A critical analysis of the tax consequences of debt reductons, in the context of insolvency, death and the liquidaton of a deceased estate
- Authors: Simango, Samuel
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/54464 , vital:26567
- Description: The present research was conducted in an effort to address certain problems and a legal anomaly that is specifically related to the tax treatment of reduced debts stemming from the death or insolvency of natural persons in South Africa. At the beginning of 2013 the National Treasury enacted certain amendments to the debt reduction provisions of the Income Tax Act 58 of 1962 with the intention of streamlining the tax treatment of reduced debts and granting debt relief to financially distressed debtors. In spite of these recent amendments to the provisions of the Income Tax Act, there are certain problems and a legal anomaly which still currently relate to the tax consequences of reduced debts in South Africa. These problems and the legal anomaly are based on the failure of the recent amendments to successfully address debt reduction which arises in the context of the death and/or insolvency of natural persons. The objective of this research was therefore to analyse the tax consequences of reduced debts arising in the context of the death and the insolvency of natural persons and to explain how the problems and legal anomaly associated with these tax consequences can be rectified. The research design was qualitative within the framework of an interpretive paradigm. A mixed methodology approach was followed as identified in the Arthurs Report (1983), namely the interdisciplinary and the doctrinal methodologies. This approach encompassed two legal research methods namely the expository and legal reform research methods. The research explained the underlying nature of the tax consequences of reduced debts arising in the context of the death and the insolvency of natural persons and formulated specific reform measures aimed at remedying the problems and the legal anomaly that currently exist. Two amendments were proposed. It was proposed that the tax liability which arises when debts are reduced through the wills of deceased persons and the reduction of debts stemming from the insolvency of natural persons should be expressly excluded from falling within the ambit of the provisions which give rise to tax consequences whenever debt reduction takes place.
- Full Text:
- Date Issued: 2014
- Authors: Simango, Samuel
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/54464 , vital:26567
- Description: The present research was conducted in an effort to address certain problems and a legal anomaly that is specifically related to the tax treatment of reduced debts stemming from the death or insolvency of natural persons in South Africa. At the beginning of 2013 the National Treasury enacted certain amendments to the debt reduction provisions of the Income Tax Act 58 of 1962 with the intention of streamlining the tax treatment of reduced debts and granting debt relief to financially distressed debtors. In spite of these recent amendments to the provisions of the Income Tax Act, there are certain problems and a legal anomaly which still currently relate to the tax consequences of reduced debts in South Africa. These problems and the legal anomaly are based on the failure of the recent amendments to successfully address debt reduction which arises in the context of the death and/or insolvency of natural persons. The objective of this research was therefore to analyse the tax consequences of reduced debts arising in the context of the death and the insolvency of natural persons and to explain how the problems and legal anomaly associated with these tax consequences can be rectified. The research design was qualitative within the framework of an interpretive paradigm. A mixed methodology approach was followed as identified in the Arthurs Report (1983), namely the interdisciplinary and the doctrinal methodologies. This approach encompassed two legal research methods namely the expository and legal reform research methods. The research explained the underlying nature of the tax consequences of reduced debts arising in the context of the death and the insolvency of natural persons and formulated specific reform measures aimed at remedying the problems and the legal anomaly that currently exist. Two amendments were proposed. It was proposed that the tax liability which arises when debts are reduced through the wills of deceased persons and the reduction of debts stemming from the insolvency of natural persons should be expressly excluded from falling within the ambit of the provisions which give rise to tax consequences whenever debt reduction takes place.
- Full Text:
- Date Issued: 2014
A study of South African computer users' password usage habits and attitude towards password security
- Authors: Friendman, Brandon
- Date: 2014
- Subjects: Computers -- Access control -- Passwords , Computer users -- Attitudes , Internet -- Access control , Internet -- Security measures , Internet -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: vital:4700
- Description: The challenge of having to create and remember a secure password for each user account has become a problem for many computer users and can lead to bad password management practices. Simpler and less secure passwords are often selected and are regularly reused across multiple user accounts. Computer users within corporations and institutions are subject to password policies, policies which require users to create passwords of a specified length and composition and change passwords regularly. These policies often prevent users from reusing previous selected passwords. Security vendors and professionals have sought to improve or even replace password authentication. Technologies such as multi-factor authentication and single sign-on have been developed to complement or even replace password authentication. The objective of the study was to investigate the password habits of South African computer and internet users. The aim was to assess their attitudes toward password security, to determine whether password policies a↵ect the manner in which they manage their passwords and to investigate their exposure to alternate authentication technologies. The results from the online survey demonstrated that password practices of the participants across their professional and personal contexts were generally insecure. Participants often used shorter, simpler and ultimately less secure passwords. Participants would try to memorise all of their passwords or reuse the same password on most of their accounts. Many participants had not received any security awareness training, and additional security technologies (such as multi-factor authentication or password managers) were seldom used or provided to them. The password policies encountered by the participants in their organisations did little towards encouraging the users to apply more secure password practices. Users lack the knowledge and understanding about password security as they had received little or no training pertaining to it.
- Full Text:
- Date Issued: 2014
- Authors: Friendman, Brandon
- Date: 2014
- Subjects: Computers -- Access control -- Passwords , Computer users -- Attitudes , Internet -- Access control , Internet -- Security measures , Internet -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: vital:4700
- Description: The challenge of having to create and remember a secure password for each user account has become a problem for many computer users and can lead to bad password management practices. Simpler and less secure passwords are often selected and are regularly reused across multiple user accounts. Computer users within corporations and institutions are subject to password policies, policies which require users to create passwords of a specified length and composition and change passwords regularly. These policies often prevent users from reusing previous selected passwords. Security vendors and professionals have sought to improve or even replace password authentication. Technologies such as multi-factor authentication and single sign-on have been developed to complement or even replace password authentication. The objective of the study was to investigate the password habits of South African computer and internet users. The aim was to assess their attitudes toward password security, to determine whether password policies a↵ect the manner in which they manage their passwords and to investigate their exposure to alternate authentication technologies. The results from the online survey demonstrated that password practices of the participants across their professional and personal contexts were generally insecure. Participants often used shorter, simpler and ultimately less secure passwords. Participants would try to memorise all of their passwords or reuse the same password on most of their accounts. Many participants had not received any security awareness training, and additional security technologies (such as multi-factor authentication or password managers) were seldom used or provided to them. The password policies encountered by the participants in their organisations did little towards encouraging the users to apply more secure password practices. Users lack the knowledge and understanding about password security as they had received little or no training pertaining to it.
- Full Text:
- Date Issued: 2014
Adherence to antiretroviral therapy in children in Zimbabwe: a randomized control trial to validate a new self-reported adherence monitoring tool
- Authors: Mugore, Linnetie
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54734 , vital:26607
- Description: Background: Among children taking antiretroviral therapy (ART), self-reports have been widely reported to over-estimate adherence levels. Pill count adherence levels are often lower than self-reported levels, with unannounced home pill count adherence being lower than facility based pill count adherence. There is often poor agreement between pill count adherence levels and those measured using other objective adherence measuring methods such as Medication Event Monitoring Systems (MEMS®), which is widely viewed as the gold standard for adherence measurement. Objectives: The aim of this study was to design and evaluate a new self-reported paediatric adherence monitoring tool, assess the feasibility of using pill count methods in monitoring adherence and identify challenges to reporting adherence among children on ART in rural and urban Zimbabwe. Methods A dual centre, superiority, parallel design RCT was conducted to evaluate the newly-developed visually- and verbally-cued „past 10 days‟ tool for the assessment of adherence in children on ART at two sites in Zimbabwe; Harare Central Children‟s Hospital in an urban setting, and Murambinda Mission Hospital, a rural site. Child-caregiver pairs presenting to one of these facilities for the child‟s review of ART and refill of the medication were recruited, signed informed consent obtained, and were randomised for self-reported adherence monitoring into either the experimental group („new 10-day tool‟) or the control group („PACTG-style‟ self-report tool). Data (demographic, socioeconomic, and reported adherence) were collected in individual interviews with child-caregiver pairs. Additional adherence monitoring methods used for both groups included the Morisky-8-Item Medication Adherence Scale (MMAS-8) and a facility based pill count. FGDs were held with groups of caregivers and groups of children ≥13 years of age to understand reasons for non-adherence as well as issues around reporting non-adherence. Superiority testing was conducted by comparing adherent proportions and their confidence intervals (95% CI). Further concurrent validity test was done using the Mann-Whitney U test to evaluate the relationship between the new tool and the MMAS-8 scores. Agreement between the child and caregiver reports of adherence was used as a test of reliability of the new tool using the kappa statistic. Socio-demographic, clinical and care-related factors associated with adherence were identified using reported adherence in both child and caregiver groups in a logistic regression model. Two pill count methods were assessed for feasibility using the proportions of children with complete data for calculating adherence levels, and their CI and a comparison of the two methods, a routinely-used method and one that incorporated the reported residual quantity (RRQ) of medication at last refill. Results : Analysis included 245 child-caregiver pairs, 123 in the experimental group and 122 in the control group. The median age for children was 9 years. In the experimental group, adherence by caregiver and child reports ranged from 94.3% - 98.4% and 78.4% - 96.1%, and those in the control group ranged from 89.2% - 97.5% and 71.2% - 98.1%, respectively. There was no significant difference between adherence levels in the two groups. Adherence levels measured by both the experimental and control tools were found to be associated with MMAS-8 adherence levels (p <0.05). Agreement between child- and caregiver-reported adherence was moderate though significant (kappa; 0.407, p <0.05). Only about half of the children had adequate data to compute pill counts. Proportions adherent at 95% cut-off were 39% by the „routine pill count‟ and 58% by the „Pill count RRQ‟. Being an orphan was associated with child reported-adherence whereas use of non-human reminders, having a maternal relative as a primary caregiver and knowledge of dose frequency, were all associated with caregiver-reported adherence. Major causes of non-adherence mentioned during the FGDs included interference of medication administration times with scheduling of routine socio-economic activities and lack of support from some non-biological caregivers. Reporting of non-adherence appeared to be hampered by perceptions of negative reactions by healthcare workers to these reports and by caregivers being unaware that the child missed some doses. Conclusions: The „new 10-day tool‟ was not shown to be superior to the „PACTG-style tool‟ in detecting non-adherence, however this new tool was found to be a valid and reliable adherence monitoring tool that included a moderately long recall period of 10 days, can be applied without the need for the respondent to remember names of individual medicines in the
- Full Text:
- Date Issued: 2014
- Authors: Mugore, Linnetie
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54734 , vital:26607
