Effect of grazing systems on growth performance, carcass characteristic, meat quality of beef cattle and economic performance of the enterprise
- Authors: Dayimani, Siyavuya
- Date: 2019
- Subjects: Grazing -- Environmental aspects Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/17294 , vital:40873
- Description: Under conditions of adaptive Holistic Management™, we tested whether rotational grazing approaches such as holistic planned grazing (HPG) and four-camp grazing (FCG) influence growth, carcass and meat quality attributes of beef steers compared to continuous, seasonlong (SLG) grazing. Thirty steers (250 ±19.56 kg, 16-17-month-old) were randomly assigned to SLG, HPG and FCG systems (10 steers/ treatment) at a private farm in Cedarville, Eastern Cape Province, South Africa where grazing was managed using an adaptive approach involving inter alia planned grazing charts, seasonal movement of cattle, and supplemental feeding. The steers were slaughtered at 40-41 months for carcass measurements and longissimus et lumborum was sampled for meat quality analyses. All the grazing systems had comparable live weights and average daily gain. All the investigated carcass attributes were also similar across grazing treatments (P > 0.05). Meat from steers on the SLG system had higher (P<0.05) drip loss, protein and fat contents and lower (P <0.05) shear force, moisture and ash contents than the two rotational grazing approaches (HPG and FCG). The HPG had higher (P < 0.05) total running and capital costs compared to SLG and FCG grazing systems. The SLG system had greater (P ≤ 0.05) gross and net income compared to FCG and HPG systems, respectively. Overall, all the grazing systems had comparable growth performance, carcass characteristics and meat quality but rotational grazing systems had lower gross income relative to the SLG grazing system.
- Full Text:
- Date Issued: 2019
- Authors: Dayimani, Siyavuya
- Date: 2019
- Subjects: Grazing -- Environmental aspects Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/17294 , vital:40873
- Description: Under conditions of adaptive Holistic Management™, we tested whether rotational grazing approaches such as holistic planned grazing (HPG) and four-camp grazing (FCG) influence growth, carcass and meat quality attributes of beef steers compared to continuous, seasonlong (SLG) grazing. Thirty steers (250 ±19.56 kg, 16-17-month-old) were randomly assigned to SLG, HPG and FCG systems (10 steers/ treatment) at a private farm in Cedarville, Eastern Cape Province, South Africa where grazing was managed using an adaptive approach involving inter alia planned grazing charts, seasonal movement of cattle, and supplemental feeding. The steers were slaughtered at 40-41 months for carcass measurements and longissimus et lumborum was sampled for meat quality analyses. All the grazing systems had comparable live weights and average daily gain. All the investigated carcass attributes were also similar across grazing treatments (P > 0.05). Meat from steers on the SLG system had higher (P<0.05) drip loss, protein and fat contents and lower (P <0.05) shear force, moisture and ash contents than the two rotational grazing approaches (HPG and FCG). The HPG had higher (P < 0.05) total running and capital costs compared to SLG and FCG grazing systems. The SLG system had greater (P ≤ 0.05) gross and net income compared to FCG and HPG systems, respectively. Overall, all the grazing systems had comparable growth performance, carcass characteristics and meat quality but rotational grazing systems had lower gross income relative to the SLG grazing system.
- Full Text:
- Date Issued: 2019
The integration of effluent treatment using constructed wetlands, with crop production and aquaculture
- Authors: de Jong, Martyn
- Date: 2019
- Subjects: Recycling (Waste, etc.) , Brewery waste , Sewage -- Purification , Beets , Mozambique tilapia
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95767 , vital:31197
- Description: Breweries are major consumers of water and produce nutrient rich wastewater. Therefore, it is important to research technologies that optimise the reuse and recycling of this waste. This study compared different constructed wetlands (CWs) in terms of their potential for cleaning brewery effluent and simultaneously producing crops Beta vulgaris and fish Oreochromis mossambicus. Filling and draining times (FDT; 15 min, 30 min and 60 min) in tidal CWs were compared in Experiment 1. The 15 min FDT (6.52 ± 0.09 mg/l) and 30 min FDT (5.74 ± 0.09 mg/l) had higher dissolved oxygen (DO) than the 60 min FDT (5.40 ± 0.09 mg/l; p<0.05). This resulted in the 15 and 30 min FDT treatments reaching ammonia effluent discharge standards sooner than the 60 min FDT. Total plant harvest increased with increasing FDT; therefore, 15 min FDT was used as the FDT in tidal treatments in the following experiments. The aerated CW (5.81 ± 0.07 mg/l) and tidal CW (5.67 ± 0.07 mg/l) treatments had higher DO concentrations than the unaerated CW treatment (3.76 ± 0.07 mg/l; p<0.05) in Experiment 2. This resulted in lower ammonia concentrations on day 5 in the aerated and tidal CWs compared with the unaerated treatment (p<0.05). The tidal CW (23.97 ± 2.57 kg) had a total harvest that was approximately four times higher than the unaerated CW (p<0.05), which had the highest frequency of chlorosis and plant mortality; and was unable to treat ammonia to discharge standards. In Experiment 3, the aerated and tidal CW were compared with municipal-water as water sources for aquaculture. There were no differences in fish growth (p > 0.05). However, there were differences in water quality; with the municipal treatment having the lowest pH, EC and nitrate concentration (p<0.05); but all water quality parameters remained in a range suitably for fish production. Due to the tidal CW having the highest plant harvest and lowest frequency of chlorosis and mortality; it was the most suitable CW technology to clean the brewery effluent, and to produce B. vulgaris and water that could be used downstream in aquaculture.
- Full Text:
- Date Issued: 2019
- Authors: de Jong, Martyn
- Date: 2019
- Subjects: Recycling (Waste, etc.) , Brewery waste , Sewage -- Purification , Beets , Mozambique tilapia
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/95767 , vital:31197
- Description: Breweries are major consumers of water and produce nutrient rich wastewater. Therefore, it is important to research technologies that optimise the reuse and recycling of this waste. This study compared different constructed wetlands (CWs) in terms of their potential for cleaning brewery effluent and simultaneously producing crops Beta vulgaris and fish Oreochromis mossambicus. Filling and draining times (FDT; 15 min, 30 min and 60 min) in tidal CWs were compared in Experiment 1. The 15 min FDT (6.52 ± 0.09 mg/l) and 30 min FDT (5.74 ± 0.09 mg/l) had higher dissolved oxygen (DO) than the 60 min FDT (5.40 ± 0.09 mg/l; p<0.05). This resulted in the 15 and 30 min FDT treatments reaching ammonia effluent discharge standards sooner than the 60 min FDT. Total plant harvest increased with increasing FDT; therefore, 15 min FDT was used as the FDT in tidal treatments in the following experiments. The aerated CW (5.81 ± 0.07 mg/l) and tidal CW (5.67 ± 0.07 mg/l) treatments had higher DO concentrations than the unaerated CW treatment (3.76 ± 0.07 mg/l; p<0.05) in Experiment 2. This resulted in lower ammonia concentrations on day 5 in the aerated and tidal CWs compared with the unaerated treatment (p<0.05). The tidal CW (23.97 ± 2.57 kg) had a total harvest that was approximately four times higher than the unaerated CW (p<0.05), which had the highest frequency of chlorosis and plant mortality; and was unable to treat ammonia to discharge standards. In Experiment 3, the aerated and tidal CW were compared with municipal-water as water sources for aquaculture. There were no differences in fish growth (p > 0.05). However, there were differences in water quality; with the municipal treatment having the lowest pH, EC and nitrate concentration (p<0.05); but all water quality parameters remained in a range suitably for fish production. Due to the tidal CW having the highest plant harvest and lowest frequency of chlorosis and mortality; it was the most suitable CW technology to clean the brewery effluent, and to produce B. vulgaris and water that could be used downstream in aquaculture.
- Full Text:
- Date Issued: 2019
Investigating assay formats for screening malaria Hsp90-Hop interaction inhibitors
- Authors: Derry, Leigh-Anne Tracy Kim
- Date: 2019
- Subjects: Antimalarials , Heat shock proteins , Drug interactions , Drug resistance , Plasmodium falciparum , High throughput screening (Drug development) , Bioluminescence resonance energy transfer (BRET) , Fluorescence resonance energy transfer (FRET)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63345 , vital:28395
- Description: Although significant gains have been made in the combat against malaria in the last decade, the persistent threat of drug and insecticide resistance continues to motivate the search for new classes of antimalarial drug compounds and targets. Due to their predominance in cellular reactions, protein-protein interactions (P-PIs) are emerging as a promising general target class for therapeutic development. The P-PI which is the focus of this project is the interaction between the chaperone heat shock protein 90 (Hsp90) and its co-chaperone Hsp70/Hsp90 organising protein (Hop). Hop binds to Hsp70 and Hsp90 and facilitates the transfer of client proteins (proteins undergoing folding) from the former to the latter and also regulates nucleotide exchange on Hsp90. Due to its role in correcting protein misfolding during cell stress, Hsp90 is being pursued as a cancer drug target and compounds that inhibit its ATPase activity have entered clinical trials. However, it has been proposed that inhibiting the interaction between Hsp90 and Hop may be alternative approach for inhibiting Hsp90 function for cancer therapy. The malaria parasite Plasmodium falciparum experiences temperature fluctuations during vector-host transitions and febrile episodes and cell stress due to rapid growth and immune responses. Hence, it also depends on chaperones, including PfHsp90, to maintain protein functionality and pathogenesis, demonstrated inter alia by the sensitivity of parasites to Hsp90 inhibitors. In addition, PfHsp90 exists as a complex with the malarial Hop homologue, PfHop, in parasite lysates. Consequently, the purpose of this study was to explore P-PI assay formats that can confirm the interaction of PfHsp90 and PfHop and can be used to identify inhibitors of the interaction, preferably in a medium- to high-throughput screening mode. As a first approach, cell-based bioluminescence and fluorescence resonance energy transfer (BRET and FRET) assays were performed in HeLa cells. To facilitate this, expression plasmid constructs containing coding sequences of P. falciparum and mammalian Hsp90 and Hop and their interacting domains (Hsp90 C-domain and Hop TPR2A domain) fused to the BRET and FRET reporter proteins – yellow fluorescent protein (YFP), cyan fluorescent protein (CFP) and Renilla luciferase (Rluc) - were prepared and used for HeLa cell transient transfections. The FRET assay produced positive interaction signals for the full-length P. falciparum and mammalian Hsp90-Hop interactions. However, C-domain-TPR2A domain interactions were not detected, no interactions could be demonstrated with the BRET assay and western blotting experiments failed to detect expression of all the interaction partners in transiently transfected HeLa cells. Consequently, an alternative in vitro FRET assay format using recombinant proteins was investigated. Expression constructs for the P. falciparum and mammalian C-domains and TPR2A domains fused respectively to YFP and CFP were prepared and the corresponding fusion proteins expressed and purified from E. coli. No interaction was found with the mammalian interaction partners, but interaction of the P. falciparum C-domain and TPR2A domain was consistently detected with a robust Z’ factor value of 0.54. A peptide corresponding to the PfTPR2A domain sequence primarily responsible for Hsp90 binding (based on a human TPR2A peptide described by Horibe et al., 2011) was designed and showed dose-dependent inhibition of the interaction, with 53.7% inhibition at 100 μM. The components of the assay are limited to the purified recombinant proteins, requires minimal liquid steps and may thus be a useful primary screening format for identifying inhibitors of P. falciparum Hsp90-Hop interaction.
