A case study on the incidence and extent of medullated and coloured fibres in the commercially produced South African wool clip 2010 – 2017
- Authors: Zietsman, Jolandrie
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55445 , vital:52002
- Description: No formal study on the incidence and extent of medullated and coloured fibres has been performed in South Africa. The purpose of this research project was to investigate the validity of the claims that there has been an increase in the production of wool contaminated with medullated and coloured fibres. Therefore, the main aim of this study was to determine whether the incidence and extent of medullated and coloured fibres in the South African wool clip have changed over time. Secondly, the study aimed to determine whether the incidence and extent of medullated and coloured fibres have a distinct geographic distribution. This study explored eight years of wool production records (2010 to 2017) obtained from BKB, the largest wool broker in South Africa. For the purpose of this research, the wool-producing areas of South Africa were divided into 6 regions, according to average annual rainfall, vegetation type and major farming practices applied in the area. Statistical analysis of the data included descriptive statistics, analysis of variance and post-hoc tests, as well as regression analyses. This study succeeded in quantifying the extent and prevalence of contamination with medullated and coloured fibres in the South African wool clip. The overarching conclusions were: • Floating kemp is the most important contaminant of wool in South Africa, with the incidence of harsh kemp and coloured fibres being very low. • Generally, the most important areas that need attention in combatting contamination in the South African wool clip, are the Mixed Farming Summer Rainfall Region, the Semi-Arid Grassveld and the High Rainfall Grassland. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Zietsman, Jolandrie
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55445 , vital:52002
- Description: No formal study on the incidence and extent of medullated and coloured fibres has been performed in South Africa. The purpose of this research project was to investigate the validity of the claims that there has been an increase in the production of wool contaminated with medullated and coloured fibres. Therefore, the main aim of this study was to determine whether the incidence and extent of medullated and coloured fibres in the South African wool clip have changed over time. Secondly, the study aimed to determine whether the incidence and extent of medullated and coloured fibres have a distinct geographic distribution. This study explored eight years of wool production records (2010 to 2017) obtained from BKB, the largest wool broker in South Africa. For the purpose of this research, the wool-producing areas of South Africa were divided into 6 regions, according to average annual rainfall, vegetation type and major farming practices applied in the area. Statistical analysis of the data included descriptive statistics, analysis of variance and post-hoc tests, as well as regression analyses. This study succeeded in quantifying the extent and prevalence of contamination with medullated and coloured fibres in the South African wool clip. The overarching conclusions were: • Floating kemp is the most important contaminant of wool in South Africa, with the incidence of harsh kemp and coloured fibres being very low. • Generally, the most important areas that need attention in combatting contamination in the South African wool clip, are the Mixed Farming Summer Rainfall Region, the Semi-Arid Grassveld and the High Rainfall Grassland. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Plastic particle characterization and concentrations found in the river and marine water environment of Algoa Bay, South Africa
- Authors: Moss, Kerry-Leigh
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53874 , vital:46025
- Description: Only 12% of the world's published plastic research includes references to Africa despite it being a significant contributor to the global plastic waste and mismanagement problem (~88.5% of Africa's plastic waste is mismanaged). Ocean plastics are transported from land by rivers to the sea. However, source contextualization is complex. Many African rivers predominantly run alongside human settlements that host informal waste dumpsites. In this study a simple cost effective, easily deployed, consistent and replicable survey methodology was employed. The study quantified macro plastic in three rivers discharging into Algoa Bay, South Africa. The results indicated that industrial Swartkops and metropolitan Baakens Rivers both illustrate moderate plastic pollution (>3000 plastic particles/day), with the relatively natural Sundays River to showing minimal evidence of river macroplastic (<100 plastic particles/day). The types of plastic were noted using the RIMMEL app (premier African implementation), enabling proportional comparison of different plastic litter types to be completed. , Thesis (MSc) -- Faculty of Science, Oceanography Department,2021
- Full Text:
- Date Issued: 2021-12
- Authors: Moss, Kerry-Leigh
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53874 , vital:46025
- Description: Only 12% of the world's published plastic research includes references to Africa despite it being a significant contributor to the global plastic waste and mismanagement problem (~88.5% of Africa's plastic waste is mismanaged). Ocean plastics are transported from land by rivers to the sea. However, source contextualization is complex. Many African rivers predominantly run alongside human settlements that host informal waste dumpsites. In this study a simple cost effective, easily deployed, consistent and replicable survey methodology was employed. The study quantified macro plastic in three rivers discharging into Algoa Bay, South Africa. The results indicated that industrial Swartkops and metropolitan Baakens Rivers both illustrate moderate plastic pollution (>3000 plastic particles/day), with the relatively natural Sundays River to showing minimal evidence of river macroplastic (<100 plastic particles/day). The types of plastic were noted using the RIMMEL app (premier African implementation), enabling proportional comparison of different plastic litter types to be completed. , Thesis (MSc) -- Faculty of Science, Oceanography Department,2021
- Full Text:
- Date Issued: 2021-12
Spatial and temporal analysis of the critical zone in the Western rift valley corridor: towards earth stewardship science in East Africa
- Authors: Miller, Warren David
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/59771 , vital:62423
- Description: Over the coming decades, Africa is expected to experience disturbing effects due to climate change and increased land cover change due to human influences presenting a significant concern for the future well-being of human and biological systems, the latter being the foundation of ecosystem services supplied to humanity. Therefore, unprecedented transdisciplinary cooperation, coordination, and integration amongst researchers, government, and civil society are necessary to increase the resiliency of these systems. This study aims to provide an outline of the Africa Alive Corridors (AAC) as an essential model for the encouragement of sustainable development through Earth Stewardship science. These aims are accompanied by the quantification and forward modelling for land cover change of the Critical Zone over 10 Great Lake Basins across one of the AAC, the Western Rift Valley Corridor (WRVC), in East Africa between the years 2018 and 2060. This approach provides the foundation for implementing improved regional governance, better encouragement of sustainable development beyond the 2030 United Nations Sustainable Development Goals, and education programs, such as the AAC, that promote socio-ecological resilience through Earth Stewardship Science. The AAC archives a portion of East Africa as the WRVC, a corridor along the western branch of the East African Rift System that highlights twenty heritage nodes, primarily great lakes, mountain ranges, national parks, and biological hotspots. These heritage entities are associated with ca. 12-million-years of evolution and transformation of the East African topography and related African Great Lake (AGL) systems. The thesis defines the study area by delineating AGL basins intersected by the WRVC. Across these basins, land cover change analysis provides a platform for an integrated assessment of the projected health of the corridor region. Existing land cover datasets provide the initial conditions of the study area for 2008 and 2013. Land cover between 2008 and 2013 is cross-tabulated using the Land Cover Module in the Terrset software, followed by the iii delineation of sub-models and driver variable identification. The Multi-Layer Perceptron algorithm provides the transition potentials between tree cover, urban area, cropland, wetland, and open area classes. Change quantification and prediction using Markov Chain analysis are then established for 2018, 2030, and 2060. The model successfully simulated future land cover change and concluded that: (1) proximity to existing human activity, proximity to existing tree cover, and population are the primary drivers of change; (2) the dominant land cover of the ten lake basins for 2018 was cropland at ca. 48%, followed by tree cover at ca. 33%; (3) total anthropogenic change over the coming four decades equates to over ca. 52 000 km2 (5 200 000 ha), and particularly (4) an urban area is expected to increase by >130%. This assessment ultimately provides a platform for regional governance development at the basin scale and Earth Stewardship science in East Africa. These changes require transdisciplinary action from researchers to civil society. The AAC provides the foundation for understanding the dynamics of the systems that support life across broader spatial and temporal resolutions in Africa, highlighting the need for future generations to build socio-ecological resilience to anticipate challenges such as biodiversity loss posed by climate change and excessive land cover change. , Thesis (DSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Miller, Warren David
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/59771 , vital:62423
- Description: Over the coming decades, Africa is expected to experience disturbing effects due to climate change and increased land cover change due to human influences presenting a significant concern for the future well-being of human and biological systems, the latter being the foundation of ecosystem services supplied to humanity. Therefore, unprecedented transdisciplinary cooperation, coordination, and integration amongst researchers, government, and civil society are necessary to increase the resiliency of these systems. This study aims to provide an outline of the Africa Alive Corridors (AAC) as an essential model for the encouragement of sustainable development through Earth Stewardship science. These aims are accompanied by the quantification and forward modelling for land cover change of the Critical Zone over 10 Great Lake Basins across one of the AAC, the Western Rift Valley Corridor (WRVC), in East Africa between the years 2018 and 2060. This approach provides the foundation for implementing improved regional governance, better encouragement of sustainable development beyond the 2030 United Nations Sustainable Development Goals, and education programs, such as the AAC, that promote socio-ecological resilience through Earth Stewardship Science. The AAC archives a portion of East Africa as the WRVC, a corridor along the western branch of the East African Rift System that highlights twenty heritage nodes, primarily great lakes, mountain ranges, national parks, and biological hotspots. These heritage entities are associated with ca. 12-million-years of evolution and transformation of the East African topography and related African Great Lake (AGL) systems. The thesis defines the study area by delineating AGL basins intersected by the WRVC. Across these basins, land cover change analysis provides a platform for an integrated assessment of the projected health of the corridor region. Existing land cover datasets provide the initial conditions of the study area for 2008 and 2013. Land cover between 2008 and 2013 is cross-tabulated using the Land Cover Module in the Terrset software, followed by the iii delineation of sub-models and driver variable identification. The Multi-Layer Perceptron algorithm provides the transition potentials between tree cover, urban area, cropland, wetland, and open area classes. Change quantification and prediction using Markov Chain analysis are then established for 2018, 2030, and 2060. The model successfully simulated future land cover change and concluded that: (1) proximity to existing human activity, proximity to existing tree cover, and population are the primary drivers of change; (2) the dominant land cover of the ten lake basins for 2018 was cropland at ca. 48%, followed by tree cover at ca. 33%; (3) total anthropogenic change over the coming four decades equates to over ca. 52 000 km2 (5 200 000 ha), and particularly (4) an urban area is expected to increase by >130%. This assessment ultimately provides a platform for regional governance development at the basin scale and Earth Stewardship science in East Africa. These changes require transdisciplinary action from researchers to civil society. The AAC provides the foundation for understanding the dynamics of the systems that support life across broader spatial and temporal resolutions in Africa, highlighting the need for future generations to build socio-ecological resilience to anticipate challenges such as biodiversity loss posed by climate change and excessive land cover change. , Thesis (DSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Spatial modelling of accessibility to tuberculosis treatment: the case of Ngaka Modiri Molema District