- Description: Background: Among children taking antiretroviral therapy (ART), self-reports have been widely reported to over-estimate adherence levels. Pill count adherence levels are often lower than self-reported levels, with unannounced home pill count adherence being lower than facility based pill count adherence. There is often poor agreement between pill count adherence levels and those measured using other objective adherence measuring methods such as Medication Event Monitoring Systems (MEMS®), which is widely viewed as the gold standard for adherence measurement. Objectives: The aim of this study was to design and evaluate a new self-reported paediatric adherence monitoring tool, assess the feasibility of using pill count methods in monitoring adherence and identify challenges to reporting adherence among children on ART in rural and urban Zimbabwe. Methods A dual centre, superiority, parallel design RCT was conducted to evaluate the newly-developed visually- and verbally-cued „past 10 days‟ tool for the assessment of adherence in children on ART at two sites in Zimbabwe; Harare Central Children‟s Hospital in an urban setting, and Murambinda Mission Hospital, a rural site. Child-caregiver pairs presenting to one of these facilities for the child‟s review of ART and refill of the medication were recruited, signed informed consent obtained, and were randomised for self-reported adherence monitoring into either the experimental group („new 10-day tool‟) or the control group („PACTG-style‟ self-report tool). Data (demographic, socioeconomic, and reported adherence) were collected in individual interviews with child-caregiver pairs. Additional adherence monitoring methods used for both groups included the Morisky-8-Item Medication Adherence Scale (MMAS-8) and a facility based pill count. FGDs were held with groups of caregivers and groups of children ≥13 years of age to understand reasons for non-adherence as well as issues around reporting non-adherence. Superiority testing was conducted by comparing adherent proportions and their confidence intervals (95% CI). Further concurrent validity test was done using the Mann-Whitney U test to evaluate the relationship between the new tool and the MMAS-8 scores. Agreement between the child and caregiver reports of adherence was used as a test of reliability of the new tool using the kappa statistic. Socio-demographic, clinical and care-related factors associated with adherence were identified using reported adherence in both child and caregiver groups in a logistic regression model. Two pill count methods were assessed for feasibility using the proportions of children with complete data for calculating adherence levels, and their CI and a comparison of the two methods, a routinely-used method and one that incorporated the reported residual quantity (RRQ) of medication at last refill. Results : Analysis included 245 child-caregiver pairs, 123 in the experimental group and 122 in the control group. The median age for children was 9 years. In the experimental group, adherence by caregiver and child reports ranged from 94.3% - 98.4% and 78.4% - 96.1%, and those in the control group ranged from 89.2% - 97.5% and 71.2% - 98.1%, respectively. There was no significant difference between adherence levels in the two groups. Adherence levels measured by both the experimental and control tools were found to be associated with MMAS-8 adherence levels (p <0.05). Agreement between child- and caregiver-reported adherence was moderate though significant (kappa; 0.407, p <0.05). Only about half of the children had adequate data to compute pill counts. Proportions adherent at 95% cut-off were 39% by the „routine pill count‟ and 58% by the „Pill count RRQ‟. Being an orphan was associated with child reported-adherence whereas use of non-human reminders, having a maternal relative as a primary caregiver and knowledge of dose frequency, were all associated with caregiver-reported adherence. Major causes of non-adherence mentioned during the FGDs included interference of medication administration times with scheduling of routine socio-economic activities and lack of support from some non-biological caregivers. Reporting of non-adherence appeared to be hampered by perceptions of negative reactions by healthcare workers to these reports and by caregivers being unaware that the child missed some doses. Conclusions: The „new 10-day tool‟ was not shown to be superior to the „PACTG-style tool‟ in detecting non-adherence, however this new tool was found to be a valid and reliable adherence monitoring tool that included a moderately long recall period of 10 days, can be applied without the need for the respondent to remember names of individual medicines in the
- Full Text:
- Date Issued: 2014
Adolescent pregnancy: a community engaged participatory approach to design and implement an educational intervention
- Authors: Siruma, Amanda Tatenda
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/54656 , vital:26597
- Description: Millennium Development Goal (MDG) 5 focuses on improving maternal health, due to global acknowledgment that no woman should have to die as a result of complications during pregnancy and childbirth. Adolescents have an increased risk of maternal death compared with older women. Adolescent pregnancy also poses a threat to the empowerment of young girls by mitigating their physical, educational, social, and economic development. In this context, maternal health promotion strategies which inclusively target adolescents are crucial, not only in improving maternal health outcomes, but also in optimising the overall transition of adolescent girls to adulthood. This study was a first time collaborative partnership of the Faculty of Pharmacy and Community Engagement Office of Rhodes University with the Angus Gillis Foundation (a non-profit community development organisation), and community participants of Glenmore and Ndwayana, two rural communities in the Eastern Cape. The aim of this study was to identify the maternal health issue of most concern to community participants and to design and implement an appropriate educational intervention for a suitable target group. During the baseline phase of this study, ten focus group discussions (FGDs) were conducted with 76 community stakeholders. Semi-structured interviews (SSIs) were conducted with two Sisters-in-Charge from each Primary Health Care (PHC) facility in the study setting. Data on the stock status of World Health Organization (WHO) identified lifesaving priority medicines for women’s health was also collected at both PHCs. Thereafter, pre- and posteducational interventions SSIs with female adolescent participants were conducted. The educational intervention was followed up with the development of a booklet on reproductive health. FGD participants identified adolescent pregnancy as the maternal health issue of most concern. They also highlighted challenges in service delivery of ambulance services for expectant mothers in urgent need of transportation to a referral hospital. A majority of preintervention SSI participants indicated coercion from both younger and older men as a factor influencing early sexual debut amongst adolescent girls in their communities. Despite availability in the PHCs, challenges in accessing contraceptives were highlighted by the participants. Additionally, a number of sexually active adolescent girls defaulted on their next allocated visit to the PHC due to myths regarding use of oral and injectable contraceptives. During the educational intervention sessions, participants recognised knowledge gaps regarding reproductive health issues and the influence of peer pressure as constraining factors in preventing adolescent pregnancy. During the post-intervention phase, participants highlighted that the educational intervention of this study had provided a forum to discuss ways of preventing adolescent pregnancy. The educational booklet developed is intended to serve as a resource tool of the educational programme on prevention of adolescent pregnancy, which is expected to be incorporated into the Angus Gillis Foundation’s existing ‘Positive Health’ Programme. The results of this study show that community-based participatory research facilitated the identification of the maternal health issue of most concern to these communities. Working synergistically with key stakeholders in designing and implementing an educational intervention for preventing adolescent pregnancy provides a good foundation for future up scaling and sustainability of this educational programme.
- Full Text:
- Date Issued: 2014
- Authors: Siruma, Amanda Tatenda
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/54656 , vital:26597
- Description: Millennium Development Goal (MDG) 5 focuses on improving maternal health, due to global acknowledgment that no woman should have to die as a result of complications during pregnancy and childbirth. Adolescents have an increased risk of maternal death compared with older women. Adolescent pregnancy also poses a threat to the empowerment of young girls by mitigating their physical, educational, social, and economic development. In this context, maternal health promotion strategies which inclusively target adolescents are crucial, not only in improving maternal health outcomes, but also in optimising the overall transition of adolescent girls to adulthood. This study was a first time collaborative partnership of the Faculty of Pharmacy and Community Engagement Office of Rhodes University with the Angus Gillis Foundation (a non-profit community development organisation), and community participants of Glenmore and Ndwayana, two rural communities in the Eastern Cape. The aim of this study was to identify the maternal health issue of most concern to community participants and to design and implement an appropriate educational intervention for a suitable target group. During the baseline phase of this study, ten focus group discussions (FGDs) were conducted with 76 community stakeholders. Semi-structured interviews (SSIs) were conducted with two Sisters-in-Charge from each Primary Health Care (PHC) facility in the study setting. Data on the stock status of World Health Organization (WHO) identified lifesaving priority medicines for women’s health was also collected at both PHCs. Thereafter, pre- and posteducational interventions SSIs with female adolescent participants were conducted. The educational intervention was followed up with the development of a booklet on reproductive health. FGD participants identified adolescent pregnancy as the maternal health issue of most concern. They also highlighted challenges in service delivery of ambulance services for expectant mothers in urgent need of transportation to a referral hospital. A majority of preintervention SSI participants indicated coercion from both younger and older men as a factor influencing early sexual debut amongst adolescent girls in their communities. Despite availability in the PHCs, challenges in accessing contraceptives were highlighted by the participants. Additionally, a number of sexually active adolescent girls defaulted on their next allocated visit to the PHC due to myths regarding use of oral and injectable contraceptives. During the educational intervention sessions, participants recognised knowledge gaps regarding reproductive health issues and the influence of peer pressure as constraining factors in preventing adolescent pregnancy. During the post-intervention phase, participants highlighted that the educational intervention of this study had provided a forum to discuss ways of preventing adolescent pregnancy. The educational booklet developed is intended to serve as a resource tool of the educational programme on prevention of adolescent pregnancy, which is expected to be incorporated into the Angus Gillis Foundation’s existing ‘Positive Health’ Programme. The results of this study show that community-based participatory research facilitated the identification of the maternal health issue of most concern to these communities. Working synergistically with key stakeholders in designing and implementing an educational intervention for preventing adolescent pregnancy provides a good foundation for future up scaling and sustainability of this educational programme.
- Full Text:
- Date Issued: 2014
An electrospun nanofiber colorimetric probe for detection of Alkaline Phosphatase for diagnosis of liver toxicity
- Authors: Mohale, Mamello
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54532 , vital:26581
- Description: A novel electrospun nanofiber colorimetric probe for the detection of Alkaline Phosphatase (ALP) for diagnosis of liver toxicity was developed through electrospinning of a para nitrophenyl phosphate (pNPP) functionalised nylon polymer. The chemical stability of the enzyme substrate (pNPP) and its two products (para nitrophenol (pNP) and para nitrophenolate (pNPL)) was evaluated in biological (pH 7.4), acidic (pH 2) and alkaline (pH 9) pH, respectively. Enzyme kinetics models of Michaelis Menten (MM) and Lineweaver Burk (LB) were used to characterise free ALP. Solution and nanofiber assaying of free ALP and 10x diluted serum (spiked with ALP) was also carried out. The results demonstrated that pNPP and pNP were colourless while pNPL was yellow which indicated that all reagents were chemically stable. In addition, the chromophore of pNPL exhibited a strong molar extinction coefficient (ε) of 18,458 M-1 cm-1. LB plot being the most accurate compared to MM showed Vmax, Km and excess substrate concentration of 5.5 × 10-3 μmol/min-1, 0.025 mM and 0.25 mM respectively. Solution and nanofiber assaying of free ALP and serum confirmed a direct proportional correlation between the pNPL yellow colour intensity and enzyme activity up to 858 IU/L and 820 IU/L respectively. The dipping of the nanofiber layer into solution showed that the leaching rate of pNPP was extremely high at 1.37 × 10-3 A/min-1 as was observed after only the first 0.25 min interval. However, this was not of great concern since it was also observed that administration of the sample (20 μL) by a dropwise method minimised leaching compared to dipping. The preliminary findings on the effect of temperature on the chemical stability of pNPP indicated that it was stable below temperatures of 40°C while it hydrolysed at 80°C. Therefore a sensitive, rapid and simple colorimetric probe for the detection of ALP was developed. The probe exhibited characteristics that make it suitable to be incorporated into point of care colorimetric liver toxicity diagnostic devices for applications in resource poor settings and telemedicine.
- Full Text:
- Date Issued: 2014
- Authors: Mohale, Mamello
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54532 , vital:26581
- Description: A novel electrospun nanofiber colorimetric probe for the detection of Alkaline Phosphatase (ALP) for diagnosis of liver toxicity was developed through electrospinning of a para nitrophenyl phosphate (pNPP) functionalised nylon polymer. The chemical stability of the enzyme substrate (pNPP) and its two products (para nitrophenol (pNP) and para nitrophenolate (pNPL)) was evaluated in biological (pH 7.4), acidic (pH 2) and alkaline (pH 9) pH, respectively. Enzyme kinetics models of Michaelis Menten (MM) and Lineweaver Burk (LB) were used to characterise free ALP. Solution and nanofiber assaying of free ALP and 10x diluted serum (spiked with ALP) was also carried out. The results demonstrated that pNPP and pNP were colourless while pNPL was yellow which indicated that all reagents were chemically stable. In addition, the chromophore of pNPL exhibited a strong molar extinction coefficient (ε) of 18,458 M-1 cm-1. LB plot being the most accurate compared to MM showed Vmax, Km and excess substrate concentration of 5.5 × 10-3 μmol/min-1, 0.025 mM and 0.25 mM respectively. Solution and nanofiber assaying of free ALP and serum confirmed a direct proportional correlation between the pNPL yellow colour intensity and enzyme activity up to 858 IU/L and 820 IU/L respectively. The dipping of the nanofiber layer into solution showed that the leaching rate of pNPP was extremely high at 1.37 × 10-3 A/min-1 as was observed after only the first 0.25 min interval. However, this was not of great concern since it was also observed that administration of the sample (20 μL) by a dropwise method minimised leaching compared to dipping. The preliminary findings on the effect of temperature on the chemical stability of pNPP indicated that it was stable below temperatures of 40°C while it hydrolysed at 80°C. Therefore a sensitive, rapid and simple colorimetric probe for the detection of ALP was developed. The probe exhibited characteristics that make it suitable to be incorporated into point of care colorimetric liver toxicity diagnostic devices for applications in resource poor settings and telemedicine.
