Population structure, growth and recruitment of two exploited infralittoral molluscs (Haliotis midae and Turbo sarmaticus) along the south east coast, South Africa
- Authors: Proudfoot, Lee-Anne
- Date: 2007
- Subjects: Abalones -- South Africa , Abalones -- Growth -- South Africa , Turbinidae -- South Africa , Mollusks -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5744 , http://hdl.handle.net/10962/d1005430 , Abalones -- South Africa , Abalones -- Growth -- South Africa , Turbinidae -- South Africa , Mollusks -- South Africa
- Description: The two most frequently exploited species along the south east coast of South Africa are the gastropods, Haliotis midae (abalone) and Turbo sarmaticus (alikreukel). H. midae is a high valued commercial species, and suffers intense levels of illegal fishing. T. sarmaticus however, has no commercial value but is the preferred food item for impoverished subsistence communities. Owing to the fact that no legal commercial fishery exists for either species along the south coast, very few studies have been undertaken, especially in the heavily exploited infralittoral. Infralittoral size frequency distributions for both species revealed significant variation in density and size among sites of varying exploitation pressure. Densities ranged between 0 – 2.23 m⁻² (H. midae) and 0.03 – 4.93 m⁻² (T. sarmaticus) and maximum shell lengths ranged from 49.4 – 153.5 mm (H. midae) and 28.3 – 104.4 mm (T. sarmaticus). Relatively high densities and large sizes were found in marine reserves and secluded areas, and low densities and small sizes at sites near to large population centres and within the former Ciskei homeland region. Mean size of the largest 10% of the population, total density and sexually mature density were significantly related to exploitation predictors for both species. In addition, densities of H. midae juveniles were significantly related to exploitation predictors, suggesting that recruitment may be suppressed at the most exploited sites. Exploitation of T. sarmaticus tended to be localized with refuge and subtidal populations persisting. H. midae exploitation was however, far more extensive and intense. Growth of H. midae was investigated using three methods; mark-recapture, cohort analysis and growth banding analysis at Kowie Rocks, Port Alfred. The most useful of these methods for determining growth was a new technique described for growth banding analysis; which was validated using cohort analysis and measurements of shells of known age. This technique was less time consuming and labour intensive than previously described methods. Abalone growth was best described by the Schnute (1981) growth function. Systematic geographic variation in growth was observed for 10 sites along the South African coastline. Significant differences in growth among sites existed for animals between 0-4 years (P < 0.0001) and 4-6 years (P < 0.0001), and in the mean maximum sizes attained (P < 0.001). In general, abalone from the south east/east coast were found to have faster growth rates, smaller mean maximum sizes and attained sexual maturity earlier than those along the south west/ west coast. Haliotis midae recruit and juvenile densities were found to differ significantly among sites of varying exploitation pressure (P < 0.0001) and among months for recruit densities (P < 0.001). Exploited sites had low recruit and juvenile densities compared to unexploited sites and peak recruitment occurred during October/ November 2005. Recruit densities were significantly related to infralittoral adult densities during two of the three sampling months (P<0.05), when recruitment was low. No relationship was observed during the period of high recruitment, with all sites receiving high recruit densities. It was concluded that variation in recruit densities was the result of a combination of both density-dependent relationships (i.e. local spawner density and temporal variability in recruitment intensity) and the possible dispersal capabilities of H. midae. In addition, it was concluded that at present recruitment overfishing was not occurring along the south east coast. Post-recruitment mortality rates were variable but relatively constant, with hypothetical percentage survival and density curves revealing high rates and similar mortality curves among sites. Variation in juvenile densities was consequently a result of initial recruit densities and not variation in post-recruitment mortality. T. sarmaticus populations were found to be regionally sustainable and persisted along the south east coast due to adjacent intertidal and subtidal refuge populations. However, H. midae populations are becoming decimated along the south east coast. From the information obtained in this study new management proposals were suggested and discussed, such as closed areas and region-based management fisheries together with stock enhancement. These suggestions may prove to be feasible alternatives to present management strategies.
- Full Text:
- Authors: Proudfoot, Lee-Anne
- Date: 2007
- Subjects: Abalones -- South Africa , Abalones -- Growth -- South Africa , Turbinidae -- South Africa , Mollusks -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5744 , http://hdl.handle.net/10962/d1005430 , Abalones -- South Africa , Abalones -- Growth -- South Africa , Turbinidae -- South Africa , Mollusks -- South Africa
- Description: The two most frequently exploited species along the south east coast of South Africa are the gastropods, Haliotis midae (abalone) and Turbo sarmaticus (alikreukel). H. midae is a high valued commercial species, and suffers intense levels of illegal fishing. T. sarmaticus however, has no commercial value but is the preferred food item for impoverished subsistence communities. Owing to the fact that no legal commercial fishery exists for either species along the south coast, very few studies have been undertaken, especially in the heavily exploited infralittoral. Infralittoral size frequency distributions for both species revealed significant variation in density and size among sites of varying exploitation pressure. Densities ranged between 0 – 2.23 m⁻² (H. midae) and 0.03 – 4.93 m⁻² (T. sarmaticus) and maximum shell lengths ranged from 49.4 – 153.5 mm (H. midae) and 28.3 – 104.4 mm (T. sarmaticus). Relatively high densities and large sizes were found in marine reserves and secluded areas, and low densities and small sizes at sites near to large population centres and within the former Ciskei homeland region. Mean size of the largest 10% of the population, total density and sexually mature density were significantly related to exploitation predictors for both species. In addition, densities of H. midae juveniles were significantly related to exploitation predictors, suggesting that recruitment may be suppressed at the most exploited sites. Exploitation of T. sarmaticus tended to be localized with refuge and subtidal populations persisting. H. midae exploitation was however, far more extensive and intense. Growth of H. midae was investigated using three methods; mark-recapture, cohort analysis and growth banding analysis at Kowie Rocks, Port Alfred. The most useful of these methods for determining growth was a new technique described for growth banding analysis; which was validated using cohort analysis and measurements of shells of known age. This technique was less time consuming and labour intensive than previously described methods. Abalone growth was best described by the Schnute (1981) growth function. Systematic geographic variation in growth was observed for 10 sites along the South African coastline. Significant differences in growth among sites existed for animals between 0-4 years (P < 0.0001) and 4-6 years (P < 0.0001), and in the mean maximum sizes attained (P < 0.001). In general, abalone from the south east/east coast were found to have faster growth rates, smaller mean maximum sizes and attained sexual maturity earlier than those along the south west/ west coast. Haliotis midae recruit and juvenile densities were found to differ significantly among sites of varying exploitation pressure (P < 0.0001) and among months for recruit densities (P < 0.001). Exploited sites had low recruit and juvenile densities compared to unexploited sites and peak recruitment occurred during October/ November 2005. Recruit densities were significantly related to infralittoral adult densities during two of the three sampling months (P<0.05), when recruitment was low. No relationship was observed during the period of high recruitment, with all sites receiving high recruit densities. It was concluded that variation in recruit densities was the result of a combination of both density-dependent relationships (i.e. local spawner density and temporal variability in recruitment intensity) and the possible dispersal capabilities of H. midae. In addition, it was concluded that at present recruitment overfishing was not occurring along the south east coast. Post-recruitment mortality rates were variable but relatively constant, with hypothetical percentage survival and density curves revealing high rates and similar mortality curves among sites. Variation in juvenile densities was consequently a result of initial recruit densities and not variation in post-recruitment mortality. T. sarmaticus populations were found to be regionally sustainable and persisted along the south east coast due to adjacent intertidal and subtidal refuge populations. However, H. midae populations are becoming decimated along the south east coast. From the information obtained in this study new management proposals were suggested and discussed, such as closed areas and region-based management fisheries together with stock enhancement. These suggestions may prove to be feasible alternatives to present management strategies.
