Effects of elevated temperature, rainfall and soil nutrients on acacia mearnsii invasion
- Authors: Kharivha, Tshililo
- Date: 2021-10
- Subjects: Acacia mearnsii , Acacia mearnsii Effect of high temperatures on South Africa , Acacia mearnsii Climatic factors South Africa , Plant invasions South Africa , Invasive plants , Climatic changes South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/189997 , vital:44954
- Description: Climate change is associated with the risk of plant invasion hence a better understanding of the effects of elevated temperature, precipitation and soil nutrients on dominant invasive plants is needed for effective ecological planning. This study was set out to: (i) examine how elevated temperature (±2°C increase), (ii) high (above local average) and low (below local average) precipitation, (iii) elevated soil nutrient content (increase in soil N), and (iv) a combination of the above manipulations affects germination and growth of Acacia mearnsii, a dominant invasive plant in South Africa. The study further evaluated how the above-mentioned treatments affect soil chemical properties following A. mearnsii germination and growth. The above-mentioned specific objectives were tested under manipulated greenhouse conditions over six experimental months. The results indicated that the above-mentioned climate change scenarios have the potential to facilitate germination and growth of the invasive species A. mearnsii, and this is likely to proliferate its invasion in future. Results showed that seed germination was significantly high under all climate change manipulation treatments (˃50%) with highest seed germination recorded under high rainfall treatment (64%). Plant height was significantly higher under high temperature and high rainfall treatments throughout all the experimental months, though it was lowest under high nitrogen and combined treatment with high rainfall. The numbers of branches were high under higher temperature and low rainfall treatments than under high rainfall, high nitrogen and both combined treatments of low and high rainfall. Relative to the control, plants grown under climate change scenarios increased their root lengths, but this varied across different treatments. Total dry biomass was relatively high under high temperature treatment (0,7 g). Lower plant dry biomass was observed under low and high rainfall treatments (0,4 g), high nitrogen and combined treatments with both low and high rainfall treatments (0,1 g). Concerning the effects of climate change scenarios on soil chemical properties, soil pH levels were significantly higher after A. mearnsii germination and growth than before the experiment was setup. Soil resistivity was significantly higher in climate change treatments receiving nitrogen and combined treatments of low rainfall than other treatments and the soils before experiment. Soil total P was significantly higher in all the climate change treatments after A. mearnsii germination experiment than the before experiment soils. Soils receiving high temperature, high nitrogen, and combined treatment of low rainfall had significantly higher soil total N than other treatments and the before experiment soils. Soil total C was significantly higher in soils receiving high temperature, high nitrogen, and combined treatment of low rainfall after A. mearnsii germination than other treatments and before experiment soils. The findings suggest that future climate change scenarios of increased temperature and rainfall with soil nutrients could considerably enhance growth and germination success of the invasive plant A. mearnsii. Similarly, climate change scenarios could enhance some soil nutrient properties, which in turn, is likely to give the invasive plant A. mearnsii a germination and growth advantage. These results are the first in South Africa to show that future climate changes have the potential to facilitate A. mearnsii germination and growth, making it more invasive. The findings have implications for invasive plants management, especially action for managing the plant through clearing of the plant in sensitive ecosystems (e.g. riparian systems). , Thesis (MSc) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Kharivha, Tshililo
- Date: 2021-10
- Subjects: Acacia mearnsii , Acacia mearnsii Effect of high temperatures on South Africa , Acacia mearnsii Climatic factors South Africa , Plant invasions South Africa , Invasive plants , Climatic changes South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/189997 , vital:44954
- Description: Climate change is associated with the risk of plant invasion hence a better understanding of the effects of elevated temperature, precipitation and soil nutrients on dominant invasive plants is needed for effective ecological planning. This study was set out to: (i) examine how elevated temperature (±2°C increase), (ii) high (above local average) and low (below local average) precipitation, (iii) elevated soil nutrient content (increase in soil N), and (iv) a combination of the above manipulations affects germination and growth of Acacia mearnsii, a dominant invasive plant in South Africa. The study further evaluated how the above-mentioned treatments affect soil chemical properties following A. mearnsii germination and growth. The above-mentioned specific objectives were tested under manipulated greenhouse conditions over six experimental months. The results indicated that the above-mentioned climate change scenarios have the potential to facilitate germination and growth of the invasive species A. mearnsii, and this is likely to proliferate its invasion in future. Results showed that seed germination was significantly high under all climate change manipulation treatments (˃50%) with highest seed germination recorded under high rainfall treatment (64%). Plant height was significantly higher under high temperature and high rainfall treatments throughout all the experimental months, though it was lowest under high nitrogen and combined treatment with high rainfall. The numbers of branches were high under higher temperature and low rainfall treatments than under high rainfall, high nitrogen and both combined treatments of low and high rainfall. Relative to the control, plants grown under climate change scenarios increased their root lengths, but this varied across different treatments. Total dry biomass was relatively high under high temperature treatment (0,7 g). Lower plant dry biomass was observed under low and high rainfall treatments (0,4 g), high nitrogen and combined treatments with both low and high rainfall treatments (0,1 g). Concerning the effects of climate change scenarios on soil chemical properties, soil pH levels were significantly higher after A. mearnsii germination and growth than before the experiment was setup. Soil resistivity was significantly higher in climate change treatments receiving nitrogen and combined treatments of low rainfall than other treatments and the soils before experiment. Soil total P was significantly higher in all the climate change treatments after A. mearnsii germination experiment than the before experiment soils. Soils receiving high temperature, high nitrogen, and combined treatment of low rainfall had significantly higher soil total N than other treatments and the before experiment soils. Soil total C was significantly higher in soils receiving high temperature, high nitrogen, and combined treatment of low rainfall after A. mearnsii germination than other treatments and before experiment soils. The findings suggest that future climate change scenarios of increased temperature and rainfall with soil nutrients could considerably enhance growth and germination success of the invasive plant A. mearnsii. Similarly, climate change scenarios could enhance some soil nutrient properties, which in turn, is likely to give the invasive plant A. mearnsii a germination and growth advantage. These results are the first in South Africa to show that future climate changes have the potential to facilitate A. mearnsii germination and growth, making it more invasive. The findings have implications for invasive plants management, especially action for managing the plant through clearing of the plant in sensitive ecosystems (e.g. riparian systems). , Thesis (MSc) -- Faculty of Science, Environmental Science, 2021
