Photosynthetic and evolutionary determinants of the response of selected C3 and C4 (NADP-ME) grasses to fire
- Authors: Martin, Tarryn
- Date: 2009
- Subjects: Photosynthesis , Carbon -- Metabolism , Grasses -- Adaptation , Plants -- Effect of fires on , Grasses -- Research , Grasses -- Physiology , Grasses -- Evolution , Grasslands -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4211 , http://hdl.handle.net/10962/d1003780 , Photosynthesis , Carbon -- Metabolism , Grasses -- Adaptation , Plants -- Effect of fires on , Grasses -- Research , Grasses -- Physiology , Grasses -- Evolution , Grasslands -- Research
- Description: Species possess characteristics that are considered adapted to burning and these allow them to outcompete species and dominate in fire prone environments. It has therefore been proposed that fire might have played a critical role in the observed expansion of the grasslands, during the late Miocene. The aim of this study was (i) to investigate whether plant response to fire was a result of physiology or (ii) whether it was due to phylogenetic history. This was achieved by doing a pair-wise comparison between Panicoideae (and Panicoideae) and non-Panicoideae (Danthonioideae and Aristidoideae) species. Pre-fire characteristics, that would enhance fire frequency and assist with plant recovery after burning, were compared across phylogenies and photosynthetic type. Post fire plant recovery was then followed in a field and pot comparison which examined the re-growth of the leaf canopy area, leaf mass, above-ground biomass and the cost of this to the below-ground biomass. The pre-fire characteristics showed both a photosynthetic and phylogenetic response. It was found that the species showed a greater canopy death during winter and had a lower moisture content than the species. These characteristics would potentially contribute towards a larger fuel load in the species. However, the comparison of the dead standing biomass at the end of winter and the below-ground biomass, showed a phylogenetic response with the Panicoideae having a proportionally larger dead standing biomass and below-ground biomass than the non-Panicoideae. These results suggest that not only did the Panicoideae have a larger potential fuel load but that they also shunted carbon below-ground, enabling a fast recovery after being burned. The post-fire results were more strongly determined by phylogeny than by photosynthetic type. The Panicoideae recovered faster and more completely than the non-Panicoideae grasses, possibly contributing to their success and expansion under conditions of increased fire frequency. Although recovery of the and Panicoideae were similar, frequently burnt grasslands are dominated by the Panicoideae. Hence, this dominance cannot be explained by differences in their fire responses and may be determined by the post-fire environmental conditions that potentially advantage species possessing the photosynthetic pathway. Panicoideae dominance is limited to mesic environments where fire is the likely driver of grassland expansion while more arid environments are dominated by non-Panicoideae species. Representative species from these non-Panicoid subfamilies showed poor recovery after fire. This suggests that factors other than fire were the likely drivers of these xeric grassland expansions. The ability of these subfamilies, and particularly the species, to cope with drought remains a likely selective mechanism that requires further research.
- Full Text:
- Date Issued: 2009
- Authors: Martin, Tarryn
- Date: 2009
- Subjects: Photosynthesis , Carbon -- Metabolism , Grasses -- Adaptation , Plants -- Effect of fires on , Grasses -- Research , Grasses -- Physiology , Grasses -- Evolution , Grasslands -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4211 , http://hdl.handle.net/10962/d1003780 , Photosynthesis , Carbon -- Metabolism , Grasses -- Adaptation , Plants -- Effect of fires on , Grasses -- Research , Grasses -- Physiology , Grasses -- Evolution , Grasslands -- Research
- Description: Species possess characteristics that are considered adapted to burning and these allow them to outcompete species and dominate in fire prone environments. It has therefore been proposed that fire might have played a critical role in the observed expansion of the grasslands, during the late Miocene. The aim of this study was (i) to investigate whether plant response to fire was a result of physiology or (ii) whether it was due to phylogenetic history. This was achieved by doing a pair-wise comparison between Panicoideae (and Panicoideae) and non-Panicoideae (Danthonioideae and Aristidoideae) species. Pre-fire characteristics, that would enhance fire frequency and assist with plant recovery after burning, were compared across phylogenies and photosynthetic type. Post fire plant recovery was then followed in a field and pot comparison which examined the re-growth of the leaf canopy area, leaf mass, above-ground biomass and the cost of this to the below-ground biomass. The pre-fire characteristics showed both a photosynthetic and phylogenetic response. It was found that the species showed a greater canopy death during winter and had a lower moisture content than the species. These characteristics would potentially contribute towards a larger fuel load in the species. However, the comparison of the dead standing biomass at the end of winter and the below-ground biomass, showed a phylogenetic response with the Panicoideae having a proportionally larger dead standing biomass and below-ground biomass than the non-Panicoideae. These results suggest that not only did the Panicoideae have a larger potential fuel load but that they also shunted carbon below-ground, enabling a fast recovery after being burned. The post-fire results were more strongly determined by phylogeny than by photosynthetic type. The Panicoideae recovered faster and more completely than the non-Panicoideae grasses, possibly contributing to their success and expansion under conditions of increased fire frequency. Although recovery of the and Panicoideae were similar, frequently burnt grasslands are dominated by the Panicoideae. Hence, this dominance cannot be explained by differences in their fire responses and may be determined by the post-fire environmental conditions that potentially advantage species possessing the photosynthetic pathway. Panicoideae dominance is limited to mesic environments where fire is the likely driver of grassland expansion while more arid environments are dominated by non-Panicoideae species. Representative species from these non-Panicoid subfamilies showed poor recovery after fire. This suggests that factors other than fire were the likely drivers of these xeric grassland expansions. The ability of these subfamilies, and particularly the species, to cope with drought remains a likely selective mechanism that requires further research.
- Full Text:
- Date Issued: 2009
Raman spectroscopy of ternary III-V semiconducting films
- Authors: Mashigo, Donald
- Date: 2009
- Subjects: Raman spectroscopy , Semiconductor films , Compound semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10522 , http://hdl.handle.net/10948/1011 , Raman spectroscopy , Semiconductor films , Compound semiconductors
- Description: The III-V semiconductor compounds (i.e. In Ga As x 1-x , 1 x x InAs Sb - , In Ga Sb x 1-x and Al Ga As x 1-x ) have been studied using room temperature Raman spectroscopy. X-ray diffraction has been used as a complementary characterization technique. In this study all the III-V semiconductor compounds were grown by metal organic chemical vapour deposition (MOCVD) on GaAs and GaSb substrates. The layers were studied with respect to composition, strain variation and critical thickness. Raman spectroscopy has been employed to assess the composition dependence of optical phonons in the layers. The alloy composition was varied, while the thickness was kept constant in order to investigate compositional effects. A significant frequency shift of the phonon modes were observed as the composition changed. The composition dependence of the phonon frequencies were described by linear and polynomial expressions. The results of this study were compared with previous Raman and infrared work on III-V semiconductor compounds. Strain relaxation in InGaAs and InGaSb has been investigated by Raman and X-ray diffraction. Measurements were performed on several series of layers. For each series, the thickness was varied, while keeping the composition constant. For a given composition, the layer thicknesses were such that some layers should be fully strained, some partially relaxed and some fully relaxed. The Raman peak shifts and XRD confirm that a layer grows up to the critical thickness and then releases the strain as the thickness increases. Critical layer thickness values measured in this study were compared with published data, in which various techniques had been used to estimate the critical thickness.
- Full Text:
- Date Issued: 2009
- Authors: Mashigo, Donald
- Date: 2009
- Subjects: Raman spectroscopy , Semiconductor films , Compound semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10522 , http://hdl.handle.net/10948/1011 , Raman spectroscopy , Semiconductor films , Compound semiconductors
- Description: The III-V semiconductor compounds (i.e. In Ga As x 1-x , 1 x x InAs Sb - , In Ga Sb x 1-x and Al Ga As x 1-x ) have been studied using room temperature Raman spectroscopy. X-ray diffraction has been used as a complementary characterization technique. In this study all the III-V semiconductor compounds were grown by metal organic chemical vapour deposition (MOCVD) on GaAs and GaSb substrates. The layers were studied with respect to composition, strain variation and critical thickness. Raman spectroscopy has been employed to assess the composition dependence of optical phonons in the layers. The alloy composition was varied, while the thickness was kept constant in order to investigate compositional effects. A significant frequency shift of the phonon modes were observed as the composition changed. The composition dependence of the phonon frequencies were described by linear and polynomial expressions. The results of this study were compared with previous Raman and infrared work on III-V semiconductor compounds. Strain relaxation in InGaAs and InGaSb has been investigated by Raman and X-ray diffraction. Measurements were performed on several series of layers. For each series, the thickness was varied, while keeping the composition constant. For a given composition, the layer thicknesses were such that some layers should be fully strained, some partially relaxed and some fully relaxed. The Raman peak shifts and XRD confirm that a layer grows up to the critical thickness and then releases the strain as the thickness increases. Critical layer thickness values measured in this study were compared with published data, in which various techniques had been used to estimate the critical thickness.
- Full Text:
- Date Issued: 2009
Synthesis and electrochemistry of octapentylthio phthalocyanine complexes of manganese, titanium and vanadium
- Authors: Mbambisa, Gcineka
- Date: 2009
- Subjects: Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4368 , http://hdl.handle.net/10962/d1005033 , Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Description: Synthesis of new thio derivatised Pcs with manganese, titanium and vanadium as a central metal is reported. The complexes synthesised were characterised using spectroscopic and electrochemical means. The complexes displayed interesting spectroscopic properties with absorption of the Q band being observed in the near infrared region. These complexes have unusual colours for MPc complexes, with purple or red colour being observed in solution. Interesting electrochemical properties were observed, with rare observation of the MnIV/MnIII redox couple. There was observation of oxidation peaks for the pentylthio derivatised Pc with titanium as the central metal; this is unusual since for reported thio derivatives based on TiPc, no oxidation was observed. The vanadium based Pc showed an interesting spectrum for the first ring based reduction. The absorption spectrum obtained for the 1st reduction of the vanadium complex using spectroelectrochemistry would normally indicate a metal based process but comparing with literature it was concluded that it is a ring based reduction process. Generally all the MPc complexes formed a well ordered stable monolayer on the gold electrode. Electrocatalytic studies using L-cysteine revealed that the SAM based on manganese (III) octapentylthio phthalocyanine (AcOMnOPTPc) was the most effective since it catalyses L-cysteine at much lower oxidation potentials and it is also much more stable.
- Full Text:
- Date Issued: 2009
- Authors: Mbambisa, Gcineka
- Date: 2009
- Subjects: Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4368 , http://hdl.handle.net/10962/d1005033 , Electrochemistry , Phthalocyanines -- Synthesis , Manganese , Titanium , Vanadium
- Description: Synthesis of new thio derivatised Pcs with manganese, titanium and vanadium as a central metal is reported. The complexes synthesised were characterised using spectroscopic and electrochemical means. The complexes displayed interesting spectroscopic properties with absorption of the Q band being observed in the near infrared region. These complexes have unusual colours for MPc complexes, with purple or red colour being observed in solution. Interesting electrochemical properties were observed, with rare observation of the MnIV/MnIII redox couple. There was observation of oxidation peaks for the pentylthio derivatised Pc with titanium as the central metal; this is unusual since for reported thio derivatives based on TiPc, no oxidation was observed. The vanadium based Pc showed an interesting spectrum for the first ring based reduction. The absorption spectrum obtained for the 1st reduction of the vanadium complex using spectroelectrochemistry would normally indicate a metal based process but comparing with literature it was concluded that it is a ring based reduction process. Generally all the MPc complexes formed a well ordered stable monolayer on the gold electrode. Electrocatalytic studies using L-cysteine revealed that the SAM based on manganese (III) octapentylthio phthalocyanine (AcOMnOPTPc) was the most effective since it catalyses L-cysteine at much lower oxidation potentials and it is also much more stable.
