Assessing linkages between local ecological knowledge, HIV/AIDS and the commercialisation of natural resources across Southern Africa
- Authors: Weyer, Dylan James
- Date: 2012
- Subjects: AIDS (Disease) -- Africa, Southern , HIV infections -- Africa, Southern , Natural resources -- Management -- Africa, Southern , Traditional ecological knowledge -- Africa, Southern , Households -- Economic aspects -- Africa, Southern , Poverty -- Environmental aspects -- Africa, Southern , Ecology -- Economic aspects -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4769 , http://hdl.handle.net/10962/d1007180 , AIDS (Disease) -- Africa, Southern , HIV infections -- Africa, Southern , Natural resources -- Management -- Africa, Southern , Traditional ecological knowledge -- Africa, Southern , Households -- Economic aspects -- Africa, Southern , Poverty -- Environmental aspects -- Africa, Southern , Ecology -- Economic aspects -- Africa, Southern
- Description: That natural resources (NRs) are important to those experiencing adversity, and, especially, vulnerability associated with HIV/AIDS, is well documented, particularly with respect to food and energy security. What is unclear is where HIV/AIDS ranks in terms of its significance in comparison to other household shocks, the role local ecological knowledge may (LEK) play in households' response to shock, a propos the types of coping strategies that are employed. Consequently, this research aims to bridge the knowledge gap between HIV/AIDS and the degree to which it is contributing to the expansion of NR commercialisation and to explore the unknowns surrounding the influence of LEK on people's choice of coping strategy. A two phase study was designed to provide quantitative rigour with qualitative depth. Phase one was an extensive, rapid survey of NR traders within urban and rural settings in five southern Africa countries. The principle objective was to profile the trade, the livelihoods of those involved and their reasons for entering the trade, to ultimately establish to what degree HIV/AIDS may have been a catalyst for this. Almost one third of the sample entered the trade in response to illness and/or death in their households, with 80% of deaths being of breadwinners. The findings illustrated considerable dependence on the sale of NRs; for almost 60% of the sample it was their household's only source of income. There was evidently increased blurring of the lines between rural and urban NR use with a greater diversity of products being traded in urban areas. Phase two involved in-depth interviews and work with a smaller sample at two sites selected based on the findings from the first phase. It incorporated three groups of households; non-trading, inexperienced trading and experienced trading households. Key areas of focus were household shocks, coping strategies employed in response to these and the role LEK may be playing in the choice of coping strategies. Within a two year period, 95% of households registered at least one shock, of which 80% recorded AIDS-related proxy shocks. Non-trading households were significantly worse-off in this regard, while in the case of non-AIDS proxy shocks, there was no such difference between groups. The most frequently employed coping strategy was the consumption and sale of NRs and was of particular importance when households were faced with AIDS proxy shocks. Trading households emerged as having superior levels of LEK in comparison to non-trading households, even for non-traded NRs, suggesting that prior LEK of NRs opened up opportunities to trade in NR as a coping strategy. Further inspection of the latter group however revealed that the portion of non-trading households who traded on a very ad hoc basis actually had comparable levels of LEK to the trading households. Despite the ad hoc trading households' vulnerable state and their disproportionately high level of AIDS proxy measures, they had at their disposal, sufficient LEK to unlock certain key coping strategies, namely the NR trade. In this sense there are apparent linkages between LEK, HIV/AIDS and the expansion of the commercialisation of NRs.
- Full Text:
- Date Issued: 2012
- Authors: Weyer, Dylan James
- Date: 2012
- Subjects: AIDS (Disease) -- Africa, Southern , HIV infections -- Africa, Southern , Natural resources -- Management -- Africa, Southern , Traditional ecological knowledge -- Africa, Southern , Households -- Economic aspects -- Africa, Southern , Poverty -- Environmental aspects -- Africa, Southern , Ecology -- Economic aspects -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4769 , http://hdl.handle.net/10962/d1007180 , AIDS (Disease) -- Africa, Southern , HIV infections -- Africa, Southern , Natural resources -- Management -- Africa, Southern , Traditional ecological knowledge -- Africa, Southern , Households -- Economic aspects -- Africa, Southern , Poverty -- Environmental aspects -- Africa, Southern , Ecology -- Economic aspects -- Africa, Southern
- Description: That natural resources (NRs) are important to those experiencing adversity, and, especially, vulnerability associated with HIV/AIDS, is well documented, particularly with respect to food and energy security. What is unclear is where HIV/AIDS ranks in terms of its significance in comparison to other household shocks, the role local ecological knowledge may (LEK) play in households' response to shock, a propos the types of coping strategies that are employed. Consequently, this research aims to bridge the knowledge gap between HIV/AIDS and the degree to which it is contributing to the expansion of NR commercialisation and to explore the unknowns surrounding the influence of LEK on people's choice of coping strategy. A two phase study was designed to provide quantitative rigour with qualitative depth. Phase one was an extensive, rapid survey of NR traders within urban and rural settings in five southern Africa countries. The principle objective was to profile the trade, the livelihoods of those involved and their reasons for entering the trade, to ultimately establish to what degree HIV/AIDS may have been a catalyst for this. Almost one third of the sample entered the trade in response to illness and/or death in their households, with 80% of deaths being of breadwinners. The findings illustrated considerable dependence on the sale of NRs; for almost 60% of the sample it was their household's only source of income. There was evidently increased blurring of the lines between rural and urban NR use with a greater diversity of products being traded in urban areas. Phase two involved in-depth interviews and work with a smaller sample at two sites selected based on the findings from the first phase. It incorporated three groups of households; non-trading, inexperienced trading and experienced trading households. Key areas of focus were household shocks, coping strategies employed in response to these and the role LEK may be playing in the choice of coping strategies. Within a two year period, 95% of households registered at least one shock, of which 80% recorded AIDS-related proxy shocks. Non-trading households were significantly worse-off in this regard, while in the case of non-AIDS proxy shocks, there was no such difference between groups. The most frequently employed coping strategy was the consumption and sale of NRs and was of particular importance when households were faced with AIDS proxy shocks. Trading households emerged as having superior levels of LEK in comparison to non-trading households, even for non-traded NRs, suggesting that prior LEK of NRs opened up opportunities to trade in NR as a coping strategy. Further inspection of the latter group however revealed that the portion of non-trading households who traded on a very ad hoc basis actually had comparable levels of LEK to the trading households. Despite the ad hoc trading households' vulnerable state and their disproportionately high level of AIDS proxy measures, they had at their disposal, sufficient LEK to unlock certain key coping strategies, namely the NR trade. In this sense there are apparent linkages between LEK, HIV/AIDS and the expansion of the commercialisation of NRs.
- Full Text:
- Date Issued: 2012
Investigating tools and techniques for improving software performance on multiprocessor computer systems
- Authors: Tristram, Waide Barrington
- Date: 2012
- Subjects: Multiprocessors , Multiprogramming (Electronic computers) , Parallel programming (Computer science) , Linux , Abstract data types (Computer science) , Threads (Computer programs) , Computer programming
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4655 , http://hdl.handle.net/10962/d1006651 , Multiprocessors , Multiprogramming (Electronic computers) , Parallel programming (Computer science) , Linux , Abstract data types (Computer science) , Threads (Computer programs) , Computer programming
- Description: The availability of modern commodity multicore processors and multiprocessor computer systems has resulted in the widespread adoption of parallel computers in a variety of environments, ranging from the home to workstation and server environments in particular. Unfortunately, parallel programming is harder and requires more expertise than the traditional sequential programming model. The variety of tools and parallel programming models available to the programmer further complicates the issue. The primary goal of this research was to identify and describe a selection of parallel programming tools and techniques to aid novice parallel programmers in the process of developing efficient parallel C/C++ programs for the Linux platform. This was achieved by highlighting and describing the key concepts and hardware factors that affect parallel programming, providing a brief survey of commonly available software development tools and parallel programming models and libraries, and presenting structured approaches to software performance tuning and parallel programming. Finally, the performance of several parallel programming models and libraries was investigated, along with the programming effort required to implement solutions using the respective models. A quantitative research methodology was applied to the investigation of the performance and programming effort associated with the selected parallel programming models and libraries, which included automatic parallelisation by the compiler, Boost Threads, Cilk Plus, OpenMP, POSIX threads (Pthreads), and Threading Building Blocks (TBB). Additionally, the performance of the GNU C/C++ and Intel C/C++ compilers was examined. The results revealed that the choice of parallel programming model or library is dependent on the type of problem being solved and that there is no overall best choice for all classes of problem. However, the results also indicate that parallel programming models with higher levels of abstraction require less programming effort and provide similar performance compared to explicit threading models. The principle conclusion was that the problem analysis and parallel design are an important factor in the selection of the parallel programming model and tools, but that models with higher levels of abstractions, such as OpenMP and Threading Building Blocks, are favoured.
- Full Text:
- Date Issued: 2012
- Authors: Tristram, Waide Barrington
- Date: 2012
- Subjects: Multiprocessors , Multiprogramming (Electronic computers) , Parallel programming (Computer science) , Linux , Abstract data types (Computer science) , Threads (Computer programs) , Computer programming
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4655 , http://hdl.handle.net/10962/d1006651 , Multiprocessors , Multiprogramming (Electronic computers) , Parallel programming (Computer science) , Linux , Abstract data types (Computer science) , Threads (Computer programs) , Computer programming
- Description: The availability of modern commodity multicore processors and multiprocessor computer systems has resulted in the widespread adoption of parallel computers in a variety of environments, ranging from the home to workstation and server environments in particular. Unfortunately, parallel programming is harder and requires more expertise than the traditional sequential programming model. The variety of tools and parallel programming models available to the programmer further complicates the issue. The primary goal of this research was to identify and describe a selection of parallel programming tools and techniques to aid novice parallel programmers in the process of developing efficient parallel C/C++ programs for the Linux platform. This was achieved by highlighting and describing the key concepts and hardware factors that affect parallel programming, providing a brief survey of commonly available software development tools and parallel programming models and libraries, and presenting structured approaches to software performance tuning and parallel programming. Finally, the performance of several parallel programming models and libraries was investigated, along with the programming effort required to implement solutions using the respective models. A quantitative research methodology was applied to the investigation of the performance and programming effort associated with the selected parallel programming models and libraries, which included automatic parallelisation by the compiler, Boost Threads, Cilk Plus, OpenMP, POSIX threads (Pthreads), and Threading Building Blocks (TBB). Additionally, the performance of the GNU C/C++ and Intel C/C++ compilers was examined. The results revealed that the choice of parallel programming model or library is dependent on the type of problem being solved and that there is no overall best choice for all classes of problem. However, the results also indicate that parallel programming models with higher levels of abstraction require less programming effort and provide similar performance compared to explicit threading models. The principle conclusion was that the problem analysis and parallel design are an important factor in the selection of the parallel programming model and tools, but that models with higher levels of abstractions, such as OpenMP and Threading Building Blocks, are favoured.
