The control of a multi-variable industrial process, by means of intelligent technology
- Authors: Naidoo, Puramanathan
- Date: 2001
- Subjects: Fuzzy systems , Intelligent control systems
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10813 , http://hdl.handle.net/10948/48 , Fuzzy systems , Intelligent control systems
- Description: Conventional control systems express control solutions by means of expressions, usually mathematically based. In order to completely express the control solution, a vast amount of data is required. In contrast, knowledge-based solutions require far less plant data and mathematical expression. This reduces development time proportionally. In addition, because this type of processing does not require involved calculations, processing speed is increased, since rule process is separate and all processes can be performed simultaneously. These results in improved product quality, better plant efficiency, simplified process, etc. Within this project, conventional PID control has already been implemented, with the control parameter adjustment and loop tuning being problematic. This is mainly due to a number of external parameters that affects the stability of the process. In maintaining a consistent temperature, for example, the steam flow rate varies, the hot well temperature varies, the ambient may temperature vary. Another contributing factor, the time delay, also affects the optimization of the system, due to the fact that temperature measurement is based on principle of absorption. The normal practice in industry to avoid an unstable control condition is to have an experienced operator to switch the controller to manual, and make adjustments. After obtaining the desired PV, the controller is switched back to automatic. This research project focuses on eliminating this time loss, by implementing a knowledge-based controller, for intelligent decision-making. A FLC design tool, which allows full interaction, whilst designing the control algorithm, was used to optimize the control system. The design tool executed on a PC is connected to a PLC, which in turn is successfully integrated into the process plant.
- Full Text:
- Date Issued: 2001
- Authors: Naidoo, Puramanathan
- Date: 2001
- Subjects: Fuzzy systems , Intelligent control systems
- Language: English
- Type: Thesis , Masters , MTech (Electrical Engineering)
- Identifier: vital:10813 , http://hdl.handle.net/10948/48 , Fuzzy systems , Intelligent control systems
- Description: Conventional control systems express control solutions by means of expressions, usually mathematically based. In order to completely express the control solution, a vast amount of data is required. In contrast, knowledge-based solutions require far less plant data and mathematical expression. This reduces development time proportionally. In addition, because this type of processing does not require involved calculations, processing speed is increased, since rule process is separate and all processes can be performed simultaneously. These results in improved product quality, better plant efficiency, simplified process, etc. Within this project, conventional PID control has already been implemented, with the control parameter adjustment and loop tuning being problematic. This is mainly due to a number of external parameters that affects the stability of the process. In maintaining a consistent temperature, for example, the steam flow rate varies, the hot well temperature varies, the ambient may temperature vary. Another contributing factor, the time delay, also affects the optimization of the system, due to the fact that temperature measurement is based on principle of absorption. The normal practice in industry to avoid an unstable control condition is to have an experienced operator to switch the controller to manual, and make adjustments. After obtaining the desired PV, the controller is switched back to automatic. This research project focuses on eliminating this time loss, by implementing a knowledge-based controller, for intelligent decision-making. A FLC design tool, which allows full interaction, whilst designing the control algorithm, was used to optimize the control system. The design tool executed on a PC is connected to a PLC, which in turn is successfully integrated into the process plant.
- Full Text:
- Date Issued: 2001
The determination of geomorphologically effective flows for selected eastern sea-Board Rivers in South Africa
- Authors: Dollar, E S J
- Date: 2001
- Subjects: Rivers--South Africa River channels Geomorphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4824 , http://hdl.handle.net/10962/d1005499
- Description: In South Africa the need to protect and manage the national water resource has led to the development of the Reserve as a basic right under the National Water Act (1998). The Ecological Reserve relates to the quality and quantity of water necessary to protect the sustainable functioning of aquatic ecosystems. The geomorphological contribution to setting the Reserve has focussed on three groups of information requirements: the spatial and temporal availability of habitat, the maintenance of substratum characteristics, and the maintenance of channel form. This thesis focusses on the second and third information requirements. The thesis has attempted to achieve this by adding value to the theoretical and applied understanding of the magnitude and frequency of channel forming discharge for selected southern African rivers. Many of the eastern sea-board rivers are strongly influenced by bed rock in the channel perimeter, and by a highly variable hydrological regime. This has resulted in characteristic channel forms, with an active channel incised into a larger macro-channel being a common feature of eastern seaboard rivers. Within the active channel inset channel benches commonly occur. This alluvial architecture is used to provide clues as to the types of flows necessary to meet the Reserve. Three river basins are considered : the Mkomazi, Mhlathuze and Olifants. The Mkomazi is a relatively un-impacted perennial eastern-sea board river and forms the research component of the study. The Mhlathuze and Olifants rivers are highly regulated systems and form the application component of the study. Utilising synthesised daily hydrological data, bed material data, cross-sectional surveys, hydraulic data and relevant bed material transport equations, channel form was related to dominant discharge and effective discharge in an attempt to identify the magnitude and frequency offlows that can be considered to be ' effective'. Results from the Mkomazi River indicate that no single effective discharge exists, but rather that there is a range of effective discharges in the 5-0.1% range on the 1-day daily flow duration curves that are responsible for the bulk (>80%) of the bed material transport. Only large floods (termed 'reset'discharges) with average return periods of around 20 years generate sufficient stream power and shear stress to mobilise the entire bed. The macro-channel is thus maintained by the large ' reset' flood events, and the active channel is maintained both by the range of effective discharges and the ' reset 'discharges. These are the geomorphologically 'effective' flows. Results from the Mhlathuze River have indicated that the Goedertrouw Dam has had a considerable impact on the downstream channel morphology and bed material transport capacity and consequently the effective and dominant discharges. It has been suggested that the Mhlathuze River is now adjusting its channel geometry in sympathy with the regulated flow environment. Under present-day conditions it has been demonstrated that the total bed material load has been reduced by up to three times, but there has also been a clear change in the way in which the load has been distributed around the duration curve. Under present-day conditions, over 90% of the total bed material load is transported by the top 5% of the flows, whereas under virgin flow conditions 90% of the total bed material load was transported by the top 20% of the flows. For the Olifants River there appears to be no relationship between the estimated bankfull discharge and any hydrological statistic. The effective discharge flow class is in the 5-0.01% range on the 1-day daily flow duration curve. It has also been pointed out that even the highest flows simulated for the Olifants River do not generate sufficient energy to mobilise the entire bed. It is useful to consider the Olifants River as being adapted to a highly variable flow regime. It is erroneous to think of one ' effective' discharge, but rather a range of effective discharges are of significance. It has been argued that strong bed rock control and a highly variable flow regime in many southern African rivers accounts for the channel architecture, and that there is a need to develop an ' indigenous knowledge' in the management of southern African fluvial systems
- Full Text:
- Date Issued: 2001
- Authors: Dollar, E S J
- Date: 2001
- Subjects: Rivers--South Africa River channels Geomorphology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4824 , http://hdl.handle.net/10962/d1005499
- Description: In South Africa the need to protect and manage the national water resource has led to the development of the Reserve as a basic right under the National Water Act (1998). The Ecological Reserve relates to the quality and quantity of water necessary to protect the sustainable functioning of aquatic ecosystems. The geomorphological contribution to setting the Reserve has focussed on three groups of information requirements: the spatial and temporal availability of habitat, the maintenance of substratum characteristics, and the maintenance of channel form. This thesis focusses on the second and third information requirements. The thesis has attempted to achieve this by adding value to the theoretical and applied understanding of the magnitude and frequency of channel forming discharge for selected southern African rivers. Many of the eastern sea-board rivers are strongly influenced by bed rock in the channel perimeter, and by a highly variable hydrological regime. This has resulted in characteristic channel forms, with an active channel incised into a larger macro-channel being a common feature of eastern seaboard rivers. Within the active channel inset channel benches commonly occur. This alluvial architecture is used to provide clues as to the types of flows necessary to meet the Reserve. Three river basins are considered : the Mkomazi, Mhlathuze and Olifants. The Mkomazi is a relatively un-impacted perennial eastern-sea board river and forms the research component of the study. The Mhlathuze and Olifants rivers are highly regulated systems and form the application component of the study. Utilising synthesised daily hydrological data, bed material data, cross-sectional surveys, hydraulic data and relevant bed material transport equations, channel form was related to dominant discharge and effective discharge in an attempt to identify the magnitude and frequency offlows that can be considered to be ' effective'. Results from the Mkomazi River indicate that no single effective discharge exists, but rather that there is a range of effective discharges in the 5-0.1% range on the 1-day daily flow duration curves that are responsible for the bulk (>80%) of the bed material transport. Only large floods (termed 'reset'discharges) with average return periods of around 20 years generate sufficient stream power and shear stress to mobilise the entire bed. The macro-channel is thus maintained by the large ' reset' flood events, and the active channel is maintained both by the range of effective discharges and the ' reset 'discharges. These are the geomorphologically 'effective' flows. Results from the Mhlathuze River have indicated that the Goedertrouw Dam has had a considerable impact on the downstream channel morphology and bed material transport capacity and consequently the effective and dominant discharges. It has been suggested that the Mhlathuze River is now adjusting its channel geometry in sympathy with the regulated flow environment. Under present-day conditions it has been demonstrated that the total bed material load has been reduced by up to three times, but there has also been a clear change in the way in which the load has been distributed around the duration curve. Under present-day conditions, over 90% of the total bed material load is transported by the top 5% of the flows, whereas under virgin flow conditions 90% of the total bed material load was transported by the top 20% of the flows. For the Olifants River there appears to be no relationship between the estimated bankfull discharge and any hydrological statistic. The effective discharge flow class is in the 5-0.01% range on the 1-day daily flow duration curve. It has also been pointed out that even the highest flows simulated for the Olifants River do not generate sufficient energy to mobilise the entire bed. It is useful to consider the Olifants River as being adapted to a highly variable flow regime. It is erroneous to think of one ' effective' discharge, but rather a range of effective discharges are of significance. It has been argued that strong bed rock control and a highly variable flow regime in many southern African rivers accounts for the channel architecture, and that there is a need to develop an ' indigenous knowledge' in the management of southern African fluvial systems
- Full Text:
- Date Issued: 2001
The development and assessment of both a separate, once-daily modified release matrix formulation of metoprolol tartrate and a combination formulation with hydrochlorothiazide
- Authors: Arjun, Jessica
- Date: 2001
- Subjects: Metoprolol -- Controlled release , Chlorothiazide -- Controlled release , Diuretics , Hypertension -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3742 , http://hdl.handle.net/10962/d1003220 , Metoprolol -- Controlled release , Chlorothiazide -- Controlled release , Diuretics , Hypertension -- Treatment
- Description: The use of controlled release dosage forms has increased significantly in recent years as they result in increased patient compliance and higher therapeutic efficiency. This research focused on the development of a once daily dosage form that could be used for the treatment of hypertension. Both a separate sustained release dosage of metoprolol tartrate and a combination dosage form that included both an immediate release hydrochlorothiazide and a sustained release metoprolol component, were developed and evaluated. A matrix tablet, consisting of an ethylcellulose ranulation of metoprolol tartrate compressed into a hydrophilic hydroxypropyl methylcellulose polymer matrix, effectively sustained metoprolol release over a 22-hour experimental period. A multiparticulate combination dosage form that consisted of six coated mini matrix tablets of metoprolol and a powder blend of hydrochlorothiazide packed into a gelatin capsule, displayed zero order release kinetics for metoprolol release over 22 hours (r2=0.9946). The release of hydrochlorothiazide was found to be comparable to that of a commercially available product tested. Differential Scanning Calorimetry was used to identify possible incompatibilities between MPTA and excipients initially, and long term stability testing was used to assess to behaviour of the dosage form. Dissolution testing of the dosage forms was performed using USP Apparatus III, which was found to be more discriminating between the batches assessed. Dissolution curves were evaluated for similarity and difference using f1 and f2 fit factors. Samples were analyzed using a high performance liquid chromatographic method that was developed and validated for the simultaneous determination of the compounds of interest. Various factors influencing drug release from the developed dosage forms were assessed and recommendations for further optimization of the formulation are made. Factors evaluated included the quantity of granulating fluid, matrix polymer content, drug load and process variables, including drying time and compression force. The influence of various coating levels on drug release was assessed and none of the levels assessed were found to adequately retarded drug release over a 22-hour period. Combinations of tablets coated to different levels allowed for the successful development of a sustained release metoprolol component, which could be included into the combination dosage form.
