Zooplankton dynamics of Algoa Bay (South Africa) under varying oceanographic conditions
- Authors: Bizani,Mfundo
- Date: 2022-04
- Subjects: Marine zooplankton -- South Africa , Climate changes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55943 , vital:54554
- Description: the ecological significance of ocean plankton in terms of nutrient cycling and energy transfer is widely recognised, as is their mechanistic link with both oceanographic processes and climate. Consequently, plankton are widely regarded as sentinels of climate change, principally owing to their responsiveness to changing environmental conditions. Developing an understanding of the ecological as well as socio-economic consequences associated with changes in marine plankton dynamics has emerged as a key issue worldwide. Though many exciting advances in this respect have been attained with the aid of long-term plankton time series (>50 y), global environmental datasets and innovative meta-analyses, building deep knowledge of regional bio-physical dynamics and responses to specific perturbed states remains an essential component of the collective effort. Algoa Bay, situated on the warmtemperate south-east coast of South Africa presents a unique opportunity to study key elements of plankton ecology relevant to climate change problems in the regional sense. The embayment is locally subjected to frequent wind-driven upwelling and regionally, to periodic mesoscale oceanographic forcing (e.g., large solitary meanders, Agulhas Current intrusions), all of which culminate in a complex physical and biogeochemical environment. Using zooplankton as the focal component and drawing from a multi-year monthly dataset incorporating a bay-scale sampling framework, the present study addressed three key hypotheses pertaining to 1) drivers of spatio-temporal variability, 2) biomass rate of change over temporal scales using time-series analyses, and 3) community responses to a bay-scale biological perturbation event. Zooplankton biomass exhibited prominent seasonal patterns with bimodal peaks corresponding with near-consistent year-to-year autumn and spring blooms. Overall, the spatial trend showed no heterogeneity, though statistical significance between-station variability was noted per season. An analytical framework involving generalised additive models revealed zooplankton spatial heterogeneity in Algoa Bay to be a function of seasonal variation in a suite of physicochemical variables, including the combined effects of temperature, salinity, dissolved oxygen, total nitrogen and silicate, but not ammonium, phosphate or chlorophyll-a (as proxy for phytoplankton). Fronts (including river plumes), warm water intrusion from the Agulhas Current, and wind-driven upwelling were postulated to be key driving forces. Structural breaks analysis performed on station-specific time series revealed significant incremental increases in zooplankton biomass over time, which in turn, corresponded with a gradual decrease in thermocline depth. The most pronounced increasing effect was associated with a period (2013– 14) of amplified land-derived nutrient input and increasing harmful algal bloom (HAB) activity. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Bizani,Mfundo
- Date: 2022-04
- Subjects: Marine zooplankton -- South Africa , Climate changes
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55943 , vital:54554
- Description: the ecological significance of ocean plankton in terms of nutrient cycling and energy transfer is widely recognised, as is their mechanistic link with both oceanographic processes and climate. Consequently, plankton are widely regarded as sentinels of climate change, principally owing to their responsiveness to changing environmental conditions. Developing an understanding of the ecological as well as socio-economic consequences associated with changes in marine plankton dynamics has emerged as a key issue worldwide. Though many exciting advances in this respect have been attained with the aid of long-term plankton time series (>50 y), global environmental datasets and innovative meta-analyses, building deep knowledge of regional bio-physical dynamics and responses to specific perturbed states remains an essential component of the collective effort. Algoa Bay, situated on the warmtemperate south-east coast of South Africa presents a unique opportunity to study key elements of plankton ecology relevant to climate change problems in the regional sense. The embayment is locally subjected to frequent wind-driven upwelling and regionally, to periodic mesoscale oceanographic forcing (e.g., large solitary meanders, Agulhas Current intrusions), all of which culminate in a complex physical and biogeochemical environment. Using zooplankton as the focal component and drawing from a multi-year monthly dataset incorporating a bay-scale sampling framework, the present study addressed three key hypotheses pertaining to 1) drivers of spatio-temporal variability, 2) biomass rate of change over temporal scales using time-series analyses, and 3) community responses to a bay-scale biological perturbation event. Zooplankton biomass exhibited prominent seasonal patterns with bimodal peaks corresponding with near-consistent year-to-year autumn and spring blooms. Overall, the spatial trend showed no heterogeneity, though statistical significance between-station variability was noted per season. An analytical framework involving generalised additive models revealed zooplankton spatial heterogeneity in Algoa Bay to be a function of seasonal variation in a suite of physicochemical variables, including the combined effects of temperature, salinity, dissolved oxygen, total nitrogen and silicate, but not ammonium, phosphate or chlorophyll-a (as proxy for phytoplankton). Fronts (including river plumes), warm water intrusion from the Agulhas Current, and wind-driven upwelling were postulated to be key driving forces. Structural breaks analysis performed on station-specific time series revealed significant incremental increases in zooplankton biomass over time, which in turn, corresponded with a gradual decrease in thermocline depth. The most pronounced increasing effect was associated with a period (2013– 14) of amplified land-derived nutrient input and increasing harmful algal bloom (HAB) activity. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Wavelet Theory: for Economic & Financial Cycles
- Authors: Mlambo, Farai Fredric
- Date: 2019-12
- Subjects: Wavelets (Mathematics) , Finance -- Mathematical models , Economic forecasting
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/49930 , vital:41861
- Description: Cycles - their nature in existence, their implications on human-kind and the study thereof have sparked some important philosophical debates since the very pre-historic days. Notable contributions by famous, genius philosophers, mathematicians, historians and economists such as Pareto, Deulofeu, Danielewski, Kuznets, Kondratiev, Elliot and many others in itself shows how cycles and their study have been deemed important, through the history and process of scientific and philosophical inquiry. Particularly, the explication of Business, Economic and Financial cycles have seen some significant research and policy attention. Nevertheless, most of the methodologies employed in this space are either purely empirical in nature, time series based or the so-called Regime-Switching Markov model popularized in Economics by James Hamilton. In this work, we develop a Statistical, non-linear model fit based on circle geometry which is applicable for the dating of cycles. This study proposes a scalable, smooth and differentiable quarter-circular wavelet basis for the smoothing and dating of business, economic and financial cycles. The dating then necessitates the forecasting of the cyclical patterns in the evolution of business, economic and financial time series. The practical significance of dating and forecasting business and financial cycles cannot be over-emphasized. The use of wavelet decomposition in explaining cycles can be seen as an critical contribution of spectral methods of statistical modelling to finance and economic policy at large. Being a relatively new method, wavelet analysis has seen some great contribution in geophysical modelling. This study endeavours to widen the use and application of frequency-time decomposition to the economic and financial space. Wavelets are localized in both time and frequency, such that there is no loss of the time resolution. The importance of time resolution in dating of cycles is another motivation behind using wavelets. Moreover, the preservation of time resolution in wavelet analysis is a fundamental strength employed in the dating of cycles. , Thesis (DPhil) -- Faculty of Science, Mathematical Statistics, 2019
- Full Text:
- Date Issued: 2019-12
- Authors: Mlambo, Farai Fredric
- Date: 2019-12
- Subjects: Wavelets (Mathematics) , Finance -- Mathematical models , Economic forecasting
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/49930 , vital:41861
- Description: Cycles - their nature in existence, their implications on human-kind and the study thereof have sparked some important philosophical debates since the very pre-historic days. Notable contributions by famous, genius philosophers, mathematicians, historians and economists such as Pareto, Deulofeu, Danielewski, Kuznets, Kondratiev, Elliot and many others in itself shows how cycles and their study have been deemed important, through the history and process of scientific and philosophical inquiry. Particularly, the explication of Business, Economic and Financial cycles have seen some significant research and policy attention. Nevertheless, most of the methodologies employed in this space are either purely empirical in nature, time series based or the so-called Regime-Switching Markov model popularized in Economics by James Hamilton. In this work, we develop a Statistical, non-linear model fit based on circle geometry which is applicable for the dating of cycles. This study proposes a scalable, smooth and differentiable quarter-circular wavelet basis for the smoothing and dating of business, economic and financial cycles. The dating then necessitates the forecasting of the cyclical patterns in the evolution of business, economic and financial time series. The practical significance of dating and forecasting business and financial cycles cannot be over-emphasized. The use of wavelet decomposition in explaining cycles can be seen as an critical contribution of spectral methods of statistical modelling to finance and economic policy at large. Being a relatively new method, wavelet analysis has seen some great contribution in geophysical modelling. This study endeavours to widen the use and application of frequency-time decomposition to the economic and financial space. Wavelets are localized in both time and frequency, such that there is no loss of the time resolution. The importance of time resolution in dating of cycles is another motivation behind using wavelets. Moreover, the preservation of time resolution in wavelet analysis is a fundamental strength employed in the dating of cycles. , Thesis (DPhil) -- Faculty of Science, Mathematical Statistics, 2019
- Full Text:
- Date Issued: 2019-12
Variation in forage quality in subtropical thicket
- Nyembe, Khulisile Jacqueline
- Authors: Nyembe, Khulisile Jacqueline
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Biodiversity -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52088 , vital:43440