- Full Text:
- Date Issued: 2012
"Is more, less?" : insect-insect interactions in a biological control context using water hyacinth as a model
- Weyl, Philip Sebastian Richard
- Authors: Weyl, Philip Sebastian Richard
- Date: 2012
- Subjects: Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5724 , http://hdl.handle.net/10962/d1005410 , Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Description: Interactions between insects have been shown to be important regulators of population abundances and dynamics as well as drivers of spatial segregation and distribution. These are important aspects of the ecology of insects used in biological control and may have implications for the overall success of a particular programme. In the history of biological control there has been a tendency to release a suite of agents against a weed, which in some cases has increased the level of success, while in others little change has been observed. In most of these cases the implications of increasing the level of complexity of the system is not taken into account and there is little research on the effect of releasing another agent into the system. A brief meta-analysis was done on all the biological control programmes initiated in South Africa. Emphasis was placed on multi-species releases and the effects that overlapping niches were having on the number of agents responsible for the success of a programme. Where overlapping niches were present among agents released the number of agents responsible for success was lower than the number established. Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach in South Africa has more arthropod agents released against it than anywhere else in the world, yet control has been variable. If the biology and host utilisation of all the agents against water hyacinth is considered, a definite overlap of niches is apparent in at least one life stage of all the agents. Therefore the probability of these insects interacting is high, especially if they are established at the same site in the field. Three of the insects released in South Africa have been selected to investigate possible interactions. They are Neochetina eichhorniae Warner, Neochetina bruchi Hustache and Eccritotarsus catarinensis (Carvalho). Y-tube olfactometer bioassays were used to measure responses of these insects to water hyacinth with prior feeding damage by either conspecifics or heterospecifics. This was done to determine whether olfactory cues played a role in host acceptability and avoidance of conspecifics or heterospecifics. The insects were given a choice between damaged and undamaged plants in various combinations. There was a significant preference for the undamaged plants when given a choice between undamaged and damaged plants. However when the insects were given a choice between two damaged plants there was no discrimination between heterospecific or conspecific damaged plants. This may indicate that there is little or no ecological cost for the insect to share a plant with other insects utilising a similar resource. Insect – insect interactions were investigated in a common garden plot experiment to measure the impact that pairwise combinations of the insect may have on their performance. There was a significant interaction between the mirid E. catarinensis and the weevil N. eichhorniae, with the weevil not performing as well when in combination with the mirid than when alone. Interestingly there was a negative interaction between the two weevil species when in combination, however it was impossible to determine which species was being affected if not both. None of the insects performed significantly better when in combination with another insect. A field study on Wriggleswade Dam in the Eastern Cape, South Africa was initiated to determine whether the relationship between the mirid E. catarinensis and the weevil N. eichhorniae could be determined in the field. The performance of the insects at the different sites in the field suggests that there was an interaction between the agents. This interaction did not limit the establishment of either insect at a site, but it did result in one insect dominating at a site over another. Interactions between the three species of insect tested in this thesis suggest that there are both negative and neutral relationships between them. A basic comparison between the insect performances from 15 sites around the country was done to determine if the spatial segregation observed in the field could be extrapolated to the natural South African situation. The interaction observed between N. eichhorniae and E. catarinensis does seem to extrapolate to the general South African situation where there is definite spatial segregation on a landscape level. The co–occurrence of the two Neochetina weevils at these sites suggests that the negative relationship observed between them in the common garden experiment does not extrapolate to the field. The results from this thesis suggest that the interactions between the agents tested would not limit establishment or have significant ramifications on performance. However, there may be spatial and temporal segregation of these species in the introduced range.
- Full Text:
- Date Issued: 2012
- Authors: Weyl, Philip Sebastian Richard
- Date: 2012
- Subjects: Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5724 , http://hdl.handle.net/10962/d1005410 , Water hyacinth -- South Africa -- Eastern Cape , Water hyacinth -- Biological control -- South Africa -- Eastern Cape , Insects as biological pest control agents , Miridae -- South Africa -- Eastern Cape , Beetles -- South Africa -- Eastern Cape , Competition (Biology)
- Description: Interactions between insects have been shown to be important regulators of population abundances and dynamics as well as drivers of spatial segregation and distribution. These are important aspects of the ecology of insects used in biological control and may have implications for the overall success of a particular programme. In the history of biological control there has been a tendency to release a suite of agents against a weed, which in some cases has increased the level of success, while in others little change has been observed. In most of these cases the implications of increasing the level of complexity of the system is not taken into account and there is little research on the effect of releasing another agent into the system. A brief meta-analysis was done on all the biological control programmes initiated in South Africa. Emphasis was placed on multi-species releases and the effects that overlapping niches were having on the number of agents responsible for the success of a programme. Where overlapping niches were present among agents released the number of agents responsible for success was lower than the number established. Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach in South Africa has more arthropod agents released against it than anywhere else in the world, yet control has been variable. If the biology and host utilisation of all the agents against water hyacinth is considered, a definite overlap of niches is apparent in at least one life stage of all the agents. Therefore the probability of these insects interacting is high, especially if they are established at the same site in the field. Three of the insects released in South Africa have been selected to investigate possible interactions. They are Neochetina eichhorniae Warner, Neochetina bruchi Hustache and Eccritotarsus catarinensis (Carvalho). Y-tube olfactometer bioassays were used to measure responses of these insects to water hyacinth with prior feeding damage by either conspecifics or heterospecifics. This was done to determine whether olfactory cues played a role in host acceptability and avoidance of conspecifics or heterospecifics. The insects were given a choice between damaged and undamaged plants in various combinations. There was a significant preference for the undamaged plants when given a choice between undamaged and damaged plants. However when the insects were given a choice between two damaged plants there was no discrimination between heterospecific or conspecific damaged plants. This may indicate that there is little or no ecological cost for the insect to share a plant with other insects utilising a similar resource. Insect – insect interactions were investigated in a common garden plot experiment to measure the impact that pairwise combinations of the insect may have on their performance. There was a significant interaction between the mirid E. catarinensis and the weevil N. eichhorniae, with the weevil not performing as well when in combination with the mirid than when alone. Interestingly there was a negative interaction between the two weevil species when in combination, however it was impossible to determine which species was being affected if not both. None of the insects performed significantly better when in combination with another insect. A field study on Wriggleswade Dam in the Eastern Cape, South Africa was initiated to determine whether the relationship between the mirid E. catarinensis and the weevil N. eichhorniae could be determined in the field. The performance of the insects at the different sites in the field suggests that there was an interaction between the agents. This interaction did not limit the establishment of either insect at a site, but it did result in one insect dominating at a site over another. Interactions between the three species of insect tested in this thesis suggest that there are both negative and neutral relationships between them. A basic comparison between the insect performances from 15 sites around the country was done to determine if the spatial segregation observed in the field could be extrapolated to the natural South African situation. The interaction observed between N. eichhorniae and E. catarinensis does seem to extrapolate to the general South African situation where there is definite spatial segregation on a landscape level. The co–occurrence of the two Neochetina weevils at these sites suggests that the negative relationship observed between them in the common garden experiment does not extrapolate to the field. The results from this thesis suggest that the interactions between the agents tested would not limit establishment or have significant ramifications on performance. However, there may be spatial and temporal segregation of these species in the introduced range.
- Full Text:
- Date Issued: 2012
An assessment of caracal population density and human-predator conflict in the Winterberg, Eastern Cape, South Africa
- Authors: Smith, Emma Ruth
- Date: 2012
- Subjects: Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5644 , http://hdl.handle.net/10962/d1005326 , Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Description: Human-wildlife conflict frequently involves carnivores, mainly because of their large home ranges and dietary requirements. As such, carnivores tend to be the first animals to be lost in human-dominated ecosystems. This is significant because the removal of carnivores can alter the functionality of ecosystems. However, the conservation of carnivores depends as much on the socio-political and socio-economic landscapes as it does on the ecological one. The consolidation of vast, un-fragmented conservation areas in Africa and the world is unlikely. Thus, unravelling the factors (both biological and sociological) responsible for and influencing human-predator conflict is critical for carnivore conservation. The Winterberg district in the Eastern Cape, South Africa has been a sheep (Ovis aries) farming stronghold for nearly 200 years. Consequently, conflict between farmers and predators is commonplace and depredation of livestock by caracals (Caracai caracal) remains a perennial problem. However, the extent of this human-predator conflict (including a reliable assessment of caracal density) has not been quantified. This study used camera trapping to estimate the density of caracals (a nonindividually recognisable species) in the Winterberg and a structured questionnaire to gauge the general attitudes of the farmers of the region. Caracal density was estimated to be 0.20 caracals/km². This estimate equates to a population of approximately 54 caracals across the entire district. Therefore, caracals do not appear to occur at high densities in the Winterberg. However, the survey of the residents of the Winterberg Conservancy revealed that predators were rated as the greatest problem faced by farmers in the area. Although not significant, it also showed that the size of a respondent's property and sheep mortality due to caracals had the greatest probability of affecting attitudes towards predators. The farmers lost less than 10% of their stock to caracal depredation on an annual basis. Therefore, the general perception that predators were the most important factor in stock loss in the area does not appear to be fully supported by my data. The Winterberg is a male-dominated, multigenerational society and it is likely this propagates certain perceptions towards predators which are a reflection of long-held family traditions and beliefs. Such situations can result in reactions which are disproportionate to the actual scale of the problem. However, my study was limited to a sub-set of the landowners in the Winterberg. Thus, more intensive assessments of caracal space use and community attitudes towards predators are recommended.