- Full Text:
- Date Issued: 2021-10
Evaluation of Megabruchidius tonkineus (Coleoptera: Chrysomelidae: Bruchinae), a candidate biological control agent for Gleditsia triacanthos L. (Fabaceae) in South Africa
- Salgado Astudillo, Sara Elizabeth
- Authors: Salgado Astudillo, Sara Elizabeth
- Date: 2021-10
- Subjects: Honey locust South Africa , Honey locust Biological control South Africa , Invasive plants Biological control South Africa , Biogeography South Africa , Biogeography Climatic factors South Africa , Megabruchidius tonkineus South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/188386 , vital:44749
- Description: Gleditsia triacanthos L. (Fabaceae) (honey locust) is a fast-growing, deciduous tree indigenous to the United States of America. Introduced around the world as an ornamental tree, it has become invasive in a number of countries. Where it is invasive, G. triacanthos competes and replaces indigenous species; it creates dense stands along watercourses, posing a significant environmental threat. In South Africa, G. triacanthos is regarded as one of the country’s fastest spreading weeds. Gleditsia triacanthos produces numerous seeds contained in large hanging pods. Once dislodged from the pods, the seeds are dispersed by birds and mammals, including livestock, which eat the pods. It has been suggested that the seeds should be the target for biological control programme. Some invasive alien plant species are characterised by their ability to spread and establish in new ecosystems because they tolerate a wide range of environmental conditions. In order to predict areas of likely invasion, species distribution models (SDMs) are used to identify areas climatically suitable for their invasion, so enabling better targeted control of the plant species. Gleditsia triacanthos adapts to a wide range of climates and soil types, and tolerates salinity, drought and frost. Currently primarily restricted to the Grassland Biome of South Africa, G. triacanthos has doubled its distribution area in the past 15 years, and it is not known how far the species will spread. In this study we used two different modelling programmes, CLIMEX and MaxEnt, to predict areas where G. triacanthos could find favourable growing conditions; both SDMs showed that most of the country is suitable for G. triacanthos and that it will probably continue to spread, if left unmanaged, into new bioregions, such as the Karoo. In South Africa, the Asian seed-feeding bruchid, Megabruchidius tonkineus (Pic, 1914) (Coleoptera: Chrysomelidae: Bruchinae) has been recorded in the plant’s seed pods and has been considered as a biological control agent. The insect was not released as part of a formal biological control programme and neither host-specificity nor impact studies were conducted on the species prior to its discovery. In 2017 a decision was made to re-consider its status as a Abstract biological control agent until further details of its biology, host specificity, and impact on the seeds of G. triacanthos in South Africa were available. This study shows that Megabruchidius tonkineus has established across the entire G. triacanthos population in South Africa damaging approximately 9% of seeds. Laboratory studies show that, Megabruchidius tonkineus completes its larval development in the seeds of G. triacanthos in about 66.80 ± 0.6880 SE days before eclosing. In addition, the adult females oviposit on the following Fabaceae species: Arachis hypogaea, Albizia, julibrissin, Cicer arietinum, Pisum sativum, Dipogon lignosus, Peltophorum africanum, Podalyria buxifolia Senegalia burkei, Umtiza listerina and Vachellia sieberiana. However, larval development was limited to G. triacanthos. It is concluded that the seed-feeding beetle is not a threat to native Fabaceae species in South Africa, however, it does not damage enough G. triacanthos seeds to be considered a valuable biological control agent at this stage, and additional seed-feeding biological control agents should be considered to reduce the number of G. triacanthos seeds entering the environment. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Salgado Astudillo, Sara Elizabeth
- Date: 2021-10
- Subjects: Honey locust South Africa , Honey locust Biological control South Africa , Invasive plants Biological control South Africa , Biogeography South Africa , Biogeography Climatic factors South Africa , Megabruchidius tonkineus South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/188386 , vital:44749
- Description: Gleditsia triacanthos L. (Fabaceae) (honey locust) is a fast-growing, deciduous tree indigenous to the United States of America. Introduced around the world as an ornamental tree, it has become invasive in a number of countries. Where it is invasive, G. triacanthos competes and replaces indigenous species; it creates dense stands along watercourses, posing a significant environmental threat. In South Africa, G. triacanthos is regarded as one of the country’s fastest spreading weeds. Gleditsia triacanthos produces numerous seeds contained in large hanging pods. Once dislodged from the pods, the seeds are dispersed by birds and mammals, including livestock, which eat the pods. It has been suggested that the seeds should be the target for biological control programme. Some invasive alien plant species are characterised by their ability to spread and establish in new ecosystems because they tolerate a wide range of environmental conditions. In order to predict areas of likely invasion, species distribution models (SDMs) are used to identify areas climatically suitable for their invasion, so enabling better targeted control of the plant species. Gleditsia triacanthos adapts to a wide range of climates and soil types, and tolerates salinity, drought and frost. Currently primarily restricted to the Grassland Biome of South Africa, G. triacanthos has doubled its distribution area in the past 15 years, and it is not known how far the species will spread. In this study we used two different modelling programmes, CLIMEX and MaxEnt, to predict areas where G. triacanthos could find favourable growing conditions; both SDMs showed that most of the country is suitable for G. triacanthos and that it will probably continue to spread, if left unmanaged, into new bioregions, such as the Karoo. In South Africa, the Asian seed-feeding bruchid, Megabruchidius tonkineus (Pic, 1914) (Coleoptera: Chrysomelidae: Bruchinae) has been recorded in the plant’s seed pods and has been considered as a biological control agent. The insect was not released as part of a formal biological control programme and neither host-specificity nor impact studies were conducted on the species prior to its discovery. In 2017 a decision was made to re-consider its status as a Abstract biological control agent until further details of its biology, host specificity, and impact on the seeds of G. triacanthos in South Africa were available. This study shows that Megabruchidius tonkineus has established across the entire G. triacanthos population in South Africa damaging approximately 9% of seeds. Laboratory studies show that, Megabruchidius tonkineus completes its larval development in the seeds of G. triacanthos in about 66.80 ± 0.6880 SE days before eclosing. In addition, the adult females oviposit on the following Fabaceae species: Arachis hypogaea, Albizia, julibrissin, Cicer arietinum, Pisum sativum, Dipogon lignosus, Peltophorum africanum, Podalyria buxifolia Senegalia burkei, Umtiza listerina and Vachellia sieberiana. However, larval development was limited to G. triacanthos. It is concluded that the seed-feeding beetle is not a threat to native Fabaceae species in South Africa, however, it does not damage enough G. triacanthos seeds to be considered a valuable biological control agent at this stage, and additional seed-feeding biological control agents should be considered to reduce the number of G. triacanthos seeds entering the environment. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-10