- Authors: Ramotsongwa, Karabo Naome
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55435 , vital:52000
- Description: Accessibility to healthcare refers to the availability, or the provision of healthcare-byhealthcare professionals and stakeholders and individuals' ability to obtain care and treatment. It affects overall physical, social, and mental health; disease and disability prevention; detection and treatment of health conditions; standard of living; preventable death; and life expectancy, and it is crucial to the performance of health care systems around the world. If healthcare services are available and are in sufficient supply, people will be able to seek health care, and a population will have access to services. The leading cause of death globally is Tuberculosis (TB) and South Africa is amongst the top 5 countries most affected by TB. This is aggravated by high HIV/AIDS statistics. Children belowthe age of 4, between the ages of 4- 15, and women and men of working ages are highly affected by TB and it is the primary cause of death in these groups in the Ngaka Modiri Molema District. This study used study tools like Spatial Modelling, Geographic Information Systems and software like ArcGIS 10.5, TerrSet IDRISI 18.30, and secondary data from the North West Departmentof Health (Tier.net &DHIS) and also TB patients’ home addresses to investigate the accessibility of TB treatment in Ngaka Modiri Molema, in order to spatially visualize the distribution of a communicable disease like TB and public healthcare facilities in the Ngaka Modiri Molema (NMM) District and suggest optimum sites for hospital facilities. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Ramotsongwa, Karabo Naome
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55435 , vital:52000
- Description: Accessibility to healthcare refers to the availability, or the provision of healthcare-byhealthcare professionals and stakeholders and individuals' ability to obtain care and treatment. It affects overall physical, social, and mental health; disease and disability prevention; detection and treatment of health conditions; standard of living; preventable death; and life expectancy, and it is crucial to the performance of health care systems around the world. If healthcare services are available and are in sufficient supply, people will be able to seek health care, and a population will have access to services. The leading cause of death globally is Tuberculosis (TB) and South Africa is amongst the top 5 countries most affected by TB. This is aggravated by high HIV/AIDS statistics. Children belowthe age of 4, between the ages of 4- 15, and women and men of working ages are highly affected by TB and it is the primary cause of death in these groups in the Ngaka Modiri Molema District. This study used study tools like Spatial Modelling, Geographic Information Systems and software like ArcGIS 10.5, TerrSet IDRISI 18.30, and secondary data from the North West Departmentof Health (Tier.net &DHIS) and also TB patients’ home addresses to investigate the accessibility of TB treatment in Ngaka Modiri Molema, in order to spatially visualize the distribution of a communicable disease like TB and public healthcare facilities in the Ngaka Modiri Molema (NMM) District and suggest optimum sites for hospital facilities. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Encapsulation of flame retardants for lithium-ion battery safety
- Authors: Ntombela, Nompilo Princess
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55412 , vital:51993
- Description: Lithium-ion technology takes the lead in electric mobility systems, resulting in an increase in the global demand for Li-ion batteries; however, these batteries are associated with numerous safety concerns. Additionally, there are high costs, high energy and power issues which are some of its key limitations. Research efforts are focused on overcoming these obstacles, with different approaches being explored, such as the investigation of more stable salts, modification of active materials and organic solvents, and the use of electrolyte additives. This study focused specifically on electrolyte additives since the electrolyte is one of the most unstable components of the battery. The electrolyte’s decomposition is one of the reactions that occur inside a battery, which may occur due to overcharging or due to an internal short circuit, amongst others. The electrolyte’s decomposition occurs at the early stages of the thermal runaway process and forms part of the reactions that lead to fires and explosions. Thus, this research aims to develop suitable electrolyte additives to improve the safety aspects of Li-ion batteries. Flame retardant additives show great promise in reducing the flammability of the electrolyte in Li-ion batteries, since they serve to suppress the chemical reactions associated with battery ignition. They retard the fires by scavenging the active radical species formed during the decomposition reaction. In this study, the use of flame retardants was investigated. Flame retardant additives have shown to have flame impeding properties inside a battery; however, their direct addition to the electrolyte tends to cause adverse effects on the ionic conductivity and electrochemical performance of the cells. This study investigated an alternative option - the option to microencapsulate such additives into a neutral compound to ensure that the flame retardant has minimal/no effect on the performance of the battery. This investigation looked at tris(2-butoxyethyl) phosphate (TBP) and bis(2,2,2-trifluoroethyl) methylphosphonate (BFP) as flame retardant additives for the electrolyte. The TBP and BFP flame retardants were microencapsulated in poly(urea formaldehyde) (PUF) coating material via in situ polymerization method. The capsules were characterized using various analytical techniques - to prove it was successfully encapsulated. Electrochemical studies were further done on the capsules and neat flame retardants inside a coin cell. Self-extinguishing time (SET), which is the flammability test, proved that the additives have flame retarding abilities. Opto-digital microscopy (DSX) and scanning electron microscopy (SEM) did confirm the spherical shape of the microcapsules, where SEM also showed the smooth outer layer of the microcapsules and its hollow inner side. Fourier transform infrared spectroscopy (FTIR) proved the presence of the TBP and BFP inside the PUF resin by showing that the chemical composition of microcapsules consisted of both the PUF and flame retardant additives. Simultaneous DSC-TGA (DST) was also performed which showed that the microcapsules were stable before 200 °C, which indicates it would not decompose before the thermal runaway events are occurring. TGA analysis did show that the microcapsules underwent multiple decomposition steps upon heating. Additionally, 31P nuclear magnetic resonance (NMR) was used to quantify the amount of flame retardants additives encapsulated inside PUF shell, and also confirmed the stability of the microcapsules for one month in the electrolyte and at temperatures up to 200 °C. The ionic conductivity was vastly decreased when the flame retardants were added directly to the electrolyte. However, adding the flame retardants in a form of capsules had minimal effect on the ionic conductivity. The cycle capacities of the capsules were also improved when the capsules were added to the cell compared to that of neat flame retardants. The same effect was also noticed when doing Electrochemical Impedance Spectroscopy (EIS). This shows that microencapsulation improves the resistance of the cell caused by the flame retardant in comparison to when added directly to the electrolyte of the cell. , Thesis (MSC) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Ntombela, Nompilo Princess
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55412 , vital:51993
- Description: Lithium-ion technology takes the lead in electric mobility systems, resulting in an increase in the global demand for Li-ion batteries; however, these batteries are associated with numerous safety concerns. Additionally, there are high costs, high energy and power issues which are some of its key limitations. Research efforts are focused on overcoming these obstacles, with different approaches being explored, such as the investigation of more stable salts, modification of active materials and organic solvents, and the use of electrolyte additives. This study focused specifically on electrolyte additives since the electrolyte is one of the most unstable components of the battery. The electrolyte’s decomposition is one of the reactions that occur inside a battery, which may occur due to overcharging or due to an internal short circuit, amongst others. The electrolyte’s decomposition occurs at the early stages of the thermal runaway process and forms part of the reactions that lead to fires and explosions. Thus, this research aims to develop suitable electrolyte additives to improve the safety aspects of Li-ion batteries. Flame retardant additives show great promise in reducing the flammability of the electrolyte in Li-ion batteries, since they serve to suppress the chemical reactions associated with battery ignition. They retard the fires by scavenging the active radical species formed during the decomposition reaction. In this study, the use of flame retardants was investigated. Flame retardant additives have shown to have flame impeding properties inside a battery; however, their direct addition to the electrolyte tends to cause adverse effects on the ionic conductivity and electrochemical performance of the cells. This study investigated an alternative option - the option to microencapsulate such additives into a neutral compound to ensure that the flame retardant has minimal/no effect on the performance of the battery. This investigation looked at tris(2-butoxyethyl) phosphate (TBP) and bis(2,2,2-trifluoroethyl) methylphosphonate (BFP) as flame retardant additives for the electrolyte. The TBP and BFP flame retardants were microencapsulated in poly(urea formaldehyde) (PUF) coating material via in situ polymerization method. The capsules were characterized using various analytical techniques - to prove it was successfully encapsulated. Electrochemical studies were further done on the capsules and neat flame retardants inside a coin cell. Self-extinguishing time (SET), which is the flammability test, proved that the additives have flame retarding abilities. Opto-digital microscopy (DSX) and scanning electron microscopy (SEM) did confirm the spherical shape of the microcapsules, where SEM also showed the smooth outer layer of the microcapsules and its hollow inner side. Fourier transform infrared spectroscopy (FTIR) proved the presence of the TBP and BFP inside the PUF resin by showing that the chemical composition of microcapsules consisted of both the PUF and flame retardant additives. Simultaneous DSC-TGA (DST) was also performed which showed that the microcapsules were stable before 200 °C, which indicates it would not decompose before the thermal runaway events are occurring. TGA analysis did show that the microcapsules underwent multiple decomposition steps upon heating. Additionally, 31P nuclear magnetic resonance (NMR) was used to quantify the amount of flame retardants additives encapsulated inside PUF shell, and also confirmed the stability of the microcapsules for one month in the electrolyte and at temperatures up to 200 °C. The ionic conductivity was vastly decreased when the flame retardants were added directly to the electrolyte. However, adding the flame retardants in a form of capsules had minimal effect on the ionic conductivity. The cycle capacities of the capsules were also improved when the capsules were added to the cell compared to that of neat flame retardants. The same effect was also noticed when doing Electrochemical Impedance Spectroscopy (EIS). This shows that microencapsulation improves the resistance of the cell caused by the flame retardant in comparison to when added directly to the electrolyte of the cell. , Thesis (MSC) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Optimizing herbicide-use for the killing of eucalypt stumps
- Authors: Mavhungu, Tshilidzi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53857 , vital:46023
