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
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
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
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 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 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
The potential of Raman spectroscopy in distinguishing between wool and mohair fibres
- Authors: Notayi, Mzwamadoda
- Date: 2020
- Subjects: Textile fabrics , Textile fibers -- Mechanical properties Wool -- Dissertations Mohair -- Dissertations
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49248 , vital:41614
- Description: The possible application of the FT Raman, Raman micro-spectroscopy and ATR-FTIR micro-spectroscopy, have been investigated for distinguishing between wool and mohair. Highly identical Raman and FTIR spectra were obtained from the two fibre types, indicating that indeed they share similar basic molecular structural chemistry. The analysis of the amide I through curve fitting of wool and mohair FT Raman spectra showed that the protein and polypeptide secondary structure exists mainly in the α-helical structural conformation with smaller proportions of β-pleated sheet and β-Turns. These proportions, however, could not be used to distinguish between wool and mohair, due to the significant overlap observed between the two fibres. This study also determined the disulphide contents for possibly distinguishing between wool and mohair fibres, with the average and standard deviation values of 0.20±0.04 and 0.17±0.03 for wool and mohair, respectively, being found. Despite the mean values being found to differ statistically significant (p<0.05), a considerable overlap was observed, posing a doubt in the possible application of the method for distinguishing between the two fibres and blend composition analysis of the two fibres. The application of ratiometric analysis, based on the relative peak heights of certain FT Raman bands, showed that a combination of ratios A (I2932/I1450) and D (I508/I1450) could hold great potential in distinguishing between wool and mohair fibre samples. The individual values of ratios A and D varied a great deal from one mohair sample to the other and even more from one wool sample to another, with the individual values for ratio A ranging from 2.71-3.68 and 2.35-3.08 for wool and mohair, respectively, while ratio D ranged from 0.18-0.32 and 0.17-0.22 for wool and mohair, respectively. An important observation from this study is that if, for an unknown sample, if individual values of ratios A and D exceed 3.1 and 0.22, respectively, are found then the sample is most likely to be either a pure wool or blend of wool and mohair, whereas if all the values fall below the two threshold values, then the unknown sample can be declared a pure mohair sample. A Raman spectral database or library of approximately 100 high quality Raman average spectra of wool and mohair fibres has been established for the Bruker 80V FTIR/Raman spectrophotometer at the Nelson Mandela University (NMU). Although this has not been fully validated due to the unforeseen frequent breakdown encountered with the FT Raman system, at this stage, it has been realized that verification of unknown materials is highly possible. A great need for the development of a classification model based on multivariate or chemometrics has been realized. An ATR-FTIR LUMOS micro-spectroscopic system was also investigated for the possible application in distinguishing between wool and mohair single fibres. The amide I/II band ratios were determined for both wool and mohair fibres to distinguish between the two fibre types. The mean and standard deviation values of 1.20±0.02 and 1.21±0.01 for mohair and wool, respectively, were found and were shown not to differ statistically significant (p˃0.05). The secondary structure analysis showed that the content of the α-helical secondary structure might be different between the two fibre types, with a great overlap of individual values, however, being observed between the two fibre types (wool and mohair), raising concerns in the possible application of the α-helical content for distinguishing the two fibres.
- Full Text:
- Date Issued: 2020
- Authors: Notayi, Mzwamadoda
- Date: 2020
- Subjects: Textile fabrics , Textile fibers -- Mechanical properties Wool -- Dissertations Mohair -- Dissertations
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49248 , vital:41614
- Description: The possible application of the FT Raman, Raman micro-spectroscopy and ATR-FTIR micro-spectroscopy, have been investigated for distinguishing between wool and mohair. Highly identical Raman and FTIR spectra were obtained from the two fibre types, indicating that indeed they share similar basic molecular structural chemistry. The analysis of the amide I through curve fitting of wool and mohair FT Raman spectra showed that the protein and polypeptide secondary structure exists mainly in the α-helical structural conformation with smaller proportions of β-pleated sheet and β-Turns. These proportions, however, could not be used to distinguish between wool and mohair, due to the significant overlap observed between the two fibres. This study also determined the disulphide contents for possibly distinguishing between wool and mohair fibres, with the average and standard deviation values of 0.20±0.04 and 0.17±0.03 for wool and mohair, respectively, being found. Despite the mean values being found to differ statistically significant (p<0.05), a considerable overlap was observed, posing a doubt in the possible application of the method for distinguishing between the two fibres and blend composition analysis of the two fibres. The application of ratiometric analysis, based on the relative peak heights of certain FT Raman bands, showed that a combination of ratios A (I2932/I1450) and D (I508/I1450) could hold great potential in distinguishing between wool and mohair fibre samples. The individual values of ratios A and D varied a great deal from one mohair sample to the other and even more from one wool sample to another, with the individual values for ratio A ranging from 2.71-3.68 and 2.35-3.08 for wool and mohair, respectively, while ratio D ranged from 0.18-0.32 and 0.17-0.22 for wool and mohair, respectively. An important observation from this study is that if, for an unknown sample, if individual values of ratios A and D exceed 3.1 and 0.22, respectively, are found then the sample is most likely to be either a pure wool or blend of wool and mohair, whereas if all the values fall below the two threshold values, then the unknown sample can be declared a pure mohair sample. A Raman spectral database or library of approximately 100 high quality Raman average spectra of wool and mohair fibres has been established for the Bruker 80V FTIR/Raman spectrophotometer at the Nelson Mandela University (NMU). Although this has not been fully validated due to the unforeseen frequent breakdown encountered with the FT Raman system, at this stage, it has been realized that verification of unknown materials is highly possible. A great need for the development of a classification model based on multivariate or chemometrics has been realized. An ATR-FTIR LUMOS micro-spectroscopic system was also investigated for the possible application in distinguishing between wool and mohair single fibres. The amide I/II band ratios were determined for both wool and mohair fibres to distinguish between the two fibre types. The mean and standard deviation values of 1.20±0.02 and 1.21±0.01 for mohair and wool, respectively, were found and were shown not to differ statistically significant (p˃0.05). The secondary structure analysis showed that the content of the α-helical secondary structure might be different between the two fibre types, with a great overlap of individual values, however, being observed between the two fibre types (wool and mohair), raising concerns in the possible application of the α-helical content for distinguishing the two fibres.
- Full Text:
- Date Issued: 2020
The influence of the environment on nature-based adventure tourism
- Authors: Giddy, Julia K
- Date: 2016
- Subjects: Human ecology , Tourism -- Environmental aspects , Adventure travel
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/9296 , vital:26561
- Description: Adventure tourism (AT) is a rapidly growing subsector of the tourism industry. With the recent increase in AT, the nature of the industry is undergoing major changes. Originally a small and relatively specialized sector of tourism, AT is now expanding to include ommercialized and larger scale operations. This creates a need to re-evaluate the AT industry in the context of these new, highly commercialized and often “manufactured” adventure experiences. Although there are many definitions and conceptualizations of what onstitutes AT, it is most often referred to as tourism experiences that involve some element of risk and typically take place in outdoor natural environments. Inherent in the definition of AT is the natural environment, however very little research has focused on the role of the environment in AT. The interaction between humans and the environment is one of the most fundamental relationships of human existence. Within this context, existing research largely focuses on the influence of humans on the environment. However, it is important to also understand how the environment influences human behaviour. This thesis, therefore, seeks to examine the influence of the environment on humans in the AT context. It does so by analyzing three primary aspects of human-environment interaction in AT participation. The first is participants’ ‘value system’including their general perspectives of the environment and previous experience with AT. The second focuses on the relative strength and nature of environmental influences on AT motivations. The final aspect delves into the role of the environment in enhancing AT experiences and satisfaction. These assessments were done by analyzing questionnaires collected from participants in eight commercial AT operations along the Cape South Coast of South Africa. Data was primarily based on responses to statements using a 5 point Likert Scale. The responses were analyzed and discussions utilized results based on descriptive statistics, significance levels based on onesample t-tests, frequency distributions and analysis of variance (ANOVAs) which divided the data based on activity type. In addition Pearson’s Product Moment Correlations were conducted to assess linkages between different components of the thesis. The results that emerged from this thesis show that the environment plays an important role in AT participation. The value system of commercial AT participants demonstrated a level of general experience with AT as well as moderate environmental values. The strength of the environment in the motivations to participate in AT emerged quite substantially. Reflective interactions with nature (i.e. learning about the environment, and appreciating nature’s beauty) were found to be amongst the most significant internal motivation factors for participation. Interestingly, although the vast majority of research focuses on the Risk/Thrill element of AT motivations, it was not found to be an important motivation factor amongst the vast majority of AT participants. The environmental aspects of the destination were found to be, by far, the most significant external motivation factor, implying that the selection of destination for AT participation is largely based on the environment in which the activity takes place. Participants were also found to have strong, positive emotional experiences as a result of AT participation,which were significantly enhanced by the environment in which the activities took place. In addition, as a result of these positive experiences, emotionally and with the environment, participants were highly satisfied with the AT experiences. The culmination of the results discussed above was the development of a modified, empirically-tested framework for human-environment interaction in the AT context. The final framework demonstrated links between various components of human-environment interaction. Strong links were found between motivations, experiences and satisfaction while relatively weak links were found between the value system of participants and their subsequent motivations. The framework was developed for the possibility of applying it to other contexts. The findings in this thesis demonstrate that the environment does, in fact, play an important role in the interaction between humans and the environment in AT. They emphasize the relatively significant influence that the environment has on the motivations and experiences of AT participants.
