The effect of Cannabis extract on the morphological and metabolic characteristics of various fat depots in diet-induced Obese and STZ-induced male wistar rats
- Authors: Ramlugon, Sonaal
- Date: 2023-04
- Subjects: Rats as laboratory animals , Diabetes in practice , Cannabis -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61282 , vital:70044
- Description: To investigate the potential anti-diabetic/obesity properties of oral cannabis administration in an obese and streptozotocin (STZ)-induced diabetic rat model, as well as an obese rat model, and to determine the mechanism of action, with a focus on the peritoneal and intramuscular fat depots. Experimental Design: Obese and STZ-induced diabetic rats were allocated a high fat diet (HFD) and intraperitoneally injected with STZ to mimic an obese and diabetic state. The rats were then orally administered cannabis extract (CE) of 1.25, 2.5 and 5.0 mg/kg body weight (relative to tetrahydrocannabinol (THC) content) or metformin as a positive control. For the obese rat model, the rats were allocated either a high carbohydrate diet (HCD) or high fat diet (HFD) and orally administered with cannabis extract of 1.25 mg/kg body weight (relative to THC content). Weight, blood and insulin-resistant parameters of the rats were monitored. The mitochondrial to genomic DNA ratio (MT:18S DNA), average adipocyte area of the various adipose tissues, citrate synthase and carnitine palmitoyltransferase 1 (CPT1) enzyme activities of the peritoneal and intramuscular fat were measured. Gene expression levels of uncoupling protein 1 (UCP1), cell-death inducing DNA fragmentation factor alpha like effector-a (Cidea), perilipin, hormone-sensitive lipase (HSL) and mitochondrial transcription factor A (TFAM) were measured in peritoneal fat, intramuscular fat and brown adipose tissue (BAT). Main Findings: Obese and STZ-induced diabetic rat model: Due to the biphasic nature of cannabinoids, cannabis dosage plays an important role in the observed effects. CE1.25 was the only cannabis treatment effective in improving the insulinresistant parameters of the rats unlike the other higher cannabis concentrations (CE2.5 and CE5.0). In the peritoneal fat, CE1.25 increased MT:18S DNA, increased citrate synthase activity, and decreased the average adipocyte area when compared to the STZ group. CE1.25 also induced fat beigeing by upregulating gene expression levels of UCP1 and Cidea. XIX Furthermore, an increase in gene expression levels of perilipin, HSL, and TFAM showed increased fat mobilization and metabolic activity. In the intramuscular fat, CE1.25 also reduced the average adipocytes area. However, a different mechanism of action was observed where CE1.25 did not induce fat beigeing, but instead increased both citrate synthase and CPT1 enzyme activities and gene expression levels of HSL, thereby indicating increased fat oxidation and mitochondrial activity. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Ramlugon, Sonaal
- Date: 2023-04
- Subjects: Rats as laboratory animals , Diabetes in practice , Cannabis -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61282 , vital:70044
- Description: To investigate the potential anti-diabetic/obesity properties of oral cannabis administration in an obese and streptozotocin (STZ)-induced diabetic rat model, as well as an obese rat model, and to determine the mechanism of action, with a focus on the peritoneal and intramuscular fat depots. Experimental Design: Obese and STZ-induced diabetic rats were allocated a high fat diet (HFD) and intraperitoneally injected with STZ to mimic an obese and diabetic state. The rats were then orally administered cannabis extract (CE) of 1.25, 2.5 and 5.0 mg/kg body weight (relative to tetrahydrocannabinol (THC) content) or metformin as a positive control. For the obese rat model, the rats were allocated either a high carbohydrate diet (HCD) or high fat diet (HFD) and orally administered with cannabis extract of 1.25 mg/kg body weight (relative to THC content). Weight, blood and insulin-resistant parameters of the rats were monitored. The mitochondrial to genomic DNA ratio (MT:18S DNA), average adipocyte area of the various adipose tissues, citrate synthase and carnitine palmitoyltransferase 1 (CPT1) enzyme activities of the peritoneal and intramuscular fat were measured. Gene expression levels of uncoupling protein 1 (UCP1), cell-death inducing DNA fragmentation factor alpha like effector-a (Cidea), perilipin, hormone-sensitive lipase (HSL) and mitochondrial transcription factor A (TFAM) were measured in peritoneal fat, intramuscular fat and brown adipose tissue (BAT). Main Findings: Obese and STZ-induced diabetic rat model: Due to the biphasic nature of cannabinoids, cannabis dosage plays an important role in the observed effects. CE1.25 was the only cannabis treatment effective in improving the insulinresistant parameters of the rats unlike the other higher cannabis concentrations (CE2.5 and CE5.0). In the peritoneal fat, CE1.25 increased MT:18S DNA, increased citrate synthase activity, and decreased the average adipocyte area when compared to the STZ group. CE1.25 also induced fat beigeing by upregulating gene expression levels of UCP1 and Cidea. XIX Furthermore, an increase in gene expression levels of perilipin, HSL, and TFAM showed increased fat mobilization and metabolic activity. In the intramuscular fat, CE1.25 also reduced the average adipocytes area. However, a different mechanism of action was observed where CE1.25 did not induce fat beigeing, but instead increased both citrate synthase and CPT1 enzyme activities and gene expression levels of HSL, thereby indicating increased fat oxidation and mitochondrial activity. , Thesis (PhD) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Distinguishing elephant induced thicket degradation and climate related factors in Addo Elephant National Park, Eastern Cape, South Africa
- Authors: Mapheto, Tlhologelo James
- Date: 2023-04
- Subjects: Elephant – Behaviour -- South Africa -- Addo Elephant National Park , Wildlife conservation -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60753 , vital:66741
- Description: The Addo Elephant National Park (AENP) is an ecologically sensitive environment where the increase in elephant population, especially in a changing climate is a recipe for landscape degradation and biodiversity loss. The Park is situated in the drought prone Eastern Cape Province, however, the effects of drought on thicket vegetation is less understood. This study aimed to distinguish elephant-induced thicket degradation from the effects of climatic factors, using remote sensing, GIS, and statistical techniques. To characterise and map vegetation conditions of the reserve temporal series Landsat imagery (n = 22) from 1998 to 2018 were analysed. Vegetation states were determined using Normalised Difference Vegetation Index (NDVI) derived from the growing season of the study period. Using supervised per-pixel image classification technique, the NDVI values characterized into distinct land cover classes viz (1) Intact Thicket, (2) Transformed Thicket, (3) Degraded Thicket, (4) Bare Ground and (6) Water Bodies. Post-classification change detection and landscape fragmentation analysis was performed. Climatic data were obtained from existing weather stations and raster surface of accumulated rainfall and mean maximum temperature were developed using the Inverse Distance Weighting (IDW). Time series analysis was implemented on the NDVI and climatic condition data by plotting annual measures to indicate variable trends. Temporal trend analysis was performed on the NDVI data using the nonparametric Mann-Kendall trend analysis test to indicate thicket vegetation condition improvement and general degradation. The Residual Trend (RESTREND) approach was employed to remove the effect of rainfall on vegetation productivity. This involved using the Ordinary Least Square regression functionality in ArcMap to compute the relationship between ∑NDVI and accumulated rainfall for every pixel for the study period. The products of the regression were assessed using Pearson’s Correlation (r) at a significance level of 90% (p-value ≤ 0.1) to distinguish strong relationships. Overlay analysis was performed, using the NDVI trend slope and the correlation coefficient (r) raster surfaces, to model vegetation dynamics influenced by elephant activities. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Mapheto, Tlhologelo James
- Date: 2023-04
- Subjects: Elephant – Behaviour -- South Africa -- Addo Elephant National Park , Wildlife conservation -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60753 , vital:66741
- Description: The Addo Elephant National Park (AENP) is an ecologically sensitive environment where the increase in elephant population, especially in a changing climate is a recipe for landscape degradation and biodiversity loss. The Park is situated in the drought prone Eastern Cape Province, however, the effects of drought on thicket vegetation is less understood. This study aimed to distinguish elephant-induced thicket degradation from the effects of climatic factors, using remote sensing, GIS, and statistical techniques. To characterise and map vegetation conditions of the reserve temporal series Landsat imagery (n = 22) from 1998 to 2018 were analysed. Vegetation states were determined using Normalised Difference Vegetation Index (NDVI) derived from the growing season of the study period. Using supervised per-pixel image classification technique, the NDVI values characterized into distinct land cover classes viz (1) Intact Thicket, (2) Transformed Thicket, (3) Degraded Thicket, (4) Bare Ground and (6) Water Bodies. Post-classification change detection and landscape fragmentation analysis was performed. Climatic data were obtained from existing weather stations and raster surface of accumulated rainfall and mean maximum temperature were developed using the Inverse Distance Weighting (IDW). Time series analysis was implemented on the NDVI and climatic condition data by plotting annual measures to indicate variable trends. Temporal trend analysis was performed on the NDVI data using the nonparametric Mann-Kendall trend analysis test to indicate thicket vegetation condition improvement and general degradation. The Residual Trend (RESTREND) approach was employed to remove the effect of rainfall on vegetation productivity. This involved using the Ordinary Least Square regression functionality in ArcMap to compute the relationship between ∑NDVI and accumulated rainfall for every pixel for the study period. The products of the regression were assessed using Pearson’s Correlation (r) at a significance level of 90% (p-value ≤ 0.1) to distinguish strong relationships. Overlay analysis was performed, using the NDVI trend slope and the correlation coefficient (r) raster surfaces, to model vegetation dynamics influenced by elephant activities. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
