Automatic termination clauses in employment contracts
- Authors: Ndzendze, Kutala
- Date: 2019
- Subjects: Labor contract -- South Africa , Employees -- Dismissal of -- Law and legislation -- South Africa Unfair labor practices -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/41808 , vital:36594
- Description: This study aims to establish Automatic Termination Clauses in Employment contracts by analyzing the provisions of the Constitution of the Republic of South Africa, Labour Relations Act and the precedents. The automatic termination of employment contract means that the contract is terminated without giving an employee the opportunity to state his or her version as per the audi alteram partem principle. In essence, the employee is deprived of his or her right to a fair dismissal as outlined in the Labour Relations Act. The automatic termination clauses in employment contract means that the employment contract will come to an end when the employee’s services are no longer required or when the employer simply does no longer want to keep the employee at work. The Constitution of the Republic of South Africa provides that “everyone has the right to fair labour practices”.1 In terms of the Labour Relations Act (hereinafter referred to as “the LRA”),2 every employee has the right not to be unfairly dismissed. An employment contract between an employee and employer arises out of a contract to perform services. This is so whether the contract is in writing or not. Dismissal is defined in the LRA3 as where the employer has terminated employment with or without a notice. The thesis is composed of five chapters, each of them dealing with different aspects of automatic termination clauses in employment contracts.
- Full Text:
- Date Issued: 2019
- Authors: Ndzendze, Kutala
- Date: 2019
- Subjects: Labor contract -- South Africa , Employees -- Dismissal of -- Law and legislation -- South Africa Unfair labor practices -- South Africa
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10948/41808 , vital:36594
- Description: This study aims to establish Automatic Termination Clauses in Employment contracts by analyzing the provisions of the Constitution of the Republic of South Africa, Labour Relations Act and the precedents. The automatic termination of employment contract means that the contract is terminated without giving an employee the opportunity to state his or her version as per the audi alteram partem principle. In essence, the employee is deprived of his or her right to a fair dismissal as outlined in the Labour Relations Act. The automatic termination clauses in employment contract means that the employment contract will come to an end when the employee’s services are no longer required or when the employer simply does no longer want to keep the employee at work. The Constitution of the Republic of South Africa provides that “everyone has the right to fair labour practices”.1 In terms of the Labour Relations Act (hereinafter referred to as “the LRA”),2 every employee has the right not to be unfairly dismissed. An employment contract between an employee and employer arises out of a contract to perform services. This is so whether the contract is in writing or not. Dismissal is defined in the LRA3 as where the employer has terminated employment with or without a notice. The thesis is composed of five chapters, each of them dealing with different aspects of automatic termination clauses in employment contracts.
- Full Text:
- Date Issued: 2019
Avoiding business failure in south africa
- Authors: Court, Nadine viargaret
- Date: 2019
- Subjects: Business failures -- Prevention -- South Africa , Business failures Success in business Business enterprises -- Management -- South Africa Small business -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/38024 , vital:34284
- Description: The purpose of this study was to develop a comprehensive framework to forecast that a business is entering a distressed situation and to identify the warning signs to look out for before it is too late to turn the business around in order to maintain a sustainable future. The possible solution lies in what business owners and management can do, and look out for, to avoid business failure. The intended contribution of the study was to design a framework for most businesses, especially SMMEs, to follow to avoid business failure. Therefore, it can be seen from this study that it is critical for business owners and management to be innovative in their business to achieve competitive advantage and, as such, remain sustainable. Stakeholder relationships are critical to achieving a competitive advantage. Financial Analysis, Technology Management, Innovation, Organisational Design and Risk Management are interrelated and are very inter-dependent when seeking to avoid business failure. However, innovation and technology management have a significant influence on business failure and, as such, are critical to the success of the business.
- Full Text:
- Date Issued: 2019
- Authors: Court, Nadine viargaret
- Date: 2019
- Subjects: Business failures -- Prevention -- South Africa , Business failures Success in business Business enterprises -- Management -- South Africa Small business -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/38024 , vital:34284
- Description: The purpose of this study was to develop a comprehensive framework to forecast that a business is entering a distressed situation and to identify the warning signs to look out for before it is too late to turn the business around in order to maintain a sustainable future. The possible solution lies in what business owners and management can do, and look out for, to avoid business failure. The intended contribution of the study was to design a framework for most businesses, especially SMMEs, to follow to avoid business failure. Therefore, it can be seen from this study that it is critical for business owners and management to be innovative in their business to achieve competitive advantage and, as such, remain sustainable. Stakeholder relationships are critical to achieving a competitive advantage. Financial Analysis, Technology Management, Innovation, Organisational Design and Risk Management are interrelated and are very inter-dependent when seeking to avoid business failure. However, innovation and technology management have a significant influence on business failure and, as such, are critical to the success of the business.
- Full Text:
- Date Issued: 2019
Bait collecting by subsistence and recreational fishers in Knysna Estuary may impact management and conservation
- Simon, C, du Toit, A N, Smith, M K S, Claassens, Louw, Smith, F, Smith, P
- Authors: Simon, C , du Toit, A N , Smith, M K S , Claassens, Louw , Smith, F , Smith, P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447056 , vital:74581 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: To facilitate development of tailored management strategies for bait species within Knysna Estuary (South Africa), demand for bait, harvesting activity and perceptions around conservation among recreational and subsistence bait fishers were investigated. In 2015 and 2016, bait collectors were interviewed (n = 84) and observed (n = 167) during low tides at six sites during peak and off-peak holiday periods. Significant associations among subsistence and recreational fishers and their favoured bait species, collecting spots and method, frequency of collection, views on regulations and desired daily limit for mudprawns suggest differences that may warrant different management strategies. Furthermore, observed methods and duration of bait collecting differed according to site, suggesting spatial variation in baiting pressures. Subsistence fishers potentially collect more mudprawns more frequently than do recreational fishers and consequently have a greater impact on mudprawn populations. By contrast, recreational fishers collect more polychaete worms, but because they are mainly active during holidays, their impact on these species may be localised and not yet critical. Most subsistence fishers would like increased daily bag limits, to sell bait and would welcome a rotational zonation scheme to replace the current permanent exclusion zone. The merits and disadvantages of these management options and suggestions are discussed.
- Full Text:
- Date Issued: 2019
- Authors: Simon, C , du Toit, A N , Smith, M K S , Claassens, Louw , Smith, F , Smith, P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/447056 , vital:74581 , https://hdl.handle.net/10520/EJC-1d75666653
- Description: To facilitate development of tailored management strategies for bait species within Knysna Estuary (South Africa), demand for bait, harvesting activity and perceptions around conservation among recreational and subsistence bait fishers were investigated. In 2015 and 2016, bait collectors were interviewed (n = 84) and observed (n = 167) during low tides at six sites during peak and off-peak holiday periods. Significant associations among subsistence and recreational fishers and their favoured bait species, collecting spots and method, frequency of collection, views on regulations and desired daily limit for mudprawns suggest differences that may warrant different management strategies. Furthermore, observed methods and duration of bait collecting differed according to site, suggesting spatial variation in baiting pressures. Subsistence fishers potentially collect more mudprawns more frequently than do recreational fishers and consequently have a greater impact on mudprawn populations. By contrast, recreational fishers collect more polychaete worms, but because they are mainly active during holidays, their impact on these species may be localised and not yet critical. Most subsistence fishers would like increased daily bag limits, to sell bait and would welcome a rotational zonation scheme to replace the current permanent exclusion zone. The merits and disadvantages of these management options and suggestions are discussed.
- Full Text:
- Date Issued: 2019
Behaviour of an alpine range-restricted species is described by interactions between microsite use and temperature
- Oswald, Krista N, Smit, Ben, Lee, Alan T K, Cunningham, Susan J
- Authors: Oswald, Krista N , Smit, Ben , Lee, Alan T K , Cunningham, Susan J
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441531 , vital:73896 , https://doi.org/10.1016/j.anbehav.2019.09.006
- Description: Climate change predictions include increased mean temperatures and increased frequency of heatwaves. Short-term responses to high air temperatures can allow animals to conserve water while maintaining a safe body temperature. For birds, cooling is often through evaporative water loss, which can be physiologically costly. Microsite use is an effective means of conserving water via reducing environmental heat load, so long as there are no negative trade-offs with other necessary functions, such as foraging. We examined behavioural responses to temperature in Cape rockjumpers, Chaetops frenatus (hereafter: ‘rockjumper’), an alpine specialist bird. We hypothesized that rockjumper behaviours would be temperature and microsite dependent. We collected data on rockjumper microsite use (sun, rock shade), behaviour (activity, foraging, preening, panting) and temperature (air, environmental). Rockjumpers made increased use of rock shade as air temperature increased. However, birds in rock shade foraged less. Depending on where their main food source is located, this suggests that when foraging demands are high, birds may need to remain in the sun despite risks of high thermal load, or else may suffer costs of lost foraging opportunities when using shade. The relationship between air temperature and heat dissipation behaviour (panting) was also mediated by microsite: birds showed significant increases in panting with increasing air temperature only when in the sun. The lack of increase in panting for birds in rock shade suggests that shade seeking may buffer physiological thermoregulatory costs (i.e. water expenditure). Individuals may therefore be able to mitigate some potential negative effects of high temperatures by making use of cooler microsites, although this could come at a cost to foraging.
- Full Text:
- Date Issued: 2019
- Authors: Oswald, Krista N , Smit, Ben , Lee, Alan T K , Cunningham, Susan J
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/441531 , vital:73896 , https://doi.org/10.1016/j.anbehav.2019.09.006
- Description: Climate change predictions include increased mean temperatures and increased frequency of heatwaves. Short-term responses to high air temperatures can allow animals to conserve water while maintaining a safe body temperature. For birds, cooling is often through evaporative water loss, which can be physiologically costly. Microsite use is an effective means of conserving water via reducing environmental heat load, so long as there are no negative trade-offs with other necessary functions, such as foraging. We examined behavioural responses to temperature in Cape rockjumpers, Chaetops frenatus (hereafter: ‘rockjumper’), an alpine specialist bird. We hypothesized that rockjumper behaviours would be temperature and microsite dependent. We collected data on rockjumper microsite use (sun, rock shade), behaviour (activity, foraging, preening, panting) and temperature (air, environmental). Rockjumpers made increased use of rock shade as air temperature increased. However, birds in rock shade foraged less. Depending on where their main food source is located, this suggests that when foraging demands are high, birds may need to remain in the sun despite risks of high thermal load, or else may suffer costs of lost foraging opportunities when using shade. The relationship between air temperature and heat dissipation behaviour (panting) was also mediated by microsite: birds showed significant increases in panting with increasing air temperature only when in the sun. The lack of increase in panting for birds in rock shade suggests that shade seeking may buffer physiological thermoregulatory costs (i.e. water expenditure). Individuals may therefore be able to mitigate some potential negative effects of high temperatures by making use of cooler microsites, although this could come at a cost to foraging.
