Ecological role of estuarine brachyuran crabs in mangrove and salt marsh estuaries, Eastern Cape, South Africa
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
- Authors: Vorsatz, Jeanne Pauline
- Date: 2009
- Subjects: Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10698 , http://hdl.handle.net/10948/1108 , Crabs -- South Africa -- Mangrove Estuary , Crabs -- South Africa -- Salt Marsh Estuary , Salt marsh ecology , Mangrove ecology
- Description: Crabs are conspicuous inhabitants of temperate salt marshes and tropical mangroves and interact with their environment through several processes. However, detailed information on crab community processes is absent for most South African estuaries and nearshore coastal regions. This study evaluated the primary producers supporting crab species in the salt marsh dominated Swartkops estuary and the mangrove Mngazana estuary. Various methods estimating crab abundances were also assessed in different microhabitats and the larval distribution of crabs in the coastal zone was also investigated. Various methods for estimating crab abundance have been employed in the past, each with its inherent biases. The microhabitat of a mangrove forest in Australia was structurally altered by the manipulation of the litter, pneumatophores and the associated algae. These alterations did not affect the behavioural activity or the numbers of crabs recorded in any of the experimental treatments by either visual counts or pitfall traps. However, the number of crabs caught in the pitfall traps differed between the sites. Species-specific behaviour which was not investigated in this study may bias crab abundance estimates when using pitfall traps and therefore requires further investigation. Benthic consumers inhabiting shallow coastal environments may ultimately have the origin of their nutrition in a number of possible sources. Isotopic and gut content analysis of Thalamita crenata and juvenile Scylla serrata in the Mngazana estuary in South Africa revealed that these two portunids are able to share a habitat by resource partitioning. Differences were noted for species-specific utilization of primary producers not only between seasons within a site, but also between sites. This highlighted the use of locally produced primary producers sustaining food webs in estuaries. Mangrove production in the Mngazana estuary is very important and contributes to most of the carbon in the underlying sediments in the mangrove forest. However, the relatively large number of species and biomass encountered in this estuary may also be attributed to the fact that the different species are able to exploit of a number of different resources. The variation in stable isotope analysis of the different crab species throughout the estuary indicated that these crabs able to occupy the same habitat by feeding on a number of different resources and may preferentially select for a specific primary producer. A stable isotope of crabs in the salt marsh Swartkops estuary indicated that the dominant primary producer sustaining crab communities may even take place on a relatively smallscale. Sesarma catenata found at the inner marsh site recorded more depleted carbon signatures than those encountered in the other sites approximately 100 m away, and reflected signatures similar to the locally-encountered inner marsh plants. The relatively enriched nitrogen signatures of the anthropogenically-impacted Swartkops estuary is an indication of extensive inputs due to urbanization and industrialization, in contrast to the relatively pristine Mngazana estuary which exhibited low nitrogen signatures. Emphasis has been placed on the abiotic component of the exchange of nutrients and energy, although living organisms may also be transported, both actively and passively, between ecosystems. Little variation in either species composition or abundance was found between seasons for the larval distribution of brachyuran crabs on the east coast of South Africa. Due to the lack of published larval descriptions, larvae could not be identified to species level and it was therefore not possible to identify whether the larvae were hatched or spawned in an estuary or in a marine environment, or whether the larvae originated in the northern tropical regions. Frequent wind-reversals which are common in this region may retain larvae close inshore and supply the southern temperate locations with larvae from the northern locations. In conclusion, this study has shown that in highly productive systems with a number of potential primary producers, the crabs that inhabit the estuary show a marked diversity in resource utilization which could potentially allow a number of closely related species to occupy different trophic levels. This study also highlights the importance of locally produced sources in an estuary, which may occur on very small scales and this needs to be factored in with the design of any future stable isotope studies of this nature.
- Full Text:
- Date Issued: 2009
An exploration of the nature of a private general medical practice as a social system : a case study
- Authors: Visser, Henriette
- Date: 2009
- Subjects: Physicians (General practice) , Physicians -- Family relationships , Family medicine , Physician and patient
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:16146 , http://hdl.handle.net/10948/884 , Physicians (General practice) , Physicians -- Family relationships , Family medicine , Physician and patient
- Description: This research study explores in general the nature of a private general medical practice [PGMP] and whether analysis of the PGMP as a social system can lead the Group Dynamics Practitioner towards developing interventions that will enhance group effectiveness in the PGMP support staff group. The main assumption is that, through the application of a framework of analysis based on that of G. C. Homans and the AGIL functional prerequisites developed by T. Parsons, a structured analysis of the external and internal variables that impact on the PGMP as a social system can be undertaken. The findings of the analysis would lead to the formulation of interventions that would improve the performance effectiveness of the PGMP as a social system. Following a two-questionnaire survey of 17 practices that provided demographic information as well as soft skills training needs, a single PGMP was identified for the case study. Data pertaining to the group as a social system were collected, and by using direct observation, content analysis and a sociometric test, the practice support staff sub-system, being the main focus of this research, could be analysed. By linking the findings to the elements of the framework of analysis, areas of ineffective group functioning could be identified and interventions suggested. This research indicates that the choice of soft skills is associated with the nature and size of the practice, as well as the dynamics of the sociometric patterns characteristic of the relations within the practice support staff subsystem; that while some practice support staff have preferences for sociometric task and socio-emotional relations outside their work clusters, these seem to serve as a buffer against clique forming, thus enhancing the function of integration within the social system as a whole; and that the physical practice layout, and the interaction dynamics that it creates, tend to hinder integration between the members of the practice support staff group, as a social subsystem.
- Full Text:
- Date Issued: 2009
An exploration of the nature of a private general medical practice as a social system : a case study
- Authors: Visser, Henriette
- Date: 2009
- Subjects: Physicians (General practice) , Physicians -- Family relationships , Family medicine , Physician and patient
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:16146 , http://hdl.handle.net/10948/884 , Physicians (General practice) , Physicians -- Family relationships , Family medicine , Physician and patient
- Description: This research study explores in general the nature of a private general medical practice [PGMP] and whether analysis of the PGMP as a social system can lead the Group Dynamics Practitioner towards developing interventions that will enhance group effectiveness in the PGMP support staff group. The main assumption is that, through the application of a framework of analysis based on that of G. C. Homans and the AGIL functional prerequisites developed by T. Parsons, a structured analysis of the external and internal variables that impact on the PGMP as a social system can be undertaken. The findings of the analysis would lead to the formulation of interventions that would improve the performance effectiveness of the PGMP as a social system. Following a two-questionnaire survey of 17 practices that provided demographic information as well as soft skills training needs, a single PGMP was identified for the case study. Data pertaining to the group as a social system were collected, and by using direct observation, content analysis and a sociometric test, the practice support staff sub-system, being the main focus of this research, could be analysed. By linking the findings to the elements of the framework of analysis, areas of ineffective group functioning could be identified and interventions suggested. This research indicates that the choice of soft skills is associated with the nature and size of the practice, as well as the dynamics of the sociometric patterns characteristic of the relations within the practice support staff subsystem; that while some practice support staff have preferences for sociometric task and socio-emotional relations outside their work clusters, these seem to serve as a buffer against clique forming, thus enhancing the function of integration within the social system as a whole; and that the physical practice layout, and the interaction dynamics that it creates, tend to hinder integration between the members of the practice support staff group, as a social subsystem.
- Full Text:
- Date Issued: 2009
Putting the ‘T’ into South African human rights: transsexuality in the post-apartheid order
- Vincent, Louise, Camminga, Bianca
- Authors: Vincent, Louise , Camminga, Bianca
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141606 , vital:37989 , DOI: 10.1177/1363460709346108
- Description: Informed by narratives provided by self-identified South African transsexuals, whose lives span different periods of South Africa’s political and social history, this article seeks to explore how South Africa’s medical, legal and military establishments have exerted power over the transsexual body. A variety of studies outline the extent to which the apartheid state was a highly gendered state characterized by inflexible patriarchal norms and the dominance of violent and authoritarian forms of masculine expression. Hyper masculinization and militarization were explicit goals of the apartheid state. Deviance from the state’s prescribed gender norms was not simply socially unacceptable, it was, in many cases, punishable. South Africa’s post-1994 democratic Constitution, in contrast, explicitly outlaws discrimination on the basis of sexual orientation. But the democratic legal framework, which provides significant protections for freedom of sexual expression and freedom from discrimination for homosexuals has arguably had less of an impact on the lives of South Africa’s transsexual community. The state, even the post-apartheid state, has been loathe to move beyond the idea of a necessary correlation between the physical make-up of the body and the gender identity of a person in the way in which it has treated the idea of transsexualism.