- Full Text:
Preface to Rhodes University Research Report, 2007
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7654 , http://hdl.handle.net/10962/d1015782
- Full Text:
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7654 , http://hdl.handle.net/10962/d1015782
- Full Text:
Pricing exotic options using C++
- Authors: Nhongo, Tawuya D R
- Date: 2007
- Subjects: C++ (Computer program language) , Monte Carlo method , Simulation methods , Options (Finance) -- Mathematical models , Pricing -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5577 , http://hdl.handle.net/10962/d1008373 , C++ (Computer program language) , Monte Carlo method , Simulation methods , Options (Finance) -- Mathematical models , Pricing -- Mathematical models
- Description: This document demonstrates the use of the C++ programming language as a simulation tool in the efficient pricing of exotic European options. Extensions to the basic problem of simulation pricing are undertaken including variance reduction by conditional expectation, control and antithetic variates. Ultimately we were able to produce a modularized, easily extend-able program which effectively makes use of Monte Carlo simulation techniques to price lookback, Asian and barrier exotic options. Theories of variance reduction were validated except in cases where we used control variates in combination with the other variance reduction techniques in which case we observed increased variance. Again, the main aim of this half thesis was to produce a C++ program which would produce stable pricings of exotic options.
- Full Text:
- Authors: Nhongo, Tawuya D R
- Date: 2007
- Subjects: C++ (Computer program language) , Monte Carlo method , Simulation methods , Options (Finance) -- Mathematical models , Pricing -- Mathematical models
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5577 , http://hdl.handle.net/10962/d1008373 , C++ (Computer program language) , Monte Carlo method , Simulation methods , Options (Finance) -- Mathematical models , Pricing -- Mathematical models
- Description: This document demonstrates the use of the C++ programming language as a simulation tool in the efficient pricing of exotic European options. Extensions to the basic problem of simulation pricing are undertaken including variance reduction by conditional expectation, control and antithetic variates. Ultimately we were able to produce a modularized, easily extend-able program which effectively makes use of Monte Carlo simulation techniques to price lookback, Asian and barrier exotic options. Theories of variance reduction were validated except in cases where we used control variates in combination with the other variance reduction techniques in which case we observed increased variance. Again, the main aim of this half thesis was to produce a C++ program which would produce stable pricings of exotic options.
- Full Text:
Public sector industrial relations in the context of alliance politics: the case of Makana Local Municipality, South Africa (1994-2006)
- Authors: Makwembere, Sandra
- Date: 2007
- Subjects: Makana Municipality , South African Municipal Workers Union , African National Congress , Cosatu , South African Communist Party , Local government -- South Africa -- Eastern Cape , Industrial relations -- South Africa -- Eastern Cape , Labor unions -- South Africa , South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3301 , http://hdl.handle.net/10962/d1003089 , Makana Municipality , South African Municipal Workers Union , African National Congress , Cosatu , South African Communist Party , Local government -- South Africa -- Eastern Cape , Industrial relations -- South Africa -- Eastern Cape , Labor unions -- South Africa , South Africa -- Politics and government -- 1994-
- Description: This thesis is in the field of Industrial Relations. It concerns a micro-level investigation of the dynamics of public sector industrial relations in post-apartheid South Africa. It focuses on the Tripartite Alliance between the African National Congress (ANC), the South African Communist Party (SACP) and the Congress of South African Trade Unions (COSATU) and explores what the Alliance relationship has meant for the traditional roles of employees and their representatives on the one hand, and employers and their representatives on the other. The thesis examines the political, organisational and societal contradictions and implications for COSATU public sector union affiliates and their members in their relationship to the ANC as an ally (via the Alliance) and the context in which ANC members form part of management (in government). The South African Municipal Workers’ Union (SAMWU) was used as an archetype of a COSATU public sector union affiliate that engages with the State as employer at the municipal level. It is a case study of Makana Local Municipality (Eastern Cape Province, South Africa) using qualitative research techniques and content analysis to derive the relevant information. The author conducted a series of in-depth interviews of key informants and observations at Makana Local Municipality were done. Based on the empirical data obtained from the investigation, the thesis argues that the traditional roles in the employment relationship at the workplace have been affected by the political alliance. Industrial relations roles have become increasingly vague especially since many within local government share ANC/SACP memberships with members of the trade union. The study also highlights that within an increasingly globalising post-apartheid environment, the Alliance provides mixture of benefits and challenges for workplace negotiations and employment relations in ways that macro-level analyses of employer-employee relationships do not always capture.
- Full Text:
- Authors: Makwembere, Sandra
- Date: 2007
- Subjects: Makana Municipality , South African Municipal Workers Union , African National Congress , Cosatu , South African Communist Party , Local government -- South Africa -- Eastern Cape , Industrial relations -- South Africa -- Eastern Cape , Labor unions -- South Africa , South Africa -- Politics and government -- 1994-
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3301 , http://hdl.handle.net/10962/d1003089 , Makana Municipality , South African Municipal Workers Union , African National Congress , Cosatu , South African Communist Party , Local government -- South Africa -- Eastern Cape , Industrial relations -- South Africa -- Eastern Cape , Labor unions -- South Africa , South Africa -- Politics and government -- 1994-
- Description: This thesis is in the field of Industrial Relations. It concerns a micro-level investigation of the dynamics of public sector industrial relations in post-apartheid South Africa. It focuses on the Tripartite Alliance between the African National Congress (ANC), the South African Communist Party (SACP) and the Congress of South African Trade Unions (COSATU) and explores what the Alliance relationship has meant for the traditional roles of employees and their representatives on the one hand, and employers and their representatives on the other. The thesis examines the political, organisational and societal contradictions and implications for COSATU public sector union affiliates and their members in their relationship to the ANC as an ally (via the Alliance) and the context in which ANC members form part of management (in government). The South African Municipal Workers’ Union (SAMWU) was used as an archetype of a COSATU public sector union affiliate that engages with the State as employer at the municipal level. It is a case study of Makana Local Municipality (Eastern Cape Province, South Africa) using qualitative research techniques and content analysis to derive the relevant information. The author conducted a series of in-depth interviews of key informants and observations at Makana Local Municipality were done. Based on the empirical data obtained from the investigation, the thesis argues that the traditional roles in the employment relationship at the workplace have been affected by the political alliance. Industrial relations roles have become increasingly vague especially since many within local government share ANC/SACP memberships with members of the trade union. The study also highlights that within an increasingly globalising post-apartheid environment, the Alliance provides mixture of benefits and challenges for workplace negotiations and employment relations in ways that macro-level analyses of employer-employee relationships do not always capture.