- Description: Several studies have assumed that the plant communities of the Subtropical Thicket biome are nutritious throughout the year. This is based on the observation that they are evergreen, palatable and grow on fertile soils; however this assumption has not been tested. Therefore the aim of this study was to assess forage quality variation in the Subtropical Thicket. This was done at three levels; first we measured the plant quality of dominant plant species in the diets of Thicket herbivores. Secondly, we measured the realised diet quality of Thicket herbivores through the analysis of faecal samples. Lastly we assessed the body condition of Thicket herbivores. The study was conducted at the Colchester (plant quality and diet quality) and Addo Main Camp (body condition assessment) sections of Addo Elephant National Park. To measure the food quality of Thicket plants we analysed 10 plants that are dominant in the diets of Thicket herbivores. To measure diet quality we collected faecal samples from ten herbivores with body mass ranging from 25 kg to 6000 kg. Plant quality results showed that only 30% of the sampled plants met the high energy goat diet protein requirements and that all the sampled plants did not meet the high energy goat diet fibre requirements. This indicates that Thicket plants are not as highly nutritious as they were thought to be. The principle components analysis together with overlapping confidence intervals showed that there was no significant difference between the summer plant samples and the winter plant samples. The faecal quality results showed that there was significant seasonal difference and that faecal diet quality was a function of body size. The body condition results showed that all the sampled herbivores lost condition in the cold dry months. The evidence from faecal diet quality and body condition assessment is sufficient for us to reject the assumption that Thicket forage is consistently nutritious throughout the year. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Nyembe, Khulisile Jacqueline
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Biodiversity -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52088 , vital:43440
- Description: Several studies have assumed that the plant communities of the Subtropical Thicket biome are nutritious throughout the year. This is based on the observation that they are evergreen, palatable and grow on fertile soils; however this assumption has not been tested. Therefore the aim of this study was to assess forage quality variation in the Subtropical Thicket. This was done at three levels; first we measured the plant quality of dominant plant species in the diets of Thicket herbivores. Secondly, we measured the realised diet quality of Thicket herbivores through the analysis of faecal samples. Lastly we assessed the body condition of Thicket herbivores. The study was conducted at the Colchester (plant quality and diet quality) and Addo Main Camp (body condition assessment) sections of Addo Elephant National Park. To measure the food quality of Thicket plants we analysed 10 plants that are dominant in the diets of Thicket herbivores. To measure diet quality we collected faecal samples from ten herbivores with body mass ranging from 25 kg to 6000 kg. Plant quality results showed that only 30% of the sampled plants met the high energy goat diet protein requirements and that all the sampled plants did not meet the high energy goat diet fibre requirements. This indicates that Thicket plants are not as highly nutritious as they were thought to be. The principle components analysis together with overlapping confidence intervals showed that there was no significant difference between the summer plant samples and the winter plant samples. The faecal quality results showed that there was significant seasonal difference and that faecal diet quality was a function of body size. The body condition results showed that all the sampled herbivores lost condition in the cold dry months. The evidence from faecal diet quality and body condition assessment is sufficient for us to reject the assumption that Thicket forage is consistently nutritious throughout the year. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Validation and adaptation of statistical models based on the SAPS III score to predict in-hospital mortality in a South African ICU
- Authors: Pazi, Sisa
- Date: 2023-04
- Subjects: Police -- South Africa -- Eastern Cape , Statistics – South Africa , Mortality – South Africa
- Language: English
- Type: Doctoral's theses , text
- Identifier: http://hdl.handle.net/10948/61360 , vital:70602
- Description: In-hospital mortality prediction remains an important task in Intensive Care Units (ICUs). In particular, the estimated in-hospital mortality risk is essential to describe case-mix, for research and clinical auditing purposes. Furthermore, in settings with limited hospital resources (e.g beds) such as the South African public health care system, the estimated in-hospital mortality risk is essential for resource allocation and to inform local patient triage guidelines. Commonly used models for prediction of in-hospital mortality in ICU patients includes, but not limited to, the Simplified Acute Physiology Score III (SAPS III). The SAPS III model was developed in 2005. Notably, the SAPS III model was developed without data collected from African based hospitals. Given the general application of the SAPS III model, including benchmarking and quality control, the development of such a model based on local data is of paramount importance. To this end, this study developed a model for prediction of in-hospital mortality based on data collected in a hospital in South Africa. Logistic regression modelling was used to develop the proposed mortality risk assessment model. The results indicated that the proposed model exhibited superior discrimination and classification abilities compared to the SAPS III model. Future research includes the external validation of the proposed model in different hospitals in South Africa. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Pazi, Sisa
- Date: 2023-04
- Subjects: Police -- South Africa -- Eastern Cape , Statistics – South Africa , Mortality – South Africa
- Language: English
- Type: Doctoral's theses , text
- Identifier: http://hdl.handle.net/10948/61360 , vital:70602
- Description: In-hospital mortality prediction remains an important task in Intensive Care Units (ICUs). In particular, the estimated in-hospital mortality risk is essential to describe case-mix, for research and clinical auditing purposes. Furthermore, in settings with limited hospital resources (e.g beds) such as the South African public health care system, the estimated in-hospital mortality risk is essential for resource allocation and to inform local patient triage guidelines. Commonly used models for prediction of in-hospital mortality in ICU patients includes, but not limited to, the Simplified Acute Physiology Score III (SAPS III). The SAPS III model was developed in 2005. Notably, the SAPS III model was developed without data collected from African based hospitals. Given the general application of the SAPS III model, including benchmarking and quality control, the development of such a model based on local data is of paramount importance. To this end, this study developed a model for prediction of in-hospital mortality based on data collected in a hospital in South Africa. Logistic regression modelling was used to develop the proposed mortality risk assessment model. The results indicated that the proposed model exhibited superior discrimination and classification abilities compared to the SAPS III model. Future research includes the external validation of the proposed model in different hospitals in South Africa. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2023
- Full Text:
- Date Issued: 2023-04
Utilising new technology to enable sustainable chemical and drug manufacturing in Africa
- Authors: Watts, Paul
- Subjects: Drug development , Pharmacology , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/21000 , vital:29426
- Description: Over the last few decades organic chemists have developed highly sophisticated chemical reactions to prepare very complex molecules. The pharmaceutical industry uses the methodology that academics develop within research programmes to manufacture drugs to treat a plethora of medical conditions. When unwell, all citizens expect treatment, however it needs to be remembered that the pharmaceutical industry is a business in order to make a profit for its shareholders, and consequently only rich nations can afford access to the most modern treatments available.
- Full Text:
- Authors: Watts, Paul
- Subjects: Drug development , Pharmacology , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/21000 , vital:29426
- Description: Over the last few decades organic chemists have developed highly sophisticated chemical reactions to prepare very complex molecules. The pharmaceutical industry uses the methodology that academics develop within research programmes to manufacture drugs to treat a plethora of medical conditions. When unwell, all citizens expect treatment, however it needs to be remembered that the pharmaceutical industry is a business in order to make a profit for its shareholders, and consequently only rich nations can afford access to the most modern treatments available.
- Full Text:
Using spatial explicit capture-recapture model to investigate the demography and spatial dynamics of lion prides in Pilanesberg National Park
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Bettings, Isabella Aletta
- Date: 2022-12
- Subjects: Lions--Behavior--South Africa , Animals tracks -- Pilanesberg National Park -- North West
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59655 , vital:62318
- Description: Lions are apex predators that play a vital role in the ecosystem. They regulate prey species through predation and other non-consumptive means. Factors that have influenced the decline of lion populations across Africa in the last half century, are loss of habitat, human wildlife conflict and the depletion of prey species. Extensive reintroductions of lions have been conducted across South Africa in order to restore their numbers in protected areas. The Pilanesberg National Park (PNP) was one of many protected areas that reintroduced lions. Their numbers were well documented by management until 2005 where they lost track of the population numbers. During this unfortunate period, there was an observed decline in prey numbers. The aim of this dissertation was to estimate the abundance, movement, and sex ratio of lions, in PNP. Abundance, movement, and sex ratio were determined by a three-month intensive lion survey. The location of each lion encounter was recorded on a mobile device which had an application installed called Cybertracker (v3). Photographs were taken of each Lion to build identification kits. For the data analysis, I used the Bayesian spatial explicit capture-recapture (SECR) model. This model takes time, space, and the robustness of an individual lion into account. Robustness is the measure of how well a lion maintains their functionality, when various stressors are applied (Harmsen, Foster, & Quigley, 2020). The estimated lion population in PNP was 44 lions (>1 year) with a density of 8.8 lions per 100 km2 . The estimated mean home range size of male lions was 279 km2 with a highest probability density (HPD) range of 179 – 385 km2 . The estimated mean home range of female lions was 191 km2 with a HPD range of 135 – 262 km2 . The larger home range size for male lions and smaller home range size for females is found v throughout the African continent in protected areas. The estimated sex ratio was 0.9♀:1♂, which is unexpected as PNP sex ratios between male and female lions is usually 2♀:1♂. A future sampling design for PNP was produced from the completed lion survey dataset. I drove a total of 7350 km and evaluated the influence of varied sampling efforts (i.e., kms driven) on precision estimates and relative bias for abundance, movement, and sex ratio. I found that a minimum of 4 000 km was needed to adequately estimate the lion abundance, movement, and sex ratio in this small fenced protected area. These findings can be used to help guide management to the most cost-effective sampling method and still obtain accurate estimates for monitoring lions. By showing management what is required for appropriate lion surveys this might help improve future monitoring. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-12