- Full Text:
- Date Issued: 2019
Behavioural flexibility in an endangered seabird during current changes
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
- Authors: Traisnel, Gwendoline
- Date: 2019
- Subjects: Penguins -- South Africa , Penguins -- Behavior Sea birds -- Behavior Sea birds -- Ecology
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/43800 , vital:37048
- Description: Penguins spend a large part of their life cycle at sea and are amongst the most threatened seabirds as they suffer high mortality and have low reproductive success. Across the world, many populations are currently declining despite the constant development of conservation actions. The lack of information at the individual level reduces the understanding of individual variability and its potential role in the population dynamics of these vulnerable species. For example, long-lived species are characterised by substantial individual heterogeneity in their contribution to the overall population dynamic that should be understood when considering the implemention of conservation policies. This thesis explored some of the primary mechanisms behind inter-individual differences in behaviour and breeding success in the endangered African penguin Spheniscus demersus. On Bird island (Algoa Bay), nest defence behaviours were investigated on adults brooding chicks 1-3 weeks-old and chicks were measured at regular intervals (every 5 days) to assess their growth rate, a proxy for breeding success in this species. All adults were sexed and implanted with a passive integrated transponder which was used for individual identification. In this species, males are usually larger than females and have a higher survival rates both as juveniles and as adults. A subsample of them was equipped with tracking devices (GPSs and Time Depth Recorders), sometimes over consecutive foraging trips and across years. Finally, mate and nest fidelity were investigated to understand the drivers and consequences of this trait in that population. Breeding success was linked to nest defence behaviours, with bolder birds generally showing lower breeding success. This relation could not, however, be explained by differences in foraging strategies. Males were generally bolder than females when defending the nests, but their foraging behaviour did not vary with their personality. They generally had lower foraging effort than females. By contrast, bolder females performed more sinuous path, more wiggles and travelled larger vertical distances than shyer ones. Overall, females were more flexible than males over consecutive trips, suggesting that they probably adjust their behaviours to the offspring needs in this species. However, no sex difference in behavioural flexibility between sexes was visible across years, indicating that environmental variability may equally impact females and males’ behaviour over such time-scale. Generally, consistency was time-scale dependent as penguins increased their foraging flexibility across years, potentially adjusting to the variability of the environment. Interestingly, foraging consistency over consecutive trips increased during years of poor environmental conditions, and individuals with consistent foraging strategies were more successful than more flexible individuals when resources were extremely scarce. Finally, while nest and mate fidelity were high in this species, individuals that changed nest/partners, improved their breeding outcome. Particularly, after low breeding success females were more likely to change nest site and thereby partner to possibly improve their fitness. The potential biased adult sex ratio towards males in this population may facilitate changes in females which may have more partners available to re-mate than males. The present thesis reveals the existence of individual differences in behaviour and breeding success which relate to personality in penguins. These findings highlight the importance to integrate individual variability to predict future population dynamics in the context of global changes to understand the resilience and vulnerability of the species.
- Full Text:
- Date Issued: 2019
Benchmarking a Decision Support System for Aquatic Toxicity Testing
- Griffin, Neil J, Odume, Oghenekaro N, Mensah, Paul K, Palmer, Carolyn G
- Authors: Griffin, Neil J , Odume, Oghenekaro N , Mensah, Paul K , Palmer, Carolyn G
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/437798 , vital:73413 , ISBN 978-0-6392-0108-5 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2445_final1.pdf
- Description: This book was written for the catchment management forum (CMF) in the Upper Komati Forum (UKF), and they share their experience in order to help other CMFs understand the damage coal mining does to our water resources. This booklet should be used with How to think and act in ways that make Adaptive IWRM practi-cally possible and How to establish and run a Catchment Management Forum.
- Full Text:
- Date Issued: 2019
- Authors: Griffin, Neil J , Odume, Oghenekaro N , Mensah, Paul K , Palmer, Carolyn G
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , report
- Identifier: http://hdl.handle.net/10962/437798 , vital:73413 , ISBN 978-0-6392-0108-5 , https://wrcwebsite.azurewebsites.net/wp-content/uploads/mdocs/2445_final1.pdf
- Description: This book was written for the catchment management forum (CMF) in the Upper Komati Forum (UKF), and they share their experience in order to help other CMFs understand the damage coal mining does to our water resources. This booklet should be used with How to think and act in ways that make Adaptive IWRM practi-cally possible and How to establish and run a Catchment Management Forum.
- Full Text:
- Date Issued: 2019
Benefits and limitation of informal trading in promoting sustainable local economic development in the Intsika Yethu Municipality
- Authors: Makubalo, Zukiswa
- Date: 2019
- Subjects: Municipal government -- South Africa -- Eastern Cape Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MPA
- Identifier: http://hdl.handle.net/10353/12425 , vital:39262
- Description: The informal sector refers to all economic activities by workers and economic units that are not covered or insufficiently covered by formal arrangements which can be carried out across all the sectors of the economy both in public and private spaces. The study was conducted to determine the benefits and limitation of informal trading in promoting sustainable local economic development in the Intsika Yethu Municipality. South African municipalities for various reasons fail in providing local economic development friendly environment and more developmental and inclusive informal economy policies and by-laws. The objective of the study was to assess the benefits and challenges which might hinder the maximisation of benefits in the sector. The literature was reviewed with the aim to integrate published academic data on the benefits and limitations of informal trading in promoting sustainable local economic development. Data for the study was sourced from the literature and questionnaires administered to respondents who were selected by means of a purposive sampling technique. The respondents from which data was collected were 18 and a qualitative research approach was used as a main research methodology. The responses obtained were subjected to content analyses. The main findings of the study include; informal traders are uncoordinated, informal traders are faced with challenges which hinder their success, majority of respondents see benefits from informal trading, the informal sector of responds to triple social ills and all respondents started up businesses due to the inability of the formal sector to create job opportunities that are permanent and enough for everyone. In response to the findings about the main recommendation made is the improvement of communication between government and informal trader for the sustainability of municipal programs.
- Full Text:
- Date Issued: 2019
- Authors: Makubalo, Zukiswa
- Date: 2019
- Subjects: Municipal government -- South Africa -- Eastern Cape Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MPA
- Identifier: http://hdl.handle.net/10353/12425 , vital:39262
- Description: The informal sector refers to all economic activities by workers and economic units that are not covered or insufficiently covered by formal arrangements which can be carried out across all the sectors of the economy both in public and private spaces. The study was conducted to determine the benefits and limitation of informal trading in promoting sustainable local economic development in the Intsika Yethu Municipality. South African municipalities for various reasons fail in providing local economic development friendly environment and more developmental and inclusive informal economy policies and by-laws. The objective of the study was to assess the benefits and challenges which might hinder the maximisation of benefits in the sector. The literature was reviewed with the aim to integrate published academic data on the benefits and limitations of informal trading in promoting sustainable local economic development. Data for the study was sourced from the literature and questionnaires administered to respondents who were selected by means of a purposive sampling technique. The respondents from which data was collected were 18 and a qualitative research approach was used as a main research methodology. The responses obtained were subjected to content analyses. The main findings of the study include; informal traders are uncoordinated, informal traders are faced with challenges which hinder their success, majority of respondents see benefits from informal trading, the informal sector of responds to triple social ills and all respondents started up businesses due to the inability of the formal sector to create job opportunities that are permanent and enough for everyone. In response to the findings about the main recommendation made is the improvement of communication between government and informal trader for the sustainability of municipal programs.
- Full Text:
- Date Issued: 2019
Betty, Zorg and Me
- Authors: Krueger, Anton
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225552 , vital:49234 , xlink:href="https://doi.org/10.1080/00138398.2019.1636529"
- Description: This essay reminisces about the author’s encounters with Betty Blue at three different stages in his life. It reflects on stylistic elements of the film (as exemplar of Jean-Jacques Beineix’s Cinéma du look) as well as its portrayal of gender, sexuality, artistic aspiration and the concept of freedom. The essay also ruminates on the concept of having favourites and the synchronicity required to make a magical movie.
- Full Text:
- Date Issued: 2019
- Authors: Krueger, Anton
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/225552 , vital:49234 , xlink:href="https://doi.org/10.1080/00138398.2019.1636529"
- Description: This essay reminisces about the author’s encounters with Betty Blue at three different stages in his life. It reflects on stylistic elements of the film (as exemplar of Jean-Jacques Beineix’s Cinéma du look) as well as its portrayal of gender, sexuality, artistic aspiration and the concept of freedom. The essay also ruminates on the concept of having favourites and the synchronicity required to make a magical movie.
- Full Text:
- Date Issued: 2019
Between drones and al-Shabaab: United States extra-judicial killings in Somalia, sovereignty and the future of liberal intervention
- Authors: Koloko, Mojalefa
- Date: 2019
- Subjects: Somalia -- Politics and government -- 1991- , Somalia -- History -- 1991- , Somalia -- Foreign relations -- United States , Somalia -- Foreign relations -- 1991- , Military assistance, American -- Somalia , Extrajudicial exeutions -- Somalia , Shabaab (Organization)
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/67657 , vital:29125
- Description: This study examines the nature of the United States intervention in Somalia, specifically the use of drone strikes that first targeted the militant Sunni Islamist transnational group, al-Qaeda, which claimed responsibility for the 11 September 2001 attacks on the United States, and now target the Somali organisation, Harakat al-Shabaab al-Mujahidin, commonly known as al-Shabaab. The use of drone strikes in the US led war on terror has raised concerns about sovereignty as the extra-judicial killings are conducted without the consent of the concerned states. Furthermore, drone strikes also raise questions about the processes of liberal intervention as the US conducts them without the approval of the United Nations Security Council. It is argued in this study that what is understood to be the “golden era” of liberal interventionism is a legacy of the post-Cold War unipolar dominance of the United States in global governance and security. It is argued that US unipolarity was accompanied by a shifting perception regarding the security position of weak states, whose weakness becomes understood as a source of global insecurity. This perception that so called “weak” and “fragile” states are sources of threats is a departure in International Relations theory, because the discipline is historically preoccupied with studying the actions of powerful states and their consequence for the global order. It is argued that the discourse on the war on terror, and its focus on “failed states” as breeding grounds for alleged terrorists, represents the height of the repositioning of less powerful states from a peripheral status in IR analysis and practice, to their current position that are now being represented as core sources of threat to international peace and security. Through life history interviews with Somali nationals in Grahamstown, Port Elizabeth and Uitenhage, South Africa, the study examines the consequences of US actions from the eyes of Somali people. The findings of this study show that despite all the controversy surrounding the legitimacy of the war on terror, the manner in which it is conducted, as well as the tactics that it employs, the majority of Somali participants showed an overwhelming support for the US intervention. Participants expressed support for the US extra-judicial killings because they are understood to undermine al-Shabaab strength which is a major source of insecurity. The study also shows that the lack of necessary collaboration between the US intelligence and the Somali ground forces has resulted in high numbers of civilian deaths, which participants fear can be used by al-Shabaab to recruit and radicalise more Somalis. The study also shows that most Somalis resent the presence of the African Union Mission in Somalia because Kenya and Ethiopia are seen as 10 pursuing national interests that are not invested in Somali peace and stability. The study concludes that US extra-judicial killings have failed to constrain the actions of al-Shabaab. Somalis expressed that the leadership of current president, Mohamed Abdullahi Mohamed Farmaajo, holds the unique possibilities of creating national unity that rises above clan divisions and the radical Jihadist ideology of al-Shabaab.
