Understanding the image in art therapy: a phenomenological-hermeneutic investigation
- Authors: Douglas, Blanche Daw
- Date: 1999
- Subjects: Art therapy Art -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2966 , http://hdl.handle.net/10962/d1002475
- Description: Part One of the research seeks to establish a context wherein certain assumptions pertaining to the interpretative dimensions of understanding the image in art therapy can be considered and reviewed. Notions about the image, meaning and reality are discussed both in terms of how they relate to current art therapy practice, and how they may be alternatively thought about, both from the perspective of ancient Hellenic Greek thought, and more contemporary thought, particularly that of phenomenological and philosophical-hermeneutics. Part Two of the research investigates the phenomenon of understanding the image in an art therapy situation, with a view to reconsidering certain of the assumptions raised in the first part of the thesis (phrased in the form of research questions). It did this utilizing a qualitative method, by exposing four respondents (patients), and two therapists to an art therapy situation in which images were created out of clay. The respondents (patients) and therapists articulated their understanding of the image production procedure, and the meaning of the images created. The way understanding occurred in the empirical part of the research was explained and illustrated by means of the hermeneutic circle, which was operational on a number of different levels. The results of the research suggest that the meaning of the image in art therapy is a creative synthesis, which emerges from within a dialectics of exchange. This exchange involves a number of meaning-generating contexts, of which the patient’s experience, and the therapist’s knowledge, form only a part. The outcome of this exchange is the derived meaning of the image, which represents a ‘fictional’ world that gives the patient and therapist a way of understanding the patient’s situation. The process of the research, which investigates the way understanding of the image in art therapy occurs, is at the same time, an application of the principles of understanding
- Full Text:
- Date Issued: 1999
- Authors: Douglas, Blanche Daw
- Date: 1999
- Subjects: Art therapy Art -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2966 , http://hdl.handle.net/10962/d1002475
- Description: Part One of the research seeks to establish a context wherein certain assumptions pertaining to the interpretative dimensions of understanding the image in art therapy can be considered and reviewed. Notions about the image, meaning and reality are discussed both in terms of how they relate to current art therapy practice, and how they may be alternatively thought about, both from the perspective of ancient Hellenic Greek thought, and more contemporary thought, particularly that of phenomenological and philosophical-hermeneutics. Part Two of the research investigates the phenomenon of understanding the image in an art therapy situation, with a view to reconsidering certain of the assumptions raised in the first part of the thesis (phrased in the form of research questions). It did this utilizing a qualitative method, by exposing four respondents (patients), and two therapists to an art therapy situation in which images were created out of clay. The respondents (patients) and therapists articulated their understanding of the image production procedure, and the meaning of the images created. The way understanding occurred in the empirical part of the research was explained and illustrated by means of the hermeneutic circle, which was operational on a number of different levels. The results of the research suggest that the meaning of the image in art therapy is a creative synthesis, which emerges from within a dialectics of exchange. This exchange involves a number of meaning-generating contexts, of which the patient’s experience, and the therapist’s knowledge, form only a part. The outcome of this exchange is the derived meaning of the image, which represents a ‘fictional’ world that gives the patient and therapist a way of understanding the patient’s situation. The process of the research, which investigates the way understanding of the image in art therapy occurs, is at the same time, an application of the principles of understanding
- Full Text:
- Date Issued: 1999
Understanding the harm of rape
- Authors: Kelland, Lindsay-Ann
- Date: 2013-04-19
- Subjects: Rape -- Social aspects--Research -- South Africa Rape -- Psychological aspects -- Research -- South Africa Rape trauma syndrome -- Research -- South Africa Rape victims -- South Africa Patriarchy -- South Africa Sexual dominance and submission -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2700 , http://hdl.handle.net/10962/d1001582
- Description: The aims of this thesis are twofold: to provide an account of the lived experience of the harm of male-on-female rape in patriarchal societies and, on the basis of this account, to generate suggestions that could be of use in the recovery process for survivors of this type of rape. In order to reach these aims my thesis is divided into three parts. In the first part, I propose a phenomenologically based account of women’s situation as a group under patriarchy, according to which women as a group are subjugated to the hegemonic rule of patriarchal ideology. I argue, further, that the meaning, place and pervasiveness of sexual objectification in the lives of women under patriarchy typically results in women’s alienation from their bodies and creates an atmosphere of threat under which women qua women are especially vulnerable to rape. In the second part, I explore the lived experience of the harm of rape; focusing, first, on the reflexive process whereby a survivor attempts to understand how she has been harmed and, second, on providing explanations based on shared features in the lives of women for two phenomena reported to be experienced by rape victims in the aftermath of the trauma, which I call ‘shattering’ and ‘fragmentation'. My discussion of the lived experience of the harm of rape is meant to supplement existing accounts in the contemporary literature that, I argue, are limited to a thirdperson, objective point of view and so fail to provide a link between the harms they describe and the victim’s actual experience of these harms. Finally, I defend two suggestions for the building up of the survivor’s agency and personhood in the aftermath of rape—the deliberate therapeutic use of feminist consciousness-raising and the use of narrative understanding. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Authors: Kelland, Lindsay-Ann
- Date: 2013-04-19
- Subjects: Rape -- Social aspects--Research -- South Africa Rape -- Psychological aspects -- Research -- South Africa Rape trauma syndrome -- Research -- South Africa Rape victims -- South Africa Patriarchy -- South Africa Sexual dominance and submission -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2700 , http://hdl.handle.net/10962/d1001582
- Description: The aims of this thesis are twofold: to provide an account of the lived experience of the harm of male-on-female rape in patriarchal societies and, on the basis of this account, to generate suggestions that could be of use in the recovery process for survivors of this type of rape. In order to reach these aims my thesis is divided into three parts. In the first part, I propose a phenomenologically based account of women’s situation as a group under patriarchy, according to which women as a group are subjugated to the hegemonic rule of patriarchal ideology. I argue, further, that the meaning, place and pervasiveness of sexual objectification in the lives of women under patriarchy typically results in women’s alienation from their bodies and creates an atmosphere of threat under which women qua women are especially vulnerable to rape. In the second part, I explore the lived experience of the harm of rape; focusing, first, on the reflexive process whereby a survivor attempts to understand how she has been harmed and, second, on providing explanations based on shared features in the lives of women for two phenomena reported to be experienced by rape victims in the aftermath of the trauma, which I call ‘shattering’ and ‘fragmentation'. My discussion of the lived experience of the harm of rape is meant to supplement existing accounts in the contemporary literature that, I argue, are limited to a thirdperson, objective point of view and so fail to provide a link between the harms they describe and the victim’s actual experience of these harms. Finally, I defend two suggestions for the building up of the survivor’s agency and personhood in the aftermath of rape—the deliberate therapeutic use of feminist consciousness-raising and the use of narrative understanding. , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
Understanding defiant identities: an ethnography of gays and lesbians in Harare, Zimbabwe
- Authors: Muparamoto, Nelson
- Date: 2019
- Subjects: Gays -- Zimbabwe , Gays -- Abuse of -- Zimbabwe , Homosexuality -- Zimbabwe , Homosexuality -- Political aspects -- Zimbabwe , Homosexuality -- Social aspects -- Zimbabwe , Homosexuality -- Religious aspects -- Zimbabwe , Homophobia -- Zimbabwe
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/67720 , vital:29133
- Description: Over the years, western and local media have mediated a narrative of a thoroughly homophobic Zimbabwe, not the least emanating from the former president Robert Mugabe’s ongoing homocritical utterances which recurrently generated global news stories. The country does indeed have a protracted history characterised by various forms of attacks on Gays and Lesbians of Zimbabwe, its membership, and the general lesbian, gay, bisexual, and transgender (LGBT) community. A dominant discourse has framed homosexual identities as on or beyond the border of what is acceptable, giving the clear message that they should not be tolerated. However, the narrative needs a more nuanced analysis than what has been popularised. That homophobia has played a significant role in Zimbabwe is of great import, but it is not and cannot be all there is to say about LGBT lives in the country. And, while scholarship on Zimbabwean homosexualities has engaged with debates about its indigeneity, morality and acceptability, it has as of yet not significantly explored the lived realities of non-heterosexual individuals from their own point of view. This thesis aims to begin doing exactly that, addressing the experiences of same-sex loving and attracted individuals in Harare. Drawing on ethnographic sociology, the thesis focuses on understanding how gay and lesbian identities are constructed, negotiated and experienced within an environment that is in many ways overtly homophobic, where, for example, the risk for social exclusion is considerable. It explores what characterises and shapes gay and lesbian identities in Harare in an attempt to interrogate how they reinforce, modify and challenge dominant social categories and relate to globally circulating queer identity categories. The thesis demonstrates that the construction of identities among same sex loving people in Harare variously draws on both locally and globally circulating ideas and insights. The thesis reveals that beyond the considerable attacks on homosexual identities in Zimbabwe, the intersection of local and international discourses on gay and lesbian identities produces identities that are to varying degrees emergent, fluid and perhaps fragmented. Despite attempts to expunge non-heterosexuals from Zimbabwean citizenry by drawing borders on the basis of sexual orientation, same sex loving individuals in Harare have defiantly expressed, negotiated and managed their sexual identities. The thesis describes and analyses things like dating patterns, decision making in same sex relations as well as family and religious experiences. Invoking Goffman’s concept of self-presentation enables one to understand how participants expressed themselves in the midst of like-minded or homo-tolerant individuals and how they deployed themselves in ‘spaces’ considered homocritical or where resentment was likely to be provoked by them openly expressing their sexual orientation. Crucially, same-sex loving and attracted individuals are agentic individuals who have variously stretched the traditional meanings associated with gender and sexuality in a context characterised by heteronormativity. This thesis usefully deploys Giddens’ (1991, 1992) theorisation of late modernity as characterised by conditions allowing a profusion of competing and sometimes contradictory identity discourses which offers the opportunity for self-reflexivity and identity negotiation. This helps us to understand the defiant identities. Whereas western circulating identity politics tout ‘coming out of the closet’, for most of the participants overt indiscriminate disclosure was to be avoided with participants therein deploying strategies that would help them to remain closeted to some family members as well as in religious circles. The consequences of ‘outing’ or disclosure are ostensibly not straightforward but complex, thus requiring a nuanced analysis that goes beyond the binary categories framed as either negative or positive. The thesis shows that experiences of same sex loving people in their families are complex rather than simply situated on the polar ends of either rejection or acceptance. Whilst dominant discourse has depicted religion as fuelling homophobia as it depicts a Christian identity and queer identities as incompatible, the thesis also explores how some participants challenge the borders drawn in religious circles and maintain a relatively active religious life but not always without conflict.
- Full Text:
- Date Issued: 2019
- Authors: Muparamoto, Nelson
- Date: 2019
- Subjects: Gays -- Zimbabwe , Gays -- Abuse of -- Zimbabwe , Homosexuality -- Zimbabwe , Homosexuality -- Political aspects -- Zimbabwe , Homosexuality -- Social aspects -- Zimbabwe , Homosexuality -- Religious aspects -- Zimbabwe , Homophobia -- Zimbabwe
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/67720 , vital:29133
- Description: Over the years, western and local media have mediated a narrative of a thoroughly homophobic Zimbabwe, not the least emanating from the former president Robert Mugabe’s ongoing homocritical utterances which recurrently generated global news stories. The country does indeed have a protracted history characterised by various forms of attacks on Gays and Lesbians of Zimbabwe, its membership, and the general lesbian, gay, bisexual, and transgender (LGBT) community. A dominant discourse has framed homosexual identities as on or beyond the border of what is acceptable, giving the clear message that they should not be tolerated. However, the narrative needs a more nuanced analysis than what has been popularised. That homophobia has played a significant role in Zimbabwe is of great import, but it is not and cannot be all there is to say about LGBT lives in the country. And, while scholarship on Zimbabwean homosexualities has engaged with debates about its indigeneity, morality and acceptability, it has as of yet not significantly explored the lived realities of non-heterosexual individuals from their own point of view. This thesis aims to begin doing exactly that, addressing the experiences of same-sex loving and attracted individuals in Harare. Drawing on ethnographic sociology, the thesis focuses on understanding how gay and lesbian identities are constructed, negotiated and experienced within an environment that is in many ways overtly homophobic, where, for example, the risk for social exclusion is considerable. It explores what characterises and shapes gay and lesbian identities in Harare in an attempt to interrogate how they reinforce, modify and challenge dominant social categories and relate to globally circulating queer identity categories. The thesis demonstrates that the construction of identities among same sex loving people in Harare variously draws on both locally and globally circulating ideas and insights. The thesis reveals that beyond the considerable attacks on homosexual identities in Zimbabwe, the intersection of local and international discourses on gay and lesbian identities produces identities that are to varying degrees emergent, fluid and perhaps fragmented. Despite attempts to expunge non-heterosexuals from Zimbabwean citizenry by drawing borders on the basis of sexual orientation, same sex loving individuals in Harare have defiantly expressed, negotiated and managed their sexual identities. The thesis describes and analyses things like dating patterns, decision making in same sex relations as well as family and religious experiences. Invoking Goffman’s concept of self-presentation enables one to understand how participants expressed themselves in the midst of like-minded or homo-tolerant individuals and how they deployed themselves in ‘spaces’ considered homocritical or where resentment was likely to be provoked by them openly expressing their sexual orientation. Crucially, same-sex loving and attracted individuals are agentic individuals who have variously stretched the traditional meanings associated with gender and sexuality in a context characterised by heteronormativity. This thesis usefully deploys Giddens’ (1991, 1992) theorisation of late modernity as characterised by conditions allowing a profusion of competing and sometimes contradictory identity discourses which offers the opportunity for self-reflexivity and identity negotiation. This helps us to understand the defiant identities. Whereas western circulating identity politics tout ‘coming out of the closet’, for most of the participants overt indiscriminate disclosure was to be avoided with participants therein deploying strategies that would help them to remain closeted to some family members as well as in religious circles. The consequences of ‘outing’ or disclosure are ostensibly not straightforward but complex, thus requiring a nuanced analysis that goes beyond the binary categories framed as either negative or positive. The thesis shows that experiences of same sex loving people in their families are complex rather than simply situated on the polar ends of either rejection or acceptance. Whilst dominant discourse has depicted religion as fuelling homophobia as it depicts a Christian identity and queer identities as incompatible, the thesis also explores how some participants challenge the borders drawn in religious circles and maintain a relatively active religious life but not always without conflict.