- Full Text:
- Date Issued: 2012
- Authors: Smith, Emma Ruth
- Date: 2012
- Subjects: Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5644 , http://hdl.handle.net/10962/d1005326 , Felis -- South Africa -- Eastern Cape , Felis -- Effect of human beings on -- South Africa -- Eastern Cape , Predatory animals -- Control -- South Africa -- Eastern Cape , Wildlife depredation -- South Africa -- Eastern Cape , Human-animal relationships , Felis -- Conservation -- South Africa -- Eastern Cape , Felis -- Monitoring -- South Africa -- Eastern Cape , Animal populations -- Estimates
- Description: Human-wildlife conflict frequently involves carnivores, mainly because of their large home ranges and dietary requirements. As such, carnivores tend to be the first animals to be lost in human-dominated ecosystems. This is significant because the removal of carnivores can alter the functionality of ecosystems. However, the conservation of carnivores depends as much on the socio-political and socio-economic landscapes as it does on the ecological one. The consolidation of vast, un-fragmented conservation areas in Africa and the world is unlikely. Thus, unravelling the factors (both biological and sociological) responsible for and influencing human-predator conflict is critical for carnivore conservation. The Winterberg district in the Eastern Cape, South Africa has been a sheep (Ovis aries) farming stronghold for nearly 200 years. Consequently, conflict between farmers and predators is commonplace and depredation of livestock by caracals (Caracai caracal) remains a perennial problem. However, the extent of this human-predator conflict (including a reliable assessment of caracal density) has not been quantified. This study used camera trapping to estimate the density of caracals (a nonindividually recognisable species) in the Winterberg and a structured questionnaire to gauge the general attitudes of the farmers of the region. Caracal density was estimated to be 0.20 caracals/km². This estimate equates to a population of approximately 54 caracals across the entire district. Therefore, caracals do not appear to occur at high densities in the Winterberg. However, the survey of the residents of the Winterberg Conservancy revealed that predators were rated as the greatest problem faced by farmers in the area. Although not significant, it also showed that the size of a respondent's property and sheep mortality due to caracals had the greatest probability of affecting attitudes towards predators. The farmers lost less than 10% of their stock to caracal depredation on an annual basis. Therefore, the general perception that predators were the most important factor in stock loss in the area does not appear to be fully supported by my data. The Winterberg is a male-dominated, multigenerational society and it is likely this propagates certain perceptions towards predators which are a reflection of long-held family traditions and beliefs. Such situations can result in reactions which are disproportionate to the actual scale of the problem. However, my study was limited to a sub-set of the landowners in the Winterberg. Thus, more intensive assessments of caracal space use and community attitudes towards predators are recommended.
- Full Text:
- Date Issued: 2012
The effects of sustained attention, workload and task-related fatigue on physiological measures and performance during a tracking task
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
- Full Text:
- Date Issued: 2012
- Authors: De Gray Birch, Casey
- Date: 2012
- Subjects: Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5120 , http://hdl.handle.net/10962/d1005198 , Fatigue -- Physiological aspects -- Research , Attention -- Physiological aspects -- Research , Human engineering -- Research
- Description: Despite extensive research into the concept of mental fatigue there is as yet no “gold standard” definition or measurement technique available. Because of this a large amount of fatigue-related errors are still seen in the workplace. The complexity of the problem lies with the inability to directly measure mental processes as well as the various endogenous and exogenous factors that interact to produce the experienced fatigue. Fatigue has been divided into sleep-related and task-related fatigue; however the task-related aspect is evident both during normal waking hours as well as during periods of sleep deprivation, therefore this aspect is considered important in the understanding of fatigue in general. The concept of task-related fatigue has further been divided into active and passive fatigue states; however differentiation between the two requires careful consideration. Various physiological measures have been employed in an attempt to gain a better understanding of the mechanisms involved in the generation of fatigue, however often studies have produced dissociating results. The current study considered the task-related fatigue elicited by a tracking task requiring sustained attention, in order to evaluate the usefulness of various cardiovascular and oculomotor measures as indicators of fatigue. A secondary aim was to determine whether the behavioural and physiological parameter responses could be used to infer the type of fatigue incurred (i.e. an active versus passive fatigue state) as well as the energetical mechanisms involved during task performance. A simple driving simulator task was used as the main tracking task, requiring constant attention and concentration. This task was performed for approximately two hours. Three experimental groups (consisting of 14 subjects each) were used: a control group that performed the tracking task only, a group that performed a five minute auditory memory span task concurrently with the driving task after every 20 minutes of pure driving, and a group that performed a visual choice reaction task for five minutes following every 20 minute driving period. The secondary tasks were employed in order to evaluate the extent of resource allocation as well as arousal level. Performance measures included various driving performance parameters, as well as secondary task performance. Physiological measures included heart rate frequency (HR) and various time- and frequency-domain heart rate variability (HRV)parameters, pupil dilation, blink frequency and duration, fixations, and saccadic parameters as well as critical flicker fusion frequency (CFFF). The Borg CR-10 scale was used to evaluate subjective fatigue during the task, and the NASA-TLX was completed following the task. A decline in driving performance over time was supplemented by measures such as HR, HRV and pupil dilation indicating an increase in parasympathetic activity (or a reduction in arousal). An increase in blink frequency was considered as a sign of withdrawal of attentional resources over time. Longer and faster saccades were also evident over time, coupled with shorter fixations. With regards to the secondary task influence, the choice RT task did not affect any behavioural or physiological parameters, thereby contesting the active fatigue theory of resource depletion, as well as implying that the increase in demand for the same resources used by the primary task was insufficient to affect the state of the subjects. The increased load elicited by the memory span task improved driving performance and increased measures of HR, HRV, pupil dilation and blink frequency. Some of these measures produced opposite effects to what was expected; an attempt to explain the dissociation of the various physiological parameters was expressed in terms of arousal, effort and resource theories. Overall, the results indicate that the fatigue and/or reduced arousal accompanying a monotonous sustained attention task can, to some degree, be alleviated through intermittent performance of a secondary task engaging mental resources other than the ones used for the primary task. The degree to which such a task is beneficial, however, requires careful consideration as while an immediate increase in arousal and primary task performance is noted, the impact of the task on general attentional resources may be detrimental in the case of reacting should an emergency situation occur.
- Full Text:
- Date Issued: 2012
A baculovirus-mediated expression system for the analysis of HaSV RNA packaging
- Authors: Mendes, Adriano
- Date: 2012
- Subjects: RNA , Baculoviruses , Helicoverpa armigera , Plasmids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4025 , http://hdl.handle.net/10962/d1004085 , RNA , Baculoviruses , Helicoverpa armigera , Plasmids
- Description: The Helicoverpa armigera stunt virus (HaSV) is a member of a family of small nonenveloped (+) ssRNA insect viruses currently known as the Tetraviridae. This family is unique in terms of the T=4 quasi-symmetry of its capsid particles and the unusually narrow host range and tissue tropism. Assembly of tetraviral particles has been well characterised and involves the combination of 240 copies of a single capsid precursor protein (VCap) into a procapsid followed by autoproteolytic cleavage to yield the major (β) and minor (γ) capsid subunits within the mature particle. HaSV has two genomic RNAs, RNA 1 encoding the replicase and RNA 2 encoding VCap and p17, the ORF of which lies upstream of and overlaping with the 5’ end of the VCap ORF. Prior to this study, Vlok (2009) used a plasmid expression system to study RNA packaging in HaSV VLPs assembled in Spodoptera frugiperda 9 (Sf9) cells co-expressing p17 and VCap. The study showed that the p17 ORF was required for the packaging of RNA 2 during capsid assembly but it was unclear whether p17 expression was required for packaging. In addition, expression from the transfected plasmids was sub-optimal affecting both the yield of VLPs and the detection of p17. The aim of this study was to use the plasmid system to test whether p17 expression was required for plasmid-derived VLP RNA packaging and then develop a baculovirus-mediated system to test this hypothesis. By using a plasmid in which the start codon of p17 was mutated, it was shown that p17 expression was required for RNA 2 packaging into plasmid-VLPs. For the baculovirus system, four recombinant baculoviruses based upon the pFastBac Dual expression system, were constructed. These included Bac20, expressing wild type RNA 2, Bac21, RNA 2 with p17 silenced, Bac23, RNA 2 and p17 expressed on a separate transcript and Bac24, RNA 2 with p17 silenced plus p17 expressed on a separate transcript. Assembly of VLPs was more efficient using the baculovirus expression system and p17 expression was observed in cells infected with Bac20, Bac23 and Bac24, but not Bac21. In contrast to the plasmid-VLPs, bac-VLPs did not require p17 for the encapsidation of RNA 2. In addition to RNA 2, Bac23 and Bac24 packaged the p17 mRNA transcribed separately from RNA 2. This insinuated that bac-VLPs may be packaging RNA non-selectively. It was proposed that p17 may play a role in packaging in an RNA-limiting environment (plasmid system) but functioned differently when viral RNA was in excess (baculovirus system). This data points to the importance of developing a replication system for the analysis of the packaging pathways of these viruses and this study has laid down the foundations for such a system in which RNA 1 and RNA 2 can be introduced into a single cell by means of a single recombinant virus.
- Full Text:
- Date Issued: 2012
- Authors: Mendes, Adriano
- Date: 2012
- Subjects: RNA , Baculoviruses , Helicoverpa armigera , Plasmids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4025 , http://hdl.handle.net/10962/d1004085 , RNA , Baculoviruses , Helicoverpa armigera , Plasmids
- Description: The Helicoverpa armigera stunt virus (HaSV) is a member of a family of small nonenveloped (+) ssRNA insect viruses currently known as the Tetraviridae. This family is unique in terms of the T=4 quasi-symmetry of its capsid particles and the unusually narrow host range and tissue tropism. Assembly of tetraviral particles has been well characterised and involves the combination of 240 copies of a single capsid precursor protein (VCap) into a procapsid followed by autoproteolytic cleavage to yield the major (β) and minor (γ) capsid subunits within the mature particle. HaSV has two genomic RNAs, RNA 1 encoding the replicase and RNA 2 encoding VCap and p17, the ORF of which lies upstream of and overlaping with the 5’ end of the VCap ORF. Prior to this study, Vlok (2009) used a plasmid expression system to study RNA packaging in HaSV VLPs assembled in Spodoptera frugiperda 9 (Sf9) cells co-expressing p17 and VCap. The study showed that the p17 ORF was required for the packaging of RNA 2 during capsid assembly but it was unclear whether p17 expression was required for packaging. In addition, expression from the transfected plasmids was sub-optimal affecting both the yield of VLPs and the detection of p17. The aim of this study was to use the plasmid system to test whether p17 expression was required for plasmid-derived VLP RNA packaging and then develop a baculovirus-mediated system to test this hypothesis. By using a plasmid in which the start codon of p17 was mutated, it was shown that p17 expression was required for RNA 2 packaging into plasmid-VLPs. For the baculovirus system, four recombinant baculoviruses based upon the pFastBac Dual expression system, were constructed. These included Bac20, expressing wild type RNA 2, Bac21, RNA 2 with p17 silenced, Bac23, RNA 2 and p17 expressed on a separate transcript and Bac24, RNA 2 with p17 silenced plus p17 expressed on a separate transcript. Assembly of VLPs was more efficient using the baculovirus expression system and p17 expression was observed in cells infected with Bac20, Bac23 and Bac24, but not Bac21. In contrast to the plasmid-VLPs, bac-VLPs did not require p17 for the encapsidation of RNA 2. In addition to RNA 2, Bac23 and Bac24 packaged the p17 mRNA transcribed separately from RNA 2. This insinuated that bac-VLPs may be packaging RNA non-selectively. It was proposed that p17 may play a role in packaging in an RNA-limiting environment (plasmid system) but functioned differently when viral RNA was in excess (baculovirus system). This data points to the importance of developing a replication system for the analysis of the packaging pathways of these viruses and this study has laid down the foundations for such a system in which RNA 1 and RNA 2 can be introduced into a single cell by means of a single recombinant virus.
