The effect of carbohydrate on dusky kob, Argyrosomus japonicus, fed pelleted diets
- Authors: Mabasa, Nyiko Charity
- Date: 2017
- Subjects: Carbohydrates in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44895 , vital:25450
- Description: The dusky kob, Argyrosomus japonicus, is an emerging commercial marine aquaculture species in South Africa. Attributes such as market acceptance, fast growth rates, tolerance to sibling density, acceptance of pelleted feed and adaptability to intensive aquaculture conditions make it a good candidate. Feed, the largest running cost in most aquaculture operations, is a limiting factor in dusky kob production as its nutritional requirements are not well understood. The present project formed part of a research program to develop a locally produced, least cost and sustainable feed that will support the growth and health of dusky kob. The approximate protein and energy requirements for kob fed formulated feeds have been established in earlier research, but the ability of kob to utilize carbohydrates as an energy source has not previously been investigated. The aim of this study was to determine the efficiency of dusky kob to utilize graded levels of carbohydrate (pregelatinized maize starch - PGMS) in pelleted diets. The research objectives were to determine the effect of dietary carbohydrate levels on:i) growth and feed utilization; ii) post prandial blood glucose levels; and iii) general fish health, gut bacterial composition and liver glycogen content of juvenile dusky kob. Hatchery reared juvenile dusky kob (5 g) were acclimatized in a recirculating experimental aquaculture system at the Department of Ichthyology and Fisheries Science at Rhodes University. They were fed trout crumble starter feed for three weeks before the start of the feeding experiment. Five diets containing 4.1, 8.2, 16.4 and 24.6% carbohydrate, hereafter referred to as 4.1C, 8.2C, 16.4C and 24.6C respectively, were formulated with pregelatinized maize starch as a carbohydrate source and fishmeal as the main protein source. Fish were fed these diets twice daily at 3.85% body weight per day for three months. Specific growth rates and feed conversion rations differed significantly between the four dietary treatments. Growth rate increased with increasing carbohydrate up to 16.4%, after which a significant decline was observed. Diet 16.4C produced the highest specific growth rate (SGR) of 1.84 ± 0.05% body weight/day, and the lowest feed conversion ratio of 1.28 ± 0.08. While the lowest specific growth rate and highest feed conversion ratio of 0.79 ± 0.05 and 2.14 ± 0.13 respectively, were found for diet 24.6C. A third order polynomial regression, using SGR, determined the optimum carbohydrate inclusion for dusky kob to be 16.72%. The general structure of the liver was similar between all fish fed the dietary treatments and all fish liver samples displayed a certain degree of lipid vacuolization of the hepatocytes. Evidence of starvation was observed in the livers of fish fed diet 24.6C. However, no differences in the amount of liver glycogen were observed. Gut bacterial composition did not differ among the different diets or between the different sections of the gut. Differences were however observed in the diversity of the bacterial community structure at the start (when they were fed commercial trout feed) and end of the experimental period (after being fed a fishmeal-maize diet). The rate at which glucose was cleared from the blood differed significantly between diets. The low carbohydrate diets (i.e. diet 4.1C and 8.2C) showed a steady rate of glucose removal from the blood over a 48 h experimental period. Sharp increases in blood glucose concentration were observed in diet 16.4C and diet 24.6C, with highest glucose concentrations of 7.18 ± 1.81 and 8.05 ± 2.35 mmol/l respectively, observed 24 h after feeding. The blood glucose concentration of the fish fed diet 16.4C however returned to resting glucose concentration after 48 h, while that of the fish fed diet 24.6C did not. The results demonstrated that the level of dietary carbohydrate inclusion has a significant effect on the growth and health of the fish. The optimum carbohydrate inclusion in dusky kob diets is indicated to be 16.7%, which gave the best growth rate and maximum protein sparing effect without adverse effects on fish health. These findings are important for diet formulation and producing ‘least-cost’ diets for dusky kob farming.
- Full Text:
- Authors: Mabasa, Nyiko Charity
- Date: 2017
- Subjects: Carbohydrates in animal nutrition , Fishes -- Feeding and feeds , Argyrosomus japonicus , Argyrosomus , Argyrosomus japonicus -- Nutrition , Argyrosomus -- Nutrition , Argyrosomus japonicus -- Feeding and feeds , Argyrosomus -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44895 , vital:25450
- Description: The dusky kob, Argyrosomus japonicus, is an emerging commercial marine aquaculture species in South Africa. Attributes such as market acceptance, fast growth rates, tolerance to sibling density, acceptance of pelleted feed and adaptability to intensive aquaculture conditions make it a good candidate. Feed, the largest running cost in most aquaculture operations, is a limiting factor in dusky kob production as its nutritional requirements are not well understood. The present project formed part of a research program to develop a locally produced, least cost and sustainable feed that will support the growth and health of dusky kob. The approximate protein and energy requirements for kob fed formulated feeds have been established in earlier research, but the ability of kob to utilize carbohydrates as an energy source has not previously been investigated. The aim of this study was to determine the efficiency of dusky kob to utilize graded levels of carbohydrate (pregelatinized maize starch - PGMS) in pelleted diets. The research objectives were to determine the effect of dietary carbohydrate levels on:i) growth and feed utilization; ii) post prandial blood glucose levels; and iii) general fish health, gut bacterial composition and liver glycogen content of juvenile dusky kob. Hatchery reared juvenile dusky kob (5 g) were acclimatized in a recirculating experimental aquaculture system at the Department of Ichthyology and Fisheries Science at Rhodes University. They were fed trout crumble starter feed for three weeks before the start of the feeding experiment. Five diets containing 4.1, 8.2, 16.4 and 24.6% carbohydrate, hereafter referred to as 4.1C, 8.2C, 16.4C and 24.6C respectively, were formulated with pregelatinized maize starch as a carbohydrate source and fishmeal as the main protein source. Fish were fed these diets twice daily at 3.85% body weight per day for three months. Specific growth rates and feed conversion rations differed significantly between the four dietary treatments. Growth rate increased with increasing carbohydrate up to 16.4%, after which a significant decline was observed. Diet 16.4C produced the highest specific growth rate (SGR) of 1.84 ± 0.05% body weight/day, and the lowest feed conversion ratio of 1.28 ± 0.08. While the lowest specific growth rate and highest feed conversion ratio of 0.79 ± 0.05 and 2.14 ± 0.13 respectively, were found for diet 24.6C. A third order polynomial regression, using SGR, determined the optimum carbohydrate inclusion for dusky kob to be 16.72%. The general structure of the liver was similar between all fish fed the dietary treatments and all fish liver samples displayed a certain degree of lipid vacuolization of the hepatocytes. Evidence of starvation was observed in the livers of fish fed diet 24.6C. However, no differences in the amount of liver glycogen were observed. Gut bacterial composition did not differ among the different diets or between the different sections of the gut. Differences were however observed in the diversity of the bacterial community structure at the start (when they were fed commercial trout feed) and end of the experimental period (after being fed a fishmeal-maize diet). The rate at which glucose was cleared from the blood differed significantly between diets. The low carbohydrate diets (i.e. diet 4.1C and 8.2C) showed a steady rate of glucose removal from the blood over a 48 h experimental period. Sharp increases in blood glucose concentration were observed in diet 16.4C and diet 24.6C, with highest glucose concentrations of 7.18 ± 1.81 and 8.05 ± 2.35 mmol/l respectively, observed 24 h after feeding. The blood glucose concentration of the fish fed diet 16.4C however returned to resting glucose concentration after 48 h, while that of the fish fed diet 24.6C did not. The results demonstrated that the level of dietary carbohydrate inclusion has a significant effect on the growth and health of the fish. The optimum carbohydrate inclusion in dusky kob diets is indicated to be 16.7%, which gave the best growth rate and maximum protein sparing effect without adverse effects on fish health. These findings are important for diet formulation and producing ‘least-cost’ diets for dusky kob farming.
- Full Text:
The effect of different seating conditions, in aircrafts, on passenger comfort and the use of cabin space
- Authors: Olley, Emma-Jane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19734 , vital:22479
- Description: Although aircraft cabin design has improved over the years, passengers continue to complain about sitting discomfort whilst flying. These complaints are often centred on the cramped and restricted seating conditions. Whilst passenger comfort is important, in order for airline companies to attract and retain customers, it is also important to design for cabin space needs. Denel Aviation intends to build a South African Regional Aircraft (SARA) that will fly point-to-point, linking regional centres and intends to design aircraft seats that not only optimise passenger comfort, but which also save cabin space. The aim of this investigation was two-fold. The first aim was to determine how aircraft backrest angle affected passenger comfort, ease of seat access, perceived restriction and legroom, with different seat pan angles and seat heights. The second aim was to determine whether passenger comfort was affected with the most preferred backrest angle for each seat pan angle and seat height. Determining how seat pan angle and seat height affect the preferred angle of the backrest was considered important as Denel intend to use aircraft seats with a non-adjustable backrest angle. For this study, 80 participants were recruited from Rhodes University and the general Grahamstown population. The participants consisted of 40 males and 40 females and were not limited by race, ethnicity or culture. The participants were classified into two age groups; 18-30 years of age and 31-60 years of age. Participant stature, body mass, BMI and lower leg length was recorded to determine the effect these factors had on sitting comfort when the participants were seated in different seating conditions. From the results obtained, it was found that, by altering seat height, seat pan angle, and backrest angle, passenger comfort can be optimised. Furthermore, it was found that certain combinations of seat height, seat pan angle and backrest angle are more beneficial with regards to saving aircraft cabin space. However, this means that a compromise needs to be found for SARA as passenger comfort needs to be optimised, whilst decreasing the use of cabin space to reduce costs.