- Full Text:
- Date Issued: 2009
- Authors: Vincent, Louise , Camminga, Bianca
- Date: 2009
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141606 , vital:37989 , DOI: 10.1177/1363460709346108
- Description: Informed by narratives provided by self-identified South African transsexuals, whose lives span different periods of South Africa’s political and social history, this article seeks to explore how South Africa’s medical, legal and military establishments have exerted power over the transsexual body. A variety of studies outline the extent to which the apartheid state was a highly gendered state characterized by inflexible patriarchal norms and the dominance of violent and authoritarian forms of masculine expression. Hyper masculinization and militarization were explicit goals of the apartheid state. Deviance from the state’s prescribed gender norms was not simply socially unacceptable, it was, in many cases, punishable. South Africa’s post-1994 democratic Constitution, in contrast, explicitly outlaws discrimination on the basis of sexual orientation. But the democratic legal framework, which provides significant protections for freedom of sexual expression and freedom from discrimination for homosexuals has arguably had less of an impact on the lives of South Africa’s transsexual community. The state, even the post-apartheid state, has been loathe to move beyond the idea of a necessary correlation between the physical make-up of the body and the gender identity of a person in the way in which it has treated the idea of transsexualism.
- Full Text:
- Date Issued: 2009
Polygamy in the recognition of Customary Marriages Act:
- Authors: Vincent, Louise
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141809 , vital:38006 , DOI: 10.1080/10130950.2009.9676275
- Description: The Recognition of Customary Marriages Act (RCMA) 1998, recognises customary marriages which are “negotiated, celebrated or concluded according to any of the systems of indigenous African customary law which exist in South Africa” including polygamous marriages. The Act arises in the context of South Africa's Constitution which bans discrimination on grounds of culture and sexual orientation and allows for heterogeneity in its definitions of marriage and the family. A pluralist approach to family jurisprudence, however, is sometimes conceived of as setting up an irresolvable tension between the constitutional commitment to gender equality and protection for patriarchal prerogatives sanctioned by customary law. The fact that rights sometimes collide with one another is one of the reasons why it is impossible always to treat rights as absolute. When rights clash the question that arises is which of the rights that find themselves in tension with one another should give way and why?
- Full Text:
- Date Issued: 2011
- Authors: Vincent, Louise
- Date: 2011
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141809 , vital:38006 , DOI: 10.1080/10130950.2009.9676275
- Description: The Recognition of Customary Marriages Act (RCMA) 1998, recognises customary marriages which are “negotiated, celebrated or concluded according to any of the systems of indigenous African customary law which exist in South Africa” including polygamous marriages. The Act arises in the context of South Africa's Constitution which bans discrimination on grounds of culture and sexual orientation and allows for heterogeneity in its definitions of marriage and the family. A pluralist approach to family jurisprudence, however, is sometimes conceived of as setting up an irresolvable tension between the constitutional commitment to gender equality and protection for patriarchal prerogatives sanctioned by customary law. The fact that rights sometimes collide with one another is one of the reasons why it is impossible always to treat rights as absolute. When rights clash the question that arises is which of the rights that find themselves in tension with one another should give way and why?
- Full Text:
- Date Issued: 2011
“The Two Cultures reunited: entomology for everyone”
- Authors: Villet, Martin H
- Date: 2009
- Language: English
- Type: Audio , text
- Identifier: vital:587 , http://hdl.handle.net/10962/d1018947
- Description: Fifty years ago C.P. Snow delivered his essay, "The Two Cultures", sparking the schism between the Humanities and the Sciences. This lecture explores cultural entomology as a means of reconciling two other cultures: academia and society, and suggests one way of addressing this alienating dilemma.
- Full Text:
- Date Issued: 2009
- Authors: Villet, Martin H
- Date: 2009
- Language: English
- Type: Audio , text
- Identifier: vital:587 , http://hdl.handle.net/10962/d1018947
- Description: Fifty years ago C.P. Snow delivered his essay, "The Two Cultures", sparking the schism between the Humanities and the Sciences. This lecture explores cultural entomology as a means of reconciling two other cultures: academia and society, and suggests one way of addressing this alienating dilemma.
- Full Text:
- Date Issued: 2009
Managing leader member exchange frequency effectively in a South African retail company
- Viljoen, Petrus Johannes Jacobus
- Authors: Viljoen, Petrus Johannes Jacobus
- Date: 2009
- Subjects: Communication in organizations -- South Africa , Communication in management -- South Africa , Leadership -- South Africa , Organizational behavior -- South Africa , Organizational effectiveness -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8692 , http://hdl.handle.net/10948/1106 , Communication in organizations -- South Africa , Communication in management -- South Africa , Leadership -- South Africa , Organizational behavior -- South Africa , Organizational effectiveness -- South Africa
- Description: The purpose of this research is to highlight the importance of identifying the communication frequency within the leader-member exchange (LMX) relationship, and to appreciate what the positive or negative effect of a low or high LMX frequency has on this relationship and on staff morale. Management is for the most part responsible for communication frequency and is in a position and has the means to change such frequency or to add additional communication channels. The research was based on a program introduced in a South African retail company three years ago. Data was collected from 64 stores in the Western Cape and the results were statistically analysed on the SPSS16 program. The results clearly supported the hypotheses that, in a low-communication frequency area, an increase in communication frequency has a positive effect on staff morale and that the proximity to head office (or lack of it) does not have a negative effect on staff morale.
- Full Text:
- Date Issued: 2009
- Authors: Viljoen, Petrus Johannes Jacobus
- Date: 2009
- Subjects: Communication in organizations -- South Africa , Communication in management -- South Africa , Leadership -- South Africa , Organizational behavior -- South Africa , Organizational effectiveness -- South Africa
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: vital:8692 , http://hdl.handle.net/10948/1106 , Communication in organizations -- South Africa , Communication in management -- South Africa , Leadership -- South Africa , Organizational behavior -- South Africa , Organizational effectiveness -- South Africa
- Description: The purpose of this research is to highlight the importance of identifying the communication frequency within the leader-member exchange (LMX) relationship, and to appreciate what the positive or negative effect of a low or high LMX frequency has on this relationship and on staff morale. Management is for the most part responsible for communication frequency and is in a position and has the means to change such frequency or to add additional communication channels. The research was based on a program introduced in a South African retail company three years ago. Data was collected from 64 stores in the Western Cape and the results were statistically analysed on the SPSS16 program. The results clearly supported the hypotheses that, in a low-communication frequency area, an increase in communication frequency has a positive effect on staff morale and that the proximity to head office (or lack of it) does not have a negative effect on staff morale.
- Full Text:
- Date Issued: 2009
A framework towards effective control in information security governance
- Authors: Viljoen, Melanie
- Date: 2009
- Subjects: Data protection , Computer networks -- Security measures , Electronic data processing departments -- Security measures
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9773 , http://hdl.handle.net/10948/887 , Data protection , Computer networks -- Security measures , Electronic data processing departments -- Security measures
- Description: The importance of information in business today has made the need to properly secure this asset evident. Information security has become a responsibility for all managers of an organization. To better support more efficient management of information security, timely information security management information should be made available to all managers. Smaller organizations face special challenges with regard to information security management and reporting due to limited resources (Ross, 2008). This dissertation discusses a Framework for Information Security Management Information (FISMI) that aims to improve the visibility and contribute to better management of information security throughout an organization by enabling the provision of summarized, comprehensive information security management information to all managers in an affordable manner.
- Full Text:
- Date Issued: 2009
- Authors: Viljoen, Melanie
- Date: 2009
- Subjects: Data protection , Computer networks -- Security measures , Electronic data processing departments -- Security measures
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9773 , http://hdl.handle.net/10948/887 , Data protection , Computer networks -- Security measures , Electronic data processing departments -- Security measures
- Description: The importance of information in business today has made the need to properly secure this asset evident. Information security has become a responsibility for all managers of an organization. To better support more efficient management of information security, timely information security management information should be made available to all managers. Smaller organizations face special challenges with regard to information security management and reporting due to limited resources (Ross, 2008). This dissertation discusses a Framework for Information Security Management Information (FISMI) that aims to improve the visibility and contribute to better management of information security throughout an organization by enabling the provision of summarized, comprehensive information security management information to all managers in an affordable manner.