Exploring affordances and hindrances when using Grade 8 Physical Science learners’ home language to mediate learning of chemical bonding
- Shilongo, Wilhelm Nghidiputate
- Authors: Shilongo, Wilhelm Nghidiputate
- Date: 2021-10
- Subjects: Science Study and teaching (Secondary) Namibia , Code switching (Linguistics) , Chemical bonds , Education, Bilingual Namibia , Native language and education Namibia , Socio-cultural theory
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191079 , vital:45056
- Description: It seems code-switching from English to learners’ home language is a regular practice in Namibian schools. That is, science teachers mediate specific challenging science topics such as chemical bonding through code-switching from English to learners’ home languages. Based on anecdotal evidence and on Grade 10 Examiners’ Reports for previous years, chemical bonding is one of the challenging key concepts in Physical Science, and yet it is an important concept in the study of chemistry. Therefore, the purpose of this interventionist study was to investigate how the use of learners’ home language enables and/or constrains Grade 8 Physical Science learners’ sense making of the topic, chemical bonding. The study is a convergent parallel mixed method case study and was underpinned by an interpretive paradigm. It was conducted with 17 Grade 8 learners in a rural school, where I teach, in the Oshana region. I used a diagnostic test to elicit learners’ prior knowledge on this topic, a post-intervention test, observation, reflections, focus group interview and stimulated recall interviews as my data collection methods. I used Vygotsky’s (1978) Socio-Cultural Theory as my theoretical framework to help explain how learners make sense of the concept of chemical bonding when learners’ home language is used in a Physical Science class. To analyse the quantitative data obtained, I used a descriptive statistics and inferential statistics method. In the descriptive statistics, data were compiled into graphs, tables, and other visual representations, while for the inferential statistics, a t-test was used to establish the significant difference of the data collected. On the other hand, a thematic approach to analyse the qualitative data was employed to come up with sub-themes and themes. The findings of the study revealed that learners’ home language stimulates learners’ interest to learn new concepts, and enhances learners’ understanding and participation during the science lessons. Another finding of the study revealed that learners’ prior knowledge in chemical bonding contained some misconceptions. Furthermore, the findings of the study also revealed that learners learn best when their prior knowledge are elicited before they are introduced to new concepts in their science classrooms. The study recommends that learners’ home language should be incorporated into Physical Science lessons, especially when the teachers are teaching challenging concepts such as chemical bonding. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Shilongo, Wilhelm Nghidiputate
- Date: 2021-10
- Subjects: Science Study and teaching (Secondary) Namibia , Code switching (Linguistics) , Chemical bonds , Education, Bilingual Namibia , Native language and education Namibia , Socio-cultural theory
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191079 , vital:45056
- Description: It seems code-switching from English to learners’ home language is a regular practice in Namibian schools. That is, science teachers mediate specific challenging science topics such as chemical bonding through code-switching from English to learners’ home languages. Based on anecdotal evidence and on Grade 10 Examiners’ Reports for previous years, chemical bonding is one of the challenging key concepts in Physical Science, and yet it is an important concept in the study of chemistry. Therefore, the purpose of this interventionist study was to investigate how the use of learners’ home language enables and/or constrains Grade 8 Physical Science learners’ sense making of the topic, chemical bonding. The study is a convergent parallel mixed method case study and was underpinned by an interpretive paradigm. It was conducted with 17 Grade 8 learners in a rural school, where I teach, in the Oshana region. I used a diagnostic test to elicit learners’ prior knowledge on this topic, a post-intervention test, observation, reflections, focus group interview and stimulated recall interviews as my data collection methods. I used Vygotsky’s (1978) Socio-Cultural Theory as my theoretical framework to help explain how learners make sense of the concept of chemical bonding when learners’ home language is used in a Physical Science class. To analyse the quantitative data obtained, I used a descriptive statistics and inferential statistics method. In the descriptive statistics, data were compiled into graphs, tables, and other visual representations, while for the inferential statistics, a t-test was used to establish the significant difference of the data collected. On the other hand, a thematic approach to analyse the qualitative data was employed to come up with sub-themes and themes. The findings of the study revealed that learners’ home language stimulates learners’ interest to learn new concepts, and enhances learners’ understanding and participation during the science lessons. Another finding of the study revealed that learners’ prior knowledge in chemical bonding contained some misconceptions. Furthermore, the findings of the study also revealed that learners learn best when their prior knowledge are elicited before they are introduced to new concepts in their science classrooms. The study recommends that learners’ home language should be incorporated into Physical Science lessons, especially when the teachers are teaching challenging concepts such as chemical bonding. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10
Green Synthesis of HIV-1 Protease Inhibitors
- Authors: Hartley, Shaun Neil
- Date: 2021-10
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190145 , vital:44967
- Description: Thesis embargoed until October 2022 , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Hartley, Shaun Neil
- Date: 2021-10
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190145 , vital:44967
- Description: Thesis embargoed until October 2022 , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
In a novel landscape, in the Eastern Cape, South Africa, what are the key vegetation resources that support livestock production?