- Full Text:
- Date Issued: 2019
- Authors: Koloko, Mojalefa
- Date: 2019
- Subjects: Somalia -- Politics and government -- 1991- , Somalia -- History -- 1991- , Somalia -- Foreign relations -- United States , Somalia -- Foreign relations -- 1991- , Military assistance, American -- Somalia , Extrajudicial exeutions -- Somalia , Shabaab (Organization)
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/67657 , vital:29125
- Description: This study examines the nature of the United States intervention in Somalia, specifically the use of drone strikes that first targeted the militant Sunni Islamist transnational group, al-Qaeda, which claimed responsibility for the 11 September 2001 attacks on the United States, and now target the Somali organisation, Harakat al-Shabaab al-Mujahidin, commonly known as al-Shabaab. The use of drone strikes in the US led war on terror has raised concerns about sovereignty as the extra-judicial killings are conducted without the consent of the concerned states. Furthermore, drone strikes also raise questions about the processes of liberal intervention as the US conducts them without the approval of the United Nations Security Council. It is argued in this study that what is understood to be the “golden era” of liberal interventionism is a legacy of the post-Cold War unipolar dominance of the United States in global governance and security. It is argued that US unipolarity was accompanied by a shifting perception regarding the security position of weak states, whose weakness becomes understood as a source of global insecurity. This perception that so called “weak” and “fragile” states are sources of threats is a departure in International Relations theory, because the discipline is historically preoccupied with studying the actions of powerful states and their consequence for the global order. It is argued that the discourse on the war on terror, and its focus on “failed states” as breeding grounds for alleged terrorists, represents the height of the repositioning of less powerful states from a peripheral status in IR analysis and practice, to their current position that are now being represented as core sources of threat to international peace and security. Through life history interviews with Somali nationals in Grahamstown, Port Elizabeth and Uitenhage, South Africa, the study examines the consequences of US actions from the eyes of Somali people. The findings of this study show that despite all the controversy surrounding the legitimacy of the war on terror, the manner in which it is conducted, as well as the tactics that it employs, the majority of Somali participants showed an overwhelming support for the US intervention. Participants expressed support for the US extra-judicial killings because they are understood to undermine al-Shabaab strength which is a major source of insecurity. The study also shows that the lack of necessary collaboration between the US intelligence and the Somali ground forces has resulted in high numbers of civilian deaths, which participants fear can be used by al-Shabaab to recruit and radicalise more Somalis. The study also shows that most Somalis resent the presence of the African Union Mission in Somalia because Kenya and Ethiopia are seen as 10 pursuing national interests that are not invested in Somali peace and stability. The study concludes that US extra-judicial killings have failed to constrain the actions of al-Shabaab. Somalis expressed that the leadership of current president, Mohamed Abdullahi Mohamed Farmaajo, holds the unique possibilities of creating national unity that rises above clan divisions and the radical Jihadist ideology of al-Shabaab.
- Full Text:
- Date Issued: 2019
Beyond Pierre Hadot’s promethean and orphic framework: critical reflections on Leonardo Dicaprio’s environmental documentaries in relation to the veil of ISIS
- Authors: Kotze, Mieke
- Date: 2019
- Subjects: Philosophy of nature , Documentary films -- United States -- History and criticism Environmental films -- United States -- History and criticism Motion pictures -- United States -- History -- 21st century
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/40599 , vital:36186
- Description: In his book The Veil of Isis: An Essay on the History of the Idea of Nature (2006), Pierre Hadot details two opposing paradigmatic attitudes to nature that have prevailed over the ages, namely, the Promethean and Orphic approaches, which entail, respectively, the violent unmasking of nature’s secrets through technology and the gentle approximation of them through aesthetic means. However, while this dichotomy does constitute a useful tool for understanding broad attitudes toward nature, it does not allow for consideration of the more nuanced, responses to nature across the various epochs, including the contemporary context of the looming ecological crisis. For this reason in what follows, Hadot’s Promethean-Orphic binary will be extended into a more comprehensive framework that allows for the contemplation of three additional approaches to nature, namely Socratic withdrawal, Aristotelian-inspired faith in teleology and the Hippocratic pursuit of balance with nature – which Hadot sees as either displaced by or incorporated into the Promethean attitude. Thereafter, various historical epochs will be explored through the lens of this extended Hadotian framework in order to assess the manner in which the abovementioned attitudes and approaches to nature have been adopted and progressively rearticulated, from Archaic Greece to Deleuze’s control society. And it will be advanced that, while at the outset, these approaches were more or less equivalent in terms of their discursive influence, over time Prometheanism, and the rearticulated permutations of Socratic withdrawal and Aristotelian-inspired faith in teleology, have combined to constitute what is here referred to as the Promethean/Socratic/Aristotelian nexus; a nexus which, as will be discussed, has progressively eclipsed the less invasive approaches of Hippocratic balance and Orphism, to the detriment of both nature and human relations to it. The progression of such tendencies will then be examined in relation to the two contemporary environmental films associated with Leonardo DiCaprio, namely The 11th Hour (2007) and Before the Flood (2016). This will be done in order to draw into conspicuity the intensification of discourses surrounding the technological dominance of the environment by humans who have withdrawn from nature, inspired by faith in the telos of the free-market economy, along with and the attendant marginalization of balance-seeking and aesthetically-oriented approaches to nature. Furthermore, it will be advanced, in concluding that such discursive patterns could account for the widespread apathy and indifference which characterizes contemporary responses to the environmental crisis.
- Full Text:
- Date Issued: 2019
- Authors: Kotze, Mieke
- Date: 2019
- Subjects: Philosophy of nature , Documentary films -- United States -- History and criticism Environmental films -- United States -- History and criticism Motion pictures -- United States -- History -- 21st century
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/40599 , vital:36186
- Description: In his book The Veil of Isis: An Essay on the History of the Idea of Nature (2006), Pierre Hadot details two opposing paradigmatic attitudes to nature that have prevailed over the ages, namely, the Promethean and Orphic approaches, which entail, respectively, the violent unmasking of nature’s secrets through technology and the gentle approximation of them through aesthetic means. However, while this dichotomy does constitute a useful tool for understanding broad attitudes toward nature, it does not allow for consideration of the more nuanced, responses to nature across the various epochs, including the contemporary context of the looming ecological crisis. For this reason in what follows, Hadot’s Promethean-Orphic binary will be extended into a more comprehensive framework that allows for the contemplation of three additional approaches to nature, namely Socratic withdrawal, Aristotelian-inspired faith in teleology and the Hippocratic pursuit of balance with nature – which Hadot sees as either displaced by or incorporated into the Promethean attitude. Thereafter, various historical epochs will be explored through the lens of this extended Hadotian framework in order to assess the manner in which the abovementioned attitudes and approaches to nature have been adopted and progressively rearticulated, from Archaic Greece to Deleuze’s control society. And it will be advanced that, while at the outset, these approaches were more or less equivalent in terms of their discursive influence, over time Prometheanism, and the rearticulated permutations of Socratic withdrawal and Aristotelian-inspired faith in teleology, have combined to constitute what is here referred to as the Promethean/Socratic/Aristotelian nexus; a nexus which, as will be discussed, has progressively eclipsed the less invasive approaches of Hippocratic balance and Orphism, to the detriment of both nature and human relations to it. The progression of such tendencies will then be examined in relation to the two contemporary environmental films associated with Leonardo DiCaprio, namely The 11th Hour (2007) and Before the Flood (2016). This will be done in order to draw into conspicuity the intensification of discourses surrounding the technological dominance of the environment by humans who have withdrawn from nature, inspired by faith in the telos of the free-market economy, along with and the attendant marginalization of balance-seeking and aesthetically-oriented approaches to nature. Furthermore, it will be advanced, in concluding that such discursive patterns could account for the widespread apathy and indifference which characterizes contemporary responses to the environmental crisis.
