Developing an ionospheric map for South Africa
- Authors: Okoh, Daniel Izuikeninachi
- Date: 2009
- Subjects: Ionosphere -- South Africa , Shortwave radio , Ionospheric electron density -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5459 , http://hdl.handle.net/10962/d1005244 , Ionosphere -- South Africa , Shortwave radio , Ionospheric electron density -- South Africa
- Description: This thesis describes the development of an ionospheric map for the South African region using the current available resources. The International Reference Ionosphere (IRI) model, the South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network, were incorporated into the map. An accurate ionospheric map depicting the foF2 and hmF2 parameters as well as electron density profiles at any location within South Africa is a useful tool for, amongst others, High Frequency (HF) communicators and space weather centers. A major product of the work is software, written in MATLAB, which produces spatial and temporal representations of the South African ionosphere. The map was validated and demonstrated for practical application, since a significant aim of the project was to make the map as applicable as possible. It is hoped that the map will find immense application in HF radio communication industries, research industries, aviation industries, and other industries that make use of Earth-Space systems. A potential user of the map is GrinTek Ewation (GEW) who is currently evaluating it for their purposes
- Full Text:
- Date Issued: 2009
- Authors: Okoh, Daniel Izuikeninachi
- Date: 2009
- Subjects: Ionosphere -- South Africa , Shortwave radio , Ionospheric electron density -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5459 , http://hdl.handle.net/10962/d1005244 , Ionosphere -- South Africa , Shortwave radio , Ionospheric electron density -- South Africa
- Description: This thesis describes the development of an ionospheric map for the South African region using the current available resources. The International Reference Ionosphere (IRI) model, the South African Bottomside Ionospheric Model (SABIM), and measurements from ionosondes in the South African Ionosonde Network, were incorporated into the map. An accurate ionospheric map depicting the foF2 and hmF2 parameters as well as electron density profiles at any location within South Africa is a useful tool for, amongst others, High Frequency (HF) communicators and space weather centers. A major product of the work is software, written in MATLAB, which produces spatial and temporal representations of the South African ionosphere. The map was validated and demonstrated for practical application, since a significant aim of the project was to make the map as applicable as possible. It is hoped that the map will find immense application in HF radio communication industries, research industries, aviation industries, and other industries that make use of Earth-Space systems. A potential user of the map is GrinTek Ewation (GEW) who is currently evaluating it for their purposes
- Full Text:
- Date Issued: 2009
Development and validation of a stability-indicating method for the quantitation of paclitaxel in pharmaceutical dosage forms
- Mohammadi, Ali, Esimaeili, Farnaz, Dinarvand, Rasoul, Atyabi, Fatemeh, Walker, Roderick B
- Authors: Mohammadi, Ali , Esimaeili, Farnaz , Dinarvand, Rasoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184278 , vital:44196 , xlink:href="https://doi.org/10.1093/chromsci/47.7.599"
- Description: A simple, rapid stability-indicating isocratic assay has been developed and validated for the determination of Paclitaxel (PTX) in commercial injection formulations. The assay is performed using a Nucleosil RP-18 (5 µm, 250 × 4.0 mm i.d) column protected by a Nucleosil C18 precolumn (5 µm, 4.0 × 4.0 mm i.d.) with a mobile phase of methanol–water (80:20) and UV detection at 230 nm. The method was found to be specific for PTX in the presence of degradation products with an overall analytical run time of ~ 9 min. Accuracy reported as % bias was found to be 0.1–2.5% bias for all samples tested. Intra-assay precision (repeatability) was found to be 0.22–2.65% RSD, while inter-day precision (intermediate precision) was found to be 1.0–3.0% RSD for the samples studied. The calibration curve was found to be linear with the equation y = 29.78x + 7.65, and a linear regression coefficient of 0.9994 over the concentration range 0.05–20 µg/mL. The limits of quantitation and detection were 0.05 and 0.02 µg/mL, respectively. Taxol (30 mg/5 mL), a commercially available dosage form of PTX, was assayed and 100.6–103.6% of the label claim was recovered.
- Full Text:
- Date Issued: 2009
- Authors: Mohammadi, Ali , Esimaeili, Farnaz , Dinarvand, Rasoul , Atyabi, Fatemeh , Walker, Roderick B
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184278 , vital:44196 , xlink:href="https://doi.org/10.1093/chromsci/47.7.599"
- Description: A simple, rapid stability-indicating isocratic assay has been developed and validated for the determination of Paclitaxel (PTX) in commercial injection formulations. The assay is performed using a Nucleosil RP-18 (5 µm, 250 × 4.0 mm i.d) column protected by a Nucleosil C18 precolumn (5 µm, 4.0 × 4.0 mm i.d.) with a mobile phase of methanol–water (80:20) and UV detection at 230 nm. The method was found to be specific for PTX in the presence of degradation products with an overall analytical run time of ~ 9 min. Accuracy reported as % bias was found to be 0.1–2.5% bias for all samples tested. Intra-assay precision (repeatability) was found to be 0.22–2.65% RSD, while inter-day precision (intermediate precision) was found to be 1.0–3.0% RSD for the samples studied. The calibration curve was found to be linear with the equation y = 29.78x + 7.65, and a linear regression coefficient of 0.9994 over the concentration range 0.05–20 µg/mL. The limits of quantitation and detection were 0.05 and 0.02 µg/mL, respectively. Taxol (30 mg/5 mL), a commercially available dosage form of PTX, was assayed and 100.6–103.6% of the label claim was recovered.
- Full Text:
- Date Issued: 2009
Development of a neural network based model for predicting the occurrence of spread F within the Brazilian sector
- Authors: Paradza, Masimba Wellington
- Date: 2009
- Subjects: Neural networks (Computer science) , Ionosphere , F region
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5460 , http://hdl.handle.net/10962/d1005245 , Neural networks (Computer science) , Ionosphere , F region
- Description: Spread F is a phenomenon of the ionosphere in which the pulses returned from the ionosphere are of a much greater duration than the transmitted ones. The occurrence of spread F can be predicted using the technique of Neural Networks (NNs). This thesis presents the development and evaluation of NN based models (two single station models and a regional model) for predicting the occurrence of spread F over selected stations within the Brazilian sector. The input space for the NNs included the day number (seasonal variation), hour (diurnal variation), sunspot number (measure of the solar activity), magnetic index (measure of the magnetic activity) and magnetic position (latitude, magnetic declination and inclination). Twelve years of spread F data measured during 1978 to 1989 inclusively at the equatorial site Fortaleza and low latitude site Cachoeira Paulista are used in the development of an input space and NN architecture for the NN models. Spread F data that is believed to be related to plasma bubble developments (range spread F) were used in the development of the models while those associated with narrow spectrum irregularities that occur near the F layer (frequency spread F) were excluded. The results of the models show the dependency of the probability of spread F as a function of local time, season and latitude. The models also illustrate some characteristics of spread F such as the onset and peak occurrence of spread F as a function of distance from the equator. Results from these models are presented in this thesis and compared to measured data and to modelled data obtained with an empirical model developed for the same purpose.