- Full Text:
- Date Issued: 2001
- Authors: Arjun, Jessica
- Date: 2001
- Subjects: Metoprolol -- Controlled release , Chlorothiazide -- Controlled release , Diuretics , Hypertension -- Treatment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3742 , http://hdl.handle.net/10962/d1003220 , Metoprolol -- Controlled release , Chlorothiazide -- Controlled release , Diuretics , Hypertension -- Treatment
- Description: The use of controlled release dosage forms has increased significantly in recent years as they result in increased patient compliance and higher therapeutic efficiency. This research focused on the development of a once daily dosage form that could be used for the treatment of hypertension. Both a separate sustained release dosage of metoprolol tartrate and a combination dosage form that included both an immediate release hydrochlorothiazide and a sustained release metoprolol component, were developed and evaluated. A matrix tablet, consisting of an ethylcellulose ranulation of metoprolol tartrate compressed into a hydrophilic hydroxypropyl methylcellulose polymer matrix, effectively sustained metoprolol release over a 22-hour experimental period. A multiparticulate combination dosage form that consisted of six coated mini matrix tablets of metoprolol and a powder blend of hydrochlorothiazide packed into a gelatin capsule, displayed zero order release kinetics for metoprolol release over 22 hours (r2=0.9946). The release of hydrochlorothiazide was found to be comparable to that of a commercially available product tested. Differential Scanning Calorimetry was used to identify possible incompatibilities between MPTA and excipients initially, and long term stability testing was used to assess to behaviour of the dosage form. Dissolution testing of the dosage forms was performed using USP Apparatus III, which was found to be more discriminating between the batches assessed. Dissolution curves were evaluated for similarity and difference using f1 and f2 fit factors. Samples were analyzed using a high performance liquid chromatographic method that was developed and validated for the simultaneous determination of the compounds of interest. Various factors influencing drug release from the developed dosage forms were assessed and recommendations for further optimization of the formulation are made. Factors evaluated included the quantity of granulating fluid, matrix polymer content, drug load and process variables, including drying time and compression force. The influence of various coating levels on drug release was assessed and none of the levels assessed were found to adequately retarded drug release over a 22-hour period. Combinations of tablets coated to different levels allowed for the successful development of a sustained release metoprolol component, which could be included into the combination dosage form.
- Full Text:
- Date Issued: 2001
The development and evaluation of procedures for the synthesis of phenolic ethers by Baeyer-Villiger oxidation
- Authors: Hoffmann, Petra
- Date: 2001
- Subjects: Ethers , Phenols
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10955 , http://hdl.handle.net/10948/51 , Ethers , Phenols
- Description: A novel preparative method has been discovered in our laboratories which produces hydroxy-substituted phenolic ethers in a simple one-pot process. Initially it was found that 4-hydroxyacetophenone, when oxidized in the presence of ammonium peroxydisulfate and concentrated sulfuric acid in methanol, resulted in 4- methoxyphenol as product in high yield. Being novel, no information about the method was available in the literature, and hence it was our task to study the reaction more extensively. The scope of the reaction was investigated in that different reagents and substrates, as well as alternative oxidants, catalysts and alcohols (or reagents which may be envisaged to behave similarly to alcohols) were used. The studies showed that 4- hydroxy-substituted benzaldehyde and acetophenone, vanillin, fuchsones and stilbenequinones as substrates all successfully afforded the phenolic ether. Other oxidants such as hydrogen peroxide, sodium perborate etc. also afforded the phenolic ether but were less effective. The use of other acids than sulfuric acid resulted in comparable or lower yields of the desired phenolic ether. When the use of alcohols or similar reagents was varied, it was found that methanol, ethanol, benzyl alcohol, allyl alcohol, but-3-en-1-ol, hex-5-en-1-ol and undec-10-en-1-ol all afforded the desired ethers in significant yields. In an investigation to determine how this method may be useful for industrial applications, it was observed that compounds such as 3,5-di-tert-butyl-4-hydroxysubstituted alkenyloxy phenols, having potential application as antioxidant precursors in the polymer industry, may be prepared. Results showed that the reaction became less efficient when the alkenyl chain length was increased. The use of different acids and oxidants, the change of the oxidant:substrate ratio and the addition of a potential lanthanide catalyst did not improve the yield of the desired ether. A mechanism for the reaction was proposed which involved an initial Baeyer-Villiger oxygen insertion step to afford an ester which was hydrolysed in situ to hydroquinone. The remaining oxidant was then involved in oxidizing some of the soformed hydroquinone to benzoquinone. It was then proposed that these two compounds, i.e., hydroquinone and benzoquinone, interacted with each other in solution, forming a charge-transfer complex. According to our proposal, the carbonyl group of the benzoquinone, when complexed with hydroquinone in solution, was then attacked by nucleophilic reagents such as alcohols. Etherification hence resulted as a consequence of this attack. A statistical experimental evaluation and optimization study was then performed which led to a system that produced the phenolic ether, 4-methoxyphenol, in an 86% yield. An analysis of the effects of the reaction parameters on the reaction showed that the reaction temperature and the oxidant:substrate ratio played a major role in deciding the effectiveness of the reaction, while the amount of substrate and acidic catalyst had a much smaller influence on the ether yields.
- Full Text:
- Date Issued: 2001
- Authors: Hoffmann, Petra
- Date: 2001
- Subjects: Ethers , Phenols
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10955 , http://hdl.handle.net/10948/51 , Ethers , Phenols
- Description: A novel preparative method has been discovered in our laboratories which produces hydroxy-substituted phenolic ethers in a simple one-pot process. Initially it was found that 4-hydroxyacetophenone, when oxidized in the presence of ammonium peroxydisulfate and concentrated sulfuric acid in methanol, resulted in 4- methoxyphenol as product in high yield. Being novel, no information about the method was available in the literature, and hence it was our task to study the reaction more extensively. The scope of the reaction was investigated in that different reagents and substrates, as well as alternative oxidants, catalysts and alcohols (or reagents which may be envisaged to behave similarly to alcohols) were used. The studies showed that 4- hydroxy-substituted benzaldehyde and acetophenone, vanillin, fuchsones and stilbenequinones as substrates all successfully afforded the phenolic ether. Other oxidants such as hydrogen peroxide, sodium perborate etc. also afforded the phenolic ether but were less effective. The use of other acids than sulfuric acid resulted in comparable or lower yields of the desired phenolic ether. When the use of alcohols or similar reagents was varied, it was found that methanol, ethanol, benzyl alcohol, allyl alcohol, but-3-en-1-ol, hex-5-en-1-ol and undec-10-en-1-ol all afforded the desired ethers in significant yields. In an investigation to determine how this method may be useful for industrial applications, it was observed that compounds such as 3,5-di-tert-butyl-4-hydroxysubstituted alkenyloxy phenols, having potential application as antioxidant precursors in the polymer industry, may be prepared. Results showed that the reaction became less efficient when the alkenyl chain length was increased. The use of different acids and oxidants, the change of the oxidant:substrate ratio and the addition of a potential lanthanide catalyst did not improve the yield of the desired ether. A mechanism for the reaction was proposed which involved an initial Baeyer-Villiger oxygen insertion step to afford an ester which was hydrolysed in situ to hydroquinone. The remaining oxidant was then involved in oxidizing some of the soformed hydroquinone to benzoquinone. It was then proposed that these two compounds, i.e., hydroquinone and benzoquinone, interacted with each other in solution, forming a charge-transfer complex. According to our proposal, the carbonyl group of the benzoquinone, when complexed with hydroquinone in solution, was then attacked by nucleophilic reagents such as alcohols. Etherification hence resulted as a consequence of this attack. A statistical experimental evaluation and optimization study was then performed which led to a system that produced the phenolic ether, 4-methoxyphenol, in an 86% yield. An analysis of the effects of the reaction parameters on the reaction showed that the reaction temperature and the oxidant:substrate ratio played a major role in deciding the effectiveness of the reaction, while the amount of substrate and acidic catalyst had a much smaller influence on the ether yields.
