Occurrence of mugilid and sparid fishes in Zostera capensis and bare sediment habitats of the Knysna Estuary
- Authors: Pollard, Melissa
- Date: 2018
- Subjects: Gray mullets South Africa Knysna Lagoon , Sparidae South Africa Knysna Lagoon , Seagrasses South Africa Knysna Lagoon , Eelgrass South Africa Knysna Lagoon , Gray mullets Habitat South Africa Knysna Lagoon , Sparidae Habitat South Africa Knysna Lagoon , Underwater videography in wildlife monitoring , Seining , Zostera capensis Setchel
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54979 , vital:26641
- Description: Seagrass meadows are regarded as one of the most unique and valuable ecosystems in the biosphere, primarily because of the variety of services that they provide. Seagrass meadows serve as nursery grounds for many species and often play an important role in the juvenile stages of economically and recreationally important fish. Zostera capensis Setchell is one of the most dominant submerged macrophytes and the most common seagrass in South African estuaries and is often referred to as eelgrass. Zostera capensis meadows occupy a large area within the Knysna Estuary but little is known about their importance to associated fish assemblages. With Z. capensis meadows being under increased pressure from anthropogenic influences, it is important to establish which fish species and families utilize these habitats and what role they play in the ecology of fish assemblages within the Knysna Estuary. The primary objective of this study was to compare the use of Z. capensis and adjacent bare sediment areas by mainly large juvenile and subadult sparids and mugilids using different techniques. The two main hypotheses were as follows; 1) Mugilidae are likely to be more dominant in the unvegetated areas of the estuary littoral and Sparidae are likely to predominate within the Z. capensis bed areas of the estuary littoral. 2) The non-destructive underwater video monitoring method would yield similar fish composition data to seine netting sampling of the identical sites. Both hypotheses were assessed using data collected during this study and the analysis of historical unpublished data. Overall, Mugilidae were more abundant at bare unvegetated areas where they did most of their foraging. Sparidae were more abundant in the Z. capensis beds, which was also the habitat where they primarily foraged. With regards to the comparison of two different sampling methods, namely underwater video monitoring and seine netting, similar patterns arose with regards to the fish species observed in camera footage and those captured in the seine net, although the abundances were not always comparable.
- Full Text:
- Date Issued: 2018
- Authors: Pollard, Melissa
- Date: 2018
- Subjects: Gray mullets South Africa Knysna Lagoon , Sparidae South Africa Knysna Lagoon , Seagrasses South Africa Knysna Lagoon , Eelgrass South Africa Knysna Lagoon , Gray mullets Habitat South Africa Knysna Lagoon , Sparidae Habitat South Africa Knysna Lagoon , Underwater videography in wildlife monitoring , Seining , Zostera capensis Setchel
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/54979 , vital:26641
- Description: Seagrass meadows are regarded as one of the most unique and valuable ecosystems in the biosphere, primarily because of the variety of services that they provide. Seagrass meadows serve as nursery grounds for many species and often play an important role in the juvenile stages of economically and recreationally important fish. Zostera capensis Setchell is one of the most dominant submerged macrophytes and the most common seagrass in South African estuaries and is often referred to as eelgrass. Zostera capensis meadows occupy a large area within the Knysna Estuary but little is known about their importance to associated fish assemblages. With Z. capensis meadows being under increased pressure from anthropogenic influences, it is important to establish which fish species and families utilize these habitats and what role they play in the ecology of fish assemblages within the Knysna Estuary. The primary objective of this study was to compare the use of Z. capensis and adjacent bare sediment areas by mainly large juvenile and subadult sparids and mugilids using different techniques. The two main hypotheses were as follows; 1) Mugilidae are likely to be more dominant in the unvegetated areas of the estuary littoral and Sparidae are likely to predominate within the Z. capensis bed areas of the estuary littoral. 2) The non-destructive underwater video monitoring method would yield similar fish composition data to seine netting sampling of the identical sites. Both hypotheses were assessed using data collected during this study and the analysis of historical unpublished data. Overall, Mugilidae were more abundant at bare unvegetated areas where they did most of their foraging. Sparidae were more abundant in the Z. capensis beds, which was also the habitat where they primarily foraged. With regards to the comparison of two different sampling methods, namely underwater video monitoring and seine netting, similar patterns arose with regards to the fish species observed in camera footage and those captured in the seine net, although the abundances were not always comparable.
- Full Text:
- Date Issued: 2018
On the characterization of solar cells using advanced imaging techniques
- Authors: Dix-Peek, Ross Michael
- Date: 2018
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17944 , vital:28544
- Description: Photovoltaic (PV) cells are devices capable of producing electricity - in particular, from the abundant resource of sunlight. Solar energy (from PV cells) provides a sustainable alternative to fossil fuel energy sources such as coal and oil. PV cells are typically strung in series in PV modules to generate the current and voltage required for commercial use. However, PV cell performance can be limited by defects and degradation. Under operational conditions due to mismatch and shading, individual cells within a PV module can be forced to operate in their reverse bias regime. Depending on the severity of the reverse bias and the defects present in the cell, the longevity of the cell and/or the module can be affected. Reverse bias (assuming bypass diodes are absent) can result in localised heating that can affect the encapsulant polymer’s longevity as well as degrade the cell’s performance over time. However, under more severe reverse bias, the cell could fail, drastically affecting the performance of the module. PV cells can be characterised using various opto-electronic non-destructive techniques, this provides a set of powerful tools which allow the application of multiple such techniques to the same sample. Furthermore, this allows for an in-depth study of the device. Dark Current-Voltage (I-V) measurements, Electroluminescence (EL), Infrared (IR) thermography, Light Beam Induced Current (LBIC) measurements, and the associated techniques are all examples of such tools and are used within this study. An experimental setup was developed to perform dark I-V measurements, EL imaging, IR thermography and LBIC measurements. Part of the development of the experimental setup was the design of an enclosure in which to perform all the measurements. The enclosure minimised internal reflection, and isolated the experiment from electromagnetic radiation. Due to the complex mathematical model applied to the I-V curve, an Evolutionary Algorithm was used to determine optimal parameter values for the equation. More specifically, a Genetic Algorithm was used in the Parameter Optimisation (or Extraction) of the dark I-V parameters based upon the two-diode model for PV cells. The resulting parameters give an indication of the material and device quality. However, to determine the spatial distribution of the defects that effect the I-V response of the device, various imaging techniques were utilised. LBIC is a technique that uses a focussed light beam to raster scan across the surface of a PV cell. The local photo-induced current/voltage can then be measured and compiled into a response map. LBIC was used to determine the local current response across the device. The intensity distribution of EL signal is related to the local junction voltage and the local quantum efficiency. EL intensity imaging with a Si CCD camera was used to determine the spatial distribution of features visible both in the forward bias and in the reverse bias. The experimental setup utilised had a micron scale resolution. A voltage dependent approach was utilised to further characterise features observed. In forward bias, the local junction varies across the device due to parasitic resistances such as series and shunt resistance. At higher forward bias conditions (in the vicinity of and higher than maximum power voltage), series resistance becomes a limiting factor. Therefore, utilising a voltage dependent approach allows for the determination of a series resistance map from voltage dependent EL images. In reverse bias, localised radiative processes can be imaged. These radiative processes are related to defects in the device, such as Al stains, FeSi2 needles and avalanche breakdown. The processes are related to highly localised current flow; this causes localised heating which degrades the device. The voltage dependent Reverse Bias EL (ReBEL) imaging was also used to determine the local breakdown voltage of radiative reverse features. Dark IR thermography is a technique used in the identification of high current sites that leads to localised Joule heating, particularly in reverse bias. In this study, thermography was used to identify breakdown sites and shunts. The results of this study allow for an in-depth analysis of defects found in multi-crystalline Si PV cells using the opto-electronic techniques mentioned above. The multi-pronged approach allowed from a comparison of the various opto-electronic techniques, as well as a more in-depth characterisation of the defects than if only one technique was used.
- Full Text:
- Date Issued: 2018
- Authors: Dix-Peek, Ross Michael
- Date: 2018
- Subjects: Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17944 , vital:28544
- Description: Photovoltaic (PV) cells are devices capable of producing electricity - in particular, from the abundant resource of sunlight. Solar energy (from PV cells) provides a sustainable alternative to fossil fuel energy sources such as coal and oil. PV cells are typically strung in series in PV modules to generate the current and voltage required for commercial use. However, PV cell performance can be limited by defects and degradation. Under operational conditions due to mismatch and shading, individual cells within a PV module can be forced to operate in their reverse bias regime. Depending on the severity of the reverse bias and the defects present in the cell, the longevity of the cell and/or the module can be affected. Reverse bias (assuming bypass diodes are absent) can result in localised heating that can affect the encapsulant polymer’s longevity as well as degrade the cell’s performance over time. However, under more severe reverse bias, the cell could fail, drastically affecting the performance of the module. PV cells can be characterised using various opto-electronic non-destructive techniques, this provides a set of powerful tools which allow the application of multiple such techniques to the same sample. Furthermore, this allows for an in-depth study of the device. Dark Current-Voltage (I-V) measurements, Electroluminescence (EL), Infrared (IR) thermography, Light Beam Induced Current (LBIC) measurements, and the associated techniques are all examples of such tools and are used within this study. An experimental setup was developed to perform dark I-V measurements, EL imaging, IR thermography and LBIC measurements. Part of the development of the experimental setup was the design of an enclosure in which to perform all the measurements. The enclosure minimised internal reflection, and isolated the experiment from electromagnetic radiation. Due to the complex mathematical model applied to the I-V curve, an Evolutionary Algorithm was used to determine optimal parameter values for the equation. More specifically, a Genetic Algorithm was used in the Parameter Optimisation (or Extraction) of the dark I-V parameters based upon the two-diode model for PV cells. The resulting parameters give an indication of the material and device quality. However, to determine the spatial distribution of the defects that effect the I-V response of the device, various imaging techniques were utilised. LBIC is a technique that uses a focussed light beam to raster scan across the surface of a PV cell. The local photo-induced current/voltage can then be measured and compiled into a response map. LBIC was used to determine the local current response across the device. The intensity distribution of EL signal is related to the local junction voltage and the local quantum efficiency. EL intensity imaging with a Si CCD camera was used to determine the spatial distribution of features visible both in the forward bias and in the reverse bias. The experimental setup utilised had a micron scale resolution. A voltage dependent approach was utilised to further characterise features observed. In forward bias, the local junction varies across the device due to parasitic resistances such as series and shunt resistance. At higher forward bias conditions (in the vicinity of and higher than maximum power voltage), series resistance becomes a limiting factor. Therefore, utilising a voltage dependent approach allows for the determination of a series resistance map from voltage dependent EL images. In reverse bias, localised radiative processes can be imaged. These radiative processes are related to defects in the device, such as Al stains, FeSi2 needles and avalanche breakdown. The processes are related to highly localised current flow; this causes localised heating which degrades the device. The voltage dependent Reverse Bias EL (ReBEL) imaging was also used to determine the local breakdown voltage of radiative reverse features. Dark IR thermography is a technique used in the identification of high current sites that leads to localised Joule heating, particularly in reverse bias. In this study, thermography was used to identify breakdown sites and shunts. The results of this study allow for an in-depth analysis of defects found in multi-crystalline Si PV cells using the opto-electronic techniques mentioned above. The multi-pronged approach allowed from a comparison of the various opto-electronic techniques, as well as a more in-depth characterisation of the defects than if only one technique was used.