- Full Text:
Race against democracy: a case study of the Mail & Guardian during the early years of the Mbeki presidency, 1999-2002
- Authors: Steenveld, Lynette Noreen
- Date: 2007
- Subjects: Mbeki, Thabo -- In mass media , Mail & Guardian , South African newspapers , Press -- South Africa , Press and politics -- South Africa , Journalism -- South Africa , Mass media and race relations -- South Africa , Racism in the press -- South Africa , Mass media -- Political aspects -- South Africa , South Africa -- Politics and government -- 20th century
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3537 , http://hdl.handle.net/10962/d1015572
- Description: This thesis examines the 1998 complaint of racism against the Mail & Guardian, a leading exponent of South Africa's alternative press in the 1980s, and important contemporary producer of investigative journalism. The study is framed within a cultural studies approach, analysing the Mail & Guardian as constituted by a 'circuit of production': its social context, production, texts, and audiences. The thesis makes three main arguments. First, that the claim of racism cannot be understood outside of a consideration of both the changing political milieu, and subtle changes within the Mail & Guardian itself. Significant social changes relate to the reconfiguration of racial and class identities wrought by the 'Mbeki state'. Within the Mail & Guardian, the thesis argues for the importance of the power and subjectivity of the editor as a key 'factor' shaping the identity of the paper, evidenced in its production practices and textual outputs. In this regard, the thesis departs from a functionalist analysis of particular 'roles' within the newsroom, drawing instead on a post-structuralist approach to organisational studies. Based on this production and social context, the thesis examines key texts which deal with aspects of South Africa's social transformation, and which exemplify aspects of the Mail & Guardian's reporting which led to the complaint of racism by the Black Lawyers Association (BLA) and the Association of Black Accountants (ABASA). Their complaint was that the Mail & Guardian's reporting impugned the dignity of black people, and in so doing was a violation of their rights to dignity and equality which are constitutionally guaranteed. However, as freedom of the press is also guaranteed by the South African constitution, their complaint to the South African Human Rights Commission (SAHRC) resulted in public debate about these contending rights. My second argument relates to the jurisprudential approach to racism, and the related issue of affirmative action, which informed the complaint against the paper. Contrary to the 'normative', liberal approach to these issues, this thesis highlights Critical Race Theory as the jurisprudential basis for both the claimants' accusation of racism against the Mail & Guardian, and aspects of its implicit use in South African human rights adjudication. The thesis argues that in failing to recognise these different philosophical and political bases of legal reasoning, the media, including the Mail & Guardian, in reporting on these matters failed in their purported role of serving the public interest. The thesis concludes by applying Fraser's critique of Habermas's notion of a single, bourgeois public sphere to journalism, thereby suggesting ways in which the critiques of some of the Mail & Guardian's own journalists could be employed to enlarge its approach to journalism - giving voice to constituencies seldom heard in mainstream media.
- Full Text:
- Authors: Steenveld, Lynette Noreen
- Date: 2007
- Subjects: Mbeki, Thabo -- In mass media , Mail & Guardian , South African newspapers , Press -- South Africa , Press and politics -- South Africa , Journalism -- South Africa , Mass media and race relations -- South Africa , Racism in the press -- South Africa , Mass media -- Political aspects -- South Africa , South Africa -- Politics and government -- 20th century
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3537 , http://hdl.handle.net/10962/d1015572
- Description: This thesis examines the 1998 complaint of racism against the Mail & Guardian, a leading exponent of South Africa's alternative press in the 1980s, and important contemporary producer of investigative journalism. The study is framed within a cultural studies approach, analysing the Mail & Guardian as constituted by a 'circuit of production': its social context, production, texts, and audiences. The thesis makes three main arguments. First, that the claim of racism cannot be understood outside of a consideration of both the changing political milieu, and subtle changes within the Mail & Guardian itself. Significant social changes relate to the reconfiguration of racial and class identities wrought by the 'Mbeki state'. Within the Mail & Guardian, the thesis argues for the importance of the power and subjectivity of the editor as a key 'factor' shaping the identity of the paper, evidenced in its production practices and textual outputs. In this regard, the thesis departs from a functionalist analysis of particular 'roles' within the newsroom, drawing instead on a post-structuralist approach to organisational studies. Based on this production and social context, the thesis examines key texts which deal with aspects of South Africa's social transformation, and which exemplify aspects of the Mail & Guardian's reporting which led to the complaint of racism by the Black Lawyers Association (BLA) and the Association of Black Accountants (ABASA). Their complaint was that the Mail & Guardian's reporting impugned the dignity of black people, and in so doing was a violation of their rights to dignity and equality which are constitutionally guaranteed. However, as freedom of the press is also guaranteed by the South African constitution, their complaint to the South African Human Rights Commission (SAHRC) resulted in public debate about these contending rights. My second argument relates to the jurisprudential approach to racism, and the related issue of affirmative action, which informed the complaint against the paper. Contrary to the 'normative', liberal approach to these issues, this thesis highlights Critical Race Theory as the jurisprudential basis for both the claimants' accusation of racism against the Mail & Guardian, and aspects of its implicit use in South African human rights adjudication. The thesis argues that in failing to recognise these different philosophical and political bases of legal reasoning, the media, including the Mail & Guardian, in reporting on these matters failed in their purported role of serving the public interest. The thesis concludes by applying Fraser's critique of Habermas's notion of a single, bourgeois public sphere to journalism, thereby suggesting ways in which the critiques of some of the Mail & Guardian's own journalists could be employed to enlarge its approach to journalism - giving voice to constituencies seldom heard in mainstream media.
- Full Text:
Reading the Sowetan's mediation of the public's response to the Jacob Zuma rape trial: a critical discourse analysis
- Authors: Stent, Alison
- Date: 2007
- Subjects: Zuma, Jacob -- Trials, litigation etc Zuma, Jacob -- Public opinion Sowetan (Johannesburg, South Africa) Populism -- South Africa Social choice -- South Africa Social justice -- South Africa Ethnicity -- Political aspects -- South Africa Rape -- Public opinion Women -- Crimes against -- South Africa Sex discrimination against women -- South Africa Trials (Rape) -- South Africa Rape in mass media Crime and the press -- South Africa Mass media and women -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3485 , http://hdl.handle.net/10962/d1002940
- Description: In this minithesis I conduct a critical discourse analysis to take on a double-pronged task. On the one hand I explore the social phenomenon of the contestation between supporters of then-ANC deputy president Jacob Zuma and supporters of his rape accuser. The trial, which took place in the Johannesburg High Court between mid-February and early May 2006, stirred intense public interest, both locally and internationally. The performance of thousands of Zuma’s supporters and a far smaller number of gender rights lobby groups, both of whom kept a presence outside the court building throughout the trial, received similar attention. Second, I examine how the Sowetan, a national daily tabloid with a black, middle-class readership, mediated the trial through pictures of the theatre outside the court and letters to the editor. The study is informed by post-Marxist and cultural studies perspectives, both approaches that are concerned with issues of power, ideology and the circulation of meaning within specific sociocultural contexts. A rudimentary thematic content analysis draws out some of the main themes from the material, while the critical discourse analysis is located within a theoretical framework based on concepts from Laclau & Mouffe’s theory of meaning, which assumes a power struggle between contesting positions seeking to invalidate one another and to either challenge or support existing hegemonies. This is further informed by, first, Laclau’s theorisation of populism, which assumes that diverse groupings can unite under a demagogue’s banner in shared antagonism towards existing power, and second, by concepts from Mamdani’s theorisation of power and resistance in colonial and post-colonial Africa, which explicates three overarching ideological discourses of human rights, social justice and traditional ethnic practices. The study, then, explores how these three discourses were operationalised by the localised contestations over the trial.
