Interest rate behaviour in a more transparent South African monetary policy environment
- Authors: Ballim, Goolam Hoosen
- Date: 2005
- Subjects: South African Reserve Bank , Monetary policy -- South Africa , Banks and banking -- South Africa , Interest rates -- South Africa , South Africa -- Economic policy , South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1034 , http://hdl.handle.net/10962/d1004462 , South African Reserve Bank , Monetary policy -- South Africa , Banks and banking -- South Africa , Interest rates -- South Africa , South Africa -- Economic policy , South Africa -- Economic conditions
- Description: South Africa introduced inflation targeting as a monetary policy framework in 2000. This marked a sizable shift in monetary policy management from the previous "eclectic" approach and the explicit focus on M3 money supply before that. The study appraises the effectiveness of monetary policy under this new dispensation. However, the analysis does not centre on inflation outcomes, which can be a measure of effectiveness because they are the overriding objective of the South African Reserve Bank in effect, it is possible to have a target-friendly inflation rate for a length of time despite monetary policy that is ambiguous and encourages unpredictability in market interest rates. However, persistent policy opaqueness can, over time, damage a favourable inflation scenario. For instance, if the public is unsure about the Reserve Bank's desired inflation target, price setting in the wage and goods markets may eventually produce an inflation outcome that is higher than the Bank may have intended. Rather, this study adjudicates the effectiveness of monetary policy within the context of policy transparency, which is an intrinsic part of the inflation targeting framework. The study looks at the extent to which monetary policy transparency has enhanced both the anticipatory nature of the market's response to policy actions and the force that policy has on all interest rates in the financial system, particularly long-term rates. These concepts are important because through the transmission mechanism of monetary policy, the more deft market participants are at anticipating future Reserve Bank policy the greater the Bank's ability to steady the economy before the actual policy event. With the aid of regression models to estimate the response of market rates to policy changes, the results show that there is significant movement in market rates in anticipation of policy action, rather than on the day of the event or the day after. Indeed, the estimates for market rates movement on the day of and even the day after the policy action are generally minute. For instance, the R157 long-term government bond yield changes by a significant 41 basis points in response to a one percentage point change in the Reserve Bank's benchmark repo rate in the period between the last policy action and the day preceding the current action. In contrast, the R157 bond yield changes by an insignificant 2 basis points on the day of the current repo rate change and about 1 basis point the day after the current change. The results point to a robust relationship between policy transparency and the market's ability to foresee rate action. If this were not the case, it is likely that there would be persistent market surprise and, hence, noticeable movement in interest rates on the day of the rate action and perhaps even the day after. Another important observation is that monetary policy impacts significantly on both short- and long-term market rates. Again, certifying the robustness of monetary policy under the inflation targeting regime
- Full Text:
- Date Issued: 2005
- Authors: Ballim, Goolam Hoosen
- Date: 2005
- Subjects: South African Reserve Bank , Monetary policy -- South Africa , Banks and banking -- South Africa , Interest rates -- South Africa , South Africa -- Economic policy , South Africa -- Economic conditions
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1034 , http://hdl.handle.net/10962/d1004462 , South African Reserve Bank , Monetary policy -- South Africa , Banks and banking -- South Africa , Interest rates -- South Africa , South Africa -- Economic policy , South Africa -- Economic conditions
- Description: South Africa introduced inflation targeting as a monetary policy framework in 2000. This marked a sizable shift in monetary policy management from the previous "eclectic" approach and the explicit focus on M3 money supply before that. The study appraises the effectiveness of monetary policy under this new dispensation. However, the analysis does not centre on inflation outcomes, which can be a measure of effectiveness because they are the overriding objective of the South African Reserve Bank in effect, it is possible to have a target-friendly inflation rate for a length of time despite monetary policy that is ambiguous and encourages unpredictability in market interest rates. However, persistent policy opaqueness can, over time, damage a favourable inflation scenario. For instance, if the public is unsure about the Reserve Bank's desired inflation target, price setting in the wage and goods markets may eventually produce an inflation outcome that is higher than the Bank may have intended. Rather, this study adjudicates the effectiveness of monetary policy within the context of policy transparency, which is an intrinsic part of the inflation targeting framework. The study looks at the extent to which monetary policy transparency has enhanced both the anticipatory nature of the market's response to policy actions and the force that policy has on all interest rates in the financial system, particularly long-term rates. These concepts are important because through the transmission mechanism of monetary policy, the more deft market participants are at anticipating future Reserve Bank policy the greater the Bank's ability to steady the economy before the actual policy event. With the aid of regression models to estimate the response of market rates to policy changes, the results show that there is significant movement in market rates in anticipation of policy action, rather than on the day of the event or the day after. Indeed, the estimates for market rates movement on the day of and even the day after the policy action are generally minute. For instance, the R157 long-term government bond yield changes by a significant 41 basis points in response to a one percentage point change in the Reserve Bank's benchmark repo rate in the period between the last policy action and the day preceding the current action. In contrast, the R157 bond yield changes by an insignificant 2 basis points on the day of the current repo rate change and about 1 basis point the day after the current change. The results point to a robust relationship between policy transparency and the market's ability to foresee rate action. If this were not the case, it is likely that there would be persistent market surprise and, hence, noticeable movement in interest rates on the day of the rate action and perhaps even the day after. Another important observation is that monetary policy impacts significantly on both short- and long-term market rates. Again, certifying the robustness of monetary policy under the inflation targeting regime
- Full Text:
- Date Issued: 2005
International relations and change: a Kuhnian interpretation
- Authors: Schoeman, Jacobus
- Date: 2005
- Subjects: Kuhn, Thomas S Kuhn, Thomas S -- Criticism and interpretation International relations International relations -- Philosophy Knowledge, Theory of
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2830 , http://hdl.handle.net/10962/d1003040
- Description: Using notions of change developed by Thomas Kuhn, the thesis argues that the rise of globalisation and the end of the Cold War presented the Westphalian or state-centric paradigm of international relations with a Kuhnian paradigm “crisis”. As a result, both the theory and the practice of international relations are in the midst of (what Kuhn calls) a “paradigm shift”. Emerging from this shift is (what is described in this work as) “Access World” and “Denial World” – a particular global configuration of the practice of international relations. Kuhn’s idea of “incommensurability” seems to typify the relationship between the two components of this bifurcated configuration of the international. Both intellectual risk-taking and political courage are required if the ontological struggle raging between “Access World” and “Denial World” is to be settled. This will pave the way for a new paradigm to emerge. Kuhn provides us with the insight that, to achieve this ontological breakthrough, a fundamental change in our vision of the discipline of International Relations, but also of the world of everyday international relations, is required. This entails recasting the study of International Relations as an emancipatory project and by recognising the centrality of human beings in the practice of international relations. Only if this is done, will we be able to arrive at a cosmopolitan political bargain that is appropriate for the 21st century.
- Full Text:
- Date Issued: 2005
- Authors: Schoeman, Jacobus
- Date: 2005
- Subjects: Kuhn, Thomas S Kuhn, Thomas S -- Criticism and interpretation International relations International relations -- Philosophy Knowledge, Theory of
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2830 , http://hdl.handle.net/10962/d1003040
- Description: Using notions of change developed by Thomas Kuhn, the thesis argues that the rise of globalisation and the end of the Cold War presented the Westphalian or state-centric paradigm of international relations with a Kuhnian paradigm “crisis”. As a result, both the theory and the practice of international relations are in the midst of (what Kuhn calls) a “paradigm shift”. Emerging from this shift is (what is described in this work as) “Access World” and “Denial World” – a particular global configuration of the practice of international relations. Kuhn’s idea of “incommensurability” seems to typify the relationship between the two components of this bifurcated configuration of the international. Both intellectual risk-taking and political courage are required if the ontological struggle raging between “Access World” and “Denial World” is to be settled. This will pave the way for a new paradigm to emerge. Kuhn provides us with the insight that, to achieve this ontological breakthrough, a fundamental change in our vision of the discipline of International Relations, but also of the world of everyday international relations, is required. This entails recasting the study of International Relations as an emancipatory project and by recognising the centrality of human beings in the practice of international relations. Only if this is done, will we be able to arrive at a cosmopolitan political bargain that is appropriate for the 21st century.
- Full Text:
- Date Issued: 2005
Intraspecific comparison of Phanerochaete chrysosporium strains peroxidase production, pollutant degradation and mycelial differentiation
- Authors: Fraser, Sheena Janet
- Date: 2005
- Subjects: Phanerochaete Pollutants -- Biodegradation Lignin -- Biodegradation Bioremediation Peroxidase Fungi -- Differentiation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3964 , http://hdl.handle.net/10962/d1004023
- Description: The wood-degrading basidiomycete, Phanerochaete chrysosporium, has been studied as a model organism in elucidating the mechanisms and pathways enabling this white-rot fungus to degrade recalcitrant lignin. These same mechanisms are implicated in the mineralisation of environmentally persistent, toxic phenolic chemicals. For this reason, P. chrysosporium has been exploited in a number of environmentally sound technologies, including the degradation of the indigestible lignin component in agricultural waste for the generation of digestible animal feedstocks or high sugar content raw materials for ethanol production; brightening processes in the pulp and paper industry; the detoxification and decolourisation of industrial effluents; and the bioremediation of hazardous waste sites. The improvement of these technologies is dependant on ongoing research involving strain selection, strain development using genetic engineering approaches and process development. Strain improvement using non-recombinant methods is beneficial in that it does not limit the inherent robustness observed amongst natural variants. In this research, through a breeding programme, ten P.chrysosporium sibling strains were screened for variable ligninase activities and pollutant degradation capabilities in order to further describe previously identified differences between these organisms. A conventional stationary liquid culture technique was effectively miniaturised from 10 ml flask cultures to a 96-well microtitre plate format, for the assessment of multigenic traits amongst sibling strains. Using the 96-well microtitre plate method, the relationships between P. chrysosporium growth kinetics, peroxidase production, pollutant sensitivity and pollutant degradation was explored. Significant correlations were primarily associated with P. chrysosporium growth [P < 0.05]. Percentage p-cresol removal and tannic acid tolerance were both correlated with a shorter lag phase in growth [tannic acid: r = 0.7698, P < 0.05; p-cresol: r = 0.7584, P < 0.05] and lower stationary phase biomass levels [tannic acid: r = 0.8177, P < 0.05; p-cresol: r = 0.7803, P < 0.05]. A significant correlation (linear relationship) was also detected between percentage Poly-R478 decolourisation and time of onset of MnP [r = 0.9689, P < 0.001]. No correlation was observed between dye decolourisation, p-cresol degradation, lignin degradation and lignin peroxidase (LiP) or manganese peroxidase (MnP) activities [P > 0.05]. These results imply that differences in the biosynthetic pathways for biomass accumulation in sibling strains play a significant role in the intraspecific variation observed in pollutant sensitivity, pollutant degradation, and enzyme production. Categorical analysis of intraspecific differences was assessed according to four criterions. These included growth, extracellular peroxidase activities, tolerance to toxic pollutants and the biodegradation of model pollutants. Sibling strains showing the most variable responses in three or more of the selective criterion were recommended for further studies. These strains include P. chrysosporium ME446, BS 2.52, BS 13, BS 17, BS 18, and BS 24. Interestingly, BS 2.52 (a dikaryotic strain generating from the crossing of two haploid progeny) showed significantly lower degradation capabilities than the wildtype parent strain ME446. The inherited variability observed between sibling strains is to be further explored through proteome and transcriptome analysis and genetic linkage studies aimed at describing the mechanisms or pathways conferring tolerance to or degradation of environmental pollutants. In examining fewer organisms at this next level, the number of replicates examined can be increased and thus the power of detection of experimental procedures improved, enabling the detection of multigenic traits amongst genetically related organisms. Growth was shown to play a significant role in the intraspecific differences detected in pollutant sensitivity and degradation between sibling strains. Little is known about the mechanism of growth and differentiation, or the role of differentiation in regulating the lignolytic activity in this organism. The membrane gradostat bioreactor and a unique plug-flow membrane bioreactor were evaluated as novel tools with which to further explore the relationship between secondary metabolism, pollutant degradation and biofilm development in sibling strains. High yield MnP production at levels as high as 1478.8 U.l-1 was achieved using a laboratory scale membrane gradostat bioreactor. Furthermore, extensive mycelial differentiation and tissue formation are reported for P. chrysosporium in both the membrane gradostat bioreactor and plug-flow membrane bioreactor. Intraspecific differences in the extent of this differentiation were observed in strains ME446, BS 13, BS 17 and BS 26 cultured using the membrane gradostat bioreactor, highlighting the potential of these techniques as a platform for future strain improvement strategies.