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
An investigation of alternative separation strategies for common chemical mixtures by means of host-guest chemistry protocols with host compounds N,N′- bis(5-phenyl-5-dibenzo[a,d]cycloheptenyl)ethylenediamine and N,N’-bis(5-phenyl-10,11- dihydro-5-dibenzo[a,d]cycloheptenyl)ethylenediamine
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Barton, Danica Brione
- Date: 2023-04
- Subjects: Ethylenediaminetetraacetic acid -- South Africa , Enzymes –Analysis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61176 , vital:69791
- Description: In this work, the selectivity behaviour of two host compounds, namely N,N’-bis(5-phenyl-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H1) and N,N’-bis(5-phenyl-10,11-dihydro-5- ibenzo[a,d]cycloheptenyl)ethylenediamine (H2), was assessed in mixtures of difficult-toseparate compounds, including the xylenes and ethylbenzene, pyridine and methylpyridines, and anisole and methylanisoles. These host compounds were synthesized using Grignard addition reactions with phenylmagnesium bromide on dibenzo[a,d]cyclohepten-5-one and 10,11- dihydrodibenzo[a,d]cyclohepten-5-one, respectively. The resultant alcohols were treated with perchloric acid to form the corresponding perchlorate salts, which were then reacted with ethylenediamine to afford the required H1 and H2 host compounds. Yields were 95 ad 52% for this final step in each case. An investigation of the conformations, both from experiment (using single crystal X-ray diffractometry (SCXRD) on the apohost compound) and computational calculations was undertaken. Unfortunately, H1 always crystallized out as a powder unless this host compound formed a complex with a guest species, and so could not be subjected to SCXRD analysis as apohost alone. However, a single crystal structure for apohost H2 was successfully obtained and compared with computational data from a previous investigation. It was observed that the conformation of apohost H2 compared favourably with that of the lowest energy conformer from that work. In single solvent recrystallization experiments with o-, m-, p-xylene (o-Xy, m-Xy, p-Xy) and ethylbenzene (EB), both H1 and H2 formed complexes with only one of the four guest species, namely p-Xy and o-Xy, respectively. The host:guest (H:G) ratios were 1:1 for both of these complexes. In the equimolar guest/guest competition experiments, inclusion complexes only formed when p-Xy or o-Xy, respectively, were present in the mixtures; if p-Xy (for experiments with H1) or o-Xy (H2) was absent from these mixtures, only apohost was recovered from the glass vessels. Three selectivity profiles were constructed for each of these host compounds, in which each one was recrystallized from binary mixed guests in various proportions. These demonstrated an overwhelming preference of H1 for p-Xy and H2 for o-Xy, which concurred with the results from the equimolar experiments. Thermal analysis using H1∙p-Xy revealed that this complex was unstable at ambient conditions, while SCXRD explained this observation: this complex may be defined as a true clathrate since no host‧‧‧guest interactions were identified at all, and the guest was retained in the complex by means of steric factors alone. Furthermore, the guest molecules resided in wide open channels that may have facilitated the guest release process. H2∙o-Xy, on the other hand, was stable at room temperature, and the guest release event only commenced at 69.7 °C (Ton). This too was explained by SCXRD analyses in that interactions between host and guest species were observed in this case. Additionally, the guest molecules were housed in discrete cages, which made their escape more challenging compared with p-Xy in H1∙p-Xy. It was concluded that, in this guest series, both of the host compounds would be effective as separatory tools employing host-guest chemistry protocols due to their remarkable selectivities for p-Xy (H1) and o-Xy (H2). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
An exploration of the Participatory Guarantee System (PGS) facilitating the growth and certification of small-scale organic farmers: Giyani, Garden Route and Overberg case studies
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
The influence of site characteristics on growth and wood properties of Pinus radiata and Pinus elliottii in the Southern and Eastern Cape forestry regions of South Africa
- Authors: Sigcau, Chulumanco
- Date: 2023-04
- Subjects: Forests and forestry -- Environmental aspects , Pine – Growth -- South Africa , Pinus radiata
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61234 , vital:69828
- Description: The intensive nature of plantation forestry in South Africa requires efficiency and financial viability in production systems, amidst a complex growing environment subjected to changing macro-climatic patterns. The success of plantation forestry operations depends, amongst others, on our understanding of tree growth and wood formation patterns in response to variable growing conditions in both space and time. This study was conducted on the two most commonly used species in the southern and Eastern Cape forestry regions, i.e., Pinus radiata and P. elliottii. The region is regarded as highly suitable for plantation forestry in terms of climatic conditions, but soil characteristics pose several challenges due to nutritional disorders and poor drainage. The study focused on investigating the influence of both soil and climatic conditions on the growth and Wood Density properties of the two species, and to establish functional relationships where possible. The two species showed comparable growth rates at the reference age of 13 years on the range of sites sampled in the study area. An analysis of variance showed greater differences in Site Index between than within sample plots, pointing towards the possible influence of site on growth variation. Correlations between climatic variables and the growth of both species were generally weak and contradictory. Possible reasons for this phenomenon are discussed. It is proposed that the general favourable climatic profile of the region and hydromorphic nature of soils reduce the chances of significant correlations between variables influencing moisture availability and tree growth. The analysis of correlations between soil parameters and tree growth revealed some influence of soil organic C and Na on the growth of P. elliottii. This is discussed in terms of our understanding of the influence of soil parent material and soil ecology. The absence of any correlations between soil chemical parameters and the growth of P. radiata was conspicuous. This is in contradiction with earlier studies on the species in the region and can possibly be explained in terms of the site-specific fertilizing policy of the industry, as well as the less diverse range of sites sampled than in the past, which can mask or reduce nutrient limitations for tree growth. However, P. radiata did show a high level of sensitivity towards effective soil depth. Site-quality prediction models are proposed for the two species, but with variable application value due to the limited options of significant control variables that can be considered for inclusion in the models. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Sigcau, Chulumanco
- Date: 2023-04
- Subjects: Forests and forestry -- Environmental aspects , Pine – Growth -- South Africa , Pinus radiata
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61234 , vital:69828
- Description: The intensive nature of plantation forestry in South Africa requires efficiency and financial viability in production systems, amidst a complex growing environment subjected to changing macro-climatic patterns. The success of plantation forestry operations depends, amongst others, on our understanding of tree growth and wood formation patterns in response to variable growing conditions in both space and time. This study was conducted on the two most commonly used species in the southern and Eastern Cape forestry regions, i.e., Pinus radiata and P. elliottii. The region is regarded as highly suitable for plantation forestry in terms of climatic conditions, but soil characteristics pose several challenges due to nutritional disorders and poor drainage. The study focused on investigating the influence of both soil and climatic conditions on the growth and Wood Density properties of the two species, and to establish functional relationships where possible. The two species showed comparable growth rates at the reference age of 13 years on the range of sites sampled in the study area. An analysis of variance showed greater differences in Site Index between than within sample plots, pointing towards the possible influence of site on growth variation. Correlations between climatic variables and the growth of both species were generally weak and contradictory. Possible reasons for this phenomenon are discussed. It is proposed that the general favourable climatic profile of the region and hydromorphic nature of soils reduce the chances of significant correlations between variables influencing moisture availability and tree growth. The analysis of correlations between soil parameters and tree growth revealed some influence of soil organic C and Na on the growth of P. elliottii. This is discussed in terms of our understanding of the influence of soil parent material and soil ecology. The absence of any correlations between soil chemical parameters and the growth of P. radiata was conspicuous. This is in contradiction with earlier studies on the species in the region and can possibly be explained in terms of the site-specific fertilizing policy of the industry, as well as the less diverse range of sites sampled than in the past, which can mask or reduce nutrient limitations for tree growth. However, P. radiata did show a high level of sensitivity towards effective soil depth. Site-quality prediction models are proposed for the two species, but with variable application value due to the limited options of significant control variables that can be considered for inclusion in the models. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