- Full Text:
- Authors: Olley, Emma-Jane
- Date: 2017
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/19734 , vital:22479
- Description: Although aircraft cabin design has improved over the years, passengers continue to complain about sitting discomfort whilst flying. These complaints are often centred on the cramped and restricted seating conditions. Whilst passenger comfort is important, in order for airline companies to attract and retain customers, it is also important to design for cabin space needs. Denel Aviation intends to build a South African Regional Aircraft (SARA) that will fly point-to-point, linking regional centres and intends to design aircraft seats that not only optimise passenger comfort, but which also save cabin space. The aim of this investigation was two-fold. The first aim was to determine how aircraft backrest angle affected passenger comfort, ease of seat access, perceived restriction and legroom, with different seat pan angles and seat heights. The second aim was to determine whether passenger comfort was affected with the most preferred backrest angle for each seat pan angle and seat height. Determining how seat pan angle and seat height affect the preferred angle of the backrest was considered important as Denel intend to use aircraft seats with a non-adjustable backrest angle. For this study, 80 participants were recruited from Rhodes University and the general Grahamstown population. The participants consisted of 40 males and 40 females and were not limited by race, ethnicity or culture. The participants were classified into two age groups; 18-30 years of age and 31-60 years of age. Participant stature, body mass, BMI and lower leg length was recorded to determine the effect these factors had on sitting comfort when the participants were seated in different seating conditions. From the results obtained, it was found that, by altering seat height, seat pan angle, and backrest angle, passenger comfort can be optimised. Furthermore, it was found that certain combinations of seat height, seat pan angle and backrest angle are more beneficial with regards to saving aircraft cabin space. However, this means that a compromise needs to be found for SARA as passenger comfort needs to be optimised, whilst decreasing the use of cabin space to reduce costs.
- Full Text:
The effect of shade on the biological control of Salvinia molesta D.S. Mitchell [Salviniaceae] by the weevil, Cyrtobagous salviniae Calder and Sands [Curculionidae]
- Authors: Maseko, Zolile
- Date: 2017
- Subjects: Salvinia molesta , Aquatic weeds -- Biological control , Beetles , Insects as biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4808 , vital:20726
- Description: Salvinia molesta, a floating aquatic weed, is a global menace in many water bodies and waterways. The weed disrupts the ecological balance wherever it invades and also has wide ranging economic and health impacts. Its impact has resulted in the need to control it, and while chemical and mechanical control are often ineffective, biological control by the weevil Cyrtobagous salviniae is largely successful. However, in many parts of the world, including South Africa, biological control of S. molesta has been less effective where the weed grows as an understory species. Shallow and shaded waters characteristically found at the margins of water bodies provide a refuge for S. molesta. Therefore, the aim of the study was to determine the effect of shade on the efficacy of biological control of S. molesta. Investigations into the problems associated with control in the shade were carried out in a greenhouse and in the field. In controlled greenhouse experiments, plants were grown at high and low nutrient levels in individual mesocosms, at three varying levels of shade, where half the mesocosms were inoculated with C. salviniae. Plants in high nutrient conditions were significantly more productive in terms of biomass accumulation, compared to those grown at low nutrient levels, in both the absence and presence of herbivory at all levels of shade tested. Plants grown in the shade and in high nutrient conditions had significantly higher quality compared to the ones exposed to full sun. Higher plant quality in the shade consequently resulted in accelerated fecundity for C. salviniae resulting in significantly higher weevil populations. Furthermore, less damage was recorded on plants in the shade, possibly due to the high nitrogen concentrations which may have deterred grazing by C. salviniae. However, in the absence of shading, plants were of lower quality and consequently sustained more damage from herbivores despite lower weevil populations. In contrast to the greenhouse, there were no differences in biomass recorded in the field at two nutrient levels and in the presence of herbivory for both shade and open sites. Nutrients added to high nutrient treatment quadrats diffused evenly across the water body resulting in uniform nutrient distribution, hence uniform plant biomass and carbon-nitrogen ratio. Despite the lack of statistical differences, more weevils were found in the full sun plots, while modest populations were recorded in the shade. Higher weevil populations consequently led to more damage in the sun, a situation that has been observed in most field sites in South Africa. The results therefore suggest that nutrients were pivotal in plant growth compared to light regimes (amount of PAR). Plant quality significantly influenced weevil populations and plant damage in both studies, demonstrating that plant nitrogen plays a crucial role in the plant- herbivore system. Furthermore, in both the greenhouse and field, despite lack of statistical differences, plants exposed to full sunlight suffered more damage than shade plants, pointing towards better control in the sun compared to the shade, suggesting that there is greater preference of sun-exposed plants for grazing by the weevils. The results from this study add to the growing body of literature that plant quality is a major factor in determining the success of aquatic weed biological control programmes.
- Full Text:
- Authors: Maseko, Zolile
- Date: 2017
- Subjects: Salvinia molesta , Aquatic weeds -- Biological control , Beetles , Insects as biological pest control agents
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4808 , vital:20726
- Description: Salvinia molesta, a floating aquatic weed, is a global menace in many water bodies and waterways. The weed disrupts the ecological balance wherever it invades and also has wide ranging economic and health impacts. Its impact has resulted in the need to control it, and while chemical and mechanical control are often ineffective, biological control by the weevil Cyrtobagous salviniae is largely successful. However, in many parts of the world, including South Africa, biological control of S. molesta has been less effective where the weed grows as an understory species. Shallow and shaded waters characteristically found at the margins of water bodies provide a refuge for S. molesta. Therefore, the aim of the study was to determine the effect of shade on the efficacy of biological control of S. molesta. Investigations into the problems associated with control in the shade were carried out in a greenhouse and in the field. In controlled greenhouse experiments, plants were grown at high and low nutrient levels in individual mesocosms, at three varying levels of shade, where half the mesocosms were inoculated with C. salviniae. Plants in high nutrient conditions were significantly more productive in terms of biomass accumulation, compared to those grown at low nutrient levels, in both the absence and presence of herbivory at all levels of shade tested. Plants grown in the shade and in high nutrient conditions had significantly higher quality compared to the ones exposed to full sun. Higher plant quality in the shade consequently resulted in accelerated fecundity for C. salviniae resulting in significantly higher weevil populations. Furthermore, less damage was recorded on plants in the shade, possibly due to the high nitrogen concentrations which may have deterred grazing by C. salviniae. However, in the absence of shading, plants were of lower quality and consequently sustained more damage from herbivores despite lower weevil populations. In contrast to the greenhouse, there were no differences in biomass recorded in the field at two nutrient levels and in the presence of herbivory for both shade and open sites. Nutrients added to high nutrient treatment quadrats diffused evenly across the water body resulting in uniform nutrient distribution, hence uniform plant biomass and carbon-nitrogen ratio. Despite the lack of statistical differences, more weevils were found in the full sun plots, while modest populations were recorded in the shade. Higher weevil populations consequently led to more damage in the sun, a situation that has been observed in most field sites in South Africa. The results therefore suggest that nutrients were pivotal in plant growth compared to light regimes (amount of PAR). Plant quality significantly influenced weevil populations and plant damage in both studies, demonstrating that plant nitrogen plays a crucial role in the plant- herbivore system. Furthermore, in both the greenhouse and field, despite lack of statistical differences, plants exposed to full sunlight suffered more damage than shade plants, pointing towards better control in the sun compared to the shade, suggesting that there is greater preference of sun-exposed plants for grazing by the weevils. The results from this study add to the growing body of literature that plant quality is a major factor in determining the success of aquatic weed biological control programmes.
- Full Text:
The effect of submersion in water and breathing modality (assisted breathing and apnea) on different stages of the information processing chain
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
- Full Text:
- Authors: Goodenough, Luke Brian
- Date: 2017
- Subjects: Deep diving -- Physiological aspects , Scuba diving -- Physiological aspects , Apnea , Cognition -- Testing , Neurophysiology , Underwater breathing apparatus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7448 , vital:21261
- Description: Limited research has explored the impact of working underwater on the cognitive functioning of divers and even less has focused on the effect of breathing modality (assisted breathing and apnea) underwater. Research on the effect of submersion in water and apnea on cognitive performance is also very limited. As a result, the purpose of this study was to determine the effect of submersion in water and breathing modality on different stages of the information processing chain. This was achieved by testing participants in a laboratory setting under three conditions; on land, underwater with assisted breathing and underwater in apnea. Five different tests were used to determine which aspects of cognitive functioning were impaired in which condition. The recognition task result in the assisted breathing condition was significantly faster (p=0.04) but less accurate (p=0.01) than on land. The memory task was significantly (p=0.042) worse in terms of speed in the apnea condition compared to land, however accuracy was not affected. Performance in the visual detection task was impacted on in both underwater conditions compared to land with speed and accuracy being significantly worse (p<0.01) in the underwater conditions. These results indicate that simple tasks, (reaction time and tracking task) are not affected by condition whereas more complex tasks are. For tasks where an effect was found for only one condition, the effect was attributed to a specific aspect of that condition; either the breath hold or assisted breathing component of the condition. For tasks that were found to be affected in both underwater conditions, the effect was attributed to the actual submersion in water. The effect of the different conditions and the nature of the task they impact on should be considered for underwater work places as the general equipment used may impact on the quality of observations that are made.
