The contribution of the trade in medicinal plants to urban livelihoods: a case study of the informal markets in Nelson Mandela Bay Municipality, Eastern Cape
- Ah Goo, Delia Felecia Stephanie
- Authors: Ah Goo, Delia Felecia Stephanie
- Date: 2012
- Subjects: Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10654 , http://hdl.handle.net/10948/d1011601 , Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Description: The commercialisation of natural resources such as medicinal plants is a strategy that is increasingly being employed by poor people in developing countries such as South Africa, as a means of generating an income. Increasing economic hardship and a lack of employment opportunities in the formal sector of the economy has led to many urban dwellers seeking alternative means of meeting their everyday livelihood needs. Although the contribution of natural resources to subsistence economies is widely recognised, there are few studies that have examined the significance of the trade in medicinal plants to the livelihoods of poor and marginalised people. Thirty informal street traders were interviewed to investigate the role of the medicinal plant trade in sustaining the livelihoods of the traders who operate in the informal sector of the Nelson Mandela Bay Municipality, South Africa. The findings of the research indicate that the sale and collection of medicinal plants is an activity which is exploited by people with limited resources, few skills, little or no education and often without any other source of household income. Middle-aged women from impoverished, single income households dominated the trade. Although income from the trade is modest, it contributed substantially to the total household cash income of the traders. Other benefits of the trade included independence and having a sense of purpose in life, as the traders felt that they were not only helping their families but also the wider community. However, without the income from the trade, many of the traders and their families would be destitute and thus the medicinal plant trade is vital to the wellbeing of these people.
- Full Text:
- Date Issued: 2012
- Authors: Ah Goo, Delia Felecia Stephanie
- Date: 2012
- Subjects: Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10654 , http://hdl.handle.net/10948/d1011601 , Medicinal plants -- South Africa -- Port Elizabeth , Informal sector (Economics) -- South Africa -- Eastern Cape , Traditional medicine -- South Africa -- Port Elizabeth -- Markets
- Description: The commercialisation of natural resources such as medicinal plants is a strategy that is increasingly being employed by poor people in developing countries such as South Africa, as a means of generating an income. Increasing economic hardship and a lack of employment opportunities in the formal sector of the economy has led to many urban dwellers seeking alternative means of meeting their everyday livelihood needs. Although the contribution of natural resources to subsistence economies is widely recognised, there are few studies that have examined the significance of the trade in medicinal plants to the livelihoods of poor and marginalised people. Thirty informal street traders were interviewed to investigate the role of the medicinal plant trade in sustaining the livelihoods of the traders who operate in the informal sector of the Nelson Mandela Bay Municipality, South Africa. The findings of the research indicate that the sale and collection of medicinal plants is an activity which is exploited by people with limited resources, few skills, little or no education and often without any other source of household income. Middle-aged women from impoverished, single income households dominated the trade. Although income from the trade is modest, it contributed substantially to the total household cash income of the traders. Other benefits of the trade included independence and having a sense of purpose in life, as the traders felt that they were not only helping their families but also the wider community. However, without the income from the trade, many of the traders and their families would be destitute and thus the medicinal plant trade is vital to the wellbeing of these people.
- Full Text:
- Date Issued: 2012
Creation of clay flameless burner for vaporizing an insect repellent containing pmd as an active ingredient
- Authors: Akwi, Faith Mary
- Date: 2012
- Subjects: Insect baits and repellents , Montmorillonite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10383 , http://hdl.handle.net/10948/d1008406 , Insect baits and repellents , Montmorillonite
- Description: Insecticide treated mosquito bed nets, insecticide aerosol sprays, repellent lotions and creams, repellent candles, vaporizable repellent essential oils, mosquito mats and coils are some of the many malaria personal protection tools that are in use. The latter of these measures are the most accessible and affordable options for the rural population in sub-Saharan Africa. It is therefore important to determine how effective these personal protection measures are by determining their ability to efficiently disperse an active ingredient when the protection measure is in use. In this study, a copper II oxide montmorillonite clay burner (CuOMontmorillonite clay burner) was created to vaporize repellent formulations containing various concentrations of p-menthane-3,8-diol (PMD) as the active ingredient with the aim of determining the percentage of the active ingredient that is released into the air and the rate of release. The performance of the CuO-Montmorillonite clay burner was also compared to that of the Lampe Berger fragrance burner (LBFB). In addition to this, the percentage of PMD released from 6 percentage wt PMD candles of diameters 40mm, 69mm and 83mm was determined and compared to that released when the CuO-Montmorillonite clay burner and Lampe Berger Fragrance burner where used to vaporize PMD repellent formulations. It was found that the rate of vaporization of the various PMD repellent formulations vaporized using the Lampe Berger fragrance burner is affected by the mass of PMD present in the repellent formulations. The 6 percentage wt PMD repellent candles released the least percentage of PMD as compared to that released when the CuO-Montmorillonite clay burner and the Lampe Berger fragrance burner were used to vaporize the PMD repellent formulations.
- Full Text:
- Date Issued: 2012
- Authors: Akwi, Faith Mary
- Date: 2012
- Subjects: Insect baits and repellents , Montmorillonite
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10383 , http://hdl.handle.net/10948/d1008406 , Insect baits and repellents , Montmorillonite
- Description: Insecticide treated mosquito bed nets, insecticide aerosol sprays, repellent lotions and creams, repellent candles, vaporizable repellent essential oils, mosquito mats and coils are some of the many malaria personal protection tools that are in use. The latter of these measures are the most accessible and affordable options for the rural population in sub-Saharan Africa. It is therefore important to determine how effective these personal protection measures are by determining their ability to efficiently disperse an active ingredient when the protection measure is in use. In this study, a copper II oxide montmorillonite clay burner (CuOMontmorillonite clay burner) was created to vaporize repellent formulations containing various concentrations of p-menthane-3,8-diol (PMD) as the active ingredient with the aim of determining the percentage of the active ingredient that is released into the air and the rate of release. The performance of the CuO-Montmorillonite clay burner was also compared to that of the Lampe Berger fragrance burner (LBFB). In addition to this, the percentage of PMD released from 6 percentage wt PMD candles of diameters 40mm, 69mm and 83mm was determined and compared to that released when the CuO-Montmorillonite clay burner and Lampe Berger Fragrance burner where used to vaporize PMD repellent formulations. It was found that the rate of vaporization of the various PMD repellent formulations vaporized using the Lampe Berger fragrance burner is affected by the mass of PMD present in the repellent formulations. The 6 percentage wt PMD repellent candles released the least percentage of PMD as compared to that released when the CuO-Montmorillonite clay burner and the Lampe Berger fragrance burner were used to vaporize the PMD repellent formulations.
- Full Text:
- Date Issued: 2012
Investigation of the performance of photovoltaic systems
- Authors: Alistoun, Warren James
- Date: 2012
- Subjects: Photovoltaic power systems -- South Africa , Photovoltaic power generation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10517 , http://hdl.handle.net/10948/d1008396 , Photovoltaic power systems -- South Africa , Photovoltaic power generation -- South Africa
- Description: The main objective of this study was to investigate the performance of grid integrated PV systems. A data acquisition (DAQ) system was developed to monitor the performance of an existing grid integrated PV system with battery storage. This system is referred to as a grid assisted PV system. A data logger was used together with the inverters built in data logger to monitor environmental and electrical data on a grid tie PV system which was deployed during this study. To investigate the performance of these grid integrated PV systems PV and BOS device characterization was performed. This was achieved by using current voltage curve tracers and the DAQ system developed. Energy yield estimations were calculated referring to the literature review and a meteorological reference for comparison with measured energy yields from the grid tie PV system.
- Full Text:
- Date Issued: 2012
- Authors: Alistoun, Warren James
- Date: 2012
- Subjects: Photovoltaic power systems -- South Africa , Photovoltaic power generation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10517 , http://hdl.handle.net/10948/d1008396 , Photovoltaic power systems -- South Africa , Photovoltaic power generation -- South Africa
- Description: The main objective of this study was to investigate the performance of grid integrated PV systems. A data acquisition (DAQ) system was developed to monitor the performance of an existing grid integrated PV system with battery storage. This system is referred to as a grid assisted PV system. A data logger was used together with the inverters built in data logger to monitor environmental and electrical data on a grid tie PV system which was deployed during this study. To investigate the performance of these grid integrated PV systems PV and BOS device characterization was performed. This was achieved by using current voltage curve tracers and the DAQ system developed. Energy yield estimations were calculated referring to the literature review and a meteorological reference for comparison with measured energy yields from the grid tie PV system.
- Full Text:
- Date Issued: 2012
In vitro cytotoxic effects of selected Nigerian medicinal plant extracts on cancer cell lines
- Authors: Baatjies, Lucinda
- Date: 2012
- Subjects: Cancer -- Treatment , Cancer cells , Medicinal plants , Plant extracts , Traditional medicine , Public health
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10316 , http://hdl.handle.net/10948/d1008191 , Cancer -- Treatment , Cancer cells , Medicinal plants , Plant extracts , Traditional medicine , Public health
- Description: Cancer is a disease that imposes a heavy burden on public health and poses a challenge to science. The World Health Organization estimates that 80 percent of people in developing countries of the world rely on traditional medicine for their primary health needs, and about 85 percent of traditional medicine involves the use of plant extracts. This is particularly true in Africa where a large percentage of the population depends upon medicinal plants for health care. Therefore, detailed screening and evaluation of bioactive substances for chemotherapeutic purposes of African plants are urgently warranted. Furthermore, this will serve to validate the efficacy and safety of African traditional medicine. The current study investigated the in vitro cytotoxic effects of 17 ethanolic extracts of the following 16 plants used in traditional anticancer medicine in Nigeria: Sapium ellipticum leaves, Sapium ellipticum stembark, Combretum paniculatum, Celosia trigyna, Pupalia lappacea, Justica extensa, Hedranthera barteri leaves, Alternanthera sessilis, Ethulia conyzoides leaves, Lannea nigritana stembark, Combretum zenkeri root, Combretum molle leaves, Adenanthera parvoniana, Lannea acida, Cyathula achyranthoides, Drymaria cordata, Cyathula prostrata, against HeLa cancer cells. Five of the most promising extracts (Sapium ellipticum leaves, Combretum paniculatum, Celosia trigyna, Drymaria cordata, Cyathula prostrata) were selected for further screening against HT29 and MCF-7 cancer cells. Of the five, the first two were investigated further based on their activities in the screening phase. The S. ellipticum leaf extract yielded IC50 values of 88.60 ± 0.03 and 93.03 ± 0.03 μg/ml against HeLa and MCF-7, respectively. The toxicity was also evaluated on normal cells and an IC50 of 77.66 μg/ml was obtained for peripheral blood mononuclear cells (PBMCs). The IC50 values for proliferating and confluent Chang liver cells were both >125 μg/ml. These results suggest that the extract may be selective for specific cell types. Bio-assay guided fractionation of the S. ellipticum ethanolic extract yielded two active fractions; chloroform and ethyl acetate. Two compounds isolated from the chloroform extract were screened against the three cancer cell lines and found to be inactive. Three compounds were isolated from the ethyl acetate fraction and revealed IC50 values < 62.5 and < 31 μg/ml against MCF-7. Unfortunately these two compounds soon lost activity before any further work could be done on them and work was continued with the crude extract.