- Full Text:
- Date Issued: 2009
The effect of progressive resistance training on the blood lipid profile in post-menopausal women
- Authors: Viljoen, Janet Erica
- Date: 2009
- Subjects: Weight training for women -- Physiological aspects , Weight training -- Physiological aspects , Exercise for women -- Physiological aspects , Physical fitness for women -- Physiological aspects , Energy metabolism , Middle aged women -- Health and hygiene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5113 , http://hdl.handle.net/10962/d1005191 , Weight training for women -- Physiological aspects , Weight training -- Physiological aspects , Exercise for women -- Physiological aspects , Physical fitness for women -- Physiological aspects , Energy metabolism , Middle aged women -- Health and hygiene
- Description: The main purpose of this study was to assess the effect of progressive resistance training on the blood lipid profile in post-menopausal women. Thirty-four female subjects aged 50 to 75 years were selected from the population of Grahamstown, South Africa. All participants were previously sedentary and possessed at least one lipid profile abnormality but were otherwise healthy. Pre-tests included a sub-maximal stress Electrocardiogram, measures of stature, mass, central and limb girths as well as an oral glucose tolerance test (OGTT) and a total blood lipid profile. Participants took part in a 24-week progressive resistance training programme, consisting of three supervised sessions per week, each lasting 45 minutes and were not permitted to lose more than 10% of initial body mass during the 24-week study. All pre-test measures, excluding the stress ECG and the OGTT, were repeated every four weeks for the duration of the study. Results were that body mass, body mass index and waist-to-hip ratio did not change. Girth measures at mid-humerus, chest, waist, hip, mid-quadricep and mid-gastrocnemius all decreased significantly (p=0.05). LDL-cholesterol increased significantly over the course of 24 weeks (3.61mmol.L-1 to 4.07mmol.L-1) as did total cholesterol (5.81mmol.L-1 to 6.24mmol.L-1). Triglyceride concentration remained unchanged and HDL-cholesterol decreased significantly between the pre-test measure (1.55mmol.L-1) and the measure after six months (1.42mmol.L-1). It can be concluded that the blood lipid profile in a sample of post-menopausal women was not positively affected by a progressive resistance training programme over a 24 week period. , Maiden name: Kelly, Janet Erica
- Full Text:
- Date Issued: 2009
- Authors: Viljoen, Janet Erica
- Date: 2009
- Subjects: Weight training for women -- Physiological aspects , Weight training -- Physiological aspects , Exercise for women -- Physiological aspects , Physical fitness for women -- Physiological aspects , Energy metabolism , Middle aged women -- Health and hygiene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5113 , http://hdl.handle.net/10962/d1005191 , Weight training for women -- Physiological aspects , Weight training -- Physiological aspects , Exercise for women -- Physiological aspects , Physical fitness for women -- Physiological aspects , Energy metabolism , Middle aged women -- Health and hygiene
- Description: The main purpose of this study was to assess the effect of progressive resistance training on the blood lipid profile in post-menopausal women. Thirty-four female subjects aged 50 to 75 years were selected from the population of Grahamstown, South Africa. All participants were previously sedentary and possessed at least one lipid profile abnormality but were otherwise healthy. Pre-tests included a sub-maximal stress Electrocardiogram, measures of stature, mass, central and limb girths as well as an oral glucose tolerance test (OGTT) and a total blood lipid profile. Participants took part in a 24-week progressive resistance training programme, consisting of three supervised sessions per week, each lasting 45 minutes and were not permitted to lose more than 10% of initial body mass during the 24-week study. All pre-test measures, excluding the stress ECG and the OGTT, were repeated every four weeks for the duration of the study. Results were that body mass, body mass index and waist-to-hip ratio did not change. Girth measures at mid-humerus, chest, waist, hip, mid-quadricep and mid-gastrocnemius all decreased significantly (p=0.05). LDL-cholesterol increased significantly over the course of 24 weeks (3.61mmol.L-1 to 4.07mmol.L-1) as did total cholesterol (5.81mmol.L-1 to 6.24mmol.L-1). Triglyceride concentration remained unchanged and HDL-cholesterol decreased significantly between the pre-test measure (1.55mmol.L-1) and the measure after six months (1.42mmol.L-1). It can be concluded that the blood lipid profile in a sample of post-menopausal women was not positively affected by a progressive resistance training programme over a 24 week period. , Maiden name: Kelly, Janet Erica
- Full Text:
- Date Issued: 2009
A model for enhancing presence handling in instant messaging
- Authors: Victor, Rudi
- Date: 2009
- Subjects: Instant messaging , Mobile communication systems , Data transmission systems
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9774 , http://hdl.handle.net/10948/877 , Instant messaging , Mobile communication systems , Data transmission systems
- Description: Instant Messaging (IM) is becoming increasingly popular in social as well as workplace environments. In fact, many employees use the same IM client to communicate with both colleagues and social contacts. Thus, there are valid concerns about the impact of IM on employee productivity. One of the major advantages of IM over other workplace communication tools such as e-mail and the telephone is the implementation of presence information. In particular, presence awareness is used to determine the avail- ability and willingness of a contact to engage in communication. A current problem with IM is the one-for-all approach to presence: all contacts receive the same set of presence information. However, presence is rooted in social psychology where it is known that the awareness of another person changes the behavior of oneself. Therefore the identity of a contact affects the availability and willingness directed towards that contact. In order for presence information to be provided to contacts, it must be represented in some type of data format. The Internet Engineering Task Force (IETF) has done much work in standardizing IM and presence systems. In particular their data format for presence describes a rich set of presence information including, but not limited to, location, activity, awareness, and mood information. Such information may be sensitive and access to it needs to be controlled to ensure privacy. As with access control policies, managing the information as the number of contacts increases becomes cumbersome and complex. This dissertation draws on the theoretical foundations of presence, current standards in the domain of IM, and lessons from access control to present an enhanced presence handling model for IM. The model is developed in stages, with each stage providing a specific improvement. The first stage of the model is grounded on the current work of the IETF. As such it distributes presence on a per-watcher basis. In the second stage of the model watchers fulfill a specific role and based on this role they receive only the entrusted presence information. In practice, it implies that a "friend" may get more (or less) information than a "colleague". The third stage of the model introduces the concept of availability profiles by drawing on social awareness principles. Availability profiles add the ability to transform presence and change the presentity's behavior to incoming messages according to the provided presence information. Finally the dissertation reports on the development of the RoBIM (Role- Based Instant Messenger) prototype. RoBIM is a standards-based IM system that conforms to the IETF SIMPLE protocol and provides various standard IM features. Here, RoBIM serves as a proof-of-concept for the proposed model. This study contributed to the domain of IM and presence by addressing some of the current presence handling issues. Most importantly, the proposed model takes into account the interpersonal effects of individualizing presence information for different contacts. Thus, the model challenges conventional thought and implementation of presence in IM.
- Full Text:
- Date Issued: 2009
- Authors: Victor, Rudi
- Date: 2009
- Subjects: Instant messaging , Mobile communication systems , Data transmission systems
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:9774 , http://hdl.handle.net/10948/877 , Instant messaging , Mobile communication systems , Data transmission systems
- Description: Instant Messaging (IM) is becoming increasingly popular in social as well as workplace environments. In fact, many employees use the same IM client to communicate with both colleagues and social contacts. Thus, there are valid concerns about the impact of IM on employee productivity. One of the major advantages of IM over other workplace communication tools such as e-mail and the telephone is the implementation of presence information. In particular, presence awareness is used to determine the avail- ability and willingness of a contact to engage in communication. A current problem with IM is the one-for-all approach to presence: all contacts receive the same set of presence information. However, presence is rooted in social psychology where it is known that the awareness of another person changes the behavior of oneself. Therefore the identity of a contact affects the availability and willingness directed towards that contact. In order for presence information to be provided to contacts, it must be represented in some type of data format. The Internet Engineering Task Force (IETF) has done much work in standardizing IM and presence systems. In particular their data format for presence describes a rich set of presence information including, but not limited to, location, activity, awareness, and mood information. Such information may be sensitive and access to it needs to be controlled to ensure privacy. As with access control policies, managing the information as the number of contacts increases becomes cumbersome and complex. This dissertation draws on the theoretical foundations of presence, current standards in the domain of IM, and lessons from access control to present an enhanced presence handling model for IM. The model is developed in stages, with each stage providing a specific improvement. The first stage of the model is grounded on the current work of the IETF. As such it distributes presence on a per-watcher basis. In the second stage of the model watchers fulfill a specific role and based on this role they receive only the entrusted presence information. In practice, it implies that a "friend" may get more (or less) information than a "colleague". The third stage of the model introduces the concept of availability profiles by drawing on social awareness principles. Availability profiles add the ability to transform presence and change the presentity's behavior to incoming messages according to the provided presence information. Finally the dissertation reports on the development of the RoBIM (Role- Based Instant Messenger) prototype. RoBIM is a standards-based IM system that conforms to the IETF SIMPLE protocol and provides various standard IM features. Here, RoBIM serves as a proof-of-concept for the proposed model. This study contributed to the domain of IM and presence by addressing some of the current presence handling issues. Most importantly, the proposed model takes into account the interpersonal effects of individualizing presence information for different contacts. Thus, the model challenges conventional thought and implementation of presence in IM.
