An erosion hazard assessment technique for Ciskei
- Authors: Weaver, Alex van Breda
- Date: 1989
- Subjects: Soil erosion -- South Africa -- Ciskei
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4792 , http://hdl.handle.net/10962/d1001892
- Description: The study examines the relationship between the spatial variation in soil erosion and various natural and anthropogenic attributes of the region between the coastal plateau and the Winterberg escarpment of Ciskei. A raster-based geographical information system is derived for four separate study catchments and data on soil erosion and various soil erosion hazard indices are read into a computerised data matrix. The independent variables (soil erosion hazard indices) used in the study are selected on the basis of a review of the literature and on the availability of data in the Ciskei region. Multivariate analyses of the relationship between soil erosion and the various independent variables reveals that the primary variables affecting the spatial variation in soil erosion are land use, dominant soil type, geology, veld type and mean annual precipitation. All of these variables are readily quantifiable at the regional scale for large areas of Ciskei. An erosion hazard assessment model for use in central Ciskei is developed based on the results of the statistical analyses. The model is tested in separate study areas and is shown to provide an efficient method of identifying areas of differing susceptibility to soil erosion. The derived model is simple to operate and has input requirements which are easily met. It can be applied without the aid of computers, or where large areas are to be mapped it is well suited to computerisation
- Full Text:
- Date Issued: 1989
- Authors: Weaver, Alex van Breda
- Date: 1989
- Subjects: Soil erosion -- South Africa -- Ciskei
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4792 , http://hdl.handle.net/10962/d1001892
- Description: The study examines the relationship between the spatial variation in soil erosion and various natural and anthropogenic attributes of the region between the coastal plateau and the Winterberg escarpment of Ciskei. A raster-based geographical information system is derived for four separate study catchments and data on soil erosion and various soil erosion hazard indices are read into a computerised data matrix. The independent variables (soil erosion hazard indices) used in the study are selected on the basis of a review of the literature and on the availability of data in the Ciskei region. Multivariate analyses of the relationship between soil erosion and the various independent variables reveals that the primary variables affecting the spatial variation in soil erosion are land use, dominant soil type, geology, veld type and mean annual precipitation. All of these variables are readily quantifiable at the regional scale for large areas of Ciskei. An erosion hazard assessment model for use in central Ciskei is developed based on the results of the statistical analyses. The model is tested in separate study areas and is shown to provide an efficient method of identifying areas of differing susceptibility to soil erosion. The derived model is simple to operate and has input requirements which are easily met. It can be applied without the aid of computers, or where large areas are to be mapped it is well suited to computerisation
- Full Text:
- Date Issued: 1989
An explication of the dual nature of narcissism in Patrick White's novel The solid mandala
- Authors: Watts, Jacqueline Anne
- Date: 1989
- Subjects: White, Patrick, 1912-1990. The Solid Mandala White, Patrick, 1912-1990 -- Criticism and interpretation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2907 , http://hdl.handle.net/10962/d1002072
- Description: The focus of this thesis has been to engage in a hermeneutic dialogue with Patrick White's novel The solid mandala, to provide an explication of the dual nature of narcissistic wounding. To this end a brief review of Patrick White's novels is given, which traces a thematic development of the hero's strivings to attain wholeness and merger with an idealized image. This struggle is understood to reflect man's strivings to return to a state of omnipotent fusion with the maternal image, be it God, nature, the idealized other, or the self. Literature which reflects the dual nature of narcissistic wounding is reviewed, and the concept of narcissism is traced from the historical roots of Freud, to current understandings of the function and experience of narcissism. Emphasis is given to understanding the experiential nature of narcissistic wounding. As such it is implied that narcissism is a normal developmental component which requires the facilitation of containment and reflection for its transformation into appropriate adult functioning. The importance of the maternal environment is discussed, together with the various theoretical conceptualizations of the consequences of failure of the environment. The hermeneutic dialogue with the novel's description of the experiences of the twins, Waldo and Arthur provides the basis for an amplification of the experience of narcissistic wounding. This amplification is used as clinical material from which a number of psychoanalytic formulations are drawn. These formulations are supported by a number of clinical examples from the researcher's own practice. There appears to be evidence for the value of focusing on the dual nature of the experience of narcissistic wounding. This focus reveals two aspects of experience, a damaged, positive, libidinal aspect and a defensive, pathological destructive aspect. Amplification of these two aspects of experience contribute to further the understanding of the conflictual experience of narcissistic wounding, and suggest the necessity for such an understanding for effective therapeutic intervention
- Full Text:
- Date Issued: 1989
- Authors: Watts, Jacqueline Anne
- Date: 1989
- Subjects: White, Patrick, 1912-1990. The Solid Mandala White, Patrick, 1912-1990 -- Criticism and interpretation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2907 , http://hdl.handle.net/10962/d1002072
- Description: The focus of this thesis has been to engage in a hermeneutic dialogue with Patrick White's novel The solid mandala, to provide an explication of the dual nature of narcissistic wounding. To this end a brief review of Patrick White's novels is given, which traces a thematic development of the hero's strivings to attain wholeness and merger with an idealized image. This struggle is understood to reflect man's strivings to return to a state of omnipotent fusion with the maternal image, be it God, nature, the idealized other, or the self. Literature which reflects the dual nature of narcissistic wounding is reviewed, and the concept of narcissism is traced from the historical roots of Freud, to current understandings of the function and experience of narcissism. Emphasis is given to understanding the experiential nature of narcissistic wounding. As such it is implied that narcissism is a normal developmental component which requires the facilitation of containment and reflection for its transformation into appropriate adult functioning. The importance of the maternal environment is discussed, together with the various theoretical conceptualizations of the consequences of failure of the environment. The hermeneutic dialogue with the novel's description of the experiences of the twins, Waldo and Arthur provides the basis for an amplification of the experience of narcissistic wounding. This amplification is used as clinical material from which a number of psychoanalytic formulations are drawn. These formulations are supported by a number of clinical examples from the researcher's own practice. There appears to be evidence for the value of focusing on the dual nature of the experience of narcissistic wounding. This focus reveals two aspects of experience, a damaged, positive, libidinal aspect and a defensive, pathological destructive aspect. Amplification of these two aspects of experience contribute to further the understanding of the conflictual experience of narcissistic wounding, and suggest the necessity for such an understanding for effective therapeutic intervention
- Full Text:
- Date Issued: 1989
Grahamstown: a socio-ecological study of a small South African Town
- Authors: Watts, Hilstan Lett
- Date: 1958
- Subjects: Grahamstown (South Africa) -- Buildings , Grahamstown (South Africa) -- History , Grahamstown (South Africa) -- Social conditions , Grahamstown (South Africa) -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3386 , http://hdl.handle.net/10962/d1013424
- Description: Little is known at present about the development, structure, and functions of small towns in the Union of South Africa, and there is a need to fill this gap in our knowledge. A study has been made of Grahamstown, a small South African town. This study is monographic and intensive in character, and heuristic in aim. Ad hoc hypotheses have been formulated on the basis of the findings of the study, and these must be tested by subsequent studies of other small towns. Grahamstown, the subject of the study, was chosen largely for reasons of convenience, and also because of its interesting development. It is suggested that in many ways the town is possibly a typical small town, but at this stage we cannot know if this is so. Only the white population of the town was investigated, as it was necessary to limit research to manageable proportions, and in addition several studies have already been made of the non-white populations of the town. The analysis has been described as socio-ecological, as basically the methodological approach used is an attempt to wed the methods of the urban demographer and the social ecologist. Time and space are used as the two co-ordinates for the analysis, so that both a social historical and an ecological-demographic analysis of the town have been made. The historical analysis of the development and functions of Grahamstown relies heavily on material collected from the early newspapers of the town. Grahamstown, once the most important town in the Eastern Cape Province, known as the ''Emporium" and ''Metropolis" of the Eastern Cape, and the most progressive town in the Colony, is to-day a small static town with, on the whole, relatively restricted influence. This fundamental change in the historical development of the town, hitherto unexplained, is the result of the changes in the socioecological make-up of the region around the town. Founded in 1812 as a strategic outpost on the frontier of the Colony, Grahamstown dominated a wide region; as the gateway to and the supply centre for, the frontier, the town flourished and reigned supreme. From the mid 19th Century onwards the region began to change to a developed one, with the frontier more and more inland. Grahamstown, no longer a strategic outpost in a frontier region, lost its dominant ecological position to Port Elizabeth, the natural supply base for, and gateway to, the new settled region. As one town among many in the new settled region, Grahamstown gradually lost many of its former functions, and began to stagnate. The town is to-day mainly known for its important educational function. This function, a relic from the days of the town's zenith, has saved the town from complete stagnation. The town is what it is to-day largely because of the socio-ecological regional influences which have operated on it since its foundation. To-day Grahamstown is located within the Port Elizabeth metropolitan district. The town is the centre of a wide variety of regional services of an ad hoc type, and the modal region served seems to be that settled by the 1820 Settlers - basically the town is mainly a supply centre for its surrounding rural areas. The demographic structure of the town reveals a static population. Growth of the white population has been practically static since about 1880, and the age structure is that of a stationary population. Particularly noticeable is the under-representation of the young working group in the population, and it is suggested that due to the lack of economic opportunities in the town, the young workers of the town, especially the unmarried males, migrate to larger urban areas to seek employment, and advancement. The sex-ratio of the population shows an excess of females, and this may be due to migration out of an excess of young males, and possibly migration in of older spinsters. Retired persons definitely migrate to the town to settle. The town, a predominantly English speaking one, has practically no industries, and so the population contains a majority of workers engaged in professional, administrative, and commercial activities. This stresses the service and supply functions of the town. The ecological analysis delineated various natural areas and zones in the town. The pattern approximates to patterns revealed by studies of American towns. Although the areas involved were relatively small, ecological differentiation was marked. The spatial distribution of demographic and other social phenomena was studied in detail. The results of the study have allowed several ad hoc hypotheses concerning the development, functions, and structures of small towns in South Africa to be formulated. These may be tested by subsequent studies, and so ultimately knowledge and theories about our small towns may be built up.