- Full Text:
- Date Issued: 2012
- Authors: Baatjies, Lucinda
- Date: 2012
- Subjects: Cancer -- Treatment , Cancer cells , Medicinal plants , Plant extracts , Traditional medicine , Public health
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10316 , http://hdl.handle.net/10948/d1008191 , Cancer -- Treatment , Cancer cells , Medicinal plants , Plant extracts , Traditional medicine , Public health
- Description: Cancer is a disease that imposes a heavy burden on public health and poses a challenge to science. The World Health Organization estimates that 80 percent of people in developing countries of the world rely on traditional medicine for their primary health needs, and about 85 percent of traditional medicine involves the use of plant extracts. This is particularly true in Africa where a large percentage of the population depends upon medicinal plants for health care. Therefore, detailed screening and evaluation of bioactive substances for chemotherapeutic purposes of African plants are urgently warranted. Furthermore, this will serve to validate the efficacy and safety of African traditional medicine. The current study investigated the in vitro cytotoxic effects of 17 ethanolic extracts of the following 16 plants used in traditional anticancer medicine in Nigeria: Sapium ellipticum leaves, Sapium ellipticum stembark, Combretum paniculatum, Celosia trigyna, Pupalia lappacea, Justica extensa, Hedranthera barteri leaves, Alternanthera sessilis, Ethulia conyzoides leaves, Lannea nigritana stembark, Combretum zenkeri root, Combretum molle leaves, Adenanthera parvoniana, Lannea acida, Cyathula achyranthoides, Drymaria cordata, Cyathula prostrata, against HeLa cancer cells. Five of the most promising extracts (Sapium ellipticum leaves, Combretum paniculatum, Celosia trigyna, Drymaria cordata, Cyathula prostrata) were selected for further screening against HT29 and MCF-7 cancer cells. Of the five, the first two were investigated further based on their activities in the screening phase. The S. ellipticum leaf extract yielded IC50 values of 88.60 ± 0.03 and 93.03 ± 0.03 μg/ml against HeLa and MCF-7, respectively. The toxicity was also evaluated on normal cells and an IC50 of 77.66 μg/ml was obtained for peripheral blood mononuclear cells (PBMCs). The IC50 values for proliferating and confluent Chang liver cells were both >125 μg/ml. These results suggest that the extract may be selective for specific cell types. Bio-assay guided fractionation of the S. ellipticum ethanolic extract yielded two active fractions; chloroform and ethyl acetate. Two compounds isolated from the chloroform extract were screened against the three cancer cell lines and found to be inactive. Three compounds were isolated from the ethyl acetate fraction and revealed IC50 values < 62.5 and < 31 μg/ml against MCF-7. Unfortunately these two compounds soon lost activity before any further work could be done on them and work was continued with the crude extract.
- Full Text:
- Date Issued: 2012
Using an intelligent self-service solution to support telecommunication service provisioning
- Authors: Barlow, Sherwin Riaan
- Date: 2012
- Subjects: Telecommunication systems -- Management , Electronic commerce -- Computer programs , Web applications
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10484 , http://hdl.handle.net/10948/d1013417
- Description: The increasing competition between telecommunication service providers (TSPs) and the large amounts of human resource costs incurred to provision telecommunication services to small, medium and micro enterprises (SMMEs), highlight the need for effective self-service provisioning methods to reduce costs. Existing service provisioning methods do not effectively support SMMEs in the service provisioning process. The current methods used are manual and Web-based. The manual service provisioning method is labour and time-intensive. TSPs are being forced to cut human resource costs as the profit margins for provisioning services are narrow due to competition. The current web-based systems do not allow SMMEs to effectively purchase services as they provide long textual lists to consult and limited information about services. The objective of this research was to develop an intelligent web-based self-service system to support SMMEs in telecommunication service provisioning, using a Design Science Research methodology. A constraint-based, knowledge-based recommender system was selected as the most appropriate intelligent system to support telecommunication service provisioning. A prototype called SelPro was developed as a solution to address the shortcomings of the current ineffective service provisioning methods available for SMMEs. SelPro incorporates an interactive wizard-style user interface with dynamic recommendations to support novice users as well as an expert interface which provides less user support. An expert review and a user study were conducted to determine if SelPro was usable, useful and effective. SelPro was perceived as being usable for SMMEs wishing to purchase telecommunication services. Expert participants were satisfied with the usability of SelPro and perceived it as being useful, easy to use and easy to learn. SelPro was considered effective because of the high task success ratings provided by the participants using the two interfaces. The research determined that intelligent web-based self-service provisioning can be used to effectively support SMMEs in telecommunication service provisioning. General design recommendations for similar systems were proposed and future work will involve using intelligent systems to support large enterprises in telecommunication service provisioning.
- Full Text:
- Date Issued: 2012
- Authors: Barlow, Sherwin Riaan
- Date: 2012
- Subjects: Telecommunication systems -- Management , Electronic commerce -- Computer programs , Web applications
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10484 , http://hdl.handle.net/10948/d1013417
- Description: The increasing competition between telecommunication service providers (TSPs) and the large amounts of human resource costs incurred to provision telecommunication services to small, medium and micro enterprises (SMMEs), highlight the need for effective self-service provisioning methods to reduce costs. Existing service provisioning methods do not effectively support SMMEs in the service provisioning process. The current methods used are manual and Web-based. The manual service provisioning method is labour and time-intensive. TSPs are being forced to cut human resource costs as the profit margins for provisioning services are narrow due to competition. The current web-based systems do not allow SMMEs to effectively purchase services as they provide long textual lists to consult and limited information about services. The objective of this research was to develop an intelligent web-based self-service system to support SMMEs in telecommunication service provisioning, using a Design Science Research methodology. A constraint-based, knowledge-based recommender system was selected as the most appropriate intelligent system to support telecommunication service provisioning. A prototype called SelPro was developed as a solution to address the shortcomings of the current ineffective service provisioning methods available for SMMEs. SelPro incorporates an interactive wizard-style user interface with dynamic recommendations to support novice users as well as an expert interface which provides less user support. An expert review and a user study were conducted to determine if SelPro was usable, useful and effective. SelPro was perceived as being usable for SMMEs wishing to purchase telecommunication services. Expert participants were satisfied with the usability of SelPro and perceived it as being useful, easy to use and easy to learn. SelPro was considered effective because of the high task success ratings provided by the participants using the two interfaces. The research determined that intelligent web-based self-service provisioning can be used to effectively support SMMEs in telecommunication service provisioning. General design recommendations for similar systems were proposed and future work will involve using intelligent systems to support large enterprises in telecommunication service provisioning.
- Full Text:
- Date Issued: 2012
On the optical and electrical design of low concentrator photovoltaic modules
- Authors: Benecke, Mario Andrew
- Date: 2012
- Subjects: Photovoltaic cells -- Design and construction , Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10543 , http://hdl.handle.net/10948/d1013102
- Description: The increasing interest in non-fossil fuel based electricity generation has caused a prominent boost for the renewable energy sector, especially the field of Photovoltaics (PV) with one of the main reasons being the decrease in cost of PV electricity generation. However, over the last few years a saturation in the efficiency of solar cells have been reached leading into a renewed search for other means to further reduce the cost of electricity generation from photovoltaic sources. One of the technologies that has attracted a lot of attention is low concentration photovoltaics (LCPV). LCPV investigates an alternative strategy to replace costly semiconductor material with relatively cheap optical materials by developing a Low Concentration Photovoltaic (LCPV) module. A LCPV module is divided into three subsystems, namely, the optical, electrical and thermal subsystem. This study focussed on the design, construction and characterisation of an optical subsystem accompanied by a thorough investigation into the design of an electrical subsystem. A facetted parabolic concentrator using a vertical receiver was modelled and a first prototype was constructed having a geometric concentration factor of 6.00 X. Upon electrical characterisation of this first vertical receiver LCPV prototype a concentration of only 4.53 X (receiver 1) and 4.71 X (receiver 2) was obtained. The first vertical receiver LCPV prototype did not reach the expected concentration factor due to optical losses and misalignment of optical elements. The illumination profile obtained from the reflector element was investigated and an undesirable non-uniform illumination profile was discovered. A second vertical receiver LCPV prototype was constructed in an attempt to improve on the first prototype, this second vertical receiver prototype had a geometrical concentration factor of 5.80 X. The results indicated a much improved illumination profile, yet still containing a number of non-uniformities. The second vertical receiver LCPV module yielded an operational concentration factor of 5.34 X. From the preliminary results obtained it was discovered that under concentrated illumination there was a limitation on the maximum power that could be obtained from the receiver. Upon further investigation it was discovered that this limitation was due to the higher current levels under concentrated illumination accompanied by a high series resistance of the receiver. This lead to the construction of new PV receivers, where this limitation could be minimised. 3 cell, 4 cell, 6 cell and 8 cell string configurations were constructed and used for the electrical characterisation of the prototypes. Due to non-uniformity of the illumination profile obtained from the second LCPV prototype a third vertical receiver LCPV prototype was constructed. This vertical receiver design illustrated more uniformity in the obtained illumination distribution and had a geometrical concentration factor of 4.61 X, although under operation only 4.26 X could be obtained. It is important to note that the geometric concentration factor does not account for reflective losses of the reflective material. One of the main reasons for the difficulty in obtaining a uniform illumination profile with the vertical receiver design is that the facetted reflector element is far away from the PV receiver. This enhances the effect of the slightest misalignment of any of the optical elements. This large distance also increases the effect of lensing from each facet. These factors lead to the consideration of a second design, which would counteract these factors. A horizontal receiver LCPV module design implementing a facetted parabolic reflector was considered to counteract these effects. From a mathematical model a horizontal receiver LCPV prototype was constructed having a geometrical concentration factor 5.3 X. The optical characterisation of the illumination profile showed a much improved illumination profile, which was much more uniform than the previous illumination profiles obtained from the other LCPV prototypes. The uniformity of the illumination profile could be seen in results obtained from the electrical characterisation where the concentrator reached operational concentration factor of 5.01 X. The reliability of the third vertical receiver LCPV prototype and the horizontal receiver LCPV prototype as well as the receivers were investigated by placing each receiver under stressed operational conditions for 60 sun hours. I-V characteristics were obtained after every five sun hours to investigate any signs of degradation. After 60 sun hours none of the receiver displayed any signs of degradation or reduction in electrical performance.