- Full Text:
- Date Issued: 2005
- Authors: Fraser, Sheena Janet
- Date: 2005
- Subjects: Phanerochaete Pollutants -- Biodegradation Lignin -- Biodegradation Bioremediation Peroxidase Fungi -- Differentiation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3964 , http://hdl.handle.net/10962/d1004023
- Description: The wood-degrading basidiomycete, Phanerochaete chrysosporium, has been studied as a model organism in elucidating the mechanisms and pathways enabling this white-rot fungus to degrade recalcitrant lignin. These same mechanisms are implicated in the mineralisation of environmentally persistent, toxic phenolic chemicals. For this reason, P. chrysosporium has been exploited in a number of environmentally sound technologies, including the degradation of the indigestible lignin component in agricultural waste for the generation of digestible animal feedstocks or high sugar content raw materials for ethanol production; brightening processes in the pulp and paper industry; the detoxification and decolourisation of industrial effluents; and the bioremediation of hazardous waste sites. The improvement of these technologies is dependant on ongoing research involving strain selection, strain development using genetic engineering approaches and process development. Strain improvement using non-recombinant methods is beneficial in that it does not limit the inherent robustness observed amongst natural variants. In this research, through a breeding programme, ten P.chrysosporium sibling strains were screened for variable ligninase activities and pollutant degradation capabilities in order to further describe previously identified differences between these organisms. A conventional stationary liquid culture technique was effectively miniaturised from 10 ml flask cultures to a 96-well microtitre plate format, for the assessment of multigenic traits amongst sibling strains. Using the 96-well microtitre plate method, the relationships between P. chrysosporium growth kinetics, peroxidase production, pollutant sensitivity and pollutant degradation was explored. Significant correlations were primarily associated with P. chrysosporium growth [P < 0.05]. Percentage p-cresol removal and tannic acid tolerance were both correlated with a shorter lag phase in growth [tannic acid: r = 0.7698, P < 0.05; p-cresol: r = 0.7584, P < 0.05] and lower stationary phase biomass levels [tannic acid: r = 0.8177, P < 0.05; p-cresol: r = 0.7803, P < 0.05]. A significant correlation (linear relationship) was also detected between percentage Poly-R478 decolourisation and time of onset of MnP [r = 0.9689, P < 0.001]. No correlation was observed between dye decolourisation, p-cresol degradation, lignin degradation and lignin peroxidase (LiP) or manganese peroxidase (MnP) activities [P > 0.05]. These results imply that differences in the biosynthetic pathways for biomass accumulation in sibling strains play a significant role in the intraspecific variation observed in pollutant sensitivity, pollutant degradation, and enzyme production. Categorical analysis of intraspecific differences was assessed according to four criterions. These included growth, extracellular peroxidase activities, tolerance to toxic pollutants and the biodegradation of model pollutants. Sibling strains showing the most variable responses in three or more of the selective criterion were recommended for further studies. These strains include P. chrysosporium ME446, BS 2.52, BS 13, BS 17, BS 18, and BS 24. Interestingly, BS 2.52 (a dikaryotic strain generating from the crossing of two haploid progeny) showed significantly lower degradation capabilities than the wildtype parent strain ME446. The inherited variability observed between sibling strains is to be further explored through proteome and transcriptome analysis and genetic linkage studies aimed at describing the mechanisms or pathways conferring tolerance to or degradation of environmental pollutants. In examining fewer organisms at this next level, the number of replicates examined can be increased and thus the power of detection of experimental procedures improved, enabling the detection of multigenic traits amongst genetically related organisms. Growth was shown to play a significant role in the intraspecific differences detected in pollutant sensitivity and degradation between sibling strains. Little is known about the mechanism of growth and differentiation, or the role of differentiation in regulating the lignolytic activity in this organism. The membrane gradostat bioreactor and a unique plug-flow membrane bioreactor were evaluated as novel tools with which to further explore the relationship between secondary metabolism, pollutant degradation and biofilm development in sibling strains. High yield MnP production at levels as high as 1478.8 U.l-1 was achieved using a laboratory scale membrane gradostat bioreactor. Furthermore, extensive mycelial differentiation and tissue formation are reported for P. chrysosporium in both the membrane gradostat bioreactor and plug-flow membrane bioreactor. Intraspecific differences in the extent of this differentiation were observed in strains ME446, BS 13, BS 17 and BS 26 cultured using the membrane gradostat bioreactor, highlighting the potential of these techniques as a platform for future strain improvement strategies.
- Full Text:
- Date Issued: 2005
Introducing hippocratic log files for personal privacy control
- Authors: Rutherford, Andrew
- Date: 2005
- Subjects: Computer security , Internet -- Security measures
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9743 , http://hdl.handle.net/10948/171 , Computer security , Internet -- Security measures
- Description: The rapid growth of the Internet has served to intensify existing privacy concerns of the individual, to the point that privacy is the number one concern amongst Internet users today. Tools exist that can provide users with a choice of anonymity or pseudonymity. However, many Web transactions require the release of personally identifying information, thus rendering such tools infeasible in many instances. Since it is then a given that users are often required to release personal information, which could be recorded, it follows that they require a greater degree of control over the information they release. Hippocratic databases, designed by Agrawal, Kiernan, Srikant, and Xu (2002), aim to give users greater control over information stored in a data- base. Their design was inspired by the medical Hippocratic oath, and makes data privacy protection a fundamental responsibility of the database itself. To achieve the privacy of data, Hippocratic databases are governed by 10 key privacy principles. This dissertation argues, that asides from a few challenges, the 10 prin- ciples of Hippocratic databases can be applied to log ¯les. This argument is supported by presenting a high-level functional view of a Hippocratic log file architecture. This architecture focuses on issues that highlight the con- trol users gain over their personal information that is collected in log files. By presenting a layered view of the aforementioned architecture, it was, fur- thermore, possible to provide greater insight into the major processes that would be at work in a Hippocratic log file implementation. An exploratory prototype served to understand and demonstrate certain of the architectural components of Hippocratic log files. This dissertation, thus, makes a contribution to the ideal of providing users with greater control over their personal information, by proposing the use of Hippocratic logfiles.
- Full Text:
- Date Issued: 2005
- Authors: Rutherford, Andrew
- Date: 2005
- Subjects: Computer security , Internet -- Security measures
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9743 , http://hdl.handle.net/10948/171 , Computer security , Internet -- Security measures
- Description: The rapid growth of the Internet has served to intensify existing privacy concerns of the individual, to the point that privacy is the number one concern amongst Internet users today. Tools exist that can provide users with a choice of anonymity or pseudonymity. However, many Web transactions require the release of personally identifying information, thus rendering such tools infeasible in many instances. Since it is then a given that users are often required to release personal information, which could be recorded, it follows that they require a greater degree of control over the information they release. Hippocratic databases, designed by Agrawal, Kiernan, Srikant, and Xu (2002), aim to give users greater control over information stored in a data- base. Their design was inspired by the medical Hippocratic oath, and makes data privacy protection a fundamental responsibility of the database itself. To achieve the privacy of data, Hippocratic databases are governed by 10 key privacy principles. This dissertation argues, that asides from a few challenges, the 10 prin- ciples of Hippocratic databases can be applied to log ¯les. This argument is supported by presenting a high-level functional view of a Hippocratic log file architecture. This architecture focuses on issues that highlight the con- trol users gain over their personal information that is collected in log files. By presenting a layered view of the aforementioned architecture, it was, fur- thermore, possible to provide greater insight into the major processes that would be at work in a Hippocratic log file implementation. An exploratory prototype served to understand and demonstrate certain of the architectural components of Hippocratic log files. This dissertation, thus, makes a contribution to the ideal of providing users with greater control over their personal information, by proposing the use of Hippocratic logfiles.