- Full Text:
- Date Issued: 2009
- Authors: Paradza, Masimba Wellington
- Date: 2009
- Subjects: Neural networks (Computer science) , Ionosphere , F region
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5460 , http://hdl.handle.net/10962/d1005245 , Neural networks (Computer science) , Ionosphere , F region
- Description: Spread F is a phenomenon of the ionosphere in which the pulses returned from the ionosphere are of a much greater duration than the transmitted ones. The occurrence of spread F can be predicted using the technique of Neural Networks (NNs). This thesis presents the development and evaluation of NN based models (two single station models and a regional model) for predicting the occurrence of spread F over selected stations within the Brazilian sector. The input space for the NNs included the day number (seasonal variation), hour (diurnal variation), sunspot number (measure of the solar activity), magnetic index (measure of the magnetic activity) and magnetic position (latitude, magnetic declination and inclination). Twelve years of spread F data measured during 1978 to 1989 inclusively at the equatorial site Fortaleza and low latitude site Cachoeira Paulista are used in the development of an input space and NN architecture for the NN models. Spread F data that is believed to be related to plasma bubble developments (range spread F) were used in the development of the models while those associated with narrow spectrum irregularities that occur near the F layer (frequency spread F) were excluded. The results of the models show the dependency of the probability of spread F as a function of local time, season and latitude. The models also illustrate some characteristics of spread F such as the onset and peak occurrence of spread F as a function of distance from the equator. Results from these models are presented in this thesis and compared to measured data and to modelled data obtained with an empirical model developed for the same purpose.
- Full Text:
- Date Issued: 2009
Development of a performance management system for the SABC (Port Elizabeth)
- Authors: Nyembezi, Vuyo
- Date: 2009
- Subjects: Performance standards -- South Africa -- Port Elizabeth , Performance -- Management -- Evaluation , Performance -- Measurement , Employees -- Rating of -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8678 , http://hdl.handle.net/10948/1148 , Performance standards -- South Africa -- Port Elizabeth , Performance -- Management -- Evaluation , Performance -- Measurement , Employees -- Rating of -- South Africa -- Port Elizabeth
- Description: This study focused on exploring and finding the ideal performance management system suitable for the South African Broadcasting Corporation by establishing an understanding of employees’ experiences and perceptions of the previous and a proposed performance management systems and their value to SABC employees. This was done by eliciting how employees see, make sense of and interpret their everyday experiences of performance management systems, in order to develop a more suitable inclusive performance management system. A qualitative study was used to seek answers to the research questions. A focus group interview was selected for data collection. The data was analysed according to guidelines indicated and proposed by Creswell (1998:147-148). The researcher made use of convenience sampling to select 45 participants in 5 groups for the focus groups. One group consisted of managers/supervisors, and the other four groups were employees from four different business units. Participants were guaranteed confidentiality. Credibility, transferability, dependability and conformability were used as the main components in the model, to determine the truth-value of the study. Findings indicated that there was a fair understanding of the previous performance management system but there had been poor implementation of the system. The participants concurred that the previous performance iv management systems in the organisations were not adding any value to their lives. They pointed out that there was no reward in place for high performers and no action taken for non-performers, and this impacted negatively on how implementation was perceived and experienced. The recommendations are that the revised performance management system should have a stronger emphasis on effective management, monitoring, feedback and reward. Furthermore, the system should close the current gaps of reward for high performance and correction of low performance. It was further concluded that for a performance management system to be effective, it should incorporate updated job descriptions, performance measures and standards, as well as evaluator training and guidelines for improvement, employee input, compensation and/or rewards.
- Full Text:
- Date Issued: 2009
- Authors: Nyembezi, Vuyo
- Date: 2009
- Subjects: Performance standards -- South Africa -- Port Elizabeth , Performance -- Management -- Evaluation , Performance -- Measurement , Employees -- Rating of -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8678 , http://hdl.handle.net/10948/1148 , Performance standards -- South Africa -- Port Elizabeth , Performance -- Management -- Evaluation , Performance -- Measurement , Employees -- Rating of -- South Africa -- Port Elizabeth
- Description: This study focused on exploring and finding the ideal performance management system suitable for the South African Broadcasting Corporation by establishing an understanding of employees’ experiences and perceptions of the previous and a proposed performance management systems and their value to SABC employees. This was done by eliciting how employees see, make sense of and interpret their everyday experiences of performance management systems, in order to develop a more suitable inclusive performance management system. A qualitative study was used to seek answers to the research questions. A focus group interview was selected for data collection. The data was analysed according to guidelines indicated and proposed by Creswell (1998:147-148). The researcher made use of convenience sampling to select 45 participants in 5 groups for the focus groups. One group consisted of managers/supervisors, and the other four groups were employees from four different business units. Participants were guaranteed confidentiality. Credibility, transferability, dependability and conformability were used as the main components in the model, to determine the truth-value of the study. Findings indicated that there was a fair understanding of the previous performance management system but there had been poor implementation of the system. The participants concurred that the previous performance iv management systems in the organisations were not adding any value to their lives. They pointed out that there was no reward in place for high performers and no action taken for non-performers, and this impacted negatively on how implementation was perceived and experienced. The recommendations are that the revised performance management system should have a stronger emphasis on effective management, monitoring, feedback and reward. Furthermore, the system should close the current gaps of reward for high performance and correction of low performance. It was further concluded that for a performance management system to be effective, it should incorporate updated job descriptions, performance measures and standards, as well as evaluator training and guidelines for improvement, employee input, compensation and/or rewards.
- Full Text:
- Date Issued: 2009
Development of a process for the preparation of linalool from CIS-2-pinanol
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
- Authors: Buddoo, Subash Ramnarain
- Date: 2009
- Subjects: Odors , Perfumes -- History , Perfumes -- Formulae , Fermentation
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:10425 , http://hdl.handle.net/10948/d1016219
- Description: Linalool is a key intermediate for the production of important fragrance chemicals such as geraniol, nerol, geranial, and neral. Linalool can be produced via a two-step process from α-pinene which is a major component of crude sulphated turpentine (CST) a foul-smelling, volatile waste product of the pulp and paper industry. The key step in this process is the pyrolysis step which involves the isomerisation of cis-2-pinanol to linalool and requires high temperatures (600-650°C) and is not very selective due to the decomposition of the product itself under these conditions. A client of the CSIR, Teubes Pty. Ltd., is a manufacturer of flavour and fragrance compounds for the local and international fragrance market and expressed an interest in producing linalool since the company would then gain access to other valuable fragrance chemicals via relatively simple processes. Earlier work conducted by AECI, R & D did not meet with much success since the selectivity to linalool was very poor and the process could hardly be deemed as scalable. The main objective of this project was therefore to develop a process for the selective isomerisation of cis-2-pinanol to linalool with minimum by-product formation and using process equipment that could be scaled to full-scale production. Since cis-2- pinanol could not be purchased in sufficient quantities for process development, a process had to be developed for the bench-scale preparation of kilogram quantities of cis-2-pinanol from α-pinene obtained from the client. Although this synthesis formed a minor part of this investigation, several process improvements and innovations were introduced to produce high quality cis-2-pinanol, in very good yields at kilogram scale. A major part of this investigation was the design and set up of a pyrolyis rig capable of operating at elevated temperatures (400 - 750°C) for the evaluation of various process parameters. Various vaporizer, reactor, and condensation systems were evaluated for their ability to cope with the demanding conditions on a consistent basis. The initial part of the investigation was a screening exercise to evaluate various process parameters as well as solvents, materials of construction, catalysts, etc. A comprehensive statistical design was also conducted to determine the critical process parameters and the model obtained was used to predict the optimum conditions required for the preparation of in-specification product on a consistent basis. These conditions were used in the preparation of a 1kg sample which was required by theclient for market evaluation purposes. The use of a novel microreactor system was also evaluated for the pinanol pyrolysis reaction. To our knowledge, this is the first time that a microreactor has been successfully used for this type of reaction in the Fragrance industry and a patent application is being filed by the CSIR. The kinetics of the reaction in both the tubular reactor system and the microreactor system was investigated. Computer modelling studies on both the systems were also conducted. The raw material cost to produce a kilogram of linalool is $1.40. There is a significant margin of 60.8 percent between the raw material cost of linalool and the current selling price ($3.57/kg). This clearly indicates that the project is potentially feasible from an economic point of view and we can now proceed with confidence to the next stage which is the engineering design, building and commissioning of the large scale pyrolysis rig. The rest of the process steps will be conducted on existing equipment currently present at the CSIR’s large scale facility (Imbiza in Isando, Gauteng).