- Full Text: false
- Authors: Stent, Alison
- Date: 2007
- Subjects: Zuma, Jacob -- Trials, litigation etc Zuma, Jacob -- Public opinion Sowetan (Johannesburg, South Africa) Populism -- South Africa Social choice -- South Africa Social justice -- South Africa Ethnicity -- Political aspects -- South Africa Rape -- Public opinion Women -- Crimes against -- South Africa Sex discrimination against women -- South Africa Trials (Rape) -- South Africa Rape in mass media Crime and the press -- South Africa Mass media and women -- South Africa
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3485 , http://hdl.handle.net/10962/d1002940
- Description: In this minithesis I conduct a critical discourse analysis to take on a double-pronged task. On the one hand I explore the social phenomenon of the contestation between supporters of then-ANC deputy president Jacob Zuma and supporters of his rape accuser. The trial, which took place in the Johannesburg High Court between mid-February and early May 2006, stirred intense public interest, both locally and internationally. The performance of thousands of Zuma’s supporters and a far smaller number of gender rights lobby groups, both of whom kept a presence outside the court building throughout the trial, received similar attention. Second, I examine how the Sowetan, a national daily tabloid with a black, middle-class readership, mediated the trial through pictures of the theatre outside the court and letters to the editor. The study is informed by post-Marxist and cultural studies perspectives, both approaches that are concerned with issues of power, ideology and the circulation of meaning within specific sociocultural contexts. A rudimentary thematic content analysis draws out some of the main themes from the material, while the critical discourse analysis is located within a theoretical framework based on concepts from Laclau & Mouffe’s theory of meaning, which assumes a power struggle between contesting positions seeking to invalidate one another and to either challenge or support existing hegemonies. This is further informed by, first, Laclau’s theorisation of populism, which assumes that diverse groupings can unite under a demagogue’s banner in shared antagonism towards existing power, and second, by concepts from Mamdani’s theorisation of power and resistance in colonial and post-colonial Africa, which explicates three overarching ideological discourses of human rights, social justice and traditional ethnic practices. The study, then, explores how these three discourses were operationalised by the localised contestations over the trial.
- Full Text: false
Regulation of hyu gene expression in Agrobacterium tumefaciens strains RU-AE01 and RU-OR
- Authors: Jiwaji, Meesbah
- Date: 2007
- Subjects: Agrobacterium tumefaciens Amino acids Gene expression Hydrolysis Hydantoin Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3983 , http://hdl.handle.net/10962/d1004042
- Description: Several Agrobacterium tumefaciens strains have been isolated for their ability to produce D-amino acids from D, L-substituted hydantoins. The optically pure D-amino acids are used in the synthesis of pharmaceuticals, as food additives and as insecticides. This hydrolysis of D, L-substituted hydantoins is catalysed by two hydantoin-hydrolyzing enzymes, an hydantoinase and an N-carbamyl amino acid amidohydrolase. While the hydantoin-hydrolyzing enzymes have been studied in detail, the mechanisms that control expression of the hyu genes have not. The research reported in this work elucidates some of the mechanisms involved in the regulation of the hyu genes in A. tumefaciens strains. The hydantoin-hydrolyzing enzyme activity from the environmental isolate A. tumefaciens RU-AE01 was characterized. A broad host range vector for the simultaneous analysis of divergent promoters was constructed. The promoter regions responsible for the activation of transcription of hyuH and hyuC were identified by deletion analysis. It was proposed that transcription of hyuH was activated by a putative σ[superscript 54]-dependent promoter or a putative σ[superscript 70]-dependent promoter identified upstream of the hyuH gene. The hyuC gene was activated by a putative σ[superscript 70]-dependent promoter identified upstream of the hyuC gene. The regulation of hydantoinase and N-carbamyl amino acid amidohydrolase enzyme activity was compared to the regulation of transcription from the RU-AE01 hyuH-hyuC region. Expression of the hydantoin-hydrolyzing enzymes was regulated by induction which correlated with reporter enzyme expression from the hyuH and hyuC promoter regions. However, the expression of the hydantoin-hydrolyzing enzymes was also regulated by nitrogen catabolite repression (NCR). This did not correlate to the reporter gene expression of the hyuH promoter region but did compare to the reporter gene expression of the hyuC promoter region. This suggested that NCR of hyuH was at the post-translational level whereas NCR of the hyuC promoter was at the transcriptional level. Pathways involved in the regulation of the hyu genes were characterized. The production of the hydantoin-hydrolyzing enzymes in both A. tumefaciens strains RU-AE01 and RU-OR were regulated by proteins involved in the global ntr pathway. The levels of the hydantoin-hydrolyzing enzymes in strain RU-AE01 were elevated in the presence of increased levels of NtrB and NtrC illustrating the importance of the ntr pathway in the regulation of the levels of the hydantoin-hydrolyzing enzymes. Similarly, in RU-OR the presence of exogenous NtrB and NtrC elevated levels of N-carbamyl amino acid amidohydrolase activity. However, the levels of hydantoinase enzyme activity in strain RU-OR were elevated in the presence of NtrC alone. In addition, the presence of a His6-tagged NtrC molecule abolished the elevation in the levels of the hydantoinase but not the N-carbamyl amino acid amidohydrolase enzyme activity in strain RU-OR. This suggests that NtrC has a direct role in the regulation of the expression of hyuH in RU-OR. In addition, it indicates that the hyu genes in the two A. tumefaciens strains RU-AE01 and RU-OR are different. The presence of the RU-AE01 hyuH-hyuC fragment caused a dramatic increase in the hydantoin-hydrolyzing enzyme activity in strain RU-OR but not strain RU-AE01. This implied the incidence of a possible repressor protein in RU-OR, which is titrated out by the presence of the RU-AE01 hyuH-hyuC fragment. Protein-DNA binding assays suggest that this putative repressor may be 38 kDa in RU-OR cells.