- Description: The South Africa (SA) forest industry relies on plantations of exotic forestry trees (Pinus, Acacia and Eucalyptus) to fulfil its timber requirements. With 52.0% of the afforested land in South Africa planted to various eucalypts and their hybrid combinations. Of the total area planted to eucalypts in SA, 75 000 ha is re-established annually by means of silvicultural regimes and operations matched to site productivity, desired end-product and method of regeneration. Unlike other commercially grown tree species, eucalypt species have the ability to coppice after felling. Coppicing is a common form of regeneration in South African forestry as it allows the plantation owner the option of a second timber rotation without replanting. However, if any factors affecting coppicing are compromised, and the site is to be replanted, then it is important to kill the stumps before replanting as rapid initial growth of the coppice shoots will require earlier control than that associated with normal weeding operations. Over time, various methods of woody plant control have been proposed and tested, with most of these making use of herbicides as opposed to the repeated manual removal of coppice regrowth. Globally, most industries subscribe to standards associated with sustainable production (economic, environmental and social) against which they are measured. Within SA, 80% of the forests are certified though either the Forest Stewardship Council (FSC) or International Standards Organisation (ISO) which recommend the identification and avoidance of ‘highly hazardous’ chemicals; the promotion of ‘non-chemical’ methods for pest management as an element of an integrated pest and vegetation management strategy; and the appropriate use of chemicals that are used. To test the current recommendations for killing eucalypt stumps to include other species, the potential of reducing herbicides used, and the influence of time after application on the survival of eucalypt stumps, two trials were initiated at Entabeni plantation (Venda, Limpopo) and one at Wilgeboom plantation (Bushbuckridge, Mpumalanga) between 2018 and 2020. Extending eucalypt cut-stump control practices: Most of the trial work on killing of eucalypts in SA has been conducted on Eucalyptus grandis, Eucalyptus camaldulensis or Eucalyptus macarthurii, with all grown on shorter pulpwood rotations. To extend current recommendation to include Eucalyptus cloeziana (grown on a longer rotation for poles), a trial was established in 2018 at Entabeni plantation (Limpopo Province) to quantify the interaction between Application method (basal-frill; cut-surface; foliar) and Herbicide (no herbicide applied; Roundup; Garlon; Roundup + Garlon) for the killing of 12 year-old stumps following harvesting. Assessments were carried out at 1, 3 and 6 months following application and included Stump survival, Stump quarter with coppice and Coppice heath. Relative to the control plots (100% survival), all herbicides tested were equally effective, 70–90% of the stumps killed. This study confirms previous research regarding the killing of eucalypt stumps. Roundup, Garlon or a combination of two, when applied according to label recommendations to a stump as a basal-frill or cut-surface application (within 30 minutes of felling) resulted in 70-90% of the stumps killed. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Mavhungu, Tshilidzi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53857 , vital:46023
- Description: The South Africa (SA) forest industry relies on plantations of exotic forestry trees (Pinus, Acacia and Eucalyptus) to fulfil its timber requirements. With 52.0% of the afforested land in South Africa planted to various eucalypts and their hybrid combinations. Of the total area planted to eucalypts in SA, 75 000 ha is re-established annually by means of silvicultural regimes and operations matched to site productivity, desired end-product and method of regeneration. Unlike other commercially grown tree species, eucalypt species have the ability to coppice after felling. Coppicing is a common form of regeneration in South African forestry as it allows the plantation owner the option of a second timber rotation without replanting. However, if any factors affecting coppicing are compromised, and the site is to be replanted, then it is important to kill the stumps before replanting as rapid initial growth of the coppice shoots will require earlier control than that associated with normal weeding operations. Over time, various methods of woody plant control have been proposed and tested, with most of these making use of herbicides as opposed to the repeated manual removal of coppice regrowth. Globally, most industries subscribe to standards associated with sustainable production (economic, environmental and social) against which they are measured. Within SA, 80% of the forests are certified though either the Forest Stewardship Council (FSC) or International Standards Organisation (ISO) which recommend the identification and avoidance of ‘highly hazardous’ chemicals; the promotion of ‘non-chemical’ methods for pest management as an element of an integrated pest and vegetation management strategy; and the appropriate use of chemicals that are used. To test the current recommendations for killing eucalypt stumps to include other species, the potential of reducing herbicides used, and the influence of time after application on the survival of eucalypt stumps, two trials were initiated at Entabeni plantation (Venda, Limpopo) and one at Wilgeboom plantation (Bushbuckridge, Mpumalanga) between 2018 and 2020. Extending eucalypt cut-stump control practices: Most of the trial work on killing of eucalypts in SA has been conducted on Eucalyptus grandis, Eucalyptus camaldulensis or Eucalyptus macarthurii, with all grown on shorter pulpwood rotations. To extend current recommendation to include Eucalyptus cloeziana (grown on a longer rotation for poles), a trial was established in 2018 at Entabeni plantation (Limpopo Province) to quantify the interaction between Application method (basal-frill; cut-surface; foliar) and Herbicide (no herbicide applied; Roundup; Garlon; Roundup + Garlon) for the killing of 12 year-old stumps following harvesting. Assessments were carried out at 1, 3 and 6 months following application and included Stump survival, Stump quarter with coppice and Coppice heath. Relative to the control plots (100% survival), all herbicides tested were equally effective, 70–90% of the stumps killed. This study confirms previous research regarding the killing of eucalypt stumps. Roundup, Garlon or a combination of two, when applied according to label recommendations to a stump as a basal-frill or cut-surface application (within 30 minutes of felling) resulted in 70-90% of the stumps killed. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2021-12
The synthesis, empirical and theoretical studies of various (N→B) diarylborinate esters
- Authors: Manana, Pholani Sakhile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53869 , vital:46027
- Description: A series of core-functionalized borinic acids was synthesized from Grignard reagents and tributylborate and reacted with ethanolamine, amino acids, 2-pyridylmethanol as well as 2-(ethyl amino ethanol). Among the borinic acids synthesized were the ones bearing: para-(2, 15, 16, 22, 27)-methyl, (3, 20, 25)-chloro, (4, 23, 26)-fluoro, (5)-methoxy; meta-(7, 17)-methyl, (9)-fluoro; ortho-(6)-methyl, (8)-chloro, (10, 18, 19)-methoxy substituents on their respective aromatic systems. All compounds obtained by condensation of the borinic acids with the aforementioned nitrogen-containing substrates were characterized structurally by means of diffraction studies based on single crystals and found to constitute chelate esters/amides featuring covalent B-O and dative N→B bonds. The chelate compounds researched in this study could be classified into four families and represent the compounds: ethanol amine: (1) 2,2-diphenyl-1,3,2-oxazaborolidines, (2) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (3) 2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (4) 2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (5) 2,2-bis(p-methoxyphenyl)-1,3,2-oxazaborolidines, (6) 2,2-bis(o-tolyl)-1,3,2-oxazaborolidines, (7) 2,2-bis(m-tolyl)-1,3,2-oxazaborolidines, (8) 2,2-bis(o-chlorophenyl)-1,3,2-oxazaborolidines, (9) 2,2-bis(m-fluorophenyl)-1,3,2-oxazaborolidines, (10) 2,2-bis(o-methoxyphenyl)-1,3,2-oxazaborolidines. α-amino acids : (14) 4-methyl-2,2-diphenyl-1,3,2-oxazaborolidin-5-ones, (15) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (16) 4-methyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (17) 4-isopropyl-2,2-bis(m-tolyl)-1,3,2-oxazaborolidin-5-ones, (18) 4-methyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (19) 4-acetamidyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (20) 4-phenylethane-2,2-bis(p-chlorophenyl)-1,3,2 oxazaborolidin-5-ones. 2-pyridylmethanol: (21) 1,3-hydroxypyridyl-2,2-diphenyl 1,3,2-oxazaborolidines, (22) 1,3-hydroxypyridyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (23) 1,3-hydroxypyridyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines 2-(ethyl amino ethanol): (24) 3-ethyl-2,2-diphenyl-1,3,2-oxazaborolidines, (25) 3-ethyl-2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (26) 3-ethyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (27) 3-ethyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines. Apart from structural studies in the solid state, the compounds were also characterized by means of multinuclear NMR spectroscopy (1H, 11B, 13C) as well as UV/vis and FTIR. The typical 11B resonances were found in the range of (4-10 ppm). A series of characteristic metrical parameters for the compounds in the solid state as well as typical NMR shifts for the chelate target molecules was established that allowed for the determination of the coordination induced shift. The carbon atom bonded to the oxygen atom shifted upfield, while the carbon atom bonded to the nitrogen atom shifted downfield. Factors mentioned in the literature that has an influence on the hydrolytic stability on the heterocyclic borinate motif have been taken into consideration and verified for the systems researched in this study. The substitution at the nitrogen atom with one ethyl group caused the greatest increases in the N→B bond length (27) 1.714 Å, due to the increase in the nitrogen Lewis basicity, making it the least hydrolytically stable, these include compounds (24-26). Furthermore, DFT calculations were performed by employing Becke’s three parameter hybrid exchange functional with Lee–Yang–Parr functional (B3LYP) method using the Gaussian 16 program package (Rev. B01) employing the basis set 6-311++G(d,p), to corroborate and correlate the experimental findings, which gave a general R-squared value of 0.9978 for calculated vs experimental 13C chemical shifts. Thermal properties are recorded for select compounds, indicating the ΔH and the melting points. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Manana, Pholani Sakhile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53869 , vital:46027
- Description: A series of core-functionalized borinic acids was synthesized from Grignard reagents and tributylborate and reacted with ethanolamine, amino acids, 2-pyridylmethanol as well as 2-(ethyl amino ethanol). Among the borinic acids synthesized were the ones bearing: para-(2, 15, 16, 22, 27)-methyl, (3, 20, 25)-chloro, (4, 23, 26)-fluoro, (5)-methoxy; meta-(7, 17)-methyl, (9)-fluoro; ortho-(6)-methyl, (8)-chloro, (10, 18, 19)-methoxy substituents on their respective aromatic systems. All compounds obtained by condensation of the borinic acids with the aforementioned nitrogen-containing substrates were characterized structurally by means of diffraction studies based on single crystals and found to constitute chelate esters/amides featuring covalent B-O and dative N→B bonds. The chelate compounds researched in this study could be classified into four families and represent the compounds: ethanol amine: (1) 2,2-diphenyl-1,3,2-oxazaborolidines, (2) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (3) 2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (4) 2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (5) 2,2-bis(p-methoxyphenyl)-1,3,2-oxazaborolidines, (6) 2,2-bis(o-tolyl)-1,3,2-oxazaborolidines, (7) 2,2-bis(m-tolyl)-1,3,2-oxazaborolidines, (8) 2,2-bis(o-chlorophenyl)-1,3,2-oxazaborolidines, (9) 2,2-bis(m-fluorophenyl)-1,3,2-oxazaborolidines, (10) 2,2-bis(o-methoxyphenyl)-1,3,2-oxazaborolidines. α-amino acids : (14) 4-methyl-2,2-diphenyl-1,3,2-oxazaborolidin-5-ones, (15) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (16) 4-methyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (17) 4-isopropyl-2,2-bis(m-tolyl)-1,3,2-oxazaborolidin-5-ones, (18) 4-methyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (19) 4-acetamidyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (20) 4-phenylethane-2,2-bis(p-chlorophenyl)-1,3,2 oxazaborolidin-5-ones. 2-pyridylmethanol: (21) 1,3-hydroxypyridyl-2,2-diphenyl 1,3,2-oxazaborolidines, (22) 1,3-hydroxypyridyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (23) 1,3-hydroxypyridyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines 2-(ethyl amino ethanol): (24) 3-ethyl-2,2-diphenyl-1,3,2-oxazaborolidines, (25) 3-ethyl-2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (26) 3-ethyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (27) 3-ethyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines. Apart from structural studies in the solid state, the compounds were also characterized by means of multinuclear NMR spectroscopy (1H, 11B, 13C) as well as UV/vis and FTIR. The typical 11B resonances were found in the range of (4-10 ppm). A series of characteristic metrical parameters for the compounds in the solid state as well as typical NMR shifts for the chelate target molecules was established that allowed for the determination of the coordination induced shift. The carbon atom bonded to the oxygen atom shifted upfield, while the carbon atom bonded to the nitrogen atom shifted downfield. Factors mentioned in the literature that has an influence on the hydrolytic stability on the heterocyclic borinate motif have been taken into consideration and verified for the systems researched in this study. The substitution at the nitrogen atom with one ethyl group caused the greatest increases in the N→B bond length (27) 1.714 Å, due to the increase in the nitrogen Lewis basicity, making it the least hydrolytically stable, these include compounds (24-26). Furthermore, DFT calculations were performed by employing Becke’s three parameter hybrid exchange functional with Lee–Yang–Parr functional (B3LYP) method using the Gaussian 16 program package (Rev. B01) employing the basis set 6-311++G(d,p), to corroborate and correlate the experimental findings, which gave a general R-squared value of 0.9978 for calculated vs experimental 13C chemical shifts. Thermal properties are recorded for select compounds, indicating the ΔH and the melting points. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