- Full Text:
- Date Issued: 2019
- Authors: Derry, Leigh-Anne Tracy Kim
- Date: 2019
- Subjects: Antimalarials , Heat shock proteins , Drug interactions , Drug resistance , Plasmodium falciparum , High throughput screening (Drug development) , Bioluminescence resonance energy transfer (BRET) , Fluorescence resonance energy transfer (FRET)
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/63345 , vital:28395
- Description: Although significant gains have been made in the combat against malaria in the last decade, the persistent threat of drug and insecticide resistance continues to motivate the search for new classes of antimalarial drug compounds and targets. Due to their predominance in cellular reactions, protein-protein interactions (P-PIs) are emerging as a promising general target class for therapeutic development. The P-PI which is the focus of this project is the interaction between the chaperone heat shock protein 90 (Hsp90) and its co-chaperone Hsp70/Hsp90 organising protein (Hop). Hop binds to Hsp70 and Hsp90 and facilitates the transfer of client proteins (proteins undergoing folding) from the former to the latter and also regulates nucleotide exchange on Hsp90. Due to its role in correcting protein misfolding during cell stress, Hsp90 is being pursued as a cancer drug target and compounds that inhibit its ATPase activity have entered clinical trials. However, it has been proposed that inhibiting the interaction between Hsp90 and Hop may be alternative approach for inhibiting Hsp90 function for cancer therapy. The malaria parasite Plasmodium falciparum experiences temperature fluctuations during vector-host transitions and febrile episodes and cell stress due to rapid growth and immune responses. Hence, it also depends on chaperones, including PfHsp90, to maintain protein functionality and pathogenesis, demonstrated inter alia by the sensitivity of parasites to Hsp90 inhibitors. In addition, PfHsp90 exists as a complex with the malarial Hop homologue, PfHop, in parasite lysates. Consequently, the purpose of this study was to explore P-PI assay formats that can confirm the interaction of PfHsp90 and PfHop and can be used to identify inhibitors of the interaction, preferably in a medium- to high-throughput screening mode. As a first approach, cell-based bioluminescence and fluorescence resonance energy transfer (BRET and FRET) assays were performed in HeLa cells. To facilitate this, expression plasmid constructs containing coding sequences of P. falciparum and mammalian Hsp90 and Hop and their interacting domains (Hsp90 C-domain and Hop TPR2A domain) fused to the BRET and FRET reporter proteins – yellow fluorescent protein (YFP), cyan fluorescent protein (CFP) and Renilla luciferase (Rluc) - were prepared and used for HeLa cell transient transfections. The FRET assay produced positive interaction signals for the full-length P. falciparum and mammalian Hsp90-Hop interactions. However, C-domain-TPR2A domain interactions were not detected, no interactions could be demonstrated with the BRET assay and western blotting experiments failed to detect expression of all the interaction partners in transiently transfected HeLa cells. Consequently, an alternative in vitro FRET assay format using recombinant proteins was investigated. Expression constructs for the P. falciparum and mammalian C-domains and TPR2A domains fused respectively to YFP and CFP were prepared and the corresponding fusion proteins expressed and purified from E. coli. No interaction was found with the mammalian interaction partners, but interaction of the P. falciparum C-domain and TPR2A domain was consistently detected with a robust Z’ factor value of 0.54. A peptide corresponding to the PfTPR2A domain sequence primarily responsible for Hsp90 binding (based on a human TPR2A peptide described by Horibe et al., 2011) was designed and showed dose-dependent inhibition of the interaction, with 53.7% inhibition at 100 μM. The components of the assay are limited to the purified recombinant proteins, requires minimal liquid steps and may thus be a useful primary screening format for identifying inhibitors of P. falciparum Hsp90-Hop interaction.
- Full Text:
- Date Issued: 2019
Using four different methods to reach a taxonomic conclusion in dung beetles (Scarabaeinae)
- Authors: Deschodt, Christian Michel
- Date: 2019
- Subjects: Dung beetles -- Classification , Scarabaeidae -- Classification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67845 , vital:29156
- Description: Four different techniques to make taxonomic decisions concerning different species in Scarabaeinae are being investigated. Firstly, I made measurements of the body dimensions which are plotted on a two dimensional graph. This method is successfully used to erect one new species, Copris crassus Deschodt and Davis, 2015, and to establish the synonymy of Copris bihamatus Balthasar, 1965 with Copris fidius (Olivier, 1789). Thereafter the classical or traditional comparative method is used to propose seven new species Scarabaeolus soutpansbergensis (Deschodt and Davis 2015), Scarabaeolus megaparvulus (Davis and Deschodt 2015), Scarabaeolus niemandi (Deschodt and Davis 2015), Scarabaeolus carniphilus (Davis and Deschodt 2015), Scarabaeolus ermienae (Deschodt and Davis 2015), Scarabaeolus planipennis (Davis and Deschodt 2015) and Scarabaeolus afronitidus (Davis and Deschodt 2015) and formally synonymise Scarabaeolus vansoni (Ferreira, 1958) with Scarabaeolus lucidulus (Boheman, 1860) and Scarabaeolus xavieri (Ferreira, 1968) with Scarabaeolus andreaei (zur Strassen, 1963). Morphometric measurements of external structures of a group of flightless relict beetles in the tribe Canthonini are used to compile a nexus file which is analysed with computer software. The interpretation of these results is used here to support the erection of a new genus Drogo Deschodt, Davis & Scholtz 2016, Lastly I analysed the DNA sequences of specimens from different species belonging to a species complex in the genus Epirinus Reiche, 1841 occurring over a wide geographic range. These sequences are used together with external morphological characters to propose the synonymy of Epirinus hluhluwensis Medina & Scholtz 2005 and Epirinus ngomae Medina & Scholtz 2005 with Epirinus davisi Scholtz & Howden 1987.
- Full Text:
- Date Issued: 2019
- Authors: Deschodt, Christian Michel
- Date: 2019
- Subjects: Dung beetles -- Classification , Scarabaeidae -- Classification
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67845 , vital:29156
- Description: Four different techniques to make taxonomic decisions concerning different species in Scarabaeinae are being investigated. Firstly, I made measurements of the body dimensions which are plotted on a two dimensional graph. This method is successfully used to erect one new species, Copris crassus Deschodt and Davis, 2015, and to establish the synonymy of Copris bihamatus Balthasar, 1965 with Copris fidius (Olivier, 1789). Thereafter the classical or traditional comparative method is used to propose seven new species Scarabaeolus soutpansbergensis (Deschodt and Davis 2015), Scarabaeolus megaparvulus (Davis and Deschodt 2015), Scarabaeolus niemandi (Deschodt and Davis 2015), Scarabaeolus carniphilus (Davis and Deschodt 2015), Scarabaeolus ermienae (Deschodt and Davis 2015), Scarabaeolus planipennis (Davis and Deschodt 2015) and Scarabaeolus afronitidus (Davis and Deschodt 2015) and formally synonymise Scarabaeolus vansoni (Ferreira, 1958) with Scarabaeolus lucidulus (Boheman, 1860) and Scarabaeolus xavieri (Ferreira, 1968) with Scarabaeolus andreaei (zur Strassen, 1963). Morphometric measurements of external structures of a group of flightless relict beetles in the tribe Canthonini are used to compile a nexus file which is analysed with computer software. The interpretation of these results is used here to support the erection of a new genus Drogo Deschodt, Davis & Scholtz 2016, Lastly I analysed the DNA sequences of specimens from different species belonging to a species complex in the genus Epirinus Reiche, 1841 occurring over a wide geographic range. These sequences are used together with external morphological characters to propose the synonymy of Epirinus hluhluwensis Medina & Scholtz 2005 and Epirinus ngomae Medina & Scholtz 2005 with Epirinus davisi Scholtz & Howden 1987.
- Full Text:
- Date Issued: 2019
Bootstrap-based tolerance intervals for photovoltaic energy yield assessments
- Authors: Deyzel, Jani Igna
- Date: 2019
- Subjects: Bootstrap (Statistics) , Mathematical statistics Photovoltaic power systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39469 , vital:35256
- Description: The assessment of the energy yield of a photovoltaic (PV) system is one of the key assessments required by investors and developers. Currently, available methods used for this assessment only provide a point estimate as the final assessment. This study proposes a statistical technique which provides an additional energy yield assessment method by using tolerance intervals. Variance component models are used to better account for the variability present in the daily and hourly energy yields of three different PV modules. A bootstrap-based technique is used to obtain 𝛽-expectation and (𝛼,𝛽) two-sided tolerance intervals. These tolerance intervals provided more information with a content and confidence level for seasonal and yearly time-periods. In addition, the comparisons of the PV modules provide valuable information to investors and developers.
- Full Text:
- Date Issued: 2019
- Authors: Deyzel, Jani Igna
- Date: 2019
- Subjects: Bootstrap (Statistics) , Mathematical statistics Photovoltaic power systems
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39469 , vital:35256
- Description: The assessment of the energy yield of a photovoltaic (PV) system is one of the key assessments required by investors and developers. Currently, available methods used for this assessment only provide a point estimate as the final assessment. This study proposes a statistical technique which provides an additional energy yield assessment method by using tolerance intervals. Variance component models are used to better account for the variability present in the daily and hourly energy yields of three different PV modules. A bootstrap-based technique is used to obtain 𝛽-expectation and (𝛼,𝛽) two-sided tolerance intervals. These tolerance intervals provided more information with a content and confidence level for seasonal and yearly time-periods. In addition, the comparisons of the PV modules provide valuable information to investors and developers.
- Full Text:
- Date Issued: 2019
Testing potential groundwater reservoir connectivity using isotopes in the south-central Karoo region
- Authors: Dlakavu, Sinazo
- Date: 2019
- Subjects: Groundwater -- South Africa -- Karoo , Hydrogeology -- South Africa Water-supply -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39447 , vital:35248
- Description: Documenting areas with natural groundwater reservior connectivity using isotopes before the anticipated shale gas development in the Karoo Basin of South Africa could contribute to developing legislative framework for hydraulic fracturing. In this study, groundwater dynamics (primarily connectivity between old/deep and low temperature modern/shallow (<25°C) groundwater) are studied using isotopes (14C, δ18O-δ2H, 3H, and δ13C) in conjunction with geochemical parameters (sampling depth (masl) and (mbgl), temperature (°C), Electrical Conductivity (EC) (μS/m) and sustainable yield (l/s)). Previous groundwater studies conducted in the Karoo Basin suggest that 14C (pMC) has the least overlap among isotope signature constraints between the different aquifer/groundwater groups. The outcomes of 14C analysis for this study suggest that one groundwater sample is an old/deep groundwater sample (<53 pMC), and that three groundwater samples are composed of shallow/young groundwater mixed with old/deep groundwater (<74 pMC). These four relatively older samples have calculated 14C ages ≥ 1700 years and were collected from boreholes that are north-east of the Cape Mountains (~50 km). The position of these samples suggests that deep-seated faults within the Cape Mountains and the basement of the southern Karoo Basin act as preferential pathways for deep groundwater migration (as is consistent with existing deep geophysical data) to shallower depths (<60 mbgl) where it cools and/or mixes with low temperature groundwater (<25°C). Three more groundwater samples were found to match the relatively old calculated 14C ages (≥ 1700 years) of the groundwater samples collected close to the Cape Mountains even though they have modern 14C (pMC) concentrations (>74 pMC). This implies that adjusting the 14C content in Dissolved Inorganic Carbon (DIC) based on its dilution by 14C free carbonates is influential in controlling the mixed groundwater ages, and that relatively older groundwater occurs at shallow depths in other parts of the study area possibly due to linked fault systems between deep and shallow aquifers. δ18O-δ2H relationships for the sampled groundwater suggest that groundwater samples collected within the main drainage of the Great Fish River plot close to the Global Meteoric Water Line (GMWL) indicating that the recharge water to this groundwater does not experience significant evaporation. The average isotope composition of the recharging water for the all of the sampled groundwater is -7.90 ‰ and -46.72 ‰ for δ18O and δ2H, respectively. This result plots halfway between rainwater 18O-2H relationship lines for the Indian Ocean and the Atlantic Ocean. This suggests that the rainwater from which the sampled groundwater was derived from evolved from both the Indian and Atlantic Ocean waters.