Using information visualization to support the self-management of type 2 diabetes mellitus
- Authors: Nauder, Meggan Kate
- Date: 2022-04
- Subjects: Information visualization , Diabetics --Treatment --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55711 , vital:53409
- Description: The globally increasing number of individuals suffering from Type 2 Diabetes Mellitus (T2DM), a completely preventable incurable disease of the pancreas, highlights the need for an effective tool for users to understand the relationship between their behaviours and the effect that those behaviours can have on their blood glucose levels (BGLs). There are few Information Visualisation (IV) tools available that can be used to reduce the cognition required to understand correlations between behaviour and BGLs. Existing tools require time-consuming, lengthy inputs and provide simple visualisations that do not show correlations. This leads to ineffective self-management of T2DM. Information Visualisation (IV) techniques can be used to support effective self-management of T2DM and reduce the cognition required to interpret DM data. Suitable IV techniques were identified and used to visualize T2DM data to aid in the self-management of the disease. Temporal charts, i.e. The Bar, Pie and Line Chart as well as heat maps, were selected as the most appropriate IV techniques to visualize T2DM data as they support time-series data well. A prototype, MedicMetric was created as an IV tool for visualizing T2DM data. MedicMetric incorporated three designed charts, namely the Change Rate Line View, the Radial Progress View, and the Annotated Line View. The Change Rate Line View and Annotated Line View both used line IV techniques, while the Radial Progress View made use of the bar IV technique. The Change Rate Line View performed the worst overall. A usability evaluation was conducted to compare these techniques and to determine which technique is most suitable for visualizing T2DM data. The results leaned significantly in favour of the Annotated Line View. This view is most similar to the line charts typically used in other IV tools. For this reason, the MedicMetric app was briefly compared to the MySygr and Diabetes:M application. In effectiveness and efficiency, MedicMetric and MySugr obtained almost identical results. However, participants indicated that MedicMetric supported their tasks using the Visual Information Seeking Mantra (VISM) the best overall, with 100% of participants stating that they would prefer to use the MedicMetric application. Several usability problems were identified with the IV techniques and they were addressed shortly after the study was complete. Overall participants were most satisfied with the Annotated Line View. , Thesis (MSc) -- Faculty of Science, Computing Sciences, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Nauder, Meggan Kate
- Date: 2022-04
- Subjects: Information visualization , Diabetics --Treatment --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55711 , vital:53409
- Description: The globally increasing number of individuals suffering from Type 2 Diabetes Mellitus (T2DM), a completely preventable incurable disease of the pancreas, highlights the need for an effective tool for users to understand the relationship between their behaviours and the effect that those behaviours can have on their blood glucose levels (BGLs). There are few Information Visualisation (IV) tools available that can be used to reduce the cognition required to understand correlations between behaviour and BGLs. Existing tools require time-consuming, lengthy inputs and provide simple visualisations that do not show correlations. This leads to ineffective self-management of T2DM. Information Visualisation (IV) techniques can be used to support effective self-management of T2DM and reduce the cognition required to interpret DM data. Suitable IV techniques were identified and used to visualize T2DM data to aid in the self-management of the disease. Temporal charts, i.e. The Bar, Pie and Line Chart as well as heat maps, were selected as the most appropriate IV techniques to visualize T2DM data as they support time-series data well. A prototype, MedicMetric was created as an IV tool for visualizing T2DM data. MedicMetric incorporated three designed charts, namely the Change Rate Line View, the Radial Progress View, and the Annotated Line View. The Change Rate Line View and Annotated Line View both used line IV techniques, while the Radial Progress View made use of the bar IV technique. The Change Rate Line View performed the worst overall. A usability evaluation was conducted to compare these techniques and to determine which technique is most suitable for visualizing T2DM data. The results leaned significantly in favour of the Annotated Line View. This view is most similar to the line charts typically used in other IV tools. For this reason, the MedicMetric app was briefly compared to the MySygr and Diabetes:M application. In effectiveness and efficiency, MedicMetric and MySugr obtained almost identical results. However, participants indicated that MedicMetric supported their tasks using the Visual Information Seeking Mantra (VISM) the best overall, with 100% of participants stating that they would prefer to use the MedicMetric application. Several usability problems were identified with the IV techniques and they were addressed shortly after the study was complete. Overall participants were most satisfied with the Annotated Line View. , Thesis (MSc) -- Faculty of Science, Computing Sciences, 2022
- Full Text:
- Date Issued: 2022-04
Use of flow reactors for an improved synthesis of Tenofovir derivatives
- Authors: Sonti, Thembela
- Date: 2023-04
- Subjects: Antiviral agents -- South Africa , HIV infections –Treatment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61190 , vital:69792
- Description: Tenofovir disoproxil fumarate (TDF) is a prescription drug used to treat and prevent human immunodeficiency virus (HIV) infections. It aids in the reduction of HIV in the body, allowing the immune system to function more effectively. This reduces the risk of HIV complications, such as infections, whilst improving the quality of life. TDF belongs to the nucleotide reverse transcriptase inhibitors category of drugs. These drugs limit the ability of the reverse transcriptase, an enzyme essential for each virus to replicate itself. A reduction in the cost of HIV treatment could improve supply security and make it more accessible to patients in need. Thus, this project aims to use flow technology to achieve a guaranteed supply chain and access. In this thesis, a method for the synthesis of TDF was developed using microreactors starting from the readily available adenine. The method was adapted from the traditional batch synthesis as currently there is no literature on the synthesis of TDF in flow chemistry. The batch methods used for the synthesis of the working standards were successfully translated to flow systems. For the best results to be obtained, optimisation of the reaction temperature, reagent molar equivalents and concentration was critical. From the optimisation studies, an improvement in conversion is evident throughout all stages. The flow synthesis of the first intermediate resulted in a conversion of 100 % in N,N-dimethylformamide in 6 min residence time. This study was conducted at 200 °C, which is higher than the boiling point of the solvent with the aid of a back pressure regulator. A key reagent in the synthesis of tenofovir, namely ((tosyloxy)methyl)phosphonic acid, had to be synthesised and it was successfully produced in 96 % yield. The second intermediate was synthesised through a successful coupling reaction between (R)-9-(2-hydroxypropyl)adenine and ((tosyloxy)methyl)- phosphonic acid, which afforded a 100 % conversion of tenofovir in 20 min total residence time. The multistep synthesis of tenofovir was a success as it afforded a 65 % overall conversion. The prodrug TDF was successfully synthesised at 120 °C with a 30 min residence time, yielding a conversion of 100 %. ii | P a g e This thesis consists of four chapters. Chapter one describes the background on HIV and a literature review on HIV drugs. This chapter also demonstrates flow chemistry and microreactors in detail and different routes for the synthesis of TDF in traditional batch methods. Chapter two provides a detailed methodology for batch synthesis and flow synthesis with analytical data. 1H-NMR, 13C-NMR and FTIR spectroscopy was used to evaluate all the compounds synthesised in this chapter. Chapter three thoroughly discusses the results that were obtained graphically, showing that the flow synthesis gives better yields than batch synthesis. In chapter 4, the conclusion of the whole investigation is stated along with the future work for the preparation of TDF. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Sonti, Thembela
- Date: 2023-04
- Subjects: Antiviral agents -- South Africa , HIV infections –Treatment
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61190 , vital:69792
- Description: Tenofovir disoproxil fumarate (TDF) is a prescription drug used to treat and prevent human immunodeficiency virus (HIV) infections. It aids in the reduction of HIV in the body, allowing the immune system to function more effectively. This reduces the risk of HIV complications, such as infections, whilst improving the quality of life. TDF belongs to the nucleotide reverse transcriptase inhibitors category of drugs. These drugs limit the ability of the reverse transcriptase, an enzyme essential for each virus to replicate itself. A reduction in the cost of HIV treatment could improve supply security and make it more accessible to patients in need. Thus, this project aims to use flow technology to achieve a guaranteed supply chain and access. In this thesis, a method for the synthesis of TDF was developed using microreactors starting from the readily available adenine. The method was adapted from the traditional batch synthesis as currently there is no literature on the synthesis of TDF in flow chemistry. The batch methods used for the synthesis of the working standards were successfully translated to flow systems. For the best results to be obtained, optimisation of the reaction temperature, reagent molar equivalents and concentration was critical. From the optimisation studies, an improvement in conversion is evident throughout all stages. The flow synthesis of the first intermediate resulted in a conversion of 100 % in N,N-dimethylformamide in 6 min residence time. This study was conducted at 200 °C, which is higher than the boiling point of the solvent with the aid of a back pressure regulator. A key reagent in the synthesis of tenofovir, namely ((tosyloxy)methyl)phosphonic acid, had to be synthesised and it was successfully produced in 96 % yield. The second intermediate was synthesised through a successful coupling reaction between (R)-9-(2-hydroxypropyl)adenine and ((tosyloxy)methyl)- phosphonic acid, which afforded a 100 % conversion of tenofovir in 20 min total residence time. The multistep synthesis of tenofovir was a success as it afforded a 65 % overall conversion. The prodrug TDF was successfully synthesised at 120 °C with a 30 min residence time, yielding a conversion of 100 %. ii | P a g e This thesis consists of four chapters. Chapter one describes the background on HIV and a literature review on HIV drugs. This chapter also demonstrates flow chemistry and microreactors in detail and different routes for the synthesis of TDF in traditional batch methods. Chapter two provides a detailed methodology for batch synthesis and flow synthesis with analytical data. 1H-NMR, 13C-NMR and FTIR spectroscopy was used to evaluate all the compounds synthesised in this chapter. Chapter three thoroughly discusses the results that were obtained graphically, showing that the flow synthesis gives better yields than batch synthesis. In chapter 4, the conclusion of the whole investigation is stated along with the future work for the preparation of TDF. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Ureaplasma species in the placenta and histopathology associated with preterm birth