- Full Text:
- Date Issued: 2019
Understanding current teacher implementation of Zimbabwe's primary school AIDS curriculum: a case study
- Authors: Musingarabwi, Starlin
- Date: 2013
- Subjects: Teacher participation in curriculum planning -- Zimbabwe , Primary school teachers -- Zimbabwe , Education -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9584 , http://hdl.handle.net/10948/d1020912
- Description: Zimbabwe’s Ministry of Education Sport, Arts and Culture offers as one of the primary school curricula, an AIDS curriculum which all Grades 4 to 7 teachers in Zimbabwe’s primary schools mandatorily implement with a view to contributing towards the prevention of the spread of HIV/AIDS among the young primary school learners. The purpose of this research was to explore and describe teachers’ understanding and implementation of Zimbabwe’s primary school AIDS curriculum regarding the ways in which they articulated teaching practices and processes in their classrooms. The study also aimed to elicit the teachers’ views on how personal and contextual factors impact their adaptation and enactment of the curriculum. The study also sought to establish teachers’ perceptions of their practical experiences with the implementation of Zimbabwe’s primary school AIDS curriculum and their suggestions for improving practice. The study follows a qualitative case study design with minimal quantitative results. It involved three purposively selected primary school grade six teachers (n=3) each of whom was asked to teach five lessons while being observed over a period of three months. Each teacher availed his or her teaching scheme/plan to the researcher who conducted document analysis to glean their symbolic conceptualisation of actual classroom practice of the curriculum. This was followed by three semi-structured interviews with each participating teacher to elicit their perceptions. A content analysis using ideas borrowed from the grounded theory approach was employed resulting in thematic findings. The findings of the study confirm and enhance the theoretical significance of the phenomenological-adaptive perspective of educational change and Honig’s (people, policy, places) and cognition model for describing teacher implementation of the mandatory AIDS curriculum. The findings also confirm the complex ways in which human-generated personal and contextual factors played out in framing and shaping teachers’ personal adaptation of the mandatory AIDS curriculum. The study confirms the adaptation claim that as cognitive sense-makers, teachers mutate and enact a curriculum according to their personal subjective interpretations in the context of unique use-setting implementation realities. Although one of the participants’ understanding and practice displayed considerable comprehension of the requirements of the curriculum, the other teachers displayed an understanding of this curriculum in a superficial way, and experienced few positive experiences and several conceptual and operational constraints in its implementation. Drawing on their practical experiences with the implementation of the curriculum, teachers offered suggestions for transforming the implementation proficiency of this curriculum, which formed part of the conceptual strategy I developed for improving practice. Thus the resultant achievement of the study was a conceptual strategy that was constructed from the key findings of the study to provide educational change leaders with nuanced ideas and insights for improving practice.
- Full Text:
- Date Issued: 2013
- Authors: Musingarabwi, Starlin
- Date: 2013
- Subjects: Teacher participation in curriculum planning -- Zimbabwe , Primary school teachers -- Zimbabwe , Education -- Zimbabwe
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:9584 , http://hdl.handle.net/10948/d1020912
- Description: Zimbabwe’s Ministry of Education Sport, Arts and Culture offers as one of the primary school curricula, an AIDS curriculum which all Grades 4 to 7 teachers in Zimbabwe’s primary schools mandatorily implement with a view to contributing towards the prevention of the spread of HIV/AIDS among the young primary school learners. The purpose of this research was to explore and describe teachers’ understanding and implementation of Zimbabwe’s primary school AIDS curriculum regarding the ways in which they articulated teaching practices and processes in their classrooms. The study also aimed to elicit the teachers’ views on how personal and contextual factors impact their adaptation and enactment of the curriculum. The study also sought to establish teachers’ perceptions of their practical experiences with the implementation of Zimbabwe’s primary school AIDS curriculum and their suggestions for improving practice. The study follows a qualitative case study design with minimal quantitative results. It involved three purposively selected primary school grade six teachers (n=3) each of whom was asked to teach five lessons while being observed over a period of three months. Each teacher availed his or her teaching scheme/plan to the researcher who conducted document analysis to glean their symbolic conceptualisation of actual classroom practice of the curriculum. This was followed by three semi-structured interviews with each participating teacher to elicit their perceptions. A content analysis using ideas borrowed from the grounded theory approach was employed resulting in thematic findings. The findings of the study confirm and enhance the theoretical significance of the phenomenological-adaptive perspective of educational change and Honig’s (people, policy, places) and cognition model for describing teacher implementation of the mandatory AIDS curriculum. The findings also confirm the complex ways in which human-generated personal and contextual factors played out in framing and shaping teachers’ personal adaptation of the mandatory AIDS curriculum. The study confirms the adaptation claim that as cognitive sense-makers, teachers mutate and enact a curriculum according to their personal subjective interpretations in the context of unique use-setting implementation realities. Although one of the participants’ understanding and practice displayed considerable comprehension of the requirements of the curriculum, the other teachers displayed an understanding of this curriculum in a superficial way, and experienced few positive experiences and several conceptual and operational constraints in its implementation. Drawing on their practical experiences with the implementation of the curriculum, teachers offered suggestions for transforming the implementation proficiency of this curriculum, which formed part of the conceptual strategy I developed for improving practice. Thus the resultant achievement of the study was a conceptual strategy that was constructed from the key findings of the study to provide educational change leaders with nuanced ideas and insights for improving practice.
- Full Text:
- Date Issued: 2013
Understanding climate variability and livelihoods adaptation in rural Zimbabwe : case of Charewa, Mutoko
- Authors: Bhatasara, Sandra
- Date: 2015
- Subjects: Climatic changes -- Zimbabwe -- Mutoko , Sustainable agriculture -- Zimbabwe -- Mutoko , Environmental impact analysis -- Zimbabwe -- Mutoko , Farmers -- Zimbabwe -- Mutoko -- Economic conditions , Food supply -- Zimbabwe -- Mutoko , Farms -- Zimbabwe -- Mutoko , Land use, Rural -- Zimbabwe -- Mutoko , Crops and climate -- Zimbabwe -- Mutoko
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3403 , http://hdl.handle.net/10962/d1018928 , Climatic changes -- Zimbabwe -- Mutoko , Sustainable agriculture -- Zimbabwe -- Mutoko , Environmental impact analysis -- Zimbabwe -- Mutoko , Farmers -- Zimbabwe -- Mutoko -- Economic conditions , Food supply -- Zimbabwe -- Mutoko , Farms -- Zimbabwe -- Mutoko , Land use, Rural -- Zimbabwe -- Mutoko , Crops and climate -- Zimbabwe -- Mutoko
- Description: Rural farmers in Zimbabwe have been grappling with various changes and challenges occurring in the country since the early 1990s. Amongst these, climate variability has emerged as one significant aspect. It has introduced new challenges for these farmers who are already facing various difficulties in maintaining their insecure livelihoods. Yet, current adaptation theories and inquiries have failed to sufficiently account for and analyse the capacity of these farmers to adequately respond to changing climatic conditions. In this respect, a number of studies have been heavily embedded in deterministic concepts that regard rural farmers as passive victims who play only a minor part in decisions and actions that affect their own livelihoods and well-being. Similarly, although some studies have acknowledged farmers’ capacity to adapt and build elements of resilience, they have not adequately shown how farmers interpret changes in climate and the structures, processes and conditions underpinning adaptation. Following that, my study uses a case study of a rural community in a semi-arid region of Mutoko district in eastern Zimbabwe and Margaret Archer’s sociological theory to understand and analyse how farmers problematise climate variability and respond to it. The study utilises a qualitative approach to divulge the subtleties on how rural people interpret processes of change and adapt to such changes. The thesis found that farmers are encountering increasingly unpredictable and unreliable rainfall patterns as well as shifting temperature conditions which are inducing labyrinthian livelihoods conundrums. However, these climatic shifts are not being experienced in a discrete manner hence farmers are also discontented with the obtaining socio-economic circumstances in the country. Simultaneously, whilst farmers in large part conceived changes in rainfall and temperature to be caused by natural shifts in climate, they also ascribed them to cultural and religious facets. Importantly, the thesis reveals considerable resourcefulness by farmers in the face of nascent changes in climate variability. Farmers have therefore constructed versatile coping and adaptive strategies. What is crucial to mention here is that climatic and non-climatic challenges are negotiated concurrently. Therein, farmers are adapting to climate variability and at the same time navigating difficult socio-economic landscapes. All the same, the process of adaptation is ostensibly not straightforward but complex. As it evolves, farmers find themselves facing numerous constraining structures and processes. Nonetheless, farmers in this study are able to circumvent the constraints presented to them and at the same time activate the corresponding enabling structures, processes and conditions.
- Full Text:
- Date Issued: 2015
- Authors: Bhatasara, Sandra
- Date: 2015
- Subjects: Climatic changes -- Zimbabwe -- Mutoko , Sustainable agriculture -- Zimbabwe -- Mutoko , Environmental impact analysis -- Zimbabwe -- Mutoko , Farmers -- Zimbabwe -- Mutoko -- Economic conditions , Food supply -- Zimbabwe -- Mutoko , Farms -- Zimbabwe -- Mutoko , Land use, Rural -- Zimbabwe -- Mutoko , Crops and climate -- Zimbabwe -- Mutoko
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3403 , http://hdl.handle.net/10962/d1018928 , Climatic changes -- Zimbabwe -- Mutoko , Sustainable agriculture -- Zimbabwe -- Mutoko , Environmental impact analysis -- Zimbabwe -- Mutoko , Farmers -- Zimbabwe -- Mutoko -- Economic conditions , Food supply -- Zimbabwe -- Mutoko , Farms -- Zimbabwe -- Mutoko , Land use, Rural -- Zimbabwe -- Mutoko , Crops and climate -- Zimbabwe -- Mutoko
- Description: Rural farmers in Zimbabwe have been grappling with various changes and challenges occurring in the country since the early 1990s. Amongst these, climate variability has emerged as one significant aspect. It has introduced new challenges for these farmers who are already facing various difficulties in maintaining their insecure livelihoods. Yet, current adaptation theories and inquiries have failed to sufficiently account for and analyse the capacity of these farmers to adequately respond to changing climatic conditions. In this respect, a number of studies have been heavily embedded in deterministic concepts that regard rural farmers as passive victims who play only a minor part in decisions and actions that affect their own livelihoods and well-being. Similarly, although some studies have acknowledged farmers’ capacity to adapt and build elements of resilience, they have not adequately shown how farmers interpret changes in climate and the structures, processes and conditions underpinning adaptation. Following that, my study uses a case study of a rural community in a semi-arid region of Mutoko district in eastern Zimbabwe and Margaret Archer’s sociological theory to understand and analyse how farmers problematise climate variability and respond to it. The study utilises a qualitative approach to divulge the subtleties on how rural people interpret processes of change and adapt to such changes. The thesis found that farmers are encountering increasingly unpredictable and unreliable rainfall patterns as well as shifting temperature conditions which are inducing labyrinthian livelihoods conundrums. However, these climatic shifts are not being experienced in a discrete manner hence farmers are also discontented with the obtaining socio-economic circumstances in the country. Simultaneously, whilst farmers in large part conceived changes in rainfall and temperature to be caused by natural shifts in climate, they also ascribed them to cultural and religious facets. Importantly, the thesis reveals considerable resourcefulness by farmers in the face of nascent changes in climate variability. Farmers have therefore constructed versatile coping and adaptive strategies. What is crucial to mention here is that climatic and non-climatic challenges are negotiated concurrently. Therein, farmers are adapting to climate variability and at the same time navigating difficult socio-economic landscapes. All the same, the process of adaptation is ostensibly not straightforward but complex. As it evolves, farmers find themselves facing numerous constraining structures and processes. Nonetheless, farmers in this study are able to circumvent the constraints presented to them and at the same time activate the corresponding enabling structures, processes and conditions.
- Full Text:
- Date Issued: 2015
Understanding climate change and rural livelihoods in Zimbabwe: adaptation by communal farmers in Ngundu, Chivi District
- Authors: Nciizah, Elinah
- Date: 2020
- Subjects: Agriculture -- Zimbabwe , Agriculture -- Climatic factors -- Chivi District (Zimbabwe) , Chivi District (Zimbabwe) -- Rural conditions
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/118765 , vital:34666
- Description: Climate change and variability is a global phenomenon which has deeply localised patterns, dynamics and effects. Amongst those people who are particularly vulnerable to climate change effects are small-scale farmers who are dependent in large part on rain-fed agriculture in pursuing their livelihoods. This is true of small-scale farmers in contemporary Zimbabwe and, more specifically, farmers in communal areas. At the same time, at international and national levels, there are attempts currently to minimise the effects of, and to adapt to, climate change. However, adaptation measures also exist at local levels amongst small-scale farmers, such as communal farmers in Zimbabwe. In this context, as its main objective, this thesis examines climate change and small-scale farmer livelihood adaptation to climate change with specific reference to communal farmers in Chivi District in Zimbabwe and, in particular, in Ward 25 which is popularly known as Ngundu. In pursuing this main objective, a number of subsidiary objectives are addressed, including a focus on the established livelihoods of Ngundu farmers, the perceptions and concerns of Ngundu farmers about climate change, the coping and adaptation measures of Ngundu farmers, and the enablements and constraints which affect attempts by Ngundu farmers to adopt such measures. The fieldwork for the thesis involved a diverse array of research methods, such as a questionnaire survey, life-history interviews, key informant interviews, focus group discussions and transect walks. In terms of theoretical framing, the thesis makes use of both middle-level theory (the Sustainable Livelihoods Framework) and macro-theory in the form of the sociological work of Margaret Archer. Combined, these two theories allow for a focus on both structure and agency when seeking to understand livelihood adaptations to climate change by communal farmers in Ngundu. The thesis concludes that there are massive constraints inhibiting adaptation measures by Ngundu farmers, but that this should not distract from the deep, often historically-embedded, concerns of Ngundu farmers about climate change and the multiple ways in which they express agency in and through adaptation and coping activities. It also highlights the need for more specifically sociological investigations of climate change and small-scale farmer adaptation, as well as the need for localised studies which are able to identify and analyse the specificities of adaptation.