- Full Text:
- Date Issued: 2019
- Authors: Dlakavu, Sinazo
- Date: 2019
- Subjects: Groundwater -- South Africa -- Karoo , Hydrogeology -- South Africa Water-supply -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39447 , vital:35248
- Description: Documenting areas with natural groundwater reservior connectivity using isotopes before the anticipated shale gas development in the Karoo Basin of South Africa could contribute to developing legislative framework for hydraulic fracturing. In this study, groundwater dynamics (primarily connectivity between old/deep and low temperature modern/shallow (<25°C) groundwater) are studied using isotopes (14C, δ18O-δ2H, 3H, and δ13C) in conjunction with geochemical parameters (sampling depth (masl) and (mbgl), temperature (°C), Electrical Conductivity (EC) (μS/m) and sustainable yield (l/s)). Previous groundwater studies conducted in the Karoo Basin suggest that 14C (pMC) has the least overlap among isotope signature constraints between the different aquifer/groundwater groups. The outcomes of 14C analysis for this study suggest that one groundwater sample is an old/deep groundwater sample (<53 pMC), and that three groundwater samples are composed of shallow/young groundwater mixed with old/deep groundwater (<74 pMC). These four relatively older samples have calculated 14C ages ≥ 1700 years and were collected from boreholes that are north-east of the Cape Mountains (~50 km). The position of these samples suggests that deep-seated faults within the Cape Mountains and the basement of the southern Karoo Basin act as preferential pathways for deep groundwater migration (as is consistent with existing deep geophysical data) to shallower depths (<60 mbgl) where it cools and/or mixes with low temperature groundwater (<25°C). Three more groundwater samples were found to match the relatively old calculated 14C ages (≥ 1700 years) of the groundwater samples collected close to the Cape Mountains even though they have modern 14C (pMC) concentrations (>74 pMC). This implies that adjusting the 14C content in Dissolved Inorganic Carbon (DIC) based on its dilution by 14C free carbonates is influential in controlling the mixed groundwater ages, and that relatively older groundwater occurs at shallow depths in other parts of the study area possibly due to linked fault systems between deep and shallow aquifers. δ18O-δ2H relationships for the sampled groundwater suggest that groundwater samples collected within the main drainage of the Great Fish River plot close to the Global Meteoric Water Line (GMWL) indicating that the recharge water to this groundwater does not experience significant evaporation. The average isotope composition of the recharging water for the all of the sampled groundwater is -7.90 ‰ and -46.72 ‰ for δ18O and δ2H, respectively. This result plots halfway between rainwater 18O-2H relationship lines for the Indian Ocean and the Atlantic Ocean. This suggests that the rainwater from which the sampled groundwater was derived from evolved from both the Indian and Atlantic Ocean waters.
- Full Text:
- Date Issued: 2019
A clip composition case study of communal wool production in the Eastern Cape, South Africa
- Authors: Dreyer, Susanna Maria
- Date: 2019
- Subjects: Wool industry -- South Africa -- Eastern Cape , Wool -- South Africa -- Eastern Cape Sheep industry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39480 , vital:35265
- Description: Previous studies conducted on wool production in the communal areas of the Eastern Cape have concluded future research should focus on whether the observed differences in average wool price received between shearing sheds are due to differences in clip preparation (i.e. classing) or differences in the quality of the wool being produced (i.e. genetics).The objective of this study was to establish whether there are indeed geographical differences in the average wool price received by communal wool producers in the Eastern Cape and, if so, whether this difference in earnings is attributable to differences in the quality of wool produced and/or clip preparation. The current research explored eight years of wool production records of communal wool farmers (2009/10 to 2016/17) obtained from BKB, the largest wool broker in South Africa. Statistical analyses included descriptive statistics, analysis of variance, parametric tests (i.e. t-test) and multiple regression analysis. The conclusions drawn from this study are: that there are indeed statistically significant differences in the average wool price received between the different geographic areas of the Eastern Cape communal regions, and that the primary determining factor is wool quality, while clip preparation also plays an important but secondary role. The study identified specific geographic areas where developmental interventions are most critical, with specific emphasis on improving the genetic composition of the wool sheep flocks. Specific strategies are recommended, namely:Removing inferior-quality rams and replacing them with superior-quality rams to prevent any inferior nondescript rams from breeding and producing progeny; Replacing the inferior-quality nondescript ewes in specific areas with superior-quality ewes, and Improving the survival rate of lambs and thereby contributing towards expediting the rate of genetic improvement of the communal wool sheep flocks.
- Full Text:
- Date Issued: 2019
- Authors: Dreyer, Susanna Maria
- Date: 2019
- Subjects: Wool industry -- South Africa -- Eastern Cape , Wool -- South Africa -- Eastern Cape Sheep industry -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39480 , vital:35265
- Description: Previous studies conducted on wool production in the communal areas of the Eastern Cape have concluded future research should focus on whether the observed differences in average wool price received between shearing sheds are due to differences in clip preparation (i.e. classing) or differences in the quality of the wool being produced (i.e. genetics).The objective of this study was to establish whether there are indeed geographical differences in the average wool price received by communal wool producers in the Eastern Cape and, if so, whether this difference in earnings is attributable to differences in the quality of wool produced and/or clip preparation. The current research explored eight years of wool production records of communal wool farmers (2009/10 to 2016/17) obtained from BKB, the largest wool broker in South Africa. Statistical analyses included descriptive statistics, analysis of variance, parametric tests (i.e. t-test) and multiple regression analysis. The conclusions drawn from this study are: that there are indeed statistically significant differences in the average wool price received between the different geographic areas of the Eastern Cape communal regions, and that the primary determining factor is wool quality, while clip preparation also plays an important but secondary role. The study identified specific geographic areas where developmental interventions are most critical, with specific emphasis on improving the genetic composition of the wool sheep flocks. Specific strategies are recommended, namely:Removing inferior-quality rams and replacing them with superior-quality rams to prevent any inferior nondescript rams from breeding and producing progeny; Replacing the inferior-quality nondescript ewes in specific areas with superior-quality ewes, and Improving the survival rate of lambs and thereby contributing towards expediting the rate of genetic improvement of the communal wool sheep flocks.
- Full Text:
- Date Issued: 2019
Mapping soil factors influencing erosion using machine leaerning algorithms in the t35 d-e catchment in the Eastern Cape Province
- Du Plessis, Casparus Jacobus
- Authors: Du Plessis, Casparus Jacobus
- Date: 2019
- Subjects: Soils -- Analysis Soil erosion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/17106 , vital:40850
- Description: The need for detailed spatial soil information is increasing in the fields of environmental studies, agriculture as well as engineering practices. Regarding soil erosion in South Africa, border lines between sensitive soil forms in the Duplex soil group and resistant soil forms in the Oxidic soil group need to be mapped to a high accuracy to prevent/manage erosion and major soil losses. In third world countries like South Africa, digital soil mapping (DSM) with the use of machine learning can provide the solutions to fill numerous gaps in these related fields. Local DSM research has been ongoing at the University of the Free State and related institutions for the past eleven years. It has also been used commercially and can therefore be regarded as fruitful. The National Resource Management unit of the Department of Environmental Affairs required a soil map regarding the susceptibility of the soil to erosion for catchment T35 D-E (87 000 hectares) in the Mzimvubu management area of the Eastern Cape, South Africa. Through a DSM approach, machine learning was used to predict the occurrence of soil forms and soil families in accordance with the South African Soil Classification System. A total of 591 soil observations were made at specific points, pre-determined with the conditioned Latin Hypercube sampling (cLHS) method. These pre-determined points were classified into nineteen soil forms and forty eight soil families. The soils were then further divided into nine soil groups, based on their inherent sensitivity to erosion. Outlier observations were omitted from the dataset to create a reliable framework to predict the soil groups as influenced by the SCORPAN factors. These soil groups were mapped and evaluated with an accuracy of 68% and a Kappa statistic value of 0.42 that compare well with other soil maps, both locally and internationally. Mapping soil with an acceptable accuracy with such a high level of detail on catchment scale would be a tremendous advantage to soil scientists and environmental workforces in southern Africa. Future work should focus on DSM training, to broaden the base of DSM skills available in southern Africa. This will ensure that soil information would be included in addressing an increasing amount of real world problems at catchment scales.
- Full Text:
- Date Issued: 2019
- Authors: Du Plessis, Casparus Jacobus
- Date: 2019
- Subjects: Soils -- Analysis Soil erosion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/17106 , vital:40850
- Description: The need for detailed spatial soil information is increasing in the fields of environmental studies, agriculture as well as engineering practices. Regarding soil erosion in South Africa, border lines between sensitive soil forms in the Duplex soil group and resistant soil forms in the Oxidic soil group need to be mapped to a high accuracy to prevent/manage erosion and major soil losses. In third world countries like South Africa, digital soil mapping (DSM) with the use of machine learning can provide the solutions to fill numerous gaps in these related fields. Local DSM research has been ongoing at the University of the Free State and related institutions for the past eleven years. It has also been used commercially and can therefore be regarded as fruitful. The National Resource Management unit of the Department of Environmental Affairs required a soil map regarding the susceptibility of the soil to erosion for catchment T35 D-E (87 000 hectares) in the Mzimvubu management area of the Eastern Cape, South Africa. Through a DSM approach, machine learning was used to predict the occurrence of soil forms and soil families in accordance with the South African Soil Classification System. A total of 591 soil observations were made at specific points, pre-determined with the conditioned Latin Hypercube sampling (cLHS) method. These pre-determined points were classified into nineteen soil forms and forty eight soil families. The soils were then further divided into nine soil groups, based on their inherent sensitivity to erosion. Outlier observations were omitted from the dataset to create a reliable framework to predict the soil groups as influenced by the SCORPAN factors. These soil groups were mapped and evaluated with an accuracy of 68% and a Kappa statistic value of 0.42 that compare well with other soil maps, both locally and internationally. Mapping soil with an acceptable accuracy with such a high level of detail on catchment scale would be a tremendous advantage to soil scientists and environmental workforces in southern Africa. Future work should focus on DSM training, to broaden the base of DSM skills available in southern Africa. This will ensure that soil information would be included in addressing an increasing amount of real world problems at catchment scales.
- Full Text:
- Date Issued: 2019
An analysis of the use of DNS for malicious payload distribution
- Authors: Dube, Ishmael
- Date: 2019
- Subjects: Internet domain names , Computer networks -- Security measures , Computer security , Computer network protocols , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97531 , vital:31447
- Description: The Domain Name System (DNS) protocol is a fundamental part of Internet activities that can be abused by cybercriminals to conduct malicious activities. Previous research has shown that cybercriminals use different methods, including the DNS protocol, to distribute malicious content, remain hidden and avoid detection from various technologies that are put in place to detect anomalies. This allows botnets and certain malware families to establish covert communication channels that can be used to send or receive data and also distribute malicious payloads using the DNS queries and responses. Cybercriminals use the DNS to breach highly protected networks, distribute malicious content, and exfiltrate sensitive information without being detected by security controls put in place by embedding certain strings in DNS packets. This research undertaking broadens this research field and fills in the existing research gap by extending the analysis of DNS being used as a payload distribution channel to detection of domains that are used to distribute different malicious payloads. This research undertaking analysed the use of the DNS in detecting domains and channels that are used for distributing malicious payloads. Passive DNS data which replicate DNS queries on name servers to detect anomalies in DNS queries was evaluated and analysed in order to detect malicious payloads. The research characterises the malicious payload distribution channels by analysing passive DNS traffic and modelling the DNS query and response patterns. The research found that it is possible to detect malicious payload distribution channels through the analysis of DNS TXT resource records.
- Full Text:
- Date Issued: 2019
- Authors: Dube, Ishmael
- Date: 2019
- Subjects: Internet domain names , Computer networks -- Security measures , Computer security , Computer network protocols , Data protection
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97531 , vital:31447
- Description: The Domain Name System (DNS) protocol is a fundamental part of Internet activities that can be abused by cybercriminals to conduct malicious activities. Previous research has shown that cybercriminals use different methods, including the DNS protocol, to distribute malicious content, remain hidden and avoid detection from various technologies that are put in place to detect anomalies. This allows botnets and certain malware families to establish covert communication channels that can be used to send or receive data and also distribute malicious payloads using the DNS queries and responses. Cybercriminals use the DNS to breach highly protected networks, distribute malicious content, and exfiltrate sensitive information without being detected by security controls put in place by embedding certain strings in DNS packets. This research undertaking broadens this research field and fills in the existing research gap by extending the analysis of DNS being used as a payload distribution channel to detection of domains that are used to distribute different malicious payloads. This research undertaking analysed the use of the DNS in detecting domains and channels that are used for distributing malicious payloads. Passive DNS data which replicate DNS queries on name servers to detect anomalies in DNS queries was evaluated and analysed in order to detect malicious payloads. The research characterises the malicious payload distribution channels by analysing passive DNS traffic and modelling the DNS query and response patterns. The research found that it is possible to detect malicious payload distribution channels through the analysis of DNS TXT resource records.
