Effects of CO2-induced ocean acidification on the early development, growth, survival and skeletogenesis of the estuarine-dependant sciaenid Argyrosomus japonicus
- Authors: Erasmus, Bernard
- Date: 2018
- Subjects: Argyrosomus , Argyrosomus -- Growth , Argyrosomus -- Mortality , Argyrosomus -- Ecology , Argyrosomus -- Physiology , Ocean acidification , Marine ecology -- South Africa , Carbon dioxide -- Physiological effect
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60585 , vital:27799
- Description: Although it is increasingly accepted that ocean acidification poses a considerable threat to marine organisms, little is known about the likely response of fishes to this phenomenon. While initial research concluded that adult fishes may be tolerant to changes predicted in the next 300 years, the response of early life stages to end-of-century CO2 levels (~ 1100 µatm according to the IPCC RCP 8.5) remains unclear. To date, literature on the early growth and survival of fishes has yielded conflicting results, suggesting that vulnerability may be species dependant. The paucity of ocean acidification research on fishes is particularly evident when one considers larval skeletogenesis, with no robust studies on its impacts on bone and cartilage development. This study addresses the early life embryogenesis, hatching success, growth, skeletogenesis and survival of an estuarine-dependant species. Dusky kob (Argyrosomus japonicus) were reared in a control (pCO2 = 327.50 ± 80.07 qatm at pH 8.15), intermediate (pCO2 477.40 ± 59.46 qatm at pH 8.03) and high pCO2 treatment (pCO2 910.20 ± 136.45 qatm at pH 7.78) from egg to 29 days post-hatch (dph). Sixty individuals from each treatment were sacrificed at the egg stage and at 2, 6, 13, 18, 21 and 26 dph, measured and stained using an acid-free double- staining solution to prevent the deterioration of calcified matrices in fragile larval skeletons. The proportion of bone and cartilage was quantified at each stage using a novel pixel-counting method. Growth and skeletal development were identical between treatments until the onset of metamorphosis (21 dph). However, from the metamorphosis stage, the growth and skeletal development rate was significantly faster in the intermediate treatment and significantly slower in the high treatment when compared to the control treatment. By 26 dph, A. japonicus reared in high pCO2 were, on average, 47.2% smaller than the control treatment, and the relative proportion of bone in the body was 45.3% lower in the high pCO2 treatment when compared with the control. In addition, none of the fish in the high pCO2 treatment survived after 26 dph. It appears that the combination of the increased energy requirements during metamorphosis and the increased energy cost associated with acid-base regulation may account for reduced growth, skeletogenesis and poor survival in high pCO2. Regardless of the driver, the results of this study suggest that the pCO2 levels predicted for the end of the century may have negative effects on the growth, skeletal development, and survival during metamorphosis.
- Full Text:
- Date Issued: 2018
- Authors: Erasmus, Bernard
- Date: 2018
- Subjects: Argyrosomus , Argyrosomus -- Growth , Argyrosomus -- Mortality , Argyrosomus -- Ecology , Argyrosomus -- Physiology , Ocean acidification , Marine ecology -- South Africa , Carbon dioxide -- Physiological effect
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/60585 , vital:27799
- Description: Although it is increasingly accepted that ocean acidification poses a considerable threat to marine organisms, little is known about the likely response of fishes to this phenomenon. While initial research concluded that adult fishes may be tolerant to changes predicted in the next 300 years, the response of early life stages to end-of-century CO2 levels (~ 1100 µatm according to the IPCC RCP 8.5) remains unclear. To date, literature on the early growth and survival of fishes has yielded conflicting results, suggesting that vulnerability may be species dependant. The paucity of ocean acidification research on fishes is particularly evident when one considers larval skeletogenesis, with no robust studies on its impacts on bone and cartilage development. This study addresses the early life embryogenesis, hatching success, growth, skeletogenesis and survival of an estuarine-dependant species. Dusky kob (Argyrosomus japonicus) were reared in a control (pCO2 = 327.50 ± 80.07 qatm at pH 8.15), intermediate (pCO2 477.40 ± 59.46 qatm at pH 8.03) and high pCO2 treatment (pCO2 910.20 ± 136.45 qatm at pH 7.78) from egg to 29 days post-hatch (dph). Sixty individuals from each treatment were sacrificed at the egg stage and at 2, 6, 13, 18, 21 and 26 dph, measured and stained using an acid-free double- staining solution to prevent the deterioration of calcified matrices in fragile larval skeletons. The proportion of bone and cartilage was quantified at each stage using a novel pixel-counting method. Growth and skeletal development were identical between treatments until the onset of metamorphosis (21 dph). However, from the metamorphosis stage, the growth and skeletal development rate was significantly faster in the intermediate treatment and significantly slower in the high treatment when compared to the control treatment. By 26 dph, A. japonicus reared in high pCO2 were, on average, 47.2% smaller than the control treatment, and the relative proportion of bone in the body was 45.3% lower in the high pCO2 treatment when compared with the control. In addition, none of the fish in the high pCO2 treatment survived after 26 dph. It appears that the combination of the increased energy requirements during metamorphosis and the increased energy cost associated with acid-base regulation may account for reduced growth, skeletogenesis and poor survival in high pCO2. Regardless of the driver, the results of this study suggest that the pCO2 levels predicted for the end of the century may have negative effects on the growth, skeletal development, and survival during metamorphosis.
- Full Text:
- Date Issued: 2018
Effects of Pluronic F127 micelles as delivering agents on the vitro dark toxicity and photodynamic therapy activity of carboxy and pyrene substituted porphyrins
- Managa, Muthumuni, Britton, Jonathan, Prinsloo, Earl, Nyokong, Tebello
- Authors: Managa, Muthumuni , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234439 , vital:50196 , xlink:href="https://doi.org/10.1016/j.poly.2018.06.031"
- Description: Metal free, Zn and ClGa containing carboxyphenoxy and phenoxy groups (complexes 1) and pyrene groups (complexes 2) were synthesized and embedded into Pluronic F127 micelles (represented as F127). Dark toxicity and photodynamic therapy activities of the embedded porphyrins were successfully studied on MCF-7 breast cancer cells. Dark toxicity showed more than 80% cell viability for all complexes. It was found that 1-Zn + F127 showed better photodynamic therapy activity compared to 1-H2 + F127, and 1-ClGa + F127, corresponding to the high partition coefficient for the Zn porphyrin derivatives. The same applies to 2-Zn + F127 compared to 2-H2 + F127, 2-ClGa + F127. 1-ClGa and 1-Zn were also linked to Pluronic F127 silica nanoparticles. PDT activities for embedded 1-ClGa + F127 and 1-Zn + F127 were much higher than when linked to Pluronic silica nanoparticles (PluS NPs), showing the importance of loading of porphyrins into Pluronic F127 as a drug delivering agent rather than linking. PDT studies at the highest concentration of 60 µg/ml showed decrease in cell viability down to 15.9% for 2-Zn + F127. The Kp was determined in biphasic octanol and water system.