- Full Text:
The effect of total standing duration during sit-stand regimes on cognitive performance, rating of perceived exertion and heart rate frequency
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
- Full Text:
- Authors: Berndt, Ethan
- Date: 2017
- Subjects: Standing position , Sedentary behavior , Work environment , Employee health promotion , Office furniture -- Design , Industrial hygiene , Employees -- Health risk assessment , Human engineering
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7433 , vital:21260
- Description: Although there may be numerous health benefits of sit-stand workstations, the effects of sedentary or non-sedentary work configurations on cognitive performance and executive function remain unclear (Bantoft et al., 2016). It is essential to determine any performance effects of these different work configurations; as improvements in the workplace, working posture and discomfort need to be justified in terms of improvements (or no deterioration) in work performance (Liao and Drury, 2000). The aim of the current research was to investigate the effect of two sit-stand regimes differing in total standing duration, on cognitive task performance, physiological responses and subjective ratings of perceived exertion. This laboratory based investigation incorporated a repeated measures design, where a test battery was utilized. Three experimental conditions were tested during three separate testing sessions by 30 participants. Condition 2 (15 minutes standing, followed by 45 minutes seated) and Condition 3 (15 minutes seated, followed by 15 minutes standing, followed by 15 minutes seated, followed by 15 minutes standing) were compared to each other and Condition 1 (60 minutes seated). The findings of this study show that even though the two different sit-stand regimes did not result in a significant impact on cognitive task performance, an immediate postural effect for psychomotor response time and a delayed postural effect for working memory were found. The participants perceived Condition 3 as the most physically exerting condition. Heart rate frequency was not significantly different between the conditions, but the immediate seated posture had a significantly lower heart rate frequency compared to the standing posture; indicating that being seated elicited lower energy expenditure compared to standing. Heart rate frequency while standing had a greater degree of variation compared to being seated. Taking the findings of this study into account, it is recommended that: one should be seated while performing this type of working memory task; that one should be standing while performing this type of psychomotor task; that the recommendation that implementing standing at work can be used as a blanket strategy to increase energy expenditure in all individuals needs to be explored further and that individual differences may impact energy expenditure.
- Full Text:
The effects of a lion (Panthera Leo) re-introduction on a resident cheetah (Acinonyx Jubatus) population In Mountain Zebra National Park, Eastern Cape, South Africa
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
- Authors: Van de Vyver, Daniel
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7420 , vital:21259
- Description: The global decline of large (> 10 kg) carnivores has resulted in a variety of conservation measures being put into practice to prevent extinctions. The establishment of predator-proof fences around protected areas has been a successful tool for reducing human-predator conflict. Furthermore, the re-introduction of large carnivores into small (< 1 000 km²), enclosed reserves has aided in the conservation of many species. Cheetahs (Acinonyx jubatus) and lions (Panthera leo) have benefitted from such re-introductions. The re-introduction of cheetahs before lions into the Mountain Zebra National Park (MZNP) in the Eastern Cape Province of South Africa provided a unique opportunity to study the effects of lions on an already established cheetah population. Spatial data were downloaded remotely from GPS collared individuals (n=4) and cheetah kill data were collected using the GPS cluster method before (2012-2013) and after (2013-2014) the lion (n=3) re-introduction. The same methods were used for lion kill data collection once they had been re-introduced. In general, cheetah home range size did not change after the lion re-introduction. Cheetahs selected areas with a combination of open and closed vegetation covers, while lions selected either open or closed areas of vegetation covers. In addition, as vegetation cover became thicker, the presence of cheetahs decreased. The cheetahs preyed upon seven species before and 11 species after the lion re-introduction. Medium sized prey comprised the bulk of the cheetah diet with kudu (Tragelaphus strepsiceros) and springbok (Antidorcas marsupialis) being the preferred species both before and after the lion re-introduction. The lion diets consisted of medium to large sized prey, with the male lions selecting eland (Tragelaphus oryx) and buffalo (Syncerus caffer) and the lioness selecting red hartebeest (Alcelaphus buselaphus). The cheetahs had no significant dietary overlap with the lions and there was only one record of kleptoparasitism. The results of my study indicate that cheetahs are able to co-exist with lions when lions are at low densities in an enclosed reserve. The cheetahs did not experience landscape-level displacement because they made fine-scale adjustments to avoid lions within their environment. This adaptability may have important management implications for future re-introductions of cheetahs into enclosed game reserves.
- Full Text:
The effects of changing western worldviews on morals and ethics in economics: a protestant perspective
- Authors: Appalraju, Nerusha
- Date: 2017
- Subjects: Economics -- Moral and ethical aspects , Neoclassical school of economics , Capitalism -- Religious aspects -- Protestant churches , Feminist economics , Economics -- Religious aspects , Environmental economics -- Moral and ethical aspects , Smith, Adam, 1723-1790 , Weber, Max, 1864-1920
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/32480 , vital:24050
- Description: The World Economics Association held an online conference in 2012 where they published many papers on ethics in economics. The topic of ethics in economics became more serious and popular following the 2008 financial crisis. However the case for a professional code of ethics in economics is difficult to introduce and implement due to the multidisciplinary approach of the discipline. Therefore authors such as Dow (2012), De Martino (2012), Freeman (2012) and Earl (2012) urged economists to start thinking about ethics in economics from a pluralistic view. This thesis studied the effects of changing Western worldviews on morals and ethics in economics from a Protestant perspective. Numerous authoritative sources were considered and used to create a discussion and analysis of how diverse Western worldviews impact on the type of economics which is prescribed and practiced. It was found that different Western worldviews create various standards of understanding and evaluation, which result in varying opinions on what constitutes as morally or ethically acceptable within the discipline of economics.
- Full Text:
- Authors: Appalraju, Nerusha
- Date: 2017
- Subjects: Economics -- Moral and ethical aspects , Neoclassical school of economics , Capitalism -- Religious aspects -- Protestant churches , Feminist economics , Economics -- Religious aspects , Environmental economics -- Moral and ethical aspects , Smith, Adam, 1723-1790 , Weber, Max, 1864-1920
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/32480 , vital:24050
- Description: The World Economics Association held an online conference in 2012 where they published many papers on ethics in economics. The topic of ethics in economics became more serious and popular following the 2008 financial crisis. However the case for a professional code of ethics in economics is difficult to introduce and implement due to the multidisciplinary approach of the discipline. Therefore authors such as Dow (2012), De Martino (2012), Freeman (2012) and Earl (2012) urged economists to start thinking about ethics in economics from a pluralistic view. This thesis studied the effects of changing Western worldviews on morals and ethics in economics from a Protestant perspective. Numerous authoritative sources were considered and used to create a discussion and analysis of how diverse Western worldviews impact on the type of economics which is prescribed and practiced. It was found that different Western worldviews create various standards of understanding and evaluation, which result in varying opinions on what constitutes as morally or ethically acceptable within the discipline of economics.
- Full Text:
The effects of the type of rest breaks on return-to-task performance in semi-automated tasks with varying complexities
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
- Full Text:
- Authors: Hoyi, Zandile
- Date: 2017
- Subjects: Rest periods , Rest periods -- Physiological effect , Human-robot interaction , Aeronautics -- Human factors , Human engineering , Drowsiness
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/44490 , vital:25412
- Description: Automation in the aviation industry is acknowledged as a useful tool in reducing pilot workload (Hoh, Smith & Hinton, 1987; Beringer & Harris Jr., 1999). Typically, the role of the pilot (operator) shifts from active participation in a process to a task of monitoring the system with the resumption of control should the automation ‘fail’ (Byrne & Parasuraman, 1996). Unfortunately, the skills necessary to do so would likely degrade from non-use, during this process (Landry, 2012). This project investigates the “attentional demands” for the human operator during interaction with semi-automated operations of the flight. According to Dr Abbott (1996), FAA human factors specialist, one of the problems causing disharmony between crews and their automated systems is the incorrect upset recovery, owing to the human being out-of-the-loop (OOTL) from the system. Recovery, or rather return to task, is the ability of the pilot to loop back into control, once situational awareness has been decreased due to lack of alertness and a decrease in arousal. Different types of rest tasks are commonly prescribed fatigue countermeasures in the industrial setting and have been showed to elicit beneficial effects on prolonged human performance. Understanding the effects of different rest break activity and time out-of-the-loop during semi-automated flying on return to task performance has been adequately studied, thus highlighting its importance in the context of flight safety. The present study requested participants to perform a tracking task in a laboratory where they changed from activity (30 minutes) to a break (2 vs. 30 minutes) and back to the activity (20 minutes). The task varied in the complexity of the activity (pure tracking vs. tracking plus memory plus rule-based decision making), the type of break (passive rest vs. actively supervising) and the duration of the break (2 minutes vs. 30 minutes). Performance was measured as effective response time in the tracking task and number of correct responses to secondary cognitive tasks. Physiological measures included heart rate (HR), heart rate variability (HRV- time and frequency-domain), eye blink frequency and duration. The Karolinska Sleepiness Scale was used as a subjective measure. With regards to the most appropriate rest break tasks, the study concluded that active, administrative tasks, which allowed the operator to maintain some form of situational awareness by monitoring the automated system, achieved favourable effects of being more alert than the passive rest break of being disengaged from the system. In terms of the most appropriate rest break durations, the shorter duration of being out-of-the-loop from controlling the system proved to be more advantageous than the longer out-of-the-loop duration. In looking at the workload levels of arousal, the results suggest that the higher workload level is better at maintaining the alertness of operators. This study functions as a foundational framework for future investigations around the topic of human-automation interaction, looking specifically at return-to-task performance.