Continuous flow synthesis of a key intermediate towards the antidiabetic drug repaglinide
- Authors: Williams, Arushan
- Date: 2023-04
- Subjects: Diabetes -- Miscellanea -- South Africa , Diabetes –Treatment
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61064 , vital:69715
- Description: Across the world, diabetes is one of the leading causes of deaths attributed to noncommunicable diseases (NCDs). In Africa, a huge proportion of African countries’ annual healthcare budgets are consumed by diabetes (7 %) with many already experiencing healthcare budget deficits. The prevalence of diabetes is rapidly growing and threatens the economic productivity and livelihood of many families within the region. The world leaders have invested heavily in reducing the pandemic by focusing on increasing the availability of affordable essential medicines in developing countries. The majority of diabetes cases are due to type 2 diabetes (90 %) and may be treated using oral hypoglycaemic drugs (OHDs). Repaglinide (REP) is a non-sulfonylurea insulin secretagogue (meglitinide) with greater HbA1c reduction than metformin in newly onset type 2 diabetic patients, however due to the high price of REP outside Asia, cheaper and less effective OHDs are prescribed to patients. Many of the reported synthetic routes towards REP utilize a key intermediate, 2-(3-ethoxy-4- iethoxycarbonyl)phenyl)acetic acid. The key intermediate contributes significantly to the price of REP as many of the intermediate’s synthetic routes suffer from long reaction times, low yields and industrial complex approaches. Therefore, this has prompted us to investigate an efficient process towards the synthesis of 2-(3-ethoxy-4-(ethoxycarbonyl)phenyl)acetic acid using multiple continuous flow systems. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Williams, Arushan
- Date: 2023-04
- Subjects: Diabetes -- Miscellanea -- South Africa , Diabetes –Treatment
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61064 , vital:69715
- Description: Across the world, diabetes is one of the leading causes of deaths attributed to noncommunicable diseases (NCDs). In Africa, a huge proportion of African countries’ annual healthcare budgets are consumed by diabetes (7 %) with many already experiencing healthcare budget deficits. The prevalence of diabetes is rapidly growing and threatens the economic productivity and livelihood of many families within the region. The world leaders have invested heavily in reducing the pandemic by focusing on increasing the availability of affordable essential medicines in developing countries. The majority of diabetes cases are due to type 2 diabetes (90 %) and may be treated using oral hypoglycaemic drugs (OHDs). Repaglinide (REP) is a non-sulfonylurea insulin secretagogue (meglitinide) with greater HbA1c reduction than metformin in newly onset type 2 diabetic patients, however due to the high price of REP outside Asia, cheaper and less effective OHDs are prescribed to patients. Many of the reported synthetic routes towards REP utilize a key intermediate, 2-(3-ethoxy-4- iethoxycarbonyl)phenyl)acetic acid. The key intermediate contributes significantly to the price of REP as many of the intermediate’s synthetic routes suffer from long reaction times, low yields and industrial complex approaches. Therefore, this has prompted us to investigate an efficient process towards the synthesis of 2-(3-ethoxy-4-(ethoxycarbonyl)phenyl)acetic acid using multiple continuous flow systems. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
An evaluation of the effectiveness of area-based conservation intervention in avoiding biodiversity loss in South Africa
- Authors: Van Straten, Maurice Oswald
- Date: 2023-04
- Subjects: Soil conservation -- South Africa , Livestock farms – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61132 , vital:69765
- Description: Habitat degradation, livestock farming, crop cultivation, rangeland overutilization and veld mismanagement are among the factors causing biodiversity loss worldwide. Rangelands in arid and semi-arid environments are no exception, as they are under stress from conversion into cropland and pressure from livestock farming. In these arid areas, rainfall is unpredictable and plant recruitment levels low, resulting in veld rehabilitation being a potentially expensive and time-consuming undertaking for landowners. Landowners implement different rehabilitation methods to increase overall vegetation cover and prevent further soil and vegetation degradation. These rehabilitation methods may include the creation of micro-catchments, mulching, brushpacking, ripping, geotextiles, stone cobbling and erosion control fences, individually or in combination with the addition of reseeding, replanting, and use of manure or fertilizer to supplement land rehabilitation. This study investigated the significance of three rehabilitation methods (hollows, brush packing and a combination of these two methods) on water infiltration rates, soil moisture content, and vegetation canopy cover with associated growth form canopy cover over a period of 17 months (March 2021 to August 2022). This study showed that rehabilitation methods implemented had no significant impact on water infiltration rates and vegetation canopy cover. However, rehabilitation methods had a significant impact on soil moisture content. The use of a hollows is recommended when attempting to increase the soil moisture content percentage when performing rehabilitation. Overall vegetation canopy cover is influenced more by seasonal changes than by the rehabilitation methods implemented. This study indicated that the creation of micro-catchments is an effective rehabilitation method to use in an arid area, as it promotes vegetation establishment and growth. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management , 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Van Straten, Maurice Oswald
- Date: 2023-04
- Subjects: Soil conservation -- South Africa , Livestock farms – South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61132 , vital:69765
- Description: Habitat degradation, livestock farming, crop cultivation, rangeland overutilization and veld mismanagement are among the factors causing biodiversity loss worldwide. Rangelands in arid and semi-arid environments are no exception, as they are under stress from conversion into cropland and pressure from livestock farming. In these arid areas, rainfall is unpredictable and plant recruitment levels low, resulting in veld rehabilitation being a potentially expensive and time-consuming undertaking for landowners. Landowners implement different rehabilitation methods to increase overall vegetation cover and prevent further soil and vegetation degradation. These rehabilitation methods may include the creation of micro-catchments, mulching, brushpacking, ripping, geotextiles, stone cobbling and erosion control fences, individually or in combination with the addition of reseeding, replanting, and use of manure or fertilizer to supplement land rehabilitation. This study investigated the significance of three rehabilitation methods (hollows, brush packing and a combination of these two methods) on water infiltration rates, soil moisture content, and vegetation canopy cover with associated growth form canopy cover over a period of 17 months (March 2021 to August 2022). This study showed that rehabilitation methods implemented had no significant impact on water infiltration rates and vegetation canopy cover. However, rehabilitation methods had a significant impact on soil moisture content. The use of a hollows is recommended when attempting to increase the soil moisture content percentage when performing rehabilitation. Overall vegetation canopy cover is influenced more by seasonal changes than by the rehabilitation methods implemented. This study indicated that the creation of micro-catchments is an effective rehabilitation method to use in an arid area, as it promotes vegetation establishment and growth. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management , 2023
- Full Text:
- Date Issued: 2023-04
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
An evaluation of the effectiveness of area-based conservation interventions in avoiding biodiversity loss in South Africa
- Authors: Von Staden, Lize
- Date: 2023-04
- Subjects: Environmental policy , Conservation of natural resources -- Government policy -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61115 , vital:69762
- Description: Counterfactual impact evaluation studies form an important evidence base for the effectiveness of conservation projects, programs, and policies (collectively referred to as conservation interventions). In South Africa, counterfactual impact evaluation methods have rarely been applied to local conservation interventions, and therefore evidence for the effectiveness of key strategic national conservation approaches is lacking. This study evaluated three area-based interventions that together aim to avoid the loss of areas most important for the persistence of biodiversity in the terrestrial realm as evidence towards the effectiveness of South Africa’s landscape approach to biodiversity conservation. The first intervention, South Africa’s National Protected Area Expansion Strategy (NPAES), set ambitious targets to double the extent of South Africa’s protected area network while ensuring that the expansion preferentially occurs in areas of under-represented biodiversity. The strategy was evaluated in terms of its effectiveness in guiding protected area expansion towards more equitable representation of South Africa’s biodiversity through an assessment of changes in indicators of protected area expansion decision-making before and after the implementation of the strategy. The second intervention is the use of maps of biodiversity priorities to guide land use change decisions outside protected areas. Impact was evaluated as avoided loss of Critical Biodiversity Areas (CBAs), which need to remain in a natural condition to meet in situ conservation targets for species, ecosystems, and ecological processes. Avoided loss in CBAs was benchmarked against avoided loss in protected areas, to contextualize the effectiveness of land use planning as a conservation intervention. Lastly, the effectiveness of stricter land use regulations for threatened ecosystems to reduce land conversion pressure on these ecosystems was evaluated. Key findings were that protected areas are highly effective conservation interventions where they can be implemented, but their capacity for conservation impact is limited by severe constraints on strategic expansion. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Von Staden, Lize