- Full Text:
- Date Issued: 2014
An investigation into the development of knowledge and strategies for the teaching of visual literacy in under-resourced Eastern Cape schools
- Authors: Mbelani, Madeyandile
- Date: 2014
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64401 , vital:28540
- Description: This thesis reports on a multiple case study PhD project that aimed to investigate meaningful and critical development of knowledge and strategies to teach visual literacy, a component of English First Additional Language (FAL) in six under-resourced schools of the Eastern Cape of South Africa. The study begins by locating visual literacy within a broad framework of literacy as a social practice, and discusses its importance. Further, it discusses complexities of making sense of and teaching visual literacy, especially for the majority of in-service teachers who experienced visual literacy neither as learners nor as teacher trainees. The gap between the curriculum and teachers’ classroom practices is what triggered this study to adopt a transformative paradigm. The main research question is, “How can teacher professional development in English Language Teaching advance in-service teachers’ knowledge of and strategies for meaningful and critical teaching and learning of visual literacy?” To respond to this question, I drew on cultural historical activity theory (CHAT) and critical realism (CR) to design four phases of this study that incorporated the seven stages of an expansive learning cycle. These phases focussed on exploring and expanding teachers’ sense making and teaching of visual literacy. I collected data through interviews, document analysis, videoed lessons and change laboratory (CL) workshops. I designed a data analysis tool that brought together CHAT, CR, multimodal social semiotics, critical discourse analysis and pedagogical discourse to make sense of the data. Through a process of reflexivity, the study illuminated layers of factors that constrained meaningful and critical teaching of visual literacy in the empirical, the actual and the real domains of reality. These factors include teachers’ unconscious reproduction of discourses of domination, their intolerance of diverse cultural discourses, resistance to curriculum change, and the fact that they are comfortable with the status quo. I brought these factors to CL workshops for expansive learning. The study contributes in-depth insight into English FAL in-service teacher development in the area of visual literacy. By locating the study within meaning making and teaching of visual literacy, it was possible to interrogate access, diversity, domination and design in teachers’ classroom practices. As a result of this study participants were made aware of the extent to which these factors enabled or hindered meaningful and critical teaching. Participants repositioned themselves as subjects of the activity system, thereby mobilising their agency to take control of the structures and cultures that condition their teaching.
- Full Text:
- Date Issued: 2014
- Authors: Mbelani, Madeyandile
- Date: 2014
- Subjects: Uncatalogued
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/64401 , vital:28540
- Description: This thesis reports on a multiple case study PhD project that aimed to investigate meaningful and critical development of knowledge and strategies to teach visual literacy, a component of English First Additional Language (FAL) in six under-resourced schools of the Eastern Cape of South Africa. The study begins by locating visual literacy within a broad framework of literacy as a social practice, and discusses its importance. Further, it discusses complexities of making sense of and teaching visual literacy, especially for the majority of in-service teachers who experienced visual literacy neither as learners nor as teacher trainees. The gap between the curriculum and teachers’ classroom practices is what triggered this study to adopt a transformative paradigm. The main research question is, “How can teacher professional development in English Language Teaching advance in-service teachers’ knowledge of and strategies for meaningful and critical teaching and learning of visual literacy?” To respond to this question, I drew on cultural historical activity theory (CHAT) and critical realism (CR) to design four phases of this study that incorporated the seven stages of an expansive learning cycle. These phases focussed on exploring and expanding teachers’ sense making and teaching of visual literacy. I collected data through interviews, document analysis, videoed lessons and change laboratory (CL) workshops. I designed a data analysis tool that brought together CHAT, CR, multimodal social semiotics, critical discourse analysis and pedagogical discourse to make sense of the data. Through a process of reflexivity, the study illuminated layers of factors that constrained meaningful and critical teaching of visual literacy in the empirical, the actual and the real domains of reality. These factors include teachers’ unconscious reproduction of discourses of domination, their intolerance of diverse cultural discourses, resistance to curriculum change, and the fact that they are comfortable with the status quo. I brought these factors to CL workshops for expansive learning. The study contributes in-depth insight into English FAL in-service teacher development in the area of visual literacy. By locating the study within meaning making and teaching of visual literacy, it was possible to interrogate access, diversity, domination and design in teachers’ classroom practices. As a result of this study participants were made aware of the extent to which these factors enabled or hindered meaningful and critical teaching. Participants repositioned themselves as subjects of the activity system, thereby mobilising their agency to take control of the structures and cultures that condition their teaching.
- Full Text:
- Date Issued: 2014
An investigation of the role of mitochondrial STAT3 and modulation of Reactive Oxygen Species in adipocyte differentiation
- Authors: Kramer, Adam Hildyard
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54632 , vital:26595
- Description: Stem cells have the ability to differentiate into a myriad of different cell types. The understanding of the differentiation process is of paramount importance if we are to use these cells in the lab as well as in therapeutics. Here, the levels and localization of the signal transducer and activator of transcription 3 (STAT3), with particular attention focused on the mitochondrial serine 727 phosphorylated form of STAT3 (pSTAT3S727) during differentiation, was investigated. Using the murine preadipocyte progenitor cell line 3T3-L1, as well as adipose derived human mesenchymal stem cells (HMSC-ad) as differentiation models, the relative levels of Reactive Oxygen Species (ROS) and the levels and localization of STAT3 were investigated during the differentiation process. ROS is known to play an important signalling role during differentiation and is well reported during the events of adipogenesis. ROS are generated as a by-product in the Electron Transport Chain (ETC), and it has recently been reported that pSTAT3S727 plays an important role at complex I of the ETC. Various techniques including fluorescence confocal microscopy, flow cytometry and Western blots were utilized to investigate the non-canonical role STAT3 plays during adipogenesis. Mitochondrial isolations were performed to investigate the levels of STAT3 in the mitochondria during differentiation. Further to this, an impedance based real time differentiation assay was developed using the xCELLigence Real Time Cell Analyser to monitor differentiation and the affects various compounds, including a STAT3 inhibitor, have on differentiation. Results indicate that upon induction of differentiation, levels of mitochondrial pSTAT3S727 dramatically decrease and leave the mitochondria. This corresponds to increasing levels of ROS. The canonical active form of STAT3 following phosphorylation on tyrosine 705 (pSTAT3Y705) was found to decrease and lose its nuclear localization. These initial results indicate that STAT3 plays an important non-canonical role in the mitochondria during differentiation.
- Full Text:
- Date Issued: 2014
- Authors: Kramer, Adam Hildyard
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54632 , vital:26595
- Description: Stem cells have the ability to differentiate into a myriad of different cell types. The understanding of the differentiation process is of paramount importance if we are to use these cells in the lab as well as in therapeutics. Here, the levels and localization of the signal transducer and activator of transcription 3 (STAT3), with particular attention focused on the mitochondrial serine 727 phosphorylated form of STAT3 (pSTAT3S727) during differentiation, was investigated. Using the murine preadipocyte progenitor cell line 3T3-L1, as well as adipose derived human mesenchymal stem cells (HMSC-ad) as differentiation models, the relative levels of Reactive Oxygen Species (ROS) and the levels and localization of STAT3 were investigated during the differentiation process. ROS is known to play an important signalling role during differentiation and is well reported during the events of adipogenesis. ROS are generated as a by-product in the Electron Transport Chain (ETC), and it has recently been reported that pSTAT3S727 plays an important role at complex I of the ETC. Various techniques including fluorescence confocal microscopy, flow cytometry and Western blots were utilized to investigate the non-canonical role STAT3 plays during adipogenesis. Mitochondrial isolations were performed to investigate the levels of STAT3 in the mitochondria during differentiation. Further to this, an impedance based real time differentiation assay was developed using the xCELLigence Real Time Cell Analyser to monitor differentiation and the affects various compounds, including a STAT3 inhibitor, have on differentiation. Results indicate that upon induction of differentiation, levels of mitochondrial pSTAT3S727 dramatically decrease and leave the mitochondria. This corresponds to increasing levels of ROS. The canonical active form of STAT3 following phosphorylation on tyrosine 705 (pSTAT3Y705) was found to decrease and lose its nuclear localization. These initial results indicate that STAT3 plays an important non-canonical role in the mitochondria during differentiation.
- Full Text:
- Date Issued: 2014
Assessing the genetic diversity of catface rockcod epinephelus andersoni in the subtropical Western Indian Ocean and modelling the effects of climate change on their distribution
- Authors: Coppinger, Christine Rose
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54499 , vital:26570
- Description: The catface rockcod Epinephelus andersoni is a range-restricted species that is endemic to the southeast coast of Africa from Quissico in Mozambique (subtropical) to Knysna in South Africa (warmtemperate). Its complex life-history, long-lived nature and high residency make E. andersoni potentially vulnerable to over-exploitation. Epinephelus andersoni is an important fishery species and has shown signs of depletion. Due to inadequate information necessary for management and conservation, further research is vital, particularly in the face of potentially significant climatic changes which could put further pressure on E. andersoni. The aim of the study was to provide information for the management of E. andersoni, with considerations for the possibly detrimental effects of future climate change. The objectives of this study were to describe the genetic structure and diversity of E. andersoni and to determine possible range shifts of E. andersoni with future changes in sea surface temperature. Genetic samples were collected throughout the distribution of E. andersoni. Standard DNA extraction and PCR using universal primers were conducted and nuclear (RPS7-1) and mitochondrial (cytochrome b) data were analysed to determine genetic diversity. A combination of nuclear and mitochondrial markers was used to ensure that the results were robust. RPS7-1 haplotype diversity was high (0.801) and an AMOVA on the RPS7-1 data showed significantly high among group variation (ΦCT = 0.204, p < 0.05) between five groups: 1. Quissico to Inhaca; 2. Cape Vidal to Port Edward; 3 Port St Johns to Coffee Bay; 4. Mbashe; 5. Port Alfred. This geographic structuring could be attributed to low gene flow across barriers such as the Port Alfred upwelling cell, the Mozambique Channel eddies and smaller more localised upwelling cells such as the Port St Johns cell. The cytochrome b results contrastingly indicate low haplotype diversity (0.309) and no differentiation (ΦCT = 0.265, p = 0.074) between groups and support the hypothesis of a historical population bottleneck. This may be due to an unusually slower mutation rate of the cytochrome b region than the RPS7-1 region, resulting in the RPS7-1 data showing a more recent picture of diversification. To complement the genetic results, niche modelling techniques were used to determine range shifts of E. andersoni with future temperature trends using species distribution and climatic data. The model illustrated a contraction of the E. andersoni distribution as well as future intensification of various upwelling cells along the south-east African coast including the Port Alfred upwelling cell. Due to the low gene flow across these barriers this intensification could decrease the resilience of E. andersoni, as its range becomes more limited with global change. The genetic data and modelling results combined provide useful information on which to base future fisheries management.
- Full Text:
- Date Issued: 2014
- Authors: Coppinger, Christine Rose
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54499 , vital:26570
- Description: The catface rockcod Epinephelus andersoni is a range-restricted species that is endemic to the southeast coast of Africa from Quissico in Mozambique (subtropical) to Knysna in South Africa (warmtemperate). Its complex life-history, long-lived nature and high residency make E. andersoni potentially vulnerable to over-exploitation. Epinephelus andersoni is an important fishery species and has shown signs of depletion. Due to inadequate information necessary for management and conservation, further research is vital, particularly in the face of potentially significant climatic changes which could put further pressure on E. andersoni. The aim of the study was to provide information for the management of E. andersoni, with considerations for the possibly detrimental effects of future climate change. The objectives of this study were to describe the genetic structure and diversity of E. andersoni and to determine possible range shifts of E. andersoni with future changes in sea surface temperature. Genetic samples were collected throughout the distribution of E. andersoni. Standard DNA extraction and PCR using universal primers were conducted and nuclear (RPS7-1) and mitochondrial (cytochrome b) data were analysed to determine genetic diversity. A combination of nuclear and mitochondrial markers was used to ensure that the results were robust. RPS7-1 haplotype diversity was high (0.801) and an AMOVA on the RPS7-1 data showed significantly high among group variation (ΦCT = 0.204, p < 0.05) between five groups: 1. Quissico to Inhaca; 2. Cape Vidal to Port Edward; 3 Port St Johns to Coffee Bay; 4. Mbashe; 5. Port Alfred. This geographic structuring could be attributed to low gene flow across barriers such as the Port Alfred upwelling cell, the Mozambique Channel eddies and smaller more localised upwelling cells such as the Port St Johns cell. The cytochrome b results contrastingly indicate low haplotype diversity (0.309) and no differentiation (ΦCT = 0.265, p = 0.074) between groups and support the hypothesis of a historical population bottleneck. This may be due to an unusually slower mutation rate of the cytochrome b region than the RPS7-1 region, resulting in the RPS7-1 data showing a more recent picture of diversification. To complement the genetic results, niche modelling techniques were used to determine range shifts of E. andersoni with future temperature trends using species distribution and climatic data. The model illustrated a contraction of the E. andersoni distribution as well as future intensification of various upwelling cells along the south-east African coast including the Port Alfred upwelling cell. Due to the low gene flow across these barriers this intensification could decrease the resilience of E. andersoni, as its range becomes more limited with global change. The genetic data and modelling results combined provide useful information on which to base future fisheries management.
