The effect of load and technique on biomechanical and psychophysical responses to level dynamic pushing and pulling
- Authors: Bennett, Anthea Iona
- Date: 2009
- Subjects: Work -- Physiological aspects , Human engineering -- Case studies , Lifting and carrying -- Case studies , Biomechanics -- Case studies , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5110 , http://hdl.handle.net/10962/d1005188 , Work -- Physiological aspects , Human engineering -- Case studies , Lifting and carrying -- Case studies , Biomechanics -- Case studies , Musculoskeletal system -- Wounds and injuries
- Description: Pushing and pulling research has yet to fully elucidate the demands placed on manual workers despite established epidemiological links to musculoskeletal disorders. The current study therefore aimed to quantify biomechanical and perceptual responses of male operators to dynamic pushing and pulling tasks. Three common push/pull techniques (pushing, one handed and two handed pulling) were performed at loads of 250kg and 500kg using an industrial pallet jack in a laboratory environment. Thirty six healthy male subjects (age: 21 ±2 years, stature: 1791 ±43 mm and body mass: 77 ±10 kg) were required to perform six loaded experimental and two unloaded control conditions. Hand force exertion, muscle activity and gait pattern responses were collected during 10m push/pull trials on a coefficient controlled walkway; body discomfort was assessed on completion of the condition. Horizontal hand force responses were significantly (p<0.05) affected by load, with a linear relationship existing between the two. This relationship is determined by specific environmental and trolley factors and is context specific, depending on factors such as trolley maintenance and type of flooring. Hand force exertion responses were tenuously affected by technique at higher loads in the initial and sustained phases, with pushing inducing the greatest hand forces. Comparison of the motion phases revealed significant differences between all three phases, with the initial phase evidencing the greatest hand forces. Muscle activity responses demonstrated that unloaded backward walking evoked significantly higher muscle activation than did unloaded forward walking whilst increased muscular activity during load movement compared to unloaded walking was observed. However increasing load from 250kg to 500kg did not significantly impact the majority of muscle activity responses. When considering technique effects on muscle activity, of the significant differences found, all indicated that pushing imposed the least demand on the musculoskeletal system. Gait pattern responses were not significantly affected by load/technique combinations and were similar to those elicited during normal, unloaded walking. Perceptually, increased load led to increased perception of discomfort while pushing resulted in the least discomfort at both loads. From these psychophysical responses, the calves, shoulders and biceps were identified as areas of potential musculoskeletal injury, particularly during one and two handed pulling. Pushing elicited the highest hand forces and the lowest muscle activity responses in the majority of the conditions whilst psychophysical responses identified this technique as most satisfactory. Current results advocate the use of pushing when moving a load using a wheeled device. Suitability of one and two handed pulling remains contradictory, however results suggest that one handed pulling be employed at lower loads and two handed pulling at higher loads.
- Full Text:
- Authors: Bennett, Anthea Iona
- Date: 2009
- Subjects: Work -- Physiological aspects , Human engineering -- Case studies , Lifting and carrying -- Case studies , Biomechanics -- Case studies , Musculoskeletal system -- Wounds and injuries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5110 , http://hdl.handle.net/10962/d1005188 , Work -- Physiological aspects , Human engineering -- Case studies , Lifting and carrying -- Case studies , Biomechanics -- Case studies , Musculoskeletal system -- Wounds and injuries
- Description: Pushing and pulling research has yet to fully elucidate the demands placed on manual workers despite established epidemiological links to musculoskeletal disorders. The current study therefore aimed to quantify biomechanical and perceptual responses of male operators to dynamic pushing and pulling tasks. Three common push/pull techniques (pushing, one handed and two handed pulling) were performed at loads of 250kg and 500kg using an industrial pallet jack in a laboratory environment. Thirty six healthy male subjects (age: 21 ±2 years, stature: 1791 ±43 mm and body mass: 77 ±10 kg) were required to perform six loaded experimental and two unloaded control conditions. Hand force exertion, muscle activity and gait pattern responses were collected during 10m push/pull trials on a coefficient controlled walkway; body discomfort was assessed on completion of the condition. Horizontal hand force responses were significantly (p<0.05) affected by load, with a linear relationship existing between the two. This relationship is determined by specific environmental and trolley factors and is context specific, depending on factors such as trolley maintenance and type of flooring. Hand force exertion responses were tenuously affected by technique at higher loads in the initial and sustained phases, with pushing inducing the greatest hand forces. Comparison of the motion phases revealed significant differences between all three phases, with the initial phase evidencing the greatest hand forces. Muscle activity responses demonstrated that unloaded backward walking evoked significantly higher muscle activation than did unloaded forward walking whilst increased muscular activity during load movement compared to unloaded walking was observed. However increasing load from 250kg to 500kg did not significantly impact the majority of muscle activity responses. When considering technique effects on muscle activity, of the significant differences found, all indicated that pushing imposed the least demand on the musculoskeletal system. Gait pattern responses were not significantly affected by load/technique combinations and were similar to those elicited during normal, unloaded walking. Perceptually, increased load led to increased perception of discomfort while pushing resulted in the least discomfort at both loads. From these psychophysical responses, the calves, shoulders and biceps were identified as areas of potential musculoskeletal injury, particularly during one and two handed pulling. Pushing elicited the highest hand forces and the lowest muscle activity responses in the majority of the conditions whilst psychophysical responses identified this technique as most satisfactory. Current results advocate the use of pushing when moving a load using a wheeled device. Suitability of one and two handed pulling remains contradictory, however results suggest that one handed pulling be employed at lower loads and two handed pulling at higher loads.
- Full Text:
The workload of flight attendants during short-haul flight operations: a system analysis
- Authors: Bennett, Chloe Kayla
- Date: 2020
- Subjects: Flight attendants -- Health and hygiene , Employees -- South Africa -- Workload
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123431 , vital:35437
- Description: Background and aim: Flight attendants forms a significant part in 24-hour aviation industry. Flight attendant fatigue is a significant problem in the aviation industry as it continues to jeopardize the ability to fulfil important safety and security roles which is critical in performance duty of a flight attendant. However, little attention has been accomplished to the workload, working conditions and fatigue of flight attendants crew in transport aircraft. In addition, there is currently less research that have also embraced the problematic of smaller regional/commercial operation (short-haul flight operations) inducing fatigue among short-haul flight attendants as the nature of this operation are often characterised with high productivity expectations in a demanding environment with high time pressures resulting in high workloads and fatigue. Thus, flight attendant fatigue and workload is a worldwide challenge in this operational environment and less attention has been given to the determining factors. Therefore, the aim of the study was to determine the workload factors contributing to flight attendant fatigue during short-haul flight operations. Methods (System analysis): To achieve the research aim, the work system analysis, based on the Smith and Carayon-Sainfort model was chosen as the main research approach which was conducted in two ways; based on existing literature and secondly based on expert interviews. This method provided a systemic aspect to understand the whole work system of flight attendants work during short-haul operations in order to identify all the contributing factors to flight attendant fatigue and workload. Results: The literature analysis and the data from the expert interviews highlighted significant findings to flight attendant fatigue and workload. The reasons for flight attendant fatigue operating short-haul flights can be found at organizational, task, individual, environmental levels and tools and technologies and due to the interaction of the factors. The main factors of flight attendants’ fatigue are thought primarily as a function of scheduling due to irregular, mixed schedules with early starts and late finishes, extended duty days (long working hours), as well as high workload, due to the short turnaround flights, the number of sectors flown in a single duty period and duty length and high jobs demands. In addition, flight duty and rest regulations, confined work space in the cabin, vibrations, noise and lighting, sleeping in an unfamiliar environment, family responsibilities all add to additional stress placed on the body which can influence workload and sleep and consequently influencing fatigue. Conclusion: Overall the study determined that flight attendant fatigue is a significant problem in modern industry of short-haul operations. Using this systematic approach (work system analysis based on the framework of the work system model developed by Smith and Carayon-Sainfort (1989) allowed for an accurate representation of the complexity of flight attendant work environment in short-haul aviation industries, thus contributed to an increased understanding of fatigue and risk factors that span the entire work system and aid in identifying the patterns in combination of work system variables that are associated with increased risk to flight attendant fatigue. Overall flight attendant fatigue is a product of interactions with the short-haul environment. It can have a negative impact on safety, performance and well-being. Therefore, it needs to be managed and dealt with in the near future.
- Full Text:
- Authors: Bennett, Chloe Kayla
- Date: 2020
- Subjects: Flight attendants -- Health and hygiene , Employees -- South Africa -- Workload
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/123431 , vital:35437
- Description: Background and aim: Flight attendants forms a significant part in 24-hour aviation industry. Flight attendant fatigue is a significant problem in the aviation industry as it continues to jeopardize the ability to fulfil important safety and security roles which is critical in performance duty of a flight attendant. However, little attention has been accomplished to the workload, working conditions and fatigue of flight attendants crew in transport aircraft. In addition, there is currently less research that have also embraced the problematic of smaller regional/commercial operation (short-haul flight operations) inducing fatigue among short-haul flight attendants as the nature of this operation are often characterised with high productivity expectations in a demanding environment with high time pressures resulting in high workloads and fatigue. Thus, flight attendant fatigue and workload is a worldwide challenge in this operational environment and less attention has been given to the determining factors. Therefore, the aim of the study was to determine the workload factors contributing to flight attendant fatigue during short-haul flight operations. Methods (System analysis): To achieve the research aim, the work system analysis, based on the Smith and Carayon-Sainfort model was chosen as the main research approach which was conducted in two ways; based on existing literature and secondly based on expert interviews. This method provided a systemic aspect to understand the whole work system of flight attendants work during short-haul operations in order to identify all the contributing factors to flight attendant fatigue and workload. Results: The literature analysis and the data from the expert interviews highlighted significant findings to flight attendant fatigue and workload. The reasons for flight attendant fatigue operating short-haul flights can be found at organizational, task, individual, environmental levels and tools and technologies and due to the interaction of the factors. The main factors of flight attendants’ fatigue are thought primarily as a function of scheduling due to irregular, mixed schedules with early starts and late finishes, extended duty days (long working hours), as well as high workload, due to the short turnaround flights, the number of sectors flown in a single duty period and duty length and high jobs demands. In addition, flight duty and rest regulations, confined work space in the cabin, vibrations, noise and lighting, sleeping in an unfamiliar environment, family responsibilities all add to additional stress placed on the body which can influence workload and sleep and consequently influencing fatigue. Conclusion: Overall the study determined that flight attendant fatigue is a significant problem in modern industry of short-haul operations. Using this systematic approach (work system analysis based on the framework of the work system model developed by Smith and Carayon-Sainfort (1989) allowed for an accurate representation of the complexity of flight attendant work environment in short-haul aviation industries, thus contributed to an increased understanding of fatigue and risk factors that span the entire work system and aid in identifying the patterns in combination of work system variables that are associated with increased risk to flight attendant fatigue. Overall flight attendant fatigue is a product of interactions with the short-haul environment. It can have a negative impact on safety, performance and well-being. Therefore, it needs to be managed and dealt with in the near future.
