Meso-and axially-modified IrIIItriarylcorroles with tunable electrocatalytic properties
- Zhang, Xifeng, Wang, Yu, Zhu, Weihua, Mack, John, Soy, Rodah C, Nyokong, Tebello, Liang, Xu
- Authors: Zhang, Xifeng , Wang, Yu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190851 , vital:45034 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: The synthesis of three A2B type Ir(III)triarylcorroles with meso-aryl substituents that provide electron donating (push) and withdrawing (pull) properties and three A3 type IrIIItriphenylcorroles with differing pyridine axial ligands is reported, along with their structural characterization. An analysis of the structure-property relationships in the optical and redox properties has been carried out by comparing their optical spectroscopy and electrochemistry to trends predicted in DFT and TD-DFT calculations. The results demonstrate that A2B type IrIIItriarylcorroles are highly efficient electrocatalyzed oxygen reduction reactions (ORRs) and that their reactivity can be modulated by modulating the electronic structure by changing the nature of the meso-substituent at the B-positions, and even axial pyridine ligands.
- Full Text:
- Date Issued: 2015
- Authors: Zhang, Xifeng , Wang, Yu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Liang, Xu
- Date: 2015
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/190851 , vital:45034 , xlink:href="https://doi.org/10.1016/j.molstruc.2015.02.040"
- Description: The synthesis of three A2B type Ir(III)triarylcorroles with meso-aryl substituents that provide electron donating (push) and withdrawing (pull) properties and three A3 type IrIIItriphenylcorroles with differing pyridine axial ligands is reported, along with their structural characterization. An analysis of the structure-property relationships in the optical and redox properties has been carried out by comparing their optical spectroscopy and electrochemistry to trends predicted in DFT and TD-DFT calculations. The results demonstrate that A2B type IrIIItriarylcorroles are highly efficient electrocatalyzed oxygen reduction reactions (ORRs) and that their reactivity can be modulated by modulating the electronic structure by changing the nature of the meso-substituent at the B-positions, and even axial pyridine ligands.
- Full Text:
- Date Issued: 2015
Aza boron-pyridyl-isoindoline analogues
- Zhang, Hui, Wu, Yanping, Fan, Minhui, Xiao, Xuqiong, Mack, John, Kubheka, Gugu, Nyokong, Tebello, Lu, Hua
- Authors: Zhang, Hui , Wu, Yanping , Fan, Minhui , Xiao, Xuqiong , Mack, John , Kubheka, Gugu , Nyokong, Tebello , Lu, Hua
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232912 , vital:50037 , xlink:href="https://doi.org/10.1039/C7NJ00707H"
- Description: Several aza boron-pyridyl-isoindoline analogues are synthesized through a facile and scale-up two step reaction using 1,2-naphthalenedicarbonitrile as a starting material. These analogues show broad envelopes of intense vibrational bands in the absorption spectra with moderate fluorescence quantum yields in solution and the solid-state. An analysis of the structure–property relationships is described based on X-ray crystallography, optical spectroscopy, and theoretical calculations.
- Full Text:
- Date Issued: 2017
- Authors: Zhang, Hui , Wu, Yanping , Fan, Minhui , Xiao, Xuqiong , Mack, John , Kubheka, Gugu , Nyokong, Tebello , Lu, Hua
- Date: 2017
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/232912 , vital:50037 , xlink:href="https://doi.org/10.1039/C7NJ00707H"
- Description: Several aza boron-pyridyl-isoindoline analogues are synthesized through a facile and scale-up two step reaction using 1,2-naphthalenedicarbonitrile as a starting material. These analogues show broad envelopes of intense vibrational bands in the absorption spectra with moderate fluorescence quantum yields in solution and the solid-state. An analysis of the structure–property relationships is described based on X-ray crystallography, optical spectroscopy, and theoretical calculations.
- Full Text:
- Date Issued: 2017
Cordidepsine is A Potential New Anti-HIV Depsidone from Cordia millenii
- Zeukang, Rostanie D, Siwe-Noundou, Xavier, Fotsing, Maurice T, Mbafor, Joseph T, Krause, Rui W M, Choudhary, Muhammad I, Atchade, Alex de Theodore
- Authors: Zeukang, Rostanie D , Siwe-Noundou, Xavier , Fotsing, Maurice T , Mbafor, Joseph T , Krause, Rui W M , Choudhary, Muhammad I , Atchade, Alex de Theodore
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193988 , vital:45413 , xlink:href="https://doi.org/10.3390/molecules24173202"
- Description: Chemical investigation of Cordia millenii, Baker resulted in the isolation of a new depsidone, cordidepsine (1), along with twelve known compounds including cyclooctasulfur (2), lup-20(29)-en-3-triacontanoate (3), 1-(26-hydroxyhexacosanoyl)glycerol (4), glyceryl-1-hexacosanoate (5) betulinic acid (6), lupenone (7), β-amyrone (8), lupeol (9), β-amyrin (10), allantoin (11), 2′-(4-hydroxyphenyl)ethylpropanoate (12) and stigmasterol glycoside (13). Hemi-synthetic reactions were carried out on two isolated compounds (5 and 6) to afford two new derivatives, that is, cordicerol A (14) and cordicerol B (15), respectively. The chemical structures of all the compounds were established based on analysis and interpretation of spectroscopic data such as electron ionization mass spectrometry (EI–MS), high resolution electrospray ionization mass spectrometry (HR-ESI–MS), fast atom bombardment mass spectrometry (FAB–MS), one dimension and two dimension nuclear magnetic resonance (1D and 2D-NMR) spectral data as well as X-ray crystallography (XRC). Lupeol ester derivatives [Lup-20(29)-en-3-triacontanoate (3)], monoglycerol derivatives [1-(26-hydroxyhexacosanoyl)glycerol (4) and glyceryl-1 hexacosanoate (5)] were isolated for the first time from Cordia genus while sulfur allotrope [cyclooctasulfur (2)] was isolated for the first time from plant origin. Biological assays cordidepsine (1) exhibited significant anti-HIV integrase activity with IC50 = 4.65 μM; EtOAc extract of stem barks, EtOAc fraction of roots and leaves were not toxic against 3T3 cells.
- Full Text:
- Date Issued: 2019
- Authors: Zeukang, Rostanie D , Siwe-Noundou, Xavier , Fotsing, Maurice T , Mbafor, Joseph T , Krause, Rui W M , Choudhary, Muhammad I , Atchade, Alex de Theodore
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193988 , vital:45413 , xlink:href="https://doi.org/10.3390/molecules24173202"
- Description: Chemical investigation of Cordia millenii, Baker resulted in the isolation of a new depsidone, cordidepsine (1), along with twelve known compounds including cyclooctasulfur (2), lup-20(29)-en-3-triacontanoate (3), 1-(26-hydroxyhexacosanoyl)glycerol (4), glyceryl-1-hexacosanoate (5) betulinic acid (6), lupenone (7), β-amyrone (8), lupeol (9), β-amyrin (10), allantoin (11), 2′-(4-hydroxyphenyl)ethylpropanoate (12) and stigmasterol glycoside (13). Hemi-synthetic reactions were carried out on two isolated compounds (5 and 6) to afford two new derivatives, that is, cordicerol A (14) and cordicerol B (15), respectively. The chemical structures of all the compounds were established based on analysis and interpretation of spectroscopic data such as electron ionization mass spectrometry (EI–MS), high resolution electrospray ionization mass spectrometry (HR-ESI–MS), fast atom bombardment mass spectrometry (FAB–MS), one dimension and two dimension nuclear magnetic resonance (1D and 2D-NMR) spectral data as well as X-ray crystallography (XRC). Lupeol ester derivatives [Lup-20(29)-en-3-triacontanoate (3)], monoglycerol derivatives [1-(26-hydroxyhexacosanoyl)glycerol (4) and glyceryl-1 hexacosanoate (5)] were isolated for the first time from Cordia genus while sulfur allotrope [cyclooctasulfur (2)] was isolated for the first time from plant origin. Biological assays cordidepsine (1) exhibited significant anti-HIV integrase activity with IC50 = 4.65 μM; EtOAc extract of stem barks, EtOAc fraction of roots and leaves were not toxic against 3T3 cells.