- Full Text:
- Date Issued: 2014
Bacterial degradation of waste coal
- Authors: Madikiza, Lwazikazi
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54576 , vital:26590
- Description: As an energy source coal has one of the largest agglomerations in the world. Consequently mining of coal creates large volumes of waste in the form of low ranks coals. The complex structure of coal makes it difficult for the microorganisms to degrade and relatively few bacteria and fungi have been shown to break down coal. This study aimed to investigate bacteria not previously known to degrade coal. In this study bacteria were isolated from hydrocarbon contaminated sites and inoculated in coal medium where coal served as the only carbon source. Three strains produced a yellow – brown supernatant after 14 d of incubation at 30 °C. Bacteria generating a yellow – brown coloured supernatant were presumed to possess coal degrading capabilities and the best performing of these bacterial species was identified using 16s rDNA as Bacillus flexus. Scanning electron microscopy showed that there was a close association between the bacterium and substrate coal. The close association of bacteria to substrate suggested that these organisms were able to maximize solubilisation. FT-IR spectroscopic analysis demonstrated the addition of single bonded compounds COOH, OH, CN and CH that were absent prior to bacterial interaction. The increase in oxygen rich regions indicated degradation of the coal substrate. Elemental analysis showed that there was a decrease in carbon content from 47 % to 24 % during the 14 day incubation period. Reduction in coal carbon content was assumed to be due to bacterial utilization for metabolism and growth particularly as untreated coal substrate showed minimal loss of carbon. Analysis of the residual culture medium revealed that there was a linear increase in humic-like substance concentration for 8 d, coincident with increased coal biosolubilisation and colour change. Laccase activity was insignificant, and at 13 d enzyme activity was only 5×10-3 U/L suggesting that B. flexus may use a different mechanism to degrade coal. Residual culture medium remaining after bacterial action on the coal substrate appeared to possess plant growth promoting activity. This soluble biodegradation product with characteristics similar to humic acid-like substances was shown to impact growth of radish cotyledons. Expansion of isolated radish cotyledons was enhanced by 140% when incubated in coal biodegradation product. In conclusion, this study has yielded B. flexus and two other unidentified bacteria, isolated from polyaromatic hydrocarbon contaminated soils, and demonstrated the ability of these microorganisms to degrade waste coal. Further studies to elucidate the mechanism of coal breakdown by B. flexus, synergies with other coal degrading microorganisms, and incorporation of bacterium into Fungcoal bioprocess technology is imminent.
- Full Text:
- Date Issued: 2014
- Authors: Madikiza, Lwazikazi
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54576 , vital:26590
- Description: As an energy source coal has one of the largest agglomerations in the world. Consequently mining of coal creates large volumes of waste in the form of low ranks coals. The complex structure of coal makes it difficult for the microorganisms to degrade and relatively few bacteria and fungi have been shown to break down coal. This study aimed to investigate bacteria not previously known to degrade coal. In this study bacteria were isolated from hydrocarbon contaminated sites and inoculated in coal medium where coal served as the only carbon source. Three strains produced a yellow – brown supernatant after 14 d of incubation at 30 °C. Bacteria generating a yellow – brown coloured supernatant were presumed to possess coal degrading capabilities and the best performing of these bacterial species was identified using 16s rDNA as Bacillus flexus. Scanning electron microscopy showed that there was a close association between the bacterium and substrate coal. The close association of bacteria to substrate suggested that these organisms were able to maximize solubilisation. FT-IR spectroscopic analysis demonstrated the addition of single bonded compounds COOH, OH, CN and CH that were absent prior to bacterial interaction. The increase in oxygen rich regions indicated degradation of the coal substrate. Elemental analysis showed that there was a decrease in carbon content from 47 % to 24 % during the 14 day incubation period. Reduction in coal carbon content was assumed to be due to bacterial utilization for metabolism and growth particularly as untreated coal substrate showed minimal loss of carbon. Analysis of the residual culture medium revealed that there was a linear increase in humic-like substance concentration for 8 d, coincident with increased coal biosolubilisation and colour change. Laccase activity was insignificant, and at 13 d enzyme activity was only 5×10-3 U/L suggesting that B. flexus may use a different mechanism to degrade coal. Residual culture medium remaining after bacterial action on the coal substrate appeared to possess plant growth promoting activity. This soluble biodegradation product with characteristics similar to humic acid-like substances was shown to impact growth of radish cotyledons. Expansion of isolated radish cotyledons was enhanced by 140% when incubated in coal biodegradation product. In conclusion, this study has yielded B. flexus and two other unidentified bacteria, isolated from polyaromatic hydrocarbon contaminated soils, and demonstrated the ability of these microorganisms to degrade waste coal. Further studies to elucidate the mechanism of coal breakdown by B. flexus, synergies with other coal degrading microorganisms, and incorporation of bacterium into Fungcoal bioprocess technology is imminent.
- Full Text:
- Date Issued: 2014
Characterization and application of phthalocyanine-magnetic nanoparticle conjugates anchored to electrospun polyamide nanofibers
- Authors: Ledwaba, Mpho
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54610 , vital:26593
- Description: This work presents the syntheses, photophysical and photochemical characterization of zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc, 3) and its gadolinium oxide nanoparticle conjugate (4). By means of spectroscopic and microscopic characterization, the conjugation of the ZnTCPPc to the silica coated gadolinium oxide nanoparticles (Si-Gd2O3 NPs, 2) through an amide bond was confirmed. The thermal stability, morphology, nanoparticle sizes and their conjugates with the Pc were studied using ThermoGravimetric Analysis (TGA), Fourier Transform Infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and powder X-ray diffractometry (XRD). Conjugation of ZnTCPPc to the magnetic nanoparticles, proved to have a negligible effect on the photophysical parameters of the phthalocyanine, where a slight decrease in fluorescence and triplet quantum yields and lifetimes was observed. The singlet oxygen quantum yield, however, increased slightly upon conjugation, suggesting that the overall efficiency of the ZnTCPPc as a photosensitizer had improved. Physical mixing of the ZnTCPPc and the silica-coated gadolinium nanoparticles also showed an improvement in the singlet oxygen quantum yield and triplet lifetime, also showing an enhanced efficiency for the photosensitizer and therefore photocatalysis. ZnTCPPc (3) alone and the Pc-gadolinium oxide nanoparticle conjugate (4) were therefore electrospun into nanofibers to create a solid support. The fibers were characterized and their diameter sizes and composition was studied confirming the incorporation of the phthalocyanine and gadolinium oxide nanoparticle. Increased singlet oxygen generation resulted in increased Photodegradation of the environmental pollutant Orange G and the fibers were found to be more efficient as photocatalysts compared to the photosensitizer in solution. The nanomaterial may therefore be applied to the photodegradation of Orange G.
- Full Text:
- Date Issued: 2014
- Authors: Ledwaba, Mpho
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54610 , vital:26593
- Description: This work presents the syntheses, photophysical and photochemical characterization of zinc tetracarboxyphenoxy phthalocyanine (ZnTCPPc, 3) and its gadolinium oxide nanoparticle conjugate (4). By means of spectroscopic and microscopic characterization, the conjugation of the ZnTCPPc to the silica coated gadolinium oxide nanoparticles (Si-Gd2O3 NPs, 2) through an amide bond was confirmed. The thermal stability, morphology, nanoparticle sizes and their conjugates with the Pc were studied using ThermoGravimetric Analysis (TGA), Fourier Transform Infrared spectroscopy (FTIR), Transmission Electron Microscopy (TEM) and powder X-ray diffractometry (XRD). Conjugation of ZnTCPPc to the magnetic nanoparticles, proved to have a negligible effect on the photophysical parameters of the phthalocyanine, where a slight decrease in fluorescence and triplet quantum yields and lifetimes was observed. The singlet oxygen quantum yield, however, increased slightly upon conjugation, suggesting that the overall efficiency of the ZnTCPPc as a photosensitizer had improved. Physical mixing of the ZnTCPPc and the silica-coated gadolinium nanoparticles also showed an improvement in the singlet oxygen quantum yield and triplet lifetime, also showing an enhanced efficiency for the photosensitizer and therefore photocatalysis. ZnTCPPc (3) alone and the Pc-gadolinium oxide nanoparticle conjugate (4) were therefore electrospun into nanofibers to create a solid support. The fibers were characterized and their diameter sizes and composition was studied confirming the incorporation of the phthalocyanine and gadolinium oxide nanoparticle. Increased singlet oxygen generation resulted in increased Photodegradation of the environmental pollutant Orange G and the fibers were found to be more efficient as photocatalysts compared to the photosensitizer in solution. The nanomaterial may therefore be applied to the photodegradation of Orange G.
- Full Text:
- Date Issued: 2014
Dangerous people and places : a community newspaper's constructions of crime
- Authors: Raymond, Leigh Alice
- Date: 2014
- Subjects: Grocott's Mail (Grahamstown, South Africa) , Community newspapers -- South Africa -- Grahamstown , Crime and the press -- South Africa -- Grahamstown , Newspapers -- Objectivity , Mass media policy -- South Africa -- Grahamstown , Social responsibility of business -- South Africa -- Grahamstown , Police and the press -- South Africa -- Grahamstown
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:3527 , http://hdl.handle.net/10962/d1013091
- Description: This thesis argues that there is a clear imbalance in the representation of crime in the newspaper, Grocott’s Mail, in Grahamstown, in the Eastern Cape of South Africa. The thesis concludes that the system of marginalisation and segregation which was established during the apartheid era is the foundation for the continued segregation and marginalisation of certain groups of people in Grahamstown as depicted in crime journalism. Previous research shows that not only people, but spaces are marginalised through media representations of crime. As people are represented as dangerous, so too the spaces they occupy become dangerous spaces. Importantly, the research shows that discourses of marginalisation are present in newspaper reports reproducing the discourses prominent in society, and in turn, the newspaper itself perpetuates these marginalising discourses. This extends into the coverage that different crimes receive in newspapers. For instance, the reports show that a middle-class audience will be more concerned with property crime in middle-class neighbourhoods, than other crimes in lower-class neighbourhoods. I argue that not only the type of crime, but the severity, the effect, and the necessity for justice represented by the newspaper, are all largely determined by the region of the crime. Further, I show that the criminal is not only demonised and represented as individually deviant in the reports in the newspaper, but that these representations are made by this newspaper because they are deeply imbedded as a discourse in society. This is partly because this newspaper has taken on a monitorial role, requiring neutral reporting from journalists, and a dedication to surveying the processes of state institutions, like the police and courts. As a result, the ways in which crime is reported on in the newspaper is fairly well fixed, making it difficult for journalists to conceive of different ways of reporting crime. The representations of the criminal justice system that the monitorial media, this newspaper included present, are a careful balance between the interest of the public, and the need to preserve relationships with sources. The monitorial media in general, and this newspaper in particular, represent the criminal justice system. The relationship between the police and the newspaper, and the courts and the media, therefore strongly influences the way in which crime news is reported. In particular, crime news is represented from the perspective of the criminal justice system. This research was carried out using Critical Discourse Analysis, qualitative interviews, and focus group interviews.
- Full Text:
- Date Issued: 2014
- Authors: Raymond, Leigh Alice
- Date: 2014
- Subjects: Grocott's Mail (Grahamstown, South Africa) , Community newspapers -- South Africa -- Grahamstown , Crime and the press -- South Africa -- Grahamstown , Newspapers -- Objectivity , Mass media policy -- South Africa -- Grahamstown , Social responsibility of business -- South Africa -- Grahamstown , Police and the press -- South Africa -- Grahamstown
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: vital:3527 , http://hdl.handle.net/10962/d1013091
- Description: This thesis argues that there is a clear imbalance in the representation of crime in the newspaper, Grocott’s Mail, in Grahamstown, in the Eastern Cape of South Africa. The thesis concludes that the system of marginalisation and segregation which was established during the apartheid era is the foundation for the continued segregation and marginalisation of certain groups of people in Grahamstown as depicted in crime journalism. Previous research shows that not only people, but spaces are marginalised through media representations of crime. As people are represented as dangerous, so too the spaces they occupy become dangerous spaces. Importantly, the research shows that discourses of marginalisation are present in newspaper reports reproducing the discourses prominent in society, and in turn, the newspaper itself perpetuates these marginalising discourses. This extends into the coverage that different crimes receive in newspapers. For instance, the reports show that a middle-class audience will be more concerned with property crime in middle-class neighbourhoods, than other crimes in lower-class neighbourhoods. I argue that not only the type of crime, but the severity, the effect, and the necessity for justice represented by the newspaper, are all largely determined by the region of the crime. Further, I show that the criminal is not only demonised and represented as individually deviant in the reports in the newspaper, but that these representations are made by this newspaper because they are deeply imbedded as a discourse in society. This is partly because this newspaper has taken on a monitorial role, requiring neutral reporting from journalists, and a dedication to surveying the processes of state institutions, like the police and courts. As a result, the ways in which crime is reported on in the newspaper is fairly well fixed, making it difficult for journalists to conceive of different ways of reporting crime. The representations of the criminal justice system that the monitorial media, this newspaper included present, are a careful balance between the interest of the public, and the need to preserve relationships with sources. The monitorial media in general, and this newspaper in particular, represent the criminal justice system. The relationship between the police and the newspaper, and the courts and the media, therefore strongly influences the way in which crime news is reported. In particular, crime news is represented from the perspective of the criminal justice system. This research was carried out using Critical Discourse Analysis, qualitative interviews, and focus group interviews.
