Evaluating and predicting impacts of Australian redclaw crayfish Cherax quadricarinatus and Louisiana red swamp crayfish Procambarus clarkii invasions
- Madzivanzira, Takudzwa Comfort
- Authors: Madzivanzira, Takudzwa Comfort
- Date: 2021-10-29
- Subjects: Cherax Africa , Procambarus clarkii Africa , Freshwater crabs Africa , Crayfish Zambezi River , Crayfish Food Zambezi River , Aquatic biodiversity Africa , Conservation biology Zambezi River , Fishing Catch effort Africa , Introduced freshwater organisms Africa , Fish populations Africa , Functional response (FR)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191137 , vital:45064 , 10.21504/10962/191137
- Description: Freshwater crayfish have become one of the most widely introduced freshwater taxa globally. Crayfish introductions have not spared the African continent, which, apart from Madagascar, is naturally devoid of native freshwater crayfish. These introductions are of concern because invasive crayfish have generally been shown to cause strong impacts on recipient ecosystems outside Africa. This study therefore set out to compile up-to-date information regarding crayfish introductions in Africa, their pathways and distributions and to improve our understanding of the nature and magnitude of their environmental impacts. A systematic review revealed that nine crayfish species have been introduced into the continent with five of those, Astacus astacus, Cherax quadricarinatus, Faxonius limosus, Procambarus clarkii and Procambarus virginalis, having established naturalised populations in fourteen African countries (Chapter 2). The main driver of these crayfish introductions was to provide socio-economic benefits but there is limited evidence of success. The thesis further documents attempts made to address crayfish knowledge gaps in Africa, including standardisation of C. quadricarinatus sampling gear (Chapter 3), determination of the distribution of C. quadricarinatus in the recently invaded Upper Zambezi Basin (Chapter 4), and predicting ecological and socioeconomic impacts of two crayfish species that are spreading rapidly in Southern Africa, namely, C. quadricarinatus and P. clarkii (Chapters 5 – 8). To standardise C. quadricarinatus sampling methods in Africa, two methods used in Southern Africa were compared and the Promar® collapsible trap baited with dry pellets was recommended as the best approach for C. quadricarinatus abundance studies due to the high catch per unit effort (CPUE), probability of capture and the suitability of dry dog food as a standard bait. This standard approach was used for crayfish surveys in the Zambezi Basin to comprehensively determine the spread and establishment of C. quadricarinatus across the basin. The establishment of C. quadricarinatus in the Barotse Floodplain, Upper Zambezi Floodplains freshwater ecoregion was confirmed. Although the probability of capture and catch per unit effort (CPUE) of C. quadricarinatus in the Barotse floodplain were similar to that of older invasions in the basin (Lake Kariba and Kafue River), morphometric differences among C. quadricarinatus populations sampled from these invaded regions were detected. Although crayfish were not detected in other regions, for example, the Okavango Floodplains ecoregions, C. quadricarinatus have the potential to spread at a downstream and upstream rate of 49 and 12 km·year-1, impacting native biota therein. To evaluate the potential for ecological impacts, the consumer-resource dynamics of C. quadricarinatus and P. clarkii were described in comparison to a native trophic analogue, the freshwater crab of the Potamonautes genus, preying on various native taxa ubiquitous to African aquatic and terrestrial ecosystems. The use of functional response (FR) and consumption experiments in this study showed the potential impacts of the two crayfish species on native resources and on resources that support livelihoods in invaded ecosystems. This in most cases was a result of their high attack parameter, which also resulted in high functional responses ratios (FRRs) compared to native crabs. The crayfish FR, FRRs and consumption rates were mostly enhanced under the high temperature treatments. The FRs and consumption results were then combined with the field biomasses of crayfish and crabs to calculate the relative impact potential (RIP) to successfully predict the degree of impact caused by crayfish species relative to crabs. Crayfish species consistently displayed RIP scores > 1 relative to the native crab irrespective of region, which were higher for the summer than the winter season, suggesting greater impact of the invaders compared to the native species. This study further estimated the socioeconomic losses due to catch spoilage by C. quadricarinatus which are up to 1500 t per year in the invaded Kafue River Basin, which translates to an annual income loss of US$ 2 million. Information provided in this study is vital for conservation management and to compel policymakers to develop appropriate conservation management tools within regulatory frameworks, which could stop or minimise the spread of crayfish species and protect Africa from further losing aquatic biodiversity. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Madzivanzira, Takudzwa Comfort
- Date: 2021-10-29
- Subjects: Cherax Africa , Procambarus clarkii Africa , Freshwater crabs Africa , Crayfish Zambezi River , Crayfish Food Zambezi River , Aquatic biodiversity Africa , Conservation biology Zambezi River , Fishing Catch effort Africa , Introduced freshwater organisms Africa , Fish populations Africa , Functional response (FR)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191137 , vital:45064 , 10.21504/10962/191137
- Description: Freshwater crayfish have become one of the most widely introduced freshwater taxa globally. Crayfish introductions have not spared the African continent, which, apart from Madagascar, is naturally devoid of native freshwater crayfish. These introductions are of concern because invasive crayfish have generally been shown to cause strong impacts on recipient ecosystems outside Africa. This study therefore set out to compile up-to-date information regarding crayfish introductions in Africa, their pathways and distributions and to improve our understanding of the nature and magnitude of their environmental impacts. A systematic review revealed that nine crayfish species have been introduced into the continent with five of those, Astacus astacus, Cherax quadricarinatus, Faxonius limosus, Procambarus clarkii and Procambarus virginalis, having established naturalised populations in fourteen African countries (Chapter 2). The main driver of these crayfish introductions was to provide socio-economic benefits but there is limited evidence of success. The thesis further documents attempts made to address crayfish knowledge gaps in Africa, including standardisation of C. quadricarinatus sampling gear (Chapter 3), determination of the distribution of C. quadricarinatus in the recently invaded Upper Zambezi Basin (Chapter 4), and predicting ecological and socioeconomic impacts of two crayfish species that are spreading rapidly in Southern Africa, namely, C. quadricarinatus and P. clarkii (Chapters 5 – 8). To standardise C. quadricarinatus sampling methods in Africa, two methods used in Southern Africa were compared and the Promar® collapsible trap baited with dry pellets was recommended as the best approach for C. quadricarinatus abundance studies due to the high catch per unit effort (CPUE), probability of capture and the suitability of dry dog food as a standard bait. This standard approach was used for crayfish surveys in the Zambezi Basin to comprehensively determine the spread and establishment of C. quadricarinatus across the basin. The establishment of C. quadricarinatus in the Barotse Floodplain, Upper Zambezi Floodplains freshwater ecoregion was confirmed. Although the probability of capture and catch per unit effort (CPUE) of C. quadricarinatus in the Barotse floodplain were similar to that of older invasions in the basin (Lake Kariba and Kafue River), morphometric differences among C. quadricarinatus populations sampled from these invaded regions were detected. Although crayfish were not detected in other regions, for example, the Okavango Floodplains ecoregions, C. quadricarinatus have the potential to spread at a downstream and upstream rate of 49 and 12 km·year-1, impacting native biota therein. To evaluate the potential for ecological impacts, the consumer-resource dynamics of C. quadricarinatus and P. clarkii were described in comparison to a native trophic analogue, the freshwater crab of the Potamonautes genus, preying on various native taxa ubiquitous to African aquatic and terrestrial ecosystems. The use of functional response (FR) and consumption experiments in this study showed the potential impacts of the two crayfish species on native resources and on resources that support livelihoods in invaded ecosystems. This in most cases was a result of their high attack parameter, which also resulted in high functional responses ratios (FRRs) compared to native crabs. The crayfish FR, FRRs and consumption rates were mostly enhanced under the high temperature treatments. The FRs and consumption results were then combined with the field biomasses of crayfish and crabs to calculate the relative impact potential (RIP) to successfully predict the degree of impact caused by crayfish species relative to crabs. Crayfish species consistently displayed RIP scores > 1 relative to the native crab irrespective of region, which were higher for the summer than the winter season, suggesting greater impact of the invaders compared to the native species. This study further estimated the socioeconomic losses due to catch spoilage by C. quadricarinatus which are up to 1500 t per year in the invaded Kafue River Basin, which translates to an annual income loss of US$ 2 million. Information provided in this study is vital for conservation management and to compel policymakers to develop appropriate conservation management tools within regulatory frameworks, which could stop or minimise the spread of crayfish species and protect Africa from further losing aquatic biodiversity. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Exploring indiginising the university’s science curriculum through bottom-up decolonisation: Affordances and hindrances
- Authors: Mutanho, Chrispen
- Date: 2021-10-29
- Subjects: Decolonization South Africa , Ethnoscience South Africa , Ubuntu (Philosophy) , Pedagogical content knowledge , Culturally relevant pedagogy , Science Study and teaching South Africa , Science teachers In-service training South Africa , Transformative learning South Africa , Cultural-historical activity theory (CHAT)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191668 , vital:45146 , 10.21504/10962/191668
- Description: The integration of indigenous knowledge (IK) in the science curriculum is a spreading phenomenon driven by the need to bring about relevancy and equality in science education. In South Africa, for instance, the need to integrate IK in science education is part of the global effort to build a democratic state from the debris of apartheid. Henceforth, the integration of IK is backed up by both the National Constitution of the Republic of South Africa (Act 108 of 1996) and the South African Department of Basic Education’s (2011) National Curriculum Assessment Policy Statement. However, the success of this policy seems to be hindered in part by the fact that the teachers who are the implementers of the curriculum changes seem to lack the relevant pedagogical content knowledge (PCK) to integrate IK in their science teaching repertoires. Such a trend is often blamed on their Eurocentric educational background. Interestingly, very little research has been done to explore ways of supporting teachers to develop the relevant conceptual tools and teaching strategies that will enable them to integrate IK in science teaching. It is against this background that an interventionist case study on how to support the Bachelor of Education Natural Sciences in-service teachers in particular to develop exemplar science lessons that integrate IK as easily accessible resources was conducted. The study is underpinned by three complementary paradigms, namely, the interpretive, the critical, and indigenous research paradigms. While the interpretive paradigm enabled me to understand and interpret descriptive data, the critical paradigm enabled me to take an emancipatory stance and challenge the micro-aggressive elements embedded in conventional research practices; within the indigenous research paradigm, Ubuntu was the relational perspective that informed the researcher-participant relationships in this study. Vygotsky’s sociocultural theory was used as an overarching theoretical framework, in conjunction with the cultural historical activity theory. Additionally, the topic-specific pedagogical content knowledge provided the methodological and analytical tools. Data were gathered through questionnaires, individual face-to-face interviews, focus group interview, participatory observation, and the teachers’ reflections. This study established that if teachers are given back the agency to collaboratively resolve the contradictions that confront them in their workplaces, they can generate their own ideas on how to integrate IK in science vii teaching. The teachers in this study experienced a shift in their agency from a paralysed state of resisting the integration of IK at the beginning of the intervention to an ‘I can do it’ attitude at the end of the intervention. Thus, it could be argued that this study’s major contribution to new knowledge lies in demonstrating possible ways of supporting teachers to integrate IK as easily accessible resources in their science teaching. Additionally, the study also challenged the Eurocentric approach to ethics and offered Ubuntu as a relational perspective that can be used to complement the shortcomings of Eurocentric research paradigms. The study thus recommends that continuing professional development or professional learning communities should afford teachers the opportunity to collaboratively engage with the challenges that they face in their workplaces in order to resolve the contradictions that confront them. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mutanho, Chrispen
- Date: 2021-10-29
- Subjects: Decolonization South Africa , Ethnoscience South Africa , Ubuntu (Philosophy) , Pedagogical content knowledge , Culturally relevant pedagogy , Science Study and teaching South Africa , Science teachers In-service training South Africa , Transformative learning South Africa , Cultural-historical activity theory (CHAT)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191668 , vital:45146 , 10.21504/10962/191668
- Description: The integration of indigenous knowledge (IK) in the science curriculum is a spreading phenomenon driven by the need to bring about relevancy and equality in science education. In South Africa, for instance, the need to integrate IK in science education is part of the global effort to build a democratic state from the debris of apartheid. Henceforth, the integration of IK is backed up by both the National Constitution of the Republic of South Africa (Act 108 of 1996) and the South African Department of Basic Education’s (2011) National Curriculum Assessment Policy Statement. However, the success of this policy seems to be hindered in part by the fact that the teachers who are the implementers of the curriculum changes seem to lack the relevant pedagogical content knowledge (PCK) to integrate IK in their science teaching repertoires. Such a trend is often blamed on their Eurocentric educational background. Interestingly, very little research has been done to explore ways of supporting teachers to develop the relevant conceptual tools and teaching strategies that will enable them to integrate IK in science teaching. It is against this background that an interventionist case study on how to support the Bachelor of Education Natural Sciences in-service teachers in particular to develop exemplar science lessons that integrate IK as easily accessible resources was conducted. The study is underpinned by three complementary paradigms, namely, the interpretive, the critical, and indigenous research paradigms. While the interpretive paradigm enabled me to understand and interpret descriptive data, the critical paradigm enabled me to take an emancipatory stance and challenge the micro-aggressive elements embedded in conventional research practices; within the indigenous research paradigm, Ubuntu was the relational perspective that informed the researcher-participant relationships in this study. Vygotsky’s sociocultural theory was used as an overarching theoretical framework, in conjunction with the cultural historical activity theory. Additionally, the topic-specific pedagogical content knowledge provided the methodological and analytical tools. Data were gathered through questionnaires, individual face-to-face interviews, focus group interview, participatory observation, and the teachers’ reflections. This study established that if teachers are given back the agency to collaboratively resolve the contradictions that confront them in their workplaces, they can generate their own ideas on how to integrate IK in science vii teaching. The teachers in this study experienced a shift in their agency from a paralysed state of resisting the integration of IK at the beginning of the intervention to an ‘I can do it’ attitude at the end of the intervention. Thus, it could be argued that this study’s major contribution to new knowledge lies in demonstrating possible ways of supporting teachers to integrate IK as easily accessible resources in their science teaching. Additionally, the study also challenged the Eurocentric approach to ethics and offered Ubuntu as a relational perspective that can be used to complement the shortcomings of Eurocentric research paradigms. The study thus recommends that continuing professional development or professional learning communities should afford teachers the opportunity to collaboratively engage with the challenges that they face in their workplaces in order to resolve the contradictions that confront them. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