- Full Text:
- Date Issued: 2009
The spatial ecology and activity patterns of leopards (Panthera pardus) in the Baviaanskloof and Greater Addo Elephant National Park (GAENP), Eastern Cape Province, South Africa
- Authors: McManus, Jeannine Stephanie
- Date: 2009
- Subjects: Leopard -- South Africa -- Eastern Cape , Leopard -- Monitoring -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Eastern Cape , Leopard -- Ecology -- South Africa -- Eastern Cape , Spatial ecology -- South Africa -- Eastern Cape , Wildlife monitoring -- South Africa -- Eastern Cape , Animal populations -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5823 , http://hdl.handle.net/10962/d1007601 , Leopard -- South Africa -- Eastern Cape , Leopard -- Monitoring -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Eastern Cape , Leopard -- Ecology -- South Africa -- Eastern Cape , Spatial ecology -- South Africa -- Eastern Cape , Wildlife monitoring -- South Africa -- Eastern Cape , Animal populations -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
- Description: The conservation of leopards in the Eastern Cape Province requires a holistic approach that considers both predator-human interactions as well as the biology of the carnivore. Numerous studies have been conducted on leopards within protected areas; however more information regarding the species is needed outside these areas to facilitate effective management of predators. The spatial ecology of the leopard (Panthera pardus) were studied in the Baviaanskloof and GAENP in the Eastern Cape. The Baviaanskloof is an extensive area of mountainous terrain (approximately 2665km²) which has a mosaic of land uses, and leopards move from conservation areas to farmland where they come into contact and conflict with farmers. This study examined the spatial ecology of leopards living on farmlands adjacent to protected land. The space utilization and activity patterns of six leopards were analysed. These animals were caught and released on farmlands in the Baviaanskloof (n=4) or translocated (n=2) when not possible to release on site. The animals were caught by means of fall-door, walk-in traps and fitted with Vectronic GPS collars that facilitated the collection of high quality GPS fixes from each animal. Data was collected using VHF and UHF telemetry to download data. An understanding of spatial requirements in areas with different land use, and the extent of overlap of space use with other leopards allow, for the first time in the region, the calculation of possible maximum population size. Analysis of range size was carried out using two methods: minimum convex polygon, and Kernel Utilization Distribution. Finally, a key predictor of space use is prey availability. I assessed the prey base using a grid of camera traps. The studied leopards revealed large range utilization with minimal overlap. The activity patterns suggest there is no preference between diurnal and nocturnal activity patterns and the population density was estimated between 0.3 - 1.3 leopards per 100km². Large home range sizes and low population densities suggest that leopards require large areas of suitable habitat, and that conservation efforts need to be extended beyond protected areas to ensure the long-term viability of leopard populations in such areas.
- Full Text:
- Date Issued: 2009
- Authors: McManus, Jeannine Stephanie
- Date: 2009
- Subjects: Leopard -- South Africa -- Eastern Cape , Leopard -- Monitoring -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Eastern Cape , Leopard -- Ecology -- South Africa -- Eastern Cape , Spatial ecology -- South Africa -- Eastern Cape , Wildlife monitoring -- South Africa -- Eastern Cape , Animal populations -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5823 , http://hdl.handle.net/10962/d1007601 , Leopard -- South Africa -- Eastern Cape , Leopard -- Monitoring -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Eastern Cape , Leopard -- Ecology -- South Africa -- Eastern Cape , Spatial ecology -- South Africa -- Eastern Cape , Wildlife monitoring -- South Africa -- Eastern Cape , Animal populations -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape
- Description: The conservation of leopards in the Eastern Cape Province requires a holistic approach that considers both predator-human interactions as well as the biology of the carnivore. Numerous studies have been conducted on leopards within protected areas; however more information regarding the species is needed outside these areas to facilitate effective management of predators. The spatial ecology of the leopard (Panthera pardus) were studied in the Baviaanskloof and GAENP in the Eastern Cape. The Baviaanskloof is an extensive area of mountainous terrain (approximately 2665km²) which has a mosaic of land uses, and leopards move from conservation areas to farmland where they come into contact and conflict with farmers. This study examined the spatial ecology of leopards living on farmlands adjacent to protected land. The space utilization and activity patterns of six leopards were analysed. These animals were caught and released on farmlands in the Baviaanskloof (n=4) or translocated (n=2) when not possible to release on site. The animals were caught by means of fall-door, walk-in traps and fitted with Vectronic GPS collars that facilitated the collection of high quality GPS fixes from each animal. Data was collected using VHF and UHF telemetry to download data. An understanding of spatial requirements in areas with different land use, and the extent of overlap of space use with other leopards allow, for the first time in the region, the calculation of possible maximum population size. Analysis of range size was carried out using two methods: minimum convex polygon, and Kernel Utilization Distribution. Finally, a key predictor of space use is prey availability. I assessed the prey base using a grid of camera traps. The studied leopards revealed large range utilization with minimal overlap. The activity patterns suggest there is no preference between diurnal and nocturnal activity patterns and the population density was estimated between 0.3 - 1.3 leopards per 100km². Large home range sizes and low population densities suggest that leopards require large areas of suitable habitat, and that conservation efforts need to be extended beyond protected areas to ensure the long-term viability of leopard populations in such areas.
- Full Text:
- Date Issued: 2009
An investigation of issues of privacy, anonymity and multi-factor authentication in an open environment
- Authors: Miles, Shaun Graeme
- Date: 2012-06-20
- Subjects: Electronic data processing departments -- Security measures , Electronic data processing departments , Privacy, Right of , Computer security , Data protection , Computers -- Access control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4656 , http://hdl.handle.net/10962/d1006653 , Electronic data processing departments -- Security measures , Electronic data processing departments , Privacy, Right of , Computer security , Data protection , Computers -- Access control
- Description: This thesis performs an investigation into issues concerning the broad area ofIdentity and Access Management, with a focus on open environments. Through literature research the issues of privacy, anonymity and access control are identified. The issue of privacy is an inherent problem due to the nature of the digital network environment. Information can be duplicated and modified regardless of the wishes and intentions ofthe owner of that information unless proper measures are taken to secure the environment. Once information is published or divulged on the network, there is very little way of controlling the subsequent usage of that information. To address this issue a model for privacy is presented that follows the user centric paradigm of meta-identity. The lack of anonymity, where security measures can be thwarted through the observation of the environment, is a concern for users and systems. By an attacker observing the communication channel and monitoring the interactions between users and systems over a long enough period of time, it is possible to infer knowledge about the users and systems. This knowledge is used to build an identity profile of potential victims to be used in subsequent attacks. To address the problem, mechanisms for providing an acceptable level of anonymity while maintaining adequate accountability (from a legal standpoint) are explored. In terms of access control, the inherent weakness of single factor authentication mechanisms is discussed. The typical mechanism is the user-name and password pair, which provides a single point of failure. By increasing the factors used in authentication, the amount of work required to compromise the system increases non-linearly. Within an open network, several aspects hinder wide scale adoption and use of multi-factor authentication schemes, such as token management and the impact on usability. The framework is developed from a Utopian point of view, with the aim of being applicable to many situations as opposed to a single specific domain. The framework incorporates multi-factor authentication over multiple paths using mobile phones and GSM networks, and explores the usefulness of such an approach. The models are in tum analysed, providing a discussion into the assumptions made and the problems faced by each model. , Adobe Acrobat Pro 9.5.1 , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Authors: Miles, Shaun Graeme
- Date: 2012-06-20
- Subjects: Electronic data processing departments -- Security measures , Electronic data processing departments , Privacy, Right of , Computer security , Data protection , Computers -- Access control
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4656 , http://hdl.handle.net/10962/d1006653 , Electronic data processing departments -- Security measures , Electronic data processing departments , Privacy, Right of , Computer security , Data protection , Computers -- Access control
- Description: This thesis performs an investigation into issues concerning the broad area ofIdentity and Access Management, with a focus on open environments. Through literature research the issues of privacy, anonymity and access control are identified. The issue of privacy is an inherent problem due to the nature of the digital network environment. Information can be duplicated and modified regardless of the wishes and intentions ofthe owner of that information unless proper measures are taken to secure the environment. Once information is published or divulged on the network, there is very little way of controlling the subsequent usage of that information. To address this issue a model for privacy is presented that follows the user centric paradigm of meta-identity. The lack of anonymity, where security measures can be thwarted through the observation of the environment, is a concern for users and systems. By an attacker observing the communication channel and monitoring the interactions between users and systems over a long enough period of time, it is possible to infer knowledge about the users and systems. This knowledge is used to build an identity profile of potential victims to be used in subsequent attacks. To address the problem, mechanisms for providing an acceptable level of anonymity while maintaining adequate accountability (from a legal standpoint) are explored. In terms of access control, the inherent weakness of single factor authentication mechanisms is discussed. The typical mechanism is the user-name and password pair, which provides a single point of failure. By increasing the factors used in authentication, the amount of work required to compromise the system increases non-linearly. Within an open network, several aspects hinder wide scale adoption and use of multi-factor authentication schemes, such as token management and the impact on usability. The framework is developed from a Utopian point of view, with the aim of being applicable to many situations as opposed to a single specific domain. The framework incorporates multi-factor authentication over multiple paths using mobile phones and GSM networks, and explores the usefulness of such an approach. The models are in tum analysed, providing a discussion into the assumptions made and the problems faced by each model. , Adobe Acrobat Pro 9.5.1 , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
Studies towards the synthesis of novel tridentate ligands for use in ruthenium metathesis catalysts
- Authors: Millward, Tanya
- Date: 2009
- Subjects: Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4360 , http://hdl.handle.net/10962/d1005025 , Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Description: This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.
- Full Text:
- Date Issued: 2009
- Authors: Millward, Tanya
- Date: 2009
- Subjects: Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4360 , http://hdl.handle.net/10962/d1005025 , Ligands , Catalysis , Metathesis (Chemistry) , Ruthenium , Complex compounds
- Description: This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.