- Full Text:
- Date Issued: 2012
Automated grid fault detection and repair
- Authors: Luyt, Leslie
- Date: 2012 , 2012-05-24
- Subjects: Computational grids (Computer systems) -- Maintenance and repair , Cloud computing -- Maintenance and repair , Computer architecture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4670 , http://hdl.handle.net/10962/d1006693 , Computational grids (Computer systems) -- Maintenance and repair , Cloud computing -- Maintenance and repair , Computer architecture
- Description: With the rise in interest in the field of grid and cloud computing, it is becoming increasingly necessary for the grid to be easily maintainable. This maintenance of the grid and grid services can be made easier by using an automated system to monitor and repair the grid as necessary. We propose a novel system to perform automated monitoring and repair of grid systems. To the best of our knowledge, no such systems exist. The results show that certain faults can be easily detected and repaired. , TeX , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
- Authors: Luyt, Leslie
- Date: 2012 , 2012-05-24
- Subjects: Computational grids (Computer systems) -- Maintenance and repair , Cloud computing -- Maintenance and repair , Computer architecture
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4670 , http://hdl.handle.net/10962/d1006693 , Computational grids (Computer systems) -- Maintenance and repair , Cloud computing -- Maintenance and repair , Computer architecture
- Description: With the rise in interest in the field of grid and cloud computing, it is becoming increasingly necessary for the grid to be easily maintainable. This maintenance of the grid and grid services can be made easier by using an automated system to monitor and repair the grid as necessary. We propose a novel system to perform automated monitoring and repair of grid systems. To the best of our knowledge, no such systems exist. The results show that certain faults can be easily detected and repaired. , TeX , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
COIN : a customisable, incentive driven video on demand framework for low-cost IPTV services
- Authors: Musvibe, Ray
- Date: 2012 , 2012-03-02
- Subjects: Internet television , Digital television , Television broadcasting -- Technological innovations , Multicasting (Computer networks) , Video dial tone , Open source software , Telecommunication , Capital investments
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4654 , http://hdl.handle.net/10962/d1006650 , Internet television , Digital television , Television broadcasting -- Technological innovations , Multicasting (Computer networks) , Video dial tone , Open source software , Telecommunication , Capital investments
- Description: There has been a significant rise in the provision of television and video services over IP (IPTV) in recent years. Increasing network capacity and falling bandwidth costs have made it both technically and economically feasible for service providers to deliver IPTV services. Several telecommunications (telco) operators worldwide are rolling out IPTV solutions and view IPTV as a major service differentiator and alternative revenue source. The main challenge that IPTV providers currently face, however, is the increasingly congested television service provider market, which also includes Internet Television. IPTV solutions therefore need strong service differentiators to succeed. IPTV solutions can doubtlessly sell much faster if they are more affordable or low-cost. Advertising has already been used in many service sectors to help lower service costs, including traditional broadcast television. This thesis therefore explores the role that advertising can play in helping to lower the cost of IPTV services and to incentivise IPTV billing. Another approach that IPTV providers can use to help sell their product is by addressing the growing need for control by today's multimedia users. This thesis will therefore explore the varied approaches that can be used to achieve viewer focused IPTV implementations. To further lower the cost of IPTV services, telcos can also turn to low-cost, open source platforms for service delivery. The adoption of low-cost infrastructure by telcos can lead to reduced Capital Expenditure (CAPEX), which in turn can lead to lower service fees, and ultimately to higher subscriptions and revenue. Therefore, in this thesis, the author proposes a CustOmisable, INcentive (COIN) driven Video on Demand (VoD) framework to be developed and deployed using the Mobicents Communication Platform, an open source service creation and execution platform. The COIN framework aims to provide a viewer focused, economically competitive service that combines the potential cost savings of using free and open source software (FOSS), with an innovative, incentive-driven billing approach. This project will also aim to evaluate whether the Mobicents Platform is a suitable service creation and execution platform for the proposed framework. Additionally, the proposed implementation aims to be interoperable with other IPTV implementations, hence shall follow current IPTV standardisation architectures and trends. The service testbed and its implementation are described in detail and only free and open source software is used; this is to enable its easy duplication and extension for future research. , TeX output 2012.03.02:1241 , Adobe Acrobat 9.2 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
- Authors: Musvibe, Ray
- Date: 2012 , 2012-03-02
- Subjects: Internet television , Digital television , Television broadcasting -- Technological innovations , Multicasting (Computer networks) , Video dial tone , Open source software , Telecommunication , Capital investments
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4654 , http://hdl.handle.net/10962/d1006650 , Internet television , Digital television , Television broadcasting -- Technological innovations , Multicasting (Computer networks) , Video dial tone , Open source software , Telecommunication , Capital investments
- Description: There has been a significant rise in the provision of television and video services over IP (IPTV) in recent years. Increasing network capacity and falling bandwidth costs have made it both technically and economically feasible for service providers to deliver IPTV services. Several telecommunications (telco) operators worldwide are rolling out IPTV solutions and view IPTV as a major service differentiator and alternative revenue source. The main challenge that IPTV providers currently face, however, is the increasingly congested television service provider market, which also includes Internet Television. IPTV solutions therefore need strong service differentiators to succeed. IPTV solutions can doubtlessly sell much faster if they are more affordable or low-cost. Advertising has already been used in many service sectors to help lower service costs, including traditional broadcast television. This thesis therefore explores the role that advertising can play in helping to lower the cost of IPTV services and to incentivise IPTV billing. Another approach that IPTV providers can use to help sell their product is by addressing the growing need for control by today's multimedia users. This thesis will therefore explore the varied approaches that can be used to achieve viewer focused IPTV implementations. To further lower the cost of IPTV services, telcos can also turn to low-cost, open source platforms for service delivery. The adoption of low-cost infrastructure by telcos can lead to reduced Capital Expenditure (CAPEX), which in turn can lead to lower service fees, and ultimately to higher subscriptions and revenue. Therefore, in this thesis, the author proposes a CustOmisable, INcentive (COIN) driven Video on Demand (VoD) framework to be developed and deployed using the Mobicents Communication Platform, an open source service creation and execution platform. The COIN framework aims to provide a viewer focused, economically competitive service that combines the potential cost savings of using free and open source software (FOSS), with an innovative, incentive-driven billing approach. This project will also aim to evaluate whether the Mobicents Platform is a suitable service creation and execution platform for the proposed framework. Additionally, the proposed implementation aims to be interoperable with other IPTV implementations, hence shall follow current IPTV standardisation architectures and trends. The service testbed and its implementation are described in detail and only free and open source software is used; this is to enable its easy duplication and extension for future research. , TeX output 2012.03.02:1241 , Adobe Acrobat 9.2 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
Trophic ecology of breeding northern rockhopper penguins, Eudyptes Moseleyi, at Tristan da Cunha, South Atlantic Ocean
- Authors: Booth, Jenny Marie
- Date: 2012
- Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
- Full Text:
- Date Issued: 2012
- Authors: Booth, Jenny Marie
- Date: 2012
- Subjects: Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5788 , http://hdl.handle.net/10962/d1005476 , Penguins -- Breeding -- Tristan da Cunha , Penguins -- Ecology -- Tristan da Cunha , Penguins -- Food
- Description: Northern Rockhopper penguin populations, Eudyptes moseleyi, are declining globally, and at Tristan da Cunha have undergone severe declines (> 90% in the last 130 years), the cause(s)of which are unknown. There is a paucity of data on this species in the South Atlantic Ocean, therefore their trophic ecology at Tristan da Cunha was studied, specifically focusing on diet, using stomach content analysis and stable isotope analysis (SIA), in conjunction with an analysis of diving behaviour, assessed using temperature-depth recorders. In order to evaluate the influence of gender on foraging, a morphometric investigation of sexual dimorphism was confirmed using molecular analysis. Additionally, plasma corticosterone levels were measured to examine breeding stage and presence of blood parasites as potential sources of stress during the breeding season. Northern Rockhopper penguins at Tristan da Cunha displayed a high degree of foraging plasticity, and fed opportunistically on a wide variety of prey, probably reflecting local small-scale changes in prey distribution. Zooplankton dominated (by mass) the diet of guard stage females, whereas small meso-pelagic fish (predominantly Photichthyidae)dominated diet of adults of both sexes in the crèche stage, with cephalopods contributing equally in both stages. Adults consistently fed chicks on lower-trophic level prey (assessed using SIA), probably zooplankton, than they consumed themselves indicating that the increasing demands of growing chicks were not met by adults through provisioning of higher- quality prey. SIA also indicated that adults foraged in different oceanic water masses when feeding for self-maintenance and for chick provisioning, thus temporally segregating the prey consumed for different purposes. It is possible that adults ‘selected’ these higher quality prey for themselves, or this may be a reflection of opportunistic behaviour. At Tristan da Cunha sexual dimorphism was observed in culmen dimensions (length, depth, width), with males having larger beaks and feeding on larger individuals of squid and fish than females. No sexual segregation in terms of foraging habitat (i.e. different water masses, based on ð¹³N or trophic level ð¹⁵N) during the breeding season or pre-moult period was revealed through SIA, and stomach content analysis revealed no sexual differences in prey species targeted. The results of SIA of feathers indicate that during the pre-moult period birds foraged in different water masses than during the breeding period. The fact that throughout the breeding season birds foraged in similar habitats suggests no intra-specific competition, despite both sexes feeding on the same prey.Birds were generally diurnal, daily foragers (12 – 16 hr trips), with extended trips (maximum duration 35.5 hours) and nocturnal diving recorded in a few individuals. Birds dived well within their physiological limits, predominantly utilising the upper 20m of the water column, employing two different strategies to target different prey items. Long, deep (30 – 40 m), energetically costly dives were performed when targeting energy-rich prey (fish), and a greater number of shorter, shallower (5 – 20 m), energy-efficient dives were performed when targeting prey with a lower energy content (zooplankton). More than half of the sampled study population were infected with the intra-cellular blood parasite Babesia, but infection showed no relationship to body mass, corticosterone levels or breeding success. Fasting birds showed no signs of elevated corticosterone levels, suggesting they had acquired sufficient fat reserves prior to breeding. Failed breeders did not exhibit elevated corticosterone levels. Tristan skuas, Catharacta antarctica hamiltoni, were observed to be a significant cause of egg and chick mortality. The absence of sex-based differences in foraging, and the absence of any signs of stress in relation to body mass, presence of Babesia or breeding stage, suggest that there are no obvious signs of high levels of stress or food limitations during breeding at Tristan da Cunha.