- Full Text:
- Date Issued: 2018
Passive acoustic monitoring of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay: temporal patterns and group dynamics
- Authors: Hlati, Kuhle
- Date: 2018
- Subjects: Marine mammals -- Effect of noise on -- Research , Oceanography Aquatic ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30050 , vital:30813
- Description: In this study, passive acoustic monitoring (PAM) was used to investigate the diel patterns of occurrence and activities of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay, during April 2015 - July 2017. Automatic detectors were used to extract dolphin whistles and echolocation clicks from the acoustic recordings. The vocalizations were extracted without identifying the dolphin species due to insufficient visual observation data collected concurrent with the acoustic recordings to conclusively discriminate the two species. The correct detection performance and false alarm rate of the detectors for each acoustic recorder were evaluated and automatic detection protocols were developed. For a recorder that was initially deployed in the study (DSG recorder), the detectors achieved 64 - 80% true detection rates with false alarm rates of 10 - 22%. A more modern recorder (MicroMARS recorder) which replaced this one had a lower signal-to-noise ratio (SNR) and could sample at a higher frequency, the detectors achieved greater than 80% true detection rates and less than 5% false alarm rates. It was evident that SNR and sampling rate influenced the detection performance of the detectors. When acoustic recordings were compared to visual observations which were conducted concurrently with some of the recordings, it was apparent that acoustic recorders performed nearly twice as well as land-based observers in terms of overall detection of dolphin groups. Group size and behaviour affected acoustic detection rates of dolphins; large groups that were visually detected and which were foraging at the time, were more likely to be acoustically detected than small groups or single animals or groups associated travelling at the time. The detection rates of echolocation clicks and whistles showed a diel pattern of occurrence of coastal dolphins in Plettenberg Bay with a higher nighttime than daytime occurrence. The detection rates were higher from midday to midnight with a peak during dusk. The high activity of dolphins in the late afternoon and evening reported in this study was also supported by visual data (afternoons) in the area and acoustic studies in other regions. Comparison of acoustic detection rates and visual data from this study with past observations suggest that the occurrence patterns of T. aduncus in the bay appear to have changed; such a change may be influenced by changes in prey behaviour or distribution, or other factors. The significally higher detection rates of echolocation clicks than whistles and dominant foraging behaviour based on visual data suggest that Robberg may be an important feeding ground for the coastal dolphins that are frequenting Plettenberg Bay. The current study builds on a growing body of literature demonstrating that PAM and automatic detectors are powerful and effective tools for monitoring cetacean species. However, there are several factors that limit the detection of vocalization such as direction of the sound source, distance from hydrophone, sound propagation conditions, low SNR and acoustic masking. Regardless of these limitations, results from PAM showed diel patterns of occurrence of the coastal dolphins in the bay which could have not been achieved from visual monitoring, in particular the high nighttime occurrence patterns. PAM holds potential to be largely utilized in South Africa for dolphin and other cetacean studies. Further research and monitoring using PAM could potentially assist to better understand the drivers of the dolphin occurrence and activity patterns in the bay.
- Full Text:
- Date Issued: 2018
- Authors: Hlati, Kuhle
- Date: 2018
- Subjects: Marine mammals -- Effect of noise on -- Research , Oceanography Aquatic ecology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30050 , vital:30813
- Description: In this study, passive acoustic monitoring (PAM) was used to investigate the diel patterns of occurrence and activities of coastal dolphins (Sousa plumbea and Tursiops aduncus) in Plettenberg Bay, during April 2015 - July 2017. Automatic detectors were used to extract dolphin whistles and echolocation clicks from the acoustic recordings. The vocalizations were extracted without identifying the dolphin species due to insufficient visual observation data collected concurrent with the acoustic recordings to conclusively discriminate the two species. The correct detection performance and false alarm rate of the detectors for each acoustic recorder were evaluated and automatic detection protocols were developed. For a recorder that was initially deployed in the study (DSG recorder), the detectors achieved 64 - 80% true detection rates with false alarm rates of 10 - 22%. A more modern recorder (MicroMARS recorder) which replaced this one had a lower signal-to-noise ratio (SNR) and could sample at a higher frequency, the detectors achieved greater than 80% true detection rates and less than 5% false alarm rates. It was evident that SNR and sampling rate influenced the detection performance of the detectors. When acoustic recordings were compared to visual observations which were conducted concurrently with some of the recordings, it was apparent that acoustic recorders performed nearly twice as well as land-based observers in terms of overall detection of dolphin groups. Group size and behaviour affected acoustic detection rates of dolphins; large groups that were visually detected and which were foraging at the time, were more likely to be acoustically detected than small groups or single animals or groups associated travelling at the time. The detection rates of echolocation clicks and whistles showed a diel pattern of occurrence of coastal dolphins in Plettenberg Bay with a higher nighttime than daytime occurrence. The detection rates were higher from midday to midnight with a peak during dusk. The high activity of dolphins in the late afternoon and evening reported in this study was also supported by visual data (afternoons) in the area and acoustic studies in other regions. Comparison of acoustic detection rates and visual data from this study with past observations suggest that the occurrence patterns of T. aduncus in the bay appear to have changed; such a change may be influenced by changes in prey behaviour or distribution, or other factors. The significally higher detection rates of echolocation clicks than whistles and dominant foraging behaviour based on visual data suggest that Robberg may be an important feeding ground for the coastal dolphins that are frequenting Plettenberg Bay. The current study builds on a growing body of literature demonstrating that PAM and automatic detectors are powerful and effective tools for monitoring cetacean species. However, there are several factors that limit the detection of vocalization such as direction of the sound source, distance from hydrophone, sound propagation conditions, low SNR and acoustic masking. Regardless of these limitations, results from PAM showed diel patterns of occurrence of the coastal dolphins in the bay which could have not been achieved from visual monitoring, in particular the high nighttime occurrence patterns. PAM holds potential to be largely utilized in South Africa for dolphin and other cetacean studies. Further research and monitoring using PAM could potentially assist to better understand the drivers of the dolphin occurrence and activity patterns in the bay.
- Full Text:
- Date Issued: 2018
Perceptions, determinants and consumption patterns of indigenous fruits and vegetables in rural areas : evidence from Mutale Local Municipality, Limpopo Province, South Africa
- Authors: Nengovhela, Rudzani
- Date: 2018
- Subjects: Vegetables in human nutrition Indigenous crops Food security
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10123 , vital:35356
- Description: Rural households across South Africa experience food and nutrition insecurity. Given the fact that indigenous fruits and vegetables (IF&Vs) have numerous health benefits including their wide availability and accessibility in rural areas, these indigenous varieties can significantly contribute to food and nutrition security in rural household. However, the consumption of IF&Vs in recent years has generally remained low and has been declining. The present study investigated the perceptions of IF&Vs, consumption patterns and determinants of IF&V consumption among 200 rural households (n = 200) from 10 villages within the Mutale Local Municipality of Limpopo Province, South Africa. The results revealed that, respondents held overwhelmingly positive perceptions of IF&Vs. The majority of the respondents believed that IF&Vs were healthier, less expensive and more visually attractive than exotic varieties. Consumption of the selected IF&Vs was generally high among the sample size. There were more households that consumed each of the selected IF&Vs than those that did not consume. Most of the selected IF&Vs were consumed only in summer and consumed on a weekly basis rather than daily or monthly basis. Age, marital status, occupation, education level and household size, as well as, perceptions of indigenous fruits’ longevity promotion, health beneficiation and relative visual attractiveness were found to be significant determinants of indigenous fruit consumption. On the other hand, the education level, in addition to perceptions of indigenous vegetables’ comparative healthiness, longevity promotion, health beneficiation and preparative ease were significant determinants of respondents’ indigenous vegetable consumption.
- Full Text:
- Date Issued: 2018
- Authors: Nengovhela, Rudzani
- Date: 2018
- Subjects: Vegetables in human nutrition Indigenous crops Food security
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10123 , vital:35356
- Description: Rural households across South Africa experience food and nutrition insecurity. Given the fact that indigenous fruits and vegetables (IF&Vs) have numerous health benefits including their wide availability and accessibility in rural areas, these indigenous varieties can significantly contribute to food and nutrition security in rural household. However, the consumption of IF&Vs in recent years has generally remained low and has been declining. The present study investigated the perceptions of IF&Vs, consumption patterns and determinants of IF&V consumption among 200 rural households (n = 200) from 10 villages within the Mutale Local Municipality of Limpopo Province, South Africa. The results revealed that, respondents held overwhelmingly positive perceptions of IF&Vs. The majority of the respondents believed that IF&Vs were healthier, less expensive and more visually attractive than exotic varieties. Consumption of the selected IF&Vs was generally high among the sample size. There were more households that consumed each of the selected IF&Vs than those that did not consume. Most of the selected IF&Vs were consumed only in summer and consumed on a weekly basis rather than daily or monthly basis. Age, marital status, occupation, education level and household size, as well as, perceptions of indigenous fruits’ longevity promotion, health beneficiation and relative visual attractiveness were found to be significant determinants of indigenous fruit consumption. On the other hand, the education level, in addition to perceptions of indigenous vegetables’ comparative healthiness, longevity promotion, health beneficiation and preparative ease were significant determinants of respondents’ indigenous vegetable consumption.
- Full Text:
- Date Issued: 2018
Performance comparison of the residential types of air source heat pump water heaters in South Africa due to the refrigerant thermo-physical properties
- Authors: Sikhonza, Mandlenkosi
- Date: 2018
- Subjects: Heat pumps Water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9275 , vital:34317
- Description: Globally hot water heating contributes enormously to the increase in energy consumption in the residential sector. Coal being a fossil fuel and non-renewable source of energy remains the major source used for electricity generation. The burning of coal is the primary cause of CO2 emission into the environment which causes climate change and global warming. Energy efficiency and renewable energy technologies were employed as one of the alternative ways of reducing global warming. In most residential areas in South Africa, the water heating generates 30 -50percent of the monthly electricity bill (Zhang and Huan, 2013). In this light, residential load management (RLM) is a significant part of the load management programme of Eskom’s overall demand side management strategy. Through RLM, the electricity load is being transferred from peak times to off times by switching the geysers during peak hours because geysers consume more electricity and contribute significantly to the national grid constraint problem (Eskom, 2012).
- Full Text:
- Date Issued: 2018
- Authors: Sikhonza, Mandlenkosi
- Date: 2018
- Subjects: Heat pumps Water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/9275 , vital:34317
- Description: Globally hot water heating contributes enormously to the increase in energy consumption in the residential sector. Coal being a fossil fuel and non-renewable source of energy remains the major source used for electricity generation. The burning of coal is the primary cause of CO2 emission into the environment which causes climate change and global warming. Energy efficiency and renewable energy technologies were employed as one of the alternative ways of reducing global warming. In most residential areas in South Africa, the water heating generates 30 -50percent of the monthly electricity bill (Zhang and Huan, 2013). In this light, residential load management (RLM) is a significant part of the load management programme of Eskom’s overall demand side management strategy. Through RLM, the electricity load is being transferred from peak times to off times by switching the geysers during peak hours because geysers consume more electricity and contribute significantly to the national grid constraint problem (Eskom, 2012).