- Full Text:
- Date Issued: 2001
The development of a balanced scorecard for strategic planning in a frozen vegetable processing plant
- Authors: Du Plessis, Francois
- Date: 2001
- Subjects: Food industry and trade -- South Africa -- Management , Strategic planning
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10887 , http://hdl.handle.net/10948/52 , Food industry and trade -- South Africa -- Management , Strategic planning
- Description: This research investigated the development of a balanced scorecard for a frozen vegetable processing plant. The balanced scorecard can be utilised as a strategic management and performance measurement system. First, an overview of the balanced scorecard concept was presented. Its four perspectives, namely financial, customer, internal business process, and learning and growth were explained. Thereafter, the process of developing a balanced scorecard was outlined and the translation of a firm’s vision into measurable objectives and targets was discussed. Finally, the literature study evaluated the development of balanced scorecards by means of selected case studies. This included an analysis of the successes and failures of balanced scorecards in practice. The research methodology consisted of: (a) A literature study to determine a framework for developing a balanced scorecard. (b) Interviews and workshops to gather the primary data required to develop a balanced scorecard. The development of a balanced scorecard for a frozen vegetable processing plant using the findings from (a) and (b) above. The following recommendations were made: · Targets and action plans should be developed for the outstanding strategic objectives of the plant, and all key performance measurements should be formalised on key performance area documents. All role players should be involved in this process. · All employees must be exposed to, and understand the plant’s vision, mission statement and the purpose of the balanced scorecard. · All employees need to understand how their actions impact on other employees and the well-being of the plant. They must have set objectives and targets that can be measured. · To increase the chance of a successful scorecard implementation, regular feedback must be provided to all employees, and managers must hold people accountable for using the system.
- Full Text:
- Date Issued: 2001
- Authors: Du Plessis, Francois
- Date: 2001
- Subjects: Food industry and trade -- South Africa -- Management , Strategic planning
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:10887 , http://hdl.handle.net/10948/52 , Food industry and trade -- South Africa -- Management , Strategic planning
- Description: This research investigated the development of a balanced scorecard for a frozen vegetable processing plant. The balanced scorecard can be utilised as a strategic management and performance measurement system. First, an overview of the balanced scorecard concept was presented. Its four perspectives, namely financial, customer, internal business process, and learning and growth were explained. Thereafter, the process of developing a balanced scorecard was outlined and the translation of a firm’s vision into measurable objectives and targets was discussed. Finally, the literature study evaluated the development of balanced scorecards by means of selected case studies. This included an analysis of the successes and failures of balanced scorecards in practice. The research methodology consisted of: (a) A literature study to determine a framework for developing a balanced scorecard. (b) Interviews and workshops to gather the primary data required to develop a balanced scorecard. The development of a balanced scorecard for a frozen vegetable processing plant using the findings from (a) and (b) above. The following recommendations were made: · Targets and action plans should be developed for the outstanding strategic objectives of the plant, and all key performance measurements should be formalised on key performance area documents. All role players should be involved in this process. · All employees must be exposed to, and understand the plant’s vision, mission statement and the purpose of the balanced scorecard. · All employees need to understand how their actions impact on other employees and the well-being of the plant. They must have set objectives and targets that can be measured. · To increase the chance of a successful scorecard implementation, regular feedback must be provided to all employees, and managers must hold people accountable for using the system.
- Full Text:
- Date Issued: 2001
The development of a model of factors promoting leadership effectiveness in the private hospitals of Afrox Healthcare in the Port Elizabeth area
- Authors: Bosch, Wouter Conrad
- Date: 2001
- Subjects: Leadership
- Language: English
- Type: Thesis , Masters , MTech (Management)
- Identifier: vital:10901 , http://hdl.handle.net/10948/53 , Leadership
- Description: Effective leadership is essential for the achievement of organisational success in the long term. Leadership is the central ingredient necessary for progress as well as for the development and survival of organisations, especially in a changing environment such as South Africa. In this study an evaluation of various leadership models was conducted and a model of factors promoting effective leadership has been developed and proposed. This model was then tested amongst managers in the Private Hospitals of Afrox Healthcare in the Port Elizabeth area. The following procedure was followed: Firstly, a literature study was undertaken to identify the various leadership approaches. Attention was mainly focused on the most recent or advanced approaches to leadership. Secondly, based on the most recent approaches to leadership, a model of factors promoting effective leadership has been developed and proposed. The key elements identified for effective leadership are contained in this model. Thirdly, an empirical study was conducted to test the proposed model of leadership. Lastly, the results of the empirical study were evaluated, conclusions were drawn and recommendations made, based on the information obtained from both the literature study and the empirical study. The model of factors of effective leadership that has been developed is a combination of : · Leader Behaviours, which includes the elements of vision, communication, planning and empowerment; · Follower Behaviours, consisting of identification with the leader and the leader’s vision, commitment, motivation and goal pursuit, as well as trust; and · Organisational Environmental factors, including organisational configuration, organisational structure and organisational culture. It is argued that when the factors contained in the model achieve synergy, leadership will be effective, leading to enhanced organisational performance and success.
- Full Text:
- Date Issued: 2001
- Authors: Bosch, Wouter Conrad
- Date: 2001
- Subjects: Leadership
- Language: English
- Type: Thesis , Masters , MTech (Management)
- Identifier: vital:10901 , http://hdl.handle.net/10948/53 , Leadership
- Description: Effective leadership is essential for the achievement of organisational success in the long term. Leadership is the central ingredient necessary for progress as well as for the development and survival of organisations, especially in a changing environment such as South Africa. In this study an evaluation of various leadership models was conducted and a model of factors promoting effective leadership has been developed and proposed. This model was then tested amongst managers in the Private Hospitals of Afrox Healthcare in the Port Elizabeth area. The following procedure was followed: Firstly, a literature study was undertaken to identify the various leadership approaches. Attention was mainly focused on the most recent or advanced approaches to leadership. Secondly, based on the most recent approaches to leadership, a model of factors promoting effective leadership has been developed and proposed. The key elements identified for effective leadership are contained in this model. Thirdly, an empirical study was conducted to test the proposed model of leadership. Lastly, the results of the empirical study were evaluated, conclusions were drawn and recommendations made, based on the information obtained from both the literature study and the empirical study. The model of factors of effective leadership that has been developed is a combination of : · Leader Behaviours, which includes the elements of vision, communication, planning and empowerment; · Follower Behaviours, consisting of identification with the leader and the leader’s vision, commitment, motivation and goal pursuit, as well as trust; and · Organisational Environmental factors, including organisational configuration, organisational structure and organisational culture. It is argued that when the factors contained in the model achieve synergy, leadership will be effective, leading to enhanced organisational performance and success.
- Full Text:
- Date Issued: 2001
The development of a model to effectively utilise computer mediated communication to support assessment in a virtual learning environment
- Authors: Pullen, Grant
- Date: 2001
- Subjects: Computer-assisted instruction , Students -- Rating of , Communication in education -- Data processing
- Language: English
- Type: Thesis , Masters , MTech (Information Technology)
- Identifier: vital:10795 , http://hdl.handle.net/10948/54 , Computer-assisted instruction , Students -- Rating of , Communication in education -- Data processing
- Description: Programming lecturers are faced with logistical problems associated with evaluating students’ assignments. This dissertation will discuss the problems associated with paper- and electronic-based submission and evaluation systems. Managing student assignments is thus an important issue and this dissertation investigates how the computer can be used to help in both the management of programming assignments and giving of feedback for those assignments. Computer Mediated Communication (CMC) technologies offer a technical solution for the submission of assignments. CMC technologies are therefore studied and their use in the educational sphere discussed. Information Security is another important feature that is needed when using CMC for assignment management. A guideline showing the different features that an assignment management and feedback system would need was developed. Current systems that offer some assignment management features were studied and evaluated according to the guideline. A model was developed for the management of programming assignments. The model addresses the problems of paper-based and previous electronic submission systems and includes the assessment of the assignments. The viability of the model was determined by building and testing a prototype based on the model’s specifications. The prototype was evaluated within a second year Visual Basic programming class. The evaluation determined that there were areas that needed improvement, however the feedback was generally positive.
- Full Text:
- Date Issued: 2001
- Authors: Pullen, Grant
- Date: 2001
- Subjects: Computer-assisted instruction , Students -- Rating of , Communication in education -- Data processing
- Language: English
- Type: Thesis , Masters , MTech (Information Technology)
- Identifier: vital:10795 , http://hdl.handle.net/10948/54 , Computer-assisted instruction , Students -- Rating of , Communication in education -- Data processing
- Description: Programming lecturers are faced with logistical problems associated with evaluating students’ assignments. This dissertation will discuss the problems associated with paper- and electronic-based submission and evaluation systems. Managing student assignments is thus an important issue and this dissertation investigates how the computer can be used to help in both the management of programming assignments and giving of feedback for those assignments. Computer Mediated Communication (CMC) technologies offer a technical solution for the submission of assignments. CMC technologies are therefore studied and their use in the educational sphere discussed. Information Security is another important feature that is needed when using CMC for assignment management. A guideline showing the different features that an assignment management and feedback system would need was developed. Current systems that offer some assignment management features were studied and evaluated according to the guideline. A model was developed for the management of programming assignments. The model addresses the problems of paper-based and previous electronic submission systems and includes the assessment of the assignments. The viability of the model was determined by building and testing a prototype based on the model’s specifications. The prototype was evaluated within a second year Visual Basic programming class. The evaluation determined that there were areas that needed improvement, however the feedback was generally positive.