- Full Text:
- Date Issued: 2012
In silico characterisation of the four canonical plasmodium falciparum 70 kDa heat shock proteins
- Authors: Hatherley, Rowan
- Date: 2012
- Subjects: Heat shock proteins -- Research , Plasmodium falciparum -- Research , Plasmodium -- Research , Endoplasmic reticulum , Cytosol , Mitochondria -- Formation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4026 , http://hdl.handle.net/10962/d1004086 , Heat shock proteins -- Research , Plasmodium falciparum -- Research , Plasmodium -- Research , Endoplasmic reticulum , Cytosol , Mitochondria -- Formation
- Description: The 70 kDa heat shock proteins expressed by Plasmodium falciparum (PfHsp70s) are believed to be essential to both the survival and virulence of the malaria parasite. A total of six Hsp70 genes have been identified in the genome of P. falciparum. However, only four of these encode canonical Hsp70s, which are believed to localise predominantly in the cytosol (PfHsp70-1 and PfHsp70-x), the endoplasmic reticulum (PfHsp70-2) and mitochondria (PfHsp70-3) of the parasite. These proteins bind and release peptide substrates in an ATP-dependent manner, with the aid of a J-domain protein cochaperone and a nucleotide exchange factor (NEF). The aim of this study was to identify the residues involved in the interaction of these PfHsp70s with their peptide substrates, their J-domain cochaperones and potential NEFs. These residues were then mapped to three-dimensional (3D) structures of the proteins, modelled in three different conformations; each representing a different stage in the ATPase cycle. Additionally, these proteins were compared to different types of Hsp70s from a variety of different organisms and sequence features found to be specific to each PfHsp70 were mapped to their 3D structures. Finally, a novel modelling method was suggested, in which the structures of templates were remodelled to improve their quality before they were used in the homology modelling process. Based on the analysis of residues involved in interactions with other proteins, it was revealed that each PfHsp70 displayed features that were specific to its cellular localisation and each type of Hsp70 was predicted to interact with a different set of NEFs. The study of conserved features in each PfHsp70 revealed that PfHsp70-x displayed various sequence features atypical of both Plasmodium cytosolic Hsp70s and cytosolic Hsp70s in general. Additionally, residues conserved specifically in Hsp70s of Apicomplexa, Plasmodium and P. falciparum were identified and mapped to the each PfHsp70 model. Although these residues were too numerous to reveal any information of specific value, these models may be useful for the purposes of aiding the design of drug compounds against each PfHsp70. Finally, the novel modelling approach did show some promise. Half of the models produced using the modified templates were of a higher quality than their counterparts modelled using the original templates. This approach does still require a lot of validation work and statistical evaluation. It is hoped that it could prove to be a useful approach to homology modelling when the only templates available are poor quality structures.
- Full Text:
- Date Issued: 2012
- Authors: Hatherley, Rowan
- Date: 2012
- Subjects: Heat shock proteins -- Research , Plasmodium falciparum -- Research , Plasmodium -- Research , Endoplasmic reticulum , Cytosol , Mitochondria -- Formation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4026 , http://hdl.handle.net/10962/d1004086 , Heat shock proteins -- Research , Plasmodium falciparum -- Research , Plasmodium -- Research , Endoplasmic reticulum , Cytosol , Mitochondria -- Formation
- Description: The 70 kDa heat shock proteins expressed by Plasmodium falciparum (PfHsp70s) are believed to be essential to both the survival and virulence of the malaria parasite. A total of six Hsp70 genes have been identified in the genome of P. falciparum. However, only four of these encode canonical Hsp70s, which are believed to localise predominantly in the cytosol (PfHsp70-1 and PfHsp70-x), the endoplasmic reticulum (PfHsp70-2) and mitochondria (PfHsp70-3) of the parasite. These proteins bind and release peptide substrates in an ATP-dependent manner, with the aid of a J-domain protein cochaperone and a nucleotide exchange factor (NEF). The aim of this study was to identify the residues involved in the interaction of these PfHsp70s with their peptide substrates, their J-domain cochaperones and potential NEFs. These residues were then mapped to three-dimensional (3D) structures of the proteins, modelled in three different conformations; each representing a different stage in the ATPase cycle. Additionally, these proteins were compared to different types of Hsp70s from a variety of different organisms and sequence features found to be specific to each PfHsp70 were mapped to their 3D structures. Finally, a novel modelling method was suggested, in which the structures of templates were remodelled to improve their quality before they were used in the homology modelling process. Based on the analysis of residues involved in interactions with other proteins, it was revealed that each PfHsp70 displayed features that were specific to its cellular localisation and each type of Hsp70 was predicted to interact with a different set of NEFs. The study of conserved features in each PfHsp70 revealed that PfHsp70-x displayed various sequence features atypical of both Plasmodium cytosolic Hsp70s and cytosolic Hsp70s in general. Additionally, residues conserved specifically in Hsp70s of Apicomplexa, Plasmodium and P. falciparum were identified and mapped to the each PfHsp70 model. Although these residues were too numerous to reveal any information of specific value, these models may be useful for the purposes of aiding the design of drug compounds against each PfHsp70. Finally, the novel modelling approach did show some promise. Half of the models produced using the modified templates were of a higher quality than their counterparts modelled using the original templates. This approach does still require a lot of validation work and statistical evaluation. It is hoped that it could prove to be a useful approach to homology modelling when the only templates available are poor quality structures.
- Full Text:
- Date Issued: 2012
A spatial and temporal analysis of the changes in alien macrophyte communities and a baseline assessment of the macroinvertebrates associated with Eurasian watermilfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River
- Authors: Fordham, Colin Justin
- Date: 2012
- Subjects: Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5767 , http://hdl.handle.net/10962/d1005455 , Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Description: The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
- Full Text:
- Date Issued: 2012
- Authors: Fordham, Colin Justin
- Date: 2012
- Subjects: Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5767 , http://hdl.handle.net/10962/d1005455 , Water hyacinth -- Control -- South Africa , Aquatic weeds -- Control -- South Africa , Eurasian watermilfoil -- South Africa , Water quality management -- South Africa , Freshwater invertebrates -- Ecology -- South Africa
- Description: The majority of South Africa’s fresh water (lotic and lentic), is eutrophic and this has resulted in water hyacinth, Eichhornia crassipes (C.Mart.) Solms. (Pontederiaceae) becoming South Africa’s most damaging aquatic macrophyte. Recently however, concerns have also been voiced over the presence of highly invasive submerged macrophyte species, such as Eurasian water-milfoil, Myriophyllum spicatum L. (Haloragaceae) in the Vaal River. Interaction studies between floating and submerged macrophytes have shown that floating macrophyte dominance restricts light penetration into the water column shading out submerged macrophytes while submerged macrophyte dominance reduces nutrient availability in the water column limiting floating macrophyte growth. This cycle ensures that these species cannot coexist in the same habitat for extended periods of time. The aims of this thesis were to: 1. Investigate changes in the historical and current macrophyte dominance in the Vaal River 2. Determine whether these changes could be attributed to stochastic events, such as floods and herbicide control measures. 3. The physio-chemical conditions of the water column, and whether pressure from herbivory by macroinvertebrates had possibly influenced Eurasian water-milfoil’s ability to dominate. Spatial and temporal analysis of satellite imagery revealed that water hyacinth and submerged macrophyte species dominated different regions of the study area over different periods of time from 2006 to 2010. This was significantly correlated with nitrate concentrations of the water column. One of the lower Vaal River Water Management Areas (WMA) had changed from a water hyacinth dominated state in 2006 to an alternative submerged macrophyte dominated stable state in 2008. It was concluded that this change could be attributed to: a stochastic flooding event in 2006; perturbation from integrated control measures implemented against water hyacinth; and low nitrate concentrations of the WMA. The lack of any substantial macroinvertebrate herbivory pressure or control measures implemented against Eurasian water-milfoil, compared to similar surveys conducted in the U.S.A. and its native range in Eurasia was shown to contribute to its dominance. Future successful integrated control programmes, including biological control against Eurasian water-milfoil, could provide the perturbation required to restore the ecosystem. However, without the reduction in nitrate concentration levels, water hyacinth will remain the dominant stable state of the rest of the Vaal River.