- Full Text:
- Date Issued: 1958
- Authors: Watts, Hilstan Lett
- Date: 1958
- Subjects: Grahamstown (South Africa) -- Buildings , Grahamstown (South Africa) -- History , Grahamstown (South Africa) -- Social conditions , Grahamstown (South Africa) -- Economic conditions
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3386 , http://hdl.handle.net/10962/d1013424
- Description: Little is known at present about the development, structure, and functions of small towns in the Union of South Africa, and there is a need to fill this gap in our knowledge. A study has been made of Grahamstown, a small South African town. This study is monographic and intensive in character, and heuristic in aim. Ad hoc hypotheses have been formulated on the basis of the findings of the study, and these must be tested by subsequent studies of other small towns. Grahamstown, the subject of the study, was chosen largely for reasons of convenience, and also because of its interesting development. It is suggested that in many ways the town is possibly a typical small town, but at this stage we cannot know if this is so. Only the white population of the town was investigated, as it was necessary to limit research to manageable proportions, and in addition several studies have already been made of the non-white populations of the town. The analysis has been described as socio-ecological, as basically the methodological approach used is an attempt to wed the methods of the urban demographer and the social ecologist. Time and space are used as the two co-ordinates for the analysis, so that both a social historical and an ecological-demographic analysis of the town have been made. The historical analysis of the development and functions of Grahamstown relies heavily on material collected from the early newspapers of the town. Grahamstown, once the most important town in the Eastern Cape Province, known as the ''Emporium" and ''Metropolis" of the Eastern Cape, and the most progressive town in the Colony, is to-day a small static town with, on the whole, relatively restricted influence. This fundamental change in the historical development of the town, hitherto unexplained, is the result of the changes in the socioecological make-up of the region around the town. Founded in 1812 as a strategic outpost on the frontier of the Colony, Grahamstown dominated a wide region; as the gateway to and the supply centre for, the frontier, the town flourished and reigned supreme. From the mid 19th Century onwards the region began to change to a developed one, with the frontier more and more inland. Grahamstown, no longer a strategic outpost in a frontier region, lost its dominant ecological position to Port Elizabeth, the natural supply base for, and gateway to, the new settled region. As one town among many in the new settled region, Grahamstown gradually lost many of its former functions, and began to stagnate. The town is to-day mainly known for its important educational function. This function, a relic from the days of the town's zenith, has saved the town from complete stagnation. The town is what it is to-day largely because of the socio-ecological regional influences which have operated on it since its foundation. To-day Grahamstown is located within the Port Elizabeth metropolitan district. The town is the centre of a wide variety of regional services of an ad hoc type, and the modal region served seems to be that settled by the 1820 Settlers - basically the town is mainly a supply centre for its surrounding rural areas. The demographic structure of the town reveals a static population. Growth of the white population has been practically static since about 1880, and the age structure is that of a stationary population. Particularly noticeable is the under-representation of the young working group in the population, and it is suggested that due to the lack of economic opportunities in the town, the young workers of the town, especially the unmarried males, migrate to larger urban areas to seek employment, and advancement. The sex-ratio of the population shows an excess of females, and this may be due to migration out of an excess of young males, and possibly migration in of older spinsters. Retired persons definitely migrate to the town to settle. The town, a predominantly English speaking one, has practically no industries, and so the population contains a majority of workers engaged in professional, administrative, and commercial activities. This stresses the service and supply functions of the town. The ecological analysis delineated various natural areas and zones in the town. The pattern approximates to patterns revealed by studies of American towns. Although the areas involved were relatively small, ecological differentiation was marked. The spatial distribution of demographic and other social phenomena was studied in detail. The results of the study have allowed several ad hoc hypotheses concerning the development, functions, and structures of small towns in South Africa to be formulated. These may be tested by subsequent studies, and so ultimately knowledge and theories about our small towns may be built up.
- Full Text:
- Date Issued: 1958
A history of the South African police in Port Elizabeth, 1913-1956
- Authors: Watson, Kelvin Innes
- Date: 2000
- Subjects: Police -- South Africa -- Eastern Cape South African Police -- South Africa -- Port Elizabeth -- History Police -- South Africa -- Port Elizabeth -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2570 , http://hdl.handle.net/10962/d1002423
- Description: This thesis investigates the policing activities of the South African Police (SAP) in Port Elizabeth from the formation of the SAP in 1913 to the creation of two separate police districts in the city in 1956. It begins with the recruitment and training of police personnel, outlining the difficulty in obtaining sufficient white recruits for most of the period while at the same time stressing the ease with which the Force was able to obtain black recruits. The preponderance of Afrikaner policemen serving in Port Elizabeth from the 1920s onwards is made clear, as is the para-military nature of the SAP, which was maintained and reinforced as a result of training methods and the process of socialisation. As state servants, police personnel were expected to serve loyally and obediently a state becoming increasingly repressive towards its black citizens. Generally inadequate conditions of service remained the norm throughout the period yet the SAP’s commitment to the state never wavered, bar one isolated, short-lived incidence. The administration and functioning of policing in Port Elizabeth is explored by focussing on specific organisational features pertinent to the city and the changes wrought by the police hierarchy to deal with the city’s demographic and spatial expansion. The SAP tended to employ three different forms of policing in the city as a result of its apartheid-driven agenda which compelled it to differentiate between the various population groups in terms of maintaining law and order. The privileged white community experienced routine, civil policing whereas the black community was policed largely in a socially and politically oppressive manner; this was in line with government policy. On the whole, however, the more brutal and sinister nature of policing was yet to come to the fore although this thesis does point towards the increasingly repressive nature of policing in South Africa during the apartheid era.
- Full Text:
- Date Issued: 2000
- Authors: Watson, Kelvin Innes
- Date: 2000
- Subjects: Police -- South Africa -- Eastern Cape South African Police -- South Africa -- Port Elizabeth -- History Police -- South Africa -- Port Elizabeth -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2570 , http://hdl.handle.net/10962/d1002423
- Description: This thesis investigates the policing activities of the South African Police (SAP) in Port Elizabeth from the formation of the SAP in 1913 to the creation of two separate police districts in the city in 1956. It begins with the recruitment and training of police personnel, outlining the difficulty in obtaining sufficient white recruits for most of the period while at the same time stressing the ease with which the Force was able to obtain black recruits. The preponderance of Afrikaner policemen serving in Port Elizabeth from the 1920s onwards is made clear, as is the para-military nature of the SAP, which was maintained and reinforced as a result of training methods and the process of socialisation. As state servants, police personnel were expected to serve loyally and obediently a state becoming increasingly repressive towards its black citizens. Generally inadequate conditions of service remained the norm throughout the period yet the SAP’s commitment to the state never wavered, bar one isolated, short-lived incidence. The administration and functioning of policing in Port Elizabeth is explored by focussing on specific organisational features pertinent to the city and the changes wrought by the police hierarchy to deal with the city’s demographic and spatial expansion. The SAP tended to employ three different forms of policing in the city as a result of its apartheid-driven agenda which compelled it to differentiate between the various population groups in terms of maintaining law and order. The privileged white community experienced routine, civil policing whereas the black community was policed largely in a socially and politically oppressive manner; this was in line with government policy. On the whole, however, the more brutal and sinister nature of policing was yet to come to the fore although this thesis does point towards the increasingly repressive nature of policing in South Africa during the apartheid era.
- Full Text:
- Date Issued: 2000
A framework for interpreting noisy, two-dimensional images, based on a fuzzification of programmed, attributed graph grammars
- Authors: Watkins, Gregory Shroll
- Date: 1998
- Subjects: Music -- Data processing Computer sound processing Artificial intelligence -- Musical applications Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4604 , http://hdl.handle.net/10962/d1004862
- Description: This thesis investigates a fuzzy syntactic approach to the interpretation of noisy two-dimensional images. This approach is based on a modification of the attributed graph grammar formalism to utilise fuzzy membership functions in the applicability predicates. As far as we are aware, this represents the first such modification of graph grammars. Furthermore, we develop a method for programming the resultant fuzzy attributed graph grammars through the use of non-deterministic control diagrams. To do this, we modify the standard programming mechanism to allow it to cope with the fuzzy certainty values associated with productions in our grammar. Our objective was to develop a flexible framework which can be used for the recognition of a wide variety of image classes, and which is adept at dealing with noise in these images. Programmed graph grammars are specifically chosen for the ease with which they allow one to specify a new two-dimensional image class. We implement a prototype system for Optical Music Recognition using our framework. This system allows us to test the capabilities of the framework for coping with noise in the context of handwritten music score recognition. Preliminary results from the prototype system show that the framework copes well with noisy images.
- Full Text:
- Date Issued: 1998
- Authors: Watkins, Gregory Shroll
- Date: 1998
- Subjects: Music -- Data processing Computer sound processing Artificial intelligence -- Musical applications Fuzzy systems
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4604 , http://hdl.handle.net/10962/d1004862
- Description: This thesis investigates a fuzzy syntactic approach to the interpretation of noisy two-dimensional images. This approach is based on a modification of the attributed graph grammar formalism to utilise fuzzy membership functions in the applicability predicates. As far as we are aware, this represents the first such modification of graph grammars. Furthermore, we develop a method for programming the resultant fuzzy attributed graph grammars through the use of non-deterministic control diagrams. To do this, we modify the standard programming mechanism to allow it to cope with the fuzzy certainty values associated with productions in our grammar. Our objective was to develop a flexible framework which can be used for the recognition of a wide variety of image classes, and which is adept at dealing with noise in these images. Programmed graph grammars are specifically chosen for the ease with which they allow one to specify a new two-dimensional image class. We implement a prototype system for Optical Music Recognition using our framework. This system allows us to test the capabilities of the framework for coping with noise in the context of handwritten music score recognition. Preliminary results from the prototype system show that the framework copes well with noisy images.
- Full Text:
- Date Issued: 1998
An investigation into the bacterial biosynthetic origins of bioactive natural products isolated from South African latrunculid sponges
- Authors: Waterworth, Samantha Che
- Date: 2018
- Subjects: Marine biodiversity , Metagenomics , Sponges Biotechnology , Spirochetes , Natural products Biotechnology
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61826 , vital:28065
- Description: Several pyrroloiminoquinone alkaloids exhibiting cytotoxic, anti-tumour activity have been isolated from sponges within the Latrunculiidae family that are endemic to the South African coastline. Other, structurally similar pyrroloiminoquinone compounds have been isolated from geographically distant and phylogenetically distinct marine sponges, as well as terrestrial myxomycetes which suggested that sponge-associated bacteria may be the true biosynthetic origin of pyrroloiminoquinone compounds. Previous studies have shown that there is conservation of spirochete and betaproteobacterial species in the bacterial communities associated with South African Latrunculiidae sponges and it was proposed that these conserved bacteria represented candidate pyrroloiminoquinone-producers. This study aimed to confirm the conserved dominance of betaproteobacteria and spirochetes within bacterial communities associated with South African latrunculid sponges and employed a shotgun metagenomic approach to assess the functional and biosynthetic potential of associated microbiota in Tsitsikamma favus sponges. Clustering of assembled contigs revealed twenty-three putative bacterial genomes, of which, two were identified as representatives of the conserved betaproteobacteria and spirochete species previously identified in Tsitsikamma sponges. It was shown that the spirochete was most likely an obligate symbiont that benefitted the host sponge through possible defence against pathogenic bacteria and/or nutrient acquisition. The putative genome representing the conserved betaproteobacteria was found to be heavily contaminated and further sequencing is required to accurately resolve the genome for functional characterization. Several biosynthetic gene clusters were identified and demonstrated the bioactive potential of Tsitsikamma favus-associated bacteria. A biosynthetic gene cluster was identified on an unclustered contig that included several genetic features that were indicative of possible pyrroloiminoquinone production.
- Full Text:
- Date Issued: 2018
- Authors: Waterworth, Samantha Che
- Date: 2018
- Subjects: Marine biodiversity , Metagenomics , Sponges Biotechnology , Spirochetes , Natural products Biotechnology
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/61826 , vital:28065
- Description: Several pyrroloiminoquinone alkaloids exhibiting cytotoxic, anti-tumour activity have been isolated from sponges within the Latrunculiidae family that are endemic to the South African coastline. Other, structurally similar pyrroloiminoquinone compounds have been isolated from geographically distant and phylogenetically distinct marine sponges, as well as terrestrial myxomycetes which suggested that sponge-associated bacteria may be the true biosynthetic origin of pyrroloiminoquinone compounds. Previous studies have shown that there is conservation of spirochete and betaproteobacterial species in the bacterial communities associated with South African Latrunculiidae sponges and it was proposed that these conserved bacteria represented candidate pyrroloiminoquinone-producers. This study aimed to confirm the conserved dominance of betaproteobacteria and spirochetes within bacterial communities associated with South African latrunculid sponges and employed a shotgun metagenomic approach to assess the functional and biosynthetic potential of associated microbiota in Tsitsikamma favus sponges. Clustering of assembled contigs revealed twenty-three putative bacterial genomes, of which, two were identified as representatives of the conserved betaproteobacteria and spirochete species previously identified in Tsitsikamma sponges. It was shown that the spirochete was most likely an obligate symbiont that benefitted the host sponge through possible defence against pathogenic bacteria and/or nutrient acquisition. The putative genome representing the conserved betaproteobacteria was found to be heavily contaminated and further sequencing is required to accurately resolve the genome for functional characterization. Several biosynthetic gene clusters were identified and demonstrated the bioactive potential of Tsitsikamma favus-associated bacteria. A biosynthetic gene cluster was identified on an unclustered contig that included several genetic features that were indicative of possible pyrroloiminoquinone production.