- Full Text:
- Date Issued: 2001
The development of a scale to measure sexual orientation and an examination of its psychometric properties
- Authors: Heath, Lance Julien
- Date: 2001
- Subjects: Sexual orientation , Sexual orientation -- Research -- Psychological aspects , Psychometrics
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3145 , http://hdl.handle.net/10962/d1007408 , Sexual orientation , Sexual orientation -- Research -- Psychological aspects , Psychometrics
- Description: The purpose of the study was to develop a scale to measure sexual orientation and to examine its psychometric properties. Previous scales were critically examined and compared and the need for a scale which simultaneously measures same and opposite sex responsiveness independently, and accounts for dynamic changes over time, while testing a number of overt and covert dimensions of sexual orientations, was established. A 48-item scale was designed to tap self-reported intensity and frequency of Emotional Attachment, Sexual Fantasy, Sexual Attraction and Sexual Contact towards males and females in the Past, Present and Future. An initial study was conducted with 13 undergraduate university students of both genders, representing a variety of sexual orientations and nationalities, and qualitative feedback was obtained and utilized to make appropriate adjustments and refinements to the scale. The scale was then administered to 133 Rhodes University undergraduate psychology students to obtain quantitative data with regard to its internal structure. The scale was found to have a good internal consistency reliability Cronbach alpha coefficient of 0.8106. Existing sub-scales had lower alpha coefficients. Factor analysis, a form of construct validation, was performed and four factors emerged. These had very good internal consistency reliability alpha coefficients: Sexual Responsiveness to Females (0.9894), Sexual Responsiveness to Males (0.9741), Emotional Attachment to Females (0.8403) and Emotional Attachment to Males (0.8372). These factors were further statistically analysed to ascertain how they relate to one another and to the demographics of gender, age, relational status and sexual orientation identity. Future research will need to assess other forms of reliability and validity and focus on larger and more varied samples.
- Full Text:
- Date Issued: 2001
- Authors: Heath, Lance Julien
- Date: 2001
- Subjects: Sexual orientation , Sexual orientation -- Research -- Psychological aspects , Psychometrics
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3145 , http://hdl.handle.net/10962/d1007408 , Sexual orientation , Sexual orientation -- Research -- Psychological aspects , Psychometrics
- Description: The purpose of the study was to develop a scale to measure sexual orientation and to examine its psychometric properties. Previous scales were critically examined and compared and the need for a scale which simultaneously measures same and opposite sex responsiveness independently, and accounts for dynamic changes over time, while testing a number of overt and covert dimensions of sexual orientations, was established. A 48-item scale was designed to tap self-reported intensity and frequency of Emotional Attachment, Sexual Fantasy, Sexual Attraction and Sexual Contact towards males and females in the Past, Present and Future. An initial study was conducted with 13 undergraduate university students of both genders, representing a variety of sexual orientations and nationalities, and qualitative feedback was obtained and utilized to make appropriate adjustments and refinements to the scale. The scale was then administered to 133 Rhodes University undergraduate psychology students to obtain quantitative data with regard to its internal structure. The scale was found to have a good internal consistency reliability Cronbach alpha coefficient of 0.8106. Existing sub-scales had lower alpha coefficients. Factor analysis, a form of construct validation, was performed and four factors emerged. These had very good internal consistency reliability alpha coefficients: Sexual Responsiveness to Females (0.9894), Sexual Responsiveness to Males (0.9741), Emotional Attachment to Females (0.8403) and Emotional Attachment to Males (0.8372). These factors were further statistically analysed to ascertain how they relate to one another and to the demographics of gender, age, relational status and sexual orientation identity. Future research will need to assess other forms of reliability and validity and focus on larger and more varied samples.
- Full Text:
- Date Issued: 2001
The development of a technique to establish the security requirements of an organization
- Authors: Gerber, Mariana
- Date: 2001
- Subjects: Computer security -- Management , Electronic data processing departments -- Security measures , Businesses -- Data processing -- Security measures , Computers -- Access control
- Language: English
- Type: Thesis , Masters , MTech (Information Technology)
- Identifier: vital:10789 , http://hdl.handle.net/10948/89 , Computer security -- Management , Electronic data processing departments -- Security measures , Businesses -- Data processing -- Security measures , Computers -- Access control
- Description: To perform their business activities effectively, organizations rely heavily on the use of information (ISO/IEC TR 13335-2, 1996, p 1). Owens (1998) reiterates this by claiming that all organizations depend on information for their everyday operation and without it business will fail to operate (Owens, 1998, p 1-2). For an organization it means that if the right information is not available at the right time, it can make the difference between profit and loss or success and failure (Royds, 2000, p 2). Information is an asset and just like other important business assets within the organization, it has extreme value to an organization (BS 7799-1, 1999, p 1; Humphreys, Moses & Plate, 1998, p 8). For this reason it has become very important that business information is sufficiently protected. There are many different ways in which information can exist. Information can be printed or written on paper, stored electronically, transmitted electronically or by post, even spoken in conversation or any other way in which knowledge and ideas can be conveyed (URN 99/703, 1999, p. 2; Humphreys, Moses & Plate, 1998, p 8; URN 96/702, 1996, p 3).It is, therefore, critical to protect information, and to ensure that the security of IT (Information Technology) systems within organizations is properly managed. This requirement to protect information is even more important today, since many organizations are internally and externally connected by networks of IT systems (ISO/IEC TR 13335-2, 1996, p 1). Information security is therefore required to assist in the process of controlling and securing of information from accidental or malicious changes, deletions or unauthorized disclosure (Royds, 2000, p 2; URN 96/702, 1996, p 3). By preventing and minimizing the impact of security incidents, information security can ensure business continuity and reduce business damage (Owens, 1998, p 7). Information security in an organization can be regarded as a management opportunity and should become an integral part of the whole management activity of the organization. Obtaining commitment from management is therefore extremely important for effective information security. One way in which management can show their commitment to ensuring information security, is to adopt and enforce a security policy. A security policy ensures that people understand exactly what important role they play in securing information assets.
- Full Text:
- Date Issued: 2001
- Authors: Gerber, Mariana
- Date: 2001
- Subjects: Computer security -- Management , Electronic data processing departments -- Security measures , Businesses -- Data processing -- Security measures , Computers -- Access control
- Language: English
- Type: Thesis , Masters , MTech (Information Technology)
- Identifier: vital:10789 , http://hdl.handle.net/10948/89 , Computer security -- Management , Electronic data processing departments -- Security measures , Businesses -- Data processing -- Security measures , Computers -- Access control
- Description: To perform their business activities effectively, organizations rely heavily on the use of information (ISO/IEC TR 13335-2, 1996, p 1). Owens (1998) reiterates this by claiming that all organizations depend on information for their everyday operation and without it business will fail to operate (Owens, 1998, p 1-2). For an organization it means that if the right information is not available at the right time, it can make the difference between profit and loss or success and failure (Royds, 2000, p 2). Information is an asset and just like other important business assets within the organization, it has extreme value to an organization (BS 7799-1, 1999, p 1; Humphreys, Moses & Plate, 1998, p 8). For this reason it has become very important that business information is sufficiently protected. There are many different ways in which information can exist. Information can be printed or written on paper, stored electronically, transmitted electronically or by post, even spoken in conversation or any other way in which knowledge and ideas can be conveyed (URN 99/703, 1999, p. 2; Humphreys, Moses & Plate, 1998, p 8; URN 96/702, 1996, p 3).It is, therefore, critical to protect information, and to ensure that the security of IT (Information Technology) systems within organizations is properly managed. This requirement to protect information is even more important today, since many organizations are internally and externally connected by networks of IT systems (ISO/IEC TR 13335-2, 1996, p 1). Information security is therefore required to assist in the process of controlling and securing of information from accidental or malicious changes, deletions or unauthorized disclosure (Royds, 2000, p 2; URN 96/702, 1996, p 3). By preventing and minimizing the impact of security incidents, information security can ensure business continuity and reduce business damage (Owens, 1998, p 7). Information security in an organization can be regarded as a management opportunity and should become an integral part of the whole management activity of the organization. Obtaining commitment from management is therefore extremely important for effective information security. One way in which management can show their commitment to ensuring information security, is to adopt and enforce a security policy. A security policy ensures that people understand exactly what important role they play in securing information assets.
- Full Text:
- Date Issued: 2001
The development of the common fraction concept in grade three learners
- Authors: Fraser, Claire Anne
- Date: 2001
- Subjects: Mathematics -- Study and teaching (Elementary) Mathematics Problems, exercises, etc Fractions -- Study and teaching (Elementary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1497 , http://hdl.handle.net/10962/d1003379
- Description: Over a period of nine months in 1999, a longitudinal teaching intervention was undertaken with Grade 3 learners in the Fort Beaufort district, Eastern Cape. Working in the interpretive paradigm, the intervention focussed on: - the development of the common fraction concept, - the relevance of the hierarchy of Murray and Olivier’s Four Levels of Development in common fractions and - whether learners’ informal knowledge could be utilised in developing this concept. Using the Problem-centred approach to teaching mathematics, problems set in reallife contexts were used as vehicles for learning. Learners were required to discuss, reflect and make sense of the mathematics they were doing. Participant observation, completed worksheets and unstructured interviews with learners, formed the primary method of data collection. Learners’ work was analysed and classified according to the method used and manner in which the solution was notated. Results showed that learners were able to achieve a significant degree of success in developing a stable common fraction concept. Learners were afforded opportunities to construct their own ideas and to develop a deeper understanding of the concept. Many methods used were based on their informal knowledge of sharing. Learners made sense of realistic problems using drawings, and invented their own procedures. Apart from Level One, Phase Three, all Murray and Olivier’s Levels of Development could be identified during the research. This study will provide educators with valuable information on how learners solve mathematical problems involving fractions and how informal knowledge can be used as a foundation on which to build.
- Full Text:
- Date Issued: 2001
- Authors: Fraser, Claire Anne
- Date: 2001
- Subjects: Mathematics -- Study and teaching (Elementary) Mathematics Problems, exercises, etc Fractions -- Study and teaching (Elementary)
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1497 , http://hdl.handle.net/10962/d1003379
- Description: Over a period of nine months in 1999, a longitudinal teaching intervention was undertaken with Grade 3 learners in the Fort Beaufort district, Eastern Cape. Working in the interpretive paradigm, the intervention focussed on: - the development of the common fraction concept, - the relevance of the hierarchy of Murray and Olivier’s Four Levels of Development in common fractions and - whether learners’ informal knowledge could be utilised in developing this concept. Using the Problem-centred approach to teaching mathematics, problems set in reallife contexts were used as vehicles for learning. Learners were required to discuss, reflect and make sense of the mathematics they were doing. Participant observation, completed worksheets and unstructured interviews with learners, formed the primary method of data collection. Learners’ work was analysed and classified according to the method used and manner in which the solution was notated. Results showed that learners were able to achieve a significant degree of success in developing a stable common fraction concept. Learners were afforded opportunities to construct their own ideas and to develop a deeper understanding of the concept. Many methods used were based on their informal knowledge of sharing. Learners made sense of realistic problems using drawings, and invented their own procedures. Apart from Level One, Phase Three, all Murray and Olivier’s Levels of Development could be identified during the research. This study will provide educators with valuable information on how learners solve mathematical problems involving fractions and how informal knowledge can be used as a foundation on which to build.