- Full Text:
- Date Issued: 2009
Drought, change and resilience in South Africa's arid and semi-arid rangelands
- Authors: Vetter, Susan M
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6557 , http://hdl.handle.net/10962/d1006017
- Description: Droughts can have serious ecological and economic consequences and will pose an increasing challenge to rangeiand users as the global climate is changing. Finding ways to reduce ecological and economic impacts of drought should thus be a major research thrust. Resilience, defined as the amount of perturbation a social or ecological system can absorb without shifting to a qualitatively different state, has emerged as a prominent concept in ecosystem ecology and more recently as a conceptual framework for understanding and managing complex social-ecological systems. This paper discusses the application and relevance of resilience to understanding and managing ecosystem change, and enhancing the capacity of land users to adapt to droughts. Drought can trigger vegetation change and factors such as grazing management can influence the likelihood of such transitions. Drought can cause differential mortality of perennial plants and this could provide an opportunity for rangeland restoration by opening up establishment sites for desirable species. The capacity of land users to cope with drought is influenced by the resilience of their agro-ecosystems, the diversity of livelihood options, access to resources and institutional support. By these criteria, current agricultural development approaches in South Africa, particularly in communal rangelands and areas of land reform, are unlikely to enhance land users' resilience to drought and other perturbations.
- Full Text:
- Date Issued: 2009
- Authors: Vetter, Susan M
- Date: 2009
- Language: English
- Type: Article
- Identifier: vital:6557 , http://hdl.handle.net/10962/d1006017
- Description: Droughts can have serious ecological and economic consequences and will pose an increasing challenge to rangeiand users as the global climate is changing. Finding ways to reduce ecological and economic impacts of drought should thus be a major research thrust. Resilience, defined as the amount of perturbation a social or ecological system can absorb without shifting to a qualitatively different state, has emerged as a prominent concept in ecosystem ecology and more recently as a conceptual framework for understanding and managing complex social-ecological systems. This paper discusses the application and relevance of resilience to understanding and managing ecosystem change, and enhancing the capacity of land users to adapt to droughts. Drought can trigger vegetation change and factors such as grazing management can influence the likelihood of such transitions. Drought can cause differential mortality of perennial plants and this could provide an opportunity for rangeland restoration by opening up establishment sites for desirable species. The capacity of land users to cope with drought is influenced by the resilience of their agro-ecosystems, the diversity of livelihood options, access to resources and institutional support. By these criteria, current agricultural development approaches in South Africa, particularly in communal rangelands and areas of land reform, are unlikely to enhance land users' resilience to drought and other perturbations.
- Full Text:
- Date Issued: 2009
A new light on the pre-colonial history of South-East Africa, where the 'Other' is the European and the 'Silence' has a voice, based on evidence from shipwreck survivor narratives 1552-1782
- Authors: Vernon, Gillian Noël
- Date: 2009
- Subjects: Shipwrecks -- South Africa -- History Shipwrecks -- Mozambique -- Personal narratives
- Language: English
- Type: Thesis , Doctoral , PhD (History)
- Identifier: http://hdl.handle.net/10353/7930 , vital:30924
- Description: The aim of this dissertation is to extract information from shipwreck survivor narratives, which will add to the known body of knowledge of the pre-colonial history of Southern Africa during the years 1552 to 1782. The discourse analysis focuses on the voice of the African peoples where the Europeans are the 'Strangers', the 'Other', reversing the view that the people of non-European cultures were termed as the 'Other'. Indigenous inhabitants of south-east Africa, south of Kosi Bay, first encountered Europeans in 1552 when a Portuguese ship was wrecked at present-day Port Edward. Subsequently, eight more Portuguese ships were wrecked between Plettenberg Bay and Kosi Bay between the years 1554 to 1647. Two Dutch ships landed on the shore, one south of the Bay of Natal in 1686, and the other being wrecked near the mouth of the Keiskamma River in 1713. There were also two English ships, with one striking the rocks on Bird Island in Algoa Bay in 1755 and the other, the more famous Grosvenor of 1782, coming aground at Lambazi Bay, north of the Mzimvubu River. The survivor groups were large, varying in size from 72 to 500, and most included a large complements of slaves. The survivors of the Portuguese ships made their way to present-day Mozambique where the Portuguese had trading outposts. The survivors of the Dutch ships, as well as those of the Grosvenor tried, with limited success, to make their way to Cape Town. The survivors from two of the Portuguese wrecks and the English group on Bird Island, constructed small ships and managed to sail away.
- Full Text:
- Date Issued: 2009
- Authors: Vernon, Gillian Noël
- Date: 2009
- Subjects: Shipwrecks -- South Africa -- History Shipwrecks -- Mozambique -- Personal narratives
- Language: English
- Type: Thesis , Doctoral , PhD (History)
- Identifier: http://hdl.handle.net/10353/7930 , vital:30924
- Description: The aim of this dissertation is to extract information from shipwreck survivor narratives, which will add to the known body of knowledge of the pre-colonial history of Southern Africa during the years 1552 to 1782. The discourse analysis focuses on the voice of the African peoples where the Europeans are the 'Strangers', the 'Other', reversing the view that the people of non-European cultures were termed as the 'Other'. Indigenous inhabitants of south-east Africa, south of Kosi Bay, first encountered Europeans in 1552 when a Portuguese ship was wrecked at present-day Port Edward. Subsequently, eight more Portuguese ships were wrecked between Plettenberg Bay and Kosi Bay between the years 1554 to 1647. Two Dutch ships landed on the shore, one south of the Bay of Natal in 1686, and the other being wrecked near the mouth of the Keiskamma River in 1713. There were also two English ships, with one striking the rocks on Bird Island in Algoa Bay in 1755 and the other, the more famous Grosvenor of 1782, coming aground at Lambazi Bay, north of the Mzimvubu River. The survivor groups were large, varying in size from 72 to 500, and most included a large complements of slaves. The survivors of the Portuguese ships made their way to present-day Mozambique where the Portuguese had trading outposts. The survivors of the Dutch ships, as well as those of the Grosvenor tried, with limited success, to make their way to Cape Town. The survivors from two of the Portuguese wrecks and the English group on Bird Island, constructed small ships and managed to sail away.