- Authors: Sprong, Kaitlin Elizabeth
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54128 , vital:46310
- Description: The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasma spp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalence of Ureaplasma urealyticum, Ureaplasma parvumand Mycoplasma hominisin the placenta and its role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasma spp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasma spp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasma spp. in the placenta and adverse maternal, obstetric and neonatal outcomes. iiiABSTRACTBackground The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasmaspp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalenceof Ureaplasmaurealyticum,UreaplasmaparvumandMycoplasmahominisin the placenta andits role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasmaspp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasmaspp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasmaspp. inthe placenta and adverse maternal, obstetric and neonatal outcomes. MethodsPlacentas were collected from patients presenting with preterm birth (n=100; 28-34 weeks gestational age) and term birth (n=20; >38 weeks) regardless of the APGAR score. Placentas were submitted for histopathology and used for detection of Ureaplasmaspp. by culture (U9 broth, MycoDuo kits;BioRad) and PCR (DNA was extracted from culture and homogenized placental tissue). Antibiotic susceptibility profiles of Ureaplasmaspp isolates were determined by the SIR Antibiogram kit (BioRad) and microbroth dilution method. Molecular mechanisms of resistance were ascertained by PCR amplification of target genes. Placentas were sent to National Health Laboratory Servicesfor routine histopathology. Next generation sequencing was performed on 16S rRNA amplicons from placental DNA for analysis of microbial diversity. , Thesis (PhD) -- Faculty of Science, Journalsim and Media Studies, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Sprong, Kaitlin Elizabeth
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54128 , vital:46310
- Description: The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasma spp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalence of Ureaplasma urealyticum, Ureaplasma parvumand Mycoplasma hominisin the placenta and its role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasma spp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasma spp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasma spp. in the placenta and adverse maternal, obstetric and neonatal outcomes. iiiABSTRACTBackground The Eastern Cape province is known for its high perinatal morbidity and mortality rate. Studies from other countries indicate that Ureaplasmaspp. have been associated with clinical chorioamnionitis, spontaneous preterm labor and preterm premature rupture of the fetal membranes. The prevalenceof Ureaplasmaurealyticum,UreaplasmaparvumandMycoplasmahominisin the placenta andits role in preterm birth is unknown in South Africa. Objectives The objectives of this study were to: (i) analyze placental histology, maternal and neonatal outcomes and clinical presentation of preterm birth, (ii) detect Ureaplasmaspp. and M. hominisin the placenta from cases of preterm birth, (iii) determine antibiotic susceptibility profiles of Ureaplasmaspp. isolates and investigate mechanisms of antibiotic resistance, (iv) characterize the microbial diversity in the placenta using 16S rRNA next generation sequencing and(v) review pathologies to ascertain whether there is any association between Ureaplasmaspp. inthe placenta and adverse maternal, obstetric and neonatal outcomes. MethodsPlacentas were collected from patients presenting with preterm birth (n=100; 28-34 weeks gestational age) and term birth (n=20; >38 weeks) regardless of the APGAR score. Placentas were submitted for histopathology and used for detection of Ureaplasmaspp. by culture (U9 broth, MycoDuo kits;BioRad) and PCR (DNA was extracted from culture and homogenized placental tissue). Antibiotic susceptibility profiles of Ureaplasmaspp isolates were determined by the SIR Antibiogram kit (BioRad) and microbroth dilution method. Molecular mechanisms of resistance were ascertained by PCR amplification of target genes. Placentas were sent to National Health Laboratory Servicesfor routine histopathology. Next generation sequencing was performed on 16S rRNA amplicons from placental DNA for analysis of microbial diversity. , Thesis (PhD) -- Faculty of Science, Journalsim and Media Studies, 2021
- Full Text:
- Date Issued: 2021-12
Upwelling over submarine canyons: an in-situ and modelling approach
- Authors: Rautenbach, Gustav
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Oceanography -- Research -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52078 , vital:43442
- Description: The iSimangaliso Wetland Park, located along the coastline of northern KwaZulu-Natal (KZN), hosts South Africa's only tropical coral reef system and is clustered with submarine canyons. These ecosystems support a flourishing diving and pelagic sportfishing industry in the area that contributes tens of millions of rand to the South African Gross Domestic Profit (GDP) annually as well as to provide income and job security for the majority of the local residents. Understanding the oceanographic dynamics, particularly upwelling events, will improve current knowledge of how the ecosystem works and may enhance conservation techniques. The upwelling events within the iSimangaliso Wetland Park results in the influx of cold and nutrient rich waters that supports biological productivity in the area. The complex oceanography, dominated by the Northern Agulhas Current and mesoscale eddies that stem from the Mozambique Channel and South East Madagascar Current (SEMC) is understudied and lacks understanding. This thesis aims to build upon the current knowledge of the upwelling events over the submarine canyons and the concurrent influence on the Mixed Layer Depth (MLD). At the submarine canyons, six anomalous cooling events were identified from surface and subsurface measurements extracted from the Operational Sea Surface Temperature and Ice Analysis (OSTIA) Sea Surface Temperature (SST) and from data collected using Underwater Temperature Recorders (UTRs) over a 12-month period. Depth-integrated lagged correlations showed a 2-to-7-hour lag period from the deep to shallow stations, suggesting that the anomalous cooling events are in fact upwelling events. Wind measurements from the Mbazwana Weather Station and snapshots of sea-level anomalies illustrated that the weaker and shorter upwelling events are driven either by alongshore wind stress or a cyclonic eddy event solely; whereas the stronger event was driven by the combination of both forcing mechanisms. An idealized canyon ocean model is used to interrogate the two forcing mechanisms more fully and showed that the most intense upwelling events are driven by the combined effect of upwelling-favourable alongshore wind stress and a cyclonic eddy which results in strong upward vertical velocity anomalies and the greatest shallowing (6.88 m) of the MLD. With the contribution of the in-situ measurements as a baseline study it is apparent that the idealised model does provide an improved understanding of the upwelling events and forcing mechanism over the submarine canyons within the iSimangaliso Wetland Park. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Rautenbach, Gustav
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Oceanography -- Research -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52078 , vital:43442
- Description: The iSimangaliso Wetland Park, located along the coastline of northern KwaZulu-Natal (KZN), hosts South Africa's only tropical coral reef system and is clustered with submarine canyons. These ecosystems support a flourishing diving and pelagic sportfishing industry in the area that contributes tens of millions of rand to the South African Gross Domestic Profit (GDP) annually as well as to provide income and job security for the majority of the local residents. Understanding the oceanographic dynamics, particularly upwelling events, will improve current knowledge of how the ecosystem works and may enhance conservation techniques. The upwelling events within the iSimangaliso Wetland Park results in the influx of cold and nutrient rich waters that supports biological productivity in the area. The complex oceanography, dominated by the Northern Agulhas Current and mesoscale eddies that stem from the Mozambique Channel and South East Madagascar Current (SEMC) is understudied and lacks understanding. This thesis aims to build upon the current knowledge of the upwelling events over the submarine canyons and the concurrent influence on the Mixed Layer Depth (MLD). At the submarine canyons, six anomalous cooling events were identified from surface and subsurface measurements extracted from the Operational Sea Surface Temperature and Ice Analysis (OSTIA) Sea Surface Temperature (SST) and from data collected using Underwater Temperature Recorders (UTRs) over a 12-month period. Depth-integrated lagged correlations showed a 2-to-7-hour lag period from the deep to shallow stations, suggesting that the anomalous cooling events are in fact upwelling events. Wind measurements from the Mbazwana Weather Station and snapshots of sea-level anomalies illustrated that the weaker and shorter upwelling events are driven either by alongshore wind stress or a cyclonic eddy event solely; whereas the stronger event was driven by the combination of both forcing mechanisms. An idealized canyon ocean model is used to interrogate the two forcing mechanisms more fully and showed that the most intense upwelling events are driven by the combined effect of upwelling-favourable alongshore wind stress and a cyclonic eddy which results in strong upward vertical velocity anomalies and the greatest shallowing (6.88 m) of the MLD. With the contribution of the in-situ measurements as a baseline study it is apparent that the idealised model does provide an improved understanding of the upwelling events and forcing mechanism over the submarine canyons within the iSimangaliso Wetland Park. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
Uptake and storage of nutrients by primary producers in the Swartkops Estuary
- Authors: Whitfield, Emily Cailyn
- Date: 2022-12
- Subjects: Estuarine ecology --South Africa --Swartkops River Estuary , Eutrophication—Research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59611 , vital:62195
- Description: Estuaries occur at the interface between the terrestrial and marine environment and as such act as the last ‘filtering’ mechanism prior to nutrient pollution entering the adjacent ocean. This study focused on the Swartkops Estuary which is eutrophic and requires the removal of nutrients. The role of phytoplankton as nutrient filters and storage of nutrients by seagrass and salt marsh was investigated. This study found that phytoplankton temporarily took up a large percentage of dissolved inorganic nitrogen (max. 99%) and dissolved silica (max. 76%) and limited amounts of dissolved inorganic phosphorus (max. 18%). The amount of carbon, nitrogen and phosphorus stored by the salt marsh species Spartina maritima and Salicornia tegetaria and the seagrass species Zostera capensis were determined. It was found that the salt marsh grass Spartina maritima stored the most nutrients (149.61 ± 16.59 N g m-2 ; 105.44 ± 13.41 P g m-2 ; 1690.52 ± 168.90 C g m-2 ), while for the salt marsh succulent Salicornia tegetaria less nutrients were stored (27.01 ± 4.17 N g m-2 ; 22.97 ± 3.21 P g m-2 ; 458.66 ± 69.43 C g m-2 ). Zostera capensis also acted as a nutrient store (22.17 ± 6.94 N g m-2 ; 23.75 ± 4.70 P g m-2 ; 221.10 ± 26.74 C g m-2 ). The macrophytes were able to store nutrients for longer periods and thus prevent these nutrients from being exported into the adjacent ocean. On the contrary, phytoplankton uptake was temporary as the nutrients are released once the bloom decays. Without intervention there will be an increase of harmful algal blooms (HABs) and fish kills in the eutrophic Swartkops Estuary. Nutrient input from upstream wastewater treatment works, canals and stormwater run-off must be reduced. Conservation and management of the seagrass and salt marsh habitats is needed to ensure the long-term storage of nutrients , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