- Full Text:
- Date Issued: 2001
The distinction between a contract of employment and a contract with an independent contractor
- Authors: Slater, Henry John
- Date: 2001
- Subjects: Labor contract -- South Africa , Independent contractors -- South Africa , Contracts -- South Africa -- Cases , Liability (Law) -- South Africa , Labor laws and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:11060 , http://hdl.handle.net/10948/276 , Labor contract -- South Africa , Independent contractors -- South Africa , Contracts -- South Africa -- Cases , Liability (Law) -- South Africa , Labor laws and legislation -- South Africa
- Description: The purpose of this treatise was to determine the distinction between the contract of service (employment) and the contract of work (independent contractor). A comprehensive literary survey was undertaken so as to establish if such a distinction does indeed exist. A logical point of departure was to study the contract of service and determine how the employment relationship is established by it. It is also necessary to establish under what circumstances a contract may be terminated and what the rights and obligations of the parties to the contract were. The contract between the parties will determine remedies to the breach of contract or applicability of labour legislation. It is also necessary to establish the definition of an employee under various statutes so as to understand what remedies exist should rights be infringed upon. Statutes considered include the Constitution of the Republic of South Africa, Labour Relations Act, Basic Conditions of Employment Act, Employment Equity Act, Unemployment Insurance Act, Compensation for Occupational Injuries and Diseases Act, Skills Development Act and the Income Tax Act. The effect of insolvency of the employer on the employee is also discussed. Outsourcing has played a major role in the emergence of the independent contractor. This phenomenon is considered from the point of the employer in terms of the reasons for choosing the option of outsourcing and the associated risks. The employee perspective is also dealt with in terms of why an employee would change his/her employment status. The various tests historically applied to determine the status of a worker is also discussed. These include the control, organisation, dominant impression and economic tests. Currently the dominant impression test is the one that is being applied to determine the employment relationship. Extensive reference was made to case law. United States of America cases are referred to with specific reference to the 20 Factor Test applied by the Internal Revenue Service. South African case law is dealt wit in terms of enforcement of Bargaining Council agreements, commission-earning persons, payment for services rendered, the intention of the parties and the identity of the true employer. The emergence of the dependent contractor is also addressed. This form of worker normally falls outside of the protection of labour legislation and social security. Amendments have been proposed to various statutes to remedy the situation in South Africa. A final aspect that is dealt with is that of vicarious liability. The applicability of this aspect lies in the liability of the employer for damages inflicted by the employee.
- Full Text:
- Date Issued: 2001
- Authors: Slater, Henry John
- Date: 2001
- Subjects: Labor contract -- South Africa , Independent contractors -- South Africa , Contracts -- South Africa -- Cases , Liability (Law) -- South Africa , Labor laws and legislation -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: vital:11060 , http://hdl.handle.net/10948/276 , Labor contract -- South Africa , Independent contractors -- South Africa , Contracts -- South Africa -- Cases , Liability (Law) -- South Africa , Labor laws and legislation -- South Africa
- Description: The purpose of this treatise was to determine the distinction between the contract of service (employment) and the contract of work (independent contractor). A comprehensive literary survey was undertaken so as to establish if such a distinction does indeed exist. A logical point of departure was to study the contract of service and determine how the employment relationship is established by it. It is also necessary to establish under what circumstances a contract may be terminated and what the rights and obligations of the parties to the contract were. The contract between the parties will determine remedies to the breach of contract or applicability of labour legislation. It is also necessary to establish the definition of an employee under various statutes so as to understand what remedies exist should rights be infringed upon. Statutes considered include the Constitution of the Republic of South Africa, Labour Relations Act, Basic Conditions of Employment Act, Employment Equity Act, Unemployment Insurance Act, Compensation for Occupational Injuries and Diseases Act, Skills Development Act and the Income Tax Act. The effect of insolvency of the employer on the employee is also discussed. Outsourcing has played a major role in the emergence of the independent contractor. This phenomenon is considered from the point of the employer in terms of the reasons for choosing the option of outsourcing and the associated risks. The employee perspective is also dealt with in terms of why an employee would change his/her employment status. The various tests historically applied to determine the status of a worker is also discussed. These include the control, organisation, dominant impression and economic tests. Currently the dominant impression test is the one that is being applied to determine the employment relationship. Extensive reference was made to case law. United States of America cases are referred to with specific reference to the 20 Factor Test applied by the Internal Revenue Service. South African case law is dealt wit in terms of enforcement of Bargaining Council agreements, commission-earning persons, payment for services rendered, the intention of the parties and the identity of the true employer. The emergence of the dependent contractor is also addressed. This form of worker normally falls outside of the protection of labour legislation and social security. Amendments have been proposed to various statutes to remedy the situation in South Africa. A final aspect that is dealt with is that of vicarious liability. The applicability of this aspect lies in the liability of the employer for damages inflicted by the employee.
- Full Text:
- Date Issued: 2001
The ecology and physiology of the springhare (Pedetes capensis) in the Eastern Cape Province of South Africa
- Authors: Peinke, Dean Michael
- Date: 2001
- Subjects: Hares -- South Africa -- Eastern Cape Hares -- Breeding -- South Africa -- Eastern Cape Hares -- Ecology -- South Africa -- Eastern Cape Hares -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5670 , http://hdl.handle.net/10962/d1005355
- Description: Springhare are large, bipedal, nocturnal, herbivorous, burrowing rodents that are found in arid and semi-arid parts of southern and eastern Africa. In this thesis I examine the general ecology, biology and physiology of these animals in the Eastern Cape Province of South Africa. An investigation of their distribution and activity in the study site showed that springhare exhibit a preference for flat, open, recently disturbed habitat that is dominated by the grass Cynodon dactylon and the sedge Cyperus esculentus. These two species constitute a major proportion of their diet. The impact of spring hare on chicory and grazing is also discussed. Nightly activity generally peaks soon after dark and decreases in the 2-4 hour period before sunrise. This pattern is, however, modified by moonlight. Springhare typically respond to moonlight by reducing aboveground activity, shifting their activity to dark moonless periods of the night, and by reducing their use of open space. Contrary to earlier reports, springhare utilise several different burrow systems spread over large areas. They regularly change burrow systems and seldom spend more than a few consecutive days in each. Springhare do not appear to defend territories but recently used burrows appear to be avoided by conspecifics. Males and females on average use a similar number of burrows, scattered over similar sized areas. Burrows are shown to provide a stable microclimate of moderate temperature and high humidity throughout the year. Reproduction is continuous and there is no synchronised breeding season. The ability to reproduce throughout the year is attributed primarily to their ability to utilise subterranean food stores. The overall reproductive strategy of springhare (a single young with long gestation and weaning) is unusual for a mammal of this size but may be linked to low levels of adult and juvenile mortality. Physiologically, springhare are reasonably well adapted to life in hot, arid environments. They produce a concentrated urine, exhibit a high tolerance to dehydration, are good osmoregulators capable of maintaining plasma volume, osmolality and ion balance over long periods of water deprivation, and are able to produce dry faeces. They are also good thermoregulators at low ambient temperatures, which are usually encountered at night, but are poor thermoregulators at high ambient temperatures, which they avoid behaviourally.
- Full Text:
- Date Issued: 2001
- Authors: Peinke, Dean Michael
- Date: 2001
- Subjects: Hares -- South Africa -- Eastern Cape Hares -- Breeding -- South Africa -- Eastern Cape Hares -- Ecology -- South Africa -- Eastern Cape Hares -- Physiology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5670 , http://hdl.handle.net/10962/d1005355
- Description: Springhare are large, bipedal, nocturnal, herbivorous, burrowing rodents that are found in arid and semi-arid parts of southern and eastern Africa. In this thesis I examine the general ecology, biology and physiology of these animals in the Eastern Cape Province of South Africa. An investigation of their distribution and activity in the study site showed that springhare exhibit a preference for flat, open, recently disturbed habitat that is dominated by the grass Cynodon dactylon and the sedge Cyperus esculentus. These two species constitute a major proportion of their diet. The impact of spring hare on chicory and grazing is also discussed. Nightly activity generally peaks soon after dark and decreases in the 2-4 hour period before sunrise. This pattern is, however, modified by moonlight. Springhare typically respond to moonlight by reducing aboveground activity, shifting their activity to dark moonless periods of the night, and by reducing their use of open space. Contrary to earlier reports, springhare utilise several different burrow systems spread over large areas. They regularly change burrow systems and seldom spend more than a few consecutive days in each. Springhare do not appear to defend territories but recently used burrows appear to be avoided by conspecifics. Males and females on average use a similar number of burrows, scattered over similar sized areas. Burrows are shown to provide a stable microclimate of moderate temperature and high humidity throughout the year. Reproduction is continuous and there is no synchronised breeding season. The ability to reproduce throughout the year is attributed primarily to their ability to utilise subterranean food stores. The overall reproductive strategy of springhare (a single young with long gestation and weaning) is unusual for a mammal of this size but may be linked to low levels of adult and juvenile mortality. Physiologically, springhare are reasonably well adapted to life in hot, arid environments. They produce a concentrated urine, exhibit a high tolerance to dehydration, are good osmoregulators capable of maintaining plasma volume, osmolality and ion balance over long periods of water deprivation, and are able to produce dry faeces. They are also good thermoregulators at low ambient temperatures, which are usually encountered at night, but are poor thermoregulators at high ambient temperatures, which they avoid behaviourally.