- Full Text:
- Date Issued: 2018
Compensation for polarization mode dispersion and nonlinear birefringence in a multichannel optical fibre system
- Authors: Waswa, David Wafula
- Date: 2009
- Subjects: Fiber optics , Nonlinear optics , Polarization (Light)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10375 , http://hdl.handle.net/10948/885 , Fiber optics , Nonlinear optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) is stochastic in nature and continues evolving in an unpredictable manner according to the changing environment. Nonlinear birefringence in multichannel systems alters the polarization states of the bits, so that they vary from one bit to the next in a way that is difficult to predict. These are the two major signal-impairment effects that are inherent in optical fibre transmission links which can seriously degrade network performance. It is therefore extremely challenging to compensate for both linear and nonlinear birefringence in multichannel systems. The purpose of this thesis is to investigate the interaction between PMD and nonlinear induced birefringence in a fibre with consideration of mode coupling. A sound knowledge of this interaction is necessary in designing a linear and nonlinear polarization mode dispersion compensator for WDM systems, as was successfully carried out in this study. The investigation shows that the effect of nonlinear birefringence alone depolarizes the signal, while in high PMD links where polarization mode coupling is high, the nonlinear birefringence effect couples with second-order PMD such that it may reduce the penalty and improve the signal DOP. Further investigation shows that when nonlinear birefringence becomes significant, asymmetry arises between the two principal axes of the fibre, such that it is only one axis which experiences the effect of nonlinear birefringence. It is found out that along this vii axis, there exists a critical point in pump power where the nonlinear birefringence cancels PMD in the link and improves the signal. An adaptive compensator to cancel PMD and nonlinear birefringence was designed based on feedforward DOP-monitoring signal. The compensator was tested both at laboratory level and on the Telkom buried fibre link and found to be functioning as intended. It was able to adaptively track and compensate PMD in the link in less than a second. The compensator was able to cancel PMD in the link up to a maximum of 30 ps. The compensator improved the DOP of the worst signal by more than 100 percent.
- Full Text:
- Date Issued: 2009
- Authors: Waswa, David Wafula
- Date: 2009
- Subjects: Fiber optics , Nonlinear optics , Polarization (Light)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10375 , http://hdl.handle.net/10948/885 , Fiber optics , Nonlinear optics , Polarization (Light)
- Description: Polarization mode dispersion (PMD) is stochastic in nature and continues evolving in an unpredictable manner according to the changing environment. Nonlinear birefringence in multichannel systems alters the polarization states of the bits, so that they vary from one bit to the next in a way that is difficult to predict. These are the two major signal-impairment effects that are inherent in optical fibre transmission links which can seriously degrade network performance. It is therefore extremely challenging to compensate for both linear and nonlinear birefringence in multichannel systems. The purpose of this thesis is to investigate the interaction between PMD and nonlinear induced birefringence in a fibre with consideration of mode coupling. A sound knowledge of this interaction is necessary in designing a linear and nonlinear polarization mode dispersion compensator for WDM systems, as was successfully carried out in this study. The investigation shows that the effect of nonlinear birefringence alone depolarizes the signal, while in high PMD links where polarization mode coupling is high, the nonlinear birefringence effect couples with second-order PMD such that it may reduce the penalty and improve the signal DOP. Further investigation shows that when nonlinear birefringence becomes significant, asymmetry arises between the two principal axes of the fibre, such that it is only one axis which experiences the effect of nonlinear birefringence. It is found out that along this vii axis, there exists a critical point in pump power where the nonlinear birefringence cancels PMD in the link and improves the signal. An adaptive compensator to cancel PMD and nonlinear birefringence was designed based on feedforward DOP-monitoring signal. The compensator was tested both at laboratory level and on the Telkom buried fibre link and found to be functioning as intended. It was able to adaptively track and compensate PMD in the link in less than a second. The compensator was able to cancel PMD in the link up to a maximum of 30 ps. The compensator improved the DOP of the worst signal by more than 100 percent.
- Full Text:
- Date Issued: 2009
Direct and indirect effects of zooplanktivorous predators on the estuarine plankton community
- Authors: Wasserman, Ryan John
- Date: 2014
- Subjects: Zooplankton -- Effect of predation on , Predation (Biology) , Zooplankton -- Predators of , Copepoda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5870 , http://hdl.handle.net/10962/d1012938
- Description: Although predation has been identified as a potentially important driver in terrestrial and freshwater ecosystems, estuarine planktonic research has focused largely on the so-called "bottom-up" drivers of community assemblages. As such, this thesis focuses on the direct and indirect effects of zooplanktivorous predators on the planktonic community in an estuarine environment. By using a suite of in situ mesocosm experiments, a number of hypotheses, pertaining to the major research themes associated with predator-prey interactions, are tested. These themes included trophic cascading, risk effects associated with predation events and the importance of predator diversity in maintaining prey communities. The first experiment assessed the significance of apex predation pressure for the planktonic community through trophic cascades. Various treatments using in situ mesocosms were established in a closed oligotrophic estuary to highlight the importance of predation in stabilising estuarine plankton abundances. Through either the removal (filtration) or addition of certain planktonic groups, varied trophic scenarios were established. The experimental treatment containing apex zooplanktivores had consequences for multiple trophic levels, exerting a stabilising pressure throughout the food web (Chapter 3). Furthermore, pyrosequencing of filtered water samples revealed that when compared to the remaining treatments, the treatment containing stable apex predatory pressure experienced limited temporal deviation-from-initial in bacterial community structure (Chapter 4). These findings are consistent with trophic cascade theory whereby predators mediate interactions at multiple lower trophic levels with consequent repercussions for diversity. To assess the non-consumptive effects of predators on prey, two experiments were conducted. Firstly, using egg numbers per clutch as a measure of potential reproductive output, the non-lethal effects of predatory pressure on reproductive success in a key planktonic copepod was investigated. In this study, the average clutch size of fecund female copepods was found to be consistently lower in the presence of predators when compared to females not exposed to predation threat (Chapter 5). The second study assessed the effects of conspecific chemical alarm cues associated with predation, on population dynamics of a copepod species. This study revealed that the copepods appear to detect the presence of chemical alarm cues associated with predation events, with repercussions for population demographics over time. Furthermore, it showed that in the absence of actual predation, copepod prey responses to alarm cues were adjusted over time, consistent with the threat sensitive predator avoidance hypothesis (Chapter 6). The final data chapter dealt with predator diversity and its implications for zooplankton community structure. By experimentally monitoring the effects of two alternate model predators on the metazoan community over time, dissimilarities in community level control emerged. Alternate key prey populations were regulated by the different model predators, highlighting the importance of predator and prey behaviour in mediating predator-prey interactions (Chapter 7). These results highlight the potential importance of predators in maintaining community dynamics in estuarine planktonic communities under certain conditions. This study represents some of the first work to address these various aspects of predator-prey dynamics within the context of planktonic estuarine ecology.
- Full Text:
- Date Issued: 2014
- Authors: Wasserman, Ryan John
- Date: 2014
- Subjects: Zooplankton -- Effect of predation on , Predation (Biology) , Zooplankton -- Predators of , Copepoda
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5870 , http://hdl.handle.net/10962/d1012938
- Description: Although predation has been identified as a potentially important driver in terrestrial and freshwater ecosystems, estuarine planktonic research has focused largely on the so-called "bottom-up" drivers of community assemblages. As such, this thesis focuses on the direct and indirect effects of zooplanktivorous predators on the planktonic community in an estuarine environment. By using a suite of in situ mesocosm experiments, a number of hypotheses, pertaining to the major research themes associated with predator-prey interactions, are tested. These themes included trophic cascading, risk effects associated with predation events and the importance of predator diversity in maintaining prey communities. The first experiment assessed the significance of apex predation pressure for the planktonic community through trophic cascades. Various treatments using in situ mesocosms were established in a closed oligotrophic estuary to highlight the importance of predation in stabilising estuarine plankton abundances. Through either the removal (filtration) or addition of certain planktonic groups, varied trophic scenarios were established. The experimental treatment containing apex zooplanktivores had consequences for multiple trophic levels, exerting a stabilising pressure throughout the food web (Chapter 3). Furthermore, pyrosequencing of filtered water samples revealed that when compared to the remaining treatments, the treatment containing stable apex predatory pressure experienced limited temporal deviation-from-initial in bacterial community structure (Chapter 4). These findings are consistent with trophic cascade theory whereby predators mediate interactions at multiple lower trophic levels with consequent repercussions for diversity. To assess the non-consumptive effects of predators on prey, two experiments were conducted. Firstly, using egg numbers per clutch as a measure of potential reproductive output, the non-lethal effects of predatory pressure on reproductive success in a key planktonic copepod was investigated. In this study, the average clutch size of fecund female copepods was found to be consistently lower in the presence of predators when compared to females not exposed to predation threat (Chapter 5). The second study assessed the effects of conspecific chemical alarm cues associated with predation, on population dynamics of a copepod species. This study revealed that the copepods appear to detect the presence of chemical alarm cues associated with predation events, with repercussions for population demographics over time. Furthermore, it showed that in the absence of actual predation, copepod prey responses to alarm cues were adjusted over time, consistent with the threat sensitive predator avoidance hypothesis (Chapter 6). The final data chapter dealt with predator diversity and its implications for zooplankton community structure. By experimentally monitoring the effects of two alternate model predators on the metazoan community over time, dissimilarities in community level control emerged. Alternate key prey populations were regulated by the different model predators, highlighting the importance of predator and prey behaviour in mediating predator-prey interactions (Chapter 7). These results highlight the potential importance of predators in maintaining community dynamics in estuarine planktonic communities under certain conditions. This study represents some of the first work to address these various aspects of predator-prey dynamics within the context of planktonic estuarine ecology.
- Full Text:
- Date Issued: 2014
Impacts of wildlife and cattle grazing on spider (araneae) biodiversity in a highland savanna ecosystem, in Laikipia, Central Kenya
- Authors: Warui, Charles Mwaura
- Date: 2005
- Subjects: Spiders -- Kenya Environmental monitoring -- Kenya Savanna ecology -- Kenya Biodiversity -- Kenya Species diversity -- Kenya Wildlife management -- Kenya Herbivores -- Ecology -- Kenya
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5712 , http://hdl.handle.net/10962/d1005398
- Description: Spiders were sampled at Mpala Research Centre, Laikipia, Kenya by pitfall-trapping and sweep-netting from May 2001 to July 2002, at a Kenyan Long-term Exclosure Experiment. The aim was to establish species composition, checklist and examine spider responses to disturbances caused by cattle, megaherbivores (giraffe and elephants) and mesoherbivores (other ungulates) by looking at three levels of resolution, namely the overall community, guilds and individual species. This is the first controlled replicated experimental study on the effects on invertebrates (spiders) by different land uses (access by large herbivores). A total of 10,487 individuals from 132 species belonging to 30 families were recorded. The family Salticidae had the highest number of species (24), followed by Gnaphosidae (20), Araneidae and Lycosidae (15 each), Theridiidae and Thomisidae (8 each) and Zodariidae (4). Most of the other families had fewer than 4 species. Throughout the study period, species not previously sampled emerged after rainfall peaks. Exclosure treatments affected plant cover, spider diversity and total species mainly through the effects of cattle, whose presence significantly reduced relative vegetation cover. An increase in vegetation cover significantly increased the diversity, total species and species evenness of the overall spider community (total samples data set). Megaherbivores and mesoherbivores had no effects on overall spider diversity. Relative vegetation cover explained approximately 20-30% of variation in community diversity, species richness and species evenness. At the guild level of resolution, the exclosure treatments had no significant effects on diversity, species richness and species evenness of web builders, plant wanderers and ground wanderers. Plant wanderers were significantly and positively correlated with relative vegetation cover, which explained 17% of variation in their diversity. Six individual species responded strongly and in contrasting ways to the same environmental variables, indicating that this level was more sensitive to environmental changes than guilds or the overall spider community. Spider diversity, relative vegetation cover and rainfall varied at a temporal scale of months and not at a spatial scale of hundreds of metres. Only species diversity and species richness from sweep-netting samples and total species from pitfall-trapping varied significantly at a spatial scale of hundreds of metres. Ordination analysis revealed that sweep-netting samples were a better indicator of grazing impacts than pitfalltrapping or combined samples and grouped to reflect cattle grazing, non-cattle grazing and to a small extent the control treatments. Other ordination analyses showed that only samples from sweep-netting and not from pitfall-trapping, were spatially partitioned at a scale of hundreds of metres. This study concludes that the spider fauna of black cotton soil habitats is rich and useful for environmental monitoring and that monitoring of several individual species as indicator of grazing impacts in savanna could be useful and relatively easy.
