β-N-Methylamino-L-Alanine is a developmental neurotoxin
- Authors: Scott, Laura Louise
- Date: 2019
- Subjects: Neurotoxic agents , Nervous system -- Diseases
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43633 , vital:36949
- Description: β-N-methylamino-L-alanine (BMAA) has been implicated in the development of the neurodegenerative diseases Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC), Amyotrophic Lateral Sclerosis (ALS) and Alzheimer’s Disease (AD), but to date no animal model has adequately substantiated this link at environmentally relevant or even exaggerated BMAA exposure levels. The resulting controversy over a possible role for BMAA in neurodegenerative diseases was further hampered by a lack of evidence for mechanistic explanation for the disease pathology associated with these diseases However, the different responses to BMAA that have been observed in neonatal compared to adult rats, together with the findings of epidemiological studies that exposure to environmental factors in utero or in the early stages of life may be important for the development of ALS several years later, suggested that age of exposure might be the determining factor of BMAA neurotoxicity. This study therefore specifically addresses the developmental nature of BMAA as a neurotoxin, and investigates the pathology and progressive nature of that pathology after exposure to the toxin at the most susceptible age. This study demonstrated the importance of BMAA exposure age over total BMAA dose by showing that the administration of a single neonatal dose of BMAA to rodents on postnatal day (PND) 3, 4 and 5, and not prenatally or on PND 6, 7 and 10, caused behavioural, locomotor, emotional and long-term cognitive deficits, clinical symptoms of neurodegeneration as well as pathological hallmarks of AD, PD and ALS in the central nervous system. Furthermore, the observed behavioural deficits and distribution of neuronal loss and proteinopathies in the rodent central nervous system following exposure to BMAA on PND 3, 4 and 5 (corresponding to the developing age of an infant during the third trimester of pregnancy) is consistent with that typically associated with the disruption of normal dopamine and/or serotonin signaling in the brain and the consequent alteration in normal hippocampal and striatal neurogenesis that is modulated, in part, by dopamine. The pattern of spread and rate of propagation of pathology in this neonatal rat BMAA model provided further evidence that BMAA potentially exerts its effect by acting on neurotransmitter signaling. The observed late onset of typical ALS symptoms and pathology suggest that in this BMAA model AD and/or PD related symptoms develop first, followed by the start of ALS symptoms only after the AD and/or PD neuropathological deficits have severely progressed. This study also demonstrated that BMAA exposure at different doses and at different developmental ages resulted in the development of different combinations of either AD and/or PD and/or ALS pathology and/or symptoms in rats, and it is therefore feasible that in humans the age and/or frequency of exposure as well as the BMAA dose might similarly be a major determinant of the variant of AD, PD and/or ALS that might develop in adulthood. Based on the low BMAA dose that was able to cause AD and/or PD-like neuropathological abnormalities in rats in this study, it is feasible that a pregnant human could over the course of her pregnancy, and specifically during the third trimester of pregnancy, consume sufficient BMAA to result in her unborn child developing AD and/or PD and/or ALS up to 30-50 years later. This neonatal BMAA model is the only non-transgenic rodent model that reproduces the behavioural deficits, neuropathology and clinical symptoms that are typically associated with AD, PD and ALS in humans and that, more importantly, mimics the delayed onset of disease symptoms and typical slow progression of these neurodegenerative diseases with age. It now seems very likely that BMAA is a developmental neurotoxin that, as a result of perinatal, but probably prenatal exposure, causes or contributes significantly to the development of neurodegenerative diseases in humans.
- Full Text:
- Date Issued: 2019
- Authors: Scott, Laura Louise
- Date: 2019
- Subjects: Neurotoxic agents , Nervous system -- Diseases
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43633 , vital:36949
- Description: β-N-methylamino-L-alanine (BMAA) has been implicated in the development of the neurodegenerative diseases Amyotrophic Lateral Sclerosis/Parkinsonism Dementia Complex (ALS/PDC), Amyotrophic Lateral Sclerosis (ALS) and Alzheimer’s Disease (AD), but to date no animal model has adequately substantiated this link at environmentally relevant or even exaggerated BMAA exposure levels. The resulting controversy over a possible role for BMAA in neurodegenerative diseases was further hampered by a lack of evidence for mechanistic explanation for the disease pathology associated with these diseases However, the different responses to BMAA that have been observed in neonatal compared to adult rats, together with the findings of epidemiological studies that exposure to environmental factors in utero or in the early stages of life may be important for the development of ALS several years later, suggested that age of exposure might be the determining factor of BMAA neurotoxicity. This study therefore specifically addresses the developmental nature of BMAA as a neurotoxin, and investigates the pathology and progressive nature of that pathology after exposure to the toxin at the most susceptible age. This study demonstrated the importance of BMAA exposure age over total BMAA dose by showing that the administration of a single neonatal dose of BMAA to rodents on postnatal day (PND) 3, 4 and 5, and not prenatally or on PND 6, 7 and 10, caused behavioural, locomotor, emotional and long-term cognitive deficits, clinical symptoms of neurodegeneration as well as pathological hallmarks of AD, PD and ALS in the central nervous system. Furthermore, the observed behavioural deficits and distribution of neuronal loss and proteinopathies in the rodent central nervous system following exposure to BMAA on PND 3, 4 and 5 (corresponding to the developing age of an infant during the third trimester of pregnancy) is consistent with that typically associated with the disruption of normal dopamine and/or serotonin signaling in the brain and the consequent alteration in normal hippocampal and striatal neurogenesis that is modulated, in part, by dopamine. The pattern of spread and rate of propagation of pathology in this neonatal rat BMAA model provided further evidence that BMAA potentially exerts its effect by acting on neurotransmitter signaling. The observed late onset of typical ALS symptoms and pathology suggest that in this BMAA model AD and/or PD related symptoms develop first, followed by the start of ALS symptoms only after the AD and/or PD neuropathological deficits have severely progressed. This study also demonstrated that BMAA exposure at different doses and at different developmental ages resulted in the development of different combinations of either AD and/or PD and/or ALS pathology and/or symptoms in rats, and it is therefore feasible that in humans the age and/or frequency of exposure as well as the BMAA dose might similarly be a major determinant of the variant of AD, PD and/or ALS that might develop in adulthood. Based on the low BMAA dose that was able to cause AD and/or PD-like neuropathological abnormalities in rats in this study, it is feasible that a pregnant human could over the course of her pregnancy, and specifically during the third trimester of pregnancy, consume sufficient BMAA to result in her unborn child developing AD and/or PD and/or ALS up to 30-50 years later. This neonatal BMAA model is the only non-transgenic rodent model that reproduces the behavioural deficits, neuropathology and clinical symptoms that are typically associated with AD, PD and ALS in humans and that, more importantly, mimics the delayed onset of disease symptoms and typical slow progression of these neurodegenerative diseases with age. It now seems very likely that BMAA is a developmental neurotoxin that, as a result of perinatal, but probably prenatal exposure, causes or contributes significantly to the development of neurodegenerative diseases in humans.
- Full Text:
- Date Issued: 2019
Water balance processes in indigenous and introduced spaces three production system in the Southern Cape region of South Africa
- Authors: Mapeto, Tatenda
- Date: 2020
- Subjects: Hydrology -- Research -- South Africa , Groundwater -- Research -- South Africa Trees -- Breeding Sustainable forestry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49325 , vital:41621
- Description: Forests and trees are important modulators of water flow and their position in the landscape impacts the spatial and temporal availability of ground water and surface water resources. As such, the global extent of natural forests is linked to the availability of water. In the circumstances where tree production systems have been introduced and are managed in landscapes previously populated with other forms of vegetation, it is necessary to understand their hydrological impact so as to ensure that the benefits derived from these tree systems do not outweigh the costs of water availability for sustaining human and environmental water requirements.
- Full Text: false
- Date Issued: 2020
- Authors: Mapeto, Tatenda
- Date: 2020
- Subjects: Hydrology -- Research -- South Africa , Groundwater -- Research -- South Africa Trees -- Breeding Sustainable forestry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49325 , vital:41621
- Description: Forests and trees are important modulators of water flow and their position in the landscape impacts the spatial and temporal availability of ground water and surface water resources. As such, the global extent of natural forests is linked to the availability of water. In the circumstances where tree production systems have been introduced and are managed in landscapes previously populated with other forms of vegetation, it is necessary to understand their hydrological impact so as to ensure that the benefits derived from these tree systems do not outweigh the costs of water availability for sustaining human and environmental water requirements.
- Full Text: false
- Date Issued: 2020
Vapour phase dehydrogenation of cyclohexane on microstructured reactors
- Authors: Mpuhlu, Batsho
- Date: 2012
- Subjects: Dehydrogenation , Cyclohexane
- Language: English
- Type: Thesis , Doctoral , DTech (Chemistry)
- Identifier: http://hdl.handle.net/10948/8661 , vital:26418
- Description: The work that is described in this thesis forms part of the research and development projects at InnoVenton: NMMU Institute of Chemical Technology in collaboration with Sasol Technologies. The broader view of the project was testing on the so-called “Small Production Platforms” (SPP’s). In particular the main aim of this study was to investigate the effect of micro-structuring on the heterogeneous catalysed, vapour-phase oxidative dehydrogenation of cyclohexane in the presence of air. Ground work studies were done to provide a proper comparison of the micro-structured reactor with a traditional fixed-bed reactor. These included evaluation of a proper vanadium pyrophosphate catalyst for the reaction, testing of reaction parameters for the oxidative dehydrogenation reaction on a fixed-bed reactor and lastly comparing the performance of the micro-structured reactor to that of the fixed-bed reactor Various vanadium pyrophosphate catalysts that were tested for activity included: bulk (VO)2P2O7, bulk (VO)2P2O7 promoted with Fe, (VO)2P2O7 supported on -Al2O3 and Fe promoted (VO)2P2O7 supported on -Al2O3. These catalysts showed significant differences in TOF, however it was not conclusive from the results whether these differences may be traced to increased activity for dehydrogenation for different catalysts since all reactions were run under conditions of oxygen deficiency. It is, however, clear that Fe promotion significantly increase activity, irrespective of the relative degrees of oxidative dehydrogenation and normal dehydrogenation. The Fe promoted catalyst was further tested for long term stability in-view of using it as the catalyst in the micro-structured reactor. These studies showed the catalyst to have a high degree of stability with minimal structural changes under the reaction conditions used. Various response surface models describing the variation in each of the cyclohexane conversion, cyclohexene selectivity, and benzene selectivity, respectively when changing reaction condition, were derived by means of multiple regression. To obtain some idea of the degree and nature of the normal dehydrogenation reaction, the amount of deficit oxygen was estimated from the measured results for cyclohexane conversion and cyclohexene and benzene selectivities. These estimated values were also modelled as described above. The regression models were used to interpret specific trends in the responses for the oxidative dehydrogenation of cyclohexane and account for the oxygen deficit in the system. The performance of a fixed bed tubular reactor (FBR) and micro-structured sandwich reactor (MSSR) were compared over an Fe promoted vanadium pyrophosphate. Reactor performance was evaluated by varying specific reaction conditions (temperature and space velocity). Subsequently the turn-over frequencies, conversion and selectivities from the two reactors were compared. The conversion achieved in the micro-structured reactor was observed to be significantly higher than that achieved in the fixed-bed reactor at all reaction parameters. This is despite the fact that the total amount of catalyst in the micro-structured reactor is approximately 5 times less than that used in the fixed bed reactor. In addition, the contact time (1/MHSV) in the micro-structured reactor is also significantly shorter than in the fixed-bed reactor.
- Full Text:
- Date Issued: 2012
- Authors: Mpuhlu, Batsho
- Date: 2012
- Subjects: Dehydrogenation , Cyclohexane
- Language: English
- Type: Thesis , Doctoral , DTech (Chemistry)
- Identifier: http://hdl.handle.net/10948/8661 , vital:26418
- Description: The work that is described in this thesis forms part of the research and development projects at InnoVenton: NMMU Institute of Chemical Technology in collaboration with Sasol Technologies. The broader view of the project was testing on the so-called “Small Production Platforms” (SPP’s). In particular the main aim of this study was to investigate the effect of micro-structuring on the heterogeneous catalysed, vapour-phase oxidative dehydrogenation of cyclohexane in the presence of air. Ground work studies were done to provide a proper comparison of the micro-structured reactor with a traditional fixed-bed reactor. These included evaluation of a proper vanadium pyrophosphate catalyst for the reaction, testing of reaction parameters for the oxidative dehydrogenation reaction on a fixed-bed reactor and lastly comparing the performance of the micro-structured reactor to that of the fixed-bed reactor Various vanadium pyrophosphate catalysts that were tested for activity included: bulk (VO)2P2O7, bulk (VO)2P2O7 promoted with Fe, (VO)2P2O7 supported on -Al2O3 and Fe promoted (VO)2P2O7 supported on -Al2O3. These catalysts showed significant differences in TOF, however it was not conclusive from the results whether these differences may be traced to increased activity for dehydrogenation for different catalysts since all reactions were run under conditions of oxygen deficiency. It is, however, clear that Fe promotion significantly increase activity, irrespective of the relative degrees of oxidative dehydrogenation and normal dehydrogenation. The Fe promoted catalyst was further tested for long term stability in-view of using it as the catalyst in the micro-structured reactor. These studies showed the catalyst to have a high degree of stability with minimal structural changes under the reaction conditions used. Various response surface models describing the variation in each of the cyclohexane conversion, cyclohexene selectivity, and benzene selectivity, respectively when changing reaction condition, were derived by means of multiple regression. To obtain some idea of the degree and nature of the normal dehydrogenation reaction, the amount of deficit oxygen was estimated from the measured results for cyclohexane conversion and cyclohexene and benzene selectivities. These estimated values were also modelled as described above. The regression models were used to interpret specific trends in the responses for the oxidative dehydrogenation of cyclohexane and account for the oxygen deficit in the system. The performance of a fixed bed tubular reactor (FBR) and micro-structured sandwich reactor (MSSR) were compared over an Fe promoted vanadium pyrophosphate. Reactor performance was evaluated by varying specific reaction conditions (temperature and space velocity). Subsequently the turn-over frequencies, conversion and selectivities from the two reactors were compared. The conversion achieved in the micro-structured reactor was observed to be significantly higher than that achieved in the fixed-bed reactor at all reaction parameters. This is despite the fact that the total amount of catalyst in the micro-structured reactor is approximately 5 times less than that used in the fixed bed reactor. In addition, the contact time (1/MHSV) in the micro-structured reactor is also significantly shorter than in the fixed-bed reactor.