- Full Text:
- Date Issued: 2019
A qualitative ecological risk assessment of the invasive Nile tilapia, Oreochromis niloticus in a sub-tropical African river system (Limpopo River, South Africa)
- Zengeya, Tsungai A, Robertson, Mark P, Booth, Anthony J, Chimimba, Christian T
- Authors: Zengeya, Tsungai A , Robertson, Mark P , Booth, Anthony J , Chimimba, Christian T
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123575 , vital:35457 , https://doi.10.1002/aqc.2258
- Description: 1. This study outlines the development of a qualitative risk assessment method and its application as a screening tool for determining the risk of establishment and spread of the invasive Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), within the central sub-catchment of the Limpopo River basin in northern South Africa. 2. The assessment used known physiological tolerance limits of O. niloticus in relation to minimum water temperature, presence or absence of dams, seasonality of river flows, and the presence of indigenous fish species of concern to identify river systems that would be suitable for O. niloticus establishment. 3. River sections along the Limpopo main river channel and the immediate reaches of its associated tributaries east of the Limpopo/Lephalala river confluence along the Botswana–South Africa–Zimbabwe border were identified as being highly vulnerable to O. niloticus invasion. Rivers in the upper Bushveld catchment (Upper Limpopo, Mogalakwena, Lephalala, Mokolo, Matlabas and Crocodile rivers) were categorized as of medium ecological risk, while headwater streams were considered to be of low ecological risk. The decrease in vulnerability between lowveld and highveld river sections was mainly a function of low water temperatures (8–12˚C) associated with increasing altitude. 4. Oreochromis niloticus is already established in the lower catchment of the Limpopo River basin where indigenous congenerics are at an extinction risk through hybridization and competition exclusion. Oreochromis niloticus, therefore, poses an ecologically unacceptable risk to river systems in the upper catchment where it is yet to establish. The current risk assessment model provides a useful preliminary framework for the identification of river systems that are vulnerable to an O. niloticus invasion where conservation measures should be directed and implemented to prevent its introduction and spread within the Limpopo river system.
- Full Text:
- Date Issued: 2013
- Authors: Zengeya, Tsungai A , Robertson, Mark P , Booth, Anthony J , Chimimba, Christian T
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123575 , vital:35457 , https://doi.10.1002/aqc.2258
- Description: 1. This study outlines the development of a qualitative risk assessment method and its application as a screening tool for determining the risk of establishment and spread of the invasive Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), within the central sub-catchment of the Limpopo River basin in northern South Africa. 2. The assessment used known physiological tolerance limits of O. niloticus in relation to minimum water temperature, presence or absence of dams, seasonality of river flows, and the presence of indigenous fish species of concern to identify river systems that would be suitable for O. niloticus establishment. 3. River sections along the Limpopo main river channel and the immediate reaches of its associated tributaries east of the Limpopo/Lephalala river confluence along the Botswana–South Africa–Zimbabwe border were identified as being highly vulnerable to O. niloticus invasion. Rivers in the upper Bushveld catchment (Upper Limpopo, Mogalakwena, Lephalala, Mokolo, Matlabas and Crocodile rivers) were categorized as of medium ecological risk, while headwater streams were considered to be of low ecological risk. The decrease in vulnerability between lowveld and highveld river sections was mainly a function of low water temperatures (8–12˚C) associated with increasing altitude. 4. Oreochromis niloticus is already established in the lower catchment of the Limpopo River basin where indigenous congenerics are at an extinction risk through hybridization and competition exclusion. Oreochromis niloticus, therefore, poses an ecologically unacceptable risk to river systems in the upper catchment where it is yet to establish. The current risk assessment model provides a useful preliminary framework for the identification of river systems that are vulnerable to an O. niloticus invasion where conservation measures should be directed and implemented to prevent its introduction and spread within the Limpopo river system.
- Full Text:
- Date Issued: 2013
Ecological niche modeling of the invasive potential of Nile tilapia Oreochromis niloticus in African river systems: concerns and implications for the conservation of indigenous congenerics
- Zengeya, Tsungai A, Robertson, Mark P, Booth, Anthony J, Chimimba, Christian T
- Authors: Zengeya, Tsungai A , Robertson, Mark P , Booth, Anthony J , Chimimba, Christian T
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124341 , vital:35596 , https://doi.10.1007/s10530-012-0386-7
- Description: This study applied ecological niche models to determine the potential invasive range of Nile tilapia, Oreochromis niloticus, with a particular focus on river systems in southern Africa where it is now established and spreading. Computational tools such as niche models are useful in predicting the potential range of invasive species, but there are limitations to their application. In particular, models trained on native records may fail to predict the full extent of an invasion. This failure is often attributed to changes in either the niche of the invading species or the variables used to develop the models. In this study, we therefore evaluated the differences in the predictive power of models trained with different environmental variables, the effect of species range (native vs. introduced) on model performance and assessed whether or not there is evidence suggestive of a niche shift in Nile tilapia following its introduction. Niche models were constructed using Maxent and the degree of niche similarity was assessed using Schoener‘s index. Null models were used to test for significance. Model performance and niche conservatism varied significantly with variable selection and species range. This indicates that the environmental conditions available to Nile tilapia in its native and introduced ranges are not congruent. Nile tilapia exhibited broad invasive potential over most of southern Africa that overlaps the natural range of endemic congenerics. Of particular concern are areas which are free of exotic species but are now vulnerable due to the promotion of fish introductions mainly for aquaculture and sport fishing.
- Full Text:
- Date Issued: 2013
- Authors: Zengeya, Tsungai A , Robertson, Mark P , Booth, Anthony J , Chimimba, Christian T
- Date: 2013
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/124341 , vital:35596 , https://doi.10.1007/s10530-012-0386-7
- Description: This study applied ecological niche models to determine the potential invasive range of Nile tilapia, Oreochromis niloticus, with a particular focus on river systems in southern Africa where it is now established and spreading. Computational tools such as niche models are useful in predicting the potential range of invasive species, but there are limitations to their application. In particular, models trained on native records may fail to predict the full extent of an invasion. This failure is often attributed to changes in either the niche of the invading species or the variables used to develop the models. In this study, we therefore evaluated the differences in the predictive power of models trained with different environmental variables, the effect of species range (native vs. introduced) on model performance and assessed whether or not there is evidence suggestive of a niche shift in Nile tilapia following its introduction. Niche models were constructed using Maxent and the degree of niche similarity was assessed using Schoener‘s index. Null models were used to test for significance. Model performance and niche conservatism varied significantly with variable selection and species range. This indicates that the environmental conditions available to Nile tilapia in its native and introduced ranges are not congruent. Nile tilapia exhibited broad invasive potential over most of southern Africa that overlaps the natural range of endemic congenerics. Of particular concern are areas which are free of exotic species but are now vulnerable due to the promotion of fish introductions mainly for aquaculture and sport fishing.