- Liversage-Quinlan, William Peter
- Authors: Liversage-Quinlan, William Peter
- Date: 2021-10
- Subjects: Mzimvubu River Watershed (South Africa) , Livestock productivity South Africa Mzimvubu River Watershed , Range ecology South Africa Mzimvubu River Watershed , Land degradation South Africa Mzimvubu River Watershed , Vegetation dynamics South Africa Mzimvubu River Watershed , Novel landscapes
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190053 , vital:44959
- Description: The Tsitsa River is the largest remaining river that is without a dam in South Africa, and so the government has pledged to install two major dams for irrigation and hydroelectricity, under the Mzimvubu Water Project. These dams are intended to supply water and electricity to surrounding communities as well as the large neighbouring urban areas of Mthatha and Tsolo. However, large areas of the Tsitsa Catchment (~494 000 ha) are degraded, posing the possibility that if these dams were to be created, they would inevitably fill with sediment and silt within a few decades. To address these issues, the Tsitsa Project was established in 2014 to co-ordinate actions by government, developers and local communities in order to restore the landscape condition and prevent soil erosion, as well as to improve the livelihoods of the people who live there (Fabricius, Biggs, & Powell, 2016). Research into the landscape condition as well and the environmental interactions with local communities are therefore highly necessary in order to guide restoration practices to their best effect. The economic necessity for livestock production in the catchment indicates its urgent need for a better understanding of its current effects on the catchment landscape and vegetation. The overall goal of this study is to contribute to the knowledge needed to manage the area in a sustainable way. This paper will therefore examine the key vegetation resources that support livestock production in an area of the Tsitsa River Catchment, by describing the various types that exist, and by determining their relative production levels of usable livestock forage. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Liversage-Quinlan, William Peter
- Date: 2021-10
- Subjects: Mzimvubu River Watershed (South Africa) , Livestock productivity South Africa Mzimvubu River Watershed , Range ecology South Africa Mzimvubu River Watershed , Land degradation South Africa Mzimvubu River Watershed , Vegetation dynamics South Africa Mzimvubu River Watershed , Novel landscapes
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190053 , vital:44959
- Description: The Tsitsa River is the largest remaining river that is without a dam in South Africa, and so the government has pledged to install two major dams for irrigation and hydroelectricity, under the Mzimvubu Water Project. These dams are intended to supply water and electricity to surrounding communities as well as the large neighbouring urban areas of Mthatha and Tsolo. However, large areas of the Tsitsa Catchment (~494 000 ha) are degraded, posing the possibility that if these dams were to be created, they would inevitably fill with sediment and silt within a few decades. To address these issues, the Tsitsa Project was established in 2014 to co-ordinate actions by government, developers and local communities in order to restore the landscape condition and prevent soil erosion, as well as to improve the livelihoods of the people who live there (Fabricius, Biggs, & Powell, 2016). Research into the landscape condition as well and the environmental interactions with local communities are therefore highly necessary in order to guide restoration practices to their best effect. The economic necessity for livestock production in the catchment indicates its urgent need for a better understanding of its current effects on the catchment landscape and vegetation. The overall goal of this study is to contribute to the knowledge needed to manage the area in a sustainable way. This paper will therefore examine the key vegetation resources that support livestock production in an area of the Tsitsa River Catchment, by describing the various types that exist, and by determining their relative production levels of usable livestock forage. , Thesis (MSc) -- Faculty of Science, Institute for Water Research, 2021
- Full Text:
- Date Issued: 2021-10
Investigation of sediment buffering function of the Gatberg Floodplain Wetland in the upper Tsitsa River Catchment, South Africa
- Pakati, Sibuyisele Sweetness
- Authors: Pakati, Sibuyisele Sweetness
- Date: 2021-10
- Subjects: Sedimentation and deposition South Africa Eastern Cape , Sediment transport South Africa Eastern Cape , Floodplain morphology South Africa Eastern Cape , Wetlands South Africa Eastern Cape , Suspended sediments South Africa Eastern Cape , Floods South Africa Eastern Cape , Fluvial geomorphology South Africa Eastern Cape , Floodplain plants South Africa Eastern Cape , Inundation depth
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190792 , vital:45028
- Description: Floodplain wetlands are important components of river systems that provide various ecosystem services such as sediment buffering. These wide and often expansive storage areas have a substantial impact on downstream water quality by trapping sediment and storing ‘contaminants’ adhered to sediment thus improving water quality. The planned construction of the Ntabelanga and Lalini Dams in the Tsitsa River Catchment has been proposed; however, due to the steep landscapes and erodible soils, this promotes high erosion rates that can potentially reduce the lifespan of the proposed dams. The existing wetlands in the Tsitsa River Catchment have therefore been identified as key sediment buffers that can reduce sediment transport, but the effectiveness of these buffers is poorly researched. This study attempts to investigate the current sediment buffering function of the Gatberg Floodplain Wetland over one wet season (August 2019 to August 2020). Time integrated samplers were installed above and below the wetland to determine relative sediment volume and character coming in and out of the wetland. Five transects were surveyed across the wetland width to evaluate the topography and vegetation characteristics. Surface sediment samples on the floodplain were taken at key morphological features along each transect and along the river longitudinal profile to determine organic content, particle size, and type of stored sediment. Astro turf mats were deployed on targeted transects and on key floodplain features to determine sediment accumulation rates. Field measurements of vegetation parameters (height, density, and stem diameter) were taken to calculate vegetation-induced hydraulic roughness to understand possible sedimentation feedbacks. The relative sediment volume coming into the wetland was greater than that leaving the wetland. This implies that some of the sediment is buffered within the wetland. An approximate proportion of 73% trapping efficiency of the incoming sediment was buffered within the floodplain wetland during the wet season. This accumulated approximately 4 tons within the wetland over the monitoring frame. Bed particle size in the longitudinal profile increased with distance downstream, this was due to localized tributary and hillslope inputs. Inundation depth varied across the floodplain wetland with deeper inundation depths at the head of the wetland than at the bottom; where particle size was larger with an increase in water level depth. This may be linked to both high stream velocities and variability of the floodplain topography. However, the observed trends were inconclusive and uncertain. Stronger correlations with particle size were shown by vegetation roughness (b* = 0.41) and distance from the channel (b* = -0.38). Flood benches and banks had a coarser D50 particle size than back swamps and oxbows. Coarser sediment in flood benches are associated with proximity to the sediment-laden water that experiences abrupt flow velocity changes, while finer material in oxbows are due to minimal flow velocities which reduce with distance from the channel. Finer particles remain in suspension and are carried aloft for longer periods at very low velocities. Therefore, particle size decreased with distance from the channel due to