- Full Text:
- Date Issued: 2019
Mesoscale alongshore and cross-shore transport and settlement of invertebrate larvae on the south east coast of South Africa
- Authors: Dyantyi, Siphelele Buntu
- Date: 2019
- Subjects: Marine invertebrates -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Benthic animals -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mexilhao mussel -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mytilus galloprovincialis -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Oysters -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97007 , vital:31386
- Description: Pelagic larval stages of most marine benthic species are important in maintaining coastal populations of adults. Several physio-chemical factors such as currents, winds, larval behaviour and time have an influence on the dispersal and transport of larvae to the adult habitat but their role is however still poorly understood. The aim of this study was to investigate the alongshore and cross-shore transport and temporal delivery of invertebrate larvae at four sites (Kenton on Sea, Cannon Rocks, Schoenmakerskop and Cape St Francis) along the south east coast of Eastern Cape, South Africa. Larval distribution of several taxa was determined during two sampling periods, by collecting water samples at nearshore line transects (3 distances: 900m, 1500m and 2400m – perpendicular to the shore) and at three depths (surface, thermocline/middle, bottom), which ranged from 15m (inshore) to 50m (offshore). Physical properties (current speed and direction, dissolved oxygen, fluorescence, turbidity, temperature, salinity, pH, pressure, density and conductivity) were measured and coupled in order to further understand larval distribution. The larvae were analysed as both total abundance and separately as the abundances of a variety of taxa which were: Perna perna, Mytilus galloprovincialis, oysters, early and late nauplii and cyprids. Larval settlement and recruitment on the rocky shores were measured by monthly deployment and collection of 20 (10 each for barnacles and mussels) artificial collectors at each site, which were preserved in ethanol or frozen for further processing. Multiple Permutational Multivariate Analysis of Variance (PERMANOVA) analyses were used to test the effects of site, depth and distance from the shore for the nearshore larvae (taxa analysed separately). In addition, a distance based linear model (distLM) was performed to analyse the relationship between the total larval abundance and the above mentioned physical variables. Multiple two-way analyses of variance (ANOVA) were performed to test the effects of months and sites on the settlement and recruitment of the larvae (P. perna, M. galloprovincialis, other bivalves, cyprids and juvenile barnacles) arriving on the shore. For the nearshore larval distribution, results from the PERMANOVAs revealed that most taxa showed a significant site and depth interactions with the exception of ‘early nauplii’ taxon. Also nearly all taxa were found within the thermocline, besides ‘oyster’ and ‘cyprids’ which were located at thermocline or bottom. Larvae were also located at variable distances from the shore, with most occurring at the offshore stations. Furthermore, there was a geographical separation of larval abundance according to sites, with most larvae located at Cannon Rocks and Kenton on Sea and least at Schoenmakerskop and Cape St Francis. For the settlement and recruitment, most taxa showed a seasonal trend, with the highest abundance of settlers and recruits expectedly appearing during the summer months of the sampling period. Additionally there was a site effect for most taxa (P. perna, M. galloprovincialis, other bivalves and juvenile barnacles), where settlers and recruits were mostly found at Cannon Rocks. Significant differences in abundance of settlers and recruits amongst the four sites indicate spatial and temporal variability for the targeted 180km stretch of coast. Overall for this study, taxon and ontogenetic stage of larvae were important in the distribution and abundance of larvae. Throughout the time frame of nearshore and intertidal sampling, Cannon Rocks consistently resulted as a ‘hot spot’ for larval abundance, settlement and recruitment, while a broad west to east separation was also observed. These results hence highlight that within this stretch of c.180km coast, time, taxon, ontogeny and post-settlement factors influence early dynamics of benthic populations.
- Full Text:
- Date Issued: 2019
- Authors: Dyantyi, Siphelele Buntu
- Date: 2019
- Subjects: Marine invertebrates -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Benthic animals -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mexilhao mussel -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Mytilus galloprovincialis -- Larvae -- Dispersal -- South Africa -- Eastern Cape , Oysters -- Larvae -- Dispersal -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/97007 , vital:31386
- Description: Pelagic larval stages of most marine benthic species are important in maintaining coastal populations of adults. Several physio-chemical factors such as currents, winds, larval behaviour and time have an influence on the dispersal and transport of larvae to the adult habitat but their role is however still poorly understood. The aim of this study was to investigate the alongshore and cross-shore transport and temporal delivery of invertebrate larvae at four sites (Kenton on Sea, Cannon Rocks, Schoenmakerskop and Cape St Francis) along the south east coast of Eastern Cape, South Africa. Larval distribution of several taxa was determined during two sampling periods, by collecting water samples at nearshore line transects (3 distances: 900m, 1500m and 2400m – perpendicular to the shore) and at three depths (surface, thermocline/middle, bottom), which ranged from 15m (inshore) to 50m (offshore). Physical properties (current speed and direction, dissolved oxygen, fluorescence, turbidity, temperature, salinity, pH, pressure, density and conductivity) were measured and coupled in order to further understand larval distribution. The larvae were analysed as both total abundance and separately as the abundances of a variety of taxa which were: Perna perna, Mytilus galloprovincialis, oysters, early and late nauplii and cyprids. Larval settlement and recruitment on the rocky shores were measured by monthly deployment and collection of 20 (10 each for barnacles and mussels) artificial collectors at each site, which were preserved in ethanol or frozen for further processing. Multiple Permutational Multivariate Analysis of Variance (PERMANOVA) analyses were used to test the effects of site, depth and distance from the shore for the nearshore larvae (taxa analysed separately). In addition, a distance based linear model (distLM) was performed to analyse the relationship between the total larval abundance and the above mentioned physical variables. Multiple two-way analyses of variance (ANOVA) were performed to test the effects of months and sites on the settlement and recruitment of the larvae (P. perna, M. galloprovincialis, other bivalves, cyprids and juvenile barnacles) arriving on the shore. For the nearshore larval distribution, results from the PERMANOVAs revealed that most taxa showed a significant site and depth interactions with the exception of ‘early nauplii’ taxon. Also nearly all taxa were found within the thermocline, besides ‘oyster’ and ‘cyprids’ which were located at thermocline or bottom. Larvae were also located at variable distances from the shore, with most occurring at the offshore stations. Furthermore, there was a geographical separation of larval abundance according to sites, with most larvae located at Cannon Rocks and Kenton on Sea and least at Schoenmakerskop and Cape St Francis. For the settlement and recruitment, most taxa showed a seasonal trend, with the highest abundance of settlers and recruits expectedly appearing during the summer months of the sampling period. Additionally there was a site effect for most taxa (P. perna, M. galloprovincialis, other bivalves and juvenile barnacles), where settlers and recruits were mostly found at Cannon Rocks. Significant differences in abundance of settlers and recruits amongst the four sites indicate spatial and temporal variability for the targeted 180km stretch of coast. Overall for this study, taxon and ontogenetic stage of larvae were important in the distribution and abundance of larvae. Throughout the time frame of nearshore and intertidal sampling, Cannon Rocks consistently resulted as a ‘hot spot’ for larval abundance, settlement and recruitment, while a broad west to east separation was also observed. These results hence highlight that within this stretch of c.180km coast, time, taxon, ontogeny and post-settlement factors influence early dynamics of benthic populations.
- Full Text:
- Date Issued: 2019
A Statistical assessment of available solar resource across multiple sites in South Africa
- Authors: Eastwood, Kirstie
- Date: 2019
- Subjects: Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39907 , vital:35505
- Description: Around the globe, fossil fuels remain the primary source of energy at around 78% of the world’s total energy consumption. However, the associated carbon emissions, environmental impact, the depletion of fossil fuels and price and cost volatility are factors influencing the growing popularity of research into renewable energy. Solar power is acknowledged as the fastest-growing renewable energy, but the uncertainty surrounding the long-term projections of solar irradiance available for energy conversion is a hindrance when discussing the financial risk with potential investors. This study investigates the quality of freely available solar resource data in South Africa as well as proposes techniques for potential solar farm site comparisons. Tolerance intervals derived within a Bayesian framework provide information on the future available solar resource across multiple sites. These techniques capture the inherent variability in the available solar resource which equips investors with statistical methods that lead to the better understanding of the solar resource and thus aids in better decision-making.
- Full Text:
- Date Issued: 2019
- Authors: Eastwood, Kirstie
- Date: 2019
- Subjects: Mathematical statistics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39907 , vital:35505
- Description: Around the globe, fossil fuels remain the primary source of energy at around 78% of the world’s total energy consumption. However, the associated carbon emissions, environmental impact, the depletion of fossil fuels and price and cost volatility are factors influencing the growing popularity of research into renewable energy. Solar power is acknowledged as the fastest-growing renewable energy, but the uncertainty surrounding the long-term projections of solar irradiance available for energy conversion is a hindrance when discussing the financial risk with potential investors. This study investigates the quality of freely available solar resource data in South Africa as well as proposes techniques for potential solar farm site comparisons. Tolerance intervals derived within a Bayesian framework provide information on the future available solar resource across multiple sites. These techniques capture the inherent variability in the available solar resource which equips investors with statistical methods that lead to the better understanding of the solar resource and thus aids in better decision-making.
- Full Text:
- Date Issued: 2019
Micro-structures, mineralogy, and chemistry of peritidal tufa stromatolites along the Eastern Cape coast
- Edwards, Mark Joseph Kalahari, Rishworth, Gavin M
- Authors: Edwards, Mark Joseph Kalahari , Rishworth, Gavin M
- Date: 2019
- Subjects: Mineralogy -- Analysis -- South Africa , Environmental forensics Environmental chemistry Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39896 , vital:35503
- Description: Peritidal tufa microbialites occurring along the coast near Port Elizabeth, South Africa have been investigated from multiple disciplines and are found to be similar to supratidal tufa deposits in South West Australia. Studies have been conducted on the biological factors, geomorphology, ecosystems, and associated water chemistry. However, to date no mineralogical, micro-fabric, or geochemical analyses have been reported on these tufa deposits. This work, carried out at a previously well-studied area, provides the first study of this kind on the tufa. Chapter 1 is a mineralogical and micro-fabric analysis of the tufa deposits near Port Elizabeth for the purpose of classification and contextualisation. Chapter 2 provides the first geochemical study of these peritidal microbialites. X-Ray diffraction (XRD) investigations reveal dominance of low-Mg calcite in the mineral make-up of the tufa. A micro-structure analysis via thin section exposes a number of fabrics, suggesting various micro-facies: phytoherm boundstone (layered), phytoherm framestone (non-layered), lithoclast, and minor metazoan tufa. Scanning electron microscopy (SEM) images show micro- to nano- scale variation in calcite grains and epitaxial forms of needlefibre calcite (NFC). The elemental composition of the tufa deposits were examined by X-ray fluorescence (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), and Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). XRF and LA-ICP-MS were used to analyse the bulk rock chemistry while SEM/EDS was used to scrutinize specific areas within the tufa. These observations suggest the deposits are better classified as tufa microbialites (rather than exclusively “stromatolites”) and outline similarities and disparities to the micro-fabrics of supratidal tufa deposits in South West Australia, and Cape Morgan, South Africa. Here the Port Elizabeth tufa is shown to be similar, in terms of the dominant elements (O, Ca and to a lesser extent, Mg and Sr), to the Australian deposits despite subtle dissimilarities in water chemistry. Increasing trends toward more marine tufa for many elements are also shown here and can be explained by the interaction with increased amounts of sedimentary products and/or interactions with more saline water that contains a higher TDS (Total Dissolved Salts). This is also the first study to report needle-fibre calcite formation in stromatolites and the first to geochemically analyse modern peritidal microbialites.