- Full Text:
- Date Issued: 2012
- Authors: Benecke, Mario Andrew
- Date: 2012
- Subjects: Photovoltaic cells -- Design and construction , Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10543 , http://hdl.handle.net/10948/d1013102
- Description: The increasing interest in non-fossil fuel based electricity generation has caused a prominent boost for the renewable energy sector, especially the field of Photovoltaics (PV) with one of the main reasons being the decrease in cost of PV electricity generation. However, over the last few years a saturation in the efficiency of solar cells have been reached leading into a renewed search for other means to further reduce the cost of electricity generation from photovoltaic sources. One of the technologies that has attracted a lot of attention is low concentration photovoltaics (LCPV). LCPV investigates an alternative strategy to replace costly semiconductor material with relatively cheap optical materials by developing a Low Concentration Photovoltaic (LCPV) module. A LCPV module is divided into three subsystems, namely, the optical, electrical and thermal subsystem. This study focussed on the design, construction and characterisation of an optical subsystem accompanied by a thorough investigation into the design of an electrical subsystem. A facetted parabolic concentrator using a vertical receiver was modelled and a first prototype was constructed having a geometric concentration factor of 6.00 X. Upon electrical characterisation of this first vertical receiver LCPV prototype a concentration of only 4.53 X (receiver 1) and 4.71 X (receiver 2) was obtained. The first vertical receiver LCPV prototype did not reach the expected concentration factor due to optical losses and misalignment of optical elements. The illumination profile obtained from the reflector element was investigated and an undesirable non-uniform illumination profile was discovered. A second vertical receiver LCPV prototype was constructed in an attempt to improve on the first prototype, this second vertical receiver prototype had a geometrical concentration factor of 5.80 X. The results indicated a much improved illumination profile, yet still containing a number of non-uniformities. The second vertical receiver LCPV module yielded an operational concentration factor of 5.34 X. From the preliminary results obtained it was discovered that under concentrated illumination there was a limitation on the maximum power that could be obtained from the receiver. Upon further investigation it was discovered that this limitation was due to the higher current levels under concentrated illumination accompanied by a high series resistance of the receiver. This lead to the construction of new PV receivers, where this limitation could be minimised. 3 cell, 4 cell, 6 cell and 8 cell string configurations were constructed and used for the electrical characterisation of the prototypes. Due to non-uniformity of the illumination profile obtained from the second LCPV prototype a third vertical receiver LCPV prototype was constructed. This vertical receiver design illustrated more uniformity in the obtained illumination distribution and had a geometrical concentration factor of 4.61 X, although under operation only 4.26 X could be obtained. It is important to note that the geometric concentration factor does not account for reflective losses of the reflective material. One of the main reasons for the difficulty in obtaining a uniform illumination profile with the vertical receiver design is that the facetted reflector element is far away from the PV receiver. This enhances the effect of the slightest misalignment of any of the optical elements. This large distance also increases the effect of lensing from each facet. These factors lead to the consideration of a second design, which would counteract these factors. A horizontal receiver LCPV module design implementing a facetted parabolic reflector was considered to counteract these effects. From a mathematical model a horizontal receiver LCPV prototype was constructed having a geometrical concentration factor 5.3 X. The optical characterisation of the illumination profile showed a much improved illumination profile, which was much more uniform than the previous illumination profiles obtained from the other LCPV prototypes. The uniformity of the illumination profile could be seen in results obtained from the electrical characterisation where the concentrator reached operational concentration factor of 5.01 X. The reliability of the third vertical receiver LCPV prototype and the horizontal receiver LCPV prototype as well as the receivers were investigated by placing each receiver under stressed operational conditions for 60 sun hours. I-V characteristics were obtained after every five sun hours to investigate any signs of degradation. After 60 sun hours none of the receiver displayed any signs of degradation or reduction in electrical performance.
- Full Text:
- Date Issued: 2012
Environmental cues and sensory preferences directing the nesting process in loggerhead turtles, caretta caretta, nesting in Maputaland, South Africa
- Authors: Brazier, Wayne
- Date: 2012
- Subjects: Sea turtles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10721 , http://hdl.handle.net/10948/d1015688
- Description: Animals use their senses for everything on an immediate, and day to day fashion – detecting danger, finding food, finding mates among other activities. In sea turtles and other migratory species senses are used for long-distance migrations. Senses such as smell, vision and hearing, have been studied experimentally under laboratory conditions but seldom have been investigated in the field. This thesis takes a combination of field and laboratory experiments and investigates some of the hypotheses involved in natal homing and nest site selection. The loggerhead’s nesting distribution in Maputaland is distinct with characteristic high and low density nesting areas which are consistent from year to year. Investigations by earlier researchers on these beaches suggested that beach characteristics, such as beach morphodynamic type and beach width, do not appear to influence the beaches at which loggerheads emerge to nest. The high density nesting area (with approximately 440 loggerhead emergences/km) have similar beach characteristics as the low density nesting area (with <50 loggerhead emergences/km). It is therefore suggested that there is another cue that drives nest site selection. It can either be related to a physical characteristic not yet realised, or is a non-physical (but chemical or biological) cue. This dissertation aims to identify the sensory inputs received during the nest selection process, as well as sea-finding ability after nesting. To investigate the mechanism causing the high-density as opposed to the low-density nesting area, three potential drivers were investigated namely: chemical imprinting (as a natal beach cue), ambient and artificial light (as deterrents) and social facilitation (as a learned behaviour). It was also attempted to identify the strength of the most common senses – vision, hearing and smell. As animal ethics restricts interfering with emerging or nesting turtles, the strengths of these senses were tested during sea-finding by adult loggerheads. The results indicate that sulfide concentrations appear to be used as chemical cues for nesting as these concentrations are elevated (>150 percent) in the high density nesting beaches compared to the low density nesting beaches within and among seasons however further investigations are required. Artificial light (range: 0.045–0.5 lux) is an active deterrent of female emergences while ambient light, even under extreme conditions such as lightning during electric storms (up to 8.2 lux), appears to have no observable influence on the spatial or temporal distributions of emergences. Social facilitation appears unlikely as a primary nest site selection factor for loggerheads. It may however, play a minor secondary role to preferred areas or hotspots. Sea-finding in post-nesting female loggerheads appears to be driven exclusively by visual cues such as the light horizon, with minimal to no influence from other cues (the sound of the breakers, slope or smell of the ocean) which solidify the visual system’s use in sea-finding. This research on the nest site selection of loggerheads and the sensory systems involved in this process has added valuable information to the limited pool of knowledge already present and has created a solid framework on which further investigations can be based. Future work in this field should focus on integrating a suite of sensory stimuli and cues to receive a greater understanding of the sensory systems used in nest site selection.
- Full Text:
- Date Issued: 2012
- Authors: Brazier, Wayne
- Date: 2012
- Subjects: Sea turtles
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10721 , http://hdl.handle.net/10948/d1015688
- Description: Animals use their senses for everything on an immediate, and day to day fashion – detecting danger, finding food, finding mates among other activities. In sea turtles and other migratory species senses are used for long-distance migrations. Senses such as smell, vision and hearing, have been studied experimentally under laboratory conditions but seldom have been investigated in the field. This thesis takes a combination of field and laboratory experiments and investigates some of the hypotheses involved in natal homing and nest site selection. The loggerhead’s nesting distribution in Maputaland is distinct with characteristic high and low density nesting areas which are consistent from year to year. Investigations by earlier researchers on these beaches suggested that beach characteristics, such as beach morphodynamic type and beach width, do not appear to influence the beaches at which loggerheads emerge to nest. The high density nesting area (with approximately 440 loggerhead emergences/km) have similar beach characteristics as the low density nesting area (with <50 loggerhead emergences/km). It is therefore suggested that there is another cue that drives nest site selection. It can either be related to a physical characteristic not yet realised, or is a non-physical (but chemical or biological) cue. This dissertation aims to identify the sensory inputs received during the nest selection process, as well as sea-finding ability after nesting. To investigate the mechanism causing the high-density as opposed to the low-density nesting area, three potential drivers were investigated namely: chemical imprinting (as a natal beach cue), ambient and artificial light (as deterrents) and social facilitation (as a learned behaviour). It was also attempted to identify the strength of the most common senses – vision, hearing and smell. As animal ethics restricts interfering with emerging or nesting turtles, the strengths of these senses were tested during sea-finding by adult loggerheads. The results indicate that sulfide concentrations appear to be used as chemical cues for nesting as these concentrations are elevated (>150 percent) in the high density nesting beaches compared to the low density nesting beaches within and among seasons however further investigations are required. Artificial light (range: 0.045–0.5 lux) is an active deterrent of female emergences while ambient light, even under extreme conditions such as lightning during electric storms (up to 8.2 lux), appears to have no observable influence on the spatial or temporal distributions of emergences. Social facilitation appears unlikely as a primary nest site selection factor for loggerheads. It may however, play a minor secondary role to preferred areas or hotspots. Sea-finding in post-nesting female loggerheads appears to be driven exclusively by visual cues such as the light horizon, with minimal to no influence from other cues (the sound of the breakers, slope or smell of the ocean) which solidify the visual system’s use in sea-finding. This research on the nest site selection of loggerheads and the sensory systems involved in this process has added valuable information to the limited pool of knowledge already present and has created a solid framework on which further investigations can be based. Future work in this field should focus on integrating a suite of sensory stimuli and cues to receive a greater understanding of the sensory systems used in nest site selection.
- Full Text:
- Date Issued: 2012
Incorporating prey demographics and predator social structure into prey selection and carrying capacity estimates for cheetah
- Authors: Clements, Hayley Susan
- Date: 2012
- Subjects: Carnivorous animals , Cheetah
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10754 , http://hdl.handle.net/10948/d1018606
- Description: There is a need for a refined understanding of large carnivore prey preference and carrying capacity (K). To date, K estimates for large carnivores have been developed from predictions of carnivore diet at a prey and predator species-level. These predictions therefore assume that all social classes within a carnivore species display similar prey preferences and that all demographic classes within a prey species are equally preferred or avoided. The objective of this study was to investigate the importance of including prey demographics and carnivore social class in carnivore diet descriptions and thereby K estimates, using cheetah Acinonyx jubatus as a study species. It was predicted that prey sex, prey age and cheetah social class influence cheetah prey preferences, when they influence the risk and ease of prey capture, and that their inclusion in a K model would improve its predictive strength. Based on an analysis of 1290 kills from South Africa, male coalition cheetah were found to prefer a broader weight range of prey than solitary cheetah. Prey demographics further influenced cheetah prey preference, when it corresponded to differences in prey size and the presence of horns. The current species-level K regression model for cheetah is based on preferred prey and thus omits highly abundant antelope that often comprise the majority of the diet, an artefact of the way in which preferences are calculated. A refinement of the species-level K regression model, to account for prey demographic- and cheetah social class-level differences in diet and the biomass of accessible prey (defined in this study as all non-avoided prey) instead of just preferred prey, doubled the predictive strength of the K model. Because group-hunting enabled predation on a broader weight range of prey, cheetah K was influenced by the ratio of male coalition cheetah to solitary cheetah in the population. The refined K regression model is derived from ecosystems supporting an intact carnivore guild. A mechanistic approach to estimating K, based on Caughley‟s (1977) maximum sustainable yield model, therefore better predicted cheetah K in systems devoid of lion Panthera leo and African wild dog Lycaon pictus, which were found to suppress cheetah density. This study improves our understanding of the relationships between prey demographics, cheetah social classes and intra-guild competition in determining cheetah prey preferences and K. This study therefore paves the way for similar work on other large carnivores.
- Full Text:
- Date Issued: 2012
- Authors: Clements, Hayley Susan
- Date: 2012
- Subjects: Carnivorous animals , Cheetah
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10754 , http://hdl.handle.net/10948/d1018606
- Description: There is a need for a refined understanding of large carnivore prey preference and carrying capacity (K). To date, K estimates for large carnivores have been developed from predictions of carnivore diet at a prey and predator species-level. These predictions therefore assume that all social classes within a carnivore species display similar prey preferences and that all demographic classes within a prey species are equally preferred or avoided. The objective of this study was to investigate the importance of including prey demographics and carnivore social class in carnivore diet descriptions and thereby K estimates, using cheetah Acinonyx jubatus as a study species. It was predicted that prey sex, prey age and cheetah social class influence cheetah prey preferences, when they influence the risk and ease of prey capture, and that their inclusion in a K model would improve its predictive strength. Based on an analysis of 1290 kills from South Africa, male coalition cheetah were found to prefer a broader weight range of prey than solitary cheetah. Prey demographics further influenced cheetah prey preference, when it corresponded to differences in prey size and the presence of horns. The current species-level K regression model for cheetah is based on preferred prey and thus omits highly abundant antelope that often comprise the majority of the diet, an artefact of the way in which preferences are calculated. A refinement of the species-level K regression model, to account for prey demographic- and cheetah social class-level differences in diet and the biomass of accessible prey (defined in this study as all non-avoided prey) instead of just preferred prey, doubled the predictive strength of the K model. Because group-hunting enabled predation on a broader weight range of prey, cheetah K was influenced by the ratio of male coalition cheetah to solitary cheetah in the population. The refined K regression model is derived from ecosystems supporting an intact carnivore guild. A mechanistic approach to estimating K, based on Caughley‟s (1977) maximum sustainable yield model, therefore better predicted cheetah K in systems devoid of lion Panthera leo and African wild dog Lycaon pictus, which were found to suppress cheetah density. This study improves our understanding of the relationships between prey demographics, cheetah social classes and intra-guild competition in determining cheetah prey preferences and K. This study therefore paves the way for similar work on other large carnivores.