Applying a systems analysis approach to support marine spatial planning in Algoa Bay, South Africa
- Authors: Vermeulen, Estee Ann
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54121 , vital:46312
- Description: Ocean health provides the foundation for human health through the provisioning of ecosystem services. Increasing demands on ocean space and resources are, however, resulting in a decline in ocean health, with direct and indirect knock-on effects on marine uses and ultimately on human health. In response, there is a growing need to acknowledge and better manage complex human-ocean interactions. This has been recognised in global sustainable development goals and in integrated ocean management processes, leading to widespread endorsement of an ecosystem-based marine spatial planning (MSP) process, including in South Africa. In support of the national MSP process, significant progress has been made in understanding the spatial extent of marine activities and associated marine pressures, but the temporal dynamics of marine activities and interconnections with the marine environment are less well understood. To plan for the growth of marine activities and associated user conflicts, the drivers of these temporal dynamics and associated feedback effects need to be analysed and potential policy and management interventions identified and tested. To support South Africa’s national MSP process, this study adopts a systems analysis approach, using system dynamics modelling, to explore the temporal change in marine uses under alternative growth scenarios in Algoa Bay. Algoa Bay is an appropriate study area because it is experiencing a rapid expansion of marine activities, coupled with a growing uncertainty regarding marine sustainability outcomes. To assist future marine management decisions, the Algoa Marine Systems Analysis Tool (Algoa MSAT) was developed, comprising seven sub-models. Five of the sub-models represent selected marine uses in Algoa Bay, whereas the sixth and seventh integrate the outputs from each marine use in terms of sustainable management indicators (marine health, marine wealth and marine labour). Model development primarily adopted an expert-based model ling approach, although the involvement of stakeholders, through a collaborative modelling process, assisted in integrating knowledge on different marine sectors’ activities, impacts and planning visions into the model framework. Model results were generated under different scenarios to investigate changes in the growth of marine activities and marine sustainability indicators under different levels of ocean governance. Under the baseline (or business-as-usual) model scenario, marine activities were shown to grow increasingly within their respective management limits, with an increase in marine wealth and labour and a consequential decrease in marine health. This scenario particularly highlights that current ocean governance practices are ineffective in sustaining the projected growth of the marine uses, particularly for those that are vulnerable to negative changes in marine health. Conversely, sectors that hold more value in marine wealth and are more resilient to changes in marine health, may continue to grow regardless of negative knock-on effects of the health of the marine environment and on other uses in the bay. This emphasises that an alternative governance strategy is needed to achieve the long-term goal of an ecosystem-based MSP process, as required by South African MSP legislation. To achieve this will require multiple, adaptive cross-sectoral management interventions that are directed towards the ‘deeper leverage points’ that are able to maintain the growth of marine activities within appropriate limits defined by marine health. Using the model interface developed in this project, decision-makers and stakeholders can use the model to explore the temporal dynamics in marine activities under different governance scenarios. Although the model is limited to Algoa Bay, the model boundary can be adapted to assist in marine planning processes at national or trans-national scales. Such analytical assessments and tools are critical to progress the ecosystem-based management approach in MSP, as is required to achieve global sustainable development goals. , Thesis (PhD) -- Faculty of Science, Coastal and Marine Research Unit, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Vermeulen, Estee Ann
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54121 , vital:46312
- Description: Ocean health provides the foundation for human health through the provisioning of ecosystem services. Increasing demands on ocean space and resources are, however, resulting in a decline in ocean health, with direct and indirect knock-on effects on marine uses and ultimately on human health. In response, there is a growing need to acknowledge and better manage complex human-ocean interactions. This has been recognised in global sustainable development goals and in integrated ocean management processes, leading to widespread endorsement of an ecosystem-based marine spatial planning (MSP) process, including in South Africa. In support of the national MSP process, significant progress has been made in understanding the spatial extent of marine activities and associated marine pressures, but the temporal dynamics of marine activities and interconnections with the marine environment are less well understood. To plan for the growth of marine activities and associated user conflicts, the drivers of these temporal dynamics and associated feedback effects need to be analysed and potential policy and management interventions identified and tested. To support South Africa’s national MSP process, this study adopts a systems analysis approach, using system dynamics modelling, to explore the temporal change in marine uses under alternative growth scenarios in Algoa Bay. Algoa Bay is an appropriate study area because it is experiencing a rapid expansion of marine activities, coupled with a growing uncertainty regarding marine sustainability outcomes. To assist future marine management decisions, the Algoa Marine Systems Analysis Tool (Algoa MSAT) was developed, comprising seven sub-models. Five of the sub-models represent selected marine uses in Algoa Bay, whereas the sixth and seventh integrate the outputs from each marine use in terms of sustainable management indicators (marine health, marine wealth and marine labour). Model development primarily adopted an expert-based model ling approach, although the involvement of stakeholders, through a collaborative modelling process, assisted in integrating knowledge on different marine sectors’ activities, impacts and planning visions into the model framework. Model results were generated under different scenarios to investigate changes in the growth of marine activities and marine sustainability indicators under different levels of ocean governance. Under the baseline (or business-as-usual) model scenario, marine activities were shown to grow increasingly within their respective management limits, with an increase in marine wealth and labour and a consequential decrease in marine health. This scenario particularly highlights that current ocean governance practices are ineffective in sustaining the projected growth of the marine uses, particularly for those that are vulnerable to negative changes in marine health. Conversely, sectors that hold more value in marine wealth and are more resilient to changes in marine health, may continue to grow regardless of negative knock-on effects of the health of the marine environment and on other uses in the bay. This emphasises that an alternative governance strategy is needed to achieve the long-term goal of an ecosystem-based MSP process, as required by South African MSP legislation. To achieve this will require multiple, adaptive cross-sectoral management interventions that are directed towards the ‘deeper leverage points’ that are able to maintain the growth of marine activities within appropriate limits defined by marine health. Using the model interface developed in this project, decision-makers and stakeholders can use the model to explore the temporal dynamics in marine activities under different governance scenarios. Although the model is limited to Algoa Bay, the model boundary can be adapted to assist in marine planning processes at national or trans-national scales. Such analytical assessments and tools are critical to progress the ecosystem-based management approach in MSP, as is required to achieve global sustainable development goals. , Thesis (PhD) -- Faculty of Science, Coastal and Marine Research Unit, 2021
- Full Text:
- Date Issued: 2021-12
The synthesis of anastrazole intermediates using continuous flow systems
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
Microstructural characterization of Swift Heavy Ion (SHI) induced rotation in single crystal NiO
- Authors: Douglas-Henry, Danielle
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53648 , vital:45685
- Description: Swift Heavy Ions (SHI) are characterised by having energies greater than 1 MeV per nucleon with an atomic mass greater than 6 amu. Exposure to irradiation of this type has been known to produce latent tracks in insulators. This is due to the energy loss through the material being governed by electronic excitation processes. The extent of the track formation and microstructural changes induced has been reported to be material specific. Models such as the thermal spike model have been used to explain these changes, however rough approximations are still made. A particularly under studied phenomena is the collective rotation seen in materials exposed to off-normal incidence irradiation. To date the only available experimental data is X-Ray Diffraction (XRD) spectra and surface shifts. This does not allow for depth-dependent rotation studies and very little can be deduced regarding the microstructure of the modified volume. In this study, the microstructural changes in single crystal Nickel Oxide (NiO) have been studied using electron microscopy techniques. A depth dependent investigation of the crystal rotation was performed using Selected Area Electron Diffraction (SAED), Transmission Kikuchi Diffraction (TKD) and Electron Backscatter Diffraction (EBSD). Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) were utilized to interrogate the microstructural changes facilitating the bulk rotation. Five different NiO specimens were investigated. Specimens had surfaces parallel to either the {0 0 1} or {1 1 1} planes. Ion energies used were 593 MeV, 940 MeV and 1.6 GeV, while fluences ranged from 1.0 x 1011 ions/cm² to 9.6 x 1014 ions/cm². Latent track formation in both low fluence (nonoverlapping regime) and high fluence (overlapping regime) specimens were investigated and compared. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Douglas-Henry, Danielle
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53648 , vital:45685
- Description: Swift Heavy Ions (SHI) are characterised by having energies greater than 1 MeV per nucleon with an atomic mass greater than 6 amu. Exposure to irradiation of this type has been known to produce latent tracks in insulators. This is due to the energy loss through the material being governed by electronic excitation processes. The extent of the track formation and microstructural changes induced has been reported to be material specific. Models such as the thermal spike model have been used to explain these changes, however rough approximations are still made. A particularly under studied phenomena is the collective rotation seen in materials exposed to off-normal incidence irradiation. To date the only available experimental data is X-Ray Diffraction (XRD) spectra and surface shifts. This does not allow for depth-dependent rotation studies and very little can be deduced regarding the microstructure of the modified volume. In this study, the microstructural changes in single crystal Nickel Oxide (NiO) have been studied using electron microscopy techniques. A depth dependent investigation of the crystal rotation was performed using Selected Area Electron Diffraction (SAED), Transmission Kikuchi Diffraction (TKD) and Electron Backscatter Diffraction (EBSD). Transmission Electron Microscopy (TEM) and Scanning Transmission Electron Microscopy (STEM) were utilized to interrogate the microstructural changes facilitating the bulk rotation. Five different NiO specimens were investigated. Specimens had surfaces parallel to either the {0 0 1} or {1 1 1} planes. Ion energies used were 593 MeV, 940 MeV and 1.6 GeV, while fluences ranged from 1.0 x 1011 ions/cm² to 9.6 x 1014 ions/cm². Latent track formation in both low fluence (nonoverlapping regime) and high fluence (overlapping regime) specimens were investigated and compared. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