- Full Text:
- Date Issued: 2013
From the lens of isiXhosa female writers: female protagonists and the use of non-conformity in challenging gender roles in the post liberation isixhosa literature
- Authors: Zeleni, Olwethu
- Date: 2022-01
- Subjects: Women in literature , Feminism and literature , Xhosa literature
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/23840 , vital:60915
- Description: This dissertation explored the way women are presented in five isiXhosa literary works by female writers in post independence South Africa, with particular focus on how non-conformity is used to challenge gender roles. The study analysed two novels entitled Iqhina lomtshato (1995) by Nomlamli Mayosi and Uzenzile akakhalelwa (2016) by Yolisa Madolo, as well as four drama books titled Nyana nank’unyoko (1997) by Yoliswa Taleni, Akwaba (2004) by Thenjiswa Ntwana, Hamba nam ndipheleke and Imida (2015) by Nompumezo Buzani. Structural, Afrocentrism and African feminism were used to guide the study. The structural theory gave the researcher to review language contructs in relation to gender, African feminism and Afrocentrism gave the researcher the lenses to view gender issues within the African context, in line with the peculiar challenges that women continue to face in the content. Another important factor which is the focus of the study is the depiction of women by female writers, in order to challenge the roles that are given to women. The question that one ask then is: How do female writers lend their voices to female characters to address gender issues in society, with particular focus on gender roles? This thesis argues that the five isiXhosa female writers, who are contemporary African women writers, have noticed gender related assumptions and in their works, they are making an attempt to debunk these assumptions. It is hoped that this study will contribute to the existing debates on gender and division of labour. , Thesis (MA) -- Faculty of Social Sciences and Humanities, 2022
- Full Text:
- Date Issued: 2022-01
- Authors: Zeleni, Olwethu
- Date: 2022-01
- Subjects: Women in literature , Feminism and literature , Xhosa literature
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/23840 , vital:60915
- Description: This dissertation explored the way women are presented in five isiXhosa literary works by female writers in post independence South Africa, with particular focus on how non-conformity is used to challenge gender roles. The study analysed two novels entitled Iqhina lomtshato (1995) by Nomlamli Mayosi and Uzenzile akakhalelwa (2016) by Yolisa Madolo, as well as four drama books titled Nyana nank’unyoko (1997) by Yoliswa Taleni, Akwaba (2004) by Thenjiswa Ntwana, Hamba nam ndipheleke and Imida (2015) by Nompumezo Buzani. Structural, Afrocentrism and African feminism were used to guide the study. The structural theory gave the researcher to review language contructs in relation to gender, African feminism and Afrocentrism gave the researcher the lenses to view gender issues within the African context, in line with the peculiar challenges that women continue to face in the content. Another important factor which is the focus of the study is the depiction of women by female writers, in order to challenge the roles that are given to women. The question that one ask then is: How do female writers lend their voices to female characters to address gender issues in society, with particular focus on gender roles? This thesis argues that the five isiXhosa female writers, who are contemporary African women writers, have noticed gender related assumptions and in their works, they are making an attempt to debunk these assumptions. It is hoped that this study will contribute to the existing debates on gender and division of labour. , Thesis (MA) -- Faculty of Social Sciences and Humanities, 2022
- Full Text:
- Date Issued: 2022-01
Heritage–A conceptually evolving and dissonant phenomenon: Implications for heritage management and education practices in post-colonial Southern Africa
- Authors: Zazu, Clayton
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387208 , vital:68215 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122250"
- Description: This conceptual paper is based on experiences and insights which have emerged from my quest to develop a conceptual framework for working with the term ‘heritage’ within an education for sustainable development study that I am currently conducting. Of specific interest to me, and having potential to improve the relevance and quality of heritage education in southern Africa, given the region’s inherent cultural diversity and colonial history, is the need for ‘heritage construct inclusivity’ within the processes constituting heritage education practices. Working around this broad research goal, I therefore needed to be clear about what I mean or refer to as heritage. I realised, however, how elusive and conceptually problematic the term ‘heritage’ is. I therefore, drawing from literature and experiences gained during field observations and focus group interviews, came up with the idea of working with three viewpoints of heritage. Drawing on real life cases I argue that current heritage management and education practices’ failure to recognise and respect the evolving, interconnectedness and multi layered nature of heritage, partly explain the same practices’ lack of relevance and agency to enhance the sustainable management of local heritage resources. I also suggest a few ideas which heritage educators in the context of post-colonial southern Africa may need to consider in their everyday heritage education practices. I also introduce the notion of conceptualising heritage as ‘cultural landscapes’, within which the evolving, dissonant and interconnected nature of heritage, and associated heritage constructs, may be reconciled.
- Full Text:
- Date Issued: 2011
- Authors: Zazu, Clayton
- Date: 2011
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/387208 , vital:68215 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/122250"
- Description: This conceptual paper is based on experiences and insights which have emerged from my quest to develop a conceptual framework for working with the term ‘heritage’ within an education for sustainable development study that I am currently conducting. Of specific interest to me, and having potential to improve the relevance and quality of heritage education in southern Africa, given the region’s inherent cultural diversity and colonial history, is the need for ‘heritage construct inclusivity’ within the processes constituting heritage education practices. Working around this broad research goal, I therefore needed to be clear about what I mean or refer to as heritage. I realised, however, how elusive and conceptually problematic the term ‘heritage’ is. I therefore, drawing from literature and experiences gained during field observations and focus group interviews, came up with the idea of working with three viewpoints of heritage. Drawing on real life cases I argue that current heritage management and education practices’ failure to recognise and respect the evolving, interconnectedness and multi layered nature of heritage, partly explain the same practices’ lack of relevance and agency to enhance the sustainable management of local heritage resources. I also suggest a few ideas which heritage educators in the context of post-colonial southern Africa may need to consider in their everyday heritage education practices. I also introduce the notion of conceptualising heritage as ‘cultural landscapes’, within which the evolving, dissonant and interconnected nature of heritage, and associated heritage constructs, may be reconciled.
- Full Text:
- Date Issued: 2011
Perceptions and determinants of genetically modified (GM) maize production among rural households: The case of Ngqushwa Local Municipality, South Africa
- Zamisa, Owethu https://orcid.org/0000-0002-7303-4469
- Authors: Zamisa, Owethu https://orcid.org/0000-0002-7303-4469
- Date: 2022-03
- Subjects: Genetically modified foods , Agricultural biotechnology , Sustainable agriculture -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/22479 , vital:52343
- Description: Rural South Africa is faced with immense challenges including poverty, unemployment, low agriculture productivity, food and nutritional insecurity and inequalities. Against this background, enhancing rural agricultural productivity using proven technologies such as genetically modified (GM) maize production is suggested as a pathway to economic development and poverty reduction. Literature suggests that GM technology can increase crop yields, drought tolerance, reduced weeding labour costs and chemical spray costs. However, GM maize varieties available on the market currently were created to fit large-scale, capital-intensive, industrialised, and economically oriented agricultural systems. As a result, their uptake has been significantly slow especially in rural areas where several stakeholders are now questioning the potential of GM technology. With that background, this study aimed to understand determinants of gm maize production among rural farming households and their perceptions using the case of Ngqushwa Local Municipality. Specifically, the study sought to analyse types of maize varieties grown by rural households, associated yields, area allocation, rural households’ perceptions of GM maize, and to estimate factors that influence GM maize awareness, participation and intensity of production among this subsector. Using a cross-sectional survey research design, a sample size of 400 households was randomly selected and interviewed using a semi-structured questionnaire. The types of maize varieties grown by rural households, associated yields, area allocation and rural households’ perceptions of GM maize were analysed using descriptive statistics. Factors that influence GM maize awareness, participation, and intensity of production were estimated using a triple hurdle model where the 1st and 2nd hurdle were estimated using Probit regression, and 3rd hurdle a Tobit regression. The study revealed that landrace maize varieties are currently the most popular maize varieties grown by the majority of rural farming households from the study area producing higher yields (0.6t/ha) as compared to other hybrids (GM – 0.5t/ha, conventional hybrids -0.3t/ha and improved OPVs – 0.1t/ha). Descriptive statistics results also indicated that farming households from the study area allocated more land to landrace maize varieties (42percent) compared to other maize varieties (GM maize (30percent), hybrids (21percent) and improved OPVs (7percent) further supporting the notion that landrace maize varieties dominate the rural farming subsector. Perception results revealed that the majority (57percent) of the households perceived GM maize as an expensive variety which, however, has a potential to produce relatively higher yields than other hybrids on the market and eliminates several production problems (manual weeding, pest spraying) making farm management easier. Findings further indicate that the majority (52percent) of the farming households from the study area did not have sufficient knowledge of GM maize. Econometrics results revealed that GM maize awareness is negatively influenced by age and gender and positively influenced by marital status, employment status and number of years in school. Conditional on awareness of GM maize varieties, both participation and intensity of participation in GM maize production are positively influenced by land size, gender, group membership, size of arable land and negatively influenced by employment status and income. Against this background, the study concludes that farming households from the study area produced more compared to the other varieties. Furthermore, the study concludes that households get higher yields from landrace maize varieties and allocate more of their land to landrace maize production. In addition, the study also concludes that most rural farmers perceive participation in GM maize as beneficial especially towards elimination of farm management problems, produces higher yields, and makes farm management easier. Lastly, the study concludes that GM maize awareness is negatively influenced by age and gender and positively influenced by marital status, employment status and number of years in school. Both participation and intensity of participation in GM maize production are positively influenced by land size, gender, group membership, arable land and negatively influenced by employment status and income. The study recommends that priority should be given to these socio-economic and institutional factors and this may be addressed by targeting GM maize awareness campaigns and platforms more suited to female-headed, older, lowly educated and unemployed rural farming households. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Date Issued: 2022-03