- Full Text:
- Date Issued: 2001
The effect of increased propolis production on the productivity of a honeybee farming system
- Authors: De Jager, Andries Johannes
- Date: 2001
- Subjects: Propolis
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10952 , http://hdl.handle.net/10948/d1001743 , Propolis
- Description: This study was conducted to investigate a method for stimulating increased propolis production in Cape honeybee hives. The study took place near George situated in the Southern Cape region of South Africa. Standard Langstroth hives were used (n = 12) containing honeybee colonies of equal strength from the species Apis mellifera capensis. Propolis production in colonies equipped with commercial propolis traps (n = 6) was compared to propolis production in control colonies (n = 6). The strength of the colonies was determined by calculating the area of worker brood cells and the number of frames containing bees. For a ninemonth period propolis production, honey production, brood area, resin percentage, frames containing bees and income generated were measured on a monthly basis with the removal of the traps. There were no significant difference (p > 0.5) in honey production (24.66 ± 1.19 kg and 26.53 ± 1.31 kg), worker brood area (1967.3 ± 258.61 cm2 and 1085.4 ± 312.99 cm2) and frames containing bees (10 ± 1.13 frames and 9.8 ± 1.2 frames) between the hives with traps and hives without traps. However, propolis production was significantly influenced (p < 0.01) by the propolis traps, with the hives containing traps producing 361.87 ± 8.78g propolis compared to 38.2 ± 2.17g propolis in the control group. Propolis production in both control (28 g) and treatment groups (260.2 g) was significantly influenced by honey flow (p = 0.027). From December to March the production of honey was 22.12 (control) and 24.25 kg (treatment). A positive correlation was also found between frames containing bees and worker brood area (R = 0.73). Hives containing propolis traps were more profitable than the control group when honey and propolis income were pooled (467.17 ± 19.47 Rand vs. 353.8 ± 17.03 Rand). Therefore, the increased propolis production significantly improved profitability of the hive without affecting overall hive productivity.
- Full Text:
- Date Issued: 2001
- Authors: De Jager, Andries Johannes
- Date: 2001
- Subjects: Propolis
- Language: English
- Type: Thesis , Masters , MTech (Agricultural Management)
- Identifier: vital:10952 , http://hdl.handle.net/10948/d1001743 , Propolis
- Description: This study was conducted to investigate a method for stimulating increased propolis production in Cape honeybee hives. The study took place near George situated in the Southern Cape region of South Africa. Standard Langstroth hives were used (n = 12) containing honeybee colonies of equal strength from the species Apis mellifera capensis. Propolis production in colonies equipped with commercial propolis traps (n = 6) was compared to propolis production in control colonies (n = 6). The strength of the colonies was determined by calculating the area of worker brood cells and the number of frames containing bees. For a ninemonth period propolis production, honey production, brood area, resin percentage, frames containing bees and income generated were measured on a monthly basis with the removal of the traps. There were no significant difference (p > 0.5) in honey production (24.66 ± 1.19 kg and 26.53 ± 1.31 kg), worker brood area (1967.3 ± 258.61 cm2 and 1085.4 ± 312.99 cm2) and frames containing bees (10 ± 1.13 frames and 9.8 ± 1.2 frames) between the hives with traps and hives without traps. However, propolis production was significantly influenced (p < 0.01) by the propolis traps, with the hives containing traps producing 361.87 ± 8.78g propolis compared to 38.2 ± 2.17g propolis in the control group. Propolis production in both control (28 g) and treatment groups (260.2 g) was significantly influenced by honey flow (p = 0.027). From December to March the production of honey was 22.12 (control) and 24.25 kg (treatment). A positive correlation was also found between frames containing bees and worker brood area (R = 0.73). Hives containing propolis traps were more profitable than the control group when honey and propolis income were pooled (467.17 ± 19.47 Rand vs. 353.8 ± 17.03 Rand). Therefore, the increased propolis production significantly improved profitability of the hive without affecting overall hive productivity.
- Full Text:
- Date Issued: 2001
The effect of photoperiod on some aspects of reproduction in a Southern African rodent : the pouched mouse (Saccostomus Campestris)
- Authors: Gray, Janine
- Date: 2001
- Subjects: Mice -- Reproduction Antechinus -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5676 , http://hdl.handle.net/10962/d1005361
- Description: The pouched mouse, Saccostomus campestris is widely distributed south of the Sahara, inhabiting both subtropical and tropical latitudes and a number of different biotic zones, where it breeds seasonally. In North temperate latitudes, reproduction in small mammals is controlled by photoperiod however this cue becomes less influential as latitude decreases towards the equator. The aim of the present study is to establish the role of photoperiod in the environmental control of reproduction in a seasonally breeding small mammal at low latitudes in a highly unpredictable environment. Spermatogenesis of domesticated and Fl-generation pouched mice was not inhibited by short daylength while decreasing daylength significantly affected the oestrous cycle of adult domesticated female pouched mice. Photoperiod had little effect on the oestrous cycle of F I-generation females while a possible inherent circannual endogenous rhythm controlled inhibition of reproduction in these females. Body mass of male and female juvenile pouched mice was consistently lower in short daylength and in juvenile female pouched mice the onset of fertility may be weight-dependent. The attainment of sexual maturity of domesticated and FIlF2-generation females was retarded but not halted in short daylength and females in long daylength reached puberty 7.8 - 10.2 days earlier. Short daylength also lengthened the interval between vaginal perforation and first oestrus. Puberty in juvenile females was age-dependent as both domesticated and FIlF2-generation males attained puberty at 50 days of age, although fewer males were fertile in long daylength than short daylength. Although litter size of pouched mice was smaller in short daylength for both domesticated and wildcaught females this was not due to a reduction in the ovulation rate. Domesticated females had significantly larger litters than wild-caught females. Male and female pouched mice have evolved different reproductive strategies as males become sexually mature at the same age irrespective of photoperiod and remain fertile throughout the year. In contrast, females tend to be more complex as juveniles delay reproductive maturity and adults become nonreproductive in short daylength. However, in the presence of a fertile male and if environmental conditions are favourable, in short daylength, females can become reproductively active within approximately 3 days. Thus, although the pouched mouse has adopted a purely opportunistic reproductive strategy, vestiges of photoresponsiveness are still present in the female. The seasonality exhibited in the wild is therefore due to the female. Pouched mice live in a highly unpredictable environment so the sole use of photoperiod to regulate reproduction would be disadvantageous.
- Full Text:
- Date Issued: 2001
- Authors: Gray, Janine
- Date: 2001
- Subjects: Mice -- Reproduction Antechinus -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5676 , http://hdl.handle.net/10962/d1005361
- Description: The pouched mouse, Saccostomus campestris is widely distributed south of the Sahara, inhabiting both subtropical and tropical latitudes and a number of different biotic zones, where it breeds seasonally. In North temperate latitudes, reproduction in small mammals is controlled by photoperiod however this cue becomes less influential as latitude decreases towards the equator. The aim of the present study is to establish the role of photoperiod in the environmental control of reproduction in a seasonally breeding small mammal at low latitudes in a highly unpredictable environment. Spermatogenesis of domesticated and Fl-generation pouched mice was not inhibited by short daylength while decreasing daylength significantly affected the oestrous cycle of adult domesticated female pouched mice. Photoperiod had little effect on the oestrous cycle of F I-generation females while a possible inherent circannual endogenous rhythm controlled inhibition of reproduction in these females. Body mass of male and female juvenile pouched mice was consistently lower in short daylength and in juvenile female pouched mice the onset of fertility may be weight-dependent. The attainment of sexual maturity of domesticated and FIlF2-generation females was retarded but not halted in short daylength and females in long daylength reached puberty 7.8 - 10.2 days earlier. Short daylength also lengthened the interval between vaginal perforation and first oestrus. Puberty in juvenile females was age-dependent as both domesticated and FIlF2-generation males attained puberty at 50 days of age, although fewer males were fertile in long daylength than short daylength. Although litter size of pouched mice was smaller in short daylength for both domesticated and wildcaught females this was not due to a reduction in the ovulation rate. Domesticated females had significantly larger litters than wild-caught females. Male and female pouched mice have evolved different reproductive strategies as males become sexually mature at the same age irrespective of photoperiod and remain fertile throughout the year. In contrast, females tend to be more complex as juveniles delay reproductive maturity and adults become nonreproductive in short daylength. However, in the presence of a fertile male and if environmental conditions are favourable, in short daylength, females can become reproductively active within approximately 3 days. Thus, although the pouched mouse has adopted a purely opportunistic reproductive strategy, vestiges of photoresponsiveness are still present in the female. The seasonality exhibited in the wild is therefore due to the female. Pouched mice live in a highly unpredictable environment so the sole use of photoperiod to regulate reproduction would be disadvantageous.
- Full Text:
- Date Issued: 2001
The effect of variations in pH and temperature on stability of melatonin in aqueous solution
- Daya, Santylal, Walker, Roderick B, Glass, Beverley D, Anoopkumar-Dukie, Shailendra
- Authors: Daya, Santylal , Walker, Roderick B , Glass, Beverley D , Anoopkumar-Dukie, Shailendra
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184314 , vital:44207 , xlink:href="https://doi.org/10.1034/j.1600-079x.2001.310209.x"
- Description: Melatonin (N-acetyl-5-methoxytryptamine) has a diverse range of functions, including the control of neuroendocrine events. A number of studies have shown that melatonin may be of potential benefit for the treatment of insomnia, as well as neurodegenerative disorders. At present, there are numerous dosage forms of melatonin, with the oral route of administration being most popular. Presently, there is little information on the stability of melatonin over a pH range. With the changes in pH in the gastro-intestinal tract, as well as in different experimental conditions, information on the stability of melatonin would be important. We used a high-performance liquid chromatography method to determine the stability of melatonin solutions over a pH range (1.2–12) at room temperature and at 37°C over a period of 21 days. The results show that no melatonin degradation occurred in the first 2 days. From days 3 to 21, there was a gradual decline in melatonin at all pHs, with the decline not exceeding 30%. No decline in melatonin levels occurred in the first 2 days at 37°C. From days 3 to 21, melatonin levels declined gradually, with the decline not exceeding 29%.
- Full Text:
- Date Issued: 2001
- Authors: Daya, Santylal , Walker, Roderick B , Glass, Beverley D , Anoopkumar-Dukie, Shailendra
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/184314 , vital:44207 , xlink:href="https://doi.org/10.1034/j.1600-079x.2001.310209.x"
- Description: Melatonin (N-acetyl-5-methoxytryptamine) has a diverse range of functions, including the control of neuroendocrine events. A number of studies have shown that melatonin may be of potential benefit for the treatment of insomnia, as well as neurodegenerative disorders. At present, there are numerous dosage forms of melatonin, with the oral route of administration being most popular. Presently, there is little information on the stability of melatonin over a pH range. With the changes in pH in the gastro-intestinal tract, as well as in different experimental conditions, information on the stability of melatonin would be important. We used a high-performance liquid chromatography method to determine the stability of melatonin solutions over a pH range (1.2–12) at room temperature and at 37°C over a period of 21 days. The results show that no melatonin degradation occurred in the first 2 days. From days 3 to 21, there was a gradual decline in melatonin at all pHs, with the decline not exceeding 30%. No decline in melatonin levels occurred in the first 2 days at 37°C. From days 3 to 21, melatonin levels declined gradually, with the decline not exceeding 29%.