- Full Text:
- Date Issued: 2009
Habitat and foraging models as aids in the identification of priority areas for mitigating actions to reduce the incidence of electrocutions of the threatened Cape Griffon Gyps coprotheres in the Eastern Cape
- Authors: Minnie, Johan Charles
- Date: 2009
- Subjects: Gyps -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10658 , http://hdl.handle.net/10948/1047 , http://hdl.handle.net/10948/d1012887 , Gyps -- South Africa -- Eastern Cape
- Description: The Cape Griffon Gyps coprotheres is listed as a globally threatened species, because of threats posed by, inter alia, poisoning, loss of habitat, food shortages, electrocutions and drowning in high-walled farm reservoirs. The Cape Griffon has undergone major decline in South Africa, including the Eastern Cape. A detailed investigation into the causes of this decline is vital to ensure the survival of the species. Since it is known that electrocution on powerlines is a major cause of mortality of the griffons in the Eastern Cape, the study therefore focuses on this factor in this region. More specifically, the overall aim or objective of the study is to investigate, through the application of appropriate GIS techniques, the use of descriptive, empirical, habitat and foraging models to prioritise powerline networks, in the Eastern Cape, for mitigation to prevent electrocution of Cape Griffons Gyps coprotheres. The specific activities associated with the aim of the study are: (1) to identify the broad habitat types used by the griffons, (2) to determine the mean daily foraging range size of the griffons, (3) to map currently active foraging ranges and to categorise them according to their role, and the level of importance, in the foraging and breeding behaviour of the species, (4) to map the locations of networks of griffon-unfriendly powerline networks, and (5) to integrate the outcomes of (1) to (4) above, to produce a spatially explicit product that ranks griffon-unfriendly powerline networks according to their priority level for mitigation. The study uses simple descriptive models to investigate, spatially, the threat posed by griffon-unfriendly powerlines to the Cape Griffon in the Eastern Cape. The modelling approach includes a broad level simple habitat model (Categorical model), a Maxent model, a spatial foraging model and an electrocution model. Several map outputs were produced from the analyses. Cape Griffon habitat was successfully modelled using ecological input variables: biome, vegetation xvii type (suitable/unsuitable for griffon foraging), stock (cattle, sheep and goats), and stock farming types (commercial & communal). All outputs were modelled through the use of a Geographical Information System (GIS). Opportunistic sightings data were used for the study, which means that the data were collected on a non-systematic basis and are therefore considered incomplete. In ecology and zoogeography, incomplete datasets are common. To address this issue, a maximum entropy (Maxent) model was applied to the available dataset. Maxent produces predictions or conclusions from incomplete information, and was therefore useful for this study. The mean daily foraging area (coverage) of the Cape Griffon in the study area was estimated from published and unpublished marked bird studies conducted elsewhere, but in generally similar habitats. Based on all the data from these studies, it was considered appropriate to use a circular area, with a radius of 40 km, to represent the mean daily foraging range of the Cape Griffon in the Eastern Cape. It was considered appropriate to use a roughly circular area to depict the daily foraging area, given that the Cape Griffon qualifies as a central place forager. This means that the griffons are tied to a permanent site (roosting site or breeding site) and forage within a certain area around that central site. The mean daily foraging area (40 km) was applied to the currently active griffon sites: breeding sites, regular roosting sites, seasonal/occasional sites, and roosting sites (uncertain status). This produced four foraging area types, which formed the basis for the creation of two spatial foraging area models: Hierarchical Foraging Area Model (HFAM) and the Intersecting Foraging Area Model (IFAM). The HFAM produced three outputs: Primary, Secondary and Tertiary Foraging Areas. These three areas represent the hierarchical presentation of the relative importance of the four foraging area types. The outcome was areas of different predicted griffon occurrence: ‘high’, ‘medium’, ‘low’. The IFAM is essentially an extension of the HFAM, which represents a single area where foraging ranges based on all four types are intersected. The outcome represents the area of predicted highest griffon occurrence. The identified areas of different predicted griffon occurrence, or density (outputs of the HFAM and IFAM), were individually intersected with the layer that indicates the locations of the ‘unsafe’ powerlines. These intersects are depicted in hierarchical mode and expressed according to a number of four risk categories (very high, high, medium and low). The final spatial output of the study is a map that identifies priority powerlines for mitigation against griffon mortality caused by electrocutions and collisions with powerline infrastructure.
- Full Text:
- Date Issued: 2009
- Authors: Minnie, Johan Charles
- Date: 2009
- Subjects: Gyps -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10658 , http://hdl.handle.net/10948/1047 , http://hdl.handle.net/10948/d1012887 , Gyps -- South Africa -- Eastern Cape
- Description: The Cape Griffon Gyps coprotheres is listed as a globally threatened species, because of threats posed by, inter alia, poisoning, loss of habitat, food shortages, electrocutions and drowning in high-walled farm reservoirs. The Cape Griffon has undergone major decline in South Africa, including the Eastern Cape. A detailed investigation into the causes of this decline is vital to ensure the survival of the species. Since it is known that electrocution on powerlines is a major cause of mortality of the griffons in the Eastern Cape, the study therefore focuses on this factor in this region. More specifically, the overall aim or objective of the study is to investigate, through the application of appropriate GIS techniques, the use of descriptive, empirical, habitat and foraging models to prioritise powerline networks, in the Eastern Cape, for mitigation to prevent electrocution of Cape Griffons Gyps coprotheres. The specific activities associated with the aim of the study are: (1) to identify the broad habitat types used by the griffons, (2) to determine the mean daily foraging range size of the griffons, (3) to map currently active foraging ranges and to categorise them according to their role, and the level of importance, in the foraging and breeding behaviour of the species, (4) to map the locations of networks of griffon-unfriendly powerline networks, and (5) to integrate the outcomes of (1) to (4) above, to produce a spatially explicit product that ranks griffon-unfriendly powerline networks according to their priority level for mitigation. The study uses simple descriptive models to investigate, spatially, the threat posed by griffon-unfriendly powerlines to the Cape Griffon in the Eastern Cape. The modelling approach includes a broad level simple habitat model (Categorical model), a Maxent model, a spatial foraging model and an electrocution model. Several map outputs were produced from the analyses. Cape Griffon habitat was successfully modelled using ecological input variables: biome, vegetation xvii type (suitable/unsuitable for griffon foraging), stock (cattle, sheep and goats), and stock farming types (commercial & communal). All outputs were modelled through the use of a Geographical Information System (GIS). Opportunistic sightings data were used for the study, which means that the data were collected on a non-systematic basis and are therefore considered incomplete. In ecology and zoogeography, incomplete datasets are common. To address this issue, a maximum entropy (Maxent) model was applied to the available dataset. Maxent produces predictions or conclusions from incomplete information, and was therefore useful for this study. The mean daily foraging area (coverage) of the Cape Griffon in the study area was estimated from published and unpublished marked bird studies conducted elsewhere, but in generally similar habitats. Based on all the data from these studies, it was considered appropriate to use a circular area, with a radius of 40 km, to represent the mean daily foraging range of the Cape Griffon in the Eastern Cape. It was considered appropriate to use a roughly circular area to depict the daily foraging area, given that the Cape Griffon qualifies as a central place forager. This means that the griffons are tied to a permanent site (roosting site or breeding site) and forage within a certain area around that central site. The mean daily foraging area (40 km) was applied to the currently active griffon sites: breeding sites, regular roosting sites, seasonal/occasional sites, and roosting sites (uncertain status). This produced four foraging area types, which formed the basis for the creation of two spatial foraging area models: Hierarchical Foraging Area Model (HFAM) and the Intersecting Foraging Area Model (IFAM). The HFAM produced three outputs: Primary, Secondary and Tertiary Foraging Areas. These three areas represent the hierarchical presentation of the relative importance of the four foraging area types. The outcome was areas of different predicted griffon occurrence: ‘high’, ‘medium’, ‘low’. The IFAM is essentially an extension of the HFAM, which represents a single area where foraging ranges based on all four types are intersected. The outcome represents the area of predicted highest griffon occurrence. The identified areas of different predicted griffon occurrence, or density (outputs of the HFAM and IFAM), were individually intersected with the layer that indicates the locations of the ‘unsafe’ powerlines. These intersects are depicted in hierarchical mode and expressed according to a number of four risk categories (very high, high, medium and low). The final spatial output of the study is a map that identifies priority powerlines for mitigation against griffon mortality caused by electrocutions and collisions with powerline infrastructure.
- Full Text:
- Date Issued: 2009
Socio-economic and ecological correlates of leopard-stock farmer conflict in the Baviaanskloof mega-reserve, Eastern Cape
- Authors: Minnie, Liaan
- Date: 2009
- Subjects: Leopard -- Ecology -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Baviaanskloof , Leopard -- Conservation -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape , Leopard -- Effect of human beings on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10702 , http://hdl.handle.net/10948/1044 , Leopard -- Ecology -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Baviaanskloof , Leopard -- Conservation -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape , Leopard -- Effect of human beings on
- Description: The leopard, Panthera pardus, is particularly threatened outside conservation areas in South Africa. This has been attributed to a reduction in natural habitat, decreasing natural prey populations, and commercial exploitation such as trophy hunting, and most importantly, persecution by stock farmers (Woodroffe 2001). The leopard population in the Baviaanskloof Mega-Reserve (BMR) has undergone a substantial decrease in range and numbers in the past 200 years, resulting in a highly fragmented population in the Baviaanskloof Mega-Reserve, and is regarded as being insecure. There is thus a need to investigate the nature and extent of leopard-stock farmer interactions to provide the foundation for an effective leopard conservation plan. Here I investigated the ecological and socio-economic factors influencing leopard-stock farmer conflict via landowner surveys and estimated potential leopard numbers using a prey-based density model. Leopards are not necessarily the most important causes of livestock mortality in the BMR. On average, leopards killed significantly less livestock (0.7 percent livestock per year) than black-backed jackals (4.7 percent per year) and caracal (2.5 percent per year), yet 67 percent of farmers had negative attitudes towards leopards. These negative attitudes were not significantly related to stock losses. However, most of the farmers that had negative attitudes towards leopards did not have any stock losses attributed to leopards. Thus if predator-stock conflict is not reduced it will result in the retaliatory killing of leopards. This will have severe consequences for this relatively small population (estimated at 59 – 104 individuals by the prey-based model), which may ultimately lead to the local extinction of these leopards (Woodroffe & Ginsberg 1998).
- Full Text:
- Date Issued: 2009
- Authors: Minnie, Liaan
- Date: 2009
- Subjects: Leopard -- Ecology -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Baviaanskloof , Leopard -- Conservation -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape , Leopard -- Effect of human beings on
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10702 , http://hdl.handle.net/10948/1044 , Leopard -- Ecology -- South Africa -- Eastern Cape , Leopard -- Conservation -- South Africa -- Baviaanskloof , Leopard -- Conservation -- South Africa -- Eastern Cape , Wildlife conservation -- South Africa -- Eastern Cape , Leopard -- Effect of human beings on
- Description: The leopard, Panthera pardus, is particularly threatened outside conservation areas in South Africa. This has been attributed to a reduction in natural habitat, decreasing natural prey populations, and commercial exploitation such as trophy hunting, and most importantly, persecution by stock farmers (Woodroffe 2001). The leopard population in the Baviaanskloof Mega-Reserve (BMR) has undergone a substantial decrease in range and numbers in the past 200 years, resulting in a highly fragmented population in the Baviaanskloof Mega-Reserve, and is regarded as being insecure. There is thus a need to investigate the nature and extent of leopard-stock farmer interactions to provide the foundation for an effective leopard conservation plan. Here I investigated the ecological and socio-economic factors influencing leopard-stock farmer conflict via landowner surveys and estimated potential leopard numbers using a prey-based density model. Leopards are not necessarily the most important causes of livestock mortality in the BMR. On average, leopards killed significantly less livestock (0.7 percent livestock per year) than black-backed jackals (4.7 percent per year) and caracal (2.5 percent per year), yet 67 percent of farmers had negative attitudes towards leopards. These negative attitudes were not significantly related to stock losses. However, most of the farmers that had negative attitudes towards leopards did not have any stock losses attributed to leopards. Thus if predator-stock conflict is not reduced it will result in the retaliatory killing of leopards. This will have severe consequences for this relatively small population (estimated at 59 – 104 individuals by the prey-based model), which may ultimately lead to the local extinction of these leopards (Woodroffe & Ginsberg 1998).