- Full Text:
- Date Issued: 2012
Evaluation of noise levels of micro-wind turbines using a randomised experiment
- Authors: Clohessy, Chantelle May
- Date: 2012
- Subjects: Wind turbines -- Noise , Wind turbines -- valuation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10508 , http://hdl.handle.net/10948/d1015974
- Description: One of the biggest environmental concerns of a wind turbine is the wind turbine noise (Prospathopoulos and Voutsinas, 2007). This study assesses the noise impacts of wind turbines on the environment by comparing the micro-wind turbine noise to traditional accepted surrounding sounds. The collection of the sound level data was done by using a randomised experiment. The sound level data was then fitted to a General Linear Model to determine the relationship between the sound levels generated at a given site to the time of day, wind speed, wind direction and distance from the sound source. An additional study was conducted to determine the relationship between wind speed and the sound levels of wind turbines. The distribution of frequency components of wind turbine sound was also determined.
- Full Text:
- Date Issued: 2012
- Authors: Clohessy, Chantelle May
- Date: 2012
- Subjects: Wind turbines -- Noise , Wind turbines -- valuation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10508 , http://hdl.handle.net/10948/d1015974
- Description: One of the biggest environmental concerns of a wind turbine is the wind turbine noise (Prospathopoulos and Voutsinas, 2007). This study assesses the noise impacts of wind turbines on the environment by comparing the micro-wind turbine noise to traditional accepted surrounding sounds. The collection of the sound level data was done by using a randomised experiment. The sound level data was then fitted to a General Linear Model to determine the relationship between the sound levels generated at a given site to the time of day, wind speed, wind direction and distance from the sound source. An additional study was conducted to determine the relationship between wind speed and the sound levels of wind turbines. The distribution of frequency components of wind turbine sound was also determined.
- Full Text:
- Date Issued: 2012
Characterization of cell mismatch in photovoltaic modules using electroluminescence and associated electro-optic techniques
- Authors: Crozier, Jacqueline Louise
- Date: 2012
- Subjects: Photovoltaic cells , Solar cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10545 , http://hdl.handle.net/10948/d1015059
- Description: Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy much more environmentally friendly than fossil fuel energy sources. These solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of the PV module is limited by the performance of the individual cells. Cell mismatch occurs when some cells are damaged or shaded and produce lower current output than the other cells in the series connected string. The cell mismatch lowers the module performance and can result in further damage as the weak cells are reverse biased and dissipate heat. Bypass diodes can be connected into the module to increase the module current output and prevent further damage. Since cell mismatch results in a significant decrease in the performance of deployed modules it is important to fully understand and characterise its effect on PV modules. PV modules can be characterised using various techniques, each providing important information about the performance of the module. Most commonly the current-voltage (I-V) characteristic curve of a module is measured in outdoor, fully illuminated conditions. This allows performance parameters such as short circuit current (Isc), open circuit voltage (Voc) and maximum power (Pmax) to be determined. In addition to this the shape of the curve allows device parameters like series and shunt resistances to be determined using parameter extraction algorithms like Particle Swarm Optimisation (PSO). The extracted parameters can be entered into the diode equation to model the I-V curve of the module. The I-V characteristic of the module can also be used to identify poor current producing cells in the module by using the worst-case cell determination method. In this technique a cell is shaded and the greater the drop in current in the whole module the better the current production of the shaded cell. The photoresponse of cells in a module can be determined by the Large-area Light Beam Induced Current (LA-LBIC) technique which involves scanning a module with a laser beam and recording the current generated. Electroluminescence (EL) is emitted by a forward biased PV module and is used to identify defects in cell material. Defects such as cracks and broken fingers can be detected as well as material features such as grain boundaries. These techniques are used to in conjunction to characterise the modules used in this study. The modules investigated in this study each exhibit cell mismatch resulting from different causes. Each module is characterised using a combination of characterisation techniques which allows the effect of cell mismatch be investigated. EL imaging enabled cracks and defects, invisible to the naked eye, to be detected allowing the reduced performance observed in I-V curves to be explained. It was seen that the cracked cells have a significant effect on the current produced by a string, while the effect of delaminated areas is less severe. Hot spots are observed on weak cells indicating they are in reverse bias conditions and will degrade further with time. PSO parameter extraction from I-V curves revealed that the effect of module degradation of device parameters like series and shunt resistances. A module with cracked cells and degradation of the antireflective coating has low shunt resistance indicating current losses due to shunting. Similar shunting is observed in a module with delamination and moisture ingress. The extracted parameters are used to simulate the I-V curves of modules with reasonable fit. The fit could be improved around the “knee” of the I-V curve by improving the methods of parameter extraction. This study has shown the effects of cell mismatch on the performance and I-V curves of the PV modules. The different causes of cell mismatch are discussed and modules with different cell configuration and damage are characterised. The characterisation techniques used on each module provide information about the photoresponse, current generation, material properties and cell defects. A comprehensive understanding of these techniques allows the cell mismatch in the modules to be fully characterized.
- Full Text:
- Date Issued: 2012
- Authors: Crozier, Jacqueline Louise
- Date: 2012
- Subjects: Photovoltaic cells , Solar cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10545 , http://hdl.handle.net/10948/d1015059
- Description: Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy much more environmentally friendly than fossil fuel energy sources. These solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of the PV module is limited by the performance of the individual cells. Cell mismatch occurs when some cells are damaged or shaded and produce lower current output than the other cells in the series connected string. The cell mismatch lowers the module performance and can result in further damage as the weak cells are reverse biased and dissipate heat. Bypass diodes can be connected into the module to increase the module current output and prevent further damage. Since cell mismatch results in a significant decrease in the performance of deployed modules it is important to fully understand and characterise its effect on PV modules. PV modules can be characterised using various techniques, each providing important information about the performance of the module. Most commonly the current-voltage (I-V) characteristic curve of a module is measured in outdoor, fully illuminated conditions. This allows performance parameters such as short circuit current (Isc), open circuit voltage (Voc) and maximum power (Pmax) to be determined. In addition to this the shape of the curve allows device parameters like series and shunt resistances to be determined using parameter extraction algorithms like Particle Swarm Optimisation (PSO). The extracted parameters can be entered into the diode equation to model the I-V curve of the module. The I-V characteristic of the module can also be used to identify poor current producing cells in the module by using the worst-case cell determination method. In this technique a cell is shaded and the greater the drop in current in the whole module the better the current production of the shaded cell. The photoresponse of cells in a module can be determined by the Large-area Light Beam Induced Current (LA-LBIC) technique which involves scanning a module with a laser beam and recording the current generated. Electroluminescence (EL) is emitted by a forward biased PV module and is used to identify defects in cell material. Defects such as cracks and broken fingers can be detected as well as material features such as grain boundaries. These techniques are used to in conjunction to characterise the modules used in this study. The modules investigated in this study each exhibit cell mismatch resulting from different causes. Each module is characterised using a combination of characterisation techniques which allows the effect of cell mismatch be investigated. EL imaging enabled cracks and defects, invisible to the naked eye, to be detected allowing the reduced performance observed in I-V curves to be explained. It was seen that the cracked cells have a significant effect on the current produced by a string, while the effect of delaminated areas is less severe. Hot spots are observed on weak cells indicating they are in reverse bias conditions and will degrade further with time. PSO parameter extraction from I-V curves revealed that the effect of module degradation of device parameters like series and shunt resistances. A module with cracked cells and degradation of the antireflective coating has low shunt resistance indicating current losses due to shunting. Similar shunting is observed in a module with delamination and moisture ingress. The extracted parameters are used to simulate the I-V curves of modules with reasonable fit. The fit could be improved around the “knee” of the I-V curve by improving the methods of parameter extraction. This study has shown the effects of cell mismatch on the performance and I-V curves of the PV modules. The different causes of cell mismatch are discussed and modules with different cell configuration and damage are characterised. The characterisation techniques used on each module provide information about the photoresponse, current generation, material properties and cell defects. A comprehensive understanding of these techniques allows the cell mismatch in the modules to be fully characterized.
- Full Text:
- Date Issued: 2012
The biota of the Swartkops Solar Saltworks and their potential for producing biofuels
- Authors: De Lauwere, Monique Simone
- Date: 2012
- Subjects: Organisms , Biomass energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10625 , http://hdl.handle.net/10948/d1011657 , Organisms , Biomass energy
- Description: The Swartkops and Missionvale salinas in Port Elizabeth on the east coast of South Africa are surrounding by large informal settlements. The runoff from these settlements contributes largely to the eutrophication of the solar saltworks which in turn has an effect on the biotic functioning of the systems, ultimately affecting the quantity and quality of the salt produced. Inorganic nutrients and organic composition, as well as important biological groups were examined within the brine with the aim of comparing the current condition of the same salinas to their condition twelve years ago. Comparisons between inorganic nutrient concentrations and biological groups showed significantly higher inorganic nutrients, with chlorophyll a concentrations in the Swartkops salina in 2011 being significantly higher than in 2012 and the 1999 and 2011 chlorophyll a concentrations being significantly higher than 2012 in the Missionvale salina. Microalgae found in the salinas were cultured in four different growth media. Cells were stained with Nile Red fluorescent dye in order to estimate the extent of lipids production. Five of the most promising lipid producing species were isolated into a monoculture and grown at different salinities to establish the growth and lipid production in response to salinity. Halamphora coffeaeformis and Navicula sp. were found to be the best candidate species. They grew best at salinities between 50 and 70 psu and produced lipid vesicles consuming approximately 10 percent of the cell.
- Full Text:
- Date Issued: 2012
- Authors: De Lauwere, Monique Simone
- Date: 2012
- Subjects: Organisms , Biomass energy
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10625 , http://hdl.handle.net/10948/d1011657 , Organisms , Biomass energy
- Description: The Swartkops and Missionvale salinas in Port Elizabeth on the east coast of South Africa are surrounding by large informal settlements. The runoff from these settlements contributes largely to the eutrophication of the solar saltworks which in turn has an effect on the biotic functioning of the systems, ultimately affecting the quantity and quality of the salt produced. Inorganic nutrients and organic composition, as well as important biological groups were examined within the brine with the aim of comparing the current condition of the same salinas to their condition twelve years ago. Comparisons between inorganic nutrient concentrations and biological groups showed significantly higher inorganic nutrients, with chlorophyll a concentrations in the Swartkops salina in 2011 being significantly higher than in 2012 and the 1999 and 2011 chlorophyll a concentrations being significantly higher than 2012 in the Missionvale salina. Microalgae found in the salinas were cultured in four different growth media. Cells were stained with Nile Red fluorescent dye in order to estimate the extent of lipids production. Five of the most promising lipid producing species were isolated into a monoculture and grown at different salinities to establish the growth and lipid production in response to salinity. Halamphora coffeaeformis and Navicula sp. were found to be the best candidate species. They grew best at salinities between 50 and 70 psu and produced lipid vesicles consuming approximately 10 percent of the cell.