- Full Text:
- Date Issued: 2009
Development of biological control strategies against sirex noctilio (Fabricius) on Sappi Forests (Ltd) Landholdings in the summer rainfall regions of South Africa
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
- Authors: Verleur, Peter Marcel
- Date: 2009
- Subjects: Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10741 , http://hdl.handle.net/10948/1273 , Pests -- Biological control -- South Africa , Nonindigenous pests -- Control
- Description: The commercial forest industry in South Africa is predominantly dependent on large tracts of exotic monoculture plantations. While this simplifies management practice, there is always the inherent danger posed by introduced pests and diseases. Classical biological control is usually the most effective control method against introduced exotic pests. Climatic factors and seasonal differences may negatively affect the ability of the natural enemies to establish successfully at the new location. Successful establishment of the natural enemies usually results in control over the pest within four years. Sirex noctilio naturally occurs in the mediterranean countries of Europe and North Africa. It is the only member of the Siricid family capable of killing living pine trees. Sirex noctilio was accidentally introduced into New Zealand from Europe during the early 1900s. It has since been found in Australia, Brazil, Argentina South Africa and Chile. Initial biological control in New Zealand and Tasmania was through the release of Siricid specific parasitoid wasps from Europe and North America. The discovery of the accidental introduction of the entomophagous nematode Beddingia siricidicola and its subsequent artificial culturing for release provided the platform for the biological control methodology, which brought the Sirex woodwasp under control. The methods and natural enemies used in New Zealand and Australia were introduced by the South American countries and in the Western Cape of South Africa. Successful biological control was achieved in the Western Cape within two years after the initial introduction of the nematode B. siricidicola. The migration of S. noctilio into the summer rainfall regions of South Africa occurred in the absence of the associated natural enemies. This resulted in rapid population growth of the pest and substantial damage was caused to plantations of Pinus patula in the Eastern Cape and KwaZulu-Natal. Initial attempts at introducing B. siricidicola during 2004 were not very successful. This study contributes to the understanding and adaptation of the biological control methods to the summer rainfall climate. The key finding was that in the summer rainfall climate, only the bottom third of nematode inoculated S. noctilio infested trees produced parasitized adults during the emergence period. A comparative study was done on log samples from S. noctilio infested trees collected in the Western Cape and KwaZulu-Natal. iv An adapted nematode inoculation technique for pulpwood plantations in the summer rainfall regions was developed and implemented in mass inoculations with B. siricidicola during 2007 and 2008. Locally available herbicides were tested for suitability of use in the establishment of trap trees, which would attract ovipositing S. noctilio females in situations where low numbers of the woodwasp occur. Determination of the levels of natural B. siricidicola parasitism in S. noctilio adults during the 2008 emergence period indicate successful establishment of the nematode in KwaZulu-Natal. Successful introduction of the parasitoid wasp Ibalia leucospoides into the summer rainfall regions has also been achieved.
- Full Text:
- Date Issued: 2009
Transnational civil society's ability to successfully influence state actors on human rights issues through international non-governmental organizations (INGOs) : a case study of the coalition to stop the use of child soldiers
- Authors: VerHage, Alicia
- Date: 2009
- Subjects: International Campaign to Ban Landmines , Convention on the Rights of the Child (1989 November 20) , Non-governmental organizations , Child soldiers , Children's rights , Human rights , Children (International law)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2884 , http://hdl.handle.net/10962/d1015249
- Description: The international dilemma of child soldiers is a humanitarian concern throughout the world. The Coalition to Stop the Use of Child Soldiers (CSUCS) began in 1998 and is currently the leading collaborative movement to address the issue. However, because of its emphasis on a universal 'Straight 18' approach and support of the Optional Protocol of the Convention on the Rights of a Child (CRC), the CSUCS ignores contextual realities that affect the implementation ofthe international legislation and the development of norms concerning child soldiers. This research project will examine the current international nongovernmental organization (INGO) response to child soldiers- focusing on the CSCUS - and formulate suggestions for potential avenues to further INGO involvement with policies and projects. The argument is based on a neoliberal institutionalist platform that argues in favour ofiNGOs' ability to successfully influence actions taken by state actors to address human right issues. Highlighting the successful INGO influence on states during the International Campaign to Ban Landmines, I will present this example as a potential model for the Coalition to Stop the Use of Child Soldiers, and explore the feasibility of this model whilst making suggestions for more effective involvement of INGOs with regard to the issue of child soldiers.
- Full Text:
- Date Issued: 2009
- Authors: VerHage, Alicia
- Date: 2009
- Subjects: International Campaign to Ban Landmines , Convention on the Rights of the Child (1989 November 20) , Non-governmental organizations , Child soldiers , Children's rights , Human rights , Children (International law)
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2884 , http://hdl.handle.net/10962/d1015249
- Description: The international dilemma of child soldiers is a humanitarian concern throughout the world. The Coalition to Stop the Use of Child Soldiers (CSUCS) began in 1998 and is currently the leading collaborative movement to address the issue. However, because of its emphasis on a universal 'Straight 18' approach and support of the Optional Protocol of the Convention on the Rights of a Child (CRC), the CSUCS ignores contextual realities that affect the implementation ofthe international legislation and the development of norms concerning child soldiers. This research project will examine the current international nongovernmental organization (INGO) response to child soldiers- focusing on the CSCUS - and formulate suggestions for potential avenues to further INGO involvement with policies and projects. The argument is based on a neoliberal institutionalist platform that argues in favour ofiNGOs' ability to successfully influence actions taken by state actors to address human right issues. Highlighting the successful INGO influence on states during the International Campaign to Ban Landmines, I will present this example as a potential model for the Coalition to Stop the Use of Child Soldiers, and explore the feasibility of this model whilst making suggestions for more effective involvement of INGOs with regard to the issue of child soldiers.
- Full Text:
- Date Issued: 2009
The development and evaluation of gaze selection techniques
- Authors: Van Tonder, Martin Stephen
- Date: 2009
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Gaze
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10469 , http://hdl.handle.net/10948/882 , Human-computer interaction , User interfaces (Computer systems) , Gaze
- Description: Eye gaze interaction enables users to interact with computers using their eyes. A wide variety of eye gaze interaction techniques have been developed to support this type of interaction. Gaze selection techniques, a class of eye gaze interaction techniques which support target selection, are the subject of this research. Researchers developing these techniques face a number of challenges. The most significant challenge is the limited accuracy of eye tracking equipment (due to the properties of the human eye). The design of gaze selection techniques is dominated by this constraint. Despite decades of research, existing techniques are still significantly less accurate than the mouse. A recently developed technique, EyePoint, represents the state of the art in gaze selection techniques. EyePoint combines gaze input with keyboard input. Evaluation results for this technique are encouraging, but accuracy is still a concern. Early trigger errors, resulting from users triggering a selection before looking at the intended target, were found to be the most commonly occurring errors for this technique. The primary goal of this research was to improve the usability of gaze selection techniques. In order to achieve this goal, novel gaze selection techniques were developed. New techniques were developed by combining elements of existing techniques in novel ways. Seven novel gaze selection techniques were developed. Three of these techniques were selected for evaluation. A software framework was developed for implementing and evaluating gaze selection techniques. This framework was used to implement the gaze selection techniques developed during this research. Implementing and evaluating all of the techniques using a common framework ensured consistency when comparing the techniques. The novel techniques which were developed were evaluated against EyePoint and the mouse using the framework. The three novel techniques evaluated were named TargetPoint, StaggerPoint and ScanPoint. TargetPoint combines motor space expansion with a visual feedback highlight whereas the StaggerPoint and TargetPoint designs explore novel approaches to target selection disambiguation. A usability evaluation of the three novel techniques alongside EyePoint and the mouse revealed some interesting trends. TargetPoint was found to be more usable and accurate than EyePoint. This novel technique also proved more popular with test participants. One aspect of TargetPoint which proved particularly popular was the visual feedback highlight, a feature which was found to be a more effective method of combating early trigger errors than existing approaches. StaggerPoint was more efficient than EyePoint, but was less effective and satisfying. ScanPoint was the least popular technique. The benefits of providing a visual feedback highlight and test participants' positive views thereof contradict views expressed in existing research regarding the usability of visual feedback. These results have implications for the design of future gaze selection techniques. A set of design principles was developed for designing new gaze selection techniques. The designers of gaze selection techniques can benefit from these design principles by applying them to their techniques
- Full Text:
- Date Issued: 2009
- Authors: Van Tonder, Martin Stephen
- Date: 2009
- Subjects: Human-computer interaction , User interfaces (Computer systems) , Gaze
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:10469 , http://hdl.handle.net/10948/882 , Human-computer interaction , User interfaces (Computer systems) , Gaze