- Full Text:
- Date Issued: 2020
- Authors: Nciizah, Elinah
- Date: 2020
- Subjects: Agriculture -- Zimbabwe , Agriculture -- Climatic factors -- Chivi District (Zimbabwe) , Chivi District (Zimbabwe) -- Rural conditions
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/118765 , vital:34666
- Description: Climate change and variability is a global phenomenon which has deeply localised patterns, dynamics and effects. Amongst those people who are particularly vulnerable to climate change effects are small-scale farmers who are dependent in large part on rain-fed agriculture in pursuing their livelihoods. This is true of small-scale farmers in contemporary Zimbabwe and, more specifically, farmers in communal areas. At the same time, at international and national levels, there are attempts currently to minimise the effects of, and to adapt to, climate change. However, adaptation measures also exist at local levels amongst small-scale farmers, such as communal farmers in Zimbabwe. In this context, as its main objective, this thesis examines climate change and small-scale farmer livelihood adaptation to climate change with specific reference to communal farmers in Chivi District in Zimbabwe and, in particular, in Ward 25 which is popularly known as Ngundu. In pursuing this main objective, a number of subsidiary objectives are addressed, including a focus on the established livelihoods of Ngundu farmers, the perceptions and concerns of Ngundu farmers about climate change, the coping and adaptation measures of Ngundu farmers, and the enablements and constraints which affect attempts by Ngundu farmers to adopt such measures. The fieldwork for the thesis involved a diverse array of research methods, such as a questionnaire survey, life-history interviews, key informant interviews, focus group discussions and transect walks. In terms of theoretical framing, the thesis makes use of both middle-level theory (the Sustainable Livelihoods Framework) and macro-theory in the form of the sociological work of Margaret Archer. Combined, these two theories allow for a focus on both structure and agency when seeking to understand livelihood adaptations to climate change by communal farmers in Ngundu. The thesis concludes that there are massive constraints inhibiting adaptation measures by Ngundu farmers, but that this should not distract from the deep, often historically-embedded, concerns of Ngundu farmers about climate change and the multiple ways in which they express agency in and through adaptation and coping activities. It also highlights the need for more specifically sociological investigations of climate change and small-scale farmer adaptation, as well as the need for localised studies which are able to identify and analyse the specificities of adaptation.
- Full Text:
- Date Issued: 2020
Understanding biotic interactions in invaded pond communities in the Sundays River irrigation network, South Africa
- Authors: Mofu, Lubabalo
- Date: 2020
- Subjects: Mozambique tilapia -- South Africa -- Sundays River (Eastern Cape) , Western mosquitofish -- South Africa -- Sundays River (Eastern Cape) , Gobiidae -- South Africa -- Sundays River (Eastern Cape) , Clupeidae -- South Africa -- Sundays River (Eastern Cape) , Reservoirs -- South Africa -- Sundays River (Eastern Cape) , Zooplankton -- South Africa -- Sundays River (Eastern Cape) , Freshwater ecology -- South Africa -- Sundays River (Eastern Cape) , Biotic communities -- South Africa -- Sundays River (Eastern Cape) , Fishes -- Effect of temperature on -- South Africa -- Sundays River (Eastern Cape) , Stable isotopes , Relative Impact Potential
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167089 , vital:41436
- Description: The Sundays River valley irrigation ponds provide a unique opportunity to investigate biotic interactions within a biological invasions context, as they contain both native and non-native fish species. This study focusses on two native species (Glossogobius callidus and Gilchristella aestuaria) and two non-native species (Oreochromis mossambicus and Gambusia affinis). The ecology of the ponds was driven by physico-chemical variables, mainly temperature, but the interactions between fishes were a complex interplay between temperature, pond community ecology and food web structure. Seasonal changes in temperature and subsequent fluctuations in water levels resulted in changes in zooplankton community. Chlorophyll-a, temperature, G. callidus and G. affinis were the drivers of the seasonal changes in macroinvertebrate composition. Stable isotope analysis identified substantial ontogenetic dietary shifts in all species, corresponding to changes in body size. Stable isotope analysis revealed that the niche space occupied by G. affinis was broad and overlapped with that of the other three focal species. Stable isotope metrics showed that G. affinis and O. mossambicus utilised a wide range of resources compared to G. callidus and G. aestuaria. Stomach content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, while G. aestuaria fed mainly plankton resources. Functional response experiments revealed that G. callidus and G. affinis both displayed Type II functional responses. In single fish trials, G. affinis had significantly higher functional responses than G. callidus. In heterospecific G. callidus-G. affinis combinations the functional response of G. callidus was reduced by the presence of G. affinis, whereas, this combination greatly enhanced G. affinis functional response magnitudes. The functional response of G. callidus, O. mossambicus and G. affinis under two temperature treatments along with fish abundance data was used to determine temporal differences in the ecological impacts of each fish species between seasons. The relative impact potential of O. mossambicus was consistently higher than that of G. callidus and G. affinis. This study demonstrates how seasonal temperature fluctuations affect the relative impact capacities of introduced species. Overall, this thesis showed that high temperature along with life-history traits contributes to the biotic interactions between native and non-native species in novel environments.
- Full Text:
- Date Issued: 2020
- Authors: Mofu, Lubabalo
- Date: 2020
- Subjects: Mozambique tilapia -- South Africa -- Sundays River (Eastern Cape) , Western mosquitofish -- South Africa -- Sundays River (Eastern Cape) , Gobiidae -- South Africa -- Sundays River (Eastern Cape) , Clupeidae -- South Africa -- Sundays River (Eastern Cape) , Reservoirs -- South Africa -- Sundays River (Eastern Cape) , Zooplankton -- South Africa -- Sundays River (Eastern Cape) , Freshwater ecology -- South Africa -- Sundays River (Eastern Cape) , Biotic communities -- South Africa -- Sundays River (Eastern Cape) , Fishes -- Effect of temperature on -- South Africa -- Sundays River (Eastern Cape) , Stable isotopes , Relative Impact Potential
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167089 , vital:41436
- Description: The Sundays River valley irrigation ponds provide a unique opportunity to investigate biotic interactions within a biological invasions context, as they contain both native and non-native fish species. This study focusses on two native species (Glossogobius callidus and Gilchristella aestuaria) and two non-native species (Oreochromis mossambicus and Gambusia affinis). The ecology of the ponds was driven by physico-chemical variables, mainly temperature, but the interactions between fishes were a complex interplay between temperature, pond community ecology and food web structure. Seasonal changes in temperature and subsequent fluctuations in water levels resulted in changes in zooplankton community. Chlorophyll-a, temperature, G. callidus and G. affinis were the drivers of the seasonal changes in macroinvertebrate composition. Stable isotope analysis identified substantial ontogenetic dietary shifts in all species, corresponding to changes in body size. Stable isotope analysis revealed that the niche space occupied by G. affinis was broad and overlapped with that of the other three focal species. Stable isotope metrics showed that G. affinis and O. mossambicus utilised a wide range of resources compared to G. callidus and G. aestuaria. Stomach content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, while G. aestuaria fed mainly plankton resources. Functional response experiments revealed that G. callidus and G. affinis both displayed Type II functional responses. In single fish trials, G. affinis had significantly higher functional responses than G. callidus. In heterospecific G. callidus-G. affinis combinations the functional response of G. callidus was reduced by the presence of G. affinis, whereas, this combination greatly enhanced G. affinis functional response magnitudes. The functional response of G. callidus, O. mossambicus and G. affinis under two temperature treatments along with fish abundance data was used to determine temporal differences in the ecological impacts of each fish species between seasons. The relative impact potential of O. mossambicus was consistently higher than that of G. callidus and G. affinis. This study demonstrates how seasonal temperature fluctuations affect the relative impact capacities of introduced species. Overall, this thesis showed that high temperature along with life-history traits contributes to the biotic interactions between native and non-native species in novel environments.
- Full Text:
- Date Issued: 2020
Understanding and modelling of surface and groundwater interactions
- Authors: Tanner, Jane Louise
- Date: 2014
- Subjects: Groundwater -- South Africa , Water-supply -- Management , Integrated water development , Hydrogeology , Water resources development -- South Africa , Water -- Analysis , Groundwater -- Management , Watersheds -- South Africa , Hydrologic models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6043 , http://hdl.handle.net/10962/d1012994
- Description: The connections between surface water and groundwater systems remain poorly understood in many catchments throughout the world and yet they are fundamental to effectively managing water resources. Managing water resources in an integrated manner is not straightforward, particularly if both resources are being utilised, and especially in those regions that suffer problems of data scarcity. This study explores some of the principle issues associated with understanding and practically modelling surface and groundwater interactions. In South Africa, there remains much controversy over the most appropriate type of integrated model to be used and the way forward in terms of the development of the discipline; part of the disagreement stems from the fact that we cannot validate models adequately. This is largely due to traditional forms of model testing having limited power as it is difficult to differentiate between the uncertainties within different model structures, different sets of alternative parameter values and in the input data used to run the model. While model structural uncertainties are important to consider, the uncertainty from input data error together with parameter estimation error are often more significant to the overall residual error, and essential to consider if we want to achieve reliable predictions for water resource decisions. While new philosophies and theories on modelling and results validation have been developed (Beven, 2002; Gupta et al., 2008), in many cases models are not only still being validated and compared using sparse and uncertain datasets, but also expected to produce reliable predictions based on the flawed data. The approach in this study is focused on fundamental understanding of hydrological systems rather than calibration based modelling and promotes the use of all the available 'hard' and 'soft' data together with thoughtful conceptual examination of the processes occurring in an environment to ensure as far as possible that a model is generating sensible results by simulating the correct processes. The first part of the thesis focuses on characterising the 'typical' interaction environments found in South Africa. It was found that many traditional perceptual models are not necessarily applicable to South African conditions, largely due to the relative importance of unsaturated zone processes and the complexity of the dominantly fractured rock environments. The interaction environments were categorised into four main 'types' of environment. These include karst, primary, fractured rock (secondary), and alluvial environments. Processes critical to Integrated Water Resource Management (IWRM) were defined within each interaction type as a guideline to setting a model up to realistically represent the dominant processes in the respective settings. The second part of the thesis addressed the application and evaluation of the modified Pitman model (Hughes, 2004), which allows for surface and groundwater interaction behaviour at the catchment scale to be simulated. The issue is whether, given the different sources of uncertainty in the modelling process, we can differentiate one conceptual flow path from another in trying to refine the understanding and consequently have more faith in model predictions. Seven example catchments were selected from around South Africa to assess whether reliable integrated assessments can be carried out given the existing data. Specific catchment perceptual models were used to identify the critical processes occurring in each setting and the Pitman model was assessed on whether it could represent them (structural uncertainty). The available knowledge of specific environments or catchments was then examined in an attempt to resolve the parameter uncertainty present within each catchment and ensure the subsequent model setup was correctly representing the process understanding as far as possible. The confidence in the quantitative results inevitably varied with the amount and quality of the data available. While the model was deemed to be robust based on the behavioural results obtained in the majority of the case studies, in many cases a quantitative validation of the outputs was just not possible based on the available data. In these cases, the model was judged on its ability to represent the conceptualisation of the processes occurring in the catchments. While the lack of appropriate data means there will always be considerable uncertainty surrounding model validation, it can be argued that improved process understanding in an environment can be used to validate model outcomes to a degree, by assessing whether a model is getting the right results for the right reasons. Many water resource decisions are still made without adequate account being taken of the uncertainties inherent in assessing the response of hydrological systems. Certainly, with all the possible sources of uncertainty in a data scarce country such as South Africa, pure calibration based modelling is unlikely to produce reliable information for water resource managers as it can produce the right results for the wrong reasons. Thus it becomes essential to incorporate conceptual thinking into the modelling process, so that at the very least we are able to conclude that a model generates estimates that are consistent with, and reflect, our understanding (however limited) of the catchment processes. It is fairly clear that achieving the optimum model of a hydrological system may be fraught with difficulty, if not impossible. This makes it very difficult from a practitioner's point of view to decide which model and uncertainty estimation method to use. According to Beven (2009), this may be a transitional problem and in the future it may become clearer as we learn more about how to estimate the uncertainties associated with hydrological systems. Until then, a better understanding of the fundamental and most critical hydrogeological processes should be used to critically test and improve model predictions as far as possible. A major focus of the study was to identify whether the modified Pitman model could provide a practical tool for water resource managers by reliably determining the available water resource. The incorporation of surface and groundwater interaction routines seems to have resulted in a more robust and realistic model of basin hydrology. The overall conclusion is that the model, although simplified, is capable of representing the catchment scale processes that occur under most South African conditions.
- Full Text:
- Date Issued: 2014
- Authors: Tanner, Jane Louise
- Date: 2014
- Subjects: Groundwater -- South Africa , Water-supply -- Management , Integrated water development , Hydrogeology , Water resources development -- South Africa , Water -- Analysis , Groundwater -- Management , Watersheds -- South Africa , Hydrologic models
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6043 , http://hdl.handle.net/10962/d1012994
- Description: The connections between surface water and groundwater systems remain poorly understood in many catchments throughout the world and yet they are fundamental to effectively managing water resources. Managing water resources in an integrated manner is not straightforward, particularly if both resources are being utilised, and especially in those regions that suffer problems of data scarcity. This study explores some of the principle issues associated with understanding and practically modelling surface and groundwater interactions. In South Africa, there remains much controversy over the most appropriate type of integrated model to be used and the way forward in terms of the development of the discipline; part of the disagreement stems from the fact that we cannot validate models adequately. This is largely due to traditional forms of model testing having limited power as it is difficult to differentiate between the uncertainties within different model structures, different sets of alternative parameter values and in the input data used to run the model. While model structural uncertainties are important to consider, the uncertainty from input data error together with parameter estimation error are often more significant to the overall residual error, and essential to consider if we want to achieve reliable predictions for water resource decisions. While new philosophies and theories on modelling and results validation have been developed (Beven, 2002; Gupta et al., 2008), in many cases models are not only still being validated and compared using sparse and uncertain datasets, but also expected to produce reliable predictions based on the flawed data. The approach in this study is focused on fundamental understanding of hydrological systems rather than calibration based modelling and promotes the use of all the available 'hard' and 'soft' data together with thoughtful conceptual examination of the processes occurring in an environment to ensure as far as possible that a model is generating sensible results by simulating the correct processes. The first part of the thesis focuses on characterising the 'typical' interaction environments found in South Africa. It was found that many traditional perceptual models are not necessarily applicable to South African conditions, largely due to the relative importance of unsaturated zone processes and the complexity of the dominantly fractured rock environments. The interaction environments were categorised into four main 'types' of environment. These include karst, primary, fractured rock (secondary), and alluvial environments. Processes critical to Integrated Water Resource Management (IWRM) were defined within each interaction type as a guideline to setting a model up to realistically represent the dominant processes in the respective settings. The second part of the thesis addressed the application and evaluation of the modified Pitman model (Hughes, 2004), which allows for surface and groundwater interaction behaviour at the catchment scale to be simulated. The issue is whether, given the different sources of uncertainty in the modelling process, we can differentiate one conceptual flow path from another in trying to refine the understanding and consequently have more faith in model predictions. Seven example catchments were selected from around South Africa to assess whether reliable integrated assessments can be carried out given the existing data. Specific catchment perceptual models were used to identify the critical processes occurring in each setting and the Pitman model was assessed on whether it could represent them (structural uncertainty). The available knowledge of specific environments or catchments was then examined in an attempt to resolve the parameter uncertainty present within each catchment and ensure the subsequent model setup was correctly representing the process understanding as far as possible. The confidence in the quantitative results inevitably varied with the amount and quality of the data available. While the model was deemed to be robust based on the behavioural results obtained in the majority of the case studies, in many cases a quantitative validation of the outputs was just not possible based on the available data. In these cases, the model was judged on its ability to represent the conceptualisation of the processes occurring in the catchments. While the lack of appropriate data means there will always be considerable uncertainty surrounding model validation, it can be argued that improved process understanding in an environment can be used to validate model outcomes to a degree, by assessing whether a model is getting the right results for the right reasons. Many water resource decisions are still made without adequate account being taken of the uncertainties inherent in assessing the response of hydrological systems. Certainly, with all the possible sources of uncertainty in a data scarce country such as South Africa, pure calibration based modelling is unlikely to produce reliable information for water resource managers as it can produce the right results for the wrong reasons. Thus it becomes essential to incorporate conceptual thinking into the modelling process, so that at the very least we are able to conclude that a model generates estimates that are consistent with, and reflect, our understanding (however limited) of the catchment processes. It is fairly clear that achieving the optimum model of a hydrological system may be fraught with difficulty, if not impossible. This makes it very difficult from a practitioner's point of view to decide which model and uncertainty estimation method to use. According to Beven (2009), this may be a transitional problem and in the future it may become clearer as we learn more about how to estimate the uncertainties associated with hydrological systems. Until then, a better understanding of the fundamental and most critical hydrogeological processes should be used to critically test and improve model predictions as far as possible. A major focus of the study was to identify whether the modified Pitman model could provide a practical tool for water resource managers by reliably determining the available water resource. The incorporation of surface and groundwater interaction routines seems to have resulted in a more robust and realistic model of basin hydrology. The overall conclusion is that the model, although simplified, is capable of representing the catchment scale processes that occur under most South African conditions.