- Authors: Zamisa, Owethu https://orcid.org/0000-0002-7303-4469
- Date: 2022-03
- Subjects: Genetically modified foods , Agricultural biotechnology , Sustainable agriculture -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/22479 , vital:52343
- Description: Rural South Africa is faced with immense challenges including poverty, unemployment, low agriculture productivity, food and nutritional insecurity and inequalities. Against this background, enhancing rural agricultural productivity using proven technologies such as genetically modified (GM) maize production is suggested as a pathway to economic development and poverty reduction. Literature suggests that GM technology can increase crop yields, drought tolerance, reduced weeding labour costs and chemical spray costs. However, GM maize varieties available on the market currently were created to fit large-scale, capital-intensive, industrialised, and economically oriented agricultural systems. As a result, their uptake has been significantly slow especially in rural areas where several stakeholders are now questioning the potential of GM technology. With that background, this study aimed to understand determinants of gm maize production among rural farming households and their perceptions using the case of Ngqushwa Local Municipality. Specifically, the study sought to analyse types of maize varieties grown by rural households, associated yields, area allocation, rural households’ perceptions of GM maize, and to estimate factors that influence GM maize awareness, participation and intensity of production among this subsector. Using a cross-sectional survey research design, a sample size of 400 households was randomly selected and interviewed using a semi-structured questionnaire. The types of maize varieties grown by rural households, associated yields, area allocation and rural households’ perceptions of GM maize were analysed using descriptive statistics. Factors that influence GM maize awareness, participation, and intensity of production were estimated using a triple hurdle model where the 1st and 2nd hurdle were estimated using Probit regression, and 3rd hurdle a Tobit regression. The study revealed that landrace maize varieties are currently the most popular maize varieties grown by the majority of rural farming households from the study area producing higher yields (0.6t/ha) as compared to other hybrids (GM – 0.5t/ha, conventional hybrids -0.3t/ha and improved OPVs – 0.1t/ha). Descriptive statistics results also indicated that farming households from the study area allocated more land to landrace maize varieties (42percent) compared to other maize varieties (GM maize (30percent), hybrids (21percent) and improved OPVs (7percent) further supporting the notion that landrace maize varieties dominate the rural farming subsector. Perception results revealed that the majority (57percent) of the households perceived GM maize as an expensive variety which, however, has a potential to produce relatively higher yields than other hybrids on the market and eliminates several production problems (manual weeding, pest spraying) making farm management easier. Findings further indicate that the majority (52percent) of the farming households from the study area did not have sufficient knowledge of GM maize. Econometrics results revealed that GM maize awareness is negatively influenced by age and gender and positively influenced by marital status, employment status and number of years in school. Conditional on awareness of GM maize varieties, both participation and intensity of participation in GM maize production are positively influenced by land size, gender, group membership, size of arable land and negatively influenced by employment status and income. Against this background, the study concludes that farming households from the study area produced more compared to the other varieties. Furthermore, the study concludes that households get higher yields from landrace maize varieties and allocate more of their land to landrace maize production. In addition, the study also concludes that most rural farmers perceive participation in GM maize as beneficial especially towards elimination of farm management problems, produces higher yields, and makes farm management easier. Lastly, the study concludes that GM maize awareness is negatively influenced by age and gender and positively influenced by marital status, employment status and number of years in school. Both participation and intensity of participation in GM maize production are positively influenced by land size, gender, group membership, arable land and negatively influenced by employment status and income. The study recommends that priority should be given to these socio-economic and institutional factors and this may be addressed by targeting GM maize awareness campaigns and platforms more suited to female-headed, older, lowly educated and unemployed rural farming households. , Thesis (MSc) -- Faculty of Science and Agriculture, 2022
- Full Text:
- Date Issued: 2022-03
The importance of public officials’ knowledge and understanding of the constitutional principles of public administration
- Authors: Zameko, Zamuxolo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54596 , vital:46732
- Description: Public officials in South Africa have been accused of lacking accountability, transparency, corruption, inefficiencies, unethical practices and a general unmotivated approach to service delivery. Section 195 of the 1996 constitution emphasises the need for public officials to be efficient, effective and not to be partial in their execution of duty. On that basis the research sought to investigate whether the public officials can improve on their performance if they are exposed to and are knowledgeable of the constitution. The study utilized a qualitative research method and a document analysis in which documents which served as sources of information were selected based on their relevance to the subject area of Public Administration. The documents selected were legal instruments used to enforce the operations of public officials including the Constitution of South Africa (1996), Batho Pele, White Paper on the Transformation of the Public Service, 1995; Promotion of Access to Information (Act no 2 of 2000 and Promotion of Equality & Prevention of Unfair Discrimination (Ac no 4 of 2000) Findings of the research indicate that key skills of the public officials like effective communication, change management, conflict resolution, decision-making, negotiation and accountability can be enhanced if they are knowledgeable of their constitutional mandate. The Public Service board should among others emphasize on constitutional principles training of all its employees upon recruitment such that they are aware of the public expectations. Continuous on the job training should also be offered to public officials so that their operations are always adjusted to the prevailing environmental and technological conditions. , Thesis (MA) -- Faculty of Humanities, School of Governmental and Social Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Zameko, Zamuxolo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54596 , vital:46732
- Description: Public officials in South Africa have been accused of lacking accountability, transparency, corruption, inefficiencies, unethical practices and a general unmotivated approach to service delivery. Section 195 of the 1996 constitution emphasises the need for public officials to be efficient, effective and not to be partial in their execution of duty. On that basis the research sought to investigate whether the public officials can improve on their performance if they are exposed to and are knowledgeable of the constitution. The study utilized a qualitative research method and a document analysis in which documents which served as sources of information were selected based on their relevance to the subject area of Public Administration. The documents selected were legal instruments used to enforce the operations of public officials including the Constitution of South Africa (1996), Batho Pele, White Paper on the Transformation of the Public Service, 1995; Promotion of Access to Information (Act no 2 of 2000 and Promotion of Equality & Prevention of Unfair Discrimination (Ac no 4 of 2000) Findings of the research indicate that key skills of the public officials like effective communication, change management, conflict resolution, decision-making, negotiation and accountability can be enhanced if they are knowledgeable of their constitutional mandate. The Public Service board should among others emphasize on constitutional principles training of all its employees upon recruitment such that they are aware of the public expectations. Continuous on the job training should also be offered to public officials so that their operations are always adjusted to the prevailing environmental and technological conditions. , Thesis (MA) -- Faculty of Humanities, School of Governmental and Social Sciences, 2021
- Full Text:
- Date Issued: 2021-12
Assessing the Role of Women on Small-Scale Agribusiness at Wincanton Estate in Kariega, South Africa
- Authors: Zalwango, Joanita
- Date: 2023-04
- Subjects: Leadership in women , Women in agriculture --Eastern Cape – Kariega , Climate change -- Kariega
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61054 , vital:69690
- Description: Agricultural development is a prerequisite for most economies to grow. Agricultural activities are key to food security and sustaining livelihoods globally. Within the African continent, more women are employed in agriculture and agribusiness activities than other sectors. As main contributors to the labour force in the agricultural sector, women get involved in many agricultural and agribusiness activities to sustain their families. With over 60% of women in Sub–Saharan Africa involved in agriculture, there is need to explore and assess the role they play in promoting agribusiness with special focus on Kariega, in South Africa. The identified participants in the study, as self-employed farmers, participate in agribusiness, thereby creating employment opportunities whilst generating personal incomes. Several benefits to female involvement in agribusiness were identified, including the ability to sustain families, stable cash flow, and empowerment. Several challenges were identified, including adequate capital, inaccessibility to private land, droughts, water scarcity, climate change effects and stigmatisation. Through a feminist qualitative methodology, the study utilised semi- structured interviews to collect data from 10 women involved in agribusiness around Kariega, Nelson Mandela Bay. Themes from the findings are analysed to highlight the important role played by women toward agribusiness, their achievements, government and private sector role and the hinderances still faced by these women in agricultural cooperatives. Discussion from the analysis included a framework of recommendations, for policy makers, development practitioners and future researchers. The study found that all stakeholders involved in the agricultural sector should work together for sustainable agricultural development and sustainable development goals to be achieved. Sustainability among women farmers can be achieved by (a) Increasing government intervention and support (b) Climate smart agriculture practices (c) Overcoming stigmatisation (d) Encouraging and involving the youth (e) Diversification and integration of farm businesses and (f) Using contract farming. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text: false