- Full Text:
- Date Issued: 2012
Using social marketing to bridge the gap between systematic conservation planning and implementation at the local government level
- Authors: Wilhelm-Rechmann, Angelika
- Date: 2011
- Subjects: Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10603 , http://hdl.handle.net/10948/1550 , Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Description: The study presented here describes an attempt to bridge the gap between systematic conservation assessment and decision-making for land-use planning in the Eastern Cape province, South Africa. The aim was to investigate how to effectively convince officials concerned with land use planning processes in the local municipal sphere to include conservation priorities meaningfully in their processes. The approach used to reach this aim was social marketing, the use of marketing technologies and concepts to effect behavior changes to further societal good. So far social marketing is not commonly used in the conservation domain; I therefore aimed also at proving the usefulness of this approach for conservation. Following the introduction which provides background to the project and a more detailed summary, Chapter 2 provides a detailed and comprehensive review of the considerations and concepts regarding the use of social marketing in a context geared at protecting nature. The research on the primary target group for this study, officials concerned with land use planning processes in the local municipal sphere is described in Chapter 3. The main outcomes were that land use planners perceive few needs with regards to implementing the incorporation of biodiversity conservation issues in the land use planning process, and that the deficiencies in the land use planning process per se, as well as the lack of recognition in the political sphere (the domain of elected councilors), represent the core barriers to adopting the conservation priorities. I conclude that to effect behavior change towards adoption of conservation priorities the land use planning processes need to be supported and the political sphere need to be included in the behavior change process. 6 Chapter 4 therefore focuses on the new target group that emerged as essential in the previous chapter, locally elected councilors. I found that councilors do actually consider land use planning procedures as being important, but also as being dysfunctional. Councilors do value their natural environment for themselves as well as for its tourism value, but most councilors had little understanding of what the term “biodiversity” means and did not connect the term “sustainability” with the natural environment. It became also evident, that councilors do not see conservation in a predominantly positive manner. Chapter 5 therefore yields insight on councilor’s perception that environmental protection and development are mutually exclusive, and the negative frames attached to the conservation endeavor as being socially unjust, disrespectful and utopian. In Chapter 6 I investigated the usefulness of a tractable and well established measure of environmental attitudes or beliefs. I assessed my target audience’s responses to the New Ecological Paradigm scale and the Inclusion of Nature in Self scale. I conclude in Chapter 7 with an account of the difficulties I encountered during the project, an assessment of my project from a social marketing perspective, components of my project that did not yield the results expected, and a proposal for future research.
- Full Text:
- Date Issued: 2011
- Authors: Wilhelm-Rechmann, Angelika
- Date: 2011
- Subjects: Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10603 , http://hdl.handle.net/10948/1550 , Nature conservation -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape
- Description: The study presented here describes an attempt to bridge the gap between systematic conservation assessment and decision-making for land-use planning in the Eastern Cape province, South Africa. The aim was to investigate how to effectively convince officials concerned with land use planning processes in the local municipal sphere to include conservation priorities meaningfully in their processes. The approach used to reach this aim was social marketing, the use of marketing technologies and concepts to effect behavior changes to further societal good. So far social marketing is not commonly used in the conservation domain; I therefore aimed also at proving the usefulness of this approach for conservation. Following the introduction which provides background to the project and a more detailed summary, Chapter 2 provides a detailed and comprehensive review of the considerations and concepts regarding the use of social marketing in a context geared at protecting nature. The research on the primary target group for this study, officials concerned with land use planning processes in the local municipal sphere is described in Chapter 3. The main outcomes were that land use planners perceive few needs with regards to implementing the incorporation of biodiversity conservation issues in the land use planning process, and that the deficiencies in the land use planning process per se, as well as the lack of recognition in the political sphere (the domain of elected councilors), represent the core barriers to adopting the conservation priorities. I conclude that to effect behavior change towards adoption of conservation priorities the land use planning processes need to be supported and the political sphere need to be included in the behavior change process. 6 Chapter 4 therefore focuses on the new target group that emerged as essential in the previous chapter, locally elected councilors. I found that councilors do actually consider land use planning procedures as being important, but also as being dysfunctional. Councilors do value their natural environment for themselves as well as for its tourism value, but most councilors had little understanding of what the term “biodiversity” means and did not connect the term “sustainability” with the natural environment. It became also evident, that councilors do not see conservation in a predominantly positive manner. Chapter 5 therefore yields insight on councilor’s perception that environmental protection and development are mutually exclusive, and the negative frames attached to the conservation endeavor as being socially unjust, disrespectful and utopian. In Chapter 6 I investigated the usefulness of a tractable and well established measure of environmental attitudes or beliefs. I assessed my target audience’s responses to the New Ecological Paradigm scale and the Inclusion of Nature in Self scale. I conclude in Chapter 7 with an account of the difficulties I encountered during the project, an assessment of my project from a social marketing perspective, components of my project that did not yield the results expected, and a proposal for future research.
- Full Text:
- Date Issued: 2011
Using ambient noise tomography to image the Eastern Cape-Karoo and Karoo regions, South Africa
- Bezuidenhout, Lucian John-Ross
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2018
- Subjects: Geometric tomography -- South Africa , Geobiology Geology -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23602 , vital:30585
- Description: The primary aim of this thesis was to explore the use of ambient seismic noise as a tool to map the subsurface of the Cape-Karoo and Karoo region of South Africa. The Karoo is an ideal laboratory to use ambient seismic signal to map the shallow subsurface, as it is a quiet and pristine environment with a relatively well known geology. Ambient seismic signals were continuously recorded at three independent networks (ArrayA, ArrayB and ArrayC). ArrayA and ArrayB comprised 17 temporary stand-alone seismic stations each and recorded ambient noise wavefields for a ten week period between August and October 2015. ArrayC comprised 19 temporary stand-alone seismic stations, recording ambient seismic noise for a period of six weeks between June and July 2016. ArrayA and ArrayB were installed in the south-eastern Cape-Karoo region, near the town of Jansenville and ArrayC was installed near the Cradock-Tarkastad region of South Africa. This thesis is made up of two separate studies. Firstly, the retrieval and coherency of Rayleigh surface waves extracted from the vertical component recordings. For the first time in the south-eastern Cape-Karoo and Karoo area, estimates of Green’s function from cross-correlating ambient noise data between stations pairs were reconstructed and shown, which can be successfully used to image the subsurface. The stacked cross-correlations between all station pairs show clear arrivals of the Rayleigh surface waves. The group velocities of the Rayleigh waves in the 2 to 7 seconds period range were picked and inverted to compute the 2-D group velocity maps. For ArrayA and ArrayB, the resulting 2-D group velocity maps at different periods resulted in a group velocity model from approximately 2 to 7 km depth, which generally show a high velocity anomaly in the north of the study area, most likely imaging the denser, thick sedimentary basin of the Karoo (Carboniferous-Permian). To the south, the low velocity anomaly likely corresponds to the overlying Jurassic- Cretaceous sequences of the younger Algoa Basin (Uitenhage Group). For ArrayC, the group velocity maps showed high velocity regions, which is consistent with the dolerite sill intrusions in the Karoo and the low velocity structures, which was interpreted as the Karoo sediments. Secondly, the study comprised of characterizing the ambient seismic noise source. The first order analysis of the symmetry of the cross-correlation function showed that, although the ambient noise sources are relatively homogeneously distributed in the study area, most (energetic) of the ambient seismic noise propagates from the coast of South Africa. This was verified by analyzing the azimuthal distribution of the ambient seismic noise.
- Full Text:
- Date Issued: 2018
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2018
- Subjects: Geometric tomography -- South Africa , Geobiology Geology -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23602 , vital:30585
- Description: The primary aim of this thesis was to explore the use of ambient seismic noise as a tool to map the subsurface of the Cape-Karoo and Karoo region of South Africa. The Karoo is an ideal laboratory to use ambient seismic signal to map the shallow subsurface, as it is a quiet and pristine environment with a relatively well known geology. Ambient seismic signals were continuously recorded at three independent networks (ArrayA, ArrayB and ArrayC). ArrayA and ArrayB comprised 17 temporary stand-alone seismic stations each and recorded ambient noise wavefields for a ten week period between August and October 2015. ArrayC comprised 19 temporary stand-alone seismic stations, recording ambient seismic noise for a period of six weeks between June and July 2016. ArrayA and ArrayB were installed in the south-eastern Cape-Karoo region, near the town of Jansenville and ArrayC was installed near the Cradock-Tarkastad region of South Africa. This thesis is made up of two separate studies. Firstly, the retrieval and coherency of Rayleigh surface waves extracted from the vertical component recordings. For the first time in the south-eastern Cape-Karoo and Karoo area, estimates of Green’s function from cross-correlating ambient noise data between stations pairs were reconstructed and shown, which can be successfully used to image the subsurface. The stacked cross-correlations between all station pairs show clear arrivals of the Rayleigh surface waves. The group velocities of the Rayleigh waves in the 2 to 7 seconds period range were picked and inverted to compute the 2-D group velocity maps. For ArrayA and ArrayB, the resulting 2-D group velocity maps at different periods resulted in a group velocity model from approximately 2 to 7 km depth, which generally show a high velocity anomaly in the north of the study area, most likely imaging the denser, thick sedimentary basin of the Karoo (Carboniferous-Permian). To the south, the low velocity anomaly likely corresponds to the overlying Jurassic- Cretaceous sequences of the younger Algoa Basin (Uitenhage Group). For ArrayC, the group velocity maps showed high velocity regions, which is consistent with the dolerite sill intrusions in the Karoo and the low velocity structures, which was interpreted as the Karoo sediments. Secondly, the study comprised of characterizing the ambient seismic noise source. The first order analysis of the symmetry of the cross-correlation function showed that, although the ambient noise sources are relatively homogeneously distributed in the study area, most (energetic) of the ambient seismic noise propagates from the coast of South Africa. This was verified by analyzing the azimuthal distribution of the ambient seismic noise.
- Full Text:
- Date Issued: 2018
Tree toppling by elephants and its consequences in thicket mosaic vegetation of Addo Elephant National Park
- Authors: Mgqatsa, Nokubonga
- Date: 2017
- Subjects: Elephants -- Behavior -- South Africa -- Addo Elephant National Park Woody plants -- South Africa -- Addo Elephant National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/19365 , vital:28859
- Description: This study explored the extent of elephant tree toppling and possible cascading effects in Karoo Thicket Mosaic habitat in the Eastern Cape Province, South Africa. While the notion that elephants topple trees is well recognised, little is known about their indirect effects and the possible influence on several trophic levels. Changes brought about by elephants have the potential to influence microclimatic conditions, soil litter processes, plant community composition and other animals. Therefore, this study determined the impacts of elephants on tree toppling, and hence the production of coarse woody debris and the Coarse Woody Debris Profile. Additionally, I explored the consequences of elephant tree toppling on the plant community, small mammals and seed removal. Furthermore, I explored the potential factors facilitating the coexistence of woody plants and elephants. I compared coarse woody debris production and the Coarse Woody Debris Profile between sites with and without elephants. Further, I assessed the consequences of tree toppling in the elephant present site at a patch scale to explore the possible cascading effects of elephants. Firstly, I showed that elephants impacted woody plants through branch/stem breakages and toppling of trees, but that effects vary for different categories of the Coarse Woody Debris Profile. This result confirms the most recent findings that woody plants are at risk from elephant herbivory in Karoo Thicket Mosaic habitat. The elephant toppling effect on these landscapes is largely influenced by plant growth form, with woody trees suffering high levels of elephant toppling than shrubs of comparable size. However, toppled Pappea capensis is able to persist from being toppled by elephants, either through coppicing or resprouting. Additionally, I showed that toppled trees form discrete patches on the landscape, with altered microclimate and browsing pressures. While I detected no significant effect of these changes on plant composition and abundance within these patches, these findings indicate the possible influence of elephants on facilitating plant recruitment and altering plant communities of thicket through toppling of trees. Moreover, I showed that elephant toppling of trees provide habitat patches for small mammals, thus affecting seed removal by vertebrates within patches. These changes had no discernable effect on soil seed banks. However, they highlight the need to better understand the temporal dynamics of these patches and implications for seed dynamics and plant communities on the landscape. The results show the patterns of elephant impacts on woody plants and possible cascading effects in the presence of elephants. Therefore, the study advances our understanding of top-down effects of elephants and shows the relevance of understanding these effects in order to effectively manage elephant impacts in different systems.