- Authors: Whitfield, Emily Cailyn
- Date: 2022-12
- Subjects: Estuarine ecology --South Africa --Swartkops River Estuary , Eutrophication—Research
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/59611 , vital:62195
- Description: Estuaries occur at the interface between the terrestrial and marine environment and as such act as the last ‘filtering’ mechanism prior to nutrient pollution entering the adjacent ocean. This study focused on the Swartkops Estuary which is eutrophic and requires the removal of nutrients. The role of phytoplankton as nutrient filters and storage of nutrients by seagrass and salt marsh was investigated. This study found that phytoplankton temporarily took up a large percentage of dissolved inorganic nitrogen (max. 99%) and dissolved silica (max. 76%) and limited amounts of dissolved inorganic phosphorus (max. 18%). The amount of carbon, nitrogen and phosphorus stored by the salt marsh species Spartina maritima and Salicornia tegetaria and the seagrass species Zostera capensis were determined. It was found that the salt marsh grass Spartina maritima stored the most nutrients (149.61 ± 16.59 N g m-2 ; 105.44 ± 13.41 P g m-2 ; 1690.52 ± 168.90 C g m-2 ), while for the salt marsh succulent Salicornia tegetaria less nutrients were stored (27.01 ± 4.17 N g m-2 ; 22.97 ± 3.21 P g m-2 ; 458.66 ± 69.43 C g m-2 ). Zostera capensis also acted as a nutrient store (22.17 ± 6.94 N g m-2 ; 23.75 ± 4.70 P g m-2 ; 221.10 ± 26.74 C g m-2 ). The macrophytes were able to store nutrients for longer periods and thus prevent these nutrients from being exported into the adjacent ocean. On the contrary, phytoplankton uptake was temporary as the nutrients are released once the bloom decays. Without intervention there will be an increase of harmful algal blooms (HABs) and fish kills in the eutrophic Swartkops Estuary. Nutrient input from upstream wastewater treatment works, canals and stormwater run-off must be reduced. Conservation and management of the seagrass and salt marsh habitats is needed to ensure the long-term storage of nutrients , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2022-12
Towards mineral beneficiation: from basic chemistry to applications
- Authors: Tshentu, Zenixole
- Subjects: Metallurgy , Ore-dressing , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55783 , vital:53876
- Description: The role of mineral beneficiation in the survival, growth, development and sustainability of a developing economy cannot be overstated. Our development as a human species has always been involvedly linked with the use of mineral resources from the stone, bronze and iron ages through the early modern eras to the present. In the current modern era, characterized by highly technological equipment, fourth industrial revolution (4IR) and new energy technologies, the role of mineral beneficiation has been elevated. Precious metals find use in the fine chemicals and petrochemicals industry, fuel cells, electrical and electronic products, medical and dentistry applications, jewellery, autocatalysts, and glass and ceramics. The markets for precious metals keep growing and the supply does not meet demand. The development of methods for recovery of metal value from feeds of mineral ore solutions, solutions of spent secondary resources and from mining wastewaters remains of great importance. Further beneficiation strategies for utilization of mineral products in other “value-added” applications are also important for the growth of the mineral markets. The usage of platinum, palladium and rhodium in the autocatalyst industry has grown significantly and this has further elevated the importance of platinum group metals (PGMs), but other areas of application of the strategic metals need to be harnessed. The four stages of beneficiation, namely, primary, secondary, tertiary and final stage, provide an opportunity to beneficiate to greater value for domestic or export use. Our own research work is engaged in several of these stages, from hydrometallurgical recovery of base metals and platinum group metals from feeds of primary mining and solutions of waste secondary resources such as spent catalytic converters and e-waste to the use of metals in “value added” products such as metalbased catalysts for the fuel industry and in metallodrugs. Examples of “value added” products include rhodium as a promoter in molybdenum sulfide as a catalyst for hydrodesulfurization of fuel oil, vanadium as a catalyst in oxidative desulfurization of fuel oil, vanadium and palladium as therapeutic agents for diabetes and cancer, respectively. Current and future work involves (i) the development of metal-selective scavengers to recover lost metal value in mining wastewaters, and (ii) the design of metal-based catalytic materials for refinement of bio-based oils to biofuel as well as for production of green LPG through hydroprocessing. Our work centres around both basic and applied chemistry towards mineral beneficiation and with a bias towards greener production.
- Full Text:
- Authors: Tshentu, Zenixole
- Subjects: Metallurgy , Ore-dressing , f-sa
- Language: English
- Type: text , Lectures
- Identifier: http://hdl.handle.net/10948/55783 , vital:53876
- Description: The role of mineral beneficiation in the survival, growth, development and sustainability of a developing economy cannot be overstated. Our development as a human species has always been involvedly linked with the use of mineral resources from the stone, bronze and iron ages through the early modern eras to the present. In the current modern era, characterized by highly technological equipment, fourth industrial revolution (4IR) and new energy technologies, the role of mineral beneficiation has been elevated. Precious metals find use in the fine chemicals and petrochemicals industry, fuel cells, electrical and electronic products, medical and dentistry applications, jewellery, autocatalysts, and glass and ceramics. The markets for precious metals keep growing and the supply does not meet demand. The development of methods for recovery of metal value from feeds of mineral ore solutions, solutions of spent secondary resources and from mining wastewaters remains of great importance. Further beneficiation strategies for utilization of mineral products in other “value-added” applications are also important for the growth of the mineral markets. The usage of platinum, palladium and rhodium in the autocatalyst industry has grown significantly and this has further elevated the importance of platinum group metals (PGMs), but other areas of application of the strategic metals need to be harnessed. The four stages of beneficiation, namely, primary, secondary, tertiary and final stage, provide an opportunity to beneficiate to greater value for domestic or export use. Our own research work is engaged in several of these stages, from hydrometallurgical recovery of base metals and platinum group metals from feeds of primary mining and solutions of waste secondary resources such as spent catalytic converters and e-waste to the use of metals in “value added” products such as metalbased catalysts for the fuel industry and in metallodrugs. Examples of “value added” products include rhodium as a promoter in molybdenum sulfide as a catalyst for hydrodesulfurization of fuel oil, vanadium as a catalyst in oxidative desulfurization of fuel oil, vanadium and palladium as therapeutic agents for diabetes and cancer, respectively. Current and future work involves (i) the development of metal-selective scavengers to recover lost metal value in mining wastewaters, and (ii) the design of metal-based catalytic materials for refinement of bio-based oils to biofuel as well as for production of green LPG through hydroprocessing. Our work centres around both basic and applied chemistry towards mineral beneficiation and with a bias towards greener production.
- Full Text:
Top-down control by grapsoid crabs in South African estuarine salt marshes
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
- Authors: Smith, Leigh-Ann
- Date: 2023-04
- Subjects: Salt marsh ecology – South Africa , Crabs --South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61223 , vital:69807
- Description: Salt marshes are one of the most productive ecosystems globally. These ‘blue carbon’ habitats are in many respects resilient to climate change effects, able to track sea level rise and act as carbon sinks. Since salt marshes are economically and ecologically essential habitats (for example providing foraging grounds for invertebrates, fish, birds and humans), understanding the processes that control their structure is crucial to best maintain ecosystem services provided by these habitats. For decades the importance of top-down forces, such as grazing, has not been recognised as being important in controlling salt marsh plant productivity. Rather, bottom-up forces, such as the availability of oxygen, was thought to be the main constraint to primary production. Therefore, a better understanding of salt marsh ecosystem dynamics and whether grazer control exists is needed. Although grazer top-down control has been demonstrated in salt marshes in locations such as the United States, this has not been investigated in South Africa. This is a crucial knowledge gap locally considering the importance of salt marsh ecosystems. The aim of this study was therefore to determine what role consumers play in structuring South Africa’s estuarine salt marsh vegetation, thereby also contextualising this process internationally. In order to achieve this, the abundance of grapsoid crabs was estimated and related to key salt marsh features, such as Spartina maritima stem height and stem density, which was quantified from observational surveys. Sampling took place at the beginning and end of the early-spring and late-summer growth period (September 2021 and April 2022) in the Knysna, Kromme and Swartkops estuaries. If a correlation was observed between crab density and salt marsh features, it was important to determine whether they consume the salt marsh vegetation or if the effect was due to their burrowing activities. Hence, the diet of grapsoid crabs was investigated using stable isotope and gut content analysis. To examine the importance of crab grazing in controlling the growth of salt marsh vegetation, crab abundance was manipulated in situ by means of exclusion cages. This experiment ran for five months in the Kromme Estuary, from November 2021 to March 2022 over the salt marsh growing season. An ex situ feeding experiment was also conducted on 30 crab specimens collected from the Kromme Estuary, during May 2022. These crabs were starved for 48 hours and thereafter fed different components of Spartina (growing and dead blades, and roots and rhizomes). The food consumed was quantified as the change in plant length and dry weight after 48 hours, which gave a maximum grazing rate for the different food sources. It was found that crabs are having a minimal impact on the salt marsh vegetation structure. Spartina maritima does form an important component of the diet of grapsoid crabs, however, this is not their only source of food, and possibly not their preferred source of food. They are however contributing to sediment properties through their burrowing activities. The iii ex situ feeding experiment showed that grapsoid crabs can consume all vegetative components of Spartina, with a significantly greater amount of roots and rhizomes consumed. There was no consistent effect in terms of the exclusion of grazers, indicating that other mitigating factors could be reducing the impacts of grapsoid exclusion in situ. Together, these findings contribute knowledge that can be used to inform conservation by quantifying what the salt marsh risks losing in the absence or overabundance of crabs, as has occurred elsewhere globally. These results influence how salt marshes are managed, and highlight how not recognising the importance of consumers, such as crabs, could misalign management objectives. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2022