- Date Issued: 2023-04
Assessing the Role of Women on Small-Scale Agribusiness at Wincanton Estate in Kariega, South Africa
- Authors: Zalwango, Joanita
- Date: 2023-04
- Subjects: Leadership in women , Women in agriculture --Eastern Cape – Kariega , Climate change -- Kariega
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61054 , vital:69690
- Description: Agricultural development is a prerequisite for most economies to grow. Agricultural activities are key to food security and sustaining livelihoods globally. Within the African continent, more women are employed in agriculture and agribusiness activities than other sectors. As main contributors to the labour force in the agricultural sector, women get involved in many agricultural and agribusiness activities to sustain their families. With over 60% of women in Sub–Saharan Africa involved in agriculture, there is need to explore and assess the role they play in promoting agribusiness with special focus on Kariega, in South Africa. The identified participants in the study, as self-employed farmers, participate in agribusiness, thereby creating employment opportunities whilst generating personal incomes. Several benefits to female involvement in agribusiness were identified, including the ability to sustain families, stable cash flow, and empowerment. Several challenges were identified, including adequate capital, inaccessibility to private land, droughts, water scarcity, climate change effects and stigmatisation. Through a feminist qualitative methodology, the study utilised semi- structured interviews to collect data from 10 women involved in agribusiness around Kariega, Nelson Mandela Bay. Themes from the findings are analysed to highlight the important role played by women toward agribusiness, their achievements, government and private sector role and the hinderances still faced by these women in agricultural cooperatives. Discussion from the analysis included a framework of recommendations, for policy makers, development practitioners and future researchers. The study found that all stakeholders involved in the agricultural sector should work together for sustainable agricultural development and sustainable development goals to be achieved. Sustainability among women farmers can be achieved by (a) Increasing government intervention and support (b) Climate smart agriculture practices (c) Overcoming stigmatisation (d) Encouraging and involving the youth (e) Diversification and integration of farm businesses and (f) Using contract farming. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text: false
- Date Issued: 2023-04
Metallophthalocyanine-based molecular materials as catalysts for electrochemical reactions
- Zagal, José H, Griveau, Sophie J, Silva, Francisco, Nyokong, Tebello, Bedioui, Fethi
- Authors: Zagal, José H , Griveau, Sophie J , Silva, Francisco , Nyokong, Tebello , Bedioui, Fethi
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:7239 , http://hdl.handle.net/10962/d1019718
- Description: Metallophthalocyanines confined on the surface of electrodes are active catalysts for a large variety of electrochemical reactions and electrode surfaces modified by these complexes can be obtained by simple adsorption on graphite and carbon. However, more stable electrodes can be achieved by coating their surfaces with electropolymerized layers of the complexes, that show similar activity than their monomer counterparts. In all cases, fundamental studies carried out with adsorbed layers of these complexes have shown that the redox potential is a very good reactivity index for predicting the catalytic activity of the complexes. Volcano-shaped correlations have been found between the electrocatalytic activity (as log I at constant E) versus the Co(II)/(I) formal potential (E°′) of Co-macrocyclics for the oxidation of several thiols, hydrazine and glucose. For the electroreduction of O2 only linear correlations between the electrocatalytic activity versus the M(III)/M(II) formal potential have been found using Cr, Mn, Fe and Co phthalocyanines but it is likely that these correlations are “incomplete volcano” correlations. The volcano correlations strongly suggest that E°′, the formal potential of the complex needs to be in a rather narrow potential window for achieving maximum activity, probably corresponding to surface coverages of an M-molecule adduct equal to 0.5 and to standard free energies of adsorption of the reacting molecule on the complex active site equal to zero. These results indicate that the catalytic activity of metallophthalocyanines for the oxidation of several molecules can be “tuned” by manipulating the E°′ formal potential, using proper groups on the macrocyclic ligand. This review emphasizes once more that metallophthalocyanines are extremely versatile materials with many applications in electrocatalysis, electroanalysis, just to mention a few, and they provide very good models for testing their catalytic activity for several reactions. Even though the earlier applications of these complexes were focused on providing active materials for electroreduction of O2, for making active cathodes for fuel cells, the main trend in the literature nowadays is to use these complexes for making active electrodes for electrochemical sensors. , Original publication is available at http://dx.doi.org/10.1016/j.ccr.2010.05.001
- Full Text: false
- Date Issued: 2010
- Authors: Zagal, José H , Griveau, Sophie J , Silva, Francisco , Nyokong, Tebello , Bedioui, Fethi
- Date: 2010
- Language: English
- Type: text , Article
- Identifier: vital:7239 , http://hdl.handle.net/10962/d1019718
- Description: Metallophthalocyanines confined on the surface of electrodes are active catalysts for a large variety of electrochemical reactions and electrode surfaces modified by these complexes can be obtained by simple adsorption on graphite and carbon. However, more stable electrodes can be achieved by coating their surfaces with electropolymerized layers of the complexes, that show similar activity than their monomer counterparts. In all cases, fundamental studies carried out with adsorbed layers of these complexes have shown that the redox potential is a very good reactivity index for predicting the catalytic activity of the complexes. Volcano-shaped correlations have been found between the electrocatalytic activity (as log I at constant E) versus the Co(II)/(I) formal potential (E°′) of Co-macrocyclics for the oxidation of several thiols, hydrazine and glucose. For the electroreduction of O2 only linear correlations between the electrocatalytic activity versus the M(III)/M(II) formal potential have been found using Cr, Mn, Fe and Co phthalocyanines but it is likely that these correlations are “incomplete volcano” correlations. The volcano correlations strongly suggest that E°′, the formal potential of the complex needs to be in a rather narrow potential window for achieving maximum activity, probably corresponding to surface coverages of an M-molecule adduct equal to 0.5 and to standard free energies of adsorption of the reacting molecule on the complex active site equal to zero. These results indicate that the catalytic activity of metallophthalocyanines for the oxidation of several molecules can be “tuned” by manipulating the E°′ formal potential, using proper groups on the macrocyclic ligand. This review emphasizes once more that metallophthalocyanines are extremely versatile materials with many applications in electrocatalysis, electroanalysis, just to mention a few, and they provide very good models for testing their catalytic activity for several reactions. Even though the earlier applications of these complexes were focused on providing active materials for electroreduction of O2, for making active cathodes for fuel cells, the main trend in the literature nowadays is to use these complexes for making active electrodes for electrochemical sensors. , Original publication is available at http://dx.doi.org/10.1016/j.ccr.2010.05.001
- Full Text: false
- Date Issued: 2010
Developmental and reproductive performance of a specialist herbivore depend on seasonality of, and light conditions experienced by, the host plant
- Zachariades, Uyi O O,, Heshula, L U P, Hill, Martin P
- Authors: Zachariades, Uyi O O, , Heshula, L U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
- Authors: Zachariades, Uyi O O, , Heshula, L U P , Hill, Martin P
- Date: 2018
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59845 , vital:27667 , https://doi.org/10.1371/journal.pone.0190700
- Description: Host plant phenology (as influenced by seasonality) and light-mediated changes in the phenotypic and phytochemical properties of leaves have been hypothesised to equivocally influence insect herbivore performance. Here, we examined the effects of seasonality, through host plant phenology (late growth-season = autumn vs flowering-season = winter) and light environment (shade vs full-sun habitat) on the leaf characteristics of the invasive alien plant, Chromolaena odorata. In addition, the performance of a specialist folivore, Pareuchaetes insulata, feeding on leaves obtained from both shaded and full-sun habitats during autumn and winter, was evaluated over two generations. Foliar nitrogen and magnesium contents were generally higher in shaded plants with much higher levels during winter. Leaf water content was higher in shaded and in autumn plants. Total non-structural carbohydrate (TNC) and phosphorus contents did not differ as a function of season, but were higher in shaded foliage compared to full-sun leaves. Leaf toughness was noticeably higher on plants growing in full-sun during winter. With the exception of shaded leaves in autumn that supported the best performance [fastest development, heaviest pupal mass, and highest growth rate and Host Suitability Index (HSI) score], full-sun foliage in autumn surprisingly also supported an improved performance of the moth compared to shaded or full-sun leaves in winter. Our findings suggest that shaded and autumn foliage are nutritionally more suitable for the growth and reproduction of P. insulata. However, the heavier pupal mass, increased number of eggs and higher HSI score in individuals that fed on full-sun foliage in autumn compared to their counterparts that fed on shaded or full-sun foliage in winter suggest that full-sun foliage during autumn is also a suitable food source for larvae of the moth. In sum, our study demonstrates that seasonal and light-modulated changes in leaf characteristics can affect insect folivore performance in ways that are not linear.
- Full Text:
- Date Issued: 2018
Assessing the status of biological control as a management tool for suppression of invasive alien plants in South Africa
- Zachariades, Costas, Paterson, Iain D, Strathie, Lorraine W, Hill, Martin P, van Wilgen, Brian W
- Authors: Zachariades, Costas , Paterson, Iain D , Strathie, Lorraine W , Hill, Martin P , van Wilgen, Brian W
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59762 , vital:27646 , https://doi.org/10.4102/abc.v47i2.2142
- Description: Biological control of invasive alien plant (IAP) species is the use of introduced, highly selective natural enemies (usually herbivorous arthropods or pathogens) to control plants. It has been used in 130 countries as a valuable tool for the control of IAP species, with a total of over 550 biological control agents having been released (Winston et al. 2014). The benefits of biological control to natural ecosystems are significant (Van Driesch et al. 2010), with some specific examples of threatened indigenous species being protected by the action of biological control agents (Barton et al. 2007; Meyer, Fourdrigniez & Taputuarai 2011). Detailed analyses of programmes on biological control of IAPs have also clearly indicated that the risks of non-target effects from biological control agents are minimal (Fowler, Syrett & Hill 2000; Funasaki et al. 1988; Moran & Hoffmann 2015; Paynter et al. 2004; Pemberton 2000; Suckling & Sforza 2014). Less than 1% of all the agents released have a negative impact on non-target plant populations, and those that do could have been predicted to do so, and would not be released today (Suckling & Sforza 2014).
