for the Re(III)/Re(IV) redox couple were found to be 0.022, 0.142 and 0.126 V for [Re(Hatp)(ibsq)2].OPPh3, [Re(sbsq)3].OPPh3 and [Re(obsq)3].OPPh3 respectively. The reactions of the benzoxazole ligands, 3-(benzoxazol-2-yl)pyridin-2-ol (Hbop) and 5-amino-2-(benzoxazol-2-yl)phenol (Habo) with a [ReO]3+ precursor led to the rhenium(III) complex, [ReCl2(bop)(PPh3)2], and the complex salt, [ReO(abo)I(PPh3)2]ReO4, respectively. A variety of benzothiazole and benzimidazole derivatives were reacted with [Re(CO)5Br]. In the case of bis(benzothiazol-2-ylethyl)sulfide (bts), the neutral complex fac-[Re(CO)3(bts)Br] was obtained. The dimeric complexes (μ-dbt)2[Re(CO)3]2 and (μ-mbt)2[Re(CO)3]2 were formed when 1,3-bis(benzothiazol-2-yl)thiourea (Hdbt) and 1-(benzothiazol-2-ylidene)-3-methylthiourea (Hmbt) were used as ligands. The reaction of 2,2’-(oxybis(methylene))bis(benzimidazole) (bmb) with [Re(CO)5Cl] resulted in the rhenium(I) complex salt fac-[Re(CO)3(bmb)]+, with the tri-μ-chlorohexacarbonyl dirhenate [Re2(CO)6Cl3]- as the counter anion. The neutral complex fac-[Re(CO)3(btp)Cl] was isolated from the reaction of the 2,9-bis(benzothiazol-2-yl)-1,10-phenanthroline (btp) ligand and [Re(CO)5Cl]. The reactions of trans-[ReOCl3(PPh3)2] with bis(benzimidazol-2-ylethyl)sulfide (btn) and 1-(benzothiazol-2-ylidene)-3-methylthiourea (Hmbt) led to the formation of the cationic compounds (μ-O)2[Re2O2(btn)2]I2 and [ReCl2(bte)(PPh3)2]Cl (bte = (benzothiazole-2-yl)-N-ethylidenemethanamine) respectively.
- Full Text:
- Date Issued: 2012
- Authors: Potgieter, Kim Carey
- Date: 2012
- Subjects: Rhenium , Benzimidazoles , Ligands (Biochemistry)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10438 , http://hdl.handle.net/10948/d1020773
- Description: The coordination behaviour of 4-aminoantipyrine (H2pap) and its Schiff base derivatives with the oxorhenium(V) and tricarbonyl rhenium(I) cores are reported. The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with H2pap were studied, and the complexes cis-[ReX2(pap)(H2pap)(PPh3)](ReO4) were isolated. The ligand pap is coordinated monodentately through the doubly deprotonated amino nitrogen as an imide, and H2pap acts as a neutral bidentate chelate, with coordination through the neutral amino nitrogen and the ketonic oxygen. The reactions of trans-[ReOBr3(PPh3)2] and cis-[ReO2I(PPh3)2] with -(2-aminobenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (H2nap) and 4-(2-hydroxybenzylideneamino)-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one (Hoap) are also reported. The complexes cis-[Re(nap)Br2(PPh3)]Br, [ReO(OEt)(Hnap)(PPh3)]I and [ReO(OMe)(oap)(PPh3)]I were isolated and structurally characterized. The reactions of the Schiff base derivatives 1,2-(diimino-4’-antipyrinyl)ethane (dae) and 2,6-bis(4-amino-1,2-dihydro-2,3-dimethyl-1-phenylpyrazol-5-one)pyridine (bap) with [Re(CO)5X] (X = Br or Cl) produced fac-[Re(CO)3(dae)Cl] and fac-[Re(CO)3(bap)Br] respectively. A series of rhenium(I) tricarbonyl complexes containing bidentate derivatives of aniline was synthesized and structurally characterized. With 1,2-diaminobenzene (Hpda) the ‘2+1’ complex salt fac-[Re(CO)3(κ1-Hpda)(κ2-Hpda)]Br was isolated, but with 2-mercaptophenol (Hspo) the bridged dimer [Re2(CO)7(spo)2] was found. The neutral complex [Re(CO)3(ons)(Hno)] was isolated from the reaction of [Re(CO)5Br] with 2-[(2-methylthio)benzylideneimino]phenol (Hons; Hno = 2-aminophenol), with ons coordinated as a bidentate chelate with a free SCH3 group. In the complex [Re(CO)3(Htpn)Br] (Htpn = N-(2-(methylthio)benzylidene)benzene-1,2-diamine) the potentially tridentate ligand Htpn is coordinated via the methylthiol sulfur and imino nitrogen atoms only, with a free amino group. These rhenium(I) complexes, with the exception of [Re2(CO)7(spo)2], revealed broad emissions centred around 535 nm. The reactions of the rhenium(V) complex cis-[ReO2I(PPh3)2] with 2-aminothiophenol (H2atp), benzene-1,2-dithiol (H2tdt) and 2-hydroxybenzenethiol (H2otp) led to the formation of the rhenium(III) compounds [Re(Hatp)(ibsq)2].OPPh3, [Re(sbsq)3].OPPh3 and [Re(obsq)3].OPPh3 (ibsq = 2-iminothiobenzosemiquinonate, sbsq = 1,2-dithiobenzosemiquinonate, obsq = 2-hydroxothiobenzosemiquinonate) respectively. The complexes adopt a trigonal prismatic geometry around the rhenium centre with average twists angles between 3.20-26.10˚. The E1/2 values for the Re(III)/Re(IV) redox couple were found to be 0.022, 0.142 and 0.126 V for [Re(Hatp)(ibsq)2].OPPh3, [Re(sbsq)3].OPPh3 and [Re(obsq)3].OPPh3 respectively. The reactions of the benzoxazole ligands, 3-(benzoxazol-2-yl)pyridin-2-ol (Hbop) and 5-amino-2-(benzoxazol-2-yl)phenol (Habo) with a [ReO]3+ precursor led to the rhenium(III) complex, [ReCl2(bop)(PPh3)2], and the complex salt, [ReO(abo)I(PPh3)2]ReO4, respectively. A variety of benzothiazole and benzimidazole derivatives were reacted with [Re(CO)5Br]. In the case of bis(benzothiazol-2-ylethyl)sulfide (bts), the neutral complex fac-[Re(CO)3(bts)Br] was obtained. The dimeric complexes (μ-dbt)2[Re(CO)3]2 and (μ-mbt)2[Re(CO)3]2 were formed when 1,3-bis(benzothiazol-2-yl)thiourea (Hdbt) and 1-(benzothiazol-2-ylidene)-3-methylthiourea (Hmbt) were used as ligands. The reaction of 2,2’-(oxybis(methylene))bis(benzimidazole) (bmb) with [Re(CO)5Cl] resulted in the rhenium(I) complex salt fac-[Re(CO)3(bmb)]+, with the tri-μ-chlorohexacarbonyl dirhenate [Re2(CO)6Cl3]- as the counter anion. The neutral complex fac-[Re(CO)3(btp)Cl] was isolated from the reaction of the 2,9-bis(benzothiazol-2-yl)-1,10-phenanthroline (btp) ligand and [Re(CO)5Cl]. The reactions of trans-[ReOCl3(PPh3)2] with bis(benzimidazol-2-ylethyl)sulfide (btn) and 1-(benzothiazol-2-ylidene)-3-methylthiourea (Hmbt) led to the formation of the cationic compounds (μ-O)2[Re2O2(btn)2]I2 and [ReCl2(bte)(PPh3)2]Cl (bte = (benzothiazole-2-yl)-N-ethylidenemethanamine) respectively.