- Full Text:
- Date Issued: 2001
The effects of assembly line-side supply on individuals employed in satellite operations within automotive manufacturers
- Authors: Bocchi, Carlo
- Date: 2001
- Subjects: Faurecia East London (Firm) , Job satisfaction , Employee motivation , Automobile industry and trade -- Management , Automobile industry and trade -- Case studies
- Language: English
- Type: Thesis , Masters , MTech (Business Administration)
- Identifier: vital:10849 , http://hdl.handle.net/10948/56 , Faurecia East London (Firm) , Job satisfaction , Employee motivation , Automobile industry and trade -- Management , Automobile industry and trade -- Case studies
- Description: The adoption of just-in-time in satellite operations within an automotive manufacturer, is rapidly becoming a trend within motor industry clusters. This type of organisation within an organisation adopts a lean structure to operate effectively and efficiently. The objective of this paper is to unveil factors which influence this type of workplace, particularly focusing on which factors which are relevant to Faurecia East London Plant. The literature study was used to illustrate the various theories relevant to manufacturing techniques, employee motivational and job satisfaction theories. The empirical study tested factors illustrated in the literature study. The empirical study was also to develop a specific model suitable for satellite organisations. The model presented together with the literature and empirical study was used to formulate findings and solve the main and sub-problems.
- Full Text:
- Date Issued: 2001
- Authors: Bocchi, Carlo
- Date: 2001
- Subjects: Faurecia East London (Firm) , Job satisfaction , Employee motivation , Automobile industry and trade -- Management , Automobile industry and trade -- Case studies
- Language: English
- Type: Thesis , Masters , MTech (Business Administration)
- Identifier: vital:10849 , http://hdl.handle.net/10948/56 , Faurecia East London (Firm) , Job satisfaction , Employee motivation , Automobile industry and trade -- Management , Automobile industry and trade -- Case studies
- Description: The adoption of just-in-time in satellite operations within an automotive manufacturer, is rapidly becoming a trend within motor industry clusters. This type of organisation within an organisation adopts a lean structure to operate effectively and efficiently. The objective of this paper is to unveil factors which influence this type of workplace, particularly focusing on which factors which are relevant to Faurecia East London Plant. The literature study was used to illustrate the various theories relevant to manufacturing techniques, employee motivational and job satisfaction theories. The empirical study tested factors illustrated in the literature study. The empirical study was also to develop a specific model suitable for satellite organisations. The model presented together with the literature and empirical study was used to formulate findings and solve the main and sub-problems.
- Full Text:
- Date Issued: 2001
The effects of level and quality of education on a South African sample of English and African first language speakers, for WAIS-III digit symbol-incidental learning
- Donnelly, Martin Joseph Rhodes
- Authors: Donnelly, Martin Joseph Rhodes
- Date: 2001
- Subjects: Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2965 , http://hdl.handle.net/10962/d1002474 , Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Description: This study examined the effects of level and quality of education on WAIS-III Digit Symbol-Incidental Learning performance. The Pairing and Free Recall measures were administered to a South African sample (N = 68, age range 19-30), which was stratified for English and African language, level of education attained (Grade 12s and Graduates) and quality of education (advantaged and disadvantaged schooling). Results yielded no significant main or interaction effects between acculturation factors of level and quality of education. Normative guidelines of 13 or more pairs and 8 or more free recall symbols, appropriate to a non-clinical sample in a multicultural setting, are provided. Digit Symbol-Incidental Learning proved to be a culture-fair test, which contributes to its clinical utility as a sensitive memory screening tool.
- Full Text:
- Date Issued: 2001
- Authors: Donnelly, Martin Joseph Rhodes
- Date: 2001
- Subjects: Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2965 , http://hdl.handle.net/10962/d1002474 , Wechsler Adult Intelligence Scale , Intelligence tests -- South Africa , Wechsler Adult Intelligence Scale -- South Africa
- Description: This study examined the effects of level and quality of education on WAIS-III Digit Symbol-Incidental Learning performance. The Pairing and Free Recall measures were administered to a South African sample (N = 68, age range 19-30), which was stratified for English and African language, level of education attained (Grade 12s and Graduates) and quality of education (advantaged and disadvantaged schooling). Results yielded no significant main or interaction effects between acculturation factors of level and quality of education. Normative guidelines of 13 or more pairs and 8 or more free recall symbols, appropriate to a non-clinical sample in a multicultural setting, are provided. Digit Symbol-Incidental Learning proved to be a culture-fair test, which contributes to its clinical utility as a sensitive memory screening tool.
- Full Text:
- Date Issued: 2001
The effects of melatonin on the testis, epididymis and sperm physiology of the Wistar rat
- Authors: Gwayi, Noluzuko
- Date: 2001
- Subjects: Rats as laboratory animals , Rats -- physiology , Spermatozoa , Melatonin , Testis , Epididymis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5681 , http://hdl.handle.net/10962/d1005366 , Rats as laboratory animals , Rats -- physiology , Spermatozoa , Melatonin , Testis , Epididymis
- Description: Melatonin is a product of the pineal gland and is postulated to play an antigonadotropic role in the reproductive system of mammals. The reproductive system of non-seasonally breeding mammals is believed to be not as responsive to melatonin treatment as that of seasonally breeding mammals. Recently, there has been increasing support from in vivo and in vitro studies, for the hypothesis that melatonin has negative effects on sperm physiology, especially on sperm motility. High and/or low seminal concentrations of melatonin have been associated with abnormalities in human sperm motility and concentration. In this study, I examined the effects of melatonin on the testis, epididymis and sperm physiology, using in vivo and in vitro experiments, in a non-seasonally breeding mammal. Treatment, in vivo, with exogenous melatonin for six weeks did not inhibit testosterone production or spermatogenesis, nor did it affect the mass of the testes and epididymides at dissection, the concentration the morphology of speimatozoa. However, melatonin in vivo had a small, but significant negative effect on sperm motility and sperm motility index. In vitro incubation of spermatozoa Fith melatonin reduced the percentage (%) of forward progressive movement (fpm), increased the % reduction in fpm, reduced the vigor or quality of sperm motility, reduced the sperm motility index, and delayed and/or prolonged the transition of one pattern of sperm motility to the subsequent patterns. Melatonin increased the pH of the culture medium, and the increased pH, and the ethanol utilized as a solvent for melatonin, both negatively affected all the sperm motility parameters that were assessed in my study. The effects of ethanol increased with time, and the effects of pH increased with both time and increasing pH. Melatonin in vitro did not inhibit capacitation and the acrosome reaction, but it delayed the onset and the progression of capacitation and the acrosome reaction. These results suggest that while melatonin did not inhibit spermatogenesis in the Wistar rat, it may influence sperm motility. Therefore, the presence of high concentrations of melatonin in the reproductive fluids may inhibit sperm motility. With further detailed research, melatonin may have a potential use as a contraceptive drug.
- Full Text:
- Date Issued: 2001
- Authors: Gwayi, Noluzuko
- Date: 2001
- Subjects: Rats as laboratory animals , Rats -- physiology , Spermatozoa , Melatonin , Testis , Epididymis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5681 , http://hdl.handle.net/10962/d1005366 , Rats as laboratory animals , Rats -- physiology , Spermatozoa , Melatonin , Testis , Epididymis
- Description: Melatonin is a product of the pineal gland and is postulated to play an antigonadotropic role in the reproductive system of mammals. The reproductive system of non-seasonally breeding mammals is believed to be not as responsive to melatonin treatment as that of seasonally breeding mammals. Recently, there has been increasing support from in vivo and in vitro studies, for the hypothesis that melatonin has negative effects on sperm physiology, especially on sperm motility. High and/or low seminal concentrations of melatonin have been associated with abnormalities in human sperm motility and concentration. In this study, I examined the effects of melatonin on the testis, epididymis and sperm physiology, using in vivo and in vitro experiments, in a non-seasonally breeding mammal. Treatment, in vivo, with exogenous melatonin for six weeks did not inhibit testosterone production or spermatogenesis, nor did it affect the mass of the testes and epididymides at dissection, the concentration the morphology of speimatozoa. However, melatonin in vivo had a small, but significant negative effect on sperm motility and sperm motility index. In vitro incubation of spermatozoa Fith melatonin reduced the percentage (%) of forward progressive movement (fpm), increased the % reduction in fpm, reduced the vigor or quality of sperm motility, reduced the sperm motility index, and delayed and/or prolonged the transition of one pattern of sperm motility to the subsequent patterns. Melatonin increased the pH of the culture medium, and the increased pH, and the ethanol utilized as a solvent for melatonin, both negatively affected all the sperm motility parameters that were assessed in my study. The effects of ethanol increased with time, and the effects of pH increased with both time and increasing pH. Melatonin in vitro did not inhibit capacitation and the acrosome reaction, but it delayed the onset and the progression of capacitation and the acrosome reaction. These results suggest that while melatonin did not inhibit spermatogenesis in the Wistar rat, it may influence sperm motility. Therefore, the presence of high concentrations of melatonin in the reproductive fluids may inhibit sperm motility. With further detailed research, melatonin may have a potential use as a contraceptive drug.
