Molecularly imprinted polymeric materials for adsorptive removal of nitrogen compounds from fuel oils
- Abdul-Quadir, Muhammad Sabiu
- Authors: Abdul-Quadir, Muhammad Sabiu
- Date: 2018
- Subjects: Polymerization , Organonitrogen compounds Nitrogen compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23426 , vital:30542
- Description: The deleterious effects of refractory polyaromatic hydrocarbons found in fuels such as organonitrogen compounds (quinoline, carbazole and its alkylated derivatives) are such that they emit NOx to the environment when combusted, thereby reducing air quality. These compounds also deactivate the catalyst used during fuel refinement and in catalytic converters of cars. Hydro-denitrogenation (HDN), a process currently being employed in petroleum refineries to eliminate organonitrogen compounds in fuels, is limited in treating these refractory compounds. Hence, this thesis describes the use of two separate complimentary approaches for the removal of organonitrogen compounds in fuel such as oxidative denitrogenation and adsorptive denitrogenation. The catalyzed oxidation of fuel oil model nitrogen containing compound, quinoline to quinoline N-oxide, was conducted under batch and continuous flow microreactor at 70°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant and silica supported V2O5 as catalyst, followed by the selective adsorption of the quinoline N-oxide. An overall conversion of 62% quinoline N-oxide was observed. Quinoline-N-oxide in model fuel was absorbed by employing synthesized molecularly imprinted 2,6-pyridine-polybenzimidazole (2,6-PyPBI) nanofibers, 86% of quinoline-N-oxide was removed to give an adsorption capacity (qe) of 4.8 mg/g. DFT calculations to study the interactions of quinoline-N-oxide vs 2,6-PyPBI indicated that: (i) hydrogen bonding (through amino group of 2,6-PyPBI and oxygen atoms of the quinoline-N-oxide), (ii) pi-pi stacking and (iii) extensive number of van der Waals interactions took place. Several oxygenates from N-compounds were produced, thus, complicating the fuel matrix. Therefore, there is a need to move towards adsorptive denitrogenation. Poly-2-(1H-imidazol-2-yl)-4-phenol (PIMH) imprinted microspheres was prepared by suspension polymerization using 2-(2’-hydroxy-4-ethenylphenyl) imidazole as a functional monomer and ethylene glycol dimethacrylate as a crosslinker in the presence of various organonitrogen compounds (templates) to produce 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH). Imprinted microspheres show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 6.8 ± 0.2 mg/g, 6.3 ± 0.3 mg/g and 5.8 ± 0.3 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of quinoline (αi-r = 136.9) ˃ pyrimidine (αi-r = 126.2) ˃carbazole (αi-r = 86.3), when naphthalene was selected as a reference compound. Though, imprinted microspheres displayed excellent nitrogen compound removal both in model and real fuel, there was a need to improve the adsorbent adsorption capacity for N-compounds in fuel through the fabrication of imprinted nanofibers. Molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol nanofibers was prepared by electrospinning of 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH) in the presence of various organonitrogen compounds. These imprinted nanofibers show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 11.7 ± 0.9 mg/g, 11.9 ± 0.8 mg/g and 11.3 ± 1.1 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 258.8) ˃ quinoline (αi-r = 235.5) ˃ carbazole (αi-r = 168.2). It further displayed excellent nitrogen removal in real fuel. The use of polybenzimidazole (PBI) nanofibers showed selective adsorption of organonitrogen compounds as imprinted sorbent also displayed high selectivity for their target model nitrogen-containing compounds with adsorption capacities of 11.4 ± 0.4 mg/g, 11.9 ± 0.2 mg/g and 10.9 ± 0.7 mg/g for quinoline, pyrimidine and carbazole respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 241.5) ˃ quinoline (αi-r = 237.6) ˃ carbazole (αi-r = 170). Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) revealed that quinoline-PIMH/PBI and pyrimidine-PIMH/PBI interactions are exothermic in nature, while carbazole-PIMH/PBI is endothermic in nature. DFT calculations indicated that π-π interactions/stacking and hydrogen bond interactions took place between N-compounds (carbazole, quinoline and pyrimidine) and adsorbent (PIMH and PBI). A significant reduction in the quantity of nitrogen containing compounds in hydrotreated fuel was observed (peak area reduction) when adsorbents (PIMH and PBI) was employed, however, the complex nature of organonitrogen compounds in fuel complicate the structure/function approach on MIPs for targeting these unwanted compounds.
- Full Text:
- Date Issued: 2018
- Authors: Abdul-Quadir, Muhammad Sabiu
- Date: 2018
- Subjects: Polymerization , Organonitrogen compounds Nitrogen compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23426 , vital:30542
- Description: The deleterious effects of refractory polyaromatic hydrocarbons found in fuels such as organonitrogen compounds (quinoline, carbazole and its alkylated derivatives) are such that they emit NOx to the environment when combusted, thereby reducing air quality. These compounds also deactivate the catalyst used during fuel refinement and in catalytic converters of cars. Hydro-denitrogenation (HDN), a process currently being employed in petroleum refineries to eliminate organonitrogen compounds in fuels, is limited in treating these refractory compounds. Hence, this thesis describes the use of two separate complimentary approaches for the removal of organonitrogen compounds in fuel such as oxidative denitrogenation and adsorptive denitrogenation. The catalyzed oxidation of fuel oil model nitrogen containing compound, quinoline to quinoline N-oxide, was conducted under batch and continuous flow microreactor at 70°C by using tert-butylhydroperoxide (t-BuOOH) as oxidant and silica supported V2O5 as catalyst, followed by the selective adsorption of the quinoline N-oxide. An overall conversion of 62% quinoline N-oxide was observed. Quinoline-N-oxide in model fuel was absorbed by employing synthesized molecularly imprinted 2,6-pyridine-polybenzimidazole (2,6-PyPBI) nanofibers, 86% of quinoline-N-oxide was removed to give an adsorption capacity (qe) of 4.8 mg/g. DFT calculations to study the interactions of quinoline-N-oxide vs 2,6-PyPBI indicated that: (i) hydrogen bonding (through amino group of 2,6-PyPBI and oxygen atoms of the quinoline-N-oxide), (ii) pi-pi stacking and (iii) extensive number of van der Waals interactions took place. Several oxygenates from N-compounds were produced, thus, complicating the fuel matrix. Therefore, there is a need to move towards adsorptive denitrogenation. Poly-2-(1H-imidazol-2-yl)-4-phenol (PIMH) imprinted microspheres was prepared by suspension polymerization using 2-(2’-hydroxy-4-ethenylphenyl) imidazole as a functional monomer and ethylene glycol dimethacrylate as a crosslinker in the presence of various organonitrogen compounds (templates) to produce 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH). Imprinted microspheres show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 6.8 ± 0.2 mg/g, 6.3 ± 0.3 mg/g and 5.8 ± 0.3 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of quinoline (αi-r = 136.9) ˃ pyrimidine (αi-r = 126.2) ˃carbazole (αi-r = 86.3), when naphthalene was selected as a reference compound. Though, imprinted microspheres displayed excellent nitrogen compound removal both in model and real fuel, there was a need to improve the adsorbent adsorption capacity for N-compounds in fuel through the fabrication of imprinted nanofibers. Molecularly imprinted poly-2-(1H-imidazol-2-yl)-4-phenol nanofibers was prepared by electrospinning of 2-(2’-hydroxy-4-ethenylphenyl) imidazole (PIMH) in the presence of various organonitrogen compounds. These imprinted nanofibers show selectivity for various target model nitrogen-containing compounds with adsorption capacities of 11.7 ± 0.9 mg/g, 11.9 ± 0.8 mg/g and 11.3 ± 1.1 mg/g for quinoline, pyrimidine and carbazole, respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 258.8) ˃ quinoline (αi-r = 235.5) ˃ carbazole (αi-r = 168.2). It further displayed excellent nitrogen removal in real fuel. The use of polybenzimidazole (PBI) nanofibers showed selective adsorption of organonitrogen compounds as imprinted sorbent also displayed high selectivity for their target model nitrogen-containing compounds with adsorption capacities of 11.4 ± 0.4 mg/g, 11.9 ± 0.2 mg/g and 10.9 ± 0.7 mg/g for quinoline, pyrimidine and carbazole respectively. Adsorption selectivity increased in the order of pyrimidine (αi-r = 241.5) ˃ quinoline (αi-r = 237.6) ˃ carbazole (αi-r = 170). Thermodynamic parameters obtained from isothermal titration calorimetry (ITC) revealed that quinoline-PIMH/PBI and pyrimidine-PIMH/PBI interactions are exothermic in nature, while carbazole-PIMH/PBI is endothermic in nature. DFT calculations indicated that π-π interactions/stacking and hydrogen bond interactions took place between N-compounds (carbazole, quinoline and pyrimidine) and adsorbent (PIMH and PBI). A significant reduction in the quantity of nitrogen containing compounds in hydrotreated fuel was observed (peak area reduction) when adsorbents (PIMH and PBI) was employed, however, the complex nature of organonitrogen compounds in fuel complicate the structure/function approach on MIPs for targeting these unwanted compounds.
- Full Text:
- Date Issued: 2018
Investigating long-term host-parasite dynamics in odontocetes in Southern Africa
- Authors: Adams, Inge Alison
- Date: 2018
- Subjects: Biological invasions -- Environmental aspects , Cetacea -- Indian Ocean , Ecological disturbances
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23437 , vital:30543
- Description: Cetaceans are a very diverse family and globally, various aspects about their biology have been studied, including infection by parasites. Twenty-five dolphin species can be found in the South African subregion and very little information is available detailing which parasites are infecting them. Parasite samples have been collected opportunistically since the 1970’s from dolphins incidentally caught in shark nets off the KwaZulu-Natal coastline as well as from dolphins stranded along the Eastern Cape coastline. These samples have been stored in the Graham Ross Marine Mammal Collection at the Port Elizabeth Museum and samples belonging to eight odontocete species have been used in the present analysis. These eight species are: the Indian Ocean Humpback Dolphin (Sousa plumbea), the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus), the Long-beaked Common Dolphin (Delphinus capensis), the Risso’s Dolphin (Grampus griseus), the Pantropical Spotted Dolphin (Stenella attenuata), the Striped Dolphin (Stenella coeruleoalba), the Pygmy Sperm Whale (Kogia breviceps) and the Dwarf Sperm Whale (Kogia breviceps). This study aims to investigate which parasites are infecting odontocetes in Southern Africa. Secondly, this study aims to investigate whether any trends in infection exist between sexes, age groups, cause of death and over time. Eighteen parasite species were found to infect odontocetes in Southern Africa. Two could only be identified to family level, seven to genus level and eight to species level. Only one parasite, a trematode, could not be identified and several parasite species were new host records for the subregion. Results showed that the prevalence of parasitic infection has increased over the last four decades, prompting questions regarding the health of our oceans. This study is the first to comprehensively investigate which parasite species are found in these eight odontocete species in Southern Africa. This baseline data will contribute greatly to other types of research involving parasites and provides us with information regarding the health of our ocean.
- Full Text:
- Date Issued: 2018
- Authors: Adams, Inge Alison
- Date: 2018
- Subjects: Biological invasions -- Environmental aspects , Cetacea -- Indian Ocean , Ecological disturbances
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23437 , vital:30543
- Description: Cetaceans are a very diverse family and globally, various aspects about their biology have been studied, including infection by parasites. Twenty-five dolphin species can be found in the South African subregion and very little information is available detailing which parasites are infecting them. Parasite samples have been collected opportunistically since the 1970’s from dolphins incidentally caught in shark nets off the KwaZulu-Natal coastline as well as from dolphins stranded along the Eastern Cape coastline. These samples have been stored in the Graham Ross Marine Mammal Collection at the Port Elizabeth Museum and samples belonging to eight odontocete species have been used in the present analysis. These eight species are: the Indian Ocean Humpback Dolphin (Sousa plumbea), the Indo-Pacific Bottlenose Dolphin (Tursiops aduncus), the Long-beaked Common Dolphin (Delphinus capensis), the Risso’s Dolphin (Grampus griseus), the Pantropical Spotted Dolphin (Stenella attenuata), the Striped Dolphin (Stenella coeruleoalba), the Pygmy Sperm Whale (Kogia breviceps) and the Dwarf Sperm Whale (Kogia breviceps). This study aims to investigate which parasites are infecting odontocetes in Southern Africa. Secondly, this study aims to investigate whether any trends in infection exist between sexes, age groups, cause of death and over time. Eighteen parasite species were found to infect odontocetes in Southern Africa. Two could only be identified to family level, seven to genus level and eight to species level. Only one parasite, a trematode, could not be identified and several parasite species were new host records for the subregion. Results showed that the prevalence of parasitic infection has increased over the last four decades, prompting questions regarding the health of our oceans. This study is the first to comprehensively investigate which parasite species are found in these eight odontocete species in Southern Africa. This baseline data will contribute greatly to other types of research involving parasites and provides us with information regarding the health of our ocean.
- Full Text:
- Date Issued: 2018
In vivo toxicological evaluation of peptide conjugated gold nanoparticles for potential application in colorectal cancer diagnosis
- Authors: Adewale, Olusola Bolaji
- Date: 2018
- Subjects: Nanostructured materials -- Toxicology , Colon (Anatomy) -- Cancer Rectum -- Cancer
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50133 , vital:42050
- Description: Colorectal cancer (CRC) is among the leading cause of cancer-related deaths in South Africa and worldwide. Efforts are being made at finding improved diagnostic tools, as early detection (before metastasis) is a major factor in CRC treatment. Colonoscopy is the most reliable detection method, but is a specialised and expensive procedure, which is invasive, not readily available and not patient-friendly. There is a risk of developing interval cancers, as colonoscopies are performed every 10 years after the age of 40. The development of non-invasive, cost efficient and readily available diagnostic tools to CRC, which can be performed at more regular intervals, using tumour-targeting molecular imaging agents, is of urgent attention. Gold nanoparticles (AuNPs) possess several physicochemical properties, including ease of synthesis, biocompatibility, and the ability to be conjugated by ligands or biomolecules such as polyethylene glycol (PEG) and peptides for improved stability, tissue targeting and selectivity. These factors potentiate the role in biomedical applications, including cancer theranostics. Conjugation of AuNPs with a targeting molecule (e.g. antibody or peptide) is directed against cancer cell receptors. The peptides, p.C, p.L, and p.14, bind to CRC cells in vitro. Conjugation of AuNPs with these peptides should be investigated for CRC diagnosis in vivo, as it is hypothesised to allow examinations at shorter intervals through imaging techniques. This could reduce the risk of interval cancers, but before developing this novel tool, in vivo toxicity evaluations are essential. This study was therefore aimed at investigating the short- and long-term toxicological effects of a single intravenous injection of peptides (p.C, p.L, and p.14) conjugated to AuNPs in a healthy rat model. Citrate-capped AuNPs were synthesised by the citrate-reduction method, and conjugated with each peptide (biotinylated) using a combination of PEG (99% PEG-OH and 1% PEG-biotin) as a stabilising agent and linker, via biotin-streptavidin interaction. Healthy male Wistar rats were intravenously injected with 14 nm citrate-AuNPs, PEG-, p.C-PEG, p.L-PEG, and p.14-PEG-AuNPs (100 μg/kg body weight), and the control rats were injected with phosphate buffered saline. The animals were monitored for behavioural, physiological, biochemical, haematological and histological changes, as well as inflammatory responses. Phase 1 rats were sacrificed 2 weeks post-injection to determine the immediate or acute toxicity of the AuNPs, while phase 2 animals were sacrificed 12 weeks post-injection, to investigate the delayed or persistence toxicity of the AuNPs. Results revealed no significant toxicities with the citrate, PEG-, p.C-PEG and p.14-PEG-AuNPs over 12 weeks post-exposure, as evidenced by biochemical assays such as serum marker enzymes, liver and kidney function markers, and cholestatic indicators; haematological parameters; oxidative stress markers; and histopathological examinations. P.L-PEG-AuNPs, however, caused significant toxicity (p<0.05) to rats, as evidenced by increased relative liver weight, increased malondialdehyde levels, and total white blood cell counts 2 weeks post-exposure when compared to the control group. This was, however, reversed during the 12 weeks post-exposure. Further, there were no evidence of inflammatory responses, using pro-inflammatory markers including phospho interleukin 18 (IL-18) and interferon-γ (IFN-γ), as indicated by immunohistochemical staining of the liver, spleen, kidney and colon of rats 2 weeks post-injection of AuNPs. Citrate, PEG-, p.C-PEG, and p.14-PEG-AuNPs did not induce immediate, acute or persistent toxicity, while p.L-PEG-AuNPs induced a transient acute toxicity. It can be concluded that 14 nm spherical citrate-AuNPs at 100 μg/kg body weight is a good candidate for biomedical applications, and as a suitable carrier for diagnostic and/or therapeutic molecules. Combination of 99% PEG-OH and 1% PEG-biotin is an appropriate option for stabilising AuNPs in biological environment, and conjugating secondary diagnostic or therapeutic biomolecules or agents to citrate-capped AuNPs. Peptide-conjugated AuNPs are suitable for the development into a diagnostic tool for CRC in vivo.
- Full Text:
- Date Issued: 2018
- Authors: Adewale, Olusola Bolaji
- Date: 2018
- Subjects: Nanostructured materials -- Toxicology , Colon (Anatomy) -- Cancer Rectum -- Cancer
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/50133 , vital:42050
- Description: Colorectal cancer (CRC) is among the leading cause of cancer-related deaths in South Africa and worldwide. Efforts are being made at finding improved diagnostic tools, as early detection (before metastasis) is a major factor in CRC treatment. Colonoscopy is the most reliable detection method, but is a specialised and expensive procedure, which is invasive, not readily available and not patient-friendly. There is a risk of developing interval cancers, as colonoscopies are performed every 10 years after the age of 40. The development of non-invasive, cost efficient and readily available diagnostic tools to CRC, which can be performed at more regular intervals, using tumour-targeting molecular imaging agents, is of urgent attention. Gold nanoparticles (AuNPs) possess several physicochemical properties, including ease of synthesis, biocompatibility, and the ability to be conjugated by ligands or biomolecules such as polyethylene glycol (PEG) and peptides for improved stability, tissue targeting and selectivity. These factors potentiate the role in biomedical applications, including cancer theranostics. Conjugation of AuNPs with a targeting molecule (e.g. antibody or peptide) is directed against cancer cell receptors. The peptides, p.C, p.L, and p.14, bind to CRC cells in vitro. Conjugation of AuNPs with these peptides should be investigated for CRC diagnosis in vivo, as it is hypothesised to allow examinations at shorter intervals through imaging techniques. This could reduce the risk of interval cancers, but before developing this novel tool, in vivo toxicity evaluations are essential. This study was therefore aimed at investigating the short- and long-term toxicological effects of a single intravenous injection of peptides (p.C, p.L, and p.14) conjugated to AuNPs in a healthy rat model. Citrate-capped AuNPs were synthesised by the citrate-reduction method, and conjugated with each peptide (biotinylated) using a combination of PEG (99% PEG-OH and 1% PEG-biotin) as a stabilising agent and linker, via biotin-streptavidin interaction. Healthy male Wistar rats were intravenously injected with 14 nm citrate-AuNPs, PEG-, p.C-PEG, p.L-PEG, and p.14-PEG-AuNPs (100 μg/kg body weight), and the control rats were injected with phosphate buffered saline. The animals were monitored for behavioural, physiological, biochemical, haematological and histological changes, as well as inflammatory responses. Phase 1 rats were sacrificed 2 weeks post-injection to determine the immediate or acute toxicity of the AuNPs, while phase 2 animals were sacrificed 12 weeks post-injection, to investigate the delayed or persistence toxicity of the AuNPs. Results revealed no significant toxicities with the citrate, PEG-, p.C-PEG and p.14-PEG-AuNPs over 12 weeks post-exposure, as evidenced by biochemical assays such as serum marker enzymes, liver and kidney function markers, and cholestatic indicators; haematological parameters; oxidative stress markers; and histopathological examinations. P.L-PEG-AuNPs, however, caused significant toxicity (p<0.05) to rats, as evidenced by increased relative liver weight, increased malondialdehyde levels, and total white blood cell counts 2 weeks post-exposure when compared to the control group. This was, however, reversed during the 12 weeks post-exposure. Further, there were no evidence of inflammatory responses, using pro-inflammatory markers including phospho interleukin 18 (IL-18) and interferon-γ (IFN-γ), as indicated by immunohistochemical staining of the liver, spleen, kidney and colon of rats 2 weeks post-injection of AuNPs. Citrate, PEG-, p.C-PEG, and p.14-PEG-AuNPs did not induce immediate, acute or persistent toxicity, while p.L-PEG-AuNPs induced a transient acute toxicity. It can be concluded that 14 nm spherical citrate-AuNPs at 100 μg/kg body weight is a good candidate for biomedical applications, and as a suitable carrier for diagnostic and/or therapeutic molecules. Combination of 99% PEG-OH and 1% PEG-biotin is an appropriate option for stabilising AuNPs in biological environment, and conjugating secondary diagnostic or therapeutic biomolecules or agents to citrate-capped AuNPs. Peptide-conjugated AuNPs are suitable for the development into a diagnostic tool for CRC in vivo.
- Full Text:
- Date Issued: 2018
Potential use of carbon nanotubes as a nanofiller for natural rubber latex condoms
- Authors: Agbakoba, Victor Chike
- Date: 2018
- Subjects: Nanotubes , Rubber chemistry Nanocomposites (Materials) Nanostructured materials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23393 , vital:30538
- Description: The recent advancement in the field of nano-technology has raised much interest in the area of natural rubber latex (NRL) processing. This interest stems from the exceptional properties of nano-material and the promising results obtained by several researchers. Studies have shown that very low loadings of inorganic nanomaterials such as carbon nanotube (CNT) in NRL matrix leads to enhanced tensile strength, tensile modulus, tear resistance and aberration resistance. Thus providing a great prospect for reinforcement of thin film NRL articles such as condom. In this research, prevulcanised natural rubber latex (PvNRL) composite blends containing single walled carbon nanotubes (SWCNTs) were prepared via direct mixing. A progressive discolouration of PvNRL was observed with increased loadings of CNTs. Thermal analysis revealed faster drying rates for the composite blends containing SWCNT. Results from equilibrium swelling experiments also suggested a slight increase in crosslink density in the presence of SWCNT. There was a significant influence on flow behaviour of PvNRL as a result of varying loadings of SWCNT suspension. This was reflected as a change in pseudoplasticity and apparent viscosity. For Instance, apparent viscosity at a shear rate of 1 s-1 at 25°C for PvNRL with ~0.08% SWCNT was 2.5 Pa.s, compared to 0.49 Pa.s for the blends with 0.02% SWCNT. Condoms were moulded via the straight dipping technique using custom made glass formers. A series of dilutions was performed to correct the viscosity differences. This also ensured good consistency and promoted uniform deposition of PvNRL on the glass former. The average dimensions of the condoms produced in terms of length and width were ~191.17 ± 5.17 mm and 52.67 ± 5.17 mm respectively. Thickness measurement varied slightly according to the method of determination. The water leakage test suggested the absence of holes in the condoms produced. However, results from electrical leakage test contradicted those from water leak test. The results from infrared spectroscopy (FTIR) did not confirm the presence of chemical interactions between the SWCNT and PvNRL matrix. Glass transition temperature (Tg) was also unaffected across the blends. The stiffness (or modulus) was unaffected in all the condoms, as revealed by results from indentation hardness analysis. The SWCNT showed no significant influence on thermal decomposition temperatures of the condoms. Nonetheless, images from optical microscopy revealed increased surface roughness corresponding to higher loadings of SWCNT. Results from stress relaxation studies revealed improved retention of modulus under constant strain for condom samples containing SWCNT.
- Full Text:
- Date Issued: 2018
- Authors: Agbakoba, Victor Chike
- Date: 2018
- Subjects: Nanotubes , Rubber chemistry Nanocomposites (Materials) Nanostructured materials
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23393 , vital:30538
- Description: The recent advancement in the field of nano-technology has raised much interest in the area of natural rubber latex (NRL) processing. This interest stems from the exceptional properties of nano-material and the promising results obtained by several researchers. Studies have shown that very low loadings of inorganic nanomaterials such as carbon nanotube (CNT) in NRL matrix leads to enhanced tensile strength, tensile modulus, tear resistance and aberration resistance. Thus providing a great prospect for reinforcement of thin film NRL articles such as condom. In this research, prevulcanised natural rubber latex (PvNRL) composite blends containing single walled carbon nanotubes (SWCNTs) were prepared via direct mixing. A progressive discolouration of PvNRL was observed with increased loadings of CNTs. Thermal analysis revealed faster drying rates for the composite blends containing SWCNT. Results from equilibrium swelling experiments also suggested a slight increase in crosslink density in the presence of SWCNT. There was a significant influence on flow behaviour of PvNRL as a result of varying loadings of SWCNT suspension. This was reflected as a change in pseudoplasticity and apparent viscosity. For Instance, apparent viscosity at a shear rate of 1 s-1 at 25°C for PvNRL with ~0.08% SWCNT was 2.5 Pa.s, compared to 0.49 Pa.s for the blends with 0.02% SWCNT. Condoms were moulded via the straight dipping technique using custom made glass formers. A series of dilutions was performed to correct the viscosity differences. This also ensured good consistency and promoted uniform deposition of PvNRL on the glass former. The average dimensions of the condoms produced in terms of length and width were ~191.17 ± 5.17 mm and 52.67 ± 5.17 mm respectively. Thickness measurement varied slightly according to the method of determination. The water leakage test suggested the absence of holes in the condoms produced. However, results from electrical leakage test contradicted those from water leak test. The results from infrared spectroscopy (FTIR) did not confirm the presence of chemical interactions between the SWCNT and PvNRL matrix. Glass transition temperature (Tg) was also unaffected across the blends. The stiffness (or modulus) was unaffected in all the condoms, as revealed by results from indentation hardness analysis. The SWCNT showed no significant influence on thermal decomposition temperatures of the condoms. Nonetheless, images from optical microscopy revealed increased surface roughness corresponding to higher loadings of SWCNT. Results from stress relaxation studies revealed improved retention of modulus under constant strain for condom samples containing SWCNT.
- Full Text:
- Date Issued: 2018
Development of InSb/GaSb quantum dots by MOVPE
- Authors: Ahia, Chinedu Christian
- Date: 2018
- Subjects: Semiconductors , Quantum electronics Organometallic compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23382 , vital:30537
- Description: There has been an increasing interest in the modification of semiconductor band structures through the reduction of their dimensions, which simultaneously increases the band gap energy of the material and gives rise to flexibility in device properties. Advances in III-V antimony (Sb) based semiconductor fabrication have triggered the quest for extension of the emission/absorption wavelength range of this family of compounds for optoelectronic devices operating in the mid-infrared region of the electromagnetic spectrum. An interesting material system for mid-infrared (MIR) applications is indium antimonide (InSb) quantum dots (QDs) within a gallium antimonide (GaSb) matrix. However, its band alignment and emission wavelength has been the subject of some interest and controversy over the years. This study focuses on the development of InSb/GaSb QDs by metal organic vapour phase epitaxy (MOVPE). The samples were grown on different substrates using various growth parameters in order to vary the size, density and aspect ratio of the dots. Interfacial growth interruptions while flowing various source precursors through the reactor were investigated in order to influence the chemical termination of the surface, and hence the resulting strain in the structures. The samples were characterized using photoluminescence spectroscopy, scanning probe microscopy, scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Likewise, the band alignment, energy levels, and carrier wave functions of the samples in this work were modelled theoretically using the nextnanomat software (version 3.1.0.0). A comparison of growth on two different GaSb substrates [(100) 2° off towards <111>B ± 0.1ᵒ and (111) ± 0.1ᵒ] using similar growth conditions yielded a higher dot density on the (100) substrate compared to the (111) substrate. This was attributed to the presence of terraces/atomic steps induced by the misorientation on the (100) substrate, which invariably gives rise to increased adsorption and an enhanced sticking coefficient of adatoms. Studies on the influence of a buffer layer on the morphology of uncapped dots showed that the shape and size of the dots are sensitive to the thickness of the buffer layer. In some case a corrugated buffer surface resulted, which introduced order in the arrangement of the dots, which formed preferentially inside the troughs. An increase in the V/III ratio from 1.0 to 3.0 was found to reduce the areal density of the QDs, while an analysis of the diameter histograms showed a narrowing of the size distribution with an increase in V/III ratio. The larger size distribution at low V/III was ascribed to the increase in indium species and the increased indium adatom migration length. This leads to increased dot density and nucleation sites, and thus triggers an increase in the conversion of tiny QDs into thermodynamically more suitable larger dots via coalescence. However, as the V/III ratio increased, the number of indium adatoms available for growth on the surface reduced, which automatically led to a decrease in the migration length of indium species which is unfavourable for the production of nucleation sites and to a decrease in dot density. Low growth rates were found to be beneficial for the growth of a high density (~5×1010cm-2) of QDs. Photoluminescence (PL) analysis of the capped samples at low temperature (~10 K), using an excitation power of 2 mW, showed a PL peak at ∼732 meV. Upon an increase in laser power to 120 mW, a blue shift of ∼ 8 meV was noticed. This emission typically persisted up to 60–70 K. An increase in the number of InSb QD-layers, was observed to cause an increase in the luminescence spectral line width and a long-wavelength shift of the PL lines, together with an enhancement in the strength of the PL emission. However, high resolution transmission electron microscopy (HRTEM) of the capped dots revealed the formation of an InGaSb quantum well-like structure, ∼10 nm thick, which was responsible for the PL signal mentioned above. The absence of QDs in the capped sample was attributed to inter-diffusion of Ga and In during the deposition of the cap layer, giving rise to a quantum well (QW) instead of the intended QDs. The presence of threading dislocations and stacking faults were also observed in the TEM micrographs of the samples containing multilayers, which can account for the fast quenching of the PL emission with increasing temperature from these samples. Theoretical simulations of the band alignment, wave functions and energy levels were in good agreement with the data collected from the PL spectra of the samples.
- Full Text:
- Date Issued: 2018
- Authors: Ahia, Chinedu Christian
- Date: 2018
- Subjects: Semiconductors , Quantum electronics Organometallic compounds
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23382 , vital:30537
- Description: There has been an increasing interest in the modification of semiconductor band structures through the reduction of their dimensions, which simultaneously increases the band gap energy of the material and gives rise to flexibility in device properties. Advances in III-V antimony (Sb) based semiconductor fabrication have triggered the quest for extension of the emission/absorption wavelength range of this family of compounds for optoelectronic devices operating in the mid-infrared region of the electromagnetic spectrum. An interesting material system for mid-infrared (MIR) applications is indium antimonide (InSb) quantum dots (QDs) within a gallium antimonide (GaSb) matrix. However, its band alignment and emission wavelength has been the subject of some interest and controversy over the years. This study focuses on the development of InSb/GaSb QDs by metal organic vapour phase epitaxy (MOVPE). The samples were grown on different substrates using various growth parameters in order to vary the size, density and aspect ratio of the dots. Interfacial growth interruptions while flowing various source precursors through the reactor were investigated in order to influence the chemical termination of the surface, and hence the resulting strain in the structures. The samples were characterized using photoluminescence spectroscopy, scanning probe microscopy, scanning electron microscopy, X-ray diffraction and transmission electron microscopy. Likewise, the band alignment, energy levels, and carrier wave functions of the samples in this work were modelled theoretically using the nextnanomat software (version 3.1.0.0). A comparison of growth on two different GaSb substrates [(100) 2° off towards <111>B ± 0.1ᵒ and (111) ± 0.1ᵒ] using similar growth conditions yielded a higher dot density on the (100) substrate compared to the (111) substrate. This was attributed to the presence of terraces/atomic steps induced by the misorientation on the (100) substrate, which invariably gives rise to increased adsorption and an enhanced sticking coefficient of adatoms. Studies on the influence of a buffer layer on the morphology of uncapped dots showed that the shape and size of the dots are sensitive to the thickness of the buffer layer. In some case a corrugated buffer surface resulted, which introduced order in the arrangement of the dots, which formed preferentially inside the troughs. An increase in the V/III ratio from 1.0 to 3.0 was found to reduce the areal density of the QDs, while an analysis of the diameter histograms showed a narrowing of the size distribution with an increase in V/III ratio. The larger size distribution at low V/III was ascribed to the increase in indium species and the increased indium adatom migration length. This leads to increased dot density and nucleation sites, and thus triggers an increase in the conversion of tiny QDs into thermodynamically more suitable larger dots via coalescence. However, as the V/III ratio increased, the number of indium adatoms available for growth on the surface reduced, which automatically led to a decrease in the migration length of indium species which is unfavourable for the production of nucleation sites and to a decrease in dot density. Low growth rates were found to be beneficial for the growth of a high density (~5×1010cm-2) of QDs. Photoluminescence (PL) analysis of the capped samples at low temperature (~10 K), using an excitation power of 2 mW, showed a PL peak at ∼732 meV. Upon an increase in laser power to 120 mW, a blue shift of ∼ 8 meV was noticed. This emission typically persisted up to 60–70 K. An increase in the number of InSb QD-layers, was observed to cause an increase in the luminescence spectral line width and a long-wavelength shift of the PL lines, together with an enhancement in the strength of the PL emission. However, high resolution transmission electron microscopy (HRTEM) of the capped dots revealed the formation of an InGaSb quantum well-like structure, ∼10 nm thick, which was responsible for the PL signal mentioned above. The absence of QDs in the capped sample was attributed to inter-diffusion of Ga and In during the deposition of the cap layer, giving rise to a quantum well (QW) instead of the intended QDs. The presence of threading dislocations and stacking faults were also observed in the TEM micrographs of the samples containing multilayers, which can account for the fast quenching of the PL emission with increasing temperature from these samples. Theoretical simulations of the band alignment, wave functions and energy levels were in good agreement with the data collected from the PL spectra of the samples.
- Full Text:
- Date Issued: 2018
Incidence of bacterial infections and colonisation in patients admitted to a tuberculosis hospital
- Authors: Annear, Dale John
- Date: 2018
- Subjects: Medical microbiology , Microbiology Bacteriology Tuberculosis -- Hospitals -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21482 , vital:29526
- Description: Patients with drug resistant tuberculosis (TB) are treated with multiple antibiotics including moxifloxacin, linezolid, and meropenem, which puts them at greater risk for colonisation by multi-drug resistant (MDR) bacteria. The objectives of this study were to: (i) assess the antimicrobial prescribing patterns practiced within the hospital by retrospective patient file review; (ii) determine the spectrum of bacterial colonisation in TB patients upon admission and during hospitalisation; (iii) identify bacterial isolates and evaluate antimicrobial susceptibility profiles; (iv) detect antimicrobial resistance genes in the bacterial isolates by PCR and DNA sequencing; and (v) investigate genetic relatedness of Klebsiella pneumoniae isolates using Multi Locus Sequence Typing. Nasal, groin and rectal swabs [for the detection of extended spectrum beta lactamases (EBSLs), carbapenem-resistant Enterobacteriaceae (CRE), vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA)] were analysed from a cohort of patients (n=37) admitted either from the community (n = 28) or from other healthcare facilities (n=9) to a TB hospital. Swab samples were collected at admission and at four week intervals thereafter during hospitalization. Identification and antimicrobial susceptibility testing of bacterial isolates (n=62) were determined at the National Health Laboratory Services (NHLS) by the VITEK-MS and Vitek 2 systems respectively. Additional antimicrobial susceptibility testing was conducted by Sensititre Gram Negative Xtra (GNFX2) MIC plates. PCR and DNA sequencing were used for detection of resistance genes. Patients (n=13/37; 35%) were colonized by MDR bacteria (ESBLs [n=11], MRSA [n=2]) on admission. Colonization rates were lower in patients admitted from the community (9/28; 32%) compared to those transferred from other healthcare facilities (4/9; 44%). All admitted patients who did not exhibit colonization at baseline and who were resident within the hospital for longer than 4 weeks (17/37; 46% of total patients) became colonised by an ESBL-producing Enterobacteriaceae species. No patients acquired MRSA during hospitalisation. Among ESBL Enterobacteriaceae, Escherichia coli (41/62; 66%) and K. pneumoniae [14/62; 23%]) predominated. Nineteen percent (7/37) of patients demised during their hospitalization. Both the Vitek system and Sensititre Gram Negative Xtra (GNFX2) MIC plates susceptibilities were similar for most antimicrobials, however there were discrepancies for tigecycline susceptibility profiles. A high number of isolates exhibited resistance to aminoglycosides and fluoroquinolones. Genes encoding for ESBLs (CTX-M-14, CTX-M-15, SHV-28, OXA-1, and OXY-2-9) were detected among ESBL Enterobacteriaceae. Two Enterobacteriaceae isolates with reduced carbapenem susceptibility did not contain carbapenemase-encoding genes. MLST revealed unique sequence types and genetic diversity among the K. pneumoniae isolates from hospitalised patients. However, the source and colonization routes of these isolates could not be determined, which requires further investigation. This study provides insight into the spectrum of bacterial pathogen colonisation in hospitalised TB patients and suggests a review of infection control programs and practices at the TB hospital.
- Full Text:
- Date Issued: 2018
- Authors: Annear, Dale John
- Date: 2018
- Subjects: Medical microbiology , Microbiology Bacteriology Tuberculosis -- Hospitals -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21482 , vital:29526
- Description: Patients with drug resistant tuberculosis (TB) are treated with multiple antibiotics including moxifloxacin, linezolid, and meropenem, which puts them at greater risk for colonisation by multi-drug resistant (MDR) bacteria. The objectives of this study were to: (i) assess the antimicrobial prescribing patterns practiced within the hospital by retrospective patient file review; (ii) determine the spectrum of bacterial colonisation in TB patients upon admission and during hospitalisation; (iii) identify bacterial isolates and evaluate antimicrobial susceptibility profiles; (iv) detect antimicrobial resistance genes in the bacterial isolates by PCR and DNA sequencing; and (v) investigate genetic relatedness of Klebsiella pneumoniae isolates using Multi Locus Sequence Typing. Nasal, groin and rectal swabs [for the detection of extended spectrum beta lactamases (EBSLs), carbapenem-resistant Enterobacteriaceae (CRE), vancomycin-resistant enterococci (VRE) and methicillin-resistant Staphylococcus aureus (MRSA)] were analysed from a cohort of patients (n=37) admitted either from the community (n = 28) or from other healthcare facilities (n=9) to a TB hospital. Swab samples were collected at admission and at four week intervals thereafter during hospitalization. Identification and antimicrobial susceptibility testing of bacterial isolates (n=62) were determined at the National Health Laboratory Services (NHLS) by the VITEK-MS and Vitek 2 systems respectively. Additional antimicrobial susceptibility testing was conducted by Sensititre Gram Negative Xtra (GNFX2) MIC plates. PCR and DNA sequencing were used for detection of resistance genes. Patients (n=13/37; 35%) were colonized by MDR bacteria (ESBLs [n=11], MRSA [n=2]) on admission. Colonization rates were lower in patients admitted from the community (9/28; 32%) compared to those transferred from other healthcare facilities (4/9; 44%). All admitted patients who did not exhibit colonization at baseline and who were resident within the hospital for longer than 4 weeks (17/37; 46% of total patients) became colonised by an ESBL-producing Enterobacteriaceae species. No patients acquired MRSA during hospitalisation. Among ESBL Enterobacteriaceae, Escherichia coli (41/62; 66%) and K. pneumoniae [14/62; 23%]) predominated. Nineteen percent (7/37) of patients demised during their hospitalization. Both the Vitek system and Sensititre Gram Negative Xtra (GNFX2) MIC plates susceptibilities were similar for most antimicrobials, however there were discrepancies for tigecycline susceptibility profiles. A high number of isolates exhibited resistance to aminoglycosides and fluoroquinolones. Genes encoding for ESBLs (CTX-M-14, CTX-M-15, SHV-28, OXA-1, and OXY-2-9) were detected among ESBL Enterobacteriaceae. Two Enterobacteriaceae isolates with reduced carbapenem susceptibility did not contain carbapenemase-encoding genes. MLST revealed unique sequence types and genetic diversity among the K. pneumoniae isolates from hospitalised patients. However, the source and colonization routes of these isolates could not be determined, which requires further investigation. This study provides insight into the spectrum of bacterial pathogen colonisation in hospitalised TB patients and suggests a review of infection control programs and practices at the TB hospital.
- Full Text:
- Date Issued: 2018
The use of a silica based coating to reduce moisture absorption of flax fibre reinforced composites
- Authors: Bala, Sandisiwe
- Date: 2018
- Subjects: Chromatographic analysis , Nonwoven fabrics Nanocomposites (Materials)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23349 , vital:30534
- Description: This study deals with the synthesis of silica particles, treatment of flax fabrics with silica, and the preparation and characterization of silica coated flax fibre reinforced phenolic composites treated with silica. Silica particles were successfully prepared by means of a hydrolytic sol-gel route. Two types of silica were prepared by employing either ammonium hydroxide solution as a base catalyst and acetic acid as an acid catalyst. The silica sols were then aged from three to five days in order to determine the effects of aging on the final properties of the silica. The chemical composition of the silica particles was evaluated by fourier transform infrared spectroscopy (FTIR), thermal stability was determined by using thermogravimetric analysis (TGA), and structural and physical properties of the silica particles prepared via two catalysts and aged at different time periods was investigated by x-ray diffraction (XRD). Silica sols, prepared at different conditions were then applied to treat flax fabrics (untreated/scoured) by use of the padding technique. The effects of the silica treatments on flax fabrics were evaluated by FTIR, XRD, determination of moisture content and mechanical properties. The FTIR revealed presence of silica groups on the silica treated flax fabrics, thus resulting in low moisture content for silica treated flax fabrics. XRD analysis revealed that aging the silica sols increases the crystallinity index. Silica treated flax fabrics showed enhanced tensile properties in the weft direction. The thermal, mechanical and water sorption properties of the composites were evaluated. TGA results revealed that the decomposition temperatures of the silica treated composites shifted to higher temperatures. Thus, silica treatments lead to an improvement in thermal stability for composites. A reduction in mechanical properties was also observed for silica treated composites and some composites showed a reduction in water absorption. It was quite evident from this study that the type of catalyst system used in silica preparation has a great influence on the final properties of the silica, which to a large extent changes the thermal, mechanical and water sorption properties of the composites.
- Full Text:
- Date Issued: 2018
- Authors: Bala, Sandisiwe
- Date: 2018
- Subjects: Chromatographic analysis , Nonwoven fabrics Nanocomposites (Materials)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23349 , vital:30534
- Description: This study deals with the synthesis of silica particles, treatment of flax fabrics with silica, and the preparation and characterization of silica coated flax fibre reinforced phenolic composites treated with silica. Silica particles were successfully prepared by means of a hydrolytic sol-gel route. Two types of silica were prepared by employing either ammonium hydroxide solution as a base catalyst and acetic acid as an acid catalyst. The silica sols were then aged from three to five days in order to determine the effects of aging on the final properties of the silica. The chemical composition of the silica particles was evaluated by fourier transform infrared spectroscopy (FTIR), thermal stability was determined by using thermogravimetric analysis (TGA), and structural and physical properties of the silica particles prepared via two catalysts and aged at different time periods was investigated by x-ray diffraction (XRD). Silica sols, prepared at different conditions were then applied to treat flax fabrics (untreated/scoured) by use of the padding technique. The effects of the silica treatments on flax fabrics were evaluated by FTIR, XRD, determination of moisture content and mechanical properties. The FTIR revealed presence of silica groups on the silica treated flax fabrics, thus resulting in low moisture content for silica treated flax fabrics. XRD analysis revealed that aging the silica sols increases the crystallinity index. Silica treated flax fabrics showed enhanced tensile properties in the weft direction. The thermal, mechanical and water sorption properties of the composites were evaluated. TGA results revealed that the decomposition temperatures of the silica treated composites shifted to higher temperatures. Thus, silica treatments lead to an improvement in thermal stability for composites. A reduction in mechanical properties was also observed for silica treated composites and some composites showed a reduction in water absorption. It was quite evident from this study that the type of catalyst system used in silica preparation has a great influence on the final properties of the silica, which to a large extent changes the thermal, mechanical and water sorption properties of the composites.
- Full Text:
- Date Issued: 2018
Investigation of the thermo-chemical behaviour of coal-algae agglomerates
- Authors: Baloyi, Hope
- Date: 2018
- Subjects: Biomass energy , Coal -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23913 , vital:30642
- Description: There is a growing research interest in the co-processing of biomass and coal, with the aim of addressing the negative attributes associated with the thermal processing of coal alone. Biomass feedstocks are regarded as a clean, renewable source, and the co-utilization of biomass feedstocks with coal is deemed to have a potential to reduce emission of pollutants (i.e. NOx and SOx) and volatile organic compounds (VOC’s). Moreover, biomass are thermally reactive and thus facilitate the conversion of coal during co-processing. Biomass material and coal are two autonomous fuel materials with different chemical characteristics and have a dissimilar thermal behaviour making it difficult to achieve chemical interaction between the two solid fuels to contribute to the formation of products. Coalgae® Technology developed at the Nelson Mandela University, involves the biological treatment of coal fines by adsorbing live microalgae biomass (in slurry form) onto waste coal fines to form coal-microalgae agglomerates. This new innovative approach seeks to integrate bio-based feedstock into coal thermal processing and to improve the utilization and thermal efficiency of coal fines as well as the interaction between the volatile components of biomass and coal during thermal processing (e.g. devolatilization), thereby overcoming some of the challenges that confront the co-processing of coal and biomass. Coal fines are low-ranked coals, generally characterized by high contents of sulphur, high ash yields, low calorific values and poor thermal reactivity, and these attributes limits the thermo-chemical processing of the coal fines. Therefore, this investigation was undertaken to assess the thermo-chemical behaviour of coal-microalgae agglomerates, formed by adsorbing live microalgae slurry at varying ratios onto coal fines. For this purpose, the effects of adsorbing microalgae at varying ratios on the chemical characteristics and thermal behaviour of coal fines under pyrolytic conditions were investigated. The primary aim was to assess whether the thermo-chemical behaviour of coal-microalgae agglomerates, formed by adsorption of live microalgae onto fine coal, is substantively modified compared to a simple additive model of the original coal and pre-dried microalgae biomass samples. Results obtained from the proximate analyses performed on an Eltra Thermo-gravimetric analyzer (TGA) thermostep, have shown that the adsorption of microalgae slurry onto coal fines does not possess greater influence in improving the yield of volatiles and ash in coal fines than can be expected from a simple additive model of the original raw materials. Based on the ultimate analyses results, it was found that the adsorption of microalgae slurry resulted in a systematic reduction in the sulphur content, a notable increase in the hydrogen and oxygen contents, however, no significant disparities were found between the measured ultimate properties of coal-microalgae agglomerates as compared to the theoretically-expected ultimate properties from a simple linear combination of parental coal and microalgae biomass. Assessment of the thermal behaviour of parental samples and coal-microalgae agglomerates involved the use non-isothermal (40-900ºC, 20 K/min) thermogravimetry under inert conditions. It was found that the adsorption of microalgae slurry onto coal fines resulted in an improved thermal reactivity of coal fines, although, did not affect the overall pyrolysis characteristics of the coal fines. Comparison of the thermal profiles (measured and calculated TG/DTG curves), revealed that the yield of volatile products during the pyrolysis of coal-microalgae blends do not exceed the expected volatile yields from a simple combination of coal and microalgae biomass. These results suggest that there was no positive or accelerative synergistic interaction between volatile components of adsorbed microalgae and coal fines during pyrolysis. Mild pyrolysis of raw coal and coal-microalgae performed in a fixed-bed reactor furnace (450ºC), resulted in improved yields of Fossil-Bio crude (FBC) oil (derived from coal-microalgae pyrolysis), at increased biomass ratio compared to coal tar. FBC Oil was found to contain relatively high contents of oxygen, hydrogen, and low sulphur content than coal tar. GC-MS analyses showed the presence of a heterocyclic compounds (i.e. Indole and 2, 6 dimethyl pyridine) in the FBC oil and these were not identified in the coal tar. Furthermore, high boiling compounds such as Flourene, pyrene and pentacosane were identified in the coal tar, however not identified in the FBC oil. Simulated distillation results showed notable differences between the FBC oil and coal tar in terms of the distribution of boiling point fractions particularly, high boing point components. Semi-devolatilized chars derived from coal-microalgae agglomerates showed substantial degree of decarboxylation and dehydrogenation compared to the coal chars.
- Full Text:
- Date Issued: 2018
- Authors: Baloyi, Hope
- Date: 2018
- Subjects: Biomass energy , Coal -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23913 , vital:30642
- Description: There is a growing research interest in the co-processing of biomass and coal, with the aim of addressing the negative attributes associated with the thermal processing of coal alone. Biomass feedstocks are regarded as a clean, renewable source, and the co-utilization of biomass feedstocks with coal is deemed to have a potential to reduce emission of pollutants (i.e. NOx and SOx) and volatile organic compounds (VOC’s). Moreover, biomass are thermally reactive and thus facilitate the conversion of coal during co-processing. Biomass material and coal are two autonomous fuel materials with different chemical characteristics and have a dissimilar thermal behaviour making it difficult to achieve chemical interaction between the two solid fuels to contribute to the formation of products. Coalgae® Technology developed at the Nelson Mandela University, involves the biological treatment of coal fines by adsorbing live microalgae biomass (in slurry form) onto waste coal fines to form coal-microalgae agglomerates. This new innovative approach seeks to integrate bio-based feedstock into coal thermal processing and to improve the utilization and thermal efficiency of coal fines as well as the interaction between the volatile components of biomass and coal during thermal processing (e.g. devolatilization), thereby overcoming some of the challenges that confront the co-processing of coal and biomass. Coal fines are low-ranked coals, generally characterized by high contents of sulphur, high ash yields, low calorific values and poor thermal reactivity, and these attributes limits the thermo-chemical processing of the coal fines. Therefore, this investigation was undertaken to assess the thermo-chemical behaviour of coal-microalgae agglomerates, formed by adsorbing live microalgae slurry at varying ratios onto coal fines. For this purpose, the effects of adsorbing microalgae at varying ratios on the chemical characteristics and thermal behaviour of coal fines under pyrolytic conditions were investigated. The primary aim was to assess whether the thermo-chemical behaviour of coal-microalgae agglomerates, formed by adsorption of live microalgae onto fine coal, is substantively modified compared to a simple additive model of the original coal and pre-dried microalgae biomass samples. Results obtained from the proximate analyses performed on an Eltra Thermo-gravimetric analyzer (TGA) thermostep, have shown that the adsorption of microalgae slurry onto coal fines does not possess greater influence in improving the yield of volatiles and ash in coal fines than can be expected from a simple additive model of the original raw materials. Based on the ultimate analyses results, it was found that the adsorption of microalgae slurry resulted in a systematic reduction in the sulphur content, a notable increase in the hydrogen and oxygen contents, however, no significant disparities were found between the measured ultimate properties of coal-microalgae agglomerates as compared to the theoretically-expected ultimate properties from a simple linear combination of parental coal and microalgae biomass. Assessment of the thermal behaviour of parental samples and coal-microalgae agglomerates involved the use non-isothermal (40-900ºC, 20 K/min) thermogravimetry under inert conditions. It was found that the adsorption of microalgae slurry onto coal fines resulted in an improved thermal reactivity of coal fines, although, did not affect the overall pyrolysis characteristics of the coal fines. Comparison of the thermal profiles (measured and calculated TG/DTG curves), revealed that the yield of volatile products during the pyrolysis of coal-microalgae blends do not exceed the expected volatile yields from a simple combination of coal and microalgae biomass. These results suggest that there was no positive or accelerative synergistic interaction between volatile components of adsorbed microalgae and coal fines during pyrolysis. Mild pyrolysis of raw coal and coal-microalgae performed in a fixed-bed reactor furnace (450ºC), resulted in improved yields of Fossil-Bio crude (FBC) oil (derived from coal-microalgae pyrolysis), at increased biomass ratio compared to coal tar. FBC Oil was found to contain relatively high contents of oxygen, hydrogen, and low sulphur content than coal tar. GC-MS analyses showed the presence of a heterocyclic compounds (i.e. Indole and 2, 6 dimethyl pyridine) in the FBC oil and these were not identified in the coal tar. Furthermore, high boiling compounds such as Flourene, pyrene and pentacosane were identified in the coal tar, however not identified in the FBC oil. Simulated distillation results showed notable differences between the FBC oil and coal tar in terms of the distribution of boiling point fractions particularly, high boing point components. Semi-devolatilized chars derived from coal-microalgae agglomerates showed substantial degree of decarboxylation and dehydrogenation compared to the coal chars.
- Full Text:
- Date Issued: 2018
Towards a community based conservation strategy for wetlands in Uganda
- Authors: Barakagira, Alex
- Date: 2018
- Subjects: Conservation of natural resources , Wetland conservation -- Uganda Wetlands -- Uganda -- Management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23902 , vital:30640
- Description: Conservation of natural resources in Uganda focuses primarily on protected areas, including savannah national parks, mainly for conserving big game and forests, for controlling the harvest of commercially valuable timber resources, with less concern for wetlands. Later, policies and legislation in Uganda favoured agricultural production rather than the conservation of wetlands, a situation that culminated in their degradation. In a bid to counter the effects of wetlands degradation, Wetland Management Agencies were created. These agencies excluded the input of members of the local communities who reside in the wetlands environs. Local communities were not consulted on matters concerning management and conservation strategies, a situation that may have escalated the problem of wetlands degradation. Local knowledge is needed for the effective management and conservation of the wetlands and it is essential that local communities are included in decision making. This research study is more of an initiative for providing information that may be essential for the formulation of a community based conservation strategy for wetlands in Uganda. The study aimed to identify and characterize activities carried out by members of the local communities in wetlands found in central and western Uganda that are responsible for their progressive degradation; to assess the performance of existing Wetlands Management Institutions towards protection and conservation of wetlands in Uganda; to ascertain whether the acts and policies that have been promulgated for the protection of wetlands in Uganda have been adhered to by members of the local communities and to evaluate three community based conservation case studies with two vastly different outcomes in order to come up with the community-based conservation principles Ugandan communities may need to adopt to achieve sustainable utilisation and conservation of wetland resources. To achieve the objectives stated above, the researcher used a multi-disciplinary methodology that required several areas of expertise and sources of information. Hence, to accomplish the study, primary sources of data that included quantitative and qualitative data were collected from the study participants by means of a questionnaire survey, key informant interviews and direct observations. Secondary sources of data centred on published Ugandan acts and policies; textbooks; case study articles and journal articles. The study revealed a host of activities in which members of the local community are involved that have led to the degradation of the wetlands in Uganda. These include but are not limited to crop cultivation, dairy farming and unsustainable wetland resource harvesting. A number of other reasons for the degradation of the wetlands include unclear ownership of the wetlands, unclear wetland boundaries and a lack of awareness of the indirect benefits wetlands provide for members of the local communities. The study disclosed that wetlands management institutions have not been effective in the protection and conservation of wetlands in Uganda, mainly due to political interference and inadequate funding for the institutions’ conservation activities. The acts and policies that were promulgated for the protection and conservation of wetlands have been selectively implemented in some places and in others completely ignored, culminating in the degradation of the wetlands. The study revealed that effective community based conservation of wetlands in Uganda includes: initiation of the planning, implementation, monitoring and evaluation of all wetlands activities being borne by members of the local community; government introducing alternative income-generating activities aimed to reduce over-reliance on wetland resources and education of the local communities regarding the community-based projects’ objectives in order to garner their support. Recommendations emanating from this study are that the Land Act should be amended to specify a particular land tenure system, preferably freehold, which may promote the conservation of wetlands in Uganda; fertilizers (organic) should be introduced in the study area to fertilize the uplands that have reportedly become infertile in order to reduce the pressure the local community members are exerting on the wetlands for agriculture; wetlands management institutions should be empowered financially and political interference in activities aimed at conservation of wetlands in Uganda must cease. There should be uniform implementation of the rules and regulations stipulated in the acts and policies for all members of the public concerning wetlands protection. Lastly, essential community based conservation principles, as stated above, need to be applied carefully and adhered to if effective implementation of community-based conservation of wetlands is to be achieved in Uganda.
- Full Text:
- Date Issued: 2018
- Authors: Barakagira, Alex
- Date: 2018
- Subjects: Conservation of natural resources , Wetland conservation -- Uganda Wetlands -- Uganda -- Management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23902 , vital:30640
- Description: Conservation of natural resources in Uganda focuses primarily on protected areas, including savannah national parks, mainly for conserving big game and forests, for controlling the harvest of commercially valuable timber resources, with less concern for wetlands. Later, policies and legislation in Uganda favoured agricultural production rather than the conservation of wetlands, a situation that culminated in their degradation. In a bid to counter the effects of wetlands degradation, Wetland Management Agencies were created. These agencies excluded the input of members of the local communities who reside in the wetlands environs. Local communities were not consulted on matters concerning management and conservation strategies, a situation that may have escalated the problem of wetlands degradation. Local knowledge is needed for the effective management and conservation of the wetlands and it is essential that local communities are included in decision making. This research study is more of an initiative for providing information that may be essential for the formulation of a community based conservation strategy for wetlands in Uganda. The study aimed to identify and characterize activities carried out by members of the local communities in wetlands found in central and western Uganda that are responsible for their progressive degradation; to assess the performance of existing Wetlands Management Institutions towards protection and conservation of wetlands in Uganda; to ascertain whether the acts and policies that have been promulgated for the protection of wetlands in Uganda have been adhered to by members of the local communities and to evaluate three community based conservation case studies with two vastly different outcomes in order to come up with the community-based conservation principles Ugandan communities may need to adopt to achieve sustainable utilisation and conservation of wetland resources. To achieve the objectives stated above, the researcher used a multi-disciplinary methodology that required several areas of expertise and sources of information. Hence, to accomplish the study, primary sources of data that included quantitative and qualitative data were collected from the study participants by means of a questionnaire survey, key informant interviews and direct observations. Secondary sources of data centred on published Ugandan acts and policies; textbooks; case study articles and journal articles. The study revealed a host of activities in which members of the local community are involved that have led to the degradation of the wetlands in Uganda. These include but are not limited to crop cultivation, dairy farming and unsustainable wetland resource harvesting. A number of other reasons for the degradation of the wetlands include unclear ownership of the wetlands, unclear wetland boundaries and a lack of awareness of the indirect benefits wetlands provide for members of the local communities. The study disclosed that wetlands management institutions have not been effective in the protection and conservation of wetlands in Uganda, mainly due to political interference and inadequate funding for the institutions’ conservation activities. The acts and policies that were promulgated for the protection and conservation of wetlands have been selectively implemented in some places and in others completely ignored, culminating in the degradation of the wetlands. The study revealed that effective community based conservation of wetlands in Uganda includes: initiation of the planning, implementation, monitoring and evaluation of all wetlands activities being borne by members of the local community; government introducing alternative income-generating activities aimed to reduce over-reliance on wetland resources and education of the local communities regarding the community-based projects’ objectives in order to garner their support. Recommendations emanating from this study are that the Land Act should be amended to specify a particular land tenure system, preferably freehold, which may promote the conservation of wetlands in Uganda; fertilizers (organic) should be introduced in the study area to fertilize the uplands that have reportedly become infertile in order to reduce the pressure the local community members are exerting on the wetlands for agriculture; wetlands management institutions should be empowered financially and political interference in activities aimed at conservation of wetlands in Uganda must cease. There should be uniform implementation of the rules and regulations stipulated in the acts and policies for all members of the public concerning wetlands protection. Lastly, essential community based conservation principles, as stated above, need to be applied carefully and adhered to if effective implementation of community-based conservation of wetlands is to be achieved in Uganda.
- Full Text:
- Date Issued: 2018
Deep learning applied to the semantic segmentation of tyre stockpiles
- Barfknecht, Nicholas Christopher
- Authors: Barfknecht, Nicholas Christopher
- Date: 2018
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23947 , vital:30647
- Description: The global push for manufacturing which is environmentally sustainable has disrupted standard methods of waste tyre disposal. This push is further intensified by the health and safety risks discarded tyres pose to the surrounding population. Waste tyre recycling initiatives in South Africa are on the increase; however, there is still a growing number of undocumented tyre stockpiles developing throughout the country. The plans put in place to eradicate these tyre stockpiles have been met with collection, transport and storage logistical issues caused by the remoteness and distant locales. Eastwood (2016) aimed at optimising the logistics associated with collection, by estimating the number of visible tyres from images of tyre stockpiles. This research was limited by the need for manual segmentation of each tyre stockpile located within each image. This research proposes the use of semantic segmentation to automatically segment images of tyre stockpiles. An initial review of neural network, convolutional network and semantic segmentation literature resulted in the selection of Dilated Net as the semantic segmentation architecture for this research. Dilated Net builds upon the VGG-16 classification architecture to perform semantic segmentation. This resulted in classification experiments which were evaluated using precision, recall and f1-score. The results indicated that regardless of tyre stockpile image dimension, fairly accurate levels of classification accuracy can be attained. This was followed by semantic segmentation experiments which made use of intersection over union (IoU) and pixel accuracy to evaluate the effectiveness of Dilated Net on images of tyre stockpiles. The results indicated that accurate tyre stockpile segmentation regions can be obtained and that the trained model generalises well to unseen images.
- Full Text:
- Date Issued: 2018
- Authors: Barfknecht, Nicholas Christopher
- Date: 2018
- Subjects: Neural networks (Computer science)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23947 , vital:30647
- Description: The global push for manufacturing which is environmentally sustainable has disrupted standard methods of waste tyre disposal. This push is further intensified by the health and safety risks discarded tyres pose to the surrounding population. Waste tyre recycling initiatives in South Africa are on the increase; however, there is still a growing number of undocumented tyre stockpiles developing throughout the country. The plans put in place to eradicate these tyre stockpiles have been met with collection, transport and storage logistical issues caused by the remoteness and distant locales. Eastwood (2016) aimed at optimising the logistics associated with collection, by estimating the number of visible tyres from images of tyre stockpiles. This research was limited by the need for manual segmentation of each tyre stockpile located within each image. This research proposes the use of semantic segmentation to automatically segment images of tyre stockpiles. An initial review of neural network, convolutional network and semantic segmentation literature resulted in the selection of Dilated Net as the semantic segmentation architecture for this research. Dilated Net builds upon the VGG-16 classification architecture to perform semantic segmentation. This resulted in classification experiments which were evaluated using precision, recall and f1-score. The results indicated that regardless of tyre stockpile image dimension, fairly accurate levels of classification accuracy can be attained. This was followed by semantic segmentation experiments which made use of intersection over union (IoU) and pixel accuracy to evaluate the effectiveness of Dilated Net on images of tyre stockpiles. The results indicated that accurate tyre stockpile segmentation regions can be obtained and that the trained model generalises well to unseen images.
- Full Text:
- Date Issued: 2018
Synthesis and application of novel coumarin-triazole-based polymeric sensors towards metal ion sensing
- Authors: Battison, Aidan Leigh
- Date: 2018
- Subjects: Polymers -- Optical properties , Polymers -- Electric properties Biosensors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23636 , vital:30591
- Description: One of the greatest challenges in the South African society is the pollutants which we are exposed to within our environment. The mismanagement and release of toxic analytes via different chemical, agricultural and industrial processes has led to a critical need for advanced monitoring systems for environmental protection, remediation and restoration. Industrial processes release a plethora of different pollutants into the earth, atmosphere, and aquatic ecosystems. Most pollutant causing activities are due to mining, agriculture, industry and chemical storage. Most contaminants released by these processes are not biodegradable and may be able to exude into water systems where they present an immense threat to environmental and human health. The number of different analytes released into the environment is greater than the number of sensors able to detect these species. Clearly, there is a need for a rapid and low-cost means of detection, recognition, and monitoring of these analytes. Fluorescent coumarin-triazole-based polymeric materials were designed and investigated as potential sensors for these metal ionic species. The Cu(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes was the focus method of polymerization to form the fluorescence enhancing triazole moiety. The coumarin-triazole units formed the backbone of these polymeric material. The photophysical properties of the starting monomers and polymers were investigated in THF solvent. The polymers showed to have higher absorption and emission intensities than their respective starting monomers. The chemosensing capabilities of the polymers for metal ions were investigated through their emission properties. The polymers showed to have the greatest response towards Hg2+ and Ag+. Furthermore, the polymers displayed a reversible response towards Hg2+ in the presence of EDTA. The most responsive and reversible polymer system was applied for metal sensing capabilities towards Hg2+ from a known water source. This polymer proved to be a sensitive and reversible chemosensor for Hg2+ ions. The site of metal complexation on the polymer systems was verified by 1H NMR and FT-IR spectroscopy and was found to be mainly the triazole moieties from the polymer backbone. Finally, the possible mechanism for the fluorescent response of Hg2+ and Ag+ was also investigated.
- Full Text:
- Date Issued: 2018
- Authors: Battison, Aidan Leigh
- Date: 2018
- Subjects: Polymers -- Optical properties , Polymers -- Electric properties Biosensors
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23636 , vital:30591
- Description: One of the greatest challenges in the South African society is the pollutants which we are exposed to within our environment. The mismanagement and release of toxic analytes via different chemical, agricultural and industrial processes has led to a critical need for advanced monitoring systems for environmental protection, remediation and restoration. Industrial processes release a plethora of different pollutants into the earth, atmosphere, and aquatic ecosystems. Most pollutant causing activities are due to mining, agriculture, industry and chemical storage. Most contaminants released by these processes are not biodegradable and may be able to exude into water systems where they present an immense threat to environmental and human health. The number of different analytes released into the environment is greater than the number of sensors able to detect these species. Clearly, there is a need for a rapid and low-cost means of detection, recognition, and monitoring of these analytes. Fluorescent coumarin-triazole-based polymeric materials were designed and investigated as potential sensors for these metal ionic species. The Cu(I)-catalyzed 1,3-dipolar cycloaddition of azides and alkynes was the focus method of polymerization to form the fluorescence enhancing triazole moiety. The coumarin-triazole units formed the backbone of these polymeric material. The photophysical properties of the starting monomers and polymers were investigated in THF solvent. The polymers showed to have higher absorption and emission intensities than their respective starting monomers. The chemosensing capabilities of the polymers for metal ions were investigated through their emission properties. The polymers showed to have the greatest response towards Hg2+ and Ag+. Furthermore, the polymers displayed a reversible response towards Hg2+ in the presence of EDTA. The most responsive and reversible polymer system was applied for metal sensing capabilities towards Hg2+ from a known water source. This polymer proved to be a sensitive and reversible chemosensor for Hg2+ ions. The site of metal complexation on the polymer systems was verified by 1H NMR and FT-IR spectroscopy and was found to be mainly the triazole moieties from the polymer backbone. Finally, the possible mechanism for the fluorescent response of Hg2+ and Ag+ was also investigated.
- Full Text:
- Date Issued: 2018
Using ambient noise tomography to image the Eastern Cape-Karoo and Karoo regions, South Africa
- Bezuidenhout, Lucian John-Ross
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2018
- Subjects: Geometric tomography -- South Africa , Geobiology Geology -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23602 , vital:30585
- Description: The primary aim of this thesis was to explore the use of ambient seismic noise as a tool to map the subsurface of the Cape-Karoo and Karoo region of South Africa. The Karoo is an ideal laboratory to use ambient seismic signal to map the shallow subsurface, as it is a quiet and pristine environment with a relatively well known geology. Ambient seismic signals were continuously recorded at three independent networks (ArrayA, ArrayB and ArrayC). ArrayA and ArrayB comprised 17 temporary stand-alone seismic stations each and recorded ambient noise wavefields for a ten week period between August and October 2015. ArrayC comprised 19 temporary stand-alone seismic stations, recording ambient seismic noise for a period of six weeks between June and July 2016. ArrayA and ArrayB were installed in the south-eastern Cape-Karoo region, near the town of Jansenville and ArrayC was installed near the Cradock-Tarkastad region of South Africa. This thesis is made up of two separate studies. Firstly, the retrieval and coherency of Rayleigh surface waves extracted from the vertical component recordings. For the first time in the south-eastern Cape-Karoo and Karoo area, estimates of Green’s function from cross-correlating ambient noise data between stations pairs were reconstructed and shown, which can be successfully used to image the subsurface. The stacked cross-correlations between all station pairs show clear arrivals of the Rayleigh surface waves. The group velocities of the Rayleigh waves in the 2 to 7 seconds period range were picked and inverted to compute the 2-D group velocity maps. For ArrayA and ArrayB, the resulting 2-D group velocity maps at different periods resulted in a group velocity model from approximately 2 to 7 km depth, which generally show a high velocity anomaly in the north of the study area, most likely imaging the denser, thick sedimentary basin of the Karoo (Carboniferous-Permian). To the south, the low velocity anomaly likely corresponds to the overlying Jurassic- Cretaceous sequences of the younger Algoa Basin (Uitenhage Group). For ArrayC, the group velocity maps showed high velocity regions, which is consistent with the dolerite sill intrusions in the Karoo and the low velocity structures, which was interpreted as the Karoo sediments. Secondly, the study comprised of characterizing the ambient seismic noise source. The first order analysis of the symmetry of the cross-correlation function showed that, although the ambient noise sources are relatively homogeneously distributed in the study area, most (energetic) of the ambient seismic noise propagates from the coast of South Africa. This was verified by analyzing the azimuthal distribution of the ambient seismic noise.
- Full Text:
- Date Issued: 2018
- Authors: Bezuidenhout, Lucian John-Ross
- Date: 2018
- Subjects: Geometric tomography -- South Africa , Geobiology Geology -- South Africa
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23602 , vital:30585
- Description: The primary aim of this thesis was to explore the use of ambient seismic noise as a tool to map the subsurface of the Cape-Karoo and Karoo region of South Africa. The Karoo is an ideal laboratory to use ambient seismic signal to map the shallow subsurface, as it is a quiet and pristine environment with a relatively well known geology. Ambient seismic signals were continuously recorded at three independent networks (ArrayA, ArrayB and ArrayC). ArrayA and ArrayB comprised 17 temporary stand-alone seismic stations each and recorded ambient noise wavefields for a ten week period between August and October 2015. ArrayC comprised 19 temporary stand-alone seismic stations, recording ambient seismic noise for a period of six weeks between June and July 2016. ArrayA and ArrayB were installed in the south-eastern Cape-Karoo region, near the town of Jansenville and ArrayC was installed near the Cradock-Tarkastad region of South Africa. This thesis is made up of two separate studies. Firstly, the retrieval and coherency of Rayleigh surface waves extracted from the vertical component recordings. For the first time in the south-eastern Cape-Karoo and Karoo area, estimates of Green’s function from cross-correlating ambient noise data between stations pairs were reconstructed and shown, which can be successfully used to image the subsurface. The stacked cross-correlations between all station pairs show clear arrivals of the Rayleigh surface waves. The group velocities of the Rayleigh waves in the 2 to 7 seconds period range were picked and inverted to compute the 2-D group velocity maps. For ArrayA and ArrayB, the resulting 2-D group velocity maps at different periods resulted in a group velocity model from approximately 2 to 7 km depth, which generally show a high velocity anomaly in the north of the study area, most likely imaging the denser, thick sedimentary basin of the Karoo (Carboniferous-Permian). To the south, the low velocity anomaly likely corresponds to the overlying Jurassic- Cretaceous sequences of the younger Algoa Basin (Uitenhage Group). For ArrayC, the group velocity maps showed high velocity regions, which is consistent with the dolerite sill intrusions in the Karoo and the low velocity structures, which was interpreted as the Karoo sediments. Secondly, the study comprised of characterizing the ambient seismic noise source. The first order analysis of the symmetry of the cross-correlation function showed that, although the ambient noise sources are relatively homogeneously distributed in the study area, most (energetic) of the ambient seismic noise propagates from the coast of South Africa. This was verified by analyzing the azimuthal distribution of the ambient seismic noise.
- Full Text:
- Date Issued: 2018
An appraisal of warm temperate mangrove estuaries as food patches using zooplankton and RNA: DNA ratios of Gilchristella aestuaria larvae as indicators
- Authors: Bornman, Eugin
- Date: 2018
- Subjects: Mangrove swamps Fishes -- Larvae , Mangrove ecology , Zooplankton
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17908 , vital:28481
- Description: Mangrove habitats are considered as the ideal fish nursery as they are known to increase the growth and survival of juvenile fishes by providing enhanced food availability and protection. However, most studies have focused on tropical mangroves with a few recent warm temperate studies finding conflicting results. Furthermore, the nursery value of South African mangroves to fishes remain understudied in subtropical areas, while warm temperate mangroves are yet to be evaluated. This study aimed to assess whether mangrove presence leads to any advantage to the larvae of an important estuarine resident fish species, Gilchristella aestuaria, by comparing the food patch quality of South African warm temperate mangrove and non-mangrove estuaries. Results indicate that larvae fed primarily on the dominant prey species, Pseudodiaptomus hessei, Paracrtia longipatella, and Acartiella natalensis. However, postflexion larvae consumed more of the larger species, P. hessei, within the two mangrove estuaries (16.09 %V in Nahoon and 13.79 %V in Xhora) than the two nonmangrove estuaries (12.20 %V in Gonubie and 7.05 %V in Qora), despite other prey species occurring at similar densities. Results indicate that mangrove habitats acted as sediment sinks, slightly reducing the turbidity of these estuaries which resulted in postflexion larvae actively selecting larger, more nutritious prey, which in turn, significantly increased their individual instantaneous growth rates (0.11 ± 0.21 Gi) when compared to postflexion larvae in non-mangrove estuaries (0.09 ± 0.12 Gi). This study found that mangrove presence was significantly related to postflexion larval densities when coupled with abiotic (such as temperature and turbidity) and biotic factors (such as predator-prey interactions). Understanding the spatial and temporal dynamics, predator-prey interactions as well as the growth and survival of G. aestuaria is particularly important as they are key zooplanktivores that are prey to other species in estuarine food webs.
- Full Text:
- Date Issued: 2018
- Authors: Bornman, Eugin
- Date: 2018
- Subjects: Mangrove swamps Fishes -- Larvae , Mangrove ecology , Zooplankton
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/17908 , vital:28481
- Description: Mangrove habitats are considered as the ideal fish nursery as they are known to increase the growth and survival of juvenile fishes by providing enhanced food availability and protection. However, most studies have focused on tropical mangroves with a few recent warm temperate studies finding conflicting results. Furthermore, the nursery value of South African mangroves to fishes remain understudied in subtropical areas, while warm temperate mangroves are yet to be evaluated. This study aimed to assess whether mangrove presence leads to any advantage to the larvae of an important estuarine resident fish species, Gilchristella aestuaria, by comparing the food patch quality of South African warm temperate mangrove and non-mangrove estuaries. Results indicate that larvae fed primarily on the dominant prey species, Pseudodiaptomus hessei, Paracrtia longipatella, and Acartiella natalensis. However, postflexion larvae consumed more of the larger species, P. hessei, within the two mangrove estuaries (16.09 %V in Nahoon and 13.79 %V in Xhora) than the two nonmangrove estuaries (12.20 %V in Gonubie and 7.05 %V in Qora), despite other prey species occurring at similar densities. Results indicate that mangrove habitats acted as sediment sinks, slightly reducing the turbidity of these estuaries which resulted in postflexion larvae actively selecting larger, more nutritious prey, which in turn, significantly increased their individual instantaneous growth rates (0.11 ± 0.21 Gi) when compared to postflexion larvae in non-mangrove estuaries (0.09 ± 0.12 Gi). This study found that mangrove presence was significantly related to postflexion larval densities when coupled with abiotic (such as temperature and turbidity) and biotic factors (such as predator-prey interactions). Understanding the spatial and temporal dynamics, predator-prey interactions as well as the growth and survival of G. aestuaria is particularly important as they are key zooplanktivores that are prey to other species in estuarine food webs.
- Full Text:
- Date Issued: 2018
Energy maximisation strategies of different African herbivores in a fire dominated and nutrient poor grassland ecosystem
- Authors: Brooke, Christopher
- Date: 2018
- Subjects: Grassland ecology -- South Africa -- Eastern Cape , Animals -- Food -- South Africa -- Eastern Cape , Herbivores -- Ecology -- South Africa -- Eastern Cape , Fire ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21961 , vital:29807
- Description: Fire and herbivory are both major drivers in grassland ecosystems throughout the world. Although these two driving forces act independently from one another the relationship between fire and herbivory may be more significant than either acting on their own. Heterogeneity within the landscape as a result of fire results in herbivores having to adapt their behaviour in space and time. My research focussed on 1) characterising the fire regime on Mkambati Nature Reserve (hereafter Mkambati) and 2) determining the foraging choices and energy maximisation principles displayed by herbivores in relation to the biomass of vegetation and post fire vegetation age. Fire regimes were characterised between 2007-2016 in the low nutrient coastal grasslands of Mkambati in terms of fire season, seasonality of fire-prone weather conditions, fire return interval (FRI) and influence of poaching-related ignitions. Based on these results I then assessed foraging choices in terms of energy maximisation of four large herbivore species. I explored what energy maximisation strategy was employed, i.e. maximisation of daily digestible energy (DDE) (recently burnt low biomass vegetation) or instantaneous digestible energy (IDE) (older high biomass vegetation), by herbivore species with different morpho-physiological traits. Common reedbuck (Redunca arundinum), red hartebeest (Alcelaphus buselaphus subsp. caama), zebra (Equus quagga) and eland (Tragelaphus oryx subsp. oryx) were fitted with GPS satellite tracking collars, and hourly GPS locations (observed) were taken between 2008 and 2016. Using mixed effects models, I compared observed and an associated set of random locations to determine the energy maximisation strategy employed by each species. Our results indicated that fires were concentrated in winter when monthly fire danger weather (FDI) was highest. The mean FRI at Mkambati was <3 years, but varied according to vegetation type, and whether censoring (for open ended FRIs) was applied to estimate mean FRIs. Poachers, with the intention of attracting ungulates, are an important source of ignition at Mkambati. Accordingly FRIs were shorter (approximately 2 years) in areas within 3 km of likely poacher entry points. Although all fires recorded at Mkambati during the study period were of anthropogenic origin, mean FRI still fell within the natural range reported for interior grasslands in South Africa. Based on these findings, underpinned by the fire regime information, I showed that red hartebeest and zebra maximised DDE inside and outside of fire seasons and frequently foraged in low biomass recently burnt grasslands. Eland generally favoured areas where they could maximise IDE outside of the fire season, however during the fire season they switched strategy to maximise DDE. Reedbuck did not maximise IDE or DDE at the same scale (patch scale) as the other species, but at a landscape (broader) scale they maximised both IDE and DDE. Through this research I have shown how regular fire affects the foraging and energy maximisation behaviour of large African herbivores and how morpho-physiological traits affect these decisions. In response to these results I recommend that the management of Mkambati implement a focused monitoring program comparing the frequently and less frequently burnt areas of the reserve in order to understand the complex effects of anthropogenic fire and its subsequent effects on the biota of Mkambati.
- Full Text:
- Date Issued: 2018
- Authors: Brooke, Christopher
- Date: 2018
- Subjects: Grassland ecology -- South Africa -- Eastern Cape , Animals -- Food -- South Africa -- Eastern Cape , Herbivores -- Ecology -- South Africa -- Eastern Cape , Fire ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21961 , vital:29807
- Description: Fire and herbivory are both major drivers in grassland ecosystems throughout the world. Although these two driving forces act independently from one another the relationship between fire and herbivory may be more significant than either acting on their own. Heterogeneity within the landscape as a result of fire results in herbivores having to adapt their behaviour in space and time. My research focussed on 1) characterising the fire regime on Mkambati Nature Reserve (hereafter Mkambati) and 2) determining the foraging choices and energy maximisation principles displayed by herbivores in relation to the biomass of vegetation and post fire vegetation age. Fire regimes were characterised between 2007-2016 in the low nutrient coastal grasslands of Mkambati in terms of fire season, seasonality of fire-prone weather conditions, fire return interval (FRI) and influence of poaching-related ignitions. Based on these results I then assessed foraging choices in terms of energy maximisation of four large herbivore species. I explored what energy maximisation strategy was employed, i.e. maximisation of daily digestible energy (DDE) (recently burnt low biomass vegetation) or instantaneous digestible energy (IDE) (older high biomass vegetation), by herbivore species with different morpho-physiological traits. Common reedbuck (Redunca arundinum), red hartebeest (Alcelaphus buselaphus subsp. caama), zebra (Equus quagga) and eland (Tragelaphus oryx subsp. oryx) were fitted with GPS satellite tracking collars, and hourly GPS locations (observed) were taken between 2008 and 2016. Using mixed effects models, I compared observed and an associated set of random locations to determine the energy maximisation strategy employed by each species. Our results indicated that fires were concentrated in winter when monthly fire danger weather (FDI) was highest. The mean FRI at Mkambati was <3 years, but varied according to vegetation type, and whether censoring (for open ended FRIs) was applied to estimate mean FRIs. Poachers, with the intention of attracting ungulates, are an important source of ignition at Mkambati. Accordingly FRIs were shorter (approximately 2 years) in areas within 3 km of likely poacher entry points. Although all fires recorded at Mkambati during the study period were of anthropogenic origin, mean FRI still fell within the natural range reported for interior grasslands in South Africa. Based on these findings, underpinned by the fire regime information, I showed that red hartebeest and zebra maximised DDE inside and outside of fire seasons and frequently foraged in low biomass recently burnt grasslands. Eland generally favoured areas where they could maximise IDE outside of the fire season, however during the fire season they switched strategy to maximise DDE. Reedbuck did not maximise IDE or DDE at the same scale (patch scale) as the other species, but at a landscape (broader) scale they maximised both IDE and DDE. Through this research I have shown how regular fire affects the foraging and energy maximisation behaviour of large African herbivores and how morpho-physiological traits affect these decisions. In response to these results I recommend that the management of Mkambati implement a focused monitoring program comparing the frequently and less frequently burnt areas of the reserve in order to understand the complex effects of anthropogenic fire and its subsequent effects on the biota of Mkambati.
- Full Text:
- Date Issued: 2018
Synthesis, characterization and application of novel acetals derived from Eucalyptus oil
- Authors: Burger, Kirstin.
- Date: 2018
- Subjects: Plasticizers , Eucalyptus citriodora
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23548 , vital:30579
- Description: The aim of the project was to develop new bio-plasticizer compounds which could be incorporated into infant plastics. Plasticizers increase flexibility of plastic. These plasticizer compounds were derived from crude natural oils such as Eucalyptus citriodora oil and virgin coconut oil. A reagent which could be synthesized from Eucalyptus citriodora oil was, para-menthane-3,8-diol (PMD) which was present in a 60:40 ratio of cis and trans isomers of the diol. A green procedure to synthesize the diol, where an environmentally friendly catalyst, citric acid was used. Optimal conditions were 7% aqueous citric acid as the catalyst and 12 hour reaction which resulted in a citronellal conversion of 88.4 ± 0.80% and PMD selectivity of 75.4 ± 1.22%. As the diol was present in isomers, it was of interest to separate the cis and trans isomers for characterization purposes and later for subsequent individual isomer acetalization reactions. Yields obtained for the reaction for cis and trans-PMD were 51% and 36%, respectively. The kinetics for PMD synthesis from Eucalyptus citriodora oil was determined as second order with a rate constant of 0.0008hr-1 and Ea of 15.77kJ/mol. The isomers of para-menthane-3,8-diol could be separated from the isomeric mixture by solvent extraction at -78°C with n-heptane. Individual rod-shaped crystals could be isolated with this procedure and was characterized by X-ray crystallography techniques and identified as cis-para-menthane-3,8-diol. The trans-para-menthane-3,8-diol was successfully separated, however adequate crystals were not grown for X-ray crystallography analysis. Another method of isomer separation was investigated for PMD by the formation of a complex where anhydrous copper chloride could only form a novel complex with cis-para-menthane-3,8-diol. The trans isomer remained unreacted in the filtrate. The cis-para-menthane-3,8-diol isomer could be freed from the complex to yield pure cis isomer. Aldehydes could be synthesized from virgin coconut oil with carboxylic acid extraction procedures of the crude oil. Subsequent synthesis reactions from carboxylic acid to form aldehydes were performed and octanal (85% yield), decanal (88% yield), dodecanal (86% yield) and tetradecanal (14% yield) could be successfully synthesized as precursors to the novel acetalization reactions. Eight novel cyclic acetals with a characteristic 1,3-dioxine ring were successfully synthesized. However, diastereoisomers of cis-acetal and trans-acetal were present and required separation for characterization 1H-NMR, 13C-NMR, FT-IR, GC-MS and optical rotation techniques. The eight novel acetals were further characterized according to their physical properties such as there was no data available for these compounds. The following properties were determined: molecular mass, molecular formula, density, viscosity, boiling point, refractive index, enthalpy of vaporization, flash point, UV-VIS compatibility, solubility’s, colour and odour determination. Yields of up to 97% were obtained for these acetal compounds. The synthesis of acetals was optimized with batch reactions and optimum conditions were determined where eight catalysts were screened. These catalysts included: scandium triflate, Zeolite, sulphuric acid, p-toluene-sulfonic acid, Amberlyst 15®, Amberlyst 36®, Amberlite® IRA-120 and formic acid. Optimal conditions were with Amberlyst 15® catalyst, 50 minute reaction time at 65°C reaction temperature. The kinetics of the reaction was determined as zero order with a rate constant of 11.92 hr-1 and Ea of 0.050 kJ/mol. The acetalization reaction was evaluated using a UniQsis FlowSyn continuous flow reactor. One of the eight acetals (hexanal acetal) was used for the optimization study and the remaining acetals were evaluated with the optimum flow conditions. The reaction was improved with the use of continuous flow chemistry techniques by lowering of the optimum batch conditions. Various residence times (3.46-17.30 minutes) and temperature range (25-85°C) were studied to obtain optimum conditions. This process was efficient and low maintenance, which produced high acetal product selectivity of Optimum continuous flow conditions were determined at 55°C and 17.30 minute residence time with the flow rate of 0.1 ml/min. Heterogeneous catalysts such as Amberlyst 15® and Zeolite were screened and Amberlyst 15® determined as most favourable. The effect of Amberlyst 15® catalyst loading (0.5-2 g) was investigated over a temperature range of 25-85°C. Optimum catalyst loading was determined at 1g. The 8 compounds were tested for potential as plasticizers. This included mechanical, thermal, migratory and aesthetic testing. The novel acetals had to be compared to known plasticizers. Therefore, their plasticizer properties were compared to two commercial plasticizers: DBP and Eastman 168. As the compounds were derived from natural resources, they would be classified as bio-plasticizers if they exhibited such properties. Therefore, it was of interest to compare the novel compounds to a known bio-plasticizer: PMD-citronellal acetal. This compound was also present as a diastereoisomers mixture of cis and trans isomers. Therefore, diastereoisomers of the 8 acetals were separated as cis and trans isomers in high yields for plasticizer testing purposes. All 11 compounds (8 novel acetals, PMD-citronellal acetal, DBP and Eastman 168) were formulated in PVC to produce plastic films. As previously stated, isomers were present for the acetal compounds and these individual isomers were formulated into PVC formulations to evaluate if there was an effect of stereochemistry in the plastic films. Studies on this phenomenon were limited and therefore of interest. For isomeric plasticizer testing, 9 acetals (8 novel acetals and PMD-citronellal acetal) were used in the testing. Therefore 18 test compounds were formulated in PVC films for isomer plasticizer testing. The effect of increasing the compound amount in the PVC formulation was investigated in the range of 3-12% (w/w). The following tests were evaluated for all PVC test films: elongation, stress to fracture, glass transition temperature, leaching rate, flexibility, gloss and opacity. To validate the data and observations made, statistical validation models were developed to justify experimental design and trends observed. All novel compounds had plasticizer properties and one acetal compound was concluded as superior to DBP and Eastman 168, within the testing scope of the research. It was observed that higher molecular mass acetal compounds had increased plasticizer properties. Isomers for all acetal compounds were concluded to affect plasticizer properties differently and were highly significant. As the novel acetal compounds could be synthesized from natural crude resources, it was interesting to investigate if the synthesized acetals retained their anti-bacterial properties which the precursor oils possessed. Anti-bacterial testing of isomeric mixtures of C5-C12 acetal was investigated and compared to PMD-citronellal acetal and the two commercial plasticizers: DBP and Eastman 168. As the scope of the research focussed on bio-plasticizers for infant plastic products, test bacterial strains were chosen based on the pathogenic strains which cause diseases in babies. Six strains of bacteria were evaluated. It was of interest to evaluate the potency of the compounds by determining the minimum concentration of the compounds which would be potent enough to inhibit the bacteria. The commercial plasticizers inhibited no bacteria within the scope of the research. The acetals retained their anti-bacterial properties where C12 acetal was superior in 4/6 strains of bacteria and PMD-citronellal acetal was superior in 2/6 strains of bacteria. This research is novel and there are presently no data available on this. It was concluded that 8 new bio-plasticizers were synthesized, optimized and tested, within the scope of this research. These compounds were comparable to industry standards in all tests and possessed anti-bacterial properties which the industrial standards don’t possess.
- Full Text:
- Date Issued: 2018
- Authors: Burger, Kirstin.
- Date: 2018
- Subjects: Plasticizers , Eucalyptus citriodora
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/23548 , vital:30579
- Description: The aim of the project was to develop new bio-plasticizer compounds which could be incorporated into infant plastics. Plasticizers increase flexibility of plastic. These plasticizer compounds were derived from crude natural oils such as Eucalyptus citriodora oil and virgin coconut oil. A reagent which could be synthesized from Eucalyptus citriodora oil was, para-menthane-3,8-diol (PMD) which was present in a 60:40 ratio of cis and trans isomers of the diol. A green procedure to synthesize the diol, where an environmentally friendly catalyst, citric acid was used. Optimal conditions were 7% aqueous citric acid as the catalyst and 12 hour reaction which resulted in a citronellal conversion of 88.4 ± 0.80% and PMD selectivity of 75.4 ± 1.22%. As the diol was present in isomers, it was of interest to separate the cis and trans isomers for characterization purposes and later for subsequent individual isomer acetalization reactions. Yields obtained for the reaction for cis and trans-PMD were 51% and 36%, respectively. The kinetics for PMD synthesis from Eucalyptus citriodora oil was determined as second order with a rate constant of 0.0008hr-1 and Ea of 15.77kJ/mol. The isomers of para-menthane-3,8-diol could be separated from the isomeric mixture by solvent extraction at -78°C with n-heptane. Individual rod-shaped crystals could be isolated with this procedure and was characterized by X-ray crystallography techniques and identified as cis-para-menthane-3,8-diol. The trans-para-menthane-3,8-diol was successfully separated, however adequate crystals were not grown for X-ray crystallography analysis. Another method of isomer separation was investigated for PMD by the formation of a complex where anhydrous copper chloride could only form a novel complex with cis-para-menthane-3,8-diol. The trans isomer remained unreacted in the filtrate. The cis-para-menthane-3,8-diol isomer could be freed from the complex to yield pure cis isomer. Aldehydes could be synthesized from virgin coconut oil with carboxylic acid extraction procedures of the crude oil. Subsequent synthesis reactions from carboxylic acid to form aldehydes were performed and octanal (85% yield), decanal (88% yield), dodecanal (86% yield) and tetradecanal (14% yield) could be successfully synthesized as precursors to the novel acetalization reactions. Eight novel cyclic acetals with a characteristic 1,3-dioxine ring were successfully synthesized. However, diastereoisomers of cis-acetal and trans-acetal were present and required separation for characterization 1H-NMR, 13C-NMR, FT-IR, GC-MS and optical rotation techniques. The eight novel acetals were further characterized according to their physical properties such as there was no data available for these compounds. The following properties were determined: molecular mass, molecular formula, density, viscosity, boiling point, refractive index, enthalpy of vaporization, flash point, UV-VIS compatibility, solubility’s, colour and odour determination. Yields of up to 97% were obtained for these acetal compounds. The synthesis of acetals was optimized with batch reactions and optimum conditions were determined where eight catalysts were screened. These catalysts included: scandium triflate, Zeolite, sulphuric acid, p-toluene-sulfonic acid, Amberlyst 15®, Amberlyst 36®, Amberlite® IRA-120 and formic acid. Optimal conditions were with Amberlyst 15® catalyst, 50 minute reaction time at 65°C reaction temperature. The kinetics of the reaction was determined as zero order with a rate constant of 11.92 hr-1 and Ea of 0.050 kJ/mol. The acetalization reaction was evaluated using a UniQsis FlowSyn continuous flow reactor. One of the eight acetals (hexanal acetal) was used for the optimization study and the remaining acetals were evaluated with the optimum flow conditions. The reaction was improved with the use of continuous flow chemistry techniques by lowering of the optimum batch conditions. Various residence times (3.46-17.30 minutes) and temperature range (25-85°C) were studied to obtain optimum conditions. This process was efficient and low maintenance, which produced high acetal product selectivity of Optimum continuous flow conditions were determined at 55°C and 17.30 minute residence time with the flow rate of 0.1 ml/min. Heterogeneous catalysts such as Amberlyst 15® and Zeolite were screened and Amberlyst 15® determined as most favourable. The effect of Amberlyst 15® catalyst loading (0.5-2 g) was investigated over a temperature range of 25-85°C. Optimum catalyst loading was determined at 1g. The 8 compounds were tested for potential as plasticizers. This included mechanical, thermal, migratory and aesthetic testing. The novel acetals had to be compared to known plasticizers. Therefore, their plasticizer properties were compared to two commercial plasticizers: DBP and Eastman 168. As the compounds were derived from natural resources, they would be classified as bio-plasticizers if they exhibited such properties. Therefore, it was of interest to compare the novel compounds to a known bio-plasticizer: PMD-citronellal acetal. This compound was also present as a diastereoisomers mixture of cis and trans isomers. Therefore, diastereoisomers of the 8 acetals were separated as cis and trans isomers in high yields for plasticizer testing purposes. All 11 compounds (8 novel acetals, PMD-citronellal acetal, DBP and Eastman 168) were formulated in PVC to produce plastic films. As previously stated, isomers were present for the acetal compounds and these individual isomers were formulated into PVC formulations to evaluate if there was an effect of stereochemistry in the plastic films. Studies on this phenomenon were limited and therefore of interest. For isomeric plasticizer testing, 9 acetals (8 novel acetals and PMD-citronellal acetal) were used in the testing. Therefore 18 test compounds were formulated in PVC films for isomer plasticizer testing. The effect of increasing the compound amount in the PVC formulation was investigated in the range of 3-12% (w/w). The following tests were evaluated for all PVC test films: elongation, stress to fracture, glass transition temperature, leaching rate, flexibility, gloss and opacity. To validate the data and observations made, statistical validation models were developed to justify experimental design and trends observed. All novel compounds had plasticizer properties and one acetal compound was concluded as superior to DBP and Eastman 168, within the testing scope of the research. It was observed that higher molecular mass acetal compounds had increased plasticizer properties. Isomers for all acetal compounds were concluded to affect plasticizer properties differently and were highly significant. As the novel acetal compounds could be synthesized from natural crude resources, it was interesting to investigate if the synthesized acetals retained their anti-bacterial properties which the precursor oils possessed. Anti-bacterial testing of isomeric mixtures of C5-C12 acetal was investigated and compared to PMD-citronellal acetal and the two commercial plasticizers: DBP and Eastman 168. As the scope of the research focussed on bio-plasticizers for infant plastic products, test bacterial strains were chosen based on the pathogenic strains which cause diseases in babies. Six strains of bacteria were evaluated. It was of interest to evaluate the potency of the compounds by determining the minimum concentration of the compounds which would be potent enough to inhibit the bacteria. The commercial plasticizers inhibited no bacteria within the scope of the research. The acetals retained their anti-bacterial properties where C12 acetal was superior in 4/6 strains of bacteria and PMD-citronellal acetal was superior in 2/6 strains of bacteria. This research is novel and there are presently no data available on this. It was concluded that 8 new bio-plasticizers were synthesized, optimized and tested, within the scope of this research. These compounds were comparable to industry standards in all tests and possessed anti-bacterial properties which the industrial standards don’t possess.
- Full Text:
- Date Issued: 2018
Spatial and temporal heterogeneity of plant flammability
- Authors: Calitz, Wynand
- Date: 2018
- Subjects: Forest plants , Forest ecology Plants -- Adaptation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23500 , vital:30572
- Description: Heterogeneity in the natural environment has led to plants adapting traits to fit a niche. Within natural systems, fire has been a major driver of vegetation across the globe. Flammability has been suggested by many to be a trait adapted to reoccurring fire events. Much of the literature on flammability is theoretical and little has been done to cement it as a functional trait. In this thesis, I explore flammability across a wide range of plant species from both fire-free and -driven communities and compare observed results to other functional traits to identify if any link may exist between fire and being flammable. I further focus on the impact moisture availability may have on flammability as fire regimes are often correlated to rainfall season. Lastly, I investigate how different vegetation types respond to seasonal climate in terms of flammability. As a functional trait, flammability does correlate with traits associated with fire-driven system (e.g. small leaves in dense twig matrix). However, fire associated traits were also observed in fire-free species (Forest, Thicket, and Nama-Karoo), and in some cases traits not associated to fire proved flammable (e.g. large leaves on trees). I find that at a regional scale, plant moisture only correlates to flammability when rainfall amounts are well above or below average (e.g. drought). I also identify that species have different responses to moisture fluctuations and that inherent or accidental responses may influence observed flammability (e.g. trichomes). Lastly, I note that some biomes indicate strong association to season or climate (Fynbos and Thicket), while others indicate plasticity towards weather with species having different responses (Grassland). The study is the first to present estimates of flammability across a large number of species sampled at different times of the year. Future research will have to approach flammability as a meta-analysis by experimenting on different scales, particularly temporal and spatial scales.
- Full Text:
- Date Issued: 2018
- Authors: Calitz, Wynand
- Date: 2018
- Subjects: Forest plants , Forest ecology Plants -- Adaptation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/23500 , vital:30572
- Description: Heterogeneity in the natural environment has led to plants adapting traits to fit a niche. Within natural systems, fire has been a major driver of vegetation across the globe. Flammability has been suggested by many to be a trait adapted to reoccurring fire events. Much of the literature on flammability is theoretical and little has been done to cement it as a functional trait. In this thesis, I explore flammability across a wide range of plant species from both fire-free and -driven communities and compare observed results to other functional traits to identify if any link may exist between fire and being flammable. I further focus on the impact moisture availability may have on flammability as fire regimes are often correlated to rainfall season. Lastly, I investigate how different vegetation types respond to seasonal climate in terms of flammability. As a functional trait, flammability does correlate with traits associated with fire-driven system (e.g. small leaves in dense twig matrix). However, fire associated traits were also observed in fire-free species (Forest, Thicket, and Nama-Karoo), and in some cases traits not associated to fire proved flammable (e.g. large leaves on trees). I find that at a regional scale, plant moisture only correlates to flammability when rainfall amounts are well above or below average (e.g. drought). I also identify that species have different responses to moisture fluctuations and that inherent or accidental responses may influence observed flammability (e.g. trichomes). Lastly, I note that some biomes indicate strong association to season or climate (Fynbos and Thicket), while others indicate plasticity towards weather with species having different responses (Grassland). The study is the first to present estimates of flammability across a large number of species sampled at different times of the year. Future research will have to approach flammability as a meta-analysis by experimenting on different scales, particularly temporal and spatial scales.
- Full Text:
- Date Issued: 2018
The association of the bushclumps of Calcrete Bontveld with adjacent thicket
- Authors: Carvalho, Shandon Luke
- Date: 2018
- Subjects: Plant ecology -- South Africa -- Eastern Cape , Biodiversity conservation Landscape ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21949 , vital:29806
- Description: The thicket mosaic vegetation type known as Calcrete Bontveld is now only found at three sites within the Eastern Cape Province. Consisting of thicket-like bushclumps scattered among grassy dwarf shrubland, this vegetation is isolated from other systems due to its unique geographical location and the surrounding Valley Thicket. A strong similarity between the bushclumps of Calcrete Bontveld and the adjacent Valley Thicket has led to the aim of this study, which was to demonstrate that an association exists between these two vegetation types. To investigate this, two sites, namely Grassridge (natural vegetation on a mine) and Shamwari (natural due to its status as a reserve), were selected. This provided a unique comparison of the functionality of the two vegetation types and identified key processes responsible for the existence of this association. In terms of edaphic variables, soil organic content and field capacity, values were similar between bushclumps and thicket while soil depth was the greatest in thicket at both sites. At both sites, life forms, diversity and similarity indices were similar for bushclumps and thicket. By utilizing the Island Biogeography Theory, these bushclumps show an island-type origin and the distance between them and the adjacent Valley Thicket (mainland-type), as well as their size, influenced the association between the two vegetation types. Commonality of species between thicket and bushclumps are postulated to be tied to their dispersal mechanisms and fruit types. Bushclump isolation on flat-topped ridges excluded thicket species dispersed by autochory and anemochory. Zoochorous dispersal (by birds and mammals) was the common factor in the transfer of species between thicket and bushclumps as the latter is a large resource patch for fauna. The size of the bushclumps and their distance from the thicket influenced zoochorous dispersal. Larger and closer bushclumps attracted more birds and mammals than the small or more distant ones. These effects differ at the two sites due to the complex animal interaction that occurs in the Shamwari Game Reserve as opposed to the reduced animal interaction at Grassridge. This study suggests that an association exists between the bushclumps of Calcrete Bontveld and the adjacent Valley Thicket, and is reliant on the natural zoochory that occurs at each site.
- Full Text:
- Date Issued: 2018
- Authors: Carvalho, Shandon Luke
- Date: 2018
- Subjects: Plant ecology -- South Africa -- Eastern Cape , Biodiversity conservation Landscape ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/21949 , vital:29806
- Description: The thicket mosaic vegetation type known as Calcrete Bontveld is now only found at three sites within the Eastern Cape Province. Consisting of thicket-like bushclumps scattered among grassy dwarf shrubland, this vegetation is isolated from other systems due to its unique geographical location and the surrounding Valley Thicket. A strong similarity between the bushclumps of Calcrete Bontveld and the adjacent Valley Thicket has led to the aim of this study, which was to demonstrate that an association exists between these two vegetation types. To investigate this, two sites, namely Grassridge (natural vegetation on a mine) and Shamwari (natural due to its status as a reserve), were selected. This provided a unique comparison of the functionality of the two vegetation types and identified key processes responsible for the existence of this association. In terms of edaphic variables, soil organic content and field capacity, values were similar between bushclumps and thicket while soil depth was the greatest in thicket at both sites. At both sites, life forms, diversity and similarity indices were similar for bushclumps and thicket. By utilizing the Island Biogeography Theory, these bushclumps show an island-type origin and the distance between them and the adjacent Valley Thicket (mainland-type), as well as their size, influenced the association between the two vegetation types. Commonality of species between thicket and bushclumps are postulated to be tied to their dispersal mechanisms and fruit types. Bushclump isolation on flat-topped ridges excluded thicket species dispersed by autochory and anemochory. Zoochorous dispersal (by birds and mammals) was the common factor in the transfer of species between thicket and bushclumps as the latter is a large resource patch for fauna. The size of the bushclumps and their distance from the thicket influenced zoochorous dispersal. Larger and closer bushclumps attracted more birds and mammals than the small or more distant ones. These effects differ at the two sites due to the complex animal interaction that occurs in the Shamwari Game Reserve as opposed to the reduced animal interaction at Grassridge. This study suggests that an association exists between the bushclumps of Calcrete Bontveld and the adjacent Valley Thicket, and is reliant on the natural zoochory that occurs at each site.
- Full Text:
- Date Issued: 2018
Protected area expansion and conservation stewardship in the Olifants Catchment: mechanisms, patterns and benefits
- Authors: Coetzer, Crystal Jeanne
- Date: 2018
- Subjects: Biodiversity conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30006 , vital:30808
- Description: State Conservation Areas (SCAs), as state-owned and -run parks, form the foundation of recognised conservation actions. However, park expansion on the scale required to meet urgent conservation targets is limited by state budgets and parks are increasingly framed in the context of advancing broader societal needs. Motivating for the need to assess the efficacy of alternative conservation strategies, as both contrasting governance and legal mechanisms, this study aimed to rapidly assess the role of private land conservation (PLC) strategies in expanding protection. In particular, this included the role of emerging stewardship approaches, by using semi-structured interviews with park implementers on a national scale. Evaluating the biodiversity and ecosystem service representation and complementarity of contrasting conservation strategies on a catchment scale, using open-source spatial data was employed. Questionnaires tested park managers’ perceptions of benefits across different strategies in a conservation-oriented landscape. Results indicate a strategic shift toward PLC strategies to expand parks in the form of formalised, well-planned and supported contractual and stewardship agreements. SCAs are vital baselines for biodiversity and ecosystem service representation in the catchment with a variety of private mechanisms supplementing protection, especially in highly contested areas. The perceived benefits rated by managers revealed interesting links between benefits and contrasting governance types, legal mechanisms, legal status, size and age of reserves. State parks may be more relevant for generating socio-cultural benefits, while private parks, through the need to remain economically viable, valued a diverse range of socio-economic benefits. Informal conservation areas formed integral parts of the conservation-orientated landscape, rating benefits equally to more secure mechanisms. Private land must be incorporated into conservation through diverse mechanisms to meet the range of mutually exclusive conservation objectives of the 21st century.
- Full Text:
- Date Issued: 2018
- Authors: Coetzer, Crystal Jeanne
- Date: 2018
- Subjects: Biodiversity conservation -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/30006 , vital:30808
- Description: State Conservation Areas (SCAs), as state-owned and -run parks, form the foundation of recognised conservation actions. However, park expansion on the scale required to meet urgent conservation targets is limited by state budgets and parks are increasingly framed in the context of advancing broader societal needs. Motivating for the need to assess the efficacy of alternative conservation strategies, as both contrasting governance and legal mechanisms, this study aimed to rapidly assess the role of private land conservation (PLC) strategies in expanding protection. In particular, this included the role of emerging stewardship approaches, by using semi-structured interviews with park implementers on a national scale. Evaluating the biodiversity and ecosystem service representation and complementarity of contrasting conservation strategies on a catchment scale, using open-source spatial data was employed. Questionnaires tested park managers’ perceptions of benefits across different strategies in a conservation-oriented landscape. Results indicate a strategic shift toward PLC strategies to expand parks in the form of formalised, well-planned and supported contractual and stewardship agreements. SCAs are vital baselines for biodiversity and ecosystem service representation in the catchment with a variety of private mechanisms supplementing protection, especially in highly contested areas. The perceived benefits rated by managers revealed interesting links between benefits and contrasting governance types, legal mechanisms, legal status, size and age of reserves. State parks may be more relevant for generating socio-cultural benefits, while private parks, through the need to remain economically viable, valued a diverse range of socio-economic benefits. Informal conservation areas formed integral parts of the conservation-orientated landscape, rating benefits equally to more secure mechanisms. Private land must be incorporated into conservation through diverse mechanisms to meet the range of mutually exclusive conservation objectives of the 21st century.
- Full Text:
- Date Issued: 2018
Social learning for public participation in environmental governance: the case of Knysna Municipality
- Authors: Currie, Bianca
- Date: 2018
- Subjects: Environmental policy -- South Africa -- Knysna -- Social aspects , Environmental management -- South Africa -- Knysna
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/29852 , vital:30785
- Description: Democratic environmental governance in complex systems requires an adaptive management approach involving a diversity of stakeholders in collaborative learning and decision-making. The decisions are value-laden, and local municipalities are struggling to reconcile the diversity of values, and balance varied and diverse social and ecological needs, for sustainability. Social learning has emerged as a promising approach but the challenge lies in effective implementation, practice and assessment of social learning. This thesis explored public participation practices in environmental governance in the Knysna Municipality and went on to develop a social learning procedural model for public participation, as well as assessment criteria for monitoring social learning processes. The model and criteria provide a foundation and the tools needed to operationalise social learning for adaptive management in environmental governance in complex systems.
- Full Text:
- Date Issued: 2018
- Authors: Currie, Bianca
- Date: 2018
- Subjects: Environmental policy -- South Africa -- Knysna -- Social aspects , Environmental management -- South Africa -- Knysna
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/29852 , vital:30785
- Description: Democratic environmental governance in complex systems requires an adaptive management approach involving a diversity of stakeholders in collaborative learning and decision-making. The decisions are value-laden, and local municipalities are struggling to reconcile the diversity of values, and balance varied and diverse social and ecological needs, for sustainability. Social learning has emerged as a promising approach but the challenge lies in effective implementation, practice and assessment of social learning. This thesis explored public participation practices in environmental governance in the Knysna Municipality and went on to develop a social learning procedural model for public participation, as well as assessment criteria for monitoring social learning processes. The model and criteria provide a foundation and the tools needed to operationalise social learning for adaptive management in environmental governance in complex systems.
- Full Text:
- Date Issued: 2018
The FAST fabric objective measurement properties of commercial worsted apparel fabrics available in South Africa
- Authors: Das, Sweta
- Date: 2018
- Subjects: Textile fabrics -- Testing , Textile fabrics -- Measurement , Textile fibers -- Testing , Textile design
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/17814 , vital:28458
- Description: In the last few decades, there has been a shift globally towards the objective measurement of these textile fibre, yarn and fabric properties which determine processing performance and product quality. This shift is also very apparent in the objective measurement of fabric properties, particularly those relating to handle and making-up into a garment. This study was motivated by the fact that the adoption of fabric objective measurement (FOM), specifically the FAST system, will benefit the South African worsted apparel sector, as it has done in various other countries which produce high quality worsted apparel fabrics and garments. FAST is robust and portable, yet inexpensive. The main objective of the study was to develop a FAST referencing system which can be used for benchmarking by the local apparel industry and, as a basis for encouraging and persuading the industry to adopt this system of fabric quality measurement and assurance and thereby improve their product quality and international competitiveness. To achieve the main objective, involved sourcing and FAST testing a representative cross-section of commercial worsted apparel fabrics with the emphasis on wool and wool blends from the local fabric and clothing manufacturing industry, and determining how the various FAST properties were affected by factors such as fabric weave, fibre blend and weight, since this could impact on the specific nature and validity of the referencing system. A total of some 394 worsted type commercial fabrics, mainly in wool and wool blends, were sourced from, and with the inputs of, local apparel fabric and clothing manufacturers so as to ensure the local fabric and garment representative of the sample population and after which the fabrics were tested on the FAST system. ANOVA (regression analysis) was carried out on each of the FAST parameters in order to determine whether fabric weight, weave, thickness and fibre composition (pure wool and wool blends) had a statistically significant effect on them, since this is an important aspect which needs to be clarified prior to the development of a envisaged meaningful FAST system.
- Full Text:
- Date Issued: 2018
- Authors: Das, Sweta
- Date: 2018
- Subjects: Textile fabrics -- Testing , Textile fabrics -- Measurement , Textile fibers -- Testing , Textile design
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/17814 , vital:28458
- Description: In the last few decades, there has been a shift globally towards the objective measurement of these textile fibre, yarn and fabric properties which determine processing performance and product quality. This shift is also very apparent in the objective measurement of fabric properties, particularly those relating to handle and making-up into a garment. This study was motivated by the fact that the adoption of fabric objective measurement (FOM), specifically the FAST system, will benefit the South African worsted apparel sector, as it has done in various other countries which produce high quality worsted apparel fabrics and garments. FAST is robust and portable, yet inexpensive. The main objective of the study was to develop a FAST referencing system which can be used for benchmarking by the local apparel industry and, as a basis for encouraging and persuading the industry to adopt this system of fabric quality measurement and assurance and thereby improve their product quality and international competitiveness. To achieve the main objective, involved sourcing and FAST testing a representative cross-section of commercial worsted apparel fabrics with the emphasis on wool and wool blends from the local fabric and clothing manufacturing industry, and determining how the various FAST properties were affected by factors such as fabric weave, fibre blend and weight, since this could impact on the specific nature and validity of the referencing system. A total of some 394 worsted type commercial fabrics, mainly in wool and wool blends, were sourced from, and with the inputs of, local apparel fabric and clothing manufacturers so as to ensure the local fabric and garment representative of the sample population and after which the fabrics were tested on the FAST system. ANOVA (regression analysis) was carried out on each of the FAST parameters in order to determine whether fabric weight, weave, thickness and fibre composition (pure wool and wool blends) had a statistically significant effect on them, since this is an important aspect which needs to be clarified prior to the development of a envisaged meaningful FAST system.
- Full Text:
- Date Issued: 2018