- Full Text:
- Date Issued: 2012
Factors affecting survivorship of loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles of South Africa
- Authors: De Wet, Anje
- Date: 2012
- Subjects: Loggerhead turtle -- South Africa , Leatherback turtle -- South Africa , Sea turtles -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10686 , http://hdl.handle.net/10948/d1007900 , Loggerhead turtle -- South Africa , Leatherback turtle -- South Africa , Sea turtles -- South Africa
- Description: Loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles as well as their eggs and hatchlings have been protected on their nesting beach in South Africa (SA) since 1963. Both nesting populations were expected to show similar trends in recovery following the application of identical protection and conservation measures. The loggerhead nesting population has responded favourably to these protection efforts. In contrast, the leatherback nesting population showed an initial increase but is currently stable. The reason for this difference in response is thought to be due to differential offshore mortality of these two species. This prompted an investigation into the different sources of sea turtle mortality in the South Western Indian Ocean (SWIO). Specific aims were to identify and quantify sources of loggerhead and leatherback mortality on nesting beaches as well as in the oceans. Reasonable survivorship at all age classes is important to ensure recruitment of new nesting individuals into sea turtle populations. Mortality of nests, eggs per nest and hatchlings were quantified over two seasons for the loggerheads and leatherbacks nesting in SA. The beach was patrolled on foot to encounter and record females emerging from the ocean and later, hatchlings from their nests. The nests were then monitored during the incubation period and excavated once hatched. The fates of 925 nests were determined during these two nesting seasons (2009/2010 and 2010/2011). The main source of loggerhead and leatherback nest destruction was predation (8.6 percent and 15.7 percent respectively) followed by nest erosion (2.2 percent and 6.3 percent respectively). Overall nest success was high but higher for loggerheads (89 percent) than for leatherbacks (78 percent). The main cause of egg mortality for both species was early developmental arrest, followed by predation by ants and ghost crabs. Hatchlings en route to the sea were almost exclusively predated by ghost crabs (4.2 percent of emerged loggerhead hatchlings and 3.2 percent of emerged leatherback hatchlings). It appears that both species benefit from the coastal conservation efforts. When sea turtles leave the nesting beach, either as hatchlings or adults, conservation and monitoring becomes more difficult and sea turtles are exposed to a multitude of threats, including anthropogenic threats. Age classes tend to be spatially separated due to different habitat and dietary requirements. The type of threat sea turtles are exposed to thus depends on the current age class. Offshore sources of mortality in the SWIO were identified and where possible loggerhead and leatherback mortality was quantified and mapped spatially. Loggerheads were mostly exposed to and had the highest mortality in the artisanal fisheries in the SWIO (> 1000 per annum), inshore trawling (ca. 41 per annum), shark nets (protective gill nets) (21.6 ± 6.7 per annum) and the pelagic longline fishery (5.0 ± 4.4 per annum). In contrast, leatherbacks with a pelagic lifestyle, were mostly exposed to pelagic longline fisheries (7.8 ± 7.8 per annum). A spatial analysis of fishing activities indicated that leatherback home ranges overlapped 41percent with pelagic longline fishing activity in the SA EEZ, whereas the overlap between pelagic longliners and loggerhead home ranges was 29 percent. The quantified sources of mortality provide some explanation for the trend in the loggerhead nesting population but not the trend in the leatherback nesting population. Hatchling survivorship to adulthood was estimated to determine the viability of the two nesting populations as well as to determine whether offshore mortality was responsible for the difference in recovery of the two populations. Loggerhead hatchling survivorship to adulthood was estimated at between 2 and 10 per 1000 hatchlings, the minimum requirement for an increasing population. The adopted sophisticated model shows that leatherbacks have a survival rate of 5 to 10 per 1 000 hatchlings. However, this suggests that the population is increasing, but the leatherback population is stable. Perhaps the age to maturity of SA leatherbacks is greater than 12 years, or fisheries-related mortality affects younger age classes than initially thought. It is therefore recommended that the turtle monitoring area is extended to include other potential nesting grounds. In addition, observer or monitoring programs for commercial as well as artisanal fisheries needs to be extended throughout the SWIO to quantify sea turtle mortality. Ultimately a comprehensive multi-regional approach is required for the conservation of these highly migratory species.
- Full Text:
- Date Issued: 2012
- Authors: De Wet, Anje
- Date: 2012
- Subjects: Loggerhead turtle -- South Africa , Leatherback turtle -- South Africa , Sea turtles -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10686 , http://hdl.handle.net/10948/d1007900 , Loggerhead turtle -- South Africa , Leatherback turtle -- South Africa , Sea turtles -- South Africa
- Description: Loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles as well as their eggs and hatchlings have been protected on their nesting beach in South Africa (SA) since 1963. Both nesting populations were expected to show similar trends in recovery following the application of identical protection and conservation measures. The loggerhead nesting population has responded favourably to these protection efforts. In contrast, the leatherback nesting population showed an initial increase but is currently stable. The reason for this difference in response is thought to be due to differential offshore mortality of these two species. This prompted an investigation into the different sources of sea turtle mortality in the South Western Indian Ocean (SWIO). Specific aims were to identify and quantify sources of loggerhead and leatherback mortality on nesting beaches as well as in the oceans. Reasonable survivorship at all age classes is important to ensure recruitment of new nesting individuals into sea turtle populations. Mortality of nests, eggs per nest and hatchlings were quantified over two seasons for the loggerheads and leatherbacks nesting in SA. The beach was patrolled on foot to encounter and record females emerging from the ocean and later, hatchlings from their nests. The nests were then monitored during the incubation period and excavated once hatched. The fates of 925 nests were determined during these two nesting seasons (2009/2010 and 2010/2011). The main source of loggerhead and leatherback nest destruction was predation (8.6 percent and 15.7 percent respectively) followed by nest erosion (2.2 percent and 6.3 percent respectively). Overall nest success was high but higher for loggerheads (89 percent) than for leatherbacks (78 percent). The main cause of egg mortality for both species was early developmental arrest, followed by predation by ants and ghost crabs. Hatchlings en route to the sea were almost exclusively predated by ghost crabs (4.2 percent of emerged loggerhead hatchlings and 3.2 percent of emerged leatherback hatchlings). It appears that both species benefit from the coastal conservation efforts. When sea turtles leave the nesting beach, either as hatchlings or adults, conservation and monitoring becomes more difficult and sea turtles are exposed to a multitude of threats, including anthropogenic threats. Age classes tend to be spatially separated due to different habitat and dietary requirements. The type of threat sea turtles are exposed to thus depends on the current age class. Offshore sources of mortality in the SWIO were identified and where possible loggerhead and leatherback mortality was quantified and mapped spatially. Loggerheads were mostly exposed to and had the highest mortality in the artisanal fisheries in the SWIO (> 1000 per annum), inshore trawling (ca. 41 per annum), shark nets (protective gill nets) (21.6 ± 6.7 per annum) and the pelagic longline fishery (5.0 ± 4.4 per annum). In contrast, leatherbacks with a pelagic lifestyle, were mostly exposed to pelagic longline fisheries (7.8 ± 7.8 per annum). A spatial analysis of fishing activities indicated that leatherback home ranges overlapped 41percent with pelagic longline fishing activity in the SA EEZ, whereas the overlap between pelagic longliners and loggerhead home ranges was 29 percent. The quantified sources of mortality provide some explanation for the trend in the loggerhead nesting population but not the trend in the leatherback nesting population. Hatchling survivorship to adulthood was estimated to determine the viability of the two nesting populations as well as to determine whether offshore mortality was responsible for the difference in recovery of the two populations. Loggerhead hatchling survivorship to adulthood was estimated at between 2 and 10 per 1000 hatchlings, the minimum requirement for an increasing population. The adopted sophisticated model shows that leatherbacks have a survival rate of 5 to 10 per 1 000 hatchlings. However, this suggests that the population is increasing, but the leatherback population is stable. Perhaps the age to maturity of SA leatherbacks is greater than 12 years, or fisheries-related mortality affects younger age classes than initially thought. It is therefore recommended that the turtle monitoring area is extended to include other potential nesting grounds. In addition, observer or monitoring programs for commercial as well as artisanal fisheries needs to be extended throughout the SWIO to quantify sea turtle mortality. Ultimately a comprehensive multi-regional approach is required for the conservation of these highly migratory species.
- Full Text:
- Date Issued: 2012
Evaluation for harnessing low-enthalpy geothermal energy in South Africa based on a model pilot plant in the Limpopo Mobile Belt
- Authors: Dhansay, Taufeeq
- Date: 2012
- Subjects: Geothermal resources -- South Africa -- Limpopo , Renewable energy sources -- South Africa -- Limpopo , Climatic changes -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10667 , http://hdl.handle.net/10948/d1019789
- Description: South Africa generates more than 90 percent of its total energy capacity through non-renewable sources. With coal forming the predominant energy source, South Africa became the leading carbon emissive nation in Africa, emitting 450 million tonnes of CO2 in 2011. In an international effort to restrict global average temperature rise to 2° C above the average prior the industrial revolution, the Kyoto Protocol has been extended for another 8-year commitment period. This is complementary to an expected resolution of a new legally binding climate change policy in 2015. This policy will aim to introduce financial penalties for nations failing to meet ascribed GHG emission targets by 2020. In an attempt to meet these climate change resolutions South Africa will research and develop cleaner, alternative forms of energy, including hydro, wind, and biomass forms of renewable energy, in addition to designating stringent building regulations for the Incorporation of solar energy. These measures form part of an Integrated evelopment Plan that aims to generate a target of 10,000 GWh of renewable energy in 2013. South Africa is also investigating the possibilities of extracting its shale gas reserves and implementing it as a major energy source. This energy mix has given little attention to geothermal energy. The reasons for this omission appears to be the lack of active volcanism and previous research that suggests South Africa, largely underlain by the Kaapvaal Craton, has a relatively low heat Flow profile, deemed insufficient for harnessing geothermal energy.
- Full Text:
- Date Issued: 2012
- Authors: Dhansay, Taufeeq
- Date: 2012
- Subjects: Geothermal resources -- South Africa -- Limpopo , Renewable energy sources -- South Africa -- Limpopo , Climatic changes -- South Africa -- Limpopo
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10667 , http://hdl.handle.net/10948/d1019789
- Description: South Africa generates more than 90 percent of its total energy capacity through non-renewable sources. With coal forming the predominant energy source, South Africa became the leading carbon emissive nation in Africa, emitting 450 million tonnes of CO2 in 2011. In an international effort to restrict global average temperature rise to 2° C above the average prior the industrial revolution, the Kyoto Protocol has been extended for another 8-year commitment period. This is complementary to an expected resolution of a new legally binding climate change policy in 2015. This policy will aim to introduce financial penalties for nations failing to meet ascribed GHG emission targets by 2020. In an attempt to meet these climate change resolutions South Africa will research and develop cleaner, alternative forms of energy, including hydro, wind, and biomass forms of renewable energy, in addition to designating stringent building regulations for the Incorporation of solar energy. These measures form part of an Integrated evelopment Plan that aims to generate a target of 10,000 GWh of renewable energy in 2013. South Africa is also investigating the possibilities of extracting its shale gas reserves and implementing it as a major energy source. This energy mix has given little attention to geothermal energy. The reasons for this omission appears to be the lack of active volcanism and previous research that suggests South Africa, largely underlain by the Kaapvaal Craton, has a relatively low heat Flow profile, deemed insufficient for harnessing geothermal energy.