- Full Text:
- Date Issued: 2012
A methodology to institutionalise user experience in a South African provincial government
- Authors: Pretorius, Marco Cobus
- Date: 2012
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Government Web sites -- South Africa , Web site development , Electronic government information
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10489 , http://hdl.handle.net/10948/d1019961
- Description: The number of citizens, who access e-Government websites, is growing significantly and their expectations for additional services are increasing. The Internet has become an essential instrument to distribute information to citizens. Poorly designed websites, however, can divide governments and its citizens. Consensus amongst researchers is that user experience (UX) is an important factor in designing websites specifically e-Government websites. Problems, experienced with website usability, prevent people from accessing and eventually adopting technology, such as e-Government. Countries, such as the United States, United Kingdom and Canada, have shown increased support for UX in e-Government websites. At present, a number of guidelines and design principles exists for e-Government website UX design; however, the effectiveness of the implementation of these guidelines and principles depends on the profiles of the individuals on a website development team and on an organisation’s understanding of UX. Despite the highlighted importance of UX, guidelines and principles are rarely adopted in South African e-Government websites. Usability and UX guidelines cannot be implemented; if there is no executive support; an inadequately trained staff; no routine UX practice; insufficient budget; inefficient use of usability methodologies and user-centred design (UCD) processes. The challenge at present in the UX design field is the institutionalisation of UX, specifically at government level. The goal of this research was to propose and evaluate a methodology to institutionalise UX in South African Provincial Governments (PGs), named the “Institutionalise UX in Government (IUXG) methodology”. The research used the Western Cape Government (WCG) in South Africa as a case study to evaluate the proposed methodology to institutionalise UX in a South African PG. The IUXG methodology (1.0) was proposed from five UX methodologies, as well as from best practices found in literature. The IUXG methodology (1.1) was updated, based on results of a survey to South African PGs, a survey to WCG employees, as well as literature from the WCG. The IUXG methodology (2.0) was updated a final time, based on the case study results and on a confirmation survey with WCG employees after the implementation of the case study. The research study made use of three surveys during this research. The first survey, incorporating UX maturity models, confirmed that understanding and buy-in of UX are limited and that UX maturity levels are low at South African PG level. The second and third surveys were administered to WCG e-Government website officials before and after the implementation of the IUXG methodology. The surveys measured the UX maturity level of the WCG in the component, e-Government for Citizens (e-G4C), responsible for the WCG e-Government website. The final survey results demonstrated that, after the implementation of the IUXG methodology, the WCG improved its level of UX maturity on the identified UX maturity models. Implementation of the IUXG methodology institutionalised UX in the WCG. UX activities became standard practice in the e-Government website environment after the systems development lifecycle (SDLC) incorporated UCD. UX policy, strategy and guidelines were documented for the WCG e-Government website. The WCG constructed the first usability testing facility for a South African PG and improvements to the WCG e-Government website were implemented. The proposed IUXG methodology institutionalised UX in the WCG e-Government website environment. This research is a major contribution, to addressing the current lack of UX practices in South African PGs. South African PGs can use the proposed IUXG methodology to institutionalise UX and it will assist PG officials to develop increased UX maturity levels. The advantage of the IUXG methodology is that it provides PG officials with a step-by-step method how to institutionalise UX in a PG by following the six phases of the IUXG methodology: startup, setup, organisation, method, standards and long-term. The IUXG methodology will assist South African PGs to establish UX practice as a norm. The IUXG methodology will assist PGs with the resources, methods and tools to enable them to implement UX guidelines, which will result in an improved, more usable and more user-centric PG e-Government website.
- Full Text:
- Date Issued: 2012
- Authors: Pretorius, Marco Cobus
- Date: 2012
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Government Web sites -- South Africa , Web site development , Electronic government information
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10489 , http://hdl.handle.net/10948/d1019961
- Description: The number of citizens, who access e-Government websites, is growing significantly and their expectations for additional services are increasing. The Internet has become an essential instrument to distribute information to citizens. Poorly designed websites, however, can divide governments and its citizens. Consensus amongst researchers is that user experience (UX) is an important factor in designing websites specifically e-Government websites. Problems, experienced with website usability, prevent people from accessing and eventually adopting technology, such as e-Government. Countries, such as the United States, United Kingdom and Canada, have shown increased support for UX in e-Government websites. At present, a number of guidelines and design principles exists for e-Government website UX design; however, the effectiveness of the implementation of these guidelines and principles depends on the profiles of the individuals on a website development team and on an organisation’s understanding of UX. Despite the highlighted importance of UX, guidelines and principles are rarely adopted in South African e-Government websites. Usability and UX guidelines cannot be implemented; if there is no executive support; an inadequately trained staff; no routine UX practice; insufficient budget; inefficient use of usability methodologies and user-centred design (UCD) processes. The challenge at present in the UX design field is the institutionalisation of UX, specifically at government level. The goal of this research was to propose and evaluate a methodology to institutionalise UX in South African Provincial Governments (PGs), named the “Institutionalise UX in Government (IUXG) methodology”. The research used the Western Cape Government (WCG) in South Africa as a case study to evaluate the proposed methodology to institutionalise UX in a South African PG. The IUXG methodology (1.0) was proposed from five UX methodologies, as well as from best practices found in literature. The IUXG methodology (1.1) was updated, based on results of a survey to South African PGs, a survey to WCG employees, as well as literature from the WCG. The IUXG methodology (2.0) was updated a final time, based on the case study results and on a confirmation survey with WCG employees after the implementation of the case study. The research study made use of three surveys during this research. The first survey, incorporating UX maturity models, confirmed that understanding and buy-in of UX are limited and that UX maturity levels are low at South African PG level. The second and third surveys were administered to WCG e-Government website officials before and after the implementation of the IUXG methodology. The surveys measured the UX maturity level of the WCG in the component, e-Government for Citizens (e-G4C), responsible for the WCG e-Government website. The final survey results demonstrated that, after the implementation of the IUXG methodology, the WCG improved its level of UX maturity on the identified UX maturity models. Implementation of the IUXG methodology institutionalised UX in the WCG. UX activities became standard practice in the e-Government website environment after the systems development lifecycle (SDLC) incorporated UCD. UX policy, strategy and guidelines were documented for the WCG e-Government website. The WCG constructed the first usability testing facility for a South African PG and improvements to the WCG e-Government website were implemented. The proposed IUXG methodology institutionalised UX in the WCG e-Government website environment. This research is a major contribution, to addressing the current lack of UX practices in South African PGs. South African PGs can use the proposed IUXG methodology to institutionalise UX and it will assist PG officials to develop increased UX maturity levels. The advantage of the IUXG methodology is that it provides PG officials with a step-by-step method how to institutionalise UX in a PG by following the six phases of the IUXG methodology: startup, setup, organisation, method, standards and long-term. The IUXG methodology will assist South African PGs to establish UX practice as a norm. The IUXG methodology will assist PGs with the resources, methods and tools to enable them to implement UX guidelines, which will result in an improved, more usable and more user-centric PG e-Government website.