- Full Text:
- Date Issued: 2018
Performance evaluation of an off-grid building integrated photovoltaic system in Alice, Eastern Cape province, South Africa
- Authors: Buma, Carine Lethem
- Date: 2018
- Subjects: Building-integrated photovoltaic systems Buildings -- Energy conservation Performance -- Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/13227 , vital:39623
- Description: The constant increase in the global demand for energy and the current crisis on global warming and climate change has prompted a dying quest for clean, sustainable and reliable sources of energy. Amongst numerous renewable energy technologies, harnessing energy from the sun is the most viable way of guaranteeing a clean and sustainable supply of energy. Also, photovoltaic energy is one of the ways of using energy from the sun, where sunlight is converted to electricity using photovoltaic panels. Furthermore, the integration of photovoltaic modules into buildings is one of the most elegant innovations of this technology, as it plays the dual role of supplying energy to the building as well as protecting the building from outdoor weather conditions. Moreover, operating off the grid offers the possibility of energy access to locations far off from the grid and individuals willing to gain some degree of energy independence. Evaluating the performance of existing off grid and/or building integrated photovoltaic systems is the key to guaranteeing sustainable development and advancement in the technology. Thus, the aim of this work was to evaluate the performance of an off-grid building integrated photovoltaic system that was installed at the Fort Hare Institute of Technology. This entailed performing an in-depth characterisation of the solar resource at this location, evaluating the performance of the modules under outdoor weather conditions and also evaluating the performance of the balance of system (BOS) components. The system was monitored for a period of nine months (between February and October 2017). A data acquisition system was designed for measuring and recording both electrical system parameters and meteorological parameters affecting the performance of the system. These meteorological parameters include; solar irradiance, ambient temperature, cell temperature, relative humidity, wind speed and direction. A detailed characterisation of the solar resource at this location was carried out. It was observed that the solar declination angle varied from -23.5o on the summer solstice to 23.5o on the winter solstice. Also, the solar altitude angle (at solar noon) which is a complementary angle to the zenith angle varied from 33.7o in June to 80.65o in December. During the summer months, longer day lengths were experienced because the sun traversed the sky over a longer time, rising south of east and setting south of west. Whereas, in the winter months, the path length of the sun was shorter, with the sun rising north of east and setting north of west, hence, shorter day lengths. The solar radiation incident on a 25o north facing solar collector was found to be in three components; beam, diffuse and reflected. The beam component was higher in summer whereas the diffuse component was higher in winter due to an increase in the air mass ratio. However, the total daily average radiation was highest in January (7.12 peak sun hours) and least in June (3.04 peak sun hours). Finally, a comparison between the calculated and measured values of solar radiation showed just a 1.1percent difference over the year with disparities being in the individual months.m The influence of outdoor weather conditions on the performance of the system was also evaluated. Operating temperatures were noticed to have a great impact on the output voltage and power of the PV array. Significant correlations existed between various meteorological parameters. Also, a multiple linear regression model was developed to ascertain the dependence of module temperature on solar irradiance, ambient temperature, relative humidity, wind speed and wind direction. The coefficient of determination for the model was 0.928, showing a strong relationship between cell temperature and the chosen predictors. Also, the six thermocouples installed at various locations of the PV array revealed variations in the operating temperatures of the modules. The modules on the east side of the array recorded relatively lower temperatures because of the ceiling that had been removed beneath one of the modules on this side of the array, which permitted the free flow of air. Furthermore, I-V measurements conducted on various strings of the array revealed so many steps (hotspots), indicative of module (or cell) mismatch on almost all the cell strings.
- Full Text:
- Date Issued: 2018
- Authors: Buma, Carine Lethem
- Date: 2018
- Subjects: Building-integrated photovoltaic systems Buildings -- Energy conservation Performance -- Evaluation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/13227 , vital:39623
- Description: The constant increase in the global demand for energy and the current crisis on global warming and climate change has prompted a dying quest for clean, sustainable and reliable sources of energy. Amongst numerous renewable energy technologies, harnessing energy from the sun is the most viable way of guaranteeing a clean and sustainable supply of energy. Also, photovoltaic energy is one of the ways of using energy from the sun, where sunlight is converted to electricity using photovoltaic panels. Furthermore, the integration of photovoltaic modules into buildings is one of the most elegant innovations of this technology, as it plays the dual role of supplying energy to the building as well as protecting the building from outdoor weather conditions. Moreover, operating off the grid offers the possibility of energy access to locations far off from the grid and individuals willing to gain some degree of energy independence. Evaluating the performance of existing off grid and/or building integrated photovoltaic systems is the key to guaranteeing sustainable development and advancement in the technology. Thus, the aim of this work was to evaluate the performance of an off-grid building integrated photovoltaic system that was installed at the Fort Hare Institute of Technology. This entailed performing an in-depth characterisation of the solar resource at this location, evaluating the performance of the modules under outdoor weather conditions and also evaluating the performance of the balance of system (BOS) components. The system was monitored for a period of nine months (between February and October 2017). A data acquisition system was designed for measuring and recording both electrical system parameters and meteorological parameters affecting the performance of the system. These meteorological parameters include; solar irradiance, ambient temperature, cell temperature, relative humidity, wind speed and direction. A detailed characterisation of the solar resource at this location was carried out. It was observed that the solar declination angle varied from -23.5o on the summer solstice to 23.5o on the winter solstice. Also, the solar altitude angle (at solar noon) which is a complementary angle to the zenith angle varied from 33.7o in June to 80.65o in December. During the summer months, longer day lengths were experienced because the sun traversed the sky over a longer time, rising south of east and setting south of west. Whereas, in the winter months, the path length of the sun was shorter, with the sun rising north of east and setting north of west, hence, shorter day lengths. The solar radiation incident on a 25o north facing solar collector was found to be in three components; beam, diffuse and reflected. The beam component was higher in summer whereas the diffuse component was higher in winter due to an increase in the air mass ratio. However, the total daily average radiation was highest in January (7.12 peak sun hours) and least in June (3.04 peak sun hours). Finally, a comparison between the calculated and measured values of solar radiation showed just a 1.1percent difference over the year with disparities being in the individual months.m The influence of outdoor weather conditions on the performance of the system was also evaluated. Operating temperatures were noticed to have a great impact on the output voltage and power of the PV array. Significant correlations existed between various meteorological parameters. Also, a multiple linear regression model was developed to ascertain the dependence of module temperature on solar irradiance, ambient temperature, relative humidity, wind speed and wind direction. The coefficient of determination for the model was 0.928, showing a strong relationship between cell temperature and the chosen predictors. Also, the six thermocouples installed at various locations of the PV array revealed variations in the operating temperatures of the modules. The modules on the east side of the array recorded relatively lower temperatures because of the ceiling that had been removed beneath one of the modules on this side of the array, which permitted the free flow of air. Furthermore, I-V measurements conducted on various strings of the array revealed so many steps (hotspots), indicative of module (or cell) mismatch on almost all the cell strings.
- Full Text:
- Date Issued: 2018
Periglacial landforms of the Ahlmannryggen and Jutulsessen areas of western Dronning Maud land, Antarctica
- Authors: Wilmot, Nicola Frances
- Date: 2018
- Subjects: Periglacial processes Antarctica Queen Maud Land , Geomorphology Antarctica Queen Maud Land , Permafrost Antarctica Queen Maud Land , Freezes (Meteorology) Antarctica Queen Maud Land , Thawing Antarctica Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61535 , vital:28034
- Description: Periglacial landforms are a common occurrence in Ahlmannryggen and Jutulsessen areas of western Dronning Maud land (WDML). Classification and formation of these landforms were disputed in literature. In Antarctica information on periglacial landforms is limited or confined to a specific landform. Thus a holistic approach was taken when investigating the periglacial landforms found in WDML. An overview of the existing knowledge base on periglacial landforms in WDML was given which was coupled with the analysis of archival data. The landforms found in this area were patterned ground, openwork block deposits (OBD), rock glaciers, terraces, a pronival rampart and lake ice blisters. With patterned ground being the common periglacial landform in WDML, heave monitoring was used where time-lapse videos were used to investigate the formation processes in patterned ground. From consolidating existing knowledge as well as adding new knowledge on the formation of periglacial landforms, it is clear that the landforms in Antarctica should not be compared to other examples, especially examples from the northern hemisphere. Further research in the formation of periglacial landforms is needed and can be further enhanced with more extensive use of the heave monitoring method in future research.
- Full Text:
- Date Issued: 2018
- Authors: Wilmot, Nicola Frances
- Date: 2018
- Subjects: Periglacial processes Antarctica Queen Maud Land , Geomorphology Antarctica Queen Maud Land , Permafrost Antarctica Queen Maud Land , Freezes (Meteorology) Antarctica Queen Maud Land , Thawing Antarctica Queen Maud Land
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61535 , vital:28034
- Description: Periglacial landforms are a common occurrence in Ahlmannryggen and Jutulsessen areas of western Dronning Maud land (WDML). Classification and formation of these landforms were disputed in literature. In Antarctica information on periglacial landforms is limited or confined to a specific landform. Thus a holistic approach was taken when investigating the periglacial landforms found in WDML. An overview of the existing knowledge base on periglacial landforms in WDML was given which was coupled with the analysis of archival data. The landforms found in this area were patterned ground, openwork block deposits (OBD), rock glaciers, terraces, a pronival rampart and lake ice blisters. With patterned ground being the common periglacial landform in WDML, heave monitoring was used where time-lapse videos were used to investigate the formation processes in patterned ground. From consolidating existing knowledge as well as adding new knowledge on the formation of periglacial landforms, it is clear that the landforms in Antarctica should not be compared to other examples, especially examples from the northern hemisphere. Further research in the formation of periglacial landforms is needed and can be further enhanced with more extensive use of the heave monitoring method in future research.
- Full Text:
- Date Issued: 2018
Petrophysical analysis of thermo-tectonic effects linked to Lower Jurassic dolerite intrusions in sedimentary rocks of the Main Karoo Basin, with implications for shale gas development in South Africa
- Authors: Nengovhela, Vhuhwavhohau
- Date: 2018
- Subjects: Sedimentary rocks -- South Africa -- Research , Sedimentation and deposition Geology, Structural -- South Africa Geology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/33802 , vital:33034
- Description: Prevalent dolerite sills and dikes emplaced in the sedimentary rocks of the main Karoo Basin are associated with contact metamorphism and devolatilization of carbon-rich shales of the Lower Ecca Formation. These thermal effects may have significant bearings on the potential of shale gas development in the Karoo. This research aims to study and quantify the effects of dolerite intrusions on the Karoo sedimentary rocks along contact aureoles in shales and sandstones of the Ecca Group based on drill core samples collected from deep SOEKOR boreholes, and field samples from the Lower Beaufort Group of the Eastern Cape Province. Variations in host rock minerals, chemistry, and porosity are determined using analytical techniques including: petrography, scanning electron microscopy (SEM), X-ray diffraction (XRD) on samples collected along the thermal aureoles at various distances away from the intrusions. Using the determined mineral phase equilibria, geochemistry and thermal modelling, the pressure-temperature (P/T) conditions that prevailed during contact metamorphism are evaluated to constrain the thickness of the contact aureoles in deep boreholes, and to further evaluate potential loss of shale gas. The mineral composition of the samples generally consists of quartz, feldspar, illite/smectite, calcite, muscovite, and pyrite. Metamorphic minerals close to contacts with the sills include andalusite-chiastolite, biotite, muscovite, illite, forsterite, and diopside. SEM imaging confirms that the hornfels samples are compact and that the metamorphic minerals reduce and limit porosity to grain boundaries, and in few cases intra-mineral porosity occurs within individual crystals. The porosities are in the range of mesopores (2-50 nm) and micropores (< 2 nm). The data also suggests that the thermal alteration of the Ecca shales were short lived (e.g. 10-100 years). Disequilibrium metamorphic textures such as irregular grain boundaries, and inclusions in andalusite and cordierite confirm that the elevated temperatures did not last long enough to accomplish (re)crystallization and create equilibrium textures. To test the effect of geothermal gradients on the initial host rock temperatures prior to intrusive activity, and how these temperature differences affect the contact aureole thickness, thermal models were simulated for the deep boreholes using three geothermal gradients: 30 ◦C/km, 35 ◦C/km, and 40 ◦C/km. In addition, the depths were re-calculated based on post-emplacement erosion of the overlying host rocks (2000-3000 m). Heat flow away from dolerite sills through the host shales were modelled using convection and conduction heat flow mechanism separately, to assess differences and/or similarities in cooling trends. The models show that a 10 ◦C increase in geothermal gradient (from 30 ◦C /km to 40 ◦C/km) significantly affects the initial temperature of the host rocks and in turn decreases the rate at which the dolerite sills cool. Thermal modeling data is coherent with the mineralogy of the contact zones. Andalusitechiastolite and cordierite porphyroblasts occur within 10-20 m of the contact aureole, together with biotite and authigenic muscovite. Literature data shows that crystallization of this mineral assemblage in pelitic hornfels occurs at temperatures ranging between 450 ◦C and 600 ◦C. Thermal modelling results indicate maximum temperatures of shales at the contact with dolerite sills range between 650 ◦C to 700 ◦C. Temperatures decrease rapidly to approximately 400 ◦C within 10-20 m away from the contacts. The data also shows that thermal perturbation flanking the sills were short-lived, with maximum temperatures reached within the first 100 years of cooling depending on the thickness of dolerite sills and the combined effect of multiple sill intrusions. Data acquired from the thermal models and literature was used to evaluate gas loss estimations. The calculations conducted around a 45 m thick sill, suggests that at least 4- 6 TCF of gas was liberated from the Whitehill Formation during Karoo sill emplacement. These values are significantly less than previously calculated losses (22 TCF), and thus have a significant bearing on further predictions of shale gas potential of the Karoo Basin.
