Student-generated content: an approach to harnessing the power of diversity in higher education
- Snowball, Jeanette D, McKenna, Sioux
- Authors: Snowball, Jeanette D , McKenna, Sioux
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66763 , vital:28991 , ISSN 1470-1294 , https://doi.org/10.1080/13562517.2016.1273205
- Description: Publisher version , Internationally, classes in higher education institutions are becoming larger and more diverse. Support for ‘non-traditional’ students has often taken the form of additional remedial classes offered outside the main curriculum, which has met with limited success. Sociocultural theories of learning argue that the potential clash between the sociocultural context of disciplinary knowledge and the very different home contexts of many non-traditional students needs to be acknowledged. One way to achieve this is to use student-generated content, which allows teachers to bring student experiences and voices into the community of practice and acknowledges the importance of their prior experiences in knowledge production. Building on such sociocultural approaches to teaching and learning, this paper focuses on the use of student-generated podcasts as a means to harness the diversity of student experiences in a large (nearly 600 students) first-year Economics class at a South African University.
- Full Text: false
- Date Issued: 2017
- Authors: Snowball, Jeanette D , McKenna, Sioux
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/66763 , vital:28991 , ISSN 1470-1294 , https://doi.org/10.1080/13562517.2016.1273205
- Description: Publisher version , Internationally, classes in higher education institutions are becoming larger and more diverse. Support for ‘non-traditional’ students has often taken the form of additional remedial classes offered outside the main curriculum, which has met with limited success. Sociocultural theories of learning argue that the potential clash between the sociocultural context of disciplinary knowledge and the very different home contexts of many non-traditional students needs to be acknowledged. One way to achieve this is to use student-generated content, which allows teachers to bring student experiences and voices into the community of practice and acknowledges the importance of their prior experiences in knowledge production. Building on such sociocultural approaches to teaching and learning, this paper focuses on the use of student-generated podcasts as a means to harness the diversity of student experiences in a large (nearly 600 students) first-year Economics class at a South African University.
- Full Text: false
- Date Issued: 2017
Towards a framework for assessing the sustainability of local economic development based on natural resources: honeybush tea in the Eastern Cape Province of South Africa
- Polak, James, Snowball, Jeanette D
- Authors: Polak, James , Snowball, Jeanette D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69201 , vital:29445 , https://doi.org/10.1080/13549839.2016.1196348
- Description: Despite the popularity of local economic development (LED) as a job creation and economic growth strategy in South Africa, many LED projects have not proved to be sustainable in the long-run, especially where human systems interact with biological ones. This article examines the relationship between sustainability and LED within the context of the emerging honeybush tea industry in the Eastern Cape. Data were gathered from provincial as well as local government policy documents and reports, and via key informant interviews. The data were analysed using Connelly’s [(2007). Mapping sustainable development as a contested concept. Local Environment, 12 (3), 259–278] three pronged approach to sustainable development as a lens through which to view the local industry. Findings showed that the industry offers many opportunities for development, including job creation in poorer, rural households; sustainable wild harvesting using a permit system; commercial cultivation; potential to develop social capital; potential for community-based LED; and product diversification. However, there are also corresponding challenges: There is currently no reliable data on the maximum sustainable yield, which is needed to guide quota allocations for entrepreneurial harvesters harvesting from wild stocks; possible biodiversity loss; and enforcing the permit scheme is proving difficult in remote rural areas.
- Full Text: false
- Date Issued: 2017
- Authors: Polak, James , Snowball, Jeanette D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/69201 , vital:29445 , https://doi.org/10.1080/13549839.2016.1196348
- Description: Despite the popularity of local economic development (LED) as a job creation and economic growth strategy in South Africa, many LED projects have not proved to be sustainable in the long-run, especially where human systems interact with biological ones. This article examines the relationship between sustainability and LED within the context of the emerging honeybush tea industry in the Eastern Cape. Data were gathered from provincial as well as local government policy documents and reports, and via key informant interviews. The data were analysed using Connelly’s [(2007). Mapping sustainable development as a contested concept. Local Environment, 12 (3), 259–278] three pronged approach to sustainable development as a lens through which to view the local industry. Findings showed that the industry offers many opportunities for development, including job creation in poorer, rural households; sustainable wild harvesting using a permit system; commercial cultivation; potential to develop social capital; potential for community-based LED; and product diversification. However, there are also corresponding challenges: There is currently no reliable data on the maximum sustainable yield, which is needed to guide quota allocations for entrepreneurial harvesters harvesting from wild stocks; possible biodiversity loss; and enforcing the permit scheme is proving difficult in remote rural areas.
- Full Text: false
- Date Issued: 2017
'Committed, motivated and joyful?'Job satisfaction and organisational commitment of managers at a South African public utility:
- Authors: Snowball, Jeanette D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70495 , vital:29667 , https://doi.org/10.1080/09548963.2017.1380706
- Description: The cultural and creative industries (CCIs) have been hailed as offering great potential to create jobs and to be socially inclusive. Since artistic success is defined by individual talent, or merit, the CCIs should be one sector that is especially open to, and appreciative of, social diversity in terms of race, class, cultural group and gender. However, as expected, recent studies in both the UK and the US have revealed that employment in the CCIs is heavily dominated by the middle classes, and is not as diverse in terms of other characteristics. Since the advent of democracy in South Africa in 1994, transformation of firm ownership, previously dominated by white people, to include more black, coloured and Indian/Asian-origin South Africans, has been an important part of achieving greater economic equality and social cohesion, as well as being more representative of the cultures of the majority of the population. Using data from a survey of 2400 CCIs firms in South Africa, this paper examines the extent to which the CCIs in South Africa have transformed in terms of ownership and employment. Comparisons are also made across the six UNESCO [(2009). Framework for cultural statistics. UNESCO Institute for Statistics. Retrieved from http://www.uis.unesco.org/culture/Pages/framework-cultural-statistics.aspx] “Cultural Domains” in terms of ownership, average monthly turnover and the number of full-time, part-time and contract employees. Results show some diversity in the industry, but significant differences between the Domains. Statistical analysis demonstrates that CCI funding policy in South Africa is sensitive to advancing the transformation agenda in that more transformed firms were shown to be more likely to have received some form of government grant as part of their income.
- Full Text:
- Date Issued: 2017
- Authors: Snowball, Jeanette D
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/70495 , vital:29667 , https://doi.org/10.1080/09548963.2017.1380706
- Description: The cultural and creative industries (CCIs) have been hailed as offering great potential to create jobs and to be socially inclusive. Since artistic success is defined by individual talent, or merit, the CCIs should be one sector that is especially open to, and appreciative of, social diversity in terms of race, class, cultural group and gender. However, as expected, recent studies in both the UK and the US have revealed that employment in the CCIs is heavily dominated by the middle classes, and is not as diverse in terms of other characteristics. Since the advent of democracy in South Africa in 1994, transformation of firm ownership, previously dominated by white people, to include more black, coloured and Indian/Asian-origin South Africans, has been an important part of achieving greater economic equality and social cohesion, as well as being more representative of the cultures of the majority of the population. Using data from a survey of 2400 CCIs firms in South Africa, this paper examines the extent to which the CCIs in South Africa have transformed in terms of ownership and employment. Comparisons are also made across the six UNESCO [(2009). Framework for cultural statistics. UNESCO Institute for Statistics. Retrieved from http://www.uis.unesco.org/culture/Pages/framework-cultural-statistics.aspx] “Cultural Domains” in terms of ownership, average monthly turnover and the number of full-time, part-time and contract employees. Results show some diversity in the industry, but significant differences between the Domains. Statistical analysis demonstrates that CCI funding policy in South Africa is sensitive to advancing the transformation agenda in that more transformed firms were shown to be more likely to have received some form of government grant as part of their income.
- Full Text:
- Date Issued: 2017
Seed ecology and growth comparisons of native (Virgilia divaricata) and invasive alien (Acacia mearnsii and A. melanoxylon) plants: implications for conservation
- Authors: Goets, Stefan Albert
- Date: 2017
- Subjects: Seeds -- Ecology Plants -- Reproduction , Vegetation dynamics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15248 , vital:28191
- Description: The abundance of invasive alien plants, with their numerous associated negative effects, has resulted in challenging and costly management requirements in South Africa. Management of invasives is further complicated when species have rapid inherent growth rates, atmospheric nitrogen fixing capabilities and large, persistent seed banks. Management strategies other than the usual mechanical, chemical, and biological (and combinations thereof) methods may be more effective. An alternative strategy is ’habitat management’, whereby management may be aimed at favouring native species. If the native species could compete favourably with, and possibly exclude, the invasive species, which is more likely when the species are ecologically similar, management may be more effective. This study investigated the competitive performance of two invasive species, Acacia mearnsii De Wild. and Acacia melanoxylon R.Br., and an indigenous ecological analogue, Virgilia divaricata Adamson, on the southern Cape Coast of South Africa. Both acacias are included among the five worst invasive species in the native forest and fynbos shrubland ecosystems. Performance was compared among the three species in terms of germination success (responses to five stimuli, namely chipping, hot water exposure, dry heat pulse, smoke, and control, incubated at 12 or 20°C), soil-stored seed bank densities and viability at different soil depths, and individual growth performance in seedling and sapling stages (and the effect of inter-specific competition on the latter). Virgilia divaricata performed comparably to the acacias in most aspects. Responses to germination stimuli at both temperature regimes were comparable among species, with chipping and hot water exposure resulting in the highest germination success. Acacia melanoxylon displayed poorer germination response under the cool temperature regime than the warm regime. Of the three species, A. mearnsii (7 596 seeds m-2) had the highest seed bank density, followed by V. divaricata (938 seeds m-2) and A. melanoxylon (274 seeds m-2). Seed viability was high (87-91%) in all three species. Neither seed density nor seed viability differed significantly between soil depths, and there were no clear differences in this aspect between species. In terms of growth during the seedling stage, V. divaricata outperformed A. mearnsii. In the sapling stage, growth was comparable between the three species and was not affected by the extent of competition from neighbouring saplings. Overall, the findings of this study suggest that the success of A. mearnsii as an invader is primarily attributable to its large seed banks. However, the good performance of V. divaricata seedlings and no apparent negative effect of competition on sapling growth from A. mearnsii and A. melanoxylon suggest that it may be used in the management of the acacias along with other management strategies. Due to the similarity observed between the three species, any management operation (such as fire) that would benefit V. divaricata recruitment would benefit the acacias equally (except for potentially reduced germination of A. melanoxylon in cooler seasons). Management should thus attempt to prevent the germination of Acacia seeds. Alternatively, dense localised Acacia seed banks may be reduced by repeat burning. On a small scale, areas where V. divaricata would occur naturally (or which are completely compromised ecologically) can be seeded with pre-treated (chipped or hot water exposure) V. divaricata seeds. If V. divaricata is given enough time to establish dense stands, subsequent germination and growth of the acacias should be suppressed and simultaneously promote forest re-establishment. To further decrease Acacia success, biocontrol (seed-boring weevils, flower-galling midges, and rust fungus) should be widely disseminated.
- Full Text:
- Date Issued: 2017
- Authors: Goets, Stefan Albert
- Date: 2017
- Subjects: Seeds -- Ecology Plants -- Reproduction , Vegetation dynamics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15248 , vital:28191
- Description: The abundance of invasive alien plants, with their numerous associated negative effects, has resulted in challenging and costly management requirements in South Africa. Management of invasives is further complicated when species have rapid inherent growth rates, atmospheric nitrogen fixing capabilities and large, persistent seed banks. Management strategies other than the usual mechanical, chemical, and biological (and combinations thereof) methods may be more effective. An alternative strategy is ’habitat management’, whereby management may be aimed at favouring native species. If the native species could compete favourably with, and possibly exclude, the invasive species, which is more likely when the species are ecologically similar, management may be more effective. This study investigated the competitive performance of two invasive species, Acacia mearnsii De Wild. and Acacia melanoxylon R.Br., and an indigenous ecological analogue, Virgilia divaricata Adamson, on the southern Cape Coast of South Africa. Both acacias are included among the five worst invasive species in the native forest and fynbos shrubland ecosystems. Performance was compared among the three species in terms of germination success (responses to five stimuli, namely chipping, hot water exposure, dry heat pulse, smoke, and control, incubated at 12 or 20°C), soil-stored seed bank densities and viability at different soil depths, and individual growth performance in seedling and sapling stages (and the effect of inter-specific competition on the latter). Virgilia divaricata performed comparably to the acacias in most aspects. Responses to germination stimuli at both temperature regimes were comparable among species, with chipping and hot water exposure resulting in the highest germination success. Acacia melanoxylon displayed poorer germination response under the cool temperature regime than the warm regime. Of the three species, A. mearnsii (7 596 seeds m-2) had the highest seed bank density, followed by V. divaricata (938 seeds m-2) and A. melanoxylon (274 seeds m-2). Seed viability was high (87-91%) in all three species. Neither seed density nor seed viability differed significantly between soil depths, and there were no clear differences in this aspect between species. In terms of growth during the seedling stage, V. divaricata outperformed A. mearnsii. In the sapling stage, growth was comparable between the three species and was not affected by the extent of competition from neighbouring saplings. Overall, the findings of this study suggest that the success of A. mearnsii as an invader is primarily attributable to its large seed banks. However, the good performance of V. divaricata seedlings and no apparent negative effect of competition on sapling growth from A. mearnsii and A. melanoxylon suggest that it may be used in the management of the acacias along with other management strategies. Due to the similarity observed between the three species, any management operation (such as fire) that would benefit V. divaricata recruitment would benefit the acacias equally (except for potentially reduced germination of A. melanoxylon in cooler seasons). Management should thus attempt to prevent the germination of Acacia seeds. Alternatively, dense localised Acacia seed banks may be reduced by repeat burning. On a small scale, areas where V. divaricata would occur naturally (or which are completely compromised ecologically) can be seeded with pre-treated (chipped or hot water exposure) V. divaricata seeds. If V. divaricata is given enough time to establish dense stands, subsequent germination and growth of the acacias should be suppressed and simultaneously promote forest re-establishment. To further decrease Acacia success, biocontrol (seed-boring weevils, flower-galling midges, and rust fungus) should be widely disseminated.