- Full Text:
- Date Issued: 2014
Understanding a West African recreational fishery as a complex social-ecological system – a case study of the fishery for giant African threadfin Polydactylus quadrifilis (Cuvier, 1829) in the Kwanza Estuary, Angola
- Authors: Butler, Edward C
- Date: 2020
- Subjects: Cuanza River (Angola) , Fishing -- Angola , Polynemidae , Fishes -- Angola -- Ecology
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146688 , vital:38548
- Description: Despite increasing global recognition of the importance of recreational fisheries, their management largely remains poor. This is because they exhibit unique human-nature relationships and are nested within complex social-ecological systems (SESs). Recreational fisheries in the developing world have large potential for socio-economic development, but are generally underappreciated, in terms of their value and their impact, and are poorly governed. This is particularly concerning as they are highly complex and often compete for resources with dependent artisanal and subsistence fisheries. Developing world recreational fishery SESs are not well understood and present an important research gap for improved governance. The general aim of this thesis was to explore the recreational fishery targeting Polydactylus quadrifilis on the Kwanza Estuary, Angola, and provide context for how managers should approach recreational fisheries in the developing world and in Africa. To do this, the recreational fishery SES was explored using a combination of methodologies including those characteristic of traditional fisheries science, and new methods involving biology, sociology, and economics. The thesis contains an introductory chapter, a chapter describing the background, study area and study species, five data chapters and a discussion chapter. Chapter 3 aimed to investigate the reproductive style of P. quadrifilis. Results identified the species as a protandrous hermaphrodite. Evidence to suggest this included degenerating testicular tissue and the presence of early developing ovarian tissues in transitional individuals. Early-stage oocytes were commonly found in the outer area of male regions and residual late-stage spermatids and spermatozoa were found in the luminal space of ovarian regions, suggesting a process of sex change from the outside inwards. Owing to the species’ reliance on large highly fecund females for reproduction, it is likely that P. quadrifilis will be sensitive to fisheries that target larger individuals, such as trophy recreational fisheries and line fisheries within other sectors. Chapter 4 aimed to investigate alternative methods for adequately describing the growth of P. quadrifilis individuals belonging to either one of two distinct hypothetical life-history pathways: pathway I (‘changers’) – initial maturation as a primary male followed by a sex change to female; pathway II (‘non-changers’) – initial maturation as a male fish with no subsequent sex change, using von Bertalanffy Growth Functions (VBGFs). Other specific objectives included determining the size- and age-at-maturity and size- and age-at-sex-change for P. quadrifilis. Otolith aging revealed rapid growth and early maturation (L50 = 399.2 mm FL, A50 = 1.50 years) and sex change occurred over a wide size (790–1125 mm FL) and age (3–8 years) range. There was strong evidence for partial protandry in P. quadrifilis with several extremely old male fish (up to 22 years) observed in the population. When compared to the conventional model produced for the entire population, there were significant differences in the models for the ‘non-changers’ (LRT, p < 0.01) and their parameters L∞ (full model = 130.8, ‘non-changers’ = 113.3, p < 0.01), k (0.32, 0.44, p < 0.01) and t0 (0.23, 0.43, p = 0.03) in the first approach and the models (LRT, p < 0.01) and their L∞ (‘changers’ = 113.7, p < 0.01) values in the second approach. This suggests that utilising conventional modelling techniques may be inappropriate for the stock assessment and management of P. quadrifilis and, potentially, other sequentially hermaphroditic fishery species. Chapter 5 aimed to assess the sensitivity of P. quadrifilis to recreational C&R within the foreign recreational fishery using a rapid assessment approach. To do this, a number of C&R variables including fight time, air exposure, hook placement, hooking injury, total time of the stress event, river depth and angling method were measured and related to two indicators of fish health and survival – the physiological stress indicators blood glucose and blood lactate concentration and reflex action mortality predictors (RAMPs). Air exposure was identified as a major contributor to motor impairment (Cumulative Link Model: p < 0.01) and fight time was an important contributor to motor impairment via its interaction with air exposure (Cumulative Link Model: p = 0.02). Handling practices appear to be particularly important for larger individuals as fish size was positively correlated with air exposure (Pearson’s r coefficient = 0.41, p < 0.01) and fight times (0.88, p < 0.01). The findings suggest that recreational C&R may result in mortalities directly, via C&R, and indirectly, via predation, and several recommendations were made for best practice. Chapter 6 aimed to assess the direct economic contribution of the recreational fishery for Polydactylus quadrifilis on the Kwanza Estuary. Results indicated that the recreational fishery for contributed significantly to the economy of an area that would otherwise likely receive little external input ($282 054 per four-month fishing season). However, high rates of economic leakage from the study area were identified (58.7%–92.9% of locally spent revenue) and were attributed to the sourcing of lodge supplies, services and staff outside of the local area and the repatriation of profit by foreign business owners. Capacity building within the local community is likely required to develop ‘linkages’ between the local community and the recreational fishery. Greater community involvement in the fishery is suggested to incentivise the protection of recreationally important fishery species and their associated ecosystems. Chapter 7 aimed to investigate the resource user groups involved within the SES. Results illustrated that artisanal and domestic recreational anglers are well-established and are characterised by long histories of participation. The artisanal fishery was highly valued as a source of livelihoods for the local community. Artisanal fishers were eager for involvement in the recreational sector, through the chartering of their vessels, due to the attractiveness of extra earnings. Both recreational and artisanal fishers reported recent decreases in P. quadrifilis catch and anticipated further declines. Domestic recreational anglers appeared to be highly consumptive in their use of the fishery and C&R angling was uncommon. User conflict may be problematic for future management as recreational anglers perceived the artisanal gill-net fishery to be a threat towards P. quadrifilis stocks. In conclusion, the open-access nature of the fishery was identified as the most pertinent threat to its sustainability and likely needs to be addressed. Potential solutions involve offering users the opportunity to purchase access rights (e.g. day permits), thus initiating the concept that users must pay for their use of public resources. Management should aim to protect large female fish due to their increased reproductive value and worth as trophy fish. Thus, C&R angling is likely to be an important interaction between users and the resource. However, angler behaviour will need to be manipulated to promote C&R and minimise C&R-related mortalities. Solutions include angler educational drives and interventions and the implementation of competitive C&R-only angling. Foreign recreational fisheries, although touted as potential ecotourism ventures, will only succeed in improving the lives of local people if they fully integrate the community into the operation of the fishery.
- Full Text:
- Date Issued: 2020
- Authors: Butler, Edward C
- Date: 2020
- Subjects: Cuanza River (Angola) , Fishing -- Angola , Polynemidae , Fishes -- Angola -- Ecology
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/146688 , vital:38548
- Description: Despite increasing global recognition of the importance of recreational fisheries, their management largely remains poor. This is because they exhibit unique human-nature relationships and are nested within complex social-ecological systems (SESs). Recreational fisheries in the developing world have large potential for socio-economic development, but are generally underappreciated, in terms of their value and their impact, and are poorly governed. This is particularly concerning as they are highly complex and often compete for resources with dependent artisanal and subsistence fisheries. Developing world recreational fishery SESs are not well understood and present an important research gap for improved governance. The general aim of this thesis was to explore the recreational fishery targeting Polydactylus quadrifilis on the Kwanza Estuary, Angola, and provide context for how managers should approach recreational fisheries in the developing world and in Africa. To do this, the recreational fishery SES was explored using a combination of methodologies including those characteristic of traditional fisheries science, and new methods involving biology, sociology, and economics. The thesis contains an introductory chapter, a chapter describing the background, study area and study species, five data chapters and a discussion chapter. Chapter 3 aimed to investigate the reproductive style of P. quadrifilis. Results identified the species as a protandrous hermaphrodite. Evidence to suggest this included degenerating testicular tissue and the presence of early developing ovarian tissues in transitional individuals. Early-stage oocytes were commonly found in the outer area of male regions and residual late-stage spermatids and spermatozoa were found in the luminal space of ovarian regions, suggesting a process of sex change from the outside inwards. Owing to the species’ reliance on large highly fecund females for reproduction, it is likely that P. quadrifilis will be sensitive to fisheries that target larger individuals, such as trophy recreational fisheries and line fisheries within other sectors. Chapter 4 aimed to investigate alternative methods for adequately describing the growth of P. quadrifilis individuals belonging to either one of two distinct hypothetical life-history pathways: pathway I (‘changers’) – initial maturation as a primary male followed by a sex change to female; pathway II (‘non-changers’) – initial maturation as a male fish with no subsequent sex change, using von Bertalanffy Growth Functions (VBGFs). Other specific objectives included determining the size- and age-at-maturity and size- and age-at-sex-change for P. quadrifilis. Otolith aging revealed rapid growth and early maturation (L50 = 399.2 mm FL, A50 = 1.50 years) and sex change occurred over a wide size (790–1125 mm FL) and age (3–8 years) range. There was strong evidence for partial protandry in P. quadrifilis with several extremely old male fish (up to 22 years) observed in the population. When compared to the conventional model produced for the entire population, there were significant differences in the models for the ‘non-changers’ (LRT, p < 0.01) and their parameters L∞ (full model = 130.8, ‘non-changers’ = 113.3, p < 0.01), k (0.32, 0.44, p < 0.01) and t0 (0.23, 0.43, p = 0.03) in the first approach and the models (LRT, p < 0.01) and their L∞ (‘changers’ = 113.7, p < 0.01) values in the second approach. This suggests that utilising conventional modelling techniques may be inappropriate for the stock assessment and management of P. quadrifilis and, potentially, other sequentially hermaphroditic fishery species. Chapter 5 aimed to assess the sensitivity of P. quadrifilis to recreational C&R within the foreign recreational fishery using a rapid assessment approach. To do this, a number of C&R variables including fight time, air exposure, hook placement, hooking injury, total time of the stress event, river depth and angling method were measured and related to two indicators of fish health and survival – the physiological stress indicators blood glucose and blood lactate concentration and reflex action mortality predictors (RAMPs). Air exposure was identified as a major contributor to motor impairment (Cumulative Link Model: p < 0.01) and fight time was an important contributor to motor impairment via its interaction with air exposure (Cumulative Link Model: p = 0.02). Handling practices appear to be particularly important for larger individuals as fish size was positively correlated with air exposure (Pearson’s r coefficient = 0.41, p < 0.01) and fight times (0.88, p < 0.01). The findings suggest that recreational C&R may result in mortalities directly, via C&R, and indirectly, via predation, and several recommendations were made for best practice. Chapter 6 aimed to assess the direct economic contribution of the recreational fishery for Polydactylus quadrifilis on the Kwanza Estuary. Results indicated that the recreational fishery for contributed significantly to the economy of an area that would otherwise likely receive little external input ($282 054 per four-month fishing season). However, high rates of economic leakage from the study area were identified (58.7%–92.9% of locally spent revenue) and were attributed to the sourcing of lodge supplies, services and staff outside of the local area and the repatriation of profit by foreign business owners. Capacity building within the local community is likely required to develop ‘linkages’ between the local community and the recreational fishery. Greater community involvement in the fishery is suggested to incentivise the protection of recreationally important fishery species and their associated ecosystems. Chapter 7 aimed to investigate the resource user groups involved within the SES. Results illustrated that artisanal and domestic recreational anglers are well-established and are characterised by long histories of participation. The artisanal fishery was highly valued as a source of livelihoods for the local community. Artisanal fishers were eager for involvement in the recreational sector, through the chartering of their vessels, due to the attractiveness of extra earnings. Both recreational and artisanal fishers reported recent decreases in P. quadrifilis catch and anticipated further declines. Domestic recreational anglers appeared to be highly consumptive in their use of the fishery and C&R angling was uncommon. User conflict may be problematic for future management as recreational anglers perceived the artisanal gill-net fishery to be a threat towards P. quadrifilis stocks. In conclusion, the open-access nature of the fishery was identified as the most pertinent threat to its sustainability and likely needs to be addressed. Potential solutions involve offering users the opportunity to purchase access rights (e.g. day permits), thus initiating the concept that users must pay for their use of public resources. Management should aim to protect large female fish due to their increased reproductive value and worth as trophy fish. Thus, C&R angling is likely to be an important interaction between users and the resource. However, angler behaviour will need to be manipulated to promote C&R and minimise C&R-related mortalities. Solutions include angler educational drives and interventions and the implementation of competitive C&R-only angling. Foreign recreational fisheries, although touted as potential ecotourism ventures, will only succeed in improving the lives of local people if they fully integrate the community into the operation of the fishery.