- Full Text:
- Date Issued: 2005
- Authors: Warui, Charles Mwaura
- Date: 2005
- Subjects: Spiders -- Kenya Environmental monitoring -- Kenya Savanna ecology -- Kenya Biodiversity -- Kenya Species diversity -- Kenya Wildlife management -- Kenya Herbivores -- Ecology -- Kenya
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5712 , http://hdl.handle.net/10962/d1005398
- Description: Spiders were sampled at Mpala Research Centre, Laikipia, Kenya by pitfall-trapping and sweep-netting from May 2001 to July 2002, at a Kenyan Long-term Exclosure Experiment. The aim was to establish species composition, checklist and examine spider responses to disturbances caused by cattle, megaherbivores (giraffe and elephants) and mesoherbivores (other ungulates) by looking at three levels of resolution, namely the overall community, guilds and individual species. This is the first controlled replicated experimental study on the effects on invertebrates (spiders) by different land uses (access by large herbivores). A total of 10,487 individuals from 132 species belonging to 30 families were recorded. The family Salticidae had the highest number of species (24), followed by Gnaphosidae (20), Araneidae and Lycosidae (15 each), Theridiidae and Thomisidae (8 each) and Zodariidae (4). Most of the other families had fewer than 4 species. Throughout the study period, species not previously sampled emerged after rainfall peaks. Exclosure treatments affected plant cover, spider diversity and total species mainly through the effects of cattle, whose presence significantly reduced relative vegetation cover. An increase in vegetation cover significantly increased the diversity, total species and species evenness of the overall spider community (total samples data set). Megaherbivores and mesoherbivores had no effects on overall spider diversity. Relative vegetation cover explained approximately 20-30% of variation in community diversity, species richness and species evenness. At the guild level of resolution, the exclosure treatments had no significant effects on diversity, species richness and species evenness of web builders, plant wanderers and ground wanderers. Plant wanderers were significantly and positively correlated with relative vegetation cover, which explained 17% of variation in their diversity. Six individual species responded strongly and in contrasting ways to the same environmental variables, indicating that this level was more sensitive to environmental changes than guilds or the overall spider community. Spider diversity, relative vegetation cover and rainfall varied at a temporal scale of months and not at a spatial scale of hundreds of metres. Only species diversity and species richness from sweep-netting samples and total species from pitfall-trapping varied significantly at a spatial scale of hundreds of metres. Ordination analysis revealed that sweep-netting samples were a better indicator of grazing impacts than pitfalltrapping or combined samples and grouped to reflect cattle grazing, non-cattle grazing and to a small extent the control treatments. Other ordination analyses showed that only samples from sweep-netting and not from pitfall-trapping, were spatially partitioned at a scale of hundreds of metres. This study concludes that the spider fauna of black cotton soil habitats is rich and useful for environmental monitoring and that monitoring of several individual species as indicator of grazing impacts in savanna could be useful and relatively easy.
- Full Text:
- Date Issued: 2005
Interactions between figs (Ficus spp., Moraceae) and fig wasps (Chalcidoidea, Agaonidae)
- Authors: Ware, Anthony Brian
- Date: 1993
- Subjects: Fig -- South Africa Fig wasp -- South Africa Pollination Agaonidae Chalcid wasps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5719 , http://hdl.handle.net/10962/d1005405
- Description: Fig trees (Ficus spp., Moraceae) and fig wasps (Chalcidoidea, Agaonidae) are uniquely associated. In one fig wasp group, the pollinators (Agaoninae), each species is generally host species-specific. The relationship is one of obligate mutualism where the wasps provide pollination services and in return utilises some of the ovules for larval development. Non-pollinating fig wasps (generally belonging to subfamilies other than the Agaoninae) may be gallers or parasitoids, and can also be host species-specific. In the accompanying studies we examined the factors governing the interactions between fig wasps and their host trees. Surveys of fig trees and their associated pollinating fig wasps conducted in southern Africa, Madagascar and The Comores generally confirmed their specific relationships. An examination of F. sycomorlls in Madagascar resulted in the reclassification of F. sakalavarum as a distinct species with its own specific pollinator species. Biological and chemical evidence is presented demonstrating that the pollinators were able to distinguish their hosts through volatiles which emanated from the figs when they were ready to be pollinated. Environmental factors were found to influence wasp behaviour. Ambient temperature governed the timing of wasp emergence from their natal figs. When dispersing from their natal figs, the fig wasps flew upwards and then were blown downwind. Once nearing trees bearing figs ready to be pollinated, the wasps lost height and flew upwind towards the trees. E. baijnathi females apparently avoided figs which already contained a conspecific foundress. Scanning electron microscope studies of pollinating female fig wasp antennae showed that while all the species possessed multiporous plate sensilla, in only a few species were these sensilla elongated. Multiporous plate sensilla elongation is rare or absent among other female chalcids and may have evolved within the Agaoninae in order to facilitate their location on receptive host figs. Pollinator choice specificity appears to break down in a number of cases. In the first case examined, two pollinator species were recorded from the figs of African F. sycomorus. One. C. arabicus, pollinates the figs while the other, C. galili, acts as a 'cuckoo' by utilising some of ovules for oviposition without providing pollen. In the second case three pollinating fig wasp species were recorded from the rigs of F. lutea. Two were found to be incidental visitors and were not specifically attracted to the tree. The hybrid seeds from these crosses were successfully germinated but the seedlings did not grow passed the cotyledon stage of their development. In the concluding study the consequences of Ficus phenology and the structure of the fig's unusual inflorescence on the nonpollinating fig wasp community were examined. Various factors affecting the population levels and species richness were also examined. Future possible research directions were discussed.
- Full Text:
- Date Issued: 1993
- Authors: Ware, Anthony Brian
- Date: 1993
- Subjects: Fig -- South Africa Fig wasp -- South Africa Pollination Agaonidae Chalcid wasps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5719 , http://hdl.handle.net/10962/d1005405
- Description: Fig trees (Ficus spp., Moraceae) and fig wasps (Chalcidoidea, Agaonidae) are uniquely associated. In one fig wasp group, the pollinators (Agaoninae), each species is generally host species-specific. The relationship is one of obligate mutualism where the wasps provide pollination services and in return utilises some of the ovules for larval development. Non-pollinating fig wasps (generally belonging to subfamilies other than the Agaoninae) may be gallers or parasitoids, and can also be host species-specific. In the accompanying studies we examined the factors governing the interactions between fig wasps and their host trees. Surveys of fig trees and their associated pollinating fig wasps conducted in southern Africa, Madagascar and The Comores generally confirmed their specific relationships. An examination of F. sycomorlls in Madagascar resulted in the reclassification of F. sakalavarum as a distinct species with its own specific pollinator species. Biological and chemical evidence is presented demonstrating that the pollinators were able to distinguish their hosts through volatiles which emanated from the figs when they were ready to be pollinated. Environmental factors were found to influence wasp behaviour. Ambient temperature governed the timing of wasp emergence from their natal figs. When dispersing from their natal figs, the fig wasps flew upwards and then were blown downwind. Once nearing trees bearing figs ready to be pollinated, the wasps lost height and flew upwind towards the trees. E. baijnathi females apparently avoided figs which already contained a conspecific foundress. Scanning electron microscope studies of pollinating female fig wasp antennae showed that while all the species possessed multiporous plate sensilla, in only a few species were these sensilla elongated. Multiporous plate sensilla elongation is rare or absent among other female chalcids and may have evolved within the Agaoninae in order to facilitate their location on receptive host figs. Pollinator choice specificity appears to break down in a number of cases. In the first case examined, two pollinator species were recorded from the figs of African F. sycomorus. One. C. arabicus, pollinates the figs while the other, C. galili, acts as a 'cuckoo' by utilising some of ovules for oviposition without providing pollen. In the second case three pollinating fig wasp species were recorded from the rigs of F. lutea. Two were found to be incidental visitors and were not specifically attracted to the tree. The hybrid seeds from these crosses were successfully germinated but the seedlings did not grow passed the cotyledon stage of their development. In the concluding study the consequences of Ficus phenology and the structure of the fig's unusual inflorescence on the nonpollinating fig wasp community were examined. Various factors affecting the population levels and species richness were also examined. Future possible research directions were discussed.
- Full Text:
- Date Issued: 1993
A psychobiographical study of Temple Grandin
- Authors: Wannenburg, Nicola
- Date: 2018
- Subjects: Grandin, Temple , Psychology Biographical methods , Psychoanalysis , Autistic women United States Biography , Women animal specialists United States Biography , Developmental psychology , Erikson, Erik H (Erik Homburger), 1902-1994
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/57358 , vital:26877
- Description: Psychobiographical researchers methodically formulate life histories and interpret them by means of psychological theories. The research typically focuses on exemplary and completed lives. The cases that are studied are usually of individuals who are of particular interest to society as a result of excelling in their particular fields, be they to benefit or detriment of society. Temple Grandin was chosen for this study using purposive sampling as she meets the psychobiographical requirement of being an extraordinary individual. As an individual with autism Grandin faced many challenges growing up. Despite a difficult and absent beginning, Grandin developed into a stable and scientifically creative adult who contributes to society. She excels as an animal scientist and designer of humane livestock handling facilities and has an international reputation for her contribution to the livestock industry and animal welfare. The primary aim of this study is to describe and interpret the life of Temple Grandin through Erikson’s (1950/1973) theory of psychosocial development. A mixed method approach (Yin, 2006) was employed for the conduction of this study. The overarching data processing and analysis guidelines for this study were provided by Miles and Huberman (1994, 2002a, 2002b). The conduction of the processing and analysis of data was aided by Alexander’s (1988, 1990) method of asking the data questions as well as an integration of Yin’s (2014) time series analysis with Erikson’s (1950/1973) triple bookkeeping approach. This study contributes to the development of psychobiographical research in South Africa as well as to personality and developmental theory.
- Full Text:
- Date Issued: 2018
- Authors: Wannenburg, Nicola
- Date: 2018
- Subjects: Grandin, Temple , Psychology Biographical methods , Psychoanalysis , Autistic women United States Biography , Women animal specialists United States Biography , Developmental psychology , Erikson, Erik H (Erik Homburger), 1902-1994
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/57358 , vital:26877
- Description: Psychobiographical researchers methodically formulate life histories and interpret them by means of psychological theories. The research typically focuses on exemplary and completed lives. The cases that are studied are usually of individuals who are of particular interest to society as a result of excelling in their particular fields, be they to benefit or detriment of society. Temple Grandin was chosen for this study using purposive sampling as she meets the psychobiographical requirement of being an extraordinary individual. As an individual with autism Grandin faced many challenges growing up. Despite a difficult and absent beginning, Grandin developed into a stable and scientifically creative adult who contributes to society. She excels as an animal scientist and designer of humane livestock handling facilities and has an international reputation for her contribution to the livestock industry and animal welfare. The primary aim of this study is to describe and interpret the life of Temple Grandin through Erikson’s (1950/1973) theory of psychosocial development. A mixed method approach (Yin, 2006) was employed for the conduction of this study. The overarching data processing and analysis guidelines for this study were provided by Miles and Huberman (1994, 2002a, 2002b). The conduction of the processing and analysis of data was aided by Alexander’s (1988, 1990) method of asking the data questions as well as an integration of Yin’s (2014) time series analysis with Erikson’s (1950/1973) triple bookkeeping approach. This study contributes to the development of psychobiographical research in South Africa as well as to personality and developmental theory.