- Full Text:
- Date Issued: 2012
Curriculum reform in Lesotho: exploring the interface between environmental education and geography in selected schools
- Authors: Raselimo, Mohaeka Gabriel
- Date: 2012
- Subjects: Curriculum planning -- Lesotho Curriculum change -- Lesotho Educational evaluation -- Lesotho Environmental education -- Study and teaching (Secondary) -- Lesotho Geography -- Study and teaching (Secondary) -- Lesotho Agenda 21 (Program)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1488 , http://hdl.handle.net/10962/d1003369
- Description: This study sought to explore the interface between environmental education (EE) and school geography with a view to understanding a process of curriculum reform in the context of Lesotho. The research was based on the curriculum reform process that was initiated by a Danish donor-funded project, known as the Lesotho Environmental Education Support Project (LEESP), which operated from 2001 to 2004. Driven by a sustainable development imperative, the project was intended to assist Lesotho in the implementation of local action for Agenda 21 by introducing environmental education into the formal education system. Deviating slightly from much published research on geographical and environmental education, which focuses on how geography contributes to environmental education, this study explored how the latter has shaped the former in terms of content and pedagogy. Using the lens of critical curriculum theory, I sought to understand the political nature of the curriculum and of curriculum change, focusing on the LEESP curriculum policy development, dissemination and implementation at classroom level. The study employed Bernstein's concepts of classification and framing to illuminate issues of power and control between discourses, and between teachers and learners. Operating within an interpretive qualitative research orientation, the study used a case study method focusing on five secondary/high schools in Lesotho. The data was generated through document analysis, interviews and classroom observations. The study examined the assumptions, values and ideologies underpinning environmental education curriculum intentions as reflected in LEESP documents. It also investigated the social process of conceptualising and disseminating environmental education to understand the challenges faced as education practitioners made sense of environmental education innovations in the specific contexts of Lesotho, and how these could possibly influence what happens at the classroom level. The analysis of the LEESP documents revealed that while there are many areas of synergy between the LEESP environmental education policy guidelines and the national education ideals in Lesotho, achievement of the transformational visions of action competence, which was the overarching concept in the reform process, would require major structural changes. The study also highlights issues of participation, contestations, tensions and contradictions associated with the conceptualisation and dissemination of environmental education. At implementation level, there is a disjuncture between environmental education policy intentions and practice. Geography teachers in the research schools generally understood the existence of environmental education in their schools in terms of environmental management. The findings also revealed that while there is generally a strong environmental dimension in geography content, as reflected in both curriculum materials and classroom practice, the subject still retains its disciplinary boundaries and makes little use of knowledge from other subjects or the everyday knowledge of the learners. Finally, it emerged that while the geography teachers in their rhetoric espoused learner-centred methods, in practice they generally employed traditional teacher-centred and book-centred methods. The study concludes that a lack of change in school geography in Lesotho, of the sort envisaged in LEESP, may be attributed to contextual and structural factors such as an overemphasis on examinations, and certain perceptions on the part of teachers and learners embedded in the history and culture of their society. A model of teacher professional development capable of supporting curriculum change is therefore proposed.
- Full Text:
- Date Issued: 2012
- Authors: Raselimo, Mohaeka Gabriel
- Date: 2012
- Subjects: Curriculum planning -- Lesotho Curriculum change -- Lesotho Educational evaluation -- Lesotho Environmental education -- Study and teaching (Secondary) -- Lesotho Geography -- Study and teaching (Secondary) -- Lesotho Agenda 21 (Program)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1488 , http://hdl.handle.net/10962/d1003369
- Description: This study sought to explore the interface between environmental education (EE) and school geography with a view to understanding a process of curriculum reform in the context of Lesotho. The research was based on the curriculum reform process that was initiated by a Danish donor-funded project, known as the Lesotho Environmental Education Support Project (LEESP), which operated from 2001 to 2004. Driven by a sustainable development imperative, the project was intended to assist Lesotho in the implementation of local action for Agenda 21 by introducing environmental education into the formal education system. Deviating slightly from much published research on geographical and environmental education, which focuses on how geography contributes to environmental education, this study explored how the latter has shaped the former in terms of content and pedagogy. Using the lens of critical curriculum theory, I sought to understand the political nature of the curriculum and of curriculum change, focusing on the LEESP curriculum policy development, dissemination and implementation at classroom level. The study employed Bernstein's concepts of classification and framing to illuminate issues of power and control between discourses, and between teachers and learners. Operating within an interpretive qualitative research orientation, the study used a case study method focusing on five secondary/high schools in Lesotho. The data was generated through document analysis, interviews and classroom observations. The study examined the assumptions, values and ideologies underpinning environmental education curriculum intentions as reflected in LEESP documents. It also investigated the social process of conceptualising and disseminating environmental education to understand the challenges faced as education practitioners made sense of environmental education innovations in the specific contexts of Lesotho, and how these could possibly influence what happens at the classroom level. The analysis of the LEESP documents revealed that while there are many areas of synergy between the LEESP environmental education policy guidelines and the national education ideals in Lesotho, achievement of the transformational visions of action competence, which was the overarching concept in the reform process, would require major structural changes. The study also highlights issues of participation, contestations, tensions and contradictions associated with the conceptualisation and dissemination of environmental education. At implementation level, there is a disjuncture between environmental education policy intentions and practice. Geography teachers in the research schools generally understood the existence of environmental education in their schools in terms of environmental management. The findings also revealed that while there is generally a strong environmental dimension in geography content, as reflected in both curriculum materials and classroom practice, the subject still retains its disciplinary boundaries and makes little use of knowledge from other subjects or the everyday knowledge of the learners. Finally, it emerged that while the geography teachers in their rhetoric espoused learner-centred methods, in practice they generally employed traditional teacher-centred and book-centred methods. The study concludes that a lack of change in school geography in Lesotho, of the sort envisaged in LEESP, may be attributed to contextual and structural factors such as an overemphasis on examinations, and certain perceptions on the part of teachers and learners embedded in the history and culture of their society. A model of teacher professional development capable of supporting curriculum change is therefore proposed.