- Full Text:
- Date Issued: 2018
- Authors: Managa, Muthumuni , Britton, Jonathan , Prinsloo, Earl , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234439 , vital:50196 , xlink:href="https://doi.org/10.1016/j.poly.2018.06.031"
- Description: Metal free, Zn and ClGa containing carboxyphenoxy and phenoxy groups (complexes 1) and pyrene groups (complexes 2) were synthesized and embedded into Pluronic F127 micelles (represented as F127). Dark toxicity and photodynamic therapy activities of the embedded porphyrins were successfully studied on MCF-7 breast cancer cells. Dark toxicity showed more than 80% cell viability for all complexes. It was found that 1-Zn + F127 showed better photodynamic therapy activity compared to 1-H2 + F127, and 1-ClGa + F127, corresponding to the high partition coefficient for the Zn porphyrin derivatives. The same applies to 2-Zn + F127 compared to 2-H2 + F127, 2-ClGa + F127. 1-ClGa and 1-Zn were also linked to Pluronic F127 silica nanoparticles. PDT activities for embedded 1-ClGa + F127 and 1-Zn + F127 were much higher than when linked to Pluronic silica nanoparticles (PluS NPs), showing the importance of loading of porphyrins into Pluronic F127 as a drug delivering agent rather than linking. PDT studies at the highest concentration of 60 µg/ml showed decrease in cell viability down to 15.9% for 2-Zn + F127. The Kp was determined in biphasic octanol and water system.
- Full Text:
- Date Issued: 2018
Effects of the carboxylic acid substituents on the photophysical and nonlinear optical properties of asymmetrical Zn (II) phthalocyanines–quantum dots conjugates
- Mgidlana, Sithi, Oluwole, David O, Nyokong, Tebello
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187662 , vital:44684 , xlink:href="https://doi.org/10.1080/24701556.2018.1503684"
- Description: This work reports on three asymmetrical Zn(II) phthalocyanines, namely: zinc(II) 3–(4-phenoxy)propanoic acid) phthalocyanine(1), zinc(II) 3–(4-phenoxy carboxylic acid) phthalocyanine (2) and zinc(II) 3–(4–oxy)phenoxy)acetic acid phthalocyanine (3) when covalently linked to glutathione(GSH) capped CdTe/ZnSe and CdTe/ZnSe/ZnO quantum dots (QDs). Of the Pc complexes alone, 1 afforded the highest triplet quantum yield (ΦT) value of 0.67 with corresponding largest nonlinear absorption coefficient (βeff) value of 14.0 cm/GW compared to 2 and 3. The conjugates afforded improved triplet quantum yield and nonlinear optical behavior in comparison to the Pc complexes alone.
- Full Text:
- Date Issued: 2018
- Authors: Mgidlana, Sithi , Oluwole, David O , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187662 , vital:44684 , xlink:href="https://doi.org/10.1080/24701556.2018.1503684"
- Description: This work reports on three asymmetrical Zn(II) phthalocyanines, namely: zinc(II) 3–(4-phenoxy)propanoic acid) phthalocyanine(1), zinc(II) 3–(4-phenoxy carboxylic acid) phthalocyanine (2) and zinc(II) 3–(4–oxy)phenoxy)acetic acid phthalocyanine (3) when covalently linked to glutathione(GSH) capped CdTe/ZnSe and CdTe/ZnSe/ZnO quantum dots (QDs). Of the Pc complexes alone, 1 afforded the highest triplet quantum yield (ΦT) value of 0.67 with corresponding largest nonlinear absorption coefficient (βeff) value of 14.0 cm/GW compared to 2 and 3. The conjugates afforded improved triplet quantum yield and nonlinear optical behavior in comparison to the Pc complexes alone.
- Full Text:
- Date Issued: 2018
Electrocatalytic activity of a push-pull phthalocyanine in the presence of reduced and amino functionalized graphene quantum dots towards the electrooxidation of hydrazine
- Centane, Sixolile, Sekhosana, Kutloana E, Matshitse, Refilwe, Nyokong, Tebello
- Authors: Centane, Sixolile , Sekhosana, Kutloana E , Matshitse, Refilwe , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233456 , vital:50092 , xlink:href="https://doi.org/10.1016/j.jelechem.2018.05.005"
- Description: We report on the electrochemical behaviour of reduced graphene quantum dots (rGQDs) compared to amino functionalized graphene quantum dots (NH2GQDs). Reduction of the GQDs entails the elimination of the excessive carboxyl and hydrogen groups on the GQDs surface, thereby reducing the energy band gap. The energy band gap of graphene is directly proportional to the available oxygen atoms. The two GQD types were conjugated to a novel cobalt phthalocyanine (cobalt tris-(tert-butyl phenoxy)-mono-carboxyphenoxy phthalocyanine, CoPc) via covalent and nom-covalent interactions. The resulting conjugates were tested towards the electrooxidation of hydrazine. The conjugates are represented as rGQDs(π)CoPc, NH2(π)CoPc, rGQDs@CoPc and NH2GQDs@CoPc. The resulting conjugates were adsorbed onto a glassy carbon electrode using the drop and dry method. The lowest limit of detection (LOD) was obtained for rGQDs(π)CoPc.
- Full Text:
- Date Issued: 2018
- Authors: Centane, Sixolile , Sekhosana, Kutloana E , Matshitse, Refilwe , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/233456 , vital:50092 , xlink:href="https://doi.org/10.1016/j.jelechem.2018.05.005"
- Description: We report on the electrochemical behaviour of reduced graphene quantum dots (rGQDs) compared to amino functionalized graphene quantum dots (NH2GQDs). Reduction of the GQDs entails the elimination of the excessive carboxyl and hydrogen groups on the GQDs surface, thereby reducing the energy band gap. The energy band gap of graphene is directly proportional to the available oxygen atoms. The two GQD types were conjugated to a novel cobalt phthalocyanine (cobalt tris-(tert-butyl phenoxy)-mono-carboxyphenoxy phthalocyanine, CoPc) via covalent and nom-covalent interactions. The resulting conjugates were tested towards the electrooxidation of hydrazine. The conjugates are represented as rGQDs(π)CoPc, NH2(π)CoPc, rGQDs@CoPc and NH2GQDs@CoPc. The resulting conjugates were adsorbed onto a glassy carbon electrode using the drop and dry method. The lowest limit of detection (LOD) was obtained for rGQDs(π)CoPc.
- Full Text:
- Date Issued: 2018
Electrospun 3, 5-dithienylvinyleneBODIPY embedded polystyrene nanofibers for the photocatalytic degradation of azo dyes in industrial wastewaters
- Lebechi, Augustus K, Gai, Lizhi, Shen, Zhen, Nyokong, Tebello, Mack, John
- Authors: Lebechi, Augustus K , Gai, Lizhi , Shen, Zhen , Nyokong, Tebello , Mack, John
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187679 , vital:44686 , xlink:href="https://doi.org/10.1142/S1088424618500360"
- Description: The potential utility of electrospun polystyrene (PS) nanofibers embedded with 2,6-diiodo-8-phenyl-1,7-dimethyl-3,5-di-2-thienylvinyleneBODIPY for the photocatalytic degradation of azo dyes is investigated. A comparison of the singlet oxygen quantum yield of the ππ-extended BODIPY dye in solution and in the PS nanofibers demonstrates that its photosensitizer properties are retained when it is embedded in the solid phase. The photocatalytic degradation properties of the PS nanofibers for Methyl Orange and Orange G were determined by using a Thorlabs 625 nm light emitting diode. The rate of photodegradation increases with the Orange G and Methyl Orange concentration and follows pseudo-first order kinetics at pH 6.7.