- Full Text:
- Date Issued: 2012
Enumeration of insect viruses using microscopic and molecular analyses: South African isolate of cryotophlebia leucotreta granulovirus as a case study
- Authors: Dhladhla, Busisiwe I R
- Date: 2012
- Subjects: Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10318 , http://hdl.handle.net/10948/d1008395 , Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Description: Baculoviruses have been used as biocontrol agents to control insect pests in agriculture since the 1970s. Out of the fifteen virus families known to infect insects, baculoviruses offer the greatest potential as insect biopesticides, due to their high host specificity which makes them extremely safe to humans, other vertebrates, plants and non-target microorganisms. They comprise of two genera: nucleopolyhedroviruses (NPVs) and granuloviruses (GVs). The South African isolate of Cryptophlebia leucotreta granulovirus (CrleGV-SA) which is infectious for the false codling moth (FCM), Thaumatotibia leucotreta, (Meyrick) (Lepidoptera: Tortricidae), has been successfully developed into two commercial biopesticides; Cryptogran® and Cryptex®, for the control of FCM in citrus crops. The current method of enumeration used for CrleGV-SA virus particles in routine experiments during the production of the GV as biopesticides, is dark field microscopy. However, due to the small size of GVs (300-500 nm in length), the technique is not easy to perform on these viruses, and no systemic comparison has been made of potential alternative methods. Therefore, the main objective of this study was to develop a quantitative enumeration method for CrleGV-SA occlusion bodies (OBs) which is accurate, reliable, and feasible, and compare the developed methods of enumeration to the current method. Purified and semi-purified CrleGV-SA viral stocks were prepared for enumeration studies using spectrophotometry, dark field microscopy, scanning electron microscopy (SEM) and real time qPCR. Spectrophotometry was found to be an unreliable method for enumeration of GVs in the production, standardisation, and quality control of biopesticides. Dark field microscopy and SEM were found to be accurate, and statistically comparable (p = 0.064) enumeration techniques. qPCR is currently being optimised for the enumeration of GVs. This technique was demonstrated to generate accurate standard curves for absolute quantification of virus particles for pure and semi-pure virus preparations. qPCR offers the greatest potential as an accurate enumeration method because it is not affected by contamination with non-biological contaminating debris, nor by other biological material due to the specificity of PCR primers. Further work is required to fully develop qPCR as an enumeration method for GVs. However, dark field microscopy has been successfully validated as an enumeration method. SEM, which has a high resolution compared to light microscopy, has an added advantage over dark field microscopy, which is to distinguish virus particles in semi-pure viral stock preparations during counting. Therefore, SEM currently provides the most unambiguous and feasible enumeration method for GVs in both purified and semi-purified virus samples.
- Full Text:
- Date Issued: 2012
- Authors: Dhladhla, Busisiwe I R
- Date: 2012
- Subjects: Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10318 , http://hdl.handle.net/10948/d1008395 , Baculoviruses , Insects -- Viruses , Molecular genetics , Microbial genomics
- Description: Baculoviruses have been used as biocontrol agents to control insect pests in agriculture since the 1970s. Out of the fifteen virus families known to infect insects, baculoviruses offer the greatest potential as insect biopesticides, due to their high host specificity which makes them extremely safe to humans, other vertebrates, plants and non-target microorganisms. They comprise of two genera: nucleopolyhedroviruses (NPVs) and granuloviruses (GVs). The South African isolate of Cryptophlebia leucotreta granulovirus (CrleGV-SA) which is infectious for the false codling moth (FCM), Thaumatotibia leucotreta, (Meyrick) (Lepidoptera: Tortricidae), has been successfully developed into two commercial biopesticides; Cryptogran® and Cryptex®, for the control of FCM in citrus crops. The current method of enumeration used for CrleGV-SA virus particles in routine experiments during the production of the GV as biopesticides, is dark field microscopy. However, due to the small size of GVs (300-500 nm in length), the technique is not easy to perform on these viruses, and no systemic comparison has been made of potential alternative methods. Therefore, the main objective of this study was to develop a quantitative enumeration method for CrleGV-SA occlusion bodies (OBs) which is accurate, reliable, and feasible, and compare the developed methods of enumeration to the current method. Purified and semi-purified CrleGV-SA viral stocks were prepared for enumeration studies using spectrophotometry, dark field microscopy, scanning electron microscopy (SEM) and real time qPCR. Spectrophotometry was found to be an unreliable method for enumeration of GVs in the production, standardisation, and quality control of biopesticides. Dark field microscopy and SEM were found to be accurate, and statistically comparable (p = 0.064) enumeration techniques. qPCR is currently being optimised for the enumeration of GVs. This technique was demonstrated to generate accurate standard curves for absolute quantification of virus particles for pure and semi-pure virus preparations. qPCR offers the greatest potential as an accurate enumeration method because it is not affected by contamination with non-biological contaminating debris, nor by other biological material due to the specificity of PCR primers. Further work is required to fully develop qPCR as an enumeration method for GVs. However, dark field microscopy has been successfully validated as an enumeration method. SEM, which has a high resolution compared to light microscopy, has an added advantage over dark field microscopy, which is to distinguish virus particles in semi-pure viral stock preparations during counting. Therefore, SEM currently provides the most unambiguous and feasible enumeration method for GVs in both purified and semi-purified virus samples.
- Full Text:
- Date Issued: 2012
Aspects of heterothermy in four species of afrotropical bats
- Authors: Doty, Anna Catherine
- Date: 2012
- Subjects: Body temperature -- Regulation , Afrotropical mammals , Body temperature , Bats
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10691 , http://hdl.handle.net/10948/d1008402 , Body temperature -- Regulation , Afrotropical mammals , Body temperature , Bats
- Description: Torpor and hibernation, two distinct forms of heterothermy, are physiological responses employed by many endotherms to save energy during periods of cold, climatic unpredictability and food shortage. Heterothermy is characterized by varying body temperature and has been found to occur in various subtropical mammals. However, studies on thermoregulatory capabilities of South African Microchiroptera remain relatively scant. In this study, the capacity for use of heterothermy, the seasonal metabolic rates, and capacity for non-shivering thermogenesis were studied in four species of bats, namely Rhinolophus clivosus, Rhinolophus capensis, Miniopterus natalensis and Myotis tricolor. Animals were collected from a group of three mines in Sleepy Hollow Farm, 30km from Port Elizabeth, South Africa. All species demonstrated bouts of torpor in the winter while R. clivosus interestingly established a high propensity for torpor in the summer and normothermia in the winter. To my knowledge, this is the first study that has shown the down-regulation of metabolism and body temperature in summer and constant maintenance of normothermic body temperature in winter in a species of Microchiroptera. M. natalensis was thermolabile in both summer and winter and body temperatures closely tracked ambient temperatures. Mean ± SD normothermic body temperature measured of wild-caught R. clivosus and M. natalensis was 38.6 ± 1.7°C and 37.3 ± 2.2°C, respectively. Mean torpid body temperature measured of wild-caught R. clivosus, R. capensis and M. natalensis was 22.7 ± 3.3°C, 21.1 ± 3.2 °C, and 22.6 ± 3.1°C, respectively. Non-shivering thermogenesis was measured in R. clivosus and M. natalensis to determine the role of endogenous heat production in a volant mammal. The mean noradrenalineinduced thermogenesis ± SD in R. clivosus and M. natalensis was 2.6 ± 0.8 ml g-1 hr-1 and 2.7 ± 0.6 ml O2 g-1 hr-1, respectively. Both species demonstrated capacity for non-shivering thermogenesis, and this is the first study that has quantified the maximal response to noradrenaline in an Afrotropical Microchiropteran species. Physiology of Afrotropical bats is understudied and the extent to which torpor and/or hibernation is utilized amongst them remains relatively unknown. Heterothermy clearly plays a significant role in the energetic savings and balance of all four species in the study.
- Full Text:
- Date Issued: 2012
- Authors: Doty, Anna Catherine
- Date: 2012
- Subjects: Body temperature -- Regulation , Afrotropical mammals , Body temperature , Bats
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10691 , http://hdl.handle.net/10948/d1008402 , Body temperature -- Regulation , Afrotropical mammals , Body temperature , Bats
- Description: Torpor and hibernation, two distinct forms of heterothermy, are physiological responses employed by many endotherms to save energy during periods of cold, climatic unpredictability and food shortage. Heterothermy is characterized by varying body temperature and has been found to occur in various subtropical mammals. However, studies on thermoregulatory capabilities of South African Microchiroptera remain relatively scant. In this study, the capacity for use of heterothermy, the seasonal metabolic rates, and capacity for non-shivering thermogenesis were studied in four species of bats, namely Rhinolophus clivosus, Rhinolophus capensis, Miniopterus natalensis and Myotis tricolor. Animals were collected from a group of three mines in Sleepy Hollow Farm, 30km from Port Elizabeth, South Africa. All species demonstrated bouts of torpor in the winter while R. clivosus interestingly established a high propensity for torpor in the summer and normothermia in the winter. To my knowledge, this is the first study that has shown the down-regulation of metabolism and body temperature in summer and constant maintenance of normothermic body temperature in winter in a species of Microchiroptera. M. natalensis was thermolabile in both summer and winter and body temperatures closely tracked ambient temperatures. Mean ± SD normothermic body temperature measured of wild-caught R. clivosus and M. natalensis was 38.6 ± 1.7°C and 37.3 ± 2.2°C, respectively. Mean torpid body temperature measured of wild-caught R. clivosus, R. capensis and M. natalensis was 22.7 ± 3.3°C, 21.1 ± 3.2 °C, and 22.6 ± 3.1°C, respectively. Non-shivering thermogenesis was measured in R. clivosus and M. natalensis to determine the role of endogenous heat production in a volant mammal. The mean noradrenalineinduced thermogenesis ± SD in R. clivosus and M. natalensis was 2.6 ± 0.8 ml g-1 hr-1 and 2.7 ± 0.6 ml O2 g-1 hr-1, respectively. Both species demonstrated capacity for non-shivering thermogenesis, and this is the first study that has quantified the maximal response to noradrenaline in an Afrotropical Microchiropteran species. Physiology of Afrotropical bats is understudied and the extent to which torpor and/or hibernation is utilized amongst them remains relatively unknown. Heterothermy clearly plays a significant role in the energetic savings and balance of all four species in the study.
- Full Text:
- Date Issued: 2012
On the thermal and electrical properties of low concentrator photovoltaic systems
- Authors: Gerber, Jacques Dewald
- Date: 2012
- Subjects: Photovoltaic power systems , Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10561 , http://hdl.handle.net/10948/d1021219
- Description: Low concentrator photovoltaic systems are capable of increasing the power produced by conventional silicon photovoltaic cells, thus effectively lowering the cost per kWh. However, power losses associated with resistance and temperature have limited the large scale implementation of this technology. In this study, the optical-,electrical- and thermal sub-systems of a low concentrator photovoltaic system are theoretically and experimentally evaluated with the aim of minimizing the power losses associated with series resistance and temperature. A 7-facet reflector system, with an effective concentration ratio of 4.7, is used to focus irradiance along a string of series connected poly-crystalline photovoltaic cells. I-V characteristics of 4-, 6- and 8-cell photovoltaic receivers are measured under 1-sun and 4.83-sun conditions. Under concentration, the 8-cell photovoltaic receiver produced 23 percent more power than the 4-cell photovoltaic receiver, which suggests that the effect of series resistance can be minimized if smaller, lower current photovoltaic cells are used. A thermal model, which may be used to predict operating temperatures of a low concentrator photovoltaic system, is experimentally evaluated within a thermally insulated enclosure. The temperatures predicted by the thermal model are generally within 5 percent of the experimental temperatures. The high operating temperatures associated with the low concentrator photovoltaic system are significantly reduced by the addition of aluminium heat sink. In addition, the results of a thermal stress test indicated that these high operating temperatures do not degrade the photovoltaic cells used in this study. The results of this study suggest that the power output of low concentrator photovoltaic systems can be maximized by decreasing the size of the photovoltaic cells and including an appropriate heat sink to aid convective cooling.