- Full Text:
- Date Issued: 2019
Bioavailability of nutrients in a diet enriched with moringa oleifera lam. Leaves using wistar rats
- Authors: Mhlomi, Yanga Nonelela
- Date: 2019
- Subjects: Moringa Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14594 , vital:40018
- Description: This study investigated the nutritional composition and bioavailability of nutrients in Moringa oleifera leaf meal from South African ecotype. Nutritional evaluation (proximate, mineral, vitamins and antinutrients, amino acids and fatty acids analyses) was performed using AOAC, ICP-OES and GC+MS techniques respectively. Bioavailability of nutrients involved formulation of diets deficient in minerals and vitamins; and proteins supplemented with Moringa oleifera leaf meal (MOLM) at 0, 3, 5 and 10% respectively. Growth performance, hematological, biochemical and histopathological evaluations were used to assess the effect of MOLM supplementation. Proximate and mineral evaluation revealed that the leaves were rich in protein (28.72%) and carbohydrate (28.84%), calcium content was (1603.33 mg/100g), potassium (1690 mg/100g), zinc (13.03 mg/100g) and iron (21.13 mg/100g). Vitamin E content was the highest (89.43 mg/100g) followed by vitamic C (24.9 mg/100g) and vitamin A (12.98 mg/100g). Fatty acids analysis detected were fifteen of which polyunsaturated fatty acid linoleic acid (56.36) and alpha-linolenic acid (687.58) were highest and behenic acid (22:0) characteristics of Moringa (4.11%) were detected. Seven of the detected fatty acids were saturated fatty acids, though relatively low, with stearic acid having the highest value. On the other hand fifteen of the amino acids, 7 were essential (valine, leucine, isoleucine, methionine, threonine and phenylalanine) were detected; while alanine, proline, serine, aspartic acid, cysteine, glutamic acid, asparagine and tyrosine were non- essential amino acid. Moringa oleifera had low quantities of antinutrients in relation to minerals, thus nutrients will easily ne available. Amino and fatty acids profile of nutrient deficient diets supplemented with MOLM revealed that six essential amino acids were detected in the diets. However, the essential amino acid (EAA) in MOLM with the highest value was threonine (500.47±23.03mg/L), while the lowest was methionine (75.65±5.31mg/L). Leucine was highest in PD10 (234.32±27.98 mg/l) 15 and lowest in PD3. Predominant amino acid in VMD diet was glutamic acid (966.76±208.92 mg/l), while methionine was lowest (197.14±35.90). Caproic acid was the most prominent unsaturated fatty acid in the diets and was highest in the PD diet. Palmitoleic acid was highest in the control diet (8.19±0.56 mg/L) and lowest in PD3 but an increase was observed as the levels of MOLM increased in the diets. Linoleic acid values obtained were significantly higher in PD diet, lower in control diet, compared to other diets. Linolenic acid (C18-3n6) was higher in PD10 (63.48±3.84 mg/L) compared to the control diet (6.05±0.14 mg/L). The highest unsaturated fatty acid in all the feed samples was linoleic acids ranging from 54.48±5.61 to 296.26±7.20 mg/L. the highest omega-3 (n-3) fatty acid content (63.48±3.38 mg/L) was in PD10 and was almost 10 times higher than the value recorded for control. Rats treated on vitamin mineral deficient (VMD) diet showed no significant changes in growth performances and blood parameters except in certain indices. Rats on VMD diet had lowest haemoglobin levels, whereas haemoglobin increased with MOLM levels. No significant differences in haematocrit, MCH, MCHC, platelets, RDW and MPV were observed in all treatments and control. However, VMD rats showed decrease in haemoglobin, increase in WBC and platelets. Electrolytes and glucose for all treatments and control were not significantly different, but, control and VMD10 diets rats showed significantly higher values for creatinine compared to MOLM diets; total protein and albumin increased with MOLM and were higher than in VMD and control rats. Serum activities of liver, cardiac, adrenal marker enzymes were significantly lower in MOLM rats compared to VMD and control. Mild congestion in VMD and VMD3 rat’s liver and diffused congestion in the kidney of VMD diet fed rats was observed. Protein deficient diets supplemented with MOLM had a negative impact on feed intake and growth parameters. Rats fed PD and PD5 consumed significantly less diet than those fed PD10, PD3 diets respectively. White blood cells decreased with increasing levels of MOLM 16 supplementation. Differential white cell count (Neutrophils, lymphocytes, monocytes, eosinophils and basophils) followed the same trend though not statistically significant (P>0.05). Furthermore, histopathological evaluation of organs revealed that no abnormalities were in heart and liver and kidney of rats fed on the control diet, while mild congestion in the liver and myocardium (heart) were observed in rats fed with protein deficient diet. No visible abnormalities were observed in the heart, kidney and liver of animals on the PD 10 diet, but myocardial fibres showing intense eosinophilia was detected in heart muscles of rats fed PD and PD3 diets. In this study, MOLM had a negative impact on feed intake and growth performance of animals and haematology. Blood biochemistry and histology suggest that MOLM has the potential of defending the body against infection with hematinic and blood enhancing qualities. Protein deficiency led to a significant elevation in the serum lipid profile of rats especially cholesterol even with increase in MOLM. PD10 had the highest triglycerides content when compared to the control but was lower (p>0.05) to that of PD. There was an increase in crude fat, ADF, NDF and protein in faecal samples of rats supplemented with MOLM diets while a decrease in moisture and ash was observed compared to the control.Vitamin and mineral deficiency resulted in significant decrease in serum cholesterol, triglycerides and HDL-C when compared to the control. There was a slight increase in excretion for all elements with increasing MOLM. Total removal of minerals and vitamins from the VMD experimental diets seemed not to have any visible negative impact on performance of the rats probably because of residual micronutrients present in other ingredients used in the feed formulation. MOLM could not replace protein in protein deficient diets.
- Full Text:
- Date Issued: 2019
- Authors: Mhlomi, Yanga Nonelela
- Date: 2019
- Subjects: Moringa Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/14594 , vital:40018
- Description: This study investigated the nutritional composition and bioavailability of nutrients in Moringa oleifera leaf meal from South African ecotype. Nutritional evaluation (proximate, mineral, vitamins and antinutrients, amino acids and fatty acids analyses) was performed using AOAC, ICP-OES and GC+MS techniques respectively. Bioavailability of nutrients involved formulation of diets deficient in minerals and vitamins; and proteins supplemented with Moringa oleifera leaf meal (MOLM) at 0, 3, 5 and 10% respectively. Growth performance, hematological, biochemical and histopathological evaluations were used to assess the effect of MOLM supplementation. Proximate and mineral evaluation revealed that the leaves were rich in protein (28.72%) and carbohydrate (28.84%), calcium content was (1603.33 mg/100g), potassium (1690 mg/100g), zinc (13.03 mg/100g) and iron (21.13 mg/100g). Vitamin E content was the highest (89.43 mg/100g) followed by vitamic C (24.9 mg/100g) and vitamin A (12.98 mg/100g). Fatty acids analysis detected were fifteen of which polyunsaturated fatty acid linoleic acid (56.36) and alpha-linolenic acid (687.58) were highest and behenic acid (22:0) characteristics of Moringa (4.11%) were detected. Seven of the detected fatty acids were saturated fatty acids, though relatively low, with stearic acid having the highest value. On the other hand fifteen of the amino acids, 7 were essential (valine, leucine, isoleucine, methionine, threonine and phenylalanine) were detected; while alanine, proline, serine, aspartic acid, cysteine, glutamic acid, asparagine and tyrosine were non- essential amino acid. Moringa oleifera had low quantities of antinutrients in relation to minerals, thus nutrients will easily ne available. Amino and fatty acids profile of nutrient deficient diets supplemented with MOLM revealed that six essential amino acids were detected in the diets. However, the essential amino acid (EAA) in MOLM with the highest value was threonine (500.47±23.03mg/L), while the lowest was methionine (75.65±5.31mg/L). Leucine was highest in PD10 (234.32±27.98 mg/l) 15 and lowest in PD3. Predominant amino acid in VMD diet was glutamic acid (966.76±208.92 mg/l), while methionine was lowest (197.14±35.90). Caproic acid was the most prominent unsaturated fatty acid in the diets and was highest in the PD diet. Palmitoleic acid was highest in the control diet (8.19±0.56 mg/L) and lowest in PD3 but an increase was observed as the levels of MOLM increased in the diets. Linoleic acid values obtained were significantly higher in PD diet, lower in control diet, compared to other diets. Linolenic acid (C18-3n6) was higher in PD10 (63.48±3.84 mg/L) compared to the control diet (6.05±0.14 mg/L). The highest unsaturated fatty acid in all the feed samples was linoleic acids ranging from 54.48±5.61 to 296.26±7.20 mg/L. the highest omega-3 (n-3) fatty acid content (63.48±3.38 mg/L) was in PD10 and was almost 10 times higher than the value recorded for control. Rats treated on vitamin mineral deficient (VMD) diet showed no significant changes in growth performances and blood parameters except in certain indices. Rats on VMD diet had lowest haemoglobin levels, whereas haemoglobin increased with MOLM levels. No significant differences in haematocrit, MCH, MCHC, platelets, RDW and MPV were observed in all treatments and control. However, VMD rats showed decrease in haemoglobin, increase in WBC and platelets. Electrolytes and glucose for all treatments and control were not significantly different, but, control and VMD10 diets rats showed significantly higher values for creatinine compared to MOLM diets; total protein and albumin increased with MOLM and were higher than in VMD and control rats. Serum activities of liver, cardiac, adrenal marker enzymes were significantly lower in MOLM rats compared to VMD and control. Mild congestion in VMD and VMD3 rat’s liver and diffused congestion in the kidney of VMD diet fed rats was observed. Protein deficient diets supplemented with MOLM had a negative impact on feed intake and growth parameters. Rats fed PD and PD5 consumed significantly less diet than those fed PD10, PD3 diets respectively. White blood cells decreased with increasing levels of MOLM 16 supplementation. Differential white cell count (Neutrophils, lymphocytes, monocytes, eosinophils and basophils) followed the same trend though not statistically significant (P>0.05). Furthermore, histopathological evaluation of organs revealed that no abnormalities were in heart and liver and kidney of rats fed on the control diet, while mild congestion in the liver and myocardium (heart) were observed in rats fed with protein deficient diet. No visible abnormalities were observed in the heart, kidney and liver of animals on the PD 10 diet, but myocardial fibres showing intense eosinophilia was detected in heart muscles of rats fed PD and PD3 diets. In this study, MOLM had a negative impact on feed intake and growth performance of animals and haematology. Blood biochemistry and histology suggest that MOLM has the potential of defending the body against infection with hematinic and blood enhancing qualities. Protein deficiency led to a significant elevation in the serum lipid profile of rats especially cholesterol even with increase in MOLM. PD10 had the highest triglycerides content when compared to the control but was lower (p>0.05) to that of PD. There was an increase in crude fat, ADF, NDF and protein in faecal samples of rats supplemented with MOLM diets while a decrease in moisture and ash was observed compared to the control.Vitamin and mineral deficiency resulted in significant decrease in serum cholesterol, triglycerides and HDL-C when compared to the control. There was a slight increase in excretion for all elements with increasing MOLM. Total removal of minerals and vitamins from the VMD experimental diets seemed not to have any visible negative impact on performance of the rats probably because of residual micronutrients present in other ingredients used in the feed formulation. MOLM could not replace protein in protein deficient diets.