- Full Text:
- Date Issued: 2016
- Authors: Giddy, Julia K
- Date: 2016
- Subjects: Human ecology , Tourism -- Environmental aspects , Adventure travel
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/9296 , vital:26561
- Description: Adventure tourism (AT) is a rapidly growing subsector of the tourism industry. With the recent increase in AT, the nature of the industry is undergoing major changes. Originally a small and relatively specialized sector of tourism, AT is now expanding to include ommercialized and larger scale operations. This creates a need to re-evaluate the AT industry in the context of these new, highly commercialized and often “manufactured” adventure experiences. Although there are many definitions and conceptualizations of what onstitutes AT, it is most often referred to as tourism experiences that involve some element of risk and typically take place in outdoor natural environments. Inherent in the definition of AT is the natural environment, however very little research has focused on the role of the environment in AT. The interaction between humans and the environment is one of the most fundamental relationships of human existence. Within this context, existing research largely focuses on the influence of humans on the environment. However, it is important to also understand how the environment influences human behaviour. This thesis, therefore, seeks to examine the influence of the environment on humans in the AT context. It does so by analyzing three primary aspects of human-environment interaction in AT participation. The first is participants’ ‘value system’including their general perspectives of the environment and previous experience with AT. The second focuses on the relative strength and nature of environmental influences on AT motivations. The final aspect delves into the role of the environment in enhancing AT experiences and satisfaction. These assessments were done by analyzing questionnaires collected from participants in eight commercial AT operations along the Cape South Coast of South Africa. Data was primarily based on responses to statements using a 5 point Likert Scale. The responses were analyzed and discussions utilized results based on descriptive statistics, significance levels based on onesample t-tests, frequency distributions and analysis of variance (ANOVAs) which divided the data based on activity type. In addition Pearson’s Product Moment Correlations were conducted to assess linkages between different components of the thesis. The results that emerged from this thesis show that the environment plays an important role in AT participation. The value system of commercial AT participants demonstrated a level of general experience with AT as well as moderate environmental values. The strength of the environment in the motivations to participate in AT emerged quite substantially. Reflective interactions with nature (i.e. learning about the environment, and appreciating nature’s beauty) were found to be amongst the most significant internal motivation factors for participation. Interestingly, although the vast majority of research focuses on the Risk/Thrill element of AT motivations, it was not found to be an important motivation factor amongst the vast majority of AT participants. The environmental aspects of the destination were found to be, by far, the most significant external motivation factor, implying that the selection of destination for AT participation is largely based on the environment in which the activity takes place. Participants were also found to have strong, positive emotional experiences as a result of AT participation,which were significantly enhanced by the environment in which the activities took place. In addition, as a result of these positive experiences, emotionally and with the environment, participants were highly satisfied with the AT experiences. The culmination of the results discussed above was the development of a modified, empirically-tested framework for human-environment interaction in the AT context. The final framework demonstrated links between various components of human-environment interaction. Strong links were found between motivations, experiences and satisfaction while relatively weak links were found between the value system of participants and their subsequent motivations. The framework was developed for the possibility of applying it to other contexts. The findings in this thesis demonstrate that the environment does, in fact, play an important role in the interaction between humans and the environment in AT. They emphasize the relatively significant influence that the environment has on the motivations and experiences of AT participants.
- Full Text:
- Date Issued: 2016
The influence of genetic relatedness on sociality and demography of female African elephants
- Authors: Munishi, Linus Kasian
- Date: 2011
- Subjects: African elephant , Wildlife conservation , Elephants -- Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10711 , http://hdl.handle.net/10948/d1011612 , African elephant , Wildlife conservation , Elephants -- Africa
- Description: Many elephant populations across Africa were or are being devastated by poaching and habitat loss, making population and range size for the species important issues of conservation concern in elephant ranging areas, including Tarangire National Park (TNP). Poaching and/or overhunting are known to have direct effects on the demography of elephant populations. The current understanding of the indirect effects of poaching on the sociality and demography of elephant populations is relatively poor, both at the group and an individual level. In this thesis the importance of genetic relatedness (as influenced by poaching) on sociality and demography of the female elephants was studied, using a combination of genetic, observation of behaviour and two decades of demography data collected from the northern subpopulation of TNP. I investigated and characterized the relatedness categories within elephant groups. Using a conceptual model for group size analysis in aggregation economies, I hypothesized that elephant populations subject to social disruptions due to poaching would exhibit characteristics of the free entry model, whereas more stable, closed populations would better fit the group-controlled model. I present a rare quantitative analysis of genetic relatedness and group size patterns among groups of adult female elephants in two wild populations: one in Tarangire National Park (TNP), Tanzania, and another in Addo Elephant National Park (AENP), South Africa. I demonstrate that the group size in African elephant populations is governed by genetic relatedness, and that poaching/overhunting has a significant influence upon the apparent group formation and size in elephants. I then focused on the effect of relatedness on agonistic interactions between adult females. I hypothesized that individual-based aggressive interactions among adult female African elephants would vary according to degree of kinship, with closely related dyads showing less aggression towards each other in resource-limited environments, thereby leading to indirect fitness benefits for individuals. As predicted, females did not show agonistic interactions to their close kin most often, and the frequency and intensity of aggressive interactions was inversely related to the degree of relatedness of the interactants. The effect of group relatedness and structure on reproductive success of individual female African elephant in TNP was also investigated. Adult female reproductive success was significantly influenced by within- group relatedness and structure. Higher reproductive success (with higher frequency of calf production and survival and more female calves produced) were more evident in the closely related groups than groups with low relatedness, suggesting that females from genetically disrupted groups are less likely to be reproductive than those in closely related groups. The possibility of negative effects of poaching on the subsequent generation of poached adult females and the alternative of a positive demographic response through reduced density was assessed by analysing the demographic patterns of the first generation (F1) females of prime-aged adult female African elephants in TNP using within- group relatedness and size. I also compared vital rate (age of first birth and interbirth interval) responses of first generation (F1) cows from Tarangire (poached) elephants with other females from poached (Northern Luangwa National Park, Zambia) and unpoached (Amboseli National Park, Kenya and Addo Elephant National Park, South Africa) populations. Group relatedness had no significant effect on sex ratio of the F1 cows‟ calves. There was a significant difference between the mean age of first birth and interbirth interval of F1 cows from the two (poached, Tarangire and unpoached, Amboseli National Park) elephant populations, suggesting that elephant populations reduced by poaching to low levels show an increase vigour through release from density constraints. Based on these results, the broader implications of secondary effects of poaching on elephant populations are critically evaluated. Also the importance of understanding the consequences of these effects is highlighted in light of other elephant conservation and management approaches. This understanding is useful in making conservation and management decisions for elephants and other biodiversity.