longer travel distances and high surface area relative to weight. Further results showed that finer surface sediment particle size was associated with high vegetation roughness whilst coarser material was associated with low roughness. This was due to vegetation geometry and type or changes in flow velocity and energy. Grassy vegetation induced finer particle size than shrubby vegetation that has a greater line spacing. Furthermore, vegetation roughness varied over the wet season; roughness was highest in late summer and low in early summer. Low roughness was due to fire occurrence in the study area which resulted in a decrease in biomass. Increasing vegetation roughness can be due to increased flood events, and the introduction of non-perennial species; which can increase sediment accumulation rates. Although studies have shown that vegetation density is the most essential factor affecting flow resistance and sedimentation processes; vegetation height and stem diameter for this study area seem to contrast these observations and rather may be the most significant contributing factors in sedimentation. This concluded that vegetation density may not always be the most essential component in sedimentation processes. Sediment particle size was inversely proportional to organic content; finer particle size are more cohesive and more capable of carrying organics. Regions further away from the channel such as oxbows with stable moisture conditions favour plant growth and soil formation thus are susceptible to high organic content. Flood benches are closer to the channel, thus have coarser material and fluctuating moisture conditions that have unstable high water flow velocities. High sediment accumulation rates on flood benches and oxbows is due to high connectivity to sediment-laden water and high hydroperiods or high residence time for sediment accumulation in oxbows. Sediment accumulation rate was shown to be a function of particle size itself (b* = 0.67) rather than the expected vegetation roughness. Although a true representation of sediment accumulation rates in the Gatberg Wetland was limited by the disturbance of astro turf mats by animals and possibly by high flooding events; the wetland can be regarded as a good sediment buffer as some sediment was stored (e.g. up to 48,04 kg/m2 in flood benches) within the wetland over the monitoring period. , Thesis (MSc) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Pakati, Sibuyisele Sweetness
- Date: 2021-10
- Subjects: Sedimentation and deposition South Africa Eastern Cape , Sediment transport South Africa Eastern Cape , Floodplain morphology South Africa Eastern Cape , Wetlands South Africa Eastern Cape , Suspended sediments South Africa Eastern Cape , Floods South Africa Eastern Cape , Fluvial geomorphology South Africa Eastern Cape , Floodplain plants South Africa Eastern Cape , Inundation depth
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190792 , vital:45028
- Description: Floodplain wetlands are important components of river systems that provide various ecosystem services such as sediment buffering. These wide and often expansive storage areas have a substantial impact on downstream water quality by trapping sediment and storing ‘contaminants’ adhered to sediment thus improving water quality. The planned construction of the Ntabelanga and Lalini Dams in the Tsitsa River Catchment has been proposed; however, due to the steep landscapes and erodible soils, this promotes high erosion rates that can potentially reduce the lifespan of the proposed dams. The existing wetlands in the Tsitsa River Catchment have therefore been identified as key sediment buffers that can reduce sediment transport, but the effectiveness of these buffers is poorly researched. This study attempts to investigate the current sediment buffering function of the Gatberg Floodplain Wetland over one wet season (August 2019 to August 2020). Time integrated samplers were installed above and below the wetland to determine relative sediment volume and character coming in and out of the wetland. Five transects were surveyed across the wetland width to evaluate the topography and vegetation characteristics. Surface sediment samples on the floodplain were taken at key morphological features along each transect and along the river longitudinal profile to determine organic content, particle size, and type of stored sediment. Astro turf mats were deployed on targeted transects and on key floodplain features to determine sediment accumulation rates. Field measurements of vegetation parameters (height, density, and stem diameter) were taken to calculate vegetation-induced hydraulic roughness to understand possible sedimentation feedbacks. The relative sediment volume coming into the wetland was greater than that leaving the wetland. This implies that some of the sediment is buffered within the wetland. An approximate proportion of 73% trapping efficiency of the incoming sediment was buffered within the floodplain wetland during the wet season. This accumulated approximately 4 tons within the wetland over the monitoring frame. Bed particle size in the longitudinal profile increased with distance downstream, this was due to localized tributary and hillslope inputs. Inundation depth varied across the floodplain wetland with deeper inundation depths at the head of the wetland than at the bottom; where particle size was larger with an increase in water level depth. This may be linked to both high stream velocities and variability of the floodplain topography. However, the observed trends were inconclusive and uncertain. Stronger correlations with particle size were shown by vegetation roughness (b* = 0.41) and distance from the channel (b* = -0.38). Flood benches and banks had a coarser D50 particle size than back swamps and oxbows. Coarser sediment in flood benches are associated with proximity to the sediment-laden water that experiences abrupt flow velocity changes, while finer material in oxbows are due to minimal flow velocities which reduce with distance from the channel. Finer particles remain in suspension and are carried aloft for longer periods at very low velocities. Therefore, particle size decreased with distance from the channel due to longer travel distances and high surface area relative to weight. Further results showed that finer surface sediment particle size was associated with high vegetation roughness whilst coarser material was associated with low roughness. This was due to vegetation geometry and type or changes in flow velocity and energy. Grassy vegetation induced finer particle size than shrubby vegetation that has a greater line spacing. Furthermore, vegetation roughness varied over the wet season; roughness was highest in late summer and low in early summer. Low roughness was due to fire occurrence in the study area which resulted in a decrease in biomass. Increasing vegetation roughness can be due to increased flood events, and the introduction of non-perennial species; which can increase sediment accumulation rates. Although studies have shown that vegetation density is the most essential factor affecting flow resistance and sedimentation processes; vegetation height and stem diameter for this study area seem to contrast these observations and rather may be the most significant contributing factors in sedimentation. This concluded that vegetation density may not always be the most essential component in sedimentation processes. Sediment particle size was inversely proportional to organic content; finer particle size are more cohesive and more capable of carrying organics. Regions further away from the channel such as oxbows with stable moisture conditions favour plant growth and soil formation thus are susceptible to high organic content. Flood benches are closer to the channel, thus have coarser material and fluctuating moisture conditions that have unstable high water flow velocities. High sediment accumulation rates on flood benches and oxbows is due to high connectivity to sediment-laden water and high hydroperiods or high residence time for sediment accumulation in oxbows. Sediment accumulation rate was shown to be a function of particle size itself (b* = 0.67) rather than the expected vegetation roughness. Although a true representation of sediment accumulation rates in the Gatberg Wetland was limited by the disturbance of astro turf mats by animals and possibly by high flooding events; the wetland can be regarded as a good sediment buffer as some sediment was stored (e.g. up to 48,04 kg/m2 in flood benches) within the wetland over the monitoring period. , Thesis (MSc) -- Faculty of Science, Geography, 2021