- Date: 2023-04
- Subjects: Environmental policy , Conservation of natural resources -- Government policy -- South Africa
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61115 , vital:69762
- Description: Counterfactual impact evaluation studies form an important evidence base for the effectiveness of conservation projects, programs, and policies (collectively referred to as conservation interventions). In South Africa, counterfactual impact evaluation methods have rarely been applied to local conservation interventions, and therefore evidence for the effectiveness of key strategic national conservation approaches is lacking. This study evaluated three area-based interventions that together aim to avoid the loss of areas most important for the persistence of biodiversity in the terrestrial realm as evidence towards the effectiveness of South Africa’s landscape approach to biodiversity conservation. The first intervention, South Africa’s National Protected Area Expansion Strategy (NPAES), set ambitious targets to double the extent of South Africa’s protected area network while ensuring that the expansion preferentially occurs in areas of under-represented biodiversity. The strategy was evaluated in terms of its effectiveness in guiding protected area expansion towards more equitable representation of South Africa’s biodiversity through an assessment of changes in indicators of protected area expansion decision-making before and after the implementation of the strategy. The second intervention is the use of maps of biodiversity priorities to guide land use change decisions outside protected areas. Impact was evaluated as avoided loss of Critical Biodiversity Areas (CBAs), which need to remain in a natural condition to meet in situ conservation targets for species, ecosystems, and ecological processes. Avoided loss in CBAs was benchmarked against avoided loss in protected areas, to contextualize the effectiveness of land use planning as a conservation intervention. Lastly, the effectiveness of stricter land use regulations for threatened ecosystems to reduce land conversion pressure on these ecosystems was evaluated. Key findings were that protected areas are highly effective conservation interventions where they can be implemented, but their capacity for conservation impact is limited by severe constraints on strategic expansion. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
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
Costs and consequences at the population-environment-development interface in St Francis Bay: exploring the linkages of a complex system
- Authors: Pringle, Geena
- Date: 2023-04
- Subjects: Population -- Environmental aspects , Population --Statistics , Loliginidae -- South Africa -- st francis bay
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61294 , vital:70065
- Description: Coastal zones the world over are particularly attractive for the development of human settlements. Naturally, this trend frequently results in human induced disturbances of sensitive ecosystems, often resulting in dramatic and unintended consequences. The South African coastline is no stranger to this phenomenon. Dynamics at the population-environment-development interface in the coastal zone often presents affected communities and institutions with complex challenges. An infamous case along the South African coastline is the settlement of St Francis Bay, the focus of this dissertation. St Francis Bay was established as a holiday village around sixty years ago and its economy is today firmly dependent on the fragile bond and reciprocal relationship between the tourist trade and the integrity of sandy beaches. The dissertation, against this background and drawing from complex systems theory, explores the links between human activity and the biophysical environment and the ominous costs and consequences that are produced at the local population-environment-development interface. Domains that are considered within the nexus of relevant aspects include the wind-driven sediment bypass system across the local headland; climate change; the local economy; social wellbeing, inequality and social justice; as well urban planning and political governance. The desktop study applied to St Francis Bay made use of Geographic Information Systems and statistical information to form the basis of the methodological approach in this dissertation. The Population-Environment-Development nexus was formed as a result. The results illustrate how critical levels of beach erosion are connected amidst an intricate reciprocal nexus to these and other aspects. It demonstrates that the sustainability of the settlement hinges on the understanding of such linkages and underscores the relevance of the methodological approach that is applied. The sustainability of the environment and the resulting impact on the quality of life of the human population remains a challenge for future generations as well as governance systems. By acknowledging and understanding the complexity that exists in coastal zones allows for future research on the topic to be explored and enable key role players to proactively intervene to benefit the population and the environment. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Pringle, Geena
- Date: 2023-04
- Subjects: Population -- Environmental aspects , Population --Statistics , Loliginidae -- South Africa -- st francis bay
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61294 , vital:70065
- Description: Coastal zones the world over are particularly attractive for the development of human settlements. Naturally, this trend frequently results in human induced disturbances of sensitive ecosystems, often resulting in dramatic and unintended consequences. The South African coastline is no stranger to this phenomenon. Dynamics at the population-environment-development interface in the coastal zone often presents affected communities and institutions with complex challenges. An infamous case along the South African coastline is the settlement of St Francis Bay, the focus of this dissertation. St Francis Bay was established as a holiday village around sixty years ago and its economy is today firmly dependent on the fragile bond and reciprocal relationship between the tourist trade and the integrity of sandy beaches. The dissertation, against this background and drawing from complex systems theory, explores the links between human activity and the biophysical environment and the ominous costs and consequences that are produced at the local population-environment-development interface. Domains that are considered within the nexus of relevant aspects include the wind-driven sediment bypass system across the local headland; climate change; the local economy; social wellbeing, inequality and social justice; as well urban planning and political governance. The desktop study applied to St Francis Bay made use of Geographic Information Systems and statistical information to form the basis of the methodological approach in this dissertation. The Population-Environment-Development nexus was formed as a result. The results illustrate how critical levels of beach erosion are connected amidst an intricate reciprocal nexus to these and other aspects. It demonstrates that the sustainability of the settlement hinges on the understanding of such linkages and underscores the relevance of the methodological approach that is applied. The sustainability of the environment and the resulting impact on the quality of life of the human population remains a challenge for future generations as well as governance systems. By acknowledging and understanding the complexity that exists in coastal zones allows for future research on the topic to be explored and enable key role players to proactively intervene to benefit the population and the environment. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Evaluation of the toxicity of secondary metabolites in Solanum incanum L. to advance community knowledge
- Authors: Zivanayi, William
- Date: 2023-04
- Subjects: Solanum -- Zimbabwe , Pesticides -- Toxicology , Medicinal plants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61018 , vital:69686
- Description: The effects of pests and the need to produce adequate food have influenced small-scale farmers in disadvantaged communities to adopt and utilise natural plant pesticides to improve harvests in many Southern African Development Communities. However, the phytochemistry associated with these indigenous plants’ pesticide activity still needs to be explored. The lack of evidence of scientific knowledge of the plant species has caused a lot of health issues among the users of indigenous plant pesticides. Solanum incanum is among the plants utilised to control cabbage aphids in Mkoba village, Zimbabwe. Solanum species are known for their steroidal compounds which comprise glycoalkaloids and saponins. This study evaluated the knowledge, opinions, and attitudes of the vegetable peasant farming community in Gweru regarding their use of the indigenous plant (S. incanum) as a pesticide. The study also reported the phytochemical profiling, structural characterisation of the isolated compounds, and biological and pesticidal activity evaluation of phytochemicals isolated from S. incanum. A descriptive survey was carried out to assess the knowledge, attitude, and practices of a conveniently sampled group of vegetable farmers in Mkoba village who use S. incanum as a pesticide. Forty-nine respondents comprised of 19 males and 30 females of ages ranging from 15 to above 60 years took part in the study by answering an open and closed-ended questionnaire. The survey revealed that parents and neighbours were instrumental in disseminating pesticidal information in the community. Brassica napus were the most grown.vegetable and vulnerable to cabbage aphids. Mixed opinions amongst the respondents varied regarding the health and environmental impact of S. incanum as a pesticide. Seventy-five percent (75%) of the respondents supported the use of S. incanum as a pesticide whilst 25% claimed that the use of S. incanum was the source of the health problems experienced in the community. The survey demonstrated that (45)91% of the farmers displayed poor practices regarding the disposal of empty pesticide containers and the use of personal protective clothing. The most prevalent symptoms in the community were skin rash, nausea, headache, and poor vision and these symptoms were common in the age group 30 to 60 years. , Thesis (PhD) -- Faculty of Science, School of biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Zivanayi, William