- Full Text:
- Date Issued: 2019
Biochemical characterization of the β-mannanase activity of Bacillus paralicheniformis SVD1
- Authors: Clarke, Matthew David
- Date: 2019
- Subjects: Mycobacterium avium paratuberculosis , Enzymes -- Biotechnology , Lignocellulose -- Biotechnology
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67570 , vital:29112
- Description: Products produced via the enzymatic hydrolysis of lignocellulosic biomass, the most abundant renewable terrestrial source of carbon, can potentially replace a lot of the fuels and chemicals currently produced using non-renewable hydrocarbons. Mannan is a polysaccharide component of lignocellulose that is abundant in softwoods and legume seeds. Enzymatic hydrolysis of mannan by β-mannanases has various industrial applications, including use in biofuel and prebiotic mannooligosaccharide (MOS) production for the improvement of human and animal health. The industrial use of β-mannanases depends on their biochemical characteristics, such as their activity, stability and substrate specificity. Knowledge of their synergistic interactions with other enzymes is also useful for effective hydrolysis. Bacillus paralicheniformis SVD1 was used as a source for β-mannanases. The two mannanases of B. paralicheniformis SVD1 have not been biochemically characterized apart from minor characterization of crude β-mannanase activity. The protein sequences of the two β-mannanases, of glycosyl hydrolase family 5 and 26, have a 95% - 96% identity to the β-mannanases of B. licheniformis DSM13T (=ATCC14580T). These small protein sequence differences could lead to quite different biochemical characteristics. These mannanases were characterized as these enzymes may have industrially useful characteristics. To induce mannanase production, B. paralicheniformis SVD1 was cultured in broth containing the mannan substrate locust bean gum. Various growth curve parameters were measured over 72 h. Mannanase activity was the highest after 48 h of growth - this was the time at which mannanase activity was concentrated, using 3 kDa centrifugal filtration devices, for biochemical characterization of the crude activity. Zymography revealed that the crude concentrated mannanase fraction consisted of at least two mannanases with relative molecular weights (MWs) of 29.6 kDa and 33 kDa. This was smaller than expected – based on their theoretical molecular masses. Protease activity, which was detected in the broth, was probably the reason. There were two pH optima, pH 5.0 and pH 7.0, which also indicated the presence of two mannanases. The concentrated mannanase displayed characteristics that were expected of a B. paralicheniformis β-mannanase. The temperature optimum was 50°C and the activity loss was less than 7% at 50°C after 24 h. Substrate specificity assays revealed that there was predominantly mannanase activity present. Thin layer chromatography (TLC) analysis of mannan and MOS hydrolysis showed that mainly M2 and M3 MOS were produced; only MOS with a degree of polymerization of 4 or higher were hydrolyzed. Hydrolysis was minimal on mannoligosaccharides with galactose substituents. Activity and MOS production was the highest on soluble, low branched mannan substrates. The highest activity observed was on konjac glucomannan. Purification of the mannanase activity was then attempted using various methods. Ammonium sulfate precipitation, acetone precipitation, as well as centrifugal filtration device concentration was assessed for concentration of the mannanase activity.Concentration was not very successful due to low activity yields (≤ 20%). Anion exchange chromatography (AEC) and size exclusion chromatography (SEC) was used for purification. AEC gave good activity yield and fold purification, but SDS-PAGE analysis revealed the presence of many different proteins so further purification was necessary. SDS-PAGE analysis showed that there were only a few protein contaminants in the SEC fraction. However, the yield was too low to allow for biochemical characterization. The optimized purification procedure, which partially purified the mannanase activity, used 85% ammonium sulfate precipitation, followed by AEC. The fold purification was high (88.9) and the specific activity was 29.5 U.mg-1. A zymogram of the partially purified mannanase showed a mannanase active band with a MW of 40 - 41 kDa. A serine protease inhibitor, phenylmethylsulfonyl fluoride (PMSF), was added during the purification steps. This indicated that the mannanase/s in the crude concentrate, without PMSF added, was hydrolyzed by serine protease activity. Native PAGE zymograms suggested that at least two different isoforms of mannanases were present. Additional purification would be required to determine the true characteristics of the mannanase/s. The biochemical characteristics of the crude and partially purified mannanases were similar. The pH optima of the partially purified mannanases were different; the pH optima were 6.0 and 9.0. The substrate specificities were similar, except that the partially purified mannanases displayed no cellulase and β-D-galactosidase activity, but showed a small amount of α-L-arabinase activity. The partially purified mannanase and a Cyamopsis tetragonolobus GH27 α-galactosidase synergistically hydrolyzed locust bean gum. The M50G50 combination displayed the highest extent of hydrolysis; after 24 h there was a 1.39 fold increase in reducing sugar release and the degree of synergy (DS) was 4.64. TLC analysis indicated that synergy increased the release of small MOS. These MOS could be useful as prebiotics. The synergy between the partially purified mannanase and the commercial cellulase mixture Cellic® CTec2 (Novozymes) on spent coffee grounds (SCG) was also determined. SCG is an abundant industrial waste product that has high mannan content. The SCG was pretreated using NaOH, and the monosaccharide, soluble phenolics and insoluble contents were determined. Glucose and mannose were the dominant monosaccharides in the SCG; the pretreated SCG contained 20.4% (w/w) glucose and 18.5% (w/w) mannose, respectively. The NaOH pretreatment improved mannanase hydrolysis of SCG. It resulted in the opening up and swelling of the SCG particles and removed some of the insoluble solids. The partially purified B. paralicheniformis SVD1 mannanase displayed no detectable activity on SCG, but showed synergy with CTec2, in terms of DS, on untreated and NaOH pretreated SCG. This is the first report of mannanasecellulase synergy on SCG; other studies found that increased hydrolysis was due to additive effects. The results obtained in this study are only an initial assessment of the biochemical properties of B. paralicheniformis SVD1 mannanase activity and its synergy with other enzymes. These results can be used to inform future studies.
- Full Text:
- Date Issued: 2019
- Authors: Clarke, Matthew David
- Date: 2019
- Subjects: Mycobacterium avium paratuberculosis , Enzymes -- Biotechnology , Lignocellulose -- Biotechnology
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67570 , vital:29112
- Description: Products produced via the enzymatic hydrolysis of lignocellulosic biomass, the most abundant renewable terrestrial source of carbon, can potentially replace a lot of the fuels and chemicals currently produced using non-renewable hydrocarbons. Mannan is a polysaccharide component of lignocellulose that is abundant in softwoods and legume seeds. Enzymatic hydrolysis of mannan by β-mannanases has various industrial applications, including use in biofuel and prebiotic mannooligosaccharide (MOS) production for the improvement of human and animal health. The industrial use of β-mannanases depends on their biochemical characteristics, such as their activity, stability and substrate specificity. Knowledge of their synergistic interactions with other enzymes is also useful for effective hydrolysis. Bacillus paralicheniformis SVD1 was used as a source for β-mannanases. The two mannanases of B. paralicheniformis SVD1 have not been biochemically characterized apart from minor characterization of crude β-mannanase activity. The protein sequences of the two β-mannanases, of glycosyl hydrolase family 5 and 26, have a 95% - 96% identity to the β-mannanases of B. licheniformis DSM13T (=ATCC14580T). These small protein sequence differences could lead to quite different biochemical characteristics. These mannanases were characterized as these enzymes may have industrially useful characteristics. To induce mannanase production, B. paralicheniformis SVD1 was cultured in broth containing the mannan substrate locust bean gum. Various growth curve parameters were measured over 72 h. Mannanase activity was the highest after 48 h of growth - this was the time at which mannanase activity was concentrated, using 3 kDa centrifugal filtration devices, for biochemical characterization of the crude activity. Zymography revealed that the crude concentrated mannanase fraction consisted of at least two mannanases with relative molecular weights (MWs) of 29.6 kDa and 33 kDa. This was smaller than expected – based on their theoretical molecular masses. Protease activity, which was detected in the broth, was probably the reason. There were two pH optima, pH 5.0 and pH 7.0, which also indicated the presence of two mannanases. The concentrated mannanase displayed characteristics that were expected of a B. paralicheniformis β-mannanase. The temperature optimum was 50°C and the activity loss was less than 7% at 50°C after 24 h. Substrate specificity assays revealed that there was predominantly mannanase activity present. Thin layer chromatography (TLC) analysis of mannan and MOS hydrolysis showed that mainly M2 and M3 MOS were produced; only MOS with a degree of polymerization of 4 or higher were hydrolyzed. Hydrolysis was minimal on mannoligosaccharides with galactose substituents. Activity and MOS production was the highest on soluble, low branched mannan substrates. The highest activity observed was on konjac glucomannan. Purification of the mannanase activity was then attempted using various methods. Ammonium sulfate precipitation, acetone precipitation, as well as centrifugal filtration device concentration was assessed for concentration of the mannanase activity.Concentration was not very successful due to low activity yields (≤ 20%). Anion exchange chromatography (AEC) and size exclusion chromatography (SEC) was used for purification. AEC gave good activity yield and fold purification, but SDS-PAGE analysis revealed the presence of many different proteins so further purification was necessary. SDS-PAGE analysis showed that there were only a few protein contaminants in the SEC fraction. However, the yield was too low to allow for biochemical characterization. The optimized purification procedure, which partially purified the mannanase activity, used 85% ammonium sulfate precipitation, followed by AEC. The fold purification was high (88.9) and the specific activity was 29.5 U.mg-1. A zymogram of the partially purified mannanase showed a mannanase active band with a MW of 40 - 41 kDa. A serine protease inhibitor, phenylmethylsulfonyl fluoride (PMSF), was added during the purification steps. This indicated that the mannanase/s in the crude concentrate, without PMSF added, was hydrolyzed by serine protease activity. Native PAGE zymograms suggested that at least two different isoforms of mannanases were present. Additional purification would be required to determine the true characteristics of the mannanase/s. The biochemical characteristics of the crude and partially purified mannanases were similar. The pH optima of the partially purified mannanases were different; the pH optima were 6.0 and 9.0. The substrate specificities were similar, except that the partially purified mannanases displayed no cellulase and β-D-galactosidase activity, but showed a small amount of α-L-arabinase activity. The partially purified mannanase and a Cyamopsis tetragonolobus GH27 α-galactosidase synergistically hydrolyzed locust bean gum. The M50G50 combination displayed the highest extent of hydrolysis; after 24 h there was a 1.39 fold increase in reducing sugar release and the degree of synergy (DS) was 4.64. TLC analysis indicated that synergy increased the release of small MOS. These MOS could be useful as prebiotics. The synergy between the partially purified mannanase and the commercial cellulase mixture Cellic® CTec2 (Novozymes) on spent coffee grounds (SCG) was also determined. SCG is an abundant industrial waste product that has high mannan content. The SCG was pretreated using NaOH, and the monosaccharide, soluble phenolics and insoluble contents were determined. Glucose and mannose were the dominant monosaccharides in the SCG; the pretreated SCG contained 20.4% (w/w) glucose and 18.5% (w/w) mannose, respectively. The NaOH pretreatment improved mannanase hydrolysis of SCG. It resulted in the opening up and swelling of the SCG particles and removed some of the insoluble solids. The partially purified B. paralicheniformis SVD1 mannanase displayed no detectable activity on SCG, but showed synergy with CTec2, in terms of DS, on untreated and NaOH pretreated SCG. This is the first report of mannanasecellulase synergy on SCG; other studies found that increased hydrolysis was due to additive effects. The results obtained in this study are only an initial assessment of the biochemical properties of B. paralicheniformis SVD1 mannanase activity and its synergy with other enzymes. These results can be used to inform future studies.
