South African public private partnership (PPP) projects
- Nyagwachi, Josiah Nyangaresi
- Authors: Nyagwachi, Josiah Nyangaresi
- Date: 2008
- Subjects: Public-private sector cooperation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9696 , http://hdl.handle.net/10948/716 , Public-private sector cooperation -- South Africa
- Description: The purpose of this thesis is to disseminate research work done towards a higher degree and report on the findings of the research that was conducted relative to South African Public Private Partnership (PPP) projects. The research investigated perceptions of PPP actors on the performance of operational PPP projects. The aim of the research was to fulfil the requirements for the award of the degree of philosophiae doctor in construction management; contribute to the PPP body of knowledge; contribute further understanding of the performance of PPP projects in South Africa; and develop a systemic model for a sustainable PPP system within the country and beyond. All the aforementioned have been achieved, despite the research limitations as indicated in Chapter 1. A case study approach was adopted to examine various performance aspects of operational South African PPP projects. The research was a multi-case study design. Each individual case study consisted of a ‘whole’ study, in which facts were gathered from the selected PPP projects and conclusions drawn on those facts. A web-based questionnaire was used to capture the experiences and perceptions of various actors involved directly, or indirectly in selected PPP projects. The sample stratum consisted of all operational PPP projects registered in accordance with Treasury Regulations as of December 2005 and other projects that reached financial closure before the Public Finance Management Act of 1999 became effective. PPPs involve highly complex procurement processes, are relatively new in South Africa and to date have attracted limited investigation to refine our understanding of the operational performance of PPP projects. This is notable, as significant financial and other resources are involved, and the perception exists that service delivery in most parts of the country is poor. Key empirical evidence from the research indicates that South Africa has developed a robust policy and regulatory framework for PPPs; has an inadequate level of PPP awareness and training; and lacks the project management capacity to facilitate deal flow. It is suggested that further research be conducted on a yearly basis, preferably every six months, so that trends can be established concerning various aspects of other operational PPPs. Further, it is recommended that the PPP Unit commission sector-specific studies that will conduct further research, to compare research across PPP and non-PPP contracts. The choice to conduct a multi-case study required extensive resources and time beyond the means available to the researcher. Further, the sensitive nature of PPP projects made it difficult to obtain required data at the first attempt. However, the researcher made several follow up calls and reminders before eventually obtaining the required data from the respondents. A systemic PPP model has been developed for PPP implementation and management. This model was tested for appropriateness by conducting a further survey on PPP participants attending an international conference on 'Financing of Infrastructure Development in Africa through Public Private Partnerships’ staged in August 2007, in the St. George Hotel, Johannesburg, South Africa. The findings from this research make an invaluable and original contribution to the PPP body of knowledge, provide insight for further research in this important field, refine the understanding of operational PPP projects, and provide direction for policy and decision makers in the public and private sectors, within South Africa and beyond.
- Full Text:
- Date Issued: 2008
- Authors: Nyagwachi, Josiah Nyangaresi
- Date: 2008
- Subjects: Public-private sector cooperation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9696 , http://hdl.handle.net/10948/716 , Public-private sector cooperation -- South Africa
- Description: The purpose of this thesis is to disseminate research work done towards a higher degree and report on the findings of the research that was conducted relative to South African Public Private Partnership (PPP) projects. The research investigated perceptions of PPP actors on the performance of operational PPP projects. The aim of the research was to fulfil the requirements for the award of the degree of philosophiae doctor in construction management; contribute to the PPP body of knowledge; contribute further understanding of the performance of PPP projects in South Africa; and develop a systemic model for a sustainable PPP system within the country and beyond. All the aforementioned have been achieved, despite the research limitations as indicated in Chapter 1. A case study approach was adopted to examine various performance aspects of operational South African PPP projects. The research was a multi-case study design. Each individual case study consisted of a ‘whole’ study, in which facts were gathered from the selected PPP projects and conclusions drawn on those facts. A web-based questionnaire was used to capture the experiences and perceptions of various actors involved directly, or indirectly in selected PPP projects. The sample stratum consisted of all operational PPP projects registered in accordance with Treasury Regulations as of December 2005 and other projects that reached financial closure before the Public Finance Management Act of 1999 became effective. PPPs involve highly complex procurement processes, are relatively new in South Africa and to date have attracted limited investigation to refine our understanding of the operational performance of PPP projects. This is notable, as significant financial and other resources are involved, and the perception exists that service delivery in most parts of the country is poor. Key empirical evidence from the research indicates that South Africa has developed a robust policy and regulatory framework for PPPs; has an inadequate level of PPP awareness and training; and lacks the project management capacity to facilitate deal flow. It is suggested that further research be conducted on a yearly basis, preferably every six months, so that trends can be established concerning various aspects of other operational PPPs. Further, it is recommended that the PPP Unit commission sector-specific studies that will conduct further research, to compare research across PPP and non-PPP contracts. The choice to conduct a multi-case study required extensive resources and time beyond the means available to the researcher. Further, the sensitive nature of PPP projects made it difficult to obtain required data at the first attempt. However, the researcher made several follow up calls and reminders before eventually obtaining the required data from the respondents. A systemic PPP model has been developed for PPP implementation and management. This model was tested for appropriateness by conducting a further survey on PPP participants attending an international conference on 'Financing of Infrastructure Development in Africa through Public Private Partnerships’ staged in August 2007, in the St. George Hotel, Johannesburg, South Africa. The findings from this research make an invaluable and original contribution to the PPP body of knowledge, provide insight for further research in this important field, refine the understanding of operational PPP projects, and provide direction for policy and decision makers in the public and private sectors, within South Africa and beyond.
- Full Text:
- Date Issued: 2008
Spatial and temporal variations in metals in the sediment and water of selected Eastern Cape Estuaries, South Africa
- Authors: Orr, Kyla Kathleen
- Date: 2008
- Subjects: Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5769 , http://hdl.handle.net/10962/d1005457 , Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Description: The spatio-temporal patterns in concentrations of selected metals within the sediment (Cd, Co, Cu, Fe, Pb, Ni and Zn) and water (Cd and Pb) of three permanently open estuaries (Kariega, Kowie, Great Fish) and six temporary open-closed estuaries (Mpekweni, East Kleinemonde, West Kleinemonde, Riet, Kasouga, Boknes) were investigated. The concentrations of metals were influenced by size composition and total organic content of the sediments. Enrichment factors (EFs), using Fe as a reference element, and baseline linear regression models for metals vs. Fe were calculated to assess the extent of metal enrichment in the sediments. The mean concentrations of metals in the sediments(mg·kg⁻¹) showed ranges of 0.28 – 2.31 for Cd, 1.26 – 6.24 Co, 0.69 – 6.93 for Cu, 2119 – 14912 for Fe, 2.29 –14.01 for Ni, 4.81 – 22.20 for Pb and 5.77 – 21.75 for Zn. Mean normalized enrichment factors ranged between 0.75 – 6.19 for Cd, 0.53 – 2.71 for Co, 0.22 – 0.84 for Cu, 0.30 – 1.87 for Ni, 0.99 – 3.17 for Pb and 0.14 – 0.98 for Zn. All nine estuaries had average enrichment factors of greater than 1 for Cd. In general there was no enrichment of Cu and Zn in the sediments of any of the estuaries included in this study (EFs < 1). The Kariega, East Kleinemonde, West Kleinemonde, Riet and Great Fish Estuaries showed some degree of enrichment for Co (1 < EF < 4), Ni (1 < EF < 2) and Pb (1 < EF < 4), while the Mpekweni, Kasouga, Boknes and Kowie Estuaries were unenriched with these metals (EF < 1). Enrichment factors for Cd, Co and Pb typically followed the development gradient along the estuaries, suggesting anthropogenic enrichment. The concentrations of Cd and Pb in the water of the nine estuaries were also determined. The average concentrations of Cd and Pb in the water (μg·ℓ⁻¹) ranged between 0.05 – 3.32 and 0.75 – 34.13 respectively. On average the concentrations of Cd and Pb in the water of all the estuaries were below the South African recommended water quality guidelines for coastal marine waters. Variations in metal concentrations associated with changes in hydrology (wet vs. dry season) were determined in the water and sediment of the Kariega, East Kleinemonde and Riet Estuaries. Cobalt, Pb and Ni enrichment in the Kariega Estuary sediment was significantly higher during the dry season, and the mean concentrations of Pb and Cd in the water column were 19-fold and 66-fold higher in the dry season. The elevated concentration of metals during the dry season could be related to accumulation of diffuse pollution from human activities within the catchment area. Conversely, inflow of fresh water into the estuary had the net effect of reducing the concentration and enrichment of these metals within the Kariega Estuary due to scouring and outflow of estuarine water and sediment into the marine environment. The temporal variations in metal concentrations and enrichment factors were less pronounced in the temporary open-closed estuaries than the permanently open Kariega Estuary. The observed trend can probably be related to the low anthropogenic impact within the catchment areas of these systems, and the relatively smaller size of the catchments. Significant spatial variations existed in metal enrichment in the sediment of both the East Kleinemonde and Riet estuaries, with the highest degrees of enrichment occurring in the sediments from the marine environment and lower reaches.