- Full Text:
- Date Issued: 2012
Small mammal communities at high altitude within the Sneeuberg Mountain complex, Eastern Cape Province, South Africa
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
Multi-instrument observations of ionospheric irregularities over South Africa
- Authors: Amabayo, Emirant Bertillas
- Date: 2012
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Ionospheric storms , Solar activity , Sunspots
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5476 , http://hdl.handle.net/10962/d1005261 , Ionosphere -- Research , Sudden ionospheric disturbances , Ionospheric storms , Solar activity , Sunspots
- Description: The occurrence of mid-latitude spread F (SF) over South Africa has not been extensively studied since the installation of the DPS-4 digisondes at Madimbo (30.88◦E, 22.38◦S), Grahamstown (33.32◦S, 26.50◦E) and Louisvale (28.51◦S, 21.24◦E). This study is intended to quantify the probability of the occurrence of F region disturbances associated with ionospheric spread F (SF) and L-band scintillation over South Africa. This study used available ionosonde data for 8 years (2000-2008) from the three South African stations. The SF events were identified manually on ionograms and grouped for further statistical analysis into frequency SF (FSF), range SF (RSF) and mixed SF (MSF). The results show that the diurnal pattern of SF occurrence peaks strongly between 23:00 and 00:00 UT. This pattern is true for all seasons and types of SF at Madimbo and Grahamstown during 2001 and 2005, except for RSF which had peaks during autumn and spring during 2001 at Madimbo. The probability of both MSF and FSF tends to increase with decreasing sunspot number (SSN), with a peak in 2005 (a moderate solar activity period). The seasonal peaks of MSF and FSF are more frequent during winter months at both Madimbo and Grahamstown. In this study SF was evident in ∼ 0.03% and ∼ 0.06% of the available ionograms at Madimbo and Grahamstown respectively during the eight year period. The presence of ionospheric irregularities associated with SF and scintillation was investigated using data from selected Global Positioning System (GPS) receiver stations distributed across South Africa. The results, based on GPS total electron content (TEC) and ionosonde measurements, show that SF over this region can most likely be attributed to travelling ionospheric disturbances (TIDs), caused by gravity waves (GWs) and neutral wind composition changes. The GWs were mostly associated with geomagnetic storms and sub-storms that occurred during periods of high and moderate solar activity (2001-2005). SF occurrence during the low solar activity period (2006-2008)can probably be attributed to neutral wind composition changes.
- Full Text:
- Date Issued: 2012
- Authors: Amabayo, Emirant Bertillas
- Date: 2012
- Subjects: Ionosphere -- Research , Sudden ionospheric disturbances , Ionospheric storms , Solar activity , Sunspots
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5476 , http://hdl.handle.net/10962/d1005261 , Ionosphere -- Research , Sudden ionospheric disturbances , Ionospheric storms , Solar activity , Sunspots
- Description: The occurrence of mid-latitude spread F (SF) over South Africa has not been extensively studied since the installation of the DPS-4 digisondes at Madimbo (30.88◦E, 22.38◦S), Grahamstown (33.32◦S, 26.50◦E) and Louisvale (28.51◦S, 21.24◦E). This study is intended to quantify the probability of the occurrence of F region disturbances associated with ionospheric spread F (SF) and L-band scintillation over South Africa. This study used available ionosonde data for 8 years (2000-2008) from the three South African stations. The SF events were identified manually on ionograms and grouped for further statistical analysis into frequency SF (FSF), range SF (RSF) and mixed SF (MSF). The results show that the diurnal pattern of SF occurrence peaks strongly between 23:00 and 00:00 UT. This pattern is true for all seasons and types of SF at Madimbo and Grahamstown during 2001 and 2005, except for RSF which had peaks during autumn and spring during 2001 at Madimbo. The probability of both MSF and FSF tends to increase with decreasing sunspot number (SSN), with a peak in 2005 (a moderate solar activity period). The seasonal peaks of MSF and FSF are more frequent during winter months at both Madimbo and Grahamstown. In this study SF was evident in ∼ 0.03% and ∼ 0.06% of the available ionograms at Madimbo and Grahamstown respectively during the eight year period. The presence of ionospheric irregularities associated with SF and scintillation was investigated using data from selected Global Positioning System (GPS) receiver stations distributed across South Africa. The results, based on GPS total electron content (TEC) and ionosonde measurements, show that SF over this region can most likely be attributed to travelling ionospheric disturbances (TIDs), caused by gravity waves (GWs) and neutral wind composition changes. The GWs were mostly associated with geomagnetic storms and sub-storms that occurred during periods of high and moderate solar activity (2001-2005). SF occurrence during the low solar activity period (2006-2008)can probably be attributed to neutral wind composition changes.
- Full Text:
- Date Issued: 2012
In-beam spectroscopy of ⁷²Ge
- Authors: Henninger, Katharine Rose
- Date: 2012
- Subjects: Nuclear shapes , Hyperfine structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5559 , http://hdl.handle.net/10962/d1018233
- Description: The high-spin states of the nucleus ⁷²Ge were populated via the ⁷°Zn(a,2n)⁷²Ge fusion-evaporation reaction at a beam-energy of 30 MeV. The ')'-decays were observed with the AFRODITE spectrometer array at iThemba LABS (Faure, South Africa). Twenty-seven new transitions, 18 new levels and 2 new bands were added to the ⁷²Ge level scheme, and several corrections were made to t he previously-known level scheme. Transitions were characterised using Directional Correlation from Oriented states (DCO) and polarisation measurements, and spin-parity assignments were made for 7 new levels. Spin and parity were also reassigned to a previously-known structure. One of the new bands was ident ified as part of an octupole-vibrational band. No tetrahedral states were observed in the scheme despite N = 40 and Z = 32 having been identified as tetrahedral magic numbers. The meaning of the new 14⁺ yrast level for the underlying structure of the ground state band is discussed
- Full Text:
- Date Issued: 2012
- Authors: Henninger, Katharine Rose
- Date: 2012
- Subjects: Nuclear shapes , Hyperfine structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5559 , http://hdl.handle.net/10962/d1018233
- Description: The high-spin states of the nucleus ⁷²Ge were populated via the ⁷°Zn(a,2n)⁷²Ge fusion-evaporation reaction at a beam-energy of 30 MeV. The ')'-decays were observed with the AFRODITE spectrometer array at iThemba LABS (Faure, South Africa). Twenty-seven new transitions, 18 new levels and 2 new bands were added to the ⁷²Ge level scheme, and several corrections were made to t he previously-known level scheme. Transitions were characterised using Directional Correlation from Oriented states (DCO) and polarisation measurements, and spin-parity assignments were made for 7 new levels. Spin and parity were also reassigned to a previously-known structure. One of the new bands was ident ified as part of an octupole-vibrational band. No tetrahedral states were observed in the scheme despite N = 40 and Z = 32 having been identified as tetrahedral magic numbers. The meaning of the new 14⁺ yrast level for the underlying structure of the ground state band is discussed
- Full Text:
- Date Issued: 2012
μCloud : a P2P cloud platform for computing service provision
- Authors: Fouodji Tasse, Ghislain
- Date: 2012 , 2012-08-22
- Subjects: Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4663 , http://hdl.handle.net/10962/d1006669 , Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Description: The advancements in virtualization technologies have provided a large spectrum of computational approaches. Dedicated computations can be run on private environments (virtual machines), created within the same computer. Through capable APIs, this functionality is leveraged for the service we wish to implement; a computer power service (CPS). We target peer-to-peer systems for this service, to exploit the potential of aggregating computing resources. The concept of a P2P network is mostly known for its expanded usage in distributed networks for sharing resources like content files or real-time data. This study adds computing power to the list of shared resources by describing a suitable service composition. Taking into account the dynamic nature of the platform, this CPS provision is achieved using a self stabilizing clustering algorithm. So, the resulting system of our research is based around a hierarchical P2P architecture and offers end-to-end consideration of resource provisioning and reliability. We named this system μCloud and characterizes it as a self-provisioning cloud service platform. It is designed, implemented and presented in this dissertation. Eventually, we assessed our work by showing that μCloud succeeds in providing user-centric services using a P2P computing unit. With this, we conclude that our system would be highly beneficial in both small and massively deployed environments. , KMBT_223 , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
- Authors: Fouodji Tasse, Ghislain
- Date: 2012 , 2012-08-22
- Subjects: Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4663 , http://hdl.handle.net/10962/d1006669 , Cloud computing , Peer-to-peer architecture (Computer networks) , Computer architecture , Computer service industry
- Description: The advancements in virtualization technologies have provided a large spectrum of computational approaches. Dedicated computations can be run on private environments (virtual machines), created within the same computer. Through capable APIs, this functionality is leveraged for the service we wish to implement; a computer power service (CPS). We target peer-to-peer systems for this service, to exploit the potential of aggregating computing resources. The concept of a P2P network is mostly known for its expanded usage in distributed networks for sharing resources like content files or real-time data. This study adds computing power to the list of shared resources by describing a suitable service composition. Taking into account the dynamic nature of the platform, this CPS provision is achieved using a self stabilizing clustering algorithm. So, the resulting system of our research is based around a hierarchical P2P architecture and offers end-to-end consideration of resource provisioning and reliability. We named this system μCloud and characterizes it as a self-provisioning cloud service platform. It is designed, implemented and presented in this dissertation. Eventually, we assessed our work by showing that μCloud succeeds in providing user-centric services using a P2P computing unit. With this, we conclude that our system would be highly beneficial in both small and massively deployed environments. , KMBT_223 , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
The ichthyofauna of the Wilderness Lakes System, Western Cape, with particular emphasis on alien fish species and their establishment success
- Authors: Olds, Alexis Amy
- Date: 2012
- Subjects: Introduced fishes -- South Africa -- Wilderness , Estuarine fishes -- South Africa -- Wilderness , Mozambique tilapia -- South Africa -- Wilderness , Western mosquitofish -- South Africa -- Wilderness , Carp -- South Africa -- Wilderness , Largemouth bass -- South Africa -- Wilderness , Estuarine fishes -- Effect of exotic animals on -- South Africa -- Wilderness , Fish communities -- South Africa -- Wilderness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5288 , http://hdl.handle.net/10962/d1005132 , Introduced fishes -- South Africa -- Wilderness , Estuarine fishes -- South Africa -- Wilderness , Mozambique tilapia -- South Africa -- Wilderness , Western mosquitofish -- South Africa -- Wilderness , Carp -- South Africa -- Wilderness , Largemouth bass -- South Africa -- Wilderness , Estuarine fishes -- Effect of exotic animals on -- South Africa -- Wilderness , Fish communities -- South Africa -- Wilderness
- Description: Freshwater fish species have been introduced into freshwater systems around the world, primarily for aquaculture, ornamental fish trade and sport fishing. Their introduction into estuarine systems is uncommon however, instances do occur and their establishment success and impacts on these estuarine systems is not well documented. The extent of invasion by four freshwater fishes in a RAMSAR listed estuarine system, the Wilderness Lakes, Western Cape was investigated. This thesis determined the relative abundance and distribution of alien fishes in relation to the native fish biota, their establishment success in the system, what factors inhibited their establishment and whether the introduction of alien fishes negatively impacted the native fish biota. The distribution and abundance of fishes were assessed primarily using fyke nets, seine nets and gill nets in each of the lakes, interconnecting channels and the Touw Estuary. The fish fauna was made up of euryhaline marine species comprising 46%, native estuarine species comprising 18%, catadromous species comprising 7% and freshwater alien species comprising 29% of the total biomass sampled. A total of 26 species were sampled in the system, three of which were considered alien; Oreochromis mossambicus, Gambusia affinis and Cyprinus carpio, and Micropterus salmoides were not sampled but confirmed in the system. Establishment success was determined by evidence of: a sustainable breeding population, a wide distribution, abundant in the sampling area, and all size classes of fish sampled. Gambusia affinis and Oreochromis mossambicus have been recorded in the system for a minimum of 13 and 26 years respectively. They were widely distributed and highly abundant and are established in the system. Micropterus salmoides was first recorded in the system in 1985 but abundances have remained low with fish appearing to be limited to Island Lake and Langvlei. Reproduction appeared to be limited by higher salinity and these factors indicated that this was a casual species which relies on repeated introductions for population maintenance. Cyprinus carpio spawned successfully in 2010 and was widely distributed but abundances were still low with a total of 15 fish being sampled throughout the system, and was thus in the establishing phase. As these are considered freshwater alien species, the physico-chemical parameters in the estuarine environment inhibiting the establishment success of the alien fishes were investigated. Gambusia affinis and O. mossambicus were not limited by the physical environment, and while O. mossambicus cannot tolerate temperatures below 11⁰C, temperatures only dropped below its tolerance for a total of two days between February 2010 and February 2011. Cyprinus carpio and M. salmoides were restricted by salinity in Rondevlei and Langvlei but could tolerate salinity in Island Lake and the Touw Estuary during closed mouth phases. While adults appeared to tolerate the salinity in the system, egg and larval development could be affected thus reducing the viability of the population. The abundance of alien fishes did not negatively impact the abundance of native fish species. The interactions between the native and alien fish biota tended towards biotic acceptance where, as alien abundance increased so did native fish abundance. The impacts of the alien fishes on the native fish biota were assessed by comparing the fish community from a study completed in 1985 to the findings of this study. From these two studies there were no apparent negative impacts on the native fish biota and the fish community composition would most likely be structured by estuarine mouth opening events.