- Full Text:
- Date Issued: 2005
Investigating call control using MGCP in conjuction with SIP and H.323
- Authors: Jacobs, Ashley
- Date: 2005 , 2005-03-14
- Subjects: Communication -- Technological innovations , Digital telephone systems , Computer networks , Computer network protocols , Internet telephony
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4631 , http://hdl.handle.net/10962/d1006516 , Communication -- Technological innovations , Digital telephone systems , Computer networks , Computer network protocols , Internet telephony
- Description: Telephony used to mean using a telephone to call another telephone on the Public Switched Telephone Network (PSTN), and data networks were used purely to allow computers to communicate. However, with the advent of the Internet, telephony services have been extended to run on data networks. Telephone calls within the IP network are known as Voice over IP. These calls are carried by a number of protocols, with the most popular ones currently being Session Initiation Protocol (SIP) and H.323. Calls can be made from the IP network to the PSTN and vice versa through the use of a gateway. The gateway translates the packets from the IP network to circuits on the PSTN and vice versa to facilitate calls between the two networks. Gateways have evolved and are now split into two entities using the master/slave architecture. The master is an intelligent Media Gateway Controller (MGC) that handles the call control and signalling. The slave is a "dumb" Media Gateway (MG) that handles the translation of the media. The current gateway control protocols in use are Megaco/H.248, MGCP and Skinny. These protocols have proved themselves on the edge of the network. Furthermore, since they communicate with the call signalling VoIP protocols as well as the PSTN, they have to be the lingua franca between the two networks. Within the VoIP network, the numbers of call signalling protocols make it difficult to communicate with each other and to create services. This research investigates the use of Gateway Control Protocols as the lowest common denominator between the call signalling protocols SIP and H.323. More specifically, it uses MGCP to investigate service creation. It also considers the use of MGCP as a protocol translator between SIP and H.323. A service was created using MGCP to allow H.323 endpoints to send Short Message Service (SMS) messages. This service was then extended with minimal effort to SIP endpoints. This service investigated MGCP’s ability to handle call control from the H.323 and SIP endpoints. An MGC was then successfully used to perform as a protocol translator between SIP and H.323.
- Full Text:
- Date Issued: 2005
- Authors: Jacobs, Ashley
- Date: 2005 , 2005-03-14
- Subjects: Communication -- Technological innovations , Digital telephone systems , Computer networks , Computer network protocols , Internet telephony
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4631 , http://hdl.handle.net/10962/d1006516 , Communication -- Technological innovations , Digital telephone systems , Computer networks , Computer network protocols , Internet telephony
- Description: Telephony used to mean using a telephone to call another telephone on the Public Switched Telephone Network (PSTN), and data networks were used purely to allow computers to communicate. However, with the advent of the Internet, telephony services have been extended to run on data networks. Telephone calls within the IP network are known as Voice over IP. These calls are carried by a number of protocols, with the most popular ones currently being Session Initiation Protocol (SIP) and H.323. Calls can be made from the IP network to the PSTN and vice versa through the use of a gateway. The gateway translates the packets from the IP network to circuits on the PSTN and vice versa to facilitate calls between the two networks. Gateways have evolved and are now split into two entities using the master/slave architecture. The master is an intelligent Media Gateway Controller (MGC) that handles the call control and signalling. The slave is a "dumb" Media Gateway (MG) that handles the translation of the media. The current gateway control protocols in use are Megaco/H.248, MGCP and Skinny. These protocols have proved themselves on the edge of the network. Furthermore, since they communicate with the call signalling VoIP protocols as well as the PSTN, they have to be the lingua franca between the two networks. Within the VoIP network, the numbers of call signalling protocols make it difficult to communicate with each other and to create services. This research investigates the use of Gateway Control Protocols as the lowest common denominator between the call signalling protocols SIP and H.323. More specifically, it uses MGCP to investigate service creation. It also considers the use of MGCP as a protocol translator between SIP and H.323. A service was created using MGCP to allow H.323 endpoints to send Short Message Service (SMS) messages. This service was then extended with minimal effort to SIP endpoints. This service investigated MGCP’s ability to handle call control from the H.323 and SIP endpoints. An MGC was then successfully used to perform as a protocol translator between SIP and H.323.
- Full Text:
- Date Issued: 2005
Investigation into the biological removal of sulphate from ethanol distillery wastewater using sulphate-reducing prokaryotes
- Authors: Smuts, Lizl
- Date: 2005
- Subjects: Sewage -- Purification -- Biological treatment , Prokaryotes , Sulfates , Distilleries -- Waste disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3941 , http://hdl.handle.net/10962/d1004000 , Sewage -- Purification -- Biological treatment , Prokaryotes , Sulfates , Distilleries -- Waste disposal
- Description: Ethanol production wastewater is known to be toxic, and is not easily biodegradable. It also consists of a variety of coloured components adding to the complex composition of this wastewater. Disposal of this wastewater into water courses is not recommended and yet is performed all over the world. Investigation of this wastewater found that there was a high concentration of sulphate which, in the presence of sulphate-reducing prokaryotes can cause sulphide corrosion of cement. The concentration of sulphate in the wastewater was approximately 2770 mg/L. It was also found that the wastewater pH was very low and discharge of the wastewater into the wastewater treatment works caused a negative impact on the overall quality of the final wastewater discharged to sea. It was found using FISH techniques that there were no sulphate-reducing prokaryotes present in the wastewaters but that a sulphate-reducing population existed on the sewer wall. An anaerobic contact process was designed to treat this wastewater targeting sulphate reduction to sulphide, to be converted into elemental sulphur and to increase the wastewater pH. The process did not achieve this aim and only approximately 20-30 % reduction in sulphate from the wastewater was achieved with little to no change in the pH. A 95 % reduction in sulphate concentration was needed in order to reach acceptable discharge limits. Sulphate reduction could not be carried out, even under ideal laboratory conditions. It was found that the barrier causing the digester failure was the high concentration of phenols present in the wastewater (3.3 g/L) together with the production of high concentrations of volatile fatty acids (on average 13 g acetic/L). These two components are known to cause digester failure, especially phenols, and phenols are usually only degraded by fungal species. It was concluded that the wastewater itself was not amenable to this method of biological treatment.
- Full Text:
- Date Issued: 2005
- Authors: Smuts, Lizl
- Date: 2005
- Subjects: Sewage -- Purification -- Biological treatment , Prokaryotes , Sulfates , Distilleries -- Waste disposal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3941 , http://hdl.handle.net/10962/d1004000 , Sewage -- Purification -- Biological treatment , Prokaryotes , Sulfates , Distilleries -- Waste disposal
- Description: Ethanol production wastewater is known to be toxic, and is not easily biodegradable. It also consists of a variety of coloured components adding to the complex composition of this wastewater. Disposal of this wastewater into water courses is not recommended and yet is performed all over the world. Investigation of this wastewater found that there was a high concentration of sulphate which, in the presence of sulphate-reducing prokaryotes can cause sulphide corrosion of cement. The concentration of sulphate in the wastewater was approximately 2770 mg/L. It was also found that the wastewater pH was very low and discharge of the wastewater into the wastewater treatment works caused a negative impact on the overall quality of the final wastewater discharged to sea. It was found using FISH techniques that there were no sulphate-reducing prokaryotes present in the wastewaters but that a sulphate-reducing population existed on the sewer wall. An anaerobic contact process was designed to treat this wastewater targeting sulphate reduction to sulphide, to be converted into elemental sulphur and to increase the wastewater pH. The process did not achieve this aim and only approximately 20-30 % reduction in sulphate from the wastewater was achieved with little to no change in the pH. A 95 % reduction in sulphate concentration was needed in order to reach acceptable discharge limits. Sulphate reduction could not be carried out, even under ideal laboratory conditions. It was found that the barrier causing the digester failure was the high concentration of phenols present in the wastewater (3.3 g/L) together with the production of high concentrations of volatile fatty acids (on average 13 g acetic/L). These two components are known to cause digester failure, especially phenols, and phenols are usually only degraded by fungal species. It was concluded that the wastewater itself was not amenable to this method of biological treatment.
- Full Text:
- Date Issued: 2005
Investigation of the effect of selected polypropylene fibres and ultra-fine aggregate on plastic shrinkage cracks on South African roads
- Authors: Kluyts, Grant
- Date: 2005
- Subjects: Concrete roads -- South Africa -- Design and construction , Fiber-reinforced concrete , Reinforced concrete -- Cracking , Concrete -- Expansion and contraction , Polypropylene fibers
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9592 , http://hdl.handle.net/10948/174 , Concrete roads -- South Africa -- Design and construction , Fiber-reinforced concrete , Reinforced concrete -- Cracking , Concrete -- Expansion and contraction , Polypropylene fibers
- Description: Plastic shrinkage cracks, although not inherently structurally debilitating, expose the reinforcement in low-volume reinforced concrete roads to deleterious substances, which may reduce its effectiveness leading ultimately to structural failure. In un-reinforced low-volume concrete road these cracks appear unsightly and cause the road user an unpleasant riding experience. Many researchers believe that plastic shrinkage crack development remains a concern to the concrete industry, occurring in particularly large–area pours such as low-volume concrete roads, and therefore requires further research to understand their formation and minimization. This study reports findings on the effectiveness of oxyfluorinated polypropylene fibres to control plastic shrinkage cracks, and the effect the addition of ultra-fine material has on the formation and/or propagation of these cracks. Findings indicate that low volume dosages (2 kg/m³), of oxyfluorinated polypropylene fibre significantly reduced the formation of plastic shrinkage cracks under test conditions. Furthermore, that the addition of ultra-fine material in excess of 63 kg/m³ increased the formation and/or development of plastic shrinkage cracks.
- Full Text:
- Date Issued: 2005
- Authors: Kluyts, Grant
- Date: 2005
- Subjects: Concrete roads -- South Africa -- Design and construction , Fiber-reinforced concrete , Reinforced concrete -- Cracking , Concrete -- Expansion and contraction , Polypropylene fibers
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9592 , http://hdl.handle.net/10948/174 , Concrete roads -- South Africa -- Design and construction , Fiber-reinforced concrete , Reinforced concrete -- Cracking , Concrete -- Expansion and contraction , Polypropylene fibers
- Description: Plastic shrinkage cracks, although not inherently structurally debilitating, expose the reinforcement in low-volume reinforced concrete roads to deleterious substances, which may reduce its effectiveness leading ultimately to structural failure. In un-reinforced low-volume concrete road these cracks appear unsightly and cause the road user an unpleasant riding experience. Many researchers believe that plastic shrinkage crack development remains a concern to the concrete industry, occurring in particularly large–area pours such as low-volume concrete roads, and therefore requires further research to understand their formation and minimization. This study reports findings on the effectiveness of oxyfluorinated polypropylene fibres to control plastic shrinkage cracks, and the effect the addition of ultra-fine material has on the formation and/or propagation of these cracks. Findings indicate that low volume dosages (2 kg/m³), of oxyfluorinated polypropylene fibre significantly reduced the formation of plastic shrinkage cracks under test conditions. Furthermore, that the addition of ultra-fine material in excess of 63 kg/m³ increased the formation and/or development of plastic shrinkage cracks.