- Full Text:
- Date Issued: 2023-04
Thiazole derivatives as potential hiv-1 protease inhibitors
- Authors: Hlongwe, Zola
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Enzyme kinetics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52116 , vital:43427
- Description: Series of compounds were screened using Schrodinger suite (Maestro). The DFT calculations were used for geometry optimization of the ligands using the B3YLYP functional and 6-31G basis set, and these structures were used for docking studies. Maestro was used to predict the activity of thiazole derivatives against HIV-1 protease. The range of estimated inhibition constants for these thiazole derivatives (65 nM-5 μM) indicate moderate to weak activity against HIV-1 protease, given that the activity of current protease inhibitors is typically found have experimental inhibition constants around 0.1-2.0 nM. Twenty compounds were selected based on the docking results and they were synthesized and characterized by NMR, FT-IR and elemental analysis. The cytotoxicity studies were done at two different concentrations (100 μM and 10 μM), using the brine shrimp bioassay. All compounds were highly toxic at 100 μM, with the percentage mortality between 20 to 75%. Eight compounds were selected for the enzyme bioassay based on the results obtained from lower concentration (10 μM). In the enzyme inhibition studies, the profile of HIV-1 activity was done at different inhibitor concentrations (800 μM – 10 μM) by measuring the cleavage of the synthetic substrate (Abz-Thr-lle-PNO2Phe=Gln-Arg-NH2) at excitation wavelength of 345/490 nm using fluorescence. Ligands 5 (unsubstituted derivative), 7 (4-nitro derivative) and 16 (4-methoxy derivative) gave percentage inhibition of 39, 45 and 42%, and this activity was very low compared to the activity of the positive control ritonavir (85% enzyme inhibition). Ligands 8 (4-methoxy derivative) and 12 (4-methoxy derivative) gave enzyme inhibition of 70% and 75%. These results suggest that the presence of the methoxy substituents ii increases activity of these compounds against HIV-1 protease. Most of the compounds gave good IC50 values between 12.5-42.7 nM. The bromo-substituted ligand 7 gave the lowest IC50 (12.5 nM). Ligand 11 also gave a good IC50 value of 14.86 nM. The bromo-substituted derivatives showed to be very active compared to other types of thiazole derivatives. Enzyme kinetics were carried out to compare the inhibition constants obtained via computational modelling. Ligand 7 (4-methoxy derivatives) binds better in the active site of HIV-1 protease than other compounds in Class B, with Ki = 50 nM, Km = 23.8 Nm and Vmax = 83.3 nM/min. The unsubstituted (L5), 4-bromo (L7) and 4-nitro (L8) substituted compounds gave inhibition constants of 100 to 112 nM. The in vitro testing yielded higher activity than that determined in silico. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Hlongwe, Zola
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Enzyme kinetics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52116 , vital:43427
- Description: Series of compounds were screened using Schrodinger suite (Maestro). The DFT calculations were used for geometry optimization of the ligands using the B3YLYP functional and 6-31G basis set, and these structures were used for docking studies. Maestro was used to predict the activity of thiazole derivatives against HIV-1 protease. The range of estimated inhibition constants for these thiazole derivatives (65 nM-5 μM) indicate moderate to weak activity against HIV-1 protease, given that the activity of current protease inhibitors is typically found have experimental inhibition constants around 0.1-2.0 nM. Twenty compounds were selected based on the docking results and they were synthesized and characterized by NMR, FT-IR and elemental analysis. The cytotoxicity studies were done at two different concentrations (100 μM and 10 μM), using the brine shrimp bioassay. All compounds were highly toxic at 100 μM, with the percentage mortality between 20 to 75%. Eight compounds were selected for the enzyme bioassay based on the results obtained from lower concentration (10 μM). In the enzyme inhibition studies, the profile of HIV-1 activity was done at different inhibitor concentrations (800 μM – 10 μM) by measuring the cleavage of the synthetic substrate (Abz-Thr-lle-PNO2Phe=Gln-Arg-NH2) at excitation wavelength of 345/490 nm using fluorescence. Ligands 5 (unsubstituted derivative), 7 (4-nitro derivative) and 16 (4-methoxy derivative) gave percentage inhibition of 39, 45 and 42%, and this activity was very low compared to the activity of the positive control ritonavir (85% enzyme inhibition). Ligands 8 (4-methoxy derivative) and 12 (4-methoxy derivative) gave enzyme inhibition of 70% and 75%. These results suggest that the presence of the methoxy substituents ii increases activity of these compounds against HIV-1 protease. Most of the compounds gave good IC50 values between 12.5-42.7 nM. The bromo-substituted ligand 7 gave the lowest IC50 (12.5 nM). Ligand 11 also gave a good IC50 value of 14.86 nM. The bromo-substituted derivatives showed to be very active compared to other types of thiazole derivatives. Enzyme kinetics were carried out to compare the inhibition constants obtained via computational modelling. Ligand 7 (4-methoxy derivatives) binds better in the active site of HIV-1 protease than other compounds in Class B, with Ki = 50 nM, Km = 23.8 Nm and Vmax = 83.3 nM/min. The unsubstituted (L5), 4-bromo (L7) and 4-nitro (L8) substituted compounds gave inhibition constants of 100 to 112 nM. The in vitro testing yielded higher activity than that determined in silico. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
The use of psychometric test systems as a pre-selection tool for identifying successful harvesting machine operators
- Authors: Schwegman, Kylle
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55246 , vital:51102
- Description: A shift towards fully mechanized forest activities, such as harvesting and, more recently, silviculture, has occurred from the early 2 000’s. The reason for mechanizing these activities differs for each country, although for most countries there is concern relating to the health and safety of forest workers. With mechanization in harvesting, the forest worker has moved away from the physical intensity of having to fell, debranch, debark and cross-cut trees into logs using either an axe or chainsaw, to operating a machine. Studies revolving around the human element (operator) have been conducted specifically relating to the ergonomics of the machines and how operators may influence machine productivity. Results showed that due to the repetitive nature of the work, the operators are exposed to associated stresses for longer periods. Typical injuries associated to these kinds of stressors are whole body vibrations (WBVs), repetitive hand and arm movements, non-neutral body postures and manual lifting, which lead to musculoskeletal symptoms in the lower back, neck and shoulders. However, as machine technology improves so does the ergonomic conditions which are experienced by machine operators. Machine productivity can be influenced by various factors, with the most influential being tree volume. However, a recent study showed that over 40% of variation in machine productivity has been observed amongst different machine operators operating similar machines. The specific reason for these differences has yet to be determined. However, decision making, motivation, planning capacity, concentration, memory, motor coordination, pattern recognition, logic reasoning, and spatial perception are abilities that have been described as important for successful harvesting work. The pre-selection of operators using psychometric and cognitive tests is not new to forestry, although very little information is available relating to the aptitude test known as the Vienna test system as well as the best possible demographic associated with successful harvesting operators. The overall aim of this study was to determine whether the high variation found amongst harvesting machine operators could be reduced initially through a preselection process which involves the use of aptitude tests (Vienna Test System) and demographic questionnaires. A study was implemented in Zululand, South Africa, testing whether there were significant productivity differences between nine machine operators. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Schwegman, Kylle
- Date: 2022-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/55246 , vital:51102
- Description: A shift towards fully mechanized forest activities, such as harvesting and, more recently, silviculture, has occurred from the early 2 000’s. The reason for mechanizing these activities differs for each country, although for most countries there is concern relating to the health and safety of forest workers. With mechanization in harvesting, the forest worker has moved away from the physical intensity of having to fell, debranch, debark and cross-cut trees into logs using either an axe or chainsaw, to operating a machine. Studies revolving around the human element (operator) have been conducted specifically relating to the ergonomics of the machines and how operators may influence machine productivity. Results showed that due to the repetitive nature of the work, the operators are exposed to associated stresses for longer periods. Typical injuries associated to these kinds of stressors are whole body vibrations (WBVs), repetitive hand and arm movements, non-neutral body postures and manual lifting, which lead to musculoskeletal symptoms in the lower back, neck and shoulders. However, as machine technology improves so does the ergonomic conditions which are experienced by machine operators. Machine productivity can be influenced by various factors, with the most influential being tree volume. However, a recent study showed that over 40% of variation in machine productivity has been observed amongst different machine operators operating similar machines. The specific reason for these differences has yet to be determined. However, decision making, motivation, planning capacity, concentration, memory, motor coordination, pattern recognition, logic reasoning, and spatial perception are abilities that have been described as important for successful harvesting work. The pre-selection of operators using psychometric and cognitive tests is not new to forestry, although very little information is available relating to the aptitude test known as the Vienna test system as well as the best possible demographic associated with successful harvesting operators. The overall aim of this study was to determine whether the high variation found amongst harvesting machine operators could be reduced initially through a preselection process which involves the use of aptitude tests (Vienna Test System) and demographic questionnaires. A study was implemented in Zululand, South Africa, testing whether there were significant productivity differences between nine machine operators. , Thesis (PhD) -- Faculty of Science, School of Natural Resource Management, 2022
- Full Text:
- Date Issued: 2022-04
The use of ambient seismic noise to investigate internal changes in a tailings storage facility and to image the subsurface geology in the Cradock area of the Eastern Cape
- Authors: Kunjwa, Thulisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53642 , vital:45690