- Full Text:
- Date Issued: 2012
- Authors: Gerber, Jacques Dewald
- Date: 2012
- Subjects: Photovoltaic power systems , Photovoltaic cells
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10561 , http://hdl.handle.net/10948/d1021219
- Description: Low concentrator photovoltaic systems are capable of increasing the power produced by conventional silicon photovoltaic cells, thus effectively lowering the cost per kWh. However, power losses associated with resistance and temperature have limited the large scale implementation of this technology. In this study, the optical-,electrical- and thermal sub-systems of a low concentrator photovoltaic system are theoretically and experimentally evaluated with the aim of minimizing the power losses associated with series resistance and temperature. A 7-facet reflector system, with an effective concentration ratio of 4.7, is used to focus irradiance along a string of series connected poly-crystalline photovoltaic cells. I-V characteristics of 4-, 6- and 8-cell photovoltaic receivers are measured under 1-sun and 4.83-sun conditions. Under concentration, the 8-cell photovoltaic receiver produced 23 percent more power than the 4-cell photovoltaic receiver, which suggests that the effect of series resistance can be minimized if smaller, lower current photovoltaic cells are used. A thermal model, which may be used to predict operating temperatures of a low concentrator photovoltaic system, is experimentally evaluated within a thermally insulated enclosure. The temperatures predicted by the thermal model are generally within 5 percent of the experimental temperatures. The high operating temperatures associated with the low concentrator photovoltaic system are significantly reduced by the addition of aluminium heat sink. In addition, the results of a thermal stress test indicated that these high operating temperatures do not degrade the photovoltaic cells used in this study. The results of this study suggest that the power output of low concentrator photovoltaic systems can be maximized by decreasing the size of the photovoltaic cells and including an appropriate heat sink to aid convective cooling.
- Full Text:
- Date Issued: 2012
Recolonisation of the Robberg Peninsula by the Cape Fur Seal Arctocephalus pusillus pusillus and its prey preferences
- Authors: Huisamen, Johan
- Date: 2012
- Subjects: South African fur seal -- South Africa -- Plettenberg Bay , South African fur seal -- Food -- South Africa -- Plettenberg Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10745 , http://hdl.handle.net/10948/d1006438 , South African fur seal -- South Africa -- Plettenberg Bay , South African fur seal -- Food -- South Africa -- Plettenberg Bay
- Description: The Cape fur seal Arctocephalus pusillus pusillus colony at the Robberg Peninsula, Plettenberg Bay, on the south-east coast of South Africa, was driven to extirpation by indiscriminate harvesting by the late 1800s and seals only began to recolonise this site in the 1990s. This study describes the recolonisation process from 2000 to 2009, exploring within- and between-year variation in the number of seals using the site. Numbers increased over the study period from less than 300 animals to over 3 100. Year and month were important in explaining variability in seal counts, whereas sea condition, time of day and lunar phase had minimal explanatory power. Within-year variation in seal counts decreased during the study period, which may indicate an increasing proportion of resident (as opposed to transient) seals in the colony. However, the colony is currently still in a transition phase with a low ratio of breeding to non-breeding animals and low numbers of pups born on the colony (currently still < 100 per year). The influx of seals to the Robberg area may be associated with an increase in prey availability in the area. The relative protection afforded by the Nature Reserve status of the Robberg Peninsula and the existence of a Marine Protected Area adjacent to it are likely to contribute to the growth of this colony. However, human interference associated with fishing and/or ecotourism on the Peninsula may prevent the colony from developing into a breeding colony. Faecal (scat) sampling was employed to study the diet of this increasing seal population at Robberg. Species composition and size of prey were determined, temporal variation in the diet was explored, and the potential for competition between seals and the fisheries around Plettenberg Bay was investigated. Of the 445 scats collected, 90 % contained hard prey remains. These comprised of 3 127 identified otoliths representing 15 teleost prey species, 25 cephalopod beaks representing three 6 species and three feathers representing two bird species. The seals' most important prey species in terms of numerical abundance and frequency of occurrence in the diet were anchovy, sardine, horse mackerel, sand tongue-fish and shallow-water hake (in decreasing order of importance). The proportion of anchovy in the diet increased during the study period, while sardine decreased. Sardine was the only species that increased significantly in the diet during the upwelling season. Little evidence was found of direct competition between seals and linefisheries in Plettenberg Bay, both in terms of prey species composition and quantities consumed. Scat sampling in seals holds promise as a method to track long-term changes in prey species availability. The conservation and management of this colony are discussed in light of the research findings.
- Full Text:
- Date Issued: 2012
- Authors: Huisamen, Johan
- Date: 2012
- Subjects: South African fur seal -- South Africa -- Plettenberg Bay , South African fur seal -- Food -- South Africa -- Plettenberg Bay
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10745 , http://hdl.handle.net/10948/d1006438 , South African fur seal -- South Africa -- Plettenberg Bay , South African fur seal -- Food -- South Africa -- Plettenberg Bay
- Description: The Cape fur seal Arctocephalus pusillus pusillus colony at the Robberg Peninsula, Plettenberg Bay, on the south-east coast of South Africa, was driven to extirpation by indiscriminate harvesting by the late 1800s and seals only began to recolonise this site in the 1990s. This study describes the recolonisation process from 2000 to 2009, exploring within- and between-year variation in the number of seals using the site. Numbers increased over the study period from less than 300 animals to over 3 100. Year and month were important in explaining variability in seal counts, whereas sea condition, time of day and lunar phase had minimal explanatory power. Within-year variation in seal counts decreased during the study period, which may indicate an increasing proportion of resident (as opposed to transient) seals in the colony. However, the colony is currently still in a transition phase with a low ratio of breeding to non-breeding animals and low numbers of pups born on the colony (currently still < 100 per year). The influx of seals to the Robberg area may be associated with an increase in prey availability in the area. The relative protection afforded by the Nature Reserve status of the Robberg Peninsula and the existence of a Marine Protected Area adjacent to it are likely to contribute to the growth of this colony. However, human interference associated with fishing and/or ecotourism on the Peninsula may prevent the colony from developing into a breeding colony. Faecal (scat) sampling was employed to study the diet of this increasing seal population at Robberg. Species composition and size of prey were determined, temporal variation in the diet was explored, and the potential for competition between seals and the fisheries around Plettenberg Bay was investigated. Of the 445 scats collected, 90 % contained hard prey remains. These comprised of 3 127 identified otoliths representing 15 teleost prey species, 25 cephalopod beaks representing three 6 species and three feathers representing two bird species. The seals' most important prey species in terms of numerical abundance and frequency of occurrence in the diet were anchovy, sardine, horse mackerel, sand tongue-fish and shallow-water hake (in decreasing order of importance). The proportion of anchovy in the diet increased during the study period, while sardine decreased. Sardine was the only species that increased significantly in the diet during the upwelling season. Little evidence was found of direct competition between seals and linefisheries in Plettenberg Bay, both in terms of prey species composition and quantities consumed. Scat sampling in seals holds promise as a method to track long-term changes in prey species availability. The conservation and management of this colony are discussed in light of the research findings.
- Full Text:
- Date Issued: 2012
AC3P: an architecture using cloud computing for the provision of mathematical powerpoint content to feature phones
- Authors: Joubert, Jean-Pierre
- Date: 2012
- Subjects: Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10474 , http://hdl.handle.net/10948/d1011088 , Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Description: The Govan Mbeki Mathematics Development Unit (GMMDU) provides additional mathematics content to learners via mathematics workshops and DVDs. Mathematics is presented in PPT format. The prominence of feature phone usage has been confirmed amongst learners in socio-economic disadvantaged schools, specifically those learners participating in the GMMDU mathematics workshops. Feature phones typically contain limited device resources such as memory, battery power, and network resources. Distributed computing provides the potential to facilitate a new class of mobile applications with the provision of off-device resources. The objective of this research was the design of an architecture using Cloud Computing for the provision of mathematics in the form of PPT slides to feature phones. The capabilities of typical feature phones were reviewed as well as various distributed computing architectures that demonstrate potential benefit to the mobile environment. An Architecture using Cloud Computing for Content Provision (AC3P) was subsequently designed and applied as a proof of concept to facilitate the provision of mathematics in the form of PPT slides to feature phones. The application of AC3P was evaluated for efficiency and effectiveness. It was demonstrated that the application of AC3P provided efficient and effective provision of PPT to feature phones. The successful application of AC3P provided evidence that Cloud Computing may be used to facilitate the provision of mathematics content to feature phones. It is evident that AC3P may be applied in domains other than the provision of mathematics.
- Full Text:
- Date Issued: 2012
- Authors: Joubert, Jean-Pierre
- Date: 2012
- Subjects: Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10474 , http://hdl.handle.net/10948/d1011088 , Cloud computing , Mobile computing , Mathematics -- Study and teaching.
- Description: The Govan Mbeki Mathematics Development Unit (GMMDU) provides additional mathematics content to learners via mathematics workshops and DVDs. Mathematics is presented in PPT format. The prominence of feature phone usage has been confirmed amongst learners in socio-economic disadvantaged schools, specifically those learners participating in the GMMDU mathematics workshops. Feature phones typically contain limited device resources such as memory, battery power, and network resources. Distributed computing provides the potential to facilitate a new class of mobile applications with the provision of off-device resources. The objective of this research was the design of an architecture using Cloud Computing for the provision of mathematics in the form of PPT slides to feature phones. The capabilities of typical feature phones were reviewed as well as various distributed computing architectures that demonstrate potential benefit to the mobile environment. An Architecture using Cloud Computing for Content Provision (AC3P) was subsequently designed and applied as a proof of concept to facilitate the provision of mathematics in the form of PPT slides to feature phones. The application of AC3P was evaluated for efficiency and effectiveness. It was demonstrated that the application of AC3P provided efficient and effective provision of PPT to feature phones. The successful application of AC3P provided evidence that Cloud Computing may be used to facilitate the provision of mathematics content to feature phones. It is evident that AC3P may be applied in domains other than the provision of mathematics.
- Full Text:
- Date Issued: 2012
Towards a methodology for identifying potential sites for cemeteries
- Authors: Judge, Richard David Eadie
- Date: 2012
- Subjects: Cemeteries , Environmental impact analysis , Groundwater , Pollution
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10649 , http://hdl.handle.net/10948/d1008048 , Cemeteries , Environmental impact analysis , Groundwater , Pollution
- Description: Due to death being an extremely sensitive issue, the topic of cemeteries and associated environmental impacts is often left outside the mainstream environmental critique. However, this is a topic becoming more prevalent as the population numbers and the death rate increases, while the amount of available land decreases. Recent research has indicated that poorly sited cemeteries may pose a significant threat to groundwater resources with the consequential potential for severe health hazards. This has resulted in the need for a method of determining the acceptability of a given area for the establishment of a cemetery in a South African context. Cemeteries should be sited in such a way as to mitigate potential public health and safety concerns, minimise associated environmental impacts and provide a method of body disposal that is economically viable. This study therefore provides an integrated methodology to identify and assess a given area and rank a number of potential sites, ultimately determining a single cemetery site which proves to be acceptable for the establishment of a cemetery. Cemetery site selection should be based on the factors affecting the pollution potential of a proposed cemetery. These factors were identified and quantified based on research into the mechanisms of cemetery site pollution resulting in a number of fatal flaws and criteria deemed decisive when selecting a potential cemetery site. The assessment of a site with regards to these criteria and fatal flaws is undertaken through the use of GIS analysis software utilising data layers containing information on the site selection criteria, by investigating existing studies, literature or reports relating to the relevant area, or through field investigations. Although these criteria are vital when determining the specific characteristics of a site in terms of its pollution potential, a method of assessing a number of potential sites with regards to these criteria is vital. To this end, a multi-criteria ranking matrix has been developed, allowing for an objective method of assessing individual sites and thus indicating which sites are more suited for the establishment of a cemetery. The ranking matrix identifies a range of values for each criterion, therefore identifying a minimum and maximum allowable value. A site is then assessed with regards to these criteria in relation to the values identified in the ranking matrix. Each criteria is assigned a score according to the site conditions. Once the criteria for each site has been assessed and scored, the results can be tallied allowing the sites to be ranked according to which site proved to be the most acceptable for a cemetery based on the findings of the application of the site selection criteria. The methodology developed in this study is unique to previous studies in that it provides an integrated and staged approach to identifying, assessing and applying the criteria affecting the pollution potential of a cemetery. The methodology also provides a means of ranking a number of potential sites so to determine the most suitable. Furthermore, the criteria deemed as decisive in previous investigations were in most cases not quantified by the relevant authors, therefore leaving many of the criteria values up for interpretation. For this methodology to be affective, all criteria must be quantified therefore identifying maximum and minimum allowable limits for each. This study applies minimum and maximum allowable limits to these criteria, therefore aiding in the ranking process. The integrated methodology developed was then applied to a case study where by the effectiveness in identifying a number of potential cemetery sites could be tested. Subsequent to the application of this methodology to a case study, it was concluded that an additional two criteria, not identified in previous investigations, needed to be assessed to more adequately determine the suitability or otherwise of a site for a cemetery. Ultimately, twelve major criteria have been proposed for use as the basis of the methodology. The methodology and pertinent criteria proposed in this study should be compiled as a standard for planning authorities and consultants to use as a method of determining a number of potential environmentally sound cemetery sites.
- Full Text:
- Date Issued: 2012
- Authors: Judge, Richard David Eadie
- Date: 2012
- Subjects: Cemeteries , Environmental impact analysis , Groundwater , Pollution
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10649 , http://hdl.handle.net/10948/d1008048 , Cemeteries , Environmental impact analysis , Groundwater , Pollution
- Description: Due to death being an extremely sensitive issue, the topic of cemeteries and associated environmental impacts is often left outside the mainstream environmental critique. However, this is a topic becoming more prevalent as the population numbers and the death rate increases, while the amount of available land decreases. Recent research has indicated that poorly sited cemeteries may pose a significant threat to groundwater resources with the consequential potential for severe health hazards. This has resulted in the need for a method of determining the acceptability of a given area for the establishment of a cemetery in a South African context. Cemeteries should be sited in such a way as to mitigate potential public health and safety concerns, minimise associated environmental impacts and provide a method of body disposal that is economically viable. This study therefore provides an integrated methodology to identify and assess a given area and rank a number of potential sites, ultimately determining a single cemetery site which proves to be acceptable for the establishment of a cemetery. Cemetery site selection should be based on the factors affecting the pollution potential of a proposed cemetery. These factors were identified and quantified based on research into the mechanisms of cemetery site pollution resulting in a number of fatal flaws and criteria deemed decisive when selecting a potential cemetery site. The assessment of a site with regards to these criteria and fatal flaws is undertaken through the use of GIS analysis software utilising data layers containing information on the site selection criteria, by investigating existing studies, literature or reports relating to the relevant area, or through field investigations. Although these criteria are vital when determining the specific characteristics of a site in terms of its pollution potential, a method of assessing a number of potential sites with regards to these criteria is vital. To this end, a multi-criteria ranking matrix has been developed, allowing for an objective method of assessing individual sites and thus indicating which sites are more suited for the establishment of a cemetery. The ranking matrix identifies a range of values for each criterion, therefore identifying a minimum and maximum allowable value. A site is then assessed with regards to these criteria in relation to the values identified in the ranking matrix. Each criteria is assigned a score according to the site conditions. Once the criteria for each site has been assessed and scored, the results can be tallied allowing the sites to be ranked according to which site proved to be the most acceptable for a cemetery based on the findings of the application of the site selection criteria. The methodology developed in this study is unique to previous studies in that it provides an integrated and staged approach to identifying, assessing and applying the criteria affecting the pollution potential of a cemetery. The methodology also provides a means of ranking a number of potential sites so to determine the most suitable. Furthermore, the criteria deemed as decisive in previous investigations were in most cases not quantified by the relevant authors, therefore leaving many of the criteria values up for interpretation. For this methodology to be affective, all criteria must be quantified therefore identifying maximum and minimum allowable limits for each. This study applies minimum and maximum allowable limits to these criteria, therefore aiding in the ranking process. The integrated methodology developed was then applied to a case study where by the effectiveness in identifying a number of potential cemetery sites could be tested. Subsequent to the application of this methodology to a case study, it was concluded that an additional two criteria, not identified in previous investigations, needed to be assessed to more adequately determine the suitability or otherwise of a site for a cemetery. Ultimately, twelve major criteria have been proposed for use as the basis of the methodology. The methodology and pertinent criteria proposed in this study should be compiled as a standard for planning authorities and consultants to use as a method of determining a number of potential environmentally sound cemetery sites.
- Full Text:
- Date Issued: 2012
Feeding ecology and dietary patterns of the Indo-Pacific bottlenose dolphin (Tursiops Aduncus) off KwaZulu-Natal, South Africa
- Authors: Kaiser, Sabina Marie Luise
- Date: 2012
- Subjects: Bottlenose dolphin -- Ecology -- South Africa -- KwaZulu-Natal , Bottlenose dolphin -- Feeding and feeds -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10710 , http://hdl.handle.net/10948/d1011509 , Bottlenose dolphin -- Ecology -- South Africa -- KwaZulu-Natal , Bottlenose dolphin -- Feeding and feeds -- South Africa -- KwaZulu-Natal
- Description: The Indo-Pacific bottlenose dolphin (Tursiops aduncus) is a common top predator along the KwaZulu-Natal coast. There have been several dietary studies done on this species, most of which have classed this predator as an opportunistic feeder preying on the most abundant prey species in that area. In KwaZulu-Natal (KZN) a dietary study was carried out in 1990, but there have been no followup studies to examine potential changes in diet. A number of bottlenose dolphins get entangled in the shark-nets set off the KZN coast each year. These dolphins provide a valuable source of information about different aspects of the ecology of this population. The aim of this study was to examine the diet of bottlenose dolphins off the KwaZulu-Natal coast with particular emphasis on temporal change in diet composition. The contents of 102 stomachs of bottlenose dolphins (58 females, 44 males) accidentally caught in the shark nets between 1985 and 2010 were analysed, and compared to historical data from dolphins caught between 1975 and 1986. A total of 94 different prey species from 37 families (32 fish families, five cephalopod families) were identified in the stomach contents. Teleosts made up the most important prey group in numbers and weight constituting 84 percent and 67 percent, respectively, while cephalopods made up 15 percent of the number and 30 percent of the weight of the prey items. Multi Dimensional Scaling (MDS) indicated that there is no resource partitioning between males and females, but significant partitioning between juveniles and adults. Six prey species contributed more than 60 percent of the weight of all prey species in the diet. These species are the most important according to their calculated index of relative importance score and are, in order of importance: Sepia sp. (cuttlefish)., Pomadasys olivaceus (piggy), Trachurus delagoa (maasbanker), Scomber japonicus (mackeral), Loligo sp. (squid). and Pagellus bellottii natalensis (pandora or red tjor-tjor). When compared to historic data, no changes in the main prey species has occurred, but the piggy has decreased in importance (1976-1986 percent IRI=45; 2000-2010 percent IRI=22), while the maasbanker has increased (1975-1986, percent RI=4; 2000-2010 percent RI=20). Stable carbon and nitrogen isotope analysis performed on tissue from the teeth of T. aduncus caught in the shark nets between 1970 and 2010 showed that there has been no significant shift in trophic level (δ15N) or in primary prey source (δ13C) over this time. The isotopic signatures of different tissues from an individual were used to create a base line and describe the differences in tissue signatures. Blubber was found to be significantly different from skin and muscle, which were found to be isotopically similar. Skin from remote biopsies can therefore probably be used in place of muscle for isotopic studies of bottlenose dolphins, while caution should be taken when using blubber. Given that T. aduncus is still listed as “data deficient” by the International Union for the Conservation of Nature (IUCN), and the potential for climate change and expanding fisheries to alter the distribution and abundance of their prey species, long term dietary studies such as this are important in order for their effective conservation and management.
- Full Text:
- Date Issued: 2012
- Authors: Kaiser, Sabina Marie Luise
- Date: 2012
- Subjects: Bottlenose dolphin -- Ecology -- South Africa -- KwaZulu-Natal , Bottlenose dolphin -- Feeding and feeds -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10710 , http://hdl.handle.net/10948/d1011509 , Bottlenose dolphin -- Ecology -- South Africa -- KwaZulu-Natal , Bottlenose dolphin -- Feeding and feeds -- South Africa -- KwaZulu-Natal
- Description: The Indo-Pacific bottlenose dolphin (Tursiops aduncus) is a common top predator along the KwaZulu-Natal coast. There have been several dietary studies done on this species, most of which have classed this predator as an opportunistic feeder preying on the most abundant prey species in that area. In KwaZulu-Natal (KZN) a dietary study was carried out in 1990, but there have been no followup studies to examine potential changes in diet. A number of bottlenose dolphins get entangled in the shark-nets set off the KZN coast each year. These dolphins provide a valuable source of information about different aspects of the ecology of this population. The aim of this study was to examine the diet of bottlenose dolphins off the KwaZulu-Natal coast with particular emphasis on temporal change in diet composition. The contents of 102 stomachs of bottlenose dolphins (58 females, 44 males) accidentally caught in the shark nets between 1985 and 2010 were analysed, and compared to historical data from dolphins caught between 1975 and 1986. A total of 94 different prey species from 37 families (32 fish families, five cephalopod families) were identified in the stomach contents. Teleosts made up the most important prey group in numbers and weight constituting 84 percent and 67 percent, respectively, while cephalopods made up 15 percent of the number and 30 percent of the weight of the prey items. Multi Dimensional Scaling (MDS) indicated that there is no resource partitioning between males and females, but significant partitioning between juveniles and adults. Six prey species contributed more than 60 percent of the weight of all prey species in the diet. These species are the most important according to their calculated index of relative importance score and are, in order of importance: Sepia sp. (cuttlefish)., Pomadasys olivaceus (piggy), Trachurus delagoa (maasbanker), Scomber japonicus (mackeral), Loligo sp. (squid). and Pagellus bellottii natalensis (pandora or red tjor-tjor). When compared to historic data, no changes in the main prey species has occurred, but the piggy has decreased in importance (1976-1986 percent IRI=45; 2000-2010 percent IRI=22), while the maasbanker has increased (1975-1986, percent RI=4; 2000-2010 percent RI=20). Stable carbon and nitrogen isotope analysis performed on tissue from the teeth of T. aduncus caught in the shark nets between 1970 and 2010 showed that there has been no significant shift in trophic level (δ15N) or in primary prey source (δ13C) over this time. The isotopic signatures of different tissues from an individual were used to create a base line and describe the differences in tissue signatures. Blubber was found to be significantly different from skin and muscle, which were found to be isotopically similar. Skin from remote biopsies can therefore probably be used in place of muscle for isotopic studies of bottlenose dolphins, while caution should be taken when using blubber. Given that T. aduncus is still listed as “data deficient” by the International Union for the Conservation of Nature (IUCN), and the potential for climate change and expanding fisheries to alter the distribution and abundance of their prey species, long term dietary studies such as this are important in order for their effective conservation and management.
- Full Text:
- Date Issued: 2012