- Full Text:
- Date Issued: 2005
Isolation and characterization of a novel thermostable and catalytically efficient laccase from Peniophora sp. strain UD4
- Authors: Jordaan, Justin
- Date: 2005
- Subjects: Enzymes Enzymes -- Industrial applications Peniophora Laccase
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3970 , http://hdl.handle.net/10962/d1004029
- Description: Enzymes are becoming an effective tool in industrial processes, from crude applications such as bioremediation to fine processes such as chirally selective biocatalysis. The ligninolytic enzymes have recently received considerable attention for industrial application due to both their broad substrate range and their ability to degrade the most recalcitrant natural polymer, lignin. This group of enzymes was therefore identified as the target group for this study. Improved enzyme properties are constantly being sought to enhance the range of applications for enzymes. Biodiversity provides a wide variety of enzymes. Several researchers have concentrated on extremophiles as their primary source of superior enzymes, consequently neglecting temperate environments in their search for these enzymes. The relatively neglected fungal biodiversity of South Africa provided an opportunity to test the hypothesis that potentially important industrial enzymes with unusual properties could be isolated from mesophilic basidiomycetous fungi. Subsequent screening of Eastern Cape biodiversity for thermostable ligninolytic enzymes from basidiomycetes resulted in the isolation of a novel laccase enzyme from a basidiomycetous species. This fungus was identified as Peniophora sp. UD4 by phylogenetic analysis of rDNA ITS sequences. Initial studies indicated a superior optimum temperature of 70°C and thermostability, indicated by no loss in activity at 60°C over nine hours. Further characterization of the laccase revealed a broader than usual substrate range through its unusual ability to oxidatively couple DMAB and MBTH. The laccase also exhibited a broad pH oxidation range for ABTS (pH 2 – 6.8), and a relatively high affinity (K_m_ = 0.0123 mM) and catalytic efficiency (63 252 mM^(-1)^s^(-1)^) for ABTS as a substrate. The laccase activity from Peniophora sp. UD4 was shown to be comprised of three isozymes with a molecular weight of 62 kDa and pI’s of 6.33, 6.45 and 6.50. Investigation of the nutrient and physical factors affecting ligninolytic enzyme production and growth of Peniophora sp. UD4 indicated that the wild-type organism was unsuitable for large scale production of the thermostable laccase due to the low levels of laccase production. The thermostable laccase was applied to defouling of ultrafiltration membranes, bioremediation of industrial waste streams, biocatalysis, and biosensor technology as potential applications. Application of the Peniophora sp. UD4 laccase to defouling of membranes used for ultrafiltration of brown water showed large flux recoveries of 31, 21 and 21% after the first three defouling recycles respectively, compared to 3% for the control without immobilized enzyme. The novel laccase showed potential for the bioremediation of industrial waste streams, the most successful being that of bleach plant effluent, where a reduction of 66% of the phenolic load was achieved. Application of the novel laccase to biocatalytic oxidation of ferulic acid and (±)-α-pinene showed higher product yield as compared to oxidation of these compounds by Trametes versicolor laccase in mediated and non-mediated systems. The major products of (±)-α-pinene oxidation were identified as verbenol and trans-sorberol. The Peniophora sp. UD4 laccase was successfully applied to biosensor technology, which benchmarked significantly better than Trametes versicolor laccase for the detection of 4-chlorophenol. The biosensor developed with laccase from UD4 by covalent binding to a glassy carbon electrode exhibited the best combination of sensitivity and stability. This thesis shows that a laccase with superior properties was obtained from a mesophilic South African basidiomycete. The catalytic properties displayed by the novel laccase from Peniophora sp. UD4 all contribute to the increased industrial applicability of laccases, and may be the most industrially feasible enzyme of its class isolated to date.
- Full Text:
- Date Issued: 2005
- Authors: Jordaan, Justin
- Date: 2005
- Subjects: Enzymes Enzymes -- Industrial applications Peniophora Laccase
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3970 , http://hdl.handle.net/10962/d1004029
- Description: Enzymes are becoming an effective tool in industrial processes, from crude applications such as bioremediation to fine processes such as chirally selective biocatalysis. The ligninolytic enzymes have recently received considerable attention for industrial application due to both their broad substrate range and their ability to degrade the most recalcitrant natural polymer, lignin. This group of enzymes was therefore identified as the target group for this study. Improved enzyme properties are constantly being sought to enhance the range of applications for enzymes. Biodiversity provides a wide variety of enzymes. Several researchers have concentrated on extremophiles as their primary source of superior enzymes, consequently neglecting temperate environments in their search for these enzymes. The relatively neglected fungal biodiversity of South Africa provided an opportunity to test the hypothesis that potentially important industrial enzymes with unusual properties could be isolated from mesophilic basidiomycetous fungi. Subsequent screening of Eastern Cape biodiversity for thermostable ligninolytic enzymes from basidiomycetes resulted in the isolation of a novel laccase enzyme from a basidiomycetous species. This fungus was identified as Peniophora sp. UD4 by phylogenetic analysis of rDNA ITS sequences. Initial studies indicated a superior optimum temperature of 70°C and thermostability, indicated by no loss in activity at 60°C over nine hours. Further characterization of the laccase revealed a broader than usual substrate range through its unusual ability to oxidatively couple DMAB and MBTH. The laccase also exhibited a broad pH oxidation range for ABTS (pH 2 – 6.8), and a relatively high affinity (K_m_ = 0.0123 mM) and catalytic efficiency (63 252 mM^(-1)^s^(-1)^) for ABTS as a substrate. The laccase activity from Peniophora sp. UD4 was shown to be comprised of three isozymes with a molecular weight of 62 kDa and pI’s of 6.33, 6.45 and 6.50. Investigation of the nutrient and physical factors affecting ligninolytic enzyme production and growth of Peniophora sp. UD4 indicated that the wild-type organism was unsuitable for large scale production of the thermostable laccase due to the low levels of laccase production. The thermostable laccase was applied to defouling of ultrafiltration membranes, bioremediation of industrial waste streams, biocatalysis, and biosensor technology as potential applications. Application of the Peniophora sp. UD4 laccase to defouling of membranes used for ultrafiltration of brown water showed large flux recoveries of 31, 21 and 21% after the first three defouling recycles respectively, compared to 3% for the control without immobilized enzyme. The novel laccase showed potential for the bioremediation of industrial waste streams, the most successful being that of bleach plant effluent, where a reduction of 66% of the phenolic load was achieved. Application of the novel laccase to biocatalytic oxidation of ferulic acid and (±)-α-pinene showed higher product yield as compared to oxidation of these compounds by Trametes versicolor laccase in mediated and non-mediated systems. The major products of (±)-α-pinene oxidation were identified as verbenol and trans-sorberol. The Peniophora sp. UD4 laccase was successfully applied to biosensor technology, which benchmarked significantly better than Trametes versicolor laccase for the detection of 4-chlorophenol. The biosensor developed with laccase from UD4 by covalent binding to a glassy carbon electrode exhibited the best combination of sensitivity and stability. This thesis shows that a laccase with superior properties was obtained from a mesophilic South African basidiomycete. The catalytic properties displayed by the novel laccase from Peniophora sp. UD4 all contribute to the increased industrial applicability of laccases, and may be the most industrially feasible enzyme of its class isolated to date.
- Full Text:
- Date Issued: 2005
Isolation, purification and characterization of inulin and fructooligosaccharides from chicorium intybus and inulinase from aspergillus niger
- Mavumengwana, Vuyo Bhongelethu
- Authors: Mavumengwana, Vuyo Bhongelethu
- Date: 2005
- Subjects: Aspergillus , Inulin , Chicory -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3954 , http://hdl.handle.net/10962/d1004013 , Aspergillus , Inulin , Chicory -- South Africa
- Description: Inulin is a non-digestible carbohydrate fructan polymer consisting mainly of β (1→2) fructosyl fructose links. Enzymatic hydrolysis of inulin by inulinase results in the production of low D.P (degree of polymerization) oligosaccharides also called fructooligosaccharides(FOS). Isolation of inulin from chicory root (Chicorium intybus) was achieved by first, extraction using deionized water (600C), followed by carbonation (0.1 M Ca(OH)2 and CO2 gas). This was filtered in order to remove the non sugars, thereafter, treated successfully with polyamide 6 powder. A cation exchanger and an anion exchanger were used to further exclude other components such as tannins and pigments. The extracted inulin was quantified using the Somogyi-Nelson colourimetric assay. Chicory root (207 g, 30 % being water) yielded 30 g of the raw extract. A 100 mg of the raw extract was assayed and found to contain 11 % yield of inulin which was 80.2 % in purity and 4 % free fructose. Analysis of the crude and purified inulin extracts on the MALDI TOF spectrometry showed the samples to have a DP of 2 to 22 and 2 to 27 respectively. Maximum inulinase production from Aspergillus niger grown on inulin was observed after 60 hours. The enzyme activity was found to be 1.168 U/ml with a temperature and pH optimum of 30 °C and 7.7 respectively. The enzyme proved to be unstable as it progressively lost its total activity during attempts at purification.
- Full Text:
- Date Issued: 2005
- Authors: Mavumengwana, Vuyo Bhongelethu
- Date: 2005
- Subjects: Aspergillus , Inulin , Chicory -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3954 , http://hdl.handle.net/10962/d1004013 , Aspergillus , Inulin , Chicory -- South Africa
- Description: Inulin is a non-digestible carbohydrate fructan polymer consisting mainly of β (1→2) fructosyl fructose links. Enzymatic hydrolysis of inulin by inulinase results in the production of low D.P (degree of polymerization) oligosaccharides also called fructooligosaccharides(FOS). Isolation of inulin from chicory root (Chicorium intybus) was achieved by first, extraction using deionized water (600C), followed by carbonation (0.1 M Ca(OH)2 and CO2 gas). This was filtered in order to remove the non sugars, thereafter, treated successfully with polyamide 6 powder. A cation exchanger and an anion exchanger were used to further exclude other components such as tannins and pigments. The extracted inulin was quantified using the Somogyi-Nelson colourimetric assay. Chicory root (207 g, 30 % being water) yielded 30 g of the raw extract. A 100 mg of the raw extract was assayed and found to contain 11 % yield of inulin which was 80.2 % in purity and 4 % free fructose. Analysis of the crude and purified inulin extracts on the MALDI TOF spectrometry showed the samples to have a DP of 2 to 22 and 2 to 27 respectively. Maximum inulinase production from Aspergillus niger grown on inulin was observed after 60 hours. The enzyme activity was found to be 1.168 U/ml with a temperature and pH optimum of 30 °C and 7.7 respectively. The enzyme proved to be unstable as it progressively lost its total activity during attempts at purification.