- Full Text:
- Date Issued: 2009
Phylogeography and epifauna of two intertidal seaweeds on the coast of South Africa
- Authors: Mmonwa, Lucas Kolobe
- Date: 2009
- Subjects: Phylogeography -- South Africa , Marine algae -- South Africa , Red algae -- South Africa , Gelidium -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5738 , http://hdl.handle.net/10962/d1005424 , Phylogeography -- South Africa , Marine algae -- South Africa , Red algae -- South Africa , Gelidium -- South Africa
- Description: Southern African biogeographic boundaries delimit the phylogeographic distribution of some coastal and estuarine invertebrates. This study investigated the impact of these boundaries on the phylogeographic distribution of two intertidal red seaweeds, Gelidium pristoides and Hypnea spicifera using the mitochondrial Cox2-3 spacer and the nuclear ITS1 regions. G. pristoides spores have short distance-dispersal, while long distance-dispersal is more likely in H. spicifera via spores and drifting fertile thallus fragments. Both markers revealed a south-western and south-eastern lineage within G. pristoides but the breaks between lineages do not coincide with any recognised biogeographic limits. The Cox2-3 spacer revealed a boundary between the two lineages at the Alexandria Coastal Dunefield (ACD) and ITS1 at the Gamtoos-Van Stadens Dunefields (GVD) which is approximately 80km west of the ACD. The minor difference between the two markers regarding location of the phylogeographic boundary is probably due to the dating differences between the two dunefields. The ACD as developed currently is superimposed on the ancient dunefields which formed during the Pleistocene, coinciding with the Cox2-3 spacer sequences divergence which dates back 500,000 - 580,000 years. The GVD formed during the Holocene (6,500 - 4,000 years ago), coinciding with the ITS1 sequences divergence which dates 4,224 - 4,928 years ago. Thus, these phylogeographic boundaries probably appeared without the influence of biogeographic boundaries, but rather due to the lack of suitable habitat in the dunefields, coupled with short dispersal-distances of the spores. Analysis of the ITS1 and Cox2-3 spacer regions in H. spicifera revealed that the species is characterized by uniform genetic structure along the coastline. This reflects the species`s potential for long range expansion as it inhabits both the intertidal and subtidal zones; and this presumably leads to high gene flow among populations. The ITS1 sequences showed minimal genetic variation of one substitution between the gametophyte and tetrasporophyte generations within H. spicifera. This suggests the predominance of asexual reproduction, which reduces gene flow and fixes alleles between generations. ANOSIM and Bray-Curtis cluster analyses showed scale-dependant variation in the abundances of epifauna (mainly amphipod, isopod, mollusc and polychaete species) on G. pristoides. At small local (within site) and large (among sites) scales, there were weak and no structure in epifaunal abundances respectively. However, at larger, biogeographic scales, samples from the same biogeographic region tended to be clustered together. Thus, there was a group containing predominantly south coast samples and a group containing east coast samples mixed with the remaining south coast samples. Such scale-dependant variation in epifaunal abundances is probably due to the effects of factors driving species richness at small local (within site) scales (e.g. wave exposure, seaweed biomass) and at larger, biogeographic scales (e.g. surface sea temperature). Moreover, at very small (individual samples) scales; there was no correlation between epifauna composition and genotype of the seaweed. Seaweed samples characterized by distinct ITS1 or Cox2-3 spacer sequences did not show any significant differences in epifaunal composition. Although the distributional pattern of the epifaunal community observed at large biogeographic scale is not clear, it seems to be associated with the biogeographic regions. However, phylogeographic distribution of Gelidium pristoides is not connected to biogeographic regions. Thus, at larger, biogeographic scales, there is no correlation between phylogeographic distribution of G. pristoides and distribution of the associated fauna
- Full Text:
- Date Issued: 2009
- Authors: Mmonwa, Lucas Kolobe
- Date: 2009
- Subjects: Phylogeography -- South Africa , Marine algae -- South Africa , Red algae -- South Africa , Gelidium -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5738 , http://hdl.handle.net/10962/d1005424 , Phylogeography -- South Africa , Marine algae -- South Africa , Red algae -- South Africa , Gelidium -- South Africa
- Description: Southern African biogeographic boundaries delimit the phylogeographic distribution of some coastal and estuarine invertebrates. This study investigated the impact of these boundaries on the phylogeographic distribution of two intertidal red seaweeds, Gelidium pristoides and Hypnea spicifera using the mitochondrial Cox2-3 spacer and the nuclear ITS1 regions. G. pristoides spores have short distance-dispersal, while long distance-dispersal is more likely in H. spicifera via spores and drifting fertile thallus fragments. Both markers revealed a south-western and south-eastern lineage within G. pristoides but the breaks between lineages do not coincide with any recognised biogeographic limits. The Cox2-3 spacer revealed a boundary between the two lineages at the Alexandria Coastal Dunefield (ACD) and ITS1 at the Gamtoos-Van Stadens Dunefields (GVD) which is approximately 80km west of the ACD. The minor difference between the two markers regarding location of the phylogeographic boundary is probably due to the dating differences between the two dunefields. The ACD as developed currently is superimposed on the ancient dunefields which formed during the Pleistocene, coinciding with the Cox2-3 spacer sequences divergence which dates back 500,000 - 580,000 years. The GVD formed during the Holocene (6,500 - 4,000 years ago), coinciding with the ITS1 sequences divergence which dates 4,224 - 4,928 years ago. Thus, these phylogeographic boundaries probably appeared without the influence of biogeographic boundaries, but rather due to the lack of suitable habitat in the dunefields, coupled with short dispersal-distances of the spores. Analysis of the ITS1 and Cox2-3 spacer regions in H. spicifera revealed that the species is characterized by uniform genetic structure along the coastline. This reflects the species`s potential for long range expansion as it inhabits both the intertidal and subtidal zones; and this presumably leads to high gene flow among populations. The ITS1 sequences showed minimal genetic variation of one substitution between the gametophyte and tetrasporophyte generations within H. spicifera. This suggests the predominance of asexual reproduction, which reduces gene flow and fixes alleles between generations. ANOSIM and Bray-Curtis cluster analyses showed scale-dependant variation in the abundances of epifauna (mainly amphipod, isopod, mollusc and polychaete species) on G. pristoides. At small local (within site) and large (among sites) scales, there were weak and no structure in epifaunal abundances respectively. However, at larger, biogeographic scales, samples from the same biogeographic region tended to be clustered together. Thus, there was a group containing predominantly south coast samples and a group containing east coast samples mixed with the remaining south coast samples. Such scale-dependant variation in epifaunal abundances is probably due to the effects of factors driving species richness at small local (within site) scales (e.g. wave exposure, seaweed biomass) and at larger, biogeographic scales (e.g. surface sea temperature). Moreover, at very small (individual samples) scales; there was no correlation between epifauna composition and genotype of the seaweed. Seaweed samples characterized by distinct ITS1 or Cox2-3 spacer sequences did not show any significant differences in epifaunal composition. Although the distributional pattern of the epifaunal community observed at large biogeographic scale is not clear, it seems to be associated with the biogeographic regions. However, phylogeographic distribution of Gelidium pristoides is not connected to biogeographic regions. Thus, at larger, biogeographic scales, there is no correlation between phylogeographic distribution of G. pristoides and distribution of the associated fauna
- Full Text:
- Date Issued: 2009
Synthesis and photophysical properties of antimony and lead phthalocyanines
- Modibane, Kwena Desmond, Guest
- Authors: Modibane, Kwena Desmond , Guest
- Date: 2009 , 2009-02-27
- Subjects: Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4370 , http://hdl.handle.net/10962/d1005035 , Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Description: This work hereby presents the synthesis, spectroscopic and photophysical properties of newly synthesized lead (PbPc) and antimony (SbPc) phthalocyanines. The complexes are either unsubstituted or substituted at the peripheral and non-peripheral positions with phenoxy, 4-t-butylphenoxy and 4-benzyloxyphenoxy groups. The photophysical properties of these complexes were studied in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform as solvents. The fluorescence spectra for PbPc complexes were different to that of the excitation spectra due to demetallation upon excitation. On the other hand, the excitation spectra of oxidized antimony (Sb(V)Pc) derivatives were found to be similar to absorption spectra. High triplet quantum yields for PbPc and SbPc complexes ranging from 0.70 to 0.86, low triplet lifetimes (20–60 μs in DMSO, while they were <10 μs in the rest of the solvents) and low fluorescence quantum yields were observed and is attributed to the presence of heavy atoms (Pb and Sb ions). The nonlinear optical properties of PbPc complexes were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.8 W/cm2. The photodegradation studies of the PbPc and SbPc complexes synthesized showed that then are stable.
- Full Text:
- Date Issued: 2009
- Authors: Modibane, Kwena Desmond , Guest
- Date: 2009 , 2009-02-27
- Subjects: Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4370 , http://hdl.handle.net/10962/d1005035 , Phthalocyanines , Photochemistry , Antimony compounds , Lead compounds
- Description: This work hereby presents the synthesis, spectroscopic and photophysical properties of newly synthesized lead (PbPc) and antimony (SbPc) phthalocyanines. The complexes are either unsubstituted or substituted at the peripheral and non-peripheral positions with phenoxy, 4-t-butylphenoxy and 4-benzyloxyphenoxy groups. The photophysical properties of these complexes were studied in dimethylsulfoxide, dimethylformamide, toluene, tetrahydrofuran and chloroform as solvents. The fluorescence spectra for PbPc complexes were different to that of the excitation spectra due to demetallation upon excitation. On the other hand, the excitation spectra of oxidized antimony (Sb(V)Pc) derivatives were found to be similar to absorption spectra. High triplet quantum yields for PbPc and SbPc complexes ranging from 0.70 to 0.86, low triplet lifetimes (20–60 μs in DMSO, while they were <10 μs in the rest of the solvents) and low fluorescence quantum yields were observed and is attributed to the presence of heavy atoms (Pb and Sb ions). The nonlinear optical properties of PbPc complexes were studied in dimethylsulfoxide. The optical limiting threshold intensity (Ilim) for the PbPc derivatives were calculated and ranged from 2.1 to 6.8 W/cm2. The photodegradation studies of the PbPc and SbPc complexes synthesized showed that then are stable.
- Full Text:
- Date Issued: 2009
African traditional medicines-antiretroviral drug interactions: the effect of African potato (Hypoxis hemerocallidea) on the pharmacokinetics of efavirenz in humans
- Authors: Mogatle, Seloi
- Date: 2009
- Subjects: Potatoes -- Africa Potatoes -- Therapeutic use Medicinal plants Traditional medicine AIDS (Disease) -- Treatment HIV infections -- Drug therapy Drug interactions Antiretroviral agents Pharmacokinetics Hypoxidaceae -- Therapeutic use High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3773 , http://hdl.handle.net/10962/d1003251
- Description: African Potato (Hypoxis hemerocallidea), (AP) is an African traditional medicine (TM) that is commonly used for various nutritional/medicinal purposes and also by people infected with the human immuno deficiency virus HIV and AIDS patients as an immune booster. The use of AP has also been recommended by the former Minister of Health of South Africa for use by HIV positive people. The main phytochemical component of AP is a norlignan glucoside, hypoxoside, and other relatively minor components have also been reported. A recent in vitro study reported the effects of AP extracts, hypoxoside and rooperol (the metabolite of hypoxoside) on human metabolic enzymes such as the cytochrome P450 (CYP450) group of enzymes and also on the transporter protein, p-glycoprotein (P-gp). This research focussed on investigating the clinical significance of those in vitro effects on the pharmacokinetics of efavirenz (EFV) in humans. EFV was chosen as the substrate drug because it is in first-line regimen of treatment of HIV/AIDS in South Africa, and also has been reported to be a substrate for the specific CYP isozymes, 3A4 and 2B6, in common with APs metabolic involvement with 3A4. A high performance liquid chromatography method with ultra-violet detection (HPLC-UV) for the quantitative determination of EFV in plasma was developed and successfully validated according to international standards with good reproducibility, accuracy, recovery, linear response and requisite sensitivity. The preparation of the plasma samples for analysis was effected by using a simple and rapid precipitation method, and the mobile phase consisted of readily available solvents. EFV in plasma samples was found to be stable under the relevant storage conditions studied. The oral dose of AP, administered as a freshly prepared traditional decoction, was standardised based on the hypoxoside content, and the quality of all the AP decoctions was analysed immediately prior to administration, using a validated HPLC-UV method. A single dose, two-phase sequential study was conducted over a period of 31 days in 10 healthy volunteers. The clinical study was approved by the Rhodes University Ethical Standards Committee, and all the participants agreed to the conditions of the study by giving their informed consent. On day 1 of the study, human subjects were administered a 600 mg EFV tablet and blood samples were collected before dosing and at various intervals over a period of 48 hr post dosing. From day 16, a traditionally prepared AP decoction was administered daily at a standardized dose of 15 mg/kg/day per subject until day 30. On day 29, volunteers were administered a single 600 mg dose of EFV as was done on day 1. Plasma samples were harvested immediately after blood sample collection and frozen at -80 ºC until assayed. Geometric mean ratios of relevant pharmacokinetic parameters, Cmax (maximum plasma concentration achieved following dosing) and AUC0-48 (area under the curve of a plot of drug plasma concentrations versus time representing the extent of absorption) of EFV before and after co-administration of 14 successive daily doses of AP were compared and evaluated to determine whether an interaction had occurred. All subjects completed the study and the geometric mean ratios of Cmax and AUC0-48 were 97.30 and 102.82 with corresponding 90% confidence intervals (CIs) of 78.81-120.14% and 89.04-118.80%, respectively. Whereas the acceptance criteria for the ratios of the AUCs fell within the preset 90% CIs indicating no interaction, the Cmax ratios fell outside the limits. Although the protocol was developed in accordance with the United States of America Food & Drug Administration’s Guidance for Drug Interactions, a priori stating that both criteria need to fall within the acceptance limits to indicate no interaction, an argument is presented to waive the Cmax requirement for the declaration of an interaction. As a result, the pharmacokinetic data generated during this study indicated that the effect of AP on the pharmacokinetics of EFV is not clinically significant. Hence, co-administration of AP is unlikely to affect the clinical use of EFV. In summary the objectives of this project were: 1. To develop and validate a suitable HPLC-UV method for the quantitative determination of EFV in plasma. 2. To perform a mini-validation of the determination of hypoxoside for use as a marker in the quality control and standardisation of AP decoctions. 3. To conduct a clinical interaction study in order to determine whether AP affects the pharmacokinetics of EFV following concurrent administration. 4. To apply the validated HPLC-UV method to determine plasma concentrations of EFV in plasma of human subjects. 5. To use appropriate statistical methods and treatments such as a non-compartmental pharmacokinetic analysis to determine the occurrence of an interaction.