- Full Text:
- Date Issued: 2012
- Authors: Olds, Alexis Amy
- Date: 2012
- Subjects: Introduced fishes -- South Africa -- Wilderness , Estuarine fishes -- South Africa -- Wilderness , Mozambique tilapia -- South Africa -- Wilderness , Western mosquitofish -- South Africa -- Wilderness , Carp -- South Africa -- Wilderness , Largemouth bass -- South Africa -- Wilderness , Estuarine fishes -- Effect of exotic animals on -- South Africa -- Wilderness , Fish communities -- South Africa -- Wilderness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5288 , http://hdl.handle.net/10962/d1005132 , Introduced fishes -- South Africa -- Wilderness , Estuarine fishes -- South Africa -- Wilderness , Mozambique tilapia -- South Africa -- Wilderness , Western mosquitofish -- South Africa -- Wilderness , Carp -- South Africa -- Wilderness , Largemouth bass -- South Africa -- Wilderness , Estuarine fishes -- Effect of exotic animals on -- South Africa -- Wilderness , Fish communities -- South Africa -- Wilderness
- Description: Freshwater fish species have been introduced into freshwater systems around the world, primarily for aquaculture, ornamental fish trade and sport fishing. Their introduction into estuarine systems is uncommon however, instances do occur and their establishment success and impacts on these estuarine systems is not well documented. The extent of invasion by four freshwater fishes in a RAMSAR listed estuarine system, the Wilderness Lakes, Western Cape was investigated. This thesis determined the relative abundance and distribution of alien fishes in relation to the native fish biota, their establishment success in the system, what factors inhibited their establishment and whether the introduction of alien fishes negatively impacted the native fish biota. The distribution and abundance of fishes were assessed primarily using fyke nets, seine nets and gill nets in each of the lakes, interconnecting channels and the Touw Estuary. The fish fauna was made up of euryhaline marine species comprising 46%, native estuarine species comprising 18%, catadromous species comprising 7% and freshwater alien species comprising 29% of the total biomass sampled. A total of 26 species were sampled in the system, three of which were considered alien; Oreochromis mossambicus, Gambusia affinis and Cyprinus carpio, and Micropterus salmoides were not sampled but confirmed in the system. Establishment success was determined by evidence of: a sustainable breeding population, a wide distribution, abundant in the sampling area, and all size classes of fish sampled. Gambusia affinis and Oreochromis mossambicus have been recorded in the system for a minimum of 13 and 26 years respectively. They were widely distributed and highly abundant and are established in the system. Micropterus salmoides was first recorded in the system in 1985 but abundances have remained low with fish appearing to be limited to Island Lake and Langvlei. Reproduction appeared to be limited by higher salinity and these factors indicated that this was a casual species which relies on repeated introductions for population maintenance. Cyprinus carpio spawned successfully in 2010 and was widely distributed but abundances were still low with a total of 15 fish being sampled throughout the system, and was thus in the establishing phase. As these are considered freshwater alien species, the physico-chemical parameters in the estuarine environment inhibiting the establishment success of the alien fishes were investigated. Gambusia affinis and O. mossambicus were not limited by the physical environment, and while O. mossambicus cannot tolerate temperatures below 11⁰C, temperatures only dropped below its tolerance for a total of two days between February 2010 and February 2011. Cyprinus carpio and M. salmoides were restricted by salinity in Rondevlei and Langvlei but could tolerate salinity in Island Lake and the Touw Estuary during closed mouth phases. While adults appeared to tolerate the salinity in the system, egg and larval development could be affected thus reducing the viability of the population. The abundance of alien fishes did not negatively impact the abundance of native fish species. The interactions between the native and alien fish biota tended towards biotic acceptance where, as alien abundance increased so did native fish abundance. The impacts of the alien fishes on the native fish biota were assessed by comparing the fish community from a study completed in 1985 to the findings of this study. From these two studies there were no apparent negative impacts on the native fish biota and the fish community composition would most likely be structured by estuarine mouth opening events.
- Full Text:
- Date Issued: 2012
Culturally-relevant augmented user interfaces for illiterate and semi-literate users
- Authors: Gavaza, Takayedzwa
- Date: 2012 , 2012-06-14
- Subjects: User interfaces (Computer systems) -- Research , Computer software -- Research , Graphical user interfaces (Computer systems) -- Research , Human-computer interaction , Computers and literacy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4665 , http://hdl.handle.net/10962/d1006679 , User interfaces (Computer systems) -- Research , Computer software -- Research , Graphical user interfaces (Computer systems) -- Research , Human-computer interaction , Computers and literacy
- Description: This thesis discusses guidelines for developers of Augmented User Interfaces that can be used by illiterate and semi-literate users. To discover how illiterate and semi-literate users intuitively understand interaction with a computer, a series of Wizard of Oz experiments were conducted. In the first Wizard of Oz study, users were presented with a standard desktop computer, fitted with a number of input devices to determine how they assume interaction should occur. This study found that the users preferred the use of speech and gestures which mirrored findings from other researchers. The study also found that users struggled to understand the tab metaphor which is used frequently in applications. From these findings, a localised culturally-relevant tab interface was developed to determine the feasibility of localised Graphical User Interface components. A second study was undertaken to compare the localised tab interface with the traditional tabbed interface. This study collected both quantitative and qualitative data from the participants. It found that users could interact with a localised tabbed interface faster and more accurately than with the traditional counterparts. More importantly, users stated that they intuitively understood the localised interface component, whereas they did not understand the traditional tab metaphor. These user studies have shown that the use of self-explanatory animations, video feedback, localised tabbed interface metaphors and voice output have a positive impact on enabling illiterate and semi-literate users to access information. , TeX , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
- Authors: Gavaza, Takayedzwa
- Date: 2012 , 2012-06-14
- Subjects: User interfaces (Computer systems) -- Research , Computer software -- Research , Graphical user interfaces (Computer systems) -- Research , Human-computer interaction , Computers and literacy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4665 , http://hdl.handle.net/10962/d1006679 , User interfaces (Computer systems) -- Research , Computer software -- Research , Graphical user interfaces (Computer systems) -- Research , Human-computer interaction , Computers and literacy
- Description: This thesis discusses guidelines for developers of Augmented User Interfaces that can be used by illiterate and semi-literate users. To discover how illiterate and semi-literate users intuitively understand interaction with a computer, a series of Wizard of Oz experiments were conducted. In the first Wizard of Oz study, users were presented with a standard desktop computer, fitted with a number of input devices to determine how they assume interaction should occur. This study found that the users preferred the use of speech and gestures which mirrored findings from other researchers. The study also found that users struggled to understand the tab metaphor which is used frequently in applications. From these findings, a localised culturally-relevant tab interface was developed to determine the feasibility of localised Graphical User Interface components. A second study was undertaken to compare the localised tab interface with the traditional tabbed interface. This study collected both quantitative and qualitative data from the participants. It found that users could interact with a localised tabbed interface faster and more accurately than with the traditional counterparts. More importantly, users stated that they intuitively understood the localised interface component, whereas they did not understand the traditional tab metaphor. These user studies have shown that the use of self-explanatory animations, video feedback, localised tabbed interface metaphors and voice output have a positive impact on enabling illiterate and semi-literate users to access information. , TeX , Adobe Acrobat 9.51 Paper Capture Plug-in
- Full Text:
- Date Issued: 2012
Malarial drug targets cysteine proteases as hemoglobinases
- Authors: Mokoena, Fortunate
- Date: 2012
- Subjects: Malaria -- Chemotherapy , Antimalarials , Hemoglobin , Proteolytic enzymes , Cysteine proteinases , Plasmodium falciparum , Plasmodium vivax , Papain
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4005 , http://hdl.handle.net/10962/d1004065 , Malaria -- Chemotherapy , Antimalarials , Hemoglobin , Proteolytic enzymes , Cysteine proteinases , Plasmodium falciparum , Plasmodium vivax , Papain
- Description: Malaria has consistently been rated as the worst parasitic disease in the world. This disease affects an estimated 5 billion households annually. Malaria has a high mortality rate leading to distorted socio-economic development of the world at large. The major challenge pertaining to malaria is its continuous and rapid spread together with the emergence of drug resistance in Plasmodium species (vector agent of the disease). For this reason, researchers throughout the world are following new leads for possible drug targets and therefore, investigating ways of curbing the spread of the disease. Cysteine proteases have emerged as potential antimalarial chemotherapeutic targets. These particular proteases are found in all living organisms, Plasmodium cysteine proteases are known to degrade host hemoglobin during the life cycle of the parasite within the human host. The main objective of this study was to use various in silico methods to analyze the hemoglobinase function of cysteine proteases in P. falciparum and P. vivax. Falcipain-2 (FP2) of P. falciparum is the best characterized of these enzymes, it is a validated drug target. Both the three-dimensional structures of FP2 and its close homologue falcipain-3 (FP3) have been solved by the experimental technique X-ray crystallography. However, the homologue falcipain-2 (FP2’)’ and orthologues from P.vivax vivapain-2 (VP2) and vivapain-3 (VP3) have yet to be elucidated by experimental techniques. In an effort to achieve the principal goal of the study, homology models of the protein structures not already elucidated by experimental methods (FP2’, VP2 and VP3) were calculated using the well known spatial restraint program MODELLER. The derived models, FP2 and FP3 were docked to hemoglobin (their natural substrate). The protein-protein docking was done using the unbound docking program ZDOCK. The substrate-enzyme interactions were analyzed and amino acids involved in binding were observed. It is anticipated that the results obtained from the study will help focus inhibitor design for potential drugs against malaria. The residues found in both the P. falciparum and P. vivax cysteine proteases involved in hemoglobin binding have been identified and some of these are proposed to be the main focus for the design of a peptidomimetric inhibitor.