- Full Text:
- Date Issued: 2005
Knowledge levels of school learners before and after a life skills program on rape and child abuse
- Authors: Britz, Cecelia Adonia
- Date: 2005
- Subjects: Rape -- Prevention , Child abuse -- Prevention , School children -- Life skills assessment -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:11017 , http://hdl.handle.net/10948/360 , Rape -- Prevention , Child abuse -- Prevention , School children -- Life skills assessment -- South Africa -- Port Elizabeth
- Description: Due to the early age at which children are exposed to rape and child abuse, preventative programs should be implemented as early as possible. Schools provide ample opportunity to reach learners of all ages. Educators have regular contact with learners and have a key role to play in the implementation of comprehensive health and education life skills programs. Non-Governmental Organisations (NGO) can link up with schools to combat abuse that affects children in South African communities. The Ubuntu Education Fund requested the Health and Development Research Institute (HDRI) of the University of Port Elizabeth to assist with the evaluation of the Mpilo-Lwazi life skills program for grade 6 to 9 learners at 5 primary and 5 secondary schools in the Nelson Mandela Metropole. The schools were selected by non-probability convenience sampling and the learners via simple random sampling. The life skills program addressed issues of HIV/AIDS, STI and rape and child abuse and the requested evaluation encompassed both the quantitative pretest-posttest assessment of knowledge plus a qualitative focus group assessment of perception of the content and presentation of the life skills program. A multiple pretest-post-test quasi-experimental research design was used. This study focused on the quantitative aspect of rape and child abuse and aimed to describe learners’ base line knowledge before receiving education in rape and child abuse life skills programs and acquired knowledge after the program had been implemented. Descriptive statistics were employed to describe the pre and post test information and the Hotelling’s T2 was used to identify variation in profiles. Posthoc t-tests established significant differences between grades. Structured questionnaires were used to achieve the aims of the research. Results of both the quantitative and qualitative findings were collated to be presented to the Ubuntu Education Fund. The results of the study were as follows: ix The results indicated that the overall level of knowledge regarding Rape and Child Abuse among the sample of grade six to nine learners was average. A small increase in knowledge was identified in the post-test. The area most successful for knowledge increase was the section relating to general information on the victims of Rape and Child Abuse. An area where knowledge actually decreased was that on reporting the rape or abuse. Knowledge of rape and child abuse alone is not sufficient to bring about change in behaviour. Changes in beliefs, such as increased awareness that rape and child abuse are prevalent in families and communities, and attitude change are necessary to facilitate the adoption of health-promoting behaviour. Future education efforts need to introduce health educators into the Rape and Child Abuse life skills program at schools in educating the learners. The format of teaching should also take into account the preferred method of presentation indicated by the learners as this would facilitate optimal intake of information.
- Full Text:
- Date Issued: 2005
- Authors: Britz, Cecelia Adonia
- Date: 2005
- Subjects: Rape -- Prevention , Child abuse -- Prevention , School children -- Life skills assessment -- South Africa -- Port Elizabeth
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:11017 , http://hdl.handle.net/10948/360 , Rape -- Prevention , Child abuse -- Prevention , School children -- Life skills assessment -- South Africa -- Port Elizabeth
- Description: Due to the early age at which children are exposed to rape and child abuse, preventative programs should be implemented as early as possible. Schools provide ample opportunity to reach learners of all ages. Educators have regular contact with learners and have a key role to play in the implementation of comprehensive health and education life skills programs. Non-Governmental Organisations (NGO) can link up with schools to combat abuse that affects children in South African communities. The Ubuntu Education Fund requested the Health and Development Research Institute (HDRI) of the University of Port Elizabeth to assist with the evaluation of the Mpilo-Lwazi life skills program for grade 6 to 9 learners at 5 primary and 5 secondary schools in the Nelson Mandela Metropole. The schools were selected by non-probability convenience sampling and the learners via simple random sampling. The life skills program addressed issues of HIV/AIDS, STI and rape and child abuse and the requested evaluation encompassed both the quantitative pretest-posttest assessment of knowledge plus a qualitative focus group assessment of perception of the content and presentation of the life skills program. A multiple pretest-post-test quasi-experimental research design was used. This study focused on the quantitative aspect of rape and child abuse and aimed to describe learners’ base line knowledge before receiving education in rape and child abuse life skills programs and acquired knowledge after the program had been implemented. Descriptive statistics were employed to describe the pre and post test information and the Hotelling’s T2 was used to identify variation in profiles. Posthoc t-tests established significant differences between grades. Structured questionnaires were used to achieve the aims of the research. Results of both the quantitative and qualitative findings were collated to be presented to the Ubuntu Education Fund. The results of the study were as follows: ix The results indicated that the overall level of knowledge regarding Rape and Child Abuse among the sample of grade six to nine learners was average. A small increase in knowledge was identified in the post-test. The area most successful for knowledge increase was the section relating to general information on the victims of Rape and Child Abuse. An area where knowledge actually decreased was that on reporting the rape or abuse. Knowledge of rape and child abuse alone is not sufficient to bring about change in behaviour. Changes in beliefs, such as increased awareness that rape and child abuse are prevalent in families and communities, and attitude change are necessary to facilitate the adoption of health-promoting behaviour. Future education efforts need to introduce health educators into the Rape and Child Abuse life skills program at schools in educating the learners. The format of teaching should also take into account the preferred method of presentation indicated by the learners as this would facilitate optimal intake of information.
- Full Text:
- Date Issued: 2005
Ligand isotope vibrational spectroscopic and DFT studies of Pt(II) and Cu(I) complexes
- Authors: Medina, Gerardo Juan
- Date: 2005
- Subjects: Ligands Spectrum analysis Vibrational spectra Infrared spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4324 , http://hdl.handle.net/10962/d1004982
- Description: Ligand-isotope labelling studies were performed on Zeise’s salt derivatives with pyridine N-oxide and quinoline N-oxide, their perdeuterated and O-18 isotopomers, C₂D₄ and ¹³CO, and the results of the vibrational analyses are reported. The isotopomers are modelled utilizing DFT calculations at the B3LYP level with the 6-31 G** basis set, and a pseudopotential level for the Pt atom. The calculated and observed structure and vibrational spectra correlate well. The crystal structures of [Pt(C₂2H₄)(pyO)Cl₂] and [Pt(CO)(quinO)Br₂] are reported. The frequency for the νPt-O vibration, ambiguously assigned in the literature, is here assigned unequivocally at 400 cm⁻¹. Previously observed, but inadequately described phenomena are addressed: the νN-O vibration in substituted quinoline N-oxides has been assigned previously at significantly different frequencies, depending on the nature of the substituent. This suggests that there is no specific mid-ir band associated with a high N-O character. A suitable explanation is presented for this phenomenon, showing that in low symmetry systems (eg. quinO) the N-O stretch is dispersed among several modes, whereas in high symmetry systems (eg. pyO) only a few limited modes have a high N-O character. A theoretical study of Cu(I) carbonyl compounds with macrocyclic ligands is presented. Local and global HSAB parameters applied to the donor and Cu atoms are used to explain the observed reactivities and the available spectroscopic data. Extended to [Cu(CO){H₂N(CH₂)[subscript n]NH(CH₂)[subscript m] NH₂}] BPh₄ (where n = 2, m = 2, 3 and n =3, m = 3, 4) and their -d₅ and ¹³CO isotopomers, subtle differences obtained experimentally for the CO stretching frequency in this series have been reproduced in the DFT calculations at the B3LYP level, using the 6-31 G* and 6-31 G** basis sets. Several properties (ligand pK[subscript a] values, νCO frequencies, etc.) correlate with some HSAB descriptors. Vibrational analyses are presented of Cu(I) carbonyl Schiff-base derivatives of N-Benzylidene-N’-[2-(benzyilidene-amino)-ethyl]-ethane-1,2-diamine, {2,2N3(C₆H₄R)₂}, and their -d₅ and ¹³CO isotopomers. The crystal structure of [Cu(CO){2,2N3(C₆H₅)₂}]BPh₄ is reported. From geometry optimizations and the HSAB descriptors, spectroscopic trends ([n]Cu-N and [nu]CO) are related to calculated global hardness and the Hammett substituent parameters, and are discussed in terms of σ-donation and π-backbonding of Cu- CO.
- Full Text:
- Date Issued: 2005
- Authors: Medina, Gerardo Juan
- Date: 2005
- Subjects: Ligands Spectrum analysis Vibrational spectra Infrared spectroscopy
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4324 , http://hdl.handle.net/10962/d1004982
- Description: Ligand-isotope labelling studies were performed on Zeise’s salt derivatives with pyridine N-oxide and quinoline N-oxide, their perdeuterated and O-18 isotopomers, C₂D₄ and ¹³CO, and the results of the vibrational analyses are reported. The isotopomers are modelled utilizing DFT calculations at the B3LYP level with the 6-31 G** basis set, and a pseudopotential level for the Pt atom. The calculated and observed structure and vibrational spectra correlate well. The crystal structures of [Pt(C₂2H₄)(pyO)Cl₂] and [Pt(CO)(quinO)Br₂] are reported. The frequency for the νPt-O vibration, ambiguously assigned in the literature, is here assigned unequivocally at 400 cm⁻¹. Previously observed, but inadequately described phenomena are addressed: the νN-O vibration in substituted quinoline N-oxides has been assigned previously at significantly different frequencies, depending on the nature of the substituent. This suggests that there is no specific mid-ir band associated with a high N-O character. A suitable explanation is presented for this phenomenon, showing that in low symmetry systems (eg. quinO) the N-O stretch is dispersed among several modes, whereas in high symmetry systems (eg. pyO) only a few limited modes have a high N-O character. A theoretical study of Cu(I) carbonyl compounds with macrocyclic ligands is presented. Local and global HSAB parameters applied to the donor and Cu atoms are used to explain the observed reactivities and the available spectroscopic data. Extended to [Cu(CO){H₂N(CH₂)[subscript n]NH(CH₂)[subscript m] NH₂}] BPh₄ (where n = 2, m = 2, 3 and n =3, m = 3, 4) and their -d₅ and ¹³CO isotopomers, subtle differences obtained experimentally for the CO stretching frequency in this series have been reproduced in the DFT calculations at the B3LYP level, using the 6-31 G* and 6-31 G** basis sets. Several properties (ligand pK[subscript a] values, νCO frequencies, etc.) correlate with some HSAB descriptors. Vibrational analyses are presented of Cu(I) carbonyl Schiff-base derivatives of N-Benzylidene-N’-[2-(benzyilidene-amino)-ethyl]-ethane-1,2-diamine, {2,2N3(C₆H₄R)₂}, and their -d₅ and ¹³CO isotopomers. The crystal structure of [Cu(CO){2,2N3(C₆H₅)₂}]BPh₄ is reported. From geometry optimizations and the HSAB descriptors, spectroscopic trends ([n]Cu-N and [nu]CO) are related to calculated global hardness and the Hammett substituent parameters, and are discussed in terms of σ-donation and π-backbonding of Cu- CO.