- Full Text:
- Date Issued: 2017
A water footprint assessment of dryland pasture based dairy enterprise in the Eastern Cape: a case study
- Authors: Jenje, Paige
- Date: 2017
- Subjects: Water supply, Agricultural -- South Africa , Water supply, Agricultural -- Government policy -- South Africa , Water consumption -- Measurement -- South Africa , Water demand management -- South Africa , Water-supply -- Accounting -- South Africa , Cattle -- Water requirements -- South Africa -- Cast studies
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/5362 , vital:20917
- Description: Water scarcity continues to pose a threat to South Africa, with severe water scarcity predicted within the next fifty years. As a result, national interest has been sparked over the development of market based water resource allocation strategies to alleviate pressures on South Africa's freshwater resources, and ensure compliance with the National Water Act. Agriculture is the largest water user internationally and within South Africa, highlighting the importance of improving the water use efficiency within the industry. This study performed a full water footprint assessment (WFA) of a dryland pasture based dairy enterprise in the Eastern Cape. Following the guidelines of the WFA, this study calculated the blue, green and grey water footprints of dryland pasture based dairy production from crop- to-farm gate by assessing the water footprints of pasture production, bought in feed and concentrates, drinking water and servicing water processes over a period of five years. Following the accounting the of the water footprint, economic and environmental sustainability indicators were used along with the incorporation of the Water Risk Filter tool. This revealed that the case study farm was operating efficiently with the enterprise's highest water related risk being governmental regulation. Water footprint accounting results highlighted that green water was largest contributor to the overall water footprint of over 80%, and grey water contributed the least to the water footprint of dryland pasture based dairy production. Economic productivity results indicated that milk production is highly correlated with annual rainfall due to the breeding strategy undertaken by the farm. Results also indicated little correlation between the monthly water footprint and milk production, with the majority of the enterprise's milk production occurring in the last quarter regardless of the water footprint. The study demonstrated the relationship between the water footprint and economic land and water productivity, along with the value of milk to costs ratio which indicated that approximately R1.00 worth of costs generates between R1.80 and R2.06 value of milk. The sustainability indicators suggested that the farm's management of its effluent dam requires attention to meet the Department of Water and Sanitations effluent waste quality guidelines. The overall analysis of the water footprint suggested that the highest water related risk to dryland dairy production was regulatory risk. This risk suggests that the government cannot be relied upon for the management of freshwater resources within the study area, leaving the onus on the individual dairy farmers. As such, farmers should utilise the water footprint to formulate water stewardship programmes which have the potential to influence the regulation and protection of freshwater resources.
- Full Text:
- Date Issued: 2017
- Authors: Jenje, Paige
- Date: 2017
- Subjects: Water supply, Agricultural -- South Africa , Water supply, Agricultural -- Government policy -- South Africa , Water consumption -- Measurement -- South Africa , Water demand management -- South Africa , Water-supply -- Accounting -- South Africa , Cattle -- Water requirements -- South Africa -- Cast studies
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/5362 , vital:20917
- Description: Water scarcity continues to pose a threat to South Africa, with severe water scarcity predicted within the next fifty years. As a result, national interest has been sparked over the development of market based water resource allocation strategies to alleviate pressures on South Africa's freshwater resources, and ensure compliance with the National Water Act. Agriculture is the largest water user internationally and within South Africa, highlighting the importance of improving the water use efficiency within the industry. This study performed a full water footprint assessment (WFA) of a dryland pasture based dairy enterprise in the Eastern Cape. Following the guidelines of the WFA, this study calculated the blue, green and grey water footprints of dryland pasture based dairy production from crop- to-farm gate by assessing the water footprints of pasture production, bought in feed and concentrates, drinking water and servicing water processes over a period of five years. Following the accounting the of the water footprint, economic and environmental sustainability indicators were used along with the incorporation of the Water Risk Filter tool. This revealed that the case study farm was operating efficiently with the enterprise's highest water related risk being governmental regulation. Water footprint accounting results highlighted that green water was largest contributor to the overall water footprint of over 80%, and grey water contributed the least to the water footprint of dryland pasture based dairy production. Economic productivity results indicated that milk production is highly correlated with annual rainfall due to the breeding strategy undertaken by the farm. Results also indicated little correlation between the monthly water footprint and milk production, with the majority of the enterprise's milk production occurring in the last quarter regardless of the water footprint. The study demonstrated the relationship between the water footprint and economic land and water productivity, along with the value of milk to costs ratio which indicated that approximately R1.00 worth of costs generates between R1.80 and R2.06 value of milk. The sustainability indicators suggested that the farm's management of its effluent dam requires attention to meet the Department of Water and Sanitations effluent waste quality guidelines. The overall analysis of the water footprint suggested that the highest water related risk to dryland dairy production was regulatory risk. This risk suggests that the government cannot be relied upon for the management of freshwater resources within the study area, leaving the onus on the individual dairy farmers. As such, farmers should utilise the water footprint to formulate water stewardship programmes which have the potential to influence the regulation and protection of freshwater resources.
- Full Text:
- Date Issued: 2017
Tetra 4-(propargyloxy)phenoxy phthalocyanines: synthesis, spectroscopic, nonlinear optical and electrocatalytic properties
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
- Authors: Mwanza, Daniel
- Date: 2017
- Subjects: Phthalocyanines , Nonlinear optics , Electrocatalysis , Spectrum analysis , Thermogravimetry , Phthalocyanines Spectra
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65144 , vital:28695
- Description: This study presents the synthesis, spectroscopic, photophysical and theoretical characterisation of metal-free (H2TPrOPhOPc), cobalt (CoTPrOPhOPc) and manganese (MnTPrOPhOPc) tetra 4-(4-propargyloxy) phenoxy phthalocyanines. Thermal analysis using thermogravimetric analysis (TGA) confirmed the excellent thermal stability of synthesized tetra 4-(4- propargyloxy) phenoxy phthalocyanines. The metal complexes, CoTPrOPhOPc and MnTPrOPhOPc, exhibited better thermal stability when compared to H2TPrOPhOPc. The residual percentage weight remaining was approximately 70% for CoTPrOPhOPc and MnTPrOPhOPc and 45% for H2TPrOPhOPc after 600°C, clearly confirming the stability of the metal complexes. The MTPrOPhOPcs (where M = H2, Co and Mn) complexes exhibited excellent nonlinear optical properties with strong reverse saturable absorption (RSA), especially when 560 nm excitation laser was used. Their nonlinear optical properties followed this trend: H2TPrOPhOPc > CoTPrOPhOPc > MnTPrOPhOPc. According to the trend observed, the H2TPrOPhOPc was an excellent nonlinear optical limiter when compared to the CoTPrOPhOPc and MnTPrOPhOPc. All the investigated complexes exhibited optical limiting properties comparable to the phthalocyanine complexes reported in the literature. The MTPrOPhOPc complexes were further studied for their electrocatalytic and electroanalytical properties towards the detection of hydrogen peroxide. For the electrocatalytic studies, the synthesized complexes were immobilized onto gold electrode surfaces pre-functionalized with phenylazide (Au-PAz) monolayer. Copper (I) catalyzed alkynyl-azide cycloaddition reaction was used to covalently immobilize the MTPrOPhOPcs onto the gold electrode surfaces to form Au-PAz-MTPrOPhOPc. The MTPrOPhOPcs modified gold surfaces (Au-PAz-MTPrOPhOPc) exhibited good reproducibility and stability in various electrolyte conditions. Electrochemical and surface characterisation of the functionalised gold electrode surfaces confirmed the presence of the MTPrOPhOPcs and their electroanalysis was excellent towards electrocatalytic reduction of H2O2, with the limit of detection (LoD) and limit of quantification (LoQ) in the ^M range. The electrocatalytic reduction peaks for H2O2 were observed at -0.37 V for Au-PAz-MnTPrOPhOPc and -0.31 V for Au-PAz-CoTPrOPhOPc when Ag|AgCl pseudo-reference electrode was used. The Au-PAz-MnTPrOPhOPc and Au- PAz-CoTPrOPhOPc gold electrode surfaces showed good sensitivity and reproducibility towards the electrocatalytic reduction of hydrogen peroxide in pH 7.4 phosphate buffer solution. , Thesis (MSc) -- Faculty of Science, Chemistry, 2017
- Full Text:
- Date Issued: 2017
Structural analysis of proteases from South African HIV-1 (subtype C) patients undergoing Lopinavir treatment, using comparative modeling, ligand-docking and molecular dynamics
- Authors: Sheik-Amamuddy, Olivier
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4931 , vital:20744
- Description: HIV is regarded as one of the most devastating infectious diseases of the last few decades, and has a high prevalence in South Africa, subtype C being the most common. Palliative measures used to fight HIV involve the use various types of inhibitors, including the use of HIV protease inhibitors. Representatives from this class of inhibitors are gradually losing their efficacy due to development of resistance mutations from HIV-1. In this study, compounds from the South African Natural Compound Database (SANCDB) were screened against HIV-1 protease models generated from protease protein sequences belonging to 11 South African HIV patients before and after treatment with Lopinavir. The effect of Lopinavir on the alteration of drug-binding affinity before and after treatment is investigated by molecular docking of the protease against other FDA-approved drugs and detection of mutation types using the HIVdb tool. A network representation of hydrogen bonding between docked ligands and their receptor proteases has been developed and a profiling method of visualizing receptor-ligand docking energies at the local level is presented. Four potential HIV-1 protease inhibitors were identified from the list of 599 natural compounds on the basis of receptor conformation and binding free energy. Ligand stabilities were monitored by 20ns molecular dynamics runs using the GROMACS software.
- Full Text:
- Date Issued: 2017
- Authors: Sheik-Amamuddy, Olivier
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4931 , vital:20744
- Description: HIV is regarded as one of the most devastating infectious diseases of the last few decades, and has a high prevalence in South Africa, subtype C being the most common. Palliative measures used to fight HIV involve the use various types of inhibitors, including the use of HIV protease inhibitors. Representatives from this class of inhibitors are gradually losing their efficacy due to development of resistance mutations from HIV-1. In this study, compounds from the South African Natural Compound Database (SANCDB) were screened against HIV-1 protease models generated from protease protein sequences belonging to 11 South African HIV patients before and after treatment with Lopinavir. The effect of Lopinavir on the alteration of drug-binding affinity before and after treatment is investigated by molecular docking of the protease against other FDA-approved drugs and detection of mutation types using the HIVdb tool. A network representation of hydrogen bonding between docked ligands and their receptor proteases has been developed and a profiling method of visualizing receptor-ligand docking energies at the local level is presented. Four potential HIV-1 protease inhibitors were identified from the list of 599 natural compounds on the basis of receptor conformation and binding free energy. Ligand stabilities were monitored by 20ns molecular dynamics runs using the GROMACS software.
- Full Text:
- Date Issued: 2017
Health promotion: approaches to dietary salt reduction
- Authors: Mushoriwa, Fadzai
- Date: 2017
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44761 , vital:25439
- Description: Background Globally, non-communicable diseases are the leading causes of mortality and morbidity, with the majority of these occurring in low-middle income countries. The devastating consequences of non-communicable diseases could be curtailed through better management of four modifiable factors: physical inactivity; tobacco use; harmful use of alcohol; and unhealthy diets. The World Health Organisation has recommended dietary salt reduction as a cost-effective strategy in combatting the burden of NCDs. Consumer awareness and education is one of three primary strategies that have been identified by the World Health Organisation to achieve population-wide salt reduction. It involves the provision of salt reduction knowledge and the promotion of healthy salt related practices. These campaigns are a necessity in populations with high discretionary salt use such as South Africa. For these health promotion activities to succeed, they need to be developed with consideration of factors such as the environment, culture, and socio-economic standing of the intended target population. This two-phase health promotion study was conducted at St Mary’s Development and Care Centre and the Assumption Sisters Nutrition Centre. These are two community based organisations located in Grahamstown, South Africa. A needs assessment was conducted to identify the knowledge and practices of cooks and guardians from these centres on dietary salt reduction. The aim of the second phase of the study was to conduct an educational intervention and to develop a culturally appropriate and contextually specific health information intervention through a participatory process. Method: This was a qualitative study that was supported by elements of quantitative research.. The first phase of the current study was a needs assessment. The first step involved an observational phase with cooks from the centres. The aim was to observe their discretionary salt use during food preparation and to document the salt content in the processed foods available at each centre. Semi-structured interviews were then conducted, with 3 cooks and 16 guardians1 from the centres, to assess their knowledge and practices regarding salt reduction.Parents or the people responsible for the care of the children attending both centres. Guided by findings from the needs assessment phase, an educational intervention was developed. This phase involved the participatory development of three health information leaflets and a series of educational interactive sessions were conducted. Quantitative tests to assess the readability, suitability, and actionability were conducted on the leaflets. Qualitative assessment of the leaflets involved formative evaluations conducted by health care professionals, phase 1 participants, Rhodes University peer educators, an African languages and cultural expert, and a Rhodes University student wellness manager. This step was included to assess the content validity, context specificity, acceptability, and cultural appropriateness of the materials. Educational interactive sessions were guided by constructs of the Social Cognitive Theory and were conducted on three main topics: ‘Salt and my health’, ‘Reducing salt in my diet’, and ‘Reading food labels’. Results: The majority of the processed foods available at both centres contained low to medium levels of salt. Children at the centres were not provided with salt shakers on the tables during meal times. Cooks did not use measuring utensils when adding salt during meal preparation. Semistructured interviews revealed that participants lacked both declarative and procedural knowledge. In terms of declarative knowledge, they were unaware of the daily salt intake recommendations and the relationship between salt and sodium. Participants were able to identify hypertension as one of the health related consequences of high salt consumption. Most participants were responsible for purchasing groceries in their households. Their selfreported food label reading behaviours and inability to read food labels highlighted their lack of procedural knowledge. Most participants reported that they added salt during meal preparation and at mealtimes, highlighting high discretionary salt use. Some participants were also aware of cultural or religious uses of salt. The developed health information leaflets were considered to be written at a readability level appropriate for the target audience. The leaflets were also deemed to be actionable, culturally appropriate, and contextually specific and suitable materials. The educational interactive sessions were found to be interesting and informative. Conclusions: Findings from the needs assessment revealed the need for an educational intervention to address the identified gaps in the participants’ knowledge and practices regarding dietary salt reduction. The developed health information leaflets were found to be informative, culturally appropriate, and contextually specific, as planned. Interactive sessions provided an excellent platform to supply participants with concise and accurate information, increasing the possibility of improving their salt reduction related knowledge.