- Full Text:
- Authors: Jiwaji, Meesbah
- Date: 2007
- Subjects: Agrobacterium tumefaciens Amino acids Gene expression Hydrolysis Hydantoin Enzymes
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3983 , http://hdl.handle.net/10962/d1004042
- Description: Several Agrobacterium tumefaciens strains have been isolated for their ability to produce D-amino acids from D, L-substituted hydantoins. The optically pure D-amino acids are used in the synthesis of pharmaceuticals, as food additives and as insecticides. This hydrolysis of D, L-substituted hydantoins is catalysed by two hydantoin-hydrolyzing enzymes, an hydantoinase and an N-carbamyl amino acid amidohydrolase. While the hydantoin-hydrolyzing enzymes have been studied in detail, the mechanisms that control expression of the hyu genes have not. The research reported in this work elucidates some of the mechanisms involved in the regulation of the hyu genes in A. tumefaciens strains. The hydantoin-hydrolyzing enzyme activity from the environmental isolate A. tumefaciens RU-AE01 was characterized. A broad host range vector for the simultaneous analysis of divergent promoters was constructed. The promoter regions responsible for the activation of transcription of hyuH and hyuC were identified by deletion analysis. It was proposed that transcription of hyuH was activated by a putative σ[superscript 54]-dependent promoter or a putative σ[superscript 70]-dependent promoter identified upstream of the hyuH gene. The hyuC gene was activated by a putative σ[superscript 70]-dependent promoter identified upstream of the hyuC gene. The regulation of hydantoinase and N-carbamyl amino acid amidohydrolase enzyme activity was compared to the regulation of transcription from the RU-AE01 hyuH-hyuC region. Expression of the hydantoin-hydrolyzing enzymes was regulated by induction which correlated with reporter enzyme expression from the hyuH and hyuC promoter regions. However, the expression of the hydantoin-hydrolyzing enzymes was also regulated by nitrogen catabolite repression (NCR). This did not correlate to the reporter gene expression of the hyuH promoter region but did compare to the reporter gene expression of the hyuC promoter region. This suggested that NCR of hyuH was at the post-translational level whereas NCR of the hyuC promoter was at the transcriptional level. Pathways involved in the regulation of the hyu genes were characterized. The production of the hydantoin-hydrolyzing enzymes in both A. tumefaciens strains RU-AE01 and RU-OR were regulated by proteins involved in the global ntr pathway. The levels of the hydantoin-hydrolyzing enzymes in strain RU-AE01 were elevated in the presence of increased levels of NtrB and NtrC illustrating the importance of the ntr pathway in the regulation of the levels of the hydantoin-hydrolyzing enzymes. Similarly, in RU-OR the presence of exogenous NtrB and NtrC elevated levels of N-carbamyl amino acid amidohydrolase activity. However, the levels of hydantoinase enzyme activity in strain RU-OR were elevated in the presence of NtrC alone. In addition, the presence of a His6-tagged NtrC molecule abolished the elevation in the levels of the hydantoinase but not the N-carbamyl amino acid amidohydrolase enzyme activity in strain RU-OR. This suggests that NtrC has a direct role in the regulation of the expression of hyuH in RU-OR. In addition, it indicates that the hyu genes in the two A. tumefaciens strains RU-AE01 and RU-OR are different. The presence of the RU-AE01 hyuH-hyuC fragment caused a dramatic increase in the hydantoin-hydrolyzing enzyme activity in strain RU-OR but not strain RU-AE01. This implied the incidence of a possible repressor protein in RU-OR, which is titrated out by the presence of the RU-AE01 hyuH-hyuC fragment. Protein-DNA binding assays suggest that this putative repressor may be 38 kDa in RU-OR cells.
- Full Text:
Relating indigenous knowledge practices and science concepts : an exploratory case study in a secondary school teacher-training programme
- Authors: Mandikonza, Caleb
- Date: 2007
- Subjects: Ethnoscience -- Study and teaching (Secondary) -- Zimbabwe Science -- Study and teaching (Secondary) -- Zimbabwe Teachers -- Training of -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1918 , http://hdl.handle.net/10962/d1007321
- Description: This study reports research on how student teachers in Science at Mutare Teachers' College in Zimbabwe worked with indigenous knowledge practices in relation to science concepts in the secondary school syllabus. The study was conducted among first-year science students and involved them in developing science learning activities for a peer-teaching process that was part of their course. The research was undertaken during a review ofthe college syllabus and as a study to inform the Secondary Teacher Training Environmental Education Programme (ST²EEP). The research design involved the researcher in participant observations and interviews with rural people to document indigenous knowledge practices and to develop materials for the students to work with in the lessons design part of the study. The student teachers used the documented practices to generate learning activities and lesson plans to teach the science concepts they had identified. A peer review session and focus group interviews followed the lesson presentations. Findings from the research point to the rural community being a repository of diverse indigenous knowledge practices. Student teachers showed that they had prior knowledge of both indigenous knowledge practices and science concepts when they come to class. Student teachers were able to relate indigenous knowledge practices and science concepts in ways that have the potential to enhance the learning of science in rural school contexts that lack laboratories and science equipment. The scope of the study does not allow for anything beyond tentative conclusions that point to the need for further work to be undertaken with student teachers and for the research to be extended to teaching and learning interactions in schools. Recommendations are also made for further resource-based work to be undertaken within the forthcoming St²eep implementation phase in 2007.
- Full Text:
- Authors: Mandikonza, Caleb
- Date: 2007
- Subjects: Ethnoscience -- Study and teaching (Secondary) -- Zimbabwe Science -- Study and teaching (Secondary) -- Zimbabwe Teachers -- Training of -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1918 , http://hdl.handle.net/10962/d1007321
- Description: This study reports research on how student teachers in Science at Mutare Teachers' College in Zimbabwe worked with indigenous knowledge practices in relation to science concepts in the secondary school syllabus. The study was conducted among first-year science students and involved them in developing science learning activities for a peer-teaching process that was part of their course. The research was undertaken during a review ofthe college syllabus and as a study to inform the Secondary Teacher Training Environmental Education Programme (ST²EEP). The research design involved the researcher in participant observations and interviews with rural people to document indigenous knowledge practices and to develop materials for the students to work with in the lessons design part of the study. The student teachers used the documented practices to generate learning activities and lesson plans to teach the science concepts they had identified. A peer review session and focus group interviews followed the lesson presentations. Findings from the research point to the rural community being a repository of diverse indigenous knowledge practices. Student teachers showed that they had prior knowledge of both indigenous knowledge practices and science concepts when they come to class. Student teachers were able to relate indigenous knowledge practices and science concepts in ways that have the potential to enhance the learning of science in rural school contexts that lack laboratories and science equipment. The scope of the study does not allow for anything beyond tentative conclusions that point to the need for further work to be undertaken with student teachers and for the research to be extended to teaching and learning interactions in schools. Recommendations are also made for further resource-based work to be undertaken within the forthcoming St²eep implementation phase in 2007.