- Description: Passive seismic interferometry is a process by which ambient noise data recorded at different seismic stations can be cross-correlated to estimate Green's functions. In the past, both surface waves and body waves have successfully been extracted by cross-correlation of ambient noise data on both regional and global scales. Recent advancements in ambient seismic noise techniques have the potential to provide new methods for subsurface imaging and monitoring. The ambient noise data processing procedure divides into four principal phases: (1) single station data preparation, (2) cross-correlation and temporal stacking, (3) measurement of dispersion curves and (4) inversion of dispersion curves to obtain 1-D shear wave profiles and computation of 2-D shear wave velocity cross-section. The purpose of this study is to investigate whether ambient seismic noise can be used to image and detect internal changes within a mine tailings dam wall and to image the subsurface geology of part of the Eastern Cape Karoo near Cradock. In the first experiment, the investigation consisted of continuous ambient noise data recordings over a period of 3 days with 20 three-component short period geophones. The geophones were deployed over a survey wall of roughly 100 m in length at the Harmony Gold mine tailings dam in Welkom. In the second experiment, the investigation consisted of data recordings over a period of 35 days. The geophones were deployed in Cradock. The first phase of the data processing procedure included de-trending, de-meaning and band-pass filtering the data. This was done to ensure that any long period trends associated with instrument glitches are removed from the data. A spectrogram was then computed to view the spectrum of frequencies in the signal and to check if the filter that was designed was able to cut off the unwanted frequencies. The horizontal and vertical components of the ambient noise data were cross-correlated and picked between sensor pairs to create surface wave dispersion curves. Subsequently, the dispersion curves were inverted to estimate the shear wave velocity of the dam wall and subsurface as a function of depth. The computed cross sections of shear wave velocity indicated a low-velocity zone between 2 and 10 m below the surface on the dam wall, this suggested that the phreatic surface is much closer to surface in this area. In the second experiment, the interpolated shear wave velocity profiles indicated that there is a layer of low velocity zone between depths 250 to 300 m below the surface. The cross-correlations were also used to compute group velocity maps from periods 1.5 seconds to 30 seconds. The group velocity maps showed various high and low velocity anomalies. The high velocity zones observed on the eastern section of the map were interpreted as evidence of dolerite intrusions. The low velocity zones observed in the western and southern sections of the map interpreted as Karoo sediments that belong to the Adelaide Subgroup which is dominated by mudstones. , Thesis (MSc) -- Faculty of Science, Department of Geosciences (Geology and Geography), 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Kunjwa, Thulisile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53642 , vital:45690
- Description: Passive seismic interferometry is a process by which ambient noise data recorded at different seismic stations can be cross-correlated to estimate Green's functions. In the past, both surface waves and body waves have successfully been extracted by cross-correlation of ambient noise data on both regional and global scales. Recent advancements in ambient seismic noise techniques have the potential to provide new methods for subsurface imaging and monitoring. The ambient noise data processing procedure divides into four principal phases: (1) single station data preparation, (2) cross-correlation and temporal stacking, (3) measurement of dispersion curves and (4) inversion of dispersion curves to obtain 1-D shear wave profiles and computation of 2-D shear wave velocity cross-section. The purpose of this study is to investigate whether ambient seismic noise can be used to image and detect internal changes within a mine tailings dam wall and to image the subsurface geology of part of the Eastern Cape Karoo near Cradock. In the first experiment, the investigation consisted of continuous ambient noise data recordings over a period of 3 days with 20 three-component short period geophones. The geophones were deployed over a survey wall of roughly 100 m in length at the Harmony Gold mine tailings dam in Welkom. In the second experiment, the investigation consisted of data recordings over a period of 35 days. The geophones were deployed in Cradock. The first phase of the data processing procedure included de-trending, de-meaning and band-pass filtering the data. This was done to ensure that any long period trends associated with instrument glitches are removed from the data. A spectrogram was then computed to view the spectrum of frequencies in the signal and to check if the filter that was designed was able to cut off the unwanted frequencies. The horizontal and vertical components of the ambient noise data were cross-correlated and picked between sensor pairs to create surface wave dispersion curves. Subsequently, the dispersion curves were inverted to estimate the shear wave velocity of the dam wall and subsurface as a function of depth. The computed cross sections of shear wave velocity indicated a low-velocity zone between 2 and 10 m below the surface on the dam wall, this suggested that the phreatic surface is much closer to surface in this area. In the second experiment, the interpolated shear wave velocity profiles indicated that there is a layer of low velocity zone between depths 250 to 300 m below the surface. The cross-correlations were also used to compute group velocity maps from periods 1.5 seconds to 30 seconds. The group velocity maps showed various high and low velocity anomalies. The high velocity zones observed on the eastern section of the map were interpreted as evidence of dolerite intrusions. The low velocity zones observed in the western and southern sections of the map interpreted as Karoo sediments that belong to the Adelaide Subgroup which is dominated by mudstones. , Thesis (MSc) -- Faculty of Science, Department of Geosciences (Geology and Geography), 2021
- Full Text:
- Date Issued: 2021-12
The use of a rapid incineration field test for determining soil organic carbon in the Southern Cape Region
- Authors: Ackhurst, Albert Arthur
- Date: 2014-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53336 , vital:45135
- Description: Knowledge of soil organic carbon levels is important both for agricultural effectiveness and soil carbon sequestration accounting, especially against the backdrop of increased climate change impacts and pressure on food production landscapes. However, current methods for soil carbon determination are expensive, energy intensive, time consuming and potentially hazardous leading to a call for alternative methods, which should be cheap, fast, simple, accurate, safe and usable where resources and soil analysis laboratories are limited. To this end the student invented a novel rapid incineration field test (RIFT) for determining soil organic carbon and tested its validity in this study. This method incorporates principles found in dry combustion as well as loss-on-ignition and quantifying organic carbon through gravimetric analysis. In order to illustrate effectiveness and accuracy it was necessary to correlate RIFT with a reference method, in this instance dry combustion with a Leco device as well as another commonly used indirect method namely the Walkley-Black wet chemical oxidation method. Samples from eleven soil forms were collected from the Southern Cape region and they were subjected to the three testing methods. It was found that RIFT is indeed as effective and in 72% of the soil forms even more effective than Walkley-Black. Furthermore, it was ascertained whether the accuracy of RIFT can be improved by correcting for clay content. The correlation of RIFT with clay % was not very significant and clay % as a variable was therefore not used in this study to obtain further refinement of RIFT predictions. Another finding was also that RIFT illustrated less variability than both the Leco and Walkley-Black methods. Lastly it was ascertained that the RIFT device and methodology is indeed cost effective, energy efficient, fast and safe in terms of the need to use potentially hazardous chemicals. , Thesis (MA) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2014-12
- Authors: Ackhurst, Albert Arthur
- Date: 2014-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53336 , vital:45135
- Description: Knowledge of soil organic carbon levels is important both for agricultural effectiveness and soil carbon sequestration accounting, especially against the backdrop of increased climate change impacts and pressure on food production landscapes. However, current methods for soil carbon determination are expensive, energy intensive, time consuming and potentially hazardous leading to a call for alternative methods, which should be cheap, fast, simple, accurate, safe and usable where resources and soil analysis laboratories are limited. To this end the student invented a novel rapid incineration field test (RIFT) for determining soil organic carbon and tested its validity in this study. This method incorporates principles found in dry combustion as well as loss-on-ignition and quantifying organic carbon through gravimetric analysis. In order to illustrate effectiveness and accuracy it was necessary to correlate RIFT with a reference method, in this instance dry combustion with a Leco device as well as another commonly used indirect method namely the Walkley-Black wet chemical oxidation method. Samples from eleven soil forms were collected from the Southern Cape region and they were subjected to the three testing methods. It was found that RIFT is indeed as effective and in 72% of the soil forms even more effective than Walkley-Black. Furthermore, it was ascertained whether the accuracy of RIFT can be improved by correcting for clay content. The correlation of RIFT with clay % was not very significant and clay % as a variable was therefore not used in this study to obtain further refinement of RIFT predictions. Another finding was also that RIFT illustrated less variability than both the Leco and Walkley-Black methods. Lastly it was ascertained that the RIFT device and methodology is indeed cost effective, energy efficient, fast and safe in terms of the need to use potentially hazardous chemicals. , Thesis (MA) -- Faculty of Science, School of Natural Resource Management, 2021
- Full Text:
- Date Issued: 2014-12
The synthesis, empirical and theoretical studies of various (N→B) diarylborinate esters
- Authors: Manana, Pholani Sakhile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53869 , vital:46027