- Full Text:
- Date Issued: 2014
Development and assessment of sustained release stavudine loaded microparticles
- Authors: Zindove, Chiedza Cathrine
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/54722 , vital:26603
- Description:
Stavudine (D4T) has been used as first line treatment for HIV/AIDS and is part of highly active anti retroviral treatment (HAART). It is an affordable medicine and its use is beneficial in resource limited settings. However D4T exhibits dose dependent side effects that may lead to non-adherence in patients. This study was undertaken to formulate, develop and manufacture a dosage form that could reduce dose dependent side effects by decreasing the dose of D4T but still exhibit antiretroviral (ARV) activity. The use of sustained release (SR) formulations of D4T that ensure constant levels of the D4T in the body would not only optimize therapy but also reduce the incidence of side effects thereby increasing patient adherence. SR microparticles containing 30mg D4T were manufactured and loaded into size 3 hard gelatine capsules prior to analysis. The D4T microparticles were manufactured by microencapsulation using non-aqueous oil-in-oil solvent evaporation approach. D4T-excipient, excipient-excipient interactions and D4T purity were assessed using Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Copolymers synthesized from acrylic and methacrylic acid esters viz., Eudragit® RSPO and S100 were used as rate retardant materials and the effect of microcrystalline cellulose (Avicel® PH102) on the microparticles was also investigated. Magnesium stearate was used as a droplet stabilizer and n-hexane was added to harden the microspheres formed in a liquid paraffin continuous phase. The microparticles were optimized using a Box Behnken design and Response Surface Methodology (RSM). The microparticles were characterized in terms of their flow properties and encapsulation efficiency (% EE), in addition to visualization of the surface morphology with Scanning Electron Microscopy. In vitro D4T release studies were performed using USP Apparatus III in media of different pH and the samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection that had been developed and optimized using a Central Composite Design (CCD). The method was validated according to ICH guidelines. The IR spectra and DSC thermographs revealed that D4T exhibited thermal stability and there was no evidence of D4T-excipient and excipient-excipient interactions. The microparticles that were produced were white, free flowing and were obtained in a high yield with high encapsulation efficiency. Scanning Electron Microscopy studies revealed that the microparticles were spherical and porous in nature. In vitro D4T release extended to 12 hours and the mechanism of release was established using model dependent methods by fitting the data to a Zero order, First order, Higuchi and Hixson Crowell model. It was observed that the mechanism of D4T release was diffusion-controlled and that the data was best fitted to the Higuchi model with correlation coefficients > 0.9. The release mechanism was confirmed using the Korsmeyer-Peppas model that revealed that most of the formulations exhibited anomalous transport kinetics with the release exponent, n, ranging from 0.5
- Full Text:
- Date Issued: 2014
- Authors: Zindove, Chiedza Cathrine
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/54722 , vital:26603
- Description:
Stavudine (D4T) has been used as first line treatment for HIV/AIDS and is part of highly active anti retroviral treatment (HAART). It is an affordable medicine and its use is beneficial in resource limited settings. However D4T exhibits dose dependent side effects that may lead to non-adherence in patients. This study was undertaken to formulate, develop and manufacture a dosage form that could reduce dose dependent side effects by decreasing the dose of D4T but still exhibit antiretroviral (ARV) activity. The use of sustained release (SR) formulations of D4T that ensure constant levels of the D4T in the body would not only optimize therapy but also reduce the incidence of side effects thereby increasing patient adherence. SR microparticles containing 30mg D4T were manufactured and loaded into size 3 hard gelatine capsules prior to analysis. The D4T microparticles were manufactured by microencapsulation using non-aqueous oil-in-oil solvent evaporation approach. D4T-excipient, excipient-excipient interactions and D4T purity were assessed using Infrared Spectroscopy (IR), Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Copolymers synthesized from acrylic and methacrylic acid esters viz., Eudragit® RSPO and S100 were used as rate retardant materials and the effect of microcrystalline cellulose (Avicel® PH102) on the microparticles was also investigated. Magnesium stearate was used as a droplet stabilizer and n-hexane was added to harden the microspheres formed in a liquid paraffin continuous phase. The microparticles were optimized using a Box Behnken design and Response Surface Methodology (RSM). The microparticles were characterized in terms of their flow properties and encapsulation efficiency (% EE), in addition to visualization of the surface morphology with Scanning Electron Microscopy. In vitro D4T release studies were performed using USP Apparatus III in media of different pH and the samples were analysed using a validated High Performance Liquid Chromatographic (HPLC) method with ultraviolet (UV) detection that had been developed and optimized using a Central Composite Design (CCD). The method was validated according to ICH guidelines. The IR spectra and DSC thermographs revealed that D4T exhibited thermal stability and there was no evidence of D4T-excipient and excipient-excipient interactions. The microparticles that were produced were white, free flowing and were obtained in a high yield with high encapsulation efficiency. Scanning Electron Microscopy studies revealed that the microparticles were spherical and porous in nature. In vitro D4T release extended to 12 hours and the mechanism of release was established using model dependent methods by fitting the data to a Zero order, First order, Higuchi and Hixson Crowell model. It was observed that the mechanism of D4T release was diffusion-controlled and that the data was best fitted to the Higuchi model with correlation coefficients > 0.9. The release mechanism was confirmed using the Korsmeyer-Peppas model that revealed that most of the formulations exhibited anomalous transport kinetics with the release exponent, n, ranging from 0.5
- Full Text:
- Date Issued: 2014
Development of styrene based imprinted sorbents for selective clean-up of metalloporphyrins in organic media
- Authors: Awokoya, Kehinde Nurudeen
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54521 , vital:26580
- Description: Most crude oils contain traces of vanadium and nickel complex with porphyrins (VTPP and NTPP) within their asphaltene fraction. Although these metals are only present in trace quantities, they have a significant and detrimental impact on the refining process by degrading the quality of intermediate and end products. Therefore, their selective removal is highly desirable. This thesis presents the development of nickel porphyrin, nickel vanadyl porphyrin imprinted nanofibers and vanadyl porphyrin imprinted polymer (MIP) particles for application as selective sorbents. Computational model based on the combination of molecular dynamics simulations and quantum mechanics was successfully applied to the styrene functional monomer selection. The particle was prepared by bulk polymerization and the nanofibers by a novel approach combining molecular imprinting and electrospinning technology. The morphologies, thermal stabilities and porosities of the imprinted sorbents were studied using SEM, TGA, and BET nitrogen gas adsorption. Chloroform was found to swell the polymer particles to a higher degree than methanol and acetonitrile. The adsorption characteristics of the imprinted sorbents best fitted with Freundlich isotherm model. The imprinted sorbents recorded high extraction efficiencies (EEs) of > 99 % in selectively extracting the metalloporphyrins. The impact of the template on the affinity of recognition for NTPP was evaluated. The results showed that the NTPP adsorption capacity increased as the molar ratio of NTPP to styrene was increased from 1:1 to 3:1. The optimal ratio of template to functional monomer which yielded the best specific affinity and highest recovery (99.9 %) was 3:1. The effects of trifluoroacetic acid (TFA), dichloromethane (DCM), dimethyl sulphoxide (DMSO), pentane (PEN) on electro-spinnability of the polymer solutions and the morphological appearance of the nanofibers were investigated. The imprinted nanofibers exhibited the same selectivity specialism for both NTPP and VTPP. A remarkable stability in relation to reusability was observed when imprinted nanofibers were used, as they could be reused nine times without incurring any significant loss in removal efficiency. The results were validated by analysing a certified reference material. The imprinted sorbents were therefore found to be selective sorbents that are well suited for handling trace metals in organic media.
- Full Text:
- Date Issued: 2014
- Authors: Awokoya, Kehinde Nurudeen
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54521 , vital:26580
- Description: Most crude oils contain traces of vanadium and nickel complex with porphyrins (VTPP and NTPP) within their asphaltene fraction. Although these metals are only present in trace quantities, they have a significant and detrimental impact on the refining process by degrading the quality of intermediate and end products. Therefore, their selective removal is highly desirable. This thesis presents the development of nickel porphyrin, nickel vanadyl porphyrin imprinted nanofibers and vanadyl porphyrin imprinted polymer (MIP) particles for application as selective sorbents. Computational model based on the combination of molecular dynamics simulations and quantum mechanics was successfully applied to the styrene functional monomer selection. The particle was prepared by bulk polymerization and the nanofibers by a novel approach combining molecular imprinting and electrospinning technology. The morphologies, thermal stabilities and porosities of the imprinted sorbents were studied using SEM, TGA, and BET nitrogen gas adsorption. Chloroform was found to swell the polymer particles to a higher degree than methanol and acetonitrile. The adsorption characteristics of the imprinted sorbents best fitted with Freundlich isotherm model. The imprinted sorbents recorded high extraction efficiencies (EEs) of > 99 % in selectively extracting the metalloporphyrins. The impact of the template on the affinity of recognition for NTPP was evaluated. The results showed that the NTPP adsorption capacity increased as the molar ratio of NTPP to styrene was increased from 1:1 to 3:1. The optimal ratio of template to functional monomer which yielded the best specific affinity and highest recovery (99.9 %) was 3:1. The effects of trifluoroacetic acid (TFA), dichloromethane (DCM), dimethyl sulphoxide (DMSO), pentane (PEN) on electro-spinnability of the polymer solutions and the morphological appearance of the nanofibers were investigated. The imprinted nanofibers exhibited the same selectivity specialism for both NTPP and VTPP. A remarkable stability in relation to reusability was observed when imprinted nanofibers were used, as they could be reused nine times without incurring any significant loss in removal efficiency. The results were validated by analysing a certified reference material. The imprinted sorbents were therefore found to be selective sorbents that are well suited for handling trace metals in organic media.