- Full Text:
- Date Issued: 2011
- Authors: Munishi, Linus Kasian
- Date: 2011
- Subjects: African elephant , Wildlife conservation , Elephants -- Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10711 , http://hdl.handle.net/10948/d1011612 , African elephant , Wildlife conservation , Elephants -- Africa
- Description: Many elephant populations across Africa were or are being devastated by poaching and habitat loss, making population and range size for the species important issues of conservation concern in elephant ranging areas, including Tarangire National Park (TNP). Poaching and/or overhunting are known to have direct effects on the demography of elephant populations. The current understanding of the indirect effects of poaching on the sociality and demography of elephant populations is relatively poor, both at the group and an individual level. In this thesis the importance of genetic relatedness (as influenced by poaching) on sociality and demography of the female elephants was studied, using a combination of genetic, observation of behaviour and two decades of demography data collected from the northern subpopulation of TNP. I investigated and characterized the relatedness categories within elephant groups. Using a conceptual model for group size analysis in aggregation economies, I hypothesized that elephant populations subject to social disruptions due to poaching would exhibit characteristics of the free entry model, whereas more stable, closed populations would better fit the group-controlled model. I present a rare quantitative analysis of genetic relatedness and group size patterns among groups of adult female elephants in two wild populations: one in Tarangire National Park (TNP), Tanzania, and another in Addo Elephant National Park (AENP), South Africa. I demonstrate that the group size in African elephant populations is governed by genetic relatedness, and that poaching/overhunting has a significant influence upon the apparent group formation and size in elephants. I then focused on the effect of relatedness on agonistic interactions between adult females. I hypothesized that individual-based aggressive interactions among adult female African elephants would vary according to degree of kinship, with closely related dyads showing less aggression towards each other in resource-limited environments, thereby leading to indirect fitness benefits for individuals. As predicted, females did not show agonistic interactions to their close kin most often, and the frequency and intensity of aggressive interactions was inversely related to the degree of relatedness of the interactants. The effect of group relatedness and structure on reproductive success of individual female African elephant in TNP was also investigated. Adult female reproductive success was significantly influenced by within- group relatedness and structure. Higher reproductive success (with higher frequency of calf production and survival and more female calves produced) were more evident in the closely related groups than groups with low relatedness, suggesting that females from genetically disrupted groups are less likely to be reproductive than those in closely related groups. The possibility of negative effects of poaching on the subsequent generation of poached adult females and the alternative of a positive demographic response through reduced density was assessed by analysing the demographic patterns of the first generation (F1) females of prime-aged adult female African elephants in TNP using within- group relatedness and size. I also compared vital rate (age of first birth and interbirth interval) responses of first generation (F1) cows from Tarangire (poached) elephants with other females from poached (Northern Luangwa National Park, Zambia) and unpoached (Amboseli National Park, Kenya and Addo Elephant National Park, South Africa) populations. Group relatedness had no significant effect on sex ratio of the F1 cows‟ calves. There was a significant difference between the mean age of first birth and interbirth interval of F1 cows from the two (poached, Tarangire and unpoached, Amboseli National Park) elephant populations, suggesting that elephant populations reduced by poaching to low levels show an increase vigour through release from density constraints. Based on these results, the broader implications of secondary effects of poaching on elephant populations are critically evaluated. Also the importance of understanding the consequences of these effects is highlighted in light of other elephant conservation and management approaches. This understanding is useful in making conservation and management decisions for elephants and other biodiversity.
- Full Text:
- Date Issued: 2011
The identification of criteria to be utilised in mathematical diagnostic tests
- Authors: Wagner-Welsh, Shirley Joy
- Date: 2008
- Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
- Full Text:
- Date Issued: 2008
- Authors: Wagner-Welsh, Shirley Joy
- Date: 2008
- Subjects: Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10501 , http://hdl.handle.net/10948/708 , Educational tests and measurements -- South Africa -- Port Elizabeth , Mathematical ability -- Testing , Ability -- Testing , Guidance test battery for secondary pupils , Mathematics -- Study and teaching -- South Africa
- Description: School-related mistakes and low pass rates have led this researcher to perceive that some students are not adequately prepared for Mathematics 1. To address the problem of under-preparedness overseas universities use placement or diagnostic tests. Diagnostic testing identifies areas of weakness and provides information to guide the development of appropriate remedial support. This researcher embarked on a study to identify the sub-domains (criteria) that should be included in a diagnostic Mathematics test battery at the NMMU. An analysis of first-year curricula was undertaken to determine the required Mathematical pre-knowledge and skills entry-level students should have. Thereafter, the required pre-knowledge and skills were reflected against the standard grade school syllabi. From this it was determined that the school learners should acquire the necessary pre-knowledge and skills for university success as part of the school syllabus. However, in reality this is not the case as the researcher and other Mathematics lecturers identified a number of basic errors that incoming students make. This suggests that they have not developed all the required knowledge and skills. Furthermore, their performance in the matriculation examinations does not provide an adequate measure of the requisite Mathematical pre-knowledge and skills necessary for success at university-level Mathematics. No suitable existing diagnostic Mathematics test could be found. By utilizing both an action research as well as a test development methodology, the researcher thus proceeded to delineate the sub-domains that should be included in a diagnostic Mathematics test battery. Thereafter, test specifications were developed for two pilot tests and items were developed or sourced. The constructed response item-type was chosen for the pilot tests as it was argued that this item-type was more useful to use in a diagnostic test than a multiple-choice item format, for example. The pilot test battery, which consisted of a pilot Arithmetic and Algebra and Calculus tests, was administered to a sample of first-year students at the NMMU in 2004 and their performance in Mathematics at the end of the first year was tracked. Tests were scored holistically and analytically to provide a rich source of information. Thereafter, the test results were analysed to obtain evidence on the content validity of the pilot tests, including the item difficulty values and the item-total correlations; to determine the predictive validity of performance on the pilot tests with respect to final first-year Mathematics marks; and their reliability was determined using the Cronbach’s Alpha statistic. These findings suggest that appropriate sub-domains (criteria) were delineated and the items appropriately covered these sub-domains (i.e. the content validity of the pilot tests is acceptable). Furthermore, the predictive validity of the pilot ix tests was found to be acceptable in that significant correlations were found between the pilot tests and performance in first-year Mathematics. Finally, the pilot tests were found to be reliable. Based on the results, suggestions are made regarding how to refine the diagnostic test battery and the research related to it. The final diagnostic Mathematics test battery holds much potential to be able to assist in the early identification of at-risk students who can be timeously placed in developmentally appropriate Mathematics modules or provided with appropriate remedial intervention.
- Full Text:
- Date Issued: 2008
The extraction, quantification and application of high-value biological compounds from olive oil processing waste
- Authors: Postma-Botha, Marthie
- Date: 2018
- Subjects: Organic compounds , Biochemistry , Biomass energy , Olive oil industry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/34383 , vital:33371
- Description: Olive oil processing waste (pomace) as a by-product of the olive oil industry is regarded as a rich source of high-value biological compounds exhibiting antioxidant potential. The objective of the present work was to obtain a concentrated extract of high-value biological antioxidants from the pomace. The effect of extraction conditions on the concentration of the bioactive compounds in the extracts was investigated. The simultaneous recovery of both hydrophilic and lipophilic high-value biological compounds exhibiting antioxidant potential was achieved through a one-step extraction method under reduced pressure using a non-toxic solvent blend. A multilevel experimental design was implemented with the aim of optimising the recovery of selected compounds, namely, hydroxytyrosol, tyrosol, oleuropein, α-tocopherol and squalene from olive pomace by using solvent blends of n-heptane, d-limonene, ethanol and water. The factors considered were: extraction time, percentage composition of solvent blends and extraction temperature. The results suggested that a good recovery of the hydrophilic polyphenolic compounds, namely, hydroxytyrosol, tyrosol and oleuropein, as well as the lipophilic compounds, α-tocopherol and squalene may be achieved at a solvent temperature of 60°C at 400 mbar with a solvent blend of 30% n-heptane, 50% ethanol and 20% water and an extraction time of two hours. It was found that freeze-drying the pomace before extraction minimised production of artefacts, avoided degradation of biophenols, ensured long term stability of a reproducible sample and achieved better recovery of important hydrophilic and lipophilic bioactive compounds. Since the bioactive compounds are temperature sensitive, the extraction was performed under reduced pressure in order to reduce solvent reflux temperature and to improve extraction efficiency. The quantitative and qualitative determinations of the aforementioned high-value compounds were performed by high-performance liquid chromatography (HPLC), which revealed that the hydrophilic polyphenolic as well as the lipophilic α-tocopherol and squalene were present. In this study hydroxytyrosol, tyrosol, oleuropein, α-tocopherol and squalene were extracted from the pomace of two olive cultivars (Frantoio and Coratina). A comparison among the two cultivars showed quantitative differences between the two cultivars in all five high-value biological compounds and in the antioxidant capacity of the extracts evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2- picrylhydrazyl (DPPH) free radical. Coratina cultivar was found to have a significantly higher antioxidant capacity than Frantoio due to the much greater oleuropein content in the Coratina compared to the Frantoio although Frantoio had a significantly greater amount of hydroxytyrosol. The stability of olive waste extracts stored at four temperatures was also investigated and the results show that increased temperatures caused greater extent of degradation of both the hydrophilic polyphenolic and lipophilic compounds. The proposed optimum storage condition for the olive pomace extracts was found to be at 5°C in the absence of light. The extracts were incorporated into two cosmetic formulations and were found, from a stability study, to be stable at room temperature and optimally stable at 5°C in the absence of light.