- Date: 2023-04
- Subjects: Solanum -- Zimbabwe , Pesticides -- Toxicology , Medicinal plants
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61018 , vital:69686
- Description: The effects of pests and the need to produce adequate food have influenced small-scale farmers in disadvantaged communities to adopt and utilise natural plant pesticides to improve harvests in many Southern African Development Communities. However, the phytochemistry associated with these indigenous plants’ pesticide activity still needs to be explored. The lack of evidence of scientific knowledge of the plant species has caused a lot of health issues among the users of indigenous plant pesticides. Solanum incanum is among the plants utilised to control cabbage aphids in Mkoba village, Zimbabwe. Solanum species are known for their steroidal compounds which comprise glycoalkaloids and saponins. This study evaluated the knowledge, opinions, and attitudes of the vegetable peasant farming community in Gweru regarding their use of the indigenous plant (S. incanum) as a pesticide. The study also reported the phytochemical profiling, structural characterisation of the isolated compounds, and biological and pesticidal activity evaluation of phytochemicals isolated from S. incanum. A descriptive survey was carried out to assess the knowledge, attitude, and practices of a conveniently sampled group of vegetable farmers in Mkoba village who use S. incanum as a pesticide. Forty-nine respondents comprised of 19 males and 30 females of ages ranging from 15 to above 60 years took part in the study by answering an open and closed-ended questionnaire. The survey revealed that parents and neighbours were instrumental in disseminating pesticidal information in the community. Brassica napus were the most grown.vegetable and vulnerable to cabbage aphids. Mixed opinions amongst the respondents varied regarding the health and environmental impact of S. incanum as a pesticide. Seventy-five percent (75%) of the respondents supported the use of S. incanum as a pesticide whilst 25% claimed that the use of S. incanum was the source of the health problems experienced in the community. The survey demonstrated that (45)91% of the farmers displayed poor practices regarding the disposal of empty pesticide containers and the use of personal protective clothing. The most prevalent symptoms in the community were skin rash, nausea, headache, and poor vision and these symptoms were common in the age group 30 to 60 years. , Thesis (PhD) -- Faculty of Science, School of biomolecular and Chemical Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Factors affecting pinniped skull morphology
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Penaluna, Julia Elizabeth
- Date: 2023-04
- Subjects: hybridisation -- South Africa , Sexual dimorphism (Animals) , Craniology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61306 , vital:70077
- Description: Morphologies have evolved due to trade-offs between competing selective pressures. This is especially true for the skull. Not only does it contain the brain and the organs that are responsible for sensory function, but it is also contains components that play important roles in feeding, breathing, balance, defence, aggression and communication. The pinnipeds, a group of species that has evolved from terrestrial origins and became adapted to the marine environment, are under numerous selective pressures within the marine environment. These species have had to evolve in order to capture and process food underwater, and to dive. In addition, they are also characterised by substantial sexual size dimorphism in some species. Pinnipeds also make use of numerous marine and haul-out habitats with varying characteristics and complexity. Hybridisation has been recorded among pinnipeds, resulting in the production of hybrid offspring with characteristics that are different to their parent species. The aim of the study was to investigate the effect of these life history characteristics on skull and mandible morphology of pinniped species using three dimensional geometric morphometrics. To achieve this, 43 skull and 15 mandible 3D landmarks were collected using a Microscribe G2X digitizer with 0.2mm accuracy, on the skull and mandibles of 17 species of pinnipeds across three families, and one hybrid species. In total, 96 specimens across these species were examined. Data on the different life history characteristics of each species were collected from the literature. These data were plotted onto the PCA results in order to create and visually compare minimum convex polygons for each life history category. The results found that phylogeny, feeding strategy and sexual dimorphism were the most important factors in explaining differences in pinniped skull and mandible shape and size. may have resulted in these changes. Similarly, the inclusion of more species, covering a broader range of life histories may be beneficial. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Pleistocene vertebrate trace fossils from the Cape south coast of South Africa: inferences and implications
- Authors: Helm, Charles William
- Date: 2023-04
- Subjects: Geology, Stratigraphic -- Pleistocene , Vertebrates, Fossil -- South Africa , Paleontology -- Pleistocene
- Language: English
- Type: Doctor's theses , text
- Identifier: http://hdl.handle.net/10948/60589 , vital:65942
- Description: Palaeoichnology, the study of fossil tracks and traces, has had a relatively late start on the Cape south coast of South Africa. Since its inception in 2007 the Cape south coast ichnology project has led to the identification of 326 Pleistocene vertebrate ichnosites in aeolianites (cemented dunes) and cemented foreshore deposits between the community of Arniston in the west and the Robberg Peninsula in the east, a distance of approximately 350 kilometres. As a result, significant palaeoevironmental, palaeocological and palaeoanthropological inferences have been made. This thesis brings together this corpus of work, and attempts to answer the question of how ichnology can inform the understanding of the Cape south coast Pleistocene environment, and how the trace fossil record can complement the body fossil record. Achieving this objective involves the development of a definitive regional account. This includes descriptions of the regional geological context, Quaternary sea-level changes, and the state of knowledge of the region’s Pleistocene palaeoenvironment, palaeoanthropology, and body fossil record, along with an understanding of the roles of substrate and taphonomy in regional ichnology. A discussion of geochronology includes the age results from specimens submitted for dating through optically stimulated luminescence – dated deposits range in age from Marine Isotope Stage 11 through Marine Isotope Srage 3. The body of the thesis is formed by systematic descriptions of the vertebrate ichnosites, accompanied by interpretation and comments. Three databases have been compiled: ichnosites, photographs, and photogrammetry images. In synthesizing this data, four underlying questions are addressed: what is the global relevance of the Cape south coast ichnosites, how can these studies complement the vertebrate body fossil record, how can they contribute to the understanding of Pleistocene palaeoenvironments and palaeocology, and how can they contribute to palaeoanthropology? The Cape south coast is of global ichnological importance. Unanticipated findings which augment the sparse reptilian body fossil record include tracks and traces of crocodiles, monitor lizards, very large tortoises (the first of their kind in the global record), and hatchling sea turtles. Two new ichnogenera have been erected to describe the sea turtle tracks, each containing a new ichnospecies: ustralochelichnus agulhasii and Marinerichnus latus. Avian ichnosites are the oldest in southern v Africa, and include the presence of tracks of larger-than-expected birds, which may represent large chronosubspecies or may suggest the possibility of extinctions which are not evident from the body fossil record. Unique examples of the non-hominin mammalian ichnosites include sand-swimming traces that resemble those of the ‘Namib mole’: as a result a new ichnogenus (Natatorichnus) has been erected, containing two ichnospecies, N. subarenosa and N. sulcatus. The first elephant trunk-drag impressions and the first pinniped ichnosites in the global record have been identified. The role of elephant tracks as precursors to coastal potholes was previously unsuspected. Equid tracksites indicate a widespread presence of the extinct giant Cape horse (Equus capensis). The identification of a giraffe tracksite represents a major range extension. In particular, tracks and traces of giraffe, crocodiles, breeding sea turtles, and sand-swimming golden moles have significant palaeoenvironmental implications. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Helm, Charles William
- Date: 2023-04
- Subjects: Geology, Stratigraphic -- Pleistocene , Vertebrates, Fossil -- South Africa , Paleontology -- Pleistocene
- Language: English
- Type: Doctor's theses , text
- Identifier: http://hdl.handle.net/10948/60589 , vital:65942