- Full Text:
- Date Issued: 2019
- Authors: Edwards, Mark Joseph Kalahari , Rishworth, Gavin M
- Date: 2019
- Subjects: Mineralogy -- Analysis -- South Africa , Environmental forensics Environmental chemistry Stromatolites
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39896 , vital:35503
- Description: Peritidal tufa microbialites occurring along the coast near Port Elizabeth, South Africa have been investigated from multiple disciplines and are found to be similar to supratidal tufa deposits in South West Australia. Studies have been conducted on the biological factors, geomorphology, ecosystems, and associated water chemistry. However, to date no mineralogical, micro-fabric, or geochemical analyses have been reported on these tufa deposits. This work, carried out at a previously well-studied area, provides the first study of this kind on the tufa. Chapter 1 is a mineralogical and micro-fabric analysis of the tufa deposits near Port Elizabeth for the purpose of classification and contextualisation. Chapter 2 provides the first geochemical study of these peritidal microbialites. X-Ray diffraction (XRD) investigations reveal dominance of low-Mg calcite in the mineral make-up of the tufa. A micro-structure analysis via thin section exposes a number of fabrics, suggesting various micro-facies: phytoherm boundstone (layered), phytoherm framestone (non-layered), lithoclast, and minor metazoan tufa. Scanning electron microscopy (SEM) images show micro- to nano- scale variation in calcite grains and epitaxial forms of needlefibre calcite (NFC). The elemental composition of the tufa deposits were examined by X-ray fluorescence (XRF), Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), and Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDS). XRF and LA-ICP-MS were used to analyse the bulk rock chemistry while SEM/EDS was used to scrutinize specific areas within the tufa. These observations suggest the deposits are better classified as tufa microbialites (rather than exclusively “stromatolites”) and outline similarities and disparities to the micro-fabrics of supratidal tufa deposits in South West Australia, and Cape Morgan, South Africa. Here the Port Elizabeth tufa is shown to be similar, in terms of the dominant elements (O, Ca and to a lesser extent, Mg and Sr), to the Australian deposits despite subtle dissimilarities in water chemistry. Increasing trends toward more marine tufa for many elements are also shown here and can be explained by the interaction with increased amounts of sedimentary products and/or interactions with more saline water that contains a higher TDS (Total Dissolved Salts). This is also the first study to report needle-fibre calcite formation in stromatolites and the first to geochemically analyse modern peritidal microbialites.
- Full Text:
- Date Issued: 2019
The origin of bedrock depression wetlands in the southern Cape of South Africa: a changing perspective
- Authors: Ellery, Steven
- Date: 2019
- Subjects: Wetlands -- South Africa -- Eastern Cape , Geomorphology -- South Africa -- Eastern Cape , Physical geography -- South Africa -- Eastern Cape , Erosion -- South Africa -- Eastern Cape , Evolutionary paleoecology -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67833 , vital:29152
- Description: The predominant theory of the origin of depression wetlands in southern Africa was developed by Goudie and Thomas (1985) and focuses primarily on mechanisms relating to deflation and erosion as the main drivers of wetland formation. This theory is based on wind driven deflation of animal watering areas where heavy grazing and trampling of vegetation promotes removal of sediment over short periods of time by wind, to create local depressions and impoundment of water. However, this theory applies in arid and semi-arid areas where grazing can reduce vegetation sufficiently to lead to deflation but does not fully explain the origins of depression wetlands that have formed in moist climates or on ancient erosion surfaces such as the African Erosion Surface (AES). This study investigates the origin of a depression wetland that has formed on sandstone bedrock through weathering and dissolution on the AES in South Africa. Wetlands like this act as groundwater recharge zones such that water flows away from the centre of the depression, taking with it any dissolved solutes derived from weathering of the bed of the depression. Fluctuations between wet and dry periods create both highly reducing conditions (during wet phases) and highly oxidising conditions (during dry phases) beneath the margins of these depression wetlands. Some of the main constituents of the sandstone in this wetland are iron(III) oxides, which are highly sensitive to redox conditions and have therefore been transported to and trapped in the margins of the depression. The redistribution of iron(III) oxides from the centre towards the margins of the depression has caused a net volume loss in the centre of the depression, causing sagging, and a net volume gain at the margins of the depression associated with swelling. This process occurs over periods upwards of a million years and explains the presence of depression wetlands in moist climates.
- Full Text:
- Date Issued: 2019
- Authors: Ellery, Steven
- Date: 2019
- Subjects: Wetlands -- South Africa -- Eastern Cape , Geomorphology -- South Africa -- Eastern Cape , Physical geography -- South Africa -- Eastern Cape , Erosion -- South Africa -- Eastern Cape , Evolutionary paleoecology -- South Africa -- Eastern Cape
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/67833 , vital:29152
- Description: The predominant theory of the origin of depression wetlands in southern Africa was developed by Goudie and Thomas (1985) and focuses primarily on mechanisms relating to deflation and erosion as the main drivers of wetland formation. This theory is based on wind driven deflation of animal watering areas where heavy grazing and trampling of vegetation promotes removal of sediment over short periods of time by wind, to create local depressions and impoundment of water. However, this theory applies in arid and semi-arid areas where grazing can reduce vegetation sufficiently to lead to deflation but does not fully explain the origins of depression wetlands that have formed in moist climates or on ancient erosion surfaces such as the African Erosion Surface (AES). This study investigates the origin of a depression wetland that has formed on sandstone bedrock through weathering and dissolution on the AES in South Africa. Wetlands like this act as groundwater recharge zones such that water flows away from the centre of the depression, taking with it any dissolved solutes derived from weathering of the bed of the depression. Fluctuations between wet and dry periods create both highly reducing conditions (during wet phases) and highly oxidising conditions (during dry phases) beneath the margins of these depression wetlands. Some of the main constituents of the sandstone in this wetland are iron(III) oxides, which are highly sensitive to redox conditions and have therefore been transported to and trapped in the margins of the depression. The redistribution of iron(III) oxides from the centre towards the margins of the depression has caused a net volume loss in the centre of the depression, causing sagging, and a net volume gain at the margins of the depression associated with swelling. This process occurs over periods upwards of a million years and explains the presence of depression wetlands in moist climates.
- Full Text:
- Date Issued: 2019
Carbon and nutrient storage of the Swartkops Estuary salt marsh and seagrass habitats
- Authors: Els, Jessica
- Date: 2019
- Subjects: Estuarine ecology -- South Africa -- Swartkops River Estuary , Salt marsh ecology -- South Africa -- Swartkops River Estuary Seagrasses -- Ecology Seagrasses -- Conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42196 , vital:36634
- Description: Coastal wetlands play an important role in filtering nutrient contaminants from water bodies and are also effective carbon sinks. These systems are known as blue carbon ecosystems. Blue carbon is defined as the carbon stored and sequestered by coastal vegetated habitats such as seagrasses, salt marsh and mangroves. These habitats are being lost on a global scale due to climate change and other anthropogenic pressures. Quantifying ecosystem services provided by these habitats may lead to better conservation and restoration strategies. Research on this topic has escalated over the past decade but there are no published studies in South Africa. The aim of this study was to quantify the carbon, nitrogen, and phosphorus stocks in the above and below ground tissues of Zostera capensis, Spartina maritima, and Salicornia tegetaria — a seagrass, salt marsh grass, and salt marsh succulent. This was done in both summer and winter to understand the variability of carbon and nutrient storage. The organic carbon stock of the sediment beneath these three species was also quantified. Results showed that S. maritima, S. tegetaria, and Z. capensis stored 16 ± 2.9 Mg C. ha-1, 4.3 ± 0.7 Mg C. ha-1, and 2.1 ± 0.5 Mg C. ha-1 in their respective biomass, and 247 ± 48 Mg C. ha-1, 212 ± 44 Mg C. ha-1, and 224 ± 38 Mg C. ha-1 respectively in the sediment beneath these habitats. This was determined by elemental analysis and the loss on ignition method (LOI). The sediment made up the dominant carbon pool in the estuary and there was very little seasonal variation, however spatial variation was evident. The sediment carbon stocks were similar to the global mean for salt marsh (255 Mg C. ha-1) and greater than the global mean for seagrass (108 Mg C. ha-1). The Swartkops Estuary stored a total (biomass and sediment carbon combined) of 14 094 Mg C in the Z. capensis area of 62 ha, 25 286 Mg C in the S. maritima area of 96 ha, and 5 916 Mg C in the S. tegetaria, covering an area of 27 ha. This is significantly less than what has been found globally in estuaries, but this is largely due to the smaller area cover of these macrophytes. The amount of carbon stored per hectare is much larger in this South African system than in many international studies — possibly due to the high levels of pollution coming into the system. Nitrogen and phosphorus stocks in the plants fluctuated seasonally in relation to the nutrient input to the estuary, with the greatest stocks found in winter in Z. capensis, S. maritima, and S. tegetaria (0.42 ± 0.03 Mg N. ha-1, 1.6 ± 0.13 Mg N. ha-1, and 0.37 ± 0.02 Mg N. ha-1, respectively; and 0.4 ± 0.03 Mg P. ha-1, 1.2 ± 0.10 Mg P. ha-1 in Z. capensis and S. maritima respectively) because nutrient inputs to the system were highest in winter, however the P stocks in S. tegetaria were greatest in summer (0.35 ± 0.04 Mg P. ha-1). The reason for this difference is because of their ability to store phosphorus better than nitrogen and for longer periods of time due to luxury uptake. Salicornia tegetaria N and P stocks were also lower than the other two species, possibly due to its placement along the intertidal gradient, as it is not tidally inundated for as long as the other two species. The Z. capensis and S. maritima at Site 1 showed extremely high amounts of nitrogen in their tissues (105.3 ± 1.6 g kg-1 and 74.91 ± 4.1 g kg-1 respectively). This is due to the area being a depositional site as it was an old oyster farm and experiences little tidal flushing from the sea despite its proximity to the mouth. Nutrient ratios and N: biomass were determined as an indication of nutrient pollution. The N: biomass was low in both seasons in Z. capensis, S. maritima, and S. tegetaria (0.08, 0.02, 0.04 respectively) indicating consistant eutrophic conditions in the estuary. Plant biomass was a better indicator of nutrient pollution than epiphytes which were very low in the Swartkops Estuary and did not prove as a useful indicator of nutrient enrichment. These results can inform local management plans of the ecosystem service potential of these species and how they should be protected for future and current sustainable use as filters for nutrient pollution to keep the water quality in a better state. It also outlines the current state of blue carbon and nutrient stocks in an urban South African estuary.
- Full Text:
- Date Issued: 2019
- Authors: Els, Jessica
- Date: 2019
- Subjects: Estuarine ecology -- South Africa -- Swartkops River Estuary , Salt marsh ecology -- South Africa -- Swartkops River Estuary Seagrasses -- Ecology Seagrasses -- Conservation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42196 , vital:36634
- Description: Coastal wetlands play an important role in filtering nutrient contaminants from water bodies and are also effective carbon sinks. These systems are known as blue carbon ecosystems. Blue carbon is defined as the carbon stored and sequestered by coastal vegetated habitats such as seagrasses, salt marsh and mangroves. These habitats are being lost on a global scale due to climate change and other anthropogenic pressures. Quantifying ecosystem services provided by these habitats may lead to better conservation and restoration strategies. Research on this topic has escalated over the past decade but there are no published studies in South Africa. The aim of this study was to quantify the carbon, nitrogen, and phosphorus stocks in the above and below ground tissues of Zostera capensis, Spartina maritima, and Salicornia tegetaria — a seagrass, salt marsh grass, and salt marsh succulent. This was done in both summer and winter to understand the variability of carbon and nutrient storage. The organic carbon stock of the sediment beneath these three species was also quantified. Results showed that S. maritima, S. tegetaria, and Z. capensis stored 16 ± 2.9 Mg C. ha-1, 4.3 ± 0.7 Mg C. ha-1, and 2.1 ± 0.5 Mg C. ha-1 in their respective biomass, and 247 ± 48 Mg C. ha-1, 212 ± 44 Mg C. ha-1, and 224 ± 38 Mg C. ha-1 respectively in the sediment beneath these habitats. This was determined by elemental analysis and the loss on ignition method (LOI). The sediment made up the dominant carbon pool in the estuary and there was very little seasonal variation, however spatial variation was evident. The sediment carbon stocks were similar to the global mean for salt marsh (255 Mg C. ha-1) and greater than the global mean for seagrass (108 Mg C. ha-1). The Swartkops Estuary stored a total (biomass and sediment carbon combined) of 14 094 Mg C in the Z. capensis area of 62 ha, 25 286 Mg C in the S. maritima area of 96 ha, and 5 916 Mg C in the S. tegetaria, covering an area of 27 ha. This is significantly less than what has been found globally in estuaries, but this is largely due to the smaller area cover of these macrophytes. The amount of carbon stored per hectare is much larger in this South African system than in many international studies — possibly due to the high levels of pollution coming into the system. Nitrogen and phosphorus stocks in the plants fluctuated seasonally in relation to the nutrient input to the estuary, with the greatest stocks found in winter in Z. capensis, S. maritima, and S. tegetaria (0.42 ± 0.03 Mg N. ha-1, 1.6 ± 0.13 Mg N. ha-1, and 0.37 ± 0.02 Mg N. ha-1, respectively; and 0.4 ± 0.03 Mg P. ha-1, 1.2 ± 0.10 Mg P. ha-1 in Z. capensis and S. maritima respectively) because nutrient inputs to the system were highest in winter, however the P stocks in S. tegetaria were greatest in summer (0.35 ± 0.04 Mg P. ha-1). The reason for this difference is because of their ability to store phosphorus better than nitrogen and for longer periods of time due to luxury uptake. Salicornia tegetaria N and P stocks were also lower than the other two species, possibly due to its placement along the intertidal gradient, as it is not tidally inundated for as long as the other two species. The Z. capensis and S. maritima at Site 1 showed extremely high amounts of nitrogen in their tissues (105.3 ± 1.6 g kg-1 and 74.91 ± 4.1 g kg-1 respectively). This is due to the area being a depositional site as it was an old oyster farm and experiences little tidal flushing from the sea despite its proximity to the mouth. Nutrient ratios and N: biomass were determined as an indication of nutrient pollution. The N: biomass was low in both seasons in Z. capensis, S. maritima, and S. tegetaria (0.08, 0.02, 0.04 respectively) indicating consistant eutrophic conditions in the estuary. Plant biomass was a better indicator of nutrient pollution than epiphytes which were very low in the Swartkops Estuary and did not prove as a useful indicator of nutrient enrichment. These results can inform local management plans of the ecosystem service potential of these species and how they should be protected for future and current sustainable use as filters for nutrient pollution to keep the water quality in a better state. It also outlines the current state of blue carbon and nutrient stocks in an urban South African estuary.