- Description: Eye gaze interaction enables users to interact with computers using their eyes. A wide variety of eye gaze interaction techniques have been developed to support this type of interaction. Gaze selection techniques, a class of eye gaze interaction techniques which support target selection, are the subject of this research. Researchers developing these techniques face a number of challenges. The most significant challenge is the limited accuracy of eye tracking equipment (due to the properties of the human eye). The design of gaze selection techniques is dominated by this constraint. Despite decades of research, existing techniques are still significantly less accurate than the mouse. A recently developed technique, EyePoint, represents the state of the art in gaze selection techniques. EyePoint combines gaze input with keyboard input. Evaluation results for this technique are encouraging, but accuracy is still a concern. Early trigger errors, resulting from users triggering a selection before looking at the intended target, were found to be the most commonly occurring errors for this technique. The primary goal of this research was to improve the usability of gaze selection techniques. In order to achieve this goal, novel gaze selection techniques were developed. New techniques were developed by combining elements of existing techniques in novel ways. Seven novel gaze selection techniques were developed. Three of these techniques were selected for evaluation. A software framework was developed for implementing and evaluating gaze selection techniques. This framework was used to implement the gaze selection techniques developed during this research. Implementing and evaluating all of the techniques using a common framework ensured consistency when comparing the techniques. The novel techniques which were developed were evaluated against EyePoint and the mouse using the framework. The three novel techniques evaluated were named TargetPoint, StaggerPoint and ScanPoint. TargetPoint combines motor space expansion with a visual feedback highlight whereas the StaggerPoint and TargetPoint designs explore novel approaches to target selection disambiguation. A usability evaluation of the three novel techniques alongside EyePoint and the mouse revealed some interesting trends. TargetPoint was found to be more usable and accurate than EyePoint. This novel technique also proved more popular with test participants. One aspect of TargetPoint which proved particularly popular was the visual feedback highlight, a feature which was found to be a more effective method of combating early trigger errors than existing approaches. StaggerPoint was more efficient than EyePoint, but was less effective and satisfying. ScanPoint was the least popular technique. The benefits of providing a visual feedback highlight and test participants' positive views thereof contradict views expressed in existing research regarding the usability of visual feedback. These results have implications for the design of future gaze selection techniques. A set of design principles was developed for designing new gaze selection techniques. The designers of gaze selection techniques can benefit from these design principles by applying them to their techniques
- Full Text:
- Date Issued: 2009
Land reform in South Africa: effects on land prices and productivity
- Authors: Van Rooyen, Jonathan
- Date: 2009
- Subjects: Right of property -- South Africa , Land reform -- South Africa , Agriculture and state -- South Africa , Agricultural prices -- South Africa , Land tenure -- Government policy -- South Africa , Land reform -- Economic aspects -- South Africa , Real property -- Prices -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:987 , http://hdl.handle.net/10962/d1002721
- Description: South Africa’s land redistribution policy (1994-2008) has been widely publicised, and has come under scrutiny of late from the public, private and government spheres, highlighting a need for research in this area. The research examines progress in South Africa’s land redistribution programme in two of KwaZulu-Natal’s district municipalities, Uthungulu and iLembe. Specifically the research investigates whether the government has paid above market prices when purchasing sugarcane farmland for redistribution in these districts. Moreover, it is illustrated how productivity on redistributed farms has been affected with the changes in ownership. To investigate the research questions, reviews of theories pertaining to property rights, land reform and market structures were conducted. Moreover, two cases studies were conducted in the districts of Uthungulu and iLembe, with assistance from the Department of Land Affairs, Inkezo Land Company and the South African Cane Growers Association. The case study data indicate that above ordinary market prices have been paid (2004-2006) by the government for sugarcane farmland in the districts concerned, and further that productivity has been negatively impacted ‘during’ and ‘post‘ transfer, in the majority of cases.
- Full Text:
- Date Issued: 2009
- Authors: Van Rooyen, Jonathan
- Date: 2009
- Subjects: Right of property -- South Africa , Land reform -- South Africa , Agriculture and state -- South Africa , Agricultural prices -- South Africa , Land tenure -- Government policy -- South Africa , Land reform -- Economic aspects -- South Africa , Real property -- Prices -- South Africa
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: vital:987 , http://hdl.handle.net/10962/d1002721
- Description: South Africa’s land redistribution policy (1994-2008) has been widely publicised, and has come under scrutiny of late from the public, private and government spheres, highlighting a need for research in this area. The research examines progress in South Africa’s land redistribution programme in two of KwaZulu-Natal’s district municipalities, Uthungulu and iLembe. Specifically the research investigates whether the government has paid above market prices when purchasing sugarcane farmland for redistribution in these districts. Moreover, it is illustrated how productivity on redistributed farms has been affected with the changes in ownership. To investigate the research questions, reviews of theories pertaining to property rights, land reform and market structures were conducted. Moreover, two cases studies were conducted in the districts of Uthungulu and iLembe, with assistance from the Department of Land Affairs, Inkezo Land Company and the South African Cane Growers Association. The case study data indicate that above ordinary market prices have been paid (2004-2006) by the government for sugarcane farmland in the districts concerned, and further that productivity has been negatively impacted ‘during’ and ‘post‘ transfer, in the majority of cases.
- Full Text:
- Date Issued: 2009
The integration of GIS technology into demographic and quality of life surveying of informal settlements : Nelson Mandela Bay, South Africa
- Authors: Van Niekerk, Susan
- Date: 2009
- Subjects: Demographic surveys -- South Africa -- Port Elizabeth , Geographic information systems -- Social aspects -- South Africa -- Port Elizabeth , Quality of life Statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10659 , http://hdl.handle.net/10948/881 , http://hdl.handle.net/10948/d1012888 , Demographic surveys -- South Africa -- Port Elizabeth , Geographic information systems -- Social aspects -- South Africa -- Port Elizabeth , Quality of life Statistics
- Description: A number of mostly informal areas in Nelson Mandela Bay have experienced rapid expansion over the past decade or so. Census data available for these areas is outdated and does not provide enough information for local authorities to accurately plan for tasks such as service delivery management and resource allocation. In this dissertation, a GIS based demographic and Quality of Life study of informal settlements and previously disadvantaged areas within Nelson Mandela Bay is undertaken to address this issue. The study aims to integrate GIS technology into a demographic and Quality of Life survey to significantly improve the collection, analysis, interpretation, display and management of survey data and to provide the accurate and necessary updates required between census collections. Data relating to informal settlements were captured from aerial photographs and satellite imagery and demographic and Quality of Life data were collected from field surveys. The results demonstrated that the use of GIS technology provided more accurate information for demographic variables, including the number of dwellings, dwelling type, size of the population and population dynamics. A specific demographic trend observed through spatial analysis included the identification of backyard shacks predating formal structures in settlements. The analysis and representation of the Quality of Life field survey data in GIS demonstrated how residents' perceptions of problems and issues in their neighbourhoods are better interpreted, understood and managed when analyzed within a spatial context. This research concluded that GIS based demographic and QOL studies are vital for providing accurate social and spatial information for municipalities, particularly in urban environments of developing countries, and for providing the necessary updates to censuses occurring every ten years.
- Full Text:
- Date Issued: 2009
- Authors: Van Niekerk, Susan
- Date: 2009
- Subjects: Demographic surveys -- South Africa -- Port Elizabeth , Geographic information systems -- Social aspects -- South Africa -- Port Elizabeth , Quality of life Statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10659 , http://hdl.handle.net/10948/881 , http://hdl.handle.net/10948/d1012888 , Demographic surveys -- South Africa -- Port Elizabeth , Geographic information systems -- Social aspects -- South Africa -- Port Elizabeth , Quality of life Statistics
- Description: A number of mostly informal areas in Nelson Mandela Bay have experienced rapid expansion over the past decade or so. Census data available for these areas is outdated and does not provide enough information for local authorities to accurately plan for tasks such as service delivery management and resource allocation. In this dissertation, a GIS based demographic and Quality of Life study of informal settlements and previously disadvantaged areas within Nelson Mandela Bay is undertaken to address this issue. The study aims to integrate GIS technology into a demographic and Quality of Life survey to significantly improve the collection, analysis, interpretation, display and management of survey data and to provide the accurate and necessary updates required between census collections. Data relating to informal settlements were captured from aerial photographs and satellite imagery and demographic and Quality of Life data were collected from field surveys. The results demonstrated that the use of GIS technology provided more accurate information for demographic variables, including the number of dwellings, dwelling type, size of the population and population dynamics. A specific demographic trend observed through spatial analysis included the identification of backyard shacks predating formal structures in settlements. The analysis and representation of the Quality of Life field survey data in GIS demonstrated how residents' perceptions of problems and issues in their neighbourhoods are better interpreted, understood and managed when analyzed within a spatial context. This research concluded that GIS based demographic and QOL studies are vital for providing accurate social and spatial information for municipalities, particularly in urban environments of developing countries, and for providing the necessary updates to censuses occurring every ten years.