- Full Text:
- Date Issued: 2017
- Authors: Mgqatsa, Nokubonga
- Date: 2017
- Subjects: Elephants -- Behavior -- South Africa -- Addo Elephant National Park Woody plants -- South Africa -- Addo Elephant National Park
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/19365 , vital:28859
- Description: This study explored the extent of elephant tree toppling and possible cascading effects in Karoo Thicket Mosaic habitat in the Eastern Cape Province, South Africa. While the notion that elephants topple trees is well recognised, little is known about their indirect effects and the possible influence on several trophic levels. Changes brought about by elephants have the potential to influence microclimatic conditions, soil litter processes, plant community composition and other animals. Therefore, this study determined the impacts of elephants on tree toppling, and hence the production of coarse woody debris and the Coarse Woody Debris Profile. Additionally, I explored the consequences of elephant tree toppling on the plant community, small mammals and seed removal. Furthermore, I explored the potential factors facilitating the coexistence of woody plants and elephants. I compared coarse woody debris production and the Coarse Woody Debris Profile between sites with and without elephants. Further, I assessed the consequences of tree toppling in the elephant present site at a patch scale to explore the possible cascading effects of elephants. Firstly, I showed that elephants impacted woody plants through branch/stem breakages and toppling of trees, but that effects vary for different categories of the Coarse Woody Debris Profile. This result confirms the most recent findings that woody plants are at risk from elephant herbivory in Karoo Thicket Mosaic habitat. The elephant toppling effect on these landscapes is largely influenced by plant growth form, with woody trees suffering high levels of elephant toppling than shrubs of comparable size. However, toppled Pappea capensis is able to persist from being toppled by elephants, either through coppicing or resprouting. Additionally, I showed that toppled trees form discrete patches on the landscape, with altered microclimate and browsing pressures. While I detected no significant effect of these changes on plant composition and abundance within these patches, these findings indicate the possible influence of elephants on facilitating plant recruitment and altering plant communities of thicket through toppling of trees. Moreover, I showed that elephant toppling of trees provide habitat patches for small mammals, thus affecting seed removal by vertebrates within patches. These changes had no discernable effect on soil seed banks. However, they highlight the need to better understand the temporal dynamics of these patches and implications for seed dynamics and plant communities on the landscape. The results show the patterns of elephant impacts on woody plants and possible cascading effects in the presence of elephants. Therefore, the study advances our understanding of top-down effects of elephants and shows the relevance of understanding these effects in order to effectively manage elephant impacts in different systems.
- Full Text:
- Date Issued: 2017
Towards the bioremediation of the hypertrophic Swartkops Solar Salt-works
- Authors: Difford, Mark
- Date: 2008
- Subjects: Salt industry and trade -- South Africa -- Port Elizabeth , Bioremediation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10606 , http://hdl.handle.net/10948/1506 , Salt industry and trade -- South Africa -- Port Elizabeth , Bioremediation
- Description: This thesis presents the results of three studies aimed at improving brine-quality at the Swartkops solar salt-works (Swartkops Sea Salt [Pty] Ltd) on the outskirts of Port Elizabeth, South Africa. This is a highly eutrophic salt-works, the management of which has become increasingly difficult in recent years. The fundamental problem is how best to operate the system at maximum capacity while limiting nutrient inputs from the nutrient-rich microtidal Swartkops Estuary. In the first study, brine-quality at several sites along the axis of the Swartkops Estuary, and the extent to which it is affected by a variety of factors, is compared. Sites were sampled on micro- and macrotidal time scales, and were selected by the management of the salt-works as possible locations for a new pump-house (for extracting brine from the estuary) for their salt-work operations at Swartkops and Missionvale. The study showed that there are incremental benefits to be had from moving the site of extraction downstream from its present position to a site closer to the mouth of the estuary, where the concentration of nutrients usually is lower and where salinity usually is higher. There is little to be gained from moving the site of extraction laterally, to the mouth of the Inlet from which brine currently is extracted, so that brine is extracted directly from the estuary itself. A set of models relating the concentrations of NH+ 4 , NO{u100000}3 , and PO34{u100000} to salinity is proposed. These take into account the influences of site and season and may be used to estimate the concentration of these nutrients from a measurement of salinity. The model for PO34{u100000} shows that it would be more damaging to the salt-works’ operations to pump “low”-salinity brine during the early months of summer than during autumn. Evidence is also presented to show that Wylde Bridge has no influence on nutrient concentrations in the estuary, with tidal flushing generally passing beyond the Wylde-Bridge break-point. The exceptionally heavy flooding of the estuary that occurred in September 2002 may, however, have biased this conclusion, because of its scouring effect. The second study concentrated on monitoring the effect of (1) decreasing pond depth and (2) increasing pond salinity—two readily available management tools—on brine quality at the salt-works. Pond depth throughout the salt-works was decreased by 40 cm, and the salinity of Pond 5, a pond in the middle of the system, was increased to 175 S. Both measures were kept in place for the duration of the study (Nov. 2002–Aug. 2004). The pond-depth experiment did not have the expected result, there being no evidence of the increase in microalgal growth in the water column that was predicted based on previous research. There was, however, a significant increase in benthic chlorophyll-a, and there was a general improvement in the condition of the sedimentary system of the salt-works. There was also a substantial decrease in particulate organic matter in the water column, with clear evidence that the remaining fraction was closely associated with living forms of particulate matter rather than with detritus. The pond-salinity experiment proves that there is a flourishing, and resilient, population of brine shrimp (Artemia salina L.) at the salt-works. Restocking the salina, or stocking it with a different strain of brine shrimp, is therefore not necessary. The results of this study show that the brine shrimp population at the salt-works needs salinities of greater than about 65–70 S to survive. As a living force they almost certainly need a protective salinity that is greater than about 120–140 S, perhaps even as great as 160 S. Brine shrimp thrived in the high salinity milieu of the experimental pond for the duration of the study, but dwindled from three other ponds of the system once their salinities fell to below 90 S, eventually to disappear from them, apparently completely, once salinity fell to below 65 S. The third and final study concentrated on establishing whether the products released by decomposing barley straw could be used in a solar salt-works to control macroalgal blooms without detrimentally affecting the benthic-mat. Previous research has shown that these products are effective inhibitors of macroalgal growth and that they remain effective under saline conditions. The results presented here show that the same products, or products released under similar conditions of decomposition, adversely effect both the structure and the function of the mat. Consequently, their use in a solar salt-works cannot be recommended.
- Full Text:
- Date Issued: 2008
- Authors: Difford, Mark
- Date: 2008
- Subjects: Salt industry and trade -- South Africa -- Port Elizabeth , Bioremediation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10606 , http://hdl.handle.net/10948/1506 , Salt industry and trade -- South Africa -- Port Elizabeth , Bioremediation
- Description: This thesis presents the results of three studies aimed at improving brine-quality at the Swartkops solar salt-works (Swartkops Sea Salt [Pty] Ltd) on the outskirts of Port Elizabeth, South Africa. This is a highly eutrophic salt-works, the management of which has become increasingly difficult in recent years. The fundamental problem is how best to operate the system at maximum capacity while limiting nutrient inputs from the nutrient-rich microtidal Swartkops Estuary. In the first study, brine-quality at several sites along the axis of the Swartkops Estuary, and the extent to which it is affected by a variety of factors, is compared. Sites were sampled on micro- and macrotidal time scales, and were selected by the management of the salt-works as possible locations for a new pump-house (for extracting brine from the estuary) for their salt-work operations at Swartkops and Missionvale. The study showed that there are incremental benefits to be had from moving the site of extraction downstream from its present position to a site closer to the mouth of the estuary, where the concentration of nutrients usually is lower and where salinity usually is higher. There is little to be gained from moving the site of extraction laterally, to the mouth of the Inlet from which brine currently is extracted, so that brine is extracted directly from the estuary itself. A set of models relating the concentrations of NH+ 4 , NO{u100000}3 , and PO34{u100000} to salinity is proposed. These take into account the influences of site and season and may be used to estimate the concentration of these nutrients from a measurement of salinity. The model for PO34{u100000} shows that it would be more damaging to the salt-works’ operations to pump “low”-salinity brine during the early months of summer than during autumn. Evidence is also presented to show that Wylde Bridge has no influence on nutrient concentrations in the estuary, with tidal flushing generally passing beyond the Wylde-Bridge break-point. The exceptionally heavy flooding of the estuary that occurred in September 2002 may, however, have biased this conclusion, because of its scouring effect. The second study concentrated on monitoring the effect of (1) decreasing pond depth and (2) increasing pond salinity—two readily available management tools—on brine quality at the salt-works. Pond depth throughout the salt-works was decreased by 40 cm, and the salinity of Pond 5, a pond in the middle of the system, was increased to 175 S. Both measures were kept in place for the duration of the study (Nov. 2002–Aug. 2004). The pond-depth experiment did not have the expected result, there being no evidence of the increase in microalgal growth in the water column that was predicted based on previous research. There was, however, a significant increase in benthic chlorophyll-a, and there was a general improvement in the condition of the sedimentary system of the salt-works. There was also a substantial decrease in particulate organic matter in the water column, with clear evidence that the remaining fraction was closely associated with living forms of particulate matter rather than with detritus. The pond-salinity experiment proves that there is a flourishing, and resilient, population of brine shrimp (Artemia salina L.) at the salt-works. Restocking the salina, or stocking it with a different strain of brine shrimp, is therefore not necessary. The results of this study show that the brine shrimp population at the salt-works needs salinities of greater than about 65–70 S to survive. As a living force they almost certainly need a protective salinity that is greater than about 120–140 S, perhaps even as great as 160 S. Brine shrimp thrived in the high salinity milieu of the experimental pond for the duration of the study, but dwindled from three other ponds of the system once their salinities fell to below 90 S, eventually to disappear from them, apparently completely, once salinity fell to below 65 S. The third and final study concentrated on establishing whether the products released by decomposing barley straw could be used in a solar salt-works to control macroalgal blooms without detrimentally affecting the benthic-mat. Previous research has shown that these products are effective inhibitors of macroalgal growth and that they remain effective under saline conditions. The results presented here show that the same products, or products released under similar conditions of decomposition, adversely effect both the structure and the function of the mat. Consequently, their use in a solar salt-works cannot be recommended.
- Full Text:
- Date Issued: 2008
Towards social impact assessment of copper-nickel mining in Botswana
- Authors: Mengwe, Moses Seargent
- Date: 2010
- Subjects: Copper mines and mining -- Environmental aspects -- Botswana , Nickel mines and mining -- Environmental aspects -- Botswana , Mineral industry -- Botswana , Mines and mineral resources -- Botswana
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10644 , http://hdl.handle.net/10948/1443 , Copper mines and mining -- Environmental aspects -- Botswana , Nickel mines and mining -- Environmental aspects -- Botswana , Mineral industry -- Botswana , Mines and mineral resources -- Botswana
- Description: This research study is more of an initiative towards Social Impact Assessment of copper-nickel mining in Botswana. The specific objectives of the study were centred on the assessment of the social impacts of copper-nickel mining in Botswana from the initial mining stage of exploration, surveying and mine site development to mine closure. The study was carried out under the broad hypotheses that mining influences population movement that impact on areas of mining; mining activities have both economic benefits and deleterious social impacts on the local communities found in the areas where mining is taking place; and mine closure has far reaching socio-economic, investment and developmental implications over and above the obvious interests of project owners. To achieve the broad aim as summarised above, the research study used a multi-disciplinary methodology and approach that required several kinds of expertise and sources of information. Hence it used both primary and secondary sources centred on interactive informative interviews, site visits and observations, questionnaires, census data records, mining companies’ publications, published textbooks and journal articles. The research study comprised of three different mines operated by three different mining companies in three varied socio-cultural and ethnic regions of Botswana. First was a detailed Social Impact Assessment of the initial phase of exploration, surveying and mine site development represented by Mowana mine project operated by African Copper in the rural areas of Dugwi and Mosetse. This case study yielded results showing that the social impacts of mining in the area are diverse and extensive. The findings suggest that the impacts relate not only to the possible economic benefits of foreign exchange, employment, the optimal use of available mineral resources and the possible development of Dugwi and Mosetse villages, but extends to the deleterious social impacts. The results also indicated that the social impacts have just begun in the two communities. Hence they point towards a possible disruption within the socio-cultural system of the local people if serious mitigation measures are not put in place; thus suggesting that the early stages of exploration and mine site development results in the most conflict between the mine and the local people. Second was a comprehensive Social Impact Assessment of Tati-Nickel Phoenix mining project in the peri-urban areas of Matshelagabedi and Matsiloje areas representing the mining stage of mine production and expansion. The results from this case study suggest that during vi mine production and expansion, many people were relocated. However, the overriding impression gained from the case study was Tati-Nickel Mining Company’s elaborate corporate policies that suggested good corporate governance and best practices that promote sustainable development. A notable milestone on good corporate governance and best practice that the other two case studies (mining company) could benchmark on is Tati-Nickel’s corporate social responsibility programme that has been designed to ensure that the communities within a fifty kilometre mine radius benefit from the mine. The results from the case study also distinguished the mining stage of production and expansion from the other two because it is associated with the deep entrenchment of the social impacts into the communities near to mining areas. Third was a detailed Social Impact Assessment on Bamangwato Concession Limited mine in the industrial town of Selebi-Phikwe. The case study represented the stage of mine closure. Through the findings of this case study, it became apparent that the economic dependence of Selebi-Phikwe on mining has seen the town developing into a mining town, increasing its vulnerability at mine closure. The results from the case study further suggest that mine closure will degrade the socio-economic sector of the town with ever far reaching socio-economic implications as many people lose their gainful employment, hence suggesting that a possible complete mine closure will be the most traumatic phase leading to major social conflict within the area. Thus the results suggest that at mine closure, the deleterious social impacts will overspill to other areas in Botswana with disastrous effects for the economy of the country. The results yielded through this study established in clear and passionate language that copper-nickel mining in Botswana influences population movements that lead to positive and negative impacts on the communities found in mining areas. Another major finding of the study is that copper-nickel mining activities have both economic benefits and deleterious social impacts on the local communities, hence the recommendation that the copper-nickel mining companies should embrace the concept of sustainable mining for sustainable development to avoid most of the negative impacts of their operations on the local communities.