- Full Text:
- Date Issued: 2018
- Authors: Nengovhela, Vhuhwavhohau
- Date: 2018
- Subjects: Sedimentary rocks -- South Africa -- Research , Sedimentation and deposition Geology, Structural -- South Africa Geology -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/33802 , vital:33034
- Description: Prevalent dolerite sills and dikes emplaced in the sedimentary rocks of the main Karoo Basin are associated with contact metamorphism and devolatilization of carbon-rich shales of the Lower Ecca Formation. These thermal effects may have significant bearings on the potential of shale gas development in the Karoo. This research aims to study and quantify the effects of dolerite intrusions on the Karoo sedimentary rocks along contact aureoles in shales and sandstones of the Ecca Group based on drill core samples collected from deep SOEKOR boreholes, and field samples from the Lower Beaufort Group of the Eastern Cape Province. Variations in host rock minerals, chemistry, and porosity are determined using analytical techniques including: petrography, scanning electron microscopy (SEM), X-ray diffraction (XRD) on samples collected along the thermal aureoles at various distances away from the intrusions. Using the determined mineral phase equilibria, geochemistry and thermal modelling, the pressure-temperature (P/T) conditions that prevailed during contact metamorphism are evaluated to constrain the thickness of the contact aureoles in deep boreholes, and to further evaluate potential loss of shale gas. The mineral composition of the samples generally consists of quartz, feldspar, illite/smectite, calcite, muscovite, and pyrite. Metamorphic minerals close to contacts with the sills include andalusite-chiastolite, biotite, muscovite, illite, forsterite, and diopside. SEM imaging confirms that the hornfels samples are compact and that the metamorphic minerals reduce and limit porosity to grain boundaries, and in few cases intra-mineral porosity occurs within individual crystals. The porosities are in the range of mesopores (2-50 nm) and micropores (< 2 nm). The data also suggests that the thermal alteration of the Ecca shales were short lived (e.g. 10-100 years). Disequilibrium metamorphic textures such as irregular grain boundaries, and inclusions in andalusite and cordierite confirm that the elevated temperatures did not last long enough to accomplish (re)crystallization and create equilibrium textures. To test the effect of geothermal gradients on the initial host rock temperatures prior to intrusive activity, and how these temperature differences affect the contact aureole thickness, thermal models were simulated for the deep boreholes using three geothermal gradients: 30 ◦C/km, 35 ◦C/km, and 40 ◦C/km. In addition, the depths were re-calculated based on post-emplacement erosion of the overlying host rocks (2000-3000 m). Heat flow away from dolerite sills through the host shales were modelled using convection and conduction heat flow mechanism separately, to assess differences and/or similarities in cooling trends. The models show that a 10 ◦C increase in geothermal gradient (from 30 ◦C /km to 40 ◦C/km) significantly affects the initial temperature of the host rocks and in turn decreases the rate at which the dolerite sills cool. Thermal modeling data is coherent with the mineralogy of the contact zones. Andalusitechiastolite and cordierite porphyroblasts occur within 10-20 m of the contact aureole, together with biotite and authigenic muscovite. Literature data shows that crystallization of this mineral assemblage in pelitic hornfels occurs at temperatures ranging between 450 ◦C and 600 ◦C. Thermal modelling results indicate maximum temperatures of shales at the contact with dolerite sills range between 650 ◦C to 700 ◦C. Temperatures decrease rapidly to approximately 400 ◦C within 10-20 m away from the contacts. The data also shows that thermal perturbation flanking the sills were short-lived, with maximum temperatures reached within the first 100 years of cooling depending on the thickness of dolerite sills and the combined effect of multiple sill intrusions. Data acquired from the thermal models and literature was used to evaluate gas loss estimations. The calculations conducted around a 45 m thick sill, suggests that at least 4- 6 TCF of gas was liberated from the Whitehill Formation during Karoo sill emplacement. These values are significantly less than previously calculated losses (22 TCF), and thus have a significant bearing on further predictions of shale gas potential of the Karoo Basin.
- Full Text:
- Date Issued: 2018
Pollution potential of on-site dry sanitation systems associated with the Mzimvubu Water Project, Eastern Cape, South Africa
- Authors: Mamera, Matthew
- Date: 2018
- Subjects: Water resources development Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6038 , vital:29485
- Description: Protecting the environment requires tools that can be used to monitor environmental conditions for proper sustainable management of water resources. The Mzimvubu River is the largest undeveloped river, in the poorest region of South Africa. The South African government announced plans to construct two large storage dams (Ntabelanga and Laleni) in the Tsitsa River, one of the largest tributaries to the Mzimvubu River. The dams and associated infrastructure is termed the Mzimvubu Water Project (MWP). In developing countries like South Africa, several households use pit latrines. Moreover, many people also rely upon untreated groundwater supplies for their drinking water. The shared utilization of both pit latrines and groundwater resources, can lead to human and ecological health risks from microbial and chemical pollutants. These threats can be accelerated due to a permanent rise in the water table associated with dam constructions. Four hillslope sites with pit latrines (MT1, MT2, MT3 and MT4) above 1st order tributaries to the Tsitsa River, in the vicinity of the proposed MWP were chosen for this study. The soils were described and classified at selected locations below the pit latrine and above the tributary. Undisturbed core samples were from representative soil horizons on which hydraulic properties were determined in the laboratory. Samples were also collected to determine the feacal coliform and other bacterial concentrations during a winter and summer period. Mechanistic modelling with Hydrus 2D for a 121 day period was conducted to determine the risk of pollution to surface and groundwater from the various sites. Apedal soils of the Clovelly form dominated upper slopes of MT1 and the lower slopes of MT2. A Clovelly form is hydropedologically termed a recharge soil, as morphological indicators of saturation are absent. Hydromorphic soil properties were observed in the sub-surface B horizons of a Tukulu form in MT1-3 and MT4. High clay contents and strong structure soils of the Sepane form were dominant in MT3. The soils of MT1 and MT2 are relatively sandy with slightly higher hydraulic conductivities compared to MT3 and MT4. In general higher measured faecal coliform concentrations were higher in winter as compared to summer seasons but in most sites both winter and summer seasons had counts < 1 CFU/g. The highest concentrations of total bacteria (9 x 106 CFU/ g soil) was observed in MT3-1. Other sites with potential pollution include MT3-3, with a count above 4 x 104 CFU /g soil in winter and MT1-1 with a count above 2.2 X 104 CFU /g soil in summer. In most of the sites, the E. coli bacteria detections were low (< 1 CFU/g) during both seasons. The highest value in summer of 1.8 x 102 CFU/g was observed in MT3-3 which increased from 1.2 x102 CFU/g in winter. As the soil water flow rate increase the mobility of bacteria increase as well. Hydrus simulations showed that surface water resources are threatened by pollution from MT3 and MT4 due to the prominence of lateral flow. Groundwater pollution is more likely to occur on MT1 and MT2 as the soils are freely drained. Future work should focus on the more direct measurements and modelling of the migration of bacterial pollutants from pit latrines to various water resources.
- Full Text:
- Date Issued: 2018
- Authors: Mamera, Matthew
- Date: 2018
- Subjects: Water resources development Sustainable development -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6038 , vital:29485
- Description: Protecting the environment requires tools that can be used to monitor environmental conditions for proper sustainable management of water resources. The Mzimvubu River is the largest undeveloped river, in the poorest region of South Africa. The South African government announced plans to construct two large storage dams (Ntabelanga and Laleni) in the Tsitsa River, one of the largest tributaries to the Mzimvubu River. The dams and associated infrastructure is termed the Mzimvubu Water Project (MWP). In developing countries like South Africa, several households use pit latrines. Moreover, many people also rely upon untreated groundwater supplies for their drinking water. The shared utilization of both pit latrines and groundwater resources, can lead to human and ecological health risks from microbial and chemical pollutants. These threats can be accelerated due to a permanent rise in the water table associated with dam constructions. Four hillslope sites with pit latrines (MT1, MT2, MT3 and MT4) above 1st order tributaries to the Tsitsa River, in the vicinity of the proposed MWP were chosen for this study. The soils were described and classified at selected locations below the pit latrine and above the tributary. Undisturbed core samples were from representative soil horizons on which hydraulic properties were determined in the laboratory. Samples were also collected to determine the feacal coliform and other bacterial concentrations during a winter and summer period. Mechanistic modelling with Hydrus 2D for a 121 day period was conducted to determine the risk of pollution to surface and groundwater from the various sites. Apedal soils of the Clovelly form dominated upper slopes of MT1 and the lower slopes of MT2. A Clovelly form is hydropedologically termed a recharge soil, as morphological indicators of saturation are absent. Hydromorphic soil properties were observed in the sub-surface B horizons of a Tukulu form in MT1-3 and MT4. High clay contents and strong structure soils of the Sepane form were dominant in MT3. The soils of MT1 and MT2 are relatively sandy with slightly higher hydraulic conductivities compared to MT3 and MT4. In general higher measured faecal coliform concentrations were higher in winter as compared to summer seasons but in most sites both winter and summer seasons had counts < 1 CFU/g. The highest concentrations of total bacteria (9 x 106 CFU/ g soil) was observed in MT3-1. Other sites with potential pollution include MT3-3, with a count above 4 x 104 CFU /g soil in winter and MT1-1 with a count above 2.2 X 104 CFU /g soil in summer. In most of the sites, the E. coli bacteria detections were low (< 1 CFU/g) during both seasons. The highest value in summer of 1.8 x 102 CFU/g was observed in MT3-3 which increased from 1.2 x102 CFU/g in winter. As the soil water flow rate increase the mobility of bacteria increase as well. Hydrus simulations showed that surface water resources are threatened by pollution from MT3 and MT4 due to the prominence of lateral flow. Groundwater pollution is more likely to occur on MT1 and MT2 as the soils are freely drained. Future work should focus on the more direct measurements and modelling of the migration of bacterial pollutants from pit latrines to various water resources.