- Full Text:
System analysis of fatigue in pilots and co-pilots executing short-hall flight operations
- Authors: Bennett, Cleo Taylor
- Date: 2020
- Subjects: Air pilots -- Health and hygiene , Fatigue , Work environment -- Psychological aspects , Work environment -- Physiological aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146622 , vital:38543
- Description: Background: This study was conducted as part of Denel’s South African Regional Aircraft (SARA) development project. Regional aircraft have a maximum flight time of 60 minutes. Hence, the study focuses on matters pertaining to the short-haul flight context. Pilot fatigue has been recognised as a safety concern in the aviation industry. It impacts on pilot performance across the board, not least in the short-haul context. However, the specific factors that lead to pilot fatigue in short-haul operations have not been well researched. Research Aim: To identify and examine the factors which influence pilot/co-pilot fatigue in short-haul aviation contexts. Method: Fatigue is multifaceted, and has multiple definitions and descriptions. It is acknowledged as a complex phenomenon, the development of which is dynamically influenced by various factors. Thus, a systems approach based on the work system model by Smith and Carayon-Sainfort (1989) was adopted for this study. A systems analysis was conducted in two parts: 1) a literature analysis, and 2) expert interviews. Results: Both the literature analysis and the interviews indicated that pilot fatigue in short-haul flight operations represent composite system outcomes influenced by various factors. The factors identified were structured (systematised) into categories, namely organizational factors, task-related factors, environmental factors, factors linked to technology and tools, and non-work-related factors specific to the individual pilot. An example of a task-related factor would be the performance by pilots of multiple take-offs and landings; organizational factors include work time arrangements and duty scheduling (e.g. unpredictable schedule, early starts/late finishes, number of flight sectors in a shift, extended working hours, numerous consecutive work days, standby duties, flight, duty and rest limitations (regulations and guidelines); and short turnaround periods); environmental factors might include the small pressurised cockpit environment, movement restriction, very low humidity, low air pressure, vibrations, high noise levels, low light intensity light, and inclement weather); there are many examples of how tools and technology utilized by pilots might affect their fatigue levels; and finally, pilot-specific non-work-related factors would include things like the pilot’s age, health (lifestyle), family stress, work experience and sleep environment. All of these factors were identified during the literature analysis and have a significant bearing on how fatigue could present in short-haul pilots/co-pilots. Other important fatigue-related factors revealed during the expert interviews included, organizational culture, time management, health implications of fatigue, and management of fatigue. Conclusions: Pilot fatigue is a complex and multi-factorial physiological condition. There are many interacting components which contribute to pilot fatigue in short-haul operations. These should be viewed from an integrated perspective and holistic, systems-based approaches should be taken to manage these issues, particularly in the context of short-haul operations. This would optimize pilot performance and well-being and, most importantly, improve the safety of the work environment to enhance overall operation safety. Limitations: The study does not quantify the contributions made to pilot fatigue by the various factors explored. Therefore, care needs to be taken when designing and implementing interventions based on this research.
- Full Text:
- Authors: Bennett, Cleo Taylor
- Date: 2020
- Subjects: Air pilots -- Health and hygiene , Fatigue , Work environment -- Psychological aspects , Work environment -- Physiological aspects
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/146622 , vital:38543
- Description: Background: This study was conducted as part of Denel’s South African Regional Aircraft (SARA) development project. Regional aircraft have a maximum flight time of 60 minutes. Hence, the study focuses on matters pertaining to the short-haul flight context. Pilot fatigue has been recognised as a safety concern in the aviation industry. It impacts on pilot performance across the board, not least in the short-haul context. However, the specific factors that lead to pilot fatigue in short-haul operations have not been well researched. Research Aim: To identify and examine the factors which influence pilot/co-pilot fatigue in short-haul aviation contexts. Method: Fatigue is multifaceted, and has multiple definitions and descriptions. It is acknowledged as a complex phenomenon, the development of which is dynamically influenced by various factors. Thus, a systems approach based on the work system model by Smith and Carayon-Sainfort (1989) was adopted for this study. A systems analysis was conducted in two parts: 1) a literature analysis, and 2) expert interviews. Results: Both the literature analysis and the interviews indicated that pilot fatigue in short-haul flight operations represent composite system outcomes influenced by various factors. The factors identified were structured (systematised) into categories, namely organizational factors, task-related factors, environmental factors, factors linked to technology and tools, and non-work-related factors specific to the individual pilot. An example of a task-related factor would be the performance by pilots of multiple take-offs and landings; organizational factors include work time arrangements and duty scheduling (e.g. unpredictable schedule, early starts/late finishes, number of flight sectors in a shift, extended working hours, numerous consecutive work days, standby duties, flight, duty and rest limitations (regulations and guidelines); and short turnaround periods); environmental factors might include the small pressurised cockpit environment, movement restriction, very low humidity, low air pressure, vibrations, high noise levels, low light intensity light, and inclement weather); there are many examples of how tools and technology utilized by pilots might affect their fatigue levels; and finally, pilot-specific non-work-related factors would include things like the pilot’s age, health (lifestyle), family stress, work experience and sleep environment. All of these factors were identified during the literature analysis and have a significant bearing on how fatigue could present in short-haul pilots/co-pilots. Other important fatigue-related factors revealed during the expert interviews included, organizational culture, time management, health implications of fatigue, and management of fatigue. Conclusions: Pilot fatigue is a complex and multi-factorial physiological condition. There are many interacting components which contribute to pilot fatigue in short-haul operations. These should be viewed from an integrated perspective and holistic, systems-based approaches should be taken to manage these issues, particularly in the context of short-haul operations. This would optimize pilot performance and well-being and, most importantly, improve the safety of the work environment to enhance overall operation safety. Limitations: The study does not quantify the contributions made to pilot fatigue by the various factors explored. Therefore, care needs to be taken when designing and implementing interventions based on this research.
- Full Text:
Optimisation of a sampling protocol for long-term monitoring of temperate reef fishes
- Authors: Bennett, Rhett Hamilton
- Date: 2008
- Subjects: Marine parks and reserves -- South Africa , Coastal zone management -- South Africa , Fishery management -- South Africa , Reef fishes -- South Africa , Fish communities -- South Africa , Fish stock assessment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5309 , http://hdl.handle.net/10962/d1005154 , Marine parks and reserves -- South Africa , Coastal zone management -- South Africa , Fishery management -- South Africa , Reef fishes -- South Africa , Fish communities -- South Africa , Fish stock assessment
- Description: Marine Protected Areas (MPAs), the Ecosystem Approach to Fisheries management (EAF) and Integrated Coastal Management (ICM) have been identified as possible alternatives to traditional linefish management measures, which have largely failed. Monitoring and assessment of fish communities on a long-term basis is necessary, and will provide a means to evaluate the effectiveness of such management measures. Therefore, standardised protocols and optimal sampling methods for long-term monitoring (LTM) and assessment of coastal fish communities are essential. This study aimed to identify suitable methods and develop a protocol for assessment of inshore reef fish communities. A suitable location for evaluation of proposed methods was identified in the warm temperate biogeographical region of South Africa, encompassing the well-established Tsitsikamma Coastal National Park MPA and an adjacent exploited area. Chrysoblephus laticeps (roman) was identified as an indicator species for the study, as it has been well-studied and is well represented in the area. Underwater visual census (UVC) and controlled fishing were identified as suitable methods. UVC transects were found to be superior to point counts, in terms of sampling efficiency, variability, bias and required sample size. An effort of two angler hours per fishing station was shown to provide low catch variability, while at the same time a representative catch and low overall cost and required time. The methods were incorporated in a proposed sampling protocol, and evaluated. The methods were able to detect known differences between protected and exploited communities. It is recommended that LTM within protected areas, for detection of natural change, be focused on community-level indicators, while LTM in exploited areas, aimed at detection of anthropogenic change, be focused on species-level indicators. The proposed protocol with standardised methods will allow for comparisons across a network of LTM sites and provide the opportunity for a broad-scale assessment of the effects of environmental variables on reef fish stocks. The protocol developed in this study has application in other biogeographical regions in South Africa, and other parts of the world. Shift in the focus of much marine research, in South Africa and elsewhere, to LTM, highlights the relevance and timeous nature of this study.
- Full Text:
- Authors: Bennett, Rhett Hamilton
- Date: 2008
- Subjects: Marine parks and reserves -- South Africa , Coastal zone management -- South Africa , Fishery management -- South Africa , Reef fishes -- South Africa , Fish communities -- South Africa , Fish stock assessment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5309 , http://hdl.handle.net/10962/d1005154 , Marine parks and reserves -- South Africa , Coastal zone management -- South Africa , Fishery management -- South Africa , Reef fishes -- South Africa , Fish communities -- South Africa , Fish stock assessment
- Description: Marine Protected Areas (MPAs), the Ecosystem Approach to Fisheries management (EAF) and Integrated Coastal Management (ICM) have been identified as possible alternatives to traditional linefish management measures, which have largely failed. Monitoring and assessment of fish communities on a long-term basis is necessary, and will provide a means to evaluate the effectiveness of such management measures. Therefore, standardised protocols and optimal sampling methods for long-term monitoring (LTM) and assessment of coastal fish communities are essential. This study aimed to identify suitable methods and develop a protocol for assessment of inshore reef fish communities. A suitable location for evaluation of proposed methods was identified in the warm temperate biogeographical region of South Africa, encompassing the well-established Tsitsikamma Coastal National Park MPA and an adjacent exploited area. Chrysoblephus laticeps (roman) was identified as an indicator species for the study, as it has been well-studied and is well represented in the area. Underwater visual census (UVC) and controlled fishing were identified as suitable methods. UVC transects were found to be superior to point counts, in terms of sampling efficiency, variability, bias and required sample size. An effort of two angler hours per fishing station was shown to provide low catch variability, while at the same time a representative catch and low overall cost and required time. The methods were incorporated in a proposed sampling protocol, and evaluated. The methods were able to detect known differences between protected and exploited communities. It is recommended that LTM within protected areas, for detection of natural change, be focused on community-level indicators, while LTM in exploited areas, aimed at detection of anthropogenic change, be focused on species-level indicators. The proposed protocol with standardised methods will allow for comparisons across a network of LTM sites and provide the opportunity for a broad-scale assessment of the effects of environmental variables on reef fish stocks. The protocol developed in this study has application in other biogeographical regions in South Africa, and other parts of the world. Shift in the focus of much marine research, in South Africa and elsewhere, to LTM, highlights the relevance and timeous nature of this study.
- Full Text:
Assessing the potential impact of climate change in the south-eastern Great Escarpment, Southern Africa
- Authors: Bentley, Luke Kinross
- Date: 2017
- Subjects: Mountain plants -- Climatic factors -- Drakensberg Mountains , Mountain biodiversity -- Drakensberg Mountains , Climatic changes -- Drakensberg Mountains , Rain and rainfall -- Drakensberg Mountains , Plant diversity -- Climatic factors -- Drakensberg Mountains
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4657 , vital:20709
- Description: Rapid, anthropogenic climate change is a contemporary phenomenon which is threatening natural ecosystems. Mountains are globally important, housing high levels of plant and animal biodiversity, as well as being important suppliers of water with 50% of mountainous regions being essential for the provision of water to downstream inhabitants. Owing to their importance, an assessment of the historical, current and potential impacts of climate change on the south-eastern Great Escarpment encompassing South Africa and Lesotho is necessary and is the primary aim of this thesis. In order to assess the historical and current impacts of climate change, historical rainfall records were collected from 78 sites throughout the Eastern Cape. These records were used to determine rainfall trends and trends in the frequency of daily extreme events. Climate change projections predict increasing trends in summer and annual rainfall, and a marginal increase to a slightly decreasing trend in winter rainfall, depending on if statistically downscaled or dynamically downscaled projections are examined. Extreme events are also predicted to increase in frequency. Results showed trends which generally agree with the predictions, except for extreme events for which there was insufficient data to support the projections. This has implications for farmers in the area and validates the downscaled Regional Climate Models (RCMs) to be used for the predictive analysis determining the potential future impacts of climate change on plant species' distributions in the south-eastern Great Escarpment. In order to assess montane plant species to future climate predictions, occurrence records of 46 species were correlated to rainfall and temperature predictor variables and predictions for species richness and beta diversity were made for current and future climates. This predictive analysis used and compared two correlative species distribution modelling methods - one method used one correlating algorithm in a nuanced manner and the other method used five correlating algorithms in an ensemble. A trend of range restriction to higher elevations for the 46 species analysed was as expected from a warming climate. The nuanced, single algorithm modelling method produced less conservative models. The predicted trend of an elevational increase in montane vegetation in this region points to Lesotho and the Drakensberg highlands as being an important refugium for montane plant taxa of the southeastern Great Escarpment. The Maloti Drakensberg Transfrontier Conservation Area hence needs to be expanded and its mandate properly enforced to protect this region adequately.