- Full Text:
- Date Issued: 2018
- Authors: Lebechi, Augustus K , Gai, Lizhi , Shen, Zhen , Nyokong, Tebello , Mack, John
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187679 , vital:44686 , xlink:href="https://doi.org/10.1142/S1088424618500360"
- Description: The potential utility of electrospun polystyrene (PS) nanofibers embedded with 2,6-diiodo-8-phenyl-1,7-dimethyl-3,5-di-2-thienylvinyleneBODIPY for the photocatalytic degradation of azo dyes is investigated. A comparison of the singlet oxygen quantum yield of the ππ-extended BODIPY dye in solution and in the PS nanofibers demonstrates that its photosensitizer properties are retained when it is embedded in the solid phase. The photocatalytic degradation properties of the PS nanofibers for Methyl Orange and Orange G were determined by using a Thorlabs 625 nm light emitting diode. The rate of photodegradation increases with the Orange G and Methyl Orange concentration and follows pseudo-first order kinetics at pH 6.7.
- Full Text:
- Date Issued: 2018
Elevated CO2 determines cell damage and nitrogen allocation in barley subjected to aphid herbivory
- Authors: Gallagher, Sean
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64337 , vital:28535
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2018
- Authors: Gallagher, Sean
- Date: 2018
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64337 , vital:28535
- Description: Expected release date-May 2019
- Full Text:
- Date Issued: 2018
Emplacement of inflated Pāhoehoe flows in the Naude’s Nek Pass, Lesotho remnant, Karoo continental flood basalt province: use of flow-lobe tumuli in understanding flood basalt emplacement
- Jay, Anne E, Marsh, Julian S, Fluteau, F, Courtillot, V
- Authors: Jay, Anne E , Marsh, Julian S , Fluteau, F , Courtillot, V
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/60752 , vital:27826 , https://link.springer.com/article/10.1007/s00445-017-1189-6
- Description: Physical volcanological features are presented for a 710-m-thick section, of the Naude’s Nek Pass, within the lower part of the Lesotho remnant of the Karoo Large Igneous Province. The section consists of inflated pāhoehoe lava with thin, impersistent sedimentary interbeds towards the base. There are seven discreet packages of compound and hummocky pāhoehoe lobes containing flow-lobe tumuli, making up approximately 50% of the section. Approximately 45% of the sequence consists of 14 sheet lobes, between 10 and 52-m-thick. The majority of the sheet lobes are in two packages indicating prolonged periods of lava supply capable of producing thick sheet lobes. The other sheet lobes are as individual lobes or pairs, within compound flows, suggesting brief increases in lava supply rate. We suggest, contrary to current belief, that there is no evidence that compound flows are proximal to source and sheet lobes (simple flows) are distal to source and we propose that the presence of flow-lobe tumuli in compound flows could be an indicator that a flow is distal to source. We use detailed, previously published, studies of the Thakurvadi Formation (Deccan Traps) as an example. We show that the length of a lobe and therefore the sections that are ‘medial or distal to source’ are specific to each individual lobe and are dependent on the lava supply of each eruptive event, and as such flow lobe tumuli can be used as an indicator of relative distance from source.
- Full Text:
- Date Issued: 2018
- Authors: Jay, Anne E , Marsh, Julian S , Fluteau, F , Courtillot, V
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/60752 , vital:27826 , https://link.springer.com/article/10.1007/s00445-017-1189-6
- Description: Physical volcanological features are presented for a 710-m-thick section, of the Naude’s Nek Pass, within the lower part of the Lesotho remnant of the Karoo Large Igneous Province. The section consists of inflated pāhoehoe lava with thin, impersistent sedimentary interbeds towards the base. There are seven discreet packages of compound and hummocky pāhoehoe lobes containing flow-lobe tumuli, making up approximately 50% of the section. Approximately 45% of the sequence consists of 14 sheet lobes, between 10 and 52-m-thick. The majority of the sheet lobes are in two packages indicating prolonged periods of lava supply capable of producing thick sheet lobes. The other sheet lobes are as individual lobes or pairs, within compound flows, suggesting brief increases in lava supply rate. We suggest, contrary to current belief, that there is no evidence that compound flows are proximal to source and sheet lobes (simple flows) are distal to source and we propose that the presence of flow-lobe tumuli in compound flows could be an indicator that a flow is distal to source. We use detailed, previously published, studies of the Thakurvadi Formation (Deccan Traps) as an example. We show that the length of a lobe and therefore the sections that are ‘medial or distal to source’ are specific to each individual lobe and are dependent on the lava supply of each eruptive event, and as such flow lobe tumuli can be used as an indicator of relative distance from source.
- Full Text:
- Date Issued: 2018
Energy use patterns and trends: the impact of energy policy in South African low-income households
- Israel-Akinbo, Sylvia Olawumi
- Authors: Israel-Akinbo, Sylvia Olawumi
- Date: 2018
- Subjects: Energy policy -- Social aspects -- South Africa , Energy security -- South Africa , Households -- Economic aspects -- South Africa , Poor -- Energy assistance -- South Africa , Poor -- South Africa , University of Cape Town. National Income Dynamics Study , Free Basic Electricity Policy (South Africa) , Income and Expenditure Survey (South Africa)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62264 , vital:28148
- Description: Energy poverty is a growing concern especially amongst low-income populations in developing countries. The transition to modern energy carriers is associated with welfare improvement and it is considered as an important developmental goal to achieve, in order to eradicate energy poverty. As such, the South African government has made energy poverty an issue of policy focus. Literature abounds with different measures of energy poverty; energy programmes and policies are also aimed at improving the welfare of the low-income households in terms of basic services such as electricity. As a point of entry into this study, this thesis explored energy use patterns and trends in low-income South African households. The research objectives addressed in the study included investigating the extent of energy poverty through a multidimensional energy poverty index, examining the extent to which the 'energy ladder' and 'energy stacking' models explains energy transition patterns and to examining whether the Free Basic Electricity Policy has impacted on energy choices and energy poverty. In order to contribute to energy poverty and energy policy discussion in South Africa, this study has investigated the dimensions of energy poverty amongst low-income South African households from these three different perspectives (objectives). A positivist approach, by using a quantitative method was used to underpin the study. The study utilised secondary data, which were from the National Income Dynamics Survey and Income and Expenditure Survey. The former was used for the analysis of the multidimensional energy poverty index and energy transition patterns whilst the latter was used for the analysis of the impact of the Free Basic Electricity Policy. The four waves of the National Income Dynamics Survey, with 2008 as the base year and the 2010/2011 version of the Income and Expenditure Survey were used whilst the data were processed through the quantitative software package, STATA version 12. The data were then analysed using the multidimensional energy poverty framework by Nussbaumer et al. (2011) and econometric models, which best fit the objectives. The result of the panel analysis, which assesses the multidimensional energy poverty for low-income households in South Africa showed that low-income households in both urban and rural areas are in a moderate state of energy poverty but different levels. However, the cross-sectional analysis revealed that the percentage of low-income households that are energy poor is reducing for the rural households but increasing for their urban counterparts from 2008 to 2014. The panel and cross-sectional results of the contribution of the energy dimensions in multidimensional energy poverty shows that the low-income households are especially energy poor in terms of heating fuel. The findings from the econometric estimates partly confirmed an energy ladder behaviour for the energy choice for cooking. An energy stacking behaviour was confirmed for the low- income households for these energy services - heating and lighting. Moreover, it was found that with respect to cooking and heating, low-income households living in a modern dwelling, having a small household size and residing in an urban area are less likely to use transitional or traditional energy carriers but most likely to use modern energy carriers. In addition, low-income households are more likely to use modern energy carriers for their cooking and heating in 2010, 2012 and 2014 than in 2008. For lighting energy service, low- income households living in a modern dwelling in an urban settlement are most likely to use modern energy carriers for lighting and less likely to use transitional energy carriers or candles. Only in 2014 were low-income households more likely to use modern energy carriers for lighting than in 2008. The results further showed that modern energy carriers have the highest probability of being preferred for lighting followed by cooking and lastly heating. Also emerging from the findings are that more urban low-income households are receiving the Free Basic Electricity (FBE) grant than their counterparts in the rural areas. The probability of low-income households owning entertainment/education appliance and food preserving appliance is positively influenced by access to Free Basic Electricity. The low- income households living in an urban settlement and in a modern type of dwelling supported this result. However, household size does not seems to support this result should it grow larger.