Synthesis and characterization of iron doped sodium and potassium titanates using the pechini sol-gel method
- Authors: Guga, Aluwani
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53646 , vital:45683
- Description: Iron doped (Fe: 5Ti) sodium and potassium titanates were prepared by the Pechini sol-gel method and calcined at 800 °C. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), FTIR and Raman spectroscopy were used to characterize the structure and morphology of the titanate nanomaterials. A quantitative XRD analysis using Rietveld refinement of the titanates confirmed the powders to consist of crystalline phases with the Na2Ti7O15 and K2Ti8O17 phases predominant for the sodium and potassium titanate, respectively. This was further confirmed using selected area electron diffraction (SAED) in the TEM. SEM and TEM analyses indicated that the titanates are consistent with a nanostructured material exhibiting rod-like morphology. The elemental compositions of the titanites were examined by SEM-EDS and TEM-EDS and found to agree well with the targeted Fe to Ti ratio from synthesis. Limited evidence for the segregation of iron in the titanate regions were found indicating the iron to be incorporated within the titanate lattice. Electron energy loss spectroscopy (EELS) fine-structure analysis of the Fe L2,3 core-loss edge was successfully used to match the Fe to a 2+ or 3+ valence state, consistent with its occupation at Ti lattice sites. Finally, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to study the vibrational modes of the functional group of the sodium and potassium titanates. Vibrational modes consistent with previously reported findings for the titanate phases identified were found with no evidence of isolated Fe related modes. , Thesis (MSc) -- Faculty of Science, Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Guga, Aluwani
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53646 , vital:45683
- Description: Iron doped (Fe: 5Ti) sodium and potassium titanates were prepared by the Pechini sol-gel method and calcined at 800 °C. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDS), FTIR and Raman spectroscopy were used to characterize the structure and morphology of the titanate nanomaterials. A quantitative XRD analysis using Rietveld refinement of the titanates confirmed the powders to consist of crystalline phases with the Na2Ti7O15 and K2Ti8O17 phases predominant for the sodium and potassium titanate, respectively. This was further confirmed using selected area electron diffraction (SAED) in the TEM. SEM and TEM analyses indicated that the titanates are consistent with a nanostructured material exhibiting rod-like morphology. The elemental compositions of the titanites were examined by SEM-EDS and TEM-EDS and found to agree well with the targeted Fe to Ti ratio from synthesis. Limited evidence for the segregation of iron in the titanate regions were found indicating the iron to be incorporated within the titanate lattice. Electron energy loss spectroscopy (EELS) fine-structure analysis of the Fe L2,3 core-loss edge was successfully used to match the Fe to a 2+ or 3+ valence state, consistent with its occupation at Ti lattice sites. Finally, Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy were used to study the vibrational modes of the functional group of the sodium and potassium titanates. Vibrational modes consistent with previously reported findings for the titanate phases identified were found with no evidence of isolated Fe related modes. , Thesis (MSc) -- Faculty of Science, Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
The aesthetics of hegemony: a speculative design proposal exploring the convergence of surveillance capitalism and brain-computer interface technologies in the future
- Authors: Davies, James Tibbott
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54417 , vital:46517
- Description: This study examines the power dynamics of surveillance capitalism, and its role in shaping cultural hegemony. The research was expressed using graphic design to illustrate a (potential) future where Brain-Computer Interfaces (BCIs) and surveillance capitalism converge. The critique focused on Google and Facebook’s hegemony in the data-surveillance marketplace and what role this has in shaping global discourse. Both companies are funding the development of BCIs, with the aim of using brain signals as a means of interacting with the digital world, which would give the two biggest advertising companies in the world access to new sources of data. A speculative design framework was utilized to visually question the societal implications of this emerging technology and the funding behind its development. A theoretical investigation of the concepts underpinning critical theory and critical design was conducted to help clarify and critically inform this methodological approach, promoting the use of practice-based design as a critically reflective investigative tool. The resulting artefacts designed using this process were showcased in the form of a website and video that act as a visual embodiment the research, demonstrating the efficacy of this approach and the value of using communication design as a mechanism to question the status quo. , Thesis (MA) -- Faculty of Humanities, School of Visual and Performing Arts, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Davies, James Tibbott
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54417 , vital:46517
- Description: This study examines the power dynamics of surveillance capitalism, and its role in shaping cultural hegemony. The research was expressed using graphic design to illustrate a (potential) future where Brain-Computer Interfaces (BCIs) and surveillance capitalism converge. The critique focused on Google and Facebook’s hegemony in the data-surveillance marketplace and what role this has in shaping global discourse. Both companies are funding the development of BCIs, with the aim of using brain signals as a means of interacting with the digital world, which would give the two biggest advertising companies in the world access to new sources of data. A speculative design framework was utilized to visually question the societal implications of this emerging technology and the funding behind its development. A theoretical investigation of the concepts underpinning critical theory and critical design was conducted to help clarify and critically inform this methodological approach, promoting the use of practice-based design as a critically reflective investigative tool. The resulting artefacts designed using this process were showcased in the form of a website and video that act as a visual embodiment the research, demonstrating the efficacy of this approach and the value of using communication design as a mechanism to question the status quo. , Thesis (MA) -- Faculty of Humanities, School of Visual and Performing Arts, 2021
- Full Text:
- Date Issued: 2021-12
A study of the airflow on the windward slope of a transverse dune in the Alexandria coastal dunefield
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Burkinshaw, Jennifer Ruth
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52734 , vital:43883
- Description: Our understanding of the evolution of dune morphology has been hampered by a lack of empirical observations of airflow behaviour over dune forms. Sand dunes intrude into the atmospheric boundary layer and convergence of streamlines results in an acceleration of airflow up the windward slopes of dunes. This study examines the airflow structure and corresponding bedform development on the windward slope of a 7 m high transverse dune on the edge of the Alexandria coastal dunefield, Algoa Bay, South Africa. The Alexandria dunefield is subjected to a trimodal wind regime, consisting of the dominant south-westerly which blows all year round, summer easterlies and winter northwesterlies. The morphology of the study dune, Dune13, is controlled by the easterlies and north-westerlies, and reverses seasonally with respect to these two winds. Seven section lines 30 m apart and normal to the dune crest were surveyed regularly over the period of a year to monitor the reversal process. Three detailed topographic surveys were also done during this period. Airflow behaviour was monitored during the year. Wind speed profiles on the windward slope of the dune were measured using 4 to 5 vertical arrays of anemometers positioned from the base of the dune to the crest on a 1 selected section line. Usually 4 to 5 anemometers were deployed in each vertical array, from a height of 6 to 10 cm above the surface, up to a height of 150 cm above the surface. Initially 8 microanemometers were available; ultimately 28 anemometers were run simultaneously. An independent weather station at an elevation of 6 m recorded the unaccelerated flow. Local gradient measurements and erosion and deposition rates were recorded along selected section lines. Strong summer easterly winds (14 m/sec at 1.4 m above the dune crest) were measured on a dune slope in the process of being transformed from a slipface to a stoss slope. The following winter, light north-westerly winds (typically B m/sec at 1.6 m above the dune crest) were measured on the new windward slope already reversed by the prevailing winter wind. Airflow data confirm the compression of airflow against the windward slope resulting in a non-logarithmic wind speed profile. Compression results in an increased shear velocity within 30 cm of the dune surface, and the dune slope is eroded. Higher up in the wind speed profile, shear velocity decreases to 0.1 m/sec. It is not known at what height the wind speed profile recovers from the intrusion of the dune into the boundary layer. High values of shear velocity (1.6 m/sec) above the rounded crestal area of the dune record the recovery of the wind speed profile from flow divergence, which is a response to the rapid reduction of dune gradient and is accompanied by deposition of sand in this region. 2 The erosion pin data act as a simple and sensitive test for changes in gradient, reflecting the dune's response to changes in the airflow regime. The shape of the dune plays a major role in determining the extent of the compression and the distribution of shear velocity up the slope. Increased shear velocity is experienced on that part of the slope which is nonaerodynamic with respect to the prevailing wind. Under unidirectional conditions, feedback between flow and form results ultimately in a slope with a curvature such that shear velocity increases systematically upslope. The survey data and erosion pin data record the reversal process as the dune achieves a new steady state during each wind season. The existence of a non-logarithmic wind speed profile makes it difficult to know what relevant measure of shear velocity is to be used in sand transport equations. Future work should include wind speed measurements within 10 cm of the surface. An ideal study modelling aeolian bedform development would utilise wind tunnel measurements, combined with field measurements such as obtained in this study, for comparison with numerical modelling. The study needs to be extended to 3-dimensional airflow measurements. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
The effect of silicon on palladium migration in pyrolytic carbon and graphite
- Authors: Downey, Justin Michael
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53665 , vital:45684
- Description: The pebble-bed reactor (PBR) is a graphite-moderated, gas-cooled high temperature nuclear reactor design and it is one of six nuclear reactor concepts included in the Generation IV initiative. Pebble-bed reactors use spherical fuel elements (called pebbles) which consist of pyrolytic graphite (which acts as the moderator) and contain thousands of micro-fuel particles called tristructural isotropic (TRISO) particles. These TRISO fuel particles consist of a fissile material (such as U235 in oxide or carbide form) surrounded by a carbon buffer layer, a pyrolytic carbon (PyC) layer, a silicon carbide (SiC) ceramic layer for structural integrity and metallic fission product containment, and an outer PyC layer. The PBR is claimed to be a passively safe design. The commercial development of the first pebble bed reactor was that of the German AVR reactor (German: Arbeitsgemeinschaft Versuchsreaktor) developed during the 1960s. The AVR design was later updated and marketed by a company called HTR. In 1999 the South African electricity company ESKOM obtained the right to access the HTR engineering database that included details of the Siemens/Interatom HTR-Module design. ESKOM worked with HTR on a new design and dubbed it the pebble bed modular reactor (PBMR). The PBMR Co. Ltd. was formed in 1999 and mandated to license and build PBMR reactors. One of the safety considerations which emerged from research is that of metal fission product release from the TRISO fuel particles. Ag110m is a radioactive metallic fission product found to have been released from intact TRISO particles. The release of this Ag isotope is of particular concern because it is highly gamma active and has a half-life of approximately 250 days, resulting in unsafe environments for maintenance workers of PBRs. During the past four decades, many different mechanisms for Ag transport in SiC and release from TRISO particles have been proposed. A promising more recent mechanism suggests that the metallic fission product palladium (Pd) plays a significant role in the transport and release of Ag from intact TRISO particles. In this mechanism Ag transport in irradiated TRISO particle fuel takes place in the presence of the fission product Pd. The Pd reacts with the SiC layer and penetrates the SiC layer along grain boundaries to form a silicide layer which provides a rapid diffusion path for Ag in the SiC. The presence of thin silicide layers in irradiated TRISO particles was subsequently confirmed. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Downey, Justin Michael