- Full Text:
- Date Issued: 2009
Economic responsiveness in organisational psychology curricula
- Authors: Van Niekerk, Roelf
- Date: 2009
- Subjects: Psychology, Industrial -- Study and teaching (Higher) -- South Africa Universities and colleges -- Curricula -- South Africa College graduates -- Employment -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1319 , http://hdl.handle.net/10962/d1003952
- Description: This study focused on a topic at the intersection of two contexts, namely curriculum responsiveness and industrial/organisational psychology (IOP). The rationale for this study is based on two considerations. Firstly, a review of the IOP curricula offered at ten prominent South African universities revealed little overlap. This suggests that academic departments are not guided by shared principles when they implement decisions about the content or sequencing of curriculum content. Secondly, the Department of Education urges academics to design curricula that are relevant and responsive to contemporary conditions. These two considerations motivated the investigation of the following research question: What key performance areas (KPAs) do employers specify when they advertise positions suitable for IOP graduates? The investigation had two aims, namely (a) to systematically analyse the KPAs specified in job advertisements and (b) to compile KPA templates that may be used by IOP departments who wish to revise or transform their curricula. The research design of this study has five characteristics, namely that it is: (a) qualitative, (b) naturalistic, (c), descriptive, (d) applied, and (e) strategic. The study employed a purposive sampling strategy that involved the collection of documentary data (job advertisements aimed at recruiting IOP graduates) over a 52-week period (N=1115). The data was content analysed by means of a six-step documentary analysis method. Specific strategies were employed to enhance the validity of the findings. These strategies focused on credibility, transferability, dependability, and confirmability. Similarly, the ethical standing of the investigation was promoted by addressing four considerations, namely autonomy and respect for dignity, non-maleficence, beneficence, and justice. The data analysis procedure produced comprehensive and detailed qualitative descriptions of (a) 21 occupational categories, (b) 4070 KPA themes and (c) 84 KPA clusters. In addition, the number of occupational categories, KPA themes and KPA clusters were recorded and interpreted. In addition, the data analysis procedure produced comprehensive KPA templates that IOP departments may find useful. The templates reflect the KPAs specified by advertisements aimed at recruiting IOP graduates for a range of occupational categories and were designed to be used as benchmarks against which the economic responsiveness of curricula can be compared.
- Full Text:
- Date Issued: 2009
- Authors: Van Niekerk, Roelf
- Date: 2009
- Subjects: Psychology, Industrial -- Study and teaching (Higher) -- South Africa Universities and colleges -- Curricula -- South Africa College graduates -- Employment -- South Africa
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1319 , http://hdl.handle.net/10962/d1003952
- Description: This study focused on a topic at the intersection of two contexts, namely curriculum responsiveness and industrial/organisational psychology (IOP). The rationale for this study is based on two considerations. Firstly, a review of the IOP curricula offered at ten prominent South African universities revealed little overlap. This suggests that academic departments are not guided by shared principles when they implement decisions about the content or sequencing of curriculum content. Secondly, the Department of Education urges academics to design curricula that are relevant and responsive to contemporary conditions. These two considerations motivated the investigation of the following research question: What key performance areas (KPAs) do employers specify when they advertise positions suitable for IOP graduates? The investigation had two aims, namely (a) to systematically analyse the KPAs specified in job advertisements and (b) to compile KPA templates that may be used by IOP departments who wish to revise or transform their curricula. The research design of this study has five characteristics, namely that it is: (a) qualitative, (b) naturalistic, (c), descriptive, (d) applied, and (e) strategic. The study employed a purposive sampling strategy that involved the collection of documentary data (job advertisements aimed at recruiting IOP graduates) over a 52-week period (N=1115). The data was content analysed by means of a six-step documentary analysis method. Specific strategies were employed to enhance the validity of the findings. These strategies focused on credibility, transferability, dependability, and confirmability. Similarly, the ethical standing of the investigation was promoted by addressing four considerations, namely autonomy and respect for dignity, non-maleficence, beneficence, and justice. The data analysis procedure produced comprehensive and detailed qualitative descriptions of (a) 21 occupational categories, (b) 4070 KPA themes and (c) 84 KPA clusters. In addition, the number of occupational categories, KPA themes and KPA clusters were recorded and interpreted. In addition, the data analysis procedure produced comprehensive KPA templates that IOP departments may find useful. The templates reflect the KPAs specified by advertisements aimed at recruiting IOP graduates for a range of occupational categories and were designed to be used as benchmarks against which the economic responsiveness of curricula can be compared.
- Full Text:
- Date Issued: 2009
Cost and reward as motivating factors in distributed collaborative learning assignments : a grounded theory analasis
- Van Niekerk, Johanna Cornelia
- Authors: Van Niekerk, Johanna Cornelia
- Date: 2009
- Subjects: Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9764 , http://hdl.handle.net/10948/1103 , Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Description: The objective of this research study was to obtain a better understanding of the factors that affect lecturer and student participation in distributed collaborative learning assignments (DCLAs). A substantial number of courses worldwide have included DCLAs in their curricula in an attempt to teach students virtual communication and teaming skills, and to allow distributed students to learn course content collaboratively in a virtual environment. The execution and management of these assignments have proven to be more challenging that expected. Several attempts reported on in the literature had to be abandoned when cost exceeded the rewards for both lecturers and students. In a fouryear cyclical action research project carried out at the PETech (Port Elizabeth Technikon, currently part of the Nelson Mandela Metropolitan University, South Africa), ICT students at several of the PETech campuses were required to complete a DCLA in virtual teams. This project also had to be terminated when it was realised that virtual team learning was minimal and the time investment unacceptably high. For the research study reported on in this thesis the data collected during the four “preresearch” cycles and the experiences reported in the literature were analysed. The lessons learnt were applied to a new additional DCLA cycle which formed part of an ICT course, although this execution still showed room for improvement. A second additional cycle was then executed which had a high participation rate and was overwhelmingly labelled by the participating students as a valuable and enjoyable learning experience. Analysis of the factors affecting participation in DCLAs shows that they are numerous and tightly interlinked, and that each factor is able to take on a wide range of values. This complicates descriptive reporting as each of the DCLAs was unique with unique outcomes and would have to be reported as such in order to iii ABSTRACT iv gain an understanding of the factors. Hence, a level of abstraction was needed, which was accomplished by applying the traditional Glaserian grounded theory method to the data collected during the four “preresearch” and the two additional cycles, and from the literature on the topic. The outcome is a perceived costs and rewards (PCR) theory for participation in DCLAs. As participation is crucial for the learning experience of each student as well as his/her team members in an action learning environment, deciding on participation by continually calculating the costs versus rewards became the focal point of the theory. To the best of the author’s knowledge this research study makes a theoretical contribution to the existing body of ICT educational knowledge in the form of a perceived costs and rewards theory for DCLA participation and a practical contribution in that it provides a theory that can be used to explain, understand, interpret and predict participation in DCLAs. This research study provides guidance for future research in both of these areas.
- Full Text:
- Date Issued: 2009
- Authors: Van Niekerk, Johanna Cornelia
- Date: 2009
- Subjects: Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: vital:9764 , http://hdl.handle.net/10948/1103 , Group work in education -- South Africa , Team learning approach in education -- South Africa , Education -- Experimental methods
- Description: The objective of this research study was to obtain a better understanding of the factors that affect lecturer and student participation in distributed collaborative learning assignments (DCLAs). A substantial number of courses worldwide have included DCLAs in their curricula in an attempt to teach students virtual communication and teaming skills, and to allow distributed students to learn course content collaboratively in a virtual environment. The execution and management of these assignments have proven to be more challenging that expected. Several attempts reported on in the literature had to be abandoned when cost exceeded the rewards for both lecturers and students. In a fouryear cyclical action research project carried out at the PETech (Port Elizabeth Technikon, currently part of the Nelson Mandela Metropolitan University, South Africa), ICT students at several of the PETech campuses were required to complete a DCLA in virtual teams. This project also had to be terminated when it was realised that virtual team learning was minimal and the time investment unacceptably high. For the research study reported on in this thesis the data collected during the four “preresearch” cycles and the experiences reported in the literature were analysed. The lessons learnt were applied to a new additional DCLA cycle which formed part of an ICT course, although this execution still showed room for improvement. A second additional cycle was then executed which had a high participation rate and was overwhelmingly labelled by the participating students as a valuable and enjoyable learning experience. Analysis of the factors affecting participation in DCLAs shows that they are numerous and tightly interlinked, and that each factor is able to take on a wide range of values. This complicates descriptive reporting as each of the DCLAs was unique with unique outcomes and would have to be reported as such in order to iii ABSTRACT iv gain an understanding of the factors. Hence, a level of abstraction was needed, which was accomplished by applying the traditional Glaserian grounded theory method to the data collected during the four “preresearch” and the two additional cycles, and from the literature on the topic. The outcome is a perceived costs and rewards (PCR) theory for participation in DCLAs. As participation is crucial for the learning experience of each student as well as his/her team members in an action learning environment, deciding on participation by continually calculating the costs versus rewards became the focal point of the theory. To the best of the author’s knowledge this research study makes a theoretical contribution to the existing body of ICT educational knowledge in the form of a perceived costs and rewards theory for DCLA participation and a practical contribution in that it provides a theory that can be used to explain, understand, interpret and predict participation in DCLAs. This research study provides guidance for future research in both of these areas.