- Full Text:
- Date Issued: 2018
The impact of government expenditure on economic growth of the economic community of West African states (ECOWAS)
- Authors: Wanjuu, Lazarus Zungwe
- Date: 2016
- Subjects: Economic development -- Africa Africa -- Economic conditions Developing countries -- Economic aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/13261 , vital:27169
- Description: Available statistics on growth trends in the Economic Community of West African States (ECOWAS) are wanting, particularly net per capita growth rates. The analysis of available data from 1970 to 2012 by this study, for instance, shows that the net real GDP growth rate for the ECOWAS is 0.52%. Only four countries had net growth rates above 1% per annum mean growth rate of ECOWAS region. At the estimated growth rate, the prospect of accelerated growth in ECOWAS is very weak. The Barro endogenous growth model states that government provision of services can generate externalities to the private productive activities. Government’s provision of productive services in ECOWAS can ensure long-run per capita output growth without the per capita growth rate running into steady state growth. However, there are divergent views as to whether government provision of services induces long run economic growth. These views are based on different schools of thought. For instance, the economic freedom school argues for minimum government involvement (small governments) to ensure economic and political freedom to induce private investors invest and encourage economic growth. The optimal government school of thought (medium size governments) argues that government spending enhances private productivity growth through the provision of infrastructure, spending on research and development, public education, sewage, other public goods and protection through functional law and order systems. The optimal school of thought also acknowledges that government expenditure can also reduce economic growth through increases in taxation. An increase in taxation reduces the returns on investment of physical and human capital and in research and development (R&D) of private firms. This thesis investigates the impact of government expenditure on the provision of public services on economic growth in ECOWAS. To assess the impact of government expenditure on the provision of services on economic growth of ECOWAS, this thesis assesses whether the size of government, government expenditure and economic institutions promoted economic growth in ECOWAS. The thesis also determines whether per capita government capital expenditure, per capita government consumption expenditure, per capita private capital stock, per capita manufacturing output, per capita services output and per capita agricultural output have any impact on per capita real GDP growth in ECOWAS. To carry out this study, data were collected from United Nations Conference on Trade and Development (UNCTAD) database and Transparency International (TI) database. The data used covered the period of 1970 – 2013. The statistical research methods applied are the time-series methods of panel unit root test, panel co-integration test, and panel regression analysis, using both panel OLS regression models and estimation and inferences in co-integrated panel data regression methods. The panel OLS regression models applied are the panel OLS regression; panel fixed effect model (FEM) regression and the panel random effect model (REM) regression. The estimation and inferences in co-integrated panel data regression models applied are panel VEC regression model, panel DOLS regression and panel FMOLS regression. The panel DOLS regression and panel FMOLS regression models do not have an intercept, unlike their pure time-series models, which have intercepted. To ensure that the parameters estimated are reliable, this thesis conducted diagnostic tests to subject the regression result to scrutiny. The estimated panel data regression using panel OLS regression, panel FEM regression and panel REM regression indicate that the results of the estimated parameters were spurious having both autocorrelations and heteroscedasticity. High values of adjusted R-squares that were approaching one and high significant values of t statistics but very low values of Durbin-Watson Statistics demonstrated the existence of heteroscedasticity and autocorrelation in residuals. The results of the diagnostic tests also show that the DOLS estimated regression model out-performed both VEC and FMOLS regression models based on both aggregate data and per capita data estimated parameters. The results of the parameter estimated using panel VEC and panel FMOLS regression models showed that both panel VEC and panel FMOLS regression models had the problems of their residuals having not only autocorrelations but heteroscedasticity. The panel DOLS regression results were satisfactory, having no multicollinearity, autocorrelations and heteroscedasticity. The estimated panel DOLS regression results were applied to test hypotheses formulated to guide this thesis. Results from panel DOLS estimated parameters show that the existing government size in ECOWAS stimulated economic growth. The results also showed that the government expenditure exhibited an inverted U-shape with respect to economic growth. The thesis also showed that existing government size in ECOWAS significantly stimulated economic growth in the region. The results of regression indicate that economic institutions contribute negatively to the economic growth of the ECOWAS. The results also established that government capital expenditure per capita has significantly engendered economic growth. Government consumption expenditure per capita stimulated economic growth. However, private capital stock per capita has not stimulated economic growth in ECOWAS. Service sector output per capita, agricultural output per capita and manufacturing output per capita stimulated significantly economic growth in the ECOWAS sub-region.
- Full Text:
- Date Issued: 2016
- Authors: Wanjuu, Lazarus Zungwe
- Date: 2016
- Subjects: Economic development -- Africa Africa -- Economic conditions Developing countries -- Economic aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/13261 , vital:27169
- Description: Available statistics on growth trends in the Economic Community of West African States (ECOWAS) are wanting, particularly net per capita growth rates. The analysis of available data from 1970 to 2012 by this study, for instance, shows that the net real GDP growth rate for the ECOWAS is 0.52%. Only four countries had net growth rates above 1% per annum mean growth rate of ECOWAS region. At the estimated growth rate, the prospect of accelerated growth in ECOWAS is very weak. The Barro endogenous growth model states that government provision of services can generate externalities to the private productive activities. Government’s provision of productive services in ECOWAS can ensure long-run per capita output growth without the per capita growth rate running into steady state growth. However, there are divergent views as to whether government provision of services induces long run economic growth. These views are based on different schools of thought. For instance, the economic freedom school argues for minimum government involvement (small governments) to ensure economic and political freedom to induce private investors invest and encourage economic growth. The optimal government school of thought (medium size governments) argues that government spending enhances private productivity growth through the provision of infrastructure, spending on research and development, public education, sewage, other public goods and protection through functional law and order systems. The optimal school of thought also acknowledges that government expenditure can also reduce economic growth through increases in taxation. An increase in taxation reduces the returns on investment of physical and human capital and in research and development (R&D) of private firms. This thesis investigates the impact of government expenditure on the provision of public services on economic growth in ECOWAS. To assess the impact of government expenditure on the provision of services on economic growth of ECOWAS, this thesis assesses whether the size of government, government expenditure and economic institutions promoted economic growth in ECOWAS. The thesis also determines whether per capita government capital expenditure, per capita government consumption expenditure, per capita private capital stock, per capita manufacturing output, per capita services output and per capita agricultural output have any impact on per capita real GDP growth in ECOWAS. To carry out this study, data were collected from United Nations Conference on Trade and Development (UNCTAD) database and Transparency International (TI) database. The data used covered the period of 1970 – 2013. The statistical research methods applied are the time-series methods of panel unit root test, panel co-integration test, and panel regression analysis, using both panel OLS regression models and estimation and inferences in co-integrated panel data regression methods. The panel OLS regression models applied are the panel OLS regression; panel fixed effect model (FEM) regression and the panel random effect model (REM) regression. The estimation and inferences in co-integrated panel data regression models applied are panel VEC regression model, panel DOLS regression and panel FMOLS regression. The panel DOLS regression and panel FMOLS regression models do not have an intercept, unlike their pure time-series models, which have intercepted. To ensure that the parameters estimated are reliable, this thesis conducted diagnostic tests to subject the regression result to scrutiny. The estimated panel data regression using panel OLS regression, panel FEM regression and panel REM regression indicate that the results of the estimated parameters were spurious having both autocorrelations and heteroscedasticity. High values of adjusted R-squares that were approaching one and high significant values of t statistics but very low values of Durbin-Watson Statistics demonstrated the existence of heteroscedasticity and autocorrelation in residuals. The results of the diagnostic tests also show that the DOLS estimated regression model out-performed both VEC and FMOLS regression models based on both aggregate data and per capita data estimated parameters. The results of the parameter estimated using panel VEC and panel FMOLS regression models showed that both panel VEC and panel FMOLS regression models had the problems of their residuals having not only autocorrelations but heteroscedasticity. The panel DOLS regression results were satisfactory, having no multicollinearity, autocorrelations and heteroscedasticity. The estimated panel DOLS regression results were applied to test hypotheses formulated to guide this thesis. Results from panel DOLS estimated parameters show that the existing government size in ECOWAS stimulated economic growth. The results also showed that the government expenditure exhibited an inverted U-shape with respect to economic growth. The thesis also showed that existing government size in ECOWAS significantly stimulated economic growth in the region. The results of regression indicate that economic institutions contribute negatively to the economic growth of the ECOWAS. The results also established that government capital expenditure per capita has significantly engendered economic growth. Government consumption expenditure per capita stimulated economic growth. However, private capital stock per capita has not stimulated economic growth in ECOWAS. Service sector output per capita, agricultural output per capita and manufacturing output per capita stimulated significantly economic growth in the ECOWAS sub-region.
- Full Text:
- Date Issued: 2016
Mathematical requirements for first-year BCOM students at NMMU
- Authors: Walton, Marguerite
- Date: 2009
- Subjects: Business mathematics -- South Africa , Mathematics -- Study and teaching (Higher) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10502 , http://hdl.handle.net/10948/886 , Business mathematics -- South Africa , Mathematics -- Study and teaching (Higher) -- South Africa
- Description: These studies have focused on identifying the mathematical requirements of first-year BCom students at Nelson Mandela Metropolitan University. The research methodology used in this quantitative study was to make use of interviewing, questionnaire investigation, and document analysis in the form of textbook, test and examination analysis. These methods provided data that fitted into a grounded theory approach. The study concluded by identifying the list of mathematical topics required for the first year of the core subjects in the BCom degree programme. In addition, the study found that learners who study Mathematics in the National Senior Certificate should be able to cope with the mathematical content included in their BCom degree programme, while learners studying Mathematical Literacy would probably need support in some of the areas of mathematics, especially algebra, in order to cope with the mathematical content included in their BCom degree programme. It makes a valuable contribution towards elucidating the mathematical requirements needed to improve the chances of successful BCom degree programme studies at South African universities. It also draws the contours for starting to design an efficient support course for future “at-risk” students who enter higher education studies.
- Full Text:
- Date Issued: 2009
- Authors: Walton, Marguerite
- Date: 2009
- Subjects: Business mathematics -- South Africa , Mathematics -- Study and teaching (Higher) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10502 , http://hdl.handle.net/10948/886 , Business mathematics -- South Africa , Mathematics -- Study and teaching (Higher) -- South Africa
- Description: These studies have focused on identifying the mathematical requirements of first-year BCom students at Nelson Mandela Metropolitan University. The research methodology used in this quantitative study was to make use of interviewing, questionnaire investigation, and document analysis in the form of textbook, test and examination analysis. These methods provided data that fitted into a grounded theory approach. The study concluded by identifying the list of mathematical topics required for the first year of the core subjects in the BCom degree programme. In addition, the study found that learners who study Mathematics in the National Senior Certificate should be able to cope with the mathematical content included in their BCom degree programme, while learners studying Mathematical Literacy would probably need support in some of the areas of mathematics, especially algebra, in order to cope with the mathematical content included in their BCom degree programme. It makes a valuable contribution towards elucidating the mathematical requirements needed to improve the chances of successful BCom degree programme studies at South African universities. It also draws the contours for starting to design an efficient support course for future “at-risk” students who enter higher education studies.