- Full Text:
- Date Issued: 2019
Biogenic synthesis of Silver nanoparticles (AgNPs) and its effects on Zebrafish (Danio rerio)
- Authors: Siguba, Busiswa
- Date: 2019
- Subjects: Biogenic synthesis -- Zebrafish , Nanoparticles – Silver , Zebrafish
- Language: English
- Type: Thesis , Masters , M Sc
- Identifier: http://hdl.handle.net/11260/1339 , vital:32260
- Description: The increase in use and production of engineered nanoparticles in recent years points towards their inevitable release into freshwater ecosystems. Subsequently, exposure to organisms in freshwater ecosystems is to be expected. The aim of this dissertation was to synthesize silver nanoparticles (AgNPs) using silver nitrate, gelatine and maltose as precursor, capping and reducing agent respectively. Cytotoxic effects of the as-synthesized AgNPs was evaluated at concentrations of 0.031 μg/L, 0.250 μg/L and 5.000 μg/L on selected target organs in zebrafish (Danio rerio ) after 96 hr of exposure, under a 24 hr static renewal system. Formation of AgNPs was investigated by UV-Vis spectrophotometry, which displayed absorption maxima peak characteristic of plasmon resonance band for silver at 419 nm. From transmission electron microscopy, AgNPs was found to be small, well dispersed and spherical in shape with a narrow size distribution, and an average particle size of3.76 ± 1.00 nm. Histopathological alterations following exposure to AgNPs was noticed in the gills, epidermis, muscle tissue and kidney. Secondary lamellae hypertrophy, oedema and epithelial lifting was observed in all experimental groups. Curling and clubbed tips of secondary lamellae were observed at the lowest concentration (0.031 μg/L). Hyperplasia and lamellae fusion was most common at the median concentration (0.250 μg/L) of AgNP exposure. Hypertrophy of endothelial cells along with blood vessel congestion was also observed. Reduced secondary lamellar length, lamellar erosion and thinning were observed at the highest concentration (5.000 μg/L).AgNP exposure also altered the shape of alarm cells. In addition, hyperplasia and hypertrophy of goblet cells were observed at the highest concentration (5.000 μg/L) at 96 hr. At 5.000 μg/L of AgNP, PAS reaction was intense (deep purple), while the number and size of these cells decreased. Staining with AB pH 2.5 demonstrated an intense deep purple staining at the lowest and at the median concentration (24 hr). Moderate staining was seen at the higher concentrations. Muscle bundles with severe oedema, their thickening and separation were more pronounced in all treated groups. Histopathological tubular deformation and mononuclear cell infiltration were observed in kidney tissues. In addition; an increase in melano‐macrophage aggregation intensity was identified on the 48 hr in the treated groups. An increase in tubular epithelial cell regeneration/ proliferation, resulting in production of new epithelial cells which was indicative of recovering of kidney tissues from AgNP induced injury at 96 hr of exposure. Results presented here shows that fish respond to the presence of AgNPs.
- Full Text:
- Date Issued: 2019
- Authors: Siguba, Busiswa
- Date: 2019
- Subjects: Biogenic synthesis -- Zebrafish , Nanoparticles – Silver , Zebrafish
- Language: English
- Type: Thesis , Masters , M Sc
- Identifier: http://hdl.handle.net/11260/1339 , vital:32260
- Description: The increase in use and production of engineered nanoparticles in recent years points towards their inevitable release into freshwater ecosystems. Subsequently, exposure to organisms in freshwater ecosystems is to be expected. The aim of this dissertation was to synthesize silver nanoparticles (AgNPs) using silver nitrate, gelatine and maltose as precursor, capping and reducing agent respectively. Cytotoxic effects of the as-synthesized AgNPs was evaluated at concentrations of 0.031 μg/L, 0.250 μg/L and 5.000 μg/L on selected target organs in zebrafish (Danio rerio ) after 96 hr of exposure, under a 24 hr static renewal system. Formation of AgNPs was investigated by UV-Vis spectrophotometry, which displayed absorption maxima peak characteristic of plasmon resonance band for silver at 419 nm. From transmission electron microscopy, AgNPs was found to be small, well dispersed and spherical in shape with a narrow size distribution, and an average particle size of3.76 ± 1.00 nm. Histopathological alterations following exposure to AgNPs was noticed in the gills, epidermis, muscle tissue and kidney. Secondary lamellae hypertrophy, oedema and epithelial lifting was observed in all experimental groups. Curling and clubbed tips of secondary lamellae were observed at the lowest concentration (0.031 μg/L). Hyperplasia and lamellae fusion was most common at the median concentration (0.250 μg/L) of AgNP exposure. Hypertrophy of endothelial cells along with blood vessel congestion was also observed. Reduced secondary lamellar length, lamellar erosion and thinning were observed at the highest concentration (5.000 μg/L).AgNP exposure also altered the shape of alarm cells. In addition, hyperplasia and hypertrophy of goblet cells were observed at the highest concentration (5.000 μg/L) at 96 hr. At 5.000 μg/L of AgNP, PAS reaction was intense (deep purple), while the number and size of these cells decreased. Staining with AB pH 2.5 demonstrated an intense deep purple staining at the lowest and at the median concentration (24 hr). Moderate staining was seen at the higher concentrations. Muscle bundles with severe oedema, their thickening and separation were more pronounced in all treated groups. Histopathological tubular deformation and mononuclear cell infiltration were observed in kidney tissues. In addition; an increase in melano‐macrophage aggregation intensity was identified on the 48 hr in the treated groups. An increase in tubular epithelial cell regeneration/ proliferation, resulting in production of new epithelial cells which was indicative of recovering of kidney tissues from AgNP induced injury at 96 hr of exposure. Results presented here shows that fish respond to the presence of AgNPs.
- Full Text:
- Date Issued: 2019
Bioinformatic analysis, isolation and kinetic characterisation of red algae (Gelidium capense) dehydrogenases
- Authors: Gogela, Yanga
- Date: 2019
- Subjects: Bioinformatics Chondrus crispus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19164 , vital:39878
- Description: Lactate and alcohol dehydrogenases have attracted much attention in various industries and scientific research for their ability to produce chirally pure compounds and be assayed for activity using more straightforward and reproducible assay methods. These enzymes have been previously isolated and purified from various plants, animals and microorganisms. So far, the molecular and biochemical properties of enzymes from these dehydrogenase families in red algae are mostly unknown. Red macroalgae have been used for centuries for the treatment of various diseases and as a source of ingredients in the food industry. The aim of this study was to identify genes in the sequenced red algae genomes that encode dehydrogenases, to use bioinformatic tools to confirm that the proteins encoded are dehydrogenases and to isolate and kinetically purify alcohol or lactate dehydrogenase from red algae species found along the coastline of the Eastern Cape Province. A combination of bioinformatics tools, molecular and biochemical techniques were used to identify, purify, and characterise ADH and LDH enzymes. Bioinformatics analysis revealed two alcohol dehydrogenase genes and two hypothetical genes encoding functional domains similar to D-lactate dehydrogenases from other species. The ADH and LDH-like genes shared low sequence identity at the protein level with medium-chain dehydrogenases/reductases (MDRs) and 2-hydroxy acid dehydrogenases, respectively. These two dehydrogenase genes showed a highly conserved NAD-binding motif (Rossmann-fold) similar to many other NAD-dependent dehydrogenases. The ADH and LDH proteins contained no signal peptides and may be located in the cytoplasm. The phylogenetic tree analysis showed that the two ADH genes belonged to cinnamyl and class III alcohol dehydrogenases, whereas the LDHlike genes were grouped with D-lactate dehydrogenases from other organisms. The ADH and LDH gene family showed cis-acting regulatory elements that are mostly involved in stress response and hormonal response. Structural analysis showed that the dehydrogenases 3D structure predicted models comprise of two domains, namely the substrate binding and the coenzyme binding domains that are rich in beta-strands secondary structure elements. The LDH from red algae was purified approximately 4-fold with a specific activity of 0.044 U/mg. The purified LDH enzyme had a molecular weight of approximately 37kDa. The LDH was active across a broad pH range from 5-9 with a pH optimum observed at 7.5. The LDH ii enzyme in red algae exhibits a temperature optimum of 40 ⁰C and heat stability up to 40 ⁰C. Above 50 °C the LDH activity rapidly decreased showing that the LDH in red algae is not thermostable. The LDH enzyme showed a Km value of 0.8 mM and Vmax of 0.0067 mM.min-1 when using sodium pyruvate as a substrate.
- Full Text:
- Date Issued: 2019
- Authors: Gogela, Yanga
- Date: 2019
- Subjects: Bioinformatics Chondrus crispus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19164 , vital:39878
- Description: Lactate and alcohol dehydrogenases have attracted much attention in various industries and scientific research for their ability to produce chirally pure compounds and be assayed for activity using more straightforward and reproducible assay methods. These enzymes have been previously isolated and purified from various plants, animals and microorganisms. So far, the molecular and biochemical properties of enzymes from these dehydrogenase families in red algae are mostly unknown. Red macroalgae have been used for centuries for the treatment of various diseases and as a source of ingredients in the food industry. The aim of this study was to identify genes in the sequenced red algae genomes that encode dehydrogenases, to use bioinformatic tools to confirm that the proteins encoded are dehydrogenases and to isolate and kinetically purify alcohol or lactate dehydrogenase from red algae species found along the coastline of the Eastern Cape Province. A combination of bioinformatics tools, molecular and biochemical techniques were used to identify, purify, and characterise ADH and LDH enzymes. Bioinformatics analysis revealed two alcohol dehydrogenase genes and two hypothetical genes encoding functional domains similar to D-lactate dehydrogenases from other species. The ADH and LDH-like genes shared low sequence identity at the protein level with medium-chain dehydrogenases/reductases (MDRs) and 2-hydroxy acid dehydrogenases, respectively. These two dehydrogenase genes showed a highly conserved NAD-binding motif (Rossmann-fold) similar to many other NAD-dependent dehydrogenases. The ADH and LDH proteins contained no signal peptides and may be located in the cytoplasm. The phylogenetic tree analysis showed that the two ADH genes belonged to cinnamyl and class III alcohol dehydrogenases, whereas the LDHlike genes were grouped with D-lactate dehydrogenases from other organisms. The ADH and LDH gene family showed cis-acting regulatory elements that are mostly involved in stress response and hormonal response. Structural analysis showed that the dehydrogenases 3D structure predicted models comprise of two domains, namely the substrate binding and the coenzyme binding domains that are rich in beta-strands secondary structure elements. The LDH from red algae was purified approximately 4-fold with a specific activity of 0.044 U/mg. The purified LDH enzyme had a molecular weight of approximately 37kDa. The LDH was active across a broad pH range from 5-9 with a pH optimum observed at 7.5. The LDH ii enzyme in red algae exhibits a temperature optimum of 40 ⁰C and heat stability up to 40 ⁰C. Above 50 °C the LDH activity rapidly decreased showing that the LDH in red algae is not thermostable. The LDH enzyme showed a Km value of 0.8 mM and Vmax of 0.0067 mM.min-1 when using sodium pyruvate as a substrate.