- Full Text:
- Date Issued: 2005
Making meaning, making a home: students watching Generations
- Authors: O'Shea, Catherine Mary
- Date: 2005
- Subjects: Generations (Television program) , Students, Black -- South Africa -- Attitudes , Television soap operas -- South Africa , Cross-cultural studies -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3479 , http://hdl.handle.net/10962/d1002934 , Generations (Television program) , Students, Black -- South Africa -- Attitudes , Television soap operas -- South Africa , Cross-cultural studies -- South Africa
- Description: This thesis is a reception analysis using qualitative interviews to investigate black students' watching of a South African soap opera, Generations, taking into account the context of a largely white South African university campus. The findings of this study are that students find pleasure in talking about Generations and hold seemingly contradictory views on whether it is 'realistic' or not. The analysis concludes that watching Generations does serve to affirm these students' black identity, since there is a particular need to do so on a campus where black students witness and experience racial discrimination.
- Full Text:
- Date Issued: 2005
- Authors: O'Shea, Catherine Mary
- Date: 2005
- Subjects: Generations (Television program) , Students, Black -- South Africa -- Attitudes , Television soap operas -- South Africa , Cross-cultural studies -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3479 , http://hdl.handle.net/10962/d1002934 , Generations (Television program) , Students, Black -- South Africa -- Attitudes , Television soap operas -- South Africa , Cross-cultural studies -- South Africa
- Description: This thesis is a reception analysis using qualitative interviews to investigate black students' watching of a South African soap opera, Generations, taking into account the context of a largely white South African university campus. The findings of this study are that students find pleasure in talking about Generations and hold seemingly contradictory views on whether it is 'realistic' or not. The analysis concludes that watching Generations does serve to affirm these students' black identity, since there is a particular need to do so on a campus where black students witness and experience racial discrimination.
- Full Text:
- Date Issued: 2005
Marine biotechnology : evaluation and development of methods for the discovery of natural products from fungi
- Authors: Pather, Simisha
- Date: 2005 , 2013-06-18
- Subjects: Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3839 , http://hdl.handle.net/10962/d1007652 , Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Description: One of the major impediments in the development of marine natural products is the provision of biologically active natural products in sufficient quantity for complete pharmacological evaluation, clinical trials and eventual commercial production. Marine microorganisms show great promise in providing a renewable source of biologically active natural products. The main aim of this study was to develop and evaluate methods for the isolation, identification and cultivation of marine fungi from the South African marine environment for the production of biologically active secondary metabolites. Twenty-four species of fungi were isolated from marine algae collected from the intertidal zone near Port Alfred, South Africa. The fungi were cultivated in small-scale under static and agitated conditions and their crude intra- and extracellular organic extracts were screened by ¹H NMR and a series of bioassays. Using this as a basis, one isolate was selected for further study. By analyses of the lTS1 region of the ribosomal DNA, the fungal isolate was identified as a marine-derived isolate of Eurotium rubrum (Aspergillus ruber). Although E. rubrum has been isolated from the marine environment, no investigations have been undertaken to determine the adaptation of these isolates to the marine environment. In order to optimise productivity, creativity and incubation time, the fungus was cultivated in small-scale using a variety of carbon (glucose, fructose, lactose, sucrose, marmitol and maltose) and nitrogen sources (ammonium tartrate, urea, peptone and yeast extract). An HPLC-DAD method was developed to assess the metabolic creativity and productivity under different fermentation conditions. Distinctive variations in the range and yield of metabolites produced as well as morphology and growth time were observed. The crude extracts from all fermentations were combined and six known compounds were isolated by reversed-phase chromatography and their structures elucidated by spectroscopic techniques. The known compounds were fIavoglaucin, aspergin, isodihydroauroglaucin, isotetrahydroauroglaucin, neoechinuline A and physcion. Neoechinuline A, isodihydroauroglaucin and isotetrahydroauroglaucin showed activity against oesophageal and cervical cancer cell lines.
- Full Text:
- Date Issued: 2005
- Authors: Pather, Simisha
- Date: 2005 , 2013-06-18
- Subjects: Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3839 , http://hdl.handle.net/10962/d1007652 , Marine biotechnology , Marine fungi -- South Africa , Natural products -- South Africa , Marine plants -- South Africa , Marine metabolites -- South Africa , Cancer -- Treatment , DNA
- Description: One of the major impediments in the development of marine natural products is the provision of biologically active natural products in sufficient quantity for complete pharmacological evaluation, clinical trials and eventual commercial production. Marine microorganisms show great promise in providing a renewable source of biologically active natural products. The main aim of this study was to develop and evaluate methods for the isolation, identification and cultivation of marine fungi from the South African marine environment for the production of biologically active secondary metabolites. Twenty-four species of fungi were isolated from marine algae collected from the intertidal zone near Port Alfred, South Africa. The fungi were cultivated in small-scale under static and agitated conditions and their crude intra- and extracellular organic extracts were screened by ¹H NMR and a series of bioassays. Using this as a basis, one isolate was selected for further study. By analyses of the lTS1 region of the ribosomal DNA, the fungal isolate was identified as a marine-derived isolate of Eurotium rubrum (Aspergillus ruber). Although E. rubrum has been isolated from the marine environment, no investigations have been undertaken to determine the adaptation of these isolates to the marine environment. In order to optimise productivity, creativity and incubation time, the fungus was cultivated in small-scale using a variety of carbon (glucose, fructose, lactose, sucrose, marmitol and maltose) and nitrogen sources (ammonium tartrate, urea, peptone and yeast extract). An HPLC-DAD method was developed to assess the metabolic creativity and productivity under different fermentation conditions. Distinctive variations in the range and yield of metabolites produced as well as morphology and growth time were observed. The crude extracts from all fermentations were combined and six known compounds were isolated by reversed-phase chromatography and their structures elucidated by spectroscopic techniques. The known compounds were fIavoglaucin, aspergin, isodihydroauroglaucin, isotetrahydroauroglaucin, neoechinuline A and physcion. Neoechinuline A, isodihydroauroglaucin and isotetrahydroauroglaucin showed activity against oesophageal and cervical cancer cell lines.
- Full Text:
- Date Issued: 2005
Material characterisation of laser formed dual phase steel components
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
- Authors: Els-Botes, Annelize
- Date: 2005
- Subjects: Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Language: English
- Type: Thesis , Doctoral , DTech
- Identifier: vital:9609 , http://hdl.handle.net/10948/176 , Steel -- Fatigue , Bending , Lasers , Sheet-steel -- Effect of lasers on
- Description: The nature and scope of this thesis can be divided into four categories: • FORMING PARAMETERS • Identification of various laser forming parameters in order to produce specimens of similar dimension (radius of curvature). • TEMPERATURE AND MICROSTRUCTURE • To study the effect of maximum temperature reached during the forming operation on the microstructure of the various specimens. • FATIGUE LIFE • Compare the fatigue life of the specimens produced by various laser parameters to that of the original material, and also the fatigue life of mechanical formed specimens. • RESIDUAL STRESS PROFILE Determine if the laser forming process induces detrimental residual stress magnitudes in the specimens. The main objective of this thesis was to gain an understanding of the way in which laser forming affects the fatigue performance and residual stress magnitude / distribution of dual phase steel. Although lasers have been used successfully in various manufacturing processes (welding, cutting, marking, etc.), little information is available on the influence of laser forming on many automotive alloys such as dual phase steel. The first part of the work involved a literature review of the process and factors affecting the laser forming process. It became clear from the literature overview that laser forming of sheet material thicker than 1mm is complex in nature. The variables that can influence the process are complicated and their interaction with each other is not easily controlled. The main parameters that were thus controlled in this study are as follows: • Laser power (P) • Laser head travel speed (v) • Laser beam size (mm) The chapters that follow the literature review, deals with the laser forming process of dual phase steel and the production of fatigue specimens using various laser parameters. It was found that the following laser parameters resulted in specimens with approximately the same radius of curvature: Laser power KW Beam diameter mm Interval spacing % Overlap Scanning velocity m/min Line Energy J/m 5 20 10 50 2,5 2000 3,1 14 10,5 25 2 1550 1,5 7,5 7,5 0 1,2 1250 From the results obtained from fatigue testing specimens produced with the above settings, it is clear that the laser forming process has the potential to be employed as a production stage in the manufacture of wheel centre discs while maintaining adequate fatigue strength. Large beam diameters which cause heat penetration through the thickness of the specimen and hence microstructure breakdown should be avoided, since it was shown that these specimens exhibited impaired mechanical properties than those produced with a smaller laser beam diameter. The microstructural changes observed during the forming process needs to be considered since the mechanical properties of the material changes with a change in microstructure. A dramatic change in microstructure was observed; therefore it is of crucial importance that microstructural evaluation plays an important part in deciding optimum laser parameters for the forming process of ferrous alloys. During residual stress analysis, trends were observed between measurements taken at the same location of the samples; regardless whether measurements were taken on the laser irradiated side or the reverse side of the specimen. The only difference was the magnitude of the relieved residual stress. In most cases the obtained relieved residual stress was much smaller in magnitude than that of the original plate (in the bulk of the material). The surface indicated a slight tensile residual stress for most samples evaluated. A good correlation in distribution profile was obtained between microhardness and relieved residual stress distribution at the ‘middle of sample’ location. This indicates that an increase in hardness indicates an increase in residual stress magnitude for the laser formed specimens. In conclusion, this research has proved that it is possible to deform metal plate of a 3,5mm thickness with a CO2 laser system. The research also established the effect of process parameters on the final product’s shape/bend angle and characterised the effect of the laser forming process on the material’s mechanical properties and structural integrity.