- Full Text:
- Date Issued: 2001
The evaluation of autoxidation procedures for the selective oxidation of aliphatic alcohols
- Authors: Bacela, Siyabulela Mawande
- Date: 2001
- Subjects: Oxidation , Aliphatic compounds
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10950 , http://hdl.handle.net/10948/59 , Oxidation , Aliphatic compounds
- Description: The homogeneously catalyzed oxidation of 1-propanol by dioxygen in glacial acetic acid using cobalt(II)acetate and sodium bromide as the catalyst system has been investigated with the view of determining the significance of various experimental variables during the oxidation. The results of this investigation show unequivocally that a number of reaction variables have a direct influence upon catalytic activity and hence the reaction products. It is quite evident that the major product of this autoxidation reaction is propionic acid with the respective esters as side-products. This is an indication that the autoxidation mechanism occurs via a two-stage pathway, namely, the oxidation of 1-propanol to propionaldehyde as the primary product and, subsequently, the further oxidation of the propionaldehyde to propionic acid as the major product. Thus the esterification process of the propionic acid with the substrate 1-propanol could be termed as a side-reaction because its not facilitated by the catalyst system and it consumes the formed product. The catalyst activity has been demonstrated to depend on a number of factors, including the bromide concentration, the cobalt(II)acetate concentration, the water concentration, reaction temperature, and the presence of metal acetates as co-catalysts. There is an observed decrease in catalytic activity at high bromide concentration, which may be explained in terms of cobalt bromide complexes that form at these high concentrations. Subsequently, the same trend of catalyst activity reduction at high cobalt(II)acetate concentration may be ascribed to the “inactive” metal complexes that are susceptible to form at high metal ion concentrations. The catalytic activity increases with increase in total concentration and rapidly decreases at very high concentrations. This can be explained in terms of the observations made during the investigation of the effect of cobalt(II)acetate and bromide concentrations. The high increase in catalytic activity with increasing temperature is ascribed to the Arrhenius law, which relates the rate constant for a particular reaction to temperature. However, there is an observed loss of catalyst selectivity at high temperatures which maybe due to two possible factors. The first is simply related to an increased loss of volatile material from the reactor in the oxygen gas stream as the temperature is increased. The second relates to the increasing activity of the catalyst system for the selective decarboxylation of the carboxylic acid product. The addition of water to the reaction system rapidly reduces the catalyst activity. This detrimental effect is an indication that there is an effective competition by water with bromide for coordination sites on cobalt(II), thereby preventing the formation of the active catalyst species. The introduction of metal acetates as co-catalyst reduces the catalyst activity quite dramatically. This inhibition effect is suggested to relate to the redox potential of the respective metal ions. The results of statistical analysis of the experimentally derived response surface during the oxidation of 1-propanol, show no significant lack of fit, and the residuals obtained by applying the response surface to the design settings show that the data is normally distributed. The response surface is therefore reliable, but keeping in mind that the central composite design used is not rotatable so that its predictive power, especially outside the experimental domain investigated, is quite limited. However, several interesting observations were still possible The oxidative dehydrogenation of ethanol over supported noble-metal catalysts has been investigated with the view of identifying the most active supported noble-metal and also to compare this oxidation procedure with the autoxidation procedure. Secondly, the effect of an acidic resin as a co-catalyst was also investigated during the said oxidation. On the basis of results presented in this study during oxidative dehydrogenation of ethanol, catalysts no.2 (10% Pd/C), 8 (2% Pd/Al – Pb-promoted) and 9 (2% Pt/8% Pd/C) appear to be the most active in terms of relative rates, while catalysts 6 (10% Pd/C- Pbpromoted), 7 (5% Pd/C-shell reduced-Pb -promoted) and 10 (5% Pt 5% Pd on C) are more active based on the comparison of average rates. Two other observations are of interest. Firstly, the promotion of the Pd catalysts with lead appears to improve catalyst activity to some extent as shown by the comparisons between catalysts 1 and 5, 4 and 8, 2 and 6 and 3 and 7. Secondly, the introduction of Pt up to equal amounts with palladium seems to produce the most active catalysts. On its own, platinum appears to be a better catalyst than Pd when supported on activated carbon (catalysts 1 and 12). In comparison with the homogeneous, cobalt-bromide catalyzed oxidation of 1- propanol in the liquid-phase, oxidations over noble-metal catalysts in the liquid-phase appear to be significantly less active. The presence of the resin promoted the formation of ethyl acetate to some extent, the improvements are not as dramatic as expected.
- Full Text:
- Date Issued: 2001
- Authors: Bacela, Siyabulela Mawande
- Date: 2001
- Subjects: Oxidation , Aliphatic compounds
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10950 , http://hdl.handle.net/10948/59 , Oxidation , Aliphatic compounds
- Description: The homogeneously catalyzed oxidation of 1-propanol by dioxygen in glacial acetic acid using cobalt(II)acetate and sodium bromide as the catalyst system has been investigated with the view of determining the significance of various experimental variables during the oxidation. The results of this investigation show unequivocally that a number of reaction variables have a direct influence upon catalytic activity and hence the reaction products. It is quite evident that the major product of this autoxidation reaction is propionic acid with the respective esters as side-products. This is an indication that the autoxidation mechanism occurs via a two-stage pathway, namely, the oxidation of 1-propanol to propionaldehyde as the primary product and, subsequently, the further oxidation of the propionaldehyde to propionic acid as the major product. Thus the esterification process of the propionic acid with the substrate 1-propanol could be termed as a side-reaction because its not facilitated by the catalyst system and it consumes the formed product. The catalyst activity has been demonstrated to depend on a number of factors, including the bromide concentration, the cobalt(II)acetate concentration, the water concentration, reaction temperature, and the presence of metal acetates as co-catalysts. There is an observed decrease in catalytic activity at high bromide concentration, which may be explained in terms of cobalt bromide complexes that form at these high concentrations. Subsequently, the same trend of catalyst activity reduction at high cobalt(II)acetate concentration may be ascribed to the “inactive” metal complexes that are susceptible to form at high metal ion concentrations. The catalytic activity increases with increase in total concentration and rapidly decreases at very high concentrations. This can be explained in terms of the observations made during the investigation of the effect of cobalt(II)acetate and bromide concentrations. The high increase in catalytic activity with increasing temperature is ascribed to the Arrhenius law, which relates the rate constant for a particular reaction to temperature. However, there is an observed loss of catalyst selectivity at high temperatures which maybe due to two possible factors. The first is simply related to an increased loss of volatile material from the reactor in the oxygen gas stream as the temperature is increased. The second relates to the increasing activity of the catalyst system for the selective decarboxylation of the carboxylic acid product. The addition of water to the reaction system rapidly reduces the catalyst activity. This detrimental effect is an indication that there is an effective competition by water with bromide for coordination sites on cobalt(II), thereby preventing the formation of the active catalyst species. The introduction of metal acetates as co-catalyst reduces the catalyst activity quite dramatically. This inhibition effect is suggested to relate to the redox potential of the respective metal ions. The results of statistical analysis of the experimentally derived response surface during the oxidation of 1-propanol, show no significant lack of fit, and the residuals obtained by applying the response surface to the design settings show that the data is normally distributed. The response surface is therefore reliable, but keeping in mind that the central composite design used is not rotatable so that its predictive power, especially outside the experimental domain investigated, is quite limited. However, several interesting observations were still possible The oxidative dehydrogenation of ethanol over supported noble-metal catalysts has been investigated with the view of identifying the most active supported noble-metal and also to compare this oxidation procedure with the autoxidation procedure. Secondly, the effect of an acidic resin as a co-catalyst was also investigated during the said oxidation. On the basis of results presented in this study during oxidative dehydrogenation of ethanol, catalysts no.2 (10% Pd/C), 8 (2% Pd/Al – Pb-promoted) and 9 (2% Pt/8% Pd/C) appear to be the most active in terms of relative rates, while catalysts 6 (10% Pd/C- Pbpromoted), 7 (5% Pd/C-shell reduced-Pb -promoted) and 10 (5% Pt 5% Pd on C) are more active based on the comparison of average rates. Two other observations are of interest. Firstly, the promotion of the Pd catalysts with lead appears to improve catalyst activity to some extent as shown by the comparisons between catalysts 1 and 5, 4 and 8, 2 and 6 and 3 and 7. Secondly, the introduction of Pt up to equal amounts with palladium seems to produce the most active catalysts. On its own, platinum appears to be a better catalyst than Pd when supported on activated carbon (catalysts 1 and 12). In comparison with the homogeneous, cobalt-bromide catalyzed oxidation of 1- propanol in the liquid-phase, oxidations over noble-metal catalysts in the liquid-phase appear to be significantly less active. The presence of the resin promoted the formation of ethyl acetate to some extent, the improvements are not as dramatic as expected.
- Full Text:
- Date Issued: 2001
The evaluation of pharmaceutical pictograms in a low-literate South African population
- Dowse, Roslind, Ehlers, Martina S
- Authors: Dowse, Roslind , Ehlers, Martina S
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6362 , http://hdl.handle.net/10962/d1006058
- Description: An inability to read and understand written medication instructions may be a major contributory factor to non-compliance in certain patient populations, particularly in countries with a high illiteracy rate such as South Africa. Twenty three pictograms from the USP-DI and a corresponding set of 23 locally developed, culturally sensitive pictograms for conveying medication instructions were evaluated in 46 Xhosa respondents who had attended school for a maximum of 7 years. Respondents were tested for their interpretation of all 46 pictograms at the first interview and again 3 weeks later. The correct meaning of each pictogram was explained at the end of the first interview. Preference for either the Local or USP pictograms was determined. At the follow-up interview, 20 of the Local pictograms complied with the ANSI criterion of ≥85% comprehension, compared with 11 of the USP pictograms. Respondents indicated an overwhelming preference for the Local pictograms.
- Full Text:
- Date Issued: 2001
- Authors: Dowse, Roslind , Ehlers, Martina S
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:6362 , http://hdl.handle.net/10962/d1006058
- Description: An inability to read and understand written medication instructions may be a major contributory factor to non-compliance in certain patient populations, particularly in countries with a high illiteracy rate such as South Africa. Twenty three pictograms from the USP-DI and a corresponding set of 23 locally developed, culturally sensitive pictograms for conveying medication instructions were evaluated in 46 Xhosa respondents who had attended school for a maximum of 7 years. Respondents were tested for their interpretation of all 46 pictograms at the first interview and again 3 weeks later. The correct meaning of each pictogram was explained at the end of the first interview. Preference for either the Local or USP pictograms was determined. At the follow-up interview, 20 of the Local pictograms complied with the ANSI criterion of ≥85% comprehension, compared with 11 of the USP pictograms. Respondents indicated an overwhelming preference for the Local pictograms.
- Full Text:
- Date Issued: 2001