- Full Text:
- Date Issued: 2019
Biological properties and interactions of Kalaharituber pfeilii
- Authors: Krele, Viwe
- Date: 2019
- Subjects: Kalaharituber pfeilii , Pezizales -- South Africa , Desert plants -- South Africa , Truffle culture -- South Africa , Plant biochemical genetics , Enzymes -- Analysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/72257 , vital:30022
- Description: Dessert truffles are seasonal macro fungi and have been identified in several parts of the world including South Africa. The first part of the present study dealt with the assessment of the biologically active compounds of the Kalahari truffles found in the Northern Cape of South Africa. Truffles extracts (methanol, ethanol, aqueous) were investigated for their antimicrobial properties towards Gram-positive and Gram-negative bacteria. The results demonstrated that the truffle extracts tested had no inhibitory effects against the bacterial isolates. The truffle mycelial growth was also noted to be ineffective against the selected bacteria. The bacteria tested in the present study showed some antagonistic effects against the fungus. Cultures of K. pfeilii were also screened for enzyme production including amylase, protease, cellulose, and laccase. Evaluation of the potential of K. pfeilii mycelia to produce these industrially and economically important enzymes demonstrated both amylase and protease activity. However, for laccase and cellulose, no activity was detected. The second part of the present study aimed at optimizing biomass production by K. pfeilii in liquid culture media. FF Microplate containing 95 discreet carbon sources were employed to test for substrate utilization. Blanked readings above 0.1 were regarded as positive for utilization, and 4 substrates were selected as potential substrates and were included in liquid media. Media was evaluated for mycelial biomass production. Of the carbon sources tested sucrose proved to be the most suitable for supporting mycelial growth. The third part of the current study included investigating the diversity of microbial communities colonizing the rhizosheath of Stipagrostis ciliata var. capensis (the host plant of K. pfeilii) and these were identified by means of next-generation sequencing using Illumina Miseq. Bioinformatics tools were utilized in analyzing the data. Actinobacteria were found to be the most dominant bacterial phylum, followed by unclassified bacteria, Proteobacteria, and Acidobacteria. The top 25 sequences were selected and clustered into bacterial OTUs (at 97% threshold) which were assigned into 1 phylum (Actinobacteria), 1 family (Geodermatophilaceae) and 23 genera. This phylum is well known for its secondary metabolites. Streptomyces sp. was the most frequently encountered genus. The results from this study necessitate further investigations with regards to the function and evolution of fungal-bacterial associations. Wheather these bacteria have a contribution towards the truffle development, it is still not confirmed.
- Full Text:
- Date Issued: 2019
- Authors: Krele, Viwe
- Date: 2019
- Subjects: Kalaharituber pfeilii , Pezizales -- South Africa , Desert plants -- South Africa , Truffle culture -- South Africa , Plant biochemical genetics , Enzymes -- Analysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/72257 , vital:30022
- Description: Dessert truffles are seasonal macro fungi and have been identified in several parts of the world including South Africa. The first part of the present study dealt with the assessment of the biologically active compounds of the Kalahari truffles found in the Northern Cape of South Africa. Truffles extracts (methanol, ethanol, aqueous) were investigated for their antimicrobial properties towards Gram-positive and Gram-negative bacteria. The results demonstrated that the truffle extracts tested had no inhibitory effects against the bacterial isolates. The truffle mycelial growth was also noted to be ineffective against the selected bacteria. The bacteria tested in the present study showed some antagonistic effects against the fungus. Cultures of K. pfeilii were also screened for enzyme production including amylase, protease, cellulose, and laccase. Evaluation of the potential of K. pfeilii mycelia to produce these industrially and economically important enzymes demonstrated both amylase and protease activity. However, for laccase and cellulose, no activity was detected. The second part of the present study aimed at optimizing biomass production by K. pfeilii in liquid culture media. FF Microplate containing 95 discreet carbon sources were employed to test for substrate utilization. Blanked readings above 0.1 were regarded as positive for utilization, and 4 substrates were selected as potential substrates and were included in liquid media. Media was evaluated for mycelial biomass production. Of the carbon sources tested sucrose proved to be the most suitable for supporting mycelial growth. The third part of the current study included investigating the diversity of microbial communities colonizing the rhizosheath of Stipagrostis ciliata var. capensis (the host plant of K. pfeilii) and these were identified by means of next-generation sequencing using Illumina Miseq. Bioinformatics tools were utilized in analyzing the data. Actinobacteria were found to be the most dominant bacterial phylum, followed by unclassified bacteria, Proteobacteria, and Acidobacteria. The top 25 sequences were selected and clustered into bacterial OTUs (at 97% threshold) which were assigned into 1 phylum (Actinobacteria), 1 family (Geodermatophilaceae) and 23 genera. This phylum is well known for its secondary metabolites. Streptomyces sp. was the most frequently encountered genus. The results from this study necessitate further investigations with regards to the function and evolution of fungal-bacterial associations. Wheather these bacteria have a contribution towards the truffle development, it is still not confirmed.
- Full Text:
- Date Issued: 2019
Black forest
- Authors: Sachikonye, Tsitsi S A
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/92759 , vital:30745
- Full Text:
- Date Issued: 2019
- Authors: Sachikonye, Tsitsi S A
- Date: 2019
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/92759 , vital:30745
- Full Text:
- Date Issued: 2019
Block copolymer templates for metal oxide nanostructures
- Authors: Talla, Assane
- Date: 2019
- Subjects: Nanotechnology , Nanostructured materials Metal oxide semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43889 , vital:37075
- Description: Recent advances in technology have increased the need for fabrication of devices with feature sizes of tens of nanometers, such as ultra-fine filters or membranes, and high density data storage media, to name a few. For this reason, research is now focused on block copolymer nanolithographic processes, particularly the fabrication of nanoscale templates with domains well below 100 nm. Block copolymers have the tendency to self-organise into various structures, such as lamellae, spheres or cylinders on a nanometer scale. Among these possible configurations, the perpendicular cylindrical structure is most desirable, because it can be used for templates or masks for feature development, in particular, oriented wires or rods. In this work, the aim is to create a nano-mask from a di-block copolymer thin film, for zinc oxide nanorods growth. For this purpose poly (styrene-block-methylmethacrylate) (PS-b-PMMA) was investigated as a potential nano-mask. Samples were characterized using X-ray reflectometry to determine the thicknesses of the PS-b-PMMA thin films, while scanning probe microscopy and scanning electron microscopy was used to investigate the surface morphology of the samples. PS-b-PMMA thin films were produced on a random copolymer (poly (styrene-random-methylmethacrylate) (PS-r-PMMA) coated onto a silicon substrate. The PS-r-PMMA permits a non-preferential interaction between the di-block constituents and the substrate. Thermal annealing in vacuum of PS-b-PMMA on PS-r-PMMA led to perpendicular cylinders of PMMA within a PS matrix in the di-block. The typical thicknesses measured for the di-block copolymer films ranged between 33 nm and 37 nm. During this study, a perpendicular orientation of the di-block components was also produced when PS-b-PMMA was spun onto a layer of zinc oxide nanoparticles and thermally annealed in vacuum. It was shown that the ZnO nanoparticles created a corrugated surface on silicon which induced perpendicular cylinders of PMMA within the PS matrix. This was possible for a specific surface roughness parameter and film thickness. In this case, the typical thickness determined for the di-block copolymer ranged between 33 and 35 nm and the surface roughness parameter was 0.07. For the fabrication of a di-block template or PS nano-mask, the vertically oriented PMMA cylindrical nanodomains in the PS matrix were removed by exposing the film to ultraviolet radiation at an adequate dose, followed successively by washing in acetic acid and de-ionized water. It was shown that ultraviolet exposure is necessary to ensure the degradation of PMMA. A subsequent rinse in glacial acetic acid and DI water of the film exposed to ultraviolet, left an array of ordered nanoscopic pores with sizes ranging between 10 nm and 20 nm. Finally, the growth of ZnO nanorods on the di-block template produced on zinc oxide nanoparticles, was attempted using an aqueous solution based-method, namely chemical bath deposition. The rods did not grow inside the nanopores, probably due to poor capillary action. In additional experiments, the di-block template was removed by toluene (a selective solvent for PS) followed by the growth of ZnO rods on the exposed nanoparticle surface. Vertical and well separated ZnO rods formed on this surface, in places where the underlying seed layer had been attacked by the acetic acid treatment during removal of the PMMA. The observed ZnO rod morphology can be used in applications such as solar cell.