- Full Text:
- Date Issued: 2012
A comparative polarimetric study of the 43 GHz and 86 GHz SiO masers toward the supergiant star VY CMa
- Authors: Richter, Laura
- Date: 2012
- Subjects: Masers Supergiant stars Polarization (Light) Very long baseline interferometry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5454 , http://hdl.handle.net/10962/d1005239
- Description: The aim of this thesis is to perform observational tests of SiO maser polarisation and excitation models, using component-level comparisons of multiple SiO maser transitions in the 43 GHz and 86 GHz bands at milliarcsecond resolution. These observations reqwre very long baseline interferometric imaging with very accurate polarimetric calibration. The supergiant star VY CMa was chosen as the object of this study due to its high SiO maser luminosity, many detected SiO maser lines, and intrinsic scientific interest. Two epochs of full-polarisation VLBA observations of VY CMa were performed. The Epoch 2 observations were reduced using several new data reduction methods developed as part of this work, and designed specifically to improve the accuracy of circular polarisation calibration of spectral-line VLBI observations at millimetre wavelengths. The accuracy is estimated to be better than 1% using these methods. The Epoch 2 images show a concentration of v= l and v=2 J= 1-0 SiO masers to the east and northeast of the assumed stellar position. The v=l J=2-1 masers were more evenly distributed around the star, with a notable lack of emission in the northeast. There is appreciable spatial overlap between these three lines. The nature of the overlap is generally consistent with the predictions of hydrodynamical circumstellar SiO maser simulations. Where the v=l J = 1-0 and J =2-1 features overlap, the v=l J = 2-1 emission is usually considerably weaker. This is not predicted by current hydrodynamical models, but can be explained in the context of collisional pumping in a low density environment. Six observational tests of weak-splitting maser polarisation models were performed, including intercomparisons of linear polarisation in the v=l J=1-0 and J=2-1lines, linear polarisation versus saturation level, linear polarisation versus distance from the star, circular polarisation in the v= l J = 1-0 and J=2-1 lines, circular versus linear polarisation and modeling of ~ 900 electric-vector position angle rotations. The polarisation model tests generally do not support non-Zeeman circular polarisation mechanisms. For the linear polarisation tests, the results are more consistent with models that predict similar linear polarisation across transitions. The scientific importance of these tests is described in detail and avenues for future work are described.
- Full Text:
- Date Issued: 2012
- Authors: Richter, Laura
- Date: 2012
- Subjects: Masers Supergiant stars Polarization (Light) Very long baseline interferometry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5454 , http://hdl.handle.net/10962/d1005239
- Description: The aim of this thesis is to perform observational tests of SiO maser polarisation and excitation models, using component-level comparisons of multiple SiO maser transitions in the 43 GHz and 86 GHz bands at milliarcsecond resolution. These observations reqwre very long baseline interferometric imaging with very accurate polarimetric calibration. The supergiant star VY CMa was chosen as the object of this study due to its high SiO maser luminosity, many detected SiO maser lines, and intrinsic scientific interest. Two epochs of full-polarisation VLBA observations of VY CMa were performed. The Epoch 2 observations were reduced using several new data reduction methods developed as part of this work, and designed specifically to improve the accuracy of circular polarisation calibration of spectral-line VLBI observations at millimetre wavelengths. The accuracy is estimated to be better than 1% using these methods. The Epoch 2 images show a concentration of v= l and v=2 J= 1-0 SiO masers to the east and northeast of the assumed stellar position. The v=l J=2-1 masers were more evenly distributed around the star, with a notable lack of emission in the northeast. There is appreciable spatial overlap between these three lines. The nature of the overlap is generally consistent with the predictions of hydrodynamical circumstellar SiO maser simulations. Where the v=l J = 1-0 and J =2-1 features overlap, the v=l J = 2-1 emission is usually considerably weaker. This is not predicted by current hydrodynamical models, but can be explained in the context of collisional pumping in a low density environment. Six observational tests of weak-splitting maser polarisation models were performed, including intercomparisons of linear polarisation in the v=l J=1-0 and J=2-1lines, linear polarisation versus saturation level, linear polarisation versus distance from the star, circular polarisation in the v= l J = 1-0 and J=2-1 lines, circular versus linear polarisation and modeling of ~ 900 electric-vector position angle rotations. The polarisation model tests generally do not support non-Zeeman circular polarisation mechanisms. For the linear polarisation tests, the results are more consistent with models that predict similar linear polarisation across transitions. The scientific importance of these tests is described in detail and avenues for future work are described.
- Full Text:
- Date Issued: 2012
The heuristic significance of enacted visualisation
- Authors: Samson, Duncan Alistair
- Date: 2012
- Subjects: Heuristic Visualization Problem solving Pattern perception Problem solving -- Ability testing Mathematics -- Study and teaching Education -- Research Interdisciplinary approach to knowledge
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1552 , http://hdl.handle.net/10962/d1003434
- Description: This study is centred on an analysis of pupils' lived experience while engaged in the generalisation of linear sequences/progressions presented in a pictorial context. The study is oriented within the conceptual framework of qualitative research, and is anchored within an interpretive paradigm. A case study methodological strategy was adopted, the research participants being the members of a mixed gender, high ability Grade 9 class of 23 pupils at an independent school in South Africa. The analytical framework is structured around a combination of complementary multiple perspectives provided by three theoretical ideas, enactivism, figural apprehension, and knowledge objectification. An important aspect of this analytical framework is the sensitivity it shows to the visual, phenomenological and semiotic aspects of figural pattern generalisation. It is the central thesis of this study that the combined complementary multiple perspectives of enactivism, figural apprehension and knowledge objectification provide a powerful depth of analysis to the exploration of the inter-relationship between the embodied processes of pattern generalisation and the visualisation of pictorial cues. The richly textured tapestry of activity captured through a multi-systemic semiotic analysis of participants' generalisation activity stands testament to this central thesis. Insights gleaned from this study are presented as practical strategies which support and encourage a multiple representational approach to pattern generalisation in the pedagogical context of the classroom.
- Full Text:
- Date Issued: 2012
- Authors: Samson, Duncan Alistair
- Date: 2012
- Subjects: Heuristic Visualization Problem solving Pattern perception Problem solving -- Ability testing Mathematics -- Study and teaching Education -- Research Interdisciplinary approach to knowledge
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1552 , http://hdl.handle.net/10962/d1003434
- Description: This study is centred on an analysis of pupils' lived experience while engaged in the generalisation of linear sequences/progressions presented in a pictorial context. The study is oriented within the conceptual framework of qualitative research, and is anchored within an interpretive paradigm. A case study methodological strategy was adopted, the research participants being the members of a mixed gender, high ability Grade 9 class of 23 pupils at an independent school in South Africa. The analytical framework is structured around a combination of complementary multiple perspectives provided by three theoretical ideas, enactivism, figural apprehension, and knowledge objectification. An important aspect of this analytical framework is the sensitivity it shows to the visual, phenomenological and semiotic aspects of figural pattern generalisation. It is the central thesis of this study that the combined complementary multiple perspectives of enactivism, figural apprehension and knowledge objectification provide a powerful depth of analysis to the exploration of the inter-relationship between the embodied processes of pattern generalisation and the visualisation of pictorial cues. The richly textured tapestry of activity captured through a multi-systemic semiotic analysis of participants' generalisation activity stands testament to this central thesis. Insights gleaned from this study are presented as practical strategies which support and encourage a multiple representational approach to pattern generalisation in the pedagogical context of the classroom.