- Full Text:
- Date Issued: 2009
Deliberately withheld meaning : aspects of narrative technique in four novels by William Faulkner
- Authors: Walters, Paul S
- Date: 1970
- Subjects: Faulkner, William, 1897-1962 -- Criticism and interpretation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2167 , http://hdl.handle.net/10962/d1001746
- Full Text:
- Date Issued: 1970
- Authors: Walters, Paul S
- Date: 1970
- Subjects: Faulkner, William, 1897-1962 -- Criticism and interpretation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2167 , http://hdl.handle.net/10962/d1001746
- Full Text:
- Date Issued: 1970
Wagon bridges of the Eastern Cape, c. 1840 – 1900: the contribution of engineering to infrastructural development
- Authors: Walters, Dennis Evelyn
- Date: 2018
- Subjects: Bridges Design and construction 19th century , Civil engineers South Africa Cape of Good Hope , Great Britain. Crown Agents' Office , Public works Great Britain Colonies , Wagon trains South Africa Cape of Good Hope
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63877 , vital:28500
- Description: This thesis examines an aspect of economic and technological history which has been little explored in South African history. It argues that the military subjugation and the economic development of the Cape Colony, and particularly of the Eastern Cape, were contingent upon good transportation. The geography of the country, which included relatively impassable mountains and numerous often flooded rivers, necessitated bridges as well as roads. Both were expensive. As a leader in industrial technology, Britain was well placed to extend bridge-building skills to its colonies. This thesis examines the processes by which a small and undeveloped colony strove to create an efficient technological infrastructure. As wagon traffic increased through progress, delays in crossing rivers became a hindrance leading to agitation for bridges. It will be shown that the construction of wagon bridges over the numerous rivers encountered in the Eastern Cape Colony was imperative for the initial free flow of military forces and for later commercial expansion as new towns were established. The eastward expansion was led by the military during the frontier wars followed by the Royal Engineers who built roads and bridges along the eastern frontier. The new Colonial Secretary John Montagu, who arrived in 1843, boosted the colonial finances by overhauling the administration. He established the Central Road Board, an organisation that would drive the building of mountain passes, roads and bridges. The Public Works Department succeeded the Central Road Board and with the financial intervention of the Crown Agents for the Colonies, carried on with an extensive programme of road and bridge building. From the 1870s wagon bridge building lagged behind the huge railway building enterprise in response to the opening up of the diamond and gold mines. The final quarter of the 19th century saw increased bridge building activity in the Eastern Cape with the construction of many iron lattice girder, stone masonry arch and timber trestle bridges. The surviving bridges remain as mute testimony to the skill and expertise of British engineers such as Lewis, Woodifield, Robinson, Fforde, Wakefield, Berkley, Grier, Newey, Westhoven and others.
- Full Text:
- Date Issued: 2018
- Authors: Walters, Dennis Evelyn
- Date: 2018
- Subjects: Bridges Design and construction 19th century , Civil engineers South Africa Cape of Good Hope , Great Britain. Crown Agents' Office , Public works Great Britain Colonies , Wagon trains South Africa Cape of Good Hope
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63877 , vital:28500
- Description: This thesis examines an aspect of economic and technological history which has been little explored in South African history. It argues that the military subjugation and the economic development of the Cape Colony, and particularly of the Eastern Cape, were contingent upon good transportation. The geography of the country, which included relatively impassable mountains and numerous often flooded rivers, necessitated bridges as well as roads. Both were expensive. As a leader in industrial technology, Britain was well placed to extend bridge-building skills to its colonies. This thesis examines the processes by which a small and undeveloped colony strove to create an efficient technological infrastructure. As wagon traffic increased through progress, delays in crossing rivers became a hindrance leading to agitation for bridges. It will be shown that the construction of wagon bridges over the numerous rivers encountered in the Eastern Cape Colony was imperative for the initial free flow of military forces and for later commercial expansion as new towns were established. The eastward expansion was led by the military during the frontier wars followed by the Royal Engineers who built roads and bridges along the eastern frontier. The new Colonial Secretary John Montagu, who arrived in 1843, boosted the colonial finances by overhauling the administration. He established the Central Road Board, an organisation that would drive the building of mountain passes, roads and bridges. The Public Works Department succeeded the Central Road Board and with the financial intervention of the Crown Agents for the Colonies, carried on with an extensive programme of road and bridge building. From the 1870s wagon bridge building lagged behind the huge railway building enterprise in response to the opening up of the diamond and gold mines. The final quarter of the 19th century saw increased bridge building activity in the Eastern Cape with the construction of many iron lattice girder, stone masonry arch and timber trestle bridges. The surviving bridges remain as mute testimony to the skill and expertise of British engineers such as Lewis, Woodifield, Robinson, Fforde, Wakefield, Berkley, Grier, Newey, Westhoven and others.
- Full Text:
- Date Issued: 2018
The evolution of heteronomous host relationships in Aphelinidaa (Hymenoptera Chalcidoidea) with special reference to the biology of Coccophagus Bartletti Annecke and Insley
- Authors: Walter, Grenville Hugh
- Date: 1984
- Subjects: Hymenoptera
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5620 , http://hdl.handle.net/10962/d1003746
- Description: Résumé: Heteronomous host relationships are unique to parasitoids in about 8 aphelinid genera. Males have host relationships quite distinct from those of their females. Females of ALL species are primary endoparasitoids of homopterous hosts. Males, on the other hand, may be either primary ectoparasitoids of the same host species as their conspecific females, or they may be hyperparasitic upon parasitoids within Homoptera, and some are primary endoparasitoids of moth eggs. Species in these groups are termed DIPHAGOUS PARASITOIDS, HETERONOMOUS HYPERPARASITOIDS and HETEROTROPHIC PARASITOIDS, respectively. The selective advantages proposed to explain the evolution of these unusual host relationships are examined in this thesis. The biology of a diphagous parasitoid was examined in detail because diphagous parasitism is considered the most primitive of heteronomous host relationships. Diphagous parasitism is thought to have evolved during a period when ovipositing females continuously encountered large proportions of parasitised hosts. Larval competition may have generated the selection pressures that favoured male ectoparasitism. Ectoparasitoids are known to be superior in competition against other larvae, even older ones. A series of observations was carried out on the diphagous parasitoid, Coccophagus bartletti. Information was gathered on oviposition and host-feeding behaviour, daily activity patterns, and sex ratios in the laboratory and field. This enabled the design and interpretation of a series of observations on the responses of mated C. bartletti females to already-parasitised hosts. The results indicate that competition from other parasitoids probably played no role in the evolution of diphagous host relationships. Heteronomous hyperparasitoids, thought to have evolved from diphagous parasitoids, appear to be strong competitors because their males kill other parasitoids. However, an alternative hypothesis to the competition one, and based on the present study, is presented. Implications for the generally-held view, that competition is important in moulding species' characters, are discussed.
- Full Text:
- Date Issued: 1984
- Authors: Walter, Grenville Hugh
- Date: 1984
- Subjects: Hymenoptera
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5620 , http://hdl.handle.net/10962/d1003746
- Description: Résumé: Heteronomous host relationships are unique to parasitoids in about 8 aphelinid genera. Males have host relationships quite distinct from those of their females. Females of ALL species are primary endoparasitoids of homopterous hosts. Males, on the other hand, may be either primary ectoparasitoids of the same host species as their conspecific females, or they may be hyperparasitic upon parasitoids within Homoptera, and some are primary endoparasitoids of moth eggs. Species in these groups are termed DIPHAGOUS PARASITOIDS, HETERONOMOUS HYPERPARASITOIDS and HETEROTROPHIC PARASITOIDS, respectively. The selective advantages proposed to explain the evolution of these unusual host relationships are examined in this thesis. The biology of a diphagous parasitoid was examined in detail because diphagous parasitism is considered the most primitive of heteronomous host relationships. Diphagous parasitism is thought to have evolved during a period when ovipositing females continuously encountered large proportions of parasitised hosts. Larval competition may have generated the selection pressures that favoured male ectoparasitism. Ectoparasitoids are known to be superior in competition against other larvae, even older ones. A series of observations was carried out on the diphagous parasitoid, Coccophagus bartletti. Information was gathered on oviposition and host-feeding behaviour, daily activity patterns, and sex ratios in the laboratory and field. This enabled the design and interpretation of a series of observations on the responses of mated C. bartletti females to already-parasitised hosts. The results indicate that competition from other parasitoids probably played no role in the evolution of diphagous host relationships. Heteronomous hyperparasitoids, thought to have evolved from diphagous parasitoids, appear to be strong competitors because their males kill other parasitoids. However, an alternative hypothesis to the competition one, and based on the present study, is presented. Implications for the generally-held view, that competition is important in moulding species' characters, are discussed.
- Full Text:
- Date Issued: 1984
Establishing experimental systems for studying the replication biology of Providence virus
- Authors: Walter, Cheryl Tracy
- Date: 2009
- Subjects: Insects -- Viruses Insects -- Diseases Insects -- Parasites Host-virus relationships RNA viruses DNA Insects as carriers of disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3928 , http://hdl.handle.net/10962/d1003987
- Description: Providence virus (PrV) is a member of the Tetraviridae, a family of small, positive sense, single-stranded RNA viruses, which characteristically infect the midgut tissue of heliothine larvae. PrV is the only known tetravirus that replicates in cultured insect cells. The virus comprises a monopartite genome resembling members of the genus Betatetravirus with the capsid precursor protein undergoing autoproteolytic cleavage at its C-terminus consistent with other tetravirus capsid precursor proteins. Analysis of viral cDNA predicted the presence of three potential overlapping gene products (from 5` to 3`): (1) p130, a protein of unrecognized nucleotide or amino acid homology with a 2A-like processing site at its N-terminus; (2) p104, the replicase ORF, which was found to be phylogenetically related to tombus-and umbraviruses replicases. The presence of a read-through stop signal in the p104 ORF was proposed to produce and amino terminal product with a predicted MW of 40 kDa (p40) and (3) the capsid protein precursor (81 kDa) which has two 2A-like processing sites at its N-terminus. Metabolic radiolabelling of viral translation products in persistently infected MG8 cells and in vitro translation of the individual ORFs were performed in order to analyse the expression of PrV gene products. p130 was translated with no evidence of 2A-like processing. Two products of 40 kDa and 104 kDa were translated from the p104 ORF, indicating that the read-through stop signal was likely to be functional. Finally, the capsid protein precursor ORF produced a major translation product of 68 kDa corresponding to the capsid protein precursor as well a peptide of 15 kDa that was attributed to the activity of the second 2A-like site at the N-terminus of the p81 ORF. The subcellular distribution of viral RNA (vRNA) and p40 in MG8 cells was investigated using immunofluorescence and biochemical fractionation. The results showed that p40/p104 and vRNA accumulated in polarized, punctate structures in some but not all MG8 cells and in some cases, co-localization was observed. This thesis concludes that PrV is a novel tetravirus with significant similarities plant carmolike viruses that should be re-classified at the family level.
- Full Text:
- Date Issued: 2009
- Authors: Walter, Cheryl Tracy
- Date: 2009
- Subjects: Insects -- Viruses Insects -- Diseases Insects -- Parasites Host-virus relationships RNA viruses DNA Insects as carriers of disease
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3928 , http://hdl.handle.net/10962/d1003987
- Description: Providence virus (PrV) is a member of the Tetraviridae, a family of small, positive sense, single-stranded RNA viruses, which characteristically infect the midgut tissue of heliothine larvae. PrV is the only known tetravirus that replicates in cultured insect cells. The virus comprises a monopartite genome resembling members of the genus Betatetravirus with the capsid precursor protein undergoing autoproteolytic cleavage at its C-terminus consistent with other tetravirus capsid precursor proteins. Analysis of viral cDNA predicted the presence of three potential overlapping gene products (from 5` to 3`): (1) p130, a protein of unrecognized nucleotide or amino acid homology with a 2A-like processing site at its N-terminus; (2) p104, the replicase ORF, which was found to be phylogenetically related to tombus-and umbraviruses replicases. The presence of a read-through stop signal in the p104 ORF was proposed to produce and amino terminal product with a predicted MW of 40 kDa (p40) and (3) the capsid protein precursor (81 kDa) which has two 2A-like processing sites at its N-terminus. Metabolic radiolabelling of viral translation products in persistently infected MG8 cells and in vitro translation of the individual ORFs were performed in order to analyse the expression of PrV gene products. p130 was translated with no evidence of 2A-like processing. Two products of 40 kDa and 104 kDa were translated from the p104 ORF, indicating that the read-through stop signal was likely to be functional. Finally, the capsid protein precursor ORF produced a major translation product of 68 kDa corresponding to the capsid protein precursor as well a peptide of 15 kDa that was attributed to the activity of the second 2A-like site at the N-terminus of the p81 ORF. The subcellular distribution of viral RNA (vRNA) and p40 in MG8 cells was investigated using immunofluorescence and biochemical fractionation. The results showed that p40/p104 and vRNA accumulated in polarized, punctate structures in some but not all MG8 cells and in some cases, co-localization was observed. This thesis concludes that PrV is a novel tetravirus with significant similarities plant carmolike viruses that should be re-classified at the family level.