- Description: Palaeoichnology, the study of fossil tracks and traces, has had a relatively late start on the Cape south coast of South Africa. Since its inception in 2007 the Cape south coast ichnology project has led to the identification of 326 Pleistocene vertebrate ichnosites in aeolianites (cemented dunes) and cemented foreshore deposits between the community of Arniston in the west and the Robberg Peninsula in the east, a distance of approximately 350 kilometres. As a result, significant palaeoevironmental, palaeocological and palaeoanthropological inferences have been made. This thesis brings together this corpus of work, and attempts to answer the question of how ichnology can inform the understanding of the Cape south coast Pleistocene environment, and how the trace fossil record can complement the body fossil record. Achieving this objective involves the development of a definitive regional account. This includes descriptions of the regional geological context, Quaternary sea-level changes, and the state of knowledge of the region’s Pleistocene palaeoenvironment, palaeoanthropology, and body fossil record, along with an understanding of the roles of substrate and taphonomy in regional ichnology. A discussion of geochronology includes the age results from specimens submitted for dating through optically stimulated luminescence – dated deposits range in age from Marine Isotope Stage 11 through Marine Isotope Srage 3. The body of the thesis is formed by systematic descriptions of the vertebrate ichnosites, accompanied by interpretation and comments. Three databases have been compiled: ichnosites, photographs, and photogrammetry images. In synthesizing this data, four underlying questions are addressed: what is the global relevance of the Cape south coast ichnosites, how can these studies complement the vertebrate body fossil record, how can they contribute to the understanding of Pleistocene palaeoenvironments and palaeocology, and how can they contribute to palaeoanthropology? The Cape south coast is of global ichnological importance. Unanticipated findings which augment the sparse reptilian body fossil record include tracks and traces of crocodiles, monitor lizards, very large tortoises (the first of their kind in the global record), and hatchling sea turtles. Two new ichnogenera have been erected to describe the sea turtle tracks, each containing a new ichnospecies: ustralochelichnus agulhasii and Marinerichnus latus. Avian ichnosites are the oldest in southern v Africa, and include the presence of tracks of larger-than-expected birds, which may represent large chronosubspecies or may suggest the possibility of extinctions which are not evident from the body fossil record. Unique examples of the non-hominin mammalian ichnosites include sand-swimming traces that resemble those of the ‘Namib mole’: as a result a new ichnogenus (Natatorichnus) has been erected, containing two ichnospecies, N. subarenosa and N. sulcatus. The first elephant trunk-drag impressions and the first pinniped ichnosites in the global record have been identified. The role of elephant tracks as precursors to coastal potholes was previously unsuspected. Equid tracksites indicate a widespread presence of the extinct giant Cape horse (Equus capensis). The identification of a giraffe tracksite represents a major range extension. In particular, tracks and traces of giraffe, crocodiles, breeding sea turtles, and sand-swimming golden moles have significant palaeoenvironmental implications. , Thesis (PhD) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Isolation, characterization and functionalization of cellulose fibres derived from the waste pineapple leaf fibres by hydrolysis to produce cellulose acetate
- Authors: Seyisi, Thulethu
- Date: 2023-04
- Subjects: Nonwoven fabrics -- Technological innovations , Pineapple fiber -- South Africa , Fibrous composites
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61248 , vital:69844
- Description: This thesis forms part of the Nelson Mandela University biomass and nanotechnology project, which aims at using agricultural waste for many applications, including biomedical applications, water treatment, and agricultural films. Pineapple leaf fiber (PALF) is one of the natural fibers with the highest cellulose content (about 80%), and they produce about 2.5–3.3% of the weight of green leaves. However, the other parts of the pineapple fruit, such as the leaves and crown, are still treated as waste due to a lack of understanding of the benefits and risks of these parts of the pineapple fruit. The transformation of PALF as a renewable and abundantly available natural residue into cellulose fibers (CFs) will reduce the waste accumulated in the atmosphere, and it will add value to the cultivation of pineapple. In the biomedical industry, CF is very promising in terms of drug delivery. Cellulose acetate is a remarkable biomaterial extensively used in biomedical applications due to its properties such as being non-toxic, non-irritant, biodegradable, heat resistant, and less hygroscopic. In this research, the isolation, functionalization, and characterization of cellulose from PALFs were conducted. The PALFs were dried and ground into small particles before being alkali treated with sodium hydroxide to remove the non-cellulosic components. Moreover, the remaining lignin in the residue was removed using sodium chlorite and acetic acid; this process is known as the bleaching process. The bleaching process resulted in white CFs, which was an indication of the successful removal of the non-cellulosic material. The obtained CFs were further functionalized using acetic acid, acetic anhydride, and sulfuric acid, and this reaction is known as the acetylation reaction. Subsequently, both treated, untreated, and functionalized CFs were characterised using the following instruments: FTIR, SEM, SPM, TGA, XRD, and XPS. In the FTIR data of raw PALFs, the following functional groups were more pronounced: C-O, C=C-O, and C=O, whereas peak C-O-C disappeared and peak CH2, C-O, were less pronounced. These FTIR results confirmed the successful removal of non-cellulosic components. The SEM and SPM images visually suggested the partial removal of hemicellulose and lignin from the raw PALFs after the chemical treatment, which are the cementing materials around the fiber bundles. The TGA studies revealed good thermal stability for the isolated CFs from PALFs. The XRD diffractograms of the PALFs showed a cellulose I crystal pattern where the peaks were located at angular positions (2θ) of around 18°, 26°, and 41°. Lastly, after the functionalization of CFs, the cellulose structure remained intact (not damaged); instead, the newly ix introduced functional groups (the acetyl group) were attached at the ends of the cellulose structure. These results are therefore confirmation of the successful removal of non-cellulose material from the PALFs after the chemical treatment. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Seyisi, Thulethu
- Date: 2023-04
- Subjects: Nonwoven fabrics -- Technological innovations , Pineapple fiber -- South Africa , Fibrous composites
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61248 , vital:69844
- Description: This thesis forms part of the Nelson Mandela University biomass and nanotechnology project, which aims at using agricultural waste for many applications, including biomedical applications, water treatment, and agricultural films. Pineapple leaf fiber (PALF) is one of the natural fibers with the highest cellulose content (about 80%), and they produce about 2.5–3.3% of the weight of green leaves. However, the other parts of the pineapple fruit, such as the leaves and crown, are still treated as waste due to a lack of understanding of the benefits and risks of these parts of the pineapple fruit. The transformation of PALF as a renewable and abundantly available natural residue into cellulose fibers (CFs) will reduce the waste accumulated in the atmosphere, and it will add value to the cultivation of pineapple. In the biomedical industry, CF is very promising in terms of drug delivery. Cellulose acetate is a remarkable biomaterial extensively used in biomedical applications due to its properties such as being non-toxic, non-irritant, biodegradable, heat resistant, and less hygroscopic. In this research, the isolation, functionalization, and characterization of cellulose from PALFs were conducted. The PALFs were dried and ground into small particles before being alkali treated with sodium hydroxide to remove the non-cellulosic components. Moreover, the remaining lignin in the residue was removed using sodium chlorite and acetic acid; this process is known as the bleaching process. The bleaching process resulted in white CFs, which was an indication of the successful removal of the non-cellulosic material. The obtained CFs were further functionalized using acetic acid, acetic anhydride, and sulfuric acid, and this reaction is known as the acetylation reaction. Subsequently, both treated, untreated, and functionalized CFs were characterised using the following instruments: FTIR, SEM, SPM, TGA, XRD, and XPS. In the FTIR data of raw PALFs, the following functional groups were more pronounced: C-O, C=C-O, and C=O, whereas peak C-O-C disappeared and peak CH2, C-O, were less pronounced. These FTIR results confirmed the successful removal of non-cellulosic components. The SEM and SPM images visually suggested the partial removal of hemicellulose and lignin from the raw PALFs after the chemical treatment, which are the cementing materials around the fiber bundles. The TGA studies revealed good thermal stability for the isolated CFs from PALFs. The XRD diffractograms of the PALFs showed a cellulose I crystal pattern where the peaks were located at angular positions (2θ) of around 18°, 26°, and 41°. Lastly, after the functionalization of CFs, the cellulose structure remained intact (not damaged); instead, the newly ix introduced functional groups (the acetyl group) were attached at the ends of the cellulose structure. These results are therefore confirmation of the successful removal of non-cellulose material from the PALFs after the chemical treatment. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
Microstructural based creep life assessment of 1CrMov Turbine rotor steels after long-term service
- Nyembe, Hlanganani Siphelele
- Authors: Nyembe, Hlanganani Siphelele
- Date: 2023-04
- Subjects: Materials – Creep –South Africa , Steel -- Creep
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61380 , vital:70622