Gaze patterns of expert and amateur sight-readers with particular focus on the cognitive underpinnings of reading key and time signatures
- Authors: Viljoen, Jacobus Frederick
- Date: 2021-10-29
- Subjects: Sight-reading (Music) , Eye tracking , Cognition , Musical notation , Tonality , Musical meter and rhythm
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190908 , vital:45040 , 10.21504/10962/190908
- Description: Over the last decade, eye-tracking technology has provided researchers with specific tools to study the process of reading (language and music) empirically. Most of these studies have focused on the “Eye-Hand Span” phenomenon (the ability to read ahead of the point of playing). However, little research investigates the cognitive implications of specific aspects of musical notation when performed in real time. This research aimed to observe the fixations patterns of sight-readers in order to investigate the cognitive underpinnings of key and time signatures in music scores. This research project is a quantitative study using a quasi-experimental research design. Tobii eye-tracking equipment and software were used to record the eye movements of 11 expert and 7 amateur keyboard sight-readers. Two key aspects of music notation, key and time signatures, were selected as the main focus of the study. To investigate these aspects, eighteen research participants were provided with seventeen sight-reading examples for one hand (low complexity) and two hands (high complexity) composed specifically by the researcher. Several examples contained one or more unexpected aspects (accidentals or changes of time signature) to test their effect on fixation count and duration. Two variables (fixation count and fixation duration) were utilised to analyze fixation patterns on the selected aspects of the scores. Three main results emerged from the data analysis: 1) Expert sight-readers performed with much greater accuracy than experts in both tests; 2) Expert sight-readers exhibited a higher fixation count on entire scores in complex examples; 3) Both expert and amateur sight-readers fixate more and for longer on certain notational aspects such as key and time signatures than other notational aspects such as deviations or individual notes. This selection of focused attention suggests that both expert and amateur sight-readers cognitively process music scores in a hierarchical order. In conclusion, key and time signatures appear to require more and longer fixations by both groups of readers than other aspects of the score. This supports previous research which suggests that sound musical knowledge may play a positive role in performers’ sight-reading skills, thereby contributing to more successful sight-reading performances. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Viljoen, Jacobus Frederick
- Date: 2021-10-29
- Subjects: Sight-reading (Music) , Eye tracking , Cognition , Musical notation , Tonality , Musical meter and rhythm
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190908 , vital:45040 , 10.21504/10962/190908
- Description: Over the last decade, eye-tracking technology has provided researchers with specific tools to study the process of reading (language and music) empirically. Most of these studies have focused on the “Eye-Hand Span” phenomenon (the ability to read ahead of the point of playing). However, little research investigates the cognitive implications of specific aspects of musical notation when performed in real time. This research aimed to observe the fixations patterns of sight-readers in order to investigate the cognitive underpinnings of key and time signatures in music scores. This research project is a quantitative study using a quasi-experimental research design. Tobii eye-tracking equipment and software were used to record the eye movements of 11 expert and 7 amateur keyboard sight-readers. Two key aspects of music notation, key and time signatures, were selected as the main focus of the study. To investigate these aspects, eighteen research participants were provided with seventeen sight-reading examples for one hand (low complexity) and two hands (high complexity) composed specifically by the researcher. Several examples contained one or more unexpected aspects (accidentals or changes of time signature) to test their effect on fixation count and duration. Two variables (fixation count and fixation duration) were utilised to analyze fixation patterns on the selected aspects of the scores. Three main results emerged from the data analysis: 1) Expert sight-readers performed with much greater accuracy than experts in both tests; 2) Expert sight-readers exhibited a higher fixation count on entire scores in complex examples; 3) Both expert and amateur sight-readers fixate more and for longer on certain notational aspects such as key and time signatures than other notational aspects such as deviations or individual notes. This selection of focused attention suggests that both expert and amateur sight-readers cognitively process music scores in a hierarchical order. In conclusion, key and time signatures appear to require more and longer fixations by both groups of readers than other aspects of the score. This supports previous research which suggests that sound musical knowledge may play a positive role in performers’ sight-reading skills, thereby contributing to more successful sight-reading performances. , Thesis (PhD) -- Faculty of Humanities, Music and Musicology, 2021
- Full Text:
- Date Issued: 2021-10-29
Human capital in the context of high levels of inequality in South Africa
- Authors: Friderichs, Tamaryn Jean
- Date: 2021-10-29
- Subjects: Human capital South Africa , Income distribution South Africa , Labor market South Africa , Latent variables , Confirmatory factor analysis , Education Economic aspects South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192672 , vital:45248 , 10.21504/10962/192672
- Description: Piketty’s (2014) book titled “Capital in the Twenty-First Century” sparked widespread interest in global inequality, the distinction between wealth and income inequality and the economic, social and political processes accounting for changes in economic inequality over time. Piketty’s (2014) study controversially stated that widening economic inequality is the normal state of affairs in capitalist societies. The return from capital/wealth (terms used interchangeably) will almost always outpace the returns from labour. In contrast with Piketty’s (2014) thesis that the returns on non-human capital drive growing income inequality, economists such as Leibbrandt et al. (2012), Van der Berg (2014) and Hundenborn et al. (2016) have found that the labour market and human capital (HC) are the primary sources of income inequality. The research problem for this study stems from these contrasting views. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Friderichs, Tamaryn Jean
- Date: 2021-10-29
- Subjects: Human capital South Africa , Income distribution South Africa , Labor market South Africa , Latent variables , Confirmatory factor analysis , Education Economic aspects South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192672 , vital:45248 , 10.21504/10962/192672
- Description: Piketty’s (2014) book titled “Capital in the Twenty-First Century” sparked widespread interest in global inequality, the distinction between wealth and income inequality and the economic, social and political processes accounting for changes in economic inequality over time. Piketty’s (2014) study controversially stated that widening economic inequality is the normal state of affairs in capitalist societies. The return from capital/wealth (terms used interchangeably) will almost always outpace the returns from labour. In contrast with Piketty’s (2014) thesis that the returns on non-human capital drive growing income inequality, economists such as Leibbrandt et al. (2012), Van der Berg (2014) and Hundenborn et al. (2016) have found that the labour market and human capital (HC) are the primary sources of income inequality. The research problem for this study stems from these contrasting views. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10-29
Integration of dual metallophthalocyanine catalysis and green energy for sustainable oxidative removal of endocrine disrupting compounds
- Authors: Kruid, Jan
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192820 , vital:45267
- Description: Thesis (PhD) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Kruid, Jan
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192820 , vital:45267
- Description: Thesis (PhD) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10-29
Integrative systematic structuring of the widespread psammophiid snakes (Psammophiidae): a multi-evidence species delineation approach
- Authors: Keates, Chad
- Date: 2021-10-29
- Subjects: Psammophis South Africa , Herpetology , Herpetology Africa , Molecular biology , Psammophis Classification , Psammophis Genetics , Psammophis Morphology , Psammophis Phylogeny , Morphology Mathematics , Psammophylax
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295077 , vital:57288 , DOI 10.21504/10962/295079
- Description: Species form the foundations upon which we build our understanding of the natural world. Although a focus of much scientific attention, our understanding of species is stunted by the intrinsic ‘fuzziness’ of boundaries within nature. Due to the complexity of the evolutionary process, coupled with an ever-changing abiotic landscape, species are hard to delineate, even at the best of times. Whilst various species concepts and sophisticated delimitation methods have helped scientists tease apart species, many species complexes persist. This is because taxonomy is a discrete ordering system imposed upon the continuous and intercalated structure of life. To improve our understanding of a wide-ranging family of snakes, I investigated the taxonomy and evolutionary structuring within Psammophiidae using both molecular and morphological approaches, employing phylogenetic, phylogeographic, and morphometric analyses on the group. The systematic complexity of the family (as evidenced by past research) coupled with the group’s widespread distribution and ecological importance, made the taxon an ideal candidate for a broad-sweeping multi-level systematic analysis using multiple species delimitation methods. Additionally, in this thesis I attempted to build on the ground-breaking work of Christopher Kelly by addressing several knowledge gaps identified within the family, and in so doing, produce the most thorough evolutionary and taxonomic study of Psammophiidae possible. Given the taxonomic uncertainty associated with the family, Chapter Two used a representative sampling from every available species (near complete taxon sampling approach) in the family. The chapter used both standard and time-calibrated phylogenetic modelling and distance/threshold-based species delimitation, to elucidate the finer-level structuring within the family. Geometric morphometrics was used to determine whether there were diagnosable differences in head structure between the different genera. The final phylogenetic tree incorporated 320 samples, representing the most comprehensive phylogenetic reconstruction of the family to date. By using a near-complete taxon sampling approach, I was able to resolve previously unsupported relationships within the family whilst also identifying several novel instances of an under- and over-appreciation of species diversity within the family. Geometric morphometrics also identified clear distinctions between genera based on head shape (head width and ‘beakedness’). This chapter showcased the importance of complete taxon sampling and robust methodology for species delimitation and the deleterious effect of species concepts when implemented in isolation. In Chapter Three, I narrowed the scope of the study to focus on the genus level. Psammophylax (Fitzinger 1843) is an abundant, yet poorly studied genus of grass snakes, endemic to Africa. The generalist nature of the genus and wide-spanning distributions of the constituent species has given rise to several subspecies and a poor understanding of the taxonomic structuring within the genus. The overlapping distributions (sympatry) of many of Psammophylax species, coupled with the potential for cryptic speciation via mechanisms such as convergent evolution, made the group the ideal candidate for a broad-sweeping systematic study (as evidenced in Chapter Two). By applying the suite of analyses used in Chapter Two to the generic level, we aimed to determine the effectiveness of a multi-evidence species delineation approach when tackling systematic problems at lower taxonomic levels. A genetic phylogeny of six of the seven species was estimated using multiple phylogenetic and distance/ threshold-based species delimitation methods. To support the molecular analyses, we conducted morphological analyses on the body (traditional morphology) and head (geometric morphometrics) separately. Phylogenetic analyses recovered a similar topology to past studies, but with better resolution and node support. I found substantial genetic structuring within the genus, supported by significantly different head shapes between Ps. a. acutus and other Psammophylax species. Psammophylax a. acutus was recovered as sister to its congeners, and sequence divergence values and morphometrics supported its recognition as a new genus. Increased sampling in East Africa (Tanzania, Kenya, and Ethiopia) revealed that Psammophylax multisquamis is polyphyletic, necessitating the description of a new, morphologically cryptic, species from northern Tanzania. The distribution of Ps. multisquamis sensu stricto is likely restricted to Kenya and Ethiopia. Within this chapter, taxon-specific phylogenetic analyses yielded stronger intrageneric support as compared to Chapter Two, allowing for more defensible conclusions about taxonomical amendments. Geometric morphometrics proved similarly useful (as compared to Chapter Two) in teasing apart genera within the family but lacked the robustness to delineate species within Psammophylax with confidence, highlighting the apparent convergence of form within the genus. In Chapter Four, I investigated the evolutionary structuring within the Southern African endemic Psammophylax rhombeatus. The structural and environmental heterogeneity within the region has given rise to many morphological forms distributed throughout the country, with previous studies neglecting the associated molecular significance of these forms. Irrespective of their small sample sizes, both Chapter Two and Three identified substantial phylogenetic structuring within the species, making Ps. rhombeatus the ideal candidate for a multi-faceted systematic review, using a combination of phylogenetics, geometric morphometrics and, for the first time in this species, phylogeographic analyses. By investigating a single species, in detail, I was able to assess the effectiveness of the methodologies implemented in previous chapters on systematic sorting using the multi-evidence species delineation approach. Phylogenetic and haplotype analysis retrieved four well-supported clades: southeast South Africa (SESA), southwest South Africa (SWSA), north-eastern South Africa (NESA) and western South Africa (WSA). Although not variable enough to warrant taxonomic re-evaluation, the clades represented important genetic hotspots, with relatively high intraspecific genetic divergence values separating them, irrespective of the small geographic distances separating populations. This is likely a product of the taxon’s habitat-generalist lifestyle, enabling them to bypass vicariant barriers that might otherwise cause speciation in less versatile species. The clades are also geographically distinct, with little overlap, indicating previous vicariance, a finding that is supported by the split of Ps. rhombeatus from Ps. ocellatus in the mid-Pliocene, followed by the diversification of Ps. rhombeatus into four clades throughout the Pleistocene. The genetic structuring observed in Ps. rhombeatus may be a product of population expansion following ancient refugial isolation (potentially Last Glacial Maximum [LGM]). The molecular distinctiveness of the clades was not replicated in the morphological component of this chapter, with neither dorsal nor lateral geometric morphometric analyses of head shape showing any discernible distinctiveness based on geography. Whilst head shape has not been shown to be an effective delineator of evolutionary units at the species level (within this taxon), body colour, scalation, and snout-vent length has been linked to morphotypes within the species based on the work of Broadley (1966). These morphological groupings are loosely attributable to the molecular clades identified in the phylogenetic analyses, highlighting the complex interplay of genetic and morphological characteristics in the process of speciation, and their representation in systematic accounts. This thesis represents the most thorough evolutionary and systematic study of the family currently possible. In addition to identifying and describing both a new genus and species, this thesis also highlighted several instances of an over- and under-appreciation of species diversity within Psammophiidae. By applying a multi-evidence species delineation approach to this thesis, I show the intricacy of the evolutionary process (at various taxonomic levels) and showcase the ease to which species boundaries can be confounded when species concepts are implemented in isolation. These findings also highlighted the importance of sample size, sample range, species delimitation method on the outcome of taxonomic analyses, and their interpretation. Lastly, this thesis addressed the knowledge gaps left by Christopher Kelly’s PhD work and investigated the findings of recent papers that attempted to do the same. Whilst this study answers the questions of old, the taxon-intensive focus revealed several new knowledge gaps within the family, highlighting how much we know about snake systematics, and furthermore, how much we still need to learn about evolutionary structuring. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Keates, Chad