- Full Text:
- Date Issued: 2017
- Authors: Mushoriwa, Fadzai
- Date: 2017
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44761 , vital:25439
- Description: Background Globally, non-communicable diseases are the leading causes of mortality and morbidity, with the majority of these occurring in low-middle income countries. The devastating consequences of non-communicable diseases could be curtailed through better management of four modifiable factors: physical inactivity; tobacco use; harmful use of alcohol; and unhealthy diets. The World Health Organisation has recommended dietary salt reduction as a cost-effective strategy in combatting the burden of NCDs. Consumer awareness and education is one of three primary strategies that have been identified by the World Health Organisation to achieve population-wide salt reduction. It involves the provision of salt reduction knowledge and the promotion of healthy salt related practices. These campaigns are a necessity in populations with high discretionary salt use such as South Africa. For these health promotion activities to succeed, they need to be developed with consideration of factors such as the environment, culture, and socio-economic standing of the intended target population. This two-phase health promotion study was conducted at St Mary’s Development and Care Centre and the Assumption Sisters Nutrition Centre. These are two community based organisations located in Grahamstown, South Africa. A needs assessment was conducted to identify the knowledge and practices of cooks and guardians from these centres on dietary salt reduction. The aim of the second phase of the study was to conduct an educational intervention and to develop a culturally appropriate and contextually specific health information intervention through a participatory process. Method: This was a qualitative study that was supported by elements of quantitative research.. The first phase of the current study was a needs assessment. The first step involved an observational phase with cooks from the centres. The aim was to observe their discretionary salt use during food preparation and to document the salt content in the processed foods available at each centre. Semi-structured interviews were then conducted, with 3 cooks and 16 guardians1 from the centres, to assess their knowledge and practices regarding salt reduction.Parents or the people responsible for the care of the children attending both centres. Guided by findings from the needs assessment phase, an educational intervention was developed. This phase involved the participatory development of three health information leaflets and a series of educational interactive sessions were conducted. Quantitative tests to assess the readability, suitability, and actionability were conducted on the leaflets. Qualitative assessment of the leaflets involved formative evaluations conducted by health care professionals, phase 1 participants, Rhodes University peer educators, an African languages and cultural expert, and a Rhodes University student wellness manager. This step was included to assess the content validity, context specificity, acceptability, and cultural appropriateness of the materials. Educational interactive sessions were guided by constructs of the Social Cognitive Theory and were conducted on three main topics: ‘Salt and my health’, ‘Reducing salt in my diet’, and ‘Reading food labels’. Results: The majority of the processed foods available at both centres contained low to medium levels of salt. Children at the centres were not provided with salt shakers on the tables during meal times. Cooks did not use measuring utensils when adding salt during meal preparation. Semistructured interviews revealed that participants lacked both declarative and procedural knowledge. In terms of declarative knowledge, they were unaware of the daily salt intake recommendations and the relationship between salt and sodium. Participants were able to identify hypertension as one of the health related consequences of high salt consumption. Most participants were responsible for purchasing groceries in their households. Their selfreported food label reading behaviours and inability to read food labels highlighted their lack of procedural knowledge. Most participants reported that they added salt during meal preparation and at mealtimes, highlighting high discretionary salt use. Some participants were also aware of cultural or religious uses of salt. The developed health information leaflets were considered to be written at a readability level appropriate for the target audience. The leaflets were also deemed to be actionable, culturally appropriate, and contextually specific and suitable materials. The educational interactive sessions were found to be interesting and informative. Conclusions: Findings from the needs assessment revealed the need for an educational intervention to address the identified gaps in the participants’ knowledge and practices regarding dietary salt reduction. The developed health information leaflets were found to be informative, culturally appropriate, and contextually specific, as planned. Interactive sessions provided an excellent platform to supply participants with concise and accurate information, increasing the possibility of improving their salt reduction related knowledge.
- Full Text:
- Date Issued: 2017
A comparative study of the dosimetric features of α-Al2O3: C, Mg and α-Al2O3: C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113058 , vital:33694 , https://doi.org/10.1093/rpd/ncx039
- Description: A comparative study of the dosimetric features of α-Al2O3:C,Mg and α-Al2O3:C relevant to thermoluminescence dosimetry is reported. A glow curve of α-Al2O3:C,Mg measured at 1°C/s after beta irradiation to 1 Gy shows two subsidiary peaks at 42°C (labelled as I) and 72°C (II) and the main peak at 161°C (III) whereas a glow curve of α-Al2O3:C measured under the same conditions shows the main peak at 178°C (II′) and a lower intensity peak at 48°C (I′). Apart from these ones, there are several other peaks at temperatures beyond that of the main peak in both α-Al2O3:C,Mg and α-Al2O3:C. However, the latter are not included in this study. We report a comparative quantitative analysis of dose response and fading of peaks I, II and III of α-Al2O3:C,Mg and peaks I′ and II′ of α-Al2O3:C. Analysis shows that the dose response of peaks I and III is sublinear within 1–10 Gy whereas that of peak II is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy. In comparison, the dose response of peak I′ is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy whereas that of peak II′ is sublinear within 1–4 Gy followed by a superlinear region within 4–10 Gy. As regards to fading corresponding to 1 Gy, peak I is very unstable and fades within 300 s, peak II is more stable and takes up to 43200 s to fade. In comparison, peak III fades down to 30% of its initial intensity within 2400 s. Interestingly, between 2400 and 800 s, the intensity fades by 17% only. Regarding fading in α-Al2O3:C, peak I′ fades within 600 s whereas peak II′ shows an inverse fading behaviour up to 64800 s. The rate of fading for peaks I, II and III in α-Al2O3:C,Mg was found to decrease with increase in dose. However, no such behaviour was observed in α-Al2O3:C. The fading in both samples is discussed on the basis of a charge hopping mechanism.
- Full Text:
- Date Issued: 2017
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2017
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113058 , vital:33694 , https://doi.org/10.1093/rpd/ncx039
- Description: A comparative study of the dosimetric features of α-Al2O3:C,Mg and α-Al2O3:C relevant to thermoluminescence dosimetry is reported. A glow curve of α-Al2O3:C,Mg measured at 1°C/s after beta irradiation to 1 Gy shows two subsidiary peaks at 42°C (labelled as I) and 72°C (II) and the main peak at 161°C (III) whereas a glow curve of α-Al2O3:C measured under the same conditions shows the main peak at 178°C (II′) and a lower intensity peak at 48°C (I′). Apart from these ones, there are several other peaks at temperatures beyond that of the main peak in both α-Al2O3:C,Mg and α-Al2O3:C. However, the latter are not included in this study. We report a comparative quantitative analysis of dose response and fading of peaks I, II and III of α-Al2O3:C,Mg and peaks I′ and II′ of α-Al2O3:C. Analysis shows that the dose response of peaks I and III is sublinear within 1–10 Gy whereas that of peak II is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy. In comparison, the dose response of peak I′ is superlinear within 1–4 Gy followed by a sublinear region within 4–10 Gy whereas that of peak II′ is sublinear within 1–4 Gy followed by a superlinear region within 4–10 Gy. As regards to fading corresponding to 1 Gy, peak I is very unstable and fades within 300 s, peak II is more stable and takes up to 43200 s to fade. In comparison, peak III fades down to 30% of its initial intensity within 2400 s. Interestingly, between 2400 and 800 s, the intensity fades by 17% only. Regarding fading in α-Al2O3:C, peak I′ fades within 600 s whereas peak II′ shows an inverse fading behaviour up to 64800 s. The rate of fading for peaks I, II and III in α-Al2O3:C,Mg was found to decrease with increase in dose. However, no such behaviour was observed in α-Al2O3:C. The fading in both samples is discussed on the basis of a charge hopping mechanism.
- Full Text:
- Date Issued: 2017
Composition and fate of triclosan in the sludge from wastewater treatment in Grahamstown, South Africa and Tiaret, Algeria
- Authors: Ncube, Mbonisi
- Date: 2017
- Subjects: Sewage sludge , Sewage Purification South Africa Grahamstown , Sewage Purification Algeria Tiaret , Sewage sludge as fertilizer , Anti-infective agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65156 , vital:28697
- Description: Physicochemical properties such as pH, specific surface area (SSA), cationic exchange capacity (CEC), loss on ignition (LOI), pathogens, plant nutrients (nitrates, ammonium and phosphates), and heavy metals (manganese, copper, lead and cadmium) were determined for sewage sludge from Grahamstown and Tiaret. The values obtained were log transformed thereafter a t-test at 5 % level of significance was used to test for the difference in each parameter for both sludges. The pH of sludge was determined in 1:3 water, 16 water, 1:3 0.01 M calcium chloride and 1:3 1 M potassium chloride. The pH for Grahamstown and Tiaret sludge were in the ranges of 6.66-7.11 and 7.88-8.18 respectively. The SSA values for Grahamstown and Tiaret were 218 ± 108 and 261 ± 99.9 m2/g, and the CEC values were 119 ± 2.09 and 136 ± 6.03 mEq/100, respectively. The LOI values obtained were 1.33 ± 0.03 and 1.48 ± 0.11 % for Grahamstown and Tiaret, respectively. E. coll and heterotrophic bacteria were the pathogens determined, and were extracted from sludge using sterile saline and nutrient broth. The concentration of E. coll in Grahamstown and Tiaret sludge were 468 ± 7.63 and 7769 ± 1268 CFU/g d.w and for heterotrophic bacteria were 1.17x109 ± 7.42x108 and 1.43x109 ± 9.11 x108 CFU/g d.w. For Grahamstown sludge, the concentration of nitrates, ammonium and phosphates were 55.61 ± 55.20 mg/g d.w, 6.60 ± 2.36 mg/g d.w and 1.40 ± 0.30 mg/g d.w, respectively. For Tiaret sludge, the concentration of nitrates, ammonium and phosphates were 2.56 ± 2.90 mg/g d.w, 0.64 ± 0.45 mg/g d.w and 0.24 ± 0.19 mg/g d.w, respectively. The concentration of Mn, Cu, Pb and Cd in Grahamstown sludge were 423 ± 101, 353 ± 92, 40.2 ± 20 and 0.0 mg/kg d.w respectively, and for Tiaret sludge, the corresponding concentrations were 358± 295, 549±50, 1427± 1352 and 1.54 ± 0.61 mg/kg d.w. Sewage sludge was found to contain Triclosan, and solubility studies of the compound were conducted using sodium deoxycholate and sodium lithocholate. The apparent solubilities and rate constants indicated in brackets of TCS at 37 °C were 35.4 ± 1.21 mg/L (1.28 ± 0.36 Hr-) and 14.4 ± 0.34 mg/L (0.99 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. The apparent solubilities and rate constants indicated in brackets of TCS at 15 °C were 32.3 ± 0.88 mg/L (2.16 ± 0.80 Hr-) and 14.2 ± 0.39 mg/L (1.02 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. Triclosan was extracted from sludge using 1 g/L sodium deoxycholate and the determined concentration were 142 ± 33.5 gg/g d.w for Grahamstown sludge and 0-12 gg/g d.w for Tiaret sludge. Finally plant growth studies were conducted on radish and garden cress plants using Grahamstown sludge at 0, 20, 40, 80 and 100 % treatments. Statistical analysis (t-test and Kruskal-Wallis) at 5 % level of significance was done to compare growth parameters between control and different sludge treatments. For radish plants, the values for plant height, root length, number of leaves, leaf length and dry mass were 28.4-80-7 mm, 4.3-44.7 mm, 3.3-17.0 mm, 2.3-4.0 leaves and 6.3-15.3 %, respectively. For garden cress, the values for plant height, root length, number of leaves, leaf length and dry mass were 13.7-25.0 mm, 7.7-20.3 mm, 5.7-8.3 leaves, 3.0-8.3 mm and 8.8-15.0 %, respectively. Twenty percent (20 %) sludge treatment gave the best results in radish and garden cress plants with respect to plant height, root length, number of leaves and dry mass. Triclosan concentration in radish and garden cress plants was below the detection limit of 32.4 gg/g d.w. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Date Issued: 2017
- Authors: Ncube, Mbonisi
- Date: 2017
- Subjects: Sewage sludge , Sewage Purification South Africa Grahamstown , Sewage Purification Algeria Tiaret , Sewage sludge as fertilizer , Anti-infective agents
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/65156 , vital:28697