- Full Text:
- Date Issued: 2018
- Authors: Israel-Akinbo, Sylvia Olawumi
- Date: 2018
- Subjects: Energy policy -- Social aspects -- South Africa , Energy security -- South Africa , Households -- Economic aspects -- South Africa , Poor -- Energy assistance -- South Africa , Poor -- South Africa , University of Cape Town. National Income Dynamics Study , Free Basic Electricity Policy (South Africa) , Income and Expenditure Survey (South Africa)
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/62264 , vital:28148
- Description: Energy poverty is a growing concern especially amongst low-income populations in developing countries. The transition to modern energy carriers is associated with welfare improvement and it is considered as an important developmental goal to achieve, in order to eradicate energy poverty. As such, the South African government has made energy poverty an issue of policy focus. Literature abounds with different measures of energy poverty; energy programmes and policies are also aimed at improving the welfare of the low-income households in terms of basic services such as electricity. As a point of entry into this study, this thesis explored energy use patterns and trends in low-income South African households. The research objectives addressed in the study included investigating the extent of energy poverty through a multidimensional energy poverty index, examining the extent to which the 'energy ladder' and 'energy stacking' models explains energy transition patterns and to examining whether the Free Basic Electricity Policy has impacted on energy choices and energy poverty. In order to contribute to energy poverty and energy policy discussion in South Africa, this study has investigated the dimensions of energy poverty amongst low-income South African households from these three different perspectives (objectives). A positivist approach, by using a quantitative method was used to underpin the study. The study utilised secondary data, which were from the National Income Dynamics Survey and Income and Expenditure Survey. The former was used for the analysis of the multidimensional energy poverty index and energy transition patterns whilst the latter was used for the analysis of the impact of the Free Basic Electricity Policy. The four waves of the National Income Dynamics Survey, with 2008 as the base year and the 2010/2011 version of the Income and Expenditure Survey were used whilst the data were processed through the quantitative software package, STATA version 12. The data were then analysed using the multidimensional energy poverty framework by Nussbaumer et al. (2011) and econometric models, which best fit the objectives. The result of the panel analysis, which assesses the multidimensional energy poverty for low-income households in South Africa showed that low-income households in both urban and rural areas are in a moderate state of energy poverty but different levels. However, the cross-sectional analysis revealed that the percentage of low-income households that are energy poor is reducing for the rural households but increasing for their urban counterparts from 2008 to 2014. The panel and cross-sectional results of the contribution of the energy dimensions in multidimensional energy poverty shows that the low-income households are especially energy poor in terms of heating fuel. The findings from the econometric estimates partly confirmed an energy ladder behaviour for the energy choice for cooking. An energy stacking behaviour was confirmed for the low- income households for these energy services - heating and lighting. Moreover, it was found that with respect to cooking and heating, low-income households living in a modern dwelling, having a small household size and residing in an urban area are less likely to use transitional or traditional energy carriers but most likely to use modern energy carriers. In addition, low-income households are more likely to use modern energy carriers for their cooking and heating in 2010, 2012 and 2014 than in 2008. For lighting energy service, low- income households living in a modern dwelling in an urban settlement are most likely to use modern energy carriers for lighting and less likely to use transitional energy carriers or candles. Only in 2014 were low-income households more likely to use modern energy carriers for lighting than in 2008. The results further showed that modern energy carriers have the highest probability of being preferred for lighting followed by cooking and lastly heating. Also emerging from the findings are that more urban low-income households are receiving the Free Basic Electricity (FBE) grant than their counterparts in the rural areas. The probability of low-income households owning entertainment/education appliance and food preserving appliance is positively influenced by access to Free Basic Electricity. The low- income households living in an urban settlement and in a modern type of dwelling supported this result. However, household size does not seems to support this result should it grow larger.
- Full Text:
- Date Issued: 2018
Engaging with media as a knowledge resource for making sense of climate change: a case study of the farmers of Nyanga, Zimbabwe
- Authors: Mandikonza, Blessing
- Date: 2018
- Subjects: Climatic changes in mass media , Knowledge, Sociology of , Farms, Small -- Zimbabwe -- Nyanga , Crops and climate -- Zimbabwe -- Nyanga , Agriculture -- Economic aspects -- Zimbabwe , Agriculture -- Environmental aspects -- Zimbabwe -- Nyanga , Agriculture and politics -- Zimbabwe -- Nyanga , Agriculture -- Research -- Sociological aspects , Agricultural journalism -- Zimbabwe , Land reform -- Zimbabwe -- Nyanga
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/63764 , vital:28486
- Description: This study explores how small-scale farmers in Nyanga, Zimbabwe engage with the media as a knowledge resource for achieving agricultural productivity, particularly in context of climate change. The study is contextualised by means of a literature review that maps out the history of agricultural productivity in Zimbabwe. It is argued that this history has been shaped by changes in both socio-economic context and climatic conditions. Both kinds of change impact on the degree to which small-scale farmers have access to knowledge that is of relevance to agricultural productivity. The study then examines the Zimbabwean media landscape, focusing on how history has shaped the way in which different media define their social purpose. This examination draws on Hallin and Mancini‟s „models‟ of media systems as well as Christian et al‟s traditions of media practice. It is concluded that, due to the high level of conflict that has characterised Zimbabwean history, aspects of both the polarised pluralist and democratic corporatist models are present in its media landscape. The collaborative, monitorial and radical approaches to media also exist in contestation with each other. Indeed, the media is characterised by profound contestation around the conceptualisation of social purpose. Furthermore, international media is of particular significance as a resource of knowledge within the local media landscape. The empirical component of the study explores the implications for the extent to which media are likely to serve as valuable knowledge resources for small-scale farmers. This exploration is pursued by means of a case study of the experiences of three farmers in Nyanga who were granted farms as part of the government‟s land-reform programme. In context of episodic biographical interviews, the participants share their experience of becoming farmers and of managing their farms. Attention is paid to the challenges they face with regards to producing successful crops, both in context of socio-economic and climatic conditions. The study looks at the way in which participants draw on the media as a knowledge resource to help them overcome these challenges. The participants understand international media to be a more credible knowledge resource, but also refer to the need for local media which can provides them with knowledge of local relevance. In this context they identify an absence of collaborative, developmental media that engages with the unique challenges that they face in producing crops. It is concluded that the value of media for the farmers of Nyanga as a knowledge resource for making sense of climate change would only be achieved through the establishment of locally produced, participatory media that foregrounds the use of indigenous language.