- Full Text:
- Date Issued: 2005
Metalorganic vapour phase epitaxial growth and characterisation of Sb-based semiconductors
- Authors: Vankova, Viera
- Date: 2005
- Subjects: Compound semiconductors , Epitaxy , Organometallic compounds , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10548 , http://hdl.handle.net/10948/d1019678
- Description: This study focuses on the growth and characterization of epitaxial InAs and InAs1-xSbx. Layers are grown on InAs, GaAs and GaSb substrates by metalorganic vapour phase epitaxy, using trimethylindium, trimethylantimony and arsine as precursors. The growth parameters (V/III ratio, Sb vapour phase compositions) are varied in the temperature range from 500 ºC to 700 ºC, in order to study the influence of these parameters on the structural, optical and electrical properties of the materials. The layers were assessed by X-ray diffraction, electron and optical microscopy, photoluminescence and Hall measurements. Furthermore, the influence of hydrogenation and annealing on the electrical and optical properties of GaSb was investigated. It is shown that the growth temperature and the V/III ratio play a vital role in the resulting surface morphology of homoepitaxial and heteroepitaxial InAs layers. Growth at low temperatures is found to promote three-dimensional growth in both cases, with improvements in the surface morphologies observed for higher growth temperatures. All the investigated epilayers are n-type. It is shown that the electrical properties of heteroepitaxial InAs epilayers are complicated by a competition between bulk conduction and conduction due to a surface accumulation and an interface layer. The low temperature photoluminescence spectra of homoepitaxial InAs are dominated by two transitions. These are identified as band-to-band/excitonic and donor-acceptor recombination. The incorporation efficiency of antimony (Sb) into InAs1-xSbx is dependent on the growth temperature and the V/III ratio. Under the growth conditions used in this study, the incorporation efficiency of Sb is controlled by the thermal stability of the two constituent binaries (i.e. InAs and InSb). Changes in the low temperature photoluminescence spectra are detected with increasing x. From temperature and laser power dependent measurements, the highest energy line is attributed to band-to-band/excitonic recombination, while the peak appearing approximately 15 meV below this line is assigned to donor-acceptor recombination. The origin of an additional “moving” peak observed for higher Sb mole fraction x is tentatively attributed to quasi-donor-acceptor-recombination, arising from increased impurity/defect concentrations and a higher compensation ratio in the material. However, the unusual behaviour of this peak may also be ascribed to the presence of some degree of ordering in InAsSb. The exposure of a semiconductor to a hydrogen plasma usually leads to the passivation of shallow and deep centres, thereby removing their electrical and optical activity. In this study, the passivation and thermal stability of the native acceptor in p-type GaSb is also investigated. It is shown that this acceptor can be passivated, where after improvements in the electrical and optical properties of GaSb are observed. Upon annealing the passivated samples above 300 °C, the acceptor is reactivated.
- Full Text:
- Date Issued: 2005
- Authors: Vankova, Viera
- Date: 2005
- Subjects: Compound semiconductors , Epitaxy , Organometallic compounds , Metal organic chemical vapor deposition
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10548 , http://hdl.handle.net/10948/d1019678
- Description: This study focuses on the growth and characterization of epitaxial InAs and InAs1-xSbx. Layers are grown on InAs, GaAs and GaSb substrates by metalorganic vapour phase epitaxy, using trimethylindium, trimethylantimony and arsine as precursors. The growth parameters (V/III ratio, Sb vapour phase compositions) are varied in the temperature range from 500 ºC to 700 ºC, in order to study the influence of these parameters on the structural, optical and electrical properties of the materials. The layers were assessed by X-ray diffraction, electron and optical microscopy, photoluminescence and Hall measurements. Furthermore, the influence of hydrogenation and annealing on the electrical and optical properties of GaSb was investigated. It is shown that the growth temperature and the V/III ratio play a vital role in the resulting surface morphology of homoepitaxial and heteroepitaxial InAs layers. Growth at low temperatures is found to promote three-dimensional growth in both cases, with improvements in the surface morphologies observed for higher growth temperatures. All the investigated epilayers are n-type. It is shown that the electrical properties of heteroepitaxial InAs epilayers are complicated by a competition between bulk conduction and conduction due to a surface accumulation and an interface layer. The low temperature photoluminescence spectra of homoepitaxial InAs are dominated by two transitions. These are identified as band-to-band/excitonic and donor-acceptor recombination. The incorporation efficiency of antimony (Sb) into InAs1-xSbx is dependent on the growth temperature and the V/III ratio. Under the growth conditions used in this study, the incorporation efficiency of Sb is controlled by the thermal stability of the two constituent binaries (i.e. InAs and InSb). Changes in the low temperature photoluminescence spectra are detected with increasing x. From temperature and laser power dependent measurements, the highest energy line is attributed to band-to-band/excitonic recombination, while the peak appearing approximately 15 meV below this line is assigned to donor-acceptor recombination. The origin of an additional “moving” peak observed for higher Sb mole fraction x is tentatively attributed to quasi-donor-acceptor-recombination, arising from increased impurity/defect concentrations and a higher compensation ratio in the material. However, the unusual behaviour of this peak may also be ascribed to the presence of some degree of ordering in InAsSb. The exposure of a semiconductor to a hydrogen plasma usually leads to the passivation of shallow and deep centres, thereby removing their electrical and optical activity. In this study, the passivation and thermal stability of the native acceptor in p-type GaSb is also investigated. It is shown that this acceptor can be passivated, where after improvements in the electrical and optical properties of GaSb are observed. Upon annealing the passivated samples above 300 °C, the acceptor is reactivated.
- Full Text:
- Date Issued: 2005
Modeling and measurement of torqued procession in radio pulsars
- Authors: Tiplady, Adrian John
- Date: 2005
- Subjects: Pulsars , Radio telescopes , Radio astronomy , Precession , Hartebeeshoek Radio Astronomy Observatory (HartRAO)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5475 , http://hdl.handle.net/10962/d1005260
- Description: The long term isolated pulsar monitoring program, which commenced in 1984 using the 26 m radio telescope at the Hartebeeshoek Radio Astronomy Observatory (HartRAO), has produced high resolution timing residual data over long timespans. This has enabled the analysis of observed spin down behaviour for 27 braking pulsars, most of which have dataspans longer than 14 years. The phenomenology of observed timing residuals of certain pulsars can be explained by pseudo periodic effects such as precession. Analytic and numerical models are developed to study the kinematic and dynamic behaviour of isolated but torqued precessing pulsars. The predicted timing residual behaviour of the models is characterised, and confronted with timing data from selected pulsars. Cyclic variations in the observed timing residuals of PSR B1642-03, PSR B1323-58 and PSR B1557-50 are fitted with a torqued precession model. The phenomenology of the observed timing behaviour of these pulsars can be explained by the precession models, but precise model fitting was not possible. This is not surprising given that the complexity of the pulsar systems is not completely described by the model. The extension of the pulsar monitoring program at HartRAO is used as motivation for the design and development of a new low cost, multi-purpose digital pulsar receiver. The instrument is implemented using a hybrid filterbank architecture, consisting of an analogue frontend and digital backend, to perform incoherent dedispersion. The design of a polyphase filtering system, which will consolidate multiple processing units into a single filtering solution, is discussed for future implementation.
- Full Text:
- Date Issued: 2005
- Authors: Tiplady, Adrian John
- Date: 2005
- Subjects: Pulsars , Radio telescopes , Radio astronomy , Precession , Hartebeeshoek Radio Astronomy Observatory (HartRAO)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5475 , http://hdl.handle.net/10962/d1005260
- Description: The long term isolated pulsar monitoring program, which commenced in 1984 using the 26 m radio telescope at the Hartebeeshoek Radio Astronomy Observatory (HartRAO), has produced high resolution timing residual data over long timespans. This has enabled the analysis of observed spin down behaviour for 27 braking pulsars, most of which have dataspans longer than 14 years. The phenomenology of observed timing residuals of certain pulsars can be explained by pseudo periodic effects such as precession. Analytic and numerical models are developed to study the kinematic and dynamic behaviour of isolated but torqued precessing pulsars. The predicted timing residual behaviour of the models is characterised, and confronted with timing data from selected pulsars. Cyclic variations in the observed timing residuals of PSR B1642-03, PSR B1323-58 and PSR B1557-50 are fitted with a torqued precession model. The phenomenology of the observed timing behaviour of these pulsars can be explained by the precession models, but precise model fitting was not possible. This is not surprising given that the complexity of the pulsar systems is not completely described by the model. The extension of the pulsar monitoring program at HartRAO is used as motivation for the design and development of a new low cost, multi-purpose digital pulsar receiver. The instrument is implemented using a hybrid filterbank architecture, consisting of an analogue frontend and digital backend, to perform incoherent dedispersion. The design of a polyphase filtering system, which will consolidate multiple processing units into a single filtering solution, is discussed for future implementation.
- Full Text:
- Date Issued: 2005
Motopomo: the historical-theoretical background to contemporary graphic design practices
- Authors: Economou, Inge
- Date: 2005
- Subjects: Graphic arts , Graphic arts -- 20th century , Modernism (Art)
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10764 , http://hdl.handle.net/10948/179 , Graphic arts , Graphic arts -- 20th century , Modernism (Art)
- Description: This study proposes to illustrate that the twentieth century passage from modernity to postmodernity, with its induction of socio-cultural development and attitudinal change, exists as a fundamental means of informing the character of contemporary graphic design practice1. Today, in contrast to the intentions of this study, many appraisals of graphic design work would seem to place too much emphasis on the analyses and evaluation of the stylistic character of creative practices and not enough on the theoretical, historical and attitudinal issues surrounding them. As such, this study attempts to reveal the meaning and moreover the relevance of philosophical, social, cultural and critical theory for contemporary, postmodern graphic design practices. This is done in order to provide graphic designers with a reflective awareness of the structure of the cultural context within which they work, and takes into account twentieth century cultural theory and twentieth century, western graphic design practice, within the framework of the passage from modernity to postmodernity.
- Full Text:
- Date Issued: 2005
- Authors: Economou, Inge
- Date: 2005
- Subjects: Graphic arts , Graphic arts -- 20th century , Modernism (Art)
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10764 , http://hdl.handle.net/10948/179 , Graphic arts , Graphic arts -- 20th century , Modernism (Art)
- Description: This study proposes to illustrate that the twentieth century passage from modernity to postmodernity, with its induction of socio-cultural development and attitudinal change, exists as a fundamental means of informing the character of contemporary graphic design practice1. Today, in contrast to the intentions of this study, many appraisals of graphic design work would seem to place too much emphasis on the analyses and evaluation of the stylistic character of creative practices and not enough on the theoretical, historical and attitudinal issues surrounding them. As such, this study attempts to reveal the meaning and moreover the relevance of philosophical, social, cultural and critical theory for contemporary, postmodern graphic design practices. This is done in order to provide graphic designers with a reflective awareness of the structure of the cultural context within which they work, and takes into account twentieth century cultural theory and twentieth century, western graphic design practice, within the framework of the passage from modernity to postmodernity.