- Full Text:
- Date Issued: 2017
- Authors: Zachariades, Costas , Paterson, Iain D , Strathie, Lorraine W , Hill, Martin P , van Wilgen, Brian W
- Date: 2017
- Language: English
- Type: article , text
- Identifier: http://hdl.handle.net/10962/59762 , vital:27646 , https://doi.org/10.4102/abc.v47i2.2142
- Description: Biological control of invasive alien plant (IAP) species is the use of introduced, highly selective natural enemies (usually herbivorous arthropods or pathogens) to control plants. It has been used in 130 countries as a valuable tool for the control of IAP species, with a total of over 550 biological control agents having been released (Winston et al. 2014). The benefits of biological control to natural ecosystems are significant (Van Driesch et al. 2010), with some specific examples of threatened indigenous species being protected by the action of biological control agents (Barton et al. 2007; Meyer, Fourdrigniez & Taputuarai 2011). Detailed analyses of programmes on biological control of IAPs have also clearly indicated that the risks of non-target effects from biological control agents are minimal (Fowler, Syrett & Hill 2000; Funasaki et al. 1988; Moran & Hoffmann 2015; Paynter et al. 2004; Pemberton 2000; Suckling & Sforza 2014). Less than 1% of all the agents released have a negative impact on non-target plant populations, and those that do could have been predicted to do so, and would not be released today (Suckling & Sforza 2014).
- Full Text:
- Date Issued: 2017
In silico substrate binding profiling for SARS-COV-2 main protease (mpro) using hexapeptide substrates
- Authors: Zabo, Sophakama
- Date: 2022-10-14
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/365566 , vital:65760
- Description: COVID-19, as a disease resulting from SARS-CoV-2 infection, and a pandemic has had a devastating effect on the world. There are limited effective measures that control the spread and treatment of COVID-19 illness. The homodimeric cysteine main protease (Mpro) is crucial to the life cycle of the virus, as it cleaves the large polyproteins 1a and 1ab into matured, functional non-structural proteins. The Mpro exhibits high degrees of conservation in sequence, structure and specificity across coronavirus species, making it an ideal drug target. The Mpro substrate-binding profiles remain, despite the resolution of its recognition sequence and cleavage points (Leu-Gln↓(Ser/Ala/Gly)). In this study, a series of hexapeptide sequences containing the appropriate recognition sequence and cleavage points were generated and screened against the Mpro to study these binding profiles, and to further be the basis for efficiency-driven drug design. A multi-conformer hexapeptide substrate library comprising optimised 81000 models of 810 unique sequences was generated using RDKit within the context of python. Terminal capping with ACE and NMe was effected using SMILES and SMARTS matching. Multiple hexapeptides were complexed with chain B of crystallographic Mpro (PDS ID: 6XHM), following the validation of chain B for this purpose using AutoDock Vina at high levels of exhaustiveness (480). The resulting Vina scores ranged between -8.7 and -7.0 kcal.mol-1, and the reproducibility of best poses was validated through redocking. Ligand efficiency indices were calculated to identify substrate residues with high binding efficiency at their respective positions, revealing Val (P3), Ala (P1′); and Gly and Ala (P2′ and P3′) as leading efficient binders. Binding efficiencies were lowered by molecular weight. Substrate recognition was assessed by mapping of binding subsites, and Mpro specificity was evaluated through the resolution of intermolecular interaction at the binding interface. Molecular dynamics simulations for 20 ns were performed to assess the stability and behaviour of 132 Mpro systems complexed with KLQ*** substrates. Principal component analysis (PCA), was performed to assess II protein motions and conformational changes during the simulations. A strategy was formulated to classify and evaluate relations in the Mpro PCA motions, revealing four main clades of similarity. Similarity within a clade (Group 2) and dissimilarity between clades were confirmed. Trajectory visualisation revealed complex stability, substrate unbinding and dimer dissociation for various Mpro systems. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Zabo, Sophakama
- Date: 2022-10-14
- Subjects: Uncatalogued
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/365566 , vital:65760
- Description: COVID-19, as a disease resulting from SARS-CoV-2 infection, and a pandemic has had a devastating effect on the world. There are limited effective measures that control the spread and treatment of COVID-19 illness. The homodimeric cysteine main protease (Mpro) is crucial to the life cycle of the virus, as it cleaves the large polyproteins 1a and 1ab into matured, functional non-structural proteins. The Mpro exhibits high degrees of conservation in sequence, structure and specificity across coronavirus species, making it an ideal drug target. The Mpro substrate-binding profiles remain, despite the resolution of its recognition sequence and cleavage points (Leu-Gln↓(Ser/Ala/Gly)). In this study, a series of hexapeptide sequences containing the appropriate recognition sequence and cleavage points were generated and screened against the Mpro to study these binding profiles, and to further be the basis for efficiency-driven drug design. A multi-conformer hexapeptide substrate library comprising optimised 81000 models of 810 unique sequences was generated using RDKit within the context of python. Terminal capping with ACE and NMe was effected using SMILES and SMARTS matching. Multiple hexapeptides were complexed with chain B of crystallographic Mpro (PDS ID: 6XHM), following the validation of chain B for this purpose using AutoDock Vina at high levels of exhaustiveness (480). The resulting Vina scores ranged between -8.7 and -7.0 kcal.mol-1, and the reproducibility of best poses was validated through redocking. Ligand efficiency indices were calculated to identify substrate residues with high binding efficiency at their respective positions, revealing Val (P3), Ala (P1′); and Gly and Ala (P2′ and P3′) as leading efficient binders. Binding efficiencies were lowered by molecular weight. Substrate recognition was assessed by mapping of binding subsites, and Mpro specificity was evaluated through the resolution of intermolecular interaction at the binding interface. Molecular dynamics simulations for 20 ns were performed to assess the stability and behaviour of 132 Mpro systems complexed with KLQ*** substrates. Principal component analysis (PCA), was performed to assess II protein motions and conformational changes during the simulations. A strategy was formulated to classify and evaluate relations in the Mpro PCA motions, revealing four main clades of similarity. Similarity within a clade (Group 2) and dissimilarity between clades were confirmed. Trajectory visualisation revealed complex stability, substrate unbinding and dimer dissociation for various Mpro systems. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2022
- Full Text:
- Date Issued: 2022-10-14
Conflict-induced displacement: a study of risk and support for the older refugees in South Africa
- Yusuf, Mohammed Sanusi https://orcid.org/0000-0002-6871-0186
- Authors: Yusuf, Mohammed Sanusi https://orcid.org/0000-0002-6871-0186
- Date: 2021-09
- Subjects: Migration, Internal , Displacement (Psychology) , Refugees -- Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22231 , vital:52001
- Description: With the exponential rise in conflict scenarios globally, the number of internally displaced persons (IDPs) and refugees in foreign countries continues to grow. Although there has been several international efforts and conventions aimed at alleviating the global refugee crisis, the international community has not found a sustainable answer to this knotty problem. In Africa, with some of the worst conflict situations, the scourge of social displacement resulting in migrations have caused different levels of risks and vulnerability for the refugees, as well as capacity constraints for the host communities, governments of host countries and non-governmental bodies working with refugees. In South Africa, with one of the highest numbers of refugees in Africa, especially those coming from African countries, contention for socio-economic space and cultural differences occasionally result in violence between refugees and local people. For the older refugees, the level of risk exposure and hardship have generated interests for both scholars and officials. This thesis explores the risks and support systems for older refugees in South Africa, with specific focus on the Eastern Cape province. Various stakeholders (such as government, NGOs, host communities and the older refugees) in refugee management in South Africa have argued differently on ‘how best’ to manage older refugees in the country. Using qualitative data gathered from refugee communities in the Eastern Cape province and documentary analysis, the study found that the experiences of older refugees in the Eastern Cape province are nuanced. The dominant narrative on the experiences of older refugees indicate peaceful coexistence and resilient organic community support systems, with minor conflicts – often associated with contestations for scarce economic opportunities. Although the study focuses on one province of South Africa, this finding challenges the often-overgeneralised perception of South Africa as ‘xenophobic’. It unpacks the hidden resilient social systems and networks of relationships that bind local populations and the refugees, especially the older ones. In the search for national, regional and global answers on the best way to manage refugee crisis, this study provides insights into community-level structures and dynamics that would benefit policymaking at the national and international levels , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2021
- Full Text:
- Date Issued: 2021-09
- Authors: Yusuf, Mohammed Sanusi https://orcid.org/0000-0002-6871-0186
- Date: 2021-09
- Subjects: Migration, Internal , Displacement (Psychology) , Refugees -- Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10353/22231 , vital:52001