- Full Text:
- Date Issued: 2018
- Authors: Mandikonza, Blessing
- Date: 2018
- Subjects: Climatic changes in mass media , Knowledge, Sociology of , Farms, Small -- Zimbabwe -- Nyanga , Crops and climate -- Zimbabwe -- Nyanga , Agriculture -- Economic aspects -- Zimbabwe , Agriculture -- Environmental aspects -- Zimbabwe -- Nyanga , Agriculture and politics -- Zimbabwe -- Nyanga , Agriculture -- Research -- Sociological aspects , Agricultural journalism -- Zimbabwe , Land reform -- Zimbabwe -- Nyanga
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/63764 , vital:28486
- Description: This study explores how small-scale farmers in Nyanga, Zimbabwe engage with the media as a knowledge resource for achieving agricultural productivity, particularly in context of climate change. The study is contextualised by means of a literature review that maps out the history of agricultural productivity in Zimbabwe. It is argued that this history has been shaped by changes in both socio-economic context and climatic conditions. Both kinds of change impact on the degree to which small-scale farmers have access to knowledge that is of relevance to agricultural productivity. The study then examines the Zimbabwean media landscape, focusing on how history has shaped the way in which different media define their social purpose. This examination draws on Hallin and Mancini‟s „models‟ of media systems as well as Christian et al‟s traditions of media practice. It is concluded that, due to the high level of conflict that has characterised Zimbabwean history, aspects of both the polarised pluralist and democratic corporatist models are present in its media landscape. The collaborative, monitorial and radical approaches to media also exist in contestation with each other. Indeed, the media is characterised by profound contestation around the conceptualisation of social purpose. Furthermore, international media is of particular significance as a resource of knowledge within the local media landscape. The empirical component of the study explores the implications for the extent to which media are likely to serve as valuable knowledge resources for small-scale farmers. This exploration is pursued by means of a case study of the experiences of three farmers in Nyanga who were granted farms as part of the government‟s land-reform programme. In context of episodic biographical interviews, the participants share their experience of becoming farmers and of managing their farms. Attention is paid to the challenges they face with regards to producing successful crops, both in context of socio-economic and climatic conditions. The study looks at the way in which participants draw on the media as a knowledge resource to help them overcome these challenges. The participants understand international media to be a more credible knowledge resource, but also refer to the need for local media which can provides them with knowledge of local relevance. In this context they identify an absence of collaborative, developmental media that engages with the unique challenges that they face in producing crops. It is concluded that the value of media for the farmers of Nyanga as a knowledge resource for making sense of climate change would only be achieved through the establishment of locally produced, participatory media that foregrounds the use of indigenous language.
- Full Text:
- Date Issued: 2018
Enhanced nonlinear optical response of benzothiazole substituted ball-type phthalocyanines in the presence of metallic nanoparticles
- Nwaji, Njemuwa, Mack, John, Nyokong, Tebello
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188149 , vital:44727 , xlink:href="https://doi.org/10.1016/j.optmat.2018.05.052"
- Description: The synthesis of zinc-zinc, gallium-gallium and indium-indium ball-type phthalocyanines (complexes 4, 5 and 6) and the surface assembly of the complexes onto metallic gold and silver nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical dynamics were investigated. Decreases in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to complexes 4, 5 and 6 alone were observed. The mechanism of strong reverse saturable absorption observed was found to be predominantly dependent on excited state absorption. The optical limiting thresholds range from 0.09 to 0.19 J/cm2. Enhanced triplet parameters and nonlinear optical responses were found when the complexes were conjugated to metallic nanoparticles.
- Full Text:
- Date Issued: 2018
- Authors: Nwaji, Njemuwa , Mack, John , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/188149 , vital:44727 , xlink:href="https://doi.org/10.1016/j.optmat.2018.05.052"
- Description: The synthesis of zinc-zinc, gallium-gallium and indium-indium ball-type phthalocyanines (complexes 4, 5 and 6) and the surface assembly of the complexes onto metallic gold and silver nanoparticles are reported in this work. Furthermore, their photophysical and nonlinear optical dynamics were investigated. Decreases in the fluorescence quantum yields with a corresponding increase in the triplet quantum yields of the nanoconjugates in comparison to complexes 4, 5 and 6 alone were observed. The mechanism of strong reverse saturable absorption observed was found to be predominantly dependent on excited state absorption. The optical limiting thresholds range from 0.09 to 0.19 J/cm2. Enhanced triplet parameters and nonlinear optical responses were found when the complexes were conjugated to metallic nanoparticles.
- Full Text:
- Date Issued: 2018
Erasure: A challenge to Feminist and Queer research
- Marx, Jacqueline, Macleod, Catriona I
- Authors: Marx, Jacqueline , Macleod, Catriona I
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/434210 , vital:73039 , ISBN 978-3-319-74720-0 , https://link.springer.com/chapter/10.1007/978-3-319-74721-7_20
- Description: Anonymity and confidentiality feature prominently in research ethics guidelines. In this chapter we draw on examples from a research ethics application for a project involving women who had extricated themselves from relationships in which they had experienced intimate partner violence, and an ethnographic study of cross-dressing and drag, to illustrate the multiple ways in which identity masking can be put to work, both promoting and undermining what it means to do ethical research. We argue that the requirement for anonymity and confidentiality cannot be assessed without taking into account historicity and the sociopolitical contexts in which a study and its participants are located. The chapter concludes by giving consideration to the potential of a situated ethics approach and the implications for ethics review processes.
- Full Text:
- Date Issued: 2018
- Authors: Marx, Jacqueline , Macleod, Catriona I
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/434210 , vital:73039 , ISBN 978-3-319-74720-0 , https://link.springer.com/chapter/10.1007/978-3-319-74721-7_20
- Description: Anonymity and confidentiality feature prominently in research ethics guidelines. In this chapter we draw on examples from a research ethics application for a project involving women who had extricated themselves from relationships in which they had experienced intimate partner violence, and an ethnographic study of cross-dressing and drag, to illustrate the multiple ways in which identity masking can be put to work, both promoting and undermining what it means to do ethical research. We argue that the requirement for anonymity and confidentiality cannot be assessed without taking into account historicity and the sociopolitical contexts in which a study and its participants are located. The chapter concludes by giving consideration to the potential of a situated ethics approach and the implications for ethics review processes.
- Full Text:
- Date Issued: 2018
Essence of home: relevance of home and the assertion of place amongst Centane migrants, South Africa
- Authors: Njwambe, Avela Thandisiwe
- Date: 2018
- Subjects: Rural-urban migration -- South Africa , Migrant labor -- South Africa , Immigrants -- South Africa -- Social conditions , Immigrants -- South Africa -- Eastern Cape , Immigrants -- South Africa -- Homelands , Homelands (South Africa) , Home -- Psychological aspects
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/51866 , vital:26136
- Description: South Africa is currently experiencing ever-increasing rural-urban migration with many citizens from the former homeland areas migrating to cities to seek employment. Despite long-term residence in urban areas, many township dwellers do not consider these places to be home. Research into circular migration patterns reveal the lifelong relationships that migrants (amagoduka) have with their family home (ekhayeni). This study aimed to explore this relationship, looking in particular at the meanings imbued in the locality of home. In addition, the role of natural landscapes and social components in constructing meanings and attachments to ekhayeni for Xhosa-speaking migrants in Cape Town townships, who have family linkages to rural villages in the Transkei, was also explored. The study found that the landscape of home remains central to migrants’ cultural identity, belonging and well-being. Childhood experiences in nature, and cultural and recreational activities that continue to take rural inhabitants into these landscapes, remain key to this relationship. The rural area, as a geographical entity embodied with social and cultural/spiritual components continued to supply and satisfy many human needs for migrants, which were seen as crucial for psychological, mental and spiritual well-being.