- Description: Creep-resistant 1CrMoV steels are used for high-pressure turbine rotors in fossil fuel power stations operating at steam temperatures up to 565 °C in the creep regime. The upper bainitic microstructure of 1CrMoV rotors changes when exposed to high temperature service over long periods. The aim of this study was to relate these microstructural changes for service exposed 1CrMoV rotor steels to the remaining creep life as determined using existing methods. Analytical electron microscopy was used to quantitatively study the microstructural evolution of service-exposed 1CrMoV steel rotors. 1CrMoV rotor steel samples were characterised in the initial state, and three long-term (272 h to 300 kh) service exposed states. Detailed microstructural investigations were conducted to analyse the cavities; bainitic laths and packets; dislocations; carbide phases and their size, population, composition. The creep life fractions were estimated using conventional life assessment methods based on creep cavitation and hardness. The creep life fraction consumed of the rotors, estimated based on the creep cavities and hardness data, ranged from ~0.5 to 1. Electron backscattered diffraction (EBSD) was used to analyse the bainitic packets, laths, misorientations, and dislocations, which showed that the bainitic lath surface area to volume (SV) correlated with service time. The precipitates were extracted from the Fe-matrix using extraction replication and were further investigated using transmission Kikuchi diffraction (TKD), scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDS). STEM-EDS and TKD identified M3C, MC, M2C, M7C3, and M23C6 (M = Fe, Cr, Mo, V, Mn) in the 1CrMoV steels. STEM-EDS measurements revealed that Fe/Cr ratios in M3C decreased from 4.5 (initial state) to 2.5 (>272 kh). The Fe/Cr and Fe/Mo ratios in overall carbides decreased from 5 and 10 (initial state) to 1 and 2 (>272 kh), respectively. The TKD analysis indicated that the relative phase proportion of M2C and M7C3 carbides, relative to the total extracted carbides, is positively correlated with service exposure. These microstructural features correlate with the creep life fraction consumed and could potentially be used as another indicator of the remnant creep life. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics. 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Nyembe, Hlanganani Siphelele
- Date: 2023-04
- Subjects: Materials – Creep –South Africa , Steel -- Creep
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/61380 , vital:70622
- Description: Creep-resistant 1CrMoV steels are used for high-pressure turbine rotors in fossil fuel power stations operating at steam temperatures up to 565 °C in the creep regime. The upper bainitic microstructure of 1CrMoV rotors changes when exposed to high temperature service over long periods. The aim of this study was to relate these microstructural changes for service exposed 1CrMoV rotor steels to the remaining creep life as determined using existing methods. Analytical electron microscopy was used to quantitatively study the microstructural evolution of service-exposed 1CrMoV steel rotors. 1CrMoV rotor steel samples were characterised in the initial state, and three long-term (272 h to 300 kh) service exposed states. Detailed microstructural investigations were conducted to analyse the cavities; bainitic laths and packets; dislocations; carbide phases and their size, population, composition. The creep life fractions were estimated using conventional life assessment methods based on creep cavitation and hardness. The creep life fraction consumed of the rotors, estimated based on the creep cavities and hardness data, ranged from ~0.5 to 1. Electron backscattered diffraction (EBSD) was used to analyse the bainitic packets, laths, misorientations, and dislocations, which showed that the bainitic lath surface area to volume (SV) correlated with service time. The precipitates were extracted from the Fe-matrix using extraction replication and were further investigated using transmission Kikuchi diffraction (TKD), scanning transmission electron microscopy (STEM), selected area electron diffraction (SAED), and energy dispersive spectroscopy (EDS). STEM-EDS and TKD identified M3C, MC, M2C, M7C3, and M23C6 (M = Fe, Cr, Mo, V, Mn) in the 1CrMoV steels. STEM-EDS measurements revealed that Fe/Cr ratios in M3C decreased from 4.5 (initial state) to 2.5 (>272 kh). The Fe/Cr and Fe/Mo ratios in overall carbides decreased from 5 and 10 (initial state) to 1 and 2 (>272 kh), respectively. The TKD analysis indicated that the relative phase proportion of M2C and M7C3 carbides, relative to the total extracted carbides, is positively correlated with service exposure. These microstructural features correlate with the creep life fraction consumed and could potentially be used as another indicator of the remnant creep life. , Thesis (PhD) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics. 2023
- Full Text:
- Date Issued: 2023-04
Investigating thermoregulatory responses of rhabdomys pumilio at high wet-bulb temperatures
- Authors: Hartley, Oliver
- Date: 2023-04
- Subjects: Heat stress physiology , Small mammal thermoregulation -- South Africa , Climate change - Wet-bulb temperature
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60873 , vital:68916
- Description: As the Anthropocene continues to be characterised by ever rising temperature highs, increasingly sporadic and extreme climatic events, and their accompanying mass mortality events, climate scientists now warn that the continued climate destabilisation may for the first time in recorded history prevent terrestrial homeothermic endotherms from being able to thermoregulate. Having evolved to maintain body temperatures (Tbs) well above their ambient (Ta) conditions, these endotherms have evolved a suite of adaptations to a colder environment to allow for homeothermic thermoregulation to occur. However, by the same vein, having evolved in a colder climate to stay warm also has led to a reduced capacity to prevent heat stress when temperature conditions are elevated. In absence of behavioural counter measures, the only physiological means available to thermoregulation to prevent such heat stress is that of evaporative water loss (EWL). If still inefficient, the endotherm will risk becoming hyperthermic. Literature has established that excessive heat exposure or reduced evaporative cooling capacities strain or retard thermoregulatory processes. If an endotherm experiences severe heat exposure, the rate at which passive heating is experienced will increase. Should an endotherm be in a humid environment, evaporative cooling efficiency is reduced. As a result, these two abiotic factors are therefore known to contribute towards heat storage, and therefore thermal stress. However, should both factors occur in the same environment, the heat stress effects are compounded, creating an environment dangerous for thermoregulating endotherms. For this reason, authors have emphasised that future wet-bulb (Tw) conditions may pose a penultimate threat to thermoregulating endotherms. Being a measure of coldest temperature attainable as a result of evaporative cooling, Tw has been proposed to represent a lower temperature thermal limit to endothermic thermoregulation. Once reaching a 2°C differential below an endotherms Tb (Tb – Tw = 2˚C), Tw is believed to impede the evaporative cooling process and, consequentially, commit endotherms to becoming hyperthermic. Considering that most mammals defend constant Tbs within the range of predicted Tw maxima increases that future Tw conditions may pose a significant threat to mammalian thermoregulation. However, to date, despite being well supported in the literature, ii empirical investigations into how extreme Tw conditions will affect endothermic thermoregulation are scant. Therefore, understanding of the proposed inhibitory nature of extreme Tw conditions is lacking. Considering that such conditions are to have a profound effect of endothermic survival, this dearth in understanding could prove fatal. As such, this thesis sought to provide evidence on how extreme Tw conditions may affect thermoregulatory processes in homeothermic endotherms. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Hartley, Oliver
- Date: 2023-04
- Subjects: Heat stress physiology , Small mammal thermoregulation -- South Africa , Climate change - Wet-bulb temperature
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60873 , vital:68916
- Description: As the Anthropocene continues to be characterised by ever rising temperature highs, increasingly sporadic and extreme climatic events, and their accompanying mass mortality events, climate scientists now warn that the continued climate destabilisation may for the first time in recorded history prevent terrestrial homeothermic endotherms from being able to thermoregulate. Having evolved to maintain body temperatures (Tbs) well above their ambient (Ta) conditions, these endotherms have evolved a suite of adaptations to a colder environment to allow for homeothermic thermoregulation to occur. However, by the same vein, having evolved in a colder climate to stay warm also has led to a reduced capacity to prevent heat stress when temperature conditions are elevated. In absence of behavioural counter measures, the only physiological means available to thermoregulation to prevent such heat stress is that of evaporative water loss (EWL). If still inefficient, the endotherm will risk becoming hyperthermic. Literature has established that excessive heat exposure or reduced evaporative cooling capacities strain or retard thermoregulatory processes. If an endotherm experiences severe heat exposure, the rate at which passive heating is experienced will increase. Should an endotherm be in a humid environment, evaporative cooling efficiency is reduced. As a result, these two abiotic factors are therefore known to contribute towards heat storage, and therefore thermal stress. However, should both factors occur in the same environment, the heat stress effects are compounded, creating an environment dangerous for thermoregulating endotherms. For this reason, authors have emphasised that future wet-bulb (Tw) conditions may pose a penultimate threat to thermoregulating endotherms. Being a measure of coldest temperature attainable as a result of evaporative cooling, Tw has been proposed to represent a lower temperature thermal limit to endothermic thermoregulation. Once reaching a 2°C differential below an endotherms Tb (Tb – Tw = 2˚C), Tw is believed to impede the evaporative cooling process and, consequentially, commit endotherms to becoming hyperthermic. Considering that most mammals defend constant Tbs within the range of predicted Tw maxima increases that future Tw conditions may pose a significant threat to mammalian thermoregulation. However, to date, despite being well supported in the literature, ii empirical investigations into how extreme Tw conditions will affect endothermic thermoregulation are scant. Therefore, understanding of the proposed inhibitory nature of extreme Tw conditions is lacking. Considering that such conditions are to have a profound effect of endothermic survival, this dearth in understanding could prove fatal. As such, this thesis sought to provide evidence on how extreme Tw conditions may affect thermoregulatory processes in homeothermic endotherms. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text:
- Date Issued: 2023-04
Assessing the Role of Women on Small-Scale Agribusiness at Wincanton Estate in Kariega, South Africa