- Full Text:
- Date Issued: 2009
Plaatje's African romance: the translation of tragedy in Mhudi and other writings
- Authors: Walter, Brian Ernest
- Date: 2001
- Subjects: Plaatje, Sol. T. (Solomon Tshekisho), 1876-1932. Mhudi Race in literature Politics in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2188 , http://hdl.handle.net/10962/d1002230
- Description: This study brings together Plaatje’s politicaland literary visions, arguing that the one informs the other. Plaatje’s literary work is used as a starting point for the discussion, and the first chapter explores the relationship of his political and artistic visions. Mhudi is his definitive romance text, and it is argued that Plaatje’s romance visionin this text is reflected in his political thinking, and in turn reflected by it. His romance work was part of a literary romance tradition which Plaatje both drew upon and transformed, and thus the basic features of romance are explored in Chapter Two. Plaatje’s work is situated between two influential romance models, therefore Chapter Two also discusses the romances of Shakespeare, whomPlaatje read as reflectinga non-racial humanism that was translatable into the African context, in terms of political vision and of literary text. His other models were the colonial romances of Haggard. It is argued that, while Plaatje could glean many elements fromHaggardthat suited his purposes as an African, specifically a SouthAfrican, writer, he nevertheless—despite his own pro-British leanings, qualified though they might have been by the complexities of his colonial context—would not have represented Africa and Africans in terms of the exotic other in the way Haggard clearly did. Thus Plaatje, in terms of his romance vision, may have usedmanyofthe themesand techniques of Haggardianromance, but consistently qualified these colonial works by using the more classically shaped Shakespearean romance structure at the deep level of his work. The third chapter examines Haggard’s romance, but differentiates between two Haggardian types, the completed or resolved romance, whichis more classical in its form, and evokes an image of a completed quest, as well as the necessity of the quester entering the world again. Haggard’s “completed” African romance, it is argued, is resolved only in terms of a colonial vision. Chapter Four, by contrast, examines examples of his unresolved African romance, in which African ideals implode, and show themselves to be inneed of foreign intervention. It is argued that Haggard’s image of Africa was based on the unresolved or incomplete romance. His vision of Africa was such that it could not in itself provide the materialfor completed romance. This vision saw intervention as the only option for South Africa. While Plaatje uses elements of Haggard’s “incomplete” romance models when writing Mhudi, he handles both his narrative and politicalcommentaryin this text in terms of his own politicalthought. This non-racial politicalvisionis guided by his belief that virtue and vice are not the monopoly of any colour, a non-racialism he associates with Shakespeare. However, within the context of the South Africa of his fictionand of his life, this non-racial ideal is constantly under threat. It is partly threatened by political forces, but also challenged by moral changes within individuals and societies. In Chapter Five the examination of Plaatje’s work begins withhis Boer War Diary, inwhicha romance structure is sought beneath his diurnal observations and political optimismduring a time of warfare and siege. The discussion of this text is followed by a reading of Native Life in South Africa in which it is argued that Plaatje looks, in the midst of personal and social suffering, for that which can translate a tragic situation into romance resolution. “Translation” is used in a broad sense, echoing Plaatje’s view of the importance of translation for cross-cultural understanding and harmony. The arguments of Chapter Five are extended into Chapter Six, where a reading of Mhudi places emphasis on the possibilities of change implied in romance. Plaatje’s non-racial humanism recognizes the great potential for injustice and human suffering within the context of South African racism, but constantly seeks to translate such suffering into the triumph of romance. While the narrative of Mhudi concludes on a romance peak, tensions between the tragic and romance possibilities alert the reader to the sense that, despite its romance resolution, something has been lost in the translation of the potential tragedy into romance.
- Full Text:
- Date Issued: 2001
- Authors: Walter, Brian Ernest
- Date: 2001
- Subjects: Plaatje, Sol. T. (Solomon Tshekisho), 1876-1932. Mhudi Race in literature Politics in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2188 , http://hdl.handle.net/10962/d1002230
- Description: This study brings together Plaatje’s politicaland literary visions, arguing that the one informs the other. Plaatje’s literary work is used as a starting point for the discussion, and the first chapter explores the relationship of his political and artistic visions. Mhudi is his definitive romance text, and it is argued that Plaatje’s romance visionin this text is reflected in his political thinking, and in turn reflected by it. His romance work was part of a literary romance tradition which Plaatje both drew upon and transformed, and thus the basic features of romance are explored in Chapter Two. Plaatje’s work is situated between two influential romance models, therefore Chapter Two also discusses the romances of Shakespeare, whomPlaatje read as reflectinga non-racial humanism that was translatable into the African context, in terms of political vision and of literary text. His other models were the colonial romances of Haggard. It is argued that, while Plaatje could glean many elements fromHaggardthat suited his purposes as an African, specifically a SouthAfrican, writer, he nevertheless—despite his own pro-British leanings, qualified though they might have been by the complexities of his colonial context—would not have represented Africa and Africans in terms of the exotic other in the way Haggard clearly did. Thus Plaatje, in terms of his romance vision, may have usedmanyofthe themesand techniques of Haggardianromance, but consistently qualified these colonial works by using the more classically shaped Shakespearean romance structure at the deep level of his work. The third chapter examines Haggard’s romance, but differentiates between two Haggardian types, the completed or resolved romance, whichis more classical in its form, and evokes an image of a completed quest, as well as the necessity of the quester entering the world again. Haggard’s “completed” African romance, it is argued, is resolved only in terms of a colonial vision. Chapter Four, by contrast, examines examples of his unresolved African romance, in which African ideals implode, and show themselves to be inneed of foreign intervention. It is argued that Haggard’s image of Africa was based on the unresolved or incomplete romance. His vision of Africa was such that it could not in itself provide the materialfor completed romance. This vision saw intervention as the only option for South Africa. While Plaatje uses elements of Haggard’s “incomplete” romance models when writing Mhudi, he handles both his narrative and politicalcommentaryin this text in terms of his own politicalthought. This non-racial politicalvisionis guided by his belief that virtue and vice are not the monopoly of any colour, a non-racialism he associates with Shakespeare. However, within the context of the South Africa of his fictionand of his life, this non-racial ideal is constantly under threat. It is partly threatened by political forces, but also challenged by moral changes within individuals and societies. In Chapter Five the examination of Plaatje’s work begins withhis Boer War Diary, inwhicha romance structure is sought beneath his diurnal observations and political optimismduring a time of warfare and siege. The discussion of this text is followed by a reading of Native Life in South Africa in which it is argued that Plaatje looks, in the midst of personal and social suffering, for that which can translate a tragic situation into romance resolution. “Translation” is used in a broad sense, echoing Plaatje’s view of the importance of translation for cross-cultural understanding and harmony. The arguments of Chapter Five are extended into Chapter Six, where a reading of Mhudi places emphasis on the possibilities of change implied in romance. Plaatje’s non-racial humanism recognizes the great potential for injustice and human suffering within the context of South African racism, but constantly seeks to translate such suffering into the triumph of romance. While the narrative of Mhudi concludes on a romance peak, tensions between the tragic and romance possibilities alert the reader to the sense that, despite its romance resolution, something has been lost in the translation of the potential tragedy into romance.
- Full Text:
- Date Issued: 2001
Regulation of tryptophan-2,3-dioxygenase and pineal indoleamines by selected tryptophan derivatives and antidepressants
- Authors: Walsh, Harold Archibold
- Date: 1997
- Subjects: Antidepressants Tryptophan -- Physiological effect Tryptophan -- Therapeutic use Depression, Mental -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4017 , http://hdl.handle.net/10962/d1004077
- Description: The regulation of tryptophan-2,3-dioxygenase (TDO) (EC 1.13.1.12) and, to a lesser extent, pineal indoleamines, both in vitro and in vivo, is examined in this study. Rat liver TDO is a cytosolic enzyme which plays a crucial role in the regulation of circulating tryptophan (TRP) levels. Stimulation of this enzyme by heme enhances the catabolism of TRP, making less TRP available for uptake into the brain and other tissues, and for protein synthesis. At pH 7, the enzyme has an approximate Km of 100μM, is subject to substrate inhibition immediately beyond Sopt([S] at Vmax), and response of the enzyme is cooperative in both uninhibited and inhibited regions. Hill analysis of the uninhibited region reveals a biphasic plot and two classes of binding sites. Negative cooperativity is brought about through deprotonation of the enzyme. Substrate iphibition also occurs at both acidic and basic pH values with concomitant shifts in Sopt. The results obtained indicate that substrate inhibition could be an additional mechanism whereby the flux through the TRP-kynurenine pathway is regulated. TDO is subject to a diurnal rhythm, with peak activity during the pre-dark period and the loweSt activity towards the end of the dark period. It is possible that the enzyme controls the synthesis of the neurotransmitter serotonin (5-HT), and that the circadian rhythm in TDO activity is due to the endogenous rhythm of melatonin (aMT) production by the pineal gland. In the present study, aMT displaces TRP from bovine serum albumin (BSA) in vitro, and it is therefore possible for the indoleamine to regulate the availability of TRP for uptake into the brain for conversion to its derivatives. Chronic intraperitoneal administration of aMT affects physiological hepatic parameters in rats, such as TDO activity and stromal fatty acid composition, whilst no observable effect is demonstrable with respect to protein synthesis, nucleic acid metabolism, membrane fatty acid composition and pineal indole biosynthesis. On the other hand, chronic treatment of rats with antidepressants, the tricyclic desmethylimipramine (DMI) and the selective serotonin reuptake inhibitor (SSRI), fluoxetine, reveals significant negative alterations in TDO concentrations and pineal indole amine synthesis. Combining aMT with any of these two drugs normalises the activity of the hepatic enzyme. DMI is found to be an effective inhibitor of TDO in the micromolar range in vitro, and also affects total enzyme concentrations in vivo. Fluoxetine has no effect on TDO in vitro, but in vivo also reduces total enzyme levels in the liver. However, the SSRI does not affect conjugation between apo- and holoenzyme. Instead, it decreases extant holoenzyme levels. Indoleamine synthesis by the pineal gland, in organ culture, is altered by both antidepressants, although in different ways. DMI increases N-acetylserotonin levels and reduces the output of methoxyindole acetic acid and meth6xytryptophol. Fluoxetine treatment markedly reduces aMT concentrations and also brings about high levels of the 5-HT catabolites, 5-hydroxytryptophol and 5-hydroxyindole acetic acid. Insulin also lowers aMT synthesis significantly in pineal organ cultures, via a mechamsm that involves inhibition of the enzyme, N-acetyl transferase, that regulates aMT synthesis. The effects of insulin on pineal indole metabolism are due to the observation that a carbohydrate rich diet which induces insulin release elevates plasma TRP and brain 5-HT, but has no effect on pineal TRP and indole amine synthesis. It could thus be possible for insulin to have an effect on the pineal, since the latter is outside the blood brain barrier. The finilings of this study support the biogenic amine deficiency hypothesis, implicating some of the major biogenic amines such as noradrenaline (NA), 5-HT and aMT in depression. There is believed to be a deficiency of NA and 5-HT at their respective synapses in the depressed state. The drug DMI could act, firstly, by inhibiting TDO and thus increasing plasma TRP levels, and could, secondly, stimulate NA release and inhibit NA reuptake at the pineal membrane. The combined effect would be to enhance aMT synthesis, with eventual remission. Fluoxetine, on the other hand, appears to utilize a slightly different mode of action to DMI, which seems to focus on the preservation of 5-HT. The fact that aMT counteracts the effects of both antidepressants, and restores the activity of TDO to that of the controls, is also consistent with the observation that the therapeutic action of drugs such as these coincides willi the restoration of normal plasma levels of the neurohormone in depressives. In view of the biogenic amine deficiency hypothesis of depression and the contentious claim that TDO is the major peripheral determinant of brain TRP, brain 5-HT and ultimately aMT, the regulation of TDO is investigated and discussed. The study concludes that TDO activity is regulated by a number of endogenous compounds which are mainly derivatives of TRP, such as aMT and oxidized nicotinamide adenine dinucleotide and exogenous substances, of which DMI and fluoxetine are but two. In addition, modulation of IDO activity in depression appears to be an important aspect of antidepressant action. aMT, the product of the pineal gland, also has the potential to increase plasma TRP and hence forebrain TRP levels, and ultimately 5-HT concentrations, firstly by displacing TRP from serum albumin and secondly by inhibiting TDO.