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The emergence of youth protest music and arts as alternative media in Zimbabwe: a Gramscian analysis
- Authors: Kabwato, Chris
- Date: 2017
- Subjects: Protest songs -- Zimbabwe , Protest poetry -- Zimbabwe , Hip-hop -- Political aspects -- Zimbabwe , Radical theater -- Zimbabwe
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/51228 , vital:26072
- Description: The primary goal of the research is to examine the reasons for the emergence of - hip-hop-based youth protest music and satirical video comedy in Zimbabwe in a context where democratic and media practice has been restricted. The study examines the strategies and platforms that the young urban-based, musicians and cultural activists employ as they contest the meta-narrative of political nationalists who control the public mass media. The study recognises culture as a site of struggle and seeks to tease out the meaning of specific art forms (‘conscious’ hip-hop music and faux-news satire) in this very specific period of Zimbabwe’s history. The study proposes that the rise of these new forms of hip-hop based protest music, poetry and satirical comedy indicate how through the production and circulation of popular culture, ordinary Africans are able to debate pertinent issues that are marginalised by the official media channels. The study thus sees these artists as organic intellectuals who use alternative media to engage with different publics as they seek to counter hegemonic discourses.
- Full Text:
The emergence of youth protest music and arts as alternative media in Zimbabwe: a Gramscian analysis
- Authors: Kabwato, Chris
- Date: 2017
- Subjects: Protest songs -- Zimbabwe , Protest poetry -- Zimbabwe , Hip-hop -- Political aspects -- Zimbabwe , Radical theater -- Zimbabwe
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/51228 , vital:26072
- Description: The primary goal of the research is to examine the reasons for the emergence of - hip-hop-based youth protest music and satirical video comedy in Zimbabwe in a context where democratic and media practice has been restricted. The study examines the strategies and platforms that the young urban-based, musicians and cultural activists employ as they contest the meta-narrative of political nationalists who control the public mass media. The study recognises culture as a site of struggle and seeks to tease out the meaning of specific art forms (‘conscious’ hip-hop music and faux-news satire) in this very specific period of Zimbabwe’s history. The study proposes that the rise of these new forms of hip-hop based protest music, poetry and satirical comedy indicate how through the production and circulation of popular culture, ordinary Africans are able to debate pertinent issues that are marginalised by the official media channels. The study thus sees these artists as organic intellectuals who use alternative media to engage with different publics as they seek to counter hegemonic discourses.
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The identification of key vulnerability components within Solomon Islands coastal communities
- Authors: Malherbe, Willem Stefanus
- Date: 2017
- Subjects: Solomon Islands -- Environmental conditions , Coastal ecology -- Solomon Islands , Island ecology -- Solomon Islands , Climatic changes -- Solomon Islands , Sociology, Urban -- Solomon Islands , Sociology, Rural -- Solomon Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21184 , http://hdl.handle.net/10962/6827
- Description: The impacts of climate change are disproportionally felt across the planet, with small island developing states some of the countries most at risk. Furthermore, climate change may compound existing problems such as over harvested resources, leading to knock-on effects on national economies. Both direct and indirect stressors may impact communities differently based on their level of exposure to stressors, their intrinsic sensitivity to these stressors, and their ability to adapt to stressors. This study aims to answer the primary research question: Why are some communities more vulnerable than others? A vulnerability assessment is used to identify both vulnerable and non-vulnerable attributes of Solomon Islands’ communities. Surveys comprised a comprehensive questionnaire to draw inference on each vulnerability category; sensitivity, exposure and adaptive capacity, along with their various components and subcomponents. An analysis of household and community livelihood strategies was conducted to compliment vulnerability scores and provide a deeper understanding of livelihood practises. As is expected of small island states, exposure presents the biggest threat to coastal communities. Within this category, environmental changes and personal exposure from shoreline erosion and safety at sea provide evidence of high vulnerability. Within the sensitivity category, the cultural importance of fishing, as well as attachment to place and fishing, renders communities more vulnerable. Simultaneously, local ecological knowledge and economic dependence on resources other than fishing proved to be resilient attributes by decreasing vulnerability. Low vulnerability scores for the adaptive capacity category were achieved by communities where physical capital, such as community infrastructure, was evident. A lack of both institutional support and bridging of social capital were attributes which contributed to community vulnerability. This study has identified key attributes that have both positive and negative effects on the vulnerability of Solomon Islands communities. Having done this, I have also attempted to determine the drivers that render some attributes more vulnerable than others. It is acknowledged that the drivers of all key attributes of vulnerability is required to determine areas where adaptation plans will be most effective. Importantly, drivers of high vulnerability should not be considered as the primary focus of adaptation planning, but also the drivers of low vulnerability, such as community cohesion, which provide resilience within communities.
- Full Text:
- Authors: Malherbe, Willem Stefanus
- Date: 2017
- Subjects: Solomon Islands -- Environmental conditions , Coastal ecology -- Solomon Islands , Island ecology -- Solomon Islands , Climatic changes -- Solomon Islands , Sociology, Urban -- Solomon Islands , Sociology, Rural -- Solomon Islands
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:21184 , http://hdl.handle.net/10962/6827
- Description: The impacts of climate change are disproportionally felt across the planet, with small island developing states some of the countries most at risk. Furthermore, climate change may compound existing problems such as over harvested resources, leading to knock-on effects on national economies. Both direct and indirect stressors may impact communities differently based on their level of exposure to stressors, their intrinsic sensitivity to these stressors, and their ability to adapt to stressors. This study aims to answer the primary research question: Why are some communities more vulnerable than others? A vulnerability assessment is used to identify both vulnerable and non-vulnerable attributes of Solomon Islands’ communities. Surveys comprised a comprehensive questionnaire to draw inference on each vulnerability category; sensitivity, exposure and adaptive capacity, along with their various components and subcomponents. An analysis of household and community livelihood strategies was conducted to compliment vulnerability scores and provide a deeper understanding of livelihood practises. As is expected of small island states, exposure presents the biggest threat to coastal communities. Within this category, environmental changes and personal exposure from shoreline erosion and safety at sea provide evidence of high vulnerability. Within the sensitivity category, the cultural importance of fishing, as well as attachment to place and fishing, renders communities more vulnerable. Simultaneously, local ecological knowledge and economic dependence on resources other than fishing proved to be resilient attributes by decreasing vulnerability. Low vulnerability scores for the adaptive capacity category were achieved by communities where physical capital, such as community infrastructure, was evident. A lack of both institutional support and bridging of social capital were attributes which contributed to community vulnerability. This study has identified key attributes that have both positive and negative effects on the vulnerability of Solomon Islands communities. Having done this, I have also attempted to determine the drivers that render some attributes more vulnerable than others. It is acknowledged that the drivers of all key attributes of vulnerability is required to determine areas where adaptation plans will be most effective. Importantly, drivers of high vulnerability should not be considered as the primary focus of adaptation planning, but also the drivers of low vulnerability, such as community cohesion, which provide resilience within communities.