- Authors: Zalwango, Joanita
- Date: 2023-04
- Subjects: Leadership in women , Women in agriculture --Eastern Cape – Kariega , Climate change -- Kariega
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61054 , vital:69690
- Description: Agricultural development is a prerequisite for most economies to grow. Agricultural activities are key to food security and sustaining livelihoods globally. Within the African continent, more women are employed in agriculture and agribusiness activities than other sectors. As main contributors to the labour force in the agricultural sector, women get involved in many agricultural and agribusiness activities to sustain their families. With over 60% of women in Sub–Saharan Africa involved in agriculture, there is need to explore and assess the role they play in promoting agribusiness with special focus on Kariega, in South Africa. The identified participants in the study, as self-employed farmers, participate in agribusiness, thereby creating employment opportunities whilst generating personal incomes. Several benefits to female involvement in agribusiness were identified, including the ability to sustain families, stable cash flow, and empowerment. Several challenges were identified, including adequate capital, inaccessibility to private land, droughts, water scarcity, climate change effects and stigmatisation. Through a feminist qualitative methodology, the study utilised semi- structured interviews to collect data from 10 women involved in agribusiness around Kariega, Nelson Mandela Bay. Themes from the findings are analysed to highlight the important role played by women toward agribusiness, their achievements, government and private sector role and the hinderances still faced by these women in agricultural cooperatives. Discussion from the analysis included a framework of recommendations, for policy makers, development practitioners and future researchers. The study found that all stakeholders involved in the agricultural sector should work together for sustainable agricultural development and sustainable development goals to be achieved. Sustainability among women farmers can be achieved by (a) Increasing government intervention and support (b) Climate smart agriculture practices (c) Overcoming stigmatisation (d) Encouraging and involving the youth (e) Diversification and integration of farm businesses and (f) Using contract farming. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text: false
- Date Issued: 2023-04
Assessing the Role of Women on Small-Scale Agribusiness at Wincanton Estate in Kariega, South Africa
- Authors: Zalwango, Joanita
- Date: 2023-04
- Subjects: Leadership in women , Women in agriculture --Eastern Cape – Kariega , Climate change -- Kariega
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/61054 , vital:69690
- Description: Agricultural development is a prerequisite for most economies to grow. Agricultural activities are key to food security and sustaining livelihoods globally. Within the African continent, more women are employed in agriculture and agribusiness activities than other sectors. As main contributors to the labour force in the agricultural sector, women get involved in many agricultural and agribusiness activities to sustain their families. With over 60% of women in Sub–Saharan Africa involved in agriculture, there is need to explore and assess the role they play in promoting agribusiness with special focus on Kariega, in South Africa. The identified participants in the study, as self-employed farmers, participate in agribusiness, thereby creating employment opportunities whilst generating personal incomes. Several benefits to female involvement in agribusiness were identified, including the ability to sustain families, stable cash flow, and empowerment. Several challenges were identified, including adequate capital, inaccessibility to private land, droughts, water scarcity, climate change effects and stigmatisation. Through a feminist qualitative methodology, the study utilised semi- structured interviews to collect data from 10 women involved in agribusiness around Kariega, Nelson Mandela Bay. Themes from the findings are analysed to highlight the important role played by women toward agribusiness, their achievements, government and private sector role and the hinderances still faced by these women in agricultural cooperatives. Discussion from the analysis included a framework of recommendations, for policy makers, development practitioners and future researchers. The study found that all stakeholders involved in the agricultural sector should work together for sustainable agricultural development and sustainable development goals to be achieved. Sustainability among women farmers can be achieved by (a) Increasing government intervention and support (b) Climate smart agriculture practices (c) Overcoming stigmatisation (d) Encouraging and involving the youth (e) Diversification and integration of farm businesses and (f) Using contract farming. , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2023
- Full Text: false
- Date Issued: 2023-04
Effect of livestock management and services to ecosystems on rangeland health and resilience in the NamaKaroo
- Authors: Boshoff, Mishak
- Date: 2023-04
- Subjects: Livestock – Management --South Africa—Karoo , Range ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60611 , vital:66017
- Description: Rangelands offer great opportunities for mutualisms between nature conservation and economic productivity if positive feedback loops can be identified and described. The effects of different livestock management practices are controversial. This research examined the effect of different grazing intensities on soil health using springtails (Collembola) and ants (Formicidae) as bioindicators, combined with soil and vegetation variables. The relationship between rangeland managers and rangeland ecosystems, particularly with regard to feedback loops between land care and economic production, was also investigated. Bioindicator samples were collected at different treatments of livestock grazing intensity and a questionnaire was submitted to 65 rangeland managers in the semi-arid Nama-Karoo biome of South Africa. In most cases we found no significant relationship between grazing intensity and Collembola and ant community composition, vegetation variables, and soil variables. The few significant relationships we found were contradictory in their implications for the effect of high intensity grazing on soil health. The results suggested that differences in livestock management are relatively unimportant for soil health, at least in semi-arid systems under conditions immediately following a drought. The questionnaire yielded results on outline of management practices, basis of management decisions, consequences of monitoring veld to inform management decisions, and indicators of successful management. Respondents characterized by higher ecological fluency focused on livestock production when making management decisions, stocked at higher densities, and monitored the rangeland ecosystem to inform their decisions. For monitoring the ecosystem, they used bioindicators such as diversity of biota, successional stage, and ecologically important functional groups. We concluded that the development of ecological knowledge in rangeland managers enables the establishment of feedback loops between ecosystem services and services to ecosystems, which are desirable for economic productivity and nature conservation. Development of relevant ecological knowledge and management techniques should be based on forums and dialogue among rangeland managers, developing distributed cognition and resilience in the community of rangeland managers. , Thesis (MSc) -- Faculty of Science, School Natural Resource Science and Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Boshoff, Mishak
- Date: 2023-04
- Subjects: Livestock – Management --South Africa—Karoo , Range ecology
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/60611 , vital:66017
- Description: Rangelands offer great opportunities for mutualisms between nature conservation and economic productivity if positive feedback loops can be identified and described. The effects of different livestock management practices are controversial. This research examined the effect of different grazing intensities on soil health using springtails (Collembola) and ants (Formicidae) as bioindicators, combined with soil and vegetation variables. The relationship between rangeland managers and rangeland ecosystems, particularly with regard to feedback loops between land care and economic production, was also investigated. Bioindicator samples were collected at different treatments of livestock grazing intensity and a questionnaire was submitted to 65 rangeland managers in the semi-arid Nama-Karoo biome of South Africa. In most cases we found no significant relationship between grazing intensity and Collembola and ant community composition, vegetation variables, and soil variables. The few significant relationships we found were contradictory in their implications for the effect of high intensity grazing on soil health. The results suggested that differences in livestock management are relatively unimportant for soil health, at least in semi-arid systems under conditions immediately following a drought. The questionnaire yielded results on outline of management practices, basis of management decisions, consequences of monitoring veld to inform management decisions, and indicators of successful management. Respondents characterized by higher ecological fluency focused on livestock production when making management decisions, stocked at higher densities, and monitored the rangeland ecosystem to inform their decisions. For monitoring the ecosystem, they used bioindicators such as diversity of biota, successional stage, and ecologically important functional groups. We concluded that the development of ecological knowledge in rangeland managers enables the establishment of feedback loops between ecosystem services and services to ecosystems, which are desirable for economic productivity and nature conservation. Development of relevant ecological knowledge and management techniques should be based on forums and dialogue among rangeland managers, developing distributed cognition and resilience in the community of rangeland managers. , Thesis (MSc) -- Faculty of Science, School Natural Resource Science and Management, 2023
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- Date Issued: 2023-04