- Date: 2021-10-29
- Subjects: Psammophis South Africa , Herpetology , Herpetology Africa , Molecular biology , Psammophis Classification , Psammophis Genetics , Psammophis Morphology , Psammophis Phylogeny , Morphology Mathematics , Psammophylax
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/295077 , vital:57288 , DOI 10.21504/10962/295079
- Description: Species form the foundations upon which we build our understanding of the natural world. Although a focus of much scientific attention, our understanding of species is stunted by the intrinsic ‘fuzziness’ of boundaries within nature. Due to the complexity of the evolutionary process, coupled with an ever-changing abiotic landscape, species are hard to delineate, even at the best of times. Whilst various species concepts and sophisticated delimitation methods have helped scientists tease apart species, many species complexes persist. This is because taxonomy is a discrete ordering system imposed upon the continuous and intercalated structure of life. To improve our understanding of a wide-ranging family of snakes, I investigated the taxonomy and evolutionary structuring within Psammophiidae using both molecular and morphological approaches, employing phylogenetic, phylogeographic, and morphometric analyses on the group. The systematic complexity of the family (as evidenced by past research) coupled with the group’s widespread distribution and ecological importance, made the taxon an ideal candidate for a broad-sweeping multi-level systematic analysis using multiple species delimitation methods. Additionally, in this thesis I attempted to build on the ground-breaking work of Christopher Kelly by addressing several knowledge gaps identified within the family, and in so doing, produce the most thorough evolutionary and taxonomic study of Psammophiidae possible. Given the taxonomic uncertainty associated with the family, Chapter Two used a representative sampling from every available species (near complete taxon sampling approach) in the family. The chapter used both standard and time-calibrated phylogenetic modelling and distance/threshold-based species delimitation, to elucidate the finer-level structuring within the family. Geometric morphometrics was used to determine whether there were diagnosable differences in head structure between the different genera. The final phylogenetic tree incorporated 320 samples, representing the most comprehensive phylogenetic reconstruction of the family to date. By using a near-complete taxon sampling approach, I was able to resolve previously unsupported relationships within the family whilst also identifying several novel instances of an under- and over-appreciation of species diversity within the family. Geometric morphometrics also identified clear distinctions between genera based on head shape (head width and ‘beakedness’). This chapter showcased the importance of complete taxon sampling and robust methodology for species delimitation and the deleterious effect of species concepts when implemented in isolation. In Chapter Three, I narrowed the scope of the study to focus on the genus level. Psammophylax (Fitzinger 1843) is an abundant, yet poorly studied genus of grass snakes, endemic to Africa. The generalist nature of the genus and wide-spanning distributions of the constituent species has given rise to several subspecies and a poor understanding of the taxonomic structuring within the genus. The overlapping distributions (sympatry) of many of Psammophylax species, coupled with the potential for cryptic speciation via mechanisms such as convergent evolution, made the group the ideal candidate for a broad-sweeping systematic study (as evidenced in Chapter Two). By applying the suite of analyses used in Chapter Two to the generic level, we aimed to determine the effectiveness of a multi-evidence species delineation approach when tackling systematic problems at lower taxonomic levels. A genetic phylogeny of six of the seven species was estimated using multiple phylogenetic and distance/ threshold-based species delimitation methods. To support the molecular analyses, we conducted morphological analyses on the body (traditional morphology) and head (geometric morphometrics) separately. Phylogenetic analyses recovered a similar topology to past studies, but with better resolution and node support. I found substantial genetic structuring within the genus, supported by significantly different head shapes between Ps. a. acutus and other Psammophylax species. Psammophylax a. acutus was recovered as sister to its congeners, and sequence divergence values and morphometrics supported its recognition as a new genus. Increased sampling in East Africa (Tanzania, Kenya, and Ethiopia) revealed that Psammophylax multisquamis is polyphyletic, necessitating the description of a new, morphologically cryptic, species from northern Tanzania. The distribution of Ps. multisquamis sensu stricto is likely restricted to Kenya and Ethiopia. Within this chapter, taxon-specific phylogenetic analyses yielded stronger intrageneric support as compared to Chapter Two, allowing for more defensible conclusions about taxonomical amendments. Geometric morphometrics proved similarly useful (as compared to Chapter Two) in teasing apart genera within the family but lacked the robustness to delineate species within Psammophylax with confidence, highlighting the apparent convergence of form within the genus. In Chapter Four, I investigated the evolutionary structuring within the Southern African endemic Psammophylax rhombeatus. The structural and environmental heterogeneity within the region has given rise to many morphological forms distributed throughout the country, with previous studies neglecting the associated molecular significance of these forms. Irrespective of their small sample sizes, both Chapter Two and Three identified substantial phylogenetic structuring within the species, making Ps. rhombeatus the ideal candidate for a multi-faceted systematic review, using a combination of phylogenetics, geometric morphometrics and, for the first time in this species, phylogeographic analyses. By investigating a single species, in detail, I was able to assess the effectiveness of the methodologies implemented in previous chapters on systematic sorting using the multi-evidence species delineation approach. Phylogenetic and haplotype analysis retrieved four well-supported clades: southeast South Africa (SESA), southwest South Africa (SWSA), north-eastern South Africa (NESA) and western South Africa (WSA). Although not variable enough to warrant taxonomic re-evaluation, the clades represented important genetic hotspots, with relatively high intraspecific genetic divergence values separating them, irrespective of the small geographic distances separating populations. This is likely a product of the taxon’s habitat-generalist lifestyle, enabling them to bypass vicariant barriers that might otherwise cause speciation in less versatile species. The clades are also geographically distinct, with little overlap, indicating previous vicariance, a finding that is supported by the split of Ps. rhombeatus from Ps. ocellatus in the mid-Pliocene, followed by the diversification of Ps. rhombeatus into four clades throughout the Pleistocene. The genetic structuring observed in Ps. rhombeatus may be a product of population expansion following ancient refugial isolation (potentially Last Glacial Maximum [LGM]). The molecular distinctiveness of the clades was not replicated in the morphological component of this chapter, with neither dorsal nor lateral geometric morphometric analyses of head shape showing any discernible distinctiveness based on geography. Whilst head shape has not been shown to be an effective delineator of evolutionary units at the species level (within this taxon), body colour, scalation, and snout-vent length has been linked to morphotypes within the species based on the work of Broadley (1966). These morphological groupings are loosely attributable to the molecular clades identified in the phylogenetic analyses, highlighting the complex interplay of genetic and morphological characteristics in the process of speciation, and their representation in systematic accounts. This thesis represents the most thorough evolutionary and systematic study of the family currently possible. In addition to identifying and describing both a new genus and species, this thesis also highlighted several instances of an over- and under-appreciation of species diversity within Psammophiidae. By applying a multi-evidence species delineation approach to this thesis, I show the intricacy of the evolutionary process (at various taxonomic levels) and showcase the ease to which species boundaries can be confounded when species concepts are implemented in isolation. These findings also highlighted the importance of sample size, sample range, species delimitation method on the outcome of taxonomic analyses, and their interpretation. Lastly, this thesis addressed the knowledge gaps left by Christopher Kelly’s PhD work and investigated the findings of recent papers that attempted to do the same. Whilst this study answers the questions of old, the taxon-intensive focus revealed several new knowledge gaps within the family, highlighting how much we know about snake systematics, and furthermore, how much we still need to learn about evolutionary structuring. , Thesis (PhD) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Legal ethics and the lawyer-client relationship in South Africa: A proposal for reform using local values
- Authors: Kruuse, Helen Julia
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192765 , vital:45262
- Description: Thesis (PhD) -- Faculty of Law, Law, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Kruuse, Helen Julia
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192765 , vital:45262
- Description: Thesis (PhD) -- Faculty of Law, Law, 2021
- Full Text:
- Date Issued: 2021-10-29
Mediating and examining expansive learning in the context of multidimensional complexities affecting household food security activity systems in Nyanyadzi Irrigation Scheme in the Manicaland Province of Zimbabwe
- Authors: Mukwambo, Robson
- Date: 2021-10-29
- Subjects: Active learning Zimbabwe Chimanimani District , Food security Zimbabwe Chimanimani District , Sustainable agriculture Zimbabwe Chimanimani District , Irrigation farming Zimbabwe Chimanimani District , Qualitative research , Cultural-historical activity theory (CHAT) , Nyanyadzi Irrigation Scheme
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192712 , vital:45253 , 10.21504/10962/192712
- Description: The study sought to mediate and examine expansive learning in the context of multidimensional complexities affecting household food security activity systems in Nyanyadzi Irrigation Scheme in Ward 8 of Chimanimani District in the Manicaland province of Zimbabwe. Therefore, the main foci of the study were to investigate how multidimensional complexities have come to be the way they are (historicizing) and how they enable or constrain learning of household food production. The study utilized Cultural Historical Activity Theory and the Expansive Learning Cycle (Engeström & Sannino, 2010) to examine and mediate collective learning in response to the multidimensional complexities and also to contribute to transforming the farmers’ activity systems towards more sustainable practices to ensure household food security. The study used a qualitative research approach, utilizing an insider formative intervention approach in a case study design in which Nyanyadzi irrigation scheme was the case study. I have adopted the insider formative interventionist role as a 3rd generation farmer, born and bred in Nyanyadzi area, and my family has been involved in the Nyanyadzi irrigation scheme for three generations. I see this as synergistic with the need for deep cultural understanding in CHAT research. However, this role also provided challenges for me to maintain a rigorous approach to the research in which I also reflexively review my own role and influence in the research process. Following CHAT expansive learning methodological guidance, data was generated through fifteen (15) face to face interviews with three generations of farmers in the scheme (historical ethnographic data); four focus group discussions (contemporary ethnographic data) and eight (8) sessions in a three (3) day change laboratory workshop (expansive learning data). Double stimulation and ‘mirror’ data was used to surface and prioritise responses to contradictions in the Change Laboratory Workshops (CLW), which is a methodology developed in and for CHAT research (ibid). The data was analysed using both inductive and abductive approaches and were conducted in a three-phased process focusing firstly on the history of the object, followed by current perspectives on the object of activity and lastly on transformations emerging in the object of activity via the expansive learning process. Cultural Historical Activity Theoretical tools informed activity system analysis and analysis of the history of the object and emerging contradictions; and the expansive learning cycle (ELP) process framework associated with and emergent from CHAT was used to analyse the emergence of transformative agency and expansion of the object. Four levels of contradictions were used to describe and explain the emergent contradictions namely, primary, secondary, tertiary and quaternary contradictions and are presented in this sequence as catalytic opportunities for expansive learning as proposed in CHAT. In addition, the four types of discursive manifestations of contradictions namely, dilemma, conflict, critical conflict and double bind were used to describe and explain the manifestations of contradictions in this study and their role in catalysing transformative agency. The concept of linguistic cues for discursive manifestations of contradictions was adopted and employed in the preliminary data analysis phase. In addition, the transformative agency expressions and zone of proximal development (ZPD) concept was applied in and to the CLW data to examine the learning pathways and to co-develop and expand farmers’ and other stakeholders’ transformative agency and ZPD respectively. I found myself as formative insider researcher having to take on a strong role as co-engaged researcher / participant in the irrigation scheme expansive learning process. The study concluded that the farmers’ activity system is the central activity system and it interacts with other activity systems on a partially shared object “improved crop production and marketing under irrigation scheme”. Through interactions with other neighbouring activity systems, the farmers have faced multidimensional complexities that constrain their ability to fully realise their object. These multidimensional complexities manifest in three critical contradictions as a critical conflict in leadership and management crisis; a dilemma and double bind in a lack of farmer education and training; and lastly, a dilemma and double bind in poor crop marketing. These multidimensional complexities have a historical account and they have evolved in complexity over time and I argue in the thesis that, a careful cultural-historicity of the object of activity and mediation of the situated learning can help to collectively come up with solutions to these multidimensional complexities. The study further concluded that despite these multidimensional complexities in the scheme, learning has been taking place and such learning was sometimes mediated through demonstrations as “learning by doing,” “seeing is believing” and the “winners and losers” concept. Furthermore, through the CLW process the farmers and other stakeholders’ cognitive horizons were expanded by the mirror data and double stimulation processes, and the expansive learning process developed their individual and collective transformative agency pathways and expanded their collective zone of proximal development. In this study I argue that there has been little said about collective learning in irrigation schemes and given the dearth of detail on such learning, it seems that this learning is either going unnoticed or is ignored. Hence, I further argued that the multidimensional complexities in irrigation schemes are both a stimulant for learning and provide a space (object) for collective learning, as was also shown by Baloi (2016). The study also shows that the collective learning potential in these irrigation schemes can be pro-actively mediated via expansive learning formative interventions in support of improved crop production and marketing for produce developed under irrigation in irrigation schemes such as the Nyanyadzi Irrigation scheme. Lastly, being an insider formative interventionist researcher in this study, with intergenerational engagement and perspective on the history of the object and integrational engagement with the transforming object, I became part of the intergenerational transformation of the irrigation scheme’s object. The intergenerational co-construction of the history of the object, coupled with the insider formative interventionist researcher approach opened up and allowed me as a current generation agent or actor to develop an in-depth understanding of the multidimensional nature and historicity of the object. This was crucial for opening up the transformative agency pathways. It also produced a responsibility for me as an insider formative interventionist researcher to carry the summative findings of the study back into the social context to widen the engagement and mediation of the transformation needed in the community. Overall not only does the study offer an intergenerational perspective on multidimensional complexities of the object and how this can generatively be mobilised via expansive learning into emerging transformative learning agency pathways, but it also offers a new vantage point on the role of the insider formative interventionist researcher. Through this, the study offers insight into how we as third generation members of the community can be brought closer to our communities through the application of our skills, thereby also offering a new type of engaged and rigorously framed and executed research with roots in our communities. As shown in this study, not only does this expand the knowledge and experience of those we engage with, but it also expands our own knowledge and expertise in order to be more able to contribute to both the challenges of our own communities but also that of other communities and situations similar to ours, and beyond these bounded contexts. The study’s contribution is both practical, but also methodological from this vantage point, especially in an African context where there is much critique of ‘outsider research’, yet little pro-active articulation of what insider (in this case, formative intervention) research may look like. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mukwambo, Robson