- Full Text:
- Date Issued: 2009
- Authors: Mogatle, Seloi
- Date: 2009
- Subjects: Potatoes -- Africa Potatoes -- Therapeutic use Medicinal plants Traditional medicine AIDS (Disease) -- Treatment HIV infections -- Drug therapy Drug interactions Antiretroviral agents Pharmacokinetics Hypoxidaceae -- Therapeutic use High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3773 , http://hdl.handle.net/10962/d1003251
- Description: African Potato (Hypoxis hemerocallidea), (AP) is an African traditional medicine (TM) that is commonly used for various nutritional/medicinal purposes and also by people infected with the human immuno deficiency virus HIV and AIDS patients as an immune booster. The use of AP has also been recommended by the former Minister of Health of South Africa for use by HIV positive people. The main phytochemical component of AP is a norlignan glucoside, hypoxoside, and other relatively minor components have also been reported. A recent in vitro study reported the effects of AP extracts, hypoxoside and rooperol (the metabolite of hypoxoside) on human metabolic enzymes such as the cytochrome P450 (CYP450) group of enzymes and also on the transporter protein, p-glycoprotein (P-gp). This research focussed on investigating the clinical significance of those in vitro effects on the pharmacokinetics of efavirenz (EFV) in humans. EFV was chosen as the substrate drug because it is in first-line regimen of treatment of HIV/AIDS in South Africa, and also has been reported to be a substrate for the specific CYP isozymes, 3A4 and 2B6, in common with APs metabolic involvement with 3A4. A high performance liquid chromatography method with ultra-violet detection (HPLC-UV) for the quantitative determination of EFV in plasma was developed and successfully validated according to international standards with good reproducibility, accuracy, recovery, linear response and requisite sensitivity. The preparation of the plasma samples for analysis was effected by using a simple and rapid precipitation method, and the mobile phase consisted of readily available solvents. EFV in plasma samples was found to be stable under the relevant storage conditions studied. The oral dose of AP, administered as a freshly prepared traditional decoction, was standardised based on the hypoxoside content, and the quality of all the AP decoctions was analysed immediately prior to administration, using a validated HPLC-UV method. A single dose, two-phase sequential study was conducted over a period of 31 days in 10 healthy volunteers. The clinical study was approved by the Rhodes University Ethical Standards Committee, and all the participants agreed to the conditions of the study by giving their informed consent. On day 1 of the study, human subjects were administered a 600 mg EFV tablet and blood samples were collected before dosing and at various intervals over a period of 48 hr post dosing. From day 16, a traditionally prepared AP decoction was administered daily at a standardized dose of 15 mg/kg/day per subject until day 30. On day 29, volunteers were administered a single 600 mg dose of EFV as was done on day 1. Plasma samples were harvested immediately after blood sample collection and frozen at -80 ºC until assayed. Geometric mean ratios of relevant pharmacokinetic parameters, Cmax (maximum plasma concentration achieved following dosing) and AUC0-48 (area under the curve of a plot of drug plasma concentrations versus time representing the extent of absorption) of EFV before and after co-administration of 14 successive daily doses of AP were compared and evaluated to determine whether an interaction had occurred. All subjects completed the study and the geometric mean ratios of Cmax and AUC0-48 were 97.30 and 102.82 with corresponding 90% confidence intervals (CIs) of 78.81-120.14% and 89.04-118.80%, respectively. Whereas the acceptance criteria for the ratios of the AUCs fell within the preset 90% CIs indicating no interaction, the Cmax ratios fell outside the limits. Although the protocol was developed in accordance with the United States of America Food & Drug Administration’s Guidance for Drug Interactions, a priori stating that both criteria need to fall within the acceptance limits to indicate no interaction, an argument is presented to waive the Cmax requirement for the declaration of an interaction. As a result, the pharmacokinetic data generated during this study indicated that the effect of AP on the pharmacokinetics of EFV is not clinically significant. Hence, co-administration of AP is unlikely to affect the clinical use of EFV. In summary the objectives of this project were: 1. To develop and validate a suitable HPLC-UV method for the quantitative determination of EFV in plasma. 2. To perform a mini-validation of the determination of hypoxoside for use as a marker in the quality control and standardisation of AP decoctions. 3. To conduct a clinical interaction study in order to determine whether AP affects the pharmacokinetics of EFV following concurrent administration. 4. To apply the validated HPLC-UV method to determine plasma concentrations of EFV in plasma of human subjects. 5. To use appropriate statistical methods and treatments such as a non-compartmental pharmacokinetic analysis to determine the occurrence of an interaction.
- Full Text:
- Date Issued: 2009
Dynamics of larval fish and zooplankton in selected south and west coast estuaries of South Africa
- Montoya-Maya, Phanor Hernando
- Authors: Montoya-Maya, Phanor Hernando
- Date: 2009
- Subjects: Marine zooplankton -- South Africa , Zooplankton -- South Africa , Fishes -- Larvae -- South Africa , Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Environmental monitoring -- South Africa , Coastal zone management -- South Africa , Estuarine area conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5263 , http://hdl.handle.net/10962/d1005107 , Marine zooplankton -- South Africa , Zooplankton -- South Africa , Fishes -- Larvae -- South Africa , Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Environmental monitoring -- South Africa , Coastal zone management -- South Africa , Estuarine area conservation -- South Africa
- Description: Larval fish and zooplankton assemblages were studied in nine south and west coast estuaries in the cool-temperate and the cool/warm-temperate boundary region between June 2003 and March 2004. This study served to provide new information on previously unstudied estuaries and expand on existing knowledge of larval fish and zooplankton assemblages associated with various estuary types. The south and west coast estuaries sampled in this study showed lower salinities (12.2 - 13.7), lower water temperatures (14.5 - 16.9 °C) and higher turbidities (k = 0.02 - 0.04) in winter and spring while higher salinities (21.7 - 21.8), higher water temperatures (21.7 - 23.1°C) and lower turbidities (k <0.02) were observed in summer and autumn. Mean winter and summer water temperatures in estuaries were lower than those observed in warm-temperate and subtropical systems by other researchers. A total of 49274 larval fishes were caught, comprising 9 orders, 20 families, 29 genera and 47 taxa. The clupeid Gilchristella aestuaria (78.8 %) dominated the larval fish assemblages and occurred in all estuaries. The majority (70 %) of identified species are endemic to southern Africa and 96.4 % of larval fishes caught were estuary-resident species. The zooplankton study yielded a total of 44 taxa, comprising 7 phyla, >20 orders and >35 families. The copepod Pseudodiaptomus hessei dominated (59 %) the zooplankton and occurred in similar densities to those observed in other South African estuaries. Larval fish and zooplankton varied across seasons, peaking simultaneously in summer although zooplankton showed additional density peaks during the closed phase of some estuaries. Both plankton components were more abundant in the oligohaline and mesohaline zones within the estuaries. Freshwater input, estuary type and the biogeography of the area influenced the composition and structure of larval fish and zooplankton assemblages in these estuaries. The findings suggest that the estuaries are functioning as successful breeding areas for the larvae of endemic estuary-resident fish species and that these estuaries have to be managed to ensure an adequate freshwater supply to maintain the biological integrity of the ecosystem, specially the maintenance of the highly productive River-Estuary Interface (REI) regions.
- Full Text:
- Date Issued: 2009
- Authors: Montoya-Maya, Phanor Hernando
- Date: 2009
- Subjects: Marine zooplankton -- South Africa , Zooplankton -- South Africa , Fishes -- Larvae -- South Africa , Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Environmental monitoring -- South Africa , Coastal zone management -- South Africa , Estuarine area conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5263 , http://hdl.handle.net/10962/d1005107 , Marine zooplankton -- South Africa , Zooplankton -- South Africa , Fishes -- Larvae -- South Africa , Estuarine ecology -- South Africa , Estuaries -- South Africa -- Management , Environmental monitoring -- South Africa , Coastal zone management -- South Africa , Estuarine area conservation -- South Africa
- Description: Larval fish and zooplankton assemblages were studied in nine south and west coast estuaries in the cool-temperate and the cool/warm-temperate boundary region between June 2003 and March 2004. This study served to provide new information on previously unstudied estuaries and expand on existing knowledge of larval fish and zooplankton assemblages associated with various estuary types. The south and west coast estuaries sampled in this study showed lower salinities (12.2 - 13.7), lower water temperatures (14.5 - 16.9 °C) and higher turbidities (k = 0.02 - 0.04) in winter and spring while higher salinities (21.7 - 21.8), higher water temperatures (21.7 - 23.1°C) and lower turbidities (k <0.02) were observed in summer and autumn. Mean winter and summer water temperatures in estuaries were lower than those observed in warm-temperate and subtropical systems by other researchers. A total of 49274 larval fishes were caught, comprising 9 orders, 20 families, 29 genera and 47 taxa. The clupeid Gilchristella aestuaria (78.8 %) dominated the larval fish assemblages and occurred in all estuaries. The majority (70 %) of identified species are endemic to southern Africa and 96.4 % of larval fishes caught were estuary-resident species. The zooplankton study yielded a total of 44 taxa, comprising 7 phyla, >20 orders and >35 families. The copepod Pseudodiaptomus hessei dominated (59 %) the zooplankton and occurred in similar densities to those observed in other South African estuaries. Larval fish and zooplankton varied across seasons, peaking simultaneously in summer although zooplankton showed additional density peaks during the closed phase of some estuaries. Both plankton components were more abundant in the oligohaline and mesohaline zones within the estuaries. Freshwater input, estuary type and the biogeography of the area influenced the composition and structure of larval fish and zooplankton assemblages in these estuaries. The findings suggest that the estuaries are functioning as successful breeding areas for the larvae of endemic estuary-resident fish species and that these estuaries have to be managed to ensure an adequate freshwater supply to maintain the biological integrity of the ecosystem, specially the maintenance of the highly productive River-Estuary Interface (REI) regions.