- Full Text:
- Date Issued: 2019
Production potential of lucerne (Medicago sativa) over-sown into kikuyu (Pennisetum clandestinum) based pasture
- Fourie, Ilze, Du Preez, Derek
- Authors: Fourie, Ilze , Du Preez, Derek
- Date: 2019
- Subjects: Alfalfa -- South Africa , Field crops , Agriculture -- South Africa , Botany -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39918 , vital:35510
- Description: Dairy farming in the southern Cape region of South Africa is based on irrigated kikuyu (Pennisetum clandestinum) over-sown with different ryegrass species (Lolium spp.). Although this system can be highly productive, sustainable production of kikuyu is dependent on expensive nitrogen (N) fertiliser inputs and irrigation due to a high water requirement to maintain production. The introduction of lucerne (Medicago sativa) into pasture systems can lower the risk of high input cost and droughts. Lucerne has a high nutritive value, is able to fix atmospheric N, has high water-use efficiency and is adapted to local climatic conditions. The aim of this study was to determine the DM production potential of lucerne cultivars from various dormancy groups when over-sown into an existing kikuyu pasture base on soils that are suitable for lucerne cultivation, without any N fertiliser application. The study was carried out on the Outeniqua Research Farm near George, Western Cape. Two cultivars were selected from each of the four lucerne dormancy groups and sown into an existing kikuyu pasture based on soils suited for lucerne cultivation. Three establishment methods namely glyphosate/planter (Gly/Plant), glyphosate/rotavator (Gly/Rot) and rotavator (Rot) were used. The statistical design was a randomised block design with three replicates. The botanical composition (lucerne-, kikuyu-, clover-, grass- and weed content), growth rate (kg DM ha-1 day-1), total DM production (kg DM ha-1) and DM content of the treatments were determined before every grazing. The nutritional value (CP-, ME-, NDF-, Ca-, and P content) of the treatments was determined seasonally. Establishing lucerne into kikuyu with the glyphosate/rotavator (Gly/Rot) and rotavator (Rot) method yielded an overall higher percentage of established seedlings compared to the glyphosate/planter (Gly/Plant) establishment method. The establishment method used affected the botanical composition. Lucerne established with the Gly/Plant or Gly/Rot establishment method into kikuyu had a higher lucerne content than the Rot establishment method. The seasonal growth rates of the kikuyu-lucerne pasture varied between 14.8 kg DM ha-1 day-1 during winter to 84.1 kg DM ha-1 day-1 during summer. The establishment method and cultivar influenced the seasonal growth rate and total seasonal production. The cultivar WL 711 established with Gly/Plant establishment method had the highest or did not differ significantly from the highest lucerne content, seasonal growth rate and total seasonal production within seasons. The total annual production ranged between 13805 to 19975 kg DM ha-1 year-1 with the Gly/Plant establishment method yielding the highest or did not differ significantly from the highest annual production when compared with the other establishment methods. The botanical composition affects the nutritive value of the kikuyu-lucerne pasture. The ME content of kikuyu and kikuyu-lucerne pasture did not meet the daily ME requirements for a lactating dairy cow to maintain milk production throughout both years. The CP and Ca content decreased as the lucerne content decreased and the kikuyu content increased. The P content of kikuyu-lucerne and kikuyu pasture met the daily P requirement of a lactating dairy cow. The dormancy groups D2 and D5 were the only dormancy groups that could meet the recommended Ca:P ratio for dairy cows over all the seasons. Lucerne can be successfully established into kikuyu with the use of herbicide as part of the establishment method. Kikuyu-lucerne pasture has a higher DM production with an improved quality compared to kikuyu pasture. By establishing lucerne into kikuyu the cost of N fertiliser application could be lowered as no N needs to be applied.
- Full Text:
- Date Issued: 2019
- Authors: Fourie, Ilze , Du Preez, Derek
- Date: 2019
- Subjects: Alfalfa -- South Africa , Field crops , Agriculture -- South Africa , Botany -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39918 , vital:35510
- Description: Dairy farming in the southern Cape region of South Africa is based on irrigated kikuyu (Pennisetum clandestinum) over-sown with different ryegrass species (Lolium spp.). Although this system can be highly productive, sustainable production of kikuyu is dependent on expensive nitrogen (N) fertiliser inputs and irrigation due to a high water requirement to maintain production. The introduction of lucerne (Medicago sativa) into pasture systems can lower the risk of high input cost and droughts. Lucerne has a high nutritive value, is able to fix atmospheric N, has high water-use efficiency and is adapted to local climatic conditions. The aim of this study was to determine the DM production potential of lucerne cultivars from various dormancy groups when over-sown into an existing kikuyu pasture base on soils that are suitable for lucerne cultivation, without any N fertiliser application. The study was carried out on the Outeniqua Research Farm near George, Western Cape. Two cultivars were selected from each of the four lucerne dormancy groups and sown into an existing kikuyu pasture based on soils suited for lucerne cultivation. Three establishment methods namely glyphosate/planter (Gly/Plant), glyphosate/rotavator (Gly/Rot) and rotavator (Rot) were used. The statistical design was a randomised block design with three replicates. The botanical composition (lucerne-, kikuyu-, clover-, grass- and weed content), growth rate (kg DM ha-1 day-1), total DM production (kg DM ha-1) and DM content of the treatments were determined before every grazing. The nutritional value (CP-, ME-, NDF-, Ca-, and P content) of the treatments was determined seasonally. Establishing lucerne into kikuyu with the glyphosate/rotavator (Gly/Rot) and rotavator (Rot) method yielded an overall higher percentage of established seedlings compared to the glyphosate/planter (Gly/Plant) establishment method. The establishment method used affected the botanical composition. Lucerne established with the Gly/Plant or Gly/Rot establishment method into kikuyu had a higher lucerne content than the Rot establishment method. The seasonal growth rates of the kikuyu-lucerne pasture varied between 14.8 kg DM ha-1 day-1 during winter to 84.1 kg DM ha-1 day-1 during summer. The establishment method and cultivar influenced the seasonal growth rate and total seasonal production. The cultivar WL 711 established with Gly/Plant establishment method had the highest or did not differ significantly from the highest lucerne content, seasonal growth rate and total seasonal production within seasons. The total annual production ranged between 13805 to 19975 kg DM ha-1 year-1 with the Gly/Plant establishment method yielding the highest or did not differ significantly from the highest annual production when compared with the other establishment methods. The botanical composition affects the nutritive value of the kikuyu-lucerne pasture. The ME content of kikuyu and kikuyu-lucerne pasture did not meet the daily ME requirements for a lactating dairy cow to maintain milk production throughout both years. The CP and Ca content decreased as the lucerne content decreased and the kikuyu content increased. The P content of kikuyu-lucerne and kikuyu pasture met the daily P requirement of a lactating dairy cow. The dormancy groups D2 and D5 were the only dormancy groups that could meet the recommended Ca:P ratio for dairy cows over all the seasons. Lucerne can be successfully established into kikuyu with the use of herbicide as part of the establishment method. Kikuyu-lucerne pasture has a higher DM production with an improved quality compared to kikuyu pasture. By establishing lucerne into kikuyu the cost of N fertiliser application could be lowered as no N needs to be applied.
- Full Text:
- Date Issued: 2019
Triggering biodegradation of low-density polyethylene films containing biobased additives for ecological applications
- Authors: Gada, Abongile
- Date: 2019
- Subjects: Refuse and refuse disposal , Plastics industry and trade -- Waste disposal Polyethylene Polyurethanes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39796 , vital:35460
- Description: The aims of the present study are focused on the investigation of low-density polyethylene (LDPE) films that contain biobased pro-oxidizing additives (CSIR1% and CSIR3% (w/w)) for environmental degradation in different abiotic and biotic conditions in comparison to non-biodegradable commercially available Pick n Pay (PnP) PE grocery bags. In this project, a biobased pro-oxidant additive master batch was prepared in a heat kneader mixer. A mixture of biobased radical reaction initiators and natural polymers were melt processed as a master batch. The biobased pro-oxidant additive master batch CSIR1% and CSIR3% and LDPE components were melt-extruded to form biobased pro-oxidant additive LDPE pellets using a twin screw melt extruder. The pelletized biobased pro-oxidant additive LDPE was blown into a 25 -27 μm thick film using a melt blower machine. The LDPE containing biobased pro-oxidant additive CSIR 1% and 3% test samples and the PnP polyethylene carrier bags were submitted to thermal oxidizing test conditions in a 70°C air ventilated oven and direct sunlight (photo oxidation) for a period of six months (180 days). The thermal and photo-oxidized LDPE film test samples were further subjected to biotic degradation tests in aqueous, soil and compost environments for varying periods of 180 days to 263 days in biodegradation evaluation studies. The oxidation degradation rates of the test samples were monitored and determined by evaluating carbonyl index (COi) using FT-IR spectroscopy; molecular weight determination and distribution of the test materials were analyzed by Gel Permeation Chromatography (GPC); compounds analysis was done by GC-MS; percentage crystallinity (Xc%) was quantified by DSC; thermal stability by TGA and morphological surfaces were examined by SEM analytical techniques. Biodegradation tests simulating marine salt water, burial in soil and compost conditioning methods were used to determine the “potential biodegradability” of the thermally and photo-oxidized test samples after the oxidation period. The oxidation extent and rate of LDPE films containing CSIR3% biobased additives was higher than that of LDPE films containing CSIR1% biobased additives. GPC molecular weight determination and distribution results showed a decrease for all the test samples exposed to oxidation. The molecular weight of LDPE films containing CSIR1% biobased additives decreased from 404K Mw to 111K Mw for sunlight oxidized samples and to 16KMw for the thermally oxidized LDPE samples after 200 days of oxidation exposure. Molecular weight of LDPE films containing CSIR3% biobased additives showed the most reduction from 293K Mw to 22K Mw for sunlight oxidized samples and to 2K Mw for thermally oxidized samples after 100 days of oxidation exposure. DSC analysis showed that crystallinity degree decreased after exposure to thermal and photo-oxidation. TGA results showed a reduction of initial degradation temperature by almost half compared to zero-days untreated CSIR3% samples, with higher degree temperatures observed in samples exposed to thermal oxidation than those exposed to photo-oxidation. GC-MS revealed peaks of carbonyls such as alcohols, aldehydes, ketones, carboxylic and anionic acids, and very short chain alkenes and alkanes. The SEM showed heterogeneous morphological modifications in surfaces of samples even though they were not severe. After 172 days the oxidized LDPE samples containing CSIR3% biobased additives, were investigated for potential biodegradation in aqueous, soil and composting environments. Thermally oxidized and photo-oxidized CSIR3% samples showed a mineralization degree of 10.4% and 10.7% respectively, when oxidized in 181 days aqueous biodegradation, 20% and 7.7% respectively, when oxidized in 233 days of soil burial, and 52.6% and 62% respectively, oxidized in 263 days of compost. The obtained results confirmed the abiotic oxidation step as the initiation step for PE degradation, succeeded by assimilation, by action of microorganisms (ultimate biodegradation), of lower weight molecular compounds of oxidized LDPE samples in aqueous medium, soil and composting conditions to final end products of CO2, H2O and new microbial cell biomass.