- Full Text:
Reviewing the use of environmental audits for environmental learning in school contexts: a case study of environmental auditing processes within a professional development course
- Authors: Hoffmann, Patricia Anne
- Date: 2007
- Subjects: Environmental auditing -- Study and teaching -- South Africa -- Case studies Environmental education -- South Africa -- Case studies Sustainable development -- Study and teaching -- South Africa -- Case studies Professional education -- South Africa -- Case studies Teachers -- Training of -- South Africa -- Case studies Educational change -- South Africa -- Case studies
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1746 , http://hdl.handle.net/10962/d1003630
- Description: This case study focuses on the use of environmental audits for learning, by teachers participating in the Schools and Sustainability professional development course in Durban, South Africa. It reviews ways in which audits were choreographed and used for lessons within school contexts. It explores ways in which audits shaped meaning-making interactions and environmental learning processes. This is an interpretive case study, characterized by a moderate realist perspective. Data were generated through interviews with teachers, field observations, photographs, document analysis, and group interviews with learners. Data were analyzed using the general comparative method. The research takes place in the context of educational transformation in South Africa. Some of the challenges accompanying the shift to Outcomes Based Education seem to be associated with naïve interpretations of constructivism and a view of reality as socially constructed and relative. This seems to have influenced ways in which audits are being undertaken in school contexts. This study argues that a realist orientation to auditing may be a more useful process for engaging with the world and enhancing the way learners perceive and respond to environmental risk. Ideas about reality-congruence and the interacting processes of involvement and detachment are of central importance in understanding processes of knowledge construction and meaning making in this study. The study draws on the work of Elias (1987) and Latour (1999) to shed light on the significance of auditing processes in which a close engagement with reality, coupled with a measure of detachment, can lead to the construction of a more reality-congruent account and a more realistic assessment of the environmental issue in focus. Key findings of the study suggest that the effectiveness of environmental auditing as a pedagogical process was influenced by the teachers’ intentions, knowledge and skills, choreography of the audit, nature of the teaching and learning interactions, and ways in which teachers and learners engaged with the findings. The study recommends that auditing activities should be carefully structured and mediated by teachers to be meaningful and to enable learners to identify environmental issues, gather data, engage in critical reflection and deliberate appropriate responses for social and environmental transformation.
- Full Text:
- Authors: Hoffmann, Patricia Anne
- Date: 2007
- Subjects: Environmental auditing -- Study and teaching -- South Africa -- Case studies Environmental education -- South Africa -- Case studies Sustainable development -- Study and teaching -- South Africa -- Case studies Professional education -- South Africa -- Case studies Teachers -- Training of -- South Africa -- Case studies Educational change -- South Africa -- Case studies
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1746 , http://hdl.handle.net/10962/d1003630
- Description: This case study focuses on the use of environmental audits for learning, by teachers participating in the Schools and Sustainability professional development course in Durban, South Africa. It reviews ways in which audits were choreographed and used for lessons within school contexts. It explores ways in which audits shaped meaning-making interactions and environmental learning processes. This is an interpretive case study, characterized by a moderate realist perspective. Data were generated through interviews with teachers, field observations, photographs, document analysis, and group interviews with learners. Data were analyzed using the general comparative method. The research takes place in the context of educational transformation in South Africa. Some of the challenges accompanying the shift to Outcomes Based Education seem to be associated with naïve interpretations of constructivism and a view of reality as socially constructed and relative. This seems to have influenced ways in which audits are being undertaken in school contexts. This study argues that a realist orientation to auditing may be a more useful process for engaging with the world and enhancing the way learners perceive and respond to environmental risk. Ideas about reality-congruence and the interacting processes of involvement and detachment are of central importance in understanding processes of knowledge construction and meaning making in this study. The study draws on the work of Elias (1987) and Latour (1999) to shed light on the significance of auditing processes in which a close engagement with reality, coupled with a measure of detachment, can lead to the construction of a more reality-congruent account and a more realistic assessment of the environmental issue in focus. Key findings of the study suggest that the effectiveness of environmental auditing as a pedagogical process was influenced by the teachers’ intentions, knowledge and skills, choreography of the audit, nature of the teaching and learning interactions, and ways in which teachers and learners engaged with the findings. The study recommends that auditing activities should be carefully structured and mediated by teachers to be meaningful and to enable learners to identify environmental issues, gather data, engage in critical reflection and deliberate appropriate responses for social and environmental transformation.
- Full Text:
Rhodes University 2007 Graduation Ceremonies Address
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: Text
- Identifier: vital:7628 , http://hdl.handle.net/10962/d1012595
- Full Text:
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: Text
- Identifier: vital:7628 , http://hdl.handle.net/10962/d1012595
- Full Text:
Rhodes University : into 2007 and beyond
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7655 , http://hdl.handle.net/10962/d1015783
- Full Text:
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7655 , http://hdl.handle.net/10962/d1015783
- Full Text:
Rhodes University Graduation Ceremony 2007
- Authors: Rhodes University
- Date: 2007
- Language: English
- Type: text
- Identifier: vital:8140 , http://hdl.handle.net/10962/d1007252
- Description: Rhodes University Graduation Ceremonies 1820 Settlers National Monument Thursday, 12 April 2007 at 18:00 [and] Friday, 13 April 2007 at 10:30; 14:30 & 18:00 [and] Saturday, 14 April 2007 at 10:30
- Full Text:
- Authors: Rhodes University
- Date: 2007
- Language: English
- Type: text
- Identifier: vital:8140 , http://hdl.handle.net/10962/d1007252
- Description: Rhodes University Graduation Ceremonies 1820 Settlers National Monument Thursday, 12 April 2007 at 18:00 [and] Friday, 13 April 2007 at 10:30; 14:30 & 18:00 [and] Saturday, 14 April 2007 at 10:30
- Full Text:
Rhodes University Orientation Week : Welcome address of the vice-chancellor of Rhodes University, Dr Saleem Badat, 5 February 2007
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7651 , http://hdl.handle.net/10962/d1015779
- Full Text:
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7651 , http://hdl.handle.net/10962/d1015779
- Full Text:
Rhodes University postgraduates orientation welcome, 9 Feb 2007
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7653 , http://hdl.handle.net/10962/d1015781
- Full Text:
- Authors: Badat, Saleem
- Date: 2007
- Subjects: Rhodes University
- Language: English
- Type: text
- Identifier: vital:7653 , http://hdl.handle.net/10962/d1015781
- Full Text:
Roles : "I am as intently observed as the people photograph"
- Authors: Pelser, Monique Myren
- Date: 2007
- Subjects: Hugo, Pieter Portrait photography Self-portraits Photography, Artistic -- Philosophy
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2457 , http://hdl.handle.net/10962/d1007647
- Description: With this dissertation I propose an investigation of how the photographic portrait attempts to construct and confirm identity through the representation of types. Drawing from theoretical texts by Roland Barthes and Robert Sobieszek and engaging with my own process of self-portraiture, as a means of troubling the usual power relations involved between the photographer and the sitter, I will demonstrate the dialectical nature of these roles involved in photographic portraiture. Looking at Pieter Hugo's portraits of judges in Botswana permits me to deal with issues of masquerade and how fashions and uniforms mask an individual allowing him/her to perform roles and stereotypes in society. Referring to another set of Hugo's images from his ongoing series Looking Aside, I will explore the paradoxical nature of the portrait through the dialectic of the 'self 'and 'other' subject and object split through an exploration of notions of skin and prosthetic skin and the relationship to the liminal space 'opened' between subject and object, or viewer and image.
- Full Text:
- Authors: Pelser, Monique Myren
- Date: 2007
- Subjects: Hugo, Pieter Portrait photography Self-portraits Photography, Artistic -- Philosophy
- Language: English
- Type: Thesis , Masters , MFA
- Identifier: vital:2457 , http://hdl.handle.net/10962/d1007647
- Description: With this dissertation I propose an investigation of how the photographic portrait attempts to construct and confirm identity through the representation of types. Drawing from theoretical texts by Roland Barthes and Robert Sobieszek and engaging with my own process of self-portraiture, as a means of troubling the usual power relations involved between the photographer and the sitter, I will demonstrate the dialectical nature of these roles involved in photographic portraiture. Looking at Pieter Hugo's portraits of judges in Botswana permits me to deal with issues of masquerade and how fashions and uniforms mask an individual allowing him/her to perform roles and stereotypes in society. Referring to another set of Hugo's images from his ongoing series Looking Aside, I will explore the paradoxical nature of the portrait through the dialectic of the 'self 'and 'other' subject and object split through an exploration of notions of skin and prosthetic skin and the relationship to the liminal space 'opened' between subject and object, or viewer and image.