- Full Text:
- Date Issued: 2018
Essence of home: relevance of home and the assertion of place amongst Centane migrants, South Africa
- Authors: Njwambe, Avela Thandisiwe
- Date: 2018
- Subjects: Rural-urban migration -- South Africa , Migrant labor -- South Africa , Immigrants -- South Africa -- Social conditions , Immigrants -- South Africa -- Eastern Cape , Immigrants -- South Africa -- Homelands , Homelands (South Africa) , Home -- Psychological aspects
- Language: English
- Type: text , Thesis , Masters , MSocSc
- Identifier: http://hdl.handle.net/10962/51866 , vital:26136
- Description: South Africa is currently experiencing ever-increasing rural-urban migration with many citizens from the former homeland areas migrating to cities to seek employment. Despite long-term residence in urban areas, many township dwellers do not consider these places to be home. Research into circular migration patterns reveal the lifelong relationships that migrants (amagoduka) have with their family home (ekhayeni). This study aimed to explore this relationship, looking in particular at the meanings imbued in the locality of home. In addition, the role of natural landscapes and social components in constructing meanings and attachments to ekhayeni for Xhosa-speaking migrants in Cape Town townships, who have family linkages to rural villages in the Transkei, was also explored. The study found that the landscape of home remains central to migrants’ cultural identity, belonging and well-being. Childhood experiences in nature, and cultural and recreational activities that continue to take rural inhabitants into these landscapes, remain key to this relationship. The rural area, as a geographical entity embodied with social and cultural/spiritual components continued to supply and satisfy many human needs for migrants, which were seen as crucial for psychological, mental and spiritual well-being.
- Full Text:
- Date Issued: 2018
Establishment of “The South African Bioinformatics Student Council” and activity highlights:
- Rafael, Candice Nancy, Ambler, Jon, Niehaus, Antoinette, Ross, James, Tastan Bishop, Özlem
- Authors: Rafael, Candice Nancy , Ambler, Jon , Niehaus, Antoinette , Ross, James , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148250 , vital:38723 , https://doi.org/10.14806/ej.23.0.903
- Description: The South African Society for Bioinformatics1 (SASBi) was officially formed in September 2012 during a joint Congress with the South African Genetics Society (SAGS). Prior to this there was no official body to represent bioinformatic researchers and students in the country. The establishment of SASBi also led to the establishment of the Student Society as a platform for students to meet and discuss their research activities, but also to socialise and broaden their network of knowledge and friendships. A small group of students joined as volunteers to pioneer and set up a SASBi Student Council (SASBiSC). As a first step, one representative, selected from the attendees present at the first Joint Congress of SASBi and SAGS, was elected to the main SASBi Council.
- Full Text:
- Date Issued: 2018
- Authors: Rafael, Candice Nancy , Ambler, Jon , Niehaus, Antoinette , Ross, James , Tastan Bishop, Özlem
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148250 , vital:38723 , https://doi.org/10.14806/ej.23.0.903
- Description: The South African Society for Bioinformatics1 (SASBi) was officially formed in September 2012 during a joint Congress with the South African Genetics Society (SAGS). Prior to this there was no official body to represent bioinformatic researchers and students in the country. The establishment of SASBi also led to the establishment of the Student Society as a platform for students to meet and discuss their research activities, but also to socialise and broaden their network of knowledge and friendships. A small group of students joined as volunteers to pioneer and set up a SASBi Student Council (SASBiSC). As a first step, one representative, selected from the attendees present at the first Joint Congress of SASBi and SAGS, was elected to the main SASBi Council.
- Full Text:
- Date Issued: 2018
Ethics in critical research: Stories from the field
- Macleod, Catriona I, Marx, Jacqueline, Mnyaka, Phindezwa, Treharne, Gareth J
- Authors: Macleod, Catriona I , Marx, Jacqueline , Mnyaka, Phindezwa , Treharne, Gareth J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/434223 , vital:73040 , ISBN 978-3-319-74720-0 , https://link.springer.com/chapter/10.1007/978-3-319-74721-7_1
- Description: In this chapter we introduce the approaches to ethics in critical research applied throughout this handbook. Critical research questions who benefits from research and offers critiques rooted in postmodern and liberatory theories, including feminism, Marxism, and postcolonialism. Authors of chapters in the handbook explore ethical issues faced when conducting critical research through stories from the field across a range of methodologies, disciplines, and locations. The chapter overviews the four sections of the handbook and the ethical challenges associated with conducting critical research within the bureaucracy of ethics committees and other systems of governance, blurring the boundaries between researchers and participants/co-researchers, giving voice through research whilst applying anonymity or naming participants/co-researchers, and conducting research with various configurations of power between researchers and participants/co-researchers.
- Full Text:
- Date Issued: 2018
- Authors: Macleod, Catriona I , Marx, Jacqueline , Mnyaka, Phindezwa , Treharne, Gareth J
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/434223 , vital:73040 , ISBN 978-3-319-74720-0 , https://link.springer.com/chapter/10.1007/978-3-319-74721-7_1
- Description: In this chapter we introduce the approaches to ethics in critical research applied throughout this handbook. Critical research questions who benefits from research and offers critiques rooted in postmodern and liberatory theories, including feminism, Marxism, and postcolonialism. Authors of chapters in the handbook explore ethical issues faced when conducting critical research through stories from the field across a range of methodologies, disciplines, and locations. The chapter overviews the four sections of the handbook and the ethical challenges associated with conducting critical research within the bureaucracy of ethics committees and other systems of governance, blurring the boundaries between researchers and participants/co-researchers, giving voice through research whilst applying anonymity or naming participants/co-researchers, and conducting research with various configurations of power between researchers and participants/co-researchers.
- Full Text:
- Date Issued: 2018
Ethics in transdisciplinary research: reflections on the implications of ‘Science with Society’
- Cockburn, Jessica J, Cundill, Georgina
- Authors: Cockburn, Jessica J , Cundill, Georgina
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436187 , vital:73236 , ISBN 978-3-319-74721-7 , https://doi.org/10.1007/978-3-319-74721-7_6
- Description: Transdisciplinarity is a reflexive, participatory research approach that addresses societal problems by transcending the boundaries between science and society through knowledge co-production. Research ethics clearance procedures are of-ten out of step with such forms of engaged research. Through a case study of a transdisciplinary PhD, we share our experiences of the ethical challenges involved in research that takes place beyond the bounds of procedural ethics. Our research aims to co-produce knowledge on environmental stewardship. In this chapter we consider what strategies transdisciplinary scholars can employ to ensure they fulfil the requirements of ethical research in the absence of suitably aligned institutional processes, and what changes need to be made to research ethics clearance procedures to ensure they are able to account for transdisciplinary research.