- Full Text:
- Authors: Bentley, Luke Kinross
- Date: 2017
- Subjects: Mountain plants -- Climatic factors -- Drakensberg Mountains , Mountain biodiversity -- Drakensberg Mountains , Climatic changes -- Drakensberg Mountains , Rain and rainfall -- Drakensberg Mountains , Plant diversity -- Climatic factors -- Drakensberg Mountains
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4657 , vital:20709
- Description: Rapid, anthropogenic climate change is a contemporary phenomenon which is threatening natural ecosystems. Mountains are globally important, housing high levels of plant and animal biodiversity, as well as being important suppliers of water with 50% of mountainous regions being essential for the provision of water to downstream inhabitants. Owing to their importance, an assessment of the historical, current and potential impacts of climate change on the south-eastern Great Escarpment encompassing South Africa and Lesotho is necessary and is the primary aim of this thesis. In order to assess the historical and current impacts of climate change, historical rainfall records were collected from 78 sites throughout the Eastern Cape. These records were used to determine rainfall trends and trends in the frequency of daily extreme events. Climate change projections predict increasing trends in summer and annual rainfall, and a marginal increase to a slightly decreasing trend in winter rainfall, depending on if statistically downscaled or dynamically downscaled projections are examined. Extreme events are also predicted to increase in frequency. Results showed trends which generally agree with the predictions, except for extreme events for which there was insufficient data to support the projections. This has implications for farmers in the area and validates the downscaled Regional Climate Models (RCMs) to be used for the predictive analysis determining the potential future impacts of climate change on plant species' distributions in the south-eastern Great Escarpment. In order to assess montane plant species to future climate predictions, occurrence records of 46 species were correlated to rainfall and temperature predictor variables and predictions for species richness and beta diversity were made for current and future climates. This predictive analysis used and compared two correlative species distribution modelling methods - one method used one correlating algorithm in a nuanced manner and the other method used five correlating algorithms in an ensemble. A trend of range restriction to higher elevations for the 46 species analysed was as expected from a warming climate. The nuanced, single algorithm modelling method produced less conservative models. The predicted trend of an elevational increase in montane vegetation in this region points to Lesotho and the Drakensberg highlands as being an important refugium for montane plant taxa of the southeastern Great Escarpment. The Maloti Drakensberg Transfrontier Conservation Area hence needs to be expanded and its mandate properly enforced to protect this region adequately.
- Full Text:
Granitoid related Sn-W mineralisation with special reference to southern Africa, the Variscan Belt in Europe, and the Malay Peninsula
- Authors: Bentley, Philip Nelson
- Date: 1985
- Subjects: Geotectonic settings , Granitoids , Granites , Tin-tungsten , Mineralisation , Greisen environment , Minerals , Exploration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4908 , http://hdl.handle.net/10962/d1001568
- Description: A review of the geotectonic settings of granitoids and various tin-tungsten provinces in Europe, Malaysia and southern Africa shows a close spatial and temporal association of mineralisation to S-type ilmenite series granitoids. Granitoids with these affinities are derived from crustal anatexis and are most commonly found in continental collision and different ensialic, intraplate orogenic settings, (e.g. SW England, Malaysia, Namibia) as well as in association with anorogenic magmatism (Nigeria, Brazil, South Africa). Tin-tungsten mineralisation is related to late- to post-tectonic granites, emplaced into areas of substantial tectonic thickening. Crustal anatexis leads to an observable calcalkaline chemical trend, with a source of gabbroic or amphibolite composition through anatexis to; mafic-intermediate enclaves, para-autochthonous anatectic granitoids (tonalite, granodiorite), to intermediate level quartz monzonite, granodiorite, biotite-granite, to late-tectonic highly fractionated muscovite-bearing granites, and high level porphyry intrusions. Mineralisation is spatially related to apical protrusions of the youngest most differentiated granite. Various mineralised environments are recognised, including endogranitic veins, primary disseminations, pegmatites and pipes, and exogranitic stockwork and fissure veins, and replacement bodies. A common factor to all these deposits is the inherent greisen environment, characterised by postmagmatic metasomatic alteration and mineral deposition. Common alteration mineral assemblages include albite, quartz, muscovite, tourmaline, and fluorite ∓ topaz. Ore mineral assemblages commonly display a paragenetic sequence of oxides (cassiterite, wolframite, scheelite), followed by sulphides (molybdenite, pyrite, pyrrhotite, chalcopyrite sphalerite, arsenopyrite/loëllingite, Pb-Bi(Ag) sulphosalts) and then lower temperature carbonates (calcite, siderite, ankerite). Analysis of Pan African orogenic provinces in southern Africa (Damara and Saldanian Provinces) shows there is good potential for applying integrated exploration techniques in search of endo-exogreisen Sn-W systems. Careful analysis and interpretation of granitoid geochemistry (K₂0, Na₂0, FeO/Fe₂0₃, F, B, Sn, W, Mo, Cu, Rb, Sr, Ti, Zr) should aid delineation of Sn-W and Mo-Cu metallogenic provinces in these regions. Magnetic susceptibility determinations should also aid distinction of S-type ilmenite series (less than 1 x lO⁻⁴emu/g ) from I-type magnetite series (more than 1 x lO⁻⁴emu/g ) granitoids
- Full Text:
- Authors: Bentley, Philip Nelson
- Date: 1985
- Subjects: Geotectonic settings , Granitoids , Granites , Tin-tungsten , Mineralisation , Greisen environment , Minerals , Exploration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4908 , http://hdl.handle.net/10962/d1001568
- Description: A review of the geotectonic settings of granitoids and various tin-tungsten provinces in Europe, Malaysia and southern Africa shows a close spatial and temporal association of mineralisation to S-type ilmenite series granitoids. Granitoids with these affinities are derived from crustal anatexis and are most commonly found in continental collision and different ensialic, intraplate orogenic settings, (e.g. SW England, Malaysia, Namibia) as well as in association with anorogenic magmatism (Nigeria, Brazil, South Africa). Tin-tungsten mineralisation is related to late- to post-tectonic granites, emplaced into areas of substantial tectonic thickening. Crustal anatexis leads to an observable calcalkaline chemical trend, with a source of gabbroic or amphibolite composition through anatexis to; mafic-intermediate enclaves, para-autochthonous anatectic granitoids (tonalite, granodiorite), to intermediate level quartz monzonite, granodiorite, biotite-granite, to late-tectonic highly fractionated muscovite-bearing granites, and high level porphyry intrusions. Mineralisation is spatially related to apical protrusions of the youngest most differentiated granite. Various mineralised environments are recognised, including endogranitic veins, primary disseminations, pegmatites and pipes, and exogranitic stockwork and fissure veins, and replacement bodies. A common factor to all these deposits is the inherent greisen environment, characterised by postmagmatic metasomatic alteration and mineral deposition. Common alteration mineral assemblages include albite, quartz, muscovite, tourmaline, and fluorite ∓ topaz. Ore mineral assemblages commonly display a paragenetic sequence of oxides (cassiterite, wolframite, scheelite), followed by sulphides (molybdenite, pyrite, pyrrhotite, chalcopyrite sphalerite, arsenopyrite/loëllingite, Pb-Bi(Ag) sulphosalts) and then lower temperature carbonates (calcite, siderite, ankerite). Analysis of Pan African orogenic provinces in southern Africa (Damara and Saldanian Provinces) shows there is good potential for applying integrated exploration techniques in search of endo-exogreisen Sn-W systems. Careful analysis and interpretation of granitoid geochemistry (K₂0, Na₂0, FeO/Fe₂0₃, F, B, Sn, W, Mo, Cu, Rb, Sr, Ti, Zr) should aid delineation of Sn-W and Mo-Cu metallogenic provinces in these regions. Magnetic susceptibility determinations should also aid distinction of S-type ilmenite series (less than 1 x lO⁻⁴emu/g ) from I-type magnetite series (more than 1 x lO⁻⁴emu/g ) granitoids
- Full Text:
An analysis of the risk exposure of adopting IPV6 in enterprise networks
- Authors: Berko, Istvan Sandor
- Date: 2015
- Subjects: International Workshop on Deploying the Future Infrastructure , Computer networks , Computer networks -- Security measures , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4722 , http://hdl.handle.net/10962/d1018918
- Description: The IPv6 increased address pool presents changes in resource impact to the Enterprise that, if not adequately addressed, can change risks that are locally significant in IPv4 to risks that can impact the Enterprise in its entirety. The expected conclusion is that the IPv6 environment will impose significant changes in the Enterprise environment - which may negatively impact organisational security if the IPv6 nuances are not adequately addressed. This thesis reviews the risks related to the operation of enterprise networks with the introduction of IPv6. The global trends are discussed to provide insight and background to the IPv6 research space. Analysing the current state of readiness in enterprise networks, quantifies the value of developing this thesis. The base controls that should be deployed in enterprise networks to prevent the abuse of IPv6 through tunnelling and the protection of the enterprise access layer are discussed. A series of case studies are presented which identify and analyse the impact of certain changes in the IPv6 protocol on the enterprise networks. The case studies also identify mitigation techniques to reduce risk.
- Full Text:
- Authors: Berko, Istvan Sandor
- Date: 2015
- Subjects: International Workshop on Deploying the Future Infrastructure , Computer networks , Computer networks -- Security measures , Computer network protocols
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4722 , http://hdl.handle.net/10962/d1018918
- Description: The IPv6 increased address pool presents changes in resource impact to the Enterprise that, if not adequately addressed, can change risks that are locally significant in IPv4 to risks that can impact the Enterprise in its entirety. The expected conclusion is that the IPv6 environment will impose significant changes in the Enterprise environment - which may negatively impact organisational security if the IPv6 nuances are not adequately addressed. This thesis reviews the risks related to the operation of enterprise networks with the introduction of IPv6. The global trends are discussed to provide insight and background to the IPv6 research space. Analysing the current state of readiness in enterprise networks, quantifies the value of developing this thesis. The base controls that should be deployed in enterprise networks to prevent the abuse of IPv6 through tunnelling and the protection of the enterprise access layer are discussed. A series of case studies are presented which identify and analyse the impact of certain changes in the IPv6 protocol on the enterprise networks. The case studies also identify mitigation techniques to reduce risk.