- Full Text:
- Date Issued: 2010
- Authors: Mengwe, Moses Seargent
- Date: 2010
- Subjects: Copper mines and mining -- Environmental aspects -- Botswana , Nickel mines and mining -- Environmental aspects -- Botswana , Mineral industry -- Botswana , Mines and mineral resources -- Botswana
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10644 , http://hdl.handle.net/10948/1443 , Copper mines and mining -- Environmental aspects -- Botswana , Nickel mines and mining -- Environmental aspects -- Botswana , Mineral industry -- Botswana , Mines and mineral resources -- Botswana
- Description: This research study is more of an initiative towards Social Impact Assessment of copper-nickel mining in Botswana. The specific objectives of the study were centred on the assessment of the social impacts of copper-nickel mining in Botswana from the initial mining stage of exploration, surveying and mine site development to mine closure. The study was carried out under the broad hypotheses that mining influences population movement that impact on areas of mining; mining activities have both economic benefits and deleterious social impacts on the local communities found in the areas where mining is taking place; and mine closure has far reaching socio-economic, investment and developmental implications over and above the obvious interests of project owners. To achieve the broad aim as summarised above, the research study used a multi-disciplinary methodology and approach that required several kinds of expertise and sources of information. Hence it used both primary and secondary sources centred on interactive informative interviews, site visits and observations, questionnaires, census data records, mining companies’ publications, published textbooks and journal articles. The research study comprised of three different mines operated by three different mining companies in three varied socio-cultural and ethnic regions of Botswana. First was a detailed Social Impact Assessment of the initial phase of exploration, surveying and mine site development represented by Mowana mine project operated by African Copper in the rural areas of Dugwi and Mosetse. This case study yielded results showing that the social impacts of mining in the area are diverse and extensive. The findings suggest that the impacts relate not only to the possible economic benefits of foreign exchange, employment, the optimal use of available mineral resources and the possible development of Dugwi and Mosetse villages, but extends to the deleterious social impacts. The results also indicated that the social impacts have just begun in the two communities. Hence they point towards a possible disruption within the socio-cultural system of the local people if serious mitigation measures are not put in place; thus suggesting that the early stages of exploration and mine site development results in the most conflict between the mine and the local people. Second was a comprehensive Social Impact Assessment of Tati-Nickel Phoenix mining project in the peri-urban areas of Matshelagabedi and Matsiloje areas representing the mining stage of mine production and expansion. The results from this case study suggest that during vi mine production and expansion, many people were relocated. However, the overriding impression gained from the case study was Tati-Nickel Mining Company’s elaborate corporate policies that suggested good corporate governance and best practices that promote sustainable development. A notable milestone on good corporate governance and best practice that the other two case studies (mining company) could benchmark on is Tati-Nickel’s corporate social responsibility programme that has been designed to ensure that the communities within a fifty kilometre mine radius benefit from the mine. The results from the case study also distinguished the mining stage of production and expansion from the other two because it is associated with the deep entrenchment of the social impacts into the communities near to mining areas. Third was a detailed Social Impact Assessment on Bamangwato Concession Limited mine in the industrial town of Selebi-Phikwe. The case study represented the stage of mine closure. Through the findings of this case study, it became apparent that the economic dependence of Selebi-Phikwe on mining has seen the town developing into a mining town, increasing its vulnerability at mine closure. The results from the case study further suggest that mine closure will degrade the socio-economic sector of the town with ever far reaching socio-economic implications as many people lose their gainful employment, hence suggesting that a possible complete mine closure will be the most traumatic phase leading to major social conflict within the area. Thus the results suggest that at mine closure, the deleterious social impacts will overspill to other areas in Botswana with disastrous effects for the economy of the country. The results yielded through this study established in clear and passionate language that copper-nickel mining in Botswana influences population movements that lead to positive and negative impacts on the communities found in mining areas. Another major finding of the study is that copper-nickel mining activities have both economic benefits and deleterious social impacts on the local communities, hence the recommendation that the copper-nickel mining companies should embrace the concept of sustainable mining for sustainable development to avoid most of the negative impacts of their operations on the local communities.
- Full Text:
- Date Issued: 2010
Towards knowing through doing : improving the societal relevance of systematic conservation assessments
- Authors: Knight, Andrew Thomas
- Date: 2007
- Subjects: Conservation of natural resources -- Planning , Nature conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10598 , http://hdl.handle.net/10948/711 , Conservation of natural resources -- Planning , Nature conservation -- South Africa
- Description: Systematic conservation assessments are spatially-explicit techniques for prioritising areas for the implementation of conservation action. There has been considerable reference in the peer-reviewed literature as to the usefulness of these tools, which appear to be primarily used by academics for theoretical research. A literature review and author survey reveals the peer-reviewed literature is largely theoretical, although conservation action results more frequently than reported. The effectiveness of these interventions is generally described as only ‘fairly effective’. This general trend, coupled with previous personal failures in translating systematic conservation assessments into effective conservation action triggered an explicit process of social learning implemented as action research. It examined the workings of the Subtropical Thicket Ecosystem Planning (STEP) project, which included development of a systematic conservation assessment. Systematic conservations assessments simply provide information on where action should be implemented, and so are only useful if situated within broader operational models for conservation planning. Most operational models presented in the peer-reviewed literature are primarily focused upon the testing ecological data, not upon the delivery of conservation action. A new operational model for conservation planning is presented which more accurately reflects the ‘real-world’ process of conservation planning. An implementation strategy is an essential complement to a systematic conservation assessment. It describes how specific, explicitly-stated goals will be achieved, who is accountable for undertaking these activities, and the resources required. As the Implementation Specialist for the STEP Project, I co-lead the collaborative development of an implementation strategy with stakeholders that aimed to mobilise resources towards achieving common goals. Whilst the development and initial uptake of the strategy was good, subsequent implementation has flounder. The reasons for this are explored. The ultimate pragmatic goal of a conservation planning process is the establishment of effective social learning institutions. These develop common visions, mobilise collective action, and adaptively learn and refine their conservation activities. Thicket Forum is one xi such institution established through the STEP Project. My involvement with Thicket Forum since 2004 in implementing an adaptive learning approach facilitates collaboration between land managers, government and research organisations. Systematic conservation assessments evolved in response to the ad hoc way in which protected areas were implemented, leaving unrepresentative, biased protected area networks. Most research is theoretical and without an intimate understanding of the social-ecological system of a planning region, notably opportunities and constraints for implementing conservation action. Highlighting the importance of an approach which is flexible, not only in space, but in time, which can capitalise upon implementation opportunities, is important for stemming the myth that opportunism is the nemesis of systematic conservation assessments. To this end, conservation planners have been slow to include factors influencing effective implementation in systematic conservation assessments. Many studies which identify candidate protected area networks, first, fail to identify the specific instrument(s) to be applied, and second, assume all intact land is available. Having mapped the willingness of land managers in the Albany District, South Africa, to sell their land, it is demonstrated the majority of targets fail to be achieved because land managers will not sell. Knowing this, the current focus of gathering ever-more ecological data is misplaced. Human, social and economic factors influence target achievement, efficiency and spatial configuration of priority areas. Selecting important areas for conservation, particularly at the local-scale, requires the mapping of factors which define opportunities for conservation. Land manager willingness to collaborate and participate, entrepreneurial orientation, conservation knowledge, social capital, and local champions were applied using a method of hierarchical clustering to identify land managers who represent conservation opportunities for private land conservation initiatives.
- Full Text:
- Date Issued: 2007
- Authors: Knight, Andrew Thomas
- Date: 2007
- Subjects: Conservation of natural resources -- Planning , Nature conservation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10598 , http://hdl.handle.net/10948/711 , Conservation of natural resources -- Planning , Nature conservation -- South Africa
- Description: Systematic conservation assessments are spatially-explicit techniques for prioritising areas for the implementation of conservation action. There has been considerable reference in the peer-reviewed literature as to the usefulness of these tools, which appear to be primarily used by academics for theoretical research. A literature review and author survey reveals the peer-reviewed literature is largely theoretical, although conservation action results more frequently than reported. The effectiveness of these interventions is generally described as only ‘fairly effective’. This general trend, coupled with previous personal failures in translating systematic conservation assessments into effective conservation action triggered an explicit process of social learning implemented as action research. It examined the workings of the Subtropical Thicket Ecosystem Planning (STEP) project, which included development of a systematic conservation assessment. Systematic conservations assessments simply provide information on where action should be implemented, and so are only useful if situated within broader operational models for conservation planning. Most operational models presented in the peer-reviewed literature are primarily focused upon the testing ecological data, not upon the delivery of conservation action. A new operational model for conservation planning is presented which more accurately reflects the ‘real-world’ process of conservation planning. An implementation strategy is an essential complement to a systematic conservation assessment. It describes how specific, explicitly-stated goals will be achieved, who is accountable for undertaking these activities, and the resources required. As the Implementation Specialist for the STEP Project, I co-lead the collaborative development of an implementation strategy with stakeholders that aimed to mobilise resources towards achieving common goals. Whilst the development and initial uptake of the strategy was good, subsequent implementation has flounder. The reasons for this are explored. The ultimate pragmatic goal of a conservation planning process is the establishment of effective social learning institutions. These develop common visions, mobilise collective action, and adaptively learn and refine their conservation activities. Thicket Forum is one xi such institution established through the STEP Project. My involvement with Thicket Forum since 2004 in implementing an adaptive learning approach facilitates collaboration between land managers, government and research organisations. Systematic conservation assessments evolved in response to the ad hoc way in which protected areas were implemented, leaving unrepresentative, biased protected area networks. Most research is theoretical and without an intimate understanding of the social-ecological system of a planning region, notably opportunities and constraints for implementing conservation action. Highlighting the importance of an approach which is flexible, not only in space, but in time, which can capitalise upon implementation opportunities, is important for stemming the myth that opportunism is the nemesis of systematic conservation assessments. To this end, conservation planners have been slow to include factors influencing effective implementation in systematic conservation assessments. Many studies which identify candidate protected area networks, first, fail to identify the specific instrument(s) to be applied, and second, assume all intact land is available. Having mapped the willingness of land managers in the Albany District, South Africa, to sell their land, it is demonstrated the majority of targets fail to be achieved because land managers will not sell. Knowing this, the current focus of gathering ever-more ecological data is misplaced. Human, social and economic factors influence target achievement, efficiency and spatial configuration of priority areas. Selecting important areas for conservation, particularly at the local-scale, requires the mapping of factors which define opportunities for conservation. Land manager willingness to collaborate and participate, entrepreneurial orientation, conservation knowledge, social capital, and local champions were applied using a method of hierarchical clustering to identify land managers who represent conservation opportunities for private land conservation initiatives.