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53665 , vital:45684
- Description: The pebble-bed reactor (PBR) is a graphite-moderated, gas-cooled high temperature nuclear reactor design and it is one of six nuclear reactor concepts included in the Generation IV initiative. Pebble-bed reactors use spherical fuel elements (called pebbles) which consist of pyrolytic graphite (which acts as the moderator) and contain thousands of micro-fuel particles called tristructural isotropic (TRISO) particles. These TRISO fuel particles consist of a fissile material (such as U235 in oxide or carbide form) surrounded by a carbon buffer layer, a pyrolytic carbon (PyC) layer, a silicon carbide (SiC) ceramic layer for structural integrity and metallic fission product containment, and an outer PyC layer. The PBR is claimed to be a passively safe design. The commercial development of the first pebble bed reactor was that of the German AVR reactor (German: Arbeitsgemeinschaft Versuchsreaktor) developed during the 1960s. The AVR design was later updated and marketed by a company called HTR. In 1999 the South African electricity company ESKOM obtained the right to access the HTR engineering database that included details of the Siemens/Interatom HTR-Module design. ESKOM worked with HTR on a new design and dubbed it the pebble bed modular reactor (PBMR). The PBMR Co. Ltd. was formed in 1999 and mandated to license and build PBMR reactors. One of the safety considerations which emerged from research is that of metal fission product release from the TRISO fuel particles. Ag110m is a radioactive metallic fission product found to have been released from intact TRISO particles. The release of this Ag isotope is of particular concern because it is highly gamma active and has a half-life of approximately 250 days, resulting in unsafe environments for maintenance workers of PBRs. During the past four decades, many different mechanisms for Ag transport in SiC and release from TRISO particles have been proposed. A promising more recent mechanism suggests that the metallic fission product palladium (Pd) plays a significant role in the transport and release of Ag from intact TRISO particles. In this mechanism Ag transport in irradiated TRISO particle fuel takes place in the presence of the fission product Pd. The Pd reacts with the SiC layer and penetrates the SiC layer along grain boundaries to form a silicide layer which provides a rapid diffusion path for Ag in the SiC. The presence of thin silicide layers in irradiated TRISO particles was subsequently confirmed. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
Ureaplasma species in the placenta and histopathology associated with preterm birth
- Authors: Sprong, Kaitlin Elizabeth
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54128 , vital:46310
- Description: The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasma spp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalence of Ureaplasma urealyticum, Ureaplasma parvumand Mycoplasma hominisin the placenta and its role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasma spp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasma spp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasma spp. in the placenta and adverse maternal, obstetric and neonatal outcomes. iiiABSTRACTBackground The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasmaspp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalenceof Ureaplasmaurealyticum,UreaplasmaparvumandMycoplasmahominisin the placenta andits role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasmaspp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasmaspp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasmaspp. inthe placenta and adverse maternal, obstetric and neonatal outcomes. MethodsPlacentas were collected from patients presenting with preterm birth (n=100; 28-34 weeks gestational age) and term birth (n=20; >38 weeks) regardless of the APGAR score. Placentas were submitted for histopathology and used for detection of Ureaplasmaspp. by culture (U9 broth, MycoDuo kits;BioRad) and PCR (DNA was extracted from culture and homogenized placental tissue). Antibiotic susceptibility profiles of Ureaplasmaspp isolates were determined by the SIR Antibiogram kit (BioRad) and microbroth dilution method. Molecular mechanisms of resistance were ascertained by PCR amplification of target genes. Placentas were sent to National Health Laboratory Servicesfor routine histopathology. Next generation sequencing was performed on 16S rRNA amplicons from placental DNA for analysis of microbial diversity. , Thesis (PhD) -- Faculty of Science, Journalsim and Media Studies, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Sprong, Kaitlin Elizabeth
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54128 , vital:46310
- Description: The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasma spp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalence of Ureaplasma urealyticum, Ureaplasma parvumand Mycoplasma hominisin the placenta and its role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasma spp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasma spp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasma spp. in the placenta and adverse maternal, obstetric and neonatal outcomes. iiiABSTRACTBackground The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasmaspp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalenceof Ureaplasmaurealyticum,UreaplasmaparvumandMycoplasmahominisin the placenta andits role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasmaspp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasmaspp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasmaspp. inthe placenta and adverse maternal, obstetric and neonatal outcomes. MethodsPlacentas were collected from patients presenting with preterm birth (n=100; 28-34 weeks gestational age) and term birth (n=20; >38 weeks) regardless of the APGAR score. Placentas were submitted for histopathology and used for detection of Ureaplasmaspp. by culture (U9 broth, MycoDuo kits;BioRad) and PCR (DNA was extracted from culture and homogenized placental tissue). Antibiotic susceptibility profiles of Ureaplasmaspp isolates were determined by the SIR Antibiogram kit (BioRad) and microbroth dilution method. Molecular mechanisms of resistance were ascertained by PCR amplification of target genes. Placentas were sent to National Health Laboratory Servicesfor routine histopathology. Next generation sequencing was performed on 16S rRNA amplicons from placental DNA for analysis of microbial diversity. , Thesis (PhD) -- Faculty of Science, Journalsim and Media Studies, 2021
- Full Text:
- Date Issued: 2021-12
A data-driven decision-making model for the third-party logistics industry in Africa
- Authors: Moyo, Faith
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53875 , vital:46022
- Description: Third-party logistics (3PL) providers have continued to be key players in the supply chain network and have witnessed a growth in the usage of information technology. This growth has enhanced the volume of structured and unstructured data that is collected at a high velocity, and is of rich variety, sometimes described as “Big Data”. Leaders in the 3PL industry are constantly seeking to effectively and efficiently mature their abilities to exploit this data to gain business value through data-driven decision-making (DDDM). DDDM helps the leaders to reduce the reliance they place on observations and intuition to make crucial business decisions in a volatile business environment. The aim of this research was to develop a prescriptive model for DDDM in 3PLs. The model consists of iterative elements that prescribe guidelines to decision-makers in the 3PL industry on how to adopt DDDM. A literature review of existing theoretical frameworks and models for DDDM was conducted to determine the extent to which they contribute towards DDDM for 3PLs. The Design-Science Research Methodology (DSRM) was followed to address the aim of the research and applied to pragmatically and iteratively develop and evaluate the artefact (the model for DDDM) in the real-world context of a 3PL. The literature findings revealed that the challenges with DDDM in organisations include three main categories of challenges related to data quality, data management, vision and capabilities. Once the challenges with DDDM were established, a prescriptive model was designed and developed for DDDM in 3PLs. Qualitative data was collected from semi-structured interviews to gain an understanding of the problems and possible solutions in the real-world context of 3PLs. An As-Is Analysis in the real-world case 3PL company confirmed the challenges identified in literature, and that data is still used in the 3PL company for descriptive and diagnostic analytics to aid with the decision-making processes. This highlights that there is still room for maturity into using data for predictive and prescriptive analytics that will, in turn, improve the decision-making process. An improved second version of the model was demonstrated to the participants (the targeted users), who had the opportunity to evaluate the model. The findings revealed that the model provided clear guidelines on how to make data-driven decisions and that the feedback loop and the data culture aspects highlighted in the design were some of the important features of the model. Some improvements were suggested by participants. A field study of three data analytics tools was conducted to identify the advantages and disadvantages of each as well as to highlight the status of DDDM at the real-world case 3PL. The limitations of the second version of the model, together with the recommendations from the participants were used to inform the improved and revised third version of the model. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Moyo, Faith
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53875 , vital:46022
- Description: Third-party logistics (3PL) providers have continued to be key players in the supply chain network and have witnessed a growth in the usage of information technology. This growth has enhanced the volume of structured and unstructured data that is collected at a high velocity, and is of rich variety, sometimes described as “Big Data”. Leaders in the 3PL industry are constantly seeking to effectively and efficiently mature their abilities to exploit this data to gain business value through data-driven decision-making (DDDM). DDDM helps the leaders to reduce the reliance they place on observations and intuition to make crucial business decisions in a volatile business environment. The aim of this research was to develop a prescriptive model for DDDM in 3PLs. The model consists of iterative elements that prescribe guidelines to decision-makers in the 3PL industry on how to adopt DDDM. A literature review of existing theoretical frameworks and models for DDDM was conducted to determine the extent to which they contribute towards DDDM for 3PLs. The Design-Science Research Methodology (DSRM) was followed to address the aim of the research and applied to pragmatically and iteratively develop and evaluate the artefact (the model for DDDM) in the real-world context of a 3PL. The literature findings revealed that the challenges with DDDM in organisations include three main categories of challenges related to data quality, data management, vision and capabilities. Once the challenges with DDDM were established, a prescriptive model was designed and developed for DDDM in 3PLs. Qualitative data was collected from semi-structured interviews to gain an understanding of the problems and possible solutions in the real-world context of 3PLs. An As-Is Analysis in the real-world case 3PL company confirmed the challenges identified in literature, and that data is still used in the 3PL company for descriptive and diagnostic analytics to aid with the decision-making processes. This highlights that there is still room for maturity into using data for predictive and prescriptive analytics that will, in turn, improve the decision-making process. An improved second version of the model was demonstrated to the participants (the targeted users), who had the opportunity to evaluate the model. The findings revealed that the model provided clear guidelines on how to make data-driven decisions and that the feedback loop and the data culture aspects highlighted in the design were some of the important features of the model. Some improvements were suggested by participants. A field study of three data analytics tools was conducted to identify the advantages and disadvantages of each as well as to highlight the status of DDDM at the real-world case 3PL. The limitations of the second version of the model, together with the recommendations from the participants were used to inform the improved and revised third version of the model. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