- Full Text:
Euphausiid population structure and grazing in the Indian sector of the Antarctic Polar Frontal Zone, during austral autumn
- Bernard, Anthony Thomas Firth
- Authors: Bernard, Anthony Thomas Firth
- Date: 2005
- Subjects: Euphausiacea -- Antarctic Ocean , Euphausiacea -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5913 , http://hdl.handle.net/10962/d1015960
- Description: The trophodynamics of the numerically dominant euphausiid species within a region of high mesoscale oceanographic variability in the southwest Indian sector of the Antarctic Polar Frontal Zone (PFZ) were investigated during the austral autumns April/May) of 2004 and 2005. During the 2004 survey, sub-surface (200 m) temperature profiles indicated that an intense frontal feature, formed by the convergence of the Sub-Antarctic Front (SAF) and the Antarctic Polar Front (APF) bisected the survey area into two distinct zones, the Sub- Antarctic Zone (SAZ) and the Antarctic Zone (AAZ). Total integrated chlorophyll-a (chl-a) biomass was typical for the region (< 25 mg chl-a m⁻²), and was dominated by picophytoplankton. Total euphausiid abundance and biomass ranged from 0.1 to 3.1 ind m⁻³ and 0.1 to 8.1 mg dwt m⁻³, respectively, and did not differ significantly between the stations occupied in the SAZ and AAZ (p > 0.05). The multivariate analysis identified two interacting mechanisms controlling the distribution patterns, abundance and biomass of the various euphausiid species, namely (1) diel changes in abundance and biomass, (2) and restricted distribution patterns associated with the different water masses. Ingestion rates were determined for five euphausiid species. E. triacantha was found to have the highest daily ingestion rate ranging from 1 226.1 to 6 029.1 ng pigm ind⁻¹d⁻¹, while the lowest daily ingestion rates were observed in the juvenile Thysanoessa species (6.4 to 943.0 ng pigm ind⁻¹ d⁻¹). The total grazing impact of the selected euphausiids ranged from < 0.1 to 20.1 μg pigm m⁻²d⁻¹, corresponding to < 0.15 % of the areal chl-a biomass. The daily ration estimates of autotrophic carbon for the euphausiids suggested that phytoplankton represented a minor component in their diets, with only the sub-adult E. vallentini consuming sufficient phytoplankton to meet their daily carbon requirements. A cyclonic cold-core eddy spawned from the region of the APF located in the southwest Indian sector of the PFZ was the dominant feature during the 2005 survey. The total areal chl-a biomass throughout the region was low, ranging between 5.6 and 11.4 mg chl-a m⁻², and was significantly higher within the core of the eddy compared to the surrounding waters (p < 0.05). RMT-8 and WP-2 total euphausiid abundance and biomass estimates were high, and ranged from 0.004 to 0.36 ind m⁻³ and 0.065 to 1.21 mg dwt m⁻³, and from 0.01 to 18.2 ind m⁻³ and 0.01 to 15.7 mg dwt m⁻³, respectively. A distinct spatial pattern in the euphausiid community was evident with the Antarctic species, Euphausia frigida, E. triacantha and E. superba predominating within the core of the eddy, while the PFZ waters were characterized by the sub-Antarctic species, E. longirostris, Stylocheiron maximum, Nematoscelis megalops and Thysanoessa gregaria. The eddy edge acted as a transition zone where species from both regions co-occurred. Within the survey area the combined ingestion rate of the six numerically dominant euphausiid species ranged between 0.02 and 5.31 μg pigm m⁻²d¹, which corresponded to a loss of between < 0.001 and 0.11 % of the available chl-a biomass. E. triacantha and juvenile T. macura were identified as the dominant grazers. There was no apparent spatial pattern in the grazing activity of the euphausiids within the region of investigation. The average daily rations of the euphausiids examined were < 2 % of their body carbon. The low daily ration of the euphausiids could be ascribed to the predominance of small picophytoplankton in the region of investigation, which are too small to be grazed efficiently by larger zooplankton. The marked spatial patterns in species composition and the elevated abundance and biomass of euphausiids, suggest that the mesoscale eddies contribute to the spatial and temporal heterogeneity of the planktonic community of the PFZ and may represent important foraging regions for many of the apex predators within the region.
- Full Text:
- Authors: Bernard, Anthony Thomas Firth
- Date: 2005
- Subjects: Euphausiacea -- Antarctic Ocean , Euphausiacea -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5913 , http://hdl.handle.net/10962/d1015960
- Description: The trophodynamics of the numerically dominant euphausiid species within a region of high mesoscale oceanographic variability in the southwest Indian sector of the Antarctic Polar Frontal Zone (PFZ) were investigated during the austral autumns April/May) of 2004 and 2005. During the 2004 survey, sub-surface (200 m) temperature profiles indicated that an intense frontal feature, formed by the convergence of the Sub-Antarctic Front (SAF) and the Antarctic Polar Front (APF) bisected the survey area into two distinct zones, the Sub- Antarctic Zone (SAZ) and the Antarctic Zone (AAZ). Total integrated chlorophyll-a (chl-a) biomass was typical for the region (< 25 mg chl-a m⁻²), and was dominated by picophytoplankton. Total euphausiid abundance and biomass ranged from 0.1 to 3.1 ind m⁻³ and 0.1 to 8.1 mg dwt m⁻³, respectively, and did not differ significantly between the stations occupied in the SAZ and AAZ (p > 0.05). The multivariate analysis identified two interacting mechanisms controlling the distribution patterns, abundance and biomass of the various euphausiid species, namely (1) diel changes in abundance and biomass, (2) and restricted distribution patterns associated with the different water masses. Ingestion rates were determined for five euphausiid species. E. triacantha was found to have the highest daily ingestion rate ranging from 1 226.1 to 6 029.1 ng pigm ind⁻¹d⁻¹, while the lowest daily ingestion rates were observed in the juvenile Thysanoessa species (6.4 to 943.0 ng pigm ind⁻¹ d⁻¹). The total grazing impact of the selected euphausiids ranged from < 0.1 to 20.1 μg pigm m⁻²d⁻¹, corresponding to < 0.15 % of the areal chl-a biomass. The daily ration estimates of autotrophic carbon for the euphausiids suggested that phytoplankton represented a minor component in their diets, with only the sub-adult E. vallentini consuming sufficient phytoplankton to meet their daily carbon requirements. A cyclonic cold-core eddy spawned from the region of the APF located in the southwest Indian sector of the PFZ was the dominant feature during the 2005 survey. The total areal chl-a biomass throughout the region was low, ranging between 5.6 and 11.4 mg chl-a m⁻², and was significantly higher within the core of the eddy compared to the surrounding waters (p < 0.05). RMT-8 and WP-2 total euphausiid abundance and biomass estimates were high, and ranged from 0.004 to 0.36 ind m⁻³ and 0.065 to 1.21 mg dwt m⁻³, and from 0.01 to 18.2 ind m⁻³ and 0.01 to 15.7 mg dwt m⁻³, respectively. A distinct spatial pattern in the euphausiid community was evident with the Antarctic species, Euphausia frigida, E. triacantha and E. superba predominating within the core of the eddy, while the PFZ waters were characterized by the sub-Antarctic species, E. longirostris, Stylocheiron maximum, Nematoscelis megalops and Thysanoessa gregaria. The eddy edge acted as a transition zone where species from both regions co-occurred. Within the survey area the combined ingestion rate of the six numerically dominant euphausiid species ranged between 0.02 and 5.31 μg pigm m⁻²d¹, which corresponded to a loss of between < 0.001 and 0.11 % of the available chl-a biomass. E. triacantha and juvenile T. macura were identified as the dominant grazers. There was no apparent spatial pattern in the grazing activity of the euphausiids within the region of investigation. The average daily rations of the euphausiids examined were < 2 % of their body carbon. The low daily ration of the euphausiids could be ascribed to the predominance of small picophytoplankton in the region of investigation, which are too small to be grazed efficiently by larger zooplankton. The marked spatial patterns in species composition and the elevated abundance and biomass of euphausiids, suggest that the mesoscale eddies contribute to the spatial and temporal heterogeneity of the planktonic community of the PFZ and may represent important foraging regions for many of the apex predators within the region.
- Full Text:
Mesozooplankton community structure and grazing impact in the polar frontal zone of the Southern Ocean
- Authors: Bernard, Kim Sarah
- Date: 2003
- Subjects: Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5731 , http://hdl.handle.net/10962/d1005417 , Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Description: Mesozooplankton community structure and grazing impact in the Polar Frontal Zone (PFZ) of the Southern Ocean were investigated during two cruises of the South African National Antarctic Programme (SANAP), the Marion Offshore Ecosystem Variability Study I & II (MOEVS). During the first cruise (MOEVS I), a meso-scale oceanographic grid survey was conducted in the upstream region of the Prince Edward Islands (PEI) in austral autumn (April) 2001. Mesozooplankton samples, collected using a Bongo net (fitted with 200 and 300µm mesh nets) at depths between 200 and 300 m, were separated into three size fractions: 200-500 µm; 500-1000 µm; 1000-2000 µm by reverse filtration. Total surface (depth <5 m) chlorophyll-a (chl-a) concentration (measured fluorometrically) during the study ranged between 0.11 and 0.34 µg 1^(-1) and was always dominated by picophytoplankton (<2.0 µm). Total mesozooplankton abundance and biomass during the survey ranged between 49 and 1512 ind. m^(-3) and between 0.7 and 25 mg Dwt. m^(-3), respectively. Throughout the survey, the 200-500 µm class numerically dominated the mesozooplankton community, comprising an average of ~ 69% (SD = ± 12.3%). The dominant species in the 200-500 µm size fraction were the copepods Oithona similis, Calanus simillimus and Metridia lucens and the pteropod, Limacina retroversa. However, in terms of biomass, the 1000-2000 µm group was predominant, with dry weight values constituting an average of ~ 66% (SD = ± 10.2%). Biomass was dominated by carnivorous zooplankton, particularly the euphausiids, Euphausia vallentini and Thysanoessa vicina and the chaetognaths, Sagitta gazellae and Eukrohnia hamata. Three distinct groupings of stations were identified by multivariate analysis. The different station groupings identified reflect changes in the relative contributions of the rather than different species assemblages. During the second cruise (MOEVS II), conducted in April 2002 (austral autumn), mesozooplankton community structure and grazing impact were investigated at 13 stations in the west Indian sector of the PFZ. Total integrated chl-a biomass ranged between 11.17 and 28.34 mg chl-a m^(-2) and was always dominated by nano- and picophytoplankton (<20 µm). Throughout the study, small copepods, mainly Oithona similis and Ctenocalanus vanus, numerically dominated the mesozooplankton community comprising up to 85% (range 30 to 85%) of the total abundance. Grazing activity of the four most abundant copepods (O. similis, C. vanus, Calanus simillimus and Clausocalanus spp.), which comprised up to 93% of total mesozooplankton abundance, was investigated using the gut fluorescent technique. Results of gut fluorescence analyses indicated that C. simillimus, Clausocalanus spp. and Ctenocalanus vanus exhibited diel variability in gut pigments, with maximum values at various stages of the night. In contrast, O. similis did not demonstrate diel variation in gut pigment contents. Ingestion rates of the four copepods ranged from 23.23 to 1462.02 ng (pigm.) ind^(-1) day^(-1), depending on the species. The combined grazing impact of the four copepods, ranged between 1 and 36% of the phytoplankton standing stock per day, with the highest daily impact (~ 35.86%) occurring at stations in the vicinity of the Antarctic Polar Front. Among the copepods, O. similis and C. vanus were generally the most important consumers of phytoplankton biomass; together they were responsible for up to 89% (range 15 to 89%) of the total daily grazing impact. Carbon specific ingestion rates of the copepods varied between 42 and 320% body carbon per day, depending on the species. The study highlights the importance of small copepods in terms of both their significant contribution to total mesozooplankton numbers and their grazing impact on the phytoplankton standing stocks in the PFZ during austral autumn.