- Full Text:
- Date Issued: 2007
Towards a community based conservation strategy for wetlands in Uganda
- Authors: Barakagira, Alex
- Date: 2018
- Subjects: Conservation of natural resources , Wetland conservation -- Uganda Wetlands -- Uganda -- Management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23902 , vital:30640
- Description: Conservation of natural resources in Uganda focuses primarily on protected areas, including savannah national parks, mainly for conserving big game and forests, for controlling the harvest of commercially valuable timber resources, with less concern for wetlands. Later, policies and legislation in Uganda favoured agricultural production rather than the conservation of wetlands, a situation that culminated in their degradation. In a bid to counter the effects of wetlands degradation, Wetland Management Agencies were created. These agencies excluded the input of members of the local communities who reside in the wetlands environs. Local communities were not consulted on matters concerning management and conservation strategies, a situation that may have escalated the problem of wetlands degradation. Local knowledge is needed for the effective management and conservation of the wetlands and it is essential that local communities are included in decision making. This research study is more of an initiative for providing information that may be essential for the formulation of a community based conservation strategy for wetlands in Uganda. The study aimed to identify and characterize activities carried out by members of the local communities in wetlands found in central and western Uganda that are responsible for their progressive degradation; to assess the performance of existing Wetlands Management Institutions towards protection and conservation of wetlands in Uganda; to ascertain whether the acts and policies that have been promulgated for the protection of wetlands in Uganda have been adhered to by members of the local communities and to evaluate three community based conservation case studies with two vastly different outcomes in order to come up with the community-based conservation principles Ugandan communities may need to adopt to achieve sustainable utilisation and conservation of wetland resources. To achieve the objectives stated above, the researcher used a multi-disciplinary methodology that required several areas of expertise and sources of information. Hence, to accomplish the study, primary sources of data that included quantitative and qualitative data were collected from the study participants by means of a questionnaire survey, key informant interviews and direct observations. Secondary sources of data centred on published Ugandan acts and policies; textbooks; case study articles and journal articles. The study revealed a host of activities in which members of the local community are involved that have led to the degradation of the wetlands in Uganda. These include but are not limited to crop cultivation, dairy farming and unsustainable wetland resource harvesting. A number of other reasons for the degradation of the wetlands include unclear ownership of the wetlands, unclear wetland boundaries and a lack of awareness of the indirect benefits wetlands provide for members of the local communities. The study disclosed that wetlands management institutions have not been effective in the protection and conservation of wetlands in Uganda, mainly due to political interference and inadequate funding for the institutions’ conservation activities. The acts and policies that were promulgated for the protection and conservation of wetlands have been selectively implemented in some places and in others completely ignored, culminating in the degradation of the wetlands. The study revealed that effective community based conservation of wetlands in Uganda includes: initiation of the planning, implementation, monitoring and evaluation of all wetlands activities being borne by members of the local community; government introducing alternative income-generating activities aimed to reduce over-reliance on wetland resources and education of the local communities regarding the community-based projects’ objectives in order to garner their support. Recommendations emanating from this study are that the Land Act should be amended to specify a particular land tenure system, preferably freehold, which may promote the conservation of wetlands in Uganda; fertilizers (organic) should be introduced in the study area to fertilize the uplands that have reportedly become infertile in order to reduce the pressure the local community members are exerting on the wetlands for agriculture; wetlands management institutions should be empowered financially and political interference in activities aimed at conservation of wetlands in Uganda must cease. There should be uniform implementation of the rules and regulations stipulated in the acts and policies for all members of the public concerning wetlands protection. Lastly, essential community based conservation principles, as stated above, need to be applied carefully and adhered to if effective implementation of community-based conservation of wetlands is to be achieved in Uganda.
- Full Text:
- Date Issued: 2018
- Authors: Barakagira, Alex
- Date: 2018
- Subjects: Conservation of natural resources , Wetland conservation -- Uganda Wetlands -- Uganda -- Management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23902 , vital:30640
- Description: Conservation of natural resources in Uganda focuses primarily on protected areas, including savannah national parks, mainly for conserving big game and forests, for controlling the harvest of commercially valuable timber resources, with less concern for wetlands. Later, policies and legislation in Uganda favoured agricultural production rather than the conservation of wetlands, a situation that culminated in their degradation. In a bid to counter the effects of wetlands degradation, Wetland Management Agencies were created. These agencies excluded the input of members of the local communities who reside in the wetlands environs. Local communities were not consulted on matters concerning management and conservation strategies, a situation that may have escalated the problem of wetlands degradation. Local knowledge is needed for the effective management and conservation of the wetlands and it is essential that local communities are included in decision making. This research study is more of an initiative for providing information that may be essential for the formulation of a community based conservation strategy for wetlands in Uganda. The study aimed to identify and characterize activities carried out by members of the local communities in wetlands found in central and western Uganda that are responsible for their progressive degradation; to assess the performance of existing Wetlands Management Institutions towards protection and conservation of wetlands in Uganda; to ascertain whether the acts and policies that have been promulgated for the protection of wetlands in Uganda have been adhered to by members of the local communities and to evaluate three community based conservation case studies with two vastly different outcomes in order to come up with the community-based conservation principles Ugandan communities may need to adopt to achieve sustainable utilisation and conservation of wetland resources. To achieve the objectives stated above, the researcher used a multi-disciplinary methodology that required several areas of expertise and sources of information. Hence, to accomplish the study, primary sources of data that included quantitative and qualitative data were collected from the study participants by means of a questionnaire survey, key informant interviews and direct observations. Secondary sources of data centred on published Ugandan acts and policies; textbooks; case study articles and journal articles. The study revealed a host of activities in which members of the local community are involved that have led to the degradation of the wetlands in Uganda. These include but are not limited to crop cultivation, dairy farming and unsustainable wetland resource harvesting. A number of other reasons for the degradation of the wetlands include unclear ownership of the wetlands, unclear wetland boundaries and a lack of awareness of the indirect benefits wetlands provide for members of the local communities. The study disclosed that wetlands management institutions have not been effective in the protection and conservation of wetlands in Uganda, mainly due to political interference and inadequate funding for the institutions’ conservation activities. The acts and policies that were promulgated for the protection and conservation of wetlands have been selectively implemented in some places and in others completely ignored, culminating in the degradation of the wetlands. The study revealed that effective community based conservation of wetlands in Uganda includes: initiation of the planning, implementation, monitoring and evaluation of all wetlands activities being borne by members of the local community; government introducing alternative income-generating activities aimed to reduce over-reliance on wetland resources and education of the local communities regarding the community-based projects’ objectives in order to garner their support. Recommendations emanating from this study are that the Land Act should be amended to specify a particular land tenure system, preferably freehold, which may promote the conservation of wetlands in Uganda; fertilizers (organic) should be introduced in the study area to fertilize the uplands that have reportedly become infertile in order to reduce the pressure the local community members are exerting on the wetlands for agriculture; wetlands management institutions should be empowered financially and political interference in activities aimed at conservation of wetlands in Uganda must cease. There should be uniform implementation of the rules and regulations stipulated in the acts and policies for all members of the public concerning wetlands protection. Lastly, essential community based conservation principles, as stated above, need to be applied carefully and adhered to if effective implementation of community-based conservation of wetlands is to be achieved in Uganda.
- Full Text:
- Date Issued: 2018
Time series models for paired comparisons
- Authors: Sjolander, Morne Rowan
- Date: 2011
- Subjects: Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10577 , http://hdl.handle.net/10948/d1012858
- Description: The method of paired comparisons is seen as a technique used to rank a set of objects with respect to an abstract or immeasurable property. To do this, the objects get to be compared two at a time. The results are input into a model, resulting in numbers known as weights being assigned to the objects. The weights are then used to rank the objects. The method of paired comparisons was first used for psychometric investigations. Various other applications of the method are also present, for example economic applications, and applications in sports statistics. This study involves taking paired comparison models and making them time-dependent. Not much research has been done in this area. Three new time series models for paired comparisons are created. Simulations are done to support the evidence obtained, and theoretical as well as practical examples are given to illustrate the results and to verify the efficiency of the new models. A literature study is given on the method of paired comparisons, as well as on the areas in which we apply our models. Our first two time series models for paired comparisons are the Linear-Trend Bradley- Terry Model and the Sinusoidal Bradley-Terry Model. We use the maximum likelihood approach to solve these models. We test our models using exact and randomly simulated data for various time periods and various numbers of objects. We adapt the Linear-Trend Bradley-Terry Model and received our third time series model for paired comparisons, the Log Linear-Trend Bradley-Terry Model. The daily maximum and minimum temperatures were received for Port Elizabeth, Uitenhage and Coega for 2005 until 2009. To evaluate the performance of the Linear-Trend Bradley-Terry Model and the Sinusoidal Bradley-Terry Model on estimating missing temperature data, we artificially remove observations of temperature from Coega’s temperature dataset for 2006 until 2008, and use various forms of these models to estimate the missing data points. The exchange rates for 2005 until 2008 between the following currencies: the Rand, Dollar, Euro, Pound and Yen, were obtained and various forms of our Log Linear-Trend Bradley-Terry Model are used to forecast the exchange rate for one day ahead for each month in 2006 until 2008. One of the features of this study is that we apply our time series models for paired comparisons to areas which comprise non-standard paired comparisons; and we want to encourage the use of the method of paired comparisons in a broader sense than what it is traditionally used for. The results of this study can be used in various other areas, like for example, in sports statistics, to rank the strength of sports players and predict their future scores; in Physics, to calculate weather risks of electricity generation, particularly risks related to nuclear power plants, and so forth, as well as in many other areas. It is hoped that this research will open the door to much more research in combining time series analysis with the method of paired comparisons.
- Full Text:
- Date Issued: 2011
- Authors: Sjolander, Morne Rowan
- Date: 2011
- Subjects: Paired comparisons (Statistics)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10577 , http://hdl.handle.net/10948/d1012858
- Description: The method of paired comparisons is seen as a technique used to rank a set of objects with respect to an abstract or immeasurable property. To do this, the objects get to be compared two at a time. The results are input into a model, resulting in numbers known as weights being assigned to the objects. The weights are then used to rank the objects. The method of paired comparisons was first used for psychometric investigations. Various other applications of the method are also present, for example economic applications, and applications in sports statistics. This study involves taking paired comparison models and making them time-dependent. Not much research has been done in this area. Three new time series models for paired comparisons are created. Simulations are done to support the evidence obtained, and theoretical as well as practical examples are given to illustrate the results and to verify the efficiency of the new models. A literature study is given on the method of paired comparisons, as well as on the areas in which we apply our models. Our first two time series models for paired comparisons are the Linear-Trend Bradley- Terry Model and the Sinusoidal Bradley-Terry Model. We use the maximum likelihood approach to solve these models. We test our models using exact and randomly simulated data for various time periods and various numbers of objects. We adapt the Linear-Trend Bradley-Terry Model and received our third time series model for paired comparisons, the Log Linear-Trend Bradley-Terry Model. The daily maximum and minimum temperatures were received for Port Elizabeth, Uitenhage and Coega for 2005 until 2009. To evaluate the performance of the Linear-Trend Bradley-Terry Model and the Sinusoidal Bradley-Terry Model on estimating missing temperature data, we artificially remove observations of temperature from Coega’s temperature dataset for 2006 until 2008, and use various forms of these models to estimate the missing data points. The exchange rates for 2005 until 2008 between the following currencies: the Rand, Dollar, Euro, Pound and Yen, were obtained and various forms of our Log Linear-Trend Bradley-Terry Model are used to forecast the exchange rate for one day ahead for each month in 2006 until 2008. One of the features of this study is that we apply our time series models for paired comparisons to areas which comprise non-standard paired comparisons; and we want to encourage the use of the method of paired comparisons in a broader sense than what it is traditionally used for. The results of this study can be used in various other areas, like for example, in sports statistics, to rank the strength of sports players and predict their future scores; in Physics, to calculate weather risks of electricity generation, particularly risks related to nuclear power plants, and so forth, as well as in many other areas. It is hoped that this research will open the door to much more research in combining time series analysis with the method of paired comparisons.
- Full Text:
- Date Issued: 2011
Thermal degradation of diamond compacts: a TEM investigation
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
- Authors: Westraadt, Johan Ewald
- Date: 2011
- Subjects: Materials -- Thermal properties Chemical weathering
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/10829 , vital:26827
- Description: Diamond compacts consist of fine diamond grains bonded together by using high pressure and high temperature. In this study transmission electron microscopy (TEM)was used to study thermal degradation of diamond compacts. Three different types of diamond compacts – namely cobalt polycrystalline diamond (PCD), calcium carbonate PCD, and diamond-SiC composites – were investigated with TEM to understand the processes that occur during synthesis. These compacts were then heated in inert atmospheres and the chemical changes studied with TEM. It was found that PCD, using cobalt as a bonding agent, will degrade after exposure to temperatures above 750ºC. The cobalt pools contain tungsten in solid solution. During heat treatment above 700ºC the solid solution tungsten combines with cobalt and dissolved carbon to form η-phase particles at the cobalt/diamond interface. At higher temperatures or insufficient tungsten levels the rate of dissolved carbon, into the cobalt pool, is too high and the excess carbon will form as graphite in the cobalt pool. Increased levels of solid solution tungsten, in the cobalt, is expected to delay the onset of graphitization in the diamond compact, thereby increasing the thermal stability of the diamond compact. Non-metallic PCD using calcium carbonate as a bonding agent was successfully sintered in this study. TEM revealed similar micro-structural features as in cobalt based PCD. No signs of thermal degradation were found after exposure to 1200ºC in vacuum for this PCD. Contaminants introduced during processing prevented a detailed study of the binder in this system. The effect of substitutional metal atoms and plastic deformation of diamond on the thermal stability of diamond-SiC composites were investigated. A piston cylinder press was developed and used to synthesize diamond-SiC composites with different levels of plastically deformed diamond. It was concluded that substitutional metal atoms and plastic deformation of diamond grains play no role in the thermal degradation of diamond compacts at 750ºC. The thermal degradation of cobalt PCD is therefore completely determined by the cobalt/diamond interaction at 750ºC.