- Full Text:
- Date Issued: 2009
Development of biological control strategies against sirex noctilio (Fabricius) on Sappi Forests (Ltd) Landholdings in the summer rainfall regions of South Africa
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
Development of flexible automotive measurement adaptors for the PQ25 VWSA platform
- Authors: Pretorius, Shaun
- Date: 2009
- Subjects: Automobiles -- Measurement , Optical measurements
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9626 , http://hdl.handle.net/10948/1632 , http://hdl.handle.net/10948/d1011725 , Automobiles -- Measurement , Optical measurements
- Description: The following work describes all knowledge required in the creation of new automotive optical Photogrammetrical adaptors, which allow the user thereof to measure a fully assembled vehicle in its natural position, i.e. on its wheels for the PQ25 platform at Volkswagen of South Africa. The system is the only method available to the manufacturing plant to measure a fully assembled vehicle in this manner. The FlexMess system allows for a quick portable measurement of a vehicle at all stages of Vehicle manufacturing, aligned via the Volkswagen RPS standards. In the first part of the work, the problem of establishing a system capable of measuring the PQ25 platform is achieved by redesigning the PQ24 platform (previous generation Polo) to the new PQ25 vehicle platform. Once the system was redesigned a prototype adaptor system was created. In the second part of the work, the redesigned adaptor system is checked for its accuracy and repeatability. In a statistical analysis of the adaptors ability to measure the reference points needed for alignment of a vehicle, the system is compared to a CMM and verified that the limits fall within the limits of the original FlexMesśs certified accuracy limits. The last part of the work looks at addressing some of the problems of the FlexMess system by creating concepts for an ideal future FlexMess adaptor system.
- Full Text:
- Date Issued: 2009
- Authors: Pretorius, Shaun
- Date: 2009
- Subjects: Automobiles -- Measurement , Optical measurements
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9626 , http://hdl.handle.net/10948/1632 , http://hdl.handle.net/10948/d1011725 , Automobiles -- Measurement , Optical measurements
- Description: The following work describes all knowledge required in the creation of new automotive optical Photogrammetrical adaptors, which allow the user thereof to measure a fully assembled vehicle in its natural position, i.e. on its wheels for the PQ25 platform at Volkswagen of South Africa. The system is the only method available to the manufacturing plant to measure a fully assembled vehicle in this manner. The FlexMess system allows for a quick portable measurement of a vehicle at all stages of Vehicle manufacturing, aligned via the Volkswagen RPS standards. In the first part of the work, the problem of establishing a system capable of measuring the PQ25 platform is achieved by redesigning the PQ24 platform (previous generation Polo) to the new PQ25 vehicle platform. Once the system was redesigned a prototype adaptor system was created. In the second part of the work, the redesigned adaptor system is checked for its accuracy and repeatability. In a statistical analysis of the adaptors ability to measure the reference points needed for alignment of a vehicle, the system is compared to a CMM and verified that the limits fall within the limits of the original FlexMesśs certified accuracy limits. The last part of the work looks at addressing some of the problems of the FlexMess system by creating concepts for an ideal future FlexMess adaptor system.
- Full Text:
- Date Issued: 2009
Diffraction efficiency and I–V characteristics of metal-free phthalocyanine doped nematic liquid crystals
- Köysal, Oguz, Okutan, Mustafa, San, S Eren, Nyokong, Tebello, Durmus, Mahmut
- Authors: Köysal, Oguz , Okutan, Mustafa , San, S Eren , Nyokong, Tebello , Durmus, Mahmut
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263511 , vital:53634 , xlink:href="https://doi.org/10.1016/j.matchemphys.2008.10.056"
- Description: The synthesis and characterization of the tetra-4-benzyloxyphenoxy substituted metal-free phthalocyanine (H2Pc) is reported for the first time. Formation of the photoinduced gratings has been experienced in a metal-free phthalocyanine doped nematic liquid crystal (LC) system and its I–V properties are characterized by electrical measurements. Four samples are prepared at different doping percentages and in homogenously aligned sandwiched geometry. We report the results of two set of experiments on these samples. One of them is the grating diffraction experiment for the analysis of optically induced reorientation process which is a basis for possible holographic applications. Accessible diffraction efficiency is found to be linearly increasing as the amount of the phthalocyanine doping rises. In the scope of the other set of measurements I–V peculiarity of the system is also found to be enhanced and linearly dependent on doping.
- Full Text:
- Date Issued: 2009
- Authors: Köysal, Oguz , Okutan, Mustafa , San, S Eren , Nyokong, Tebello , Durmus, Mahmut
- Date: 2009
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/263511 , vital:53634 , xlink:href="https://doi.org/10.1016/j.matchemphys.2008.10.056"
- Description: The synthesis and characterization of the tetra-4-benzyloxyphenoxy substituted metal-free phthalocyanine (H2Pc) is reported for the first time. Formation of the photoinduced gratings has been experienced in a metal-free phthalocyanine doped nematic liquid crystal (LC) system and its I–V properties are characterized by electrical measurements. Four samples are prepared at different doping percentages and in homogenously aligned sandwiched geometry. We report the results of two set of experiments on these samples. One of them is the grating diffraction experiment for the analysis of optically induced reorientation process which is a basis for possible holographic applications. Accessible diffraction efficiency is found to be linearly increasing as the amount of the phthalocyanine doping rises. In the scope of the other set of measurements I–V peculiarity of the system is also found to be enhanced and linearly dependent on doping.