- Full Text:
- Authors: Bernard, Kim Sarah
- Date: 2003
- Subjects: Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5731 , http://hdl.handle.net/10962/d1005417 , Zooplankton -- Antarctic Ocean , Copepoda -- Feeding and feeds
- Description: Mesozooplankton community structure and grazing impact in the Polar Frontal Zone (PFZ) of the Southern Ocean were investigated during two cruises of the South African National Antarctic Programme (SANAP), the Marion Offshore Ecosystem Variability Study I & II (MOEVS). During the first cruise (MOEVS I), a meso-scale oceanographic grid survey was conducted in the upstream region of the Prince Edward Islands (PEI) in austral autumn (April) 2001. Mesozooplankton samples, collected using a Bongo net (fitted with 200 and 300µm mesh nets) at depths between 200 and 300 m, were separated into three size fractions: 200-500 µm; 500-1000 µm; 1000-2000 µm by reverse filtration. Total surface (depth <5 m) chlorophyll-a (chl-a) concentration (measured fluorometrically) during the study ranged between 0.11 and 0.34 µg 1^(-1) and was always dominated by picophytoplankton (<2.0 µm). Total mesozooplankton abundance and biomass during the survey ranged between 49 and 1512 ind. m^(-3) and between 0.7 and 25 mg Dwt. m^(-3), respectively. Throughout the survey, the 200-500 µm class numerically dominated the mesozooplankton community, comprising an average of ~ 69% (SD = ± 12.3%). The dominant species in the 200-500 µm size fraction were the copepods Oithona similis, Calanus simillimus and Metridia lucens and the pteropod, Limacina retroversa. However, in terms of biomass, the 1000-2000 µm group was predominant, with dry weight values constituting an average of ~ 66% (SD = ± 10.2%). Biomass was dominated by carnivorous zooplankton, particularly the euphausiids, Euphausia vallentini and Thysanoessa vicina and the chaetognaths, Sagitta gazellae and Eukrohnia hamata. Three distinct groupings of stations were identified by multivariate analysis. The different station groupings identified reflect changes in the relative contributions of the rather than different species assemblages. During the second cruise (MOEVS II), conducted in April 2002 (austral autumn), mesozooplankton community structure and grazing impact were investigated at 13 stations in the west Indian sector of the PFZ. Total integrated chl-a biomass ranged between 11.17 and 28.34 mg chl-a m^(-2) and was always dominated by nano- and picophytoplankton (<20 µm). Throughout the study, small copepods, mainly Oithona similis and Ctenocalanus vanus, numerically dominated the mesozooplankton community comprising up to 85% (range 30 to 85%) of the total abundance. Grazing activity of the four most abundant copepods (O. similis, C. vanus, Calanus simillimus and Clausocalanus spp.), which comprised up to 93% of total mesozooplankton abundance, was investigated using the gut fluorescent technique. Results of gut fluorescence analyses indicated that C. simillimus, Clausocalanus spp. and Ctenocalanus vanus exhibited diel variability in gut pigments, with maximum values at various stages of the night. In contrast, O. similis did not demonstrate diel variation in gut pigment contents. Ingestion rates of the four copepods ranged from 23.23 to 1462.02 ng (pigm.) ind^(-1) day^(-1), depending on the species. The combined grazing impact of the four copepods, ranged between 1 and 36% of the phytoplankton standing stock per day, with the highest daily impact (~ 35.86%) occurring at stations in the vicinity of the Antarctic Polar Front. Among the copepods, O. similis and C. vanus were generally the most important consumers of phytoplankton biomass; together they were responsible for up to 89% (range 15 to 89%) of the total daily grazing impact. Carbon specific ingestion rates of the copepods varied between 42 and 320% body carbon per day, depending on the species. The study highlights the importance of small copepods in terms of both their significant contribution to total mesozooplankton numbers and their grazing impact on the phytoplankton standing stocks in the PFZ during austral autumn.
- Full Text:
Targeted attack detection by means of free and open source solutions
- Authors: Bernardo, Louis F
- Date: 2019
- Subjects: Computer networks -- Security measures , Information technology -- Security measures , Computer security -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92269 , vital:30703
- Description: Compliance requirements are part of everyday business requirements for various areas, such as retail and medical services. As part of compliance it may be required to have infrastructure in place to monitor the activities in the environment to ensure that the relevant data and environment is sufficiently protected. At the core of such monitoring solutions one would find some type of data repository, or database, to store and ultimately correlate the captured events. Such solutions are commonly called Security Information and Event Management, or SIEM for short. Larger companies have been known to use commercial solutions such as IBM's Qradar, Logrythm, or Splunk. However, these come at significant cost and arent suitable for smaller businesses with limited budgets. These solutions require manual configuration of event correlation for detection of activities that place the environment in danger. This usually requires vendor implementation assistance that also would come at a cost. Alternatively, there are open source solutions that provide the required functionality. This research will demonstrate building an open source solution, with minimal to no cost for hardware or software, while still maintaining the capability of detecting targeted attacks. The solution presented in this research includes Wazuh, which is a combination of OSSEC and the ELK stack, integrated with an Network Intrusion Detection System (NIDS). The success of the integration, is determined by measuring postive attack detection based on each different configuration options. To perform the testing, a deliberately vulnerable platform named Metasploitable will be used as a victim host. The victim host vulnerabilities were created specifically to serve as target for Metasploit. The attacks were generated by utilising Metasploit Framework on a prebuilt Kali Linux host.
- Full Text:
- Authors: Bernardo, Louis F
- Date: 2019
- Subjects: Computer networks -- Security measures , Information technology -- Security measures , Computer security -- Management , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/92269 , vital:30703
- Description: Compliance requirements are part of everyday business requirements for various areas, such as retail and medical services. As part of compliance it may be required to have infrastructure in place to monitor the activities in the environment to ensure that the relevant data and environment is sufficiently protected. At the core of such monitoring solutions one would find some type of data repository, or database, to store and ultimately correlate the captured events. Such solutions are commonly called Security Information and Event Management, or SIEM for short. Larger companies have been known to use commercial solutions such as IBM's Qradar, Logrythm, or Splunk. However, these come at significant cost and arent suitable for smaller businesses with limited budgets. These solutions require manual configuration of event correlation for detection of activities that place the environment in danger. This usually requires vendor implementation assistance that also would come at a cost. Alternatively, there are open source solutions that provide the required functionality. This research will demonstrate building an open source solution, with minimal to no cost for hardware or software, while still maintaining the capability of detecting targeted attacks. The solution presented in this research includes Wazuh, which is a combination of OSSEC and the ELK stack, integrated with an Network Intrusion Detection System (NIDS). The success of the integration, is determined by measuring postive attack detection based on each different configuration options. To perform the testing, a deliberately vulnerable platform named Metasploitable will be used as a victim host. The victim host vulnerabilities were created specifically to serve as target for Metasploit. The attacks were generated by utilising Metasploit Framework on a prebuilt Kali Linux host.
- Full Text:
Salinity induced physiological responses in juvenile dusky kob, Argyrosomus japonicus (Sciaenidae)
- Authors: Bernatzeder, Andrea Katinka
- Date: 2009
- Subjects: Osmoregulation , Argyrosomus -- Effects of salt on -- South Africa , Sciaenidae -- Effects of salt on -- South Africa , Argyrosomus -- Physiology , Sciaenidae -- Physiology , Fishes -- Physiology , Biological control systems , Marine ecology -- South Africa , Fishery management -- South Africa , Mariculture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5318 , http://hdl.handle.net/10962/d1005163 , Osmoregulation , Argyrosomus -- Effects of salt on -- South Africa , Sciaenidae -- Effects of salt on -- South Africa , Argyrosomus -- Physiology , Sciaenidae -- Physiology , Fishes -- Physiology , Biological control systems , Marine ecology -- South Africa , Fishery management -- South Africa , Mariculture -- South Africa
- Description: Fisheries management regulations for dusky kob Argyrosomus japonicus, an important commercial and recreational fisheries species, have failed and the stock is considered collapsed. It is important to take an ecosystems approach to management which includes understanding the effect of environmental factors on recruitment, abundance and distribution. The distribution of early juveniles (20-150 mm TL) in the wild appears to be restricted to the upper reaches of estuaries at salinities below 5 psu. Food availability could not explain the distribution of early juveniles. The aim of this study was to investigate the role of salinity on the distribution of early juvenile dusky kob (<150 mm TL) by examining physiological responses of juveniles exposed to a range of salinities under laboratory conditions. The hypothesis was that the physiological functioning of early juveniles would be optimised at the reduced salinities which they naturally occur at. The objectives of this study were to investigate the effect of salinity on: i) plasma osmolality; ii) growth, food conversion ratio and condition factor; and iii) gill histology with emphasis on chloride cell size and number. A preliminary study was undertaken to determine whether the use of 2-phenoxyethanol had an effect on plasma osmolality. Juveniles pithed prior to blood sampling were used as the control. Plasma osmolality was not affected by exposure or duration of exposure (2, 4, 6, 8, 10 min) to 2-phenoxyethanol. The ability of teleosts to regulate plasma osmolality over a wide range of salinities indicates their degree of ‘physiological euryhalinity’. Plasma osmolality of juveniles exposed to 5, 12 and 35 psu was measured every two weeks over a total of six weeks. Although juveniles were able to regulate plasma osmolality over the duration of the experiment, plasma osmolality at 5 and 12 psu was significantly lower than in fish maintained at 35 psu. Growth is used as an indicator of the relative energy used for osmoregulation at different salinities, as the energy used for osmoregulation becomes unavailable for growth. A nineweek growth experiment was conducted on juveniles exposed to 5, 12 and 35 psu. Juveniles grew and survived at all three salinities. However, growth of juveniles at 5 psu was significantly lower than at 12 and 35 psu. Other than a significantly greater weight gain at 35 psu relative to 12 psu, there was no significant difference in specific growth and length gain between juveniles at 12 and 35 psu. Food conversion ratio and condition factor at 12 and 35 psu were not significantly different, but food conversion ratio and condition factor at 5 psu was significantly greater and lower than at 35 psu respectively. In fish, gills are considered the major organ involved in osmoregulation. Within the gills, chloride cells are the predominant site of ion exchange which is driven by the Na⁺, K⁺- ATPase enzyme. Gill samples of juveniles exposed to 5, 12 and 35 psu for six weeks were examined histologically using light microscopy. Chloride cells of juveniles maintained at 5 psu were significantly more abundant than in juveniles at 12 and 35 psu. Chloride cells of juveniles at 5 psu were significantly larger than in juveniles kept at 12 psu, but not significantly different to those of juveniles kept at 35 psu. The ability of the juvenile fish to regulate plasma osmolality indicates that they are 'physiologically euryhaline', but the reduced growth and proliferation of chloride cells at 5 psu suggests that energy expenditure for osmoregulation is increased at hypoosmotic salinities. Salinity induced physiological responses could therefore not explain the natural distribution of early juvenile dusky kob and it is proposed that other environmental factors (e.g. temperature) are also important. It is also hypothesised that the high conductivity of an estuary in South Africa, to which our understanding is limited, may negate the effect of reduced salinity. Although freshwater input into estuaries is an important factor, further investigations to explain the distribution and abundance of early juveniles is required to make management recommendations. Dusky kob is also becoming an increasingly popular aquaculture species in South Africa. In this regard, early juvenile dusky kob can be grown at salinities as low as 12 psu without negatively affecting growth and production.