- Full Text:
- Date Issued: 2011
The taxonomic status of dolphins Tursiops spp. and Delphinus in South African waters
- Authors: Ngqulana, Sibusisiwe Gloria
- Date: 2020
- Subjects: Dolphins -- Classification -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48566 , vital:40891
- Description: There is a need for identifying important sites, taxonomic units or populations and the usual criterion used is species identification. The species is the most important taxonomic unit to define in taxonomy, as it is the primary unit of concern in biodiversity, conservation and other biological issues. Thus, taxonomy plays an important role in conservation biology. Additionally, taxonomy can contribute to the development of analytical systems that will provide information on priorities for reaching defensible targets for established conservation. This poses a problem for cetaceans as basic information is frequently deficient and therefore not suitable for conservation planning purposes. This leads to difficulties in identifying and prioritizing areas for the monitoring, management and for the protection of species or populations. Morphological and geographic data used to be the primary means used by taxonomists to define species and subspecies, and due to this, most extant species have been classified by morphological characteristics. However, in the recent years, molecular analyses have been introduced and subsequently stable isotopes were also included to assist in interpreting results. Thereafter, it became a common approach to use more than one technique or a combination of independent datasets to resolve taxonomic uncertainties. This has resulted to a proposed term known as integrative taxonomy. Integrative taxonomy has recently been used in most studies that deal with taxonomy or population structure. The use of multiple lines of evidence, which is sometimes referred to as integrative taxonomy, raises the level of confidence in clearly delineating species. Cetaceans are the most taxonomically diverse group of aquatic mammals, with 93 living species accepted. Previously, their taxonomy was based on morphological characters. However, cetaceans have recently been subjected to intense phylogenetic investigations using both morphological and molecular data. These problems are not only prevalent in larger whales, but the small toothed whales also have these challenges, particularly family Delphinidae. This family is known to be the most diverse among the toothed whales. This is because this family diverged recently, and the divergence occurred relatively fast. This study aimed to clarify the taxonomic status of Tursiops spp. and Delphinus in the family Delphinidae, inhabiting the South African waters, using a combination of morphological and molecular methods. For skull morphology, geometric morphometrics were used, while for molecular methods, the D-loop region in the mitochondrial DNA was used to detect any differences within each genus. For the genus Tursiops, this study showed the consistency of results in all analyses used to investigate the presence of two species in the genus Tursiops in South African waters. This study only analysed sequences from the mitochondrial D-loop region and has re-confirmed the presence of the two species in South Africa. Skull and external morphology both show T. truncatus to be bigger and more robust, and to have a shorter rostrum compared with T. aduncus. These external observations are helpful when identifying the species in the field. Providing evidence supporting the presence of two Tursiops species in South Africa does not only contribute to the global context of the taxonomy of this genus, but also in the local context. This study also gives insight on the distribution of the two species in the region. For the genus Delphinus, molecular analysis did not reveal any clustering in South African Delphinus specimens, which suggested a single species, D. delphis, and that this species is morphologically highly variable. Both skull and external morphology did not reflect the molecular results, supporting suggestions that morphology in this genus does not reflect genetic differences. It has been shown that morphological variation reflects feeding specialization rather than speciation. This may also reflect local adaptations. Both skull and external morphology in this study showed no significant differences. This study did not investigate the phylogeographic details of the species in South Africa and further molecular work including a larger sample size from the west coast of South Africa is needed. By attempting to unravel the taxonomy of these dolphins in South African waters, the findings of this study will be very useful in the development of effective conservation and management strategies for these dolphins.
- Full Text:
- Date Issued: 2020
- Authors: Ngqulana, Sibusisiwe Gloria
- Date: 2020
- Subjects: Dolphins -- Classification -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/48566 , vital:40891
- Description: There is a need for identifying important sites, taxonomic units or populations and the usual criterion used is species identification. The species is the most important taxonomic unit to define in taxonomy, as it is the primary unit of concern in biodiversity, conservation and other biological issues. Thus, taxonomy plays an important role in conservation biology. Additionally, taxonomy can contribute to the development of analytical systems that will provide information on priorities for reaching defensible targets for established conservation. This poses a problem for cetaceans as basic information is frequently deficient and therefore not suitable for conservation planning purposes. This leads to difficulties in identifying and prioritizing areas for the monitoring, management and for the protection of species or populations. Morphological and geographic data used to be the primary means used by taxonomists to define species and subspecies, and due to this, most extant species have been classified by morphological characteristics. However, in the recent years, molecular analyses have been introduced and subsequently stable isotopes were also included to assist in interpreting results. Thereafter, it became a common approach to use more than one technique or a combination of independent datasets to resolve taxonomic uncertainties. This has resulted to a proposed term known as integrative taxonomy. Integrative taxonomy has recently been used in most studies that deal with taxonomy or population structure. The use of multiple lines of evidence, which is sometimes referred to as integrative taxonomy, raises the level of confidence in clearly delineating species. Cetaceans are the most taxonomically diverse group of aquatic mammals, with 93 living species accepted. Previously, their taxonomy was based on morphological characters. However, cetaceans have recently been subjected to intense phylogenetic investigations using both morphological and molecular data. These problems are not only prevalent in larger whales, but the small toothed whales also have these challenges, particularly family Delphinidae. This family is known to be the most diverse among the toothed whales. This is because this family diverged recently, and the divergence occurred relatively fast. This study aimed to clarify the taxonomic status of Tursiops spp. and Delphinus in the family Delphinidae, inhabiting the South African waters, using a combination of morphological and molecular methods. For skull morphology, geometric morphometrics were used, while for molecular methods, the D-loop region in the mitochondrial DNA was used to detect any differences within each genus. For the genus Tursiops, this study showed the consistency of results in all analyses used to investigate the presence of two species in the genus Tursiops in South African waters. This study only analysed sequences from the mitochondrial D-loop region and has re-confirmed the presence of the two species in South Africa. Skull and external morphology both show T. truncatus to be bigger and more robust, and to have a shorter rostrum compared with T. aduncus. These external observations are helpful when identifying the species in the field. Providing evidence supporting the presence of two Tursiops species in South Africa does not only contribute to the global context of the taxonomy of this genus, but also in the local context. This study also gives insight on the distribution of the two species in the region. For the genus Delphinus, molecular analysis did not reveal any clustering in South African Delphinus specimens, which suggested a single species, D. delphis, and that this species is morphologically highly variable. Both skull and external morphology did not reflect the molecular results, supporting suggestions that morphology in this genus does not reflect genetic differences. It has been shown that morphological variation reflects feeding specialization rather than speciation. This may also reflect local adaptations. Both skull and external morphology in this study showed no significant differences. This study did not investigate the phylogeographic details of the species in South Africa and further molecular work including a larger sample size from the west coast of South Africa is needed. By attempting to unravel the taxonomy of these dolphins in South African waters, the findings of this study will be very useful in the development of effective conservation and management strategies for these dolphins.
- Full Text:
- Date Issued: 2020
The synthesis and assessment of thioxanthone- and xanthone- derived compounds as hosts for application in host-guest chemistry
- Authors: Greyling, Lizé
- Date: 2019
- Subjects: Chemistry, Organic , Biochemistry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/42525 , vital:36665
- Description: In this work, the host capabilities of two structurally related compounds, N,N’-bis(9-phenyl-9- thioxanthenyl)ethylenediamine (H1) and N,N’-bis(9-phenyl-9-xanthenyl)ethylenediamine (H2) were compared in the presence of a wide variety of guest species. Additionally, the selectivity displayed by these host compounds were examined when exposed to mixtures of guests in order to ascertain whether it would be feasible to employ them in alternative separation strategies for the purification of industrially relevant chemicals. H1 and H2 were synthesized by reacting thioxanthone and xanthone with phenylmagnesium bromide. The resultant alcohol was then treated with perchloric acid and, finally, two of these molecules were effectively linked by utilizing ethylenediamine to afford the two host compounds. Initially, H1 and H2 were investigated for their inclusion abilities by recrystallizing each from a number of potential isomeric and non-isomeric guest compounds such as the xylenes and ethylbenzene, methylanisoles and anisole, methylpyridines and pyridine, methylcyclohexanones and cyclohexanone, heterocyclic five- and six- membered ring compounds, alkylsubstituted benzenes, anilines, and dihaloalkanes. H1 displayed excellent inclusion ability when presented with the above-mentioned compounds, and a 1:1 H:G ratio was consistently preferred in each case. H2 also proved to be successful in this regard but did not include the methylcyclohexanones and cyclohexanone nor the heterocyclic five-membered ring solvents. Furthermore, varying host:guest ratios were observed for the complexes formed with H2. Mixed competition experiments were carried out in the presence of either isomeric or related but non-isomeric guest species. When H1 and H2 were independently recrystallized from mixtures of the former, selectivity orders correlated for both hosts, but it was observed that H2 exhibited an enhanced selectivity for the preferred guests in each case, compared with H1. Interestingly, in mixtures of the latter, host behaviours were distinctly opposing (with the exception of the dihaloalkanes). H1, and even more so H2, demonstrated very high selectivities for p-xylene, aniline and N,Ndimethylaniline from the xylene and aniline guest series, respectively, where selectivities were found to be ~90% or higher for host recrystallization experiments from respective mixtures of these guests. Single crystal X-ray diffraction, Hirshfeld surface and thermal analyses were employed in order to elucidate the reasons for any selectivity observations. The inclusion of these guests was, in most cases, found to be as a result of interactions between host and guest species, which included π∙∙∙π stacking, C‒H∙∙∙π, hydrogen bonding and various other short contact types. Guest compounds were accommodated in either cavities or channels and this was dependent on the nature of the guest. The host molecule conformations showed H1 to adopt a bent tricyclic fused ring system with the N atoms of the linker in a synclinal arrangement, while in complexes with H2, the fused ring system was near-planar and the N atoms adopted an antiperiplanar geometry. These key differences resulted in a very ordered host‒host packing for H2 as a direct result of the more planar O-containing ring and linear linker; for H1, on the other hand, the buckled S-containing ring and gauche-orientated N atoms resulted in a less ordered packing, which ultimately related to the differences in the behaviour of the two host species. Hirshfeld surface analyses, in general, did not provide much information to explain the host selectivities, with the exception of complexes containing the five-membered ring guest heterocyclics. Thermal analyses were completed on all suitable host-guest complexes and, in most cases but not all, the onset and peak temperatures (terms Ton and Tp, respectively) were related to the thermal stability of the complexes, which were used to rationalize the selectivities of these host compounds.
- Full Text:
- Date Issued: 2019
- Authors: Greyling, Lizé
- Date: 2019
- Subjects: Chemistry, Organic , Biochemistry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/42525 , vital:36665
- Description: In this work, the host capabilities of two structurally related compounds, N,N’-bis(9-phenyl-9- thioxanthenyl)ethylenediamine (H1) and N,N’-bis(9-phenyl-9-xanthenyl)ethylenediamine (H2) were compared in the presence of a wide variety of guest species. Additionally, the selectivity displayed by these host compounds were examined when exposed to mixtures of guests in order to ascertain whether it would be feasible to employ them in alternative separation strategies for the purification of industrially relevant chemicals. H1 and H2 were synthesized by reacting thioxanthone and xanthone with phenylmagnesium bromide. The resultant alcohol was then treated with perchloric acid and, finally, two of these molecules were effectively linked by utilizing ethylenediamine to afford the two host compounds. Initially, H1 and H2 were investigated for their inclusion abilities by recrystallizing each from a number of potential isomeric and non-isomeric guest compounds such as the xylenes and ethylbenzene, methylanisoles and anisole, methylpyridines and pyridine, methylcyclohexanones and cyclohexanone, heterocyclic five- and six- membered ring compounds, alkylsubstituted benzenes, anilines, and dihaloalkanes. H1 displayed excellent inclusion ability when presented with the above-mentioned compounds, and a 1:1 H:G ratio was consistently preferred in each case. H2 also proved to be successful in this regard but did not include the methylcyclohexanones and cyclohexanone nor the heterocyclic five-membered ring solvents. Furthermore, varying host:guest ratios were observed for the complexes formed with H2. Mixed competition experiments were carried out in the presence of either isomeric or related but non-isomeric guest species. When H1 and H2 were independently recrystallized from mixtures of the former, selectivity orders correlated for both hosts, but it was observed that H2 exhibited an enhanced selectivity for the preferred guests in each case, compared with H1. Interestingly, in mixtures of the latter, host behaviours were distinctly opposing (with the exception of the dihaloalkanes). H1, and even more so H2, demonstrated very high selectivities for p-xylene, aniline and N,Ndimethylaniline from the xylene and aniline guest series, respectively, where selectivities were found to be ~90% or higher for host recrystallization experiments from respective mixtures of these guests. Single crystal X-ray diffraction, Hirshfeld surface and thermal analyses were employed in order to elucidate the reasons for any selectivity observations. The inclusion of these guests was, in most cases, found to be as a result of interactions between host and guest species, which included π∙∙∙π stacking, C‒H∙∙∙π, hydrogen bonding and various other short contact types. Guest compounds were accommodated in either cavities or channels and this was dependent on the nature of the guest. The host molecule conformations showed H1 to adopt a bent tricyclic fused ring system with the N atoms of the linker in a synclinal arrangement, while in complexes with H2, the fused ring system was near-planar and the N atoms adopted an antiperiplanar geometry. These key differences resulted in a very ordered host‒host packing for H2 as a direct result of the more planar O-containing ring and linear linker; for H1, on the other hand, the buckled S-containing ring and gauche-orientated N atoms resulted in a less ordered packing, which ultimately related to the differences in the behaviour of the two host species. Hirshfeld surface analyses, in general, did not provide much information to explain the host selectivities, with the exception of complexes containing the five-membered ring guest heterocyclics. Thermal analyses were completed on all suitable host-guest complexes and, in most cases but not all, the onset and peak temperatures (terms Ton and Tp, respectively) were related to the thermal stability of the complexes, which were used to rationalize the selectivities of these host compounds.