- Full Text:
- Date Issued: 2018
- Authors: Postma-Botha, Marthie
- Date: 2018
- Subjects: Organic compounds , Biochemistry , Biomass energy , Olive oil industry
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/34383 , vital:33371
- Description: Olive oil processing waste (pomace) as a by-product of the olive oil industry is regarded as a rich source of high-value biological compounds exhibiting antioxidant potential. The objective of the present work was to obtain a concentrated extract of high-value biological antioxidants from the pomace. The effect of extraction conditions on the concentration of the bioactive compounds in the extracts was investigated. The simultaneous recovery of both hydrophilic and lipophilic high-value biological compounds exhibiting antioxidant potential was achieved through a one-step extraction method under reduced pressure using a non-toxic solvent blend. A multilevel experimental design was implemented with the aim of optimising the recovery of selected compounds, namely, hydroxytyrosol, tyrosol, oleuropein, α-tocopherol and squalene from olive pomace by using solvent blends of n-heptane, d-limonene, ethanol and water. The factors considered were: extraction time, percentage composition of solvent blends and extraction temperature. The results suggested that a good recovery of the hydrophilic polyphenolic compounds, namely, hydroxytyrosol, tyrosol and oleuropein, as well as the lipophilic compounds, α-tocopherol and squalene may be achieved at a solvent temperature of 60°C at 400 mbar with a solvent blend of 30% n-heptane, 50% ethanol and 20% water and an extraction time of two hours. It was found that freeze-drying the pomace before extraction minimised production of artefacts, avoided degradation of biophenols, ensured long term stability of a reproducible sample and achieved better recovery of important hydrophilic and lipophilic bioactive compounds. Since the bioactive compounds are temperature sensitive, the extraction was performed under reduced pressure in order to reduce solvent reflux temperature and to improve extraction efficiency. The quantitative and qualitative determinations of the aforementioned high-value compounds were performed by high-performance liquid chromatography (HPLC), which revealed that the hydrophilic polyphenolic as well as the lipophilic α-tocopherol and squalene were present. In this study hydroxytyrosol, tyrosol, oleuropein, α-tocopherol and squalene were extracted from the pomace of two olive cultivars (Frantoio and Coratina). A comparison among the two cultivars showed quantitative differences between the two cultivars in all five high-value biological compounds and in the antioxidant capacity of the extracts evaluated by measuring the radical scavenging effect on 1,1-diphenyl-2- picrylhydrazyl (DPPH) free radical. Coratina cultivar was found to have a significantly higher antioxidant capacity than Frantoio due to the much greater oleuropein content in the Coratina compared to the Frantoio although Frantoio had a significantly greater amount of hydroxytyrosol. The stability of olive waste extracts stored at four temperatures was also investigated and the results show that increased temperatures caused greater extent of degradation of both the hydrophilic polyphenolic and lipophilic compounds. The proposed optimum storage condition for the olive pomace extracts was found to be at 5°C in the absence of light. The extracts were incorporated into two cosmetic formulations and were found, from a stability study, to be stable at room temperature and optimally stable at 5°C in the absence of light.
- Full Text:
- Date Issued: 2018
The evaluation of a pedagogical-program development environment for Novice programmers : a comparative study
- Authors: Vogts, Dieter
- Date: 2007
- Subjects: Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10477 , http://hdl.handle.net/10948/638 , Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Description: It is an acknowledged fact that many novice programmers experience difficulty in the process of learning to program. One of the contributing factors to this difficulty is the Program Development Environment (PDE). Professional-PDEs are those developed specifically for professional programmers, but are often used by educational institutions in the instruction of programming. It has long been accepted that such environments are inappropriate in the instruction of programming due to unnecessary complexity and lack of support for novice programmers in the learning process. Numerous pedagogical-PDEs supporting the mechanics of programming have been developed in response to this. A review of literature, however, indicates that very limited empirical studies comparing pedagogical-PDEs and professional-PDEs have been conducted. The current study investigates whether there are measurable benefits to using a pedagogical-PDE supporting the mechanics of programming in the instruction of programming instead of a professional-PDE. A comparative study of this nature requires a representative pedagogical-PDE and representative professional-PDE be compared with one another. The first part of the current study determines a set of requirements that a pedagogical- PDE should adhere to based on literature. A set of representative features for a pedagogical-PDE is derived by examining the features of existing PDEs in conjunction with the set of requirements. Based on these features, a pedagogical-PDE, known as SimplifIDE, is developed that implements the representative set of features and that meets are the requirements for a pedagogical-PDE. The second part of the current study is the specification and administration of an empirical experiment in which SimplifIDE and Borland© DelphiTM are compared with one another. A holistic approach in determining the differences between the PDEs is taken and three main areas are examined, namely academic performance, perceptions and programming behavior.
- Full Text:
- Date Issued: 2007
- Authors: Vogts, Dieter
- Date: 2007
- Subjects: Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10477 , http://hdl.handle.net/10948/638 , Computer programming -- Study and teaching , Programming languages (Electronic computers) , Web site development
- Description: It is an acknowledged fact that many novice programmers experience difficulty in the process of learning to program. One of the contributing factors to this difficulty is the Program Development Environment (PDE). Professional-PDEs are those developed specifically for professional programmers, but are often used by educational institutions in the instruction of programming. It has long been accepted that such environments are inappropriate in the instruction of programming due to unnecessary complexity and lack of support for novice programmers in the learning process. Numerous pedagogical-PDEs supporting the mechanics of programming have been developed in response to this. A review of literature, however, indicates that very limited empirical studies comparing pedagogical-PDEs and professional-PDEs have been conducted. The current study investigates whether there are measurable benefits to using a pedagogical-PDE supporting the mechanics of programming in the instruction of programming instead of a professional-PDE. A comparative study of this nature requires a representative pedagogical-PDE and representative professional-PDE be compared with one another. The first part of the current study determines a set of requirements that a pedagogical- PDE should adhere to based on literature. A set of representative features for a pedagogical-PDE is derived by examining the features of existing PDEs in conjunction with the set of requirements. Based on these features, a pedagogical-PDE, known as SimplifIDE, is developed that implements the representative set of features and that meets are the requirements for a pedagogical-PDE. The second part of the current study is the specification and administration of an empirical experiment in which SimplifIDE and Borland© DelphiTM are compared with one another. A holistic approach in determining the differences between the PDEs is taken and three main areas are examined, namely academic performance, perceptions and programming behavior.
- Full Text:
- Date Issued: 2007
The effects of frost on Albany subtropical thicket and nama-karoo shrubland in South Africa
- Authors: Duker, Robert
- Date: 2018
- Subjects: Shrubland ecology , Desert ecology -- South Africa Ecological surveys -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/29951 , vital:30799
- Description: Numerous treeless shrublands exist in areas where climates should support tree growth. In South Africa, the predominantly lowland Albany Subtropical Thicket (thicket), and the predominantly upland Nama-Karoo semi-desert shrubland share a boundary that is often abrupt and analogous to a forest-shrubland alpine ‘treeline’. This boundary exists across similar climatic and edaphic conditions, and field observations and leaf-level experiments suggest that certain thicket component species have lower levels of frost tolerance than the Nama-Karoo shrubs. The hypothesis is that the occurrence of sub-zero temperatures and frost dictates the position of this boundary at both the local landscape and broader regional levels. I test this hypothesis by quantifying leaf-level and whole-plant freezing tolerance of thicket and Nama-Karoo shrubland species, in relation to their local- and regional-scale distribution, and by modelling the occurrence of frost in the mountainous areas of the coastal lowlands relation to 1) naturally occurring boundaries between these two vegetation types, and 2) levels of aboveground net primary productivity (NPP) of Portulacaria afra Jacq. (spekboom) cuttings (planted with the aim of restoring livestock-degraded thicket). I found that the observed and modelled occurrence of frost in the local landscape has significant negative influences on the photosynthetic health, survival and growth rates of thicket component species, and that leaf-level freezing tolerance of evergreen thicket and Nama-Karoo shrubland species is strongly related to their broader regional-scale distributional thresholds. These results support the hypothesis that the occurrence of sub-zero temperatures and frost play a major role in determining the local- and regional-scale distribution of thicket and Nama-Karoo shrubland species, via their reliance on frost-defined refugia at a variety of different scales, and that the once-widespread and regionally dominant thicket vegetation contracted into small climatic refugia during the Last Glacial Maximum (LGM). These results also have major implications for landscape- and regional-level planning of livestock-degraded thicket restoration efforts that use planting of spekboom as an ecosystem engineer, and for predicting boundary shifts under the predicted future warming of global climates.