- Full Text:
- Authors: Bernatzeder, Andrea Katinka
- Date: 2009
- Subjects: Osmoregulation , Argyrosomus -- Effects of salt on -- South Africa , Sciaenidae -- Effects of salt on -- South Africa , Argyrosomus -- Physiology , Sciaenidae -- Physiology , Fishes -- Physiology , Biological control systems , Marine ecology -- South Africa , Fishery management -- South Africa , Mariculture -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5318 , http://hdl.handle.net/10962/d1005163 , Osmoregulation , Argyrosomus -- Effects of salt on -- South Africa , Sciaenidae -- Effects of salt on -- South Africa , Argyrosomus -- Physiology , Sciaenidae -- Physiology , Fishes -- Physiology , Biological control systems , Marine ecology -- South Africa , Fishery management -- South Africa , Mariculture -- South Africa
- Description: Fisheries management regulations for dusky kob Argyrosomus japonicus, an important commercial and recreational fisheries species, have failed and the stock is considered collapsed. It is important to take an ecosystems approach to management which includes understanding the effect of environmental factors on recruitment, abundance and distribution. The distribution of early juveniles (20-150 mm TL) in the wild appears to be restricted to the upper reaches of estuaries at salinities below 5 psu. Food availability could not explain the distribution of early juveniles. The aim of this study was to investigate the role of salinity on the distribution of early juvenile dusky kob (<150 mm TL) by examining physiological responses of juveniles exposed to a range of salinities under laboratory conditions. The hypothesis was that the physiological functioning of early juveniles would be optimised at the reduced salinities which they naturally occur at. The objectives of this study were to investigate the effect of salinity on: i) plasma osmolality; ii) growth, food conversion ratio and condition factor; and iii) gill histology with emphasis on chloride cell size and number. A preliminary study was undertaken to determine whether the use of 2-phenoxyethanol had an effect on plasma osmolality. Juveniles pithed prior to blood sampling were used as the control. Plasma osmolality was not affected by exposure or duration of exposure (2, 4, 6, 8, 10 min) to 2-phenoxyethanol. The ability of teleosts to regulate plasma osmolality over a wide range of salinities indicates their degree of ‘physiological euryhalinity’. Plasma osmolality of juveniles exposed to 5, 12 and 35 psu was measured every two weeks over a total of six weeks. Although juveniles were able to regulate plasma osmolality over the duration of the experiment, plasma osmolality at 5 and 12 psu was significantly lower than in fish maintained at 35 psu. Growth is used as an indicator of the relative energy used for osmoregulation at different salinities, as the energy used for osmoregulation becomes unavailable for growth. A nineweek growth experiment was conducted on juveniles exposed to 5, 12 and 35 psu. Juveniles grew and survived at all three salinities. However, growth of juveniles at 5 psu was significantly lower than at 12 and 35 psu. Other than a significantly greater weight gain at 35 psu relative to 12 psu, there was no significant difference in specific growth and length gain between juveniles at 12 and 35 psu. Food conversion ratio and condition factor at 12 and 35 psu were not significantly different, but food conversion ratio and condition factor at 5 psu was significantly greater and lower than at 35 psu respectively. In fish, gills are considered the major organ involved in osmoregulation. Within the gills, chloride cells are the predominant site of ion exchange which is driven by the Na⁺, K⁺- ATPase enzyme. Gill samples of juveniles exposed to 5, 12 and 35 psu for six weeks were examined histologically using light microscopy. Chloride cells of juveniles maintained at 5 psu were significantly more abundant than in juveniles at 12 and 35 psu. Chloride cells of juveniles at 5 psu were significantly larger than in juveniles kept at 12 psu, but not significantly different to those of juveniles kept at 35 psu. The ability of the juvenile fish to regulate plasma osmolality indicates that they are 'physiologically euryhaline', but the reduced growth and proliferation of chloride cells at 5 psu suggests that energy expenditure for osmoregulation is increased at hypoosmotic salinities. Salinity induced physiological responses could therefore not explain the natural distribution of early juvenile dusky kob and it is proposed that other environmental factors (e.g. temperature) are also important. It is also hypothesised that the high conductivity of an estuary in South Africa, to which our understanding is limited, may negate the effect of reduced salinity. Although freshwater input into estuaries is an important factor, further investigations to explain the distribution and abundance of early juveniles is required to make management recommendations. Dusky kob is also becoming an increasingly popular aquaculture species in South Africa. In this regard, early juvenile dusky kob can be grown at salinities as low as 12 psu without negatively affecting growth and production.
- 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:
Scientific management as applied to a South African sweet factory
- Authors: Bernstein, Jack
- Date: 1956
- Subjects: Candy industry -- Management , Candy industry -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1111 , http://hdl.handle.net/10962/d1013494
- Description: From Chapter 1: Among the many problems that the sweet industry in this country has had to overcome was the prejudice which favoured imported confectionery as against the local product. Fortunately this prejudice is slowly disappearing, firstly because imported sweets are largely unobtainable, and, secondly because the quality of the South African manufactured article has improved tremendously. Both the quantity and value of sweets produced in this country have increased over the last decade...
- Full Text:
- Authors: Bernstein, Jack
- Date: 1956
- Subjects: Candy industry -- Management , Candy industry -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:1111 , http://hdl.handle.net/10962/d1013494
- Description: From Chapter 1: Among the many problems that the sweet industry in this country has had to overcome was the prejudice which favoured imported confectionery as against the local product. Fortunately this prejudice is slowly disappearing, firstly because imported sweets are largely unobtainable, and, secondly because the quality of the South African manufactured article has improved tremendously. Both the quantity and value of sweets produced in this country have increased over the last decade...
- Full Text:
A review of mineral exploration drilling with particular reference to Southern Africa
- Authors: Bertram, N G E
- Date: 1980
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4931 , http://hdl.handle.net/10962/d1004930
- Description: The field of mineral exploration drilling is reviewed with particular reference to examples, and techniques practised, in southern Africa. Drilling is the most· definitive process in exploration and the most cost intensive. It is, therefore, imperative to insure that the maximum geological information available is obtained from a borehole to warrant the cost of drilling it. Methods and techniques of obtaining this information, at little additional expense, are described and reviewed. Non-core percussion and rotary drilled boreholes cost significantly less than diamond drill holes and, as a result, many more holes can be drilled for the money available. While the logging of cuttings is notoriously neglected in most exploration programmes; a great deal of information is available to the conscientious evaluator. Down-the-hole logging and sampling techniques improve the reliability of the borehole samples and provide rapid and inexpensive analyses and lithological data. Cored, or diamond drill boreholes, are the most versatile of the drilling methods available and provide the most reliable lithological and grade information. The handling, logging, sampling and storage of core and core data is discussed. For little additional expense, comprehensive and accurate borehole surveys can be conducted and oriented cores obtained from the borehole. The natural tendency of a borehole to deviate can be used to advantage with controlled drilling techniques. Multiple ore intersections are possible through controlled deflections from a master hole. Mathematical, statistical and simulation models are available to optimise borehole siting, spacing and grid dimensions .
- Full Text:
- Authors: Bertram, N G E
- Date: 1980
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4931 , http://hdl.handle.net/10962/d1004930
- Description: The field of mineral exploration drilling is reviewed with particular reference to examples, and techniques practised, in southern Africa. Drilling is the most· definitive process in exploration and the most cost intensive. It is, therefore, imperative to insure that the maximum geological information available is obtained from a borehole to warrant the cost of drilling it. Methods and techniques of obtaining this information, at little additional expense, are described and reviewed. Non-core percussion and rotary drilled boreholes cost significantly less than diamond drill holes and, as a result, many more holes can be drilled for the money available. While the logging of cuttings is notoriously neglected in most exploration programmes; a great deal of information is available to the conscientious evaluator. Down-the-hole logging and sampling techniques improve the reliability of the borehole samples and provide rapid and inexpensive analyses and lithological data. Cored, or diamond drill boreholes, are the most versatile of the drilling methods available and provide the most reliable lithological and grade information. The handling, logging, sampling and storage of core and core data is discussed. For little additional expense, comprehensive and accurate borehole surveys can be conducted and oriented cores obtained from the borehole. The natural tendency of a borehole to deviate can be used to advantage with controlled drilling techniques. Multiple ore intersections are possible through controlled deflections from a master hole. Mathematical, statistical and simulation models are available to optimise borehole siting, spacing and grid dimensions .
- Full Text:
Evaluating the cyber security skills gap relating to penetration testing
- Authors: Beukes, Dirk Johannes
- Date: 2021
- Subjects: Computer networks -- Security measures , Computer networks -- Monitoring , Computer networks -- Management , Data protection , Information technology -- Security measures , Professionals -- Supply and demand , Electronic data personnel -- Supply and demand
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/171120 , vital:42021
- Description: Information Technology (IT) is growing rapidly and has become an integral part of daily life. It provides a boundless list of services and opportunities, generating boundless sources of information, which could be abused or exploited. Due to this growth, there are thousands of new users added to the grid using computer systems in a static and mobile environment; this fact alone creates endless volumes of data to be exploited and hardware devices to be abused by the wrong people. The growth in the IT environment adds challenges that may affect users in their personal, professional, and business lives. There are constant threats on corporate and private computer networks and computer systems. In the corporate environment companies try to eliminate the threat by testing networks making use of penetration tests and by implementing cyber awareness programs to make employees more aware of the cyber threat. Penetration tests and vulnerability assessments are undervalued; are seen as a formality and are not used to increase system security. If used regularly the computer system will be more secure and attacks minimized. With the growth in technology, industries all over the globe become fully dependent on information systems in doing their day-to-day business. As technology evolves and new technology becomes available, the bigger the risk becomes to protect against the dangers which come with this new technology. For industry to protect itself against this growth in technology, personnel with a certain skill set is needed. This is where cyber security plays a very important role in the protection of information systems to ensure the confidentiality, integrity and availability of the information system itself and the data on the system. Due to this drive to secure information systems, the need for cyber security by professionals is on the rise as well. It is estimated that there is a shortage of one million cyber security professionals globally. What is the reason for this skills shortage? Will it be possible to close this skills shortage gap? This study is about identifying the skills gap and identifying possible ways to close this skills gap. In this study, research was conducted on the cyber security international standards, cyber security training at universities and international certification focusing specifically on penetration testing, the evaluation of the need of industry while recruiting new penetration testers, finishing with suggestions on how to fill possible gaps in the skills market with a conclusion.
- Full Text:
- Authors: Beukes, Dirk Johannes
- Date: 2021
- Subjects: Computer networks -- Security measures , Computer networks -- Monitoring , Computer networks -- Management , Data protection , Information technology -- Security measures , Professionals -- Supply and demand , Electronic data personnel -- Supply and demand
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/171120 , vital:42021
- Description: Information Technology (IT) is growing rapidly and has become an integral part of daily life. It provides a boundless list of services and opportunities, generating boundless sources of information, which could be abused or exploited. Due to this growth, there are thousands of new users added to the grid using computer systems in a static and mobile environment; this fact alone creates endless volumes of data to be exploited and hardware devices to be abused by the wrong people. The growth in the IT environment adds challenges that may affect users in their personal, professional, and business lives. There are constant threats on corporate and private computer networks and computer systems. In the corporate environment companies try to eliminate the threat by testing networks making use of penetration tests and by implementing cyber awareness programs to make employees more aware of the cyber threat. Penetration tests and vulnerability assessments are undervalued; are seen as a formality and are not used to increase system security. If used regularly the computer system will be more secure and attacks minimized. With the growth in technology, industries all over the globe become fully dependent on information systems in doing their day-to-day business. As technology evolves and new technology becomes available, the bigger the risk becomes to protect against the dangers which come with this new technology. For industry to protect itself against this growth in technology, personnel with a certain skill set is needed. This is where cyber security plays a very important role in the protection of information systems to ensure the confidentiality, integrity and availability of the information system itself and the data on the system. Due to this drive to secure information systems, the need for cyber security by professionals is on the rise as well. It is estimated that there is a shortage of one million cyber security professionals globally. What is the reason for this skills shortage? Will it be possible to close this skills shortage gap? This study is about identifying the skills gap and identifying possible ways to close this skills gap. In this study, research was conducted on the cyber security international standards, cyber security training at universities and international certification focusing specifically on penetration testing, the evaluation of the need of industry while recruiting new penetration testers, finishing with suggestions on how to fill possible gaps in the skills market with a conclusion.