- Full Text:
- Date Issued: 2014
Ecological consequences of non-native fish invasion in Eastern Cape headwater streams
- Authors: Ellender, Bruce Robert
- Date: 2014
- Subjects: Fishery management -- South Africa -- Eastern Cape Fishes -- Conservation -- South Africa Introduced fishes -- South Africa -- Eastern Cape Introduced organisms
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/69065 , vital:29380
- Description: The introduction, spread and concomitant impacts of non-native species are a global problem. Fish are among the most widely introduced vertebrate groups, with their impacts affecting multiple levels of organisation- from individuals, populations and communities, to entire ecosystems. In South Africa, the largest perceived threat to range-restricted endemic headwater stream fishes is said to be invasion by non-native fishes, however, as is the case elsewhere, invasive impacts are often a case of risk perception rather than actual risk analysis. Two range-restricted headwater species, the Eastern Cape redfin Pseudobarbus afer and the Border barb Barbus trevelyani are redlisted by the International Union for the Conservation of Nature (IUCN) as ‘Endangered’, primarily due to invasion by non-native fishes. To investigate invasions in South Africa, and provide a quantitative estimate of the impact of non-native fishes on the two imperilled endemics, P. afer and B. trevelyani, the overall aims of this thesis were to: (A) Provide a literature review on non-native fish invasions in South Africa; (B) Using two case studies on the headwaters of the perennial Keiskamma and episodic Swartkops River systems, investigate the naturalisation-invasion continuum to provide a holistic view of the invasion process in these variable environments. The specific thesis objectives were: (1) Reviewing current knowledge of invasive impacts of non-native fishes in South Africa; (2) Investigating invasibility of headwater stream environments by non-native fishes; (3) Determining the establishment success of non-native fishes, (4) Assessing the spatial and temporal impacts of invasion; (5) Understanding mechanisms responsible for non-native fish impacts; (6) Investigating the threat of non-native fish invasion on the genetic diversity of two the two headwater fishes, P. afer and B. trevelyani. Results from the literature review of fish invasions (Chapter 1) showed that South Africa has a long history of non-native fish introductions, spanning two and a half centuries. Currently, 55 species have been introduced or translocated. Many of these introduced species have become fully invasive (36%). Their impacts also span multiple levels of biological organisation. There was a general paucity of studies on fish invasions (38 studies), however, of those conducted, reviewed studies placed emphases on invasive impacts (25 studies) and the transport, introduction, establishment and spread stages of the invasion process were largely ignored. The two study systems, the Swartkops and Keiskamma Rivers, were heavily invaded and numbers of introduced species surpassed that of natives (Chapter 2, 3 and 5). Headwater streams had varying invasibility and a number of non-native species were successfully established (Chapter 2, 3, 5 and 6). The remainder of the invasions were casual incursions into headwater streams from source populations in mainstream and impoundment environments which were invasion hotspots. Irrespective of establishment, four predatory invaders (largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss) impacted heavily on native fish communities (Chapter 3, 4 and 5). Two broad types of invasion were documented, top down invasion by non-native O. mykiss and S. trutta and upstream invasion by M. salmoides and M. dolomieu (Chapter 3 and 5). Their impacts included changes in community structure, extirpation from invaded stream reaches resulting in contracted distribution, and isolation and fragmentation of native fish populations. The impacts of non-native predatory fishes were particularly acute for P. afer and B. trevelyani. Where non-native predatory fish occurred, P. afer and B. trevelyani had been extirpated (Chapter 3 and 5). As a result both native species exhibited contracted distributions (>20% habitat loss due to invasion). Upstream invasion by centrarchids isolated and fragmented P. afer populations into headwater refugia, while top down invasion by salmonids excluded B. trevelyani from invaded, more pristine stream reaches, by forcing the species into degraded unsuitable lower stream reaches. Predation also disrupted population processes such as adult dispersal for P. afer, and centrarchid-invaded zones acted as demographic sinks, where adults dispersing through invaded reaches were rapidly depleted. While the Mandela lineage of P. afer exhibited little within or between drainage genetic structuring, B. trevelyani was >4% divergent between drainages, and up to 2% divergent between streams within the Keiskamma River system (Chapter 7). The distribution of genetic diversity for B. trevelyani also indicated that the loss of diversity was imminent without immediate conservation interventions. This thesis has provided conclusive evidence that native fishes are vulnerable to invasion and that non-native predatory fishes have significant impacts on native fishes in Eastern Cape headwater streams. If management and conservation measures are implemented, the unwanted introduction and spread of non-native fishes may be restricted, allowing native fishes opportunities for recovery.
- Full Text:
- Date Issued: 2014
- Authors: Ellender, Bruce Robert
- Date: 2014
- Subjects: Fishery management -- South Africa -- Eastern Cape Fishes -- Conservation -- South Africa Introduced fishes -- South Africa -- Eastern Cape Introduced organisms
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/69065 , vital:29380
- Description: The introduction, spread and concomitant impacts of non-native species are a global problem. Fish are among the most widely introduced vertebrate groups, with their impacts affecting multiple levels of organisation- from individuals, populations and communities, to entire ecosystems. In South Africa, the largest perceived threat to range-restricted endemic headwater stream fishes is said to be invasion by non-native fishes, however, as is the case elsewhere, invasive impacts are often a case of risk perception rather than actual risk analysis. Two range-restricted headwater species, the Eastern Cape redfin Pseudobarbus afer and the Border barb Barbus trevelyani are redlisted by the International Union for the Conservation of Nature (IUCN) as ‘Endangered’, primarily due to invasion by non-native fishes. To investigate invasions in South Africa, and provide a quantitative estimate of the impact of non-native fishes on the two imperilled endemics, P. afer and B. trevelyani, the overall aims of this thesis were to: (A) Provide a literature review on non-native fish invasions in South Africa; (B) Using two case studies on the headwaters of the perennial Keiskamma and episodic Swartkops River systems, investigate the naturalisation-invasion continuum to provide a holistic view of the invasion process in these variable environments. The specific thesis objectives were: (1) Reviewing current knowledge of invasive impacts of non-native fishes in South Africa; (2) Investigating invasibility of headwater stream environments by non-native fishes; (3) Determining the establishment success of non-native fishes, (4) Assessing the spatial and temporal impacts of invasion; (5) Understanding mechanisms responsible for non-native fish impacts; (6) Investigating the threat of non-native fish invasion on the genetic diversity of two the two headwater fishes, P. afer and B. trevelyani. Results from the literature review of fish invasions (Chapter 1) showed that South Africa has a long history of non-native fish introductions, spanning two and a half centuries. Currently, 55 species have been introduced or translocated. Many of these introduced species have become fully invasive (36%). Their impacts also span multiple levels of biological organisation. There was a general paucity of studies on fish invasions (38 studies), however, of those conducted, reviewed studies placed emphases on invasive impacts (25 studies) and the transport, introduction, establishment and spread stages of the invasion process were largely ignored. The two study systems, the Swartkops and Keiskamma Rivers, were heavily invaded and numbers of introduced species surpassed that of natives (Chapter 2, 3 and 5). Headwater streams had varying invasibility and a number of non-native species were successfully established (Chapter 2, 3, 5 and 6). The remainder of the invasions were casual incursions into headwater streams from source populations in mainstream and impoundment environments which were invasion hotspots. Irrespective of establishment, four predatory invaders (largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss) impacted heavily on native fish communities (Chapter 3, 4 and 5). Two broad types of invasion were documented, top down invasion by non-native O. mykiss and S. trutta and upstream invasion by M. salmoides and M. dolomieu (Chapter 3 and 5). Their impacts included changes in community structure, extirpation from invaded stream reaches resulting in contracted distribution, and isolation and fragmentation of native fish populations. The impacts of non-native predatory fishes were particularly acute for P. afer and B. trevelyani. Where non-native predatory fish occurred, P. afer and B. trevelyani had been extirpated (Chapter 3 and 5). As a result both native species exhibited contracted distributions (>20% habitat loss due to invasion). Upstream invasion by centrarchids isolated and fragmented P. afer populations into headwater refugia, while top down invasion by salmonids excluded B. trevelyani from invaded, more pristine stream reaches, by forcing the species into degraded unsuitable lower stream reaches. Predation also disrupted population processes such as adult dispersal for P. afer, and centrarchid-invaded zones acted as demographic sinks, where adults dispersing through invaded reaches were rapidly depleted. While the Mandela lineage of P. afer exhibited little within or between drainage genetic structuring, B. trevelyani was >4% divergent between drainages, and up to 2% divergent between streams within the Keiskamma River system (Chapter 7). The distribution of genetic diversity for B. trevelyani also indicated that the loss of diversity was imminent without immediate conservation interventions. This thesis has provided conclusive evidence that native fishes are vulnerable to invasion and that non-native predatory fishes have significant impacts on native fishes in Eastern Cape headwater streams. If management and conservation measures are implemented, the unwanted introduction and spread of non-native fishes may be restricted, allowing native fishes opportunities for recovery.
- Full Text:
- Date Issued: 2014
Electrospun fiber based colorimetric probes for aspartate aminotransferase and I7ß-estradiol
- Authors: Pule, Bellah Oreeditse
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54869 , vital:26623
- Description: Fabrication, characterization and application of electrospun polymer composite based colorimetric probes are presented in this thesis. The first part of the thesis involved the development of a protocol for in situ reduction of gold trication (Au³+) into metallic gold atoms with sodium borohydride. The prepared PS-Au NPs showed an SPR band at 542 nm. Furthermore the absorbance of the colloidal Au NPs in polystyrene exhibited a good linear correlation (r2 = 0.9934) to E2 concentration in the range 5 to 50 ppb. The lowest naked eye detection limit was found to be 0.5 ppb and could further be easily monitored by UV-vis spectrophotometer. Upon interaction with E2 Au NPs aggregated to give nanoparticle clusters, confirmed through TEM analysis. Different concentrations of Au NPs were found to have a significant effect on the conductivity of the PS-Au NPs solution. At low concentrations of Au NPs (0.002, 0.015 and 0.025% w/v) PS-Au NPs solution could be electrospun without clogging. The FE-SEM images showed a non-beaded morphology of PS-Au NPs composite fibers. Upon interaction of the colorimetric probe strips with various E2 concentrations it was observed that with increasing E2 concentrations (50 ng/ml to 1000 µg/ml) the colour of the probe changed gradually from white to shades of pink and eventually to shades of blue at higher E2 concentrations. The visible cut-off concentration was 100 ng/ml. The second component of the thesis focussed on the development of diazonium dye-nylon 6 colorimetric probe for aspartate aminotransferase. At optimal pH 7.4 the enzyme was stable, highly active and catalyzed a reaction that was susceptible to detailed kinetic analysis by continuous optical methods. The KM values for L-aspartate, a- ketoglutarate and oxaloacetate were 2.60, 0.59 and 0.066 mM, respectively. On the basis of these KM values the solid-state colorimetric probe was developed. A colour change occurred when an electrospun dye-N 6 probes were exposed to visibly detectable concentrations of oxaloacetate, an AST-catalyzed reaction product. While monitoring AST activity at 530 run, a linear relation was obtained between oxaloacetate concentrations ranging from 0.4 - 7.4 µg/ml. Naked eye detection limit of 2.4 µg/ml oxalaoacetate equivalence of 10 times the normal AST activity was attained. The colorimetric probe was in addition, tested against co-substrates aspartate, ketoglutarate and a variety of other compounds such as alanine, pryruvate, as well as glutamic, malaic and succinic acids known to interfere with AST activity. Each compound elicited a distinct and unambiguous colour change upon interaction with the colorimetric probe. Further X-ray powder diffraction (XRD), duNouy ring tensiometer, Brunauer- Emmett- Teller (BET) and energy dispersive X-ray spectroscopy (EDS/EDX) characterization confirmed composition and stability of the colorimetric probes. Colorimetric probes developed in this thesis are relatively cost effective, simple and "rugged" for measurement of analytes with visual detection without sample pretreatment in matrices, such as plasma and dairy effluents. The probes warrant further investigation as they have shown potential and offer a promising solid-state platform for both clinical diagnostics and environmental monitoring.
- Full Text:
- Date Issued: 2014
- Authors: Pule, Bellah Oreeditse
- Date: 2014
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/54869 , vital:26623
- Description: Fabrication, characterization and application of electrospun polymer composite based colorimetric probes are presented in this thesis. The first part of the thesis involved the development of a protocol for in situ reduction of gold trication (Au³+) into metallic gold atoms with sodium borohydride. The prepared PS-Au NPs showed an SPR band at 542 nm. Furthermore the absorbance of the colloidal Au NPs in polystyrene exhibited a good linear correlation (r2 = 0.9934) to E2 concentration in the range 5 to 50 ppb. The lowest naked eye detection limit was found to be 0.5 ppb and could further be easily monitored by UV-vis spectrophotometer. Upon interaction with E2 Au NPs aggregated to give nanoparticle clusters, confirmed through TEM analysis. Different concentrations of Au NPs were found to have a significant effect on the conductivity of the PS-Au NPs solution. At low concentrations of Au NPs (0.002, 0.015 and 0.025% w/v) PS-Au NPs solution could be electrospun without clogging. The FE-SEM images showed a non-beaded morphology of PS-Au NPs composite fibers. Upon interaction of the colorimetric probe strips with various E2 concentrations it was observed that with increasing E2 concentrations (50 ng/ml to 1000 µg/ml) the colour of the probe changed gradually from white to shades of pink and eventually to shades of blue at higher E2 concentrations. The visible cut-off concentration was 100 ng/ml. The second component of the thesis focussed on the development of diazonium dye-nylon 6 colorimetric probe for aspartate aminotransferase. At optimal pH 7.4 the enzyme was stable, highly active and catalyzed a reaction that was susceptible to detailed kinetic analysis by continuous optical methods. The KM values for L-aspartate, a- ketoglutarate and oxaloacetate were 2.60, 0.59 and 0.066 mM, respectively. On the basis of these KM values the solid-state colorimetric probe was developed. A colour change occurred when an electrospun dye-N 6 probes were exposed to visibly detectable concentrations of oxaloacetate, an AST-catalyzed reaction product. While monitoring AST activity at 530 run, a linear relation was obtained between oxaloacetate concentrations ranging from 0.4 - 7.4 µg/ml. Naked eye detection limit of 2.4 µg/ml oxalaoacetate equivalence of 10 times the normal AST activity was attained. The colorimetric probe was in addition, tested against co-substrates aspartate, ketoglutarate and a variety of other compounds such as alanine, pryruvate, as well as glutamic, malaic and succinic acids known to interfere with AST activity. Each compound elicited a distinct and unambiguous colour change upon interaction with the colorimetric probe. Further X-ray powder diffraction (XRD), duNouy ring tensiometer, Brunauer- Emmett- Teller (BET) and energy dispersive X-ray spectroscopy (EDS/EDX) characterization confirmed composition and stability of the colorimetric probes. Colorimetric probes developed in this thesis are relatively cost effective, simple and "rugged" for measurement of analytes with visual detection without sample pretreatment in matrices, such as plasma and dairy effluents. The probes warrant further investigation as they have shown potential and offer a promising solid-state platform for both clinical diagnostics and environmental monitoring.
- Full Text:
- Date Issued: 2014
Gold mineralization in a high grade metamorphic terrane in the Handeni District, Eastern Tanzania
- Bitesigirwe, Godfrey Stephen
- Authors: Bitesigirwe, Godfrey Stephen
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54756 , vital:26609
- Description: Most orogenic type gold deposits are formed under low greenschist facies to mid amphibolite facies metamorphic conditions and deposition is either structurally or lithologically controlled. A few known gold deposits found in high grade metamorphic terranes include those in the Yilgarn craton in Australia, Renco in Zimbabwe, Hemlo in Canada and the recently discovered Handeni deposit in Tanzania. Within Tanzania, gold deposits are mainly hosted in Archaean low grade metamorphic rocks commonly known as the Lake Victoria greenstone belt. The greenstone belts of Tanzania are of Nyanzian age (> 2.5Ga) and are located to the south and east of Lake Victoria on the Tanzania craton. The Tanzania Craton is surrounded by Usagaran 1.9 Ga rocks (the east African orogenic belt (EAO) better known as the Mozambique belt) to the east and the Ubendian belt to the south and west. Published reports show that the eastern part of the Tanzania Craton is dominated by the fragments of Archaean rocks. Metamorphism along East Africa and the Tanzania Craton is due to several geological events. These geological events include the intrusion of granites in the Archaean Tanzania Craton (3 Ga), subduction of ocean plate resulted to the formation of Usagaran belt (1.9 Ga), opening and closure of Mozambique Ocean, which resulted in the formation of the Mozambique belt between 700 – 800 Ma and the Pan African orogeny at 640 – 620 Ma, which is associated with the formation of Gondwana. It is believed that fragments from the Archaean Tanzania craton were re - metamorphosed during these events. The Handeni project (the focus of this thesis) is located in the northern portion of the eastern part of the Usagaran belt (1.9 Ga) comprising the eastern part of Archaean Tanzania Craton. The area is characterized by Proterozic rocks of basaltic composition. The documented 2.7 Ga rocks at the Kilindi Handeni Superterrane at the northern part of the Usagaran belt correlate well with 2.7 Ga of Nyanzian rocks of Archaean Tanzania craton. The Handeni project area is geologically dominated by metamorphosed and deformed units of quartzofeldspathic gneisses, migmatitic gneiss, garnet silicified rock, garnetiferous amphibolite, garnetiferous granulite, graphitic schist and hornblende pyroxenite. Intensive deformation features that were developed include folds (sheath folds, micro and macro scales), faults, shears and regional thrusts. This thesis focuses on identifying the protolith of the rocks, alteration minerals, and metamorphic assemblages in the project area in order to understand the timing of gold mineralization. Geological investigation of core, ore petrology and mineralogy, mineral composition by using JEOL microprobe analysis and XRF analysis of bulk rocks were utilized. All the analytical work was done at the Geology laboratory, Rhodes University. Petrographic analysis shows that the rocks sampled in the study area are characterized by alteration minerals such as calcite, dolomite and sericite. Sulphide minerals including chalcopyrite, pyrrhotite, pyrite, pentlandite and gersdorffite were identified. Gold mineralization is associated with disseminated sulphides in association with trace amounts of base metals. Four rock types were proposed as host rocks for the mineralization, namely garnet silicified rock with superimposed quartz veins, garnetiferous amphibolite, garnetiferous granulite and hornblende pyroxenite. Fold troughs, filled fractures associated with episodes of folding, quartz veins and shear zones are suggested as gold precipitation sites. The presence of high grade metamorphic rocks containing gold, intermediate to low grade assemblages with sulphides and associated hydrothermal alteration as well as a complex deformation history suggests that the Handeni mineralization took place over an extended time period stretching from a ductile to a brittle environment.
- Full Text:
- Date Issued: 2014
- Authors: Bitesigirwe, Godfrey Stephen
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54756 , vital:26609
- Description: Most orogenic type gold deposits are formed under low greenschist facies to mid amphibolite facies metamorphic conditions and deposition is either structurally or lithologically controlled. A few known gold deposits found in high grade metamorphic terranes include those in the Yilgarn craton in Australia, Renco in Zimbabwe, Hemlo in Canada and the recently discovered Handeni deposit in Tanzania. Within Tanzania, gold deposits are mainly hosted in Archaean low grade metamorphic rocks commonly known as the Lake Victoria greenstone belt. The greenstone belts of Tanzania are of Nyanzian age (> 2.5Ga) and are located to the south and east of Lake Victoria on the Tanzania craton. The Tanzania Craton is surrounded by Usagaran 1.9 Ga rocks (the east African orogenic belt (EAO) better known as the Mozambique belt) to the east and the Ubendian belt to the south and west. Published reports show that the eastern part of the Tanzania Craton is dominated by the fragments of Archaean rocks. Metamorphism along East Africa and the Tanzania Craton is due to several geological events. These geological events include the intrusion of granites in the Archaean Tanzania Craton (3 Ga), subduction of ocean plate resulted to the formation of Usagaran belt (1.9 Ga), opening and closure of Mozambique Ocean, which resulted in the formation of the Mozambique belt between 700 – 800 Ma and the Pan African orogeny at 640 – 620 Ma, which is associated with the formation of Gondwana. It is believed that fragments from the Archaean Tanzania craton were re - metamorphosed during these events. The Handeni project (the focus of this thesis) is located in the northern portion of the eastern part of the Usagaran belt (1.9 Ga) comprising the eastern part of Archaean Tanzania Craton. The area is characterized by Proterozic rocks of basaltic composition. The documented 2.7 Ga rocks at the Kilindi Handeni Superterrane at the northern part of the Usagaran belt correlate well with 2.7 Ga of Nyanzian rocks of Archaean Tanzania craton. The Handeni project area is geologically dominated by metamorphosed and deformed units of quartzofeldspathic gneisses, migmatitic gneiss, garnet silicified rock, garnetiferous amphibolite, garnetiferous granulite, graphitic schist and hornblende pyroxenite. Intensive deformation features that were developed include folds (sheath folds, micro and macro scales), faults, shears and regional thrusts. This thesis focuses on identifying the protolith of the rocks, alteration minerals, and metamorphic assemblages in the project area in order to understand the timing of gold mineralization. Geological investigation of core, ore petrology and mineralogy, mineral composition by using JEOL microprobe analysis and XRF analysis of bulk rocks were utilized. All the analytical work was done at the Geology laboratory, Rhodes University. Petrographic analysis shows that the rocks sampled in the study area are characterized by alteration minerals such as calcite, dolomite and sericite. Sulphide minerals including chalcopyrite, pyrrhotite, pyrite, pentlandite and gersdorffite were identified. Gold mineralization is associated with disseminated sulphides in association with trace amounts of base metals. Four rock types were proposed as host rocks for the mineralization, namely garnet silicified rock with superimposed quartz veins, garnetiferous amphibolite, garnetiferous granulite and hornblende pyroxenite. Fold troughs, filled fractures associated with episodes of folding, quartz veins and shear zones are suggested as gold precipitation sites. The presence of high grade metamorphic rocks containing gold, intermediate to low grade assemblages with sulphides and associated hydrothermal alteration as well as a complex deformation history suggests that the Handeni mineralization took place over an extended time period stretching from a ductile to a brittle environment.
- Full Text:
- Date Issued: 2014
Inside the river
- Authors: Buzani, Mangaliso Welcome
- Date: 2014
- Subjects: South African poetry (English) , Xhosa poetry
- Language: English , Xhosa
- Type: text , Thesis , Masters , MA
- Identifier: vital:5971
- Description: My collection is of imagistic associative poetry, influenced by Spanish and other kinds of modernism, and written in my two languages, isiXhosa and English. My approach to producing these poems is first via the mastery of sound, not on the actual meaning of a poem; working on the meaning would be the last stage. The language of each poem will be encountered as it comes down on the paper, leading me to the words meaningful for that particular poem.
- Full Text:
- Date Issued: 2014
- Authors: Buzani, Mangaliso Welcome
- Date: 2014
- Subjects: South African poetry (English) , Xhosa poetry
- Language: English , Xhosa
- Type: text , Thesis , Masters , MA
- Identifier: vital:5971
- Description: My collection is of imagistic associative poetry, influenced by Spanish and other kinds of modernism, and written in my two languages, isiXhosa and English. My approach to producing these poems is first via the mastery of sound, not on the actual meaning of a poem; working on the meaning would be the last stage. The language of each poem will be encountered as it comes down on the paper, leading me to the words meaningful for that particular poem.
- Full Text:
- Date Issued: 2014
Invariant optimal control on the three-dimensional semi-Euclidean group: control affine and quadratic Hamilton-Poisson systems
- Authors: Barrett, Dennis Ian
- Date: 2014
- Subjects: Automorphisms , Symmetry (Mathematics) , Lyapunov stability , Geometry, Riemannian , Geometry, Affine , Elliptic functions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64805 , vital:28605
- Description: In this thesis we consider invariant control systems and Hamilton-Poisson systems on the three dimensional semi-Euclidean group SE(1,1). We first classify the left-invariant control affine systems (under detached feedback equivalence). We provide a complete list of normal forms, as well as classifying conditions. As a corollary to this classification, we derive controllability criteria for control affine systems on SE(1,1). Secondly, we consider quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space se(1,1)*. These systems are classified up to an affine isomorphism. Six normal forms are identified for the homogeneous case, whereas sixteen representatives (including several infinite families) are obtained for the inhomogeneous systems. Thereafter we consider the stability and integration of the normal forms obtained. For all homogeneous systems, and a subclass of inhomogeneous systems, we perform a complete stability analysis and derive explicit expressions for all integral curves. (The extremal controls of a large class of optimal control problems on SE(1,1) are linearly related to these integral curves.) Lastly, we discuss the Riemannian and sub-Riemannian problems. The (left-invariant) Riemannian and sub-Riemannian structures on SE(1,1) are classified, up to isometric group automorphisms and scaling. Explicit expressions for the geodesics of the normalised structures are found.
- Full Text:
- Date Issued: 2014
- Authors: Barrett, Dennis Ian
- Date: 2014
- Subjects: Automorphisms , Symmetry (Mathematics) , Lyapunov stability , Geometry, Riemannian , Geometry, Affine , Elliptic functions
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64805 , vital:28605
- Description: In this thesis we consider invariant control systems and Hamilton-Poisson systems on the three dimensional semi-Euclidean group SE(1,1). We first classify the left-invariant control affine systems (under detached feedback equivalence). We provide a complete list of normal forms, as well as classifying conditions. As a corollary to this classification, we derive controllability criteria for control affine systems on SE(1,1). Secondly, we consider quadratic Hamilton-Poisson systems on the (minus) Lie-Poisson space se(1,1)*. These systems are classified up to an affine isomorphism. Six normal forms are identified for the homogeneous case, whereas sixteen representatives (including several infinite families) are obtained for the inhomogeneous systems. Thereafter we consider the stability and integration of the normal forms obtained. For all homogeneous systems, and a subclass of inhomogeneous systems, we perform a complete stability analysis and derive explicit expressions for all integral curves. (The extremal controls of a large class of optimal control problems on SE(1,1) are linearly related to these integral curves.) Lastly, we discuss the Riemannian and sub-Riemannian problems. The (left-invariant) Riemannian and sub-Riemannian structures on SE(1,1) are classified, up to isometric group automorphisms and scaling. Explicit expressions for the geodesics of the normalised structures are found.