- Description: With the exponential rise in conflict scenarios globally, the number of internally displaced persons (IDPs) and refugees in foreign countries continues to grow. Although there has been several international efforts and conventions aimed at alleviating the global refugee crisis, the international community has not found a sustainable answer to this knotty problem. In Africa, with some of the worst conflict situations, the scourge of social displacement resulting in migrations have caused different levels of risks and vulnerability for the refugees, as well as capacity constraints for the host communities, governments of host countries and non-governmental bodies working with refugees. In South Africa, with one of the highest numbers of refugees in Africa, especially those coming from African countries, contention for socio-economic space and cultural differences occasionally result in violence between refugees and local people. For the older refugees, the level of risk exposure and hardship have generated interests for both scholars and officials. This thesis explores the risks and support systems for older refugees in South Africa, with specific focus on the Eastern Cape province. Various stakeholders (such as government, NGOs, host communities and the older refugees) in refugee management in South Africa have argued differently on ‘how best’ to manage older refugees in the country. Using qualitative data gathered from refugee communities in the Eastern Cape province and documentary analysis, the study found that the experiences of older refugees in the Eastern Cape province are nuanced. The dominant narrative on the experiences of older refugees indicate peaceful coexistence and resilient organic community support systems, with minor conflicts – often associated with contestations for scarce economic opportunities. Although the study focuses on one province of South Africa, this finding challenges the often-overgeneralised perception of South Africa as ‘xenophobic’. It unpacks the hidden resilient social systems and networks of relationships that bind local populations and the refugees, especially the older ones. In the search for national, regional and global answers on the best way to manage refugee crisis, this study provides insights into community-level structures and dynamics that would benefit policymaking at the national and international levels , Thesis (PhD) -- Faculty of Social Sciences and Humanities, 2021
- Full Text:
- Date Issued: 2021-09
Core-modified rubyrins with phenanthrene-fused pyrrole rings
- Yuan, Xuemei, Li, Minzhi, Meng, Ting, Mack, John, Soy, Rodah, Nyokong, Tebello, Zhu, Weihua, Xu, Haijun, Liang, Xu
- Authors: Yuan, Xuemei , Li, Minzhi , Meng, Ting , Mack, John , Soy, Rodah , Nyokong, Tebello , Zhu, Weihua , Xu, Haijun , Liang, Xu
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234568 , vital:50209 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.05.045"
- Description: Three fused-ring-expanded rubyrins with modified macrocyclic core have been synthesized and characterized. A series of spectroscopic, electrochemical measurements and a set of theoretical calculations demonstrate that the core-modification of the inner core of rubyrins has a large influence on the electronic structure. Colorimetric changes are observe that demonstrate that these core-modified rubyrins could be used as selective Hg2+ ion sensors. These properties can be fine-tuned by introducing lipophilic substituents on the meso-aryl rings.
- Full Text:
- Date Issued: 2018
- Authors: Yuan, Xuemei , Li, Minzhi , Meng, Ting , Mack, John , Soy, Rodah , Nyokong, Tebello , Zhu, Weihua , Xu, Haijun , Liang, Xu
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234568 , vital:50209 , xlink:href="https://doi.org/10.1016/j.dyepig.2018.05.045"
- Description: Three fused-ring-expanded rubyrins with modified macrocyclic core have been synthesized and characterized. A series of spectroscopic, electrochemical measurements and a set of theoretical calculations demonstrate that the core-modification of the inner core of rubyrins has a large influence on the electronic structure. Colorimetric changes are observe that demonstrate that these core-modified rubyrins could be used as selective Hg2+ ion sensors. These properties can be fine-tuned by introducing lipophilic substituents on the meso-aryl rings.
- Full Text:
- Date Issued: 2018
Comparative structural bioinformatics analysis of Bacillus amyloliquefaciens chemotaxis proteins within Bacillus subtilis group
- Yssel, Anna, Reva, Oleg, Tastan Bishop, Özlem
- Authors: Yssel, Anna , Reva, Oleg , Tastan Bishop, Özlem
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123966 , vital:35521 , https://doi.10.1007/s00253-011-3582-y
- Description: Chemotaxis is a process in which bacteria sense their chemical environment and move towards more favorable conditions. Since plant colonization by bacteria is a multifaceted process which requires a response to the complex chemical environment, a finely tuned and sensitive chemotaxis system is needed. Members of the Bacillus subtilis group including Bacillus amyloliquefaciens are industrially important, for example, as bio-pesticides. The group exhibits plant growth-promoting characteristics, with different specificity towards certain host plants. Therefore, we hypothesize that while the principal molecular mechanisms of bacterial chemotaxis may be conserved, the bacterial chemotaxis system may need an evolutionary tweaking to adapt it to specific requirements, particularly in the process of evolution of free-living soil organisms, towards plant colonization behaviour. To date, almost nothing is known about what parts of the chemotaxis proteins are subjected to positive amino acid substitutions, involved in adjusting the chemotaxis system of bacteria during speciation. In this novel study, positively selected and purified sites of chemotaxis proteins were calculated, and these residues were mapped onto homology models that were built for the chemotaxis proteins, in an attempt to understand the spatial evolution of the chemotaxis proteins. Various positively selected amino acids were identified in semi-conserved regions of the proteins away from the known active sites.
- Full Text:
- Date Issued: 2011
- Authors: Yssel, Anna , Reva, Oleg , Tastan Bishop, Özlem
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/123966 , vital:35521 , https://doi.10.1007/s00253-011-3582-y
- Description: Chemotaxis is a process in which bacteria sense their chemical environment and move towards more favorable conditions. Since plant colonization by bacteria is a multifaceted process which requires a response to the complex chemical environment, a finely tuned and sensitive chemotaxis system is needed. Members of the Bacillus subtilis group including Bacillus amyloliquefaciens are industrially important, for example, as bio-pesticides. The group exhibits plant growth-promoting characteristics, with different specificity towards certain host plants. Therefore, we hypothesize that while the principal molecular mechanisms of bacterial chemotaxis may be conserved, the bacterial chemotaxis system may need an evolutionary tweaking to adapt it to specific requirements, particularly in the process of evolution of free-living soil organisms, towards plant colonization behaviour. To date, almost nothing is known about what parts of the chemotaxis proteins are subjected to positive amino acid substitutions, involved in adjusting the chemotaxis system of bacteria during speciation. In this novel study, positively selected and purified sites of chemotaxis proteins were calculated, and these residues were mapped onto homology models that were built for the chemotaxis proteins, in an attempt to understand the spatial evolution of the chemotaxis proteins. Various positively selected amino acids were identified in semi-conserved regions of the proteins away from the known active sites.
- Full Text:
- Date Issued: 2011
A review of the implementation of the CAPS Life Skills curriculum training, as a recontextualising process, in engaging teachers in environmental education in two districts of the Eastern Cape Province
- Authors: Yoyo, Sindiswa
- Date: 2018
- Subjects: Life skills Study and teaching (Continuing education) South Africa Eastern Cape , Environmental education Curricula South Africa Eastern Cape , Teachers In-service training South Africa Eastern Cape , Curriculum change South Africa Eastern Cape , Teachers Education (Continuing education) South Africa Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/61767 , vital:28057
- Description: This study examines how the implementation of CAPS Life Skills curriculum training (as a recontextualising process) is engaging teachers in environmental education. The research was centred on training manuals for Life Skills (Official Recontextualisation Field) and their use in CAPS training at district level in two Eastern Cape sites of recontextualisation (Professional Recontextualisation Field). During the training, teachers developed lesson plans that were reviewed and group interviews were conducted on the training process and its outcomes. The manuals, training process, lesson plans and interview transcripts were analysed for evidence of environmental education, notably content, teaching and learning methods and assessment strategies. Bernstein’s (1990) framework of the pedagogic device underpins this study. Here the concept of the relay is key for tracking the "relay” of the content, teaching and learning methods and assessment strategies through the processes of recontextualisation into the lesson plans for the field of production. During the process of de-location and relocation, gaps are created and this study sought to track and probe patterns of omissions that took place during the relay process in two cases of training. The review of the in-service training course process of recontextualisation and its cascading approach exposed challenges of omission as it became clear that at each level of the recontextualisation process, gaps were apparent. The study highlighted how the 3-5 day workshop process reviewed was not a robust model for professional development. It was not effective and changes in the mode of delivery and processes of support that reach into curriculum practice in the context of the school are recommended. The study concludes that there is a need for continuous professional development as teachers need ongoing support especially for a "new” curriculum like CAPS that is content driven.