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The illegal diamond trade in South Africa and its tax consequences
- Authors: Kumm-Schmidt, Megan
- Date: 2017
- Subjects: Diamond industry and trade -- South Africa , Diamond industry and trade -- Corrupt practices -- South Africa , Diamond industry and trade -- South Africa -- Taxation , Conflict diamonds -- South Africa , Income tax -- Law and legislation -- South Africa , Tax evasion -- South Africa , South Africa. Income Tax Act, 1962 , South Africa. Prevention and Combating of Corrupt Activities Act, 2004 , South Africa. Tax Administration Act, 2011 , South Africa. ǂt Value-Added Tax Act, 1991 , Kimberley Process Certification Scheme
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/4389 , vital:20656
- Description: The object of the research was to discuss the taxability of the illegal diamond trade in South Africa and to identify the consequences of not declaring income obtained from the illegal diamond trade to the South African Revenue Services. The research was conducted by means of a critical analysis of documentary data with specific reference to the Income Tax Act, the Value-Added Tax (VAT) Act, the Tax Administration Act and relevant case law. The Income Tax Act and the Value-Added Tax Act were referred to in relation to the tax consequences of the illegal diamond trade and the Tax Administration Act was used to determine the consequences of not declaring income to the South African Revenue Services. It was established that amounts received from the sale of illegal diamonds are to be included in the taxpayer's gross income, whilst in relation to income received from diamond theft it was not as clear. The MP Finance Group case held that the nature of the receipt and the way in which the transaction occurred in each individual situation will be the deciding factor as to whether or not the stolen diamonds will be taxable in the hands of the thief. The buying and selling of "blood" or stolen diamonds can amount to a trade. As there have been no definitive case decisions in South Africa, it remains unclear whether expenses relating to an illegal trade are deductible. Assuming that expenses relating to an illegal trade are deductible, the provisions of section 11(a) will apply to expenses incurred as a result of dealing in illegal diamonds and it was concluded that qualifying expenses will be deductible. A taxpayer buying and selling "blood" or stolen diamonds is required to register for VAT if sales exceed the threshold and would be required to account for VAT on these transactions. If the taxpayer does not declare the income for income tax purposes or register for and pay VAT to the South African Revenue Services from either the sale of illegal diamonds or the theft of diamonds, this will amount to tax evasion and the dealer will be subject to penalties and even imprisonment
- Full Text:
- Authors: Kumm-Schmidt, Megan
- Date: 2017
- Subjects: Diamond industry and trade -- South Africa , Diamond industry and trade -- Corrupt practices -- South Africa , Diamond industry and trade -- South Africa -- Taxation , Conflict diamonds -- South Africa , Income tax -- Law and legislation -- South Africa , Tax evasion -- South Africa , South Africa. Income Tax Act, 1962 , South Africa. Prevention and Combating of Corrupt Activities Act, 2004 , South Africa. Tax Administration Act, 2011 , South Africa. ǂt Value-Added Tax Act, 1991 , Kimberley Process Certification Scheme
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/4389 , vital:20656
- Description: The object of the research was to discuss the taxability of the illegal diamond trade in South Africa and to identify the consequences of not declaring income obtained from the illegal diamond trade to the South African Revenue Services. The research was conducted by means of a critical analysis of documentary data with specific reference to the Income Tax Act, the Value-Added Tax (VAT) Act, the Tax Administration Act and relevant case law. The Income Tax Act and the Value-Added Tax Act were referred to in relation to the tax consequences of the illegal diamond trade and the Tax Administration Act was used to determine the consequences of not declaring income to the South African Revenue Services. It was established that amounts received from the sale of illegal diamonds are to be included in the taxpayer's gross income, whilst in relation to income received from diamond theft it was not as clear. The MP Finance Group case held that the nature of the receipt and the way in which the transaction occurred in each individual situation will be the deciding factor as to whether or not the stolen diamonds will be taxable in the hands of the thief. The buying and selling of "blood" or stolen diamonds can amount to a trade. As there have been no definitive case decisions in South Africa, it remains unclear whether expenses relating to an illegal trade are deductible. Assuming that expenses relating to an illegal trade are deductible, the provisions of section 11(a) will apply to expenses incurred as a result of dealing in illegal diamonds and it was concluded that qualifying expenses will be deductible. A taxpayer buying and selling "blood" or stolen diamonds is required to register for VAT if sales exceed the threshold and would be required to account for VAT on these transactions. If the taxpayer does not declare the income for income tax purposes or register for and pay VAT to the South African Revenue Services from either the sale of illegal diamonds or the theft of diamonds, this will amount to tax evasion and the dealer will be subject to penalties and even imprisonment
- Full Text:
The impact of good news and bad news on South Africa’s sectoral stock return volatility: an asymmetric GARCH analysis
- Authors: Muzinda, Edmond Toreva
- Date: 2017
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/6425 , vital:21108
- Description: This study explores the impact of good news and bad news on South Africa’s sectoral stock return volatility using an asymmetric GARCH analysis. Understanding the different impact of news on stock return volatility in different economic sectors has important implications for investors’ risk management practices, portfolio allocation strategies and asset pricing. The study employs data of daily closing prices for nine sectors and three benchmark indices for the period 2nd January 1997 - 17th August 2016. The data was split into sub-samples of pre-, during and post-global financial crisis, as well as the overall sample period. The incorporation of sub-samples was to help explain the outcomes of the overall sample period. To capture the different impact of good news and bad news on stock return volatility for each sector, asymmetric GARCH models namely, TGARCH and EGARCH were employed. The findings from this study revealed that volatility asymmetry was present in all sectors and benchmark indices of South African equity market. Bad news had more impact on stock return volatility for all sectors except the Oil and Gas sector, than good news of the same magnitude. In the Oil and Gas sector, good news was found to have an amplified effect on return volatility compared with bad news of the same magnitude. High volatility persistence was also found to be present in the Consumer goods, Financials, Industrials, All-share index and Mid-cap index. High differential impact of good and bad news were found in the Industrials, Financials, Basic materials, Consumer goods and the All-share index. Since the main objective of this study was to provide explanations of volatility asymmetry found in the South African sectors, the following were proposed as possible explanations of the findings. Within sectors, volatility asymmetry was explained by financial leverage, the role of the media, loss-averse investors and the behaviour of traders (overconfidence and extrapolation bias). Volatility asymmetry across sectors was explained by information flow, the uneven distribution of information by the media, investor sentiments, investor expectations and trading volumes. Overall, the results indicate that the stock return volatility of individual sectors of the South African equity market is driven mainly by bad news (except for Oil and Gas) and that leverage effects exist in all the sectors and in the benchmark indices.
- Full Text:
- Authors: Muzinda, Edmond Toreva
- Date: 2017
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/6425 , vital:21108
- Description: This study explores the impact of good news and bad news on South Africa’s sectoral stock return volatility using an asymmetric GARCH analysis. Understanding the different impact of news on stock return volatility in different economic sectors has important implications for investors’ risk management practices, portfolio allocation strategies and asset pricing. The study employs data of daily closing prices for nine sectors and three benchmark indices for the period 2nd January 1997 - 17th August 2016. The data was split into sub-samples of pre-, during and post-global financial crisis, as well as the overall sample period. The incorporation of sub-samples was to help explain the outcomes of the overall sample period. To capture the different impact of good news and bad news on stock return volatility for each sector, asymmetric GARCH models namely, TGARCH and EGARCH were employed. The findings from this study revealed that volatility asymmetry was present in all sectors and benchmark indices of South African equity market. Bad news had more impact on stock return volatility for all sectors except the Oil and Gas sector, than good news of the same magnitude. In the Oil and Gas sector, good news was found to have an amplified effect on return volatility compared with bad news of the same magnitude. High volatility persistence was also found to be present in the Consumer goods, Financials, Industrials, All-share index and Mid-cap index. High differential impact of good and bad news were found in the Industrials, Financials, Basic materials, Consumer goods and the All-share index. Since the main objective of this study was to provide explanations of volatility asymmetry found in the South African sectors, the following were proposed as possible explanations of the findings. Within sectors, volatility asymmetry was explained by financial leverage, the role of the media, loss-averse investors and the behaviour of traders (overconfidence and extrapolation bias). Volatility asymmetry across sectors was explained by information flow, the uneven distribution of information by the media, investor sentiments, investor expectations and trading volumes. Overall, the results indicate that the stock return volatility of individual sectors of the South African equity market is driven mainly by bad news (except for Oil and Gas) and that leverage effects exist in all the sectors and in the benchmark indices.
- Full Text:
The influence of environmental variability on the catch of chokka, Loligo reynaudii, off the coast of South Africa
- Authors: Joyner, Jessica Mary
- Date: 2017
- Subjects: Loligo reynaudii , Loligo fisheries -- South Africa , Squid fisheries -- South Africa , Loligo fisheries -- Environmental aspects -- South Africa , Squid fisheries -- Environmental aspects - South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/32130 , vital:24013
- Description: Globally, cephalopod fisheries are being relied on more heavily due to the depletion of longer-lived teleost species. The South African chokka squid (Loligo reynaudii) fishery is a case in point. Although previously numerous squid were often caught as bycatch, the fishery has officially been in place since 1985. Since the inception of the chokka fishery in South Africa, several studies have investigated the relationship between environmental drivers and annual chokka squid catch, with varying degrees of success. Recently, in 2013, chokka squid catches hit a record low, prompting resurgence in the topic of the squid environment-catch relationship. This study was initiated in an attempt to provide a quantitative relationship between the chokka squid catch and environmental variability, and to build a predictive model that could be used in fisheries management strategies. Historical data were obtained from various sources and included the mean and standard deviation in ocean bottom temperature; the mean and standard deviation in sea surface temperature; the maximum and minimum as well as the variation in wind speed; the mean, predominant and standard deviation in wind direction; the mean and standard deviation in atmospheric pressure; the mean chlorophyll concentration; the number of upwelling events; the hours of easterly winds blowing per day; and two large variation-in-climate indices, namely, the oceanic Nino index and the Antarctic Oscillation index. The monthly catch data were also provided. These data were initially analysed for inter-annual and intra-annual cyclic trends and followed by analysis of the delay in response of catch to the environmental variables, anticipating some impact on the different stages of the chokka life cycle. These lagged data were incorporated into a negative binomial generalised linear model, as well as a generalised additive model, which revealed a strong relationship (r²=0.707) between the catch and environmental variability. The inclusion of all the parameters was necessary; however, the mean bottom temperature and the standard deviation in sea surface temperature were the only parameters that had a significant effect on the catch. These results were used to build a predictive model that indicated that, although the relationship was strong, the ability of the model to predict catch was weak, particularly from the year 2005 onwards.