- Description: Physicochemical properties such as pH, specific surface area (SSA), cationic exchange capacity (CEC), loss on ignition (LOI), pathogens, plant nutrients (nitrates, ammonium and phosphates), and heavy metals (manganese, copper, lead and cadmium) were determined for sewage sludge from Grahamstown and Tiaret. The values obtained were log transformed thereafter a t-test at 5 % level of significance was used to test for the difference in each parameter for both sludges. The pH of sludge was determined in 1:3 water, 16 water, 1:3 0.01 M calcium chloride and 1:3 1 M potassium chloride. The pH for Grahamstown and Tiaret sludge were in the ranges of 6.66-7.11 and 7.88-8.18 respectively. The SSA values for Grahamstown and Tiaret were 218 ± 108 and 261 ± 99.9 m2/g, and the CEC values were 119 ± 2.09 and 136 ± 6.03 mEq/100, respectively. The LOI values obtained were 1.33 ± 0.03 and 1.48 ± 0.11 % for Grahamstown and Tiaret, respectively. E. coll and heterotrophic bacteria were the pathogens determined, and were extracted from sludge using sterile saline and nutrient broth. The concentration of E. coll in Grahamstown and Tiaret sludge were 468 ± 7.63 and 7769 ± 1268 CFU/g d.w and for heterotrophic bacteria were 1.17x109 ± 7.42x108 and 1.43x109 ± 9.11 x108 CFU/g d.w. For Grahamstown sludge, the concentration of nitrates, ammonium and phosphates were 55.61 ± 55.20 mg/g d.w, 6.60 ± 2.36 mg/g d.w and 1.40 ± 0.30 mg/g d.w, respectively. For Tiaret sludge, the concentration of nitrates, ammonium and phosphates were 2.56 ± 2.90 mg/g d.w, 0.64 ± 0.45 mg/g d.w and 0.24 ± 0.19 mg/g d.w, respectively. The concentration of Mn, Cu, Pb and Cd in Grahamstown sludge were 423 ± 101, 353 ± 92, 40.2 ± 20 and 0.0 mg/kg d.w respectively, and for Tiaret sludge, the corresponding concentrations were 358± 295, 549±50, 1427± 1352 and 1.54 ± 0.61 mg/kg d.w. Sewage sludge was found to contain Triclosan, and solubility studies of the compound were conducted using sodium deoxycholate and sodium lithocholate. The apparent solubilities and rate constants indicated in brackets of TCS at 37 °C were 35.4 ± 1.21 mg/L (1.28 ± 0.36 Hr-) and 14.4 ± 0.34 mg/L (0.99 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. The apparent solubilities and rate constants indicated in brackets of TCS at 15 °C were 32.3 ± 0.88 mg/L (2.16 ± 0.80 Hr-) and 14.2 ± 0.39 mg/L (1.02 ± 0.17 Hr-) in sodium lithocholate and sodium deoxycholate, respectively. Triclosan was extracted from sludge using 1 g/L sodium deoxycholate and the determined concentration were 142 ± 33.5 gg/g d.w for Grahamstown sludge and 0-12 gg/g d.w for Tiaret sludge. Finally plant growth studies were conducted on radish and garden cress plants using Grahamstown sludge at 0, 20, 40, 80 and 100 % treatments. Statistical analysis (t-test and Kruskal-Wallis) at 5 % level of significance was done to compare growth parameters between control and different sludge treatments. For radish plants, the values for plant height, root length, number of leaves, leaf length and dry mass were 28.4-80-7 mm, 4.3-44.7 mm, 3.3-17.0 mm, 2.3-4.0 leaves and 6.3-15.3 %, respectively. For garden cress, the values for plant height, root length, number of leaves, leaf length and dry mass were 13.7-25.0 mm, 7.7-20.3 mm, 5.7-8.3 leaves, 3.0-8.3 mm and 8.8-15.0 %, respectively. Twenty percent (20 %) sludge treatment gave the best results in radish and garden cress plants with respect to plant height, root length, number of leaves and dry mass. Triclosan concentration in radish and garden cress plants was below the detection limit of 32.4 gg/g d.w. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Date Issued: 2017
Bush clumps as indicators of thresholds of change in Arid Thicket mosaic piospheres
- Authors: Schmidt, Anton George
- Date: 2017
- Subjects: Biodiversity conservation Ecological processes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20811 , vital:29403
- Description: In the literature, Arid Thicket transformation by domestic meso-herbivores is purported to follow a state-and-transition model, whereby the ecosystem is initially resilient to herbivory until some threshold is crossed, where after there is a rapid shift to a new alternative stable state. My study represents a first attempt to verify this hypothesis by searching for evidence of stable ecosystem states separated by structural, functional and degradation thresholds in Pruim-Spekboomveld, a variation of Arid Thicket found in the southern Cape of South Africa. In this variation, thicket bush clumps ranging in size from approximately 1 m2 to 100 m2 are interspersed in a matrix of Succulent Karoo vegetation. I correlate structural and functional attributes of the thicket bush clumps and the soil environment beneath them (indicators of ecosystem function) to distance from artificial watering points in four piosphere treatments that have had a different rangeland management history. I mostly fit linear, exponential and sigmoid regression models to my data and use Akaike’s Information Criterion to select the best fitting model. When analysing data on changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, I additionally fit Generalized Additive Models to the data to take into account more complex predicted patterns of change. Furthermore, I compare the end regions of my data in the piosphere treatments to each other and to similar data collected in a transformed and untransformed reference site. I use both the pattern and extent of transformation within and between the treatments and the reference sites, to verify the existence of stable states and structural, functional and degradation thresholds. I also subject my entire dataset to multivariate analysis using ordination and permutation procedures, in an attempt to corroborate my results from the univariate analysis and to assess the response of bush clump community composition to herbivory. My results indicate that at the scale of a bush clump, a threshold reduction in species richness, functional type diversity, succulent shrub redundancy and cover, palatable shrub cover and bush clump leaf mass below 1.5 m occurs in regions intensively used by domestic meso-herbivores. Furthermore, at the landscape scale there is a threshold reduction in canopy tree cover and bush clump density. In addition to these structural threshold changes, results from a Landscape Function Analysis indicate that soil nutrient cycling, soil water infiltration and soil stability thresholds are crossed at the landscape scale. The soil nutrient cycling threshold is affirmed by soil chemical analyses which indicate that the most rested treatment in the study area has low carbon and nitrogen levels. Furthermore, the keystone species, Portulacaria afra, is unable to re-establish itself in any of the treatments. High pH and potassium levels in all the treatments, relative to the untransformed reference site, indicate that Portulacaria afra (which prefers moderate soil conditions) is unlikely to re-establish in the study area. This finding suggests that all my treatments have crossed a degradation threshold and therefore represent an alternative stable state to the untransformed reference site. My multivariate analysis supports this finding and further indicates that the sampling zones within 25 m of the watering points in the most utilized treatments have crossed a second degradation threshold. This finding is supported by my results that indicate that structural and function thresholds (related to the size, density and ability of bush clumps to capture and retain soil resources) have been crossed. Furthermore, excessively high concentrations of base cations in these sampling zones, relative to the untransformed reference site, affirm the crossing of a degradation threshold. My results on the changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, support the growing body of evidence in the literature that suggests that increases in the variance of ecosystem processes and services are important indicators of impending ecological thresholds. In general, my findings support the prediction in the literature that domestic meso-herbivore induced transformation of Arid Mosaic Thicket will follow a state-andtransition model.
- Full Text:
- Date Issued: 2017
- Authors: Schmidt, Anton George
- Date: 2017
- Subjects: Biodiversity conservation Ecological processes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20811 , vital:29403
- Description: In the literature, Arid Thicket transformation by domestic meso-herbivores is purported to follow a state-and-transition model, whereby the ecosystem is initially resilient to herbivory until some threshold is crossed, where after there is a rapid shift to a new alternative stable state. My study represents a first attempt to verify this hypothesis by searching for evidence of stable ecosystem states separated by structural, functional and degradation thresholds in Pruim-Spekboomveld, a variation of Arid Thicket found in the southern Cape of South Africa. In this variation, thicket bush clumps ranging in size from approximately 1 m2 to 100 m2 are interspersed in a matrix of Succulent Karoo vegetation. I correlate structural and functional attributes of the thicket bush clumps and the soil environment beneath them (indicators of ecosystem function) to distance from artificial watering points in four piosphere treatments that have had a different rangeland management history. I mostly fit linear, exponential and sigmoid regression models to my data and use Akaike’s Information Criterion to select the best fitting model. When analysing data on changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, I additionally fit Generalized Additive Models to the data to take into account more complex predicted patterns of change. Furthermore, I compare the end regions of my data in the piosphere treatments to each other and to similar data collected in a transformed and untransformed reference site. I use both the pattern and extent of transformation within and between the treatments and the reference sites, to verify the existence of stable states and structural, functional and degradation thresholds. I also subject my entire dataset to multivariate analysis using ordination and permutation procedures, in an attempt to corroborate my results from the univariate analysis and to assess the response of bush clump community composition to herbivory. My results indicate that at the scale of a bush clump, a threshold reduction in species richness, functional type diversity, succulent shrub redundancy and cover, palatable shrub cover and bush clump leaf mass below 1.5 m occurs in regions intensively used by domestic meso-herbivores. Furthermore, at the landscape scale there is a threshold reduction in canopy tree cover and bush clump density. In addition to these structural threshold changes, results from a Landscape Function Analysis indicate that soil nutrient cycling, soil water infiltration and soil stability thresholds are crossed at the landscape scale. The soil nutrient cycling threshold is affirmed by soil chemical analyses which indicate that the most rested treatment in the study area has low carbon and nitrogen levels. Furthermore, the keystone species, Portulacaria afra, is unable to re-establish itself in any of the treatments. High pH and potassium levels in all the treatments, relative to the untransformed reference site, indicate that Portulacaria afra (which prefers moderate soil conditions) is unlikely to re-establish in the study area. This finding suggests that all my treatments have crossed a degradation threshold and therefore represent an alternative stable state to the untransformed reference site. My multivariate analysis supports this finding and further indicates that the sampling zones within 25 m of the watering points in the most utilized treatments have crossed a second degradation threshold. This finding is supported by my results that indicate that structural and function thresholds (related to the size, density and ability of bush clumps to capture and retain soil resources) have been crossed. Furthermore, excessively high concentrations of base cations in these sampling zones, relative to the untransformed reference site, affirm the crossing of a degradation threshold. My results on the changes in the variation of vegetation production with distance from water using the Normalized Difference Vegetation Index, support the growing body of evidence in the literature that suggests that increases in the variance of ecosystem processes and services are important indicators of impending ecological thresholds. In general, my findings support the prediction in the literature that domestic meso-herbivore induced transformation of Arid Mosaic Thicket will follow a state-andtransition model.
- Full Text:
- Date Issued: 2017
Fraction-specific geochemistry across the Asbestos Hills BIF of the Transvaal Supergroup, South Africa: implications for the origin of BIF and the history of atmospheric oxygen
- Oonk, Paul Bernardus Hendrikus
- Authors: Oonk, Paul Bernardus Hendrikus
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/50721 , vital:26021
- Description: Banded iron formations (BIF), deposited prior to and concurrent with the Great Oxidation Event (GOE) at ca. 2.4 Ga, record changes in oceanic and atmospheric chemistry during this critical time interval. Four previously unstudied drill-cores from the Griqualand West Basin, South Africa, capturing the rhythmically mesobanded, deep-water Kuruman BIF and the overlying granular, shallower Griquatown BIF, were sampled every ca. 10 m along core depth. Mineralogically, these BIFs consist of three iron-bearing fractions: (1) Fe-Ca-Mg-Mn carbonates, (2) magnetite with/without minor hematite and (3) Fe-silicates. These fractions are typically fine-grained on a sub-μm scale and their co-occurrence in varying amounts means that bulk-rock or microanalytical geochemical and stable isotope data are influenced by mineralogy.
- Full Text:
- Date Issued: 2017
- Authors: Oonk, Paul Bernardus Hendrikus
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/50721 , vital:26021
- Description: Banded iron formations (BIF), deposited prior to and concurrent with the Great Oxidation Event (GOE) at ca. 2.4 Ga, record changes in oceanic and atmospheric chemistry during this critical time interval. Four previously unstudied drill-cores from the Griqualand West Basin, South Africa, capturing the rhythmically mesobanded, deep-water Kuruman BIF and the overlying granular, shallower Griquatown BIF, were sampled every ca. 10 m along core depth. Mineralogically, these BIFs consist of three iron-bearing fractions: (1) Fe-Ca-Mg-Mn carbonates, (2) magnetite with/without minor hematite and (3) Fe-silicates. These fractions are typically fine-grained on a sub-μm scale and their co-occurrence in varying amounts means that bulk-rock or microanalytical geochemical and stable isotope data are influenced by mineralogy.