- Full Text:
- Date Issued: 2008
- Authors: Orr, Kyla Kathleen
- Date: 2008
- Subjects: Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5769 , http://hdl.handle.net/10962/d1005457 , Marine sediments -- South Africa -- Eastern Cape , Metals -- South Africa -- Eastern Cape , Metals -- Environmental aspects , Estuaries -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Estuarine sediments -- South Africa -- Eastern Cape , Water quality -- South Africa -- Eastern Cape , Water pollution -- South Africa -- Eastern Cape , Environmental toxicology -- South Africa -- Eastern Cape
- Description: The spatio-temporal patterns in concentrations of selected metals within the sediment (Cd, Co, Cu, Fe, Pb, Ni and Zn) and water (Cd and Pb) of three permanently open estuaries (Kariega, Kowie, Great Fish) and six temporary open-closed estuaries (Mpekweni, East Kleinemonde, West Kleinemonde, Riet, Kasouga, Boknes) were investigated. The concentrations of metals were influenced by size composition and total organic content of the sediments. Enrichment factors (EFs), using Fe as a reference element, and baseline linear regression models for metals vs. Fe were calculated to assess the extent of metal enrichment in the sediments. The mean concentrations of metals in the sediments(mg·kg⁻¹) showed ranges of 0.28 – 2.31 for Cd, 1.26 – 6.24 Co, 0.69 – 6.93 for Cu, 2119 – 14912 for Fe, 2.29 –14.01 for Ni, 4.81 – 22.20 for Pb and 5.77 – 21.75 for Zn. Mean normalized enrichment factors ranged between 0.75 – 6.19 for Cd, 0.53 – 2.71 for Co, 0.22 – 0.84 for Cu, 0.30 – 1.87 for Ni, 0.99 – 3.17 for Pb and 0.14 – 0.98 for Zn. All nine estuaries had average enrichment factors of greater than 1 for Cd. In general there was no enrichment of Cu and Zn in the sediments of any of the estuaries included in this study (EFs < 1). The Kariega, East Kleinemonde, West Kleinemonde, Riet and Great Fish Estuaries showed some degree of enrichment for Co (1 < EF < 4), Ni (1 < EF < 2) and Pb (1 < EF < 4), while the Mpekweni, Kasouga, Boknes and Kowie Estuaries were unenriched with these metals (EF < 1). Enrichment factors for Cd, Co and Pb typically followed the development gradient along the estuaries, suggesting anthropogenic enrichment. The concentrations of Cd and Pb in the water of the nine estuaries were also determined. The average concentrations of Cd and Pb in the water (μg·ℓ⁻¹) ranged between 0.05 – 3.32 and 0.75 – 34.13 respectively. On average the concentrations of Cd and Pb in the water of all the estuaries were below the South African recommended water quality guidelines for coastal marine waters. Variations in metal concentrations associated with changes in hydrology (wet vs. dry season) were determined in the water and sediment of the Kariega, East Kleinemonde and Riet Estuaries. Cobalt, Pb and Ni enrichment in the Kariega Estuary sediment was significantly higher during the dry season, and the mean concentrations of Pb and Cd in the water column were 19-fold and 66-fold higher in the dry season. The elevated concentration of metals during the dry season could be related to accumulation of diffuse pollution from human activities within the catchment area. Conversely, inflow of fresh water into the estuary had the net effect of reducing the concentration and enrichment of these metals within the Kariega Estuary due to scouring and outflow of estuarine water and sediment into the marine environment. The temporal variations in metal concentrations and enrichment factors were less pronounced in the temporary open-closed estuaries than the permanently open Kariega Estuary. The observed trend can probably be related to the low anthropogenic impact within the catchment areas of these systems, and the relatively smaller size of the catchments. Significant spatial variations existed in metal enrichment in the sediment of both the East Kleinemonde and Riet estuaries, with the highest degrees of enrichment occurring in the sediments from the marine environment and lower reaches.
- Full Text:
- Date Issued: 2008
Spontaneous charge transfer between zinc tetramethyl-tetra-2, 3-pyridinoporphyrazine and CdTe and ZnS quantum dots
- Moeno, Sharon, Idowu, Mopelola, Nyokong, Tebello
- Authors: Moeno, Sharon , Idowu, Mopelola , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265997 , vital:53908 , xlink:href="https://doi.org/10.1016/j.ica.2008.02.048"
- Description: Zinc tetramethyl-tetra-2,3-pyridinoporphyrazine (ZnTmtppa(-2)) gets reduced to the ZnTmtppa(-3) species on interaction with CdTe QDs capped with 2-mercaptoethanol (2-ME) or thioglycolic acid (TGA) and ZnS QDs capped with 2-ME. The interaction occurs without photolysis. The fluorescence of the QDs is quenched by ZnTmtppa resulting in large quenching constants. Binding of ZnTmtppa to QDs occurs with two molecules of the former binding to the latter.
- Full Text:
- Date Issued: 2008
- Authors: Moeno, Sharon , Idowu, Mopelola , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/265997 , vital:53908 , xlink:href="https://doi.org/10.1016/j.ica.2008.02.048"
- Description: Zinc tetramethyl-tetra-2,3-pyridinoporphyrazine (ZnTmtppa(-2)) gets reduced to the ZnTmtppa(-3) species on interaction with CdTe QDs capped with 2-mercaptoethanol (2-ME) or thioglycolic acid (TGA) and ZnS QDs capped with 2-ME. The interaction occurs without photolysis. The fluorescence of the QDs is quenched by ZnTmtppa resulting in large quenching constants. Binding of ZnTmtppa to QDs occurs with two molecules of the former binding to the latter.
- Full Text:
- Date Issued: 2008
Stakeholders' perceptions of the shift to democratic leadership in a secondary school in the Eastern Cape : a case study
- Authors: Lombo, Mzimkhulu Solomon
- Date: 2008
- Subjects: Education -- South Africa -- Eastern Cape , Education and state -- South Africa -- Eastern Cape , Education -- Political aspects -- South Africa -- Eastern Cape , Education, Secondary -- South Africa -- Eastern Cape -- Case studies , Educational change -- South Africa -- Eastern Cape , Educational leadership -- South Africa -- Eastern Cape , School management and organization -- South Africa -- Eastern Cape , South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2001 , http://hdl.handle.net/10962/d1015541
- Description: The advent of political democracy in South Africa in 1994 gave rise to new policy in education promoting democratic and participative ways of managing and leading schools. The intention was both to break from the apartheid past which was characterised by an authoritarian, nonparticipative mindset, as well as to point the way for future education development. Principals of schools were expected to develop structures and adopt management and leadership styles which were participative, inclusive and developmental. Many principals would not have been prepared for this shift in mindset, and notions of full participation in governance by parents, and representation of learners through constituted bodies would have been new to them. In this case study of one semi-urban secondary school in the Eastern Cape the researcher sought to establish whether and to what extent the school had moved towards the new management and leadership approaches. The study is interpretive in orientation, and made use of interviews and document analysis. This research has found that the school had democratised its management and leadership to a considerable degree, but that this was not necessarily due to profound changes on the part of the principal 's leadership. The principal emerged as a democratic leader by nature. More significant seem to be the structures which the school had put in place, both officially and internally, to promote widespread participation and the distribution of leadership. This decentralised system of management has contributed to a distinct organisation culture in the school characterised by warmth, openness and ubuntu.
- Full Text:
- Date Issued: 2008
- Authors: Lombo, Mzimkhulu Solomon
- Date: 2008
- Subjects: Education -- South Africa -- Eastern Cape , Education and state -- South Africa -- Eastern Cape , Education -- Political aspects -- South Africa -- Eastern Cape , Education, Secondary -- South Africa -- Eastern Cape -- Case studies , Educational change -- South Africa -- Eastern Cape , Educational leadership -- South Africa -- Eastern Cape , School management and organization -- South Africa -- Eastern Cape , South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:2001 , http://hdl.handle.net/10962/d1015541
- Description: The advent of political democracy in South Africa in 1994 gave rise to new policy in education promoting democratic and participative ways of managing and leading schools. The intention was both to break from the apartheid past which was characterised by an authoritarian, nonparticipative mindset, as well as to point the way for future education development. Principals of schools were expected to develop structures and adopt management and leadership styles which were participative, inclusive and developmental. Many principals would not have been prepared for this shift in mindset, and notions of full participation in governance by parents, and representation of learners through constituted bodies would have been new to them. In this case study of one semi-urban secondary school in the Eastern Cape the researcher sought to establish whether and to what extent the school had moved towards the new management and leadership approaches. The study is interpretive in orientation, and made use of interviews and document analysis. This research has found that the school had democratised its management and leadership to a considerable degree, but that this was not necessarily due to profound changes on the part of the principal 's leadership. The principal emerged as a democratic leader by nature. More significant seem to be the structures which the school had put in place, both officially and internally, to promote widespread participation and the distribution of leadership. This decentralised system of management has contributed to a distinct organisation culture in the school characterised by warmth, openness and ubuntu.
- Full Text:
- Date Issued: 2008
State sovereignty and alternative community in southern Africa: exploring the Zion Christian Church as the building block for deeper notions of regional community
- Authors: Radebe, Zandisiwe
- Date: 2008
- Subjects: Zionist Christian Church Southern African Development Community Community development -- Africa, Southern Regionalism -- Africa, Southern Sovereignty -- Africa, Southern Africa, Southern -- Economic integration
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2824 , http://hdl.handle.net/10962/d1003034
- Description: Regional community in southern Africa has been limited to the region’s states. As a result, deeper notions of community emanating from non-state actors, particularly transnational social movements, continue to be ignored. In an attempt to transcend state centrism, this thesis highlights alternative forms of regional community by exploring the Zion Christian Church (ZCC), one of southern Africa’s biggest and fastest growing cross-border movements. The ZCC is a potential agent for developing regional community from the bottom-up, driving a people-oriented regional integration approach in southern Africa. The ZCC, with its extensive following among the region’s poor, offers a compelling example of a grassroots and truly bottom-up approach to regional community. This thesis explores the possibility of the ZCC as a model of alternative community and identity centred on people’s daily experiences and grounded in a shared history and solidarity. It seeks to highlight the significance of transnational movements like the ZCC to policy makers in the region and it argues that grassroots communities are marching ahead of SADC member states and politicians in the area of integration. There exists a transnational cooperation amongst followers of the ZCC and other grassroots communities across the region and this cooperation transcends the traditional notion of state sovereignty, thereby highlighting deeper notions of what it means to be a community at regional level.
- Full Text:
- Date Issued: 2008
- Authors: Radebe, Zandisiwe
- Date: 2008
- Subjects: Zionist Christian Church Southern African Development Community Community development -- Africa, Southern Regionalism -- Africa, Southern Sovereignty -- Africa, Southern Africa, Southern -- Economic integration
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2824 , http://hdl.handle.net/10962/d1003034
- Description: Regional community in southern Africa has been limited to the region’s states. As a result, deeper notions of community emanating from non-state actors, particularly transnational social movements, continue to be ignored. In an attempt to transcend state centrism, this thesis highlights alternative forms of regional community by exploring the Zion Christian Church (ZCC), one of southern Africa’s biggest and fastest growing cross-border movements. The ZCC is a potential agent for developing regional community from the bottom-up, driving a people-oriented regional integration approach in southern Africa. The ZCC, with its extensive following among the region’s poor, offers a compelling example of a grassroots and truly bottom-up approach to regional community. This thesis explores the possibility of the ZCC as a model of alternative community and identity centred on people’s daily experiences and grounded in a shared history and solidarity. It seeks to highlight the significance of transnational movements like the ZCC to policy makers in the region and it argues that grassroots communities are marching ahead of SADC member states and politicians in the area of integration. There exists a transnational cooperation amongst followers of the ZCC and other grassroots communities across the region and this cooperation transcends the traditional notion of state sovereignty, thereby highlighting deeper notions of what it means to be a community at regional level.
- Full Text:
- Date Issued: 2008
Sterols and sterolins in Hypoxis hemerocallidea (African potato)
- Nair, V D P, Kanfer, Isadore
- Authors: Nair, V D P , Kanfer, Isadore
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6417 , http://hdl.handle.net/10962/d1006535
- Description: Commercially available health supplements and herbal remedies containing sterols and sterolins, either from African potato (Hypoxis hemerocallidea) alone, or whether enriched with sterols and sterolins, are claimed to be efficacious in the treatment of a variety of ailments. Sterols and sterolins in African potato are purported to be the relevant constituents that are required for the therapeutic claims of such products. A patent describing the extraction of sterolins from African potato plant material has claimed that approximately 9 mg sterolins can be isolated from 100 g of an enriched aqueous African potato extract. Our analysis of African potato plant material and its sterol and sterolin content, when similarly prepared, shows that the measureable content of sterols and sterolins in African potato is far less than the amounts of these compounds that have been claimed to be necessary for therapeutic benefit. We conclude that therapeutic claims relating to sterol and sterolin content in African potato are unsubstantiated, in view of the extremely low content of such compounds that we have isolated from our plant material, and in products containing African potato, or extracts thereof.
- Full Text:
- Date Issued: 2008
- Authors: Nair, V D P , Kanfer, Isadore
- Date: 2008
- Language: English
- Type: text , Article
- Identifier: vital:6417 , http://hdl.handle.net/10962/d1006535
- Description: Commercially available health supplements and herbal remedies containing sterols and sterolins, either from African potato (Hypoxis hemerocallidea) alone, or whether enriched with sterols and sterolins, are claimed to be efficacious in the treatment of a variety of ailments. Sterols and sterolins in African potato are purported to be the relevant constituents that are required for the therapeutic claims of such products. A patent describing the extraction of sterolins from African potato plant material has claimed that approximately 9 mg sterolins can be isolated from 100 g of an enriched aqueous African potato extract. Our analysis of African potato plant material and its sterol and sterolin content, when similarly prepared, shows that the measureable content of sterols and sterolins in African potato is far less than the amounts of these compounds that have been claimed to be necessary for therapeutic benefit. We conclude that therapeutic claims relating to sterol and sterolin content in African potato are unsubstantiated, in view of the extremely low content of such compounds that we have isolated from our plant material, and in products containing African potato, or extracts thereof.
- Full Text:
- Date Issued: 2008
Strategies for retaining talented staff and knowledge managers : a case study
- Authors: Gatyeni, Litha
- Date: 2008
- Subjects: Employee retention -- South Africa , Employee motivation -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8710 , http://hdl.handle.net/10948/958 , Employee retention -- South Africa , Employee motivation -- South Africa
- Description: The South African government is currently targeting 6 per cent economic growth for the country (Mail & Guardian, 2006). The construction industry is one of the growing forces contributing to the current economic growth of South Africa. However, in the speech made by the president Thabo Mbeki, he highlighted the labour market as one of the key constraints to achieving higher and sustainable growth. It is believed that there is a skills shortage or a mismatch in the labour market (Mail & Guardian, 2006). The construction industry has seen a steady growth over the past number of years. When South Africa won the bid to host the 2010 world cup, this required more building work to be done, such as construction of stadia, hotels, etc. This has put further strain in the construction industry. As the work load increases, the companies in the industry require more resources, with the human resources being the most affected. This has seen a high rate of talented staff turnover in the industry as companies seek to increase their capacity to allow them cope with the current work load. The consulting engineering industry plays a critical role of the construction industry. The selected company is part of the electrical and mechanical consulting engineering industry which has also been affected by the high talented staff turnover. The main purpose for this research was to identify retention strategies that can be used by the selected company to reduce the turnover of their talented staff. The research also investigated methods to retain the knowledge within the company that was possibly lost due to a high talented staff turnover rate. The first step used to resolve the issues discussed above was to complete a full literature study. The literature study sought to reveal what characteristics were required in the company that ensured staff would be happy in that company and remain there for a long time. The literature study also covered what knowledge iv management methods can be used by the company to retain its valuable knowledge. Secondly, the views of current staff, ex-staff and management of the selected company on staff and knowledge management strategies were asked in an empirical study, which involved completing questionnaires and conducting structured interviews. Based on the findings of the literature study and the empirical study, the last step was to make recommendations on what strategies should be implemented to retain staff and knowledge for the selected company.
- Full Text:
- Date Issued: 2008
- Authors: Gatyeni, Litha
- Date: 2008
- Subjects: Employee retention -- South Africa , Employee motivation -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8710 , http://hdl.handle.net/10948/958 , Employee retention -- South Africa , Employee motivation -- South Africa
- Description: The South African government is currently targeting 6 per cent economic growth for the country (Mail & Guardian, 2006). The construction industry is one of the growing forces contributing to the current economic growth of South Africa. However, in the speech made by the president Thabo Mbeki, he highlighted the labour market as one of the key constraints to achieving higher and sustainable growth. It is believed that there is a skills shortage or a mismatch in the labour market (Mail & Guardian, 2006). The construction industry has seen a steady growth over the past number of years. When South Africa won the bid to host the 2010 world cup, this required more building work to be done, such as construction of stadia, hotels, etc. This has put further strain in the construction industry. As the work load increases, the companies in the industry require more resources, with the human resources being the most affected. This has seen a high rate of talented staff turnover in the industry as companies seek to increase their capacity to allow them cope with the current work load. The consulting engineering industry plays a critical role of the construction industry. The selected company is part of the electrical and mechanical consulting engineering industry which has also been affected by the high talented staff turnover. The main purpose for this research was to identify retention strategies that can be used by the selected company to reduce the turnover of their talented staff. The research also investigated methods to retain the knowledge within the company that was possibly lost due to a high talented staff turnover rate. The first step used to resolve the issues discussed above was to complete a full literature study. The literature study sought to reveal what characteristics were required in the company that ensured staff would be happy in that company and remain there for a long time. The literature study also covered what knowledge iv management methods can be used by the company to retain its valuable knowledge. Secondly, the views of current staff, ex-staff and management of the selected company on staff and knowledge management strategies were asked in an empirical study, which involved completing questionnaires and conducting structured interviews. Based on the findings of the literature study and the empirical study, the last step was to make recommendations on what strategies should be implemented to retain staff and knowledge for the selected company.
- Full Text:
- Date Issued: 2008
Strategies to improve business success in selected industries
- Authors: Dayan, Oren
- Date: 2008
- Subjects: Success in business , Business -- Management , Customer relations -- Management
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:9366 , http://hdl.handle.net/10948/938 , Success in business , Business -- Management , Customer relations -- Management
- Description: Successful economies are dependent on successful industries.The present study explores how business success could be improved in three selected industries, namely the motorcar, high-technology and food manufacturing industries. These industries are vital to growing the economy of countries. The present study made a significant contribution towords identifying a theoretical model to improve the business success of the motorcar, high technology amd the food manufacturing industries. The study showed that various combinations of product launching stategies (distribution channel development, product image, third-party agreements, pricing, e-business, and e-saving), as well as organisational variables (TQM and market culture) are important agreements to achieve increased sales growth and CRM effectiveness.
- Full Text:
- Date Issued: 2008
- Authors: Dayan, Oren
- Date: 2008
- Subjects: Success in business , Business -- Management , Customer relations -- Management
- Language: English
- Type: Thesis , Doctoral , DCom
- Identifier: vital:9366 , http://hdl.handle.net/10948/938 , Success in business , Business -- Management , Customer relations -- Management
- Description: Successful economies are dependent on successful industries.The present study explores how business success could be improved in three selected industries, namely the motorcar, high-technology and food manufacturing industries. These industries are vital to growing the economy of countries. The present study made a significant contribution towords identifying a theoretical model to improve the business success of the motorcar, high technology amd the food manufacturing industries. The study showed that various combinations of product launching stategies (distribution channel development, product image, third-party agreements, pricing, e-business, and e-saving), as well as organisational variables (TQM and market culture) are important agreements to achieve increased sales growth and CRM effectiveness.
- Full Text:
- Date Issued: 2008
Stress and traumatic symptoms among police officers: a gender analysis
- Authors: Williams, Wendy Claudia
- Date: 2008
- Subjects: Stress (Psychology) -- South Africa , Psychic trauma -- South Africa , Post-traumatic stress disorder -- South Africa
- Language: English
- Type: Thesis , Masters , M Soc Sc (C Psy)
- Identifier: vital:11846 , http://hdl.handle.net/10353/144 , Stress (Psychology) -- South Africa , Psychic trauma -- South Africa , Post-traumatic stress disorder -- South Africa
- Description: This study assessed the extent to which exposure to traumatic events affected the traumatic stress response of male and female police officers. A convenience sample of male and female police officers (N = 66: n Male=46, n Female=20) was surveyed at an Eastern Cape police station. The following instruments were used: 1) Biographical questionnaire 2) PTSS-10 scales 3) The 39-item stress incident scale. Findings of this study indicate that the frequency of exposure to stressful incidents especially for more serious events is significant higher than that of Peltzer (2001) study. The four most frequent stressful incidents experienced by all participants were 1) Finding a corpse after murder (86.4 percent), 2) Responding to a scene involving accidental injury of a child (84.8 percent), .3) Finding a corpse (died of natural causes) (84.8 percent), 4) Duty related violence (non-shooting) (84.8 percent ).The four least frequent incidents experienced by participants were: (1) Response to the depressing social situation (71.2 percent), (2) Dragging of a corpse (74.2 percent), (3) Taking a life in the line of duty (75.8 percent), (4) Violent death of a colleague (77.3 percent ).Female participants results indicated a positive relationship between frequency of stressful incidents and total threat, anxiety, helplessness and PTSS-scale , where male participants’ results indicate no significant relationship between frequency of stressful incidents and total threat, anxiety, helplessness and PTSS-scale. Findings on male participants however indicate a positive relationship between years of service in police, age of police officers and PTSS-scale, while female participants’ results indicated no relationship between years of service in the police, age of police officer and PTSS-scale.
- Full Text:
- Date Issued: 2008
- Authors: Williams, Wendy Claudia
- Date: 2008
- Subjects: Stress (Psychology) -- South Africa , Psychic trauma -- South Africa , Post-traumatic stress disorder -- South Africa
- Language: English
- Type: Thesis , Masters , M Soc Sc (C Psy)
- Identifier: vital:11846 , http://hdl.handle.net/10353/144 , Stress (Psychology) -- South Africa , Psychic trauma -- South Africa , Post-traumatic stress disorder -- South Africa
- Description: This study assessed the extent to which exposure to traumatic events affected the traumatic stress response of male and female police officers. A convenience sample of male and female police officers (N = 66: n Male=46, n Female=20) was surveyed at an Eastern Cape police station. The following instruments were used: 1) Biographical questionnaire 2) PTSS-10 scales 3) The 39-item stress incident scale. Findings of this study indicate that the frequency of exposure to stressful incidents especially for more serious events is significant higher than that of Peltzer (2001) study. The four most frequent stressful incidents experienced by all participants were 1) Finding a corpse after murder (86.4 percent), 2) Responding to a scene involving accidental injury of a child (84.8 percent), .3) Finding a corpse (died of natural causes) (84.8 percent), 4) Duty related violence (non-shooting) (84.8 percent ).The four least frequent incidents experienced by participants were: (1) Response to the depressing social situation (71.2 percent), (2) Dragging of a corpse (74.2 percent), (3) Taking a life in the line of duty (75.8 percent), (4) Violent death of a colleague (77.3 percent ).Female participants results indicated a positive relationship between frequency of stressful incidents and total threat, anxiety, helplessness and PTSS-scale , where male participants’ results indicate no significant relationship between frequency of stressful incidents and total threat, anxiety, helplessness and PTSS-scale. Findings on male participants however indicate a positive relationship between years of service in police, age of police officers and PTSS-scale, while female participants’ results indicated no relationship between years of service in the police, age of police officer and PTSS-scale.
- Full Text:
- Date Issued: 2008
Studies directed towards the synthesis of chromone carbaldehyde-derived HIV-1 protease inhibitors
- Authors: Molefe, Duduzile Mabel
- Date: 2008
- Subjects: Protease Inhibitors , HIV infections , HIV (Viruses) , AIDS (Disease) , Proteolytic enzymes , Heterocyclic compounds -- Derivatives , Chemical kinetics , Nuclear magnetic resonance spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4526 , http://hdl.handle.net/10962/d1015542
- Description: A series of chromone-3-carbaldehydes have been prepared using Vilsmeier-Haack methodology while a corresponding series of chromone-2-carbaldeydes have been synthesized via the Kostanecki-Robinson reaction. Baylis-Hillman reactions have been conducted on both series of chromone carbaldehydes using three different catalysts, viz., 1,4-diazabicyclo(2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec- 7-ene (DBU) and 3-hydroxyquinuclidine (3HQ), and acrylonitrile, methyl acrylate and methyl vinyl ketone as the activated alkenes. These reactions have typically (but not always!) afforded both normal Baylis-Hillman and dimeric products. Attention has also been given to the use of 1-methyl-2-pyrrolidine (1-NMP), an ionic liquid, to replace normal organic solvents, and it has been found that, in the presence of DABCO, chromone-3-carbaldehydes afford the dimeric products alone. Reactions of chromone-3-carbaldehydes with methyl vinyl ketone have yielded unexpected, novel adducts, which appear to arise from preferential attack at C(2) in the chromone nucleus. Research on chromone-2-carbaldeydes under Baylis-Hillman conditions has also resulted in the formation of some interesting products instead of the expected Baylis-Hillman adducts. The Baylis-Hillman products have been explored as substrates for aza-Michael reactions using various amino derivatives including protected amino acids in the presence of the tetrabutylammonium bromide (TBAB) and the ionic liquid, 3-butyl-1- methylimidazoleboranetetrafluoride (BmimBF₄), as catalysts. The aza-Michael products have been targeted as truncated ritonavir analogues for investigation as potential HIV -1 protease inhibitors, and representative compounds have been subjected to enzyme inhibition assays to explore the extent and type of inhibition. Lineweaver-Burk and Dixon plots have indicated competitive inhibition in one case as well as non-competitive inhibition in another, and the inhibition constants (Ki) have been compared with that of the ritonavir. Computer modelling studies have also been conducted on selected chromonecontaining derivatives, using the ACCELRYS Cerius² platform. Interactive docking of the chromone-containing ligands into the HIV -1 protease receptor site, using the Ligandfit module, has indicated the importance of hydrogen-bonding interactions mediated by bridging water molecules situated in the receptor cavity. NMR spectroscopy has been used to elucidate complex and competing mechanistic pathways involved in the Baylis-Hillman reactions of selected 2-nitrobenzaldehydes with MVK in the presence of DABCO - reactions which afford the normal BaylisHillman product, the MVK dimer and syn- and anti-Baylis-Hillman type diadducts. The kinetic data confirm the concomitant operation of two pathways and reveal that, in the initial stage of the reaction, the product distribution is kinetically controlled, whereas in the latter stage, thermodynamic control results in the consumption of the normal Baylis-Hillman product and predominance of the anti-diadduct.
- Full Text:
- Date Issued: 2008
- Authors: Molefe, Duduzile Mabel
- Date: 2008
- Subjects: Protease Inhibitors , HIV infections , HIV (Viruses) , AIDS (Disease) , Proteolytic enzymes , Heterocyclic compounds -- Derivatives , Chemical kinetics , Nuclear magnetic resonance spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4526 , http://hdl.handle.net/10962/d1015542
- Description: A series of chromone-3-carbaldehydes have been prepared using Vilsmeier-Haack methodology while a corresponding series of chromone-2-carbaldeydes have been synthesized via the Kostanecki-Robinson reaction. Baylis-Hillman reactions have been conducted on both series of chromone carbaldehydes using three different catalysts, viz., 1,4-diazabicyclo(2.2.2]octane (DABCO), 1,8-diazabicyclo[5.4.0]undec- 7-ene (DBU) and 3-hydroxyquinuclidine (3HQ), and acrylonitrile, methyl acrylate and methyl vinyl ketone as the activated alkenes. These reactions have typically (but not always!) afforded both normal Baylis-Hillman and dimeric products. Attention has also been given to the use of 1-methyl-2-pyrrolidine (1-NMP), an ionic liquid, to replace normal organic solvents, and it has been found that, in the presence of DABCO, chromone-3-carbaldehydes afford the dimeric products alone. Reactions of chromone-3-carbaldehydes with methyl vinyl ketone have yielded unexpected, novel adducts, which appear to arise from preferential attack at C(2) in the chromone nucleus. Research on chromone-2-carbaldeydes under Baylis-Hillman conditions has also resulted in the formation of some interesting products instead of the expected Baylis-Hillman adducts. The Baylis-Hillman products have been explored as substrates for aza-Michael reactions using various amino derivatives including protected amino acids in the presence of the tetrabutylammonium bromide (TBAB) and the ionic liquid, 3-butyl-1- methylimidazoleboranetetrafluoride (BmimBF₄), as catalysts. The aza-Michael products have been targeted as truncated ritonavir analogues for investigation as potential HIV -1 protease inhibitors, and representative compounds have been subjected to enzyme inhibition assays to explore the extent and type of inhibition. Lineweaver-Burk and Dixon plots have indicated competitive inhibition in one case as well as non-competitive inhibition in another, and the inhibition constants (Ki) have been compared with that of the ritonavir. Computer modelling studies have also been conducted on selected chromonecontaining derivatives, using the ACCELRYS Cerius² platform. Interactive docking of the chromone-containing ligands into the HIV -1 protease receptor site, using the Ligandfit module, has indicated the importance of hydrogen-bonding interactions mediated by bridging water molecules situated in the receptor cavity. NMR spectroscopy has been used to elucidate complex and competing mechanistic pathways involved in the Baylis-Hillman reactions of selected 2-nitrobenzaldehydes with MVK in the presence of DABCO - reactions which afford the normal BaylisHillman product, the MVK dimer and syn- and anti-Baylis-Hillman type diadducts. The kinetic data confirm the concomitant operation of two pathways and reveal that, in the initial stage of the reaction, the product distribution is kinetically controlled, whereas in the latter stage, thermodynamic control results in the consumption of the normal Baylis-Hillman product and predominance of the anti-diadduct.
- Full Text:
- Date Issued: 2008
Studies in marine diterpene chemistry
- Van Wyk, Albert Wynand Wincke
- Authors: Van Wyk, Albert Wynand Wincke
- Date: 2008
- Subjects: Natural products Diterpenes Mollusks Marine metabolites Chemical oceanography
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4354 , http://hdl.handle.net/10962/d1005019
- Description: This thesis comprises both a natural product investigation and a synthetic component. The natural product investigations are presented in Chapters Two and Three. In Chapter Two the isolation and spectroscopic identification of the new isocopalane diterpene 12S,13R,14Sisocopalan- 13-ol-12,14-diacetate (2.1) and two known 3-(14S)-isocopal-12-ene-15-oyl-1- acetyl-sn-glycerol (2.2) and 3-(14S)-isocopal-12-ene-15-oyl-2-acetyl-sn-glycerol (2.3) from a single, large, unidentified sub-Antarctic nudibranch, collected near Marion Island, approximately 2000 km south of Cape Town are described. Chapter Three discusses the isolation, spectroscopic structure elucidation and anti-oesophageal cancer activity (3.1-3.4 only) of two known labdane diterpenes 6β,7α-diacetoxylabda-8,13E-dien-15-ol (3.1) and 2α,6β,7α-triacetoxylabda-8,13E-dien-15-ol (3.2) and one new 6β,7α,15-triacetoxylabda 8,13E-diene (3.3), as well as new 3α,11-dihydroxy-9,11-seco-cholest-4,7-dien-6,9-dione (3.4) and cholest 7-en-3,5,7-triol (3.5) from the endemic pulmonate mollusc, Trimusculus costatus. The absolute configuration of 3.2, and hence 3.1 and 3.3 (from biogenetic arguments) was determined through X-ray diffraction of a single crystal of the camphanate ester of 3.2. The absolute configuration of the secondary hydroxyl at C-3 of 3.4 was established using the Modified Mosher’s method. The synthetic component of the thesis commences in Chapter Four with the semi-synthesis of labdane diterpene nitriles 9α-cyano-15,16-epoxy-7β-hydroxylabda-13(16),14-dien-6-one (4.1), 9α-cyano-15,16-epoxy-7-hydroxylabda-7,13(16),14-trien-6-one (4.2) and 9α-cyano-15,16- epoxy-6β,7β dihydroxylabda-13(16),14-diene (4.3) from the terrestrial labdane diterpene, hispanolone (4.4). This work is an extension of previous synthetic studies directed towards the synthesis of T. costatus metabolites. Diterpenes 4.1-4.3 exhibited in planta activity against the economically important crop pathogens, Magnaporthea grisea and Puccinia recondita. Chapter Five describes the successful semi-synthesis of two isomeric marine molluscan labdane diterpene aldehyde metabolites, labd-13E-ene-8β-ol-15-al (5.1) and labd-13Z-ene- 8β-ol-15-al (5.2) from the commercially available, terrestrial plant derived, labdane diterpene manool (5.3). Diterpenes 5.1 and 5.2, originally isolated from the Mediterranean nudibranch,Pleurobranchaea meckelii and selected diterpenes arising from this synthesis were evaluated for their activity against an oesophageal cancer cell line (WHCO1). Chapter Six further develops the research discussed in Chapter Five, where ethyl 17-norabiet-13(15)-E-en-8β-ol- 16-oate (5.49) and ethyl 17-norabiet-13(15)-Z-en-8β-ol-16-oate (5.50) were first semisynthesized serendipitously. Based on their structural relationship to naturally occurring tricyclic diterpenes with anti-plasmodial activity, tricyclic diterpenes, 17-norpimaran-13α- ethoxy-8,16-olactone (6.6), 17-norisopimar-15-ene-8β,13β-diol (6.7), 17-norisopimarane- 8β,16-diol (6.8) and 17-norabiet-13(15)-ene-8β,16-diol (6.9) were semi-synthesized from the terrestrial labdane diterpene, 5.3, and critically evaluated for their antimalarial potential from parasite inhibition and haemolytic studies.
- Full Text:
- Date Issued: 2008
- Authors: Van Wyk, Albert Wynand Wincke
- Date: 2008
- Subjects: Natural products Diterpenes Mollusks Marine metabolites Chemical oceanography
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4354 , http://hdl.handle.net/10962/d1005019
- Description: This thesis comprises both a natural product investigation and a synthetic component. The natural product investigations are presented in Chapters Two and Three. In Chapter Two the isolation and spectroscopic identification of the new isocopalane diterpene 12S,13R,14Sisocopalan- 13-ol-12,14-diacetate (2.1) and two known 3-(14S)-isocopal-12-ene-15-oyl-1- acetyl-sn-glycerol (2.2) and 3-(14S)-isocopal-12-ene-15-oyl-2-acetyl-sn-glycerol (2.3) from a single, large, unidentified sub-Antarctic nudibranch, collected near Marion Island, approximately 2000 km south of Cape Town are described. Chapter Three discusses the isolation, spectroscopic structure elucidation and anti-oesophageal cancer activity (3.1-3.4 only) of two known labdane diterpenes 6β,7α-diacetoxylabda-8,13E-dien-15-ol (3.1) and 2α,6β,7α-triacetoxylabda-8,13E-dien-15-ol (3.2) and one new 6β,7α,15-triacetoxylabda 8,13E-diene (3.3), as well as new 3α,11-dihydroxy-9,11-seco-cholest-4,7-dien-6,9-dione (3.4) and cholest 7-en-3,5,7-triol (3.5) from the endemic pulmonate mollusc, Trimusculus costatus. The absolute configuration of 3.2, and hence 3.1 and 3.3 (from biogenetic arguments) was determined through X-ray diffraction of a single crystal of the camphanate ester of 3.2. The absolute configuration of the secondary hydroxyl at C-3 of 3.4 was established using the Modified Mosher’s method. The synthetic component of the thesis commences in Chapter Four with the semi-synthesis of labdane diterpene nitriles 9α-cyano-15,16-epoxy-7β-hydroxylabda-13(16),14-dien-6-one (4.1), 9α-cyano-15,16-epoxy-7-hydroxylabda-7,13(16),14-trien-6-one (4.2) and 9α-cyano-15,16- epoxy-6β,7β dihydroxylabda-13(16),14-diene (4.3) from the terrestrial labdane diterpene, hispanolone (4.4). This work is an extension of previous synthetic studies directed towards the synthesis of T. costatus metabolites. Diterpenes 4.1-4.3 exhibited in planta activity against the economically important crop pathogens, Magnaporthea grisea and Puccinia recondita. Chapter Five describes the successful semi-synthesis of two isomeric marine molluscan labdane diterpene aldehyde metabolites, labd-13E-ene-8β-ol-15-al (5.1) and labd-13Z-ene- 8β-ol-15-al (5.2) from the commercially available, terrestrial plant derived, labdane diterpene manool (5.3). Diterpenes 5.1 and 5.2, originally isolated from the Mediterranean nudibranch,Pleurobranchaea meckelii and selected diterpenes arising from this synthesis were evaluated for their activity against an oesophageal cancer cell line (WHCO1). Chapter Six further develops the research discussed in Chapter Five, where ethyl 17-norabiet-13(15)-E-en-8β-ol- 16-oate (5.49) and ethyl 17-norabiet-13(15)-Z-en-8β-ol-16-oate (5.50) were first semisynthesized serendipitously. Based on their structural relationship to naturally occurring tricyclic diterpenes with anti-plasmodial activity, tricyclic diterpenes, 17-norpimaran-13α- ethoxy-8,16-olactone (6.6), 17-norisopimar-15-ene-8β,13β-diol (6.7), 17-norisopimarane- 8β,16-diol (6.8) and 17-norabiet-13(15)-ene-8β,16-diol (6.9) were semi-synthesized from the terrestrial labdane diterpene, 5.3, and critically evaluated for their antimalarial potential from parasite inhibition and haemolytic studies.
- Full Text:
- Date Issued: 2008
Studies on the use of essential oils for the control of Sitophilus Zeamais (Motschulsky) (Coleoptera; Curculionidae): a pest of stored maize grains
- Odeyemi, Oluwakemi Oluwaseyi
- Authors: Odeyemi, Oluwakemi Oluwaseyi
- Date: 2008
- Subjects: Curculionidae , Essences and essential oils , Corn -- Diseases and pests -- South Africa , Biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD (Botany)
- Identifier: vital:11301 , http://hdl.handle.net/10353/168 , Curculionidae , Essences and essential oils , Corn -- Diseases and pests -- South Africa , Biological pest control agents -- South Africa
- Description: The common maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), a well known pest of stored-maize grain in most parts of the world, was identified as one of the major constraints of harvested maize grains in the Eastern Cape Province, South Africa. The use of plants or their products is one of the recent methods being investigated for insect pest control worldwide. Therefore, the main aim of the present study was to identify available plants in the Eastern Cape that could be used to combat the problem of Sitophilus zeamais in stored-maize grains. For the realization of the aims of this research, the following studies were carried out; a preliminary survey was conducted to obtain baseline information on the farmers’ knowledge and experience of indigenous insect pest control methods in the Eastern Cape. Also, studies on the insecticidal potential of the essential oils of some plants were investigated against the maize weevil. The quality parameters of maize grains treated with the essential oils was also studied and, using a rat model, the toxicity of the essential oils was investigated. The outcome from this study revealed that there is awareness amongst the farmers in the Eastern Cape on the use of plants or their products to control insect pests. Unfortunately, such methods are currently being neglected and the knowledge of their application was found to be eroding. Among the various essential oils screened were those from Mentha longifolia L. and Tagetes minuta L. which evoked an appreciable level of contact, fumigant and repellent toxicity on the maize weevil. Further work done to determine the effects of the oils on maize stored over a period of three months revealed that the two oils had no adverse effect on the proximate compositions and some quality parameters of the stored maize. However, the toxicological study conducted on rats showed that the oils at tested concentrations exhibited some level of toxicity. It is, therefore, suggested that the essential oils of M. longifolia and T. minuta should not be used to treat maize grains intended for human consumption.
- Full Text:
- Date Issued: 2008
- Authors: Odeyemi, Oluwakemi Oluwaseyi
- Date: 2008
- Subjects: Curculionidae , Essences and essential oils , Corn -- Diseases and pests -- South Africa , Biological pest control agents -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD (Botany)
- Identifier: vital:11301 , http://hdl.handle.net/10353/168 , Curculionidae , Essences and essential oils , Corn -- Diseases and pests -- South Africa , Biological pest control agents -- South Africa
- Description: The common maize weevil, Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae), a well known pest of stored-maize grain in most parts of the world, was identified as one of the major constraints of harvested maize grains in the Eastern Cape Province, South Africa. The use of plants or their products is one of the recent methods being investigated for insect pest control worldwide. Therefore, the main aim of the present study was to identify available plants in the Eastern Cape that could be used to combat the problem of Sitophilus zeamais in stored-maize grains. For the realization of the aims of this research, the following studies were carried out; a preliminary survey was conducted to obtain baseline information on the farmers’ knowledge and experience of indigenous insect pest control methods in the Eastern Cape. Also, studies on the insecticidal potential of the essential oils of some plants were investigated against the maize weevil. The quality parameters of maize grains treated with the essential oils was also studied and, using a rat model, the toxicity of the essential oils was investigated. The outcome from this study revealed that there is awareness amongst the farmers in the Eastern Cape on the use of plants or their products to control insect pests. Unfortunately, such methods are currently being neglected and the knowledge of their application was found to be eroding. Among the various essential oils screened were those from Mentha longifolia L. and Tagetes minuta L. which evoked an appreciable level of contact, fumigant and repellent toxicity on the maize weevil. Further work done to determine the effects of the oils on maize stored over a period of three months revealed that the two oils had no adverse effect on the proximate compositions and some quality parameters of the stored maize. However, the toxicological study conducted on rats showed that the oils at tested concentrations exhibited some level of toxicity. It is, therefore, suggested that the essential oils of M. longifolia and T. minuta should not be used to treat maize grains intended for human consumption.
- Full Text:
- Date Issued: 2008
Studies towards the synthesis of novel, coumarin-based HIV-1 protease inhibitors
- Authors: Rashamuse, Thompho Jason
- Date: 2008
- Subjects: Coumarins , Protease Inhibitors , HIV infections -- Treatment , HIV (Viruses) , AIDS (Disease) -- Treatment , Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4359 , http://hdl.handle.net/10962/d1005024 , Coumarins , Protease Inhibitors , HIV infections -- Treatment , HIV (Viruses) , AIDS (Disease) -- Treatment , Heterocyclic compounds -- Derivatives
- Description: A series of the Baylis-Hillman adducts have been obtained by reacting protected O-benzylated and unprotected substituted salicylaldehydes with methyl acrylate or tertbutyl acrylate, respectively, using DABCO as catalyst. Treatment of the Baylis-Hillman adducts with HCl in a mixture of acetic acid and acetic anhydride afforded the corresponding 3-(chloromethyl)coumarin derivatives with yields of up to 94%. Similar use of HI afforded the corresponding 3-(iodomethyl)coumarins but, depending on the reaction time, the reduced 3-methyl analogues could also be obtained. Arbuzov reactions of the 3-(halomethyl)coumarin derivatives have been undertaken to afford 4-phosphorylated and 1’-phosphorylated derivatives, regioselectivity being dependent on the halide-leaving group. The 3-(chloromethyl)coumarin derivatives have been subjected to nucleophilic (SN) attack by benzylamine to give the corresponding 3- [(benzylamino)methyl]coumarin derivatives in yields of up to 74%. Further treatment of the 3-[(benzylamino)methyl]coumarin derivatives with chloroacetyl chloride afforded the chloroacetamide derivatives, which exhibit hindered rotation about the amine C(O)-N bond. The acetamide derivatives have also been subjected to Arbuzov reaction conditions to afford the phosphorylated derivatives in yields of up to 86%. In a preliminary modelling study, hydrolysed analogues of the synthesized phosphorylated derivatives have been docked into the active site of the HIV-1 protease enzyme using the Cerius-2 Ligandfit software module to provide an insight into potential receptor-ligand hydrogen bonding interactions.
- Full Text:
- Date Issued: 2008
- Authors: Rashamuse, Thompho Jason
- Date: 2008
- Subjects: Coumarins , Protease Inhibitors , HIV infections -- Treatment , HIV (Viruses) , AIDS (Disease) -- Treatment , Heterocyclic compounds -- Derivatives
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4359 , http://hdl.handle.net/10962/d1005024 , Coumarins , Protease Inhibitors , HIV infections -- Treatment , HIV (Viruses) , AIDS (Disease) -- Treatment , Heterocyclic compounds -- Derivatives
- Description: A series of the Baylis-Hillman adducts have been obtained by reacting protected O-benzylated and unprotected substituted salicylaldehydes with methyl acrylate or tertbutyl acrylate, respectively, using DABCO as catalyst. Treatment of the Baylis-Hillman adducts with HCl in a mixture of acetic acid and acetic anhydride afforded the corresponding 3-(chloromethyl)coumarin derivatives with yields of up to 94%. Similar use of HI afforded the corresponding 3-(iodomethyl)coumarins but, depending on the reaction time, the reduced 3-methyl analogues could also be obtained. Arbuzov reactions of the 3-(halomethyl)coumarin derivatives have been undertaken to afford 4-phosphorylated and 1’-phosphorylated derivatives, regioselectivity being dependent on the halide-leaving group. The 3-(chloromethyl)coumarin derivatives have been subjected to nucleophilic (SN) attack by benzylamine to give the corresponding 3- [(benzylamino)methyl]coumarin derivatives in yields of up to 74%. Further treatment of the 3-[(benzylamino)methyl]coumarin derivatives with chloroacetyl chloride afforded the chloroacetamide derivatives, which exhibit hindered rotation about the amine C(O)-N bond. The acetamide derivatives have also been subjected to Arbuzov reaction conditions to afford the phosphorylated derivatives in yields of up to 86%. In a preliminary modelling study, hydrolysed analogues of the synthesized phosphorylated derivatives have been docked into the active site of the HIV-1 protease enzyme using the Cerius-2 Ligandfit software module to provide an insight into potential receptor-ligand hydrogen bonding interactions.
- Full Text:
- Date Issued: 2008
Study of the formation of artifacts following Dichloromethane reaction with some nitrogenous drugs
- Mohammadi, Ali, Amini, Mohsen, Hamedani, Moteza P, Torkabadi, Hossein H, Walker, Roderick B
- Authors: Mohammadi, Ali , Amini, Mohsen , Hamedani, Moteza P , Torkabadi, Hossein H , Walker, Roderick B
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6409 , http://hdl.handle.net/10962/d1006495
- Description: In this work, the quaternization reaction of some nitrogenous drugs in dichloromethane under stress condition and room temperature at different times are studied. Under these conditions, drug-chloromethochloride adducts or artifacts were found to be formed for clozapine, ofloxacin and olanzapine. The structures of the resultant adducts were elucidated using 1H NMR spectroscopy. In addition, the amount of intact drug was determined using in-house validated HPLC methods with UV detection.
- Full Text:
- Date Issued: 2008
- Authors: Mohammadi, Ali , Amini, Mohsen , Hamedani, Moteza P , Torkabadi, Hossein H , Walker, Roderick B
- Date: 2008
- Language: English
- Type: Article
- Identifier: vital:6409 , http://hdl.handle.net/10962/d1006495
- Description: In this work, the quaternization reaction of some nitrogenous drugs in dichloromethane under stress condition and room temperature at different times are studied. Under these conditions, drug-chloromethochloride adducts or artifacts were found to be formed for clozapine, ofloxacin and olanzapine. The structures of the resultant adducts were elucidated using 1H NMR spectroscopy. In addition, the amount of intact drug was determined using in-house validated HPLC methods with UV detection.
- Full Text:
- Date Issued: 2008
Study South Africa
- International Education Association of South Africa (IEASA), Higher Education South Africa (Organization), Kishun, Roshen
- Authors: International Education Association of South Africa (IEASA) , Higher Education South Africa (Organization) , Kishun, Roshen
- Date: 2008
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/65010 , vital:28653 , ISBN 9780620415521
- Description: [Extract from message from Minister of Higher Education, Hon. Naledi Pandor]: The International Education Association of South Africa (IEASA) has produced yet another magnificent publication on higher education in South Africa It is an excellent source of information for everyone interested in universities and research in this country. It is especially useful for international students who plan to study in South Africa, and for people involved in developing international programmes. The theme of this edition, “The role of internationalisation in South Africa’s knowledge environment, is opportune at this juncture. It provides role-players in higher education with the opportunity to examine critical issues such as the place, purposes, benefits and limitations of internationalisation in the sector and the contribution internationalisation makes to the knowledge economy of our country. To participate effectively in the knowledge economy, South Africa has to grow its research base. For this, we need a pool of vibrant young researchers. South Africa is able to provide opportunities for groundbreaking research, and internationalisation provides students, academics and researchers with prospects to broaden the scope of their research. Exchange programmes, bilateral research connections, collaborative partnerships and other international links lend themselves to pathways through which local and international staff and students can expand their horizons and skills. In this way internationalisation can assist South Africa in realising its objectives. The South African higher education sector has identified priority areas in which it needs to develop human capital. They include science, technology and engineering. We can use international programmes to accelerate our capacity building plans and in particular the training and development of postgraduate students. Through research collaborations, for example, postgraduate students can be jointly trained and co-supervised with partners. This has beneficial outcomes for students, research partners and academics, as well as for the system as a whole. Aside from benefiting from sending our students abroad, South Africa also gains by receiving foreign students. International students bring with them different viewpoints, technologies and skills, which assist in developing new perspectives and techniques in South Africa Furthermore, cultural interaction enhances our own students' experiences. By studying together students come to understand and accept cultural differences and are enriched. These interactions, in turn, build positive relations which have positive long term benefits in developing economic and social links between people and countries, and which will help overcome newly surfaced problems of xenophobia in South Africa South Africa is currently host to more than 60,000 international students and many academics. The greatest proportion of international students and academics are from Africa particularly from the Southern African Development Community. As a host country we ensure high quality courses at universities, in order for our qualifications to be recognisable worldwide. South African institutions produce professionals who are highly sought- after around the world. This publication supports South Africa's education sector by providing information and by publicising our institutions and the sector as a whole. I would like to thank IEASA for the important role it plays in higher education. , 8th Edition
- Full Text:
- Date Issued: 2008
- Authors: International Education Association of South Africa (IEASA) , Higher Education South Africa (Organization) , Kishun, Roshen
- Date: 2008
- Subjects: Education, Higher -- South Africa , Universities and colleges -- South Africa , Technical Institutes -- South Africa , Vocational guidance -- South Africa
- Language: English
- Type: text , book
- Identifier: http://hdl.handle.net/10962/65010 , vital:28653 , ISBN 9780620415521
- Description: [Extract from message from Minister of Higher Education, Hon. Naledi Pandor]: The International Education Association of South Africa (IEASA) has produced yet another magnificent publication on higher education in South Africa It is an excellent source of information for everyone interested in universities and research in this country. It is especially useful for international students who plan to study in South Africa, and for people involved in developing international programmes. The theme of this edition, “The role of internationalisation in South Africa’s knowledge environment, is opportune at this juncture. It provides role-players in higher education with the opportunity to examine critical issues such as the place, purposes, benefits and limitations of internationalisation in the sector and the contribution internationalisation makes to the knowledge economy of our country. To participate effectively in the knowledge economy, South Africa has to grow its research base. For this, we need a pool of vibrant young researchers. South Africa is able to provide opportunities for groundbreaking research, and internationalisation provides students, academics and researchers with prospects to broaden the scope of their research. Exchange programmes, bilateral research connections, collaborative partnerships and other international links lend themselves to pathways through which local and international staff and students can expand their horizons and skills. In this way internationalisation can assist South Africa in realising its objectives. The South African higher education sector has identified priority areas in which it needs to develop human capital. They include science, technology and engineering. We can use international programmes to accelerate our capacity building plans and in particular the training and development of postgraduate students. Through research collaborations, for example, postgraduate students can be jointly trained and co-supervised with partners. This has beneficial outcomes for students, research partners and academics, as well as for the system as a whole. Aside from benefiting from sending our students abroad, South Africa also gains by receiving foreign students. International students bring with them different viewpoints, technologies and skills, which assist in developing new perspectives and techniques in South Africa Furthermore, cultural interaction enhances our own students' experiences. By studying together students come to understand and accept cultural differences and are enriched. These interactions, in turn, build positive relations which have positive long term benefits in developing economic and social links between people and countries, and which will help overcome newly surfaced problems of xenophobia in South Africa South Africa is currently host to more than 60,000 international students and many academics. The greatest proportion of international students and academics are from Africa particularly from the Southern African Development Community. As a host country we ensure high quality courses at universities, in order for our qualifications to be recognisable worldwide. South African institutions produce professionals who are highly sought- after around the world. This publication supports South Africa's education sector by providing information and by publicising our institutions and the sector as a whole. I would like to thank IEASA for the important role it plays in higher education. , 8th Edition
- Full Text:
- Date Issued: 2008
Suicide ideation among police members in the Eastern Cape
- De Bruin, Carmelitia Elmarie
- Authors: De Bruin, Carmelitia Elmarie
- Date: 2008
- Subjects: Police -- South Africa -- Eastern Cape , Suicide , Suicide -- Psychological aspects , Police -- South Africa -- Job stress
- Language: English
- Type: Thesis , Masters , M Soc Sc (C Psy)
- Identifier: vital:11852 , http://hdl.handle.net/10353/146 , Police -- South Africa -- Eastern Cape , Suicide , Suicide -- Psychological aspects , Police -- South Africa -- Job stress
- Description: Suicide, the endpoint of the continuum that begins with suicide ideation, is known to be an important precursor of attempted suicides. The purpose of this study was to determine the level of suicide ideation of police members and to determine the differences between suicide ideation of various demographic variables, in particular, the gender, rank and race groups of police members. The convenience sample (N = 111) was drawn from police stations in the Nelson Mandela Metropole in the Eastern Cape Province. The Adult Suicide Ideation Questionnaire (ASIQ) and a Biographical Questionnaire were administered. The results indicated that 1.4 % of the sample showed significant levels of suicidal ideation scoring a high score above 31 (i.e., above the 97th percentile by ASIQ). The T-test, One-way (ANOVA) and the Pearson Chi-Square analysis showed no significant differences between suicide ideation and the demographic variables based on the police station, age, gender, race, rank, years of service, years of current position, educational qualifications, marital status, presence of medical conditions, number of alcoholic drinks consumed per week, smoking behaviour and exercise behaviour. However, participants with previous suicide attempts had significant high scores on ASIQ.
- Full Text:
- Date Issued: 2008
- Authors: De Bruin, Carmelitia Elmarie
- Date: 2008
- Subjects: Police -- South Africa -- Eastern Cape , Suicide , Suicide -- Psychological aspects , Police -- South Africa -- Job stress
- Language: English
- Type: Thesis , Masters , M Soc Sc (C Psy)
- Identifier: vital:11852 , http://hdl.handle.net/10353/146 , Police -- South Africa -- Eastern Cape , Suicide , Suicide -- Psychological aspects , Police -- South Africa -- Job stress
- Description: Suicide, the endpoint of the continuum that begins with suicide ideation, is known to be an important precursor of attempted suicides. The purpose of this study was to determine the level of suicide ideation of police members and to determine the differences between suicide ideation of various demographic variables, in particular, the gender, rank and race groups of police members. The convenience sample (N = 111) was drawn from police stations in the Nelson Mandela Metropole in the Eastern Cape Province. The Adult Suicide Ideation Questionnaire (ASIQ) and a Biographical Questionnaire were administered. The results indicated that 1.4 % of the sample showed significant levels of suicidal ideation scoring a high score above 31 (i.e., above the 97th percentile by ASIQ). The T-test, One-way (ANOVA) and the Pearson Chi-Square analysis showed no significant differences between suicide ideation and the demographic variables based on the police station, age, gender, race, rank, years of service, years of current position, educational qualifications, marital status, presence of medical conditions, number of alcoholic drinks consumed per week, smoking behaviour and exercise behaviour. However, participants with previous suicide attempts had significant high scores on ASIQ.
- Full Text:
- Date Issued: 2008
Sustainability assessment using a unit-based sustainability assessment tool: The case of three teaching departments at Rhodes University, South Africa
- Authors: Togo, Muchaiteyi
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386863 , vital:68182 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122776"
- Description: A sustainability assessment study was performed with three teaching departments at Rhodes University – Ichthyology and Fisheries Science, Anthropology, and Accounting. The assessment used a Unit-based Sustainability Assessment Tool (USAT) and was guided by systems thinking and the ontological framework provided by critical realism. Results of the study showed that the Department of Ichthyology and Fisheries Science had a higher integration of sustainability issues in its activities than the other departments sampled, with Accounting having the lowest integration. Interviews conducted with departmental heads and content analyses of documents revealed differences in sustainability issues addressed and in approaches used in tackling them among these departments. The study is intended to inform the Mainstreaming of Environment and Sustainability in African (MESA) Universities Partnership, which promotes mainstreaming environment and sustainability in universities during the United Nations Decade of Education for Sustainable Development. The study does not provide answers to mainstreaming activities, but opens up space to debate and deliberate how to deal with the mainstreaming of sustainability in universities. It identified some of the challenges to be addressed in university-wide mainstreaming work, and affirmed the need for systems thinking in bringing about change at institutional level to extend changes taking place in individual teaching contexts.
- Full Text:
- Date Issued: 2008
- Authors: Togo, Muchaiteyi
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/386863 , vital:68182 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122776"
- Description: A sustainability assessment study was performed with three teaching departments at Rhodes University – Ichthyology and Fisheries Science, Anthropology, and Accounting. The assessment used a Unit-based Sustainability Assessment Tool (USAT) and was guided by systems thinking and the ontological framework provided by critical realism. Results of the study showed that the Department of Ichthyology and Fisheries Science had a higher integration of sustainability issues in its activities than the other departments sampled, with Accounting having the lowest integration. Interviews conducted with departmental heads and content analyses of documents revealed differences in sustainability issues addressed and in approaches used in tackling them among these departments. The study is intended to inform the Mainstreaming of Environment and Sustainability in African (MESA) Universities Partnership, which promotes mainstreaming environment and sustainability in universities during the United Nations Decade of Education for Sustainable Development. The study does not provide answers to mainstreaming activities, but opens up space to debate and deliberate how to deal with the mainstreaming of sustainability in universities. It identified some of the challenges to be addressed in university-wide mainstreaming work, and affirmed the need for systems thinking in bringing about change at institutional level to extend changes taking place in individual teaching contexts.
- Full Text:
- Date Issued: 2008
Synthesis and electrochemical characterisation of a near infrared absorbing oxo vanadium (IV) octapentylthio-phthalocyanine
- Mbambisa, Gcineka, Nyokong, Tebello
- Authors: Mbambisa, Gcineka , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/266008 , vital:53909 , xlink:href="https://doi.org/10.1016/j.poly.2008.06.004"
- Description: The synthesis of an α-substituted phthalocyanine oxo vanadium(IV) 1,4,8,11,15,18,22,25-octapentathiophthalocyanine (4) which absorbs at 850 nm in dichloromethane is reported. The complex is purple in colour and becomes green on reduction. The cyclic and square wave voltammetries of the complex show five redox couples. The spectroelectrochemical data showed only ring based processes. The ring reduced species is observed at wavelengths greater than 680 nm rather than the usual 500–600 nm range typical of ring reduced phthalocyanine complexes.
- Full Text:
- Date Issued: 2008
- Authors: Mbambisa, Gcineka , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/266008 , vital:53909 , xlink:href="https://doi.org/10.1016/j.poly.2008.06.004"
- Description: The synthesis of an α-substituted phthalocyanine oxo vanadium(IV) 1,4,8,11,15,18,22,25-octapentathiophthalocyanine (4) which absorbs at 850 nm in dichloromethane is reported. The complex is purple in colour and becomes green on reduction. The cyclic and square wave voltammetries of the complex show five redox couples. The spectroelectrochemical data showed only ring based processes. The ring reduced species is observed at wavelengths greater than 680 nm rather than the usual 500–600 nm range typical of ring reduced phthalocyanine complexes.
- Full Text:
- Date Issued: 2008
Synthesis and photophysical properties of lead phthalocyanines
- Modibane, D.K., Nyokong, Tebello
- Authors: Modibane, D.K. , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268636 , vital:54216 , xlink:href="https://doi.org/10.1016/j.poly.2007.12.004"
- Description: This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom.
- Full Text:
- Date Issued: 2008
- Authors: Modibane, D.K. , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268636 , vital:54216 , xlink:href="https://doi.org/10.1016/j.poly.2007.12.004"
- Description: This work reports on the synthesis and photophysical parameters of tetra-and octa-substituted new lead phthalocyanines. The complexes synthesized are: 1,4-(tetraphenoxyphthalocyaninato)lead (7a), 1,4-(tetra-tert-butylphenoxyphthalocyaninato)lead (7b), 2,3-(tetraphenoxyphthalocyaninato)lead (8a), 2,3-(tetra-tert-butylphenoxyphthalocyaninato)lead (8b), 2,3-octaphenoxyphthalocyaninatolead (9a) 2,3-[octakis(4-t-butylphenoxyphthalocyaninato)]lead (9b). Photophysical properties were studied for these complexes in a dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform. The fluorescence spectra were different from excitation spectra due to demetallation upon excitation. High triplet quantum yields ranging from 0.70 to 0.88 (in DMSO, DMF and toluene) and low triplet lifetimes (20–50 μs in DMSO, and more than 10 μs in the rest of the solvents) were observed due to the presence of heavy atom.
- Full Text:
- Date Issued: 2008
Synthesis and solvent effects on the photophysicochemical properties of novel cadmium phenoxy phthalocyanines
- Chidawanyika, Wadzanai J U, Antunes, Edith M, Nyokong, Tebello
- Authors: Chidawanyika, Wadzanai J U , Antunes, Edith M , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268649 , vital:54217 , xlink:href="https://doi.org/10.1016/j.jphotochem.2007.09.020"
- Description: The syntheses of novel cadmium phenoxy complexes; tetrakis{1,(4)-tert-butylphenoxyphthalocyaninato}cadmium(II) (5a), tetrakis{1,(4)-phenoxyphthalocyaninato}cadmium(II) (5b), tetrakis{2,(3)-tert-butylphenoxyphthalocyaninato}cadmium(II) (6a) and tetrakis{2,(3)-phenoxyphthalocyaninato}cadmium(II) (6b) are presented herein. The spectroscopic and photophysicochemical properties have also been carried out and discussed together with the influence of various organic solvents on these properties. Spectroscopic properties, i.e. ground state electronic absorption and fluorescence spectra have been found to vary as a function of substituent position on the phthalocyanine macrocycle, i.e. α-substitution versus β-substitution. The photophysical parameters are reported as well as the photodegradation and singlet oxygen quantum yields, where the complexes were found to exhibit good photostability with the production of appreciable amounts of singlet oxygen.
- Full Text:
- Date Issued: 2008
- Authors: Chidawanyika, Wadzanai J U , Antunes, Edith M , Nyokong, Tebello
- Date: 2008
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/268649 , vital:54217 , xlink:href="https://doi.org/10.1016/j.jphotochem.2007.09.020"
- Description: The syntheses of novel cadmium phenoxy complexes; tetrakis{1,(4)-tert-butylphenoxyphthalocyaninato}cadmium(II) (5a), tetrakis{1,(4)-phenoxyphthalocyaninato}cadmium(II) (5b), tetrakis{2,(3)-tert-butylphenoxyphthalocyaninato}cadmium(II) (6a) and tetrakis{2,(3)-phenoxyphthalocyaninato}cadmium(II) (6b) are presented herein. The spectroscopic and photophysicochemical properties have also been carried out and discussed together with the influence of various organic solvents on these properties. Spectroscopic properties, i.e. ground state electronic absorption and fluorescence spectra have been found to vary as a function of substituent position on the phthalocyanine macrocycle, i.e. α-substitution versus β-substitution. The photophysical parameters are reported as well as the photodegradation and singlet oxygen quantum yields, where the complexes were found to exhibit good photostability with the production of appreciable amounts of singlet oxygen.
- Full Text:
- Date Issued: 2008