- Full Text:
- Authors: Joyner, Jessica Mary
- Date: 2017
- Subjects: Loligo reynaudii , Loligo fisheries -- South Africa , Squid fisheries -- South Africa , Loligo fisheries -- Environmental aspects -- South Africa , Squid fisheries -- Environmental aspects - South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/32130 , vital:24013
- Description: Globally, cephalopod fisheries are being relied on more heavily due to the depletion of longer-lived teleost species. The South African chokka squid (Loligo reynaudii) fishery is a case in point. Although previously numerous squid were often caught as bycatch, the fishery has officially been in place since 1985. Since the inception of the chokka fishery in South Africa, several studies have investigated the relationship between environmental drivers and annual chokka squid catch, with varying degrees of success. Recently, in 2013, chokka squid catches hit a record low, prompting resurgence in the topic of the squid environment-catch relationship. This study was initiated in an attempt to provide a quantitative relationship between the chokka squid catch and environmental variability, and to build a predictive model that could be used in fisheries management strategies. Historical data were obtained from various sources and included the mean and standard deviation in ocean bottom temperature; the mean and standard deviation in sea surface temperature; the maximum and minimum as well as the variation in wind speed; the mean, predominant and standard deviation in wind direction; the mean and standard deviation in atmospheric pressure; the mean chlorophyll concentration; the number of upwelling events; the hours of easterly winds blowing per day; and two large variation-in-climate indices, namely, the oceanic Nino index and the Antarctic Oscillation index. The monthly catch data were also provided. These data were initially analysed for inter-annual and intra-annual cyclic trends and followed by analysis of the delay in response of catch to the environmental variables, anticipating some impact on the different stages of the chokka life cycle. These lagged data were incorporated into a negative binomial generalised linear model, as well as a generalised additive model, which revealed a strong relationship (r²=0.707) between the catch and environmental variability. The inclusion of all the parameters was necessary; however, the mean bottom temperature and the standard deviation in sea surface temperature were the only parameters that had a significant effect on the catch. These results were used to build a predictive model that indicated that, although the relationship was strong, the ability of the model to predict catch was weak, particularly from the year 2005 onwards.
- Full Text:
The interaction of selected bacteria with tailored electrospun fibres: towards future applications in bioremediation, bacterial inactivation and electricity generation
- Authors: Mfuku, Aphiwe
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65123 , vital:28693
- Description: Expected release date-May 2019
- Full Text:
- Authors: Mfuku, Aphiwe
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/65123 , vital:28693
- Description: Expected release date-May 2019
- Full Text:
The medical profession and the universalisation of South African Health Care: analysing the response of Eastern Cape general practitioners to the National Health Insurance proposals
- Authors: Hannah, Bridget
- Date: 2017
- Subjects: Health insurance -- South Africa , Health insurance -- Government policy -- South Africa , Medical care, Cost of -- South Africa , National health insurance -- South Africa , Medical policy -- South Africa , Physicians -- South Africa -- Attitudes
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/6075 , vital:21029
- Description: In 2011, the Green Paper on National Health Insurance (NHI) in South Africa was released, committing the South African government to a 14-year plan to radically transform the currently inequitable health system towards providing comprehensive quality health care free at point of access to all citizens. The pursuit of universal health coverage (UHC) in South Africa forms part of a global aspiration to achieve more equitable healthcare delivery. One of the critical issues emerging from the Green Paper was how the NHI would be staffed. The NHI is unlikely to be adequately staffed without GPs but evidence suggests that private sector doctors have always been resistant to nationalisation or socialisation as a threat to their occupational power and professional status. The core work of this thesis is a study undertaken of 78 doctors in the Eastern Cape, focusing on private sector general practitioners (GPs), as the largest constituency of medical professionals in the country. The interview schedule was designed to gauge doctors' responses to the NHI, encourage discussion on their reactions to the reforms, and its implications in their view for private medical practice. The responses of the doctors are analysed through application of two theoretical themes, namely: (i) actor-centred policy creation, discussed through application of Walt and Gilson's (1994) shared focus on content, context, process and actors in the policy process, and (ii) the debate on medical professionalism, espoused by Freidson (1973, 1994) and argued against by Haug and Sussman (1969), and McKinlay (1972, 1993). Thus, if the process of policy making must take into account key actors in order to deliver a successful policy transition, what are the implications if these actors are actively excluded, or do not willingly cooperate? Does this indicate anything telling about the private sector's role to play in the pursuit of universal healthcare?
- Full Text:
- Authors: Hannah, Bridget
- Date: 2017
- Subjects: Health insurance -- South Africa , Health insurance -- Government policy -- South Africa , Medical care, Cost of -- South Africa , National health insurance -- South Africa , Medical policy -- South Africa , Physicians -- South Africa -- Attitudes
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/6075 , vital:21029
- Description: In 2011, the Green Paper on National Health Insurance (NHI) in South Africa was released, committing the South African government to a 14-year plan to radically transform the currently inequitable health system towards providing comprehensive quality health care free at point of access to all citizens. The pursuit of universal health coverage (UHC) in South Africa forms part of a global aspiration to achieve more equitable healthcare delivery. One of the critical issues emerging from the Green Paper was how the NHI would be staffed. The NHI is unlikely to be adequately staffed without GPs but evidence suggests that private sector doctors have always been resistant to nationalisation or socialisation as a threat to their occupational power and professional status. The core work of this thesis is a study undertaken of 78 doctors in the Eastern Cape, focusing on private sector general practitioners (GPs), as the largest constituency of medical professionals in the country. The interview schedule was designed to gauge doctors' responses to the NHI, encourage discussion on their reactions to the reforms, and its implications in their view for private medical practice. The responses of the doctors are analysed through application of two theoretical themes, namely: (i) actor-centred policy creation, discussed through application of Walt and Gilson's (1994) shared focus on content, context, process and actors in the policy process, and (ii) the debate on medical professionalism, espoused by Freidson (1973, 1994) and argued against by Haug and Sussman (1969), and McKinlay (1972, 1993). Thus, if the process of policy making must take into account key actors in order to deliver a successful policy transition, what are the implications if these actors are actively excluded, or do not willingly cooperate? Does this indicate anything telling about the private sector's role to play in the pursuit of universal healthcare?
- Full Text:
The pest status and integrated management programme of carob moth, Ectomyelois ceratoniae Zeller, attacking citrus in South Africa
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
- Authors: Thackeray, Sean Robin
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/7758 , vital:21293
- Description: The carob moth, Ectomyelois ceratoniae Zeller, is a pest of agricultural commodities and stored products around the world. Carob moth is known to infest citrus in the Mediterranean region and in southern Africa. In grapefruit cultivars, carob moth infestations are associated with high levels of mealybug. However, although this relationship has been observed in other citrus types such as Navel oranges, this has never been quantified. A recent survey of infested fruit from various production areas in South Africa indicated that the pest status of carob moth on Navel oranges may have been underestimated. As a result of the incidental pest status of carob moth on citrus in South Africa in the past, a species specific integrated pest management (IPM) programme does not exist. Therefore, the overriding aim of this theses was to evaluate the pest status of carob moth in citrus and establish a species specific IPM programme by determine the autecology of carob moth in citrus. Reliable methods for monitoring carob moth in citrus orchards both for producers and for research purposes were developed. A user-friendly monitoring method for determining weekly carob moth infestation through dropped fruit was suitable for producers. A timed scouting method was also developed; although the accuracy of this method varied with the experience of the scout. The pest status of carob moth was highest in the Loskop Valley, Nelspruit and the Vaalharts production areas and economic injury to growers ranged from R512.35 to R3 719.80 per hectare as a direct result of infestation. No infestation was recorded in the Sundays River Valley and Citrusdal production areas over both the 2014-15 and 201516 growing seasons. A laboratory study showed the survival of carob moth larvae infesting citrus is less than 10% in the absence of mealybug. However, this increases to almost 40% in the presence of mealybug residues and sooty mould. There was a significant relationship between carob infestation at harvest and mealybug infestation in the middle months of the growing season. The relationship between carob moth and mealybug indicates that current production guidelines for the management of mealybug in citrus may need to be amended. Consequently, it is proposed that an orchard with a history of carob moth infestation and a high mealybug infestation in the previous season should be subjected to an early season preventative application of a registered control product. Also, if mealybug infestation in December is higher than a 5% of fruit per tree, then a corrective application of a registered product is recommended. The application of 2,4-D at petal drop reduced the size of the navel-end opening, decreasing the proportion of mealybug found in the navel-end, subsequently reducing carob moth infestation, resulting in a direct benefit for producers. Products registered for the control of false codling moth (FCM), Thaumatotibia leucotreta Meyrick, were effective in reducing carob moth infestation. In a spray trial conducted over two seasons, Delegate® and Runner® reduced infestation significantly in the 2014-15 season (over 80%), while only Delegate® was effective in the 2015-16 season (over 80%). If a late season corrective chemical application is targeted at both FCM and carob moth, this application should take place between 6-7 weeks prior to harvest. The mating disruption product, SPLAT® EC, reduced carob moth infestation by 70% compared to the untreated control. A laboratory culture was established and head-capsule size categories were determined for all five carob moth instars. A parasitoid survey indicated that parasitism of carob moth larvae is generally less than 5% in citrus orchards and a new species of Braconidae was described as Phanterotoma carobivora van Achterberg and Thackeray. Carob moth fifth instar were found to be the most cold-tolerant larval stage, and were shown to be more cold susceptible than the most cold-tolerant FCM instars at -0.55ºC for eighteen days. This cold treatment resulted in a mortality of 94.6% fifth instar carob moth compared to a combined fourth and fifth instar mortality of 87.8% for FCM after eighteen days. These results indicate that post-harvest cold treatments targeting FCM will be as, if not more, effective against carob moth, suggesting that current phytosanitary legislation for carob moth should be amended to incorporate this study’s findings.