- Full Text:
- Date Issued: 2021-10
Is there an inverse-u relationship between financialisation and investment?: South Africa’s stock market capitalisation in comparative perspective
- Authors: Owen, Michael Robert
- Date: 2021-10
- Subjects: Monetary policy South Africa , Globalization , Economics South Africa , Capital movements South Africa , Stock exchanges South Africa , Investments South Africa , Economic development South Africa , South Africa Economic conditions 1991-
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191084 , vital:45058
- Description: In recent decades, the growth and fluctuations in the financial sector have become increasingly disjointed from events in the real economy. There has been a dramatic increase in global market integration and globalisation since the 2008 financial crisis. The argument presented in the thesis shows perspective from the two general debates in Economics. The Orthodox view, which suggests there is an efficient flow of resources between people and institutions over time, supports the argument that there is a positive relationship between financialisation and economic growth. Alternatively, the Heterodox view argues that financial liberalisation fails to anticipate market effects and requires intervention in order to limit negative consequences. More recent studies have proposed an inverse-U theory between financialisation and investment, which suggests that there is a threshold, above which further financial development and financial globalisation has detrimental effects on the real economy. With South Africa being a developing country that is highly reliant on capital inflows to finance the economy, there is space for more acute research to investigate whether South Africa has surpassed this threshold. This study focusses on one aspect of this relationship, namely the relationship between Stock Market Capitalisation and Investment. It uses panel data analysis and other methods to explore whether such an inverse-U relationship exists internationally, and whether South Africa is suffering from the effects of financialisation. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Owen, Michael Robert
- Date: 2021-10
- Subjects: Monetary policy South Africa , Globalization , Economics South Africa , Capital movements South Africa , Stock exchanges South Africa , Investments South Africa , Economic development South Africa , South Africa Economic conditions 1991-
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191084 , vital:45058
- Description: In recent decades, the growth and fluctuations in the financial sector have become increasingly disjointed from events in the real economy. There has been a dramatic increase in global market integration and globalisation since the 2008 financial crisis. The argument presented in the thesis shows perspective from the two general debates in Economics. The Orthodox view, which suggests there is an efficient flow of resources between people and institutions over time, supports the argument that there is a positive relationship between financialisation and economic growth. Alternatively, the Heterodox view argues that financial liberalisation fails to anticipate market effects and requires intervention in order to limit negative consequences. More recent studies have proposed an inverse-U theory between financialisation and investment, which suggests that there is a threshold, above which further financial development and financial globalisation has detrimental effects on the real economy. With South Africa being a developing country that is highly reliant on capital inflows to finance the economy, there is space for more acute research to investigate whether South Africa has surpassed this threshold. This study focusses on one aspect of this relationship, namely the relationship between Stock Market Capitalisation and Investment. It uses panel data analysis and other methods to explore whether such an inverse-U relationship exists internationally, and whether South Africa is suffering from the effects of financialisation. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10
Mobilising stories about cultural beliefs and practices on traditional foods to contextualise the topic on nutrition in a Grade 6 township class
- Authors: Nuntsu, Sipho Nimrod
- Date: 2021-10
- Subjects: Culturally relevant pedagogy South Africa , Science Study and teaching (Elementary) South Africa , Nutrition Study and teaching (Elementary) South Africa , Traditional ecological knowledge South Africa , Storytelling , Reasoning , Contiguity Argumentation Theory (CAT) , South African Curriculum Assessment and Policy Statement (CAPS) , Socio-cultural theory
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190940 , vital:45043
- Description: The South African Curriculum Assessment and Policy Statement (CAPS) document stipulates that science teachers should integrate indigenous knowledge (IK) into their science teaching. The rationale for this is to contextualise the content and make science accessible and relevant to learners. Despite these ideals, however, CAPS seems to be silent on how science teachers should go about doing this. Instead, it assumes that all teachers know how to integrate IK in their science teaching. As a result, many teachers are still not sure of how to integrate IK into their science classrooms. Such rhetoric and tension between curriculum formulation and implementation triggered my interest to do a study on how to mobilise stories about cultural beliefs and practices of traditional foods to mediate learning of nutrition in a Grade 6 Natural Sciences township class. The study was underpinned by an interprevist paradigm complemented with an Ubuntu paradigm to enhance explanations. Within these paradigms, a qualitative case study research design was adopted. It was conducted at Mdoko Primary school (pseudonym) in a semi-urban community in the Amathole West district of the Eastern Cape. The participants were 34 Grade 6 learners (15 boys and 19 girls), a Grade 6 Natural Sciences teacher who was my critical friend, and two expert community members. To generate data, I used a focus group discussion, group activities, classroom observations, and learners’ reflective journals. Vygotsky’s socio-cultural theory and Ogunniyi’s Contiguity Argumentation Theory (CAT) were used as theoretical and analytical frameworks, respectively. A thematic approach to data analysis was employed. That is, data were analysed inductively to identify sub-themes and subsequently similar sub-themes were grouped together to form themes. The two expert community members’ presentations equipped my learners with stories on cultural beliefs and practices that were used in the olden days (past) and how such stories are used in our days (present). For instance, the findings of this study revealed that women during menstruation must not drink amasi as it is believed that it would prolong the menstruation time. The findings also revealed that eating of amaqanda and inside meat by youths should be minimised as it is believed that it can stimulate their sex hormones. It also revealed that there is no relevance to science that men eating imifino would be weak among other men who do not eat them. The implications for this study is that science teachers should make some efforts to integrate IK in their teaching to make science accessible and relevant to their learners. To achieve this, the study thus recommends that science teachers should find ways of tapping into the cultural heritage and wisdom that is possessed by the expert community members to enable learners to cross the bridge from home to school. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Nuntsu, Sipho Nimrod
- Date: 2021-10
- Subjects: Culturally relevant pedagogy South Africa , Science Study and teaching (Elementary) South Africa , Nutrition Study and teaching (Elementary) South Africa , Traditional ecological knowledge South Africa , Storytelling , Reasoning , Contiguity Argumentation Theory (CAT) , South African Curriculum Assessment and Policy Statement (CAPS) , Socio-cultural theory