- Full Text:
- Date Issued: 2012
Nation branding: case study of Zimbabwe
- Authors: Sena, Steven
- Date: 2012
- Subjects: Branding (Marketing) -- Zimbabwe , Nation-building -- Zimbabwe , Sports and tourism -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9303 , http://hdl.handle.net/10948/d1015616
- Description: Every nation exists as a brand with either positive or negative attributes and any other nation and individual that interact with it either will positively or negatively contribute to its nation image. A nation’s brand image may have evolved over many years, shaped by wars, religion, diplomacy or the lack of it, international sporting triumph or disasters, and by the brand itself. Zimbabwe as a nation is suffering from a negative image gained during 2000-2008 that has been characterised by inter alia the fast track land reform programme, political instability, corruption, hyperinflation, and so forth. The country has experienced a major transformation in its political environment that has had a positive effect on all sectors of national development. The new inclusive government, thriving on national unity has seen the people of Zimbabwe combining effort to work together to sustain the development of the country. The aim of this study was to investigate how nation branding for Zimbabwe can help the country to brand itself as a safe destination for tourists, investors, and visitors. The major question therefore, pertains to how all sectors in the economy of Zimbabwe can combine their efforts to brand Zimbabwe and make it compete more efficiently at all levels. Empirical findings revealed that tourist attractions have a positive relationship with nation branding. The empirical results also indicated that entertainment events have a positive relationship with nation branding. It can be recommended that Zimbabwe needs to identify tourist attractions and entertainment events to increase its nation branding. The empirical results of the study also indicated that nation branding has a positive relationship with nation building in Zimbabwe. It was also shown that nation branding has a positive relationship with good governance in Zimbabwe. These results indicate that it would be easier to build the Zimbabwean nation when its brand is strong. Good governance, on the other hand, will increase if the nation’s branding improves.
- Full Text:
- Date Issued: 2012
- Authors: Sena, Steven
- Date: 2012
- Subjects: Branding (Marketing) -- Zimbabwe , Nation-building -- Zimbabwe , Sports and tourism -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9303 , http://hdl.handle.net/10948/d1015616
- Description: Every nation exists as a brand with either positive or negative attributes and any other nation and individual that interact with it either will positively or negatively contribute to its nation image. A nation’s brand image may have evolved over many years, shaped by wars, religion, diplomacy or the lack of it, international sporting triumph or disasters, and by the brand itself. Zimbabwe as a nation is suffering from a negative image gained during 2000-2008 that has been characterised by inter alia the fast track land reform programme, political instability, corruption, hyperinflation, and so forth. The country has experienced a major transformation in its political environment that has had a positive effect on all sectors of national development. The new inclusive government, thriving on national unity has seen the people of Zimbabwe combining effort to work together to sustain the development of the country. The aim of this study was to investigate how nation branding for Zimbabwe can help the country to brand itself as a safe destination for tourists, investors, and visitors. The major question therefore, pertains to how all sectors in the economy of Zimbabwe can combine their efforts to brand Zimbabwe and make it compete more efficiently at all levels. Empirical findings revealed that tourist attractions have a positive relationship with nation branding. The empirical results also indicated that entertainment events have a positive relationship with nation branding. It can be recommended that Zimbabwe needs to identify tourist attractions and entertainment events to increase its nation branding. The empirical results of the study also indicated that nation branding has a positive relationship with nation building in Zimbabwe. It was also shown that nation branding has a positive relationship with good governance in Zimbabwe. These results indicate that it would be easier to build the Zimbabwean nation when its brand is strong. Good governance, on the other hand, will increase if the nation’s branding improves.
- Full Text:
- Date Issued: 2012
Biological synthesis of metallic nanoparticles and their interactions with various biomedical targets
- Authors: Sennuga, Afolake Temitope
- Date: 2012
- Subjects: Nanoparticles Biosynthesis Nanotechnology Biomineralization Morphology Ceruloplasmin Ribonucleases Adenosine triphosphatase Acetylcholinesterase Platinum Gold Silver
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4009 , http://hdl.handle.net/10962/d1004069
- Description: The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the past decade owing to their unique properties that make them applicable in different fields of science and technology. The limitation to the use of these nanoparticles is the paucity of an effective method of synthesis that will produce homogeneous size and shape nanoparticles as well as particles with limited or no toxicity to the human health and the environment. The biological method of nanoparticle synthesis is a relatively simple, cheap and environmentally friendly method than the conventional chemical method of synthesis and thus gains an upper hand. The biomineralization of nanoparticles in protein cages is one of such biological approaches used in the generation of nanoparticles. This method of synthesis apart from being a safer method in the production of nanoparticles is also able to control particle morphology. In this study, a comparative biological synthesis, characterization and biomedical effects of metallic nanoparticles of platinum, gold and silver were investigated. Metallic nanoparticles were biologically synthesized using cage-like (apoferritin), barrel-like (GroEL) and non-caged (ribonuclease) proteins. Nanoparticles generated were characterized using common techniques such as UV-visible spectroscopy, scanning and transmission electron microscopy, inductively coupled optical emission spectroscopy, Fourier transform infra-red spectroscopy and energy dispersion analysis of X-rays (EDAX). Nanoparticles synthesised biologically using apoferritin, GroEL and RNase with exhibited similar chemical and physical properties as thoses nanoparticles generated chemically. In addition, the metallic nanoparticles fabricated within the cage-like and barrel-like cavities of apoferritin and GroEL respectively, resulted in nanoparticles with relatively uniform morphology as opposed to those obtained with the non-caged ribonuclease. The enzymatic (ferroxidase) activity of apoferritin was found to be greatly enhanced with platinum (9-fold), gold (7-fold) and silver (54-fold) nanoparticles. The ATPase activity of GroEL was inhibited by silver nanoparticles (64%), was moderately activated by gold nanoparticles (47%) and considerably enhanced by platinum nanoparticles (85%). The hydrolytic activity of RNase was however, lowered by these metallic nanoparticles (90% in Ag nanoparticles) and to a higher degree with platinum (95%) and gold nanoparticles (~100%). The effect of synthesized nanoparticles on the respective enzyme activities of these proteins was also investigated and the potential neurotoxic property of these particles was also determined by an in vitro interaction with acetylcholinesterase. Protein encapsulated nanoparticles with apoferrtin and GroEL showed a decreased inhibition of acetylcholinesterase (<50%) compared with nanoparticles attached to ribonuclease (>50%). Thus, it can be concluded that the cavities of apoferitin and GroEL acted as nanobiofactories for the synthesis and confinement of the size and shape of nanoparticles. Furthermore, the interior of these proteins provided a shielding effect for these nanoparticles and thus reduced/prevented their possible neurotoxic effect and confirmed safety in their method of production and application. The findings from this study would prove beneficial in the application of these nanoparticles as a potential drug/drug delivery vehicle for the prevention, treatment/management of diseases associated with these enzymes/proteins.