- Full Text:
- Date Issued: 2018
- Authors: Yoyo, Sindiswa
- Date: 2018
- Subjects: Life skills Study and teaching (Continuing education) South Africa Eastern Cape , Environmental education Curricula South Africa Eastern Cape , Teachers In-service training South Africa Eastern Cape , Curriculum change South Africa Eastern Cape , Teachers Education (Continuing education) South Africa Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10962/61767 , vital:28057
- Description: This study examines how the implementation of CAPS Life Skills curriculum training (as a recontextualising process) is engaging teachers in environmental education. The research was centred on training manuals for Life Skills (Official Recontextualisation Field) and their use in CAPS training at district level in two Eastern Cape sites of recontextualisation (Professional Recontextualisation Field). During the training, teachers developed lesson plans that were reviewed and group interviews were conducted on the training process and its outcomes. The manuals, training process, lesson plans and interview transcripts were analysed for evidence of environmental education, notably content, teaching and learning methods and assessment strategies. Bernstein’s (1990) framework of the pedagogic device underpins this study. Here the concept of the relay is key for tracking the "relay” of the content, teaching and learning methods and assessment strategies through the processes of recontextualisation into the lesson plans for the field of production. During the process of de-location and relocation, gaps are created and this study sought to track and probe patterns of omissions that took place during the relay process in two cases of training. The review of the in-service training course process of recontextualisation and its cascading approach exposed challenges of omission as it became clear that at each level of the recontextualisation process, gaps were apparent. The study highlighted how the 3-5 day workshop process reviewed was not a robust model for professional development. It was not effective and changes in the mode of delivery and processes of support that reach into curriculum practice in the context of the school are recommended. The study concludes that there is a need for continuous professional development as teachers need ongoing support especially for a "new” curriculum like CAPS that is content driven.
- Full Text:
- Date Issued: 2018
An analysis of ways in which the South African tax system could be simplified
- Authors: Young, Gail Jeni
- Date: 2021-04
- Subjects: Taxation -- Law and legislation -- South Africa , Income tax -- Law and legislation -- South Africa , South African Revenue Service , Tax administration and procedure -- South Africa , Tax accounting -- South Africa
- Language: English
- Type: thesis , text , Masters , MCom
- Identifier: http://hdl.handle.net/10962/178235 , vital:42923
- Description: It has been said that the fundamental paradox of tax simplification is that, despite consensus, almost every year tax rules become more complex. This thesis considers tax simplification measures which have been implemented internationally, in order to provide a basis for an analysis of ways in which the South African tax system could be simplified. A doctrinal methodology is applied, and an analysis is carried out of possible tax simplification measures, based on the commentary of experts in the field of tax law. Simplification measures adopted in the United Kingdom, Australia, the United States of America, Egypt, and certain European countries are discussed, together with their possible adoption in South Africa. Tax simplification has a broad scope. This research identifies four areas in which the South African tax system could simplified: the simplification of tax legislation, addressing the role of accounting in the simplification process, reducing the number of taxes currently levied, and finally addressing the complexities evident in the SARS e-filing system. This thesis illustrates several measures which could be used to address the current areas of complexity. Re-writing tax legislation to assist the understanding of taxpayers is suggested. An increase in the inclusion rate for individuals of capital gains in taxable income from 40% to 60% is suggested, to compensate for the loss of revenue due to the recommended repeal of donations tax and estate duty. Aligning tax legislation with accounting standards is identified as a possible area for simplification, as there are many similarities between the two systems. To address the usability of SARS’ e-filing platform, suggestions are made regarding the further pre-population of returns, introducing e-invoicing and providing a “sandbox” function that taxpayers could use to familiarise themselves with how e-filing works. This research highlights tax simplification as a process that needs to be prioritized in order to achieve the associated benefits. , Thesis (MCom) -- Faculty of Commerce, Accounting, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Young, Gail Jeni
- Date: 2021-04
- Subjects: Taxation -- Law and legislation -- South Africa , Income tax -- Law and legislation -- South Africa , South African Revenue Service , Tax administration and procedure -- South Africa , Tax accounting -- South Africa
- Language: English
- Type: thesis , text , Masters , MCom
- Identifier: http://hdl.handle.net/10962/178235 , vital:42923
- Description: It has been said that the fundamental paradox of tax simplification is that, despite consensus, almost every year tax rules become more complex. This thesis considers tax simplification measures which have been implemented internationally, in order to provide a basis for an analysis of ways in which the South African tax system could be simplified. A doctrinal methodology is applied, and an analysis is carried out of possible tax simplification measures, based on the commentary of experts in the field of tax law. Simplification measures adopted in the United Kingdom, Australia, the United States of America, Egypt, and certain European countries are discussed, together with their possible adoption in South Africa. Tax simplification has a broad scope. This research identifies four areas in which the South African tax system could simplified: the simplification of tax legislation, addressing the role of accounting in the simplification process, reducing the number of taxes currently levied, and finally addressing the complexities evident in the SARS e-filing system. This thesis illustrates several measures which could be used to address the current areas of complexity. Re-writing tax legislation to assist the understanding of taxpayers is suggested. An increase in the inclusion rate for individuals of capital gains in taxable income from 40% to 60% is suggested, to compensate for the loss of revenue due to the recommended repeal of donations tax and estate duty. Aligning tax legislation with accounting standards is identified as a possible area for simplification, as there are many similarities between the two systems. To address the usability of SARS’ e-filing platform, suggestions are made regarding the further pre-population of returns, introducing e-invoicing and providing a “sandbox” function that taxpayers could use to familiarise themselves with how e-filing works. This research highlights tax simplification as a process that needs to be prioritized in order to achieve the associated benefits. , Thesis (MCom) -- Faculty of Commerce, Accounting, 2021
- Full Text:
- Date Issued: 2021-04
Exploring patterns of Facebook usage, social capital, loneliness and well-being among a diverse South African student sample:
- Young, Charles, Strelitz, Larry N
- Authors: Young, Charles , Strelitz, Larry N
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143705 , vital:38275 , https://ischp.files.wordpress.com/2015/08/ischp_2015_abstract_booklet.pdf
- Description: There has been much debate over whether the use of social network sites isolate people and truncate their relationships or alternatively, provide beneficial connections with others. This debate has been framed by a growing international literature which explores the triadic relationship between the intensity of use of Facebook to the maintenance of social capital and in turn the relationship between social capital and wellbeing and loneliness. A random list of 1168 Rhodes University students was drawn from the total student body and invited to participate in an online survey. In total, 491 students completed the survey (42% response rate). Hierarchical regression analyses demonstrate that intensity of Facebook usage adds a very small contribution to social capital, is very weakly associated with loneliness, and is not associated with wellbeing. Results contrast with international studies that fail to recognise the extent to which race and class cleavages impact on access to and use of social media.
- Full Text:
- Date Issued: 2015
- Authors: Young, Charles , Strelitz, Larry N
- Date: 2015
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/143705 , vital:38275 , https://ischp.files.wordpress.com/2015/08/ischp_2015_abstract_booklet.pdf
- Description: There has been much debate over whether the use of social network sites isolate people and truncate their relationships or alternatively, provide beneficial connections with others. This debate has been framed by a growing international literature which explores the triadic relationship between the intensity of use of Facebook to the maintenance of social capital and in turn the relationship between social capital and wellbeing and loneliness. A random list of 1168 Rhodes University students was drawn from the total student body and invited to participate in an online survey. In total, 491 students completed the survey (42% response rate). Hierarchical regression analyses demonstrate that intensity of Facebook usage adds a very small contribution to social capital, is very weakly associated with loneliness, and is not associated with wellbeing. Results contrast with international studies that fail to recognise the extent to which race and class cleavages impact on access to and use of social media.
- Full Text:
- Date Issued: 2015