- Full Text:
- Date Issued: 2009
Disclosure of HIV status and adherence to antiretroviral therapy
- Kubashe, Nomachina Theopatra
- Authors: Kubashe, Nomachina Theopatra
- Date: 2009
- Subjects: HIV-positive persons -- South Africa , Self-disclosure -- South Africa , Antiretroviral agents -- South Africa
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: vital:10142 , http://hdl.handle.net/10948/1174 , HIV-positive persons -- South Africa , Self-disclosure -- South Africa , Antiretroviral agents -- South Africa
- Description: The Human Immunodeficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) is one of the leading chronic diseases affecting people in South Africa and throughout the world. This study aimed to investigate the effect disclosure of HIV status had on antiretroviral therapy (ART) adherence. A convenience sample of 65 HIV positive adult patients currently taking ART at a public Primary Health Care (PHC) clinic in the Nelson Mandela Metropole was selected. Participation was voluntary and confidentiality was maintained at all times. Data was collected using three tools/techniques: (1) a Patient Questionnaire (PQ) to extract information on patient's demographics, HIV disclosure status, regimen the patient was on and self-reported adherence to ART; (2) an audit of a Patient Medical Record (PMR) for information on the regimen the patient was on, the period during which the patient had been on ART medication, the adherence to ART care and the level of the patient‟s biological markers; and (3) Pill Counts (PC) performed on the patient's medical supply to validate the self-reported adherence to ART. There was no significant relationship between the disclosure of HIV status and adherence to ART (p= 0.59; Chi²). However, the relationship between the adherence to ART and increase in the CD4 count levels of patients on ART in this population was significant (p=0.03; Chi²). It can be concluded that no direct relationship was found between the disclosure of HIV status and adherence to ART in this population. However, several factors affected the reasons and decisions of individuals to disclose their HIV status and this influenced their daily taking of medication.
- Full Text:
- Date Issued: 2009
- Authors: Kubashe, Nomachina Theopatra
- Date: 2009
- Subjects: HIV-positive persons -- South Africa , Self-disclosure -- South Africa , Antiretroviral agents -- South Africa
- Language: English
- Type: Thesis , Masters , MPharm
- Identifier: vital:10142 , http://hdl.handle.net/10948/1174 , HIV-positive persons -- South Africa , Self-disclosure -- South Africa , Antiretroviral agents -- South Africa
- Description: The Human Immunodeficiency Virus (HIV)/Acquired Immune Deficiency Syndrome (AIDS) is one of the leading chronic diseases affecting people in South Africa and throughout the world. This study aimed to investigate the effect disclosure of HIV status had on antiretroviral therapy (ART) adherence. A convenience sample of 65 HIV positive adult patients currently taking ART at a public Primary Health Care (PHC) clinic in the Nelson Mandela Metropole was selected. Participation was voluntary and confidentiality was maintained at all times. Data was collected using three tools/techniques: (1) a Patient Questionnaire (PQ) to extract information on patient's demographics, HIV disclosure status, regimen the patient was on and self-reported adherence to ART; (2) an audit of a Patient Medical Record (PMR) for information on the regimen the patient was on, the period during which the patient had been on ART medication, the adherence to ART care and the level of the patient‟s biological markers; and (3) Pill Counts (PC) performed on the patient's medical supply to validate the self-reported adherence to ART. There was no significant relationship between the disclosure of HIV status and adherence to ART (p= 0.59; Chi²). However, the relationship between the adherence to ART and increase in the CD4 count levels of patients on ART in this population was significant (p=0.03; Chi²). It can be concluded that no direct relationship was found between the disclosure of HIV status and adherence to ART in this population. However, several factors affected the reasons and decisions of individuals to disclose their HIV status and this influenced their daily taking of medication.
- Full Text:
- Date Issued: 2009
Discourse and the oppression of nonhuman animals: a critical realist account
- Authors: Mitchell, Leslie Roy
- Date: 2009
- Subjects: Animal rights Animal welfare -- Moral and ethical aspects Critical realism Critical discourse analysis Animal industry -- Moral and ethical aspects Livestock -- Social aspects Human-animal relationships Agriculture -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1318 , http://hdl.handle.net/10962/d1003951
- Description: This work examines the use of nonhuman animals in the farming industry and seeks to understand why this practice takes place and what supports its continuation. The research is approached from a critical realist perspective and after a description of past and current practices in the industry, it uses abduction and retroduction to determine the essential conditions for the continuation of the phenomenon of nonhuman animal farming. One essential condition is found to be the existence of negative discourses relating to nonhuman animals and this aspect is examined in more detail by analyzing a corpus of texts from a farming magazine using Critical Discourse Analysis. Major discourses which were found to be present were those of production, science and slavery which construct the nonhumans respectively as objects of scientific investigation, as production machines and as slaves. A minor discourse of achievement relating to the nonhumans was also present. Further analysis of linguistic features examined the way in which the nonhumans are socially constructed in the discourses. Drawing on work in experimental psychology by Millgram, Zimbardo and Bandura it was found that the effects of these discourses fulfil many of the conditions for bringing about moral disengagement in people thus explaining why billions of people are able to support animal farming in various ways even though what happens in the phenomenon is contrary to their basic ethical and moral beliefs.
- Full Text:
- Date Issued: 2009
- Authors: Mitchell, Leslie Roy
- Date: 2009
- Subjects: Animal rights Animal welfare -- Moral and ethical aspects Critical realism Critical discourse analysis Animal industry -- Moral and ethical aspects Livestock -- Social aspects Human-animal relationships Agriculture -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1318 , http://hdl.handle.net/10962/d1003951
- Description: This work examines the use of nonhuman animals in the farming industry and seeks to understand why this practice takes place and what supports its continuation. The research is approached from a critical realist perspective and after a description of past and current practices in the industry, it uses abduction and retroduction to determine the essential conditions for the continuation of the phenomenon of nonhuman animal farming. One essential condition is found to be the existence of negative discourses relating to nonhuman animals and this aspect is examined in more detail by analyzing a corpus of texts from a farming magazine using Critical Discourse Analysis. Major discourses which were found to be present were those of production, science and slavery which construct the nonhumans respectively as objects of scientific investigation, as production machines and as slaves. A minor discourse of achievement relating to the nonhumans was also present. Further analysis of linguistic features examined the way in which the nonhumans are socially constructed in the discourses. Drawing on work in experimental psychology by Millgram, Zimbardo and Bandura it was found that the effects of these discourses fulfil many of the conditions for bringing about moral disengagement in people thus explaining why billions of people are able to support animal farming in various ways even though what happens in the phenomenon is contrary to their basic ethical and moral beliefs.
- Full Text:
- Date Issued: 2009
Discourses around abortion in a low-income community in the Western Cape
- Authors: Bowes, Tanya-Ann
- Date: 2009
- Subjects: Abortion -- Moral and ethical aspects , Abortion -- Religious aspects -- Christianity , Patriarchy -- South Africa , Abortion -- South Africa -- Western Cape , Male domination (Social structure)
- Language: English
- Type: text , Thesis , Masters , MSocSci
- Identifier: vital:2939 , http://hdl.handle.net/10962/d1002448
- Description: Since the introduction of the Choice on Termination of Pregnancy Act in 1996, research concerning abortion has primarily focused on public health issues or on the personal experience of women. The cultural and social context within which women experience a termination of pregnancy and in which services are offered has received less attention. The purpose of this study was to analyse public discourses around abortion in a low-income community in the Western Cape. Focus groups were used to gather data from three women’s and three men’s groups. The findings suggest that the agenda of pro-life discourses in this community is not always to defend the life of the fetus. Rather these discourses serve to protect, preserve and maintain the power of the traditional nuclear family, headed by the husband, over women’s reproduction and sexuality. Religious and moral arguments serve to disguise the gender issues at stake. However, instances also occurred where TOP was supported if the husband participated in the decision-making process. Therefore, his presence normalised abortion. Thus, the prevailing public discourses around abortion in this community either support or negate abortion in order to further the agenda of patriarchy.