- Full Text:
- Date Issued: 2009
A real time HF beacon monitoring station for South Africa
- Authors: Mudzingwa, Courage
- Date: 2009
- Subjects: Radio , Shortwave radio , Radio and television towers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5486 , http://hdl.handle.net/10962/d1005272 , Radio , Shortwave radio , Radio and television towers
- Description: High frequency, HF (3 - 30 MHz), radio communications are greatly affected by ionospheric conditions. Both civilian and military users need reliable, real time propagation information to show at any time the feasibility of communicating to any part of the world on a particular frequency band. For this thesis, an automated receiving/monitoring station for the Northern California DX Foundation (NCDXF)/ International Amateur Radio Union (IARU) International Beacon Project was setup at the Hermanus Magnetic Observatory, HMO (34.42oS, 19.22oE) to monitor international beacons on 20 m, 17 m, 15 m, 12 m and 10 m bands. The beacons form a world wide multiband network. The task of monitoring the beacons was broken down into two steps. Initially the single band station, at 14.10 MHz, was installed and later it was upgraded to a multiband station capable of automatically monitoring all the five HF bands. The single band station setup involved the construction and installation of the half-wave dipole antenna, construction and installation of an HF choke balun; and the choice of Faros 1.3 as the appropriate monitoring software. The multiband monitoring station set-up involved the installation of an MFJ-1778 G5RV multiband antenna, construction and installation of a Communication Interface - V (CI-V) level converter and configuring the Faros 1.3 software to monitor the beacons on all five HF bands. Then a web page was created on the HMO space weather website (http://spaceweather.hmo.ac.za). Here, the real-time signal to noise ratio (SNR) and short path (SP)/long path (LP) plots are uploaded every 3 minutes, showing real time HF propagation conditions on the five HF bands. Historical propagation data are archived for later analysis. A preliminary data analysis was done to confirm the peration of the monitoring station. The archived data were analysed and compared to ICEPAC (Ionospheric Communications Enhanced Profile Analysis and Circuit) predictions. Results show that the real-time signal plots as well as the archive of historical signal plots, convey information on ropagation conditions to users in terms that are easy to interpret and understand.
- Full Text:
- Date Issued: 2009
- Authors: Mudzingwa, Courage
- Date: 2009
- Subjects: Radio , Shortwave radio , Radio and television towers
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5486 , http://hdl.handle.net/10962/d1005272 , Radio , Shortwave radio , Radio and television towers
- Description: High frequency, HF (3 - 30 MHz), radio communications are greatly affected by ionospheric conditions. Both civilian and military users need reliable, real time propagation information to show at any time the feasibility of communicating to any part of the world on a particular frequency band. For this thesis, an automated receiving/monitoring station for the Northern California DX Foundation (NCDXF)/ International Amateur Radio Union (IARU) International Beacon Project was setup at the Hermanus Magnetic Observatory, HMO (34.42oS, 19.22oE) to monitor international beacons on 20 m, 17 m, 15 m, 12 m and 10 m bands. The beacons form a world wide multiband network. The task of monitoring the beacons was broken down into two steps. Initially the single band station, at 14.10 MHz, was installed and later it was upgraded to a multiband station capable of automatically monitoring all the five HF bands. The single band station setup involved the construction and installation of the half-wave dipole antenna, construction and installation of an HF choke balun; and the choice of Faros 1.3 as the appropriate monitoring software. The multiband monitoring station set-up involved the installation of an MFJ-1778 G5RV multiband antenna, construction and installation of a Communication Interface - V (CI-V) level converter and configuring the Faros 1.3 software to monitor the beacons on all five HF bands. Then a web page was created on the HMO space weather website (http://spaceweather.hmo.ac.za). Here, the real-time signal to noise ratio (SNR) and short path (SP)/long path (LP) plots are uploaded every 3 minutes, showing real time HF propagation conditions on the five HF bands. Historical propagation data are archived for later analysis. A preliminary data analysis was done to confirm the peration of the monitoring station. The archived data were analysed and compared to ICEPAC (Ionospheric Communications Enhanced Profile Analysis and Circuit) predictions. Results show that the real-time signal plots as well as the archive of historical signal plots, convey information on ropagation conditions to users in terms that are easy to interpret and understand.
- Full Text:
- Date Issued: 2009
A common analysis framework for simulated streaming-video networks
- Authors: Mulumba, Patrick
- Date: 2009
- Subjects: Computer networks -- Management , Streaming video , Mass media -- Technological innovations
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4590 , http://hdl.handle.net/10962/d1004828 , Computer networks -- Management , Streaming video , Mass media -- Technological innovations
- Description: Distributed media streaming has been driven by the combination of improved media compression techniques and an increase in the availability of bandwidth. This increase has lead to the development of various streaming distribution engines (systems/services), which currently provide the majority of the streaming media available throughout the Internet. This study aimed to analyse a range of existing commercial and open-source streaming media distribution engines, and classify them in such a way as to define a Common Analysis Framework for Simulated Streaming-Video Networks (CAFSS-Net). This common framework was used as the basis for a simulation tool intended to aid in the development and deployment of streaming media networks and predict the performance impacts of both network configuration changes, video features (scene complexity, resolution) and general scaling. CAFSS-Net consists of six components: the server, the client(s), the network simulator, the video publishing tools, the videos and the evaluation tool-set. Test scenarios are presented consisting of different network configurations, scales and external traffic specifications. From these test scenarios, results were obtained to determine interesting observations attained and to provide an overview of the different test specications for this study. From these results, an analysis of the system was performed, yielding relationships between the videos, the different bandwidths, the different measurement tools and the different components of CAFSS-Net. Based on the analysis of the results, the implications for CAFSS-Net highlighted different achievements and proposals for future work for the different components. CAFSS-Net was able to successfully integrate all of its components to evaluate the different streaming scenarios. The streaming server, client and video components accomplished their objectives. It is noted that although the video publishing tool was able to provide the necessary compression/decompression services, proposals for the implementation of alternative compression/decompression schemes could serve as a suitable extension. The network simulator and evaluation tool-set components were also successful, but future tests (particularly in low bandwidth scenarios) are suggested in order to further improve the accuracy of the framework as a whole. CAFSS-Net is especially successful with analysing high bandwidth connections with the results being similar to those of the physical network tests.
- Full Text:
- Date Issued: 2009
- Authors: Mulumba, Patrick
- Date: 2009
- Subjects: Computer networks -- Management , Streaming video , Mass media -- Technological innovations
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4590 , http://hdl.handle.net/10962/d1004828 , Computer networks -- Management , Streaming video , Mass media -- Technological innovations
- Description: Distributed media streaming has been driven by the combination of improved media compression techniques and an increase in the availability of bandwidth. This increase has lead to the development of various streaming distribution engines (systems/services), which currently provide the majority of the streaming media available throughout the Internet. This study aimed to analyse a range of existing commercial and open-source streaming media distribution engines, and classify them in such a way as to define a Common Analysis Framework for Simulated Streaming-Video Networks (CAFSS-Net). This common framework was used as the basis for a simulation tool intended to aid in the development and deployment of streaming media networks and predict the performance impacts of both network configuration changes, video features (scene complexity, resolution) and general scaling. CAFSS-Net consists of six components: the server, the client(s), the network simulator, the video publishing tools, the videos and the evaluation tool-set. Test scenarios are presented consisting of different network configurations, scales and external traffic specifications. From these test scenarios, results were obtained to determine interesting observations attained and to provide an overview of the different test specications for this study. From these results, an analysis of the system was performed, yielding relationships between the videos, the different bandwidths, the different measurement tools and the different components of CAFSS-Net. Based on the analysis of the results, the implications for CAFSS-Net highlighted different achievements and proposals for future work for the different components. CAFSS-Net was able to successfully integrate all of its components to evaluate the different streaming scenarios. The streaming server, client and video components accomplished their objectives. It is noted that although the video publishing tool was able to provide the necessary compression/decompression services, proposals for the implementation of alternative compression/decompression schemes could serve as a suitable extension. The network simulator and evaluation tool-set components were also successful, but future tests (particularly in low bandwidth scenarios) are suggested in order to further improve the accuracy of the framework as a whole. CAFSS-Net is especially successful with analysing high bandwidth connections with the results being similar to those of the physical network tests.
- Full Text:
- Date Issued: 2009
Synthesis and characterization of novel platinum complexes : their anticancer behaviour
- Authors: Myburgh, Jolanda
- Date: 2009
- Subjects: Complex compounds -- Synthesis , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10429 , http://hdl.handle.net/10948/d1018621
- Description: In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.
- Full Text:
- Date Issued: 2009
- Authors: Myburgh, Jolanda
- Date: 2009
- Subjects: Complex compounds -- Synthesis , Platinum compounds , Antineoplastic agents
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10429 , http://hdl.handle.net/10948/d1018621
- Description: In this dissertation novel non-leaving groups were employed to synthesize platinum complexes which can contribute to the understanding or improvement of anticancer action. These complexes basically consist of (NS)-chelate and amineplatinum complexes. Bidentate (NS)-donor ligands were used as non-leaving ligands in the syntheses of platinum(II) complexes with iodide, chloride, bromide and oxalate anions as leaving groups. These complexes were synthesized and studied since many questions regarding the interaction of sulfur donors and platinum still exists. These relate to thermodynamic and kinetic factors and their influence on anticancer action. In this dissertation the properties of novel platinum(II) complexes of a bidentate ligand having an aromatic nitrogen-donor atom in combination with a thioethereal sulfur atom capable of forming a five membered ring with platinum(II) were studied. The general structure of the (NS) -ligands used were N-alkyl-2-methylthioalkyl imidazole. Alkyl groups used were methyl, ethyl and propyl. Although amine complexes of platinum have been extensively studied there are some new aspects of these that are worthwhile investigating. In this dissertation amines having planar attachments which will be at an angle with the coordination plane viz. benzylamine and amines having cyclic aliphatic groups namely cyclopropyl and cyclohexyl were investigated. Some of the (NS) - and amineplatinum(II) complexes were oxidised to their mononitroplatinum(IV) analogues . The motivation for the synthesis of these complexes was the greater kinetic stability of platinum(IV) and recent research has shown that a specific type of platinum(IV) compound shows suitable properties as an anticancer agent. These complexes were characterised by a variety of spectral means (IR, NMR, mass spectroscopy) as well as elemental analysis, solubility determinations, thermal analysis (TGA), ionization studies and finally their anticancer behaviour towards three different cell lines(Hela, MCF 7, Ht29) and in this process they were compared to the behaviour of cisplatin as a reference. A few have shown promising anticancer behaviour.