Effect of fire severity on Afrotemperate forest tree survival
- Authors: Giddey, Brandon Louis
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55385 , vital:51988
- Description: Weather patterns have changed globally with increased fire danger weather conditions, along with poor management and fire suppression, likely contributing to the increase in prevalence of large wildfires. Ecosystems such as temperate broadleaved forests, where fire is limited by climatic conditions, are particularly at risk of altered fire regimes related to climate change. It is thus important to monitor the effects of fire in these ecosystems. Satellite remote sensing is a cost-effective way to assess spatial variability of fire effects on a landscape scale and has become an increasingly used tool for studying fire severity. In the southern Cape of South Africa during October-November 2018, a large wildfire burnt patches of Southern Cape Afrotemperate Forest (hereafter ‘Afrotemperate forest’). This provided an opportunity to investigate the accuracy of a satellite index for fire severity and the effect of fire on Afrotemperate forest survival. The first objective was to verify through field observations the accuracy of the differenced Normalised Burn Ratio (dNBR) as an index of fire severity derived from Sentinel 2 images in Afrotemperate forest. The second objective was to investigate the effect of fire severity and tree size on the post-fire survival of Afrotemperate forest tree species. For the first objective, stem fire severity, estimated from observed damage to the main stem, was recorded for 1 648 trees in 87 plots and linear regression used to test whether the observed measure of fire severity was related to dNBR. For the second objective, stem fire severity and tree survival 19-24 months post-fire were recorded for 40 species and 1 378 trees in 88 plots. Trees were considered to have survived if they resprouted from the main stem or had green foliage in the canopy. The survival response was assessed in relation to stem fire severity and tree size for all trees collectively and for 10 species (with sample size > 40) individually, using logistic regression. A strong linear relationship between dNBR and stem fire severity (r2 = 0.69, p < 0.001) confirmed the accuracy of dNBR as a measure of fire severity in Afrotemperate forest. In the fire investigated, 4 628 ha of Afrotemperate forest burnt of which 67% burnt at low severity, 21% at medium severity and 12% at high severity. The dNBR values associated with fire severity categories were comparable between Afrotemperate and North American forests, suggesting that dNBR values are relatively standard across forest types. Information on the distribution of fire severity facilitates investigation of further questions regarding past and future fire regimes and the fire ecology of Afrotemperate forest. The post-fire survival rate of Afrotemperate forest trees was 45% which is comparable to that in coniferous forests of North America but lower than that in temperate forests of Australia and Portugal and the neighbouring dune thicket which shares several species with Afrotemperate forest. Fire severity had a significant negative effect on survival and tree size a significant positive effect. Total variance explained by the model (for species collectively) was 40.8%, of which fire severity and tree size combined explained 13.2%, and species as random factor, 27.6%. Respective tree species showed differential survival responses – four species showed high survival (> 60% of individuals), while five species showed low survival (< 40%). This study was the first post-fire assessment of the resprouting ability of Afrotemperate forest trees and a third of the trees surveyed (for species collectively) resprouted from the stem. This suggested that resprouting from the stem is a primary means of post-fire recovery in Afrotemperate forest trees, in contrast with previous assertions that several common canopy species, including Podocarpus latifolius, Afrocarpus falcatus, Scutia myrtina, Scolopia mundii and Rapanea melanophloeos, are unable to resprout. Varying resilience to fire among species supports previous suggestions that fire affects species’ composition and diversity in these forests and calls for careful management of fire regimes in the face of global change. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text: false
- Date Issued: 2022-04
- Authors: Giddey, Brandon Louis
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55385 , vital:51988
- Description: Weather patterns have changed globally with increased fire danger weather conditions, along with poor management and fire suppression, likely contributing to the increase in prevalence of large wildfires. Ecosystems such as temperate broadleaved forests, where fire is limited by climatic conditions, are particularly at risk of altered fire regimes related to climate change. It is thus important to monitor the effects of fire in these ecosystems. Satellite remote sensing is a cost-effective way to assess spatial variability of fire effects on a landscape scale and has become an increasingly used tool for studying fire severity. In the southern Cape of South Africa during October-November 2018, a large wildfire burnt patches of Southern Cape Afrotemperate Forest (hereafter ‘Afrotemperate forest’). This provided an opportunity to investigate the accuracy of a satellite index for fire severity and the effect of fire on Afrotemperate forest survival. The first objective was to verify through field observations the accuracy of the differenced Normalised Burn Ratio (dNBR) as an index of fire severity derived from Sentinel 2 images in Afrotemperate forest. The second objective was to investigate the effect of fire severity and tree size on the post-fire survival of Afrotemperate forest tree species. For the first objective, stem fire severity, estimated from observed damage to the main stem, was recorded for 1 648 trees in 87 plots and linear regression used to test whether the observed measure of fire severity was related to dNBR. For the second objective, stem fire severity and tree survival 19-24 months post-fire were recorded for 40 species and 1 378 trees in 88 plots. Trees were considered to have survived if they resprouted from the main stem or had green foliage in the canopy. The survival response was assessed in relation to stem fire severity and tree size for all trees collectively and for 10 species (with sample size > 40) individually, using logistic regression. A strong linear relationship between dNBR and stem fire severity (r2 = 0.69, p < 0.001) confirmed the accuracy of dNBR as a measure of fire severity in Afrotemperate forest. In the fire investigated, 4 628 ha of Afrotemperate forest burnt of which 67% burnt at low severity, 21% at medium severity and 12% at high severity. The dNBR values associated with fire severity categories were comparable between Afrotemperate and North American forests, suggesting that dNBR values are relatively standard across forest types. Information on the distribution of fire severity facilitates investigation of further questions regarding past and future fire regimes and the fire ecology of Afrotemperate forest. The post-fire survival rate of Afrotemperate forest trees was 45% which is comparable to that in coniferous forests of North America but lower than that in temperate forests of Australia and Portugal and the neighbouring dune thicket which shares several species with Afrotemperate forest. Fire severity had a significant negative effect on survival and tree size a significant positive effect. Total variance explained by the model (for species collectively) was 40.8%, of which fire severity and tree size combined explained 13.2%, and species as random factor, 27.6%. Respective tree species showed differential survival responses – four species showed high survival (> 60% of individuals), while five species showed low survival (< 40%). This study was the first post-fire assessment of the resprouting ability of Afrotemperate forest trees and a third of the trees surveyed (for species collectively) resprouted from the stem. This suggested that resprouting from the stem is a primary means of post-fire recovery in Afrotemperate forest trees, in contrast with previous assertions that several common canopy species, including Podocarpus latifolius, Afrocarpus falcatus, Scutia myrtina, Scolopia mundii and Rapanea melanophloeos, are unable to resprout. Varying resilience to fire among species supports previous suggestions that fire affects species’ composition and diversity in these forests and calls for careful management of fire regimes in the face of global change. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text: false
- Date Issued: 2022-04
The use of ambient seismic noise to investigate internal changes in a tailings storage facility and to image the subsurface geology in the Cradock area of the Eastern Cape
- Authors: Kunjwa, Thulisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53642 , vital:45690
- Description: Passive seismic interferometry is a process by which ambient noise data recorded at different seismic stations can be cross-correlated to estimate Green's functions. In the past, both surface waves and body waves have successfully been extracted by cross-correlation of ambient noise data on both regional and global scales. Recent advancements in ambient seismic noise techniques have the potential to provide new methods for subsurface imaging and monitoring. The ambient noise data processing procedure divides into four principal phases: (1) single station data preparation, (2) cross-correlation and temporal stacking, (3) measurement of dispersion curves and (4) inversion of dispersion curves to obtain 1-D shear wave profiles and computation of 2-D shear wave velocity cross-section. The purpose of this study is to investigate whether ambient seismic noise can be used to image and detect internal changes within a mine tailings dam wall and to image the subsurface geology of part of the Eastern Cape Karoo near Cradock. In the first experiment, the investigation consisted of continuous ambient noise data recordings over a period of 3 days with 20 three-component short period geophones. The geophones were deployed over a survey wall of roughly 100 m in length at the Harmony Gold mine tailings dam in Welkom. In the second experiment, the investigation consisted of data recordings over a period of 35 days. The geophones were deployed in Cradock. The first phase of the data processing procedure included de-trending, de-meaning and band-pass filtering the data. This was done to ensure that any long period trends associated with instrument glitches are removed from the data. A spectrogram was then computed to view the spectrum of frequencies in the signal and to check if the filter that was designed was able to cut off the unwanted frequencies. The horizontal and vertical components of the ambient noise data were cross-correlated and picked between sensor pairs to create surface wave dispersion curves. Subsequently, the dispersion curves were inverted to estimate the shear wave velocity of the dam wall and subsurface as a function of depth. The computed cross sections of shear wave velocity indicated a low-velocity zone between 2 and 10 m below the surface on the dam wall, this suggested that the phreatic surface is much closer to surface in this area. In the second experiment, the interpolated shear wave velocity profiles indicated that there is a layer of low velocity zone between depths 250 to 300 m below the surface. The cross-correlations were also used to compute group velocity maps from periods 1.5 seconds to 30 seconds. The group velocity maps showed various high and low velocity anomalies. The high velocity zones observed on the eastern section of the map were interpreted as evidence of dolerite intrusions. The low velocity zones observed in the western and southern sections of the map interpreted as Karoo sediments that belong to the Adelaide Subgroup which is dominated by mudstones. , Thesis (MSc) -- Faculty of Science, Department of Geosciences (Geology and Geography), 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Kunjwa, Thulisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53642 , vital:45690