- Full Text:
- Date Issued: 2018
Potential impact and host range of Pereskiophaga brasiliensis Anderson (Curculionidae): a new candidate biological control agent for the control of Pereskia aculeata Miller (Cactaceae) in South Africa
- Authors: Mdodana, Lumka Anita
- Date: 2018
- Subjects: Curculionidae -- South Africa , Cactus -- South Africa , Biological pest control agents , Alien plants-- South Africa , Pereskiophaga brasiliensis Anderson (Curculionidae) , Pereskia aculeata Miller (Cactaceae)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62350 , vital:28157
- Description: Pereskia aculeata Miller (Cactaceae) is a damaging invasive alien plant in South Africa that has negative impacts to indigenous biodiversity and ecosystem functioning. Mechanical and chemical control are not effective against P. aculeata so biological control is considered the only viable option. Two biological control agents, the leaf-feeding beetle Phenrica guerini Bechyne (Chrysomelidae) and the stem-wilting bug Catorhintha schaffneri (Coreidae), have been released in South Africa thus far. Post-release evaluations have indicated that P. guerini will not reduce P. aculeata densities to acceptable levels alone, while C. schaffneri was released very recently, so it is too soon to determine how effective that agent will be. Even if C. schaffneri is extremely damaging, it is likely that further agents will be required to reduce the densities of P. aculeata to acceptable levels within a reasonable time-scale. Additional agents should target the woody stems of P. aculeata which are not impacted by the damage of either of the released agents. Pereskiophaga brasiliensis Anderson (Curculionidae) is a promising potential candidate agent that feeds on the thick woody stems of the plant in the larval stage. Climatic matching, genetic matching and field based host specificity observations all indicated that P. brasiliensis was a promising candidate. In this study, the impact of P. brasiliensis to the target weed, P. aculeata, was quantified under quarantine conditions to determine whether it was sufficiently damaging to warrant release. This was followed by host specificity testing to determine whether P. brasiliensis was suitably host specific for release in South Africa. Impact studies indicated that P. brasiliensis was damaging to P. aculeata at insect densities that would be expected in the field. Pereskiophaga brasiliensis reduced the number of leaves of P. aculeata to a greater extent than it reduced shoot lengths, but both plant parameters were significantly reduced due to the feeding damage from the insect. This suggests that the damage from P. brasiliensis may be compatible with that of C. schaffneri which reduces shoot length to a greater degree than the number of leaves. Pereskiophaga brasiliensis is therefore sufficiently damaging to warrant release, and although interaction studies with the other agents would be required, it is expected that it should complement other existing agents. Although P. brasiliensis is sufficiently damaging, at present the host specificity data indicates that it is not suitably specific for release in South Africa because oviposition and larval development to the adult stage was recorded on both indigenous and alien plant species within the families Cactaceae and Basellaceae. This non-target feeding was recorded during no-choice tests, which are very conservative, but significant non-target damage and development to the adult stage was recorded on an indigenous plant from a different family to the target weed. Further host specificity testing, including paired and multiple choice tests, are required to confirm the broad host range of P. brasiliensis. Other biological control agents that damage the woody stems of P. aculeata should be considered. The stem-borer, Acanthodoxus machacalis (Cerambycidae) is considered the most promising of the other candidate agents as it can be sourced from a climatically matched region where genetically suitable P. aculeata plants are found, it is sufficiently damaging to the woody stems of P. aculeata and there is no evidence that the species has a broad host range. Acanthodoxus machacalis should be sourced from Rio de Janeiro, Brazil, and imported into quarantine in South Africa for host specificity testing.
- Full Text:
- Date Issued: 2018
- Authors: Mdodana, Lumka Anita
- Date: 2018
- Subjects: Curculionidae -- South Africa , Cactus -- South Africa , Biological pest control agents , Alien plants-- South Africa , Pereskiophaga brasiliensis Anderson (Curculionidae) , Pereskia aculeata Miller (Cactaceae)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62350 , vital:28157
- Description: Pereskia aculeata Miller (Cactaceae) is a damaging invasive alien plant in South Africa that has negative impacts to indigenous biodiversity and ecosystem functioning. Mechanical and chemical control are not effective against P. aculeata so biological control is considered the only viable option. Two biological control agents, the leaf-feeding beetle Phenrica guerini Bechyne (Chrysomelidae) and the stem-wilting bug Catorhintha schaffneri (Coreidae), have been released in South Africa thus far. Post-release evaluations have indicated that P. guerini will not reduce P. aculeata densities to acceptable levels alone, while C. schaffneri was released very recently, so it is too soon to determine how effective that agent will be. Even if C. schaffneri is extremely damaging, it is likely that further agents will be required to reduce the densities of P. aculeata to acceptable levels within a reasonable time-scale. Additional agents should target the woody stems of P. aculeata which are not impacted by the damage of either of the released agents. Pereskiophaga brasiliensis Anderson (Curculionidae) is a promising potential candidate agent that feeds on the thick woody stems of the plant in the larval stage. Climatic matching, genetic matching and field based host specificity observations all indicated that P. brasiliensis was a promising candidate. In this study, the impact of P. brasiliensis to the target weed, P. aculeata, was quantified under quarantine conditions to determine whether it was sufficiently damaging to warrant release. This was followed by host specificity testing to determine whether P. brasiliensis was suitably host specific for release in South Africa. Impact studies indicated that P. brasiliensis was damaging to P. aculeata at insect densities that would be expected in the field. Pereskiophaga brasiliensis reduced the number of leaves of P. aculeata to a greater extent than it reduced shoot lengths, but both plant parameters were significantly reduced due to the feeding damage from the insect. This suggests that the damage from P. brasiliensis may be compatible with that of C. schaffneri which reduces shoot length to a greater degree than the number of leaves. Pereskiophaga brasiliensis is therefore sufficiently damaging to warrant release, and although interaction studies with the other agents would be required, it is expected that it should complement other existing agents. Although P. brasiliensis is sufficiently damaging, at present the host specificity data indicates that it is not suitably specific for release in South Africa because oviposition and larval development to the adult stage was recorded on both indigenous and alien plant species within the families Cactaceae and Basellaceae. This non-target feeding was recorded during no-choice tests, which are very conservative, but significant non-target damage and development to the adult stage was recorded on an indigenous plant from a different family to the target weed. Further host specificity testing, including paired and multiple choice tests, are required to confirm the broad host range of P. brasiliensis. Other biological control agents that damage the woody stems of P. aculeata should be considered. The stem-borer, Acanthodoxus machacalis (Cerambycidae) is considered the most promising of the other candidate agents as it can be sourced from a climatically matched region where genetically suitable P. aculeata plants are found, it is sufficiently damaging to the woody stems of P. aculeata and there is no evidence that the species has a broad host range. Acanthodoxus machacalis should be sourced from Rio de Janeiro, Brazil, and imported into quarantine in South Africa for host specificity testing.
- Full Text:
- Date Issued: 2018
Potential use of carbon nanotubes as a nanofiller for natural rubber latex condoms
- Authors: Agbakoba, Victor Chike
- Date: 2018
- Subjects: Nanotubes , Rubber chemistry Nanocomposites (Materials) Nanostructured materials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23393 , vital:30538
- Description: The recent advancement in the field of nano-technology has raised much interest in the area of natural rubber latex (NRL) processing. This interest stems from the exceptional properties of nano-material and the promising results obtained by several researchers. Studies have shown that very low loadings of inorganic nanomaterials such as carbon nanotube (CNT) in NRL matrix leads to enhanced tensile strength, tensile modulus, tear resistance and aberration resistance. Thus providing a great prospect for reinforcement of thin film NRL articles such as condom. In this research, prevulcanised natural rubber latex (PvNRL) composite blends containing single walled carbon nanotubes (SWCNTs) were prepared via direct mixing. A progressive discolouration of PvNRL was observed with increased loadings of CNTs. Thermal analysis revealed faster drying rates for the composite blends containing SWCNT. Results from equilibrium swelling experiments also suggested a slight increase in crosslink density in the presence of SWCNT. There was a significant influence on flow behaviour of PvNRL as a result of varying loadings of SWCNT suspension. This was reflected as a change in pseudoplasticity and apparent viscosity. For Instance, apparent viscosity at a shear rate of 1 s-1 at 25°C for PvNRL with ~0.08% SWCNT was 2.5 Pa.s, compared to 0.49 Pa.s for the blends with 0.02% SWCNT. Condoms were moulded via the straight dipping technique using custom made glass formers. A series of dilutions was performed to correct the viscosity differences. This also ensured good consistency and promoted uniform deposition of PvNRL on the glass former. The average dimensions of the condoms produced in terms of length and width were ~191.17 ± 5.17 mm and 52.67 ± 5.17 mm respectively. Thickness measurement varied slightly according to the method of determination. The water leakage test suggested the absence of holes in the condoms produced. However, results from electrical leakage test contradicted those from water leak test. The results from infrared spectroscopy (FTIR) did not confirm the presence of chemical interactions between the SWCNT and PvNRL matrix. Glass transition temperature (Tg) was also unaffected across the blends. The stiffness (or modulus) was unaffected in all the condoms, as revealed by results from indentation hardness analysis. The SWCNT showed no significant influence on thermal decomposition temperatures of the condoms. Nonetheless, images from optical microscopy revealed increased surface roughness corresponding to higher loadings of SWCNT. Results from stress relaxation studies revealed improved retention of modulus under constant strain for condom samples containing SWCNT.
- Full Text:
- Date Issued: 2018
- Authors: Agbakoba, Victor Chike
- Date: 2018
- Subjects: Nanotubes , Rubber chemistry Nanocomposites (Materials) Nanostructured materials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23393 , vital:30538
- Description: The recent advancement in the field of nano-technology has raised much interest in the area of natural rubber latex (NRL) processing. This interest stems from the exceptional properties of nano-material and the promising results obtained by several researchers. Studies have shown that very low loadings of inorganic nanomaterials such as carbon nanotube (CNT) in NRL matrix leads to enhanced tensile strength, tensile modulus, tear resistance and aberration resistance. Thus providing a great prospect for reinforcement of thin film NRL articles such as condom. In this research, prevulcanised natural rubber latex (PvNRL) composite blends containing single walled carbon nanotubes (SWCNTs) were prepared via direct mixing. A progressive discolouration of PvNRL was observed with increased loadings of CNTs. Thermal analysis revealed faster drying rates for the composite blends containing SWCNT. Results from equilibrium swelling experiments also suggested a slight increase in crosslink density in the presence of SWCNT. There was a significant influence on flow behaviour of PvNRL as a result of varying loadings of SWCNT suspension. This was reflected as a change in pseudoplasticity and apparent viscosity. For Instance, apparent viscosity at a shear rate of 1 s-1 at 25°C for PvNRL with ~0.08% SWCNT was 2.5 Pa.s, compared to 0.49 Pa.s for the blends with 0.02% SWCNT. Condoms were moulded via the straight dipping technique using custom made glass formers. A series of dilutions was performed to correct the viscosity differences. This also ensured good consistency and promoted uniform deposition of PvNRL on the glass former. The average dimensions of the condoms produced in terms of length and width were ~191.17 ± 5.17 mm and 52.67 ± 5.17 mm respectively. Thickness measurement varied slightly according to the method of determination. The water leakage test suggested the absence of holes in the condoms produced. However, results from electrical leakage test contradicted those from water leak test. The results from infrared spectroscopy (FTIR) did not confirm the presence of chemical interactions between the SWCNT and PvNRL matrix. Glass transition temperature (Tg) was also unaffected across the blends. The stiffness (or modulus) was unaffected in all the condoms, as revealed by results from indentation hardness analysis. The SWCNT showed no significant influence on thermal decomposition temperatures of the condoms. Nonetheless, images from optical microscopy revealed increased surface roughness corresponding to higher loadings of SWCNT. Results from stress relaxation studies revealed improved retention of modulus under constant strain for condom samples containing SWCNT.