- Full Text:
- Date Issued: 2017
Multiple voices: exploring fluid identities in the advanced programme English experience
- Authors: Kromhout, Jessamy
- Date: 2017
- Subjects: English language -- Study and teaching Student-centered learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/18674 , vital:28705
- Description: This study is focused on Advanced Programme English (AP English), which is an additional subject registered through the Independent Examinations Board. The subject is aimed at grades ten to twelve and it is dedicated to the study of English literature. This study explores the AP English experience from the learner perspective, thus it highlights the potential opportunities of learner participation in AP English. In a traditional school context, emphasis is placed on assessment. As a response to this achievement driven focus, this study instead seeks to understand the social context of AP English, and the way in which the AP English experience has been integrated into the learners’ lives. The focus of this study is to understand the AP English perspective through the lens of identity, and the way in which identity permeates all experiences of AP English as a whole. The construction of identity is explored through the activities of reading and writing. These are integral to the AP English experience. By incorporating a number of different perspectives from educational and literary spheres to make sense of the AP English experience, this study broadens conceptualisations of the learner perspective. It also complements traditional conceptualisations of education by including commentary from a diverse range of voices. This study characterises AP English as an alternative space that has the potential to provide a sense of belonging for its learners. The AP English social context offers learners the opportunity to construct their identities in relation to the literature they study, and to their classmates. This meaningful learner engagement may provide learners with the space and freedom to construct their identities in an authentic, self-reflexive manner. Various theories on identity support how AP English can provide a platform for learners to inhabit multiple voices or perspectives. By using literature as a reference point, learners have the opportunity to make sense of themselves through a multiplicity of perspectives. This study therefore provides insight into the way AP English might facilitate a flexible approach to conceptualising identity, which is often overlooked in the education context, thus this study advocates the AP English experience as an important aspect of identity construction. On a larger scale, it places the learner perspective at the forefront, and in this way offers an alternative conceptualisation to traditional, assessment focused schooling methods.
- Full Text:
- Date Issued: 2017
- Authors: Kromhout, Jessamy
- Date: 2017
- Subjects: English language -- Study and teaching Student-centered learning
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/18674 , vital:28705
- Description: This study is focused on Advanced Programme English (AP English), which is an additional subject registered through the Independent Examinations Board. The subject is aimed at grades ten to twelve and it is dedicated to the study of English literature. This study explores the AP English experience from the learner perspective, thus it highlights the potential opportunities of learner participation in AP English. In a traditional school context, emphasis is placed on assessment. As a response to this achievement driven focus, this study instead seeks to understand the social context of AP English, and the way in which the AP English experience has been integrated into the learners’ lives. The focus of this study is to understand the AP English perspective through the lens of identity, and the way in which identity permeates all experiences of AP English as a whole. The construction of identity is explored through the activities of reading and writing. These are integral to the AP English experience. By incorporating a number of different perspectives from educational and literary spheres to make sense of the AP English experience, this study broadens conceptualisations of the learner perspective. It also complements traditional conceptualisations of education by including commentary from a diverse range of voices. This study characterises AP English as an alternative space that has the potential to provide a sense of belonging for its learners. The AP English social context offers learners the opportunity to construct their identities in relation to the literature they study, and to their classmates. This meaningful learner engagement may provide learners with the space and freedom to construct their identities in an authentic, self-reflexive manner. Various theories on identity support how AP English can provide a platform for learners to inhabit multiple voices or perspectives. By using literature as a reference point, learners have the opportunity to make sense of themselves through a multiplicity of perspectives. This study therefore provides insight into the way AP English might facilitate a flexible approach to conceptualising identity, which is often overlooked in the education context, thus this study advocates the AP English experience as an important aspect of identity construction. On a larger scale, it places the learner perspective at the forefront, and in this way offers an alternative conceptualisation to traditional, assessment focused schooling methods.
- Full Text:
- Date Issued: 2017
Rhenium complexes of benzazole derivatives
- Authors: Van Niekerk, Xandri
- Date: 2017
- Subjects: Rhenium Benzimidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21252 , vital:29467
- Description: A series of rhenium(I) complexes with monodentate benzazole ligands containing the fac-[Re(CO)3]+ was synthesized. The rhenium(I) compound [ReCl(Hmbt)2(CO)3] was prepared from the reaction of [Re(CO)5Cl] and 2-aminobenzothiazole (Hmbt) in toluene. The ligand coordinates in a monodentate manner via the thiazole nitrogen atom. A similar reaction between [Re(CO)5Cl] and N-(1,3-benzothiazol-2-yl)-2- chloroacetamide (Hbct) resulted in the formation of [ReCl(Hbct)(CO)3(NCMe)], where only one ligand binds per rhenium in a monodentate fashion. The reaction of ligands 2-mercaptobenzimidazole (Hmbi) (dibenzothiazol-2-yl)tetraazathiapentalene (Hdbt) with rhenium(I) gave [ReCl(Hmbi)2(CO)3] and [ReCl(Hdbt)2(CO)3] respectively. The study on the coordination behaviour between ethyl-(1H-benzimidazol-2-yl-sulfanyl) acetate (Hbsa) and [Re(CO)5Cl] surprisingly gave the dimeric species (μ-Cl)2[Re(Hbsa)(CO)3]2, where the two rhenium atoms are bridged by two chloro ligands. The coordination of Hbsa occurs through the imidazole nitrogen, leaving the ethoxy tail free on each Hbsa ligand. The coordination behaviour of benzimidazole and benzothiazole derivatives gave rhenium complexes in oxidation states I, III and V, where all the ligands coordinate as bidentate N,N-chelating ligands. The study on 2-(2-aminophenyl)-1-benzothiazole (Hapt) and 2-(2-aminophenyl)-1-benzimidazole (H2apz) with [ReVOCl3(PPh3)2] resulted in the formation of [ReVOCl2(apt)(OPPh3)] and [ReVCl2(apz)(PPh3)2](ReO4), respectively. 1,2-Bis(2-benzimidazole)-1,2-ethanediol (Hbed) and 2,6-bis(2- benzimidazol-2-yl)pyridine (H2bip) were studied towards rhenium(I) and rheniumV) respectively. The former gave a dimeric species (μ-bbi)[Re(CO)4]2 (H2bbi – bisbenzimidazole) by reaction with [Re(CO)5Cl], whereas H2bip produced the rhenium(III) cationic salt [ReCl3(H3bip)(PPh3)]Cl, where the ligand coordinates as a cationic H3bip+ with protonation of an uncoordinated imidazole nitrogen atom. The pyridine derivatives 2-hydrazino-pyridinyl-2-benzothiazole (Hhpt) and (E)-1-benzo[d]thiazol-2-yl)-2- (pyridin-2-ylmethylene)hydrazine (btp) were reacted with [Re(CO)5Cl]. The neutral complex [ReCl(Hhpt)(CO)3] was isolated upon reaction with Hhpt, where Hhpt coordinates as a neutral bidentate ligand. The reaction of [Re(CO)5Cl] with btp gave two different complexes when using different solvents. In methanol, [ReCl(btp)(CO)3] was isolated, whereas in toluene, the conjugate of btp (btp1) was formed which resulted in the formation of [ReCl(btp1)(CO)3]. The study on potentially bidentate thiourea derivatives containing a benzothiazole moiety towards [ReI(CO)3]+ and [ReVO]3+ cores gave rise to a wide variety of complexes. The reaction of [Re(CO)5Cl] with N-phenyl-N-(2-benzothiazole)thiourea (Hpbt) produced the rhenium(I) complex [Re(Hpbt)(pbt)(CO)3]. Hpbt coordinates both as a monodentate neutral ligand and as a bidentate monoanionic chelate. The study of the reaction between trans-[ReOCl3(PPh3)2] and Hpbt gave the rhenium(V) product [ReOCl2(pbt)(PPh3)], with pbt acting as a bidentate ligand. The reaction of 1-(1,3- benzothiazol-2-yl)-3-benzoylthiourea (Hbbt) with [Re(CO)5Cl] led to the isolation of [ReCl(Hbbt)(CO)3]. Similar reaction of Hbbt with trans-[ReOCl3(PPh3)2] gave the unique compound [ReOCl2(Hbnt)(PPh3)], where the ligand coordinates via the ketonic oxygen and a methine carbon. The complex [Re(Hmby)(mby)(CO)3] was isolated upon reacting [Re(CO)5Cl] with methylbenzothiazol-2-ylidenecarbamodithioate (Hmby), with Hmby coordinating as a monodentate neutral ligand and mby as a bidentate monoanionic chelate. The coordination behaviour of N-(benzothiazol-2-yl)-S,S’- dimethyldithiocarboimine (Hbdc) towards rhenium(I) led to the formation of [ReCl(Hbdc)(CO)3]. The reactivity of 1-(benzothiozol-2-yl)-3,3-dimethylthiourea (Hbdm), a derivative of Hmby, was studied with trans-[ReOCl3(PPh3)2] and trans- [ReO(OEt)I2(PPh3)2] producing the square pyramidal compound [ReOCl(bdm)2] and the salt [Re(bdm)2(MeCN)2]I3, respectively. Pyrazole derivatives containing a benzothiazole ring were studied towards rhenium in oxidation states +I and +V. The reaction between 2-(3,5-dimethylpyrazol-1-yl)benzothiazole (Hdmp) and [Re(CO)5Cl] gave the neutral rhenium complex [ReCl(Hdmp)(CO)3], whereas its reaction with [ReOCl3(PPh3)2] surprisingly results in the formation of a dimeric complex (μ-O)[ReOCl2(Hdmp)]2. The study on the reactivity of 1-(benzo[d]thiazol-2-yl)-4-methyl-1H-pyrrol-2-ol (Hbtm) with [Re(CO)5Cl] gave the unexpected trimer [Re(btm)(CO)3]3 containing the fac-[Re(CO)3]+ core. The ligand btm forms a bridge between each rhenium metal, serving as a bidentate ligand to one rhenium, and a monodentate ligand to another rhenium atom. The study on the coordination chemistry between trans-[ReOCl3(PPh3)2] and Hbtm gave two different complexes when using different solvents. In ethanol, [ReOCl(btm)(btm1)] formed, whereas [ReOCl(btm1)(btz)] (Hbtz = 1-(benzo[d]thiazol-2-yl)-4-(1-iminoethyl)-3- methyl-1H-pyrazol-5-ol) was isolated in acetonitrile. The reaction of cis-[ReO2I(PPh3)2] also gave two different products when using different solvents, where the respective solvents coordinate to the metal. The rhenium(V) compound [ReO(OMe)(btm)(btm1)] was formed in methanol, whereas [ReO(OEt)(btm)(btm1)] was formed in ethanol. The coordination chemistry of 2-(2-Benzothiazoleyl)-4,5,6,7-tetrahydro-2H-indazol-3-ol (Hbth) was studied towards [Re(CO)5Cl] and trans-[ReOCl3(PPh3)2]. The resulting complexes which formed are [ReCl(Hbth)(CO)3] and [ReOCl(bth)(bth1)] respectively. The reactivity of potentially tridentate Schiff base ligands towards rhenium(I) and (V) was studied. The rhenium(I) precursor [Re(CO)5Cl] was reacted with (E)-1- (benzo[d]thiazol-2-yl)-2-(phenol-2-ylmethylene)hydrazine (H3bph) to give [ReCl(CO)3(H3bph)], which contains the kinetically inert fac-[Re(CO)3]+ core coordinated to a neutral bidentate ligand. The reaction of [ReO2(py)4Cl] with H3bph gave the dimeric species (μ-O)[ReO(Hbph)(py)]2, where the ligand coordinates as a tridentate dianionic chelate. A similar complex was isolated with (E)-1- (benzo[d]thiazol-2-yl)-2-(2,4-dihydroxy-2-ylmethylene)hydrazine (H3bdh) to give (μ-O)[ReO(Hbdh)(py)]2. The reaction of trans-[ReOCl3(PPh3)2] with H3bph afforded [Re(abt)(imp)Cl2(PPh3)] (abt = 2-aminobenzothiazole, imp = 2-(iminomethyl)phenol), where the ligand broke up into two fragments, both of which coordinated without any modification. The dioxo rhenium precursor cis-[ReO2I(PPh3)2] gave [ReO(Hbdh)(imp)] upon reaction with H3bdh. Ligand imp coordinates as a bidentate monoanionic ligand via the imine nitrogen and deprotonated phenolic oxygen and ligand Hbdh coordinatesas a tridentate dianionic chelate.