- Full Text:
- Date Issued: 2009
- Authors: Bowes, Tanya-Ann
- Date: 2009
- Subjects: Abortion -- Moral and ethical aspects , Abortion -- Religious aspects -- Christianity , Patriarchy -- South Africa , Abortion -- South Africa -- Western Cape , Male domination (Social structure)
- Language: English
- Type: text , Thesis , Masters , MSocSci
- Identifier: vital:2939 , http://hdl.handle.net/10962/d1002448
- Description: Since the introduction of the Choice on Termination of Pregnancy Act in 1996, research concerning abortion has primarily focused on public health issues or on the personal experience of women. The cultural and social context within which women experience a termination of pregnancy and in which services are offered has received less attention. The purpose of this study was to analyse public discourses around abortion in a low-income community in the Western Cape. Focus groups were used to gather data from three women’s and three men’s groups. The findings suggest that the agenda of pro-life discourses in this community is not always to defend the life of the fetus. Rather these discourses serve to protect, preserve and maintain the power of the traditional nuclear family, headed by the husband, over women’s reproduction and sexuality. Religious and moral arguments serve to disguise the gender issues at stake. However, instances also occurred where TOP was supported if the husband participated in the decision-making process. Therefore, his presence normalised abortion. Thus, the prevailing public discourses around abortion in this community either support or negate abortion in order to further the agenda of patriarchy.
- Full Text:
- Date Issued: 2009
Disjunctions in the Diptera (Insecta) fauna of the Mediterranean Province and southern Africa and a discussion of biogeographical considerations : ecological overview article
- Kirk-Spriggs, A H, McGregor, Gillian K
- Authors: Kirk-Spriggs, A H , McGregor, Gillian K
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:6880 , http://hdl.handle.net/10962/d1011636
- Description: This paper explores disjunctions in the Diptera fauna of the Mediterranean Province and southern Africa, drawing from eight families of Diptera, the more ancient Psychodidae and Vermileonidae, and the more recent Acroceridae, Asilidae, Bombyliidae, Dolichopodidae, Pipunculidae and Sciomyzidae. Information from recent published revisions is geo-referenced and plotted onto maps using GIS software. These distribution patterns are interpreted and probable means and routes of dispersal between the two regions are discussed. The concept of an Afrotropical sub-Saharan boundary is outlined and it is argued that although the vast, arid and virtually abiotic Sahara acts as a barrier to dispersal today, relict floral and faunal populations of Mediterranean provincial origin still occur on the Hoggar and Tibesti Mountains of the central Sahara, indicating that the aridification of the Sahara is a very recent event. The presence of extensive palaeolakes formerly covering ca 10% of the present-day Sahara is regarded as evidence in support of this hypothesis. These lakes and their associated catchments, situated in basins between the central Saharan mountains, could clearly have acted as a humid route of dispersal as recently as 4000 BP, when these lakes began to recede, and this route is here regarded as a "central high Africa corridor"; a filter-bridge between the Mediterranean Province and southern Africa. Examples of Mediterranean provincial species of Ephydridae and the muscid genus Lispe Latreille, 1796, occurring as far south as the AÏr Massif in northern Niger are cited as examples of relict montane Diptera of Mediterranean provincial origin in the southern Hoggar Mountains; these groups being associated with the margins of standing water. Balinsky's (1962) concept of an "arid corridor" is also re-examined, using examples from the larger, less mobile Diptera, and it is concluded that such a pattern may not be the result of aridity, but represent an "eastern high Africa corridor", broadly corresponding to the "African Supers well". Other perceived distribution pathways between the Holarctic and Afrotropical Regions are mapped. Anemochore dispersal is considered, and the extent of the Afrotropical Region is discussed. Mediterranean tectonic evolution on both a globe of constant size and on a smaller Jurassic globe is also considered. It is concluded that if all the transitional zones between the zoogeographical regions are to be given more-or-less equivalent treatment, we must avoid setting boundaries based on earlier faunal distributions. For this reason the current boundary between the Palaearctic and Afrotropical Regions, arbitrary as it is, should be retained, despite evidence suggesting recent continuity between sub-Saharan Africa, North Africa and the Arabian Peninsula, corresponding broadly to the African and Arabian lithospheric plates.
- Full Text:
- Date Issued: 2009
- Authors: Kirk-Spriggs, A H , McGregor, Gillian K
- Date: 2009
- Language: English
- Type: text , Article
- Identifier: vital:6880 , http://hdl.handle.net/10962/d1011636
- Description: This paper explores disjunctions in the Diptera fauna of the Mediterranean Province and southern Africa, drawing from eight families of Diptera, the more ancient Psychodidae and Vermileonidae, and the more recent Acroceridae, Asilidae, Bombyliidae, Dolichopodidae, Pipunculidae and Sciomyzidae. Information from recent published revisions is geo-referenced and plotted onto maps using GIS software. These distribution patterns are interpreted and probable means and routes of dispersal between the two regions are discussed. The concept of an Afrotropical sub-Saharan boundary is outlined and it is argued that although the vast, arid and virtually abiotic Sahara acts as a barrier to dispersal today, relict floral and faunal populations of Mediterranean provincial origin still occur on the Hoggar and Tibesti Mountains of the central Sahara, indicating that the aridification of the Sahara is a very recent event. The presence of extensive palaeolakes formerly covering ca 10% of the present-day Sahara is regarded as evidence in support of this hypothesis. These lakes and their associated catchments, situated in basins between the central Saharan mountains, could clearly have acted as a humid route of dispersal as recently as 4000 BP, when these lakes began to recede, and this route is here regarded as a "central high Africa corridor"; a filter-bridge between the Mediterranean Province and southern Africa. Examples of Mediterranean provincial species of Ephydridae and the muscid genus Lispe Latreille, 1796, occurring as far south as the AÏr Massif in northern Niger are cited as examples of relict montane Diptera of Mediterranean provincial origin in the southern Hoggar Mountains; these groups being associated with the margins of standing water. Balinsky's (1962) concept of an "arid corridor" is also re-examined, using examples from the larger, less mobile Diptera, and it is concluded that such a pattern may not be the result of aridity, but represent an "eastern high Africa corridor", broadly corresponding to the "African Supers well". Other perceived distribution pathways between the Holarctic and Afrotropical Regions are mapped. Anemochore dispersal is considered, and the extent of the Afrotropical Region is discussed. Mediterranean tectonic evolution on both a globe of constant size and on a smaller Jurassic globe is also considered. It is concluded that if all the transitional zones between the zoogeographical regions are to be given more-or-less equivalent treatment, we must avoid setting boundaries based on earlier faunal distributions. For this reason the current boundary between the Palaearctic and Afrotropical Regions, arbitrary as it is, should be retained, despite evidence suggesting recent continuity between sub-Saharan Africa, North Africa and the Arabian Peninsula, corresponding broadly to the African and Arabian lithospheric plates.