- Full Text:
The potential of hydrellia egeriae rodrigues (diptera: ephydridae) as a biocontrol agent for egeria densa planch. (hydrocharitaceae) in South Africa
- Authors: Smith, Rosali
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53733 , vital:26314
- Description: The integrity of South Africa’s valuable freshwater ecosystems has been threatened by aquatic invasive plants since the 1900s. Floating aquatic weeds, such as Eichhornia crassipes (C. Mart) Solms (Pondederiaceae), Pistia stratiotes L. (Araceae), Salvinia molesta D.S. Mitchell (Salviniaceae), Azolla filiculoides Lam. (Azollaceae), and the emergent weed, Myriophyllum aquaticum Verdc. (Haloragaceae) benefited from open, nutrient-rich water bodies. Due to the limitations of mechanical and chemical control in aquatic environments, classical biological control has been a huge asset in managing these weeds; consequently bringing them under complete or substantial control. However, submerged aquatic weeds are widely distributed through the aquarium trade in South Africa; facilitating their invasion into new habitats. The removal of surface mats following the successful management of floating weeds has enhanced the growth and competitive ability of submerged aquatic weeds, such as Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae) and Egeria densa Planch. (Hydrocharitaceae) in South Africa. Of these species, E. densa has become the most widely distributed, invading numerous systems across South Africa. Compared to other exotic submerged aquatic plants, E. densa is the only species capable of inhabiting freshwater systems in every province and therefore, it is vital to manage existing populations and prevent its further distribution and invasion. Hydrellia spp. (Diptera: Ephydridae) biological control agents have been used extensively in the management of submerged aquatic weeds elsewhere, particularly those in the Hydrocharitaceae (Balciunas and Burrows 1996; Wheeler and Center 2001. Hydrellia egeriae Rodrigues (Diptera: Ephydridae) has been identified as a promising candidate for E. densa and was imported into quarantine at Rhodes University, Grahamstown in 2014. The aims of this study were to conduct a pre-release assessment of the potential of H. egeriae as a biological control agent for E. densa in South Africa. The first objective of this study was to establish the life history of the agent under controlled conditions on E. densa found in South Africa, as well as its population growth parameters to predict its invasion success in the field. Secondly, laboratory host-specificity testing was conducted to validate the host range of the agent, in view of published native range host-specificity testing, and to establish potential risks to non-target species, should it be released. Finally, a biological control agent should also effectively reduce the fitness of its host plant, and therefore, impact studies were conducted. Laboratory impact studies have been limited in the past, in that they only investigate agent damage for short ecological periods, thus underestimating the damage capacity of the agent under investigation. Therefore, the damage capacity of H. egeriae was investigated over three consecutive generations in multi-generational impact trials. In a controlled environment of 22 ± 2°C, H. egeriae exhibited the ability to rapidly increase in population size within a short period of time, which will enhance agent establishment and build-up in the field. Host-specificity trials indicated that H. egeriae has a host range restricted to the Hydrocharitaceae, with exploratory feeding and development on Lagarosiphon major Ridley, L. muscoides Harvey and Vallisneria spiralis L. However, only L. major supported agent development during paired larval choice tests, and continuation trials showed that the test species was not physiologically capable of supporting viable agent populations. Risk analysis illustrated that the feeding and reproductive risks that H. egeriae pose to non-target species are very low and therefore, H. egeriae should be safe for release in South Africa. Additionally, significant damage to vital plant structures (shoot growth and side shoot length) was only recorded under high (five larvae) agent abundances. Encouragingly, the number of leaves mined at the end of the experiment was similar for both intermediate (three) and high (five) larval abundances, suggesting that cumulative leaf-mining under intermediate larval abundances has the potential to reduce the fitness of E. densa, given sufficient time. Results from pre-release assessments provide a robust understanding of the specialization of the potential biological control agent to its host plant. Nevertheless, the absolute success of a biological control programme depends on the many factors after prerelease assessments that determine agent establishment, persistence and target weed suppression, e.g. mass-rearing, release protocols and a/biotic factors within the recipient community. Considering these factors, the best mass-rearing and release protocols are proposed here and future research priorities are identified. Finally, the long term success for managing E. densa in South Africa will require a holistic approach to address the underlying factors, such as eutrophication and human-mediated distribution that drive submerged aquatic plant invasions.
- Full Text:
- Authors: Smith, Rosali
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/53733 , vital:26314
- Description: The integrity of South Africa’s valuable freshwater ecosystems has been threatened by aquatic invasive plants since the 1900s. Floating aquatic weeds, such as Eichhornia crassipes (C. Mart) Solms (Pondederiaceae), Pistia stratiotes L. (Araceae), Salvinia molesta D.S. Mitchell (Salviniaceae), Azolla filiculoides Lam. (Azollaceae), and the emergent weed, Myriophyllum aquaticum Verdc. (Haloragaceae) benefited from open, nutrient-rich water bodies. Due to the limitations of mechanical and chemical control in aquatic environments, classical biological control has been a huge asset in managing these weeds; consequently bringing them under complete or substantial control. However, submerged aquatic weeds are widely distributed through the aquarium trade in South Africa; facilitating their invasion into new habitats. The removal of surface mats following the successful management of floating weeds has enhanced the growth and competitive ability of submerged aquatic weeds, such as Hydrilla verticillata (L.f.) Royle (Hydrocharitaceae), Myriophyllum spicatum L. (Haloragaceae) and Egeria densa Planch. (Hydrocharitaceae) in South Africa. Of these species, E. densa has become the most widely distributed, invading numerous systems across South Africa. Compared to other exotic submerged aquatic plants, E. densa is the only species capable of inhabiting freshwater systems in every province and therefore, it is vital to manage existing populations and prevent its further distribution and invasion. Hydrellia spp. (Diptera: Ephydridae) biological control agents have been used extensively in the management of submerged aquatic weeds elsewhere, particularly those in the Hydrocharitaceae (Balciunas and Burrows 1996; Wheeler and Center 2001. Hydrellia egeriae Rodrigues (Diptera: Ephydridae) has been identified as a promising candidate for E. densa and was imported into quarantine at Rhodes University, Grahamstown in 2014. The aims of this study were to conduct a pre-release assessment of the potential of H. egeriae as a biological control agent for E. densa in South Africa. The first objective of this study was to establish the life history of the agent under controlled conditions on E. densa found in South Africa, as well as its population growth parameters to predict its invasion success in the field. Secondly, laboratory host-specificity testing was conducted to validate the host range of the agent, in view of published native range host-specificity testing, and to establish potential risks to non-target species, should it be released. Finally, a biological control agent should also effectively reduce the fitness of its host plant, and therefore, impact studies were conducted. Laboratory impact studies have been limited in the past, in that they only investigate agent damage for short ecological periods, thus underestimating the damage capacity of the agent under investigation. Therefore, the damage capacity of H. egeriae was investigated over three consecutive generations in multi-generational impact trials. In a controlled environment of 22 ± 2°C, H. egeriae exhibited the ability to rapidly increase in population size within a short period of time, which will enhance agent establishment and build-up in the field. Host-specificity trials indicated that H. egeriae has a host range restricted to the Hydrocharitaceae, with exploratory feeding and development on Lagarosiphon major Ridley, L. muscoides Harvey and Vallisneria spiralis L. However, only L. major supported agent development during paired larval choice tests, and continuation trials showed that the test species was not physiologically capable of supporting viable agent populations. Risk analysis illustrated that the feeding and reproductive risks that H. egeriae pose to non-target species are very low and therefore, H. egeriae should be safe for release in South Africa. Additionally, significant damage to vital plant structures (shoot growth and side shoot length) was only recorded under high (five larvae) agent abundances. Encouragingly, the number of leaves mined at the end of the experiment was similar for both intermediate (three) and high (five) larval abundances, suggesting that cumulative leaf-mining under intermediate larval abundances has the potential to reduce the fitness of E. densa, given sufficient time. Results from pre-release assessments provide a robust understanding of the specialization of the potential biological control agent to its host plant. Nevertheless, the absolute success of a biological control programme depends on the many factors after prerelease assessments that determine agent establishment, persistence and target weed suppression, e.g. mass-rearing, release protocols and a/biotic factors within the recipient community. Considering these factors, the best mass-rearing and release protocols are proposed here and future research priorities are identified. Finally, the long term success for managing E. densa in South Africa will require a holistic approach to address the underlying factors, such as eutrophication and human-mediated distribution that drive submerged aquatic plant invasions.