- Date: 2021-10-29
- Subjects: Active learning Zimbabwe Chimanimani District , Food security Zimbabwe Chimanimani District , Sustainable agriculture Zimbabwe Chimanimani District , Irrigation farming Zimbabwe Chimanimani District , Qualitative research , Cultural-historical activity theory (CHAT) , Nyanyadzi Irrigation Scheme
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192712 , vital:45253 , 10.21504/10962/192712
- Description: The study sought to mediate and examine expansive learning in the context of multidimensional complexities affecting household food security activity systems in Nyanyadzi Irrigation Scheme in Ward 8 of Chimanimani District in the Manicaland province of Zimbabwe. Therefore, the main foci of the study were to investigate how multidimensional complexities have come to be the way they are (historicizing) and how they enable or constrain learning of household food production. The study utilized Cultural Historical Activity Theory and the Expansive Learning Cycle (Engeström & Sannino, 2010) to examine and mediate collective learning in response to the multidimensional complexities and also to contribute to transforming the farmers’ activity systems towards more sustainable practices to ensure household food security. The study used a qualitative research approach, utilizing an insider formative intervention approach in a case study design in which Nyanyadzi irrigation scheme was the case study. I have adopted the insider formative interventionist role as a 3rd generation farmer, born and bred in Nyanyadzi area, and my family has been involved in the Nyanyadzi irrigation scheme for three generations. I see this as synergistic with the need for deep cultural understanding in CHAT research. However, this role also provided challenges for me to maintain a rigorous approach to the research in which I also reflexively review my own role and influence in the research process. Following CHAT expansive learning methodological guidance, data was generated through fifteen (15) face to face interviews with three generations of farmers in the scheme (historical ethnographic data); four focus group discussions (contemporary ethnographic data) and eight (8) sessions in a three (3) day change laboratory workshop (expansive learning data). Double stimulation and ‘mirror’ data was used to surface and prioritise responses to contradictions in the Change Laboratory Workshops (CLW), which is a methodology developed in and for CHAT research (ibid). The data was analysed using both inductive and abductive approaches and were conducted in a three-phased process focusing firstly on the history of the object, followed by current perspectives on the object of activity and lastly on transformations emerging in the object of activity via the expansive learning process. Cultural Historical Activity Theoretical tools informed activity system analysis and analysis of the history of the object and emerging contradictions; and the expansive learning cycle (ELP) process framework associated with and emergent from CHAT was used to analyse the emergence of transformative agency and expansion of the object. Four levels of contradictions were used to describe and explain the emergent contradictions namely, primary, secondary, tertiary and quaternary contradictions and are presented in this sequence as catalytic opportunities for expansive learning as proposed in CHAT. In addition, the four types of discursive manifestations of contradictions namely, dilemma, conflict, critical conflict and double bind were used to describe and explain the manifestations of contradictions in this study and their role in catalysing transformative agency. The concept of linguistic cues for discursive manifestations of contradictions was adopted and employed in the preliminary data analysis phase. In addition, the transformative agency expressions and zone of proximal development (ZPD) concept was applied in and to the CLW data to examine the learning pathways and to co-develop and expand farmers’ and other stakeholders’ transformative agency and ZPD respectively. I found myself as formative insider researcher having to take on a strong role as co-engaged researcher / participant in the irrigation scheme expansive learning process. The study concluded that the farmers’ activity system is the central activity system and it interacts with other activity systems on a partially shared object “improved crop production and marketing under irrigation scheme”. Through interactions with other neighbouring activity systems, the farmers have faced multidimensional complexities that constrain their ability to fully realise their object. These multidimensional complexities manifest in three critical contradictions as a critical conflict in leadership and management crisis; a dilemma and double bind in a lack of farmer education and training; and lastly, a dilemma and double bind in poor crop marketing. These multidimensional complexities have a historical account and they have evolved in complexity over time and I argue in the thesis that, a careful cultural-historicity of the object of activity and mediation of the situated learning can help to collectively come up with solutions to these multidimensional complexities. The study further concluded that despite these multidimensional complexities in the scheme, learning has been taking place and such learning was sometimes mediated through demonstrations as “learning by doing,” “seeing is believing” and the “winners and losers” concept. Furthermore, through the CLW process the farmers and other stakeholders’ cognitive horizons were expanded by the mirror data and double stimulation processes, and the expansive learning process developed their individual and collective transformative agency pathways and expanded their collective zone of proximal development. In this study I argue that there has been little said about collective learning in irrigation schemes and given the dearth of detail on such learning, it seems that this learning is either going unnoticed or is ignored. Hence, I further argued that the multidimensional complexities in irrigation schemes are both a stimulant for learning and provide a space (object) for collective learning, as was also shown by Baloi (2016). The study also shows that the collective learning potential in these irrigation schemes can be pro-actively mediated via expansive learning formative interventions in support of improved crop production and marketing for produce developed under irrigation in irrigation schemes such as the Nyanyadzi Irrigation scheme. Lastly, being an insider formative interventionist researcher in this study, with intergenerational engagement and perspective on the history of the object and integrational engagement with the transforming object, I became part of the intergenerational transformation of the irrigation scheme’s object. The intergenerational co-construction of the history of the object, coupled with the insider formative interventionist researcher approach opened up and allowed me as a current generation agent or actor to develop an in-depth understanding of the multidimensional nature and historicity of the object. This was crucial for opening up the transformative agency pathways. It also produced a responsibility for me as an insider formative interventionist researcher to carry the summative findings of the study back into the social context to widen the engagement and mediation of the transformation needed in the community. Overall not only does the study offer an intergenerational perspective on multidimensional complexities of the object and how this can generatively be mobilised via expansive learning into emerging transformative learning agency pathways, but it also offers a new vantage point on the role of the insider formative interventionist researcher. Through this, the study offers insight into how we as third generation members of the community can be brought closer to our communities through the application of our skills, thereby also offering a new type of engaged and rigorously framed and executed research with roots in our communities. As shown in this study, not only does this expand the knowledge and experience of those we engage with, but it also expands our own knowledge and expertise in order to be more able to contribute to both the challenges of our own communities but also that of other communities and situations similar to ours, and beyond these bounded contexts. The study’s contribution is both practical, but also methodological from this vantage point, especially in an African context where there is much critique of ‘outsider research’, yet little pro-active articulation of what insider (in this case, formative intervention) research may look like. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
Microalgal-bacterial flocs and extracellular polymeric substances for optimum function of integrated algal pond systems
- Authors: Jimoh, Taobat Adekilekun
- Date: 2021-10-29
- Subjects: Flocculation , Extracellular polymeric substances , Water Purification , Sewage Purification Anaerobic treatment , Integrated algae pond systems (IAPS) , Microalgal-bacterial flocs
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191214 , vital:45071 , 10.21504/10962/191214
- Description: Despite the dire state of sanitation infrastructures, water scarcity, and the dwindling reserve of natural resources due to ever-increasing population growth, implementation of a suitable technology that can provide a solution to all these issues continues to be ignored. The integrated algal pond system (IAPS) is a wastewater treatment technology that combines the processes of anaerobic digestion and photosynthetic oxygenation to achieve wastewater treatment and facilitate the recovery of treated water and resources in the form of biogas and microalgal-bacterial biomass. The natural process of bioflocculation through microalgal-bacterial mutualism and production of extracellular polymeric substances (EPS) in high rate algal oxidation ponds (HRAOPs) of an IAPS increases efficiency of wastewater treatment and potentially enhances harvestability and biomass recovery, which could contribute significantly to the successful establishment of a biorefinery. Using a 500 PE pilot-scale IAPS supplied domestic sewage coupled with laboratory experiments, this study investigated the importance and function of in situ EPS production and MaB-floc formation in HRAOP. A metagenomic study revealed the biological components of the biomass or mixed liquor suspended solids (MLSS) produced in HRAOP and showed that the suspended biomass is composed largely of eukaryotes that were dominated by the colonial microalgae Pseudopediastrum sp. and Desmodesmus sp., and a diverse range of prokaryotes including bacteria and cyanobacteria. Dominance, within the bacterial population, by a sulphur-oxidizing bacterium, Thiothrix which comprised up to 80% of the prokaryotes, coincided with a period of poor flocculation and was therefore rationalized to have contributed to bulking and poor biomass settleability. Otherwise, good flocs were formed in the MLSS with settleability up to 95% and, within 1 h. The formation of MaB-flocs appeared to be dependent on EPS concentration of the mixed liquor due to the observed positive correlation between soluble EPS (S-EPS), biomass concentration, and settleability. The contribution and role of MLSS components towards the formation and sustenance of MaB-flocs were further demonstrated in laboratory experiments using pure strains of microalgae, cyanobacteria, and bacteria. Results showed that pure cultures of dominant microalgae in MLSS, Pseudopediastrum sp. and Desmodesmus sp. achieved a rapid 92 and 75% settleability within 3 h. A self-flocculating filamentous cyanobacterium, Leptolyngbya strain ECCN 20BG was isolated, characterized, and shown to achieve 99% settleability within 5 min by forming large tightly aggregated flocs. In further experiments, this strain was found to improve the settleability of MLSS by an average of 20%. Bacterial strains identified as Bacillus strain ECCN 40b, Bacillus strain ECCN 41b, Planococcus strain ECCN 45b, and Exiguobacterium strain ECCN 46b were also observed to produce sticky EPS-like materials in pure cultures that could also contribute to the aggregation of cells in a mixed environment. Given these results, various factors and/or mechanisms that might enhance microbial aggregation and biomass recovery from HRAOP MLSS were identified in this study and include; (1) dominance by larger colonial microalgae prevents disintegration of MaB-flocs and enhances recovery of biomass from MLSS by gravity sedimentation, (2) presence of filamentous cyanobacteria species that can self-flocculate to form an interwoven network of filaments may play an important role in the structural stability and settleability of MaB-flocs in MLSS, and (3) production of EPS to form the matrix or scaffold whereon all microbial components aggregate to develop a microenvironment. Indeed, all forms of EPS, except for that produced by Bacillus strain ECCN 41b, showed bioflocculating property and were able to serve as flocculants for the recovery of Chlorella, an alga known for its poor settleability. A combination of biochemical analyses and FTIR spectroscopy revealed the importance of carbohydrate enrichment of these biopolymers. Carbohydrate concentration in all forms of EPS was between 12 and 41% suggesting that production of these compounds by microbes within the MLSS contributed to MaB-floc formation. EPS extracted from bulk MLSS and EPS produced by Bacillus strains possessed some surface-active properties that were comparable to Triton X-100, indicating potential application in bioremediation and recovery of oil from contaminated soil and water. In particular, EPS generated from Bacillus strain ECCN 41b displayed relatively distinct properties including the quantity produced (> 500 mg/L), increased viscosity, inability to flocculate microalgal cells, a rhamnolipid content of 32%, and a higher surface-activity. Based on these results, Bacillus strain ECCN 41b was rationalized to produce anionic EPS with potential application in metal or oil recovery. In addition to EPS production, the bacteria Planococcus strain ECCN 45b and Exiguobacterium strain ECCN 46b appeared pigmented. Based on partial characterization using UV/Vis spectrophotometry, thin-layer chromatography, FTIR, and NMR, the pigments produced by these two strains appeared to be identical and were tentatively identified as ketocarotenoids. This study successfully demonstrated the importance of EPS production and formation of MaB-flocs in the MLSS from HRAOP of an IAPS treating domestic sewage. It is evident that increased settleability of the biomass does contribute to the reported efficiency of wastewater treatment by IAPS and would reduce both total suspended solids (TSS) and chemical oxygen demand (COD). In addition, demonstration that this biomass contains products of value such as carotenoids and EPS with potential for commercial use strengthens the idea of using IAPS as a platform technology for innovation of the wastewater treatment process to a biorefinery. , Thesis (PhD) -- Faculty of Science, Institute for Environmental Biotechnology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Jimoh, Taobat Adekilekun
- Date: 2021-10-29
- Subjects: Flocculation , Extracellular polymeric substances , Water Purification , Sewage Purification Anaerobic treatment , Integrated algae pond systems (IAPS) , Microalgal-bacterial flocs