- Full Text:
- Date Issued: 2019
- Authors: Gada, Abongile
- Date: 2019
- Subjects: Refuse and refuse disposal , Plastics industry and trade -- Waste disposal Polyethylene Polyurethanes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39796 , vital:35460
- Description: The aims of the present study are focused on the investigation of low-density polyethylene (LDPE) films that contain biobased pro-oxidizing additives (CSIR1% and CSIR3% (w/w)) for environmental degradation in different abiotic and biotic conditions in comparison to non-biodegradable commercially available Pick n Pay (PnP) PE grocery bags. In this project, a biobased pro-oxidant additive master batch was prepared in a heat kneader mixer. A mixture of biobased radical reaction initiators and natural polymers were melt processed as a master batch. The biobased pro-oxidant additive master batch CSIR1% and CSIR3% and LDPE components were melt-extruded to form biobased pro-oxidant additive LDPE pellets using a twin screw melt extruder. The pelletized biobased pro-oxidant additive LDPE was blown into a 25 -27 μm thick film using a melt blower machine. The LDPE containing biobased pro-oxidant additive CSIR 1% and 3% test samples and the PnP polyethylene carrier bags were submitted to thermal oxidizing test conditions in a 70°C air ventilated oven and direct sunlight (photo oxidation) for a period of six months (180 days). The thermal and photo-oxidized LDPE film test samples were further subjected to biotic degradation tests in aqueous, soil and compost environments for varying periods of 180 days to 263 days in biodegradation evaluation studies. The oxidation degradation rates of the test samples were monitored and determined by evaluating carbonyl index (COi) using FT-IR spectroscopy; molecular weight determination and distribution of the test materials were analyzed by Gel Permeation Chromatography (GPC); compounds analysis was done by GC-MS; percentage crystallinity (Xc%) was quantified by DSC; thermal stability by TGA and morphological surfaces were examined by SEM analytical techniques. Biodegradation tests simulating marine salt water, burial in soil and compost conditioning methods were used to determine the “potential biodegradability” of the thermally and photo-oxidized test samples after the oxidation period. The oxidation extent and rate of LDPE films containing CSIR3% biobased additives was higher than that of LDPE films containing CSIR1% biobased additives. GPC molecular weight determination and distribution results showed a decrease for all the test samples exposed to oxidation. The molecular weight of LDPE films containing CSIR1% biobased additives decreased from 404K Mw to 111K Mw for sunlight oxidized samples and to 16KMw for the thermally oxidized LDPE samples after 200 days of oxidation exposure. Molecular weight of LDPE films containing CSIR3% biobased additives showed the most reduction from 293K Mw to 22K Mw for sunlight oxidized samples and to 2K Mw for thermally oxidized samples after 100 days of oxidation exposure. DSC analysis showed that crystallinity degree decreased after exposure to thermal and photo-oxidation. TGA results showed a reduction of initial degradation temperature by almost half compared to zero-days untreated CSIR3% samples, with higher degree temperatures observed in samples exposed to thermal oxidation than those exposed to photo-oxidation. GC-MS revealed peaks of carbonyls such as alcohols, aldehydes, ketones, carboxylic and anionic acids, and very short chain alkenes and alkanes. The SEM showed heterogeneous morphological modifications in surfaces of samples even though they were not severe. After 172 days the oxidized LDPE samples containing CSIR3% biobased additives, were investigated for potential biodegradation in aqueous, soil and composting environments. Thermally oxidized and photo-oxidized CSIR3% samples showed a mineralization degree of 10.4% and 10.7% respectively, when oxidized in 181 days aqueous biodegradation, 20% and 7.7% respectively, when oxidized in 233 days of soil burial, and 52.6% and 62% respectively, oxidized in 263 days of compost. The obtained results confirmed the abiotic oxidation step as the initiation step for PE degradation, succeeded by assimilation, by action of microorganisms (ultimate biodegradation), of lower weight molecular compounds of oxidized LDPE samples in aqueous medium, soil and composting conditions to final end products of CO2, H2O and new microbial cell biomass.
- Full Text:
- Date Issued: 2019
The development of palladium nanoparticles for radiopharmaceutical application
- Authors: Gandidzanwa, Sendibitiyosi
- Date: 2019
- Subjects: Nanotechnology , Nanostructures Nanofluids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42163 , vital:36631
- Description: The dissertation describes an in-depth synthesis and optimisation of palladium(0) nanoparticles of three distinct size ranges, respective capping agents, and cellular uptake studies using a non-toxic concentration (10 μM), laying a foundation for the design of palladium-based folate receptor-targeted theranostic nanoradiopharmaceutical. In the preliminary selection to determine the optimal diamines for the study, ethylenediamine, hexamethylenediamine, 1,10-diaminodecane, 1,12-diaminododecane, 1,4- diaminobenzene, 4,4’-ethylenedianiline, 1,2-diphenyl-1,2-diaminoethane, and tetraaminophthalocyanine were employed. The characterisation of the nanoparticles obtained from the in situ reduction of palladium(II) salt at room temperature by either 1,2,3- trihydroxybenze (pyrogallol), citric acid, sodium metabisulphite, sodium borohydride, hydrazine hydrate, or formaldehyde was performed. Ethylenediamine and sodium borohydride were found to be the best diamine capping and reducing agent, respectively. Systematic investigations determined that the nanoparticle synthesis was dependent on various reaction parameters: such as reaction temperature, time, reductant reducing power, and capping agents. The parameters effects on the nanoparticle size, morphology, shape, stability, crystallinity, and surface charge were investigated. The optical properties, elemental composition, functional group, concentration and molecular weight for the synthesised nanoparticles or conjugates were determined. These properties were analysed using Ultraviolet–visible spectroscopy (UV-Vis), high resolution transmission electron microscopy (HRTEM) coupled with selective area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), zeta potential (ZP), dynamic light scattering (DLS), elemental analysis (EA), 1H and 13C-nuclear magnetic resonance (1H- and 13CNMR), Fourier-transform infrared spectroscopy (FTIR), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and liquid chromatography-mass spectroscopy (LC-MS). The in vitro cytotoxicity, cell uptake, and internalisation studies of palladium nanoparticles (10 μM) ranging in size and different types of capping agent were performed using three breast cancer cell lines: MDA-MB-468 , MCF-7 and MDA-MB-231 , and a non-tumorigenic MCF-10A breast cell line. The cell uptake and internalisation were investigated using ICP-OES and TEM. A high dependence between reduction rate and concentration of palladium precursor was observed for the room temperature synthesis of palladium nanoparticles, and the employed synthesis procedure will be applied to the hot palladium isotope (109Pd). A facile, green, aqueous synthesis route for palladium nanoparticles at room temperature was developed, and the synthesised nanoparticles indicated narrow size distributions. A concentration dependence between cytotoxicity and palladium nanoparticles was observed, with lower concentrations (10 μM) exhibiting minimal cytotoxicity relative to higher concentrations (100 μM). The cellular uptake of palladium nanoparticles was found to be concentration, folate-receptor, capping agent, and cell line proliferation-dependent. Well-defined, monodispersed, and negatively charged folate-ethylenediamine and folate-phthalocyanine capped palladium nanoparticles were taken up by cells, with higher nanoparticle internalisation in folate receptor positive tumorigenic cells relative to folate receptor negative non-tumorigenic cells. It can be concluded that palladium(0) nanoparticles can be synthesised from the reduction of palladium(II) by sodium borohydride at room temperature. The folate-conjugated palladium nanoparticles are non-cytotoxic at 10 μM and were successfully optimised and selectively delivered to folate receptor-positive breast cancer cells (MDA-MB-231 and MCF-7) relative to non-tumorigenic breast cells (MCF-10A) and folate receptor negative cancer cells (MDA-MB-468).
- Full Text:
- Date Issued: 2019
- Authors: Gandidzanwa, Sendibitiyosi
- Date: 2019
- Subjects: Nanotechnology , Nanostructures Nanofluids
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/42163 , vital:36631
- Description: The dissertation describes an in-depth synthesis and optimisation of palladium(0) nanoparticles of three distinct size ranges, respective capping agents, and cellular uptake studies using a non-toxic concentration (10 μM), laying a foundation for the design of palladium-based folate receptor-targeted theranostic nanoradiopharmaceutical. In the preliminary selection to determine the optimal diamines for the study, ethylenediamine, hexamethylenediamine, 1,10-diaminodecane, 1,12-diaminododecane, 1,4- diaminobenzene, 4,4’-ethylenedianiline, 1,2-diphenyl-1,2-diaminoethane, and tetraaminophthalocyanine were employed. The characterisation of the nanoparticles obtained from the in situ reduction of palladium(II) salt at room temperature by either 1,2,3- trihydroxybenze (pyrogallol), citric acid, sodium metabisulphite, sodium borohydride, hydrazine hydrate, or formaldehyde was performed. Ethylenediamine and sodium borohydride were found to be the best diamine capping and reducing agent, respectively. Systematic investigations determined that the nanoparticle synthesis was dependent on various reaction parameters: such as reaction temperature, time, reductant reducing power, and capping agents. The parameters effects on the nanoparticle size, morphology, shape, stability, crystallinity, and surface charge were investigated. The optical properties, elemental composition, functional group, concentration and molecular weight for the synthesised nanoparticles or conjugates were determined. These properties were analysed using Ultraviolet–visible spectroscopy (UV-Vis), high resolution transmission electron microscopy (HRTEM) coupled with selective area electron diffraction (SAED) and energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), zeta potential (ZP), dynamic light scattering (DLS), elemental analysis (EA), 1H and 13C-nuclear magnetic resonance (1H- and 13CNMR), Fourier-transform infrared spectroscopy (FTIR), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and liquid chromatography-mass spectroscopy (LC-MS). The in vitro cytotoxicity, cell uptake, and internalisation studies of palladium nanoparticles (10 μM) ranging in size and different types of capping agent were performed using three breast cancer cell lines: MDA-MB-468 , MCF-7 and MDA-MB-231 , and a non-tumorigenic MCF-10A breast cell line. The cell uptake and internalisation were investigated using ICP-OES and TEM. A high dependence between reduction rate and concentration of palladium precursor was observed for the room temperature synthesis of palladium nanoparticles, and the employed synthesis procedure will be applied to the hot palladium isotope (109Pd). A facile, green, aqueous synthesis route for palladium nanoparticles at room temperature was developed, and the synthesised nanoparticles indicated narrow size distributions. A concentration dependence between cytotoxicity and palladium nanoparticles was observed, with lower concentrations (10 μM) exhibiting minimal cytotoxicity relative to higher concentrations (100 μM). The cellular uptake of palladium nanoparticles was found to be concentration, folate-receptor, capping agent, and cell line proliferation-dependent. Well-defined, monodispersed, and negatively charged folate-ethylenediamine and folate-phthalocyanine capped palladium nanoparticles were taken up by cells, with higher nanoparticle internalisation in folate receptor positive tumorigenic cells relative to folate receptor negative non-tumorigenic cells. It can be concluded that palladium(0) nanoparticles can be synthesised from the reduction of palladium(II) by sodium borohydride at room temperature. The folate-conjugated palladium nanoparticles are non-cytotoxic at 10 μM and were successfully optimised and selectively delivered to folate receptor-positive breast cancer cells (MDA-MB-231 and MCF-7) relative to non-tumorigenic breast cells (MCF-10A) and folate receptor negative cancer cells (MDA-MB-468).