- Full Text:
- Date Issued: 2018
- Authors: Duker, Robert
- Date: 2018
- Subjects: Shrubland ecology , Desert ecology -- South Africa Ecological surveys -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/29951 , vital:30799
- Description: Numerous treeless shrublands exist in areas where climates should support tree growth. In South Africa, the predominantly lowland Albany Subtropical Thicket (thicket), and the predominantly upland Nama-Karoo semi-desert shrubland share a boundary that is often abrupt and analogous to a forest-shrubland alpine ‘treeline’. This boundary exists across similar climatic and edaphic conditions, and field observations and leaf-level experiments suggest that certain thicket component species have lower levels of frost tolerance than the Nama-Karoo shrubs. The hypothesis is that the occurrence of sub-zero temperatures and frost dictates the position of this boundary at both the local landscape and broader regional levels. I test this hypothesis by quantifying leaf-level and whole-plant freezing tolerance of thicket and Nama-Karoo shrubland species, in relation to their local- and regional-scale distribution, and by modelling the occurrence of frost in the mountainous areas of the coastal lowlands relation to 1) naturally occurring boundaries between these two vegetation types, and 2) levels of aboveground net primary productivity (NPP) of Portulacaria afra Jacq. (spekboom) cuttings (planted with the aim of restoring livestock-degraded thicket). I found that the observed and modelled occurrence of frost in the local landscape has significant negative influences on the photosynthetic health, survival and growth rates of thicket component species, and that leaf-level freezing tolerance of evergreen thicket and Nama-Karoo shrubland species is strongly related to their broader regional-scale distributional thresholds. These results support the hypothesis that the occurrence of sub-zero temperatures and frost play a major role in determining the local- and regional-scale distribution of thicket and Nama-Karoo shrubland species, via their reliance on frost-defined refugia at a variety of different scales, and that the once-widespread and regionally dominant thicket vegetation contracted into small climatic refugia during the Last Glacial Maximum (LGM). These results also have major implications for landscape- and regional-level planning of livestock-degraded thicket restoration efforts that use planting of spekboom as an ecosystem engineer, and for predicting boundary shifts under the predicted future warming of global climates.
- Full Text:
- Date Issued: 2018
The effects of environmental variability on the physiology and ecology of Cape stumpnose Rhabdosargus holubi (Steindachner, 1881) (Sparidae)
- Authors: Kisten, Yanasivan
- Date: 2018
- Subjects: Freshwater fishes -- South Africa , Fishes -- Ecology Freshwater fishes -- Ecology Estuarine ecology -- South Africa Estuaries -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/31424 , vital:31374
- Description: Estuaries are important nursery areas for early stages of marine estuarine-dependent fishes, such as the sparid Rhabdosargus holubi. Estuaries provide food, shelter from predators and optimal habitats and environmental conditions for growth and development. However, estuaries are environmentally dynamic and resident organisms must be able to adapt to rapid changes. Such changes are potentially further exacerbated anthropogenically by water and land use practices such as freshwater abstraction, impoundment, pollution and anthropogenically driven climatic change. An effective approach to better understanding the current and future impacts of these kinds of changes, is by assessing the environmental adaptability of organisms, especially to extreme conditions such as droughts and resulting water shortages, which are prevalent in some parts of southern Africa. This thesis examines the effect of various environmental changes such as salinity, turbidity and temperature on the ecology and physiology of a South African common endemic fish species, the Cape stumpnose, R. holubi. Previous work on the species have investigated short term impacts on physiology while this study investigates medium to short term impacts. The specie’s wide distribution in South Africa and tolerance enabled a range of environmental, ecological and physiological relationships to be tested in the context of a changing world. These included: 1) determining the relationship between environmental variability and the distribution and abundance of R. holubi larvae in 25 estuaries along the temperate coast of South Africa; 2) determining the relationship between environmental variability and the movement of larvae and juveniles within two permanently open estuaries; 3) determining the impact of shock and acclimatization on R. holubi salinity tolerance ranges under hypersaline conditions; 4) II determining the impact of hypersalinity on the potential long term impacts growth and skeletal deformities of juvenile R. holubi in aquaria. The findings of these studies suggest that larval occurrence and density within estuaries is a function of salinity and turbidity, by proxy indicating a preference for high freshwater inflow especially in estuary types such as permanently open estuaries. The movement of larvae and juveniles within these estuaries is also mediated by salinity, turbidity and temperature, indicating the importance of seasonality along with environmental conditions and potential olfactory recruitment cues driven by freshwater flow. Tolerance experiments showed that slower acclimation to higher salinities can expand the previously reported tolerance range indicating the potential for adaptation. Physiological experiments showed negative impacts on respiration at salinities exceeding 45, indicating potential long-term physiological effects in hypersaline conditions. Further, living at high salinities for extended periods may have potentially negative effects on long term physiology, particularly growth and skeletal development. The overall results indicate that low salinity (5–18), high turbidity (20–30 NTU) and high temperature (5–22°C) are integral to the distribution and abundance of the species in permanently open estuaries. This conforms to the general rule that estuarine-associated marine fish have higher growth rates in salinities of 12-19. However, juveniles are also adapted to survive at higher salinities for long periods (2 months in the current thesis). This explains why R. holubi is one of the few species in the estuarine fish community that may persist during droughts. The predicted future changes in coastal temperatures and rainfall by climate change investigators, are likely to result in range shifts and changes in recruitment times of estuarine fish communities. The current work addresses novel aspects of the ecology and physiology of R. holubi and indicates that this species will play an increasingly important role within the estuaries of South Africa.
- Full Text:
- Date Issued: 2018
- Authors: Kisten, Yanasivan
- Date: 2018
- Subjects: Freshwater fishes -- South Africa , Fishes -- Ecology Freshwater fishes -- Ecology Estuarine ecology -- South Africa Estuaries -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/31424 , vital:31374
- Description: Estuaries are important nursery areas for early stages of marine estuarine-dependent fishes, such as the sparid Rhabdosargus holubi. Estuaries provide food, shelter from predators and optimal habitats and environmental conditions for growth and development. However, estuaries are environmentally dynamic and resident organisms must be able to adapt to rapid changes. Such changes are potentially further exacerbated anthropogenically by water and land use practices such as freshwater abstraction, impoundment, pollution and anthropogenically driven climatic change. An effective approach to better understanding the current and future impacts of these kinds of changes, is by assessing the environmental adaptability of organisms, especially to extreme conditions such as droughts and resulting water shortages, which are prevalent in some parts of southern Africa. This thesis examines the effect of various environmental changes such as salinity, turbidity and temperature on the ecology and physiology of a South African common endemic fish species, the Cape stumpnose, R. holubi. Previous work on the species have investigated short term impacts on physiology while this study investigates medium to short term impacts. The specie’s wide distribution in South Africa and tolerance enabled a range of environmental, ecological and physiological relationships to be tested in the context of a changing world. These included: 1) determining the relationship between environmental variability and the distribution and abundance of R. holubi larvae in 25 estuaries along the temperate coast of South Africa; 2) determining the relationship between environmental variability and the movement of larvae and juveniles within two permanently open estuaries; 3) determining the impact of shock and acclimatization on R. holubi salinity tolerance ranges under hypersaline conditions; 4) II determining the impact of hypersalinity on the potential long term impacts growth and skeletal deformities of juvenile R. holubi in aquaria. The findings of these studies suggest that larval occurrence and density within estuaries is a function of salinity and turbidity, by proxy indicating a preference for high freshwater inflow especially in estuary types such as permanently open estuaries. The movement of larvae and juveniles within these estuaries is also mediated by salinity, turbidity and temperature, indicating the importance of seasonality along with environmental conditions and potential olfactory recruitment cues driven by freshwater flow. Tolerance experiments showed that slower acclimation to higher salinities can expand the previously reported tolerance range indicating the potential for adaptation. Physiological experiments showed negative impacts on respiration at salinities exceeding 45, indicating potential long-term physiological effects in hypersaline conditions. Further, living at high salinities for extended periods may have potentially negative effects on long term physiology, particularly growth and skeletal development. The overall results indicate that low salinity (5–18), high turbidity (20–30 NTU) and high temperature (5–22°C) are integral to the distribution and abundance of the species in permanently open estuaries. This conforms to the general rule that estuarine-associated marine fish have higher growth rates in salinities of 12-19. However, juveniles are also adapted to survive at higher salinities for long periods (2 months in the current thesis). This explains why R. holubi is one of the few species in the estuarine fish community that may persist during droughts. The predicted future changes in coastal temperatures and rainfall by climate change investigators, are likely to result in range shifts and changes in recruitment times of estuarine fish communities. The current work addresses novel aspects of the ecology and physiology of R. holubi and indicates that this species will play an increasingly important role within the estuaries of South Africa.