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191214 , vital:45071 , 10.21504/10962/191214
- Description: Despite the dire state of sanitation infrastructures, water scarcity, and the dwindling reserve of natural resources due to ever-increasing population growth, implementation of a suitable technology that can provide a solution to all these issues continues to be ignored. The integrated algal pond system (IAPS) is a wastewater treatment technology that combines the processes of anaerobic digestion and photosynthetic oxygenation to achieve wastewater treatment and facilitate the recovery of treated water and resources in the form of biogas and microalgal-bacterial biomass. The natural process of bioflocculation through microalgal-bacterial mutualism and production of extracellular polymeric substances (EPS) in high rate algal oxidation ponds (HRAOPs) of an IAPS increases efficiency of wastewater treatment and potentially enhances harvestability and biomass recovery, which could contribute significantly to the successful establishment of a biorefinery. Using a 500 PE pilot-scale IAPS supplied domestic sewage coupled with laboratory experiments, this study investigated the importance and function of in situ EPS production and MaB-floc formation in HRAOP. A metagenomic study revealed the biological components of the biomass or mixed liquor suspended solids (MLSS) produced in HRAOP and showed that the suspended biomass is composed largely of eukaryotes that were dominated by the colonial microalgae Pseudopediastrum sp. and Desmodesmus sp., and a diverse range of prokaryotes including bacteria and cyanobacteria. Dominance, within the bacterial population, by a sulphur-oxidizing bacterium, Thiothrix which comprised up to 80% of the prokaryotes, coincided with a period of poor flocculation and was therefore rationalized to have contributed to bulking and poor biomass settleability. Otherwise, good flocs were formed in the MLSS with settleability up to 95% and, within 1 h. The formation of MaB-flocs appeared to be dependent on EPS concentration of the mixed liquor due to the observed positive correlation between soluble EPS (S-EPS), biomass concentration, and settleability. The contribution and role of MLSS components towards the formation and sustenance of MaB-flocs were further demonstrated in laboratory experiments using pure strains of microalgae, cyanobacteria, and bacteria. Results showed that pure cultures of dominant microalgae in MLSS, Pseudopediastrum sp. and Desmodesmus sp. achieved a rapid 92 and 75% settleability within 3 h. A self-flocculating filamentous cyanobacterium, Leptolyngbya strain ECCN 20BG was isolated, characterized, and shown to achieve 99% settleability within 5 min by forming large tightly aggregated flocs. In further experiments, this strain was found to improve the settleability of MLSS by an average of 20%. Bacterial strains identified as Bacillus strain ECCN 40b, Bacillus strain ECCN 41b, Planococcus strain ECCN 45b, and Exiguobacterium strain ECCN 46b were also observed to produce sticky EPS-like materials in pure cultures that could also contribute to the aggregation of cells in a mixed environment. Given these results, various factors and/or mechanisms that might enhance microbial aggregation and biomass recovery from HRAOP MLSS were identified in this study and include; (1) dominance by larger colonial microalgae prevents disintegration of MaB-flocs and enhances recovery of biomass from MLSS by gravity sedimentation, (2) presence of filamentous cyanobacteria species that can self-flocculate to form an interwoven network of filaments may play an important role in the structural stability and settleability of MaB-flocs in MLSS, and (3) production of EPS to form the matrix or scaffold whereon all microbial components aggregate to develop a microenvironment. Indeed, all forms of EPS, except for that produced by Bacillus strain ECCN 41b, showed bioflocculating property and were able to serve as flocculants for the recovery of Chlorella, an alga known for its poor settleability. A combination of biochemical analyses and FTIR spectroscopy revealed the importance of carbohydrate enrichment of these biopolymers. Carbohydrate concentration in all forms of EPS was between 12 and 41% suggesting that production of these compounds by microbes within the MLSS contributed to MaB-floc formation. EPS extracted from bulk MLSS and EPS produced by Bacillus strains possessed some surface-active properties that were comparable to Triton X-100, indicating potential application in bioremediation and recovery of oil from contaminated soil and water. In particular, EPS generated from Bacillus strain ECCN 41b displayed relatively distinct properties including the quantity produced (> 500 mg/L), increased viscosity, inability to flocculate microalgal cells, a rhamnolipid content of 32%, and a higher surface-activity. Based on these results, Bacillus strain ECCN 41b was rationalized to produce anionic EPS with potential application in metal or oil recovery. In addition to EPS production, the bacteria Planococcus strain ECCN 45b and Exiguobacterium strain ECCN 46b appeared pigmented. Based on partial characterization using UV/Vis spectrophotometry, thin-layer chromatography, FTIR, and NMR, the pigments produced by these two strains appeared to be identical and were tentatively identified as ketocarotenoids. This study successfully demonstrated the importance of EPS production and formation of MaB-flocs in the MLSS from HRAOP of an IAPS treating domestic sewage. It is evident that increased settleability of the biomass does contribute to the reported efficiency of wastewater treatment by IAPS and would reduce both total suspended solids (TSS) and chemical oxygen demand (COD). In addition, demonstration that this biomass contains products of value such as carotenoids and EPS with potential for commercial use strengthens the idea of using IAPS as a platform technology for innovation of the wastewater treatment process to a biorefinery. , Thesis (PhD) -- Faculty of Science, Institute for Environmental Biotechnology, 2021
- Full Text:
- Date Issued: 2021-10-29
Mitigating salt accumulation in recycled brewery effluent through the integration of water treatment, agriculture and aquaculture
- Authors: Mabasa, Nyiko Charity
- Date: 2021-10-29
- Subjects: Brewery waste South Africa Eastern Cape , Recycling (Waste, etc.) South Africa Eastern Cape , Water reuse South Africa Eastern Cape , Irrigation South Africa Eastern Cape , Sewage Purification Anaerobic treatment , Constructed wetlands , Aquaculture
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191126 , vital:45063 , 10.21504/10962/191126
- Description: Water scarcity in South Africa, and globally, presents challenges for industries. It is imperative to develop responsible water use, such as recycling and reusing wastewater from food processing industries such as breweries. The Ibhayi Brewery (SAB Ltd) employs a combination of sustainable treatment processes that include anaerobic digestion (AD), primary facultative ponds (PFP), high rate algal ponds (HRAP) and constructed wetlands (CW) to treat brewery effluent on an experimental scale. The constituent concentrations of these experimentally treated effluents are within the ranges prescribed by local regulations to allow for potential downstream use in agriculture and aquaculture. However, the sodium content in this treated effluent, which originates from upstream cleaning agents and pH control at the onsite effluent treatment facility, is a constraint to the downstream use of brewery effluent. This study addresses the salt problem, by investigating the potential of either reducing/eliminating salt addition at source, or developing alternative techniques for downstream agriculture to mitigate the effects of salt accumulation caused by irrigation with brewery effluent. Four salt-tolerant test crops; Swiss chard (Beta vulgaris), saltbush (Atriplex nummularia), Salicornia meyeriana and sorghum (Sorghum bicolor), grew efficiently in brewery effluent irrigated soils but did not stop sodium accumulation in the growth medium. Swiss chard had the best growth with a wet biomass accumulation of 8,173 g m-2, due to the plant’s ability to tolerate saline conditions and continuous cropping. Crop rotation, to limit effects of nutrient depletion in soil, had no significant effect on plant growth suggesting soils were adequately able to provide micro-nutrients in the short-term. Prolonged irrigation with brewery effluent can lead to sodium accumulation in the soil, which was successfully controlled through the addition of soil amendments (gypsum and Trichoderma cultures). These reduced soil sodium from a potentially limiting level of 1,398 mg L-1 to the acceptable levels of 240 mg L-1 and 353 mg L-1 respectively, mainly through leaching. However only Trichoderma improved Swiss chard production to 11,238 g m-2. While crop rotation in this work did not contribute to mitigating the problem of salt accumulation, soil amended with Trichoderma appears to be a potential solution when brewery effluent is reused in agriculture. In an alternative to soil cultivation, CWs were trialled with no significant differences in the sodium concentration of brewery effluent treated along a 15 m lateral flow CW, which could be attributed to evapotranspiration. This was notably accompanied by a desirable 95.21% decrease in ammonia from inlet to outlet resulting in significant improvement in water quality for reuse in aquaculture where ammonia levels are important limiting constraints. While CWs remain a suitable brewery effluent treatment solution, this technology requires additional modelling and optimisation in order to mitigate the problem of salt accumulation in the reuse of treated brewery effluent in agriculture and aquaculture. This research demonstrates the baseline information for such modelling and optimisation. African catfish (Clarias gariepinus) grew in CW treated brewery effluent; however, this growth was moderate at 0.92% bw day-1, whereas Mozambique tilapia (Oreochromis mossambicus) were shown to be unsuited to growth in this system and lost weight with an average specific growth rate (SGR) of -0.98% bw day-1; and both fish species presenting with health related concerns. Hardy fish species such as African catfish can be cultured in brewery effluent, but with risk involved. This was a preliminary study to develop parameters for future dimensional analysis modelling to allow optimisation of the CW, based on nutrient removal rates obtained which will allow for improved downstream aquaculture by reducing or eliminating risks presented in this study. This work has also contributed to a foundation for the development of guidelines that use a risk-based approach for water use in aquaculture. Alternatives to the current in place cleaning agents were considered to mitigate the effects of salt accumulation. Sodium is introduced into the effluent via the use of sodium hydroxide and sodium chlorite for cleaning and disinfection in the brewery, as well as through effluent pH adjustment in the AD plant. The widespread use of outdated legacy cleaning systems and pH adjustment regimes is entrenched in the brewery standard operating procedures (SOP). A cost-benefit analysis (CBA) demonstrated that a change of cleaning and disinfecting regimes to hydrogen peroxide in the brewery, and magnesium hydroxide pH adjustment in the effluent treatment plant addresses the sodium issue upstream in the brewery practically eliminating sodium from the effluent. In addition, a life cycle analysis (LCA) was carried out to assess the environmental impacts associated with the alternative cleaning and pH adjustment scenarios. The LCA showed that electricity consumption during use phase of the chemicals for respective purposes, as well as their production activities were major contributors to the significant environmental impact categories that were assessed. The cleaning scenario employing the use of hydrogen peroxide for both cleaning and disinfection was found to be the most environmentally sustainable. This was attributed to the reduced number of chemicals used compared to the other cleaning scenarios. Dolomitic lime was the pH adjustment alternative with the lowest average environmental impact; but, however, had a higher impact on freshwater eutrophication which is of major concern if the effluent will be reused for irrigation. Magnesium hydroxide was therefore considered to be the better option as a sodium hydroxide alternative for pH adjustment. This mitigates salt accumulation, making treated brewery effluent suitable for reuse in high value downstream agriculture and aquaculture, while employing more environmentally sustainable technologies. Notably, this converts brewery effluent from a financial liability to Ibhayi Brewery, into a product containing water and nutrients that generate income, improve food security, and can create employment in downstream agriculture and aquaculture in a sustainable manner. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mabasa, Nyiko Charity
- Date: 2021-10-29
- Subjects: Brewery waste South Africa Eastern Cape , Recycling (Waste, etc.) South Africa Eastern Cape , Water reuse South Africa Eastern Cape , Irrigation South Africa Eastern Cape , Sewage Purification Anaerobic treatment , Constructed wetlands , Aquaculture
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191126 , vital:45063 , 10.21504/10962/191126
- Description: Water scarcity in South Africa, and globally, presents challenges for industries. It is imperative to develop responsible water use, such as recycling and reusing wastewater from food processing industries such as breweries. The Ibhayi Brewery (SAB Ltd) employs a combination of sustainable treatment processes that include anaerobic digestion (AD), primary facultative ponds (PFP), high rate algal ponds (HRAP) and constructed wetlands (CW) to treat brewery effluent on an experimental scale. The constituent concentrations of these experimentally treated effluents are within the ranges prescribed by local regulations to allow for potential downstream use in agriculture and aquaculture. However, the sodium content in this treated effluent, which originates from upstream cleaning agents and pH control at the onsite effluent treatment facility, is a constraint to the downstream use of brewery effluent. This study addresses the salt problem, by investigating the potential of either reducing/eliminating salt addition at source, or developing alternative techniques for downstream agriculture to mitigate the effects of salt accumulation caused by irrigation with brewery effluent. Four salt-tolerant test crops; Swiss chard (Beta vulgaris), saltbush (Atriplex nummularia), Salicornia meyeriana and sorghum (Sorghum bicolor), grew efficiently in brewery effluent irrigated soils but did not stop sodium accumulation in the growth medium. Swiss chard had the best growth with a wet biomass accumulation of 8,173 g m-2, due to the plant’s ability to tolerate saline conditions and continuous cropping. Crop rotation, to limit effects of nutrient depletion in soil, had no significant effect on plant growth suggesting soils were adequately able to provide micro-nutrients in the short-term. Prolonged irrigation with brewery effluent can lead to sodium accumulation in the soil, which was successfully controlled through the addition of soil amendments (gypsum and Trichoderma cultures). These reduced soil sodium from a potentially limiting level of 1,398 mg L-1 to the acceptable levels of 240 mg L-1 and 353 mg L-1 respectively, mainly through leaching. However only Trichoderma improved Swiss chard production to 11,238 g m-2. While crop rotation in this work did not contribute to mitigating the problem of salt accumulation, soil amended with Trichoderma appears to be a potential solution when brewery effluent is reused in agriculture. In an alternative to soil cultivation, CWs were trialled with no significant differences in the sodium concentration of brewery effluent treated along a 15 m lateral flow CW, which could be attributed to evapotranspiration. This was notably accompanied by a desirable 95.21% decrease in ammonia from inlet to outlet resulting in significant improvement in water quality for reuse in aquaculture where ammonia levels are important limiting constraints. While CWs remain a suitable brewery effluent treatment solution, this technology requires additional modelling and optimisation in order to mitigate the problem of salt accumulation in the reuse of treated brewery effluent in agriculture and aquaculture. This research demonstrates the baseline information for such modelling and optimisation. African catfish (Clarias gariepinus) grew in CW treated brewery effluent; however, this growth was moderate at 0.92% bw day-1, whereas Mozambique tilapia (Oreochromis mossambicus) were shown to be unsuited to growth in this system and lost weight with an average specific growth rate (SGR) of -0.98% bw day-1; and both fish species presenting with health related concerns. Hardy fish species such as African catfish can be cultured in brewery effluent, but with risk involved. This was a preliminary study to develop parameters for future dimensional analysis modelling to allow optimisation of the CW, based on nutrient removal rates obtained which will allow for improved downstream aquaculture by reducing or eliminating risks presented in this study. This work has also contributed to a foundation for the development of guidelines that use a risk-based approach for water use in aquaculture. Alternatives to the current in place cleaning agents were considered to mitigate the effects of salt accumulation. Sodium is introduced into the effluent via the use of sodium hydroxide and sodium chlorite for cleaning and disinfection in the brewery, as well as through effluent pH adjustment in the AD plant. The widespread use of outdated legacy cleaning systems and pH adjustment regimes is entrenched in the brewery standard operating procedures (SOP). A cost-benefit analysis (CBA) demonstrated that a change of cleaning and disinfecting regimes to hydrogen peroxide in the brewery, and magnesium hydroxide pH adjustment in the effluent treatment plant addresses the sodium issue upstream in the brewery practically eliminating sodium from the effluent. In addition, a life cycle analysis (LCA) was carried out to assess the environmental impacts associated with the alternative cleaning and pH adjustment scenarios. The LCA showed that electricity consumption during use phase of the chemicals for respective purposes, as well as their production activities were major contributors to the significant environmental impact categories that were assessed. The cleaning scenario employing the use of hydrogen peroxide for both cleaning and disinfection was found to be the most environmentally sustainable. This was attributed to the reduced number of chemicals used compared to the other cleaning scenarios. Dolomitic lime was the pH adjustment alternative with the lowest average environmental impact; but, however, had a higher impact on freshwater eutrophication which is of major concern if the effluent will be reused for irrigation. Magnesium hydroxide was therefore considered to be the better option as a sodium hydroxide alternative for pH adjustment. This mitigates salt accumulation, making treated brewery effluent suitable for reuse in high value downstream agriculture and aquaculture, while employing more environmentally sustainable technologies. Notably, this converts brewery effluent from a financial liability to Ibhayi Brewery, into a product containing water and nutrients that generate income, improve food security, and can create employment in downstream agriculture and aquaculture in a sustainable manner. , Thesis (PhD) -- Faculty of Science, Ichthyology and Fisheries Science, 2021