- Full Text:
- Date Issued: 2020
Uncertainties in modelling hydrological responses in gauged and ungauged sub‐basins
- Authors: Tumbo, Madaka Harold
- Date: 2015
- Subjects: Hydrologic models , Watersheds -- Tanzania , Water-supply -- Tanzania -- Great Ruaha River Watershed , Water resources development -- Tanzania -- Great Ruaha River Watershed , Rain and rainfall -- Mathematical models , Rain gauges -- Tanzania -- Great Ruaha River Watershed , Great Ruaha River Watershed (Tanzania)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6053 , http://hdl.handle.net/10962/d1018568
- Description: The world is undergoing rapid changes and the future is uncertain. The changes are related to modification of the landscape due to human activities, such as large and small scale irrigation, afforestation and changes to the climate system. Understanding and predicting hydrologic change is one of the challenges facing hydrologists today. Part of this understanding can be developed from observed data, however, there often too few observations and those that are available are frequently affected by uncertainties. Hydrological models have become essential tools for understanding historical variations of catchment hydrology and for predicting future possible trends. However, most developing countries are faced with poor spatial distributions of rainfall and evaporation stations that provide the data used to force models, as well as stream flow gauging stations to provide the data for establishing models and for evaluating their success. Hydrological models are faced with a number of challenges which include poor input data (data quality and poorly quantified human activities on observed stream flow data), uncertainties associated with model complexity and structure, the methods used to quantify model parameters, together with the difficulties of understanding hydrological processes at the catchment or subbasin. Within hydrological modelling, there is currently a trend of dealing with equifinality through the evaluation of parameter identifiability and the quantification of uncertainty bands associated with the predictions of the model. Hydrological models should not only focus on reproducing the past behaviour of a basin, but also on evaluating the representativeness of the surface and subsurface model components and their ability to simulate reality for the correct reasons. Part of this modelling process therefore involves quantifying and including all the possible sources of uncertainty. Uncertainty analysis has become the standard approach to most hydrological modelling studies, but has yet to be effectively used in practical water resources assessment. This study applied a hydrological modelling approach for understanding the hydrology of a large Tanzanian drainage basin, the Great Ruaha River that has many areas that are ungauged and where the available data (climate, stream flow and existing water use) are subject to varying degrees of uncertainty. The Great Ruaha River (GRR) is an upstream tributary of the Rufiji River Basin within Tanzania and covers an area of 86 000 km2. The basin is drained by four main tributaries; the Upper Great Ruaha, the Kisigo, the Little Ruaha and the Lukosi. The majority of the runoff is generated from the Chunya escarpment, the Kipengere ranges and the Poroto Mountains. The runoff generated feeds the alluvial and seasonally flooded Usangu plains (including the Ihefu perennial swamp). The majority of the irrigation water use in the basin is located where headwater sub‐basins drain towards the Usangu plains. The overall objective was to establish uncertain but behavioural hydrological models that could be useful for future water resources assessments that are likely to include issues of land use change, changes in patterns of abstraction and water use, as well the possibility of change in future climates.
- Full Text:
- Date Issued: 2015
- Authors: Tumbo, Madaka Harold
- Date: 2015
- Subjects: Hydrologic models , Watersheds -- Tanzania , Water-supply -- Tanzania -- Great Ruaha River Watershed , Water resources development -- Tanzania -- Great Ruaha River Watershed , Rain and rainfall -- Mathematical models , Rain gauges -- Tanzania -- Great Ruaha River Watershed , Great Ruaha River Watershed (Tanzania)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6053 , http://hdl.handle.net/10962/d1018568
- Description: The world is undergoing rapid changes and the future is uncertain. The changes are related to modification of the landscape due to human activities, such as large and small scale irrigation, afforestation and changes to the climate system. Understanding and predicting hydrologic change is one of the challenges facing hydrologists today. Part of this understanding can be developed from observed data, however, there often too few observations and those that are available are frequently affected by uncertainties. Hydrological models have become essential tools for understanding historical variations of catchment hydrology and for predicting future possible trends. However, most developing countries are faced with poor spatial distributions of rainfall and evaporation stations that provide the data used to force models, as well as stream flow gauging stations to provide the data for establishing models and for evaluating their success. Hydrological models are faced with a number of challenges which include poor input data (data quality and poorly quantified human activities on observed stream flow data), uncertainties associated with model complexity and structure, the methods used to quantify model parameters, together with the difficulties of understanding hydrological processes at the catchment or subbasin. Within hydrological modelling, there is currently a trend of dealing with equifinality through the evaluation of parameter identifiability and the quantification of uncertainty bands associated with the predictions of the model. Hydrological models should not only focus on reproducing the past behaviour of a basin, but also on evaluating the representativeness of the surface and subsurface model components and their ability to simulate reality for the correct reasons. Part of this modelling process therefore involves quantifying and including all the possible sources of uncertainty. Uncertainty analysis has become the standard approach to most hydrological modelling studies, but has yet to be effectively used in practical water resources assessment. This study applied a hydrological modelling approach for understanding the hydrology of a large Tanzanian drainage basin, the Great Ruaha River that has many areas that are ungauged and where the available data (climate, stream flow and existing water use) are subject to varying degrees of uncertainty. The Great Ruaha River (GRR) is an upstream tributary of the Rufiji River Basin within Tanzania and covers an area of 86 000 km2. The basin is drained by four main tributaries; the Upper Great Ruaha, the Kisigo, the Little Ruaha and the Lukosi. The majority of the runoff is generated from the Chunya escarpment, the Kipengere ranges and the Poroto Mountains. The runoff generated feeds the alluvial and seasonally flooded Usangu plains (including the Ihefu perennial swamp). The majority of the irrigation water use in the basin is located where headwater sub‐basins drain towards the Usangu plains. The overall objective was to establish uncertain but behavioural hydrological models that could be useful for future water resources assessments that are likely to include issues of land use change, changes in patterns of abstraction and water use, as well the possibility of change in future climates.
- Full Text:
- Date Issued: 2015
Ultraviolet specular reflectance, electronic absorption and the excitation of fluorescence in single crystals of anthracene
- Authors: Wright, W H
- Date: 1966
- Subjects: Anthracene crystals -- Fluorescence , Ultraviolet spectroscopy -- Absorption , Reflectance
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5544 , http://hdl.handle.net/10962/d1013366
- Description: From introduction: The Fluorescence Excitation Spectrum or anthracene is known to vary considerably with the age and condition or the crystal. This thesis represents an attempt to improve the understanding of these variations. To put the problem on a quantitative basis it was found necessary to know both the ultraviolet reflection and absorption spectra. Reports of the reflection spectrum appear to have been confined to the case of polarised incident light. In addition the reflectivity measurements are always reported for a freshly cleaved surface. For these reasons the reflectivity of anthracene for various conditions of the reflecting surface was measured with unpolarised light. These varying reflectivities were used to further knowledge of the chemical processes at the crystal surface, as well as being used directly in the calculation of fluorescence excitation spectra. Reflection spectra with a- and b- crystallographic axis polarisations were also obtained. Since such spectra are reported in the literature it was possible, by comparison, to conclude that the experimental methods used in this thesis yielded valid results. The polarised measurements were used to obtain optical constants for the crystal. In the interests of readability most of the complicated process of converting the reflectivities to optical constants is dealt with in three appendices to the thesis.
- Full Text:
- Date Issued: 1966
- Authors: Wright, W H
- Date: 1966
- Subjects: Anthracene crystals -- Fluorescence , Ultraviolet spectroscopy -- Absorption , Reflectance
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5544 , http://hdl.handle.net/10962/d1013366
- Description: From introduction: The Fluorescence Excitation Spectrum or anthracene is known to vary considerably with the age and condition or the crystal. This thesis represents an attempt to improve the understanding of these variations. To put the problem on a quantitative basis it was found necessary to know both the ultraviolet reflection and absorption spectra. Reports of the reflection spectrum appear to have been confined to the case of polarised incident light. In addition the reflectivity measurements are always reported for a freshly cleaved surface. For these reasons the reflectivity of anthracene for various conditions of the reflecting surface was measured with unpolarised light. These varying reflectivities were used to further knowledge of the chemical processes at the crystal surface, as well as being used directly in the calculation of fluorescence excitation spectra. Reflection spectra with a- and b- crystallographic axis polarisations were also obtained. Since such spectra are reported in the literature it was possible, by comparison, to conclude that the experimental methods used in this thesis yielded valid results. The polarised measurements were used to obtain optical constants for the crystal. In the interests of readability most of the complicated process of converting the reflectivities to optical constants is dealt with in three appendices to the thesis.
- Full Text:
- Date Issued: 1966
Ultra-high precision diamond turning of advanced contact lens polymers
- Authors: Liman, Muhammad Mukhtar
- Date: 2020
- Subjects: Contact lenses , Electrostatic lenses Lenses -- Design and construction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46108 , vital:39496
- Description: Contact lens polymer-based materials are extensively used in the optical industry owing to their excellent corrosion resistance, the possibility of mass production and their ability to be processed without external lubrication. Owing to the fast growth in optical industries, contact lens (CL) requires high accuracy and a high surface quality. The demand for high-accuracy and minimal surface roughness drives the development of ultra-high precision machining technology with regard to single point diamond turning (SPDT). Ultra-high precision diamond turning is an advanced manufacturing technique employed in the machining of CLs owing to its capability of producing high optical surfaces with complex shapes and nanometric accuracy. Yet, even with the advances in ultra-high precision machining (UHPM), it is not continuously easy to achieve a highquality surface finish during polymers machining as the adhesion of the tool chip around the tool dictates the presence of electrostatic charges. The electrostatic charges encountered by a cutting tool when turning advanced CLs are important as they reflect the quality and condition of the tool, machine, fixture, and sometimes even the finished surface, which is responsible for tool wear and poor surface quality. This study investigates the role of cutting parameters, namely cutting speed, feed rate and depth of cut on surface roughness (Ra), electrostatic charge (ESC) and material removal rate (MRR), which determines machine economics and the quality of machining contact lens polymers. The experiments were mainly conducted on two different advanced polymeric materials: polymethyl methacrylate (PMMA) and Optimum Extreme (Roflufocon E) CLs. Experimentation was carried out on the Nanoform 250 ultra-grind turning machine with a monocrystalline diamond-cutting tool for machining the PMMA and Roflufocon E CL polymers, covering a wide range of machining parameters. Before conducting the experiments, a design of experiment was conducted according to the response surface methodology (RSM) that is based on the Box-Behnken Design (BBD). In addition, the research study focused on the determination of the optimum cutting conditions leading to minimum Ra and ESC as well as maximum productivity in the SPDT of the PMMA and Roflufocon E CL polymers, using a monocrystalline diamondcutting tool. The optimization was based on RSM together with the desirability function approach. In addition, a mathematical model was developed for Ra, ESC and MRR using a RSM regression analysis for PMMA and Roflufocon E CL polymers by means of Design Expert software. RSM allowed for the optimization of the cutting conditions for minimal Ra and ESC as well as maximal MRR, which provides an effective knowledge base for process parameters to enhance process performance in the SPDT of CL polymers. Furthermore, this study also deals with the development of Ra, ESC and MRR prediction models for the diamond turning of PMMA and Roflufocon E CL polymers, using the fuzzy logic based artificial intelligence (AI) method. The fuzzy logic model has been developed in terms of machining parameters for the prediction of Ra, ESC and MRR. To judge the accuracy and ability of the fuzzy logic model, an average percentage error was used. The comparative evaluation of experiments and the fuzzy logic approach suggested that the obtained average errors of Ra, ESC and MRR using the fuzzy logic system were in agreement with the experimental results. Hence, the developed fuzzy logic rules can be effectively utilized to predict the ESC, Ra and MRR of PMMA and Roflufocon E CL polymers in automated optical manufacturing environments for high accuracy and a reduction of computational cost. Moreover, owing to the brittle nature of optical polymers, the Roflufocon E CL polymer requires ductile-mode machining for improved surface quality. Molecular Dynamics (MD) simulation methods are thus applied to investigate the atomistic reaction at the tool/workpiece surface to clearly study and observe conditions occurring at nanometric scale in polymer machining. This research study is particularly concerned with the comparative analysis of experiments and a MD study of the Roflufocon E optical polymer nano cutting approach to the atomistic visualization of the plastic material flow at the tool/workpiece interface during cutting. The simulated MD acting force, machine stresses, and the temperature at the cutting region were evaluated to access the accuracy of the model. Hence, the nanomachining simulations were found to have a correlation to the experimental machining results.
- Full Text:
- Date Issued: 2020
- Authors: Liman, Muhammad Mukhtar
- Date: 2020
- Subjects: Contact lenses , Electrostatic lenses Lenses -- Design and construction
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/46108 , vital:39496
- Description: Contact lens polymer-based materials are extensively used in the optical industry owing to their excellent corrosion resistance, the possibility of mass production and their ability to be processed without external lubrication. Owing to the fast growth in optical industries, contact lens (CL) requires high accuracy and a high surface quality. The demand for high-accuracy and minimal surface roughness drives the development of ultra-high precision machining technology with regard to single point diamond turning (SPDT). Ultra-high precision diamond turning is an advanced manufacturing technique employed in the machining of CLs owing to its capability of producing high optical surfaces with complex shapes and nanometric accuracy. Yet, even with the advances in ultra-high precision machining (UHPM), it is not continuously easy to achieve a highquality surface finish during polymers machining as the adhesion of the tool chip around the tool dictates the presence of electrostatic charges. The electrostatic charges encountered by a cutting tool when turning advanced CLs are important as they reflect the quality and condition of the tool, machine, fixture, and sometimes even the finished surface, which is responsible for tool wear and poor surface quality. This study investigates the role of cutting parameters, namely cutting speed, feed rate and depth of cut on surface roughness (Ra), electrostatic charge (ESC) and material removal rate (MRR), which determines machine economics and the quality of machining contact lens polymers. The experiments were mainly conducted on two different advanced polymeric materials: polymethyl methacrylate (PMMA) and Optimum Extreme (Roflufocon E) CLs. Experimentation was carried out on the Nanoform 250 ultra-grind turning machine with a monocrystalline diamond-cutting tool for machining the PMMA and Roflufocon E CL polymers, covering a wide range of machining parameters. Before conducting the experiments, a design of experiment was conducted according to the response surface methodology (RSM) that is based on the Box-Behnken Design (BBD). In addition, the research study focused on the determination of the optimum cutting conditions leading to minimum Ra and ESC as well as maximum productivity in the SPDT of the PMMA and Roflufocon E CL polymers, using a monocrystalline diamondcutting tool. The optimization was based on RSM together with the desirability function approach. In addition, a mathematical model was developed for Ra, ESC and MRR using a RSM regression analysis for PMMA and Roflufocon E CL polymers by means of Design Expert software. RSM allowed for the optimization of the cutting conditions for minimal Ra and ESC as well as maximal MRR, which provides an effective knowledge base for process parameters to enhance process performance in the SPDT of CL polymers. Furthermore, this study also deals with the development of Ra, ESC and MRR prediction models for the diamond turning of PMMA and Roflufocon E CL polymers, using the fuzzy logic based artificial intelligence (AI) method. The fuzzy logic model has been developed in terms of machining parameters for the prediction of Ra, ESC and MRR. To judge the accuracy and ability of the fuzzy logic model, an average percentage error was used. The comparative evaluation of experiments and the fuzzy logic approach suggested that the obtained average errors of Ra, ESC and MRR using the fuzzy logic system were in agreement with the experimental results. Hence, the developed fuzzy logic rules can be effectively utilized to predict the ESC, Ra and MRR of PMMA and Roflufocon E CL polymers in automated optical manufacturing environments for high accuracy and a reduction of computational cost. Moreover, owing to the brittle nature of optical polymers, the Roflufocon E CL polymer requires ductile-mode machining for improved surface quality. Molecular Dynamics (MD) simulation methods are thus applied to investigate the atomistic reaction at the tool/workpiece surface to clearly study and observe conditions occurring at nanometric scale in polymer machining. This research study is particularly concerned with the comparative analysis of experiments and a MD study of the Roflufocon E optical polymer nano cutting approach to the atomistic visualization of the plastic material flow at the tool/workpiece interface during cutting. The simulated MD acting force, machine stresses, and the temperature at the cutting region were evaluated to access the accuracy of the model. Hence, the nanomachining simulations were found to have a correlation to the experimental machining results.