- Full Text:
- Date Issued: 2009
Dismissals within the context of collective bargaining
- Authors: Qotoyi, Thanduxolo
- Date: 2009
- Subjects: Employees -- Dismissal of -- Law and legislation -- South Africa , Unfair labor practices -- South Africa , Collective bargaining -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10223 , http://hdl.handle.net/10948/1039 , Employees -- Dismissal of -- Law and legislation -- South Africa , Unfair labor practices -- South Africa , Collective bargaining -- South Africa
- Description: Competitive forces in the market force employers to change the way they operate their businesses. The changes that employers have to make often demand an alteration of the employees’ terms and conditions of employment. By law employers are not permitted to unilaterally effect changes to the employee’s terms and conditions of employment. They have to obtain the consent of the affected employees. This is where collective bargaining fits in. The employer has to negotiate with the employees. One way in which through the process of collective bargaining an employer can exert pressure on the employees to accept the changes is to effect a lock-out. Under the Labour Relations Act 28 of 1956 within the context of a lock-out, an employer was permitted to use conditional dismissal as a bargaining weapon. This conditional dismissal had to be coupled with an offer of reemployment should the employees accept an employer’s demand. In essence, the lock-out had a bite in the form of the conditional dismissal. This made the lock-out quite effective. The 1995 Labour Relations Act prohibits in no uncertain terms the use of a dismissal as a means of compelling employees to accept an employer’s demand in any matter of mutual interest. Within the collective bargaining context, dismissal is not a legitimate option. The employer only has the lock-out as a tool of compulsion. The definition of a lock-out in terms of this Act does not accommodate the use of dismissal. This makes the lock-out option to be less potent than it was under the 1956 Labour Relations Act. However, employers are permitted to dismiss on operational grounds, provided that they follow a fair procedure. Terms and conditions of employment greatly feature in the operational requirements of a business. If the employees’ terms and conditions of employment are not responsive to the operational requirements of the business and they are unwilling to accept changes to those terms, the employer has the right to dismiss them. The employer will not be dismissing the employees as a way of inducing them to accept the changes. He will instead be dismissing them on the basis of operational requirements. iv The question that then arises is how should a dismissal that is intended to compel employees to accept an employers demand (falling within section 187(1)(c) of the 1995 Labour Relations Act be distinguished from a dismissal that is genuinely based on operational requirements as contemplated by section 188(1)(a)(ii). Doesn’t the fact that section 187(1)(c) explicitly prohibits the use of dismissal within the context of collective bargaining give rise to some tension with section 188(1)(a)(ii) which categorically gives employers the right to dismiss on operational grounds. The decision of the Labour Appeal Court in Fry’s Metals v NUMSA has stated that there is no tension whatsoever between the two sections. The court has also ruled that the dismissals that are hit by section 187(1)(c) are those dismissals that are accompanied by an offer of reemployment. According to the court, this offer is indicative of the real purpose of the employer, namely to compel employees to accept his demand. Dismissals not accompanied by an offer of re-employment are on the other hand a true reflection of the fact that the employer is indeed dismissing the employees for operational requirements. This literal interpretation of the meaning and scope of section 187(1)(c) has the potential of opening the floodgates. Instead of resorting to the use of the lock-out to secure the agreement of employees in the collective bargaining process, employers now have a potent tool in the form of a dismissal. As long as the employer makes it abundantly clear that the dismissal is final and irrevocable, he is free from the claws of section 187(1)(c). Given the fact that the lock-out option is not always effective, employers may find it hard to resist the temptation to use the threat of permanent dismissal as a bargaining chip. It is an option that is emasculated by the fact that in an employer initiated lock-out the use of replacement labour is prohibited. The threat of not just a conditional dismissal but a permanent one may force employees to capitulate to the employer’s demand during negotiations. This would effectively render negotiations about changes to terms and conditions of employment a farce. The employer would have an upper hand. The implications of this narrow interpretation are quite far-reaching. The long held view that dismissal is not a legitimate weapon of coercion in the collective bargaining process is under serious challenge. Only conditional dismissals are illegitimate in the collective bargaining v arena. Permanent dismissals are permitted. This negates the very purpose of the collective bargaining process. This study seeks to examine the anomalies that flow from this interpretation of the meaning of section 187(1)(c). The study further investigates if this interpretation is not at odds with what the legislation really intended to achieve by enacting this clause. The study also explores ways in which the sanctity of collective bargaining could be restored. Recommendations are made to that effect.
- Full Text:
- Date Issued: 2009
- Authors: Qotoyi, Thanduxolo
- Date: 2009
- Subjects: Employees -- Dismissal of -- Law and legislation -- South Africa , Unfair labor practices -- South Africa , Collective bargaining -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:10223 , http://hdl.handle.net/10948/1039 , Employees -- Dismissal of -- Law and legislation -- South Africa , Unfair labor practices -- South Africa , Collective bargaining -- South Africa
- Description: Competitive forces in the market force employers to change the way they operate their businesses. The changes that employers have to make often demand an alteration of the employees’ terms and conditions of employment. By law employers are not permitted to unilaterally effect changes to the employee’s terms and conditions of employment. They have to obtain the consent of the affected employees. This is where collective bargaining fits in. The employer has to negotiate with the employees. One way in which through the process of collective bargaining an employer can exert pressure on the employees to accept the changes is to effect a lock-out. Under the Labour Relations Act 28 of 1956 within the context of a lock-out, an employer was permitted to use conditional dismissal as a bargaining weapon. This conditional dismissal had to be coupled with an offer of reemployment should the employees accept an employer’s demand. In essence, the lock-out had a bite in the form of the conditional dismissal. This made the lock-out quite effective. The 1995 Labour Relations Act prohibits in no uncertain terms the use of a dismissal as a means of compelling employees to accept an employer’s demand in any matter of mutual interest. Within the collective bargaining context, dismissal is not a legitimate option. The employer only has the lock-out as a tool of compulsion. The definition of a lock-out in terms of this Act does not accommodate the use of dismissal. This makes the lock-out option to be less potent than it was under the 1956 Labour Relations Act. However, employers are permitted to dismiss on operational grounds, provided that they follow a fair procedure. Terms and conditions of employment greatly feature in the operational requirements of a business. If the employees’ terms and conditions of employment are not responsive to the operational requirements of the business and they are unwilling to accept changes to those terms, the employer has the right to dismiss them. The employer will not be dismissing the employees as a way of inducing them to accept the changes. He will instead be dismissing them on the basis of operational requirements. iv The question that then arises is how should a dismissal that is intended to compel employees to accept an employers demand (falling within section 187(1)(c) of the 1995 Labour Relations Act be distinguished from a dismissal that is genuinely based on operational requirements as contemplated by section 188(1)(a)(ii). Doesn’t the fact that section 187(1)(c) explicitly prohibits the use of dismissal within the context of collective bargaining give rise to some tension with section 188(1)(a)(ii) which categorically gives employers the right to dismiss on operational grounds. The decision of the Labour Appeal Court in Fry’s Metals v NUMSA has stated that there is no tension whatsoever between the two sections. The court has also ruled that the dismissals that are hit by section 187(1)(c) are those dismissals that are accompanied by an offer of reemployment. According to the court, this offer is indicative of the real purpose of the employer, namely to compel employees to accept his demand. Dismissals not accompanied by an offer of re-employment are on the other hand a true reflection of the fact that the employer is indeed dismissing the employees for operational requirements. This literal interpretation of the meaning and scope of section 187(1)(c) has the potential of opening the floodgates. Instead of resorting to the use of the lock-out to secure the agreement of employees in the collective bargaining process, employers now have a potent tool in the form of a dismissal. As long as the employer makes it abundantly clear that the dismissal is final and irrevocable, he is free from the claws of section 187(1)(c). Given the fact that the lock-out option is not always effective, employers may find it hard to resist the temptation to use the threat of permanent dismissal as a bargaining chip. It is an option that is emasculated by the fact that in an employer initiated lock-out the use of replacement labour is prohibited. The threat of not just a conditional dismissal but a permanent one may force employees to capitulate to the employer’s demand during negotiations. This would effectively render negotiations about changes to terms and conditions of employment a farce. The employer would have an upper hand. The implications of this narrow interpretation are quite far-reaching. The long held view that dismissal is not a legitimate weapon of coercion in the collective bargaining process is under serious challenge. Only conditional dismissals are illegitimate in the collective bargaining v arena. Permanent dismissals are permitted. This negates the very purpose of the collective bargaining process. This study seeks to examine the anomalies that flow from this interpretation of the meaning of section 187(1)(c). The study further investigates if this interpretation is not at odds with what the legislation really intended to achieve by enacting this clause. The study also explores ways in which the sanctity of collective bargaining could be restored. Recommendations are made to that effect.