- Full Text:
SAIAB extension opening : lunch for the Deputy-Minister of Science and Technology
- Authors: Badat, Saleem
- Date: 2007
- Subjects: South African Institute of Aquatic Biodiversity (SAIAB)
- Language: English
- Type: text
- Identifier: vital:7657 , http://hdl.handle.net/10962/d1015785
- Full Text:
- Authors: Badat, Saleem
- Date: 2007
- Subjects: South African Institute of Aquatic Biodiversity (SAIAB)
- Language: English
- Type: text
- Identifier: vital:7657 , http://hdl.handle.net/10962/d1015785
- Full Text:
Satellite television use among Zimbabwean professionals : an investigation into audience consumption of SABC Africa's '60 Minutes live in Africa'
- Authors: Mugoni, Petronella Chipo
- Date: 2007
- Subjects: Direct broadcast satellite television -- Zimbabwe Television viewers -- Zimbabwe Television viewers -- Zimbabwe -- Case studies Television broadcasting of news -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3512 , http://hdl.handle.net/10962/d1007707
- Description: Within the context of debates surrounding the consumption of global media by local audiences in Third World countries, this study explores the reasons behind satellite television subscription, and consumption of international news among a sample of young professional men and women in contemporary Zimbabwe. The study seeks to uncover how the research participants respond to news broadcast on SABC Africa's '60 minutes live in Africa', a programme which they can only access via satellite television in their country. Working within the frame of audience studies which insists on understanding media consumption and reception in context, this study examines how the respondents, situated within the specific Zimbabwe context, characterised as it is by serious social, economic and political challenges, respond to both regional news and news about their country on '60 minutes live in Africa'. Within the frame of qualitative research the study employs a two-stage sampling procedure and data collection strategy to uncover the factors that underpin international media consumption and reception by professional men and women situated in a country undergoing rapid change. The findings of the study point to the various social and individual factors that underlie media consumption choices as well as to the different socially patterned reasons why local audiences are either attracted to, or reject global media. The study found that SABC Africa's '60 minutes live in Africa' is more popular and better received than Western-broadcast programmes on channels such as BBC, CNN, and Sky News among Zimbabwean professionals. I also uncovered some evidence that cultural proximity and relevance are of supreme importance in determining which media audiences chose to consume and what level of engagement they bring to their reception of global media. These and other findings directly confront media models that privilege beliefs in cultural imperialism and the dominance of Western media and their effects on Third World audiences.
- Full Text:
- Authors: Mugoni, Petronella Chipo
- Date: 2007
- Subjects: Direct broadcast satellite television -- Zimbabwe Television viewers -- Zimbabwe Television viewers -- Zimbabwe -- Case studies Television broadcasting of news -- Zimbabwe
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:3512 , http://hdl.handle.net/10962/d1007707
- Description: Within the context of debates surrounding the consumption of global media by local audiences in Third World countries, this study explores the reasons behind satellite television subscription, and consumption of international news among a sample of young professional men and women in contemporary Zimbabwe. The study seeks to uncover how the research participants respond to news broadcast on SABC Africa's '60 minutes live in Africa', a programme which they can only access via satellite television in their country. Working within the frame of audience studies which insists on understanding media consumption and reception in context, this study examines how the respondents, situated within the specific Zimbabwe context, characterised as it is by serious social, economic and political challenges, respond to both regional news and news about their country on '60 minutes live in Africa'. Within the frame of qualitative research the study employs a two-stage sampling procedure and data collection strategy to uncover the factors that underpin international media consumption and reception by professional men and women situated in a country undergoing rapid change. The findings of the study point to the various social and individual factors that underlie media consumption choices as well as to the different socially patterned reasons why local audiences are either attracted to, or reject global media. The study found that SABC Africa's '60 minutes live in Africa' is more popular and better received than Western-broadcast programmes on channels such as BBC, CNN, and Sky News among Zimbabwean professionals. I also uncovered some evidence that cultural proximity and relevance are of supreme importance in determining which media audiences chose to consume and what level of engagement they bring to their reception of global media. These and other findings directly confront media models that privilege beliefs in cultural imperialism and the dominance of Western media and their effects on Third World audiences.
- Full Text:
Securing media streams in an Asterisk-based environment and evaluating the resulting performance cost
- Authors: Clayton, Bradley
- Date: 2007 , 2007-01-08
- Subjects: Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4647 , http://hdl.handle.net/10962/d1006606 , Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Description: When adding Confidentiality, Integrity and Availability (CIA) to a multi-user VoIP (Voice over IP) system, performance and quality are at risk. The aim of this study is twofold. Firstly, it describes current methods suitable to secure voice streams within a VoIP system and make them available in an Asterisk-based VoIP environment. (Asterisk is a well established, open-source, TDM/VoIP PBX.) Secondly, this study evaluates the performance cost incurred after implementing each security method within the Asterisk-based system, using a special testbed suite, named DRAPA, which was developed expressly for this study. The three security methods implemented and studied were IPSec (Internet Protocol Security), SRTP (Secure Real-time Transport Protocol), and SIAX2 (Secure Inter-Asterisk eXchange 2 protocol). From the experiments, it was found that bandwidth and CPU usage were significantly affected by the addition of CIA. In ranking the three security methods in terms of these two resources, it was found that SRTP incurs the least bandwidth overhead, followed by SIAX2 and then IPSec. Where CPU utilisation is concerned, it was found that SIAX2 incurs the least overhead, followed by IPSec, and then SRTP.
- Full Text:
- Authors: Clayton, Bradley
- Date: 2007 , 2007-01-08
- Subjects: Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4647 , http://hdl.handle.net/10962/d1006606 , Asterisk (Computer file) , Computer networks -- Security measures , Internet telephony -- Security measures
- Description: When adding Confidentiality, Integrity and Availability (CIA) to a multi-user VoIP (Voice over IP) system, performance and quality are at risk. The aim of this study is twofold. Firstly, it describes current methods suitable to secure voice streams within a VoIP system and make them available in an Asterisk-based VoIP environment. (Asterisk is a well established, open-source, TDM/VoIP PBX.) Secondly, this study evaluates the performance cost incurred after implementing each security method within the Asterisk-based system, using a special testbed suite, named DRAPA, which was developed expressly for this study. The three security methods implemented and studied were IPSec (Internet Protocol Security), SRTP (Secure Real-time Transport Protocol), and SIAX2 (Secure Inter-Asterisk eXchange 2 protocol). From the experiments, it was found that bandwidth and CPU usage were significantly affected by the addition of CIA. In ranking the three security methods in terms of these two resources, it was found that SRTP incurs the least bandwidth overhead, followed by SIAX2 and then IPSec. Where CPU utilisation is concerned, it was found that SIAX2 incurs the least overhead, followed by IPSec, and then SRTP.