- Full Text:
- Date Issued: 2018
Practical application of distributed ledger technology in support of digital evidence integrity verification processes
- Authors: Weilbach, William Thomas
- Date: 2018
- Subjects: Digital forensic science , Blockchains (Databases) , Bitcoin , Distributed databases , Computer systems Verification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61872 , vital:28070
- Description: After its birth in cryptocurrencies, distributed ledger (blockchain) technology rapidly grew in popularity in other technology domains. Alternative applications of this technology range from digitizing the bank guarantees process for commercial property leases (Anz and IBM, 2017) to tracking the provenance of high-value physical goods (Everledger Ltd., 2017). As a whole, distributed ledger technology has acted as a catalyst to the rise of many innovative alternative solutions to existing problems, mostly associated with trust and integrity. In this research, a niche application of this technology is proposed for use in digital forensics by providing a mechanism for the transparent and irrefutable verification of digital evidence, ensuring its integrity as established blockchains serve as an ideal mechanism to store and validate arbitrary data against. Evaluation and identification of candidate technologies in this domain is based on a set of requirements derived from previous work in this field (Weilbach, 2014). OpenTimestamps (Todd, 2016b) is chosen as the foundation of further work for its robust architecture, transparent nature and multi-platform support. A robust evaluation and discussion of OpenTimestamps is performed to reinforce why it can be trusted as an implementation and protocol. An implementation of OpenTimestamps is designed for the popular open source forensic tool, Autopsy, and an Autopsy module is subsequently developed and released to the public. OpenTimestamps is tested at scale and found to have insignificant error rates for the verification of timestamps. Through practical implementation and extensive testing, it is shown that OpenTimestamps has the potential to significantly advance the practice of digital evidence integrity verification. A conclusion is reached by discussing some of the limitations of OpenTimestamps in terms of accuracy and error rates. It is shown that although OpenTimestamps has very specific timing claims in the attestation, with a near zero error rate, the actual attestation is truly accurate to within a day. This is followed by proposing potential avenues for future work.
- Full Text:
- Date Issued: 2018
- Authors: Weilbach, William Thomas
- Date: 2018
- Subjects: Digital forensic science , Blockchains (Databases) , Bitcoin , Distributed databases , Computer systems Verification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/61872 , vital:28070
- Description: After its birth in cryptocurrencies, distributed ledger (blockchain) technology rapidly grew in popularity in other technology domains. Alternative applications of this technology range from digitizing the bank guarantees process for commercial property leases (Anz and IBM, 2017) to tracking the provenance of high-value physical goods (Everledger Ltd., 2017). As a whole, distributed ledger technology has acted as a catalyst to the rise of many innovative alternative solutions to existing problems, mostly associated with trust and integrity. In this research, a niche application of this technology is proposed for use in digital forensics by providing a mechanism for the transparent and irrefutable verification of digital evidence, ensuring its integrity as established blockchains serve as an ideal mechanism to store and validate arbitrary data against. Evaluation and identification of candidate technologies in this domain is based on a set of requirements derived from previous work in this field (Weilbach, 2014). OpenTimestamps (Todd, 2016b) is chosen as the foundation of further work for its robust architecture, transparent nature and multi-platform support. A robust evaluation and discussion of OpenTimestamps is performed to reinforce why it can be trusted as an implementation and protocol. An implementation of OpenTimestamps is designed for the popular open source forensic tool, Autopsy, and an Autopsy module is subsequently developed and released to the public. OpenTimestamps is tested at scale and found to have insignificant error rates for the verification of timestamps. Through practical implementation and extensive testing, it is shown that OpenTimestamps has the potential to significantly advance the practice of digital evidence integrity verification. A conclusion is reached by discussing some of the limitations of OpenTimestamps in terms of accuracy and error rates. It is shown that although OpenTimestamps has very specific timing claims in the attestation, with a near zero error rate, the actual attestation is truly accurate to within a day. This is followed by proposing potential avenues for future work.
- Full Text:
- Date Issued: 2018
Predicting reintroduction outcomes: assessing the feasibility of reintroducing African wild dog to a small protected area
- Authors: Vogel, John Thomas
- Date: 2018
- Subjects: African wild dog , Wild dogs -- South Africa Wild dogs -- Conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36464 , vital:33947
- Description: Large mammalian carnivores have experienced significant contractions in population sizes and geographical ranges. The conservation of large carnivores is crucially important, particularly due to their vulnerability to extinction and their functional significance and ability to structure ecosystems. Due to an expanding human footprint, large carnivores are increasingly subject to modified and spatially constrained habitats. A growing debate exists as to how to conserve and coexist with large carnivores in an anthropogenically induced environment. Reintroduction, as a conservation tool to restore locally extirpated large carnivores to portions of their former ranges is increasingly being applied. However, in South Africa, habitat to support large carnivores remain small and non-contiguous. Food is a fundamental ecological requirement to sustain reintroduced large carnivores. Therefore, an understanding of large predator foraging patterns can be informative in the context of how the predator species influences and utilises a novel ecosystem. We investigated the foraging behaviour of reintroduced African wild dog (Lycaon pictus) at five small protected areas in KwaZulu-Natal, South Africa. Wild dog utilised 16 prey species, albeit they primarily used nyala (Tragelaphus angasii) and impala (Aepyceros melampus) which collectively form 75 % of their diet. Only nyala was significantly preferred, suggesting that this prey species is used in greater proportion to their abundance. As wild dogs are social cooperative hunters, we tested whether wild dog pack size was correlated to prey mass selection. There was no evidence to suggest that larger packs use larger prey. However, the mean wild dog pack size in our sample sites, was relatively smaller than those encountered elsewhere. Furthermore, wild dog have been shown to modify their hunting behaviour in the presence of wildlife-proof fencing, by using fences to aid in the capture of larger prey species than would innately occur. We compared the prey mass of wild dog kills in relation to proximity of these hard boundaries. Despite the affinity towards kills occurring within 200 m of fences, the upward bias caused by fences on prey mass selection was inconsistent across sample sites. The relatively small size of wild dogs makes them particularly vulnerable to competition. As the energetic output of wild dog is high, interspecific competition can increase foraging costs. The reintroduction of large carnivores to small artificially induced systems may be a contentious issue as resources available to support large carnivores are expected to be relatively more finite. We compared both the potential inter- and intraspecific dietary niche dimensions of an intact large carnivore guild in context of a wild dog reintroduction. We determined cheetah (Acinonyx jubatus), leopard (Panthera pardus), and lion (Panthera leo) prey composition, diet breadth, overlap, prey preference and predicted the density of an intact large carnivore guild in a novel landscape. Further, we compared the foraging behaviour of these large carnivores to that of wild dog. Our findings suggest that large African carnivores in small protected areas are subject to a considerable dietary niche overlap. Wild dog and cheetah, particularly reproductive females with dependent offspring, displayed the greatest potential for dietary overlap and subsequent competition. Leopard and lion at the population species level exhibited greater degrees of foraging plasticity. Lion displayed a contrasting prey species preference to sympatric predators as they selected for prey items frequently avoided by cheetah, leopard and wild dog. The proposed wild dog reintroduction site is expected to sustain seven wild dog based on the availability of preferred prey biomass. However, the reintroduction of wild dog to the small protected area is expected to have negative lateral trophic influences on other species of conservation concern. This should be of vital importance to management of the protected area. As the influence of competition in food-web and population dynamics, particularly in resource poor environments may be profound, our research highlights the need to assess the influence of competitive forces in structuring and restoring large predators to portions of their historical range.
- Full Text:
- Date Issued: 2018
- Authors: Vogel, John Thomas
- Date: 2018
- Subjects: African wild dog , Wild dogs -- South Africa Wild dogs -- Conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/36464 , vital:33947
- Description: Large mammalian carnivores have experienced significant contractions in population sizes and geographical ranges. The conservation of large carnivores is crucially important, particularly due to their vulnerability to extinction and their functional significance and ability to structure ecosystems. Due to an expanding human footprint, large carnivores are increasingly subject to modified and spatially constrained habitats. A growing debate exists as to how to conserve and coexist with large carnivores in an anthropogenically induced environment. Reintroduction, as a conservation tool to restore locally extirpated large carnivores to portions of their former ranges is increasingly being applied. However, in South Africa, habitat to support large carnivores remain small and non-contiguous. Food is a fundamental ecological requirement to sustain reintroduced large carnivores. Therefore, an understanding of large predator foraging patterns can be informative in the context of how the predator species influences and utilises a novel ecosystem. We investigated the foraging behaviour of reintroduced African wild dog (Lycaon pictus) at five small protected areas in KwaZulu-Natal, South Africa. Wild dog utilised 16 prey species, albeit they primarily used nyala (Tragelaphus angasii) and impala (Aepyceros melampus) which collectively form 75 % of their diet. Only nyala was significantly preferred, suggesting that this prey species is used in greater proportion to their abundance. As wild dogs are social cooperative hunters, we tested whether wild dog pack size was correlated to prey mass selection. There was no evidence to suggest that larger packs use larger prey. However, the mean wild dog pack size in our sample sites, was relatively smaller than those encountered elsewhere. Furthermore, wild dog have been shown to modify their hunting behaviour in the presence of wildlife-proof fencing, by using fences to aid in the capture of larger prey species than would innately occur. We compared the prey mass of wild dog kills in relation to proximity of these hard boundaries. Despite the affinity towards kills occurring within 200 m of fences, the upward bias caused by fences on prey mass selection was inconsistent across sample sites. The relatively small size of wild dogs makes them particularly vulnerable to competition. As the energetic output of wild dog is high, interspecific competition can increase foraging costs. The reintroduction of large carnivores to small artificially induced systems may be a contentious issue as resources available to support large carnivores are expected to be relatively more finite. We compared both the potential inter- and intraspecific dietary niche dimensions of an intact large carnivore guild in context of a wild dog reintroduction. We determined cheetah (Acinonyx jubatus), leopard (Panthera pardus), and lion (Panthera leo) prey composition, diet breadth, overlap, prey preference and predicted the density of an intact large carnivore guild in a novel landscape. Further, we compared the foraging behaviour of these large carnivores to that of wild dog. Our findings suggest that large African carnivores in small protected areas are subject to a considerable dietary niche overlap. Wild dog and cheetah, particularly reproductive females with dependent offspring, displayed the greatest potential for dietary overlap and subsequent competition. Leopard and lion at the population species level exhibited greater degrees of foraging plasticity. Lion displayed a contrasting prey species preference to sympatric predators as they selected for prey items frequently avoided by cheetah, leopard and wild dog. The proposed wild dog reintroduction site is expected to sustain seven wild dog based on the availability of preferred prey biomass. However, the reintroduction of wild dog to the small protected area is expected to have negative lateral trophic influences on other species of conservation concern. This should be of vital importance to management of the protected area. As the influence of competition in food-web and population dynamics, particularly in resource poor environments may be profound, our research highlights the need to assess the influence of competitive forces in structuring and restoring large predators to portions of their historical range.