- Full Text:
- Date Issued: 2009
A situational analysis on the public participation processes in integrated water resources management in the Kat River Valley, Eastern Cape, South Africa
- Authors: Naidoo, Merle
- Date: 2009
- Subjects: South Africa. Dept. of Water Affairs and Forestry , Water-supply -- South Africa -- Kat River Valley , Water quality management -- South Africa -- Kat River Valley , Water-supply -- Government policy -- South Africa -- Kat River Valley , Water resources development -- South Africa -- Kat River Valley , Integrated water development -- South Africa -- Kat River Valley , Rural development -- South Africa -- Kat River Valley
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4854 , http://hdl.handle.net/10962/d1005530 , South Africa. Dept. of Water Affairs and Forestry , Water-supply -- South Africa -- Kat River Valley , Water quality management -- South Africa -- Kat River Valley , Water-supply -- Government policy -- South Africa -- Kat River Valley , Water resources development -- South Africa -- Kat River Valley , Integrated water development -- South Africa -- Kat River Valley , Rural development -- South Africa -- Kat River Valley
- Description: Public participation in water management processes is one of the internationally recognised and adopted principles of Integrated Water Resource Management. The South African Department of Water Affairs and Forestry aims to facilitate the decentralisation of water management powers to the local community level via the establishment of regional and local water management institutions, namely Catchment Management Agencies, Water User Associations and Catchment Forums. The National Water Act (No. 36 of 1998) acknowledges that the discriminatory laws and practices of the past have prevented equal access to water and the use of water resources. The contribution of water management institutions to social and economic development, in particular poverty eradication and food security, is mentioned in the water act. The participation of poor rural communities living in the Kat valley, an area where an elite minority reap the benefits of water use for agriculture, is the focus of this research. Their participation, perceptions and experiences are documented and explored to determine how the promulgation of post-apartheid water policy and legislation has affected their access to water. The results of this research are based on data collected from several methods including surveys, workshops and observation. Analysis of these data revealed the complicated and stagnant nature of participation from Kat valley rural communities in local water management initiatives and organisations. Existing water management organisations were not successful in stimulating poor people’s participation as they were unable to address their primary concerns, namely a secure source of potable water, employment and access to water for agricultural purposes. This thesis asserts that the Department of Water Affairs and Forestry, as the custodian of South Africa’s water resources, has not taken on a supportive, accountable role in assisting marginalised communities with improving their access to water for domestic purposes and securing access to water rights for productive use. This, in turn, has led to dissatisfaction among these communities and a wariness of participatory activities that focus mainly on raising environmental awareness. The establishment of effective accountability relationships among all stakeholders, pro-poor water management structures and initiatives, as well as integrated and co-operative management of natural resources, are needed to revitalise the present participation of poor communities living in rural areas.
- Full Text:
- Date Issued: 2009
- Authors: Naidoo, Merle
- Date: 2009
- Subjects: South Africa. Dept. of Water Affairs and Forestry , Water-supply -- South Africa -- Kat River Valley , Water quality management -- South Africa -- Kat River Valley , Water-supply -- Government policy -- South Africa -- Kat River Valley , Water resources development -- South Africa -- Kat River Valley , Integrated water development -- South Africa -- Kat River Valley , Rural development -- South Africa -- Kat River Valley
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4854 , http://hdl.handle.net/10962/d1005530 , South Africa. Dept. of Water Affairs and Forestry , Water-supply -- South Africa -- Kat River Valley , Water quality management -- South Africa -- Kat River Valley , Water-supply -- Government policy -- South Africa -- Kat River Valley , Water resources development -- South Africa -- Kat River Valley , Integrated water development -- South Africa -- Kat River Valley , Rural development -- South Africa -- Kat River Valley
- Description: Public participation in water management processes is one of the internationally recognised and adopted principles of Integrated Water Resource Management. The South African Department of Water Affairs and Forestry aims to facilitate the decentralisation of water management powers to the local community level via the establishment of regional and local water management institutions, namely Catchment Management Agencies, Water User Associations and Catchment Forums. The National Water Act (No. 36 of 1998) acknowledges that the discriminatory laws and practices of the past have prevented equal access to water and the use of water resources. The contribution of water management institutions to social and economic development, in particular poverty eradication and food security, is mentioned in the water act. The participation of poor rural communities living in the Kat valley, an area where an elite minority reap the benefits of water use for agriculture, is the focus of this research. Their participation, perceptions and experiences are documented and explored to determine how the promulgation of post-apartheid water policy and legislation has affected their access to water. The results of this research are based on data collected from several methods including surveys, workshops and observation. Analysis of these data revealed the complicated and stagnant nature of participation from Kat valley rural communities in local water management initiatives and organisations. Existing water management organisations were not successful in stimulating poor people’s participation as they were unable to address their primary concerns, namely a secure source of potable water, employment and access to water for agricultural purposes. This thesis asserts that the Department of Water Affairs and Forestry, as the custodian of South Africa’s water resources, has not taken on a supportive, accountable role in assisting marginalised communities with improving their access to water for domestic purposes and securing access to water rights for productive use. This, in turn, has led to dissatisfaction among these communities and a wariness of participatory activities that focus mainly on raising environmental awareness. The establishment of effective accountability relationships among all stakeholders, pro-poor water management structures and initiatives, as well as integrated and co-operative management of natural resources, are needed to revitalise the present participation of poor communities living in rural areas.
- Full Text:
- Date Issued: 2009
Statistical models for pricing weather derivatives for Port Elizabeth
- Authors: Nasila, Mark Wopicho
- Date: 2009
- Subjects: Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10567 , http://hdl.handle.net/10948/1018 , Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Description: Weather has a significant impact on business activities of many kinds. The list of economic activities subjected to the risk of the weather include: the energy producers and consumers, the industry of leisure, the insurance industry, the food industry and the agricultural industries but the primary industry, namely the energy industry, has given rise to the demand for weather derivatives and has caused the weather risk management industry to evolve actively. A derivative is a contract or security, whose payoffs depend upon the price of an underlying asset price, and is used to control the risks of naturally-arising exposures to such an asset price. Therefore weather derivatives are financial contracts with payouts that depend on weather in some form. It is a contract that provides a payoff in response to an index level based on weather phenomena (West, 2002).The underlying variable can be for example humidity, rain, snowfall, temperature, or even sunshine. The main players who take part in the weather derivatives markets industry can be grouped in to five main categories, namely: 1) End users who are also referred to as hedgers 2) Speculators 3) Market makers 4) Brokers 5) Insurance and re-insurance companies. Since the late 90’s when the first weather derivatives transactions were recorded, the underlying market has witnessed the development of a new derivative market in the United States, which is gradually expanding across Europe. However, the newly developed market for weather derivatives is not liquid in Africa and specifically South Africa mainly due to the following factors: 1) Many companies and business organisations have not yet established a hedging policy or even figured out how their businesses or industries are exposed to weather risks. 2 2) “Since many companies and industries depend on insurance companies to cover their risks, it is possible that the solutions suggested by these companies or industries looking for protection from weather risks differ according to the cover provided by these insurance organisations “(Micali, 2008). The main aim of this study is to review available statistical models for pricing derivatives, with temperature as the underlying which could enable industries, businesses and other organisations in South Africa to protect themselves against losses due to fluctuations in the weather and therefore hedge their risks.
- Full Text:
- Date Issued: 2009
- Authors: Nasila, Mark Wopicho
- Date: 2009
- Subjects: Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10567 , http://hdl.handle.net/10948/1018 , Weather derivatives -- Prices -- South Africa -- Port Elizabeth
- Description: Weather has a significant impact on business activities of many kinds. The list of economic activities subjected to the risk of the weather include: the energy producers and consumers, the industry of leisure, the insurance industry, the food industry and the agricultural industries but the primary industry, namely the energy industry, has given rise to the demand for weather derivatives and has caused the weather risk management industry to evolve actively. A derivative is a contract or security, whose payoffs depend upon the price of an underlying asset price, and is used to control the risks of naturally-arising exposures to such an asset price. Therefore weather derivatives are financial contracts with payouts that depend on weather in some form. It is a contract that provides a payoff in response to an index level based on weather phenomena (West, 2002).The underlying variable can be for example humidity, rain, snowfall, temperature, or even sunshine. The main players who take part in the weather derivatives markets industry can be grouped in to five main categories, namely: 1) End users who are also referred to as hedgers 2) Speculators 3) Market makers 4) Brokers 5) Insurance and re-insurance companies. Since the late 90’s when the first weather derivatives transactions were recorded, the underlying market has witnessed the development of a new derivative market in the United States, which is gradually expanding across Europe. However, the newly developed market for weather derivatives is not liquid in Africa and specifically South Africa mainly due to the following factors: 1) Many companies and business organisations have not yet established a hedging policy or even figured out how their businesses or industries are exposed to weather risks. 2 2) “Since many companies and industries depend on insurance companies to cover their risks, it is possible that the solutions suggested by these companies or industries looking for protection from weather risks differ according to the cover provided by these insurance organisations “(Micali, 2008). The main aim of this study is to review available statistical models for pricing derivatives, with temperature as the underlying which could enable industries, businesses and other organisations in South Africa to protect themselves against losses due to fluctuations in the weather and therefore hedge their risks.
- Full Text:
- Date Issued: 2009
Clustering algorithms and their effect on edge preservation in image compression
- Authors: Ndebele, Nothando Elizabeth
- Date: 2009
- Subjects: Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5576 , http://hdl.handle.net/10962/d1008210 , Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Description: Image compression aims to reduce the amount of data that is stored or transmitted for images. One technique that may be used to this end is vector quantization. Vectors may be used to represent images. Vector quantization reduces the number of vectors required for an image by representing a cluster of similar vectors by one typical vector that is part of a set of vectors referred to as the code book. For compression, for each image vector, only the closest codebook vector is stored or transmitted. For reconstruction, the image vectors are again replaced by the the closest codebook vectors. Hence vector quantization is a lossy compression technique and the quality of the reconstructed image depends strongly on the quality of the codebook. The design of the codebook is therefore an important part of the process. In this thesis we examine three clustering algorithms which can be used for codebook design in image compression: c-means (CM), fuzzy c-means (FCM) and learning vector quantization (LVQ). We give a description of these algorithms and their application to codebook design. Edges are an important part of the visual information contained in an image. It is essential therefore to use codebooks which allow an accurate representation of the edges. One of the shortcomings of using vector quantization is poor edge representation. We therefore carry out experiments using these algorithms to compare their edge preserving qualities. We also investigate the combination of these algorithms with classified vector quantization (CVQ) and the replication method (RM). Both these methods have been suggested as methods for improving edge representation. We use a cross validation approach to estimate the mean squared error to measure the performance of each of the algorithms and the edge preserving methods. The results reflect that the edges are less accurately represented than the non - edge areas when using CM, FCM and LVQ. The advantage of using CVQ is that the time taken for code book design is reduced particularly for CM and FCM. RM is found to be effective where the codebook is trained using a set that has larger proportions of edges than the test set.
- Full Text:
- Date Issued: 2009
- Authors: Ndebele, Nothando Elizabeth
- Date: 2009
- Subjects: Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5576 , http://hdl.handle.net/10962/d1008210 , Image compression , Vector analysis , Cluster analysis , Cluster anaylsis -- Data processing , Algorithms
- Description: Image compression aims to reduce the amount of data that is stored or transmitted for images. One technique that may be used to this end is vector quantization. Vectors may be used to represent images. Vector quantization reduces the number of vectors required for an image by representing a cluster of similar vectors by one typical vector that is part of a set of vectors referred to as the code book. For compression, for each image vector, only the closest codebook vector is stored or transmitted. For reconstruction, the image vectors are again replaced by the the closest codebook vectors. Hence vector quantization is a lossy compression technique and the quality of the reconstructed image depends strongly on the quality of the codebook. The design of the codebook is therefore an important part of the process. In this thesis we examine three clustering algorithms which can be used for codebook design in image compression: c-means (CM), fuzzy c-means (FCM) and learning vector quantization (LVQ). We give a description of these algorithms and their application to codebook design. Edges are an important part of the visual information contained in an image. It is essential therefore to use codebooks which allow an accurate representation of the edges. One of the shortcomings of using vector quantization is poor edge representation. We therefore carry out experiments using these algorithms to compare their edge preserving qualities. We also investigate the combination of these algorithms with classified vector quantization (CVQ) and the replication method (RM). Both these methods have been suggested as methods for improving edge representation. We use a cross validation approach to estimate the mean squared error to measure the performance of each of the algorithms and the edge preserving methods. The results reflect that the edges are less accurately represented than the non - edge areas when using CM, FCM and LVQ. The advantage of using CVQ is that the time taken for code book design is reduced particularly for CM and FCM. RM is found to be effective where the codebook is trained using a set that has larger proportions of edges than the test set.