- Full Text:
Securing softswitches from malicious attacks
- Authors: Opie, Jake Weyman
- Date: 2007
- Subjects: Internet telephony -- Security measures , Computer networks -- Security measures , Digital telephone systems , Communication -- Technological innovations , Computer network protocols , TCP/IP (Computer network protocol) , Switching theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4683 , http://hdl.handle.net/10962/d1007714 , Internet telephony -- Security measures , Computer networks -- Security measures , Digital telephone systems , Communication -- Technological innovations , Computer network protocols , TCP/IP (Computer network protocol) , Switching theory
- Description: Traditionally, real-time communication, such as voice calls, has run on separate, closed networks. Of all the limitations that these networks had, the ability of malicious attacks to cripple communication was not a crucial one. This situation has changed radically now that real-time communication and data have merged to share the same network. The objective of this project is to investigate the securing of softswitches with functionality similar to Private Branch Exchanges (PBX) from malicious attacks. The focus of the project will be a practical investigation of how to secure ILANGA, an ASTERISK-based system under development at Rhodes University. The practical investigation that focuses on ILANGA is based on performing six varied experiments on the different components of ILANGA. Before the six experiments are performed, basic preliminary security measures and the restrictions placed on the access to the database are discussed. The outcomes of these experiments are discussed and the precise reasons why these attacks were either successful or unsuccessful are given. Suggestions of a theoretical nature on how to defend against the successful attacks are also presented.
- Full Text:
- Authors: Opie, Jake Weyman
- Date: 2007
- Subjects: Internet telephony -- Security measures , Computer networks -- Security measures , Digital telephone systems , Communication -- Technological innovations , Computer network protocols , TCP/IP (Computer network protocol) , Switching theory
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4683 , http://hdl.handle.net/10962/d1007714 , Internet telephony -- Security measures , Computer networks -- Security measures , Digital telephone systems , Communication -- Technological innovations , Computer network protocols , TCP/IP (Computer network protocol) , Switching theory
- Description: Traditionally, real-time communication, such as voice calls, has run on separate, closed networks. Of all the limitations that these networks had, the ability of malicious attacks to cripple communication was not a crucial one. This situation has changed radically now that real-time communication and data have merged to share the same network. The objective of this project is to investigate the securing of softswitches with functionality similar to Private Branch Exchanges (PBX) from malicious attacks. The focus of the project will be a practical investigation of how to secure ILANGA, an ASTERISK-based system under development at Rhodes University. The practical investigation that focuses on ILANGA is based on performing six varied experiments on the different components of ILANGA. Before the six experiments are performed, basic preliminary security measures and the restrictions placed on the access to the database are discussed. The outcomes of these experiments are discussed and the precise reasons why these attacks were either successful or unsuccessful are given. Suggestions of a theoretical nature on how to defend against the successful attacks are also presented.
- Full Text:
Securitisation and its application to low cost housing finance in South Africa
- Authors: Zimbwa, Allan Golden
- Date: 2007
- Subjects: South Africa. Constitution , Human rights -- Government policy -- South Africa , Right to housing -- South Africa , Housing -- Law and legislation -- South Africa , Housing policy -- South Africa , Low income housing -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1011 , http://hdl.handle.net/10962/d1002746 , South Africa. Constitution , Human rights -- Government policy -- South Africa , Right to housing -- South Africa , Housing -- Law and legislation -- South Africa , Housing policy -- South Africa , Low income housing -- South Africa
- Description: Section 26 of the Constitution of South Africa Act 108 of 1996 provides that housing is a basic human right and that the government must take reasonable legislative and other measures to achieve the realisation of this right. A number of measures were taken to try to resolve this socio-economic issue. A number of housing institutions were established , various pieces of legislation were passed and housing subsidies were provided. However, housing backlogs remain a challenge. In March 1994 the housing backlog was estimated between 1,3 and 1,8 million units. When more than a million houses were provided by 2001 , the housing backlog had increased to between 2 and 3 million houses. To date subsidies in excess of R29 billion have been spent on housing provision. A study by the Department of Housing concluded that, at the current rate of increase of housing funding vis-a-vis the growing backlog and rapid urbanisation, the household backlog will not be changed in ten years' time. The United States of America (USA) had a similar low cost housing problem, but securitisation alleviated it with the participation of government agencies Fannie Mae, Ginnie Mae and Freddie Mac. In South Africa, the NHFC tried to emulate the USA model by establishing Gateway Home Loans (Pty) Limited (Gateway) in 1999. Gateway, however, was not a success. This research investigates whether securitisation can be applied in South Africa to alleviate the low cost housing issue. The study finds that there is a credit availability gap for the low income sector earning less than R8 000 per month because of the perceived risk of default and unwillingness by banks to lend to this sector. The increase in housing backlog that continues unabated, inadequate housing finance system to low income earners, the lessons learnt from the failure of Gateway, the success factors of the USA securitisation model and the sound and sophisticated South African financial system are the rationale for applying securitisation. A proposal of how to effectively apply securitisation to low cost housing in South Africa is provided with recommendations to revive the primary market.
- Full Text:
- Authors: Zimbwa, Allan Golden
- Date: 2007
- Subjects: South Africa. Constitution , Human rights -- Government policy -- South Africa , Right to housing -- South Africa , Housing -- Law and legislation -- South Africa , Housing policy -- South Africa , Low income housing -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:1011 , http://hdl.handle.net/10962/d1002746 , South Africa. Constitution , Human rights -- Government policy -- South Africa , Right to housing -- South Africa , Housing -- Law and legislation -- South Africa , Housing policy -- South Africa , Low income housing -- South Africa
- Description: Section 26 of the Constitution of South Africa Act 108 of 1996 provides that housing is a basic human right and that the government must take reasonable legislative and other measures to achieve the realisation of this right. A number of measures were taken to try to resolve this socio-economic issue. A number of housing institutions were established , various pieces of legislation were passed and housing subsidies were provided. However, housing backlogs remain a challenge. In March 1994 the housing backlog was estimated between 1,3 and 1,8 million units. When more than a million houses were provided by 2001 , the housing backlog had increased to between 2 and 3 million houses. To date subsidies in excess of R29 billion have been spent on housing provision. A study by the Department of Housing concluded that, at the current rate of increase of housing funding vis-a-vis the growing backlog and rapid urbanisation, the household backlog will not be changed in ten years' time. The United States of America (USA) had a similar low cost housing problem, but securitisation alleviated it with the participation of government agencies Fannie Mae, Ginnie Mae and Freddie Mac. In South Africa, the NHFC tried to emulate the USA model by establishing Gateway Home Loans (Pty) Limited (Gateway) in 1999. Gateway, however, was not a success. This research investigates whether securitisation can be applied in South Africa to alleviate the low cost housing issue. The study finds that there is a credit availability gap for the low income sector earning less than R8 000 per month because of the perceived risk of default and unwillingness by banks to lend to this sector. The increase in housing backlog that continues unabated, inadequate housing finance system to low income earners, the lessons learnt from the failure of Gateway, the success factors of the USA securitisation model and the sound and sophisticated South African financial system are the rationale for applying securitisation. A proposal of how to effectively apply securitisation to low cost housing in South Africa is provided with recommendations to revive the primary market.
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