- Full Text:
- Date Issued: 2012
- Authors: Mokoena, Fortunate
- Date: 2012
- Subjects: Malaria -- Chemotherapy , Antimalarials , Hemoglobin , Proteolytic enzymes , Cysteine proteinases , Plasmodium falciparum , Plasmodium vivax , Papain
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4005 , http://hdl.handle.net/10962/d1004065 , Malaria -- Chemotherapy , Antimalarials , Hemoglobin , Proteolytic enzymes , Cysteine proteinases , Plasmodium falciparum , Plasmodium vivax , Papain
- Description: Malaria has consistently been rated as the worst parasitic disease in the world. This disease affects an estimated 5 billion households annually. Malaria has a high mortality rate leading to distorted socio-economic development of the world at large. The major challenge pertaining to malaria is its continuous and rapid spread together with the emergence of drug resistance in Plasmodium species (vector agent of the disease). For this reason, researchers throughout the world are following new leads for possible drug targets and therefore, investigating ways of curbing the spread of the disease. Cysteine proteases have emerged as potential antimalarial chemotherapeutic targets. These particular proteases are found in all living organisms, Plasmodium cysteine proteases are known to degrade host hemoglobin during the life cycle of the parasite within the human host. The main objective of this study was to use various in silico methods to analyze the hemoglobinase function of cysteine proteases in P. falciparum and P. vivax. Falcipain-2 (FP2) of P. falciparum is the best characterized of these enzymes, it is a validated drug target. Both the three-dimensional structures of FP2 and its close homologue falcipain-3 (FP3) have been solved by the experimental technique X-ray crystallography. However, the homologue falcipain-2 (FP2’)’ and orthologues from P.vivax vivapain-2 (VP2) and vivapain-3 (VP3) have yet to be elucidated by experimental techniques. In an effort to achieve the principal goal of the study, homology models of the protein structures not already elucidated by experimental methods (FP2’, VP2 and VP3) were calculated using the well known spatial restraint program MODELLER. The derived models, FP2 and FP3 were docked to hemoglobin (their natural substrate). The protein-protein docking was done using the unbound docking program ZDOCK. The substrate-enzyme interactions were analyzed and amino acids involved in binding were observed. It is anticipated that the results obtained from the study will help focus inhibitor design for potential drugs against malaria. The residues found in both the P. falciparum and P. vivax cysteine proteases involved in hemoglobin binding have been identified and some of these are proposed to be the main focus for the design of a peptidomimetric inhibitor.
- Full Text:
- Date Issued: 2012
Investigation of the effect of short duration breaks in delaying the onset of performance related fatigue during long distance monotonous driving at different times of the day
- Authors: Ndaki, Ntombikayise
- Date: 2012
- Subjects: Fatigue -- Physiological aspects , Drowsiness -- Physiological aspects , Automobile driving -- Physiological aspects , Traffic safety -- South Africa , Automobile driving -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5170 , http://hdl.handle.net/10962/d1016353
- Description: Road traffic accidents are a serious burden to the health systems of many countries especially in South Africa. Research aimed at reducing traffic related accidents is of importance as traffic crashes are rated as the second leading cause of fatalities in South Africa and ninth in the world. Despite the extensive efforts into research and development of new technology, driver fatigue still remains a cause of vehicle accidents worldwide. Fatigue plays a role in up to 20% of vehicle accidents with many being serious or fatal. Numerous coping behaviours are employed by drivers to counteract the negative effects of fatigue. The most common coping behaviours include taking short naps, talking to passengers, listening to the radio, opening windows and drinking stimulants. Driving breaks have long been identified as an effective countermeasure against fatigue. Most research done in driving breaks has investigated the duration of the breaks, activity undertaken during the break and the frequency of the breaks taken outside the vehicle. However limited literature is available on the effectiveness of breaks in counteracting the effects of fatigue. The objective of the current study was aimed at assessing whether short duration breaks are an effective countermeasure against fatigue. Physiological, neurophysiological, subjective and performance measures were used as indicators for fatigue. Additional focus of the research was determining whether breaks were more or less effective at counteracting the effects of fatigue at different times of day. Twelve participants were recruited for the study, six males and six females. The participants were required to perform a driving task on a simulator for 90 minutes. The study consisted of four independent conditions, namely driving during the day with breaks, driving during the day without breaks, driving during the night with breaks and driving during the night without breaks. The without breaks conditions were similar except that they occurred at different times of the day, one session at night and the other session during day time, as was the case for the conditions with breaks. The driving task used in the current study was a low fidelity simulator tracking task. The participants were required to follow a centre line displayed on a tracking path as accurately as possible. The measurements that were recorded in this study included physiological, performance, subjective and neurophysiological. Physiological measures included heart rate and heart rate variability (frequency domain) and core body temperature. The ascending threshold of the critical flicker fusion frequency was the only neurophysiological measurement included in the current investigation. Performance was quantified by mean deviation from a centre line participants were meant to track. Two rating scales were used: Karolinska sleepiness scale and the Wits sleepiness scale were used for the measurement of subjective sleepiness. Heart rate, heart rate variability and mean deviation were measured continuously throughout the 90 minute driving task. Critical flicker fusion frequency, temperature and the subjective scales were measured before and after the 90 minute driving task. The results indicated that the short duration breaks during day time had a positive effect on driving performance; however the breaks at night had a negative effect on driving performance. Heart rate was higher during the day compared to night time and the heart rate variability high frequency spectrum values were lower during the day condition, to show the activation of the sympathetic nervous system which is characteristic of day time. The night conditions had lower heart rate values and higher heart rate variability high frequency values, which show the activation of the parasympathetic nervous system which is dominant during periods of fatigue and night time. Subjective sleepiness levels were also higher at night compared to day time.
- Full Text:
- Date Issued: 2012
- Authors: Ndaki, Ntombikayise
- Date: 2012
- Subjects: Fatigue -- Physiological aspects , Drowsiness -- Physiological aspects , Automobile driving -- Physiological aspects , Traffic safety -- South Africa , Automobile driving -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5170 , http://hdl.handle.net/10962/d1016353
- Description: Road traffic accidents are a serious burden to the health systems of many countries especially in South Africa. Research aimed at reducing traffic related accidents is of importance as traffic crashes are rated as the second leading cause of fatalities in South Africa and ninth in the world. Despite the extensive efforts into research and development of new technology, driver fatigue still remains a cause of vehicle accidents worldwide. Fatigue plays a role in up to 20% of vehicle accidents with many being serious or fatal. Numerous coping behaviours are employed by drivers to counteract the negative effects of fatigue. The most common coping behaviours include taking short naps, talking to passengers, listening to the radio, opening windows and drinking stimulants. Driving breaks have long been identified as an effective countermeasure against fatigue. Most research done in driving breaks has investigated the duration of the breaks, activity undertaken during the break and the frequency of the breaks taken outside the vehicle. However limited literature is available on the effectiveness of breaks in counteracting the effects of fatigue. The objective of the current study was aimed at assessing whether short duration breaks are an effective countermeasure against fatigue. Physiological, neurophysiological, subjective and performance measures were used as indicators for fatigue. Additional focus of the research was determining whether breaks were more or less effective at counteracting the effects of fatigue at different times of day. Twelve participants were recruited for the study, six males and six females. The participants were required to perform a driving task on a simulator for 90 minutes. The study consisted of four independent conditions, namely driving during the day with breaks, driving during the day without breaks, driving during the night with breaks and driving during the night without breaks. The without breaks conditions were similar except that they occurred at different times of the day, one session at night and the other session during day time, as was the case for the conditions with breaks. The driving task used in the current study was a low fidelity simulator tracking task. The participants were required to follow a centre line displayed on a tracking path as accurately as possible. The measurements that were recorded in this study included physiological, performance, subjective and neurophysiological. Physiological measures included heart rate and heart rate variability (frequency domain) and core body temperature. The ascending threshold of the critical flicker fusion frequency was the only neurophysiological measurement included in the current investigation. Performance was quantified by mean deviation from a centre line participants were meant to track. Two rating scales were used: Karolinska sleepiness scale and the Wits sleepiness scale were used for the measurement of subjective sleepiness. Heart rate, heart rate variability and mean deviation were measured continuously throughout the 90 minute driving task. Critical flicker fusion frequency, temperature and the subjective scales were measured before and after the 90 minute driving task. The results indicated that the short duration breaks during day time had a positive effect on driving performance; however the breaks at night had a negative effect on driving performance. Heart rate was higher during the day compared to night time and the heart rate variability high frequency spectrum values were lower during the day condition, to show the activation of the sympathetic nervous system which is characteristic of day time. The night conditions had lower heart rate values and higher heart rate variability high frequency values, which show the activation of the parasympathetic nervous system which is dominant during periods of fatigue and night time. Subjective sleepiness levels were also higher at night compared to day time.
- Full Text:
- Date Issued: 2012
A study of four-dimensional oscillator groups and the associated left-invariant control affine systems
- Authors: Biggs, Rory
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164941 , vital:41186
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Department of Mathematics, 2012
- Full Text:
- Date Issued: 2012
- Authors: Biggs, Rory
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164941 , vital:41186
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Department of Mathematics, 2012
- Full Text:
- Date Issued: 2012