- Full Text:
- Date Issued: 2009
Purification and characterization of fructosyltransferase for the synthesis of short-chain fructo-oligosaccharides and investigation into thier anti-carcinogenic properties
- Authors: Nemukula, Aluwani
- Date: 2009
- Subjects: Oligosaccharides , Polygalacturonase , Aspergillus , Fructose , Inulin , Cancer -- Prevention , Cancer -- Research , Carcinogens , High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3927 , http://hdl.handle.net/10962/d1003986 , Oligosaccharides , Polygalacturonase , Aspergillus , Fructose , Inulin , Cancer -- Prevention , Cancer -- Research , Carcinogens , High performance liquid chromatography
- Description: There is a growing attention in the synthesis of fructo-oligosaccharides (FOS) due to their excellent bio-functional and health-promoting properties. The current production processes are limited to chemical hydrolysis reactions of plant extracts, which are often associated with several drawbacks. In this study, fructosyltransferase (FTase) and polygalacturonase (PGase) activities, present in a commercial enzyme preparation (Pectinex® Ultra SP-L) sourced from Aspergillus aculeatus, have been separated and fully purified by anion-exchange and sizeexclusion chromatography. The FTase possesses fructosyl transfer activity for FOS synthesis and the PGase has pectin hydrolytic activity. Fructosyltransferase is a single-band protein with a molecular weight of 85 kDa, whereas PGase is a distinct protein of 40 kDa. The temperature and pH optima of FTase were 60 ºC and 6.0, with a half-life of 8 h; while that for PGase were 40 ºC and 6.0, respectively. FTase was slightly inhibited in the presence of Ni²⁺, Mg²⁺ and urea; but PGase was more susceptible to divalent ions such as Ca²⁺, Mg²⁺ and Mn²⁺. The kinetic parameters (Km and Vmax) of FTase for the hydrolysis of β-(2→1) linkages from sucrose were 752.3 mM and 120.5 μmol.min⁻¹.mL⁻¹, respectively; whereas the same parameters for pectin hydrolysis by PGase were 13.0 mg.mL⁻¹ and 263 μmol.min-1.mL⁻¹, respectively. The purified FTase was able to transfer fructosyl residues from sucrose, synthesizing the corresponding chains of FOS. PGase was relatively stable at 40 ºC (t½ > 3 h), depolymerizing the pectin backbone while releasing the inulins from within the chicory roots. Analysis of various mixtures of FOS by mass spectrometry, HPLC and ¹H-NMR was undertaken. Results indicated that MS with electrospray ionization and ¹H-NMR are capable of providing relative quantitative data of the FOS present in the mixtures. The pharmaceutical effects of various sc-FOS (0.5%, v/v) and SCFA (0.3%, v/v) on certain bacterial enzymes (β-glucuronidase, urease and β-glucosidase) associated with the formation of carcinogens were also studied. These enzyme activities were not directly influenced by the sc-FOS, but were found to be remarkably decreased by SCFA, pointing toward the prebiotic effect of FOS in intestinal microflora modulation.
- Full Text:
- Date Issued: 2009
- Authors: Nemukula, Aluwani
- Date: 2009
- Subjects: Oligosaccharides , Polygalacturonase , Aspergillus , Fructose , Inulin , Cancer -- Prevention , Cancer -- Research , Carcinogens , High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3927 , http://hdl.handle.net/10962/d1003986 , Oligosaccharides , Polygalacturonase , Aspergillus , Fructose , Inulin , Cancer -- Prevention , Cancer -- Research , Carcinogens , High performance liquid chromatography
- Description: There is a growing attention in the synthesis of fructo-oligosaccharides (FOS) due to their excellent bio-functional and health-promoting properties. The current production processes are limited to chemical hydrolysis reactions of plant extracts, which are often associated with several drawbacks. In this study, fructosyltransferase (FTase) and polygalacturonase (PGase) activities, present in a commercial enzyme preparation (Pectinex® Ultra SP-L) sourced from Aspergillus aculeatus, have been separated and fully purified by anion-exchange and sizeexclusion chromatography. The FTase possesses fructosyl transfer activity for FOS synthesis and the PGase has pectin hydrolytic activity. Fructosyltransferase is a single-band protein with a molecular weight of 85 kDa, whereas PGase is a distinct protein of 40 kDa. The temperature and pH optima of FTase were 60 ºC and 6.0, with a half-life of 8 h; while that for PGase were 40 ºC and 6.0, respectively. FTase was slightly inhibited in the presence of Ni²⁺, Mg²⁺ and urea; but PGase was more susceptible to divalent ions such as Ca²⁺, Mg²⁺ and Mn²⁺. The kinetic parameters (Km and Vmax) of FTase for the hydrolysis of β-(2→1) linkages from sucrose were 752.3 mM and 120.5 μmol.min⁻¹.mL⁻¹, respectively; whereas the same parameters for pectin hydrolysis by PGase were 13.0 mg.mL⁻¹ and 263 μmol.min-1.mL⁻¹, respectively. The purified FTase was able to transfer fructosyl residues from sucrose, synthesizing the corresponding chains of FOS. PGase was relatively stable at 40 ºC (t½ > 3 h), depolymerizing the pectin backbone while releasing the inulins from within the chicory roots. Analysis of various mixtures of FOS by mass spectrometry, HPLC and ¹H-NMR was undertaken. Results indicated that MS with electrospray ionization and ¹H-NMR are capable of providing relative quantitative data of the FOS present in the mixtures. The pharmaceutical effects of various sc-FOS (0.5%, v/v) and SCFA (0.3%, v/v) on certain bacterial enzymes (β-glucuronidase, urease and β-glucosidase) associated with the formation of carcinogens were also studied. These enzyme activities were not directly influenced by the sc-FOS, but were found to be remarkably decreased by SCFA, pointing toward the prebiotic effect of FOS in intestinal microflora modulation.
- Full Text:
- Date Issued: 2009
Awkward working postures and precision performance as an example of the relationship between ergonomics and production quality
- Ngcamu, Nokubonga Slindele (Sma)
- Authors: Ngcamu, Nokubonga Slindele (Sma)
- Date: 2009
- Subjects: Human engineering , Posture , Posture disorders , Musculoskeletal system -- Diseases , Work -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5105 , http://hdl.handle.net/10962/d1005183 , Human engineering , Posture , Posture disorders , Musculoskeletal system -- Diseases , Work -- Physiological aspects
- Description: Ergonomics aims to improve worker health and enhance productivity and quality. Knowledge and practical evidence of this relationship would be instrumental for optimising organisational performance particularly in industrially developing countries where the discipline is still in its developmental stages. Therefore this thesis set out to analyse the relationship between ergonomics deficiencies and performance. A survey was first conducted to establish the severity of quality problems in the South African manufacturing industry and to determine if these were related to Ergonomic deficiencies. The results indicated that quality problems continue to plague industry, a challenge associated with huge cost implications. Furthermore organisations were not cognisant of the fact that ergonomics deficiencies such as poor workstation design and awkward or constrained working postures are a major contributing factor to poor quality and performance decrements. This demonstrates that much is yet to be done in raising awareness about the benefits of ergonomics in South Africa and other industrially developing countries. However, for this to be effective, tangible evidence of these purported benefits is required. In lieu of this, a laboratory study was then conducted to establish the relationship between awkward working postures and the performance of precision tasks. Acknowledging that the task and the worker are interrelated elements, the impact of precision task demands on the postural strain experienced by the human was also investigated. A high and low precision task quantified positional precision while a force task (combination of pushing and pulling) was utilised to assess the ability to maintain a precise force over time. These three tasks were performed in eight different postures; namely seated, standing, stooping 300 and 600, working overhead, lying supine, and twisting to either side. A combination of the tasks and postures resulted in 24 experimental conditions that were tested on forty eight healthy male and female participants. The performance related dependent variables were movement time, deviation from the centre of the target, and the trend/slope followed by the force exerted. Muscle activity of eight arm, shoulder and back muscles, iii supplemented with heart rate and local ratings of perceived exertion, were utilised to quantify the impact of the tasks and the postures on the individual. The results revealed that awkward working postures do in fact influence performance outcomes. In this regard, awkward working postures (such as overhead work and lying supine and stooping) were evidenced to significantly affect movement time, deviations from the target and the ability to maintain a constant force over time. These variables have a direct relationship with organisational priorities such as productivity and quality. Furthermore, the results indicated that high precision demands augment postural strain elicited through high muscle activity responses and may have negative implications for the precipitation of musculoskeletal disorders. Essentially, the work done on this thesis reflected the complex nature of ergonomics by drawing on both macro and micro-ergonomics approaches. In so doing, challenges perceived to be relevant to industry as reported by organisations formed the foundation for further laboratory studies. Therefore, more collaborative research and knowledge transfer between industry and ergonomics researchers is a necessity particularly in industrially developing countries where ergonomics is still in its developmental stages.
- Full Text:
- Date Issued: 2009
- Authors: Ngcamu, Nokubonga Slindele (Sma)
- Date: 2009
- Subjects: Human engineering , Posture , Posture disorders , Musculoskeletal system -- Diseases , Work -- Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5105 , http://hdl.handle.net/10962/d1005183 , Human engineering , Posture , Posture disorders , Musculoskeletal system -- Diseases , Work -- Physiological aspects
- Description: Ergonomics aims to improve worker health and enhance productivity and quality. Knowledge and practical evidence of this relationship would be instrumental for optimising organisational performance particularly in industrially developing countries where the discipline is still in its developmental stages. Therefore this thesis set out to analyse the relationship between ergonomics deficiencies and performance. A survey was first conducted to establish the severity of quality problems in the South African manufacturing industry and to determine if these were related to Ergonomic deficiencies. The results indicated that quality problems continue to plague industry, a challenge associated with huge cost implications. Furthermore organisations were not cognisant of the fact that ergonomics deficiencies such as poor workstation design and awkward or constrained working postures are a major contributing factor to poor quality and performance decrements. This demonstrates that much is yet to be done in raising awareness about the benefits of ergonomics in South Africa and other industrially developing countries. However, for this to be effective, tangible evidence of these purported benefits is required. In lieu of this, a laboratory study was then conducted to establish the relationship between awkward working postures and the performance of precision tasks. Acknowledging that the task and the worker are interrelated elements, the impact of precision task demands on the postural strain experienced by the human was also investigated. A high and low precision task quantified positional precision while a force task (combination of pushing and pulling) was utilised to assess the ability to maintain a precise force over time. These three tasks were performed in eight different postures; namely seated, standing, stooping 300 and 600, working overhead, lying supine, and twisting to either side. A combination of the tasks and postures resulted in 24 experimental conditions that were tested on forty eight healthy male and female participants. The performance related dependent variables were movement time, deviation from the centre of the target, and the trend/slope followed by the force exerted. Muscle activity of eight arm, shoulder and back muscles, iii supplemented with heart rate and local ratings of perceived exertion, were utilised to quantify the impact of the tasks and the postures on the individual. The results revealed that awkward working postures do in fact influence performance outcomes. In this regard, awkward working postures (such as overhead work and lying supine and stooping) were evidenced to significantly affect movement time, deviations from the target and the ability to maintain a constant force over time. These variables have a direct relationship with organisational priorities such as productivity and quality. Furthermore, the results indicated that high precision demands augment postural strain elicited through high muscle activity responses and may have negative implications for the precipitation of musculoskeletal disorders. Essentially, the work done on this thesis reflected the complex nature of ergonomics by drawing on both macro and micro-ergonomics approaches. In so doing, challenges perceived to be relevant to industry as reported by organisations formed the foundation for further laboratory studies. Therefore, more collaborative research and knowledge transfer between industry and ergonomics researchers is a necessity particularly in industrially developing countries where ergonomics is still in its developmental stages.
- Full Text:
- Date Issued: 2009