- Full Text:
- Date Issued: 2009
Dominant and non-dominant group's perceptions of the government-led economic transformation process in South Africa: report
- Authors: Dlamini, Thobile G. K
- Date: 2009
- Subjects: Group identity -- South Africa Post-apartheid era -- South Africa South Africa -- Ethnic relations Social change -- South Africa South Africa -- Social conditions -- 1994- South Africa -- Economic conditions -- 1991-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2963 , http://hdl.handle.net/10962/d1002472
- Description: The enormous social, economic, and political government-led societal transformation South Africans have experienced over the past 15 years have brought about numerous societal and identity changes. The aim of the present study was to explore how dominant (White participants) and non-dominant (Black participants) groups experiencing the government-led societal transformation process deal with perceptions of intergroup differences based on Social Identity Theory (Tajfel & Turner, 1979, 1986) and related field research. Social Identity Theory predicts that in the presence of intergroup differences group members irrespective of their status position will apply identity management strategies to either improve or maintain their status position. The relationships between perceptions of intergroup relations and identity management strategies as proposed by Social Identity Theory were tested studying 170 second year Rhodes University psychology students. Sixty participants indicated themselves as Black South Africans (representing non-dominant group) and 110 participants identified themselves as White South Africans (dominant group). The results revealed that dominant and non-dominant groups differ systematically regarding the functional interaction between beliefs about the intergroup situation and identity management strategies. The results of the study indicate too, that ingroup identification differentiates between individual and collective strategies irrespective of the group’s status position.
- Full Text:
- Date Issued: 2009
- Authors: Dlamini, Thobile G. K
- Date: 2009
- Subjects: Group identity -- South Africa Post-apartheid era -- South Africa South Africa -- Ethnic relations Social change -- South Africa South Africa -- Social conditions -- 1994- South Africa -- Economic conditions -- 1991-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2963 , http://hdl.handle.net/10962/d1002472
- Description: The enormous social, economic, and political government-led societal transformation South Africans have experienced over the past 15 years have brought about numerous societal and identity changes. The aim of the present study was to explore how dominant (White participants) and non-dominant (Black participants) groups experiencing the government-led societal transformation process deal with perceptions of intergroup differences based on Social Identity Theory (Tajfel & Turner, 1979, 1986) and related field research. Social Identity Theory predicts that in the presence of intergroup differences group members irrespective of their status position will apply identity management strategies to either improve or maintain their status position. The relationships between perceptions of intergroup relations and identity management strategies as proposed by Social Identity Theory were tested studying 170 second year Rhodes University psychology students. Sixty participants indicated themselves as Black South Africans (representing non-dominant group) and 110 participants identified themselves as White South Africans (dominant group). The results revealed that dominant and non-dominant groups differ systematically regarding the functional interaction between beliefs about the intergroup situation and identity management strategies. The results of the study indicate too, that ingroup identification differentiates between individual and collective strategies irrespective of the group’s status position.
- Full Text:
- Date Issued: 2009
Don Maclennan (1929-2009): obituary
- Authors: Cornwell, Gareth D N
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6118 , http://hdl.handle.net/10962/d1004620
- Description: Donald Alasdair Calum Maclennan, the South African playwright, poet and critic, died in Port Elizabeth on February 9, 2009, at the age of 79. He will be remembered chiefly for the poetry that he published in the last three decades of his life.
- Full Text:
- Date Issued: 2009
- Authors: Cornwell, Gareth D N
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6118 , http://hdl.handle.net/10962/d1004620
- Description: Donald Alasdair Calum Maclennan, the South African playwright, poet and critic, died in Port Elizabeth on February 9, 2009, at the age of 79. He will be remembered chiefly for the poetry that he published in the last three decades of his life.
- Full Text:
- Date Issued: 2009
Drawing Lines in the Sand: AM v RM 2010 2 SA 223 (ECP)
- Authors: Kruuse, Helen
- Date: 2009
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54107 , vital:26391 , http://www.ufh.ac.za/speculumjuris/files/pdf/SpeculumJuris_2009_Part_2.pdf
- Description: Judge Elna Revelas’s decision in the case of Mohamed v Mohamed 1 may be described as one of those run-of-the-mill applications in terms of rule 43 which are routinely heard on motion court days in any one of our high courts across the country. This case note suggests that her decision belies such a description. Instead, this note suggests that her decision marks a move away from existing jurisprudence on Muslim marriages in a way which may undermine, rather than promote, the recognition and respect for the marriage institutions of different religious systems and beliefs. I tentatively suggest that by granting the rule 43 application the court may have effectively imposed civil marriage obligations on a religious marriage even though the parties had not concluded a marriage in terms of the Marriage Act.2 As such, the decision has potentially radical consequences for parties in Muslim marriages and highlights the complex issues that courts have had to face in the last two decades without any guiding legislation. In order to understand the judgment properly, its context has to be considered. This context includes (1) the numerous judgments extending protection to women in Muslim marriages in the last two decades against the backdrop of the coming into effect of the Constitution of the Republic of South Africa, 1996; and (2) the application by the Women’s Legal Centre Trust (hereafter “WLCT”) to the Constitutional Court to force the President and Parliament to enact legislation to recognise and protect Muslim marriages.
- Full Text:
- Date Issued: 2009
- Authors: Kruuse, Helen
- Date: 2009
- Language: English
- Type: Article , text
- Identifier: http://hdl.handle.net/10962/54107 , vital:26391 , http://www.ufh.ac.za/speculumjuris/files/pdf/SpeculumJuris_2009_Part_2.pdf
- Description: Judge Elna Revelas’s decision in the case of Mohamed v Mohamed 1 may be described as one of those run-of-the-mill applications in terms of rule 43 which are routinely heard on motion court days in any one of our high courts across the country. This case note suggests that her decision belies such a description. Instead, this note suggests that her decision marks a move away from existing jurisprudence on Muslim marriages in a way which may undermine, rather than promote, the recognition and respect for the marriage institutions of different religious systems and beliefs. I tentatively suggest that by granting the rule 43 application the court may have effectively imposed civil marriage obligations on a religious marriage even though the parties had not concluded a marriage in terms of the Marriage Act.2 As such, the decision has potentially radical consequences for parties in Muslim marriages and highlights the complex issues that courts have had to face in the last two decades without any guiding legislation. In order to understand the judgment properly, its context has to be considered. This context includes (1) the numerous judgments extending protection to women in Muslim marriages in the last two decades against the backdrop of the coming into effect of the Constitution of the Republic of South Africa, 1996; and (2) the application by the Women’s Legal Centre Trust (hereafter “WLCT”) to the Constitutional Court to force the President and Parliament to enact legislation to recognise and protect Muslim marriages.