- Full Text:
- Date Issued: 2019
The survival of micro -enteprises in Kampala, Uganda :a substainable livelihoods approach
- Authors: Twinorugyendo,Penninah
- Date: 2016
- Subjects: Microfinance -- Uganda -- Kampala New Business Enterprises -- Uganda -- Kampala -- Finance , Small business -- Uganda -- Kampala
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45333 , vital:38571
- Description: This purpose of this thesis was to explain the resilience of certain micro-enterprises (MEs) in Kampala, Uganda – by focusing on their vulnerability, the assets that they brought to bear on the situation, the role of non-governmental organizations and government institutions in supporting MEs, and the strategies used by ME owners, themselves. As such, it adopts the Sustainable-Livelihoods approach – an approach that has not been used in Kampala before. Thus, it makes a valuable contribution to the field. Designed as a qualitative study, it used in-depth interviews and focus-group discussions. The major findings on vulnerability were linked to: the rising cost of materials; unfair licensing; the struggle to win tenders; local and foreign competition; and the disruption of utilities. The assets used to sustain the welfare of the MEs included: making use of a range of skill-acquisition strategies; leveraging networks; and pooling resources. Financial assets used by MEs revolved around informal savings and credit schemes; but the support given to the MEs through government agencies and NGOs was difficult to assess. Several important strategies were used by ME owners. One of these involved linking with formal construction companies. In addition, temporary workshops constructed out of wood-and-iron, were common. This increased mobility and allowed the re-use of materials. Furthermore, MEs manufactured their own tools, developed new marketing techniques, and diversified their income-generating activities. The significance of this study is two-pronged. It demonstrates that the resilience of MEs does depend on their own positive qualities, but also on an increasingly business-friendly national and international economic environment.
- Full Text:
- Date Issued: 2016
- Authors: Twinorugyendo,Penninah
- Date: 2016
- Subjects: Microfinance -- Uganda -- Kampala New Business Enterprises -- Uganda -- Kampala -- Finance , Small business -- Uganda -- Kampala
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10948/45333 , vital:38571
- Description: This purpose of this thesis was to explain the resilience of certain micro-enterprises (MEs) in Kampala, Uganda – by focusing on their vulnerability, the assets that they brought to bear on the situation, the role of non-governmental organizations and government institutions in supporting MEs, and the strategies used by ME owners, themselves. As such, it adopts the Sustainable-Livelihoods approach – an approach that has not been used in Kampala before. Thus, it makes a valuable contribution to the field. Designed as a qualitative study, it used in-depth interviews and focus-group discussions. The major findings on vulnerability were linked to: the rising cost of materials; unfair licensing; the struggle to win tenders; local and foreign competition; and the disruption of utilities. The assets used to sustain the welfare of the MEs included: making use of a range of skill-acquisition strategies; leveraging networks; and pooling resources. Financial assets used by MEs revolved around informal savings and credit schemes; but the support given to the MEs through government agencies and NGOs was difficult to assess. Several important strategies were used by ME owners. One of these involved linking with formal construction companies. In addition, temporary workshops constructed out of wood-and-iron, were common. This increased mobility and allowed the re-use of materials. Furthermore, MEs manufactured their own tools, developed new marketing techniques, and diversified their income-generating activities. The significance of this study is two-pronged. It demonstrates that the resilience of MEs does depend on their own positive qualities, but also on an increasingly business-friendly national and international economic environment.
- Full Text:
- Date Issued: 2016
The solvent-free approach versus the use of ionic liquids in the synthesis of ferrocenes
- Authors: Elago, Elago R T
- Date: 2008
- Subjects: Ferrocene , Inorganic compounds -- Synthesis , Ionic solutions , Solvents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10396 , http://hdl.handle.net/10948/853 , Ferrocene , Inorganic compounds -- Synthesis , Ionic solutions , Solvents
- Description: The philosophy of green chemistry has seen much development in the past decade. The use of environmentally benign solvents is amongst the areas of green chemistry that have received the most attention. In this context, imidazolium ionic liquids have been widely reported to offer high product yields, fast reaction rates, excellent selectivity and generally mild working conditions, when used as reaction media. In addition, concerns about costs of solvents and the long-term environmental impact that can potentially result when solvents are discarded after their use have led to focused investigations into solvent-free procedures, as reported in recent literature. We have set out to explore the extent to which these advantages could be realized within our research. Non-volatile, non-flammable imidazolium ionic liquids [bmim][I], [bmim][BF4] and [bmim][PF6] were used as green solvents in ferrocene chemistry. Ferrocenoate esters were synthesised efficiently by the respective DCC/DMAP-promoted reactions of ferrocenecarboxylic acid and substituted benzoic acids or, alternatively, the DMAP-promoted reactions of ferrocenoyl fluoride with a range of substituted phenols in [bmim][BF4] and [bmim][PF6]. High yields and short reaction times were achieved. In addition, the ionic liquid was reused several times without a reduction in product yields. Under solvent-free conditions, DCC/DMAP-promoted reactions provided high yields within 3 min of reaction. The possible rearrangement of one of the intermediates in these reactions was modelled theoretically using density function theory (DFT) at the B3LYP/6-31G* level of approximation. Catalyst-free esterification was achieved by the application of microwave radiation to the reaction of ferrocenoyl fluoride and a range of substituted phenols. All the reactions were complete after 1 min of irradiation and products were isolated in high yield. DPAT, HfCl4, Sc(OTf)3 and Al(OTf)3 were screened as catalysts for esterification in [bmim][BF4] and under solvent-free conditions at various temperatures. All attempts at esterification of ferrocenecarboxylic acid with alcohols and phenols were unsuccessful. The Suzuki cross-coupling reaction was carried out in [bmim][BF4]. The isolated yields are, however, poor and suffer from poor reproducibility with different batches of [bmim][BF4] used.
- Full Text:
- Date Issued: 2008
- Authors: Elago, Elago R T
- Date: 2008
- Subjects: Ferrocene , Inorganic compounds -- Synthesis , Ionic solutions , Solvents
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10396 , http://hdl.handle.net/10948/853 , Ferrocene , Inorganic compounds -- Synthesis , Ionic solutions , Solvents
- Description: The philosophy of green chemistry has seen much development in the past decade. The use of environmentally benign solvents is amongst the areas of green chemistry that have received the most attention. In this context, imidazolium ionic liquids have been widely reported to offer high product yields, fast reaction rates, excellent selectivity and generally mild working conditions, when used as reaction media. In addition, concerns about costs of solvents and the long-term environmental impact that can potentially result when solvents are discarded after their use have led to focused investigations into solvent-free procedures, as reported in recent literature. We have set out to explore the extent to which these advantages could be realized within our research. Non-volatile, non-flammable imidazolium ionic liquids [bmim][I], [bmim][BF4] and [bmim][PF6] were used as green solvents in ferrocene chemistry. Ferrocenoate esters were synthesised efficiently by the respective DCC/DMAP-promoted reactions of ferrocenecarboxylic acid and substituted benzoic acids or, alternatively, the DMAP-promoted reactions of ferrocenoyl fluoride with a range of substituted phenols in [bmim][BF4] and [bmim][PF6]. High yields and short reaction times were achieved. In addition, the ionic liquid was reused several times without a reduction in product yields. Under solvent-free conditions, DCC/DMAP-promoted reactions provided high yields within 3 min of reaction. The possible rearrangement of one of the intermediates in these reactions was modelled theoretically using density function theory (DFT) at the B3LYP/6-31G* level of approximation. Catalyst-free esterification was achieved by the application of microwave radiation to the reaction of ferrocenoyl fluoride and a range of substituted phenols. All the reactions were complete after 1 min of irradiation and products were isolated in high yield. DPAT, HfCl4, Sc(OTf)3 and Al(OTf)3 were screened as catalysts for esterification in [bmim][BF4] and under solvent-free conditions at various temperatures. All attempts at esterification of ferrocenecarboxylic acid with alcohols and phenols were unsuccessful. The Suzuki cross-coupling reaction was carried out in [bmim][BF4]. The isolated yields are, however, poor and suffer from poor reproducibility with different batches of [bmim][BF4] used.
- Full Text:
- Date Issued: 2008
The social sustainability of low-cost housing: the role of social capital and sense of place
- Authors: Williams-Bruinders, Leizel
- Date: 2019
- Subjects: Housing -- South Africa , City planning -- South Africa Cities and towns -- Research Urban geography
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/44390 , vital:37161
- Description: In the past twenty years we have seen the South African government deliver the largest number of houses in the world (NDHS, 2011). However, this great effort does not appeal to the principles that policies have set out in terms of equality. Along with the delivery of this high level of state funded housing, many of the RDP dwellers feel as though they have been marginalised and forced out of the area of opportunity, namely, the CBD and the northern suburbs (Huchzermeyer, 2003). Many researchers believe that the South African housing delivery pattern resembles that of apartheid segregationist planning, which exacerbated the social inequalities in the country (Huchzermeyer, 2003; Donaldson, 2001; Harrison et al., 2003). To gain an in-depth understanding of the lived experiences of residents of a low-cost housing settlement, an interpretative phenomenological analysis was undertaken. The emergent themes emanating from the research study revealed that social problems were pertinent factors to the lack of formulation of community social cohesion. Without this aspect, community building will be hampered, and thus cohesive neighbourhoods will be lacking. To this end, social innovation is proposed as a solution to the Zanemvula development. The issue of social development needs to placed back on the housing agenda, as is stated in the latest Housing Act.
- Full Text:
- Date Issued: 2019
- Authors: Williams-Bruinders, Leizel
- Date: 2019
- Subjects: Housing -- South Africa , City planning -- South Africa Cities and towns -- Research Urban geography
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/44390 , vital:37161
- Description: In the past twenty years we have seen the South African government deliver the largest number of houses in the world (NDHS, 2011). However, this great effort does not appeal to the principles that policies have set out in terms of equality. Along with the delivery of this high level of state funded housing, many of the RDP dwellers feel as though they have been marginalised and forced out of the area of opportunity, namely, the CBD and the northern suburbs (Huchzermeyer, 2003). Many researchers believe that the South African housing delivery pattern resembles that of apartheid segregationist planning, which exacerbated the social inequalities in the country (Huchzermeyer, 2003; Donaldson, 2001; Harrison et al., 2003). To gain an in-depth understanding of the lived experiences of residents of a low-cost housing settlement, an interpretative phenomenological analysis was undertaken. The emergent themes emanating from the research study revealed that social problems were pertinent factors to the lack of formulation of community social cohesion. Without this aspect, community building will be hampered, and thus cohesive neighbourhoods will be lacking. To this end, social innovation is proposed as a solution to the Zanemvula development. The issue of social development needs to placed back on the housing agenda, as is stated in the latest Housing Act.
- Full Text:
- Date Issued: 2019
The separation of platinum and gold from an industrial feed solution
- Authors: Louw, Talana
- Date: 2008
- Subjects: Platinum -- Separation , Gold , Separation -- Technology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10400 , http://hdl.handle.net/10948/731 , Platinum -- Separation , Gold , Separation -- Technology
- Description: In this thesis, the aim was to develop resins which are platinum and gold specific to be utilized for the early removal of these metals from the industrial feed. Efforts were therefore directed towards the synthesis of silica based resins with active centra which were designed for platinum and gold specificity respectively. The large chlorometallate ions in the feed stream were characterized in terms of physical parameters relevant to phase distribution namely distortability (RD), charge density, softness (σ) etc. Matching cations for each of the types were investigated. In order to attempt the design of platinum specific resins different structural amines were used to aminate the silicone precursor and subsequently to fix these onto the silica framework. Two different solvents i.e. alcohol and dmf were used for this process, resulting in two sets of resins with different properties. For gold specific resins, various polyethers were attached to a different type of silicone precursor, which was attached to the silica framework. The design was based on previous experience with these ions with reference to their behaviour towards different types of cations. The platinum species PtCl6 2- and PtCl4 2-, the gold species AuCl4 -, as well as the most important contaminants in the feed stream were typified bearing in mind size, charge, charge density and distortability. Different types of cationic centra having differences in charge density, stereochemical crowding and extent of hydrophobicity were synthesized and tested both as solvent extractants (where possible) and silica based resins. The results indicated that partly screened secondary ammonium cationic resin species, which could be regarded as “intermediate”, proved to be satisfactory both in their high percentage extraction for PtCl4 2- and rejection of contaminants like chlororhodates, chloroiridates(III) and FeCl4 -. It was, however, necessary to work at a redox potential where iridium(IV) in the form of IrCl6 2- is absent. Various 2-aminoalkane resins were prepared with variation in the length of alkane group and synthesized in the two different solvents. The latter resulted in two sets of resins with different compactness also having significantly different properties with reference to platinum specificity, HCl effect and stripping potential. The 2- aminobutane and 2-aminoheptane resins both proved to be very satisfactory platinum specific resins with respect to selectivity, platinum capacity and stripping potential. The various physical parameters could be utilized to accommodate the chemical behaviour. To obtain gold specific resins, experiments were performed with resins having oxygen-donor atoms which can readily be protonated to form onium type cations for example amides and ether oxygen atoms. In the case of the latter, various polyethers with a different number of ether groups (polyether groups linked by ethylene and propylene groups) and variations of hydrophobicity (by substitution) have also been studied. Linked to the polyether groups were alkane and aryl groups. Those having 8 to 10 ether groups and aromatic tail ends proved to be moderately successful in terms of gold capacity and sharp breakthrough curves of their columns, however, platinum could not be very effectively rejected.