- Full Text:
- Date Issued: 2018
- Authors: Cockburn, Jessica J , Cundill, Georgina
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , book chapter
- Identifier: http://hdl.handle.net/10962/436187 , vital:73236 , ISBN 978-3-319-74721-7 , https://doi.org/10.1007/978-3-319-74721-7_6
- Description: Transdisciplinarity is a reflexive, participatory research approach that addresses societal problems by transcending the boundaries between science and society through knowledge co-production. Research ethics clearance procedures are of-ten out of step with such forms of engaged research. Through a case study of a transdisciplinary PhD, we share our experiences of the ethical challenges involved in research that takes place beyond the bounds of procedural ethics. Our research aims to co-produce knowledge on environmental stewardship. In this chapter we consider what strategies transdisciplinary scholars can employ to ensure they fulfil the requirements of ethical research in the absence of suitably aligned institutional processes, and what changes need to be made to research ethics clearance procedures to ensure they are able to account for transdisciplinary research.
- Full Text:
- Date Issued: 2018
Evaluating metabolism-induced toxicity using a non-hepatic cell line
- Authors: Weyers, Carli
- Date: 2018
- Subjects: Cytochrome P-450 , Drugs Metabolism , Drugs Design
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/61950 , vital:28087
- Description: The drug discovery pipeline is a complicated process taking roughly 15 years to complete, costing in excess of $1 billion per new chemical entity. It has been estimated that for every 100, 000 promising hit or lead compounds, only one will make it onto the market due to numerous drug candidates being discarded because of many complications. One such complication is metabolism-induced toxicity. Accordingly, an early understanding of the metabolism of any new chemical entity is becoming an integral part of the pipeline. In order to explore this, various methods have been developed including in silico and in vitro techniques. One such method involves performing cell viability assays on human liver cancer cell lines, which overexpress specific metabolic cytochrome P450 enzymes. If a toxic metabolite is produced it would result in reduced cell viability of the transformed cell line in comparison to a control. Since the liver is the primary site of metabolism in the human body, we were curious as to the extent to which background metabolism may play a role in the degree to which toxic metabolites would be produced in these cell lines. The aim of this project, therefore, was to establish if a non-hepatic cell-based system which overexpresses CYP3A4 could be used to detect the metabolism and any subsequent toxicity of compounds which have been reported to be substrates of the CYP450 enzyme. The HEK293 cell line was stably transfected with a plasmid vector for human CYP3A4 to create a model overexpression system for our metabolism studies. The activity of the enzyme was confirmed using the substrate, 7-benzyloxy-4-trifluoromethyl-coumarin. Subsequently, cytotoxicity testing was done on four known pharmaceuticals reported to generate toxic metabolites in hepatic cell-based assays. In silico metabolic predictions on the four known compounds were performed and compared to the results of published literature. Finally, the metabolism of one compound was studied using a combination of high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) in order to detect predicted metabolites. We observed no change in cellular toxicity nor did we detect the formation of metabolites, even though the overexpressed CYP3A4 enzyme was active. The results suggest that caution should be taken when interpreting the results of cell-based metabolism studies, and background metabolism may play a significant role in the data. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2018
- Full Text:
- Date Issued: 2018
- Authors: Weyers, Carli
- Date: 2018
- Subjects: Cytochrome P-450 , Drugs Metabolism , Drugs Design
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/61950 , vital:28087
- Description: The drug discovery pipeline is a complicated process taking roughly 15 years to complete, costing in excess of $1 billion per new chemical entity. It has been estimated that for every 100, 000 promising hit or lead compounds, only one will make it onto the market due to numerous drug candidates being discarded because of many complications. One such complication is metabolism-induced toxicity. Accordingly, an early understanding of the metabolism of any new chemical entity is becoming an integral part of the pipeline. In order to explore this, various methods have been developed including in silico and in vitro techniques. One such method involves performing cell viability assays on human liver cancer cell lines, which overexpress specific metabolic cytochrome P450 enzymes. If a toxic metabolite is produced it would result in reduced cell viability of the transformed cell line in comparison to a control. Since the liver is the primary site of metabolism in the human body, we were curious as to the extent to which background metabolism may play a role in the degree to which toxic metabolites would be produced in these cell lines. The aim of this project, therefore, was to establish if a non-hepatic cell-based system which overexpresses CYP3A4 could be used to detect the metabolism and any subsequent toxicity of compounds which have been reported to be substrates of the CYP450 enzyme. The HEK293 cell line was stably transfected with a plasmid vector for human CYP3A4 to create a model overexpression system for our metabolism studies. The activity of the enzyme was confirmed using the substrate, 7-benzyloxy-4-trifluoromethyl-coumarin. Subsequently, cytotoxicity testing was done on four known pharmaceuticals reported to generate toxic metabolites in hepatic cell-based assays. In silico metabolic predictions on the four known compounds were performed and compared to the results of published literature. Finally, the metabolism of one compound was studied using a combination of high performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS) in order to detect predicted metabolites. We observed no change in cellular toxicity nor did we detect the formation of metabolites, even though the overexpressed CYP3A4 enzyme was active. The results suggest that caution should be taken when interpreting the results of cell-based metabolism studies, and background metabolism may play a significant role in the data. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2018
- Full Text:
- Date Issued: 2018
Evaluating the effects of catch-and-release angling on Cape stumpnose Rhabdosargus holubi in a South African estuary
- Arkert, N K, Childs, Amber-Robyn, Parkinson, Matthew C, Winkler, Alexander C, Butler, Edward C, Mannheim, Samantha L, Potts, Warren M
- Authors: Arkert, N K , Childs, Amber-Robyn , Parkinson, Matthew C , Winkler, Alexander C , Butler, Edward C , Mannheim, Samantha L , Potts, Warren M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124439 , vital:35613 , https://doi.10.2989/1814232x.2018.1494041
- Description: Fisheries managers are increasingly promoting catch and release (C&R) as a means to manage recreational fish stocks. Several commonly used output regulations, including bag and size limits, require the mandatory release of captured fishes by anglers. In addition to mandatory C&R, conservation-conscious anglers have adopted voluntary C&R behaviour as a result of the noticeable declines in the populations of many fishery species and this behaviour is becoming increasingly popular among recreational anglers (Cooke et al. 2013a). The combination of mandatory and voluntary C&R behaviour is substantial, as Raby et al. (2014) estimated that 60% of fish captured in global recreational fisheries are released. In South Africa, Cowley et al. (2013) found that a large proportion (mean 74% [SD 7.3]) of the five most-dominant fishery species captured in the Sundays Estuary recreational fishery were released.
- Full Text:
- Date Issued: 2018
- Authors: Arkert, N K , Childs, Amber-Robyn , Parkinson, Matthew C , Winkler, Alexander C , Butler, Edward C , Mannheim, Samantha L , Potts, Warren M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124439 , vital:35613 , https://doi.10.2989/1814232x.2018.1494041
- Description: Fisheries managers are increasingly promoting catch and release (C&R) as a means to manage recreational fish stocks. Several commonly used output regulations, including bag and size limits, require the mandatory release of captured fishes by anglers. In addition to mandatory C&R, conservation-conscious anglers have adopted voluntary C&R behaviour as a result of the noticeable declines in the populations of many fishery species and this behaviour is becoming increasingly popular among recreational anglers (Cooke et al. 2013a). The combination of mandatory and voluntary C&R behaviour is substantial, as Raby et al. (2014) estimated that 60% of fish captured in global recreational fisheries are released. In South Africa, Cowley et al. (2013) found that a large proportion (mean 74% [SD 7.3]) of the five most-dominant fishery species captured in the Sundays Estuary recreational fishery were released.