- Full Text:
- Date Issued: 2019
- Authors: Talla, Assane
- Date: 2019
- Subjects: Nanotechnology , Nanostructured materials Metal oxide semiconductors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43889 , vital:37075
- Description: Recent advances in technology have increased the need for fabrication of devices with feature sizes of tens of nanometers, such as ultra-fine filters or membranes, and high density data storage media, to name a few. For this reason, research is now focused on block copolymer nanolithographic processes, particularly the fabrication of nanoscale templates with domains well below 100 nm. Block copolymers have the tendency to self-organise into various structures, such as lamellae, spheres or cylinders on a nanometer scale. Among these possible configurations, the perpendicular cylindrical structure is most desirable, because it can be used for templates or masks for feature development, in particular, oriented wires or rods. In this work, the aim is to create a nano-mask from a di-block copolymer thin film, for zinc oxide nanorods growth. For this purpose poly (styrene-block-methylmethacrylate) (PS-b-PMMA) was investigated as a potential nano-mask. Samples were characterized using X-ray reflectometry to determine the thicknesses of the PS-b-PMMA thin films, while scanning probe microscopy and scanning electron microscopy was used to investigate the surface morphology of the samples. PS-b-PMMA thin films were produced on a random copolymer (poly (styrene-random-methylmethacrylate) (PS-r-PMMA) coated onto a silicon substrate. The PS-r-PMMA permits a non-preferential interaction between the di-block constituents and the substrate. Thermal annealing in vacuum of PS-b-PMMA on PS-r-PMMA led to perpendicular cylinders of PMMA within a PS matrix in the di-block. The typical thicknesses measured for the di-block copolymer films ranged between 33 nm and 37 nm. During this study, a perpendicular orientation of the di-block components was also produced when PS-b-PMMA was spun onto a layer of zinc oxide nanoparticles and thermally annealed in vacuum. It was shown that the ZnO nanoparticles created a corrugated surface on silicon which induced perpendicular cylinders of PMMA within the PS matrix. This was possible for a specific surface roughness parameter and film thickness. In this case, the typical thickness determined for the di-block copolymer ranged between 33 and 35 nm and the surface roughness parameter was 0.07. For the fabrication of a di-block template or PS nano-mask, the vertically oriented PMMA cylindrical nanodomains in the PS matrix were removed by exposing the film to ultraviolet radiation at an adequate dose, followed successively by washing in acetic acid and de-ionized water. It was shown that ultraviolet exposure is necessary to ensure the degradation of PMMA. A subsequent rinse in glacial acetic acid and DI water of the film exposed to ultraviolet, left an array of ordered nanoscopic pores with sizes ranging between 10 nm and 20 nm. Finally, the growth of ZnO nanorods on the di-block template produced on zinc oxide nanoparticles, was attempted using an aqueous solution based-method, namely chemical bath deposition. The rods did not grow inside the nanopores, probably due to poor capillary action. In additional experiments, the di-block template was removed by toluene (a selective solvent for PS) followed by the growth of ZnO rods on the exposed nanoparticle surface. Vertical and well separated ZnO rods formed on this surface, in places where the underlying seed layer had been attacked by the acetic acid treatment during removal of the PMMA. The observed ZnO rod morphology can be used in applications such as solar cell.
- Full Text:
- Date Issued: 2019
Blockchain potential and disruptors for South Africa towards 2030
- Authors: Muntean, George
- Date: 2019
- Subjects: Electronic funds transfers -- Security measures , Blockchains (Databases) Finance -- Technological innovations Technological innovations -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/41603 , vital:36544
- Description: Blockchain (also called distributed ledger technology), the technology that underpins cryptocurrencies, is resulting in a new era of openness, decentralisation and global inclusion (World Economic Forum, 2017). Blockchain technology is set to complement another emerging field or group of technologies which are collectively defined as the Fourth Industrial Revolution. This revolution is characterised by a “range of new technologies that are blending the physical, digital and biological worlds, impacting all disciplines, economies and industries, and even challenging ideas about what it means to be human” (World Economic Forum, 2017). Certain features of Blockchain technology namely; decentralisation, implied anonymity, transparency and immutability presents people with a technology that may well transform business models and indeed entire industries in the world and in South Africa. Some of these industries are explored further in this research, delving into ideas of how Blockchains may add value to them. This research effort approaches Blockchain technology from a future studies perspective, and assesses whether South Africa is ready to embrace the technology. The research also explores what South African stakeholders can do to be better prepared for expected disruptors and opportunities that the technology will bring. South Africa is seen as a developing nation in the global context and can well benefit from strategic use of emerging technologies such as Blockchain. This research effort will implement Inayatullah’s (2008) six pillars methodology, incorporating the various tools and methodologies within each pillar, in an effort to describe and present possible future scenarios for Blockchains in South Africa. This insight will be used to provide well thought out strategic recommendations for South Africa to prepare for adoption of Blockchain technologies, which could ultimately provide a competitive advantage for the country in the global marketplace.
- Full Text:
- Date Issued: 2019
- Authors: Muntean, George
- Date: 2019
- Subjects: Electronic funds transfers -- Security measures , Blockchains (Databases) Finance -- Technological innovations Technological innovations -- Economic aspects -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/41603 , vital:36544
- Description: Blockchain (also called distributed ledger technology), the technology that underpins cryptocurrencies, is resulting in a new era of openness, decentralisation and global inclusion (World Economic Forum, 2017). Blockchain technology is set to complement another emerging field or group of technologies which are collectively defined as the Fourth Industrial Revolution. This revolution is characterised by a “range of new technologies that are blending the physical, digital and biological worlds, impacting all disciplines, economies and industries, and even challenging ideas about what it means to be human” (World Economic Forum, 2017). Certain features of Blockchain technology namely; decentralisation, implied anonymity, transparency and immutability presents people with a technology that may well transform business models and indeed entire industries in the world and in South Africa. Some of these industries are explored further in this research, delving into ideas of how Blockchains may add value to them. This research effort approaches Blockchain technology from a future studies perspective, and assesses whether South Africa is ready to embrace the technology. The research also explores what South African stakeholders can do to be better prepared for expected disruptors and opportunities that the technology will bring. South Africa is seen as a developing nation in the global context and can well benefit from strategic use of emerging technologies such as Blockchain. This research effort will implement Inayatullah’s (2008) six pillars methodology, incorporating the various tools and methodologies within each pillar, in an effort to describe and present possible future scenarios for Blockchains in South Africa. This insight will be used to provide well thought out strategic recommendations for South Africa to prepare for adoption of Blockchain technologies, which could ultimately provide a competitive advantage for the country in the global marketplace.
- Full Text:
- Date Issued: 2019
Bloodmeal analysis in Culicoides midges collected near horses, donkeys and zebras in the Eastern Cape, South Africa:
- Riddin, Megan A, Venter, G J, Labuschagne, K, Villet, Martin H
- Authors: Riddin, Megan A , Venter, G J , Labuschagne, K , Villet, Martin H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140692 , vital:37910 , DOI: 10.1111/mve.12381
- Description: An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014–2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood-fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood-fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.
- Full Text:
- Date Issued: 2019
- Authors: Riddin, Megan A , Venter, G J , Labuschagne, K , Villet, Martin H
- Date: 2019
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140692 , vital:37910 , DOI: 10.1111/mve.12381
- Description: An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014–2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood-fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood-fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.
- Full Text:
- Date Issued: 2019
BODIPY and porphyrin dyes for direct glucose sensing and optical limiting applications
- Authors: Ndebele, Nobuhle
- Date: 2019
- Subjects: Boron compounds , Boric acid , Porphyrins , Dyes and dying -- Chemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97221 , vital:31412
- Description: A series of BODIPY dyes functionalised with boronic acid in the 3,5-positions were successfully synthesised and characterised by using various analytical techniques. The dyes were prepared through a slight modification of the conventional acid catalysed condensation method. Phenylboronic acid moieties were added as styryl groups at the 3,5-positions of the 1,3,5,7-tetrametylBODIPY cores using a modified Knoevengal condensation method. The addition of the styryls resulted in the main absorption band of the dyes red-shifting to the 630−650 nm region. The photophysical and electrochemical properties of these dyes were studied to determine whether the dyes are suitable for use in the fluorescent, colourimetric and electrochemical detection of glucose. Boronic acid moieties were added as bioreceptor recognition elements because they have an affinity for carbohydrates and therefore would be able to bind and “detect” glucose. The series of BODIPY dyes did not show a “turn-on” fluorescence effect upon addition with glucose at the physiological pH. This was attributed on the basis of molecular modelling to the absence of an MO localised on the boronic-acid-substituted styryl moieties that lie close in energy to the HOMO and LUMO that facilitates the formation of an intramolecular charge transfer state. However, colourimetric changes that are visible to the naked eye are observed at basic pH when glucose was added to the dye solutions. The dyes exhibited favourable electrochemical behaviour and were able to detect glucose directly in this context when glassy carbon electrodes are modified through the drop dry method. A series of Sn(IV) porphyrins with thienyl and phenyl groups at the meso-positions were successfully synthesised and characterised. Pyridine and tetrabutyl axial ligands were added to the porphyrins to limit aggregation. The optical limiting properties of these porphyrins and three styrylated BODIPY dyes were studied in benzene and dichloromethane. Dyes were also embedded in polystyrene and studied as thin films to further gauge their suitability for use in optical limiting applications. Second-order hyperpolarizability, third-order susceptibly, non-linear absorption with reversible saturable absorption and the optical limiting threshold, were the parameters studied. Three of the four porphyrins and the three styrylated BODIPY dyes showed favourable optical limiting behaviour, which was further enhanced when the dyes are embedded in polymer thin films.
- Full Text:
- Date Issued: 2019
- Authors: Ndebele, Nobuhle
- Date: 2019
- Subjects: Boron compounds , Boric acid , Porphyrins , Dyes and dying -- Chemistry
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97221 , vital:31412
- Description: A series of BODIPY dyes functionalised with boronic acid in the 3,5-positions were successfully synthesised and characterised by using various analytical techniques. The dyes were prepared through a slight modification of the conventional acid catalysed condensation method. Phenylboronic acid moieties were added as styryl groups at the 3,5-positions of the 1,3,5,7-tetrametylBODIPY cores using a modified Knoevengal condensation method. The addition of the styryls resulted in the main absorption band of the dyes red-shifting to the 630−650 nm region. The photophysical and electrochemical properties of these dyes were studied to determine whether the dyes are suitable for use in the fluorescent, colourimetric and electrochemical detection of glucose. Boronic acid moieties were added as bioreceptor recognition elements because they have an affinity for carbohydrates and therefore would be able to bind and “detect” glucose. The series of BODIPY dyes did not show a “turn-on” fluorescence effect upon addition with glucose at the physiological pH. This was attributed on the basis of molecular modelling to the absence of an MO localised on the boronic-acid-substituted styryl moieties that lie close in energy to the HOMO and LUMO that facilitates the formation of an intramolecular charge transfer state. However, colourimetric changes that are visible to the naked eye are observed at basic pH when glucose was added to the dye solutions. The dyes exhibited favourable electrochemical behaviour and were able to detect glucose directly in this context when glassy carbon electrodes are modified through the drop dry method. A series of Sn(IV) porphyrins with thienyl and phenyl groups at the meso-positions were successfully synthesised and characterised. Pyridine and tetrabutyl axial ligands were added to the porphyrins to limit aggregation. The optical limiting properties of these porphyrins and three styrylated BODIPY dyes were studied in benzene and dichloromethane. Dyes were also embedded in polystyrene and studied as thin films to further gauge their suitability for use in optical limiting applications. Second-order hyperpolarizability, third-order susceptibly, non-linear absorption with reversible saturable absorption and the optical limiting threshold, were the parameters studied. Three of the four porphyrins and the three styrylated BODIPY dyes showed favourable optical limiting behaviour, which was further enhanced when the dyes are embedded in polymer thin films.
- Full Text:
- Date Issued: 2019