- Full Text:
- Date Issued: 2018
Preparation, characterization and in vitro analysis of polyamidoamine drug conjugates containing ferrocene and platinum analogues
- Authors: Mugogodi, Ansley
- Date: 2018
- Subjects: Ferrocene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10145 , vital:35360
- Description: Polyamidoamine drug conjugates were prepared from analogues of ferrocene and platinum. Standard reaction procedures were followed in the synthesis of platinum and ferrocene analogues. Michael addition reaction of amines to the activated double bonds of methylenebisacrylamide was applied for preparation of the water soluble polyamidoamine carriers onto which drug analogues were attached. The drug release studies of the conjugates were evaluated at different pH environments. The results obtained from drug release studies showed that rate of drug release was variable depending on the conjugate and pH environment. Mathematical drug release models by Korsmeyer-Peppas were used to determine the drug release characteristics of the ferrocene and platinum based drugs from polyamidoamine drug conjugates. Cytotoxicity potential of the analogues and polyamidoamine drug conjugates was tested on selected cell lines. Cisplatin was used as the standard for comparison of the IC50 values obtained for the compounds tested for cytotoxicity activity. The results from six polymer drug conjugates tested for cytotoxicity activity showed that conjugation of analogues to polyamidoamine carrier enhanced the activity of the analogues in some of the polyamidoamine drug conjugates. Various techniques such as Fourier Transform Infrared (FTIR) spectroscopy, Proton Nuclear Magnetic Resonance spectroscopy (1H NMR), Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX) spectroscopy were employed for the characterization of the ferrocene and platinum analogues, polyamidoamine carriers and drug conjugates.
- Full Text:
- Date Issued: 2018
- Authors: Mugogodi, Ansley
- Date: 2018
- Subjects: Ferrocene
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/10145 , vital:35360
- Description: Polyamidoamine drug conjugates were prepared from analogues of ferrocene and platinum. Standard reaction procedures were followed in the synthesis of platinum and ferrocene analogues. Michael addition reaction of amines to the activated double bonds of methylenebisacrylamide was applied for preparation of the water soluble polyamidoamine carriers onto which drug analogues were attached. The drug release studies of the conjugates were evaluated at different pH environments. The results obtained from drug release studies showed that rate of drug release was variable depending on the conjugate and pH environment. Mathematical drug release models by Korsmeyer-Peppas were used to determine the drug release characteristics of the ferrocene and platinum based drugs from polyamidoamine drug conjugates. Cytotoxicity potential of the analogues and polyamidoamine drug conjugates was tested on selected cell lines. Cisplatin was used as the standard for comparison of the IC50 values obtained for the compounds tested for cytotoxicity activity. The results from six polymer drug conjugates tested for cytotoxicity activity showed that conjugation of analogues to polyamidoamine carrier enhanced the activity of the analogues in some of the polyamidoamine drug conjugates. Various techniques such as Fourier Transform Infrared (FTIR) spectroscopy, Proton Nuclear Magnetic Resonance spectroscopy (1H NMR), Scanning Electron Microscopy (SEM), transmission electron microscopy (TEM), Transmission Electron Microscopy (TEM) and Energy Dispersive X-ray (EDX) spectroscopy were employed for the characterization of the ferrocene and platinum analogues, polyamidoamine carriers and drug conjugates.
- Full Text:
- Date Issued: 2018
Primary controls on iron and manganese distribution in sphalerite of the Gams Formation, Gamsberg zinc deposit, Namaqualand, South Africa
- Authors: Poignant-Molina, Léo
- Date: 2018
- Subjects: Sphalerite , Sphalerite South Africa Gamsberg , Manganese South Africa Gamsberg , Zinc mines and mining South Africa Gamsberg , Geochemistry South Africa Gamsberg , Metamorphism (Geology) , Electron probe microanalysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63775 , vital:28488
- Description: The Gamsberg deposit is a 200 Mt zinc reserve belonging to the world class base metalrich Aggeneys-Gamsberg mining district. A rifting environment permitted the development of four proximal SEDEX-type deposits whereby Gamsberg is localized in the eastern side of the district and characterised by a peculiar enrichment in manganese. This study investigates the geochemistry of sphalerite in the Gams Formation holding the economic units of the deposit. Microscopic petrography revealed that most of primary textures have been overprinted by recrystallization, alteration, replacement and deformational textures produced during the polyphase metamorphism of the Namaquan Orogeny. Therefore, EPMA analysis provided the bulk of information to define the geochemical distribution of sphalerite. A lateral variation was noticed throughout the Gams Formation, whereby the North orebody presents Zn-rich and Fe+Mn-poor sphalerite while the West and East orebodies contain Zn-poor and Fe-Mn-rich sphalerite. This feature has been interpreted as the association of a chemocline and a variation in the basin topography defining deep Mn+Fe-rich zones and shallow Mn+Fe-poor zones in the primitive basin. It is suggested that mineralized hot brines mixed with seawater developed the chemocline. The uneven topography shaped the geochemical variation between the actual orebodies.
- Full Text:
- Date Issued: 2018
- Authors: Poignant-Molina, Léo
- Date: 2018
- Subjects: Sphalerite , Sphalerite South Africa Gamsberg , Manganese South Africa Gamsberg , Zinc mines and mining South Africa Gamsberg , Geochemistry South Africa Gamsberg , Metamorphism (Geology) , Electron probe microanalysis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63775 , vital:28488
- Description: The Gamsberg deposit is a 200 Mt zinc reserve belonging to the world class base metalrich Aggeneys-Gamsberg mining district. A rifting environment permitted the development of four proximal SEDEX-type deposits whereby Gamsberg is localized in the eastern side of the district and characterised by a peculiar enrichment in manganese. This study investigates the geochemistry of sphalerite in the Gams Formation holding the economic units of the deposit. Microscopic petrography revealed that most of primary textures have been overprinted by recrystallization, alteration, replacement and deformational textures produced during the polyphase metamorphism of the Namaquan Orogeny. Therefore, EPMA analysis provided the bulk of information to define the geochemical distribution of sphalerite. A lateral variation was noticed throughout the Gams Formation, whereby the North orebody presents Zn-rich and Fe+Mn-poor sphalerite while the West and East orebodies contain Zn-poor and Fe-Mn-rich sphalerite. This feature has been interpreted as the association of a chemocline and a variation in the basin topography defining deep Mn+Fe-rich zones and shallow Mn+Fe-poor zones in the primitive basin. It is suggested that mineralized hot brines mixed with seawater developed the chemocline. The uneven topography shaped the geochemical variation between the actual orebodies.
- Full Text:
- Date Issued: 2018
Procurement challenges faced by Eskom contractors during the tender stage
- Authors: Hlalutye, Thandiwe
- Date: 2018
- Subjects: Management -- Procurement -- South Africa -- Northern Cape , Project management -- South Africa -- Northern Cape Contractors' operation -- South Africa -- Northern Cape -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30260 , vital:30913
- Description: The procurement process within South Africa has become an increasing focus in open market access for local economic development. The government introduced Preferential Procurement Policy Frame Act 5 of 2000 (PPPFA) which must be followed by all government owned organisations, including parastatals. Eskom, therefore, has to abide to this regulation and, since it started utilising the Act in its tendering process, there has been a challenge to getting contractors who are commercially and technically approved to be able to execute work or projects. The aim of this study is to examine challenges faced by Eskom Northern Cape Operating Unit contractors during the tender stage in terms of tender requirements, whereby they fail to submit all required tender returnables and fail to meet a set threshold in order to be successful and being awarded with the contract. This study undertook an empirical study using a case study of Eskom after a literature review. A questionnaire was used to collect data from all the active contractors on the Eskom Northern Cape Operating Unit data base. The key findings included that; contractors agreed that they still lack understanding of a quality management system. However they disagreed that they are not complying with safety health and environment and that they lack knowledge of technical requirements which leads them to not submitting objective evidence. The study concluded that contracting firms still do not comply with procurement requirements during the tender stage.
- Full Text:
- Date Issued: 2018
- Authors: Hlalutye, Thandiwe
- Date: 2018
- Subjects: Management -- Procurement -- South Africa -- Northern Cape , Project management -- South Africa -- Northern Cape Contractors' operation -- South Africa -- Northern Cape -- Finance
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30260 , vital:30913
- Description: The procurement process within South Africa has become an increasing focus in open market access for local economic development. The government introduced Preferential Procurement Policy Frame Act 5 of 2000 (PPPFA) which must be followed by all government owned organisations, including parastatals. Eskom, therefore, has to abide to this regulation and, since it started utilising the Act in its tendering process, there has been a challenge to getting contractors who are commercially and technically approved to be able to execute work or projects. The aim of this study is to examine challenges faced by Eskom Northern Cape Operating Unit contractors during the tender stage in terms of tender requirements, whereby they fail to submit all required tender returnables and fail to meet a set threshold in order to be successful and being awarded with the contract. This study undertook an empirical study using a case study of Eskom after a literature review. A questionnaire was used to collect data from all the active contractors on the Eskom Northern Cape Operating Unit data base. The key findings included that; contractors agreed that they still lack understanding of a quality management system. However they disagreed that they are not complying with safety health and environment and that they lack knowledge of technical requirements which leads them to not submitting objective evidence. The study concluded that contracting firms still do not comply with procurement requirements during the tender stage.
- Full Text:
- Date Issued: 2018
Productivity and profitability of different maize varieties and cropping systems used in the smallholder sector of the Eastern Cape Province of South Africa : implication on food security
- Authors: Kambanje, Ardinesh
- Date: 2018
- Subjects: Crop yields Crops and climate Cropping systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6237 , vital:29528
- Description: Low maize yields in the midst of abundant arable land, favourable climatic conditions, input and financial support programs, plagues smallholder maize farming in Eastern Cape Province. These scenarios have led the province to be a net importer of maize. In essence, low production may signify a mis-match between maize varieties being promoted amongst smallholder farmers and their farming system. Thus, the main objective of the study was to investigate the productivity and profitability of different maize varieties and cropping system under smallholder agriculture in selected villages of the Eastern Cape Province of South Africa as well as, the implications posed on the household food security. The study sought to assess: (i) the productivity of different maize varieties and cropping systems, (ii) the effect of GM maize adoption on food security among smallholder farmers, (iii) the profitability of GM, conventional hybrids and OPV maize varieties produced by farmers under different agro-ecological conditions and (iv) the impact of different maize varieties and cropping systems on food security in the smallholder agriculture. A cross sectional quantitative-based survey study was carried out to obtain information from a total of 650 small holder farmers. The study was conducted in three local municipalities in Oliver Reginald (OR) Tambo District Municipality of the Eastern Cape Province of South Africa. Descriptive statistics, partial factor productivity, gross margin analysis, household food insecurity access score (HFIAS), ordinal logistic and linear regression were the analytical techniques used in establishing correlations among variables. Results obtained from the survey indicated that under mono-cropping system, Genetically Modified (GM) maize variety was highly productive with an average yield of 1.9 t/ha whilst, improved OPV maize variety was productive (with an average yield of 1.6 t/ha) under mixed cropping system. Furthermore, GM maize (GM = -R418.10), and landrace (GM = -R1 140.29) maize varieties had negative gross margins whilst, conventional hybrids (GM = R5 181.21) and improved OPV (GM = R1 457.41) were profitable. There was a significant and negative correlation between use of GM maize variety and reduction of household food insecurity. GM maize varieties, improved OPV, white maize, white as well as yellow GM maize varieties had a significant impact in reducing household food insecurity; whilst using more than one variety of maize (landraces and GMO) positively influenced household food insecurity. In light of these research findings, it is recommended that, there is need to address household food security by growing improved OPVs under a mixed cropping system and GM maize under monocropping system.