- Full Text:
The principle of distinction and modern armed conflicts: a critical analysis of the protection regime based on the distinction between civilians and combatants under international humanitarian law
- Authors: Chigowe, Lloyd Tonderai
- Date: 2017
- Subjects: Humanitarian law , Military art and science -- Law and legislation , Combatants and noncombatants (International law) , Military law , National security -- Law and legislation , Private military companies (International law) , Human rights -- International cooperation , Soft law
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10962/4668 , vital:20710
- Description: This thesis interrogates the applicability of the principle of distinction in modern armed conflicts. The distinction between combatants and civilians and between civilian objects and military objectives has become blurred as a result of the changes that have taken place in modern armed conflicts. While the principle of distinction was tailor made to regulate traditional, conventional armed conflicts, an evolution in the nature, means and methods of warfare has made the application of the principle of distinction challenging. One of the challenges that arise as a result of the changes that have taken place in modern armed conflicts include the difficulty of distinguishing civilians and civilian objects, which are entitled to protection under international humanitarian law from combatants and military objectives which are legitimate targets. This has compromised the protection that the law seeks to offer during armed conflicts since civilians and civilian objects have become constant targets. Another challenge is that the involvement of civilian persons in armed conflicts has made it difficult to determine the responsibility of these individuals as well as the states that hire them for violations of international law during armed conflicts. Furthermore, the emergence of new methods of warfare has resulted in many objects and facilities that are traditionally regarded as civilian objects becoming military objectives, thus losing their protection under international humanitarian law. This thesis will use the examples of the involvement of private military and security companies in armed conflicts as well as the emergence of drone and cyber warfare to illustrate these challenges. The study will examine the application of the principle of distinction to the growing practice of outsourcing of military services to Private Military and Security Companies. Firstly, the study will examine the status of PMSC personnel under the principle of distinction, that is whether they qualify as combatants or civilians. The study will then examine the consequences of PMSC personnel’s participation in armed conflicts. Importantly, the study will explore responsibilities of states that hire private military and security personnel, PMSC companies as well as superiors in charge of PMSC personnel for any violation of international law committed by contractors during armed conflicts. The study will also examine the application of the principle of distinction to drone and cyber warfare. The study will examine the status of drone and cyber operators under the principle of distinction as well as the applicability of the principle of distinction between civilian objects and military objectives in drone and cyber warfare. The study will discuss some of the problems that arise as result of the introduction of these new methods of warfare, which makes the application of the principle of distinction to modern armed conflicts challenging. The thesis concludes by arguing that while the principle of distinction remains an indispensable concept of international humanitarian law, it needs to be adapted for it to be applicable to modern armed conflicts. Therefore, suggestions shall be made on how the principle can be adapted to ensure that it remains relevant to modern armed conflicts.
- Full Text:
- Authors: Chigowe, Lloyd Tonderai
- Date: 2017
- Subjects: Humanitarian law , Military art and science -- Law and legislation , Combatants and noncombatants (International law) , Military law , National security -- Law and legislation , Private military companies (International law) , Human rights -- International cooperation , Soft law
- Language: English
- Type: Thesis , Masters , LLM
- Identifier: http://hdl.handle.net/10962/4668 , vital:20710
- Description: This thesis interrogates the applicability of the principle of distinction in modern armed conflicts. The distinction between combatants and civilians and between civilian objects and military objectives has become blurred as a result of the changes that have taken place in modern armed conflicts. While the principle of distinction was tailor made to regulate traditional, conventional armed conflicts, an evolution in the nature, means and methods of warfare has made the application of the principle of distinction challenging. One of the challenges that arise as a result of the changes that have taken place in modern armed conflicts include the difficulty of distinguishing civilians and civilian objects, which are entitled to protection under international humanitarian law from combatants and military objectives which are legitimate targets. This has compromised the protection that the law seeks to offer during armed conflicts since civilians and civilian objects have become constant targets. Another challenge is that the involvement of civilian persons in armed conflicts has made it difficult to determine the responsibility of these individuals as well as the states that hire them for violations of international law during armed conflicts. Furthermore, the emergence of new methods of warfare has resulted in many objects and facilities that are traditionally regarded as civilian objects becoming military objectives, thus losing their protection under international humanitarian law. This thesis will use the examples of the involvement of private military and security companies in armed conflicts as well as the emergence of drone and cyber warfare to illustrate these challenges. The study will examine the application of the principle of distinction to the growing practice of outsourcing of military services to Private Military and Security Companies. Firstly, the study will examine the status of PMSC personnel under the principle of distinction, that is whether they qualify as combatants or civilians. The study will then examine the consequences of PMSC personnel’s participation in armed conflicts. Importantly, the study will explore responsibilities of states that hire private military and security personnel, PMSC companies as well as superiors in charge of PMSC personnel for any violation of international law committed by contractors during armed conflicts. The study will also examine the application of the principle of distinction to drone and cyber warfare. The study will examine the status of drone and cyber operators under the principle of distinction as well as the applicability of the principle of distinction between civilian objects and military objectives in drone and cyber warfare. The study will discuss some of the problems that arise as result of the introduction of these new methods of warfare, which makes the application of the principle of distinction to modern armed conflicts challenging. The thesis concludes by arguing that while the principle of distinction remains an indispensable concept of international humanitarian law, it needs to be adapted for it to be applicable to modern armed conflicts. Therefore, suggestions shall be made on how the principle can be adapted to ensure that it remains relevant to modern armed conflicts.
- Full Text:
The relationship between OCT4 and an aggressive phenotype in triple negative breast cancer (TNBC)
- Authors: Jackson, Hayley Claire
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59209 , vital:27477
- Description: Expected release date-April 2019
- Full Text:
- Authors: Jackson, Hayley Claire
- Date: 2017
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/59209 , vital:27477
- Description: Expected release date-April 2019
- Full Text:
The response of microalgal biomass and community composition to the chemical and physical dynamics of two Eastern Cape estuaries
- Authors: Cotiyane, Phumlile L
- Date: 2017
- Subjects: Estuarine plants -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Phytoplankton -- South Africa -- Eastern Cape , Algal blooms -- South Africa -- Eastern Cape , Algal blooms -- Monitoring-- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4999 , vital:20751
- Description: Water quality characteristics of estuaries are influenced by both natural and anthropogenic activities. Estuaries situated in coastal urban areas are exposed to more perturbations than those in rural settings. This study determined the drivers of phytoplankton biomass and community composition in two Eastern Cape estuaries and evaluated the anthropogenic activities that influence the overall health of each estuary. The estuaries were sampled in summer and winter (2014, 2015). The water quality of the estuaries was determined by measuring the variability in physico-chemical parameters (salinity, temperature, dissolved oxygen and pH), nutrients, phytoplankton biomass and composition and faecal bacteria. Results show that both Mngazana and Nahoon are well oxygenated (~ 6.0 mg l-¹) and are saline systems (~ 35 ppt) due to low freshwater inputs into both estuaries. Mngazana Estuary exhibited low nutrient inputs along the length of the estuary including Creeks 1 and 2 with low chlorophyll a (4.0 ± 0.2 µg Chl-a r¹) being recorded during this study while Nahoon Estuary had an overall chlorophyll a of 3.5 ± 0.3 µg Chl-a r¹. The two estuaries were dominated by flagellates with phytoplankton blooms recorded seasonally. Possible eutrophic conditions were evident along the upper reaches of Nahoon indicated by nutrient accumulation and by the presence of cyanobacteria. This also this reflected the possible anthropogenic nutrient inputs originating from the Nahoon catchment despite the low freshwater inflow. The presence of faecal bacteria counts along both estuaries indicates the need for further investigation into the source of faecal contamination. The use of nutrient analyses and phytoplankton composition during this study enabled a clear description of the water characteristics of the investigated estuaries. Furthermore, the need for the adherence to freshwater flow requirements of estuaries to limit the dominance of marine waters was clearly illustrated. Urban runoff due to impervious surfaces increases nutrient inputs into estuaries while rural use of estuarine waters introduces contaminants into the system; coupled with low freshwater inputs and eutrophic conditions, the deterioration of estuarine water quality over time demonstrates the need for effective monitoring of these systems.
- Full Text:
- Authors: Cotiyane, Phumlile L
- Date: 2017
- Subjects: Estuarine plants -- South Africa -- Eastern Cape , Estuarine ecology -- South Africa -- Eastern Cape , Phytoplankton -- South Africa -- Eastern Cape , Algal blooms -- South Africa -- Eastern Cape , Algal blooms -- Monitoring-- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4999 , vital:20751
- Description: Water quality characteristics of estuaries are influenced by both natural and anthropogenic activities. Estuaries situated in coastal urban areas are exposed to more perturbations than those in rural settings. This study determined the drivers of phytoplankton biomass and community composition in two Eastern Cape estuaries and evaluated the anthropogenic activities that influence the overall health of each estuary. The estuaries were sampled in summer and winter (2014, 2015). The water quality of the estuaries was determined by measuring the variability in physico-chemical parameters (salinity, temperature, dissolved oxygen and pH), nutrients, phytoplankton biomass and composition and faecal bacteria. Results show that both Mngazana and Nahoon are well oxygenated (~ 6.0 mg l-¹) and are saline systems (~ 35 ppt) due to low freshwater inputs into both estuaries. Mngazana Estuary exhibited low nutrient inputs along the length of the estuary including Creeks 1 and 2 with low chlorophyll a (4.0 ± 0.2 µg Chl-a r¹) being recorded during this study while Nahoon Estuary had an overall chlorophyll a of 3.5 ± 0.3 µg Chl-a r¹. The two estuaries were dominated by flagellates with phytoplankton blooms recorded seasonally. Possible eutrophic conditions were evident along the upper reaches of Nahoon indicated by nutrient accumulation and by the presence of cyanobacteria. This also this reflected the possible anthropogenic nutrient inputs originating from the Nahoon catchment despite the low freshwater inflow. The presence of faecal bacteria counts along both estuaries indicates the need for further investigation into the source of faecal contamination. The use of nutrient analyses and phytoplankton composition during this study enabled a clear description of the water characteristics of the investigated estuaries. Furthermore, the need for the adherence to freshwater flow requirements of estuaries to limit the dominance of marine waters was clearly illustrated. Urban runoff due to impervious surfaces increases nutrient inputs into estuaries while rural use of estuarine waters introduces contaminants into the system; coupled with low freshwater inputs and eutrophic conditions, the deterioration of estuarine water quality over time demonstrates the need for effective monitoring of these systems.
- Full Text: