Coordination polymers for denitrogenation of fuel oils
- Authors: Dembaremba, Tendai O
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53630 , vital:45682
- Description: In this thesis, we present adsorptive removal of nitrogen-containing compounds from fuel oil as an alternative to complement conventional hydrotreatment to obtain ultra-low sulfur and nitrogen levels. This is in cognizance of the challenges nitrogen-containing compounds pose to the hydrotreatment process, particularly their inhibition and/or poisoning of the catalysts used in the process, of which basic nitrogen-containing compounds are the major culprits. Selectivity is the biggest challenge for adsorptive removal of nitrogen-containing compounds. We explore reticular synthesis of metal organic frameworks and the use of coordinatively unsaturated metal sites in 1-dimensional coordination polymers to achieve good selectivity for nitrogen-containing compounds. In the first part of the thesis, reticular synthesis of metal organic frameworks to control the size of the cavity, and strategically use the linkers and metal centres was envisaged. In this work we explored variation of the metal centres in the secondary building units (SBUs of the MOFs as the first step to the testing and implementation of the design strategies. Carbazole, representing carbazoles which the major compounds that remain in hydrotreated fuel, was the target compound. Four MOFs of zinc (Zn-CDC-bpe), copper (Cu-CDC-bpe), nickel (Ni-CDC-bpe) and cobalt (Co-CDC-bpe) based on the formation of a dinuclear metal paddlewheel SBUs with the ligand 9H-Carbazole-3,6-dicarboxylic acid (H2CDC) and occupation of the axial positions of the paddlewheel by 1,2-Bis(4-pyridyl)ethane (bpe) to form porous networks were synthesized. A fifth MOF containing only CDC which forms a [Zn4O(O2C-R)5(O2HC-R)] SBU was also synthesized (Zn-CDC). The ligand H2CDC was inspired by the possibility of improving selectivity for carbazole via π–π interactions through the more preferred parallel-offset stacking as well as the possibility for further substitution of the carbazole N-H to add groups that improve selectivity. The sizes of the MOF cavities can then be controlled by choosing different lengths of ligands analogous to 1,2-Bis(4-pyridyl)ethane (bpe), e.g. 4,4’-bipyridine and pyrazine. All the MOFs showed good selectivity of carbazole. The Zn-CDC MOF also had good selectivity for the basic nitrogen-containing compounds tested: quinoline, isoquinoline, quinaldine and 1-naphthylamine. Its uptake of carbazole was also slightly higher. This was attributed to the presence of an unsaturated Zn site in the SBU. Adsorption in all the MOFs was primarily due to physisorption. It was concluded that the role of the metal centre does not play a significant role in the adsorption of carbazole besides providing a template for reticular synthesis. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Dembaremba, Tendai O
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53630 , vital:45682
- Description: In this thesis, we present adsorptive removal of nitrogen-containing compounds from fuel oil as an alternative to complement conventional hydrotreatment to obtain ultra-low sulfur and nitrogen levels. This is in cognizance of the challenges nitrogen-containing compounds pose to the hydrotreatment process, particularly their inhibition and/or poisoning of the catalysts used in the process, of which basic nitrogen-containing compounds are the major culprits. Selectivity is the biggest challenge for adsorptive removal of nitrogen-containing compounds. We explore reticular synthesis of metal organic frameworks and the use of coordinatively unsaturated metal sites in 1-dimensional coordination polymers to achieve good selectivity for nitrogen-containing compounds. In the first part of the thesis, reticular synthesis of metal organic frameworks to control the size of the cavity, and strategically use the linkers and metal centres was envisaged. In this work we explored variation of the metal centres in the secondary building units (SBUs of the MOFs as the first step to the testing and implementation of the design strategies. Carbazole, representing carbazoles which the major compounds that remain in hydrotreated fuel, was the target compound. Four MOFs of zinc (Zn-CDC-bpe), copper (Cu-CDC-bpe), nickel (Ni-CDC-bpe) and cobalt (Co-CDC-bpe) based on the formation of a dinuclear metal paddlewheel SBUs with the ligand 9H-Carbazole-3,6-dicarboxylic acid (H2CDC) and occupation of the axial positions of the paddlewheel by 1,2-Bis(4-pyridyl)ethane (bpe) to form porous networks were synthesized. A fifth MOF containing only CDC which forms a [Zn4O(O2C-R)5(O2HC-R)] SBU was also synthesized (Zn-CDC). The ligand H2CDC was inspired by the possibility of improving selectivity for carbazole via π–π interactions through the more preferred parallel-offset stacking as well as the possibility for further substitution of the carbazole N-H to add groups that improve selectivity. The sizes of the MOF cavities can then be controlled by choosing different lengths of ligands analogous to 1,2-Bis(4-pyridyl)ethane (bpe), e.g. 4,4’-bipyridine and pyrazine. All the MOFs showed good selectivity of carbazole. The Zn-CDC MOF also had good selectivity for the basic nitrogen-containing compounds tested: quinoline, isoquinoline, quinaldine and 1-naphthylamine. Its uptake of carbazole was also slightly higher. This was attributed to the presence of an unsaturated Zn site in the SBU. Adsorption in all the MOFs was primarily due to physisorption. It was concluded that the role of the metal centre does not play a significant role in the adsorption of carbazole besides providing a template for reticular synthesis. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-12
Optimization of liposomes for enhanced stability against degradation by gastrointestinal fluid content
- Authors: Scholtz, Carla Chleo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54117 , vital:46305
- Description: Motivation: Liposomes are nanoparticulate carriers consisting of a hydrophobic bilayer and a hydrophilic core. Their application as drug carrier systems arises from their unique physiochemical structure, biocompatibility and biodegradability. Their biphasic nature is significant in the delivery of peptide and protein drug molecules as it is thus able to encompass both hydrophobic and hydrophilic molecules. Liposomes are actively being used for drug delivery intravenously. These formulations have been successful in reducing side effects and improving therapeutic efficacy. However, the intravenous route poses many challenges and is not the preferred route of administration amongst patients. The oral route of administration is non-invasive, and administration is of ease, therefore it is the preferred route of administration amongst patients, especially those with complex medicine regimes. Problem: The gastrointestinal tract is a harsh environment. In order for liposomes to maintain their integrity during their course they require a level of stability against gastric and intestinal fluids and its associated constituents such as gastric and pancreatic enzymes, low pH and bile acid. Methodology: Based on recommendations extrapolated from literature, the incorporation of a bile salt, sodium glycocholate, into liposomes in conjunction with coating the surface with chitosan was selected as the optimization strategies to enhance the stability of liposomes against degradation in the gastrointestinal tract. Bilosomes with encapsulated calce in were produced using the thin-film hydration method and coated with chitosan. An in vitrocalce in release assay was conducted in simulated gastric and intestinal fluids which presented with in vivo conditions in terms of pH and enzymes and additional constituents such as a bile salt. Stability was determined by the extent of digestion within the simulated fluids with time. Results: Characterization results suggested that the addition of chitosan and sodium glycocholate to the liposomal formulation has significant effects on the physiochemical properties. The colloidal dispersions could not retain their stability during storage which was noticeable during HRTEM. Despite optimization of the liposomes, in vitro studies showed significant release in both simulated gastric and intestinal fluids, with majority release seen in the presence of pepsin and pancreatic, at low pH and in the presence of bile acid. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Scholtz, Carla Chleo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54117 , vital:46305
- Description: Motivation: Liposomes are nanoparticulate carriers consisting of a hydrophobic bilayer and a hydrophilic core. Their application as drug carrier systems arises from their unique physiochemical structure, biocompatibility and biodegradability. Their biphasic nature is significant in the delivery of peptide and protein drug molecules as it is thus able to encompass both hydrophobic and hydrophilic molecules. Liposomes are actively being used for drug delivery intravenously. These formulations have been successful in reducing side effects and improving therapeutic efficacy. However, the intravenous route poses many challenges and is not the preferred route of administration amongst patients. The oral route of administration is non-invasive, and administration is of ease, therefore it is the preferred route of administration amongst patients, especially those with complex medicine regimes. Problem: The gastrointestinal tract is a harsh environment. In order for liposomes to maintain their integrity during their course they require a level of stability against gastric and intestinal fluids and its associated constituents such as gastric and pancreatic enzymes, low pH and bile acid. Methodology: Based on recommendations extrapolated from literature, the incorporation of a bile salt, sodium glycocholate, into liposomes in conjunction with coating the surface with chitosan was selected as the optimization strategies to enhance the stability of liposomes against degradation in the gastrointestinal tract. Bilosomes with encapsulated calce in were produced using the thin-film hydration method and coated with chitosan. An in vitrocalce in release assay was conducted in simulated gastric and intestinal fluids which presented with in vivo conditions in terms of pH and enzymes and additional constituents such as a bile salt. Stability was determined by the extent of digestion within the simulated fluids with time. Results: Characterization results suggested that the addition of chitosan and sodium glycocholate to the liposomal formulation has significant effects on the physiochemical properties. The colloidal dispersions could not retain their stability during storage which was noticeable during HRTEM. Despite optimization of the liposomes, in vitro studies showed significant release in both simulated gastric and intestinal fluids, with majority release seen in the presence of pepsin and pancreatic, at low pH and in the presence of bile acid. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text:
- Date Issued: 2021-12
Perceptions of small-scale vegetable farmers on drought mitigation strategies in the Amathole District Municipality of the Eastern Cape Province
- Authors: Dingiswayo, Xolisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53676 , vital:45686
- Description: The present study aimed to investigate perceptions of small-scale vegetable farmers on drought mitigation strategies in the Amathole District Municipality of the Eastern Cape Province. The research objective was to investigate what small-scale vegetable farmers’ perceptions and readiness are in terms of strategies to cope with drought conditions. The study was conducted within the Mbashe, Mnquma, Amahlathi and Great Kei local municipalities of the Eastern Cape. Primary data collection was conducted among 44 small-scale vegetable farmers of the Amathole municipal district. These are farmers who receive social support from the government, are registered with the Department of Rural Development and Agrarian Reform and contribute to the fight against food insecurity in the Amathole district. The primary data was also collected from 13 agricultural extension officers with high experience in advising small-scale farmers residing in the Amathole district. Data collection took place in various local municipalities under Amathole District Municipality, namely: Mbashe, Mnquma, Amahlathi and Great Kei. A multi-method approach was adopted in this study as an appropriate technique to create an improved quality of research which eliminates the deep-rooted bias to either qualitative or quantitative methods alone. A self-administered questionnaires with both closed and open-ended questions – one for the small-scale farmer survey and the second for the extension officer survey – was employed as data collection instrument. The demographic characteristics of small-scale vegetable farmers in the survey area indicated that the present majority of farmers are married male Xhosa farmers between the ages of 56 and 65 years old, with a secondary level of education. The majority of the farmers are typically resource-poor − which implies that the added menace of drought poses the risk that small-scale vegetable farming could decline to mere subsistence level or worse. Drought was found to be a major problem in Mbashe, Mnquma, Amahlathi and Great Kei local municipalities within the Amathole municipal district, with an acute impact on farmers’ production and generation of income. From the data, it emerged that farmers are not sufficiently informed about and do not receive specific training in drought mitigation strategies. Farmers rely on drought alleviation methods but there is a lack of adaptive strategies and timely, long-term ii state intervention. Being resource-poor, these small-scale producers are reliant on natural resources – notably water for irrigating crops. The study established further that there is neither the resources nor sufficient training by and involvement of the extension service. Farmers therefore rely on the use of drought coping mechanisms and drought mitigation techniques and on adapting their production systems. The information-sharing sessions recommended can assist in improving rural livelihoods and the productivity of small-scale vegetable farmers. The absence of engagement of youth in farming means that modern conservation and innovative farming techniques and systems are not implemented towards reducing the impacts of climate change − as well as revitalizing rural areas such Amathole. Access to education about drought, improved drought coping mechanisms and adaptive strategies should be created to facilitate an exchange of traditional and modern agricultural information. The development of infrastructure in rural communities and farming areas is another factor crucial to improving farming systems and operations in the Amathole municipal district. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Dingiswayo, Xolisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53676 , vital:45686
- Description: The present study aimed to investigate perceptions of small-scale vegetable farmers on drought mitigation strategies in the Amathole District Municipality of the Eastern Cape Province. The research objective was to investigate what small-scale vegetable farmers’ perceptions and readiness are in terms of strategies to cope with drought conditions. The study was conducted within the Mbashe, Mnquma, Amahlathi and Great Kei local municipalities of the Eastern Cape. Primary data collection was conducted among 44 small-scale vegetable farmers of the Amathole municipal district. These are farmers who receive social support from the government, are registered with the Department of Rural Development and Agrarian Reform and contribute to the fight against food insecurity in the Amathole district. The primary data was also collected from 13 agricultural extension officers with high experience in advising small-scale farmers residing in the Amathole district. Data collection took place in various local municipalities under Amathole District Municipality, namely: Mbashe, Mnquma, Amahlathi and Great Kei. A multi-method approach was adopted in this study as an appropriate technique to create an improved quality of research which eliminates the deep-rooted bias to either qualitative or quantitative methods alone. A self-administered questionnaires with both closed and open-ended questions – one for the small-scale farmer survey and the second for the extension officer survey – was employed as data collection instrument. The demographic characteristics of small-scale vegetable farmers in the survey area indicated that the present majority of farmers are married male Xhosa farmers between the ages of 56 and 65 years old, with a secondary level of education. The majority of the farmers are typically resource-poor − which implies that the added menace of drought poses the risk that small-scale vegetable farming could decline to mere subsistence level or worse. Drought was found to be a major problem in Mbashe, Mnquma, Amahlathi and Great Kei local municipalities within the Amathole municipal district, with an acute impact on farmers’ production and generation of income. From the data, it emerged that farmers are not sufficiently informed about and do not receive specific training in drought mitigation strategies. Farmers rely on drought alleviation methods but there is a lack of adaptive strategies and timely, long-term ii state intervention. Being resource-poor, these small-scale producers are reliant on natural resources – notably water for irrigating crops. The study established further that there is neither the resources nor sufficient training by and involvement of the extension service. Farmers therefore rely on the use of drought coping mechanisms and drought mitigation techniques and on adapting their production systems. The information-sharing sessions recommended can assist in improving rural livelihoods and the productivity of small-scale vegetable farmers. The absence of engagement of youth in farming means that modern conservation and innovative farming techniques and systems are not implemented towards reducing the impacts of climate change − as well as revitalizing rural areas such Amathole. Access to education about drought, improved drought coping mechanisms and adaptive strategies should be created to facilitate an exchange of traditional and modern agricultural information. The development of infrastructure in rural communities and farming areas is another factor crucial to improving farming systems and operations in the Amathole municipal district. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-12
Optimising the uptake of [𝐈𝐫𝐂𝐥𝟔]𝟐− by a diammonium resin: HCl effect and resin performance
- Authors: Ngayeka, Mbokazi Zizipho
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54089 , vital:46284
- Description: The separation of [IrCl6]2- from [RhCl5(H2O)]2- by silica microparticles functionalized with 1,10-diamindecane (C10) and quaternized with 4-nitrobenzylchloride (NO2Benz) in various hydrochloric acid mediums was investigated by continuous column studies. The sorbent materials were synthesized using three different routes: Synthesis route 1 (NaI catalyzed synthesis of diammonium functionalized silica microparticles), Synthesis Route 2 (via silylazation of silica followed by functionalization) and Synthesis Route 3 (silane-based sorbent material). The functionalized sorbent materials were characterized by NMR, Microanalysis, SEM-EDS, FT-IR, TGA and BET surface area. The separation efficiency of the quaternary diammonium cations was investigated under dynamic flow adsorption conditions. Preliminary ICP-OES runs were done, at 6 M HCl, to assess which synthesis route gave the best performing sorbent material. [IrCl6]2- selectivity of the sorbent materials was achieved by washing with an HCl solution to remove unadsorbed metal species, then stripping off the [RhCl5(H2O)]2- with 0.05 M of sodium chlorate and the iridium species was eluted with a 20% HCl solution. From the preliminary ICP-OES, loading capacities were calculated, and it was observed that the three sorbent materials from synthesis route 2 (13.89 mg/g for (4) SSC10NO2Benz-A, 1.44 mg/g for (5) SSC10NO2Benz-HoA, and 1.0859 mg/g for (6) SSC10NO2Benz-DoA) showed the highest uptake of [IrCl6]2- and route 1 (1.89 mg/g for (1) SSC10NO2Benz-A, 1.25 mg/g for (2) SSC10NO2Benz-HoA and 0.99 mg/g for (3) SSC10NO2Benz-DoA ) and Route 3 (0.55 mg/g for (7) SC10-AI and 0.755 mg/g for (8) SC10-ACl) materials did not perform efficiently enough, thus were not used further for the HCl study. Within synthesis route 2, three sorbent materials were evaluated, which had varying quantities of the cation: SSC10NO2Benz-A (having a quantity previously used in our research and denoted A), SSC10NO2Benz-HoA (having a quantity Half of A) and SSC10NO2Benz-DoA (having a quantity double of A). SSC10NO2Benz-A showed the highest loading capacity than SSC10NO2Benz-HoA and SSC10NO2Benz-DoA; HCl studies were carried out using SSC10NO2Benz-A. HCl solution having different concentrations (5, 5.5 , 6 , 6.6 and 6.8 M) were used to prepare the metal solutions. This was done to assess which HCl concentration gave the best metal solution containing high amounts of [IrCl6]2- and [RhCl5(H2O)]2-, which would result in a more efficient separation. An auto titrator was used to standardize the HCl concentrations, and the metal ion chloride species solutions were determined by UV-Vis, and their concentrations were confirmed with ICP-OES. Column sorption of iridium and rhodium on SSC10NO2Benz-A using these HCl solutions was carried out, and loading capacities of [IrCl6]2- were obtained. The loading capacities of the 5 M, 5.5 M, 6 M, 6,6 M and 6.8 M HCl solutions for [IrCl6]2- were 2.64, 4.01, 13.89, 18.15 and 7.23 mg/g, respectively. The optimum separation conditions were thus determined by investigating effective parameters such as the method of synthesis, silica to cation ratio, HCl concentration and flow rate. This thesis presents quaternary diammonium sorbent materials that could be applied in feed solutions from ore processing for iridium recovery. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Ngayeka, Mbokazi Zizipho
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54089 , vital:46284
- Description: The separation of [IrCl6]2- from [RhCl5(H2O)]2- by silica microparticles functionalized with 1,10-diamindecane (C10) and quaternized with 4-nitrobenzylchloride (NO2Benz) in various hydrochloric acid mediums was investigated by continuous column studies. The sorbent materials were synthesized using three different routes: Synthesis route 1 (NaI catalyzed synthesis of diammonium functionalized silica microparticles), Synthesis Route 2 (via silylazation of silica followed by functionalization) and Synthesis Route 3 (silane-based sorbent material). The functionalized sorbent materials were characterized by NMR, Microanalysis, SEM-EDS, FT-IR, TGA and BET surface area. The separation efficiency of the quaternary diammonium cations was investigated under dynamic flow adsorption conditions. Preliminary ICP-OES runs were done, at 6 M HCl, to assess which synthesis route gave the best performing sorbent material. [IrCl6]2- selectivity of the sorbent materials was achieved by washing with an HCl solution to remove unadsorbed metal species, then stripping off the [RhCl5(H2O)]2- with 0.05 M of sodium chlorate and the iridium species was eluted with a 20% HCl solution. From the preliminary ICP-OES, loading capacities were calculated, and it was observed that the three sorbent materials from synthesis route 2 (13.89 mg/g for (4) SSC10NO2Benz-A, 1.44 mg/g for (5) SSC10NO2Benz-HoA, and 1.0859 mg/g for (6) SSC10NO2Benz-DoA) showed the highest uptake of [IrCl6]2- and route 1 (1.89 mg/g for (1) SSC10NO2Benz-A, 1.25 mg/g for (2) SSC10NO2Benz-HoA and 0.99 mg/g for (3) SSC10NO2Benz-DoA ) and Route 3 (0.55 mg/g for (7) SC10-AI and 0.755 mg/g for (8) SC10-ACl) materials did not perform efficiently enough, thus were not used further for the HCl study. Within synthesis route 2, three sorbent materials were evaluated, which had varying quantities of the cation: SSC10NO2Benz-A (having a quantity previously used in our research and denoted A), SSC10NO2Benz-HoA (having a quantity Half of A) and SSC10NO2Benz-DoA (having a quantity double of A). SSC10NO2Benz-A showed the highest loading capacity than SSC10NO2Benz-HoA and SSC10NO2Benz-DoA; HCl studies were carried out using SSC10NO2Benz-A. HCl solution having different concentrations (5, 5.5 , 6 , 6.6 and 6.8 M) were used to prepare the metal solutions. This was done to assess which HCl concentration gave the best metal solution containing high amounts of [IrCl6]2- and [RhCl5(H2O)]2-, which would result in a more efficient separation. An auto titrator was used to standardize the HCl concentrations, and the metal ion chloride species solutions were determined by UV-Vis, and their concentrations were confirmed with ICP-OES. Column sorption of iridium and rhodium on SSC10NO2Benz-A using these HCl solutions was carried out, and loading capacities of [IrCl6]2- were obtained. The loading capacities of the 5 M, 5.5 M, 6 M, 6,6 M and 6.8 M HCl solutions for [IrCl6]2- were 2.64, 4.01, 13.89, 18.15 and 7.23 mg/g, respectively. The optimum separation conditions were thus determined by investigating effective parameters such as the method of synthesis, silica to cation ratio, HCl concentration and flow rate. This thesis presents quaternary diammonium sorbent materials that could be applied in feed solutions from ore processing for iridium recovery. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
Corrosion and hydrogen resistant modified zirlo surfaces for nuclear fuel cladding
- Authors: Ngongo, Sinoyolo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54077 , vital:46252
- Description: Zirconium (Zr) alloys are used as fuel cladding material in all modern water cooled commercial nuclear reactors. Zr alloys have many desirable properties for the nuclear reactor core environment, however, it also has a weakness in that overheated zirconium alloy fuel rods react with hot steam resulting in the release of hydrogen. High temperatures increase the oxidation rate and hence the hydrogen production rate which in turn increase the risk of a hydrogen gas explosion such as what is surmised to have happened in the 2011 Fukushima Daiichi nuclear plant incident. The some of the hydrogen produced will also diffuse into the zirconium alloy and form zirconium hydrides which will weaken the original zirconium alloy material. The development of accident tolerant fuel became a major focus area after the Fukushima event in March 2011 with the U.S. congress directing the U.S. Department of Energy to develop fuel with enhanced accident tolerance at high temperatures. The main objective in the case of zirconium alloy cladding has been the modification of cladding surface layers by coating or doping in order to reduce the oxidation rate and hydrogen generation rate by the reaction of steam with zirconium alloy cladding at high temperatures. This thesis focuses on two surface modifications to decrease the surface corrosion rate of ZIRLOTM (the Zr alloy used in this study) and reduce hydrogen uptake by ZIRLO. The first modification involves an oxidation-resistant nano-crystalline diamond (NCD) film deposited on ZIRLO. The NCD layer was deposited in a microwave plasma-enhanced linear antenna chemical vapor deposition (MW-LA-PECVD) system after immersion of the ZIRLO tubes in a water-based solution containing nanodiamonds. ZIRLO tube samples were coated with 200 nm and 500 nm thick NCD layers. The 200 nm thick NCD coated ZIRLO was kept as control sample whereas the 500 nm thick NCD coated ZIRLO was exposed to steam oxidation at 360 °C for 90 days. The results revealed that the NCD exfoliated in some areas leaving the ZIRLO exposed to the steam. In the areas where the diamond did not exfoliate, the diamond was still attached to the ZIRLO with an amorphous carbon layer present between the NCD and the zirconium oxide layer.The transmission electron microscopy (TEM) results of this study indicate the presence a sp3 – hybridised diamond phase for the NCD layer as well as an intermediate amorphous carbon layer between the NCD and ZrO2 layers. Analyses of the area where the NCD layer had exfoliated showed no evidence of an NCD layer. It is possible that the amorphous carbon layer between the diamond and the zirconium oxide is responsible for weak interfacial bonding leading to partial exfoliation during oxidation in steam 360 °C for 90 days. In the second modification, the effectiveness of a Cr doped ZrO2 layer to reduce the migration rate of hydrogen in ZrO2 was investigated. The ZIRLO tube used for this part of the study did not have a thin oxide passivation surface layer. Two different procedures were used to create chromium doped zirconium oxide surface layers on ZIRLO. The ZIRLO surface was coated with chromium using cathodic arc deposition followed compression plasma flow (CPF) treatment to facilitate intermixing of the Cr and the ZIRLO. In procedure 1, the surface modification was achieved through the incorporation of chromium into the zirconium surface layer using a compression plasma flow (CPF) technique, followed by the oxidation of the chromium doped zirconium. The oxidation process was conducted at 500 °C for 6 hours. In procedure 2, the chromium was incorporated into the zirconium oxide layer again using the CPF technique. Hydrogen desorption was measured from pure ZIRLO and CPF modified samples using a special gas reaction controller system. The key finding of the results is that the chromium doped (incorporated) zirconium oxide layer on ZIRLO sample exhibited the lowest hydrogen desorption rate of all the samples analysed. This indicates that H in the Cr doped zirconium oxide layer had the lowest mobility of all the samples investigated. This is consistent with the theoretical predictions that the doping of ZrO2 by Cr reduces the solubility of hydrogen in ZrO2. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
- Authors: Ngongo, Sinoyolo
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/54077 , vital:46252
- Description: Zirconium (Zr) alloys are used as fuel cladding material in all modern water cooled commercial nuclear reactors. Zr alloys have many desirable properties for the nuclear reactor core environment, however, it also has a weakness in that overheated zirconium alloy fuel rods react with hot steam resulting in the release of hydrogen. High temperatures increase the oxidation rate and hence the hydrogen production rate which in turn increase the risk of a hydrogen gas explosion such as what is surmised to have happened in the 2011 Fukushima Daiichi nuclear plant incident. The some of the hydrogen produced will also diffuse into the zirconium alloy and form zirconium hydrides which will weaken the original zirconium alloy material. The development of accident tolerant fuel became a major focus area after the Fukushima event in March 2011 with the U.S. congress directing the U.S. Department of Energy to develop fuel with enhanced accident tolerance at high temperatures. The main objective in the case of zirconium alloy cladding has been the modification of cladding surface layers by coating or doping in order to reduce the oxidation rate and hydrogen generation rate by the reaction of steam with zirconium alloy cladding at high temperatures. This thesis focuses on two surface modifications to decrease the surface corrosion rate of ZIRLOTM (the Zr alloy used in this study) and reduce hydrogen uptake by ZIRLO. The first modification involves an oxidation-resistant nano-crystalline diamond (NCD) film deposited on ZIRLO. The NCD layer was deposited in a microwave plasma-enhanced linear antenna chemical vapor deposition (MW-LA-PECVD) system after immersion of the ZIRLO tubes in a water-based solution containing nanodiamonds. ZIRLO tube samples were coated with 200 nm and 500 nm thick NCD layers. The 200 nm thick NCD coated ZIRLO was kept as control sample whereas the 500 nm thick NCD coated ZIRLO was exposed to steam oxidation at 360 °C for 90 days. The results revealed that the NCD exfoliated in some areas leaving the ZIRLO exposed to the steam. In the areas where the diamond did not exfoliate, the diamond was still attached to the ZIRLO with an amorphous carbon layer present between the NCD and the zirconium oxide layer.The transmission electron microscopy (TEM) results of this study indicate the presence a sp3 – hybridised diamond phase for the NCD layer as well as an intermediate amorphous carbon layer between the NCD and ZrO2 layers. Analyses of the area where the NCD layer had exfoliated showed no evidence of an NCD layer. It is possible that the amorphous carbon layer between the diamond and the zirconium oxide is responsible for weak interfacial bonding leading to partial exfoliation during oxidation in steam 360 °C for 90 days. In the second modification, the effectiveness of a Cr doped ZrO2 layer to reduce the migration rate of hydrogen in ZrO2 was investigated. The ZIRLO tube used for this part of the study did not have a thin oxide passivation surface layer. Two different procedures were used to create chromium doped zirconium oxide surface layers on ZIRLO. The ZIRLO surface was coated with chromium using cathodic arc deposition followed compression plasma flow (CPF) treatment to facilitate intermixing of the Cr and the ZIRLO. In procedure 1, the surface modification was achieved through the incorporation of chromium into the zirconium surface layer using a compression plasma flow (CPF) technique, followed by the oxidation of the chromium doped zirconium. The oxidation process was conducted at 500 °C for 6 hours. In procedure 2, the chromium was incorporated into the zirconium oxide layer again using the CPF technique. Hydrogen desorption was measured from pure ZIRLO and CPF modified samples using a special gas reaction controller system. The key finding of the results is that the chromium doped (incorporated) zirconium oxide layer on ZIRLO sample exhibited the lowest hydrogen desorption rate of all the samples analysed. This indicates that H in the Cr doped zirconium oxide layer had the lowest mobility of all the samples investigated. This is consistent with the theoretical predictions that the doping of ZrO2 by Cr reduces the solubility of hydrogen in ZrO2. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-12
Hydraulic vulnerability of Subtropical Thicket to drought : a remote sensing and physiological perspective
- Authors: Buttner, Daniel Harry
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55455 , vital:52017
- Description: Water availability is one of largest constraints on plant survival, growth, and species distribution globally. The recent escalation in tree mortality coupled with declining precipitation and amplified temperatures has implicated drought as a major cause behind many large-scale dieback events observed across the world. Raising the question, what makes some species more resistant and persist while others dwindle and vanish from the landscape? The observed variability in species drought susceptibility demonstrates the complexity of physiological responses of plants to changes in water availability. Hydraulic dysfunction in plants has been purported to be the key mechanism behind drought-induced mortality provoking interest in hydraulic traits and critical thresholds of xylem physiological function. The capability of species to maintain hydraulic functionality under drought strongly influences the survival and general productivity towards water deficits. Hence, two core objectives, and subsequently aims, of this thesis are firstly to investigate the effect of drought on Subtropical Thicket vegetation health and productivity, and secondly to examine the underpinning physiological mechanisms and functional thresholds relaying speciesspecific drought vulnerability within this semi-arid biome. In first data chapter, this thesis offers an assessment of vegetation change under drought and its influence on plant physiological function and productivity across a subsection of Subtropical Thicket distribution. Additionally, this chapter provides a regional scale perspective of drought on Subtropical Thicket flora in the Eastern Cape of South Africa. A severe anomalous dieback event, which coincided with extreme, accumulative drought conditions was observed in 2020. Employing a combination of field-based approaches and remote sensing, this chapter aimed to provide a comprehensive report of the extent and severity of crown defoliation and canopy dieback following this event, additionally describing predisposing and compounding factors. Based on Standardized Precipitation Evapotranspiration and Standardized Precipitation Indices this event began in 2015 and coincided with amplified temperatures, exacerbating evaporative demand. Aerial UAV surveys and field-based investigations were undertaken. Remotely sensed (RS) indices provided an avenue for extensive spatiotemporal investigations to uncover the extent of drought-related impact on vegetation productivity and discuss potential underpinning mechanisms behind drought-induced mortality in Subtropical Thicket. Leveraging long-term time series RS data, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites as a proxy vegetation physiological status in combination with SPI and SPEI describing drought condition and groundbased surveying defining canopy vitality condition this study incidentally addressed the aim of endeavoring to link drought-induced mortality and early warning symptoms observed in the field with RS time series data to describe drought impacts across Subtropical Thicket. Furthermore, the findings of this chapter demonstrate the spatial and temporal heterogeneity in drought impacts on Subtropical Thicket. The recent drought of 2015 till 2021 is the longest documented period for the past 50 years in which there has been no accumulated net positive water availability, this apparently perpetual state of water deficiency has enacted a high cost for vegetation productivity and growth for the study area, exhibited well by average NDVI values of less than -0.5 for over 70% of the research site. The findings of this chapter report, to the contrary of anecdotal suggestions in the literature, on the intrinsic tolerance of Subtropical Thicket and that ii drought has a far more significant role on overall vegetation productivity, growth, and mortality in this region. The second data chapter assess whole-plant physiological functionality during a drought event in the Eastern Cape, South Africa. This is the first study in Subtropical Thicket to quantify in situ hydraulic functional integrity under a natural drought event testing the leading hypothesis describing tree mortality – hydraulic dysfunction. This chapter firstly, investigates hydraulic traits (e.g., turgor loss point) and describe key physiological thresholds (e.g., P50) for maintaining function during drought. Secondly, levels of native embolism were determined under drought conditions and combined with measurements of xylem vulnerability to embolism providing an estimation of degree of hydraulic dysfunction experienced by six dominant woody canopy species in Subtropical Thicket – to quantify interspecific drought tolerance and susceptibility. Subtropical Thicket species exhibited remarkable tolerance towards desiccation (TLP from as low as -3MPa) and hydraulic functional resistance to embolism (P50 value as low as -7.89MPa). The observed unexpected drought resilience of subtropical derived lineages highlights the intrinsic evolutionary role aridification had, selecting for greater embolism resistance and community-level conservatism in drought resistance of Subtropical Thicket. The level of native embolism and hydraulic safety margins identified two species (Schotia latifolia and Polyagla myrtifolia) that were the most vulnerable, and a third (Pappea capensis) moderately vulnerable, then the remaining studied species – this could result in community-level adjustments in species composition and structure under future projected climate change scenarios where, increased frequencies of drought events are anticipated. This retrospective assessment of canopy vigor with physiological functional thresholds evokes hydraulic dysfunction as the principal mechanism of observed Subtropical Thicket dieback to drought. This chapter provides crucial in situ data for predictive assertions around drought-induced mortality risk in a phylogenetically diverse and climatically unique biome of southern Africa; and is the first to identify critical hydraulic thresholds for tree species within this region. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Buttner, Daniel Harry
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55455 , vital:52017
- Description: Water availability is one of largest constraints on plant survival, growth, and species distribution globally. The recent escalation in tree mortality coupled with declining precipitation and amplified temperatures has implicated drought as a major cause behind many large-scale dieback events observed across the world. Raising the question, what makes some species more resistant and persist while others dwindle and vanish from the landscape? The observed variability in species drought susceptibility demonstrates the complexity of physiological responses of plants to changes in water availability. Hydraulic dysfunction in plants has been purported to be the key mechanism behind drought-induced mortality provoking interest in hydraulic traits and critical thresholds of xylem physiological function. The capability of species to maintain hydraulic functionality under drought strongly influences the survival and general productivity towards water deficits. Hence, two core objectives, and subsequently aims, of this thesis are firstly to investigate the effect of drought on Subtropical Thicket vegetation health and productivity, and secondly to examine the underpinning physiological mechanisms and functional thresholds relaying speciesspecific drought vulnerability within this semi-arid biome. In first data chapter, this thesis offers an assessment of vegetation change under drought and its influence on plant physiological function and productivity across a subsection of Subtropical Thicket distribution. Additionally, this chapter provides a regional scale perspective of drought on Subtropical Thicket flora in the Eastern Cape of South Africa. A severe anomalous dieback event, which coincided with extreme, accumulative drought conditions was observed in 2020. Employing a combination of field-based approaches and remote sensing, this chapter aimed to provide a comprehensive report of the extent and severity of crown defoliation and canopy dieback following this event, additionally describing predisposing and compounding factors. Based on Standardized Precipitation Evapotranspiration and Standardized Precipitation Indices this event began in 2015 and coincided with amplified temperatures, exacerbating evaporative demand. Aerial UAV surveys and field-based investigations were undertaken. Remotely sensed (RS) indices provided an avenue for extensive spatiotemporal investigations to uncover the extent of drought-related impact on vegetation productivity and discuss potential underpinning mechanisms behind drought-induced mortality in Subtropical Thicket. Leveraging long-term time series RS data, Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI), from Moderate Resolution Imaging Spectroradiometer (MODIS) satellites as a proxy vegetation physiological status in combination with SPI and SPEI describing drought condition and groundbased surveying defining canopy vitality condition this study incidentally addressed the aim of endeavoring to link drought-induced mortality and early warning symptoms observed in the field with RS time series data to describe drought impacts across Subtropical Thicket. Furthermore, the findings of this chapter demonstrate the spatial and temporal heterogeneity in drought impacts on Subtropical Thicket. The recent drought of 2015 till 2021 is the longest documented period for the past 50 years in which there has been no accumulated net positive water availability, this apparently perpetual state of water deficiency has enacted a high cost for vegetation productivity and growth for the study area, exhibited well by average NDVI values of less than -0.5 for over 70% of the research site. The findings of this chapter report, to the contrary of anecdotal suggestions in the literature, on the intrinsic tolerance of Subtropical Thicket and that ii drought has a far more significant role on overall vegetation productivity, growth, and mortality in this region. The second data chapter assess whole-plant physiological functionality during a drought event in the Eastern Cape, South Africa. This is the first study in Subtropical Thicket to quantify in situ hydraulic functional integrity under a natural drought event testing the leading hypothesis describing tree mortality – hydraulic dysfunction. This chapter firstly, investigates hydraulic traits (e.g., turgor loss point) and describe key physiological thresholds (e.g., P50) for maintaining function during drought. Secondly, levels of native embolism were determined under drought conditions and combined with measurements of xylem vulnerability to embolism providing an estimation of degree of hydraulic dysfunction experienced by six dominant woody canopy species in Subtropical Thicket – to quantify interspecific drought tolerance and susceptibility. Subtropical Thicket species exhibited remarkable tolerance towards desiccation (TLP from as low as -3MPa) and hydraulic functional resistance to embolism (P50 value as low as -7.89MPa). The observed unexpected drought resilience of subtropical derived lineages highlights the intrinsic evolutionary role aridification had, selecting for greater embolism resistance and community-level conservatism in drought resistance of Subtropical Thicket. The level of native embolism and hydraulic safety margins identified two species (Schotia latifolia and Polyagla myrtifolia) that were the most vulnerable, and a third (Pappea capensis) moderately vulnerable, then the remaining studied species – this could result in community-level adjustments in species composition and structure under future projected climate change scenarios where, increased frequencies of drought events are anticipated. This retrospective assessment of canopy vigor with physiological functional thresholds evokes hydraulic dysfunction as the principal mechanism of observed Subtropical Thicket dieback to drought. This chapter provides crucial in situ data for predictive assertions around drought-induced mortality risk in a phylogenetically diverse and climatically unique biome of southern Africa; and is the first to identify critical hydraulic thresholds for tree species within this region. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
An investigation into the effects of nano-carbons on the negative electrode morphology of lead acid batteries under high rate partial state of capacity cycling
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-04
A spatial assessment of riparian vegetation density and implications for streambank erosion in relation to land tenure in the Mgwalana Catchment, Eastern Cape Province, South Africa
- Authors: Maxama, Asakhile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53864 , vital:46026
- Description: Riparian vegetation provides an array of various ecosystem functions and has significantly shaped the conditions of catchments. It has strong controls on fluvial geomorphology and erosion processes. The Mgwalana catchment has been intensively studied over the years and the current environmental condition of the study has been linked to land use history. The catchment has been subjected to land use/cover changes (LUCC) over the years. However, spatial variations in riparian vegetation, their implications for stream bank stability and the contribution of land tenure systems to stream channel degradation are poorly understood. The study sought to assess the implications of the spatial variations in riparian vegetation density for stream bank erosion in relation to land tenure on a catchment scale. Land tenure units comprising the catchment of study are traditional and betterment villages (communal lands), and former white commercial farms. A three-pronged approach using GIS and remote sensing, field investigations and laboratory procedures for soil analysis was employed in this study. Variations of riparian vegetation density in the catchment were mapped using ArcGIS for the two land tenure units to assess the spatial variations of riparian density along stream reaches and to determine the spatial relationship between land tenure units and riparian vegetation diminution. Other mapped shape files include sediment accumulation zones to analyse the spatial relationship between riparian vegetation density and sediment sinks. LUCC classification and analysis of the Normalized Difference Vegetation Index (NDVI) were carried out in IDRISI Selva, using Landsat 8 TM imagery of 2018 to represent the current spatial riparian vegetation variations in the catchment. Field investigations were conducted to determine the coupling among hillslope gully erosion, riparian vegetation density and sink areas; and to assess physical characteristics of soil. This would permit an assessment of the implications of riparian vegetation for stream bank erosion and sediment accumulation within the tenure units. Soil samples were taken from scantily and densely vegetated stream reaches, as well as measurements of channel widths and depths. Analyses of soil physical properties viz; grain size distribution, bulk density, soil texture and aggregate stability were done. Results demonstrated that a sparse riparian vegetation distribution was consistent with the communal villages, confined to the upper catchment area. Dense riparian vegetation distribution was consistent with former commercial farms in the lower catchment area. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Maxama, Asakhile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53864 , vital:46026
- Description: Riparian vegetation provides an array of various ecosystem functions and has significantly shaped the conditions of catchments. It has strong controls on fluvial geomorphology and erosion processes. The Mgwalana catchment has been intensively studied over the years and the current environmental condition of the study has been linked to land use history. The catchment has been subjected to land use/cover changes (LUCC) over the years. However, spatial variations in riparian vegetation, their implications for stream bank stability and the contribution of land tenure systems to stream channel degradation are poorly understood. The study sought to assess the implications of the spatial variations in riparian vegetation density for stream bank erosion in relation to land tenure on a catchment scale. Land tenure units comprising the catchment of study are traditional and betterment villages (communal lands), and former white commercial farms. A three-pronged approach using GIS and remote sensing, field investigations and laboratory procedures for soil analysis was employed in this study. Variations of riparian vegetation density in the catchment were mapped using ArcGIS for the two land tenure units to assess the spatial variations of riparian density along stream reaches and to determine the spatial relationship between land tenure units and riparian vegetation diminution. Other mapped shape files include sediment accumulation zones to analyse the spatial relationship between riparian vegetation density and sediment sinks. LUCC classification and analysis of the Normalized Difference Vegetation Index (NDVI) were carried out in IDRISI Selva, using Landsat 8 TM imagery of 2018 to represent the current spatial riparian vegetation variations in the catchment. Field investigations were conducted to determine the coupling among hillslope gully erosion, riparian vegetation density and sink areas; and to assess physical characteristics of soil. This would permit an assessment of the implications of riparian vegetation for stream bank erosion and sediment accumulation within the tenure units. Soil samples were taken from scantily and densely vegetated stream reaches, as well as measurements of channel widths and depths. Analyses of soil physical properties viz; grain size distribution, bulk density, soil texture and aggregate stability were done. Results demonstrated that a sparse riparian vegetation distribution was consistent with the communal villages, confined to the upper catchment area. Dense riparian vegetation distribution was consistent with former commercial farms in the lower catchment area. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-12
Descriptive analysis of organic farming systems and factors affecting adoption and disadoption in Zambia : a case study
- Authors: Munthali, Robert
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Organic farming -- Zambia
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52111 , vital:43434
- Description: The last 30 years since the early 1990s has seen the heightened promotion of organic farming as a sustainable farming option in Zambia. The main objectives of this research study were to carry out an analysis of organic farming systems in order to understand factors affecting adoption, as well as reasons why some organic farmers discontinue using the approach. The study involved four districts in Zambia: Mazabuka, Chikankata, Lusaka and Chongwe. Specifically, the research investigated challenges and limitations of organic agronomic practices, and analysed factors that influence adopters and disadopters of organic agriculture. Primary data were collected through interviews and by administering semi-structured questionnaires. The research population comprised approximately 250 farmers adopters and disadopters, with the sample size being 50 farmers chosen across four districts using systematic random sampling methods. Additionally, five observation research field trials were conducted in order to gather practical data on individual farmer’s crop management practices. Farmers adopting and maintaining organic methods reported several reasons for embracing the system, some of which are: organic farming is regenerative; it is environmentally responsible; it uses manure, believed to help build healthy soils rich in organic matter with better nutrient and moisture holding capacity; pesticides and synthetic fertilizers are not used, reducing the levels of toxic residues in organic products which ultimately promotes health. Labour constraints, pest and disease challenges and weed problems were some of the reasons for disadoption. Data showed that disadopters had lower education (48% had primary education), were older and with slightly more children. Although there were more women adopting organic agriculture compared to men, the difference was small 56% and 44% women and men respectively. Among disadopters there were more women (67%) compared to men (33%). Overall, the study results suggest that promotion of organic agriculture should be encouraged through liaison with government departments such as the Zambian Department of Agriculture to include organic agriculture when developing policies. In general, organic farmers have positive opinions concerning the benefits resulting from organic agriculture. Organic farmers should enjoy equal opportunities to conventional agriculture in the provision of extension services, input support, infrastructural development, access to financial resources to procure farm machinery, and equipment and most important of all, they should get fair prices for their organic produce and products. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Munthali, Robert
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Organic farming -- Zambia
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52111 , vital:43434
- Description: The last 30 years since the early 1990s has seen the heightened promotion of organic farming as a sustainable farming option in Zambia. The main objectives of this research study were to carry out an analysis of organic farming systems in order to understand factors affecting adoption, as well as reasons why some organic farmers discontinue using the approach. The study involved four districts in Zambia: Mazabuka, Chikankata, Lusaka and Chongwe. Specifically, the research investigated challenges and limitations of organic agronomic practices, and analysed factors that influence adopters and disadopters of organic agriculture. Primary data were collected through interviews and by administering semi-structured questionnaires. The research population comprised approximately 250 farmers adopters and disadopters, with the sample size being 50 farmers chosen across four districts using systematic random sampling methods. Additionally, five observation research field trials were conducted in order to gather practical data on individual farmer’s crop management practices. Farmers adopting and maintaining organic methods reported several reasons for embracing the system, some of which are: organic farming is regenerative; it is environmentally responsible; it uses manure, believed to help build healthy soils rich in organic matter with better nutrient and moisture holding capacity; pesticides and synthetic fertilizers are not used, reducing the levels of toxic residues in organic products which ultimately promotes health. Labour constraints, pest and disease challenges and weed problems were some of the reasons for disadoption. Data showed that disadopters had lower education (48% had primary education), were older and with slightly more children. Although there were more women adopting organic agriculture compared to men, the difference was small 56% and 44% women and men respectively. Among disadopters there were more women (67%) compared to men (33%). Overall, the study results suggest that promotion of organic agriculture should be encouraged through liaison with government departments such as the Zambian Department of Agriculture to include organic agriculture when developing policies. In general, organic farmers have positive opinions concerning the benefits resulting from organic agriculture. Organic farmers should enjoy equal opportunities to conventional agriculture in the provision of extension services, input support, infrastructural development, access to financial resources to procure farm machinery, and equipment and most important of all, they should get fair prices for their organic produce and products. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Rheology behaviour of slurries as a function of particle size and ion concentration
- Authors: Kondlo, Princess Kholiwe
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53333 , vital:45141
- Description: In this work, the rheological properties of alumina slurries milled to different particle sizes were investigated. Viscosity increases as the particle size decreases. When increasing amounts of calcium hydroxide, strontium hydroxide or barium hydroxide are added, the viscosity first goes down and then goes up. This can be explained in terms of changes in pH and changes in ionic strength impacting on the surface potential of the particles in suspension. Adding the same concentration of different cations results in different viscosities, with the order being (from high to low viscosity) Ba>Sr>Ca. Effects of partial dissolution of and structural changes to the alumina particles at high pH cannot be excluded. In order to better understanding the different effects, it was attempted to measure the zeta potential of the slurries at different pH values. This resulted in highly positive zeta potential values over the complete pH range, without the observationof an iso-electric point. This does not fit to the observed changes in rheology and contrasts withliterature data. One explanation would be that the measurement system used is unsuitable to yield correct zeta potential values for the materials under investigation. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Kondlo, Princess Kholiwe
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53333 , vital:45141
- Description: In this work, the rheological properties of alumina slurries milled to different particle sizes were investigated. Viscosity increases as the particle size decreases. When increasing amounts of calcium hydroxide, strontium hydroxide or barium hydroxide are added, the viscosity first goes down and then goes up. This can be explained in terms of changes in pH and changes in ionic strength impacting on the surface potential of the particles in suspension. Adding the same concentration of different cations results in different viscosities, with the order being (from high to low viscosity) Ba>Sr>Ca. Effects of partial dissolution of and structural changes to the alumina particles at high pH cannot be excluded. In order to better understanding the different effects, it was attempted to measure the zeta potential of the slurries at different pH values. This resulted in highly positive zeta potential values over the complete pH range, without the observationof an iso-electric point. This does not fit to the observed changes in rheology and contrasts withliterature data. One explanation would be that the measurement system used is unsuitable to yield correct zeta potential values for the materials under investigation. , Thesis (MSc) -- Faculty of Science, Department of Chemistry, 2021
- Full Text:
- Date Issued: 2021-04
The co-evolution of Africa’s eastern margin and its primate fauna: implications for hominin evolution
- Authors: Mambalu, Philasande
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59755 , vital:62418
- Description: I investigated potential links between the diversification of African primate lineages and the physical evolution of the continent. I compared published phylogenetic trees based on mitochondrial and nuclear DNA for five clades: (a) Lorisoidea (galagos and pottos); (b) arboreal guenon monkeys (Cercopithecus and its allies); (c) living apes (including humans); (d) Papionini (baboons); and (e) savanna or “vervet” monkeys (Chlorocebus). I compared primate divergence dates with the ages of tectonic events, patterns of climatic change, and their palaeo-vegetational consequences. Based on present primate distributions, I estimated likely geographic locations of the divergence events. Finally, I compared the phylogenetic patterns of the primate clades with hominin evolutionary scenarios. Phylogenetic comparisons indicated three time periods when rates of speciation increased across the five primate clades: the Eocene – Oligocene transition (34 – 32 Ma); the mid-late Miocene (10 – 5 Ma); and the Pliocene – Pleistocene transition (2.7 – 2.3 Ma). Concentrated bursts of lineage splitting indicate a broadscale causal relationship between environmental change and lineage divergence. Human evolution followed similar biogeographic patterns to those of other primate clades. Tectonic events, climatic changes and palaeo-vegetational shifts are intimately connected, and have synergistic effects on biotic diversity. Tectonic events influence climatic change through their effects on oceanic circulation, planetary temperatures and rainfall patterns. Additionally, tectonic uplift and erosion may create geographic barriers to organismal dispersal across the continent, increasing the likelihood of geographic separation of populations and speciation. Recently evolved primate species show high levels of hybridisation for several generations after their initial divergence. Genus Homo generated ~10 species over 2.5 Ma. The emergence of these taxa likely involved substantial hybridisation, as demonstrated by the presence of Neanderthal genes within the H. sapiens genome. I suggest that this hybridisation contributed to the difficulties palaeoanthropologists often experience in distinguishing fossil hominin taxa. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Mambalu, Philasande
- Date: 2022-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59755 , vital:62418
- Description: I investigated potential links between the diversification of African primate lineages and the physical evolution of the continent. I compared published phylogenetic trees based on mitochondrial and nuclear DNA for five clades: (a) Lorisoidea (galagos and pottos); (b) arboreal guenon monkeys (Cercopithecus and its allies); (c) living apes (including humans); (d) Papionini (baboons); and (e) savanna or “vervet” monkeys (Chlorocebus). I compared primate divergence dates with the ages of tectonic events, patterns of climatic change, and their palaeo-vegetational consequences. Based on present primate distributions, I estimated likely geographic locations of the divergence events. Finally, I compared the phylogenetic patterns of the primate clades with hominin evolutionary scenarios. Phylogenetic comparisons indicated three time periods when rates of speciation increased across the five primate clades: the Eocene – Oligocene transition (34 – 32 Ma); the mid-late Miocene (10 – 5 Ma); and the Pliocene – Pleistocene transition (2.7 – 2.3 Ma). Concentrated bursts of lineage splitting indicate a broadscale causal relationship between environmental change and lineage divergence. Human evolution followed similar biogeographic patterns to those of other primate clades. Tectonic events, climatic changes and palaeo-vegetational shifts are intimately connected, and have synergistic effects on biotic diversity. Tectonic events influence climatic change through their effects on oceanic circulation, planetary temperatures and rainfall patterns. Additionally, tectonic uplift and erosion may create geographic barriers to organismal dispersal across the continent, increasing the likelihood of geographic separation of populations and speciation. Recently evolved primate species show high levels of hybridisation for several generations after their initial divergence. Genus Homo generated ~10 species over 2.5 Ma. The emergence of these taxa likely involved substantial hybridisation, as demonstrated by the presence of Neanderthal genes within the H. sapiens genome. I suggest that this hybridisation contributed to the difficulties palaeoanthropologists often experience in distinguishing fossil hominin taxa. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Fragmentation of the Albany Thicket Biome: consequences for the biodiversity and health of thicket vegetation
- Authors: Carvalho, Shandon Luke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Fragmented landscapes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52344 , vital:43599
- Description: The dense impenetrable vegetation of the Albany Thicket Biome is highly resistant to a wide variety of disturbances but, once disturbed, lacks the regenerative qualities that allow it to return to a stable state. Agricultural development is the main cause of degradation in this biome, creating a landscape consisting of patches of thicket vegetation scattered throughout land cleared for crops or transformed through grazing by domestic livestock. The main objective of this study is to determine the health, status and biodiversity of thicket fragments as it relates to elephant impacts. The level of fragmentation and the remaining extent of intact thicket were investigated as its current status is unknown. The findings suggest that the Thicket Biome is highly fragmented as almost 50% of solid thicket has been cleared, transformed or degraded by agricultural or urban development. For Arid Thicket, the level of fragmentation and the remaining extent of intact thicket could not be determined and both could potentially be greater. For the intact thicket of Dune, Mesic and Valley Thicket types, patch sizes ranged between almost 6 and 876 km2 while the weighted mean was between 2 and 251 km2 . Remote sensing methods (NDVI) were used to determine whether the health of thicket could be remotely assessed. The thicket within and beyond the extent of piospheres around watering holes is subjected to different levels of herbivory. These different levels were compared to corresponding NDVI values with the latter accurately measuring the impact of herbivores along a gradient and providing a method to assess the health of thicket vegetation. Ground surveys of the edge effect, along thicket fragments adjacent to open pastures and separated by cut lines, were conducted. Based on these surveys, the extent of the edge effect was established at a distance of 7 m into thicket fragments separated by cut lines but could not be determined for thicket fragments adjacent to open pastures. Ground surveys were also conducted to assess the health of thicket vegetation exposed to different levels of herbivory, including the impact of elephants (Loxodonta africana). Results showed that different elephant densities produced different levels of impact that could be described in terms of changes in species richness, species diversity, plant height and cover, and growth form composition. Lastly, the findings of the health-based assessments were combined with elephant densities to develop a model that could assess the health of thicket vegetation using a range of ecological variables and relate it to an ideal range of elephant densities. This assessment method was tested at the Addo Elephant National Park and results showed that an elephant density of 1 elephant/km2 would maintain the appropriate diversity, structure and composition of thicket. , Thesis (MSc) -- Faculty of Science, Department of Botany, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Carvalho, Shandon Luke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Fragmented landscapes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52344 , vital:43599
- Description: The dense impenetrable vegetation of the Albany Thicket Biome is highly resistant to a wide variety of disturbances but, once disturbed, lacks the regenerative qualities that allow it to return to a stable state. Agricultural development is the main cause of degradation in this biome, creating a landscape consisting of patches of thicket vegetation scattered throughout land cleared for crops or transformed through grazing by domestic livestock. The main objective of this study is to determine the health, status and biodiversity of thicket fragments as it relates to elephant impacts. The level of fragmentation and the remaining extent of intact thicket were investigated as its current status is unknown. The findings suggest that the Thicket Biome is highly fragmented as almost 50% of solid thicket has been cleared, transformed or degraded by agricultural or urban development. For Arid Thicket, the level of fragmentation and the remaining extent of intact thicket could not be determined and both could potentially be greater. For the intact thicket of Dune, Mesic and Valley Thicket types, patch sizes ranged between almost 6 and 876 km2 while the weighted mean was between 2 and 251 km2 . Remote sensing methods (NDVI) were used to determine whether the health of thicket could be remotely assessed. The thicket within and beyond the extent of piospheres around watering holes is subjected to different levels of herbivory. These different levels were compared to corresponding NDVI values with the latter accurately measuring the impact of herbivores along a gradient and providing a method to assess the health of thicket vegetation. Ground surveys of the edge effect, along thicket fragments adjacent to open pastures and separated by cut lines, were conducted. Based on these surveys, the extent of the edge effect was established at a distance of 7 m into thicket fragments separated by cut lines but could not be determined for thicket fragments adjacent to open pastures. Ground surveys were also conducted to assess the health of thicket vegetation exposed to different levels of herbivory, including the impact of elephants (Loxodonta africana). Results showed that different elephant densities produced different levels of impact that could be described in terms of changes in species richness, species diversity, plant height and cover, and growth form composition. Lastly, the findings of the health-based assessments were combined with elephant densities to develop a model that could assess the health of thicket vegetation using a range of ecological variables and relate it to an ideal range of elephant densities. This assessment method was tested at the Addo Elephant National Park and results showed that an elephant density of 1 elephant/km2 would maintain the appropriate diversity, structure and composition of thicket. , Thesis (MSc) -- Faculty of Science, Department of Botany, 2021
- Full Text: false
- Date Issued: 2021-04
A theoretical study of alkoxyl radical and radical cation mediated cyclisation reactions in unsaturated alkanols
- Authors: Lee, Peter Mattison Clarke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Density functionals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52130 , vital:43430
- Description: A large part of this computational study focussed on selectivity patterns for 4-penten- 1-oxyl radical 1,5- and 1,6-cyclisations and for those of analogous 5-hexenyl, 4- penten-1-aminyl, 4-penten-1-iminyl and 3-phenylpropan-1-oxyl radicals. The study furthermore included cyclisation reactions of the radical cations of 4-penten-1-ol and 3-phenylpropan-1-ol. Calculations were performed for all applicable species involved in the two cyclisation modes studied, i.e. 1,5- and 1,6-cyclisation. These species included radical and radical cation precursors, as well as relevant radical transition state structures and radical adducts. All cyclisation systems investigated used the Density Functional Theory (DFT) functional B3LYP with a combination of eight basis sets. Each basis set used was a progressively higher level of theory than B3LYP/6-31G* which was used as a starting point. Cyclisations for unsubstituted species, e.g. the 4-penten-1-oxyl radical 1,5- and 1,6-cyclisations, were also simulated using the ωB97X-D and ωB97X-V functionals which account for dispersive effects. The same set of eight basis sets were used with these two functionals. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Lee, Peter Mattison Clarke
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Density functionals
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/52130 , vital:43430
- Description: A large part of this computational study focussed on selectivity patterns for 4-penten- 1-oxyl radical 1,5- and 1,6-cyclisations and for those of analogous 5-hexenyl, 4- penten-1-aminyl, 4-penten-1-iminyl and 3-phenylpropan-1-oxyl radicals. The study furthermore included cyclisation reactions of the radical cations of 4-penten-1-ol and 3-phenylpropan-1-ol. Calculations were performed for all applicable species involved in the two cyclisation modes studied, i.e. 1,5- and 1,6-cyclisation. These species included radical and radical cation precursors, as well as relevant radical transition state structures and radical adducts. All cyclisation systems investigated used the Density Functional Theory (DFT) functional B3LYP with a combination of eight basis sets. Each basis set used was a progressively higher level of theory than B3LYP/6-31G* which was used as a starting point. Cyclisations for unsubstituted species, e.g. the 4-penten-1-oxyl radical 1,5- and 1,6-cyclisations, were also simulated using the ωB97X-D and ωB97X-V functionals which account for dispersive effects. The same set of eight basis sets were used with these two functionals. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
- Full Text: false
- Date Issued: 2021-04
Assessing community engagement programmes to mitigate uncontrolled, deliberately ignited fires in forestry plantation-communal land interface, Kwazulu-Natal, South Africa
- Authors: Ramantswana, Nontethelelo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Forest fires -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52008 , vital:43439
- Description: Forestry plantations in South Africa are surrounded by poor local communities that normally depend on the forestry resources for subsistence. This interface area is faced with human induced uncontrolled fires. There is a lack of understanding regarding the reasons for deliberate ignition of uncontrolled fires. There is also lack of information on the success of community engagement programs (CEPs) as fire protection intervention and / or their implementation barriers. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Ramantswana, Nontethelelo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Forest fires -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52008 , vital:43439
- Description: Forestry plantations in South Africa are surrounded by poor local communities that normally depend on the forestry resources for subsistence. This interface area is faced with human induced uncontrolled fires. There is a lack of understanding regarding the reasons for deliberate ignition of uncontrolled fires. There is also lack of information on the success of community engagement programs (CEPs) as fire protection intervention and / or their implementation barriers. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
Factors affecting the performance of the wooden furniture manufacturing industry in the Southern Cape
- Authors: Vheriwa, Prayer
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Furniture making -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52017 , vital:43449
- Description: The furniture manufacturing industry in South Africa is facing several challenges that affect the performance of firms in this sector. A literature review indicates several factors such as availability of resources; location; access to local markets; access to export markets; and development programmes that may affect the performance of wooden furniture manufacturing firms in the Southern Cape. The purpose of the current study was to fill the knowledge gap on why the performance of wooden furniture manufacturing firms in the Southern Cape has declined. The study intends to contribute to the limited formal information resources on the Southern Cape furniture manufacturing industry. A conceptual framework was developed and employed for investigating factors hypothesised to affect the performance of furniture manufacturing firms in the Southern Cape. The research conducted was explorative. An interpretive paradigm was selected to collect and interpret qualitative data and a positivist paradigm was used for the quantitative component of the study. The quantitative data was subjected to a chi-square test using IBM SPSS statistics software and qualitative data was analysed for meanings and context using ATLAS.ti software. Statistical tests on qualitative and quantitative data were conducted to determine whether sufficient evidence existed to make conclusions on the hypotheses, relating to significant relationships between the selected independent variables for the study and the performance of wooden furniture manufacturing firms in the Southern Cape. The results show that existing development programmes and availability of resources, namely: timber, skilled human resources and availability of finance, influence the performance of furniture manufacturing firms in the Southern Cape. Results further reveal that location; access to local market; and access to export market have a partial influence on the performance of the furniture manufacturing firms in the Southern Cape. The study presents information which serves to improve the capacity for growth of wooden furniture manufacturing firms. Based on the results, recommendations were made to overcome the factors affecting the performance of the furniture manufacturing firms in the Southern Cape. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Vheriwa, Prayer
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Furniture making -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52017 , vital:43449
- Description: The furniture manufacturing industry in South Africa is facing several challenges that affect the performance of firms in this sector. A literature review indicates several factors such as availability of resources; location; access to local markets; access to export markets; and development programmes that may affect the performance of wooden furniture manufacturing firms in the Southern Cape. The purpose of the current study was to fill the knowledge gap on why the performance of wooden furniture manufacturing firms in the Southern Cape has declined. The study intends to contribute to the limited formal information resources on the Southern Cape furniture manufacturing industry. A conceptual framework was developed and employed for investigating factors hypothesised to affect the performance of furniture manufacturing firms in the Southern Cape. The research conducted was explorative. An interpretive paradigm was selected to collect and interpret qualitative data and a positivist paradigm was used for the quantitative component of the study. The quantitative data was subjected to a chi-square test using IBM SPSS statistics software and qualitative data was analysed for meanings and context using ATLAS.ti software. Statistical tests on qualitative and quantitative data were conducted to determine whether sufficient evidence existed to make conclusions on the hypotheses, relating to significant relationships between the selected independent variables for the study and the performance of wooden furniture manufacturing firms in the Southern Cape. The results show that existing development programmes and availability of resources, namely: timber, skilled human resources and availability of finance, influence the performance of furniture manufacturing firms in the Southern Cape. Results further reveal that location; access to local market; and access to export market have a partial influence on the performance of the furniture manufacturing firms in the Southern Cape. The study presents information which serves to improve the capacity for growth of wooden furniture manufacturing firms. Based on the results, recommendations were made to overcome the factors affecting the performance of the furniture manufacturing firms in the Southern Cape. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text: false
- Date Issued: 2021-04
Studies on seed germination and response to fertilization of Amaranthus accessions collected in the Eastern Cape Province, South Africa
- Ramangoele, Mpaballeng Alinah
- Authors: Ramangoele, Mpaballeng Alinah
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54112 , vital:46307
- Description: Studies were conducted at Döhne Agricultural Development Institute (D.A.D.I.), geographically located between latitude 32°31'34.077"S and longitude 27°27'37.473"E in Stutterheim, Eastern Cape Province from summer 2018 until autumn 2019.The objectives were to determine seed germination and seedling vigour of four local Amaranthus accessions and to evaluate the effect of organic and inorganic fertilization on the growth, yield and nutrient composition. In the germination studies, herein referred to as Experiment 1,laboratory assessments were laid out in a Complete Randomized Design (CRD) replicated four times to test seed germination, seedling emergence and seedling vigour of four Amaranthus accessions namely: A. Hypochondriacus, A. Retroflexus 1, A. Hybridus and A. Retroflexus 2. Data collection included germination percentage, radicle length, co-efficient of velocity of germination and seedling vigour. A.Retroflexus2 gave the highest germination percentage in summer (85%) and autumn (87.75%).Seed weight resulted in the highest germination percentage and was observed to have shown a high positive correlation of {R2=0.91} in summer and{R2=0.92} in autumn respectively. The highest seedling vigour (p<0.001) in summer was attained from A. Hypochondriacus and A. Retroflexus2.In the greenhouse in summer, the highest emergence percentage was observed from A. Hypochondriacus(93.00%), whilst in autumn it was A.Retroflexus2 (88.38%).A. Retroflexus1 was the least performer in both seasons. In summer, A. Hypochondriacus and A. Retroflexus2 resulted in very high seedling vigour. In autumn A. Hypochondriacus, A. Retroflexus2 and A. Hybridus resulted in high seedling vigour and A. Retroflexus1 in moderate seedling vigour. The relationship observed between seed weight and seedling vigour showed a negative (inverse)correlation in summer {R2=0.58} and autumn {R2=0.62}.In Experiment 2, seedlings of A. Hypochondriacus and A. Retroflexus 2were transplanted in 5litrebasal perforated plastic pots which were filled with soil. The experimental layout was a CRD replicated four times. The treatments were: control (no amendment), goat manure, cattle manure and NPK fertilizer. Growth performance data were collected for plant height, the number of leaves and stem girth. In summer, when goat manure was applied both accessions resulted in the tallest plants (78.80cm) yet A. Retroflexus 2 and vA. Hypochondriacus gave the greatest stem girthand highest number of leaves respectively. In autumn, the tallest plants and highest number of leaves were observed from A. Retroflexus 2fertilized with NPK and the greatest stem girth was observed from A. Hypochondriacus fertilized with goat manure. The interaction of fertilization and accessions resulted in A. Retroflexus 2 fertilized with goat manure generating the greatest fresh shoot biomass (137.27g plant-1) and the least from the control. Both accessions fertilized with goat manure attained the greatest dry leaf biomass. Insummer, A.Retroflexus2 outperformed A. Hypochondriacus in calcium content despite the treatments. Unfertilized A. Retroflexus2 produced leaves with high potassium. Both unfertilized accessions showed the highest magnesium content. All A. Retroflexus2 treatments outperformed A. Hypochondriacus treatments on iron content except the control. The summer season was the best in terms of growth and yield of the tested accessions. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Ramangoele, Mpaballeng Alinah
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54112 , vital:46307
- Description: Studies were conducted at Döhne Agricultural Development Institute (D.A.D.I.), geographically located between latitude 32°31'34.077"S and longitude 27°27'37.473"E in Stutterheim, Eastern Cape Province from summer 2018 until autumn 2019.The objectives were to determine seed germination and seedling vigour of four local Amaranthus accessions and to evaluate the effect of organic and inorganic fertilization on the growth, yield and nutrient composition. In the germination studies, herein referred to as Experiment 1,laboratory assessments were laid out in a Complete Randomized Design (CRD) replicated four times to test seed germination, seedling emergence and seedling vigour of four Amaranthus accessions namely: A. Hypochondriacus, A. Retroflexus 1, A. Hybridus and A. Retroflexus 2. Data collection included germination percentage, radicle length, co-efficient of velocity of germination and seedling vigour. A.Retroflexus2 gave the highest germination percentage in summer (85%) and autumn (87.75%).Seed weight resulted in the highest germination percentage and was observed to have shown a high positive correlation of {R2=0.91} in summer and{R2=0.92} in autumn respectively. The highest seedling vigour (p<0.001) in summer was attained from A. Hypochondriacus and A. Retroflexus2.In the greenhouse in summer, the highest emergence percentage was observed from A. Hypochondriacus(93.00%), whilst in autumn it was A.Retroflexus2 (88.38%).A. Retroflexus1 was the least performer in both seasons. In summer, A. Hypochondriacus and A. Retroflexus2 resulted in very high seedling vigour. In autumn A. Hypochondriacus, A. Retroflexus2 and A. Hybridus resulted in high seedling vigour and A. Retroflexus1 in moderate seedling vigour. The relationship observed between seed weight and seedling vigour showed a negative (inverse)correlation in summer {R2=0.58} and autumn {R2=0.62}.In Experiment 2, seedlings of A. Hypochondriacus and A. Retroflexus 2were transplanted in 5litrebasal perforated plastic pots which were filled with soil. The experimental layout was a CRD replicated four times. The treatments were: control (no amendment), goat manure, cattle manure and NPK fertilizer. Growth performance data were collected for plant height, the number of leaves and stem girth. In summer, when goat manure was applied both accessions resulted in the tallest plants (78.80cm) yet A. Retroflexus 2 and vA. Hypochondriacus gave the greatest stem girthand highest number of leaves respectively. In autumn, the tallest plants and highest number of leaves were observed from A. Retroflexus 2fertilized with NPK and the greatest stem girth was observed from A. Hypochondriacus fertilized with goat manure. The interaction of fertilization and accessions resulted in A. Retroflexus 2 fertilized with goat manure generating the greatest fresh shoot biomass (137.27g plant-1) and the least from the control. Both accessions fertilized with goat manure attained the greatest dry leaf biomass. Insummer, A.Retroflexus2 outperformed A. Hypochondriacus in calcium content despite the treatments. Unfertilized A. Retroflexus2 produced leaves with high potassium. Both unfertilized accessions showed the highest magnesium content. All A. Retroflexus2 treatments outperformed A. Hypochondriacus treatments on iron content except the control. The summer season was the best in terms of growth and yield of the tested accessions. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2021-12
Potential suppressive effects of alien Acacia melanoxylon on Afrotemperate Forest tree recruitment
- Miles, Bayleigh, Baard, Johan
- Authors: Miles, Bayleigh , Baard, Johan
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55391 , vital:51989
- Description: Acacia melanoxylon R.Br. is a prominent alien and invasive species in many parts of the world and evidence exists of its adverse effects on indigenous forest community composition through allelopathy and alteration of light regimes. The species also occurs extensively in Southern Cape Afrotemperate Forest (South Africa) and is thought to suppress indigenous Afrotemperate Forest tree seedlings through various mechanisms such as the alteration of natural light regimes or allelopathy, although this has not been rigorously verified. This study aimed to investigate whether Acacia melanoxylon has a suppressive effect on Afrotemperate Forest tree recruitment. Firstly, we assessed the potential allelopathic effect of Acacia melanoxylon and an indigenous Afrotemperate Forest species Olea capensis macrocarpa (C.H.Wright) I.Verd. on the germination of Acacia melanoxylon and three prominent indigenous tree species’ seedlings in a nursery trial. Germination of the indigenous species failed; however, we were able to compare the germination of Acacia melanoxylon among the three treatments, namely Acacia melanoxylon leachate, Olea capensis leachate, and no leachate. The average germination of Acacia melanoxylon was 67% and germination was marginally higher under Acacia melanoxylon leachate and Olea capensis leachate, respectively, than under the control. This suggested that germination of the species is improved, or at the least, unaffected, by leachates of itself or that of a common indigenous canopy species. We then critically evaluated the germination requirements of the indigenous test species to determine probable reasons why their germination failed in our trial. The most plausible explanation for the germination failure could be that the trial period did not encompass an entire winter season and may not have provided adequate cold stratification. We concluded that the lack of sensitivity of Acacia melanoxylon to leachates of itself or a common indigenous overstorey species likely contribute to its success as an invasive species in Southern Cape Afrotemperate Forest. Secondly, we investigated, through field surveys, whether Acacia melanoxylon affects indigenous Afrotemperate Forest tree sapling composition and light regimes underneath its canopy. Using a paired plot design, we compared light intensity, tree sapling species richness, diversity, and density underneath 30 overstorey Acacia melanoxylon trees and 30 indigenous counterparts. We recorded 2506 indigenous tree saplings from 29 species in the 60 plots and found that there were no significant differences in richness, diversity, or v density of saplings underneath Acacia melanoxylon compared to that under indigenous counterparts. Light intensity did not differ significantly underneath Acacia melanoxylon and indigenous canopies, however light intensity varied significantly more underneath the canopies of Acacia melanoxylon. Canonical correspondence analysis of the abundance of sapling species confirmed that sapling composition was not largely determined by the overstorey species. We concluded that Acacia melanoxylon does not significantly alter indigenous tree species composition underneath its canopy at the typical densities (<3 trees per hectare) at which it occurred in the forests of the Garden Route National Park that we surveyed. Nevertheless, populations of Acacia melanoxylon in the forest interior still act as a source of propagules for invasion in forest margins, riparian areas, and neighbouring fynbos shrubland. These invasive attributes need to be considered in the management of the species in the region at large. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Miles, Bayleigh , Baard, Johan
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55391 , vital:51989
- Description: Acacia melanoxylon R.Br. is a prominent alien and invasive species in many parts of the world and evidence exists of its adverse effects on indigenous forest community composition through allelopathy and alteration of light regimes. The species also occurs extensively in Southern Cape Afrotemperate Forest (South Africa) and is thought to suppress indigenous Afrotemperate Forest tree seedlings through various mechanisms such as the alteration of natural light regimes or allelopathy, although this has not been rigorously verified. This study aimed to investigate whether Acacia melanoxylon has a suppressive effect on Afrotemperate Forest tree recruitment. Firstly, we assessed the potential allelopathic effect of Acacia melanoxylon and an indigenous Afrotemperate Forest species Olea capensis macrocarpa (C.H.Wright) I.Verd. on the germination of Acacia melanoxylon and three prominent indigenous tree species’ seedlings in a nursery trial. Germination of the indigenous species failed; however, we were able to compare the germination of Acacia melanoxylon among the three treatments, namely Acacia melanoxylon leachate, Olea capensis leachate, and no leachate. The average germination of Acacia melanoxylon was 67% and germination was marginally higher under Acacia melanoxylon leachate and Olea capensis leachate, respectively, than under the control. This suggested that germination of the species is improved, or at the least, unaffected, by leachates of itself or that of a common indigenous canopy species. We then critically evaluated the germination requirements of the indigenous test species to determine probable reasons why their germination failed in our trial. The most plausible explanation for the germination failure could be that the trial period did not encompass an entire winter season and may not have provided adequate cold stratification. We concluded that the lack of sensitivity of Acacia melanoxylon to leachates of itself or a common indigenous overstorey species likely contribute to its success as an invasive species in Southern Cape Afrotemperate Forest. Secondly, we investigated, through field surveys, whether Acacia melanoxylon affects indigenous Afrotemperate Forest tree sapling composition and light regimes underneath its canopy. Using a paired plot design, we compared light intensity, tree sapling species richness, diversity, and density underneath 30 overstorey Acacia melanoxylon trees and 30 indigenous counterparts. We recorded 2506 indigenous tree saplings from 29 species in the 60 plots and found that there were no significant differences in richness, diversity, or v density of saplings underneath Acacia melanoxylon compared to that under indigenous counterparts. Light intensity did not differ significantly underneath Acacia melanoxylon and indigenous canopies, however light intensity varied significantly more underneath the canopies of Acacia melanoxylon. Canonical correspondence analysis of the abundance of sapling species confirmed that sapling composition was not largely determined by the overstorey species. We concluded that Acacia melanoxylon does not significantly alter indigenous tree species composition underneath its canopy at the typical densities (<3 trees per hectare) at which it occurred in the forests of the Garden Route National Park that we surveyed. Nevertheless, populations of Acacia melanoxylon in the forest interior still act as a source of propagules for invasion in forest margins, riparian areas, and neighbouring fynbos shrubland. These invasive attributes need to be considered in the management of the species in the region at large. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-04
Antifungal activity of silver nanoparticles on Cryptococcus species
- Authors: Roman, Nasstasja
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Cryptococcus
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52089 , vital:43445
- Description: Cryptococcus neoformans is responsible for cryptococcal infections, which have become a great concern particularly in immunocompromised patients. This pulmonary disease causes damage to lung tissue and is presumed to be responsible for approximately 650,000 deaths annually. There is a major need for novel antimicrobial agents to avoid the emergence of resistant strains due to extended use of known antifungal drugs. Silver has become an important antimicrobial agent used in medical devices, cosmetics and even house-hold or clothing products. It is highly toxic and has a reduced risk of resistance. Silver nanoparticles have been broadly explored as an antimicrobial agent due to its high reactivity, large surface area and small size. They have been reported to display antimicrobial activity towards bacteria, viruses and fungi. C. neoformans is a pathogenic microorganism that possesses a number of virulence factors which increases the infectivity of the microorganism in immunocompromised individuals. Some of these include the presence of a polysaccharide capsule, melanin, urease and phospholipase production. Owing to limited availability of antifungal drugs and the possibility of drug resistance, this study focused on an alternative antimicrobial agent, namely silver nanoparticles, and the effects that silver nanoparticles had on fungal β-glucan, chitin and urease, phospholipase and melanin virulence factors. Results from our study show that silver nanoparticles inhibited the growth of C. neoformans at concentrations between 3.125 ƒM and 25 ƒM. Both 26.4 nm and 28.4 nm nanoparticles displayed growth inhibition, but were unable to kill the organism at concentrations of 200 ƒM and above. The silver nanoparticles caused a reduction in βglucan content. There was also an accumulation of intracellular ROS, and phospholipase activity, was reduced. In contrast, the organism displayed an increase in chitin content, melanin and urease activity upon exposure to the nanoparticles. This study shows that chemically synthesized silver nanoparticles are an effective antifungal alternative that greatly reduces or inhibits C. neoformans growth at very low concentrations (ƒM). For future studies it may be feasible to investigate the use of these nanoparticles in combination with known antifungal agents, to prevent the emergence of resistance and inhibit possible defense mechanisms displayed by the organism. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Roman, Nasstasja
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Cryptococcus
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52089 , vital:43445
- Description: Cryptococcus neoformans is responsible for cryptococcal infections, which have become a great concern particularly in immunocompromised patients. This pulmonary disease causes damage to lung tissue and is presumed to be responsible for approximately 650,000 deaths annually. There is a major need for novel antimicrobial agents to avoid the emergence of resistant strains due to extended use of known antifungal drugs. Silver has become an important antimicrobial agent used in medical devices, cosmetics and even house-hold or clothing products. It is highly toxic and has a reduced risk of resistance. Silver nanoparticles have been broadly explored as an antimicrobial agent due to its high reactivity, large surface area and small size. They have been reported to display antimicrobial activity towards bacteria, viruses and fungi. C. neoformans is a pathogenic microorganism that possesses a number of virulence factors which increases the infectivity of the microorganism in immunocompromised individuals. Some of these include the presence of a polysaccharide capsule, melanin, urease and phospholipase production. Owing to limited availability of antifungal drugs and the possibility of drug resistance, this study focused on an alternative antimicrobial agent, namely silver nanoparticles, and the effects that silver nanoparticles had on fungal β-glucan, chitin and urease, phospholipase and melanin virulence factors. Results from our study show that silver nanoparticles inhibited the growth of C. neoformans at concentrations between 3.125 ƒM and 25 ƒM. Both 26.4 nm and 28.4 nm nanoparticles displayed growth inhibition, but were unable to kill the organism at concentrations of 200 ƒM and above. The silver nanoparticles caused a reduction in βglucan content. There was also an accumulation of intracellular ROS, and phospholipase activity, was reduced. In contrast, the organism displayed an increase in chitin content, melanin and urease activity upon exposure to the nanoparticles. This study shows that chemically synthesized silver nanoparticles are an effective antifungal alternative that greatly reduces or inhibits C. neoformans growth at very low concentrations (ƒM). For future studies it may be feasible to investigate the use of these nanoparticles in combination with known antifungal agents, to prevent the emergence of resistance and inhibit possible defense mechanisms displayed by the organism. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Incidence of parasitic trematodes effects on the energetics and behaviour of Coryogalops sordidus (Family: Gobiidae) resident in microbialite pools, warm temperate South Africa
- Authors: Du Toit, Hendrik Daniël
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Gobiidae -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52458 , vital:43666
- Description: Coryogalops sordidus(Epaulette goby), is a cryptobenthic species of the Family Gobiidae that iscommonly foundoccupying turbulent surf zones, calm rock pools, and sand and mud flats, where they are generally carnivorous predators. The distribution of C. sordidushas been recorded for Kenya, Tanzania, Mozambique, and South Africa. The species is also resident in the microbialite pools on the temperate south east coast of South Africa. Recent reports indicated these gobies to be covered in numerous dark lesions, possibly suggesting that the microbialite pools are a sub-optimal habitat. Preliminary analyses have indicated that the dark lesions are a result of encysted metacercaria of a digenetic trematode (fluke). There werehowever,no current recorded parasiticspecies occurring within microbialite pool nor any records of any parasitic species utilizingC. sordidus as a host in South Africa. Therefore, the aim of this study was to investigate parasite-host interactions and parasite presence in and around themicrobialite pool systems of Algoa Bay using C. sordidusas a study species. Coryogalops sordiduswas identified to be parasitised by digenetic trematode metacercaria of the Family Diplostomidae Poirier, 1886, localised primarily to the host musculature, fins, eyes, and integument with no settlement on any of the visceral organs. Furthermore, C. sordidus was found additionally parasitised by a green leech (Class: Hirundinea) of the Family Piscicolidae Johnston, 1865, localised exclusively to the ventral body surface, underneath the pelvic fin of the host. Further investigation into the life cycle of the trematode, suggested that the most probable final hosts wereherons,namely Ardea cinereaand Egretta garzetta garzetta, and intermediate host likely being the freshwater gastropod Assimineacf.capensis, present inthe upper microbialite pools. In both the microbialite and neighbouring rock pools trematode prevalence was found to oscillate in response to seasonal chemical and climatic conditions, whereas the secondary piscicolid leech parasite was influencedmoreby host presence than environmental conditions. Greater prevalence and intensity were measured in the microbialite pools suggesting that these systems likely contained a suit of favourable conditions that allowed for greater trematode loads to be maintained as compared to neighbouring rock pools. As parasites often have deleterious effects on their hosts, the response can manifest as an altered host behaviour or an increased energetic debt due to elevated immune response activity and the associated cost of tissue repair at sites of parasite aggregation.This study further investigatedifgobies (C. sordidus) infected with metacercarial cysts display higher metabolic ratesordifferent swimming behaviour compared to non-infected individuals. The results indicated that the metacercarial load carried by infected hosts had on average no significant impact on energetics, swimming ability, or swimming behaviour, concluding that the average metacercarial intensity present on the gobies is therefore below the threshold of an altered host response. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
- Authors: Du Toit, Hendrik Daniël
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Gobiidae -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52458 , vital:43666
- Description: Coryogalops sordidus(Epaulette goby), is a cryptobenthic species of the Family Gobiidae that iscommonly foundoccupying turbulent surf zones, calm rock pools, and sand and mud flats, where they are generally carnivorous predators. The distribution of C. sordidushas been recorded for Kenya, Tanzania, Mozambique, and South Africa. The species is also resident in the microbialite pools on the temperate south east coast of South Africa. Recent reports indicated these gobies to be covered in numerous dark lesions, possibly suggesting that the microbialite pools are a sub-optimal habitat. Preliminary analyses have indicated that the dark lesions are a result of encysted metacercaria of a digenetic trematode (fluke). There werehowever,no current recorded parasiticspecies occurring within microbialite pool nor any records of any parasitic species utilizingC. sordidus as a host in South Africa. Therefore, the aim of this study was to investigate parasite-host interactions and parasite presence in and around themicrobialite pool systems of Algoa Bay using C. sordidusas a study species. Coryogalops sordiduswas identified to be parasitised by digenetic trematode metacercaria of the Family Diplostomidae Poirier, 1886, localised primarily to the host musculature, fins, eyes, and integument with no settlement on any of the visceral organs. Furthermore, C. sordidus was found additionally parasitised by a green leech (Class: Hirundinea) of the Family Piscicolidae Johnston, 1865, localised exclusively to the ventral body surface, underneath the pelvic fin of the host. Further investigation into the life cycle of the trematode, suggested that the most probable final hosts wereherons,namely Ardea cinereaand Egretta garzetta garzetta, and intermediate host likely being the freshwater gastropod Assimineacf.capensis, present inthe upper microbialite pools. In both the microbialite and neighbouring rock pools trematode prevalence was found to oscillate in response to seasonal chemical and climatic conditions, whereas the secondary piscicolid leech parasite was influencedmoreby host presence than environmental conditions. Greater prevalence and intensity were measured in the microbialite pools suggesting that these systems likely contained a suit of favourable conditions that allowed for greater trematode loads to be maintained as compared to neighbouring rock pools. As parasites often have deleterious effects on their hosts, the response can manifest as an altered host behaviour or an increased energetic debt due to elevated immune response activity and the associated cost of tissue repair at sites of parasite aggregation.This study further investigatedifgobies (C. sordidus) infected with metacercarial cysts display higher metabolic ratesordifferent swimming behaviour compared to non-infected individuals. The results indicated that the metacercarial load carried by infected hosts had on average no significant impact on energetics, swimming ability, or swimming behaviour, concluding that the average metacercarial intensity present on the gobies is therefore below the threshold of an altered host response. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text:
- Date Issued: 2021-04
Benthic habitat mapping using marine geophysics and machine learning on the continental shelf of South Africa
- Authors: Pillay, Talicia
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Marine geophysics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52061 , vital:43452
- Description: A method to map seafloor substrates using machine learning, based primarily on hydroacoustic data including multibeam bathymetry, backscatter, and side-scan sonar, has been developed. The aim was to produce a customdesigned benthic habitat classification method that digitally integrates marine geophysics and biological science data, with relevance to all elements of the local substrate, and this was the first time it was attempted in a South African context. The algorithm developed is able to produce bio-physical benthic habitat maps and this can be extended along the continental shelf of South Africa as new data setsare collected and the algorithm is supplemented. At the outset, this work has focused on broad categories of rock and detailed categories of sediment. Four study sites with varying substrate were selected to holistically build the algorithm that followed a tiered approach of machine learning: Table Bay, Clifton, Koeberg Harbour and Cape St Francis. Table Bay was used to develop a new method of physical seafloor classification, by comparing and contrasting a number of statistical algorithms and software programs. Clifton was used to test the developed clustering algorithm, and Koeberg which is 35 km to the north was used to validate the algorithm because sediment samples, along with drop camera footage, were integrated to better define the results. The resultant verified algorithm was tested at Cape St Francis, where Remotely Operated Vehicle (ROV) footage was acquired in addition to hydroacoustic data. In the first phase of the process towards developing an algorithm, a customised tool was created within ArcGIS using python scripting language to classify seafloor bathymetry, which can be applied to any area of seafloor whatsoever. The tool was based on pioneering work done by the National Oceanic and Atmospheric Administration (NOAA) on a benthic terrain modelling toolbox and adapted to include side-scan sonar data. In the second phase of work, multibeam bathymetry, backscatter and side-scan sonar data that were processed using Qimera, Fledermaus Geocoder Toolbox, and Navlog processing software, were classified using different machine learning techniques including Decision Trees, Random Forests, and k-means clustering computer algorithms. The results from these algorithms were compared to manually-digitised polygons which were created to classify the seafloor substrate distribution by identification of different textures. Integrating all results facilitated a quantitative comparison that illuminated advantages and disadvantages of each machine learning technique and ultimately the k-means clustering techniques were found to be the simplest to implement and understand and worked most efficiently based on their seafloor segmentation capabilities in Table Bay, against all three hydroacoustic data sets (multibeam bathymetry, backscatter and side-scan sonar). In the third phase of work, ground-truthed seafloor characterisation maps were produced for the two study areas of Clifton and Koeberg Harbour. This applied multibeam bathymetry and backscatter data that were collected and processed with machine learning clustering techniques. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Pillay, Talicia
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Marine geophysics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52061 , vital:43452
- Description: A method to map seafloor substrates using machine learning, based primarily on hydroacoustic data including multibeam bathymetry, backscatter, and side-scan sonar, has been developed. The aim was to produce a customdesigned benthic habitat classification method that digitally integrates marine geophysics and biological science data, with relevance to all elements of the local substrate, and this was the first time it was attempted in a South African context. The algorithm developed is able to produce bio-physical benthic habitat maps and this can be extended along the continental shelf of South Africa as new data setsare collected and the algorithm is supplemented. At the outset, this work has focused on broad categories of rock and detailed categories of sediment. Four study sites with varying substrate were selected to holistically build the algorithm that followed a tiered approach of machine learning: Table Bay, Clifton, Koeberg Harbour and Cape St Francis. Table Bay was used to develop a new method of physical seafloor classification, by comparing and contrasting a number of statistical algorithms and software programs. Clifton was used to test the developed clustering algorithm, and Koeberg which is 35 km to the north was used to validate the algorithm because sediment samples, along with drop camera footage, were integrated to better define the results. The resultant verified algorithm was tested at Cape St Francis, where Remotely Operated Vehicle (ROV) footage was acquired in addition to hydroacoustic data. In the first phase of the process towards developing an algorithm, a customised tool was created within ArcGIS using python scripting language to classify seafloor bathymetry, which can be applied to any area of seafloor whatsoever. The tool was based on pioneering work done by the National Oceanic and Atmospheric Administration (NOAA) on a benthic terrain modelling toolbox and adapted to include side-scan sonar data. In the second phase of work, multibeam bathymetry, backscatter and side-scan sonar data that were processed using Qimera, Fledermaus Geocoder Toolbox, and Navlog processing software, were classified using different machine learning techniques including Decision Trees, Random Forests, and k-means clustering computer algorithms. The results from these algorithms were compared to manually-digitised polygons which were created to classify the seafloor substrate distribution by identification of different textures. Integrating all results facilitated a quantitative comparison that illuminated advantages and disadvantages of each machine learning technique and ultimately the k-means clustering techniques were found to be the simplest to implement and understand and worked most efficiently based on their seafloor segmentation capabilities in Table Bay, against all three hydroacoustic data sets (multibeam bathymetry, backscatter and side-scan sonar). In the third phase of work, ground-truthed seafloor characterisation maps were produced for the two study areas of Clifton and Koeberg Harbour. This applied multibeam bathymetry and backscatter data that were collected and processed with machine learning clustering techniques. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04