- Full Text:
- Date Issued: 2020
Trophodynamics of the benthic and hyperbenthic communities inhabiting the Sub-Antarctic Prince Edward Islands : stable isotope and fatty acid signatures
- Authors: Allan, Elizabeth Louise
- Date: 2011
- Subjects: Benthos -- Prince Edward Islands Benthos -- Feeding and feeds -- Prince Edward Islands Benthos -- Nutrition -- Prince Edward Islands Prince Edward Islands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5806 , http://hdl.handle.net/10962/d1006350
- Description: The aim of this study was to investigate spatial changes in the trophic and energy pathways of the benthic community in the shallow shelf waters of the sub-Antarctic Prince Edward Islands (PEI). A combination of stable isotope and fatty acid analyses were used to provide a time-integrated view of the assimilated feeding history of selected components of the PEI benthic community. This study forms part of the larger project entitled “Variability in the Southern Ocean ecosystems” and is a contribution to the South African National Antarctic Programme (SANAP). During austral autumn 2009, benthic specimens were collected from 10 stations (from depths of 70 to 295 m) in different regions around the PEI: inter-island shelf (upstream, between and downstream of the islands) and nearshore. Historical data were combined with new data collected during 2009 to assess the long-term trends in the feeding ecology of the benthos in the region of the islands. The stable isotope and fatty acid signatures of the benthic suspension- and deposit-feeding organisms generated during this study suggested that these two communities incorporated both phytoplankton and kelp in their diets. Stable isotope, and to a lesser extent fatty acid signatures, indicated that kelp contributed more to the diets of those organisms in close proximity to the kelp beds (nearshore stations) than those from the inter-island region. Overall, however, pelagic phytoplankton was the dominant food source in the diets of all organisms, even for those living near the kelp beds. Notable exceptions were the sponges and bryozoans, in which kelp and phytoplankton contributed similar proportions to their diets, most likely resulting from a size restricted feeding mode. There were, therefore, no distinct spatial differences in the importance of the various food sources. However, fatty acid compositional data indicated increased food quality between and within the lee of the islands compared to upstream. The organisms collected upstream of the PEI had substantially lower quantities of total fatty acids (TFAs) than organisms of the same species collected from nearshore, open shelf or downstream stations. The increased food quality between and within the lee of the islands was likely a result of the “island mass effect”, which reflects increased phytoplankton concentrations at the PEI. The fatty acid profiles of hyperbenthic shrimp Nauticaris marionis, a key species in the PEI ecosystem, revealed no distinct ontogenetic or spatial patterns. This result is in contrast to the stable isotope analyses, which detected both spatial and ontogenetic differences in the diet of the shrimp. Nearshore shrimp were more ₁₃C-enriched than those from the inter-island region, suggesting increased kelp entering the food web within these regions. In addition, the shrimps demonstrated enrichment in δ₁₃C and δ₁₅N signatures with an increase in size, resulting in a relatively distinct separation of size classes, thus reflecting niche separation through their diets. The fatty acid profiles revealed that the shrimp all contained large proportions of polyunsaturated fatty acids (PUFAs) and essential fatty acids (EFAs), indicating that the quality of food consumed was similar among size class and region despite the niche separation and variation in carbon sources utilised. In addition, diatom and dinoflagellate fatty acids (20:5ω3 and 22:6ω3, respectively) occurred in the highest proportions in N. marionis, highlighting the importance of phytoplankton (indirectly) in their diet. These results represent strong evidence that phytoplankton is an importance food source in the PEI ecosystem. The temporal investigation of isotope signatures in the benthos at the PEI indicated that N. marionis demonstrated an overall depletion in δ₁₃C signatures over the period of 1984 to 2009 (nearshore: -2.55 ‰, inter-island: -2.32 ‰). Overall, the benthic community showed similar depletions in δ13C signatures (from -1.96 to -4.70 ‰), suggesting that shifts have occurred in the carbon signatures at the base of the food web. The depletion in δ₁₃C signatures of the benthos at the PEI most likely reflects increased contributions of smaller slow growing phytoplankton cells (more depleted signatures than large fast growing cells) in the diets of these organisms over time. These diet shifts, in turn, suggest a decrease in productivity has occurred at the islands, likely due to a decreased frequency and intensity of the “island mass effect”. Decreased phytoplankton productivity at the PEI likely results from the southward shift in the average position of the sub-Antarctic Front (SAF), most likely in response to climate change, which in turn promotes flow-through conditions rather than retention at the PEI.
- Full Text:
- Date Issued: 2011
- Authors: Allan, Elizabeth Louise
- Date: 2011
- Subjects: Benthos -- Prince Edward Islands Benthos -- Feeding and feeds -- Prince Edward Islands Benthos -- Nutrition -- Prince Edward Islands Prince Edward Islands
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5806 , http://hdl.handle.net/10962/d1006350
- Description: The aim of this study was to investigate spatial changes in the trophic and energy pathways of the benthic community in the shallow shelf waters of the sub-Antarctic Prince Edward Islands (PEI). A combination of stable isotope and fatty acid analyses were used to provide a time-integrated view of the assimilated feeding history of selected components of the PEI benthic community. This study forms part of the larger project entitled “Variability in the Southern Ocean ecosystems” and is a contribution to the South African National Antarctic Programme (SANAP). During austral autumn 2009, benthic specimens were collected from 10 stations (from depths of 70 to 295 m) in different regions around the PEI: inter-island shelf (upstream, between and downstream of the islands) and nearshore. Historical data were combined with new data collected during 2009 to assess the long-term trends in the feeding ecology of the benthos in the region of the islands. The stable isotope and fatty acid signatures of the benthic suspension- and deposit-feeding organisms generated during this study suggested that these two communities incorporated both phytoplankton and kelp in their diets. Stable isotope, and to a lesser extent fatty acid signatures, indicated that kelp contributed more to the diets of those organisms in close proximity to the kelp beds (nearshore stations) than those from the inter-island region. Overall, however, pelagic phytoplankton was the dominant food source in the diets of all organisms, even for those living near the kelp beds. Notable exceptions were the sponges and bryozoans, in which kelp and phytoplankton contributed similar proportions to their diets, most likely resulting from a size restricted feeding mode. There were, therefore, no distinct spatial differences in the importance of the various food sources. However, fatty acid compositional data indicated increased food quality between and within the lee of the islands compared to upstream. The organisms collected upstream of the PEI had substantially lower quantities of total fatty acids (TFAs) than organisms of the same species collected from nearshore, open shelf or downstream stations. The increased food quality between and within the lee of the islands was likely a result of the “island mass effect”, which reflects increased phytoplankton concentrations at the PEI. The fatty acid profiles of hyperbenthic shrimp Nauticaris marionis, a key species in the PEI ecosystem, revealed no distinct ontogenetic or spatial patterns. This result is in contrast to the stable isotope analyses, which detected both spatial and ontogenetic differences in the diet of the shrimp. Nearshore shrimp were more ₁₃C-enriched than those from the inter-island region, suggesting increased kelp entering the food web within these regions. In addition, the shrimps demonstrated enrichment in δ₁₃C and δ₁₅N signatures with an increase in size, resulting in a relatively distinct separation of size classes, thus reflecting niche separation through their diets. The fatty acid profiles revealed that the shrimp all contained large proportions of polyunsaturated fatty acids (PUFAs) and essential fatty acids (EFAs), indicating that the quality of food consumed was similar among size class and region despite the niche separation and variation in carbon sources utilised. In addition, diatom and dinoflagellate fatty acids (20:5ω3 and 22:6ω3, respectively) occurred in the highest proportions in N. marionis, highlighting the importance of phytoplankton (indirectly) in their diet. These results represent strong evidence that phytoplankton is an importance food source in the PEI ecosystem. The temporal investigation of isotope signatures in the benthos at the PEI indicated that N. marionis demonstrated an overall depletion in δ₁₃C signatures over the period of 1984 to 2009 (nearshore: -2.55 ‰, inter-island: -2.32 ‰). Overall, the benthic community showed similar depletions in δ13C signatures (from -1.96 to -4.70 ‰), suggesting that shifts have occurred in the carbon signatures at the base of the food web. The depletion in δ₁₃C signatures of the benthos at the PEI most likely reflects increased contributions of smaller slow growing phytoplankton cells (more depleted signatures than large fast growing cells) in the diets of these organisms over time. These diet shifts, in turn, suggest a decrease in productivity has occurred at the islands, likely due to a decreased frequency and intensity of the “island mass effect”. Decreased phytoplankton productivity at the PEI likely results from the southward shift in the average position of the sub-Antarctic Front (SAF), most likely in response to climate change, which in turn promotes flow-through conditions rather than retention at the PEI.
- Full Text:
- Date Issued: 2011
Trophic relationships of hake (Merluccius capensis Castelnau, 1851 and M. paradoxus Franca 1960) from the Northern Benguela current ecosystem (Namibia) : inferences from stable isotopes and fatty acids
- Authors: Iitembu, Johannes Angala
- Date: 2014
- Subjects: Hake -- Benguela Current , Merlucciidae -- Benguela Current , Multitrophic interactions (Ecology) , Food chains (Ecology) , Biotic communities -- Benguela Current , Merlucciidae -- Food , Fishery management -- Namibia , Stable isotopes , Fatty acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5944 , http://hdl.handle.net/10962/d1020296
- Description: Two species of hake (Merluccius capensis and Merluccius paradoxus) account for most of Namibia’s fisheries catch, and they are important secondary consumers in the Benguela Current ecosystem. Inferences on their trophic relationships have been based mainly on stomach content analyses. However, such data are limited temporally because they represent only snapshots of recent feeding, and are quantitatively biased because of variation in the digestion rates of different prey. The principal aim of the thesis was to understand the trophic relationships of two hake species relative to each other, their known prey and top predators (demersal sharks) in the northern Benguela Current ecosystem (Namibia), using time-integrating trophic biomarkers. By using stable isotope (carbon and nitrogen) and fatty acid signatures of their muscle tissues, my overall objectives were to produce new knowledge about 1) hake ontogenic trophic relationships, 2) the contributions of different prey to hake diets, 3) hake dietary differences, and 4) some aspects of hake’s trophic relationships with demersal sharks. Tissues of hake (n=358), their potential prey (n=455), and demersal sharks (n=42) were collected between 2008 and 2012 during demersal bottom trawl surveys off Namibia, for stable isotope and fatty acid analyses. And more...
- Full Text:
- Date Issued: 2014
- Authors: Iitembu, Johannes Angala
- Date: 2014
- Subjects: Hake -- Benguela Current , Merlucciidae -- Benguela Current , Multitrophic interactions (Ecology) , Food chains (Ecology) , Biotic communities -- Benguela Current , Merlucciidae -- Food , Fishery management -- Namibia , Stable isotopes , Fatty acids
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5944 , http://hdl.handle.net/10962/d1020296
- Description: Two species of hake (Merluccius capensis and Merluccius paradoxus) account for most of Namibia’s fisheries catch, and they are important secondary consumers in the Benguela Current ecosystem. Inferences on their trophic relationships have been based mainly on stomach content analyses. However, such data are limited temporally because they represent only snapshots of recent feeding, and are quantitatively biased because of variation in the digestion rates of different prey. The principal aim of the thesis was to understand the trophic relationships of two hake species relative to each other, their known prey and top predators (demersal sharks) in the northern Benguela Current ecosystem (Namibia), using time-integrating trophic biomarkers. By using stable isotope (carbon and nitrogen) and fatty acid signatures of their muscle tissues, my overall objectives were to produce new knowledge about 1) hake ontogenic trophic relationships, 2) the contributions of different prey to hake diets, 3) hake dietary differences, and 4) some aspects of hake’s trophic relationships with demersal sharks. Tissues of hake (n=358), their potential prey (n=455), and demersal sharks (n=42) were collected between 2008 and 2012 during demersal bottom trawl surveys off Namibia, for stable isotope and fatty acid analyses. And more...
- Full Text:
- Date Issued: 2014
Trials and triumphs in public office: the life and work of E J N Mabuza
- Authors: Sarimana, Ashley
- Date: 2011
- Subjects: Mabuza, E J (Enos John), 1939- Public officers -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 20th century South Africa -- Social conditions -- 20th century Homelands (South Africa) -- Politics and government -- 20th century Homelands (South Africa) -- History -- 20th century Homelands (South Africa) -- Social conditions -- 20th century Apartheid -- South Africa South Africa -- Race relations Actor-network theory
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3305 , http://hdl.handle.net/10962/d1003093
- Description: Enos John Nganani Mabuza's life and work is used as a case study to highlight the conceptual and methodological theories and challenges in academic biographical writing regarding history, memory and legacies. This thesis answers the question: Who was Mabuza and what is his place or relevance in South Africa's history? We over-simplify and stereotype people because it is convenient. We judge others but there is no saint without a past or a sinner without a future. Mabuza reconciled with the main liberation movements and moved from a maligned position on the political fringes to a respectable one within the emerging black economic elite. History, like reference systems and values is not calcified or static. It is prone to interpretation, adaptation, modification, invention, manipulation, decomposition and re-composition. Bourdieu's habitus-field analysis, theory or logic of practice, notions of capital (symbolic, political, social, cultural and economic) is used together with Latour's actor-network theory as the basis of analysis of the social contracts and trust bonds that Mabuza was able to create and which enabled him to navigate South Africa's socio-political and economic milieus during apartheid and the transition in the early 1990s. As people or actors, we believe in the mantra, nothing ventured, nothing gained. We exercise agency and take risks every day. We make choices and those choices have consequences. Mabuza's choices in the fields of education, politics and business had implications for how he is perceived or has been written into history. His choices put notions of identity, citizenship, power, legitimacy, ambition, elite accommodation, class, personal and professional networks, popular struggles, agency and structure under the spotlight. Mabuza's involvement in Bantustan politics, for instance, is contextualised in terms of a historical overview of the unpopular role played by traditional authorities in South Africa before and during colonialism and apartheid. His later foray into the world of business, however, was facilitated in part, by the personal and professional contacts that he made whilst he was in politics and the opportunities which opened up during the country's political transition. Mabuza adapted to changing circumstances and demonstrated a level of versatility which other Bantustan functionaries did not or could not exercise.