- Description: Passive seismic interferometry is a process by which ambient noise data recorded at different seismic stations can be cross-correlated to estimate Green's functions. In the past, both surface waves and body waves have successfully been extracted by cross-correlation of ambient noise data on both regional and global scales. Recent advancements in ambient seismic noise techniques have the potential to provide new methods for subsurface imaging and monitoring. The ambient noise data processing procedure divides into four principal phases: (1) single station data preparation, (2) cross-correlation and temporal stacking, (3) measurement of dispersion curves and (4) inversion of dispersion curves to obtain 1-D shear wave profiles and computation of 2-D shear wave velocity cross-section. The purpose of this study is to investigate whether ambient seismic noise can be used to image and detect internal changes within a mine tailings dam wall and to image the subsurface geology of part of the Eastern Cape Karoo near Cradock. In the first experiment, the investigation consisted of continuous ambient noise data recordings over a period of 3 days with 20 three-component short period geophones. The geophones were deployed over a survey wall of roughly 100 m in length at the Harmony Gold mine tailings dam in Welkom. In the second experiment, the investigation consisted of data recordings over a period of 35 days. The geophones were deployed in Cradock. The first phase of the data processing procedure included de-trending, de-meaning and band-pass filtering the data. This was done to ensure that any long period trends associated with instrument glitches are removed from the data. A spectrogram was then computed to view the spectrum of frequencies in the signal and to check if the filter that was designed was able to cut off the unwanted frequencies. The horizontal and vertical components of the ambient noise data were cross-correlated and picked between sensor pairs to create surface wave dispersion curves. Subsequently, the dispersion curves were inverted to estimate the shear wave velocity of the dam wall and subsurface as a function of depth. The computed cross sections of shear wave velocity indicated a low-velocity zone between 2 and 10 m below the surface on the dam wall, this suggested that the phreatic surface is much closer to surface in this area. In the second experiment, the interpolated shear wave velocity profiles indicated that there is a layer of low velocity zone between depths 250 to 300 m below the surface. The cross-correlations were also used to compute group velocity maps from periods 1.5 seconds to 30 seconds. The group velocity maps showed various high and low velocity anomalies. The high velocity zones observed on the eastern section of the map were interpreted as evidence of dolerite intrusions. The low velocity zones observed in the western and southern sections of the map interpreted as Karoo sediments that belong to the Adelaide Subgroup which is dominated by mudstones. , Thesis (MSc) -- Faculty of Science, Department of Geosciences (Geology and Geography), 2021
- Full Text:
- Date Issued: 2021-12
The use of psychometric test systems as a pre-selection tool for identifying successful harvesting machine operators
- Authors: Schwegman, Kylle
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55246 , vital:51102
- Description: A shift towards fully mechanized forest activities, such as harvesting and, more recently, silviculture, has occurred from the early 2 000’s. The reason for mechanizing these activities differs for each country, although for most countries there is concern relating to the health and safety of forest workers. With mechanization in harvesting, the forest worker has moved away from the physical intensity of having to fell, debranch, debark and cross-cut trees into logs using either an axe or chainsaw, to operating a machine. Studies revolving around the human element (operator) have been conducted specifically relating to the ergonomics of the machines and how operators may influence machine productivity. Results showed that due to the repetitive nature of the work, the operators are exposed to associated stresses for longer periods. Typical injuries associated to these kinds of stressors are whole body vibrations (WBVs), repetitive hand and arm movements, non-neutral body postures and manual lifting, which lead to musculoskeletal symptoms in the lower back, neck and shoulders. However, as machine technology improves so does the ergonomic conditions which are experienced by machine operators. Machine productivity can be influenced by various factors, with the most influential being tree volume. However, a recent study showed that over 40% of variation in machine productivity has been observed amongst different machine operators operating similar machines. The specific reason for these differences has yet to be determined. However, decision making, motivation, planning capacity, concentration, memory, motor coordination, pattern recognition, logic reasoning, and spatial perception are abilities that have been described as important for successful harvesting work. The pre-selection of operators using psychometric and cognitive tests is not new to forestry, although very little information is available relating to the aptitude test known as the Vienna test system as well as the best possible demographic associated with successful harvesting operators. The overall aim of this study was to determine whether the high variation found amongst harvesting machine operators could be reduced initially through a preselection process which involves the use of aptitude tests (Vienna Test System) and demographic questionnaires. A study was implemented in Zululand, South Africa, testing whether there were significant productivity differences between nine machine operators. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Schwegman, Kylle
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55246 , vital:51102
- Description: A shift towards fully mechanized forest activities, such as harvesting and, more recently, silviculture, has occurred from the early 2 000’s. The reason for mechanizing these activities differs for each country, although for most countries there is concern relating to the health and safety of forest workers. With mechanization in harvesting, the forest worker has moved away from the physical intensity of having to fell, debranch, debark and cross-cut trees into logs using either an axe or chainsaw, to operating a machine. Studies revolving around the human element (operator) have been conducted specifically relating to the ergonomics of the machines and how operators may influence machine productivity. Results showed that due to the repetitive nature of the work, the operators are exposed to associated stresses for longer periods. Typical injuries associated to these kinds of stressors are whole body vibrations (WBVs), repetitive hand and arm movements, non-neutral body postures and manual lifting, which lead to musculoskeletal symptoms in the lower back, neck and shoulders. However, as machine technology improves so does the ergonomic conditions which are experienced by machine operators. Machine productivity can be influenced by various factors, with the most influential being tree volume. However, a recent study showed that over 40% of variation in machine productivity has been observed amongst different machine operators operating similar machines. The specific reason for these differences has yet to be determined. However, decision making, motivation, planning capacity, concentration, memory, motor coordination, pattern recognition, logic reasoning, and spatial perception are abilities that have been described as important for successful harvesting work. The pre-selection of operators using psychometric and cognitive tests is not new to forestry, although very little information is available relating to the aptitude test known as the Vienna test system as well as the best possible demographic associated with successful harvesting operators. The overall aim of this study was to determine whether the high variation found amongst harvesting machine operators could be reduced initially through a preselection process which involves the use of aptitude tests (Vienna Test System) and demographic questionnaires. A study was implemented in Zululand, South Africa, testing whether there were significant productivity differences between nine machine operators. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-04
In-vitroevaluation of bridelia ferruginea extract gold nanoparticles for the treatment of colon cancer
- Zosela, Itumeleng, Davids, Hajierah
- Authors: Zosela, Itumeleng , Davids, Hajierah
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54124 , vital:46311
- Description: Colorectal cancer (CRC) has become a health burden, being the third common cancer worldwide. Treatment of colorectal cancer is very important to manage the high prevalence rate of this disease. The available treatments for CRC have their drawbacks and side effects. Available treatments of colon cancer include surgery, chemotherapy, and radiation. Due to the side effects associated with these treatments, alternative treatments that pose less side effects are being developed worldwide. Nanotechnologies have gained global consideration due to their potential to improve the current standards and techniques for the diagnosis and treatment. The use of plants for synthesis of gold nanoparticles has opened a new venture of synthesizing environmentally friendly and cost-effective nanoparticles which possess great properties for CRC treatment. The aim of this study was to investigate the use of green synthesized AuNPs from Bridelia ferruginea for potential cancer treatment. In this work study gold nanoparticles were synthesized utilizing Bridelia ferruginea stem bark extract. The nanoparticles were characterized using UV–Vis spectroscopy, Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR) and High-Resolution Transmission Electron Microscopy (HRTEM). The in vitroanti cancer activity of the AuNPs was investigated using Presto Blue assay, cellular morphology, caspase 3/7 assay on the human colon cancer cell line at different times to assess the optimum time for cell death. The cellular uptake and localization of AuNPs was investigated using HRTEM to assess uptake and location of the AuNPs within the cell. Results obtained from this study showed that the AuNP synthesis from Bridellia ferrugenia was successful. The Presto Blue cell viability results showed that the AuNPs reduced cell viability (%) significantly (p<0.05) after 24 h. The optimum treatment time of HT-29 cells with AuNPs was determined to be 24 h. The apoptotic effects of the AuNPs were assessed using Cell Event reagent, and the results from this assay indicated that caspase 3/7 was activated with treatment with AuNPs which induced cell death via apoptosis. The HRTEM results indicated that there was no uptake of AuNP targeting in HT-29 therefore localization could not be determined. It can be concluded that the AuNPs synthesized from Bridellia ferrugenia have anti-cancer properties and are able to induce cell death through apoptosis. Furthermore, this study revealed that optimization of the AuNPs for cellular uptake is needed to further understand the interaction between the nanoparticles and the cells. This will provide more insight on how cellular death is induced by the nanoparticles. , Thesis (MSc) -- Faculty of Science, Department of Biochemistry and Microbiology (including Physiology), 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Zosela, Itumeleng , Davids, Hajierah
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54124 , vital:46311
- Description: Colorectal cancer (CRC) has become a health burden, being the third common cancer worldwide. Treatment of colorectal cancer is very important to manage the high prevalence rate of this disease. The available treatments for CRC have their drawbacks and side effects. Available treatments of colon cancer include surgery, chemotherapy, and radiation. Due to the side effects associated with these treatments, alternative treatments that pose less side effects are being developed worldwide. Nanotechnologies have gained global consideration due to their potential to improve the current standards and techniques for the diagnosis and treatment. The use of plants for synthesis of gold nanoparticles has opened a new venture of synthesizing environmentally friendly and cost-effective nanoparticles which possess great properties for CRC treatment. The aim of this study was to investigate the use of green synthesized AuNPs from Bridelia ferruginea for potential cancer treatment. In this work study gold nanoparticles were synthesized utilizing Bridelia ferruginea stem bark extract. The nanoparticles were characterized using UV–Vis spectroscopy, Dynamic Light Scattering (DLS), Fourier Transform Infrared Spectroscopy (FTIR) and High-Resolution Transmission Electron Microscopy (HRTEM). The in vitroanti cancer activity of the AuNPs was investigated using Presto Blue assay, cellular morphology, caspase 3/7 assay on the human colon cancer cell line at different times to assess the optimum time for cell death. The cellular uptake and localization of AuNPs was investigated using HRTEM to assess uptake and location of the AuNPs within the cell. Results obtained from this study showed that the AuNP synthesis from Bridellia ferrugenia was successful. The Presto Blue cell viability results showed that the AuNPs reduced cell viability (%) significantly (p<0.05) after 24 h. The optimum treatment time of HT-29 cells with AuNPs was determined to be 24 h. The apoptotic effects of the AuNPs were assessed using Cell Event reagent, and the results from this assay indicated that caspase 3/7 was activated with treatment with AuNPs which induced cell death via apoptosis. The HRTEM results indicated that there was no uptake of AuNP targeting in HT-29 therefore localization could not be determined. It can be concluded that the AuNPs synthesized from Bridellia ferrugenia have anti-cancer properties and are able to induce cell death through apoptosis. Furthermore, this study revealed that optimization of the AuNPs for cellular uptake is needed to further understand the interaction between the nanoparticles and the cells. This will provide more insight on how cellular death is induced by the nanoparticles. , Thesis (MSc) -- Faculty of Science, Department of Biochemistry and Microbiology (including Physiology), 2021
- Full Text:
- Date Issued: 2021-12