- Full Text:
An investigation into the synergistic association between the major Clostridium cellulovorans cellulosomal endoglucanase and two hemicellulases on plant cell wall degradation
- Authors: Beukes, Natasha
- Date: 2008
- Subjects: Clostridium , Cellulose , Hemicellulose , Cellulase , Biomass conversion , Biomass energy -- South Africa , Energy crops -- South Africa , Bagasse -- Biodegradation , Pineapple -- Biodegradation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3968 , http://hdl.handle.net/10962/d1004027 , Clostridium , Cellulose , Hemicellulose , Cellulase , Biomass conversion , Biomass energy -- South Africa , Energy crops -- South Africa , Bagasse -- Biodegradation , Pineapple -- Biodegradation
- Description: The cellulosome is a multimeric enzyme complex that has the ability to metabolise a wide variety of carbonaceous compounds. Cellulosomal composition may vary according to the microbe’s nutritional requirement and allows for the anaerobic degradation of complex substrates. The complex substrates of interest in this research study were sugarcane bagasse and pineapple fibre waste, as they represent two important lignocellulosic, South African agricultural crops. The effective degradation of complex plant biomass wastes may present a valuable source of renewable compounds for the production of a variety of biofuels, for example bioethanol, and a variety of biocomposites of industrial importance. The identification of renewable energy sources for the production of biofuels is becoming increasingly important, as a result of the rapid depletion of the fossil fuels that are traditionally used as energy sources. An effective means of completely degrading lignocellulose biomass still remains elusive due to the complex heterogeneity of the substrate structure, and the fact that the effective degradation of the substrate requires a consortium of enzymes. The cellulosome not only provides a variety of enzymes with varying specificities, but also promote a close proximity between the catalytic components (enzymes). The close proximity between the enzymes promotes the synergistic degradation of complex plant biomass for the production of valuable energy products. Previous synergy studies have focused predominantly on the synergistic associations between cellulases; however, the synergy between hemicellulases has occasionally been documented. This research project established the synergistic associations between two Clostridium cellulovorans hemicellulases that may be incorporated into the cellulosome and a cellulosomal endoglucanase that is conserved in all cellulosomes. This research study indicated that there was indeed a synergistic degradation of the complex plant biomass (sugarcane bagasse and pineapple fibre). The degrees of synergy and the ratio of the enzymes varied between the two complex substrates. The initial degradation of the bagasse required the presence of all the enzymes and proceeded at an enhanced rate under sulphidogenic conditions; however, there was a low production of fermentable sugars. The low quantity of fermentable sugars produced by the degradation of the bagasse may be related to the chemical composition of the substrate. The sugarcane contains a high percentage of lignin forming a protective layer around the holocellulose, thus the glycosidic bonds are shielded extensively from enzymatic attack. In comparison, the initial degradation of the pineapple fibre required the action of hemicellulases, and proceeded at an enhanced rate under sulphidogenic conditions. The initial degradation of the pineapple fibre produced a substantially larger quantity of fermentable sugars in comparison to the bagasse. The higher production of fermentable sugars from the degradation of the pineapple fibre may be explained by the fact that this substrate may have a lower percentage of lignin than the bagasse, thus allowing a larger percentage of the glycosidic bonds to be exposed to enzymatic attack. The data obtained also indicated that the glycosidic bonds from the hemicellulosic components of the pineapple fibre shielded the glycosidic bonds of the cellulose component. The identification of the chemical components of the different substrates may allow for the initial development of an ideal enzyme complex (designer cellulosome) with enzymes in an ideal ratio with optimal synergy that will effectively degrade the complex plant biomass substrate.
- Full Text:
- Authors: Beukes, Natasha
- Date: 2008
- Subjects: Clostridium , Cellulose , Hemicellulose , Cellulase , Biomass conversion , Biomass energy -- South Africa , Energy crops -- South Africa , Bagasse -- Biodegradation , Pineapple -- Biodegradation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3968 , http://hdl.handle.net/10962/d1004027 , Clostridium , Cellulose , Hemicellulose , Cellulase , Biomass conversion , Biomass energy -- South Africa , Energy crops -- South Africa , Bagasse -- Biodegradation , Pineapple -- Biodegradation
- Description: The cellulosome is a multimeric enzyme complex that has the ability to metabolise a wide variety of carbonaceous compounds. Cellulosomal composition may vary according to the microbe’s nutritional requirement and allows for the anaerobic degradation of complex substrates. The complex substrates of interest in this research study were sugarcane bagasse and pineapple fibre waste, as they represent two important lignocellulosic, South African agricultural crops. The effective degradation of complex plant biomass wastes may present a valuable source of renewable compounds for the production of a variety of biofuels, for example bioethanol, and a variety of biocomposites of industrial importance. The identification of renewable energy sources for the production of biofuels is becoming increasingly important, as a result of the rapid depletion of the fossil fuels that are traditionally used as energy sources. An effective means of completely degrading lignocellulose biomass still remains elusive due to the complex heterogeneity of the substrate structure, and the fact that the effective degradation of the substrate requires a consortium of enzymes. The cellulosome not only provides a variety of enzymes with varying specificities, but also promote a close proximity between the catalytic components (enzymes). The close proximity between the enzymes promotes the synergistic degradation of complex plant biomass for the production of valuable energy products. Previous synergy studies have focused predominantly on the synergistic associations between cellulases; however, the synergy between hemicellulases has occasionally been documented. This research project established the synergistic associations between two Clostridium cellulovorans hemicellulases that may be incorporated into the cellulosome and a cellulosomal endoglucanase that is conserved in all cellulosomes. This research study indicated that there was indeed a synergistic degradation of the complex plant biomass (sugarcane bagasse and pineapple fibre). The degrees of synergy and the ratio of the enzymes varied between the two complex substrates. The initial degradation of the bagasse required the presence of all the enzymes and proceeded at an enhanced rate under sulphidogenic conditions; however, there was a low production of fermentable sugars. The low quantity of fermentable sugars produced by the degradation of the bagasse may be related to the chemical composition of the substrate. The sugarcane contains a high percentage of lignin forming a protective layer around the holocellulose, thus the glycosidic bonds are shielded extensively from enzymatic attack. In comparison, the initial degradation of the pineapple fibre required the action of hemicellulases, and proceeded at an enhanced rate under sulphidogenic conditions. The initial degradation of the pineapple fibre produced a substantially larger quantity of fermentable sugars in comparison to the bagasse. The higher production of fermentable sugars from the degradation of the pineapple fibre may be explained by the fact that this substrate may have a lower percentage of lignin than the bagasse, thus allowing a larger percentage of the glycosidic bonds to be exposed to enzymatic attack. The data obtained also indicated that the glycosidic bonds from the hemicellulosic components of the pineapple fibre shielded the glycosidic bonds of the cellulose component. The identification of the chemical components of the different substrates may allow for the initial development of an ideal enzyme complex (designer cellulosome) with enzymes in an ideal ratio with optimal synergy that will effectively degrade the complex plant biomass substrate.
- Full Text:
An experimental study of the effect of Acacia mearnsii (black wattle trees) on streamflow in the Sand River, Eastern Cape
- Authors: Beyers, Gregory John
- Date: 1999
- Subjects: Wattles (Plants) -- South Africa , Wattles (Plants) -- South Africa -- Eastern Cape , Sand river (South africa) , Streamflow , Streamflow -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4832 , http://hdl.handle.net/10962/d1005507 , Wattles (Plants) -- South Africa , Wattles (Plants) -- South Africa -- Eastern Cape , Sand river (South africa) , Streamflow , Streamflow -- South Africa
- Description: This thesis explores the effect of Acacia mearnsii on streamflow in the Eastern Cape. There is a need for data on the localised effects of removing alien trees from the riparian zones within the Fynbos Biome. Fynbos catchments throughout the Western and Eastern Cape yield large quantities of good quality water which is an essential resource in the region. To convince local land owners to manage their riparian zones, small scale experimental results will prove invaluable to assure them of the immediate advantages for themselves and for downstream water users. Three permanent weirs were built 500 m apart to monitor the effect of removing A. mearnsii on streamflow in the Sand River, Eastern Cape. Consecutive weirs allowed for the comparison of streamflow between a cleared and uncleared section of the river without significant differences in riparian conditions, channel morphology and vegetation densities. A site survey confirmed comparable densities of A. mearnsii in both sections. A sample of trees was weighed and a relationship was found between diameter at breast height and above ground wet biomass. Between the first two weirs, 2.5 ha of riparian zone was cleared amounting to approximately 160tlha. Streamflow was monitored from the 10th of January 1996 to the 9th of September 1996. The average streamflow reduction for the duration of the experiment was 15.1 m³/ha/day or 551 mm per annum. Initially, after a period of above average rainfall, streamflow was augmented by discharge from the riparian zone but as conditions dried out, there was a net uptake of water with the highest average uptake of 23. 7m³/ha/day in June. A comparison between weather conditions and streamflow reduction indicated there is a complex relationship, with evidence of A. mearnsii exhibiting control of water loss during dry conditions. Acacia mearnsii trees in the riparian zone have been shown to cause significant streamflow reduction. Permanent weirs were found to be appropriate for this type of study. There is a need for further research on the effect of alien trees in riparian zones around South Africa as there is potential for significant increases in streamflow.
- Full Text:
- Authors: Beyers, Gregory John
- Date: 1999
- Subjects: Wattles (Plants) -- South Africa , Wattles (Plants) -- South Africa -- Eastern Cape , Sand river (South africa) , Streamflow , Streamflow -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4832 , http://hdl.handle.net/10962/d1005507 , Wattles (Plants) -- South Africa , Wattles (Plants) -- South Africa -- Eastern Cape , Sand river (South africa) , Streamflow , Streamflow -- South Africa
- Description: This thesis explores the effect of Acacia mearnsii on streamflow in the Eastern Cape. There is a need for data on the localised effects of removing alien trees from the riparian zones within the Fynbos Biome. Fynbos catchments throughout the Western and Eastern Cape yield large quantities of good quality water which is an essential resource in the region. To convince local land owners to manage their riparian zones, small scale experimental results will prove invaluable to assure them of the immediate advantages for themselves and for downstream water users. Three permanent weirs were built 500 m apart to monitor the effect of removing A. mearnsii on streamflow in the Sand River, Eastern Cape. Consecutive weirs allowed for the comparison of streamflow between a cleared and uncleared section of the river without significant differences in riparian conditions, channel morphology and vegetation densities. A site survey confirmed comparable densities of A. mearnsii in both sections. A sample of trees was weighed and a relationship was found between diameter at breast height and above ground wet biomass. Between the first two weirs, 2.5 ha of riparian zone was cleared amounting to approximately 160tlha. Streamflow was monitored from the 10th of January 1996 to the 9th of September 1996. The average streamflow reduction for the duration of the experiment was 15.1 m³/ha/day or 551 mm per annum. Initially, after a period of above average rainfall, streamflow was augmented by discharge from the riparian zone but as conditions dried out, there was a net uptake of water with the highest average uptake of 23. 7m³/ha/day in June. A comparison between weather conditions and streamflow reduction indicated there is a complex relationship, with evidence of A. mearnsii exhibiting control of water loss during dry conditions. Acacia mearnsii trees in the riparian zone have been shown to cause significant streamflow reduction. Permanent weirs were found to be appropriate for this type of study. There is a need for further research on the effect of alien trees in riparian zones around South Africa as there is potential for significant increases in streamflow.