- Full Text:
- Date Issued: 2011
- Authors: Sarimana, Ashley
- Date: 2011
- Subjects: Mabuza, E J (Enos John), 1939- Public officers -- South Africa South Africa -- Politics and government -- 20th century South Africa -- History -- 20th century South Africa -- Social conditions -- 20th century Homelands (South Africa) -- Politics and government -- 20th century Homelands (South Africa) -- History -- 20th century Homelands (South Africa) -- Social conditions -- 20th century Apartheid -- South Africa South Africa -- Race relations Actor-network theory
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3305 , http://hdl.handle.net/10962/d1003093
- Description: Enos John Nganani Mabuza's life and work is used as a case study to highlight the conceptual and methodological theories and challenges in academic biographical writing regarding history, memory and legacies. This thesis answers the question: Who was Mabuza and what is his place or relevance in South Africa's history? We over-simplify and stereotype people because it is convenient. We judge others but there is no saint without a past or a sinner without a future. Mabuza reconciled with the main liberation movements and moved from a maligned position on the political fringes to a respectable one within the emerging black economic elite. History, like reference systems and values is not calcified or static. It is prone to interpretation, adaptation, modification, invention, manipulation, decomposition and re-composition. Bourdieu's habitus-field analysis, theory or logic of practice, notions of capital (symbolic, political, social, cultural and economic) is used together with Latour's actor-network theory as the basis of analysis of the social contracts and trust bonds that Mabuza was able to create and which enabled him to navigate South Africa's socio-political and economic milieus during apartheid and the transition in the early 1990s. As people or actors, we believe in the mantra, nothing ventured, nothing gained. We exercise agency and take risks every day. We make choices and those choices have consequences. Mabuza's choices in the fields of education, politics and business had implications for how he is perceived or has been written into history. His choices put notions of identity, citizenship, power, legitimacy, ambition, elite accommodation, class, personal and professional networks, popular struggles, agency and structure under the spotlight. Mabuza's involvement in Bantustan politics, for instance, is contextualised in terms of a historical overview of the unpopular role played by traditional authorities in South Africa before and during colonialism and apartheid. His later foray into the world of business, however, was facilitated in part, by the personal and professional contacts that he made whilst he was in politics and the opportunities which opened up during the country's political transition. Mabuza adapted to changing circumstances and demonstrated a level of versatility which other Bantustan functionaries did not or could not exercise.
- Full Text:
- Date Issued: 2011
Trespassing beyond the borders Harriet Ward as writer and commentator on the Eastern Cape frontier
- Authors: Letcher, Valerie Helen
- Date: 1996
- Subjects: Ward, Harriet, 1808-1872 Women authors, South African -- 19th century -- Biography -- History and criticism Frontier and pioneer life -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2240 , http://hdl.handle.net/10962/d1002283
- Description: The aim of this thesis is to provide an introduction to the work of writer and journalist Harriet Ward, resident in the Eastern Cape from 1842 to 1848. She was a prolific correspondent to various periodicals published both in South Africa and in London. It would be true to say, to judge from the evidence, that she fulfilled a need felt by the British public for information on life and events in South Africa, and that she became the trusted guide of the middle-class reader. Her range covers reports from the frontiers of war, journalistic articles, memoirs, short stories, novels, autobiography, and editions of other writers' work. After the publication of her articles on the Seventh Frontier War (1846-7), she was recognised and respected as a commentator on the situation at the Eastern Cape, an unusual role for a woman at this time. She was also amongst the foremost victorian women writers published from the early eighteen forties until the end of the eighteen-fifties. Harriet Ward has left a vivid historical and sociological account of the Cape frontier, and her observations and judgements provide a hitherto virtually unknown perspective on an important part of South African history and letters. What makes her even more interesting, as this study seeks to show, is that she was far from conventional in her response to her new environment, both as as a woman and as a representative of a colonialist power. The record she has left of her thoughts on the people, landscape and situations of the time has the capacity to surprise the post-colonial literary critic and historian. Her struggle to find a discursive mode in which to express her consciousness of the oppression, patriarchal and colonial, of the marginalised, whether woman, indigene, Afrikaner, or creole, reveals a significantly transgressive or subversive response to the issues of the day. In re-discovering Harriet Ward, we are forced to reassess our assumptions regarding the period of colonial history to which she was a witness.
- Full Text:
- Date Issued: 1996
- Authors: Letcher, Valerie Helen
- Date: 1996
- Subjects: Ward, Harriet, 1808-1872 Women authors, South African -- 19th century -- Biography -- History and criticism Frontier and pioneer life -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2240 , http://hdl.handle.net/10962/d1002283
- Description: The aim of this thesis is to provide an introduction to the work of writer and journalist Harriet Ward, resident in the Eastern Cape from 1842 to 1848. She was a prolific correspondent to various periodicals published both in South Africa and in London. It would be true to say, to judge from the evidence, that she fulfilled a need felt by the British public for information on life and events in South Africa, and that she became the trusted guide of the middle-class reader. Her range covers reports from the frontiers of war, journalistic articles, memoirs, short stories, novels, autobiography, and editions of other writers' work. After the publication of her articles on the Seventh Frontier War (1846-7), she was recognised and respected as a commentator on the situation at the Eastern Cape, an unusual role for a woman at this time. She was also amongst the foremost victorian women writers published from the early eighteen forties until the end of the eighteen-fifties. Harriet Ward has left a vivid historical and sociological account of the Cape frontier, and her observations and judgements provide a hitherto virtually unknown perspective on an important part of South African history and letters. What makes her even more interesting, as this study seeks to show, is that she was far from conventional in her response to her new environment, both as as a woman and as a representative of a colonialist power. The record she has left of her thoughts on the people, landscape and situations of the time has the capacity to surprise the post-colonial literary critic and historian. Her struggle to find a discursive mode in which to express her consciousness of the oppression, patriarchal and colonial, of the marginalised, whether woman, indigene, Afrikaner, or creole, reveals a significantly transgressive or subversive response to the issues of the day. In re-discovering Harriet Ward, we are forced to reassess our assumptions regarding the period of colonial history to which she was a witness.
- Full Text:
- Date Issued: 1996
Trends in fish community structure and recruitment in a temporarily open/closed South African estuary
- Authors: James, Nicola Caroline
- Date: 2007
- Subjects: Fish communities -- South Africa -- Eastern Cape Marine fishes -- South Africa -- Eastern Cape Estuarine fishes -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5332 , http://hdl.handle.net/10962/d1005178
- Description: Long-term interannual changes in richness, abundance, diversity and structure of the fish community in the temporarily open/closed East Kleinemonde Estuary, Eastern Cape, are described and the recruitment success of two estuary-dependent marine species assessed. In addition, laboratory experiments were conducted to assess the possible role of olfaction in the recruitment process of an estuary-dependent marine fish species. Multivariate analyses of the annual marine fish communites identified two distinct groups with more species recorded during years that succeeded spring (September to November) mouth opening events than in years following no mouth opening events in spring. Interannual community stability (IMD) and seriation (IMS) also increased from the ‘other’ to the ‘spring’ years. These results highlight the importance of the timing of mouth opening to the marine fish community in a temporarily open/closed estuary. This study also made use of long-term records of daily mouth state and linked them to the recruitment of distinct year-class cohorts in two spardis with contrasting lifehistory characteristics. Lithognathus lithognathus only recruited into the estuary in years when the mouth opened between late August and January. This was linked to the limited spawning season of this species and its inability to enter closed estuaries via wave overwash events. In contrast, recruitment by Rhabdosargus holubi juveniles appeared to be uninterrupted and was not determined by the seasonality of mouth opening. This species dominates the marine-spawning component of the East Kleinemonde Estuary and its success is attributed to an extended spawning season and its ability to recruit into estuaries during both overwash and open mouth conditions. Attraction of postflexion Rhabdosargus holubi larvae to estuary, surf zone and river water was also measured using a rectangular choice chamber. In two sets of experiments, conducted during peak recruitment periods, larvae from both the surf zone and estuary mouth region selected estuary water with a significantly higher frequency than sea water. Larvae collected in the mouth region showed a stronger preference for river water than those collected in the surf zone, thus suggesting that these fish are more attracted to freshwater influenced nursery areas once they have entered the estuary than those in the surf zone. Larvae collected in the marine environment also selected surf zone water with significantly higher frequencies than estuary water or offshore sea water, thus confirming the importance of the surf zone as an interim nursery area for postflexion R. holubi.
- Full Text:
- Date Issued: 2007
- Authors: James, Nicola Caroline
- Date: 2007
- Subjects: Fish communities -- South Africa -- Eastern Cape Marine fishes -- South Africa -- Eastern Cape Estuarine fishes -- South Africa -- Eastern Cape Estuarine ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5332 , http://hdl.handle.net/10962/d1005178
- Description: Long-term interannual changes in richness, abundance, diversity and structure of the fish community in the temporarily open/closed East Kleinemonde Estuary, Eastern Cape, are described and the recruitment success of two estuary-dependent marine species assessed. In addition, laboratory experiments were conducted to assess the possible role of olfaction in the recruitment process of an estuary-dependent marine fish species. Multivariate analyses of the annual marine fish communites identified two distinct groups with more species recorded during years that succeeded spring (September to November) mouth opening events than in years following no mouth opening events in spring. Interannual community stability (IMD) and seriation (IMS) also increased from the ‘other’ to the ‘spring’ years. These results highlight the importance of the timing of mouth opening to the marine fish community in a temporarily open/closed estuary. This study also made use of long-term records of daily mouth state and linked them to the recruitment of distinct year-class cohorts in two spardis with contrasting lifehistory characteristics. Lithognathus lithognathus only recruited into the estuary in years when the mouth opened between late August and January. This was linked to the limited spawning season of this species and its inability to enter closed estuaries via wave overwash events. In contrast, recruitment by Rhabdosargus holubi juveniles appeared to be uninterrupted and was not determined by the seasonality of mouth opening. This species dominates the marine-spawning component of the East Kleinemonde Estuary and its success is attributed to an extended spawning season and its ability to recruit into estuaries during both overwash and open mouth conditions. Attraction of postflexion Rhabdosargus holubi larvae to estuary, surf zone and river water was also measured using a rectangular choice chamber. In two sets of experiments, conducted during peak recruitment periods, larvae from both the surf zone and estuary mouth region selected estuary water with a significantly higher frequency than sea water. Larvae collected in the mouth region showed a stronger preference for river water than those collected in the surf zone, thus suggesting that these fish are more attracted to freshwater influenced nursery areas once they have entered the estuary than those in the surf zone. Larvae collected in the marine environment also selected surf zone water with significantly higher frequencies than estuary water or offshore sea water, thus confirming the importance of the surf zone as an interim nursery area for postflexion R. holubi.
- Full Text:
- Date Issued: 2007
Tree toppling by elephants and its consequences in thicket mosaic vegetation of Addo Elephant National Park
- Authors: Mgqatsa, Nokubonga
- Date: 2017
- Subjects: Elephants -- Behavior -- South Africa -- Addo Elephant National Park Woody plants -- South Africa -- Addo Elephant National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/19365 , vital:28859
- Description: This study explored the extent of elephant tree toppling and possible cascading effects in Karoo Thicket Mosaic habitat in the Eastern Cape Province, South Africa. While the notion that elephants topple trees is well recognised, little is known about their indirect effects and the possible influence on several trophic levels. Changes brought about by elephants have the potential to influence microclimatic conditions, soil litter processes, plant community composition and other animals. Therefore, this study determined the impacts of elephants on tree toppling, and hence the production of coarse woody debris and the Coarse Woody Debris Profile. Additionally, I explored the consequences of elephant tree toppling on the plant community, small mammals and seed removal. Furthermore, I explored the potential factors facilitating the coexistence of woody plants and elephants. I compared coarse woody debris production and the Coarse Woody Debris Profile between sites with and without elephants. Further, I assessed the consequences of tree toppling in the elephant present site at a patch scale to explore the possible cascading effects of elephants. Firstly, I showed that elephants impacted woody plants through branch/stem breakages and toppling of trees, but that effects vary for different categories of the Coarse Woody Debris Profile. This result confirms the most recent findings that woody plants are at risk from elephant herbivory in Karoo Thicket Mosaic habitat. The elephant toppling effect on these landscapes is largely influenced by plant growth form, with woody trees suffering high levels of elephant toppling than shrubs of comparable size. However, toppled Pappea capensis is able to persist from being toppled by elephants, either through coppicing or resprouting. Additionally, I showed that toppled trees form discrete patches on the landscape, with altered microclimate and browsing pressures. While I detected no significant effect of these changes on plant composition and abundance within these patches, these findings indicate the possible influence of elephants on facilitating plant recruitment and altering plant communities of thicket through toppling of trees. Moreover, I showed that elephant toppling of trees provide habitat patches for small mammals, thus affecting seed removal by vertebrates within patches. These changes had no discernable effect on soil seed banks. However, they highlight the need to better understand the temporal dynamics of these patches and implications for seed dynamics and plant communities on the landscape. The results show the patterns of elephant impacts on woody plants and possible cascading effects in the presence of elephants. Therefore, the study advances our understanding of top-down effects of elephants and shows the relevance of understanding these effects in order to effectively manage elephant impacts in different systems.