- Full Text:
- Date Issued: 2008
- Authors: Louw, Talana
- Date: 2008
- Subjects: Platinum -- Separation , Gold , Separation -- Technology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10400 , http://hdl.handle.net/10948/731 , Platinum -- Separation , Gold , Separation -- Technology
- Description: In this thesis, the aim was to develop resins which are platinum and gold specific to be utilized for the early removal of these metals from the industrial feed. Efforts were therefore directed towards the synthesis of silica based resins with active centra which were designed for platinum and gold specificity respectively. The large chlorometallate ions in the feed stream were characterized in terms of physical parameters relevant to phase distribution namely distortability (RD), charge density, softness (σ) etc. Matching cations for each of the types were investigated. In order to attempt the design of platinum specific resins different structural amines were used to aminate the silicone precursor and subsequently to fix these onto the silica framework. Two different solvents i.e. alcohol and dmf were used for this process, resulting in two sets of resins with different properties. For gold specific resins, various polyethers were attached to a different type of silicone precursor, which was attached to the silica framework. The design was based on previous experience with these ions with reference to their behaviour towards different types of cations. The platinum species PtCl6 2- and PtCl4 2-, the gold species AuCl4 -, as well as the most important contaminants in the feed stream were typified bearing in mind size, charge, charge density and distortability. Different types of cationic centra having differences in charge density, stereochemical crowding and extent of hydrophobicity were synthesized and tested both as solvent extractants (where possible) and silica based resins. The results indicated that partly screened secondary ammonium cationic resin species, which could be regarded as “intermediate”, proved to be satisfactory both in their high percentage extraction for PtCl4 2- and rejection of contaminants like chlororhodates, chloroiridates(III) and FeCl4 -. It was, however, necessary to work at a redox potential where iridium(IV) in the form of IrCl6 2- is absent. Various 2-aminoalkane resins were prepared with variation in the length of alkane group and synthesized in the two different solvents. The latter resulted in two sets of resins with different compactness also having significantly different properties with reference to platinum specificity, HCl effect and stripping potential. The 2- aminobutane and 2-aminoheptane resins both proved to be very satisfactory platinum specific resins with respect to selectivity, platinum capacity and stripping potential. The various physical parameters could be utilized to accommodate the chemical behaviour. To obtain gold specific resins, experiments were performed with resins having oxygen-donor atoms which can readily be protonated to form onium type cations for example amides and ether oxygen atoms. In the case of the latter, various polyethers with a different number of ether groups (polyether groups linked by ethylene and propylene groups) and variations of hydrophobicity (by substitution) have also been studied. Linked to the polyether groups were alkane and aryl groups. Those having 8 to 10 ether groups and aromatic tail ends proved to be moderately successful in terms of gold capacity and sharp breakthrough curves of their columns, however, platinum could not be very effectively rejected.
- Full Text:
- Date Issued: 2008
The selective dechlorination of poly-chlorophenols
- Authors: Thomas, Maxwell Paul
- Date: 2009
- Subjects: Sewage -- Purification -- Chlorination , Pesticides -- Toxicology , Chlorine -- Toxicology
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10391 , http://hdl.handle.net/10948/1124 , Sewage -- Purification -- Chlorination , Pesticides -- Toxicology , Chlorine -- Toxicology
- Description: Liquid phase catalytic hydrodechlorinations can provide a convenient and environmentally friendly method for treating organic chlorinated compounds in waste streams generated during the manufacturing of agrochemicals. During such treatment hydrochloric acid is generated as a by-product, which can be easily neutralized employing a base to yield an inorganic salt. This work describes the results obtained during the liquid phase hydrodechlorination of 2,6-dichlorophenol (2,6-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP). The hydrodechlorination of these chlorinated phenolic compounds in a mixture of methanol and water was investigated using supported and unsupported palladium catalysts to yield lower chlorinated phenols or phenol. Various parameters were investigated such as catalyst concentration, ammonium formate concentration, effect of base addition and effect of temperature. During this study two methods of hydrodechlorination were also investigated such as hydride-transfer hydrogenolysis, using ammonium formate, and hydrogenolysis, using dihydrogen. These methods offer a mild treatment in terms of the reaction temperature with temperatures used below 800C. A comparison of the palladium catalyst systems using these methods also showed that Pd/C produced the best results in terms of the hydrodechlorination rate and the selectivity towards phenol. When the ammonium formate method was used, complete hydrodechlorination of both substrates was achieved in 1h of reaction time at a selectivity of 100 percent towards phenol. A comparison of the method using dihydrogen and Pd/C showed that the reaction rate and the selectivity towards phenol during the hydrodechlorination of 2,6-DCP were 87.92 percent and 93.30 percent. Similarly, the reaction rate and selectivity during 2,4,6- TCP hydrodechlorination were 63.77 percent and 70.57 percent. These results were achieved in a reaction time of 3 hours. A high catalyst loading increases the reaction rate at the expense of selectivity, due to the formation of cyclohexanone, formed during further hydrogenation of phenol. The formation of cyclohexanone was limited at high temperatures (ca. 800C) with none detected during the hydrodechlorination of 2,6-DCP and 0.19 percent during the hydrodechlorination of 2,4,6-TCP. Evaluation of the hydrodechlorination parameters showed that the catalytic efficiency of the Pd/C catalysts was inhibited as the reaction proceeded due to the formation of HCl as by-product. A significant increase in the reaction rate was achieved when the reaction was performed in the presence of an inorganic base, which neutralized HCl.
- Full Text:
- Date Issued: 2009
- Authors: Thomas, Maxwell Paul
- Date: 2009
- Subjects: Sewage -- Purification -- Chlorination , Pesticides -- Toxicology , Chlorine -- Toxicology
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10391 , http://hdl.handle.net/10948/1124 , Sewage -- Purification -- Chlorination , Pesticides -- Toxicology , Chlorine -- Toxicology
- Description: Liquid phase catalytic hydrodechlorinations can provide a convenient and environmentally friendly method for treating organic chlorinated compounds in waste streams generated during the manufacturing of agrochemicals. During such treatment hydrochloric acid is generated as a by-product, which can be easily neutralized employing a base to yield an inorganic salt. This work describes the results obtained during the liquid phase hydrodechlorination of 2,6-dichlorophenol (2,6-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP). The hydrodechlorination of these chlorinated phenolic compounds in a mixture of methanol and water was investigated using supported and unsupported palladium catalysts to yield lower chlorinated phenols or phenol. Various parameters were investigated such as catalyst concentration, ammonium formate concentration, effect of base addition and effect of temperature. During this study two methods of hydrodechlorination were also investigated such as hydride-transfer hydrogenolysis, using ammonium formate, and hydrogenolysis, using dihydrogen. These methods offer a mild treatment in terms of the reaction temperature with temperatures used below 800C. A comparison of the palladium catalyst systems using these methods also showed that Pd/C produced the best results in terms of the hydrodechlorination rate and the selectivity towards phenol. When the ammonium formate method was used, complete hydrodechlorination of both substrates was achieved in 1h of reaction time at a selectivity of 100 percent towards phenol. A comparison of the method using dihydrogen and Pd/C showed that the reaction rate and the selectivity towards phenol during the hydrodechlorination of 2,6-DCP were 87.92 percent and 93.30 percent. Similarly, the reaction rate and selectivity during 2,4,6- TCP hydrodechlorination were 63.77 percent and 70.57 percent. These results were achieved in a reaction time of 3 hours. A high catalyst loading increases the reaction rate at the expense of selectivity, due to the formation of cyclohexanone, formed during further hydrogenation of phenol. The formation of cyclohexanone was limited at high temperatures (ca. 800C) with none detected during the hydrodechlorination of 2,6-DCP and 0.19 percent during the hydrodechlorination of 2,4,6-TCP. Evaluation of the hydrodechlorination parameters showed that the catalytic efficiency of the Pd/C catalysts was inhibited as the reaction proceeded due to the formation of HCl as by-product. A significant increase in the reaction rate was achieved when the reaction was performed in the presence of an inorganic base, which neutralized HCl.
- Full Text:
- Date Issued: 2009
The role of apex predators in ecosystem function: fear triggered cascades regulated by differential prey vulnerability
- Authors: Le Roux, Elizabeth
- Date: 2016
- Subjects: Top predators -- Ecology Predation (Biology)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/14774 , vital:27849
- Description: Trophic cascades involving large terrestrial mammals are very seldom empirically demonstrated. The high species diversity often associated with terrestrial systems is thought to modulate the strength of trophic cascades. In speciose systems, species often vary in vulnerability to consumption, hence some species are less responsive to top-down pressure. African large mammalian herbivores are highly diverse and vary greatly in body size, a characteristic linked to vulnerability to predation. Moreover, Africa is one of the last places to still support megaherbivores, species that have grown large enough to be practically impervious to non-human predation. Thus an African ecosystem is the ideal setting to explore trophic cascades in speciose terrestrial systems. In this study I explored patterns in trophic interaction amongst carnivores, vulnerable mesoherbivore and predator-invulnerable megaherbivores in an intact African savanna at a variety of spatial scales. I examined the mechanistic links between trophic levels at the patch scale through fine scale empirical manipulation of predation risk. In addition, I assessed the landscape scale biological relevance of these trophic interactions through correlative observations over large spatiotemporal scales. I present the first evidence of community level trophic cascades explicitly involving megaherbivores. I demonstrate how megaherbivores’ disregard of predation risk masks the effects of predator-triggered trophic cascades and weakens their impact on the ecosystem. The risk of predation triggered a spatial response in vulnerable species, driving them into safe areas, yet did not influence the space use of megaherbivores. This species-specific spatial response had contrasting effects on nutrient distribution. Vulnerable herbivores’ fear-induced foraging behaviour led to localised nutrient accumulation whereas the foraging behaviour of predator-invulnerable megaherbivores led to nutrient redistribution across the landscape. In addition, the fear-driven spatial differences in mesoherbivore grazing impact and nutrient deposition led to landscape scale changes in the distribution and persistence of herbivore maintained grass communities, so-called grazing lawns. However, the grazing activity of the in-vulnerable megagrazer, white rhino (Ceratotherium simum) weakened the effect of this trophic cascade by creating and maintaining grazing lawns within the risky habitat avoided by mesograzers. This study contributes to our understanding of what drives the variation among patterns of trophic control and provides the first evidence of the modulating influence that megaherbivores have on predator-triggered trophic cascades.
- Full Text:
- Date Issued: 2016
- Authors: Le Roux, Elizabeth
- Date: 2016
- Subjects: Top predators -- Ecology Predation (Biology)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/14774 , vital:27849
- Description: Trophic cascades involving large terrestrial mammals are very seldom empirically demonstrated. The high species diversity often associated with terrestrial systems is thought to modulate the strength of trophic cascades. In speciose systems, species often vary in vulnerability to consumption, hence some species are less responsive to top-down pressure. African large mammalian herbivores are highly diverse and vary greatly in body size, a characteristic linked to vulnerability to predation. Moreover, Africa is one of the last places to still support megaherbivores, species that have grown large enough to be practically impervious to non-human predation. Thus an African ecosystem is the ideal setting to explore trophic cascades in speciose terrestrial systems. In this study I explored patterns in trophic interaction amongst carnivores, vulnerable mesoherbivore and predator-invulnerable megaherbivores in an intact African savanna at a variety of spatial scales. I examined the mechanistic links between trophic levels at the patch scale through fine scale empirical manipulation of predation risk. In addition, I assessed the landscape scale biological relevance of these trophic interactions through correlative observations over large spatiotemporal scales. I present the first evidence of community level trophic cascades explicitly involving megaherbivores. I demonstrate how megaherbivores’ disregard of predation risk masks the effects of predator-triggered trophic cascades and weakens their impact on the ecosystem. The risk of predation triggered a spatial response in vulnerable species, driving them into safe areas, yet did not influence the space use of megaherbivores. This species-specific spatial response had contrasting effects on nutrient distribution. Vulnerable herbivores’ fear-induced foraging behaviour led to localised nutrient accumulation whereas the foraging behaviour of predator-invulnerable megaherbivores led to nutrient redistribution across the landscape. In addition, the fear-driven spatial differences in mesoherbivore grazing impact and nutrient deposition led to landscape scale changes in the distribution and persistence of herbivore maintained grass communities, so-called grazing lawns. However, the grazing activity of the in-vulnerable megagrazer, white rhino (Ceratotherium simum) weakened the effect of this trophic cascade by creating and maintaining grazing lawns within the risky habitat avoided by mesograzers. This study contributes to our understanding of what drives the variation among patterns of trophic control and provides the first evidence of the modulating influence that megaherbivores have on predator-triggered trophic cascades.
- Full Text:
- Date Issued: 2016