- Full Text:
- Date Issued: 2012
- Authors: Sennuga, Afolake Temitope
- Date: 2012
- Subjects: Nanoparticles Biosynthesis Nanotechnology Biomineralization Morphology Ceruloplasmin Ribonucleases Adenosine triphosphatase Acetylcholinesterase Platinum Gold Silver
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4009 , http://hdl.handle.net/10962/d1004069
- Description: The synthesis of nanostructured materials, especially metallic nanoparticles, has accrued utmost interest over the past decade owing to their unique properties that make them applicable in different fields of science and technology. The limitation to the use of these nanoparticles is the paucity of an effective method of synthesis that will produce homogeneous size and shape nanoparticles as well as particles with limited or no toxicity to the human health and the environment. The biological method of nanoparticle synthesis is a relatively simple, cheap and environmentally friendly method than the conventional chemical method of synthesis and thus gains an upper hand. The biomineralization of nanoparticles in protein cages is one of such biological approaches used in the generation of nanoparticles. This method of synthesis apart from being a safer method in the production of nanoparticles is also able to control particle morphology. In this study, a comparative biological synthesis, characterization and biomedical effects of metallic nanoparticles of platinum, gold and silver were investigated. Metallic nanoparticles were biologically synthesized using cage-like (apoferritin), barrel-like (GroEL) and non-caged (ribonuclease) proteins. Nanoparticles generated were characterized using common techniques such as UV-visible spectroscopy, scanning and transmission electron microscopy, inductively coupled optical emission spectroscopy, Fourier transform infra-red spectroscopy and energy dispersion analysis of X-rays (EDAX). Nanoparticles synthesised biologically using apoferritin, GroEL and RNase with exhibited similar chemical and physical properties as thoses nanoparticles generated chemically. In addition, the metallic nanoparticles fabricated within the cage-like and barrel-like cavities of apoferritin and GroEL respectively, resulted in nanoparticles with relatively uniform morphology as opposed to those obtained with the non-caged ribonuclease. The enzymatic (ferroxidase) activity of apoferritin was found to be greatly enhanced with platinum (9-fold), gold (7-fold) and silver (54-fold) nanoparticles. The ATPase activity of GroEL was inhibited by silver nanoparticles (64%), was moderately activated by gold nanoparticles (47%) and considerably enhanced by platinum nanoparticles (85%). The hydrolytic activity of RNase was however, lowered by these metallic nanoparticles (90% in Ag nanoparticles) and to a higher degree with platinum (95%) and gold nanoparticles (~100%). The effect of synthesized nanoparticles on the respective enzyme activities of these proteins was also investigated and the potential neurotoxic property of these particles was also determined by an in vitro interaction with acetylcholinesterase. Protein encapsulated nanoparticles with apoferrtin and GroEL showed a decreased inhibition of acetylcholinesterase (<50%) compared with nanoparticles attached to ribonuclease (>50%). Thus, it can be concluded that the cavities of apoferitin and GroEL acted as nanobiofactories for the synthesis and confinement of the size and shape of nanoparticles. Furthermore, the interior of these proteins provided a shielding effect for these nanoparticles and thus reduced/prevented their possible neurotoxic effect and confirmed safety in their method of production and application. The findings from this study would prove beneficial in the application of these nanoparticles as a potential drug/drug delivery vehicle for the prevention, treatment/management of diseases associated with these enzymes/proteins.
- Full Text:
- Date Issued: 2012
Photoconductive spectroscopy of GaSb thin films
- Authors: Shura, Megersa Wodajo
- Date: 2012
- Subjects: Photoelectron spectroscopy , Photoconductivity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10549 , http://hdl.handle.net/10948/d1019937
- Description: In this study, we have investigated the photo-response of gallium antimonide (GaSb) by measuring the spectral, injection level, as well as the temperature dependence of the steady-state photoconductivity of epitaxial films. By combining the various photo-response measurements with-galvanometric measurements, the effective excess carrier lifetimes could be calculated and described in terms of the various experimental variables considered. From a comparison of the measured and theoretical carrier lifetimes, a clear discrepancy was found for the injection dependent results. This inconsistency between the expected and measured behaviours was resolved using a two-layer model to describe the photo-conductive response of the thin film. In this model, the generation/recombination processes are considered for the bulk as well as for a depleted near-surface region. By combining these two contributions when calculating the total excess photocurrent, the various experimental results could be successfully described. The photo-response measurements revealed that the main contribution to the photocurrent came from the near-surface region, where the bandto- band and Auger recombination transitions are reduced. From the simulation of the injection level dependence of the excess carrier lifetime, some of the near-surface characteristics, such as the position of the surface Fermi-level and the surface recombination velocity, could be determined. In the case of p-type GaSb, the room temperature surface Fermi-level was found to be pinned (290±20) meV above the valence band maximum, whereas the n-type material had a pinning position of (150±20) meV above the valence band maximum. These pinning positions were shown to be independent of the doping density and relatively insensitive to the surface treatments considered. The presence of a near-surface depletion region, as well as the position of the surface Fermi-level, was corroborated by Raman spectroscopy. From a comparison of the phonon mode and the phonon-hole plasmon coupled mode, a surface Fermi-level position of (300 ± 30) meV was deduced for p-type GaSb. Finally, the effect various surface treatments have on the photo-response, and related surface properties, were investigated. Removal of the native oxide (HCl:H2O) followed by sulphur passivation (Na2S:9H2O) results in a slight decrease in the surface Fermi-level position. Aging studies however revealed that the surface characteristics reverted back to the untreated values following a few days in air. Coating the GaSb surfaces with a thin ZnS layer was found to have little effect on the surface potential, resulting only in a slight increase in the near-surface donor density. The sensitivity of the measured photocurrent to surface treatments and changes in the ambient with cooling, further validate the importance of considering the surface potential and the related space-charge when describing the photoconductive response of GaSb thin films.