- Description: A series of core-functionalized borinic acids was synthesized from Grignard reagents and tributylborate and reacted with ethanolamine, amino acids, 2-pyridylmethanol as well as 2-(ethyl amino ethanol). Among the borinic acids synthesized were the ones bearing: para-(2, 15, 16, 22, 27)-methyl, (3, 20, 25)-chloro, (4, 23, 26)-fluoro, (5)-methoxy; meta-(7, 17)-methyl, (9)-fluoro; ortho-(6)-methyl, (8)-chloro, (10, 18, 19)-methoxy substituents on their respective aromatic systems. All compounds obtained by condensation of the borinic acids with the aforementioned nitrogen-containing substrates were characterized structurally by means of diffraction studies based on single crystals and found to constitute chelate esters/amides featuring covalent B-O and dative N→B bonds. The chelate compounds researched in this study could be classified into four families and represent the compounds: ethanol amine: (1) 2,2-diphenyl-1,3,2-oxazaborolidines, (2) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (3) 2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (4) 2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (5) 2,2-bis(p-methoxyphenyl)-1,3,2-oxazaborolidines, (6) 2,2-bis(o-tolyl)-1,3,2-oxazaborolidines, (7) 2,2-bis(m-tolyl)-1,3,2-oxazaborolidines, (8) 2,2-bis(o-chlorophenyl)-1,3,2-oxazaborolidines, (9) 2,2-bis(m-fluorophenyl)-1,3,2-oxazaborolidines, (10) 2,2-bis(o-methoxyphenyl)-1,3,2-oxazaborolidines. α-amino acids : (14) 4-methyl-2,2-diphenyl-1,3,2-oxazaborolidin-5-ones, (15) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (16) 4-methyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (17) 4-isopropyl-2,2-bis(m-tolyl)-1,3,2-oxazaborolidin-5-ones, (18) 4-methyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (19) 4-acetamidyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (20) 4-phenylethane-2,2-bis(p-chlorophenyl)-1,3,2 oxazaborolidin-5-ones. 2-pyridylmethanol: (21) 1,3-hydroxypyridyl-2,2-diphenyl 1,3,2-oxazaborolidines, (22) 1,3-hydroxypyridyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (23) 1,3-hydroxypyridyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines 2-(ethyl amino ethanol): (24) 3-ethyl-2,2-diphenyl-1,3,2-oxazaborolidines, (25) 3-ethyl-2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (26) 3-ethyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (27) 3-ethyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines. Apart from structural studies in the solid state, the compounds were also characterized by means of multinuclear NMR spectroscopy (1H, 11B, 13C) as well as UV/vis and FTIR. The typical 11B resonances were found in the range of (4-10 ppm). A series of characteristic metrical parameters for the compounds in the solid state as well as typical NMR shifts for the chelate target molecules was established that allowed for the determination of the coordination induced shift. The carbon atom bonded to the oxygen atom shifted upfield, while the carbon atom bonded to the nitrogen atom shifted downfield. Factors mentioned in the literature that has an influence on the hydrolytic stability on the heterocyclic borinate motif have been taken into consideration and verified for the systems researched in this study. The substitution at the nitrogen atom with one ethyl group caused the greatest increases in the N→B bond length (27) 1.714 Å, due to the increase in the nitrogen Lewis basicity, making it the least hydrolytically stable, these include compounds (24-26). Furthermore, DFT calculations were performed by employing Becke’s three parameter hybrid exchange functional with Lee–Yang–Parr functional (B3LYP) method using the Gaussian 16 program package (Rev. B01) employing the basis set 6-311++G(d,p), to corroborate and correlate the experimental findings, which gave a general R-squared value of 0.9978 for calculated vs experimental 13C chemical shifts. Thermal properties are recorded for select compounds, indicating the ΔH and the melting points. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Manana, Pholani Sakhile
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/53869 , vital:46027
- Description: A series of core-functionalized borinic acids was synthesized from Grignard reagents and tributylborate and reacted with ethanolamine, amino acids, 2-pyridylmethanol as well as 2-(ethyl amino ethanol). Among the borinic acids synthesized were the ones bearing: para-(2, 15, 16, 22, 27)-methyl, (3, 20, 25)-chloro, (4, 23, 26)-fluoro, (5)-methoxy; meta-(7, 17)-methyl, (9)-fluoro; ortho-(6)-methyl, (8)-chloro, (10, 18, 19)-methoxy substituents on their respective aromatic systems. All compounds obtained by condensation of the borinic acids with the aforementioned nitrogen-containing substrates were characterized structurally by means of diffraction studies based on single crystals and found to constitute chelate esters/amides featuring covalent B-O and dative N→B bonds. The chelate compounds researched in this study could be classified into four families and represent the compounds: ethanol amine: (1) 2,2-diphenyl-1,3,2-oxazaborolidines, (2) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (3) 2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (4) 2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (5) 2,2-bis(p-methoxyphenyl)-1,3,2-oxazaborolidines, (6) 2,2-bis(o-tolyl)-1,3,2-oxazaborolidines, (7) 2,2-bis(m-tolyl)-1,3,2-oxazaborolidines, (8) 2,2-bis(o-chlorophenyl)-1,3,2-oxazaborolidines, (9) 2,2-bis(m-fluorophenyl)-1,3,2-oxazaborolidines, (10) 2,2-bis(o-methoxyphenyl)-1,3,2-oxazaborolidines. α-amino acids : (14) 4-methyl-2,2-diphenyl-1,3,2-oxazaborolidin-5-ones, (15) 2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (16) 4-methyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidin-5-ones, (17) 4-isopropyl-2,2-bis(m-tolyl)-1,3,2-oxazaborolidin-5-ones, (18) 4-methyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (19) 4-acetamidyl-2,2-bis(o-methoxyphenyl)-1,3,2- oxazaborolidin-5-ones, (20) 4-phenylethane-2,2-bis(p-chlorophenyl)-1,3,2 oxazaborolidin-5-ones. 2-pyridylmethanol: (21) 1,3-hydroxypyridyl-2,2-diphenyl 1,3,2-oxazaborolidines, (22) 1,3-hydroxypyridyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines, (23) 1,3-hydroxypyridyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines 2-(ethyl amino ethanol): (24) 3-ethyl-2,2-diphenyl-1,3,2-oxazaborolidines, (25) 3-ethyl-2,2-bis(p-chlorophenyl)-1,3,2-oxazaborolidines, (26) 3-ethyl-2,2-bis(p-fluorophenyl)-1,3,2-oxazaborolidines, (27) 3-ethyl-2,2-bis(p-tolyl)-1,3,2-oxazaborolidines. Apart from structural studies in the solid state, the compounds were also characterized by means of multinuclear NMR spectroscopy (1H, 11B, 13C) as well as UV/vis and FTIR. The typical 11B resonances were found in the range of (4-10 ppm). A series of characteristic metrical parameters for the compounds in the solid state as well as typical NMR shifts for the chelate target molecules was established that allowed for the determination of the coordination induced shift. The carbon atom bonded to the oxygen atom shifted upfield, while the carbon atom bonded to the nitrogen atom shifted downfield. Factors mentioned in the literature that has an influence on the hydrolytic stability on the heterocyclic borinate motif have been taken into consideration and verified for the systems researched in this study. The substitution at the nitrogen atom with one ethyl group caused the greatest increases in the N→B bond length (27) 1.714 Å, due to the increase in the nitrogen Lewis basicity, making it the least hydrolytically stable, these include compounds (24-26). Furthermore, DFT calculations were performed by employing Becke’s three parameter hybrid exchange functional with Lee–Yang–Parr functional (B3LYP) method using the Gaussian 16 program package (Rev. B01) employing the basis set 6-311++G(d,p), to corroborate and correlate the experimental findings, which gave a general R-squared value of 0.9978 for calculated vs experimental 13C chemical shifts. Thermal properties are recorded for select compounds, indicating the ΔH and the melting points. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
The synthesis of anastrazole intermediates using continuous flow systems
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
- Authors: Tanyi, Sam Tambi
- Date: 2021-12
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/54116 , vital:46304
- Description: In this study, the continuous flow synthesis of anastrozole intermediates were investigated using mesitylene as starting material. Anastrozole is an important drug used for the treatment of breast cancer. In the first step, mesitylene was brominated using N-bromosuccinimide to obtain 3,5-bis(bromomethyl)toluene. Selectivity became an issue due to the formation of two by-products; namely 1,3,5-tris(bromomethyl) benzene (the tribrominated by-product) and 1-(bromomethyl)-3,5-dimethylbenzene (the monobrominated by-product). Since the reaction parameters can be more precisely controlled in flow chemistry systems, we were able to optimize the formation the desired product 3,5-bis(bromomethyl)toluene. The reaction was initially optimized ina 15μLChemtrix glass micro reactor resulting in 100%conversion with 95%selectivity towards the desired product 3,5-bis(bromomethyl)toluenein 15 seconds, with a throughput of 0.006 g/h. The reaction was then scaled up in a 1.7 mLLTF reactor, equally yielding 100%conversion with 95%selectivityin 4minutes, with a throughput of2.01g/h. The bromination of mesitylene was also attempted in a homemade photochemical reactor consisting of a 3.02 polytetrafluoroethylene coil reactor and BLE-6T365 UV lamp. In this photochemical reactor, although 100%conversionwas again obtained only75%selectivity was achieved in 20minutes, with a throughput of 0.025g/h. This drop in selectivity was attributed to poorer mixing in the larger polytetrafluoroethylene coil reactor and possibly insufficient light penetration. The next step, involving the cyanation of 3,5-bis(bromomethyl)toluene to obtain 2,2'-(5-methyl-1,3-phenylene) diacetonitrilegave 100%conversion in 1 minute at 190 °C in a 1.7 mLLTFreactor, with a throughput of 5.2g/h. The subsequent methylation of 3,5-bis(cyanomethyl)toluene to obtain3,5-bis(1-cyano-1-methylethyl) toluene was investigated using a1mLpolytetrafluoroethylenecoil reactor, ultimatelyachieving99%conversionat40 °Cin 8minutes, with a throughput of 0.045g/h. Next, the bromination of3,5-bis(1-cyano-1-methylethyl)toluene using N-bromosuccinimideto yield 2,2'-(5-bromomethyl-1,3-phenylene)di(2-methyl propionitrile) gave 100%conversion at 120 °C in 4 minutes, with a throughput of 0.35g/h. Lastly, the multistep synthesis of 3,5-bis(cyanomethyl)toluene was done in two integrated 1.7 mLLTF reactors, using the predetermined optimum conditions to achieve 94%conversion towards 3,5-bis(cyanomethyl)toluene with a total r , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text:
- Date Issued: 2021-12
The quantification of Pinus patula recovery and productivity of manually orientated biomass collection in post mechanised full tree and semi mechanised tree length harvesting operations
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Ncongwane, Thandekile Hazel
- Date: 2023-04
- Subjects: Pinus patula – south Africa , Forest ecology , Biomass energy
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61511 , vital:70692
- Description: The use of biomass as an alternate source of energy has grown in popularity. Different types of biomass are obtained from a variety of sources including natural forests, forestry plantations and agriculture residues. However, forestry residues have been identified as the most promising source, due to the wide variety of plant products including leaves, twigs, branches, merchantable stem, stumps and roots. The main sources of plantation forest biomass are residues from thinning, clearfell and conventional products such as pulpwood and sawn timber operations. These residues can accumulate between 4.3 to 9.4 billion tonnes annually around the world. The biomass availability in plantation forests has led to the development of different harvesting systems to help collect the products from infield to sawmill. Biomass harvesting has mainly been achieved through mechanised systems because of their high yields. However, the use of manual systems has been neglected due to technical limitations and financial viability. Thus, in South Africa, there is no scientific research looking at manual systems of collecting biomass from plantations. Because of this, different forestry stakeholders, including small growers and contractors using manual systems for biomass harvesting have limited knowledge regarding what to expect in terms of recoverable amounts, productivity and cost. This research examines the productivity of the manual biomass collection and the quantification of recovered and unrecovered residues after mechanised full tree (FT) and semi mechanised tree length (TL) harvesting operations in Pinus patula compartments. A total number of 8 plots with +/-200 standing trees were marked in each system. The diameter and height of all marked trees were measured to determine tree volume. Moreover, the quantification of recoverable woody biomass was determined, where after, a residues assessment method using plots and line transects was used to determine the amount of unrecovered residues. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04