- Full Text:
- Date Issued: 2018
Evaluating the efficacy of Hypogeococcus sp. as a biological control agent of the cactaceous weed Cereus jamacaru in South Africa
- Sutton, Guy F, Klein, Hildegard, Paterson, Iain D
- Authors: Sutton, Guy F , Klein, Hildegard , Paterson, Iain D
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423350 , vital:72051 , xlink:href="https://doi.org/10.1007/s10526-018-9887-3"
- Description: We evaluated the efficacy of Hypogeococcus sp. (Hemiptera: Pseudococcidae) as a biological control agent of the cactaceous weed Cereus jamacaru De Candolle (Queen of the Night cactus) in South Africa. This weed has been described as being under complete biological control due to the action of Hypogeococcus sp., although no formal post-release evaluation had been conducted prior to this study. Biological control was associated with significant reductions in fruiting, plant survival and plant densities, while plant population age structures were negatively affected. Weed populations infected by Hypogeococcus sp. were typified by low or non-existent recruitment and are expected to diminish with time. Populations where Hypogeococcus sp. was absent displayed extensive recruitment, and are predicted to expand or self-replace, if left unchecked. These data indicate that Hypogeococcus sp. has a significant negative effect on C. jamacaru at the individual plant and population level, and given sufficient time provides complete biological control over this weed in South Africa.
- Full Text:
- Date Issued: 2018
- Authors: Sutton, Guy F , Klein, Hildegard , Paterson, Iain D
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423350 , vital:72051 , xlink:href="https://doi.org/10.1007/s10526-018-9887-3"
- Description: We evaluated the efficacy of Hypogeococcus sp. (Hemiptera: Pseudococcidae) as a biological control agent of the cactaceous weed Cereus jamacaru De Candolle (Queen of the Night cactus) in South Africa. This weed has been described as being under complete biological control due to the action of Hypogeococcus sp., although no formal post-release evaluation had been conducted prior to this study. Biological control was associated with significant reductions in fruiting, plant survival and plant densities, while plant population age structures were negatively affected. Weed populations infected by Hypogeococcus sp. were typified by low or non-existent recruitment and are expected to diminish with time. Populations where Hypogeococcus sp. was absent displayed extensive recruitment, and are predicted to expand or self-replace, if left unchecked. These data indicate that Hypogeococcus sp. has a significant negative effect on C. jamacaru at the individual plant and population level, and given sufficient time provides complete biological control over this weed in South Africa.
- Full Text:
- Date Issued: 2018
Evaluation of the photophysicochemical properties and photodynamic therapy activity of nanoconjugates of zinc phthalocyanine linked to glutathione capped Au and Au3Ag1 nanoparticles
- Oluwole, David O, Manoto, Sello L, Malabi, Rudzani, Maphanga, Charles, Ombinda-Lemboumba, Saturnin, Mthunzi-Kufa, Patience, Nyokong, Tebello
- Authors: Oluwole, David O , Manoto, Sello L , Malabi, Rudzani , Maphanga, Charles , Ombinda-Lemboumba, Saturnin , Mthunzi-Kufa, Patience , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237886 , vital:50563 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.11.019"
- Description: We report on the synthesis of glutathione capped gold (AuNPs–GSH) and gold–silver (Au3Ag1NPs–GSH) nanoparticles and their covalent attachment to Zn monocarboxyphenoxy phthalocyanine (1) via amide bond formation. The photophysicochemical properties and photodynamic therapy (PDT) activity of the complex and its nanoconjugates were assessed. The conjugates afforded improved triplet and singlet oxygen quantum yield as well as PDT activity (except for 1-Au3Ag1NPs which afforded decreased activity) in comparison to complex 1.
- Full Text:
- Date Issued: 2018
- Authors: Oluwole, David O , Manoto, Sello L , Malabi, Rudzani , Maphanga, Charles , Ombinda-Lemboumba, Saturnin , Mthunzi-Kufa, Patience , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/237886 , vital:50563 , xlink:href="https://doi.org/10.1016/j.dyepig.2017.11.019"
- Description: We report on the synthesis of glutathione capped gold (AuNPs–GSH) and gold–silver (Au3Ag1NPs–GSH) nanoparticles and their covalent attachment to Zn monocarboxyphenoxy phthalocyanine (1) via amide bond formation. The photophysicochemical properties and photodynamic therapy (PDT) activity of the complex and its nanoconjugates were assessed. The conjugates afforded improved triplet and singlet oxygen quantum yield as well as PDT activity (except for 1-Au3Ag1NPs which afforded decreased activity) in comparison to complex 1.
- Full Text:
- Date Issued: 2018
Evidence for a new regime shift between floating and submerged invasive plant dominance in South Africa
- Strange, Emily F, Hill, Martin P, Coetzee, Julie A
- Authors: Strange, Emily F , Hill, Martin P , Coetzee, Julie A
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423993 , vital:72114 , xlink:href="https://doi.org/10.1007/s10750-018-3506-2"
- Description: Classical biological control for the management of floating invasive plants has been highly successful in South Africa. However, restoring ecosystem services has been compromised by a new suite of submerged invasive plants. This study proposes that biological control of floating invasive macrophytes acts as a catalyst in a regime shift between floating and submerged invasive plant dominance. Regime shifts are large and sudden changes in the structure and functioning of ecosystems. The proposed shift is driven by the rapid decomposition of floating plants and subsequent increase in availability of nutrients and light. A mesocosm experiment explored the effect of biological control on floating Pistia stratiotes L. (Araceae) upon the growth of invasive submerged Egeria densa Planch. (Hydrocharitaceae), and native submerged plant species of the same family; Lagarosiphon major (Ridl.) Moss (Hydrocharitaceae). The results revealed a cascade effect of biological control of P. stratiotes on the availability of nitrogen, resulting in increased relative growth rates and invasive capacity for E. densa. In contrast, the native L. major could not compete with healthy or damaged P. stratiotes. These findings highlight the vulnerability of South African freshwater systems to submerged plant invasions and demonstrate the importance of a more holistic approach to invasive plant management.
- Full Text:
- Date Issued: 2018
- Authors: Strange, Emily F , Hill, Martin P , Coetzee, Julie A
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423993 , vital:72114 , xlink:href="https://doi.org/10.1007/s10750-018-3506-2"
- Description: Classical biological control for the management of floating invasive plants has been highly successful in South Africa. However, restoring ecosystem services has been compromised by a new suite of submerged invasive plants. This study proposes that biological control of floating invasive macrophytes acts as a catalyst in a regime shift between floating and submerged invasive plant dominance. Regime shifts are large and sudden changes in the structure and functioning of ecosystems. The proposed shift is driven by the rapid decomposition of floating plants and subsequent increase in availability of nutrients and light. A mesocosm experiment explored the effect of biological control on floating Pistia stratiotes L. (Araceae) upon the growth of invasive submerged Egeria densa Planch. (Hydrocharitaceae), and native submerged plant species of the same family; Lagarosiphon major (Ridl.) Moss (Hydrocharitaceae). The results revealed a cascade effect of biological control of P. stratiotes on the availability of nitrogen, resulting in increased relative growth rates and invasive capacity for E. densa. In contrast, the native L. major could not compete with healthy or damaged P. stratiotes. These findings highlight the vulnerability of South African freshwater systems to submerged plant invasions and demonstrate the importance of a more holistic approach to invasive plant management.
- Full Text:
- Date Issued: 2018