- Full Text:
- Date Issued: 2018
The effect of synthetically-derived xanthone compounds on the suppression of the progression of breast cancer and the associated complications
- Authors: Davison, Candace
- Date: 2017
- Subjects: Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Prevention , Antibacterial agents -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/13889 , vital:27354
- Description: Breast cancer is the most frequently diagnosed cancer in women worldwide.A treatment regime, both effective and safe and can only be achieved once more effective chemotherapeutic agents are discovered or identified. These “drugs” must selectively induce cell death such as apoptosis or necroptosis in the cancer cells. Apoptotic cell death allows a cell to “commit suicide” in genetically- controlled or programmed mechanism(s). The microenvironment of the tumour is important since a nurturing malignant environment is required for tumour maintenance, progression and ultimately the development of metastasis. Due to the correlation of the tumour microenvironment to aggressive tumour progression, emphasis should be placed on the constituents of the tumour’s microenvironment. In recent years, the understanding of intracellular pathways in cancer cells has increased rapidly, contributing to the development of drugs with more specific targets such as growth factors, signalling molecules, cell adhesion proteins, proteases, cell-cycle proteins, modulators of apoptosis and molecules that promote angiogenesis and metastasis. The main aim of this study was thus to identify a few potential or active compounds from a library of synthetically-derived compounds as possible alternative breast cancer treatment candidates.
- Full Text:
- Date Issued: 2017
- Authors: Davison, Candace
- Date: 2017
- Subjects: Breast -- Cancer -- Chemotherapy Breast -- Cancer -- Prevention , Antibacterial agents -- Therapeutic use
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/13889 , vital:27354
- Description: Breast cancer is the most frequently diagnosed cancer in women worldwide.A treatment regime, both effective and safe and can only be achieved once more effective chemotherapeutic agents are discovered or identified. These “drugs” must selectively induce cell death such as apoptosis or necroptosis in the cancer cells. Apoptotic cell death allows a cell to “commit suicide” in genetically- controlled or programmed mechanism(s). The microenvironment of the tumour is important since a nurturing malignant environment is required for tumour maintenance, progression and ultimately the development of metastasis. Due to the correlation of the tumour microenvironment to aggressive tumour progression, emphasis should be placed on the constituents of the tumour’s microenvironment. In recent years, the understanding of intracellular pathways in cancer cells has increased rapidly, contributing to the development of drugs with more specific targets such as growth factors, signalling molecules, cell adhesion proteins, proteases, cell-cycle proteins, modulators of apoptosis and molecules that promote angiogenesis and metastasis. The main aim of this study was thus to identify a few potential or active compounds from a library of synthetically-derived compounds as possible alternative breast cancer treatment candidates.
- Full Text:
- Date Issued: 2017
The effect of Acacia karroo tree density on grass species composition, forage yield and quality in different rainfall regimes in the Eastern Cape, South Africa
- Authors: De Ridder, Cornelius Henry
- Date: 2016
- Subjects: Grasses -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/2858 , vital:20357
- Description: It is widely believed that Acacia karroo Hayne trees compete with and negatively affect the production of grasses in their immediate surroundings. This perception formed as a result of observations by farmers of their veld as well as some research. The complexity of plant interactions in different conditions required that research be done to better explain the extent of grass and tree interactions. In response to this need, the effect of a range of Acacia karroo densities on grass production was tested in areas of differing rainfall. Results emphasize the complexity of such plant interactions but highlight rainfall as influencing the effect of tree density on grass production and grass quality. Study sites were chosen with significant differences in tree density and rainfall and this was found to be concomitant with significant differences in grass yield and crude protein (p < 0.001). Grass yield (mass produced) was negatively correlated with tree density (p < 0.001) and was affected by rainfall. High tree density reduced grass yield at the lower rainfall sites, but a reduction in yield was only recorded during dry conditions in the higher rainfall areas. By contrast, the crude protein content of grasses was positively correlated to tree density (p < 0.001). However, as with yield, rainfall played an important part in the strength of the correlation. Soil properties such as temperature (-) (p = 0.011), phosphorus content (+) (p = 0.006), calcium concentration (+) (p = 0.005), acid saturation (-) (p = 0.018), and soil pH (+) (p = 0.008) were also significantly correlated to tree density. Tree density enriched the soil, subsequently benefitting grass quality. The study sites investigated, had different plant communities and environmental conditions with Cradock, Kubusi Drift and Kei Mouth having unique communities and conditions while Adelaide and Cathcart could not be separated in either. Cradock was the driest site and the vegetation was dominated by both grasses and karroid shrubs, differing in pattern and process from the other sites. The Kubusi Drift site had high tree densities, to the extent that the trees altered the grass species composition. The effects of rainfall on grass yield and quality exceeded that of community composition differences.
- Full Text:
- Date Issued: 2016
- Authors: De Ridder, Cornelius Henry
- Date: 2016
- Subjects: Grasses -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/2858 , vital:20357
- Description: It is widely believed that Acacia karroo Hayne trees compete with and negatively affect the production of grasses in their immediate surroundings. This perception formed as a result of observations by farmers of their veld as well as some research. The complexity of plant interactions in different conditions required that research be done to better explain the extent of grass and tree interactions. In response to this need, the effect of a range of Acacia karroo densities on grass production was tested in areas of differing rainfall. Results emphasize the complexity of such plant interactions but highlight rainfall as influencing the effect of tree density on grass production and grass quality. Study sites were chosen with significant differences in tree density and rainfall and this was found to be concomitant with significant differences in grass yield and crude protein (p < 0.001). Grass yield (mass produced) was negatively correlated with tree density (p < 0.001) and was affected by rainfall. High tree density reduced grass yield at the lower rainfall sites, but a reduction in yield was only recorded during dry conditions in the higher rainfall areas. By contrast, the crude protein content of grasses was positively correlated to tree density (p < 0.001). However, as with yield, rainfall played an important part in the strength of the correlation. Soil properties such as temperature (-) (p = 0.011), phosphorus content (+) (p = 0.006), calcium concentration (+) (p = 0.005), acid saturation (-) (p = 0.018), and soil pH (+) (p = 0.008) were also significantly correlated to tree density. Tree density enriched the soil, subsequently benefitting grass quality. The study sites investigated, had different plant communities and environmental conditions with Cradock, Kubusi Drift and Kei Mouth having unique communities and conditions while Adelaide and Cathcart could not be separated in either. Cradock was the driest site and the vegetation was dominated by both grasses and karroid shrubs, differing in pattern and process from the other sites. The Kubusi Drift site had high tree densities, to the extent that the trees altered the grass species composition. The effects of rainfall on grass yield and quality exceeded that of community composition differences.