- Full Text:
- Date Issued: 1997
- Authors: Walsh, Harold Archibold
- Date: 1997
- Subjects: Antidepressants Tryptophan -- Physiological effect Tryptophan -- Therapeutic use Depression, Mental -- Treatment
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4017 , http://hdl.handle.net/10962/d1004077
- Description: The regulation of tryptophan-2,3-dioxygenase (TDO) (EC 1.13.1.12) and, to a lesser extent, pineal indoleamines, both in vitro and in vivo, is examined in this study. Rat liver TDO is a cytosolic enzyme which plays a crucial role in the regulation of circulating tryptophan (TRP) levels. Stimulation of this enzyme by heme enhances the catabolism of TRP, making less TRP available for uptake into the brain and other tissues, and for protein synthesis. At pH 7, the enzyme has an approximate Km of 100μM, is subject to substrate inhibition immediately beyond Sopt([S] at Vmax), and response of the enzyme is cooperative in both uninhibited and inhibited regions. Hill analysis of the uninhibited region reveals a biphasic plot and two classes of binding sites. Negative cooperativity is brought about through deprotonation of the enzyme. Substrate iphibition also occurs at both acidic and basic pH values with concomitant shifts in Sopt. The results obtained indicate that substrate inhibition could be an additional mechanism whereby the flux through the TRP-kynurenine pathway is regulated. TDO is subject to a diurnal rhythm, with peak activity during the pre-dark period and the loweSt activity towards the end of the dark period. It is possible that the enzyme controls the synthesis of the neurotransmitter serotonin (5-HT), and that the circadian rhythm in TDO activity is due to the endogenous rhythm of melatonin (aMT) production by the pineal gland. In the present study, aMT displaces TRP from bovine serum albumin (BSA) in vitro, and it is therefore possible for the indoleamine to regulate the availability of TRP for uptake into the brain for conversion to its derivatives. Chronic intraperitoneal administration of aMT affects physiological hepatic parameters in rats, such as TDO activity and stromal fatty acid composition, whilst no observable effect is demonstrable with respect to protein synthesis, nucleic acid metabolism, membrane fatty acid composition and pineal indole biosynthesis. On the other hand, chronic treatment of rats with antidepressants, the tricyclic desmethylimipramine (DMI) and the selective serotonin reuptake inhibitor (SSRI), fluoxetine, reveals significant negative alterations in TDO concentrations and pineal indole amine synthesis. Combining aMT with any of these two drugs normalises the activity of the hepatic enzyme. DMI is found to be an effective inhibitor of TDO in the micromolar range in vitro, and also affects total enzyme concentrations in vivo. Fluoxetine has no effect on TDO in vitro, but in vivo also reduces total enzyme levels in the liver. However, the SSRI does not affect conjugation between apo- and holoenzyme. Instead, it decreases extant holoenzyme levels. Indoleamine synthesis by the pineal gland, in organ culture, is altered by both antidepressants, although in different ways. DMI increases N-acetylserotonin levels and reduces the output of methoxyindole acetic acid and meth6xytryptophol. Fluoxetine treatment markedly reduces aMT concentrations and also brings about high levels of the 5-HT catabolites, 5-hydroxytryptophol and 5-hydroxyindole acetic acid. Insulin also lowers aMT synthesis significantly in pineal organ cultures, via a mechamsm that involves inhibition of the enzyme, N-acetyl transferase, that regulates aMT synthesis. The effects of insulin on pineal indole metabolism are due to the observation that a carbohydrate rich diet which induces insulin release elevates plasma TRP and brain 5-HT, but has no effect on pineal TRP and indole amine synthesis. It could thus be possible for insulin to have an effect on the pineal, since the latter is outside the blood brain barrier. The finilings of this study support the biogenic amine deficiency hypothesis, implicating some of the major biogenic amines such as noradrenaline (NA), 5-HT and aMT in depression. There is believed to be a deficiency of NA and 5-HT at their respective synapses in the depressed state. The drug DMI could act, firstly, by inhibiting TDO and thus increasing plasma TRP levels, and could, secondly, stimulate NA release and inhibit NA reuptake at the pineal membrane. The combined effect would be to enhance aMT synthesis, with eventual remission. Fluoxetine, on the other hand, appears to utilize a slightly different mode of action to DMI, which seems to focus on the preservation of 5-HT. The fact that aMT counteracts the effects of both antidepressants, and restores the activity of TDO to that of the controls, is also consistent with the observation that the therapeutic action of drugs such as these coincides willi the restoration of normal plasma levels of the neurohormone in depressives. In view of the biogenic amine deficiency hypothesis of depression and the contentious claim that TDO is the major peripheral determinant of brain TRP, brain 5-HT and ultimately aMT, the regulation of TDO is investigated and discussed. The study concludes that TDO activity is regulated by a number of endogenous compounds which are mainly derivatives of TRP, such as aMT and oxidized nicotinamide adenine dinucleotide and exogenous substances, of which DMI and fluoxetine are but two. In addition, modulation of IDO activity in depression appears to be an important aspect of antidepressant action. aMT, the product of the pineal gland, also has the potential to increase plasma TRP and hence forebrain TRP levels, and ultimately 5-HT concentrations, firstly by displacing TRP from serum albumin and secondly by inhibiting TDO.
- Full Text:
- Date Issued: 1997
An investigation into the bacterial diversity associated with South African latrunculid sponges that produce bioactive secondary metabolites
- Authors: Walmsley, Tara Aisling
- Date: 2014
- Subjects: Sponges -- South Africa -- Algoa Bay , Sponges -- Classification , Metabolites -- South Africa -- Algoa Bay , Marine metabolites -- South Africa -- Algoa Bay , PQQ (Biochemistry) , Bacterial diversity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4109 , http://hdl.handle.net/10962/d1012943
- Description: Algoa Bay Latrunculid sponges are well known for their production of cytotoxic pyrroloiminoquinones with speculation that these secondary metabolites may have a microbial origin. This study describes a thorough investigation into the bacterial community associated with Tsitsikamma favus, Tsitsikamma scurra a newly described Latrunculia sp. and a yellow encrusting sponge associated with T. scurra. Molecular and chemical characterisation were used in conjunction with traditional taxonomy in identification of the sponge specimens. The 28S rRNA and COX1 analysis confirmed the traditional taxonomy with T. favus and T. scurra being very closely related. Chemical analysis revealed that T. favus and T. scurra shared the discorhabdins 2,4-debromo-3-dihydrodiscorhabdin C, 7,8-dehydro-3-dihydrodiscorhabdin C and 14-bromo-1-hydroxy-discorhabdin V in common with each other and Tsitsikamma pedunculata indicating that these pyrroloiminoquinones are common to Tsitsikamma sponges in general. The bacterial community associated with T. favus was explored using 16S rRNA molecular techniques including DGGE, clonal libraries of full length 16S rRNA genes, as well as 454 pyrosequencing. DGGE analysis revealed that the bacterial community associated with T. favus appeared to be highly conserved, which was confirmed by both the clone library and 454 pyrosequencing, with the Betaproteobacteria as the most dominant class. Further exploration into T. favus, as well as T. scurra, Latrunculia sp. and the yellow encrusting sponge indicated that the bacterial populations associated with each of these sponge species were conserved and species specific. OTU analysis to the species level revealed that T. favus and T. scurra shared an abundant Spirochaete species in common while the most abundant species in the Latrunculia sp. and the yellow encrusting sponge belonged to the class Betaproteobacteria. The exclusivity of the tsitsikammamines to T. favus precipitated attempts to culture the T. favus associated bacteria, with a focus on the dominant betaproteobacterium as indicated by the 16S rRNA clone library. Actinobacteria associated with the Algoa Bay sponge specimens were also cultured and the actinobacterial isolates were sent for screening against Mycobacterium aurum with two Kocuria kristinae isolates and a Streptomyces albdioflavus isolate showing good antimycobacterial activity.
- Full Text:
- Date Issued: 2014
- Authors: Walmsley, Tara Aisling
- Date: 2014
- Subjects: Sponges -- South Africa -- Algoa Bay , Sponges -- Classification , Metabolites -- South Africa -- Algoa Bay , Marine metabolites -- South Africa -- Algoa Bay , PQQ (Biochemistry) , Bacterial diversity
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4109 , http://hdl.handle.net/10962/d1012943
- Description: Algoa Bay Latrunculid sponges are well known for their production of cytotoxic pyrroloiminoquinones with speculation that these secondary metabolites may have a microbial origin. This study describes a thorough investigation into the bacterial community associated with Tsitsikamma favus, Tsitsikamma scurra a newly described Latrunculia sp. and a yellow encrusting sponge associated with T. scurra. Molecular and chemical characterisation were used in conjunction with traditional taxonomy in identification of the sponge specimens. The 28S rRNA and COX1 analysis confirmed the traditional taxonomy with T. favus and T. scurra being very closely related. Chemical analysis revealed that T. favus and T. scurra shared the discorhabdins 2,4-debromo-3-dihydrodiscorhabdin C, 7,8-dehydro-3-dihydrodiscorhabdin C and 14-bromo-1-hydroxy-discorhabdin V in common with each other and Tsitsikamma pedunculata indicating that these pyrroloiminoquinones are common to Tsitsikamma sponges in general. The bacterial community associated with T. favus was explored using 16S rRNA molecular techniques including DGGE, clonal libraries of full length 16S rRNA genes, as well as 454 pyrosequencing. DGGE analysis revealed that the bacterial community associated with T. favus appeared to be highly conserved, which was confirmed by both the clone library and 454 pyrosequencing, with the Betaproteobacteria as the most dominant class. Further exploration into T. favus, as well as T. scurra, Latrunculia sp. and the yellow encrusting sponge indicated that the bacterial populations associated with each of these sponge species were conserved and species specific. OTU analysis to the species level revealed that T. favus and T. scurra shared an abundant Spirochaete species in common while the most abundant species in the Latrunculia sp. and the yellow encrusting sponge belonged to the class Betaproteobacteria. The exclusivity of the tsitsikammamines to T. favus precipitated attempts to culture the T. favus associated bacteria, with a focus on the dominant betaproteobacterium as indicated by the 16S rRNA clone library. Actinobacteria associated with the Algoa Bay sponge specimens were also cultured and the actinobacterial isolates were sent for screening against Mycobacterium aurum with two Kocuria kristinae isolates and a Streptomyces albdioflavus isolate showing good antimycobacterial activity.
- Full Text:
- Date Issued: 2014