- Full Text:
The effects of age on the worker capacity and mechanisation on the task demands in a South African manufacturing industry
- Bezuidenhout, Samantha Catherine
- Authors: Bezuidenhout, Samantha Catherine
- Date: 2014
- Subjects: Age and employment -- South Africa , Labor -- Social aspects -- South Africa , Brickmaking -- South Africa -- Automation , Brickmaking -- Social aspects -- South Africa , Brick trade -- South Africa , Aging -- Social aspects -- South Africa , Aging -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5151 , http://hdl.handle.net/10962/d1013167
- Description: The focus of the study was two-fold, firstly to determine the effect of age on the capacity of manual materials handling workers and secondly to determine the effect of increasing task mechanisation on the workers’ responses to task demands. The first component of this study, namely Part I, 101 male and 12 female ‘unskilled’ manual workers – of various ages – from a brick manufacturing industry were assessed. Anthropometric, health and strength factors were measured to improve the understanding of the South African manual worker capacity and more specifically, the effect of age on this capacity. Data collection was done between 7.30am and 9.30am in a laboratory-type setting on-site. Anthropometric characteristics (including body mass index, waist to hip ratio, waist circumference and body fat percentage) provided information on the state of obesity and the impact of age in the South African context. Linked to this, the health factors (including blood pressure, resting heart rate and a self-reported questionnaire) provide an extra snapshot of the disease profile in South Africa, and could potentially influence other capacity factors. Isometric strength capacities (of eight different areas, namely: back, leg, bicep, shoulder, pinch, pinch and pull) demonstrated whether South African manual workers show the same decline in strength with aging as seen in industrially advanced countries. The second component of the study, Part II, was performed in situ and measured the workers’ responses to task demands of three brick palletising tasks, one manual (n=21) and two with increasing mechanisation (n=12 each). Spinal kinematics, joint forces and working heart rate were assessed on normal work days during a 30-lift duration and body discomfort measures were taken at the start, middle and end of the work-shift. Spinal kinematics were measured dynamically using a lumbar motion monitor, whereas the spinal forces were estimated using the three dimensional static strength prediction program. The worker capacity results showed that waist to hip ratio, waist circumference and body fat percentage increased significantly with aging, whereas body mass index was not affected by age. All body morphology values were within ‘normal’ ranges. Although diastolic blood pressure increased significantly with age, systolic was not affected significantly by age. Both groups, however, showed an increasing prevalence of hypertension with aging. There were no significant changes in resting heart rate with aging, with a range of 66 bt.min⁻¹ to 74.86 bt.min⁻¹, therefore within normal ranges. Of the strength factors, age only affected shoulder and push strength significantly: Showing a decrease in shoulder strength from 49.89 kgF to 39.91 kgF in the men aged 20-29 to the 50-59 respectively and an increase in push strength from men aged 30-39 and 40-49 to those aged 50-59. Part II results revealed highly frequent lift rates and large degrees of sagittal flexion and lateral bending in all three tasks. These postures adopted for long durations are likely to lead to the development of musculoskeletal disorders. Heart rates of workers from the three tasks were significantly different and heart rates for two tasks were above the recommended 110 bt.min⁻¹. Similarly the body discomfort ratings of the three tasks differed, although a common trend was seen in that lower back pain was the most commonly reported area of discomfort in all tasks. South African manual materials handling males did not show the same responses to aging as men from industrially advanced countries, calling for further research into these differences. Due to the high risks of the three tasks assessed, future research and interventions are required to reduce the risk of injury in the assessed tasks.
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- Authors: Bezuidenhout, Samantha Catherine
- Date: 2014
- Subjects: Age and employment -- South Africa , Labor -- Social aspects -- South Africa , Brickmaking -- South Africa -- Automation , Brickmaking -- Social aspects -- South Africa , Brick trade -- South Africa , Aging -- Social aspects -- South Africa , Aging -- Research
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5151 , http://hdl.handle.net/10962/d1013167
- Description: The focus of the study was two-fold, firstly to determine the effect of age on the capacity of manual materials handling workers and secondly to determine the effect of increasing task mechanisation on the workers’ responses to task demands. The first component of this study, namely Part I, 101 male and 12 female ‘unskilled’ manual workers – of various ages – from a brick manufacturing industry were assessed. Anthropometric, health and strength factors were measured to improve the understanding of the South African manual worker capacity and more specifically, the effect of age on this capacity. Data collection was done between 7.30am and 9.30am in a laboratory-type setting on-site. Anthropometric characteristics (including body mass index, waist to hip ratio, waist circumference and body fat percentage) provided information on the state of obesity and the impact of age in the South African context. Linked to this, the health factors (including blood pressure, resting heart rate and a self-reported questionnaire) provide an extra snapshot of the disease profile in South Africa, and could potentially influence other capacity factors. Isometric strength capacities (of eight different areas, namely: back, leg, bicep, shoulder, pinch, pinch and pull) demonstrated whether South African manual workers show the same decline in strength with aging as seen in industrially advanced countries. The second component of the study, Part II, was performed in situ and measured the workers’ responses to task demands of three brick palletising tasks, one manual (n=21) and two with increasing mechanisation (n=12 each). Spinal kinematics, joint forces and working heart rate were assessed on normal work days during a 30-lift duration and body discomfort measures were taken at the start, middle and end of the work-shift. Spinal kinematics were measured dynamically using a lumbar motion monitor, whereas the spinal forces were estimated using the three dimensional static strength prediction program. The worker capacity results showed that waist to hip ratio, waist circumference and body fat percentage increased significantly with aging, whereas body mass index was not affected by age. All body morphology values were within ‘normal’ ranges. Although diastolic blood pressure increased significantly with age, systolic was not affected significantly by age. Both groups, however, showed an increasing prevalence of hypertension with aging. There were no significant changes in resting heart rate with aging, with a range of 66 bt.min⁻¹ to 74.86 bt.min⁻¹, therefore within normal ranges. Of the strength factors, age only affected shoulder and push strength significantly: Showing a decrease in shoulder strength from 49.89 kgF to 39.91 kgF in the men aged 20-29 to the 50-59 respectively and an increase in push strength from men aged 30-39 and 40-49 to those aged 50-59. Part II results revealed highly frequent lift rates and large degrees of sagittal flexion and lateral bending in all three tasks. These postures adopted for long durations are likely to lead to the development of musculoskeletal disorders. Heart rates of workers from the three tasks were significantly different and heart rates for two tasks were above the recommended 110 bt.min⁻¹. Similarly the body discomfort ratings of the three tasks differed, although a common trend was seen in that lower back pain was the most commonly reported area of discomfort in all tasks. South African manual materials handling males did not show the same responses to aging as men from industrially advanced countries, calling for further research into these differences. Due to the high risks of the three tasks assessed, future research and interventions are required to reduce the risk of injury in the assessed tasks.
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Delineation of buried stream channels using geophysical techniques
- Authors: Biedler, Murray W
- Date: 1994
- Subjects: Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4823 , http://hdl.handle.net/10962/d1005498 , Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Description: This study sets out to evaluate the use of geophysical methods for delineating buried stream channels, which can act as zones of preferential flow within a less hydraulically conductive aquifer. This information is important for gaining an understanding of flow dynamics of alluvial systems. The most reliable method of delineating the dimensions of aquifers is by drilling, which is an expensive proposition and is best preceded by a preliminary geophysical study to help define target zones for a drilling program. The study area is located adjacent to the Coerney River in the Sundays River Valley. Geologically it consists of approximately 5 metres of alluvial fines, covering 3 metres of coarse cobbles and boulders, all underlain by alternating siltstone and sandstone beds of indeterminate thickness. Throughout the area the water is very shallow at approximately 2 metres depth and the groundwater tends to be very saline. An air photo study revealed an old oxbow channel that had been covered over by subsequent agricultural land use. The geophysical methods available for the study were portable seismic refraction, electrical resistivity and electromagnetics. Preliminary field tests clearly showed that seismics did not produce valid results. The methods of electrical resistivity and electromagnetics produced good data and were subjected to further assessment. A grid was surveyed over the study area and both geophysical methods were applied at regularly spaced stations. Soil samples were taken over the same survey grid and analyzed for electrical conductivity in a soils laboratory. The results were compared to the geophysical data in an attempt to quantify the relationship between geophysical response and soil salinity. The data from the electromagnetic survey showed areas of low electrical conductivity which was a possible indication of zones of preferential groundwater flow. A transect of boreholes was drilled over selected electrical conductivity lows and successfully intersected the buried stream channel. A comparison of the borehole logs with the layered earth models from the Vertical Electrical Soundings indicated that the electrical resistivity method was not responding to the features of the buried stream channel and the cobblestone layer. This proved the electromagnetic method to be more valuable for this particular study
- Full Text:
- Authors: Biedler, Murray W
- Date: 1994
- Subjects: Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4823 , http://hdl.handle.net/10962/d1005498 , Stream channelization , Seismic refraction method , Electric prospecting , Electromagnetism , Aquifers -- South Africa , Groundwater , Hydrogeology -- South Africa
- Description: This study sets out to evaluate the use of geophysical methods for delineating buried stream channels, which can act as zones of preferential flow within a less hydraulically conductive aquifer. This information is important for gaining an understanding of flow dynamics of alluvial systems. The most reliable method of delineating the dimensions of aquifers is by drilling, which is an expensive proposition and is best preceded by a preliminary geophysical study to help define target zones for a drilling program. The study area is located adjacent to the Coerney River in the Sundays River Valley. Geologically it consists of approximately 5 metres of alluvial fines, covering 3 metres of coarse cobbles and boulders, all underlain by alternating siltstone and sandstone beds of indeterminate thickness. Throughout the area the water is very shallow at approximately 2 metres depth and the groundwater tends to be very saline. An air photo study revealed an old oxbow channel that had been covered over by subsequent agricultural land use. The geophysical methods available for the study were portable seismic refraction, electrical resistivity and electromagnetics. Preliminary field tests clearly showed that seismics did not produce valid results. The methods of electrical resistivity and electromagnetics produced good data and were subjected to further assessment. A grid was surveyed over the study area and both geophysical methods were applied at regularly spaced stations. Soil samples were taken over the same survey grid and analyzed for electrical conductivity in a soils laboratory. The results were compared to the geophysical data in an attempt to quantify the relationship between geophysical response and soil salinity. The data from the electromagnetic survey showed areas of low electrical conductivity which was a possible indication of zones of preferential groundwater flow. A transect of boreholes was drilled over selected electrical conductivity lows and successfully intersected the buried stream channel. A comparison of the borehole logs with the layered earth models from the Vertical Electrical Soundings indicated that the electrical resistivity method was not responding to the features of the buried stream channel and the cobblestone layer. This proved the electromagnetic method to be more valuable for this particular study
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A study of four-dimensional oscillator groups and the associated left-invariant control affine systems
- Authors: Biggs, Rory
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164941 , vital:41186
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Department of Mathematics, 2012
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- Authors: Biggs, Rory
- Date: 2012
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/164941 , vital:41186
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Department of Mathematics, 2012
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