- Full Text:
- Date Issued: 2017
- Authors: Van Niekerk, Xandri
- Date: 2017
- Subjects: Rhenium Benzimidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/21252 , vital:29467
- Description: A series of rhenium(I) complexes with monodentate benzazole ligands containing the fac-[Re(CO)3]+ was synthesized. The rhenium(I) compound [ReCl(Hmbt)2(CO)3] was prepared from the reaction of [Re(CO)5Cl] and 2-aminobenzothiazole (Hmbt) in toluene. The ligand coordinates in a monodentate manner via the thiazole nitrogen atom. A similar reaction between [Re(CO)5Cl] and N-(1,3-benzothiazol-2-yl)-2- chloroacetamide (Hbct) resulted in the formation of [ReCl(Hbct)(CO)3(NCMe)], where only one ligand binds per rhenium in a monodentate fashion. The reaction of ligands 2-mercaptobenzimidazole (Hmbi) (dibenzothiazol-2-yl)tetraazathiapentalene (Hdbt) with rhenium(I) gave [ReCl(Hmbi)2(CO)3] and [ReCl(Hdbt)2(CO)3] respectively. The study on the coordination behaviour between ethyl-(1H-benzimidazol-2-yl-sulfanyl) acetate (Hbsa) and [Re(CO)5Cl] surprisingly gave the dimeric species (μ-Cl)2[Re(Hbsa)(CO)3]2, where the two rhenium atoms are bridged by two chloro ligands. The coordination of Hbsa occurs through the imidazole nitrogen, leaving the ethoxy tail free on each Hbsa ligand. The coordination behaviour of benzimidazole and benzothiazole derivatives gave rhenium complexes in oxidation states I, III and V, where all the ligands coordinate as bidentate N,N-chelating ligands. The study on 2-(2-aminophenyl)-1-benzothiazole (Hapt) and 2-(2-aminophenyl)-1-benzimidazole (H2apz) with [ReVOCl3(PPh3)2] resulted in the formation of [ReVOCl2(apt)(OPPh3)] and [ReVCl2(apz)(PPh3)2](ReO4), respectively. 1,2-Bis(2-benzimidazole)-1,2-ethanediol (Hbed) and 2,6-bis(2- benzimidazol-2-yl)pyridine (H2bip) were studied towards rhenium(I) and rheniumV) respectively. The former gave a dimeric species (μ-bbi)[Re(CO)4]2 (H2bbi – bisbenzimidazole) by reaction with [Re(CO)5Cl], whereas H2bip produced the rhenium(III) cationic salt [ReCl3(H3bip)(PPh3)]Cl, where the ligand coordinates as a cationic H3bip+ with protonation of an uncoordinated imidazole nitrogen atom. The pyridine derivatives 2-hydrazino-pyridinyl-2-benzothiazole (Hhpt) and (E)-1-benzo[d]thiazol-2-yl)-2- (pyridin-2-ylmethylene)hydrazine (btp) were reacted with [Re(CO)5Cl]. The neutral complex [ReCl(Hhpt)(CO)3] was isolated upon reaction with Hhpt, where Hhpt coordinates as a neutral bidentate ligand. The reaction of [Re(CO)5Cl] with btp gave two different complexes when using different solvents. In methanol, [ReCl(btp)(CO)3] was isolated, whereas in toluene, the conjugate of btp (btp1) was formed which resulted in the formation of [ReCl(btp1)(CO)3]. The study on potentially bidentate thiourea derivatives containing a benzothiazole moiety towards [ReI(CO)3]+ and [ReVO]3+ cores gave rise to a wide variety of complexes. The reaction of [Re(CO)5Cl] with N-phenyl-N-(2-benzothiazole)thiourea (Hpbt) produced the rhenium(I) complex [Re(Hpbt)(pbt)(CO)3]. Hpbt coordinates both as a monodentate neutral ligand and as a bidentate monoanionic chelate. The study of the reaction between trans-[ReOCl3(PPh3)2] and Hpbt gave the rhenium(V) product [ReOCl2(pbt)(PPh3)], with pbt acting as a bidentate ligand. The reaction of 1-(1,3- benzothiazol-2-yl)-3-benzoylthiourea (Hbbt) with [Re(CO)5Cl] led to the isolation of [ReCl(Hbbt)(CO)3]. Similar reaction of Hbbt with trans-[ReOCl3(PPh3)2] gave the unique compound [ReOCl2(Hbnt)(PPh3)], where the ligand coordinates via the ketonic oxygen and a methine carbon. The complex [Re(Hmby)(mby)(CO)3] was isolated upon reacting [Re(CO)5Cl] with methylbenzothiazol-2-ylidenecarbamodithioate (Hmby), with Hmby coordinating as a monodentate neutral ligand and mby as a bidentate monoanionic chelate. The coordination behaviour of N-(benzothiazol-2-yl)-S,S’- dimethyldithiocarboimine (Hbdc) towards rhenium(I) led to the formation of [ReCl(Hbdc)(CO)3]. The reactivity of 1-(benzothiozol-2-yl)-3,3-dimethylthiourea (Hbdm), a derivative of Hmby, was studied with trans-[ReOCl3(PPh3)2] and trans- [ReO(OEt)I2(PPh3)2] producing the square pyramidal compound [ReOCl(bdm)2] and the salt [Re(bdm)2(MeCN)2]I3, respectively. Pyrazole derivatives containing a benzothiazole ring were studied towards rhenium in oxidation states +I and +V. The reaction between 2-(3,5-dimethylpyrazol-1-yl)benzothiazole (Hdmp) and [Re(CO)5Cl] gave the neutral rhenium complex [ReCl(Hdmp)(CO)3], whereas its reaction with [ReOCl3(PPh3)2] surprisingly results in the formation of a dimeric complex (μ-O)[ReOCl2(Hdmp)]2. The study on the reactivity of 1-(benzo[d]thiazol-2-yl)-4-methyl-1H-pyrrol-2-ol (Hbtm) with [Re(CO)5Cl] gave the unexpected trimer [Re(btm)(CO)3]3 containing the fac-[Re(CO)3]+ core. The ligand btm forms a bridge between each rhenium metal, serving as a bidentate ligand to one rhenium, and a monodentate ligand to another rhenium atom. The study on the coordination chemistry between trans-[ReOCl3(PPh3)2] and Hbtm gave two different complexes when using different solvents. In ethanol, [ReOCl(btm)(btm1)] formed, whereas [ReOCl(btm1)(btz)] (Hbtz = 1-(benzo[d]thiazol-2-yl)-4-(1-iminoethyl)-3- methyl-1H-pyrazol-5-ol) was isolated in acetonitrile. The reaction of cis-[ReO2I(PPh3)2] also gave two different products when using different solvents, where the respective solvents coordinate to the metal. The rhenium(V) compound [ReO(OMe)(btm)(btm1)] was formed in methanol, whereas [ReO(OEt)(btm)(btm1)] was formed in ethanol. The coordination chemistry of 2-(2-Benzothiazoleyl)-4,5,6,7-tetrahydro-2H-indazol-3-ol (Hbth) was studied towards [Re(CO)5Cl] and trans-[ReOCl3(PPh3)2]. The resulting complexes which formed are [ReCl(Hbth)(CO)3] and [ReOCl(bth)(bth1)] respectively. The reactivity of potentially tridentate Schiff base ligands towards rhenium(I) and (V) was studied. The rhenium(I) precursor [Re(CO)5Cl] was reacted with (E)-1- (benzo[d]thiazol-2-yl)-2-(phenol-2-ylmethylene)hydrazine (H3bph) to give [ReCl(CO)3(H3bph)], which contains the kinetically inert fac-[Re(CO)3]+ core coordinated to a neutral bidentate ligand. The reaction of [ReO2(py)4Cl] with H3bph gave the dimeric species (μ-O)[ReO(Hbph)(py)]2, where the ligand coordinates as a tridentate dianionic chelate. A similar complex was isolated with (E)-1- (benzo[d]thiazol-2-yl)-2-(2,4-dihydroxy-2-ylmethylene)hydrazine (H3bdh) to give (μ-O)[ReO(Hbdh)(py)]2. The reaction of trans-[ReOCl3(PPh3)2] with H3bph afforded [Re(abt)(imp)Cl2(PPh3)] (abt = 2-aminobenzothiazole, imp = 2-(iminomethyl)phenol), where the ligand broke up into two fragments, both of which coordinated without any modification. The dioxo rhenium precursor cis-[ReO2I(PPh3)2] gave [ReO(Hbdh)(imp)] upon reaction with H3bdh. Ligand imp coordinates as a bidentate monoanionic ligand via the imine nitrogen and deprotonated phenolic oxygen and ligand Hbdh coordinatesas a tridentate dianionic chelate.
- Full Text:
- Date Issued: 2017
Exploring feeding ecology and population growth rate responses of ungulates in Southern African arid biomes
- Authors: Vermeulen, Mika Margaret
- Date: 2017
- Subjects: Ungulates -- South Africa Arid regions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15237 , vital:28189
- Description: Limited resources, extreme temperatures and predators are some of the stresses that are faced by ungulates in arid biomes. Understanding how these stressors influence ungulate feeding ecology and population growth rates is important for managers, as these could influence the persistence of ungulates in protected areas. An understanding of these stressors is especially relevant given the significant population declines in ungulate species globally. The Nama Karoo biome and the arid Savanna, an arid form of the Savanna biome, are both arid, but have distinct rainfall seasonality and vegetation structure and represent unique characteristics that need to be properly considered in their own regard. The literature on African ungulate feeding ecology covers a range of species and biomes from southern and east Africa, however, very little is known about ungulate dietary preferences in the Nama Karoo. Unexplained population declines in springbok (Antidorcas marsupialis) and red hartebeest (Alcelaphus buselaphus caama) have occurred at local scales across the Nama Karoo and the arid Savanna, most notably springbok population declines at the Karoo National Park (Karoo NP). This study sought to improve the understanding of ungulate feeding ecology and population growth rate responses in two arid biomes of South Africa. To achieve this, ungulate dietary composition was characterised, in terms of the proportional seasonal contribution of C4 and C3 plant forms, of a range of ungulates in the Nama Karoo, at the Karoo NP and the arid Savanna, at the Tswalu Kalahari Reserve (Tswalu KR), using stable carbon isotope analysis. Fresh faecal samples of ungulate species were collected from both the biomes during the dry, early wet and late wet seasons. Species were categorised per biome into feeding guilds and the effects of season, biome and the interaction thereof on the diets of the ungulate species explored. Furthermore, the findings were interpreted against what is known about diets of the respective species elsewhere in southern and east Africa. Secondly, trends in ungulate population growth rates were assessed within the Karoo NP and the Tswalu KR over the past 12 and14 years respectively. Furthermore, the variables influencing ungulate population growth rates (and generality of trends), with emphasis on ungulate biomass and rainfall, were explored at biome and species level. Population size data were obtained from annual aerial censuses for the period 2002-2015 and used to calculate annual growth rates and biomass for each ungulate species. The contribution of C4 forage to the diets of ungulate species in the arid Savanna was generally higher than in the Nama Karoo,in line with greater relative abundance of C4 grasses in the former. During winter (dry season) C3 intake was higher in the Nama Karoo than in the arid Savanna, reflecting C3 plant growth (C3 grasses and shrubs) and rainfall during winter in the Nama Karoo. Mean population growth rates during the study period were negative in some of the threatened species considered, i.e. mountain reedbuck (Redunca fulvorufula fulvorufula), tsessebe (Damaliscus lunatus lunatus) and Hartmann’s mountain zebra (Equus zebra hartmannae). No evidence for negative density dependent regulation (~intra-/interspecific competition) of ungulate population growth rates was found, whereas bottom up (~rainfall) and positive density dependent (~biomass of the species under investigation) regulatory mechanisms were most influential. The rainfall and biomass variables influenced the population growth rates of smaller ungulate species more than those of larger bodied ungulate species. Knowledge of ungulate diets will enable managers of protected areas to better understand how climate change, and resultant changes in relative abundances of plant growth forms, will influence specific ungulate species. The finding that increased population biomass positively influenced certain ungulate species’ growth rates has potential implications for management intervention as ungulate biomass is a variable that can be manipulated in protected areas. The reinforcement of existing mountain reedbuck, springbok and red hartebeest populations, specifically, at the Karoo NP and the Tswalu KR may counter their current negative growth rates in these two protected areas. Finally, the influence of protected area size and fencing, on ungulate vulnerability to predators (~top down) and forage quality (~bottom up) mechanisms in arid biomes needs to be further explored.
- Full Text:
- Date Issued: 2017
- Authors: Vermeulen, Mika Margaret
- Date: 2017
- Subjects: Ungulates -- South Africa Arid regions -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/15237 , vital:28189
- Description: Limited resources, extreme temperatures and predators are some of the stresses that are faced by ungulates in arid biomes. Understanding how these stressors influence ungulate feeding ecology and population growth rates is important for managers, as these could influence the persistence of ungulates in protected areas. An understanding of these stressors is especially relevant given the significant population declines in ungulate species globally. The Nama Karoo biome and the arid Savanna, an arid form of the Savanna biome, are both arid, but have distinct rainfall seasonality and vegetation structure and represent unique characteristics that need to be properly considered in their own regard. The literature on African ungulate feeding ecology covers a range of species and biomes from southern and east Africa, however, very little is known about ungulate dietary preferences in the Nama Karoo. Unexplained population declines in springbok (Antidorcas marsupialis) and red hartebeest (Alcelaphus buselaphus caama) have occurred at local scales across the Nama Karoo and the arid Savanna, most notably springbok population declines at the Karoo National Park (Karoo NP). This study sought to improve the understanding of ungulate feeding ecology and population growth rate responses in two arid biomes of South Africa. To achieve this, ungulate dietary composition was characterised, in terms of the proportional seasonal contribution of C4 and C3 plant forms, of a range of ungulates in the Nama Karoo, at the Karoo NP and the arid Savanna, at the Tswalu Kalahari Reserve (Tswalu KR), using stable carbon isotope analysis. Fresh faecal samples of ungulate species were collected from both the biomes during the dry, early wet and late wet seasons. Species were categorised per biome into feeding guilds and the effects of season, biome and the interaction thereof on the diets of the ungulate species explored. Furthermore, the findings were interpreted against what is known about diets of the respective species elsewhere in southern and east Africa. Secondly, trends in ungulate population growth rates were assessed within the Karoo NP and the Tswalu KR over the past 12 and14 years respectively. Furthermore, the variables influencing ungulate population growth rates (and generality of trends), with emphasis on ungulate biomass and rainfall, were explored at biome and species level. Population size data were obtained from annual aerial censuses for the period 2002-2015 and used to calculate annual growth rates and biomass for each ungulate species. The contribution of C4 forage to the diets of ungulate species in the arid Savanna was generally higher than in the Nama Karoo,in line with greater relative abundance of C4 grasses in the former. During winter (dry season) C3 intake was higher in the Nama Karoo than in the arid Savanna, reflecting C3 plant growth (C3 grasses and shrubs) and rainfall during winter in the Nama Karoo. Mean population growth rates during the study period were negative in some of the threatened species considered, i.e. mountain reedbuck (Redunca fulvorufula fulvorufula), tsessebe (Damaliscus lunatus lunatus) and Hartmann’s mountain zebra (Equus zebra hartmannae). No evidence for negative density dependent regulation (~intra-/interspecific competition) of ungulate population growth rates was found, whereas bottom up (~rainfall) and positive density dependent (~biomass of the species under investigation) regulatory mechanisms were most influential. The rainfall and biomass variables influenced the population growth rates of smaller ungulate species more than those of larger bodied ungulate species. Knowledge of ungulate diets will enable managers of protected areas to better understand how climate change, and resultant changes in relative abundances of plant growth forms, will influence specific ungulate species. The finding that increased population biomass positively influenced certain ungulate species’ growth rates has potential implications for management intervention as ungulate biomass is a variable that can be manipulated in protected areas. The reinforcement of existing mountain reedbuck, springbok and red hartebeest populations, specifically, at the Karoo NP and the Tswalu KR may counter their current negative growth rates in these two protected areas. Finally, the influence of protected area size and fencing, on ungulate vulnerability to predators (~top down) and forage quality (~bottom up) mechanisms in arid biomes needs to be further explored.
- Full Text:
- Date Issued: 2017
Synthesis and bioassay of rationally designed DXR inhibitors as potential antimalarial lead compounds
- Authors: Nokalipa, Iviwe Cwaita
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4888 , vital:20740
- Description: Globally, the eradication of malaria has been challenging due to the problem of resistance that past and currently available drugs exhibit. This is exacerbated by the inherent need for anti-malarial drugs to be affordable to the poverty-stricken majority that is primarily affected by this burden. This research has focused on the development of potential inhibitors of 1-deoxy-D- xylulose-5 phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate- independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate into 2-C- methyl-D-erithrytol 4-phosphate. This enzyme has been determined to be a target for the development of novel antimalarial agents and extensive molecular modelling has been undertaken to develop inhibitors that fit into the DXR active site. The in silico docking data have been used to inform the design and synthesis of various N-benzyl-substituted phosphoramidate ligands that were determined to have potential as novel substrate mimics of fosmidomycin, a known DXR inhibitor. Synthesis of the N-benzyl-substituted phosphoramidate ligands involved a nine-step sequence commencing from diethyl phosphoramidate. In all, some 40 compounds have been prepared, some of them new, and were fully characterized using NMR. Attention has also been given to the mass spectrometric fragmentation patterns exhibited by selected intermediates. Four of the final products were evaluated for in vitro antimalarial activity using a PLDH assay and exhibited IC50 values < 100 µM.
- Full Text:
- Date Issued: 2017
- Authors: Nokalipa, Iviwe Cwaita
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4888 , vital:20740
- Description: Globally, the eradication of malaria has been challenging due to the problem of resistance that past and currently available drugs exhibit. This is exacerbated by the inherent need for anti-malarial drugs to be affordable to the poverty-stricken majority that is primarily affected by this burden. This research has focused on the development of potential inhibitors of 1-deoxy-D- xylulose-5 phosphate reductoisomerase (DXR), an essential enzyme in the mevalonate- independent pathway for the biosynthesis of isoprenoids in Plasmodium falciparum. DXR mediates the isomerisation and reduction of 1-deoxy-D-xylulose-5-phosphate into 2-C- methyl-D-erithrytol 4-phosphate. This enzyme has been determined to be a target for the development of novel antimalarial agents and extensive molecular modelling has been undertaken to develop inhibitors that fit into the DXR active site. The in silico docking data have been used to inform the design and synthesis of various N-benzyl-substituted phosphoramidate ligands that were determined to have potential as novel substrate mimics of fosmidomycin, a known DXR inhibitor. Synthesis of the N-benzyl-substituted phosphoramidate ligands involved a nine-step sequence commencing from diethyl phosphoramidate. In all, some 40 compounds have been prepared, some of them new, and were fully characterized using NMR. Attention has also been given to the mass spectrometric fragmentation patterns exhibited by selected intermediates. Four of the final products were evaluated for in vitro antimalarial activity using a PLDH assay and exhibited IC50 values < 100 µM.
- Full Text:
- Date Issued: 2017
Workplace health promotion: a case of Rhodes University support staff
- Chigumete, Tinatsei Gabriella
- Authors: Chigumete, Tinatsei Gabriella
- Date: 2017
- Subjects: Rhodes University -- Employees -- Health and hygiene , Employee health promotion -- South Africa -- Makhanda
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44509 , vital:25414
- Description: Background: Non-communicable diseases are rapidly advancing as leading causes of morbidity and mortality across social classes, exerting pressure on existing financial, organizational, and human resources. Health promotion is a common practice in the prevention of noncommunicable diseases, but workplace health promotion has not yet been well established in many workplaces. Identification of past workplace initiatives and exploring their facilitating and limiting factors is thus important to take into consideration when planning future initiatives. Well-informed and guided workplace health promotion initiatives are essential to improve the general health of staff, and these also need to take the broader cultural, socioeconomic, and environmental factors influencing non-communicable diseases in the target population into account. This two-phase study was conducted at Rhodes University. A needs assessment was conducted to identify current policies and practices of workplace health promotion and to identify any shortcomings of the initiatives that have previously been attempted to raise awareness of non-communicable diseases at Rhodes University. The second phase of this project aimed to address concerns raised in the first phase through a health promotion initiative for support staff that focuses on the prevention of noncommunicable diseases through heart healthy diets and physical activity. Method: The first phase of the current study involved working with the support staff and key stakeholders. Using the participatory action research approach and the PRECEDE-PROCEED model to guide the research, 11 semi-structured interviews with key stakeholders and 10 focus group discussions were conducted with support staff members to identify factors affecting workplace health promotion. Participant opinions on how to improve these initiatives were sought. The participants were asked to identify areas on which the intended intervention should focus, as well as to identify their preferred means of communicating health messages. During this phase, a group of support staff members who volunteered their involvement in the design and delivery of the educational intervention was also identified. They chose to go by the name, the Health Awareness Group.In an interim phase of the study, three health information leaflets informed by the results from the above activities were designed. These leaflets underwent a series of qualitative evaluations by other health professionals, a culture and African languages expert, and the Health Awareness Group, to assess content validity, context specificity, and cultural appropriateness for the target group. A series of quantitative tests for readability, suitability, and actionability was also conducted. The health information leaflets were then used as written materials in the educational intervention of the project. Members of the Health Awareness Group were also trained as peer educators through a series of workshops. This enabled them to promote and raise awareness of heart healthy diets and physical activity to others in the workplace. Workshops were participatory in nature and were guided by the Social Cognitive Theory. They were also equipped with the completed health information leaflets to distribute to their peers and to use as reference sources of information when needed. Results: Participants in the semi-structured interviews reported that some health promotion initiatives have previously been attempted and advertised to support staff, but the turnout was poor and most staff did not seem to understand the health benefits of these initiatives. The support staff, in turn, stated that most health talks were conducted in English, contained medical jargon, and that they would have preferred these initiatives either to be simplified or presented in their home language, and to display cultural sensitivity. Support staff have also reported that advertisements were too cliche to elicit their interest. They also suggested incentivising initiatives for better participation. Another key suggestion was to facilitate these initiatives in the university departments they work or other convenient venues, rather than at central venues. It was also suggested that these initiatives be part of the work calendar, as they are often 'impromptu' and, as a result, staff members did not have enough notice to take time off work. Several staff members requested 're-runs of these initiatives because one-time show cases are often inadequate'. Colourful visual representations on posters or leaflets, short plays or films were also proposed as modes of delivering health information. During the design of the material to be used for this project's intended intervention, the health information leaflets were deemed readable, suitable, actionable, context-specific, and culturally appropriate. Workshops conducted during Phase 2 of the study proved to be valuable in training peer educators. Members of the Health Awareness Group also deemed the workshops useful, and reported their readiness to be agents of change in the workplace. Conclusions: Based on the input of key stakeholders and support staff, health promotion policies and protocols for non-communicable diseases have not yet been developed. Health promotion initiatives, especially for support staff, that address non-communicable diseases have previously been attempted at the university but were not well-received. Factors affecting workplace health promotion were identified. Knowledge of these factors was useful in designing and tailoring the written educational materials and the educational intervention to the needs of the support staff and to redress the deficiencies of previous initiatives. The health leaflets were deemed appropriate for use by the target population. They addressed pertinent information needs. The health information leaflets and workshops were useful in equipping the Health Awareness Group with knowledge on heart healthy diets and promotion of physical activity. Continued the involvement of representatives from the Human Resources and Wellness offices will assist in ensuring the sustainability of this workplace health initiative.
- Full Text:
- Date Issued: 2017
- Authors: Chigumete, Tinatsei Gabriella
- Date: 2017
- Subjects: Rhodes University -- Employees -- Health and hygiene , Employee health promotion -- South Africa -- Makhanda
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/44509 , vital:25414
- Description: Background: Non-communicable diseases are rapidly advancing as leading causes of morbidity and mortality across social classes, exerting pressure on existing financial, organizational, and human resources. Health promotion is a common practice in the prevention of noncommunicable diseases, but workplace health promotion has not yet been well established in many workplaces. Identification of past workplace initiatives and exploring their facilitating and limiting factors is thus important to take into consideration when planning future initiatives. Well-informed and guided workplace health promotion initiatives are essential to improve the general health of staff, and these also need to take the broader cultural, socioeconomic, and environmental factors influencing non-communicable diseases in the target population into account. This two-phase study was conducted at Rhodes University. A needs assessment was conducted to identify current policies and practices of workplace health promotion and to identify any shortcomings of the initiatives that have previously been attempted to raise awareness of non-communicable diseases at Rhodes University. The second phase of this project aimed to address concerns raised in the first phase through a health promotion initiative for support staff that focuses on the prevention of noncommunicable diseases through heart healthy diets and physical activity. Method: The first phase of the current study involved working with the support staff and key stakeholders. Using the participatory action research approach and the PRECEDE-PROCEED model to guide the research, 11 semi-structured interviews with key stakeholders and 10 focus group discussions were conducted with support staff members to identify factors affecting workplace health promotion. Participant opinions on how to improve these initiatives were sought. The participants were asked to identify areas on which the intended intervention should focus, as well as to identify their preferred means of communicating health messages. During this phase, a group of support staff members who volunteered their involvement in the design and delivery of the educational intervention was also identified. They chose to go by the name, the Health Awareness Group.In an interim phase of the study, three health information leaflets informed by the results from the above activities were designed. These leaflets underwent a series of qualitative evaluations by other health professionals, a culture and African languages expert, and the Health Awareness Group, to assess content validity, context specificity, and cultural appropriateness for the target group. A series of quantitative tests for readability, suitability, and actionability was also conducted. The health information leaflets were then used as written materials in the educational intervention of the project. Members of the Health Awareness Group were also trained as peer educators through a series of workshops. This enabled them to promote and raise awareness of heart healthy diets and physical activity to others in the workplace. Workshops were participatory in nature and were guided by the Social Cognitive Theory. They were also equipped with the completed health information leaflets to distribute to their peers and to use as reference sources of information when needed. Results: Participants in the semi-structured interviews reported that some health promotion initiatives have previously been attempted and advertised to support staff, but the turnout was poor and most staff did not seem to understand the health benefits of these initiatives. The support staff, in turn, stated that most health talks were conducted in English, contained medical jargon, and that they would have preferred these initiatives either to be simplified or presented in their home language, and to display cultural sensitivity. Support staff have also reported that advertisements were too cliche to elicit their interest. They also suggested incentivising initiatives for better participation. Another key suggestion was to facilitate these initiatives in the university departments they work or other convenient venues, rather than at central venues. It was also suggested that these initiatives be part of the work calendar, as they are often 'impromptu' and, as a result, staff members did not have enough notice to take time off work. Several staff members requested 're-runs of these initiatives because one-time show cases are often inadequate'. Colourful visual representations on posters or leaflets, short plays or films were also proposed as modes of delivering health information. During the design of the material to be used for this project's intended intervention, the health information leaflets were deemed readable, suitable, actionable, context-specific, and culturally appropriate. Workshops conducted during Phase 2 of the study proved to be valuable in training peer educators. Members of the Health Awareness Group also deemed the workshops useful, and reported their readiness to be agents of change in the workplace. Conclusions: Based on the input of key stakeholders and support staff, health promotion policies and protocols for non-communicable diseases have not yet been developed. Health promotion initiatives, especially for support staff, that address non-communicable diseases have previously been attempted at the university but were not well-received. Factors affecting workplace health promotion were identified. Knowledge of these factors was useful in designing and tailoring the written educational materials and the educational intervention to the needs of the support staff and to redress the deficiencies of previous initiatives. The health leaflets were deemed appropriate for use by the target population. They addressed pertinent information needs. The health information leaflets and workshops were useful in equipping the Health Awareness Group with knowledge on heart healthy diets and promotion of physical activity. Continued the involvement of representatives from the Human Resources and Wellness offices will assist in ensuring the sustainability of this workplace health initiative.
- Full Text:
- Date Issued: 2017
Studies in the thiophenol mediated substitution and reductive dehalogenation of 3 bromoacetylcoumarins
- Authors: Magwenzi, Faith N
- Date: 2017
- Subjects: 3-bromoacetylcoumarins , Coumarins , Halogens -- Decontamination , Thiols , Plasmodium falciparum , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/45769 , vital:25546
- Description: A previous study conducted by our group identified indolyl-3-ethanone-a-thioethers (2.1a and 2.1b) as non-toxic, nanomolar, in vitro inhibitors of Plasmodium falciparum. Since the coumarin scaffold is associated with numerous biologically active compounds including antiprotozoal, anti-viral, anti-bacterial, and anti-inflammatory agents we were prompted to investigate coumaryl-3-ethanone-a-thioethers (2.1c) inspired by the activity of 2.1a and 2.1b against P. falciparum. We proposed a three-step synthesis of our target compounds 2.1c. The first step involved the Knoevenagel synthesis of 3-acetyl coumarins (2.3.1a - e) followed by a selective a-bromination to yield 3-bromoacetyl coumarin (2.2a). The final proposed step involved the nucleophilic displacement of the bromine by appropriately substituted thiophenols in either the presence or absence of base (K2CO3). Our initial findings revealed an unexpected major reductive dehalogenation of 2.2a into 2.3.1a. Further investigation revealed a close relationship between the electron withdrawing or donating nature of the thiophenol substituents and the relative formation of nucleophilic substitution or reductive dehalogenation products. Desired thioether products were obtained in higher yields when thiophenol was substituted with electron donating groups i.e. more nucleophilic thiophenols, while conversely, electron withdrawing substituents (i.e. lowered nucleophilicity) resulted in an increase of reductive dehalogenation. Furthermore, these results were consistent when experiments were conducted using either 2 or 1.2 equivalents of thiophenols which was an important observation in the context of two previous studies, by Oki et. al. and Israel et. al. Oki proposed that dehalogenation of a-chloro carbonyls occurs via sequential nucleophilic displacement of a-thioethers, while the study of Israel concluded that the dehalogenation of a-iodo carbonyls occurred in a single discreet step. Finally, in an effort to enhance nucleophilic substitution through the addition of K2CO3, we observed a Robinson annulation resulting in previously undescribed C-8 thiophenol functionalised dibenzo[b,d]pyran-6-ones (3.4a - e). In the introduction to this thesis, we briefly summarise the utility of coumarins in medicinal chemistry and related fields. Chapter two describes the rationalisation of our original research question and a retrosynthetic analysis of our desired compounds, followed by an initial description of the unexpected reductive dehalogenation. Chapter 3, begins with a brief review of reductive dehalogenation of a-halocarbonyls, and is followed by an analysis and discussion of our results in the context of the studies by Israel et. al. and Oki et. al.
- Full Text:
- Date Issued: 2017
- Authors: Magwenzi, Faith N
- Date: 2017
- Subjects: 3-bromoacetylcoumarins , Coumarins , Halogens -- Decontamination , Thiols , Plasmodium falciparum , Malaria -- Chemotherapy
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/45769 , vital:25546
- Description: A previous study conducted by our group identified indolyl-3-ethanone-a-thioethers (2.1a and 2.1b) as non-toxic, nanomolar, in vitro inhibitors of Plasmodium falciparum. Since the coumarin scaffold is associated with numerous biologically active compounds including antiprotozoal, anti-viral, anti-bacterial, and anti-inflammatory agents we were prompted to investigate coumaryl-3-ethanone-a-thioethers (2.1c) inspired by the activity of 2.1a and 2.1b against P. falciparum. We proposed a three-step synthesis of our target compounds 2.1c. The first step involved the Knoevenagel synthesis of 3-acetyl coumarins (2.3.1a - e) followed by a selective a-bromination to yield 3-bromoacetyl coumarin (2.2a). The final proposed step involved the nucleophilic displacement of the bromine by appropriately substituted thiophenols in either the presence or absence of base (K2CO3). Our initial findings revealed an unexpected major reductive dehalogenation of 2.2a into 2.3.1a. Further investigation revealed a close relationship between the electron withdrawing or donating nature of the thiophenol substituents and the relative formation of nucleophilic substitution or reductive dehalogenation products. Desired thioether products were obtained in higher yields when thiophenol was substituted with electron donating groups i.e. more nucleophilic thiophenols, while conversely, electron withdrawing substituents (i.e. lowered nucleophilicity) resulted in an increase of reductive dehalogenation. Furthermore, these results were consistent when experiments were conducted using either 2 or 1.2 equivalents of thiophenols which was an important observation in the context of two previous studies, by Oki et. al. and Israel et. al. Oki proposed that dehalogenation of a-chloro carbonyls occurs via sequential nucleophilic displacement of a-thioethers, while the study of Israel concluded that the dehalogenation of a-iodo carbonyls occurred in a single discreet step. Finally, in an effort to enhance nucleophilic substitution through the addition of K2CO3, we observed a Robinson annulation resulting in previously undescribed C-8 thiophenol functionalised dibenzo[b,d]pyran-6-ones (3.4a - e). In the introduction to this thesis, we briefly summarise the utility of coumarins in medicinal chemistry and related fields. Chapter two describes the rationalisation of our original research question and a retrosynthetic analysis of our desired compounds, followed by an initial description of the unexpected reductive dehalogenation. Chapter 3, begins with a brief review of reductive dehalogenation of a-halocarbonyls, and is followed by an analysis and discussion of our results in the context of the studies by Israel et. al. and Oki et. al.
- Full Text:
- Date Issued: 2017
The effect of point of substitution and silver based nanoparticles on the photophysical and optical nonlinearity of indium carboxyphenoxy phthalocyanine
- Oluwole, David O, Ngxeke, Sixolisile M, Britton, Jonathan, Nyokong, Tebello
- Authors: Oluwole, David O , Ngxeke, Sixolisile M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188596 , vital:44768 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.07.032"
- Description: Indium(III) chloride 1,8(11),15(18),22(25)-tetra-(3-carboxyphenoxy) phthalocyanine (1) and indium(III) chloride 2,9(10),16(17),23(24)-tetra–(3-carboxyphenoxy) phthalocyanine (2) were covalently linked to glutathione capped silver nanoparticles (AgNPs–GSH) and silver selenide/zinc sulfide (Ag2Se/ZnS–GSH) quantum dots via amide bond formation. The photophysical and nonlinear optical behaviour of the metallophthalocyanines and their conjugates with nanoparticles were investigated using the open aperture Z–scan technique. Complex 2 showed enhanced photophysical properties compared to 1. The conjugates revealed improved triplet state quantum yields (except for 1-AgNPs-GSH which afforded lower triplet state quantum yields in comparison to 1) and nonlinear optical activities in comparison to the Pc complexes. The synthesized complexes, nanoparticles and their conjugates could be potential nonlinear optical materials due to their good nonlinear optical activities.
- Full Text:
- Date Issued: 2017
- Authors: Oluwole, David O , Ngxeke, Sixolisile M , Britton, Jonathan , Nyokong, Tebello
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188596 , vital:44768 , xlink:href="https://doi.org/10.1016/j.jphotochem.2017.07.032"
- Description: Indium(III) chloride 1,8(11),15(18),22(25)-tetra-(3-carboxyphenoxy) phthalocyanine (1) and indium(III) chloride 2,9(10),16(17),23(24)-tetra–(3-carboxyphenoxy) phthalocyanine (2) were covalently linked to glutathione capped silver nanoparticles (AgNPs–GSH) and silver selenide/zinc sulfide (Ag2Se/ZnS–GSH) quantum dots via amide bond formation. The photophysical and nonlinear optical behaviour of the metallophthalocyanines and their conjugates with nanoparticles were investigated using the open aperture Z–scan technique. Complex 2 showed enhanced photophysical properties compared to 1. The conjugates revealed improved triplet state quantum yields (except for 1-AgNPs-GSH which afforded lower triplet state quantum yields in comparison to 1) and nonlinear optical activities in comparison to the Pc complexes. The synthesized complexes, nanoparticles and their conjugates could be potential nonlinear optical materials due to their good nonlinear optical activities.
- Full Text:
- Date Issued: 2017
Nonlinear optical responses of phthalocyanines in the presence of nanomaterials or when embedded in polymeric materials
- Authors: Bankole, Owolabi Mutolib
- Date: 2017
- Subjects: Phthalocyanines , Phthalocyanines -- Optical properties , Alkynes , Triazoles , Nonlinear optics , Photochemistry , Complex compounds , Amines , Mercaptopyridine
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/45794 , vital:25548
- Description: This work describes the synthesis, photophysical and nonlinear optical characterizations of alkynyl Pcs (1, 2, 3, 8 and 9), 1,2,3-triazole ZnPc (4), mercaptopyridine Pcs (5, 6 and 7) and amino Pcs (10 and 11). Complexes 1, 2, 4, 7, 8, 9 and 11 were newly synthesized and characterized using techniques including 1H-NMR, MALDI-TOF, UV-visible spectrophotometry, FTIR and elemental analysis. The results of the characterizations were in good agreement with their molecular structures, and confirmed the purity of the new molecules. Complex 10 was covalently linked to pristine graphene (GQDs), nitrogen- doped (NGQDs), and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots; gold nanoparticles (AuNPs); poly(acrylic acid) (PAA); Fe3O4@Ag core-shell and Fe3O4- Ag hybrid nanoparticles via covalent bonding. Complex 11 was linked to Agx Auy alloy nanoparticles via NH2-Au and/or Au-S bonding, 2 and 3 were linked to gold nanoparticles (AuNPs) via clicked reactions. Evidence of successful conjugation of 2, 3, 10 and 11 to nanomaterials was revealed within the UV-vis, EDS, TEM, XRD and XPS spectra. Optical limiting (OL) responses of the samples were evaluated using open aperture Z-scan technique at 532 nm and 10 ns radiation in solution or when embedded in polymer mixtures. The analyses of the Z-scan data for the studied samples did fit to a two-photon absorption mechanism (2PA), but the Pcs and Pc-nanomaterial or polymer composites also possess the multi-photon absorption mechanisms aided by the triplet-triplet population to have reverse saturable absorption (RSA) occur. Phthalocyanines doped in polymer matrices showed larger nonlinear absorption coefficients (ßeff), third-order susceptibility (Im [x(3)]) and second-order hyperpolarizability (y), with an accompanying low intensity threshold (Ium) than in solution. Aggregation in DMSO negatively affected NLO behaviour of Pcs (8 as a case study) at low laser power, and improved at relatively higher laser power. Heavy atom-substituted Pcs (6) enhanced NLO and OL properties than lighter atoms such as 5 and 7. Direct relationship between enhanced photophysical properties and nonlinear effects favoured by excited triplet absorption of the 2, 3, 10 and 11 in presence of nanomaterials was established. Major factor responsible for the enhanced nonlinearities of 10 in the presence of NGQDs and SNGQDs were fully described and attributed to the surface defects caused by the presence of heteroatoms such as nitrogen and sulfur. The studies showed that phthalocyanines-nanomaterial composites were useful in applications such as optical switching, pulse compressor and laser pulse narrowing.
- Full Text:
- Date Issued: 2017
- Authors: Bankole, Owolabi Mutolib
- Date: 2017
- Subjects: Phthalocyanines , Phthalocyanines -- Optical properties , Alkynes , Triazoles , Nonlinear optics , Photochemistry , Complex compounds , Amines , Mercaptopyridine
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/45794 , vital:25548
- Description: This work describes the synthesis, photophysical and nonlinear optical characterizations of alkynyl Pcs (1, 2, 3, 8 and 9), 1,2,3-triazole ZnPc (4), mercaptopyridine Pcs (5, 6 and 7) and amino Pcs (10 and 11). Complexes 1, 2, 4, 7, 8, 9 and 11 were newly synthesized and characterized using techniques including 1H-NMR, MALDI-TOF, UV-visible spectrophotometry, FTIR and elemental analysis. The results of the characterizations were in good agreement with their molecular structures, and confirmed the purity of the new molecules. Complex 10 was covalently linked to pristine graphene (GQDs), nitrogen- doped (NGQDs), and sulfur-nitrogen co-doped (SNGQDs) graphene quantum dots; gold nanoparticles (AuNPs); poly(acrylic acid) (PAA); Fe3O4@Ag core-shell and Fe3O4- Ag hybrid nanoparticles via covalent bonding. Complex 11 was linked to Agx Auy alloy nanoparticles via NH2-Au and/or Au-S bonding, 2 and 3 were linked to gold nanoparticles (AuNPs) via clicked reactions. Evidence of successful conjugation of 2, 3, 10 and 11 to nanomaterials was revealed within the UV-vis, EDS, TEM, XRD and XPS spectra. Optical limiting (OL) responses of the samples were evaluated using open aperture Z-scan technique at 532 nm and 10 ns radiation in solution or when embedded in polymer mixtures. The analyses of the Z-scan data for the studied samples did fit to a two-photon absorption mechanism (2PA), but the Pcs and Pc-nanomaterial or polymer composites also possess the multi-photon absorption mechanisms aided by the triplet-triplet population to have reverse saturable absorption (RSA) occur. Phthalocyanines doped in polymer matrices showed larger nonlinear absorption coefficients (ßeff), third-order susceptibility (Im [x(3)]) and second-order hyperpolarizability (y), with an accompanying low intensity threshold (Ium) than in solution. Aggregation in DMSO negatively affected NLO behaviour of Pcs (8 as a case study) at low laser power, and improved at relatively higher laser power. Heavy atom-substituted Pcs (6) enhanced NLO and OL properties than lighter atoms such as 5 and 7. Direct relationship between enhanced photophysical properties and nonlinear effects favoured by excited triplet absorption of the 2, 3, 10 and 11 in presence of nanomaterials was established. Major factor responsible for the enhanced nonlinearities of 10 in the presence of NGQDs and SNGQDs were fully described and attributed to the surface defects caused by the presence of heteroatoms such as nitrogen and sulfur. The studies showed that phthalocyanines-nanomaterial composites were useful in applications such as optical switching, pulse compressor and laser pulse narrowing.
- Full Text:
- Date Issued: 2017