- Full Text:
- Date Issued: 2014
Lived bodies: women’s experience of sex and gender
- Authors: Lothian, Julie-Anne
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/69445 , vital:29538
- Description: This thesis will discuss the category of women, as a social group, through a phenomenological understanding of women’s subjective experiences. In arguing for the phenomenological perspective of the lived body, I show the ways in which other conceptions of women’s embodied subjectivity ultimately fail to provide comprehensive accounts of the lived experience of being a woman. I begin with an investigation into how biological determinists hypothesise women’s bodies as sexed. I then move to respond to Judith Butler’s poststructuralist feminist account of the gendered body. Finally, I argue that the embodied experience of being a woman is best explained as an ambiguous relationship between socially constructed expectations of femininity and biological materiality.
- Full Text:
- Date Issued: 2014
- Authors: Lothian, Julie-Anne
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/69445 , vital:29538
- Description: This thesis will discuss the category of women, as a social group, through a phenomenological understanding of women’s subjective experiences. In arguing for the phenomenological perspective of the lived body, I show the ways in which other conceptions of women’s embodied subjectivity ultimately fail to provide comprehensive accounts of the lived experience of being a woman. I begin with an investigation into how biological determinists hypothesise women’s bodies as sexed. I then move to respond to Judith Butler’s poststructuralist feminist account of the gendered body. Finally, I argue that the embodied experience of being a woman is best explained as an ambiguous relationship between socially constructed expectations of femininity and biological materiality.
- Full Text:
- Date Issued: 2014
Modelling the spatial and genetic response of the endemic sparid: Polysteganus praeorbitalis (Pisces: Sparidae) to climate change in the Agulhas Current system
- Authors: Isemonger, Devin Neil
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54509 , vital:26576
- Description: The Scotsman Seabream, Polysteganus praeorbitalis, is one of several large, slow-growing members of the Sparidae family of fishes endemic to the Agulhas Current system in the Western Indian Ocean (WIO). Relatively little research has been conducted on this species despite its importance to both recreational and commercial line fisheries in South Africa and the drastic decline in catch per unit effort (CPUE) that has been recorded since the 1940s. Changing sea temperatures as a result of global climate change are further expected to affect the distribution and abundance of many fish species based on their thermal tolerances, life histories and population structures. The ability of these species to shift their distribution and adapt to new environments and thermal conditions will depend to some degree on the levels of genetic variation and gene flow, within and between populations. A combined approach using species distribution modelling and genetic analyses may prove to be a useful tool in investigating the potential effects of climate change on the distribution and genetic diversity of species. An ensemble species distribution model (SDM) based on 205 occurrence records and 30 years of Reynolds Optimum Interpolated (OI) sea surface temperature data was constructed to predict the distributional response of P. praeorbitalis to climate change in the Agulhas Current system. The ensemble SDM displayed a true skill statistic (TSS) of 0.975 and an area under the receiver operating curve (ROC) of 0.999, indicating good model fit. Autumn and winter minimum temperatures, as well as bathymetry, were the most important predictor variables in the majority of models, indicating that these variables may directly constrain the distribution of P. praeorbitalis. In particular, the southern range edge of this species appeared to be constrained by autumn and winter minima, with high model agreement on this range edge. Conversely, the northern range limit showed poor model agreement leading to a gradual reduction in occurrence. This indicates that this range edge may be constrained by other factors not included in the models such as species interactions. The ensemble SDM projected the current range of P. praeorbitalis to be 1500 km², smaller than the published range for this species. The model underestimated the northern range edge of this species by approximately 5° latitude when binary transformed. This is probably due to the rarity of this species in the landings of the Mozambican linefishery, which was assumed to be an indication of low abundance of P. praeorbitalis in these waters. The absence of a specimen to verify the published northern range edge of this species indicates that the northern range edge produced by this model is likely to be closer to the actual range limit of the species. A range contraction of 30% occurring at both the northern and southern edge of P. praeorbitalis’ range and range fragmentation occurring, towards its northern range edge by 2030, was predicted. These changes are modelled to be the results of cooling related to the intensification of the Port Alfred upwelling cell and of warming predicted north of the Natal Bight and in southern Mozambique. Genetic analyses of the nuclear DNA (nDNA) S7 intron 1 and mitochondrial DNA (mtDNA) control region genes were carried out using 118 tissue samples of P. praeorbitalis collected at four main localities: the Eastern Cape, Transkei, southern KwaZulu-Natal and northern KwaZulu-Natal. Analyses of genetic diversity levels revealed relatively low diversity in the mtDNA dataset (Hd = 0.488; π = 0.004) and moderate levels of diversity in the nDNA dataset (Ad = 0.922; π = 0.005). The low levels of diversity observed in the mtDNA dataset might be explained by a number of factors, including high variation in spawning success, the negative effects of over-harvesting, or a recent population bottleneck. The last explanation is supported by characteristic star-shaped haplotype networks and unimodal mismatch distributions displayed by both datasets. These results, in conjunction with a significant (p = 0.005) negative Tajimas D value (-2.029) in the mtDNA dataset and significant (p = 0.0005) negative Fu’s F statistic in both the nDNA (F = -26.5) and mtDNA (F = -11.9) datasets, provide strong evidence for a recent population expansion after a bottleneck event in this species. Spatially, mtDNA diversity was highest in the Eastern Cape and lowest in the middle localities, while nDNA diversity showed the opposite pattern. These results may be indicative of differences in the sex ratio between localities, possibly as a result of the protogynous hermaphroditism that has been postulated for this species. Although pairwise comparisons and exact tests of population differentiation revealed no significant geneticdifferentiation between populations in the mtDNA dataset, there was some evidence of low levels of differentiation in the nDNA dataset. This occurred for comparisons between the Eastern Cape and Transkei (Fst = 0.039; p <0.05), and the northern KwaZulu-Natal (Fst = 0.045; p < 0.05).. This might be the result of one or a combination of factors including the effects of the Port Alfred upwelling cell on dispersal and gene flow, or the possibility of more than one spawning ground for this species promoting sub-structuring. A SAMOVA analyses run on the nDNA dataset maximised variance by grouping the Eastern Cape and southern KwaZulu-Natal together and Transkei and northern KwaZulu-Natal together in two groups. This revealed no evidence of spatial structure (p = 0.36), with only 3.30% of variation explained by this grouping. The removal of individuals below the estimated length at 50% maturity in the nDNA dataset, in order to test for temporal structure, resulted in stronger evidence of differentiation between the Eastern Cape and all other localities: Transkei (Fst = 0.081; p< 0.05), southern KwaZulu-Natal (Fst = 0.031; p<0.05), and northern KwaZulu-Natal (Fst = 0.078; p< 0.05). This indicates that some temporal genetic structure may exist between age classes within this species. The differentiation observed between the Eastern Cape and other localities, coupled with the high percentage of private haplotypes in the mtDNA dataset in this locality, indicates that this area is where P. praeorbitalis is most vulnerable to the potential negative effects of climate change on its genetic diversity. However, the vast majority of this species genetic diversity appears to reside towards the centre of its range where it is most abundant and the lack of strong genetic structure indicates high levels of gene flow. In conclusion, while P. praeorbitalis is vulnerable to range loss as a result of climate change, its genetic diversity is unlikely to be greatly affected.
- Full Text:
- Date Issued: 2014
- Authors: Isemonger, Devin Neil
- Date: 2014
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54509 , vital:26576
- Description: The Scotsman Seabream, Polysteganus praeorbitalis, is one of several large, slow-growing members of the Sparidae family of fishes endemic to the Agulhas Current system in the Western Indian Ocean (WIO). Relatively little research has been conducted on this species despite its importance to both recreational and commercial line fisheries in South Africa and the drastic decline in catch per unit effort (CPUE) that has been recorded since the 1940s. Changing sea temperatures as a result of global climate change are further expected to affect the distribution and abundance of many fish species based on their thermal tolerances, life histories and population structures. The ability of these species to shift their distribution and adapt to new environments and thermal conditions will depend to some degree on the levels of genetic variation and gene flow, within and between populations. A combined approach using species distribution modelling and genetic analyses may prove to be a useful tool in investigating the potential effects of climate change on the distribution and genetic diversity of species. An ensemble species distribution model (SDM) based on 205 occurrence records and 30 years of Reynolds Optimum Interpolated (OI) sea surface temperature data was constructed to predict the distributional response of P. praeorbitalis to climate change in the Agulhas Current system. The ensemble SDM displayed a true skill statistic (TSS) of 0.975 and an area under the receiver operating curve (ROC) of 0.999, indicating good model fit. Autumn and winter minimum temperatures, as well as bathymetry, were the most important predictor variables in the majority of models, indicating that these variables may directly constrain the distribution of P. praeorbitalis. In particular, the southern range edge of this species appeared to be constrained by autumn and winter minima, with high model agreement on this range edge. Conversely, the northern range limit showed poor model agreement leading to a gradual reduction in occurrence. This indicates that this range edge may be constrained by other factors not included in the models such as species interactions. The ensemble SDM projected the current range of P. praeorbitalis to be 1500 km², smaller than the published range for this species. The model underestimated the northern range edge of this species by approximately 5° latitude when binary transformed. This is probably due to the rarity of this species in the landings of the Mozambican linefishery, which was assumed to be an indication of low abundance of P. praeorbitalis in these waters. The absence of a specimen to verify the published northern range edge of this species indicates that the northern range edge produced by this model is likely to be closer to the actual range limit of the species. A range contraction of 30% occurring at both the northern and southern edge of P. praeorbitalis’ range and range fragmentation occurring, towards its northern range edge by 2030, was predicted. These changes are modelled to be the results of cooling related to the intensification of the Port Alfred upwelling cell and of warming predicted north of the Natal Bight and in southern Mozambique. Genetic analyses of the nuclear DNA (nDNA) S7 intron 1 and mitochondrial DNA (mtDNA) control region genes were carried out using 118 tissue samples of P. praeorbitalis collected at four main localities: the Eastern Cape, Transkei, southern KwaZulu-Natal and northern KwaZulu-Natal. Analyses of genetic diversity levels revealed relatively low diversity in the mtDNA dataset (Hd = 0.488; π = 0.004) and moderate levels of diversity in the nDNA dataset (Ad = 0.922; π = 0.005). The low levels of diversity observed in the mtDNA dataset might be explained by a number of factors, including high variation in spawning success, the negative effects of over-harvesting, or a recent population bottleneck. The last explanation is supported by characteristic star-shaped haplotype networks and unimodal mismatch distributions displayed by both datasets. These results, in conjunction with a significant (p = 0.005) negative Tajimas D value (-2.029) in the mtDNA dataset and significant (p = 0.0005) negative Fu’s F statistic in both the nDNA (F = -26.5) and mtDNA (F = -11.9) datasets, provide strong evidence for a recent population expansion after a bottleneck event in this species. Spatially, mtDNA diversity was highest in the Eastern Cape and lowest in the middle localities, while nDNA diversity showed the opposite pattern. These results may be indicative of differences in the sex ratio between localities, possibly as a result of the protogynous hermaphroditism that has been postulated for this species. Although pairwise comparisons and exact tests of population differentiation revealed no significant geneticdifferentiation between populations in the mtDNA dataset, there was some evidence of low levels of differentiation in the nDNA dataset. This occurred for comparisons between the Eastern Cape and Transkei (Fst = 0.039; p <0.05), and the northern KwaZulu-Natal (Fst = 0.045; p < 0.05).. This might be the result of one or a combination of factors including the effects of the Port Alfred upwelling cell on dispersal and gene flow, or the possibility of more than one spawning ground for this species promoting sub-structuring. A SAMOVA analyses run on the nDNA dataset maximised variance by grouping the Eastern Cape and southern KwaZulu-Natal together and Transkei and northern KwaZulu-Natal together in two groups. This revealed no evidence of spatial structure (p = 0.36), with only 3.30% of variation explained by this grouping. The removal of individuals below the estimated length at 50% maturity in the nDNA dataset, in order to test for temporal structure, resulted in stronger evidence of differentiation between the Eastern Cape and all other localities: Transkei (Fst = 0.081; p< 0.05), southern KwaZulu-Natal (Fst = 0.031; p<0.05), and northern KwaZulu-Natal (Fst = 0.078; p< 0.05). This indicates that some temporal genetic structure may exist between age classes within this species. The differentiation observed between the Eastern Cape and other localities, coupled with the high percentage of private haplotypes in the mtDNA dataset in this locality, indicates that this area is where P. praeorbitalis is most vulnerable to the potential negative effects of climate change on its genetic diversity. However, the vast majority of this species genetic diversity appears to reside towards the centre of its range where it is most abundant and the lack of strong genetic structure indicates high levels of gene flow. In conclusion, while P. praeorbitalis is vulnerable to range loss as a result of climate change, its genetic diversity is unlikely to be greatly affected.
- Full Text:
- Date Issued: 2014