- Full Text:
- Date Issued: 2016
The economic and ecological trade-offs of wetland conversion for development projects: the case of the Kampala–Mukono corridor
- Authors: Wasswa, Hannington
- Date: 2018
- Subjects: Wetland ecology -- Uganda -- Kampala , Wetlands -- Uganda -- Kampala Wetland management -- Uganda -- Kampala Hydrogeology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/36409 , vital:33939
- Description: Wetland diminution for development projects (DPs) in the Kampala–Mukono Corridor (KMC) continues to pose threats to the socio-economic and ecological benefits of wetlands because decision-makers and wetland users at various levels often have insufficient knowledge of these benefits. This situation has resulted in unsustainable development decisions that accord little weight to wetlands and have allocated many of them to DPs. In order to inform decision making for optimal development in the KMC, the present study analysed the spatial and temporal wetland loss to DPs, estimated the economic value of the KMC wetlands, and assessed the environmental consequences of wetland conversion for DPs. Sets of ortho-rectified and cloud-free multi-temporal Landsat MSS (1974) and Landsat TM/ETM+ images (30m) for 1986, 2006, and 2013 were analysed in a spatial and temporal framework. The 79m Landsat image (MSS) of 1974 was resampled and later filtered with subsequent 30m images using a majority filter method. An unsupervised classification approach was employed to characterize the wetlands and associated DPs. The classified DPs and wetland cover types were validated by reference to topographical maps (sheets) of 1974 at a scale of 1:50,000 obtained from Uganda Lands and Surveys, apriori knowledge and Google earth images corresponding to the same spatial and temporal frames. The IDRISI Selva-based Markov Chain model was employed to model future wetland loss to DPs. The Total Economic Valuation Approach (TEV) was employed to quantify selected use values of wetland economic benefits using the market price, replacement cost and contingent valuation techniques. The ecological implications of wetland loss focused on soil organic carbon (SOC) and hydrological impacts in the KMC wetlands. The estimated SOC was assessed with climatic data in order to infer the implication of SOC loss for local climate variability. The manual wet chemistry/oxidation method by Walkley-Black (1934) was adopted to estimate SOC in various wetland cover types. Hydrological impact assessments focused on water quality analysis in various wetland cover types, with major parameters being total nitrogen (TN), total phosphorous (TP) total dissolved solids – (TDS) and total suspended sediments (TSS). Hydrologic flow data parameters across the different wetland cover types in the KMC focused on water level, speed, stream width, and bed load. Results from analysis of the spatial-temporal wetland change revealed that by 2013 the KMC wetlands had lost almost half (47%) of their 1974 areal coverage, with 56% of this loss resulting from conversion to DPs. It is projected that 26% of the KMC wetlands will be lost to more DPs by 2040. Wetland loss is attributed to intensified economic activity and preference of Kampala as an industrial zone, weakness in the previous spatial planning of Kampala, and the general lack of information flow to various institutions involved in the establishment of DPs. The KMC wetlands provide a flow of economic benefits at a minimum approximated value of US$ 3,418 / ha / per year. It is revealed that a great deal of these economic benefits (88%) accrues to the local subsistence level in the form of livelihood products, incomes, and employment benefits. The 56% wetlands loss to DPs in the KMC by 2013 brings the minimum economic value lost to US$ 19,311,700 in the sampled wetlands, and projections of future wetland loss put the minimum economic loss at US$ 48,368,118 by 2040. Continuous degradation of these wetlands means serious economic costs to the government and local communities, as reflected in high replacement expenditures for wetland services, foregone incomes, subsistence livelihood support and alternative employment. The highest carbon (C) sinks were identified in forest swamps, palms, thickets and wetlands converted to agriculture, which accounted for 25% of the KMC wetlands by 2013, while the lowest total soil organic carbon (TSOC) range occurred in converted wetland cover types (converted wetlands to industrial and settlements) that occupied 47% of the study area. A general decrease in SOC sequestration from 1974 to 2013 across the KMC wetlands is identified, with the lowest C pool registered in 2013. The dwindling SOC banks are considered to be partly responsible for varying climate and related feedbacks on wetland benefits in the KMC. The hydrologic impacts of wetland loss are felt mainly in converted wetland cover types, in the form of compromised water quality, with increased nutrient pollution and TSS. These all create negative impacts on wetland hydrological services, particularly filtration, flood attenuation, recharge and discharge benefits, all of which have profound effects on biodiversity. There is an urgent need to reduce the scale of wetland diminution in the KMC. This will be achieved if mitigation and conservation measures are undertaken. Mitigation measures should include a revision of development plans, user sensitization on wetland economic values and enforcement of regulatory mechanisms. Conservation strategies should involve the use of economic incentives and disincentives which include: a revision of historic property rights to regulate wetland use, performance bonds or subsidies for environmentally friendly activities and taxes, fees or fines for unacceptable levels of degradation and tradable permits that utilise the concept of ‘wetland banks’ to ensure no further loss of the KMC wetlands to DPs. Future research should focus on modelling the response of wetland ecosystems to multiple threats and management interventions, and on a feasibility study of wetland restoration options and the implications for local people’s livelihoods in the KMC.
- Full Text:
- Date Issued: 2018
- Authors: Wasswa, Hannington
- Date: 2018
- Subjects: Wetland ecology -- Uganda -- Kampala , Wetlands -- Uganda -- Kampala Wetland management -- Uganda -- Kampala Hydrogeology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/36409 , vital:33939
- Description: Wetland diminution for development projects (DPs) in the Kampala–Mukono Corridor (KMC) continues to pose threats to the socio-economic and ecological benefits of wetlands because decision-makers and wetland users at various levels often have insufficient knowledge of these benefits. This situation has resulted in unsustainable development decisions that accord little weight to wetlands and have allocated many of them to DPs. In order to inform decision making for optimal development in the KMC, the present study analysed the spatial and temporal wetland loss to DPs, estimated the economic value of the KMC wetlands, and assessed the environmental consequences of wetland conversion for DPs. Sets of ortho-rectified and cloud-free multi-temporal Landsat MSS (1974) and Landsat TM/ETM+ images (30m) for 1986, 2006, and 2013 were analysed in a spatial and temporal framework. The 79m Landsat image (MSS) of 1974 was resampled and later filtered with subsequent 30m images using a majority filter method. An unsupervised classification approach was employed to characterize the wetlands and associated DPs. The classified DPs and wetland cover types were validated by reference to topographical maps (sheets) of 1974 at a scale of 1:50,000 obtained from Uganda Lands and Surveys, apriori knowledge and Google earth images corresponding to the same spatial and temporal frames. The IDRISI Selva-based Markov Chain model was employed to model future wetland loss to DPs. The Total Economic Valuation Approach (TEV) was employed to quantify selected use values of wetland economic benefits using the market price, replacement cost and contingent valuation techniques. The ecological implications of wetland loss focused on soil organic carbon (SOC) and hydrological impacts in the KMC wetlands. The estimated SOC was assessed with climatic data in order to infer the implication of SOC loss for local climate variability. The manual wet chemistry/oxidation method by Walkley-Black (1934) was adopted to estimate SOC in various wetland cover types. Hydrological impact assessments focused on water quality analysis in various wetland cover types, with major parameters being total nitrogen (TN), total phosphorous (TP) total dissolved solids – (TDS) and total suspended sediments (TSS). Hydrologic flow data parameters across the different wetland cover types in the KMC focused on water level, speed, stream width, and bed load. Results from analysis of the spatial-temporal wetland change revealed that by 2013 the KMC wetlands had lost almost half (47%) of their 1974 areal coverage, with 56% of this loss resulting from conversion to DPs. It is projected that 26% of the KMC wetlands will be lost to more DPs by 2040. Wetland loss is attributed to intensified economic activity and preference of Kampala as an industrial zone, weakness in the previous spatial planning of Kampala, and the general lack of information flow to various institutions involved in the establishment of DPs. The KMC wetlands provide a flow of economic benefits at a minimum approximated value of US$ 3,418 / ha / per year. It is revealed that a great deal of these economic benefits (88%) accrues to the local subsistence level in the form of livelihood products, incomes, and employment benefits. The 56% wetlands loss to DPs in the KMC by 2013 brings the minimum economic value lost to US$ 19,311,700 in the sampled wetlands, and projections of future wetland loss put the minimum economic loss at US$ 48,368,118 by 2040. Continuous degradation of these wetlands means serious economic costs to the government and local communities, as reflected in high replacement expenditures for wetland services, foregone incomes, subsistence livelihood support and alternative employment. The highest carbon (C) sinks were identified in forest swamps, palms, thickets and wetlands converted to agriculture, which accounted for 25% of the KMC wetlands by 2013, while the lowest total soil organic carbon (TSOC) range occurred in converted wetland cover types (converted wetlands to industrial and settlements) that occupied 47% of the study area. A general decrease in SOC sequestration from 1974 to 2013 across the KMC wetlands is identified, with the lowest C pool registered in 2013. The dwindling SOC banks are considered to be partly responsible for varying climate and related feedbacks on wetland benefits in the KMC. The hydrologic impacts of wetland loss are felt mainly in converted wetland cover types, in the form of compromised water quality, with increased nutrient pollution and TSS. These all create negative impacts on wetland hydrological services, particularly filtration, flood attenuation, recharge and discharge benefits, all of which have profound effects on biodiversity. There is an urgent need to reduce the scale of wetland diminution in the KMC. This will be achieved if mitigation and conservation measures are undertaken. Mitigation measures should include a revision of development plans, user sensitization on wetland economic values and enforcement of regulatory mechanisms. Conservation strategies should involve the use of economic incentives and disincentives which include: a revision of historic property rights to regulate wetland use, performance bonds or subsidies for environmentally friendly activities and taxes, fees or fines for unacceptable levels of degradation and tradable permits that utilise the concept of ‘wetland banks’ to ensure no further loss of the KMC wetlands to DPs. Future research should focus on modelling the response of wetland ecosystems to multiple threats and management interventions, and on a feasibility study of wetland restoration options and the implications for local people’s livelihoods in the KMC.