- Full Text:
- Date Issued: 2018
- Authors: Kambanje, Ardinesh
- Date: 2018
- Subjects: Crop yields Crops and climate Cropping systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/6237 , vital:29528
- Description: Low maize yields in the midst of abundant arable land, favourable climatic conditions, input and financial support programs, plagues smallholder maize farming in Eastern Cape Province. These scenarios have led the province to be a net importer of maize. In essence, low production may signify a mis-match between maize varieties being promoted amongst smallholder farmers and their farming system. Thus, the main objective of the study was to investigate the productivity and profitability of different maize varieties and cropping system under smallholder agriculture in selected villages of the Eastern Cape Province of South Africa as well as, the implications posed on the household food security. The study sought to assess: (i) the productivity of different maize varieties and cropping systems, (ii) the effect of GM maize adoption on food security among smallholder farmers, (iii) the profitability of GM, conventional hybrids and OPV maize varieties produced by farmers under different agro-ecological conditions and (iv) the impact of different maize varieties and cropping systems on food security in the smallholder agriculture. A cross sectional quantitative-based survey study was carried out to obtain information from a total of 650 small holder farmers. The study was conducted in three local municipalities in Oliver Reginald (OR) Tambo District Municipality of the Eastern Cape Province of South Africa. Descriptive statistics, partial factor productivity, gross margin analysis, household food insecurity access score (HFIAS), ordinal logistic and linear regression were the analytical techniques used in establishing correlations among variables. Results obtained from the survey indicated that under mono-cropping system, Genetically Modified (GM) maize variety was highly productive with an average yield of 1.9 t/ha whilst, improved OPV maize variety was productive (with an average yield of 1.6 t/ha) under mixed cropping system. Furthermore, GM maize (GM = -R418.10), and landrace (GM = -R1 140.29) maize varieties had negative gross margins whilst, conventional hybrids (GM = R5 181.21) and improved OPV (GM = R1 457.41) were profitable. There was a significant and negative correlation between use of GM maize variety and reduction of household food insecurity. GM maize varieties, improved OPV, white maize, white as well as yellow GM maize varieties had a significant impact in reducing household food insecurity; whilst using more than one variety of maize (landraces and GMO) positively influenced household food insecurity. In light of these research findings, it is recommended that, there is need to address household food security by growing improved OPVs under a mixed cropping system and GM maize under monocropping system.
- Full Text:
- Date Issued: 2018
Project management in the Mauritian construction industry
- Paurobally, Mohamad Ali Zeeshan
- Authors: Paurobally, Mohamad Ali Zeeshan
- Date: 2018
- Subjects: Project management -- Mauritius , Construction industry -- Mauritius Construction industry -- Forecasting
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34499 , vital:33386
- Description: The main objective of this research study was to find out the various factors affecting the success of projects, with specific reference to the client’s related factors, consultant’s related and main contractor’s related factors. Completion of the construction project within the required cost, time and quality parameters was identified as the motivation for the study. The objectives of the study were achieved by reviewing literature relevant to the topic. The study investigated whether certain assumptions being made were corresponding with already published literature. Data were sourced both from primary and secondary sources. The quantitative part of the research was carried out by analyzing the literature and by envisaging possible scenarios which could be implemented for the completion of projects, within the three parameters (Time, cost and quality). Not being able to complete a project within the required cost, time and quality parameters will ultimately result in time and cost overruns up to the dissatisfaction of the client. As such, the various stages of the construction cycle need to be monitored and controlled as from the inception stage up to the close out stage by the various stakeholders involved on the project in order to obtain a positive project outcome. The research sample was focused mainly on professionals in the built environment, since a better understanding and reliable feedback would be obtained due to their understanding of the relevant topic. The study first introduces project management as a background, and then focuses on the different factors that influence successful project outcome.
- Full Text:
- Date Issued: 2018
- Authors: Paurobally, Mohamad Ali Zeeshan
- Date: 2018
- Subjects: Project management -- Mauritius , Construction industry -- Mauritius Construction industry -- Forecasting
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/34499 , vital:33386
- Description: The main objective of this research study was to find out the various factors affecting the success of projects, with specific reference to the client’s related factors, consultant’s related and main contractor’s related factors. Completion of the construction project within the required cost, time and quality parameters was identified as the motivation for the study. The objectives of the study were achieved by reviewing literature relevant to the topic. The study investigated whether certain assumptions being made were corresponding with already published literature. Data were sourced both from primary and secondary sources. The quantitative part of the research was carried out by analyzing the literature and by envisaging possible scenarios which could be implemented for the completion of projects, within the three parameters (Time, cost and quality). Not being able to complete a project within the required cost, time and quality parameters will ultimately result in time and cost overruns up to the dissatisfaction of the client. As such, the various stages of the construction cycle need to be monitored and controlled as from the inception stage up to the close out stage by the various stakeholders involved on the project in order to obtain a positive project outcome. The research sample was focused mainly on professionals in the built environment, since a better understanding and reliable feedback would be obtained due to their understanding of the relevant topic. The study first introduces project management as a background, and then focuses on the different factors that influence successful project outcome.
- Full Text:
- Date Issued: 2018
Protected area expansion and conservation stewardship in the Olifants Catchment: mechanisms, patterns and benefits
- Authors: Coetzer, Crystal Jeanne
- Date: 2018
- Subjects: Biodiversity conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30006 , vital:30808
- Description: State Conservation Areas (SCAs), as state-owned and -run parks, form the foundation of recognised conservation actions. However, park expansion on the scale required to meet urgent conservation targets is limited by state budgets and parks are increasingly framed in the context of advancing broader societal needs. Motivating for the need to assess the efficacy of alternative conservation strategies, as both contrasting governance and legal mechanisms, this study aimed to rapidly assess the role of private land conservation (PLC) strategies in expanding protection. In particular, this included the role of emerging stewardship approaches, by using semi-structured interviews with park implementers on a national scale. Evaluating the biodiversity and ecosystem service representation and complementarity of contrasting conservation strategies on a catchment scale, using open-source spatial data was employed. Questionnaires tested park managers’ perceptions of benefits across different strategies in a conservation-oriented landscape. Results indicate a strategic shift toward PLC strategies to expand parks in the form of formalised, well-planned and supported contractual and stewardship agreements. SCAs are vital baselines for biodiversity and ecosystem service representation in the catchment with a variety of private mechanisms supplementing protection, especially in highly contested areas. The perceived benefits rated by managers revealed interesting links between benefits and contrasting governance types, legal mechanisms, legal status, size and age of reserves. State parks may be more relevant for generating socio-cultural benefits, while private parks, through the need to remain economically viable, valued a diverse range of socio-economic benefits. Informal conservation areas formed integral parts of the conservation-orientated landscape, rating benefits equally to more secure mechanisms. Private land must be incorporated into conservation through diverse mechanisms to meet the range of mutually exclusive conservation objectives of the 21st century.
- Full Text:
- Date Issued: 2018
- Authors: Coetzer, Crystal Jeanne
- Date: 2018
- Subjects: Biodiversity conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30006 , vital:30808
- Description: State Conservation Areas (SCAs), as state-owned and -run parks, form the foundation of recognised conservation actions. However, park expansion on the scale required to meet urgent conservation targets is limited by state budgets and parks are increasingly framed in the context of advancing broader societal needs. Motivating for the need to assess the efficacy of alternative conservation strategies, as both contrasting governance and legal mechanisms, this study aimed to rapidly assess the role of private land conservation (PLC) strategies in expanding protection. In particular, this included the role of emerging stewardship approaches, by using semi-structured interviews with park implementers on a national scale. Evaluating the biodiversity and ecosystem service representation and complementarity of contrasting conservation strategies on a catchment scale, using open-source spatial data was employed. Questionnaires tested park managers’ perceptions of benefits across different strategies in a conservation-oriented landscape. Results indicate a strategic shift toward PLC strategies to expand parks in the form of formalised, well-planned and supported contractual and stewardship agreements. SCAs are vital baselines for biodiversity and ecosystem service representation in the catchment with a variety of private mechanisms supplementing protection, especially in highly contested areas. The perceived benefits rated by managers revealed interesting links between benefits and contrasting governance types, legal mechanisms, legal status, size and age of reserves. State parks may be more relevant for generating socio-cultural benefits, while private parks, through the need to remain economically viable, valued a diverse range of socio-economic benefits. Informal conservation areas formed integral parts of the conservation-orientated landscape, rating benefits equally to more secure mechanisms. Private land must be incorporated into conservation through diverse mechanisms to meet the range of mutually exclusive conservation objectives of the 21st century.
- Full Text:
- Date Issued: 2018
Pursuing cost-effective secure network micro-segmentation
- Authors: Fürst, Mark Richard
- Date: 2018
- Subjects: Computer networks -- Security measures , Computer networks -- Access control , Firewalls (Computer security) , IPSec (Computer network protocol) , Network micro-segmentation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/131106 , vital:36524
- Description: Traditional network segmentation allows discrete trust levels to be defined for different network segments, using physical firewalls or routers that control north-south traffic flowing between different interfaces. This technique reduces the attack surface area should an attacker breach one of the perimeter defences. However, east-west traffic flowing between endpoints within the same network segment does not pass through a firewall, and an attacker may be able to move laterally between endpoints within that segment. Network micro-segmentation was designed to address the challenge of controlling east-west traffic, and various solutions have been released with differing levels of capabilities and feature sets. These approaches range from simple network switch Access Control List based segmentation to complex hypervisor based software-defined security segments defined down to the individual workload, container or process level, and enforced via policy based security controls for each segment. Several commercial solutions for network micro-segmentation exist, but these are primarily focused on physical and cloud data centres, and are often accompanied by significant capital outlay and resource requirements. Given these constraints, this research determines whether existing tools provided with operating systems can be re-purposed to implement micro-segmentation and restrict east-west traffic within one or more network segments for a small-to-medium sized corporate network. To this end, a proof-of-concept lab environment was built with a heterogeneous mix of Windows and Linux virtual servers and workstations deployed in an Active Directory domain. The use of Group Policy Objects to deploy IPsec Server and Domain Isolation for controlling traffic between endpoints is examined, in conjunction with IPsec Authenticated Header and Encapsulating Security Payload modes as an additional layer of security. The outcome of the research shows that revisiting existing tools can enable organisations to implement an additional, cost-effective secure layer of defence in their network.
- Full Text:
- Date Issued: 2018
- Authors: Fürst, Mark Richard
- Date: 2018
- Subjects: Computer networks -- Security measures , Computer networks -- Access control , Firewalls (Computer security) , IPSec (Computer network protocol) , Network micro-segmentation
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/131106 , vital:36524
- Description: Traditional network segmentation allows discrete trust levels to be defined for different network segments, using physical firewalls or routers that control north-south traffic flowing between different interfaces. This technique reduces the attack surface area should an attacker breach one of the perimeter defences. However, east-west traffic flowing between endpoints within the same network segment does not pass through a firewall, and an attacker may be able to move laterally between endpoints within that segment. Network micro-segmentation was designed to address the challenge of controlling east-west traffic, and various solutions have been released with differing levels of capabilities and feature sets. These approaches range from simple network switch Access Control List based segmentation to complex hypervisor based software-defined security segments defined down to the individual workload, container or process level, and enforced via policy based security controls for each segment. Several commercial solutions for network micro-segmentation exist, but these are primarily focused on physical and cloud data centres, and are often accompanied by significant capital outlay and resource requirements. Given these constraints, this research determines whether existing tools provided with operating systems can be re-purposed to implement micro-segmentation and restrict east-west traffic within one or more network segments for a small-to-medium sized corporate network. To this end, a proof-of-concept lab environment was built with a heterogeneous mix of Windows and Linux virtual servers and workstations deployed in an Active Directory domain. The use of Group Policy Objects to deploy IPsec Server and Domain Isolation for controlling traffic between endpoints is examined, in conjunction with IPsec Authenticated Header and Encapsulating Security Payload modes as an additional layer of security. The outcome of the research shows that revisiting existing tools can enable organisations to implement an additional, cost-effective secure layer of defence in their network.
- Full Text:
- Date Issued: 2018