- Full Text:
- Date Issued: 2009
Drought, change and resilience in South Africa's arid and semi-arid rangelands
- Authors: Vetter, Susan M
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6557 , http://hdl.handle.net/10962/d1006017
- Description: Droughts can have serious ecological and economic consequences and will pose an increasing challenge to rangeiand users as the global climate is changing. Finding ways to reduce ecological and economic impacts of drought should thus be a major research thrust. Resilience, defined as the amount of perturbation a social or ecological system can absorb without shifting to a qualitatively different state, has emerged as a prominent concept in ecosystem ecology and more recently as a conceptual framework for understanding and managing complex social-ecological systems. This paper discusses the application and relevance of resilience to understanding and managing ecosystem change, and enhancing the capacity of land users to adapt to droughts. Drought can trigger vegetation change and factors such as grazing management can influence the likelihood of such transitions. Drought can cause differential mortality of perennial plants and this could provide an opportunity for rangeland restoration by opening up establishment sites for desirable species. The capacity of land users to cope with drought is influenced by the resilience of their agro-ecosystems, the diversity of livelihood options, access to resources and institutional support. By these criteria, current agricultural development approaches in South Africa, particularly in communal rangelands and areas of land reform, are unlikely to enhance land users' resilience to drought and other perturbations.
- Full Text:
- Date Issued: 2009
- Authors: Vetter, Susan M
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6557 , http://hdl.handle.net/10962/d1006017
- Description: Droughts can have serious ecological and economic consequences and will pose an increasing challenge to rangeiand users as the global climate is changing. Finding ways to reduce ecological and economic impacts of drought should thus be a major research thrust. Resilience, defined as the amount of perturbation a social or ecological system can absorb without shifting to a qualitatively different state, has emerged as a prominent concept in ecosystem ecology and more recently as a conceptual framework for understanding and managing complex social-ecological systems. This paper discusses the application and relevance of resilience to understanding and managing ecosystem change, and enhancing the capacity of land users to adapt to droughts. Drought can trigger vegetation change and factors such as grazing management can influence the likelihood of such transitions. Drought can cause differential mortality of perennial plants and this could provide an opportunity for rangeland restoration by opening up establishment sites for desirable species. The capacity of land users to cope with drought is influenced by the resilience of their agro-ecosystems, the diversity of livelihood options, access to resources and institutional support. By these criteria, current agricultural development approaches in South Africa, particularly in communal rangelands and areas of land reform, are unlikely to enhance land users' resilience to drought and other perturbations.
- Full Text:
- Date Issued: 2009
Dynamics of development intervention, the case of Peddie, Eastern Cape
- Authors: Nondumiso, Fukweni
- Date: 2009
- Subjects: Sustainable development -- South Africa -- Peddie District , Poverty -- South Africa -- Eastern Cape -- Peddie District , Natural resources -- South Africa -- Peddie District , Rural development projects -- South Africa -- Peddie District , Peddie (South Africa) -- Economic conditions , Peddie (Soutb Africa) -- Social conditions , Agriculture -- South Africa -- Eastern Cape -- Peddie District
- Language: English
- Type: Thesis , Masters , M Soc Sc (Rural Development)
- Identifier: vital:11936 , http://hdl.handle.net/10353/183 , Sustainable development -- South Africa -- Peddie District , Poverty -- South Africa -- Eastern Cape -- Peddie District , Natural resources -- South Africa -- Peddie District , Rural development projects -- South Africa -- Peddie District , Peddie (South Africa) -- Economic conditions , Peddie (Soutb Africa) -- Social conditions , Agriculture -- South Africa -- Eastern Cape -- Peddie District
- Description: A large number of development initiatives, aimed at improving the overall quality of life of communities, have had a limited success rate in addressing poverty levels. Poverty has increased drastically and more and more people are among the poorest of the poor in spite of all the development actions and programmes that are aimed at improving the quality of life (Chambers, 1997;1) The study explores the dynamics of commercialization of agriculture at Prudo and Benton villages in Peddie, Eastern Cape. These dynamics include labour issues, lack of people involvement in decision making processes and the sharing of benefits within the pineapple project at Benton. It also explores the challenges of cash cropping at Prudo. Additionally, the study looks at the challenges faced by the poor within small projects administered by the Department of Agriculture and the Department of Social Development. Finally, the study explores the role that natural resources play in livelihoods in Peddie. To achieve these objectives, a review of literature and empirical research presented in the form of case studies will be used. The central argument of this thesis is that development has failed the majority of the poor in Peddie. Despite that, rural people continue to survive. Development projects did not generally bring about any significant reduction in poverty; neither did they bring about any significant economic transformations.
- Full Text:
- Date Issued: 2009
- Authors: Nondumiso, Fukweni
- Date: 2009
- Subjects: Sustainable development -- South Africa -- Peddie District , Poverty -- South Africa -- Eastern Cape -- Peddie District , Natural resources -- South Africa -- Peddie District , Rural development projects -- South Africa -- Peddie District , Peddie (South Africa) -- Economic conditions , Peddie (Soutb Africa) -- Social conditions , Agriculture -- South Africa -- Eastern Cape -- Peddie District
- Language: English
- Type: Thesis , Masters , M Soc Sc (Rural Development)
- Identifier: vital:11936 , http://hdl.handle.net/10353/183 , Sustainable development -- South Africa -- Peddie District , Poverty -- South Africa -- Eastern Cape -- Peddie District , Natural resources -- South Africa -- Peddie District , Rural development projects -- South Africa -- Peddie District , Peddie (South Africa) -- Economic conditions , Peddie (Soutb Africa) -- Social conditions , Agriculture -- South Africa -- Eastern Cape -- Peddie District
- Description: A large number of development initiatives, aimed at improving the overall quality of life of communities, have had a limited success rate in addressing poverty levels. Poverty has increased drastically and more and more people are among the poorest of the poor in spite of all the development actions and programmes that are aimed at improving the quality of life (Chambers, 1997;1) The study explores the dynamics of commercialization of agriculture at Prudo and Benton villages in Peddie, Eastern Cape. These dynamics include labour issues, lack of people involvement in decision making processes and the sharing of benefits within the pineapple project at Benton. It also explores the challenges of cash cropping at Prudo. Additionally, the study looks at the challenges faced by the poor within small projects administered by the Department of Agriculture and the Department of Social Development. Finally, the study explores the role that natural resources play in livelihoods in Peddie. To achieve these objectives, a review of literature and empirical research presented in the form of case studies will be used. The central argument of this thesis is that development has failed the majority of the poor in Peddie. Despite that, rural people continue to survive. Development projects did not generally bring about any significant reduction in poverty; neither did they bring about any significant economic transformations.
- 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
Ecological role of estuarine brachyuran crabs in mangrove and salt marsh estuaries, Eastern Cape, South Africa
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009