- Full Text:
- Date Issued: 2009
A psychobiographical study of Helen Keller
- Van Genechten, Désirée Martina
- Authors: Van Genechten, Désirée Martina
- Date: 2009
- Subjects: Keller, Helen, 1880-1968 , Developmental psychology , Life cycle, Human -- Psychological aspects , Deafblind people
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9897 , http://hdl.handle.net/10948/1101 , Keller, Helen, 1880-1968 , Developmental psychology , Life cycle, Human -- Psychological aspects , Deafblind people
- Description: This psychobiographical study of Helen Keller’s life is exploratory-descriptive in nature. The subject was chosen through purposive sampling. The choice was based on the researcher’s personal interest and the remarkable impact this profoundly handicapped woman had within her society. Helen Keller also meets the psychobiographical requirements. These include that she is historically well known, inspirational, and her life has been completed. The study uses a qualitative, single case, interpretive research design. The design is employed to study Helen Keller’s entire life span within a formal psychological theory. The theory used in this study is Daniel Levinson’s (1996) Life Structure theory of adult development. Data for this study were collected from a variety of primary and secondary sources which provided alternative perspectives on her life. In addition, the data have been corroborated by historical texts, and newspaper and journal articles. Levinson’s (1996) theory divides the lifespan into four developmental eras, each with its own biopsychosocial character. Each era in turn is divided into shorter periods of development, each with particular developmental tasks. Cross-era transitions separate the eras. By describing and exploring the data according to this theory, Helen Keller as a profoundly handicapped person is shown to display universal patterns of development as suggested by Levinson. At the same time, the Life Structure she developed, her life components, and Satisfactoriness illuminated her uniqueness. Through the application of the theory to Helen Keller’s life, this psychobiographical study facilitated an examination of the theory. This led to suggestions for potential development of the theory.
- Full Text:
- Date Issued: 2009
- Authors: Van Genechten, Désirée Martina
- Date: 2009
- Subjects: Keller, Helen, 1880-1968 , Developmental psychology , Life cycle, Human -- Psychological aspects , Deafblind people
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:9897 , http://hdl.handle.net/10948/1101 , Keller, Helen, 1880-1968 , Developmental psychology , Life cycle, Human -- Psychological aspects , Deafblind people
- Description: This psychobiographical study of Helen Keller’s life is exploratory-descriptive in nature. The subject was chosen through purposive sampling. The choice was based on the researcher’s personal interest and the remarkable impact this profoundly handicapped woman had within her society. Helen Keller also meets the psychobiographical requirements. These include that she is historically well known, inspirational, and her life has been completed. The study uses a qualitative, single case, interpretive research design. The design is employed to study Helen Keller’s entire life span within a formal psychological theory. The theory used in this study is Daniel Levinson’s (1996) Life Structure theory of adult development. Data for this study were collected from a variety of primary and secondary sources which provided alternative perspectives on her life. In addition, the data have been corroborated by historical texts, and newspaper and journal articles. Levinson’s (1996) theory divides the lifespan into four developmental eras, each with its own biopsychosocial character. Each era in turn is divided into shorter periods of development, each with particular developmental tasks. Cross-era transitions separate the eras. By describing and exploring the data according to this theory, Helen Keller as a profoundly handicapped person is shown to display universal patterns of development as suggested by Levinson. At the same time, the Life Structure she developed, her life components, and Satisfactoriness illuminated her uniqueness. Through the application of the theory to Helen Keller’s life, this psychobiographical study facilitated an examination of the theory. This led to suggestions for potential development of the theory.
- Full Text:
- Date Issued: 2009
Characterisation of the cellulolytic and hemicellulolytic system of Bacillus Licheniformis SVD1 and the isolation and characterisation of a multi-enzyme complex
- Authors: Van Dyk, Jacoba Susanna
- Date: 2009
- Subjects: Lignocellulose Lignocellulose -- Biotechnology Lignocellulose -- Biodegradation Plant biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3936 , http://hdl.handle.net/10962/d1003995
- Description: The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.
- Full Text:
- Date Issued: 2009
- Authors: Van Dyk, Jacoba Susanna
- Date: 2009
- Subjects: Lignocellulose Lignocellulose -- Biotechnology Lignocellulose -- Biodegradation Plant biotechnology
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3936 , http://hdl.handle.net/10962/d1003995
- Description: The biological degradation of lignocellulose into fermentable sugars for the production of liquid transportation fuels is feasible and sustainable, but equires a variety of enzymes working in synergy as lignocellulose is a complex and recalcitrant substrate. The cellulosome is a multi-enzyme complex (MEC) with a variety of cellulolytic and hemicellulolytic enzymes that appears to facilitate an enhanced synergy and efficiency, as compared to free enzymes, for the degradation of recalcitrant substrates such as lignocellulose and plant cell walls. Most of the studies on cellulosomes have focused on a few organisms; C. thermocellum, C. cellulovorans and C. cellulolyticum, and there is only limited knowledge vailable on similar complexes in other organisms. Some MECs have been identified in aerobic bacteria such as Bacillus circulans and Paenibacillus curdlanolyticus, but the nature of these MECs have not been fully elucidated. This study investigated the cellulolytic and emi-cellulolytic system of Bacillus licheniformis SVD1 with specific reference to the presence of a MEC, which has never been reported in the literature for B. licheniformis. A MEC of approximately 2,000 kDa in size, based on size exclusion chromatography using Sepharose 4B, was purified from a culture of B. licheniformis. When investigating the presence of enzyme activity in the total crude fraction as well as the MEC of a birchwood xylan culture, B. licheniformis was found to display a variety of enzyme activities on a range of substrates, although xylanases were by far the predominant enzyme activity present in both the crude and MEC fractions. Based on zymogram analysis there were three CMCases, seven xylanases, three mannanases and two pectinases in the crude fraction, while the MEC had two CMCases, seven xylanases, two mannanases and one pectinase. The pectinases in the crude could be identified as a pectin methyl esterase and a lyase, while the methyl esterase was absent in the MEC. Seventeen protein species could be detected in the MEC but only nine of these displayed activity on the substrates tested. The possible presence of a β-xylosidase in the crude fraction was deduced from thin layer chromatography (TLC) which demonstrated the production of xylose by the crude fraction. It was furthermore established that B. licheniformis SVD1 was able to regulate levels of enzyme expression based on the substrate the organism was cultured on. It was found that complexed xylanase activity had a pH optimum of between pH 6.0 and 7.0 and a temperature optimum of 55oC. Complexed xylanase activity was found to be slightly inhibited by CaCl2 and inhibited to a greater extent by EDTA. Complexed xylanase activity was further shown to be activated in the presence of xylose and xylobiose, both compounds which are products of enzymatic degradation. Ethanol was found to inhibit complexed xylanase activity. The kinetic parameters for complexed xylanase activity were measured and the Km value was calculated as 2.84 mg/ml while the maximal velocity (Vmax) was calculated as 0.146 U (μmol/min/ml). Binding studies, transmission electron microscopy (TEM) and a bioinformatic analysis was conducted to investigate whether the MEC in B. licheniformis SVD1 was a putative cellulosome. The MEC was found to be unable to bind to Avicel, but was able to bind to insoluble birchwood xylan, indicating the absence of a CBM3a domain common to cellulosomal scaffoldin proteins. TEM micrographs revealed the presence of cell surface structures on cells of B. licheniformis SVD1 cultured on cellobiose and birchwood xylan. However, it could not be established whether these cell surface structures could be ascribed to the presence of the MECs on the cell surface. Bioinformatic analysis was conducted on the available genome sequence of a different strain of B. licheniformis, namely DSM 13 and ATCC 14580. No sequence homology was found with cohesin and dockerin sequences from various cellulosomal species, indicating that these strains most likely do not encode for a cellulosome. This study described and characterised a MEC that was a functional enzyme complex and did not appear to be a mere aggregation of proteins. It displayed a variety of hemi-cellulolytic activities and the available evidence suggests that it is not a cellulosome, but should rather be termed a xylanosome. Further investigation should be carried out to determine the structural basis of this MEC.
- Full Text:
- Date Issued: 2009