- Full Text:
- Date Issued: 2021-10-29
Modifcations to gravitational waves due to matter shells
- Authors: Naidoo, Monogaran
- Date: 2021-10-29
- Subjects: Gravitational waves , General relativity (Physics) , Einstein field equations , Cosmology , Matter shells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191118 , vital:45062 , 10.21504/10962/191119
- Description: As detections of gravitational waves (GWs) mount, the need to investigate various effects on the propagation of these waves from the time of emission until detection also grows. We investigate how a thin low density dust shell surrounding a gravitational wave source affects the propagation of GWs. The Bondi-Sachs (BS) formalism for the Einstein equations is used for the problem of a gravitational wave (GW) source surrounded by a spherical dust shell. Using linearised perturbation theory, we and the geometry of the regions exterior to, interior to and within the shell. We and that the dust shell causes the gravitational wave to be modified both in magnitude and phase, but without any energy being transferred to or from the dust. This finding is novel. In the context of cosmology, apart from the gravitational redshift, the effects are too small to be measurable; but the effect would be measurable if a GW event were to occur with a source surrounded by a massive shell and with the radius of the shell and the wavelength of the GWs of the same order. We extended our investigation to astrophysical scenarios such as binary black hole (BBH) mergers, binary neutron star (BNS) mergers, and core collapse supernovae (CCSNe). In these scenarios, instead of a monochromatic GW source, as we used in our initial investigation, we consider burst-like GW sources. The thin density shell approach is modified to include thick shells by considering concentric thin shells and integrating. Solutions are then found for these burst-like GW sources using Fourier transforms. We show that GW echoes that are claimed to be present in the Laser Interferometer Gravitational-Wave Observatory (LIGO) data of certain events, could not have been caused by a matter shell. We do and, however, that matter shells surrounding BBH mergers, BNS mergers, and CCSNe could make modifications of order a few percent to a GW signal. These modifications are expected to be measurable in GW data with current detectors if the event is close enough and at a detectable frequency; or in future detectors with increased frequency range and amplitude sensitivity. Substantial use is made of computer algebra in these investigations. In setting the scene for our investigations, we trace the evolution of general relativity (GR) from Einstein's postulation in 1915 to vindication of his theory with the confirmation of the existence of GWs a century later. We discuss the implications of our results to current and future considerations. Calculations of GWs, both analytical and numerical, have normally assumed their propagation from source to a detector on Earth in a vacuum spacetime, and so discounted the effect of intervening matter. As we enter an era of precision GW measurements, it becomes important to quantify any effects due to propagation of GWs through a non-vacuum spacetime Observational confirmation of the modification effect that we and in astrophysical scenarios involving black holes (BHs), neutron stars (NSs) and CCSNe, would also enhance our understanding of the details of the physics of these bodies. , Thesis (PhD) -- Faculty of Science, Mathematics (Pure and Applied), 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Naidoo, Monogaran
- Date: 2021-10-29
- Subjects: Gravitational waves , General relativity (Physics) , Einstein field equations , Cosmology , Matter shells
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/191118 , vital:45062 , 10.21504/10962/191119
- Description: As detections of gravitational waves (GWs) mount, the need to investigate various effects on the propagation of these waves from the time of emission until detection also grows. We investigate how a thin low density dust shell surrounding a gravitational wave source affects the propagation of GWs. The Bondi-Sachs (BS) formalism for the Einstein equations is used for the problem of a gravitational wave (GW) source surrounded by a spherical dust shell. Using linearised perturbation theory, we and the geometry of the regions exterior to, interior to and within the shell. We and that the dust shell causes the gravitational wave to be modified both in magnitude and phase, but without any energy being transferred to or from the dust. This finding is novel. In the context of cosmology, apart from the gravitational redshift, the effects are too small to be measurable; but the effect would be measurable if a GW event were to occur with a source surrounded by a massive shell and with the radius of the shell and the wavelength of the GWs of the same order. We extended our investigation to astrophysical scenarios such as binary black hole (BBH) mergers, binary neutron star (BNS) mergers, and core collapse supernovae (CCSNe). In these scenarios, instead of a monochromatic GW source, as we used in our initial investigation, we consider burst-like GW sources. The thin density shell approach is modified to include thick shells by considering concentric thin shells and integrating. Solutions are then found for these burst-like GW sources using Fourier transforms. We show that GW echoes that are claimed to be present in the Laser Interferometer Gravitational-Wave Observatory (LIGO) data of certain events, could not have been caused by a matter shell. We do and, however, that matter shells surrounding BBH mergers, BNS mergers, and CCSNe could make modifications of order a few percent to a GW signal. These modifications are expected to be measurable in GW data with current detectors if the event is close enough and at a detectable frequency; or in future detectors with increased frequency range and amplitude sensitivity. Substantial use is made of computer algebra in these investigations. In setting the scene for our investigations, we trace the evolution of general relativity (GR) from Einstein's postulation in 1915 to vindication of his theory with the confirmation of the existence of GWs a century later. We discuss the implications of our results to current and future considerations. Calculations of GWs, both analytical and numerical, have normally assumed their propagation from source to a detector on Earth in a vacuum spacetime, and so discounted the effect of intervening matter. As we enter an era of precision GW measurements, it becomes important to quantify any effects due to propagation of GWs through a non-vacuum spacetime Observational confirmation of the modification effect that we and in astrophysical scenarios involving black holes (BHs), neutron stars (NSs) and CCSNe, would also enhance our understanding of the details of the physics of these bodies. , Thesis (PhD) -- Faculty of Science, Mathematics (Pure and Applied), 2021
- Full Text:
- Date Issued: 2021-10-29
Museums for the Planet: Critical Realist Philosophy and the Possibility of an Eco-decolonial Museology
- Authors: Jeffery, Thomas Carnegie
- Date: 2021-10-29
- Subjects: Museums Management , Critical realism , Ontology , Decolonization , Organizational change , Social ecology , Eco-decolonial
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192692 , vital:45251 , 10.21504/10962/192692
- Description: This study introduces dialectical critical realism into museology as a philosophical underlabourer for the development of new theoretical potentials for the transformation of museum practice. The idea of the museum is in a moment of fluidity evident in emergent decolonial and ecological perspectives and in the International Council of Museum’s process of redefinition of the museum. The potential to reimagine the museum lacks a coherent philosophical and theoretical foundation. The persistence of museological dualism separates the social from the ecological and absents the emergence of relational modes of thinking and practice. This study conceives an ecological-decolonial or eco-decolonial mode of museology that is disruptive of dualism and generative of relationality, and is thus generative of agency for deeper, more effective and enduring social-ecological justice. The core of this thesis is the development of the eco-decolonial mode of museology through the DCR onto-axiological chain or ‘MELD’ schema. At 1M a depth ontological analysis augmented by interviews with key informants establishes a dialectic of society and ecology in the museological context. 1M surfaces capitalism and the implicit neoliberal ontology of museology as deep causal mechanisms of the 2E persistence of museological human-nature dualism. The paradox of ‘emancipatory neoliberalism’ is a policy-practice contradiction that absents potentials for transformation of the museum and that is held in place by the grounding ontological activity of museology, collection. The 2E perspective on absences enables the emergence of new transformative pathways towards the 3L vision of the eco-decolonial mode of museology as a (4D) new way of thinking and working to resolve neoliberal restrictions. The fundamental 4D change envisioned for museum philosophy, theory and practice is an ontological transformation from traditionalist human-nature dualism to a progressive human-nature dialectic. A case study considers instances where museum workers exercised the agency to expand practice in this way. Future work using the expansive learning methodology of Change Laboratories will develop and implement the potentials generated by the onto-axiological chain for the eco-decolonial mode to bring real change to traditional, dualist museum practice, in order to ensure the relevance and the agency of the museum as a social structure in and for a changing world. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Jeffery, Thomas Carnegie
- Date: 2021-10-29
- Subjects: Museums Management , Critical realism , Ontology , Decolonization , Organizational change , Social ecology , Eco-decolonial
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192692 , vital:45251 , 10.21504/10962/192692
- Description: This study introduces dialectical critical realism into museology as a philosophical underlabourer for the development of new theoretical potentials for the transformation of museum practice. The idea of the museum is in a moment of fluidity evident in emergent decolonial and ecological perspectives and in the International Council of Museum’s process of redefinition of the museum. The potential to reimagine the museum lacks a coherent philosophical and theoretical foundation. The persistence of museological dualism separates the social from the ecological and absents the emergence of relational modes of thinking and practice. This study conceives an ecological-decolonial or eco-decolonial mode of museology that is disruptive of dualism and generative of relationality, and is thus generative of agency for deeper, more effective and enduring social-ecological justice. The core of this thesis is the development of the eco-decolonial mode of museology through the DCR onto-axiological chain or ‘MELD’ schema. At 1M a depth ontological analysis augmented by interviews with key informants establishes a dialectic of society and ecology in the museological context. 1M surfaces capitalism and the implicit neoliberal ontology of museology as deep causal mechanisms of the 2E persistence of museological human-nature dualism. The paradox of ‘emancipatory neoliberalism’ is a policy-practice contradiction that absents potentials for transformation of the museum and that is held in place by the grounding ontological activity of museology, collection. The 2E perspective on absences enables the emergence of new transformative pathways towards the 3L vision of the eco-decolonial mode of museology as a (4D) new way of thinking and working to resolve neoliberal restrictions. The fundamental 4D change envisioned for museum philosophy, theory and practice is an ontological transformation from traditionalist human-nature dualism to a progressive human-nature dialectic. A case study considers instances where museum workers exercised the agency to expand practice in this way. Future work using the expansive learning methodology of Change Laboratories will develop and implement the potentials generated by the onto-axiological chain for the eco-decolonial mode to bring real change to traditional, dualist museum practice, in order to ensure the relevance and the agency of the museum as a social structure in and for a changing world. , Thesis (PhD) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10-29
Neutral Atomic Hydrogen in Gravitationally Lensed Systems
- Authors: Blecher, Tariq Dylan
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192776 , vital:45263
- Description: Thesis (PhD) -- Faculty of Law, Law, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Blecher, Tariq Dylan
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192776 , vital:45263
- Description: Thesis (PhD) -- Faculty of Law, Law, 2021
- Full Text:
- Date Issued: 2021-10-29
On the gravitational dual to strongly coupled fluids
- Authors: Shawa, Mark Musonda Webster
- Date: 2021-10-29
- Subjects: Quantum gravity , String models , Gauge fields (Physics) , Scattering amplitude (Nuclear physics) , Quark-gluon plasma , Anti-de Sitter/Conformal Field Theory (AdS/CFT) , Gauge/gravity duality
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192933 , vital:45280 , 10.21504/10962/192933
- Description: This thesis discusses the prospect of finding the gravitational dual to the strongly coupled conformal fluids, with a special interest in the quark-gluon plasma. Such a task can be achieved by matching certain physical observables of two apparently different theories that are dually related owing to the fact that the same string theory can be viewed in two different ways. This is particularly useful when one of the theories is intractable while its dual is manageable. We begin by postulating a particular type of gravitational theory from which we determine graviton scattering amplitudes in a special regime of high momentum. Using the gauge–gravity duality dictionary, the graviton scattering amplitudes can be mapped to stress-tensor correlation functions in the gauge theory. One of the outcomes of high-energy scattering experiments involving the quark-gluon plasma is stress-tensor correlator data. This thesis provides an algorithm for matching graviton scattering amplitudes with stress-tensor correlator data which, in principle, can be used to identify the gravitational dual to the quark-gluon plasma. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Shawa, Mark Musonda Webster
- Date: 2021-10-29
- Subjects: Quantum gravity , String models , Gauge fields (Physics) , Scattering amplitude (Nuclear physics) , Quark-gluon plasma , Anti-de Sitter/Conformal Field Theory (AdS/CFT) , Gauge/gravity duality
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192933 , vital:45280 , 10.21504/10962/192933
- Description: This thesis discusses the prospect of finding the gravitational dual to the strongly coupled conformal fluids, with a special interest in the quark-gluon plasma. Such a task can be achieved by matching certain physical observables of two apparently different theories that are dually related owing to the fact that the same string theory can be viewed in two different ways. This is particularly useful when one of the theories is intractable while its dual is manageable. We begin by postulating a particular type of gravitational theory from which we determine graviton scattering amplitudes in a special regime of high momentum. Using the gauge–gravity duality dictionary, the graviton scattering amplitudes can be mapped to stress-tensor correlation functions in the gauge theory. One of the outcomes of high-energy scattering experiments involving the quark-gluon plasma is stress-tensor correlator data. This thesis provides an algorithm for matching graviton scattering amplitudes with stress-tensor correlator data which, in principle, can be used to identify the gravitational dual to the quark-gluon plasma. , Thesis (PhD) -- Faculty of Science, Physics and Electronics, 2021