- Full Text:
- Date Issued: 2012
- Authors: Shura, Megersa Wodajo
- Date: 2012
- Subjects: Photoelectron spectroscopy , Photoconductivity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10549 , http://hdl.handle.net/10948/d1019937
- Description: In this study, we have investigated the photo-response of gallium antimonide (GaSb) by measuring the spectral, injection level, as well as the temperature dependence of the steady-state photoconductivity of epitaxial films. By combining the various photo-response measurements with-galvanometric measurements, the effective excess carrier lifetimes could be calculated and described in terms of the various experimental variables considered. From a comparison of the measured and theoretical carrier lifetimes, a clear discrepancy was found for the injection dependent results. This inconsistency between the expected and measured behaviours was resolved using a two-layer model to describe the photo-conductive response of the thin film. In this model, the generation/recombination processes are considered for the bulk as well as for a depleted near-surface region. By combining these two contributions when calculating the total excess photocurrent, the various experimental results could be successfully described. The photo-response measurements revealed that the main contribution to the photocurrent came from the near-surface region, where the bandto- band and Auger recombination transitions are reduced. From the simulation of the injection level dependence of the excess carrier lifetime, some of the near-surface characteristics, such as the position of the surface Fermi-level and the surface recombination velocity, could be determined. In the case of p-type GaSb, the room temperature surface Fermi-level was found to be pinned (290±20) meV above the valence band maximum, whereas the n-type material had a pinning position of (150±20) meV above the valence band maximum. These pinning positions were shown to be independent of the doping density and relatively insensitive to the surface treatments considered. The presence of a near-surface depletion region, as well as the position of the surface Fermi-level, was corroborated by Raman spectroscopy. From a comparison of the phonon mode and the phonon-hole plasmon coupled mode, a surface Fermi-level position of (300 ± 30) meV was deduced for p-type GaSb. Finally, the effect various surface treatments have on the photo-response, and related surface properties, were investigated. Removal of the native oxide (HCl:H2O) followed by sulphur passivation (Na2S:9H2O) results in a slight decrease in the surface Fermi-level position. Aging studies however revealed that the surface characteristics reverted back to the untreated values following a few days in air. Coating the GaSb surfaces with a thin ZnS layer was found to have little effect on the surface potential, resulting only in a slight increase in the near-surface donor density. The sensitivity of the measured photocurrent to surface treatments and changes in the ambient with cooling, further validate the importance of considering the surface potential and the related space-charge when describing the photoconductive response of GaSb thin films.
- Full Text:
- Date Issued: 2012
Synthesis, characterization and antimicrobial activity of copper (II) complexes of some hydroxybenzaldimines and their derivatives
- Authors: Sobola, Abdullahi Owolabi
- Date: 2012
- Subjects: Copper , Schiff bases , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4534 , http://hdl.handle.net/10962/d1016258
- Description: This study focuses on the antimicrobial activity of Cu(II) complexes of some orthohydroxybenzaldimines and its derivatives. Four different categories of Schiff base ligands were prepared by condensing salicylaldehyde, o-vanillin, p-vanillin and vanillin with p- and osubstituted anilines; 1-aminonaphthalene; 2- and 3-aminopyridine; 2- and 3- aminomethylpyridine as well as 2-aminobenzimidazole. The last category was prepared from ophenylenediamine and o-vanillin. The Schiff base ligands have been characterized by a combination of elemental analysis and spectral (¹H- and ¹³C-NMR, UV/Visible, infrared and Raman) data. The existence of strong intramolecular hydrogen bonding in the orthohydoxybenzaldimines was evident from the chemical shift values of the hydroxyl proton in the ¹H-NMR spectra of the Schiff base ligands. The hydroxyl proton resonates at high frequency and thus absorbed far downfield at 13.46-11.83 ppm, reflecting the presence of hydrogen bonding between the hydroxyl proton and the imine nitrogen. In the p-substituted aniline analogues of the Schiff base, a plot of the chemical shift values of the hydroxyl proton against the Hammett's substituent parameters gave a linear correlation between the electronegativities of the substituents and the chemical shift values. The nitro group with the highest electronegativity caused the least deshielding of the hydroxyl proton and thus absorbed upfield compared to the less electronegative substituents such as the CH3 and OCH3 analogues. Likewise, in the solid state infrared spectra of the ligands, the hydroxyl stretching band of the ortho-hydroxyl Schiff base ligands was observed as a very broad band and at much lower frequency, 3100-2100 cm⁻¹, indicating the existence of strong intramolecular hydrogen bonding. In the same vein, ¹H- and ¹³C-NMR spectral data for the Schiff base ligands indicated that the prepared compounds exist in the enol form in aprotic solvent, chloroform. The methine proton appeared as singlet and there was no carbonyl signal in the ¹³C-NMR spectra of the Schiff base ligands. This was supported by the infrared data having no vibrational band attributable to the carbonyl stretching of the keto-form of the Schiff base ligands in solid state. However, the UV/Visible study of the Schiff base ligands in protic solvent, methanol, suggested the existence of some of the Schiff base ligands in keto-enol form. A band at greater than 400 nm was observed in the UV/Visible spectra of the ligands and this has been attributed to the presence of the keto form of orthohydroxyl Schiff base ligands in solution. A plot of the molar absorptivity (ε) of the band at greater than 400 nm against Hammett substituent parameters revealed that the intensity of the bands increased with the electronegativity of the substituents. The Cu(II) complexes of salicylaldehyde, o-vanillin and a few p-vanillin based Schiff base ligands are reported in this work. It was observed that introduction of Cu(II) ions into the ligand system resulted in the hydrolysis of the imine band in few cases. All the isolated complexes have been characterized by elemental analysis, conductivity measurement, infrared and UV/Visible spectral data. The structures of three of the Cu(II) complexes were further confirmed by X-ray single crystal diffraction. The Schiff base ligands either coordinated as neutral base through the imine nitrogen or via the imine nitrogen and the phenolic oxygen atoms. In addition, the benzimidazole-based and ovan-2-pico analogues equally coordinated through the imidazole N-3 nitrogen and the azine nitrogen respectively; thus acted as tridentate. In general, the synthesized Cu(II) complexes fell into seven categories viz: [Cu(LH)Cl(H₂O)]Cl; [Cu(LH)₂Cl₂].xH₂O; [CuL₂]; [Cu₂L₂]; [Cu(LH)Cl(H₂O)]Cl; and [MLCl]. The Cu(II) complexes of the form, M(LH)₂Cl₂.xH₂O were either 1:1 or non-electrolyte in methanol and DMF. The third category, CuL₂, was however, non-electrolyte existing as neutral four coordinate Cu(II) complexes. X-ray single crystal structure of Cu(II) complexes derived from the ammonia-based Schiff bases revealed a square planar geometry for the complexes and this agreed with the planar geometry that has been reported for Cu(II) complexes of N-arylsalicylaldimines of the type studied in this work. The complexes, [Cu₂L₂], resulted from the ortho-hydroxyaniline analogues and were polymeric with the Schiff base ligands coordinating to the Cu(II) ions as tridentate dibasic via the imine nitrogen, phenolic oxygen and the aminophenolic oxygen atoms. Cu(II) complexes prepared from ovan-2-ampy and ovan-2-pico Schiff bases were of the forms [Cu(LH)Cl(H₂O)]Cl and [CuLCl] respectively. The X-ray crystal structure of [Cu(ovan-2- pico)Cl] revealed a four-coordinate square planar geometry for the complex. In the same vein, the o-phenylenediamine complexes were of the form [Cu(L)(H₂O)], with the X-ray crystal structure of [Cu(bis-ovanphen)(H₂O)] revealing a square pyramidal geometry. The Schiff base ligands and the isolated Cu(II) complexes have been evaluated for their antimicrobial activity against three bacterial strains (Escherichia coli ATCC® 8739™*, Staphylococcus aureus subsp. aureus ATCC® 6538™* and Bacillus subtilis subsp. spizizeni ATCC® 6633™*) and one fungal strain, Candida albicans ATCC® 2091™*, using agar disc diffusion and broth dilution techniques. It was observed that the presence of the methoxyl group at the ortho-position of the aldehyde moiety of the Schiff base ligands enhanced the activity of the ligand tremendously and thus the o-vanillin analogues showed the highest potency against the tested organisms. In addition, the hydroxyaniline analogues were equally the most promising of all the substituted aniline based Schiff bases. The o-vanillin analogues of the aminopyridines and aminomethylpyridines also exhibited significant activity against the tested organisms. All the 2-aminobenzimidazole series were active against the tested organisms. It should be noted that E. coli was the least susceptible of all the microorganisms while the highest potency was exhibited against the fungus of choice, Candida albicans. Lastly, chelation of the Schiff base ligands with Cu(II) ions did not have significant influence on the activity of the free ligands.