- Full Text:
- Date Issued: 2019
Isolation and characterization of extracts of Rosmarinus officinalis l. And comparative evaluation of its antimicrobial activity and selected types of antibiotics against some bacteria species
- Authors: Gbede,Remi
- Date: 2019
- Subjects: Rosmarinus Essences and essential oils Lamiaceae Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19142 , vital:39875
- Description: Rosmarinus officinalis L. is known extensively for its multifunctional purposes. The essential oil has been widely used in cosmeceuticals and several ethnopharmacological values. In vitro studies have demonstrated the antibacterial activity of essential oils (EOs) of Rosmarinus officinalis L. against Staphylococcus aureus ATCC 25923, Vibrio cholerae DSM 19283, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853 and Bacillus cereus. These different bacteria were screened against antibiotics such as Tetracycline, Ampicillin Sodium salt, Erythromycin and Amoxicillin, and some standards namely rosmarinic acid, carnosic acid and carnosol, and also against the methanol, acetone, chloroform and dichloromethane extracts of rosemary. The essential oils of Rosmarinus officinalis L. showed significant inhibitory properties compared to antibiotics with various degrees of growth inhibition. The standards exhibited some activities against the organisms. The GC/MS analysis of the essential oil revealed 34 compounds present with most components acting in synergy to bring about antibacterial activities. The antiplasmodial and cytotoxic activities of two leaf extracts of Rosmarinus officinalis (with hexane and dichloromethane as solvents) using standard procedure were studied. The findings justify the claims on the efficacy of plants for therapeutic uses for antifungal, antibacterial and anti-inflammatory properties. Antiplasmodial activity of Rosmarinus officinalis recorded IC50 values of 9.99 µg/ml and 9.76 µg/ml in hexane and dichloromethane respectively.
- Full Text:
- Date Issued: 2019
- Authors: Gbede,Remi
- Date: 2019
- Subjects: Rosmarinus Essences and essential oils Lamiaceae Medicinal plants
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19142 , vital:39875
- Description: Rosmarinus officinalis L. is known extensively for its multifunctional purposes. The essential oil has been widely used in cosmeceuticals and several ethnopharmacological values. In vitro studies have demonstrated the antibacterial activity of essential oils (EOs) of Rosmarinus officinalis L. against Staphylococcus aureus ATCC 25923, Vibrio cholerae DSM 19283, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853 and Bacillus cereus. These different bacteria were screened against antibiotics such as Tetracycline, Ampicillin Sodium salt, Erythromycin and Amoxicillin, and some standards namely rosmarinic acid, carnosic acid and carnosol, and also against the methanol, acetone, chloroform and dichloromethane extracts of rosemary. The essential oils of Rosmarinus officinalis L. showed significant inhibitory properties compared to antibiotics with various degrees of growth inhibition. The standards exhibited some activities against the organisms. The GC/MS analysis of the essential oil revealed 34 compounds present with most components acting in synergy to bring about antibacterial activities. The antiplasmodial and cytotoxic activities of two leaf extracts of Rosmarinus officinalis (with hexane and dichloromethane as solvents) using standard procedure were studied. The findings justify the claims on the efficacy of plants for therapeutic uses for antifungal, antibacterial and anti-inflammatory properties. Antiplasmodial activity of Rosmarinus officinalis recorded IC50 values of 9.99 µg/ml and 9.76 µg/ml in hexane and dichloromethane respectively.
- Full Text:
- Date Issued: 2019
Computational fluid dynamics design and performance testing of a cyclone heat exchanger used in a gasification plant
- Authors: George, Tomy
- Date: 2019
- Subjects: Computational fluid dynamics Renewable energy sources Biomass gasification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19087 , vital:39877
- Description: Renewable energy resources are considered to be the most promising source of energy in the coming centuries owing to its potential to get replenished by the nature itself. However, there are a number of challenges that are to be addressed prior to considering a particular resource as a reliable and effective one according to the energy demand fluctuations. Energy extracted from the biomass available in the nature has a lot of potential especially in the case of producing energy from syngas produced by the controlled burning of wood. This research deals with the minimisation of energy wastage in a gasification plant where syngas is produced from wood and transferred to an internal combustion engine to further generate electrical energy. The syngas produced from the wood is to be fed through a cyclone for purification before it can be fed into the IC engine, where the dust, carbon and other impurities are separated from the syngas by making use of the centrifugal force developed inside the cyclone. This syngas is further cooled and fed into the IC engine in its purest form as specified by the requirements of the engine. It is envisaged that if it is possible to recover the heat energy otherwise wasted in the cyclone and through the cooling circuit, it can be used for preheating the wood or for other minor heating purposes, and thereby the heat wastage can be minimised. Therefore, in this research, a series of numerical investigation conducted which involved the modelling of heat exchanger around a cyclone in order to extract heat from the surface of the cyclone. Two basic design of the Heat exchanger were considered in the study, a rectangular and a conical design. With a water flow rate of 2 l/min in conical design, the heat absorbed by the water was found to be 5.555 kJ/s and in rectangular design, the heat absorbed by the water was 4.872 kJ/s. An experimental analysis conducted to validate the simulation by a rectangular Heat exchanger shows the amount of heat absorbed by the water is 4.87 kJ/s. In a study with variable water flow rate through the jacket, it is observed that heat absorbed by the water in conical heat exchanger is more than heat absorbed by the water in rectangular jacket within the flow rate of 4 l/min. and the heat absorbed by the water in rectangular heat exchanger is higher than conical heat exchanger with water flow rate above 4 l/min.
- Full Text:
- Date Issued: 2019
- Authors: George, Tomy
- Date: 2019
- Subjects: Computational fluid dynamics Renewable energy sources Biomass gasification
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/19087 , vital:39877
- Description: Renewable energy resources are considered to be the most promising source of energy in the coming centuries owing to its potential to get replenished by the nature itself. However, there are a number of challenges that are to be addressed prior to considering a particular resource as a reliable and effective one according to the energy demand fluctuations. Energy extracted from the biomass available in the nature has a lot of potential especially in the case of producing energy from syngas produced by the controlled burning of wood. This research deals with the minimisation of energy wastage in a gasification plant where syngas is produced from wood and transferred to an internal combustion engine to further generate electrical energy. The syngas produced from the wood is to be fed through a cyclone for purification before it can be fed into the IC engine, where the dust, carbon and other impurities are separated from the syngas by making use of the centrifugal force developed inside the cyclone. This syngas is further cooled and fed into the IC engine in its purest form as specified by the requirements of the engine. It is envisaged that if it is possible to recover the heat energy otherwise wasted in the cyclone and through the cooling circuit, it can be used for preheating the wood or for other minor heating purposes, and thereby the heat wastage can be minimised. Therefore, in this research, a series of numerical investigation conducted which involved the modelling of heat exchanger around a cyclone in order to extract heat from the surface of the cyclone. Two basic design of the Heat exchanger were considered in the study, a rectangular and a conical design. With a water flow rate of 2 l/min in conical design, the heat absorbed by the water was found to be 5.555 kJ/s and in rectangular design, the heat absorbed by the water was 4.872 kJ/s. An experimental analysis conducted to validate the simulation by a rectangular Heat exchanger shows the amount of heat absorbed by the water is 4.87 kJ/s. In a study with variable water flow rate through the jacket, it is observed that heat absorbed by the water in conical heat exchanger is more than heat absorbed by the water in rectangular jacket within the flow rate of 4 l/min. and the heat absorbed by the water in rectangular heat exchanger is higher than conical heat exchanger with water flow rate above 4 l/min.
- Full Text:
- Date Issued: 2019
A deep learning approach to classifying tyres using sidewall images
- Authors: Gifford, Dean
- Date: 2019
- Subjects: Image processing -- Digital techniques , Image processing Computer science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39720 , vital:35351
- Description: End of Life Tyres (ELT's) pose a potential health and environmental risk when dumped in illegal stockpiles. For recycling to be considered feasible, a profitable business opportunity needs to be created. One method of making the recycling process of tyres more profitable is by understanding the compounds found within each tyre. This study aims at classifying these tyres in order to achieve this knowledge. A literature review was done to investigate neural networks, convolutional neural networks as well as existing deep learning architectures for image classification. A deep learning approach was applied in order to classify the logos of tyres as these approaches have proved their success in both image classification and more specifically logo classification. Although tyre classification has been implemented in the past, a deep learning approach has not been applied and the logo has not been the classifying element in any other studies. The main difference of this study compared to previous research surrounding deep learning and logo classification is the properties of the tyre logo. Logos on tyres are very similar in colour as they are purely formed in rubber and very seldom have any colour to them. Additionally, the embossed logos can contain variation among same branded tyres due to small inconsistencies in the moulds. The implementation of this deep learning solution saw multiple convolutional neural networks implemented. Some of these architectures were also implemented using transferred learning. The metrics obtained as outputs from training and testing the architectures were the accuracy, precision, recall, and F1-score. These metrics were compared in conjunction with the confusion matrix produced from testing. To ensure that variance was accounted for in the experiments, the k-fold cross-validation technique was adopted. The results of this study identified that one convolutional neural network model, MobileNet, was particularly well suited for the context of classifying logos on tyre sidewalls. The MobileNet architecture had the highest performance metrics for both training from scratch (96.7% accuracy) and transferred learning (98.8% accuracy). Three other models performed particularly well when trained from scratch, these were a modification of the LeNet architecture, ResNet50 and InceptionV3. The transferred learning results were also impressive with four out of the 5 models achieving an accuracy above 94%. Interestingly, the ResNet50 architecture failed to train when transferred learning was applied. Contrasting to this, the two models VGG16 and VGG19 failed to train when trained from scratch but performed equally as well as the other models when transferred learning was implemented. This indicates that although transferred learning can improve the performance of models, it is highly dependent on the task as well as the model. Overall the results obtained proved that a deep learning approach could be applied in order to classify tyres accurately.
- Full Text:
- Date Issued: 2019
- Authors: Gifford, Dean
- Date: 2019
- Subjects: Image processing -- Digital techniques , Image processing Computer science
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/39720 , vital:35351
- Description: End of Life Tyres (ELT's) pose a potential health and environmental risk when dumped in illegal stockpiles. For recycling to be considered feasible, a profitable business opportunity needs to be created. One method of making the recycling process of tyres more profitable is by understanding the compounds found within each tyre. This study aims at classifying these tyres in order to achieve this knowledge. A literature review was done to investigate neural networks, convolutional neural networks as well as existing deep learning architectures for image classification. A deep learning approach was applied in order to classify the logos of tyres as these approaches have proved their success in both image classification and more specifically logo classification. Although tyre classification has been implemented in the past, a deep learning approach has not been applied and the logo has not been the classifying element in any other studies. The main difference of this study compared to previous research surrounding deep learning and logo classification is the properties of the tyre logo. Logos on tyres are very similar in colour as they are purely formed in rubber and very seldom have any colour to them. Additionally, the embossed logos can contain variation among same branded tyres due to small inconsistencies in the moulds. The implementation of this deep learning solution saw multiple convolutional neural networks implemented. Some of these architectures were also implemented using transferred learning. The metrics obtained as outputs from training and testing the architectures were the accuracy, precision, recall, and F1-score. These metrics were compared in conjunction with the confusion matrix produced from testing. To ensure that variance was accounted for in the experiments, the k-fold cross-validation technique was adopted. The results of this study identified that one convolutional neural network model, MobileNet, was particularly well suited for the context of classifying logos on tyre sidewalls. The MobileNet architecture had the highest performance metrics for both training from scratch (96.7% accuracy) and transferred learning (98.8% accuracy). Three other models performed particularly well when trained from scratch, these were a modification of the LeNet architecture, ResNet50 and InceptionV3. The transferred learning results were also impressive with four out of the 5 models achieving an accuracy above 94%. Interestingly, the ResNet50 architecture failed to train when transferred learning was applied. Contrasting to this, the two models VGG16 and VGG19 failed to train when trained from scratch but performed equally as well as the other models when transferred learning was implemented. This indicates that although transferred learning can improve the performance of models, it is highly dependent on the task as well as the model. Overall the results obtained proved that a deep learning approach could be applied in order to classify tyres accurately.
- Full Text:
- Date Issued: 2019