- Full Text:
- Date Issued: 2021-10-29
Phthalocyanine-nanoparticle conjugates supported on inorganic nanofibers as photocatalysts for the treatment of biological and organic pollutants as well as for hydrogen generation
- Authors: Mapukata, Sivuyisiwe
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanofibers , Nanoparticles , Zinc , Hydrogen , Organic water pollutants , Water Purification , Electrospinning , Photocatalysis , Photodegradation , Anti-infective agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192831 , vital:45268 , 10.21504/10962/192831
- Description: This thesis reports on the synthesis, photophysicochemical and photocatalytic properties of various zinc phthalocyanines (Pcs). For enhanced properties and catalyst support, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. For increased catalyst surface area and catalyst reusability, the Pcs and some of their conjugates were also supported on electrospun inorganic nanofibers i.e. SiO2, hematite (abbreviated Hem and has formula α-Fe2O3), ZnO and TiO2 nanofibers. The effect that the number of charges on a Pc has on its antimicrobial activities was evaluated by comparing the photoactivities of neutral, octacationic and hexadecacationic Pcs against S. aureus, E. coli and C. albicans. The extent of enhancement of their antimicrobial activities upon conjugation (through chemisorption) to Ag NPs was also studied in solution and when supported on SiO2 nanofibers. The results showed that the hexadecacationic complex 3 possessed the best antimicrobial activity against all three microorganisms, in solution and when supported on the SiO2 nanofibers. Covalent conjugation of Pcs with carboxylic acid moieties (complexes 4-6) to amine functionalised NPs (Cys-Ag, NH2-Fe3O4 and Cys-Fe3O4@Ag) resulted in enhanced singlet oxygen generation and thus antibacterial efficiencies. Comparison of the photodegradation efficiencies of semiconductor nanofibers (hematite, ZnO and TiO2) when bare and when modified with a Pc (complex 6) were evaluated. Modification of the nanofibers with the Pc resulted in enhanced photoactivities for the nanofibers with the hematite nanofibers being the best. Modification of the hematite nanofibers with two different Pcs i.e. monosubstituted (complex 5) and an asymmetrical tetrasubstituted Pc (complex 6) showed that complex 6 better enhanced the activity of the nanofibers. Evaluation of the hydrogen generation efficiencies of the bare and modified TiO2 nanofibers calcined at different temperatures demonstrated that the anatase nanofibers calcined at 500 oC possessed the best catalytic efficiency. The efficiency of the TiO2 nanofibers was enhanced in the presence of the Co and Pd NPs as well as a Pc (complex 7), with the extent of enhancement being the greatest for the nanofibers modified with the Pd NPs. The reported findings therefore demonstrate the versatility of applications of Pcs for different water purification techniques when supported on different nanomaterials. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mapukata, Sivuyisiwe
- Date: 2021-10-29
- Subjects: Phthalocyanines , Nanofibers , Nanoparticles , Zinc , Hydrogen , Organic water pollutants , Water Purification , Electrospinning , Photocatalysis , Photodegradation , Anti-infective agents
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192831 , vital:45268 , 10.21504/10962/192831
- Description: This thesis reports on the synthesis, photophysicochemical and photocatalytic properties of various zinc phthalocyanines (Pcs). For enhanced properties and catalyst support, the reported Pcs were conjugated to different nanoparticles (NPs) through chemisorption as well as amide bond formation to yield Pc-NP conjugates. For increased catalyst surface area and catalyst reusability, the Pcs and some of their conjugates were also supported on electrospun inorganic nanofibers i.e. SiO2, hematite (abbreviated Hem and has formula α-Fe2O3), ZnO and TiO2 nanofibers. The effect that the number of charges on a Pc has on its antimicrobial activities was evaluated by comparing the photoactivities of neutral, octacationic and hexadecacationic Pcs against S. aureus, E. coli and C. albicans. The extent of enhancement of their antimicrobial activities upon conjugation (through chemisorption) to Ag NPs was also studied in solution and when supported on SiO2 nanofibers. The results showed that the hexadecacationic complex 3 possessed the best antimicrobial activity against all three microorganisms, in solution and when supported on the SiO2 nanofibers. Covalent conjugation of Pcs with carboxylic acid moieties (complexes 4-6) to amine functionalised NPs (Cys-Ag, NH2-Fe3O4 and Cys-Fe3O4@Ag) resulted in enhanced singlet oxygen generation and thus antibacterial efficiencies. Comparison of the photodegradation efficiencies of semiconductor nanofibers (hematite, ZnO and TiO2) when bare and when modified with a Pc (complex 6) were evaluated. Modification of the nanofibers with the Pc resulted in enhanced photoactivities for the nanofibers with the hematite nanofibers being the best. Modification of the hematite nanofibers with two different Pcs i.e. monosubstituted (complex 5) and an asymmetrical tetrasubstituted Pc (complex 6) showed that complex 6 better enhanced the activity of the nanofibers. Evaluation of the hydrogen generation efficiencies of the bare and modified TiO2 nanofibers calcined at different temperatures demonstrated that the anatase nanofibers calcined at 500 oC possessed the best catalytic efficiency. The efficiency of the TiO2 nanofibers was enhanced in the presence of the Co and Pd NPs as well as a Pc (complex 7), with the extent of enhancement being the greatest for the nanofibers modified with the Pd NPs. The reported findings therefore demonstrate the versatility of applications of Pcs for different water purification techniques when supported on different nanomaterials. , Thesis (PhD) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
Plant-fungal mutualism as a strategy for the bioremediation of hydrocarbon polluted soils
- Authors: Keshinro, Olajide Muritala
- Date: 2021-10-29
- Subjects: Mutualism (Biology) , Plant-fungus relationships , Bioremediation , Mucilage , Plant exudates , Extracellular polymeric substances , Laccase , Peroxidase , Phytoremediation , Ligninolytic enzymes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190918 , vital:45041 , 10.21504/10962/190918
- Description: Inasmuch as coal remains the linchpin for the generation of electricity and liquid petroleum products in South Africa, hydrocarbon waste and coal discard will continue to pose a threat to the environment. Therefore, the onus is on the associated industries to develop and implement efficient and sustainable strategies to mitigate the negative impacts of energy generating activities on the environment. Most conventional efforts in this regard, although successful for soil repair and the initiation of vegetation, have been deemed unsustainable. In an effort to find a sustainable remediation strategy a novel technology termed “FungCoal” was conceptualized and patented as a strategy for the rehabilitation of open cast coal mines, carbonaceous-rich spoils and coal wastes. This biotechnology, which exploits plant-fungal mutualism to achieve effective biodegradation of coal on discard dumps and the breakdown of the carbonaceous component in spoils, promotes revegetation to facilitate rehabilitation of mining-disturbed land. However, one limiting factor of the FungCoal bioprocess is that it requires oxidized weathered coal, a highly complex and variable resource for use as a co-substrate, for growth and proliferation of the coal degrading microorganisms. To fully exploit the potential of plant-fungal mutualism and its interaction for use in the remediation of coal contaminated soils, this study investigated the proposed relationship between plant roots, root exudate and the coal degrading fungus “Aspergillus sp.” (previously Neosartorya fischeri) strain 84 in more detail, in an effort to gain further insight into the mechanisms underpinning plant-fungal mutualism as a strategy for re-vegetation of coal discard dumps and the rehabilitation of hydrocarbon-contaminated soil using the FungCoal approach. A pot-on-beaker (PoB) method was developed for the easy cultivation and collection of extracellular polymeric substance (EPS)-containing exudates from Zea mays L. (maize) and Abelmuschus esculentus (okra). Characterisation of the EPS material from these exudates was carried out using a combination of physicochemical and biochemical methods. The results from analysis of phenolics and indoles showed that exudates contain some form of indoles and phenolic compounds, although in little proportions, which may fulfil a signalling function, responsible for attracting soil microorganisms into the rhizosphere. Spectroscopic analysis of the exudates using FT-IR revealed vibrations corresponding to functional groups of alkanes, alkenes, alkynes, and carboxylic acids. These compounds likely provide an easily accessible source of carbon to soil microorganisms and are also a better alternative to the poly-aromatics which are an inherent component locked-up in the supposed recalcitrant coal material. The results from biochemical analyses also revealed the presence of carbohydrate, proteins, lipids, and low amounts of α-amino-nitrogen in the EPS of maize and okra. These components of EPS are all essential for the stimulation of enzymatic activities in soil microorganisms and, which may in turn aid biodegradation. The action of the root EPS from maize was further tested on three coal-degrading fungal isolates identified as Aspergillus strain ECCN 84, Aspergillus strain ECCN 225 and Penicillium strain ECCN 243 for manganese peroxidase (MnP) and laccase (LAC) activities. The results revealed that the Aspergillus species, strains ECCN 84 and ECCN 225, showed with or without EPS, observable black halos surrounding each of the colonies after 7d incubation indicative of positive MnP activity, while no activity was observed for the Penicillium sp. strain ECCN 243. Analysis for LAC revealed little or no activity in any of the coal degrading fungi following addition of pulverized coal to the growth medium. Interestingly, the addition of EPS-containing exudate to the coal-containing medium resulted in increased LAC activity for all fungal isolates. This finding affirmed the positive contribution of EPS to extracellular LAC activity, purported as an important enzyme in the coal biodegradation process. Finally, the impact of plant-derived exudate on the colonisation and biodegradation of coal was investigated in situ using rhizoboxes, to simulate a coal environment, and was carried out for 16 weeks. Microscopic examination of coal samples after termination of the experiment showed fungal proliferation and attachment to coal particles. All of the rhizoboxes that contained plants had higher medium pH and EC, and the concentration of phenolics, indoles and humic acids was greater than that of control treatments. These observations indicated better rhizosphere colonisation, substrate biodegradation and humification. Therefore, root exudate appears to play a significant role in coordination of soil microorganisms within the rhizosphere and likely serves both as a scaffold for rhizospheric interactions by providing microorganisms with accessible carbon and as a likely ‘trigger’ for induction of coal-degrading enzymes such as fungal LAC for mobilisation of recalcitrant carbon. This study has shown that EPS exuded from roots of Zea mays together with coal degrading fungus Aspergillus strain ECCN 84 can alkalinise the coal substrate and facilitate introduction of oxygen, possibly as a result of increased laccase activity, and increase availability of nutrients (as indicated by higher EC) in a coal-polluted rhizosphere, to provide plants and their associated mycorrhizae and presumably other beneficial microorganisms a more mesic environment for sustained phytoremediation with enhanced rehabilitation potential. In conclusion, this study confirms the positive role of root exudate in mediating a mutualistic rehabilitation strategy involving plants and fungi such as the FungCoal bioprocess. , Thesis (PhD) -- Faculty of Science, Institute for Environmental Biotechnology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Keshinro, Olajide Muritala
- Date: 2021-10-29
- Subjects: Mutualism (Biology) , Plant-fungus relationships , Bioremediation , Mucilage , Plant exudates , Extracellular polymeric substances , Laccase , Peroxidase , Phytoremediation , Ligninolytic enzymes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/190918 , vital:45041 , 10.21504/10962/190918
- Description: Inasmuch as coal remains the linchpin for the generation of electricity and liquid petroleum products in South Africa, hydrocarbon waste and coal discard will continue to pose a threat to the environment. Therefore, the onus is on the associated industries to develop and implement efficient and sustainable strategies to mitigate the negative impacts of energy generating activities on the environment. Most conventional efforts in this regard, although successful for soil repair and the initiation of vegetation, have been deemed unsustainable. In an effort to find a sustainable remediation strategy a novel technology termed “FungCoal” was conceptualized and patented as a strategy for the rehabilitation of open cast coal mines, carbonaceous-rich spoils and coal wastes. This biotechnology, which exploits plant-fungal mutualism to achieve effective biodegradation of coal on discard dumps and the breakdown of the carbonaceous component in spoils, promotes revegetation to facilitate rehabilitation of mining-disturbed land. However, one limiting factor of the FungCoal bioprocess is that it requires oxidized weathered coal, a highly complex and variable resource for use as a co-substrate, for growth and proliferation of the coal degrading microorganisms. To fully exploit the potential of plant-fungal mutualism and its interaction for use in the remediation of coal contaminated soils, this study investigated the proposed relationship between plant roots, root exudate and the coal degrading fungus “Aspergillus sp.” (previously Neosartorya fischeri) strain 84 in more detail, in an effort to gain further insight into the mechanisms underpinning plant-fungal mutualism as a strategy for re-vegetation of coal discard dumps and the rehabilitation of hydrocarbon-contaminated soil using the FungCoal approach. A pot-on-beaker (PoB) method was developed for the easy cultivation and collection of extracellular polymeric substance (EPS)-containing exudates from Zea mays L. (maize) and Abelmuschus esculentus (okra). Characterisation of the EPS material from these exudates was carried out using a combination of physicochemical and biochemical methods. The results from analysis of phenolics and indoles showed that exudates contain some form of indoles and phenolic compounds, although in little proportions, which may fulfil a signalling function, responsible for attracting soil microorganisms into the rhizosphere. Spectroscopic analysis of the exudates using FT-IR revealed vibrations corresponding to functional groups of alkanes, alkenes, alkynes, and carboxylic acids. These compounds likely provide an easily accessible source of carbon to soil microorganisms and are also a better alternative to the poly-aromatics which are an inherent component locked-up in the supposed recalcitrant coal material. The results from biochemical analyses also revealed the presence of carbohydrate, proteins, lipids, and low amounts of α-amino-nitrogen in the EPS of maize and okra. These components of EPS are all essential for the stimulation of enzymatic activities in soil microorganisms and, which may in turn aid biodegradation. The action of the root EPS from maize was further tested on three coal-degrading fungal isolates identified as Aspergillus strain ECCN 84, Aspergillus strain ECCN 225 and Penicillium strain ECCN 243 for manganese peroxidase (MnP) and laccase (LAC) activities. The results revealed that the Aspergillus species, strains ECCN 84 and ECCN 225, showed with or without EPS, observable black halos surrounding each of the colonies after 7d incubation indicative of positive MnP activity, while no activity was observed for the Penicillium sp. strain ECCN 243. Analysis for LAC revealed little or no activity in any of the coal degrading fungi following addition of pulverized coal to the growth medium. Interestingly, the addition of EPS-containing exudate to the coal-containing medium resulted in increased LAC activity for all fungal isolates. This finding affirmed the positive contribution of EPS to extracellular LAC activity, purported as an important enzyme in the coal biodegradation process. Finally, the impact of plant-derived exudate on the colonisation and biodegradation of coal was investigated in situ using rhizoboxes, to simulate a coal environment, and was carried out for 16 weeks. Microscopic examination of coal samples after termination of the experiment showed fungal proliferation and attachment to coal particles. All of the rhizoboxes that contained plants had higher medium pH and EC, and the concentration of phenolics, indoles and humic acids was greater than that of control treatments. These observations indicated better rhizosphere colonisation, substrate biodegradation and humification. Therefore, root exudate appears to play a significant role in coordination of soil microorganisms within the rhizosphere and likely serves both as a scaffold for rhizospheric interactions by providing microorganisms with accessible carbon and as a likely ‘trigger’ for induction of coal-degrading enzymes such as fungal LAC for mobilisation of recalcitrant carbon. This study has shown that EPS exuded from roots of Zea mays together with coal degrading fungus Aspergillus strain ECCN 84 can alkalinise the coal substrate and facilitate introduction of oxygen, possibly as a result of increased laccase activity, and increase availability of nutrients (as indicated by higher EC) in a coal-polluted rhizosphere, to provide plants and their associated mycorrhizae and presumably other beneficial microorganisms a more mesic environment for sustained phytoremediation with enhanced rehabilitation potential. In conclusion, this study confirms the positive role of root exudate in mediating a mutualistic rehabilitation strategy involving plants and fungi such as the FungCoal bioprocess. , Thesis (PhD) -- Faculty of Science, Institute for Environmental Biotechnology, 2021