- Full Text:
- Date Issued: 2012
- Authors: Sobola, Abdullahi Owolabi
- Date: 2012
- Subjects: Copper , Schiff bases , Ligands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4534 , http://hdl.handle.net/10962/d1016258
- Description: This study focuses on the antimicrobial activity of Cu(II) complexes of some orthohydroxybenzaldimines and its derivatives. Four different categories of Schiff base ligands were prepared by condensing salicylaldehyde, o-vanillin, p-vanillin and vanillin with p- and osubstituted anilines; 1-aminonaphthalene; 2- and 3-aminopyridine; 2- and 3- aminomethylpyridine as well as 2-aminobenzimidazole. The last category was prepared from ophenylenediamine and o-vanillin. The Schiff base ligands have been characterized by a combination of elemental analysis and spectral (¹H- and ¹³C-NMR, UV/Visible, infrared and Raman) data. The existence of strong intramolecular hydrogen bonding in the orthohydoxybenzaldimines was evident from the chemical shift values of the hydroxyl proton in the ¹H-NMR spectra of the Schiff base ligands. The hydroxyl proton resonates at high frequency and thus absorbed far downfield at 13.46-11.83 ppm, reflecting the presence of hydrogen bonding between the hydroxyl proton and the imine nitrogen. In the p-substituted aniline analogues of the Schiff base, a plot of the chemical shift values of the hydroxyl proton against the Hammett's substituent parameters gave a linear correlation between the electronegativities of the substituents and the chemical shift values. The nitro group with the highest electronegativity caused the least deshielding of the hydroxyl proton and thus absorbed upfield compared to the less electronegative substituents such as the CH3 and OCH3 analogues. Likewise, in the solid state infrared spectra of the ligands, the hydroxyl stretching band of the ortho-hydroxyl Schiff base ligands was observed as a very broad band and at much lower frequency, 3100-2100 cm⁻¹, indicating the existence of strong intramolecular hydrogen bonding. In the same vein, ¹H- and ¹³C-NMR spectral data for the Schiff base ligands indicated that the prepared compounds exist in the enol form in aprotic solvent, chloroform. The methine proton appeared as singlet and there was no carbonyl signal in the ¹³C-NMR spectra of the Schiff base ligands. This was supported by the infrared data having no vibrational band attributable to the carbonyl stretching of the keto-form of the Schiff base ligands in solid state. However, the UV/Visible study of the Schiff base ligands in protic solvent, methanol, suggested the existence of some of the Schiff base ligands in keto-enol form. A band at greater than 400 nm was observed in the UV/Visible spectra of the ligands and this has been attributed to the presence of the keto form of orthohydroxyl Schiff base ligands in solution. A plot of the molar absorptivity (ε) of the band at greater than 400 nm against Hammett substituent parameters revealed that the intensity of the bands increased with the electronegativity of the substituents. The Cu(II) complexes of salicylaldehyde, o-vanillin and a few p-vanillin based Schiff base ligands are reported in this work. It was observed that introduction of Cu(II) ions into the ligand system resulted in the hydrolysis of the imine band in few cases. All the isolated complexes have been characterized by elemental analysis, conductivity measurement, infrared and UV/Visible spectral data. The structures of three of the Cu(II) complexes were further confirmed by X-ray single crystal diffraction. The Schiff base ligands either coordinated as neutral base through the imine nitrogen or via the imine nitrogen and the phenolic oxygen atoms. In addition, the benzimidazole-based and ovan-2-pico analogues equally coordinated through the imidazole N-3 nitrogen and the azine nitrogen respectively; thus acted as tridentate. In general, the synthesized Cu(II) complexes fell into seven categories viz: [Cu(LH)Cl(H₂O)]Cl; [Cu(LH)₂Cl₂].xH₂O; [CuL₂]; [Cu₂L₂]; [Cu(LH)Cl(H₂O)]Cl; and [MLCl]. The Cu(II) complexes of the form, M(LH)₂Cl₂.xH₂O were either 1:1 or non-electrolyte in methanol and DMF. The third category, CuL₂, was however, non-electrolyte existing as neutral four coordinate Cu(II) complexes. X-ray single crystal structure of Cu(II) complexes derived from the ammonia-based Schiff bases revealed a square planar geometry for the complexes and this agreed with the planar geometry that has been reported for Cu(II) complexes of N-arylsalicylaldimines of the type studied in this work. The complexes, [Cu₂L₂], resulted from the ortho-hydroxyaniline analogues and were polymeric with the Schiff base ligands coordinating to the Cu(II) ions as tridentate dibasic via the imine nitrogen, phenolic oxygen and the aminophenolic oxygen atoms. Cu(II) complexes prepared from ovan-2-ampy and ovan-2-pico Schiff bases were of the forms [Cu(LH)Cl(H₂O)]Cl and [CuLCl] respectively. The X-ray crystal structure of [Cu(ovan-2- pico)Cl] revealed a four-coordinate square planar geometry for the complex. In the same vein, the o-phenylenediamine complexes were of the form [Cu(L)(H₂O)], with the X-ray crystal structure of [Cu(bis-ovanphen)(H₂O)] revealing a square pyramidal geometry. The Schiff base ligands and the isolated Cu(II) complexes have been evaluated for their antimicrobial activity against three bacterial strains (Escherichia coli ATCC® 8739™*, Staphylococcus aureus subsp. aureus ATCC® 6538™* and Bacillus subtilis subsp. spizizeni ATCC® 6633™*) and one fungal strain, Candida albicans ATCC® 2091™*, using agar disc diffusion and broth dilution techniques. It was observed that the presence of the methoxyl group at the ortho-position of the aldehyde moiety of the Schiff base ligands enhanced the activity of the ligand tremendously and thus the o-vanillin analogues showed the highest potency against the tested organisms. In addition, the hydroxyaniline analogues were equally the most promising of all the substituted aniline based Schiff bases. The o-vanillin analogues of the aminopyridines and aminomethylpyridines also exhibited significant activity against the tested organisms. All the 2-aminobenzimidazole series were active against the tested organisms. It should be noted that E. coli was the least susceptible of all the microorganisms while the highest potency was exhibited against the fungus of choice, Candida albicans. Lastly, chelation of the Schiff base ligands with Cu(II) ions did not have significant influence on the activity of the free ligands.
- Full Text:
- Date Issued: 2012