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190940 , vital:45043
- Description: The South African Curriculum Assessment and Policy Statement (CAPS) document stipulates that science teachers should integrate indigenous knowledge (IK) into their science teaching. The rationale for this is to contextualise the content and make science accessible and relevant to learners. Despite these ideals, however, CAPS seems to be silent on how science teachers should go about doing this. Instead, it assumes that all teachers know how to integrate IK in their science teaching. As a result, many teachers are still not sure of how to integrate IK into their science classrooms. Such rhetoric and tension between curriculum formulation and implementation triggered my interest to do a study on how to mobilise stories about cultural beliefs and practices of traditional foods to mediate learning of nutrition in a Grade 6 Natural Sciences township class. The study was underpinned by an interprevist paradigm complemented with an Ubuntu paradigm to enhance explanations. Within these paradigms, a qualitative case study research design was adopted. It was conducted at Mdoko Primary school (pseudonym) in a semi-urban community in the Amathole West district of the Eastern Cape. The participants were 34 Grade 6 learners (15 boys and 19 girls), a Grade 6 Natural Sciences teacher who was my critical friend, and two expert community members. To generate data, I used a focus group discussion, group activities, classroom observations, and learners’ reflective journals. Vygotsky’s socio-cultural theory and Ogunniyi’s Contiguity Argumentation Theory (CAT) were used as theoretical and analytical frameworks, respectively. A thematic approach to data analysis was employed. That is, data were analysed inductively to identify sub-themes and subsequently similar sub-themes were grouped together to form themes. The two expert community members’ presentations equipped my learners with stories on cultural beliefs and practices that were used in the olden days (past) and how such stories are used in our days (present). For instance, the findings of this study revealed that women during menstruation must not drink amasi as it is believed that it would prolong the menstruation time. The findings also revealed that eating of amaqanda and inside meat by youths should be minimised as it is believed that it can stimulate their sex hormones. It also revealed that there is no relevance to science that men eating imifino would be weak among other men who do not eat them. The implications for this study is that science teachers should make some efforts to integrate IK in their teaching to make science accessible and relevant to their learners. To achieve this, the study thus recommends that science teachers should find ways of tapping into the cultural heritage and wisdom that is possessed by the expert community members to enable learners to cross the bridge from home to school. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10
Modification of Gelatin-Methacrylate, Hyaluronic-Methacrylate and Poly(ethylene) glycol Diacrylate hydrogel bioinks towards the additive manufacturing of articular cartilage
- Authors: Barwick, Matthew William
- Date: 2021-10
- Subjects: Cartilage Diseases , Cartilage Regeneration , Articular cartilage Diseases , Chondrogenesis , Stem cells , Scanning electron microscopy , Fourier transform infrared spectroscopy , Three-dimensional printing , Gelatin-Methacrylate , Hyaluronic-Methacrylate , Poly(ethylene) glycolDiacrylate , Hydrogel bioinks , Real-Time Quantitative Cell Analysis (RTCA) , Bioprinting
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191181 , vital:45068
- Description: Cartilage degradation is most commonly associated with Rheumatoid arthritis and Osteoarthritis, affecting millions of people worldwide. Joint transplants commonly use titanium alloys, which have a shelf life of between 10-15 years. Although the titanium transplant restores partial mobility, side effects such as inflammation, swelling, faulty implants, and metal poisoning in some cases resulting from the transplant. The use of additive manufacturing of articular cartilage sheds new, innovative prospects for joint replacements. This study sets out to formulate and characterize five different hydrogel types towards the additive manufacturing of articular cartilage. Chondrogenic and Adipogenic differentiation was carried out on two separate adipose-mesenchymal stem cell lines A270620-01A, and A311019-02T and validation and efficiency of the differentiation and chondrogenic gene expression was carried out using Alcian Blue stain, Oil Red O stain and Quantitative Reverse Transcription PCR (RT-qPCR). Hydrogel formulation and characterisation of 10 % Gelatin-methacryloyl (GelMA), 10 % Poly (ethylene) glycol diacrylate (PEGDA), 5 % GelMA/5 % PEGDA, 10 % GelMA/0.5 % Hyaluronic Acid Methacrylate (HAMA) and 10 % PEGDA/0.5 % HAMA was carried out through swelling and degradation ratios, surface area and porosity characterisation using Scanning Electron Microscopy (SEM). Hydrogel component and spectroscopic analysis were carried using Real-Time Quantitative Cell Analysis (RTCA) and Fourier-transform Infrared Spectroscopy (FTIR) analysis for each formulated hydrogel's chemical characterisation. Three-dimensional printing (3D) of 10 % PEGDA/0.5 % HAMA and 5 % GelMA/5 % PEGDA was performed using the Zortrax INKSPIRE Resin Ultra-Violet (UV) LCD Desktop 3D Printer. Hydrogel sterility and cell viability were carried out for each hydrogel type using fluorescence microscopy. Both A270620-01A and A311019-02T cell lines showed adipogenic and chondrogenic differentiation ability, with A311019-02T cell line showing greater chondrogenic differentiation of Alcian blue staining. The A270620-01A cell line resulted in a greater collagen gene expression based on the RT-qPCR results. The hydrogel 10 % GelMA showed the greatest swelling ratio of 1260 % in DPBS and 1192 % in DMEM. A significant difference between hydrogel swelling and swelling with Dulbecco's Phosphate Buffered Saline (DPBS) and Dulbecco’s Modified Eagle Medium (DMEM) was observed. The 10 % PEGDA hydrogel had the greatest degradation ratio of 59 % mass remaining, where the 10 % GelMA/0.5 % HAMA showed the least amount of degradation with a mass remaining at 91 %. The 10 % GelMA showed the greatest porosity will the largest pore size of 14 μm in diameter. Hydrogel component and spectroscopic analysis showed no cytotoxic effects for the visible light photoinitiator used to polymerize the hydrogel and no cytotoxic effects for the concentrations used in chondrogenic differentiation. The FTIR analysis showed partial gelatin and hyaluronic acid modification with methacrylic anhydride; however, the distinction between the hybrid hydrogels and single polymer hydrogels could not be made effectively. UV and ethanol washing showed to completely sterilise the hydrogel disks from any contaminants, making them suitable for tissue culture. The cell viability analysis showed the 10 % GelMA/HAMA having the highest cell viability of 77.3 % using 5000 cells/disk and 89.64 % viability using 50 000 cells/disk over a 7-day incubation period. Overall, the combination of two polymers, GelMA and HAMA, has good potential as a 3D hydrogel scaffold towards additive manufacturing of articular cartilage. , Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Barwick, Matthew William
- Date: 2021-10
- Subjects: Cartilage Diseases , Cartilage Regeneration , Articular cartilage Diseases , Chondrogenesis , Stem cells , Scanning electron microscopy , Fourier transform infrared spectroscopy , Three-dimensional printing , Gelatin-Methacrylate , Hyaluronic-Methacrylate , Poly(ethylene) glycolDiacrylate , Hydrogel bioinks , Real-Time Quantitative Cell Analysis (RTCA) , Bioprinting
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191181 , vital:45068