- Full Text:
- Date Issued: 2005
On the growth and characterisation of AIGaN alloys for optoelectronic applications
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
- Authors: James, Grant Robert
- Date: 2005
- Subjects: Gallium nitride -- Electric properties , Photoluminescence
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8824 , vital:26433
- Description: In this study the growth and characterisation of undoped and Si-doped AlxGa1-xN has been performed. The layers were grown using low-pressure metalorganic vapour phase deposition (MOCVD) on sapphire substrates. The optical and electrical properties of the AlxGa1-xN layers were studied using variable temperature Hall effect and photoluminescence measurements. AlxGa1-xN layers were grown over the entire composition range. Room temperature ultraviolet (UV) transmission measurements showed that the material quality was very good for layers with an Al content, x, of 0 _ x _ 0.5. However, the quality of layers of higher composition was seen to rapidly decrease with increasing x. The electrical and optical properties of AlxGa1-xN with x < 0.5 were also good, comparable to those reported on in literature. The study of the Si-doping of AlxGa1-xN was performed in two parts; firstly a series of Al0.23Ga0.77N samples was grown in which the doping level was increased from zero to n _ 3 × 1018 cm-3. A similar, albeit a less rigorous, study was performed for Al0.41Ga0.59N and Al0.5Ga0.5N. A second series of samples was then grown in which the doping level was kept constant, while the Al content was incrementally increased. Room temperature Hall effect measurements performed on Si-doped Al0.23Ga0.77N showed that the electron concentration did not scale linearly with the silane flow, as was the case in GaN. It was also seen that the electron mobility of the layers increased with slight Si-doping, possibly due to an improvement in the crystalline quality and/or a change in the conduction mechanism. It was also found that at higher compositions (x = 0.41 and 0.50) an increase in the doping level resulted in an increase in the mobility. Variable temperature Hall effect and photoluminescence measurements, performed on the Al0.23Ga0.77N samples, revealed a good correlation between the first PL activation energy E1 and the donor activation energy ED, prompting the conclusion that the first PL recombination channel in AlxGa1-xN is due to the delocalisation of excitons bound at neutral Si donors. Furthermore, E1 and ED were seen to decrease with n1/3, as is the case for GaN and other semiconductor materials. It was also observed that strong exciton localisation occurs in slightly Si-doped material, with the amount of localization becoming less at higher doping levels. Possible mechanisms responsible for the second PL recombination channel of activation energy E2 were also proposed. The electrical and optical properties of the second set of AlxGa1-xN samples was then studied. The PL properties of undoped AlxGa1-xN were typical of a homogeneous alloy system, with the increase in the PL FWHM and exciton localisation energies with x following the trend predicted by alloy disorder theory. The variation of the band gap energy with the Al content could not, however, be fitted over the entire composition range using a single bowing parameter. It was proposed that this was due either to an effect of the 9 7 valence band crossover, or due to exciton localisation at alloy disorder and/or impurities. As was the case for GaN and Al0.23Ga0.77N, all undoped material was highly resistive. As was mentioned earlier, the exciton localisation energies increased according to alloy disorder theory in undoped AlxGa1-xN. In the doped samples, however, a large increase in the donor localisation energy was measured for x > 0.3. The possibility that Si could become a DX-centre in AlxGa1-xN was then investigated. However, Hall effect measurements showed that the Si activation energy increased in good agreement with the model of a shallow effective mass state donor, with no sudden increase in ED being observed up to x = 0.4. It was then suggested that the increase in the E1 and E2 activation energies, as well as the exciton localisation energies, could be due to the 9 7 valence band crossover, which occurs at roughly the same composition. However, due to the scarcity of reports on the valence band structure in AlxGa1-xN no conclusions could be made at this stage as to the effect of the 9 7 valence band crossover on the PL properties of AlxGa1-xN.
- Full Text:
- Date Issued: 2005
Operationally defining sexual orientation : towards the development of a fundamental measure of adolescent sexual responsiveness variations
- Authors: Heath, Lance Julian
- Date: 2005
- Subjects: Sexual orientation Homosexuality Psychometrics Teenagers--Sexual behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1681 , http://hdl.handle.net/10962/d1003564
- Description: Much published work has pointed to the need for the development of a sound operational definition of sexual orientation in order to enable the research in this area to progress. To contribute to this process the current research set out to develop two measures of sexual orientation and examine their psychometric properties. In order to develop relevant tools historical, conceptual and operational definitions of sexual orientation were critically examined and standard questionnaire development techniques applied. The first scale consisted of 32 items and was administered to a total of 835 adolescents, comprising three sub-groups (189 Grade 11 Scholars, 547 First Year and 99 Third Year Psychology Students). A Cronbach alpha coefficient of 0.85 was calculated indicating that this instrument had very good internal consistency reliability. Similar factors emerged in each of the sample sub-groups when factor analyses were performed suggesting that this instrument has good external and construct validities. These factors each had respectable Cronbach alpha coefficients indicating their own internal consistency. The four factors which consistently emerged were Same Sex Responsiveness, Opposite Sex Responsiveness, Previous Month’s Same Sex Responsiveness and Previous Month’s Opposite Sex Responsiveness. The second scale consisted of 16 items and was administered to 646 adolescents, comprising the latter two sub-groups referred to above. A Cronbach alpha coefficient of 0.82 was calculated indicating that this instrument also had very good internal consistency reliability. Once again similar factors with generally good internal consistency emerged in factor analysis suggesting that this too was a valid instrument. The factors that emerged from the second scale were Same Sex Responsiveness, Unattractive Opposite Sex Responsiveness, Attractive Opposite Sex Responsiveness and Attraction. Future developments, adjustments and applications of the instruments as well as implications for the arena of sexual orientation research are discussed. In the light of the dearth of information with regard to the sexual orientations of South African adolescents the current study also briefly explored and presented the sample’s responses in terms of the dimensions of each questionnaire as well as how each emerging factor related to the demographics (education level, gender, sexual orientation self-label and age) of the sample.
- Full Text:
- Date Issued: 2005
- Authors: Heath, Lance Julian
- Date: 2005
- Subjects: Sexual orientation Homosexuality Psychometrics Teenagers--Sexual behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1681 , http://hdl.handle.net/10962/d1003564
- Description: Much published work has pointed to the need for the development of a sound operational definition of sexual orientation in order to enable the research in this area to progress. To contribute to this process the current research set out to develop two measures of sexual orientation and examine their psychometric properties. In order to develop relevant tools historical, conceptual and operational definitions of sexual orientation were critically examined and standard questionnaire development techniques applied. The first scale consisted of 32 items and was administered to a total of 835 adolescents, comprising three sub-groups (189 Grade 11 Scholars, 547 First Year and 99 Third Year Psychology Students). A Cronbach alpha coefficient of 0.85 was calculated indicating that this instrument had very good internal consistency reliability. Similar factors emerged in each of the sample sub-groups when factor analyses were performed suggesting that this instrument has good external and construct validities. These factors each had respectable Cronbach alpha coefficients indicating their own internal consistency. The four factors which consistently emerged were Same Sex Responsiveness, Opposite Sex Responsiveness, Previous Month’s Same Sex Responsiveness and Previous Month’s Opposite Sex Responsiveness. The second scale consisted of 16 items and was administered to 646 adolescents, comprising the latter two sub-groups referred to above. A Cronbach alpha coefficient of 0.82 was calculated indicating that this instrument also had very good internal consistency reliability. Once again similar factors with generally good internal consistency emerged in factor analysis suggesting that this too was a valid instrument. The factors that emerged from the second scale were Same Sex Responsiveness, Unattractive Opposite Sex Responsiveness, Attractive Opposite Sex Responsiveness and Attraction. Future developments, adjustments and applications of the instruments as well as implications for the arena of sexual orientation research are discussed. In the light of the dearth of information with regard to the sexual orientations of South African adolescents the current study also briefly explored and presented the sample’s responses in terms of the dimensions of each questionnaire as well as how each emerging factor related to the demographics (education level, gender, sexual orientation self-label and age) of the sample.
- Full Text:
- Date Issued: 2005
Optimising the material distribution process for the southern region of Telkom SA
- Authors: Naicker, Kosalin Ganasen
- Date: 2005
- Subjects: Business logistics -- South Africa , Telecommunication -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8547 , http://hdl.handle.net/10948/407 , Business logistics -- South Africa , Telecommunication -- South Africa
- Description: Most government owned telecommunication operators across the world have to deal with a number of regulatory, technology and service challenges, as the industry is liberalised in co-ordinance with worldwide trends. Telkom SA will be facing a number of strategic challenges that will test its ability to survive as a telecommunications company over the next number of years. To remain competitive, Telkom must develop strategies to assure survival in a competitive environment. To assure the long-term survival of Telkom SA when moving into a competitive environment, the organisation must build a sustainable competitive advantage. In the face of increasingly fierce competition, the adoption of collaborative alliances between firms is becoming more and more common and the adoption of a world-class supply chain will be an ideal scenario for Telkom SA. A worldclass supply chain goes beyond the scope of the internal operations of an organisation, therefore the material distribution process was chosen for this study, which involved the internal operations in the organisation. The study included the availability of material up to the transportation of the material to the staging areas. The aim of this research was to identify the inefficiencies of the material distribution process of the Southern Region of Telkom SA to become worldclass. A quantitative technique was used to identify the inefficiencies. It was found that the availability and transportation of material were the inefficient categories, preventing the customer to receive the product or service on time. Communication, inaccurate forecasting and inefficient transportation of material were some of the reasons for not delivering material on time. Some of the recommendations included developing a model that could overcome the current inefficiencies in transportation, improving the communication channels, training and the development of employees at all levels.
- Full Text:
- Date Issued: 2005
- Authors: Naicker, Kosalin Ganasen
- Date: 2005
- Subjects: Business logistics -- South Africa , Telecommunication -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8547 , http://hdl.handle.net/10948/407 , Business logistics -- South Africa , Telecommunication -- South Africa
- Description: Most government owned telecommunication operators across the world have to deal with a number of regulatory, technology and service challenges, as the industry is liberalised in co-ordinance with worldwide trends. Telkom SA will be facing a number of strategic challenges that will test its ability to survive as a telecommunications company over the next number of years. To remain competitive, Telkom must develop strategies to assure survival in a competitive environment. To assure the long-term survival of Telkom SA when moving into a competitive environment, the organisation must build a sustainable competitive advantage. In the face of increasingly fierce competition, the adoption of collaborative alliances between firms is becoming more and more common and the adoption of a world-class supply chain will be an ideal scenario for Telkom SA. A worldclass supply chain goes beyond the scope of the internal operations of an organisation, therefore the material distribution process was chosen for this study, which involved the internal operations in the organisation. The study included the availability of material up to the transportation of the material to the staging areas. The aim of this research was to identify the inefficiencies of the material distribution process of the Southern Region of Telkom SA to become worldclass. A quantitative technique was used to identify the inefficiencies. It was found that the availability and transportation of material were the inefficient categories, preventing the customer to receive the product or service on time. Communication, inaccurate forecasting and inefficient transportation of material were some of the reasons for not delivering material on time. Some of the recommendations included developing a model that could overcome the current inefficiencies in transportation, improving the communication channels, training and the development of employees at all levels.
- Full Text:
- Date Issued: 2005