- Full Text:
- Date Issued: 2018
The development of novel cancer targeting agents
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
- Full Text:
- Date Issued: 2011
- Authors: Knoetze, Steyn
- Date: 2011
- Subjects: Cancer -- Research , Cancer -- Treatment
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:10397 , http://hdl.handle.net/10948/d1010636 , Cancer -- Research , Cancer -- Treatment
- Description: The search for the cure for cancer is currently a multi-billion dollar industry and the search for the elusive “magic bullet”, i.e. the perfect cancer drug that would interact therapeutically with cancerous tissues while having a minimal effect on healthy cells, is the topic of many research studies in the world today. A large number of novel drugs or drug complexes and conjugates are being synthesized and subjected to rigorous evaluation in the race to find the perfect cure. ECDG (Ethylene diCysteine DeoxyGlucose) seems to have promising cancer targeting ability. Even though this compound has been described in a few publications, we could not find any reference to the current use of ECDG in oncology clinics, either as a therapeutic agent, or as a diagnostic tool for imaging purposes. It was also not possible to purchase pure ECDG anywhere in the world. This prompted us to further investigate ECDG as a possible candidate for cancer targeting research, either as an imaging agent for cancer diagnosis or complexed with an anti-cancer agent for therapeutic purposes. Detailed investigations done in our laboratory can be divided into the following categories: - Development of a synthetic method for ECDG on a multigram scale ; - Purification of prepared ECDG not using the described dialysis method that only allows the purification of small quantities of ECDG (mg scale) ; Detailed investigation of the chemistry involved in the preparation of pure ECDG and its metal complexes ; - Investigation of the stability of ECDG and its metal complexes that is essential data required for any pharmaceutical agent ; - Preparation of ECDG complexes for use as a diagnostic tool, i.e. complexation with 99mTc ; Investigation of the bio distribution of ECDG-ReO complexes ; - Preparation of an ECDG kit as a diagnostic tool for use in oncology clinics. The development of novel aromatic ligands having similar characteristics compared to ECDG, containing an N2S2 chromophore as donor atoms, to further investigate their targeting capabilities, have also been investigated. All intermediates and final compounds were characterized mainly by ESI MS, in some cases IR and NMR whenever available. Successful preparation and purification of ECDG ands its metal complexes was achieved and extensively characterized and evaluated. Efforts directed towards the development of ECDG at NECSA, South Africa, were also rewarded with significant success. Furthermore, significant development regarding the synthesis of two novel compounds with ECDG-like characteristics was also completed.
- Full Text:
- Date Issued: 2011
The design and testing of a national estuarine monitoring prgramme for South Africa
- Authors: Cilliers, Gerhard Jordaan
- Date: 2017
- Subjects: Estuaries -- South Africa Berg Estuary (South Africa)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/15490 , vital:28258
- Description: Adaptive water resource management requires sound scientific based decisions, emanating from robust scientific data. The Department of Environmental Affairs are mandated for collaborative management of the South African coast, including estuaries, through the Integrated Coastal Management Act (Act no 24 of 2008) (ICMA). The Department Water and Sanitation is mandated through the National Water Act (Act no 36 of 1998) (NWA) to design, test and implement monitoring programmes to provide water resource data. Extensive freshwater monitoring programmes exist in South Africa but there is no standard long-term monitoring programme for estuaries. This study designed and tested a National Estuarine Monitoring Programme (NESMP) that is anchored in the NWA and the ICMA. The design was based on a review of international estuary monitoring programmes, consultation with relevant role players and five decades experience in the design, testing and implementation of water resource monitoring programmes by DWS. The main objective of this thesis is 1) to design a national estuarine monitoring programme 2) test the design of the programme for practical implementation by reflecting on collected data from case studies, and 3) design a Decision Support System to translate complex monitoring data into management information. The main objective of the NESMP is 1) to collect long-term data to determine trends in the condition of estuaries in South Africa and 2) to provide management orientated information for effective estuary management. The National Estuary Monitoring programme consists of three tiers. Tier 1 focuses on basic data including system variables and nutrient data. Tier 2 collects data required for the determination of the Ecological Water Requirements (EWR) of estuaries in accordance with a standardised method used by DWS. A tailor made monitoring programme addressing specific issues including pollution incidents and localised development pressure, making use of a combination of Tier 1 and Tier 2 components, forms Tier 3 of the NESMP. This study tested the Tier 1 components of the programme on 28 estuaries across the South African coast since 2012. However, due to space constraints, the data reflected on in this thesis, is only for case studies on the Berg and Breede estuaries between 2012 and 2016. The results indicate that the establishment and operation of the NESMP on South African estuaries making use of monthly surveys, and the deployment of permanent water quality loggers, in line with the proposed protocol, are possible. This does however require collaboration with other role players in order to share responsibility and associated resources. A tiered management structure ensures national, regional and local level implementation takes place seamlessly. A decision support system (DSS) was also designed as part of this thesis to assist with data interpretation and the creation of management orientated information. This DSS includes a measurement of the percentage exceedance of the Threshold of Potential Concern (TPC), which acts as an early warning system for water resource deterioration. This study showed that effective collaboration will ensure the sustainability of the NESMP. Implementation of the more complex and resource intensive Tier 2 and Tier 3 sampling will however need to be investigated to establish the overall success of the NESMP.
- Full Text:
- Date Issued: 2017
- Authors: Cilliers, Gerhard Jordaan
- Date: 2017
- Subjects: Estuaries -- South Africa Berg Estuary (South Africa)
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/15490 , vital:28258
- Description: Adaptive water resource management requires sound scientific based decisions, emanating from robust scientific data. The Department of Environmental Affairs are mandated for collaborative management of the South African coast, including estuaries, through the Integrated Coastal Management Act (Act no 24 of 2008) (ICMA). The Department Water and Sanitation is mandated through the National Water Act (Act no 36 of 1998) (NWA) to design, test and implement monitoring programmes to provide water resource data. Extensive freshwater monitoring programmes exist in South Africa but there is no standard long-term monitoring programme for estuaries. This study designed and tested a National Estuarine Monitoring Programme (NESMP) that is anchored in the NWA and the ICMA. The design was based on a review of international estuary monitoring programmes, consultation with relevant role players and five decades experience in the design, testing and implementation of water resource monitoring programmes by DWS. The main objective of this thesis is 1) to design a national estuarine monitoring programme 2) test the design of the programme for practical implementation by reflecting on collected data from case studies, and 3) design a Decision Support System to translate complex monitoring data into management information. The main objective of the NESMP is 1) to collect long-term data to determine trends in the condition of estuaries in South Africa and 2) to provide management orientated information for effective estuary management. The National Estuary Monitoring programme consists of three tiers. Tier 1 focuses on basic data including system variables and nutrient data. Tier 2 collects data required for the determination of the Ecological Water Requirements (EWR) of estuaries in accordance with a standardised method used by DWS. A tailor made monitoring programme addressing specific issues including pollution incidents and localised development pressure, making use of a combination of Tier 1 and Tier 2 components, forms Tier 3 of the NESMP. This study tested the Tier 1 components of the programme on 28 estuaries across the South African coast since 2012. However, due to space constraints, the data reflected on in this thesis, is only for case studies on the Berg and Breede estuaries between 2012 and 2016. The results indicate that the establishment and operation of the NESMP on South African estuaries making use of monthly surveys, and the deployment of permanent water quality loggers, in line with the proposed protocol, are possible. This does however require collaboration with other role players in order to share responsibility and associated resources. A tiered management structure ensures national, regional and local level implementation takes place seamlessly. A decision support system (DSS) was also designed as part of this thesis to assist with data interpretation and the creation of management orientated information. This DSS includes a measurement of the percentage exceedance of the Threshold of Potential Concern (TPC), which acts as an early warning system for water resource deterioration. This study showed that effective collaboration will ensure the sustainability of the NESMP. Implementation of the more complex and resource intensive Tier 2 and Tier 3 sampling will however need to be investigated to establish the overall success of the NESMP.
- Full Text:
- Date Issued: 2017