- Full Text:
- Date Issued: 2017
- Authors: Mgqatsa, Nokubonga
- Date: 2017
- Subjects: Elephants -- Behavior -- South Africa -- Addo Elephant National Park Woody plants -- South Africa -- Addo Elephant National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/19365 , vital:28859
- Description: This study explored the extent of elephant tree toppling and possible cascading effects in Karoo Thicket Mosaic habitat in the Eastern Cape Province, South Africa. While the notion that elephants topple trees is well recognised, little is known about their indirect effects and the possible influence on several trophic levels. Changes brought about by elephants have the potential to influence microclimatic conditions, soil litter processes, plant community composition and other animals. Therefore, this study determined the impacts of elephants on tree toppling, and hence the production of coarse woody debris and the Coarse Woody Debris Profile. Additionally, I explored the consequences of elephant tree toppling on the plant community, small mammals and seed removal. Furthermore, I explored the potential factors facilitating the coexistence of woody plants and elephants. I compared coarse woody debris production and the Coarse Woody Debris Profile between sites with and without elephants. Further, I assessed the consequences of tree toppling in the elephant present site at a patch scale to explore the possible cascading effects of elephants. Firstly, I showed that elephants impacted woody plants through branch/stem breakages and toppling of trees, but that effects vary for different categories of the Coarse Woody Debris Profile. This result confirms the most recent findings that woody plants are at risk from elephant herbivory in Karoo Thicket Mosaic habitat. The elephant toppling effect on these landscapes is largely influenced by plant growth form, with woody trees suffering high levels of elephant toppling than shrubs of comparable size. However, toppled Pappea capensis is able to persist from being toppled by elephants, either through coppicing or resprouting. Additionally, I showed that toppled trees form discrete patches on the landscape, with altered microclimate and browsing pressures. While I detected no significant effect of these changes on plant composition and abundance within these patches, these findings indicate the possible influence of elephants on facilitating plant recruitment and altering plant communities of thicket through toppling of trees. Moreover, I showed that elephant toppling of trees provide habitat patches for small mammals, thus affecting seed removal by vertebrates within patches. These changes had no discernable effect on soil seed banks. However, they highlight the need to better understand the temporal dynamics of these patches and implications for seed dynamics and plant communities on the landscape. The results show the patterns of elephant impacts on woody plants and possible cascading effects in the presence of elephants. Therefore, the study advances our understanding of top-down effects of elephants and shows the relevance of understanding these effects in order to effectively manage elephant impacts in different systems.
- Full Text:
- Date Issued: 2017
Treatment of wine distillery wastewaters by high rate anaerobic digestion and submerged membrane systems
- Authors: Melamane, Xolisa Lorraine
- Date: 2007
- Subjects: Wine and wine making -- Waste disposal Sewage -- Purification -- Anaerobic treatment Membrane reactors Bioreactors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3963 , http://hdl.handle.net/10962/d1004022
- Description: Experiences in treating wine distillery wastewaters (WDWs) contribute to the field of oenology as many oenologists are concerned with the selection, efficiency and economy of their wastewaters. Wine distillery wastewaters are strongly acidic, have high chemical oxygen demand (COD), high polyphenol content and are highly variable. Primary attention was focussed on sustainable biological treatment of raw wine distillery wastewater (RWDW) and fungally pre-treated wine distillery wastewater (FTWDW) by energy-efficient high rate anaerobic digestion (AD). This study also explored the development of a novel dual-stage anaerobic digestion ultrafiltration (ADUF) process, using a ceramic submerged membrane bioreactor (SMBR) in the treatment of both RWDW and FTWDW. The first stage was for the selection of microorganisms that were able to treat the toxic pollutants from WDWs. It was operated at a high feed-to-microorganism ratio. The second stage, a secondary digester, was operated like a typical membrane bioreactor at a low feed-to-microorganism ratio to sustain a stable efficient population for a long period. The characteristics of RWDW were as follows: pH 3.83, 15 000 mg/l soluble COD (CODs) and 5229 mg/l of phenols. After pre-treatment of RWDW with Trametes pubescens, starting parameters for FTWDW were as follows: pH 6.7, 7000 mg/l soluble COD (CODS) and 1440 mg/l of phenols. During operation of a high rate anaerobic digester for RWDW treatment, K2HPO4 was required for buffering the digester. Volatile fatty acid concentrations were <300 mg/l throughout the study, indicating degradation of organic acids present. Mean CODS removal efficiency for the 130 day study was 87 %, while the mean polyphenol removal efficiency was 85 %. Addition of 50 mg/l Fe3+ increased the removal efficiencies of CODS to 97 % and of polyphenols to 99 %. High removal efficiencies of CODS and polyphenols were attributed to the addition of macronutrients and micronutrients that caused pH stability and stimulated microbial activity. The CODS removal efficiency of high rate anaerobic digestion of FTWDW reached 99.5%. During FTWDW digestion, pH buffering was achieved using K2HPO4. A combination of a SMBR and a secondary digester was tested for the treatment of RWDW and FTWDW during a 30 day study. Results for RWDW showed that pH buffering was achieved by dosing the feed stream with CaCO3 and K2HPO4. Buffering proved to be significant for optimum performance of the system in removal of soluble CODS, and volatile fatty acids (VFAs). Different batches of RWDW used for feeding the reactor had variable compositions with respect to concentrations of nitrates, ammonium and total phenolic compounds. Ammonium accumulated in the secondary digester after 14 days of system operation, indicated the time required for the establishment of anaerobic conditions in the system. Dosing of the SMBR treating FTWDW with CaCO3 and K2HPO4 buffered the pH; iii this proved significant for optimum performance of the system in removal of CODS. The system eliminated an average of 86 (± 4) % of CODS present in the FTWDW. The residual CODS levels in the effluent were approximately 400 mg/l, significantly lower than the concentrations observed when treating RWDW, indicating that fungal pre-treatment might have provided additional nutrients for removal of recalcitrant components of the wastewater. The resulting effluent was rich in nitrates and phosphates and might be used as a fertiliser. Alternatively, a membrane process, such as reverse osmosis (RO) or nanofiltration (NF) could be applied to raise the water quality to meet the levels required for reuse. Biomass samples were obtained from the four treatment systems and population shifts characterization using phospholipids fatty acids (PLFA) and 16S rRNA analysis to provide an indication of limitations within the microbial population. The values of the concentrations of the individual PLFAs detected in the samples indicated that ten bacterial species were present, with the GC content of the 16S rRNA increasing from 1 to 10. Analysis of denaturing gradient gel electrophoresis DGGE data indicated that the composition of the archeal community changed the consortia used for both RWDW and FTWDW treatment. Changes in band intensities indicated the presence of different components of the archeal communities. The results were not conclusive in terms of species identity as cloning, sequencing and phylogenetic analyses were not performed, but they did indicate microbial population shifts and species diversity for high rate anaerobic digestion. The results also confirmed prevalence of relatively few species during operation of SMBRs for treatment of RWDW and FTWDW, which suggested that the microorganisms that survived were either tolerant of toxic components of RWDW and FTWDW or they were able to remove polyphenols.
- Full Text:
- Date Issued: 2007
- Authors: Melamane, Xolisa Lorraine
- Date: 2007
- Subjects: Wine and wine making -- Waste disposal Sewage -- Purification -- Anaerobic treatment Membrane reactors Bioreactors
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3963 , http://hdl.handle.net/10962/d1004022
- Description: Experiences in treating wine distillery wastewaters (WDWs) contribute to the field of oenology as many oenologists are concerned with the selection, efficiency and economy of their wastewaters. Wine distillery wastewaters are strongly acidic, have high chemical oxygen demand (COD), high polyphenol content and are highly variable. Primary attention was focussed on sustainable biological treatment of raw wine distillery wastewater (RWDW) and fungally pre-treated wine distillery wastewater (FTWDW) by energy-efficient high rate anaerobic digestion (AD). This study also explored the development of a novel dual-stage anaerobic digestion ultrafiltration (ADUF) process, using a ceramic submerged membrane bioreactor (SMBR) in the treatment of both RWDW and FTWDW. The first stage was for the selection of microorganisms that were able to treat the toxic pollutants from WDWs. It was operated at a high feed-to-microorganism ratio. The second stage, a secondary digester, was operated like a typical membrane bioreactor at a low feed-to-microorganism ratio to sustain a stable efficient population for a long period. The characteristics of RWDW were as follows: pH 3.83, 15 000 mg/l soluble COD (CODs) and 5229 mg/l of phenols. After pre-treatment of RWDW with Trametes pubescens, starting parameters for FTWDW were as follows: pH 6.7, 7000 mg/l soluble COD (CODS) and 1440 mg/l of phenols. During operation of a high rate anaerobic digester for RWDW treatment, K2HPO4 was required for buffering the digester. Volatile fatty acid concentrations were <300 mg/l throughout the study, indicating degradation of organic acids present. Mean CODS removal efficiency for the 130 day study was 87 %, while the mean polyphenol removal efficiency was 85 %. Addition of 50 mg/l Fe3+ increased the removal efficiencies of CODS to 97 % and of polyphenols to 99 %. High removal efficiencies of CODS and polyphenols were attributed to the addition of macronutrients and micronutrients that caused pH stability and stimulated microbial activity. The CODS removal efficiency of high rate anaerobic digestion of FTWDW reached 99.5%. During FTWDW digestion, pH buffering was achieved using K2HPO4. A combination of a SMBR and a secondary digester was tested for the treatment of RWDW and FTWDW during a 30 day study. Results for RWDW showed that pH buffering was achieved by dosing the feed stream with CaCO3 and K2HPO4. Buffering proved to be significant for optimum performance of the system in removal of soluble CODS, and volatile fatty acids (VFAs). Different batches of RWDW used for feeding the reactor had variable compositions with respect to concentrations of nitrates, ammonium and total phenolic compounds. Ammonium accumulated in the secondary digester after 14 days of system operation, indicated the time required for the establishment of anaerobic conditions in the system. Dosing of the SMBR treating FTWDW with CaCO3 and K2HPO4 buffered the pH; iii this proved significant for optimum performance of the system in removal of CODS. The system eliminated an average of 86 (± 4) % of CODS present in the FTWDW. The residual CODS levels in the effluent were approximately 400 mg/l, significantly lower than the concentrations observed when treating RWDW, indicating that fungal pre-treatment might have provided additional nutrients for removal of recalcitrant components of the wastewater. The resulting effluent was rich in nitrates and phosphates and might be used as a fertiliser. Alternatively, a membrane process, such as reverse osmosis (RO) or nanofiltration (NF) could be applied to raise the water quality to meet the levels required for reuse. Biomass samples were obtained from the four treatment systems and population shifts characterization using phospholipids fatty acids (PLFA) and 16S rRNA analysis to provide an indication of limitations within the microbial population. The values of the concentrations of the individual PLFAs detected in the samples indicated that ten bacterial species were present, with the GC content of the 16S rRNA increasing from 1 to 10. Analysis of denaturing gradient gel electrophoresis DGGE data indicated that the composition of the archeal community changed the consortia used for both RWDW and FTWDW treatment. Changes in band intensities indicated the presence of different components of the archeal communities. The results were not conclusive in terms of species identity as cloning, sequencing and phylogenetic analyses were not performed, but they did indicate microbial population shifts and species diversity for high rate anaerobic digestion. The results also confirmed prevalence of relatively few species during operation of SMBRs for treatment of RWDW and FTWDW, which suggested that the microorganisms that survived were either tolerant of toxic components of RWDW and FTWDW or they were able to remove polyphenols.
- Full Text:
- Date Issued: 2007
Transnational habitus : Mariem Hassan as the transcultural representation of the relationship between Saharaui music and Nubenegra records
- Authors: Gimenez Amoros, Luis
- Date: 2015
- Subjects: Hassan, Mariem, 1958- , Nubenegra Records , Sahrawi (African people) -- Music -- Cross-cultural studies , Sahrawi (African people) -- Music -- Foreign influences , Transnationalism , Cross-cultural studies -- Spain
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2697 , http://hdl.handle.net/10962/d1017819
- Description: This thesis expands on primary field research conducted for my MMus degree. Undertaken in the Saharaui refugee camps of southern Algeria (2004-2005) that research - based on ethnographic data and the analysis of Saharaui music, known as Haul ¹- focussed on the musical system, the social context of musical performance and the music culture in Saharaui refugee camps. This doctoral research examines Saharaui Haul music as practised in Spain and is particularly focussed on its entry, since 1998, into the global market by way of the World Music label, Nubenegra records. The encounter between Saharaui musicians and Nubenegra records has created a new type of Saharaui Haul which is different to that played in the refugee camps. This phenomenon has emerged as a result of western music producers compelling Saharaui musicians to introduce musical changes so that both parties may be considered as musical agents occupying different positions on a continuum of tradition and change. Nubenegra undertook the commodification of Saharaui music and disseminated it from the camps to the rest of the world. A musical and social analysis of the relationship between Nubenegra and Saharaui musicians living in Spain will form the basis of the research in this thesis. In particular, Mariem Hassan is an example of a musician who had her music disseminated through the relationship with Nubenegra and she is promoted as the music ambassador of the Western Sahara. I collaborated with her as a composer and performer on her last album, El Aaiun egdat (Aaiun in fire), in 2012² and gained first hand insight into the relationship between Mariem and Nubenegra. This thesis reflects on this relationship and my role in facilitating this encounter.
- Full Text:
- Date Issued: 2015
- Authors: Gimenez Amoros, Luis
- Date: 2015
- Subjects: Hassan, Mariem, 1958- , Nubenegra Records , Sahrawi (African people) -- Music -- Cross-cultural studies , Sahrawi (African people) -- Music -- Foreign influences , Transnationalism , Cross-cultural studies -- Spain
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2697 , http://hdl.handle.net/10962/d1017819
- Description: This thesis expands on primary field research conducted for my MMus degree. Undertaken in the Saharaui refugee camps of southern Algeria (2004-2005) that research - based on ethnographic data and the analysis of Saharaui music, known as Haul ¹- focussed on the musical system, the social context of musical performance and the music culture in Saharaui refugee camps. This doctoral research examines Saharaui Haul music as practised in Spain and is particularly focussed on its entry, since 1998, into the global market by way of the World Music label, Nubenegra records. The encounter between Saharaui musicians and Nubenegra records has created a new type of Saharaui Haul which is different to that played in the refugee camps. This phenomenon has emerged as a result of western music producers compelling Saharaui musicians to introduce musical changes so that both parties may be considered as musical agents occupying different positions on a continuum of tradition and change. Nubenegra undertook the commodification of Saharaui music and disseminated it from the camps to the rest of the world. A musical and social analysis of the relationship between Nubenegra and Saharaui musicians living in Spain will form the basis of the research in this thesis. In particular, Mariem Hassan is an example of a musician who had her music disseminated through the relationship with Nubenegra and she is promoted as the music ambassador of the Western Sahara. I collaborated with her as a composer and performer on her last album, El Aaiun egdat (Aaiun in fire), in 2012² and gained first hand insight into the relationship between Mariem and Nubenegra. This thesis reflects on this relationship and my role in facilitating this encounter.
- Full Text:
- Date Issued: 2015