- Full Text:
- Date Issued: 2021-10-29
Schema modes in eating disorders: an interpretative phenomenological analysis
- Authors: Bowker, Chantal Ann
- Date: 2021-10-29
- Subjects: Eating disorders , Anorexia nervosa , Bulimia , Compulsive eating , Schema-focused cognitive therapy , Interpretative phenomenological analysis (IPA)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/196072 , vital:45723 , DOI 10.21504/10962/196072
- Description: The DSM-5 prevalence rate of anorexia nervosa is 0.4%, bulimia nervosa is 1% to 1.5%, and binge eating disorder is 1.6% (American Psychiatric Association, 2013). Although treatment approaches for eating disorders have high drop-out rates and low rates of recovery, treatment modalities that address childhood factors contributing to the eating disorder, as well as the eating disorder behaviours, have better outcomes. Schema therapy is an integrative approach that has been used for the treatment of eating disorders for more than a decade. Central features in schema therapy include the identification of early maladaptive schemas arising from unmet needs and schema modes. Schema modes, composed of schemas and coping mechanisms, are active for an individual at a particular time in response to triggers in the environment (Brown et al., 2016). Identifying an individual’s modes is a crucial aspect that reflects the underlying structure of the individual’s creation of reality. A phenomenological understanding of the modes is essential for developing a case conceptualisation and treatment plan. Differences exist in the naming and description of modes in the current schema therapy literature, which suggests the need for a phenomenological investigation of these structures. This research study used a mostly qualitative approach, in the form of clinical interviews, substantiated by questionnaires, to examine schema modes. Case presentations using the schema therapy model are provided for five women with either anorexia nervosa, bulimia nervosa or binge eating disorder. Then, through a process of interpretative phenomenological analysis, specific modes are examined as to how they are experienced by the participants and influence their behaviour. The features of schema modes in these clinical cases are compared to the existing literature to extend the understanding of schema modes in eating disorders. The participants’ experiences revealed that they had schema modes in common, regardless of the eating disorder presentation, but that the features of the individual modes varied. Modes found in the current literature such as the Detached Self-Soother and Perfectionist Overcontroller coping mode, were found in all the participants. Four of the five participants had an Eating Disordered Overcontroller mode. Features consistent with the existing descriptions of the Perfectionist Overcontroller, Eating Disordered Overcontroller and Detached Self-Soother modes were noted, and new features were identified. The Perfectionist Overcontroller and Eating Disordered Overcontroller have been presented here as complex composite modes with sub-modes that work together in a coherent way in the service of the same project (Edwards, 2020b). Twenty-three features are identified in the parent modes. Blended parent modes, with multiple features active in a situation, were described. The blended parent modes expand on the existing literature on parent modes. The findings in this research support and extend the mode structure identified in the schema therapy theory, and highlight the idiosyncratic nature of the modes. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Bowker, Chantal Ann
- Date: 2021-10-29
- Subjects: Eating disorders , Anorexia nervosa , Bulimia , Compulsive eating , Schema-focused cognitive therapy , Interpretative phenomenological analysis (IPA)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/196072 , vital:45723 , DOI 10.21504/10962/196072
- Description: The DSM-5 prevalence rate of anorexia nervosa is 0.4%, bulimia nervosa is 1% to 1.5%, and binge eating disorder is 1.6% (American Psychiatric Association, 2013). Although treatment approaches for eating disorders have high drop-out rates and low rates of recovery, treatment modalities that address childhood factors contributing to the eating disorder, as well as the eating disorder behaviours, have better outcomes. Schema therapy is an integrative approach that has been used for the treatment of eating disorders for more than a decade. Central features in schema therapy include the identification of early maladaptive schemas arising from unmet needs and schema modes. Schema modes, composed of schemas and coping mechanisms, are active for an individual at a particular time in response to triggers in the environment (Brown et al., 2016). Identifying an individual’s modes is a crucial aspect that reflects the underlying structure of the individual’s creation of reality. A phenomenological understanding of the modes is essential for developing a case conceptualisation and treatment plan. Differences exist in the naming and description of modes in the current schema therapy literature, which suggests the need for a phenomenological investigation of these structures. This research study used a mostly qualitative approach, in the form of clinical interviews, substantiated by questionnaires, to examine schema modes. Case presentations using the schema therapy model are provided for five women with either anorexia nervosa, bulimia nervosa or binge eating disorder. Then, through a process of interpretative phenomenological analysis, specific modes are examined as to how they are experienced by the participants and influence their behaviour. The features of schema modes in these clinical cases are compared to the existing literature to extend the understanding of schema modes in eating disorders. The participants’ experiences revealed that they had schema modes in common, regardless of the eating disorder presentation, but that the features of the individual modes varied. Modes found in the current literature such as the Detached Self-Soother and Perfectionist Overcontroller coping mode, were found in all the participants. Four of the five participants had an Eating Disordered Overcontroller mode. Features consistent with the existing descriptions of the Perfectionist Overcontroller, Eating Disordered Overcontroller and Detached Self-Soother modes were noted, and new features were identified. The Perfectionist Overcontroller and Eating Disordered Overcontroller have been presented here as complex composite modes with sub-modes that work together in a coherent way in the service of the same project (Edwards, 2020b). Twenty-three features are identified in the parent modes. Blended parent modes, with multiple features active in a situation, were described. The blended parent modes expand on the existing literature on parent modes. The findings in this research support and extend the mode structure identified in the schema therapy theory, and highlight the idiosyncratic nature of the modes. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2021
- Full Text:
- Date Issued: 2021-10-29
Schema therapy for anorexia nervosa: an intensive systematic individual case study
- Authors: Alexander, Graham
- Date: 2021-10-29
- Subjects: Eating disorders , Anorexia nervosa , Anorexia nervosa Treatment , Anorexia nervosa Case studies , Schema-focused cognitive therapy , Anorexic overcontroller , Interpretative phenomenological analysis (IPA)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/196082 , vital:45724 , DOI https://doi.org/10.21504/10962/196082
- Description: Developed more than three decades ago, schema therapy (ST) was born out of a need for a more effective way of working with difficult and challenging cases where patients were clearly unresponsive to the existing short-term cognitive therapies. While anchored in the primary theoretical orientation of cognitive therapy, ST has carefully integrated techniques and principles from attachment and object-relations therapies, as well as humanistic, gestalt and experiential therapies. The mode model emphasises the concept of “multiplicity” in terms of which the self is functionally divided into parts or schema modes. For a little more than a decade there has been growing interest amongst researcher-clinicians in the application of ST for the treatment of eating disorders (EDs) (Waller, et al., 2007; Simpson, 2012; Edwards, 2015; Munro et al., 2016; Simpson, 2016; Munro et al., 2016). While multivariate studies can provide quantifiable evidence for the efficacy of ST for treating EDs, systematic case-based research offers a means of engaging in an intensive analysis and description of the complex and subtle processes that unfold over time in a real-life therapeutic environment (Edwards et al., 2004; Yin, 1994). This research method also provides an opportunity for the refining of the clinical treatment model as well as its testing. Ten participants were assessed and treated with schema therapy. However, because of the large amount of data gathered, a decision was made to write up only one as an intensive systematic individual case study. Alison, an elderly woman with a longstanding history of AN who had been largely unresponsive to considerable previous therapies, received 100 ST sessions over a two-year period and showed a very positive response. The many challenges that arose and the way these were addressed within the ST framework provide an in-depth account of the application of the ST mode model for the treatment of AN. This is presented in a detailed therapy narrative. After results of the quantitative measures are provided, the next three chapters address three interpretative questions pertaining to the Healthy Adult/Vulnerable Child dyadic relationship, the processes of working with the Angry Child mode, and the conceptualising of an AN-specific coping mode. Several conclusions are drawn about the strengths of the schema therapy model and its particular application to AN. Amongst these is the importance of having a comprehensive case conceptualisation that serves as a collaborative “road map” with which to negotiate the unfolding collaborative therapeutic process. Another is the identifying of the “Anorexic Overcontroller” as a stand-alone coping mode that clarifies the functions of AN to hinder schema-based emotional injury, but paradoxically, still denies the individual’s basic core needs being met. Such a conceptualisation significantly assisted in the suspension of anorexic behaviour. A further significant observation is how emotion-focused work (especially within the context of chair work and imagery) brought therapy to life and was particularly effective in mobilising the conflict between internal voices. Another outstanding feature is how the building of a strong Healthy Adult mode proved vital in the healing process and the development of patient autonomy. Finally, therapy revealed how central the establishment of a sturdy, warm and loving therapeutic relationship is, and how influential the resonance between the therapist and patient is in the outcome of treatment. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Alexander, Graham
- Date: 2021-10-29
- Subjects: Eating disorders , Anorexia nervosa , Anorexia nervosa Treatment , Anorexia nervosa Case studies , Schema-focused cognitive therapy , Anorexic overcontroller , Interpretative phenomenological analysis (IPA)
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/196082 , vital:45724 , DOI https://doi.org/10.21504/10962/196082
- Description: Developed more than three decades ago, schema therapy (ST) was born out of a need for a more effective way of working with difficult and challenging cases where patients were clearly unresponsive to the existing short-term cognitive therapies. While anchored in the primary theoretical orientation of cognitive therapy, ST has carefully integrated techniques and principles from attachment and object-relations therapies, as well as humanistic, gestalt and experiential therapies. The mode model emphasises the concept of “multiplicity” in terms of which the self is functionally divided into parts or schema modes. For a little more than a decade there has been growing interest amongst researcher-clinicians in the application of ST for the treatment of eating disorders (EDs) (Waller, et al., 2007; Simpson, 2012; Edwards, 2015; Munro et al., 2016; Simpson, 2016; Munro et al., 2016). While multivariate studies can provide quantifiable evidence for the efficacy of ST for treating EDs, systematic case-based research offers a means of engaging in an intensive analysis and description of the complex and subtle processes that unfold over time in a real-life therapeutic environment (Edwards et al., 2004; Yin, 1994). This research method also provides an opportunity for the refining of the clinical treatment model as well as its testing. Ten participants were assessed and treated with schema therapy. However, because of the large amount of data gathered, a decision was made to write up only one as an intensive systematic individual case study. Alison, an elderly woman with a longstanding history of AN who had been largely unresponsive to considerable previous therapies, received 100 ST sessions over a two-year period and showed a very positive response. The many challenges that arose and the way these were addressed within the ST framework provide an in-depth account of the application of the ST mode model for the treatment of AN. This is presented in a detailed therapy narrative. After results of the quantitative measures are provided, the next three chapters address three interpretative questions pertaining to the Healthy Adult/Vulnerable Child dyadic relationship, the processes of working with the Angry Child mode, and the conceptualising of an AN-specific coping mode. Several conclusions are drawn about the strengths of the schema therapy model and its particular application to AN. Amongst these is the importance of having a comprehensive case conceptualisation that serves as a collaborative “road map” with which to negotiate the unfolding collaborative therapeutic process. Another is the identifying of the “Anorexic Overcontroller” as a stand-alone coping mode that clarifies the functions of AN to hinder schema-based emotional injury, but paradoxically, still denies the individual’s basic core needs being met. Such a conceptualisation significantly assisted in the suspension of anorexic behaviour. A further significant observation is how emotion-focused work (especially within the context of chair work and imagery) brought therapy to life and was particularly effective in mobilising the conflict between internal voices. Another outstanding feature is how the building of a strong Healthy Adult mode proved vital in the healing process and the development of patient autonomy. Finally, therapy revealed how central the establishment of a sturdy, warm and loving therapeutic relationship is, and how influential the resonance between the therapist and patient is in the outcome of treatment. , Thesis (PhD) -- Faculty of Humanities, Psychology, 2021
- Full Text:
- Date Issued: 2021-10-29
Shifting Norms and Practices of International Criminal Justice: Exploring African State and Non-State Agency at the International Criminal Court
- Authors: Mtero, Shingirai
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192875 , vital:45273
- Description: Thesis (PhD) -- Faculty of Humanities, Political and International Studies, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Mtero, Shingirai
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192875 , vital:45273
- Description: Thesis (PhD) -- Faculty of Humanities, Political and International Studies, 2021
- Full Text:
- Date Issued: 2021-10-29
Stable Covalent pH-Sensitive Metallophthalocyanines Thin Monolayer Films for Selective Detection of Neurotransmitters
- Idowu, Abosede Omowumi Atinuke
- Authors: Idowu, Abosede Omowumi Atinuke
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192922 , vital:45279
- Description: Thesis (PhD) -- Faculty of Humanities, Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29
- Authors: Idowu, Abosede Omowumi Atinuke
- Date: 2021-10-29
- Subjects: Uncatalogued
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/192922 , vital:45279
- Description: Thesis (PhD) -- Faculty of Humanities, Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10-29