- Description: Cartilage degradation is most commonly associated with Rheumatoid arthritis and Osteoarthritis, affecting millions of people worldwide. Joint transplants commonly use titanium alloys, which have a shelf life of between 10-15 years. Although the titanium transplant restores partial mobility, side effects such as inflammation, swelling, faulty implants, and metal poisoning in some cases resulting from the transplant. The use of additive manufacturing of articular cartilage sheds new, innovative prospects for joint replacements. This study sets out to formulate and characterize five different hydrogel types towards the additive manufacturing of articular cartilage. Chondrogenic and Adipogenic differentiation was carried out on two separate adipose-mesenchymal stem cell lines A270620-01A, and A311019-02T and validation and efficiency of the differentiation and chondrogenic gene expression was carried out using Alcian Blue stain, Oil Red O stain and Quantitative Reverse Transcription PCR (RT-qPCR). Hydrogel formulation and characterisation of 10 % Gelatin-methacryloyl (GelMA), 10 % Poly (ethylene) glycol diacrylate (PEGDA), 5 % GelMA/5 % PEGDA, 10 % GelMA/0.5 % Hyaluronic Acid Methacrylate (HAMA) and 10 % PEGDA/0.5 % HAMA was carried out through swelling and degradation ratios, surface area and porosity characterisation using Scanning Electron Microscopy (SEM). Hydrogel component and spectroscopic analysis were carried using Real-Time Quantitative Cell Analysis (RTCA) and Fourier-transform Infrared Spectroscopy (FTIR) analysis for each formulated hydrogel's chemical characterisation. Three-dimensional printing (3D) of 10 % PEGDA/0.5 % HAMA and 5 % GelMA/5 % PEGDA was performed using the Zortrax INKSPIRE Resin Ultra-Violet (UV) LCD Desktop 3D Printer. Hydrogel sterility and cell viability were carried out for each hydrogel type using fluorescence microscopy. Both A270620-01A and A311019-02T cell lines showed adipogenic and chondrogenic differentiation ability, with A311019-02T cell line showing greater chondrogenic differentiation of Alcian blue staining. The A270620-01A cell line resulted in a greater collagen gene expression based on the RT-qPCR results. The hydrogel 10 % GelMA showed the greatest swelling ratio of 1260 % in DPBS and 1192 % in DMEM. A significant difference between hydrogel swelling and swelling with Dulbecco's Phosphate Buffered Saline (DPBS) and Dulbecco’s Modified Eagle Medium (DMEM) was observed. The 10 % PEGDA hydrogel had the greatest degradation ratio of 59 % mass remaining, where the 10 % GelMA/0.5 % HAMA showed the least amount of degradation with a mass remaining at 91 %. The 10 % GelMA showed the greatest porosity will the largest pore size of 14 μm in diameter. Hydrogel component and spectroscopic analysis showed no cytotoxic effects for the visible light photoinitiator used to polymerize the hydrogel and no cytotoxic effects for the concentrations used in chondrogenic differentiation. The FTIR analysis showed partial gelatin and hyaluronic acid modification with methacrylic anhydride; however, the distinction between the hybrid hydrogels and single polymer hydrogels could not be made effectively. UV and ethanol washing showed to completely sterilise the hydrogel disks from any contaminants, making them suitable for tissue culture. The cell viability analysis showed the 10 % GelMA/HAMA having the highest cell viability of 77.3 % using 5000 cells/disk and 89.64 % viability using 50 000 cells/disk over a 7-day incubation period. Overall, the combination of two polymers, GelMA and HAMA, has good potential as a 3D hydrogel scaffold towards additive manufacturing of articular cartilage. , Thesis (MSc) -- Faculty of Science, Biotechnology Innovation Centre, 2021
- Full Text:
- Date Issued: 2021-10
Nonlinear optical properties of metal free thio alkyl and tert-butyl phenoxy phthalocyanine
- Authors: Joseph, Otto
- Date: 2021-10
- Subjects: Nonlinear optics , Phthalocyanines , Time-dependent density functional theory , Magnetic circular dichroism , Reverse saturable absorption (RSA) , Real Time Dependent Density Functional Theory (RT-TDDFT)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190712 , vital:45021
- Description: This work reports on the nonlinear optical properties of tetra - and octa substituted phthalocyanines (Pcs) utilising pentane thiol and 4-tertbutyl phenol as substituents. Their nonlinear absorption coefficient (𝛽) and absorption cross sections were determined using the Z-scan technique with a 10 ns pulse laser at 532 nm. The molecular second order hyperpolarizability Im[γ] was observed and the following Im[γ] trend was obtained for 𝛼-H2Pc(SC5H11)4 isomers, 5.93 ×10−31 (Cs) 2.24×10−32(D2h) > 1.21×10−32(C4h) > 1.05×10−32 (C2v) esu, respectively, in chloroform. Symmetry was seen to have an effect on the observed reverse saturable absorption (RSA) response. Based on the five level model rate equation nonlinear fit of the RSA response curves and Real Time Time Dependant Density Functional Theory (RT-TDDFT) results, the singlet excited state population dynamics was found to play a significant role in producing the observed Im[γ] trend. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Joseph, Otto
- Date: 2021-10
- Subjects: Nonlinear optics , Phthalocyanines , Time-dependent density functional theory , Magnetic circular dichroism , Reverse saturable absorption (RSA) , Real Time Dependent Density Functional Theory (RT-TDDFT)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190712 , vital:45021
- Description: This work reports on the nonlinear optical properties of tetra - and octa substituted phthalocyanines (Pcs) utilising pentane thiol and 4-tertbutyl phenol as substituents. Their nonlinear absorption coefficient (𝛽) and absorption cross sections were determined using the Z-scan technique with a 10 ns pulse laser at 532 nm. The molecular second order hyperpolarizability Im[γ] was observed and the following Im[γ] trend was obtained for 𝛼-H2Pc(SC5H11)4 isomers, 5.93 ×10−31 (Cs) 2.24×10−32(D2h) > 1.21×10−32(C4h) > 1.05×10−32 (C2v) esu, respectively, in chloroform. Symmetry was seen to have an effect on the observed reverse saturable absorption (RSA) response. Based on the five level model rate equation nonlinear fit of the RSA response curves and Real Time Time Dependant Density Functional Theory (RT-TDDFT) results, the singlet excited state population dynamics was found to play a significant role in producing the observed Im[γ] trend. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
Numerical evolution of plane gravitational waves
- Authors: Hakata, Jonathan
- Date: 2021-10
- Subjects: Gravitational waves , Space and time , Einstein field equations , de Sitter metric , Perturbed spacetime
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190248 , vital:44977
- Description: Unlike electromagnetic waves, gravitational waves self interact. This interaction is non-linear and can have very interesting properties which effect the curvature of space-time. A gravitational plane wave collider, implemented in the Python package COFFEE [20] that been developed in recent years by the Otago relativity group and implements the method of lines, can be reliably used to study this self-interaction. This was shown to work well numerically as profounded by Frauendiener, Stevens and Whale in 2014 [24]. For this reason, COFFEE will be used to study these gravitational wave propagations and subsequently collisions. The Einstein field equations are formulated as a well-posed initial boundary value problem (IBVP) in the Friedrich-Nagy gauge [26] and due to the large class of boundary conditions admitted by this framework, a variety of investigations into the propagation of plane gravitational waves could be carried out. This study focuses on the propagation of plane gravitational waves in the de Sitter (dS) space-time, which is the maximally symmetric solution of the Einstein’s vacuum field equations with a positive cosmological constant λ. There is substantial cosmological evidence that our universe is asymptotically de Sitter, yet no work, analytical nor numerical, has been done on gravitational plane waves propagating on such a space-time, mainly due to the increased complexity from the non-vanishing λ. Firstly, it is found analytically that with an arbitrary cosmological constant λ and a non-vanishing energy momentum tensor, the constraints will propagate. This means that we still have a wellposed IBVP, which is nontrivial since the Friedrich-Nagy gauge has only been shown to lead to a wellposed IBVP without matter [26]. Using this system, we consider one ingoing wave propagating on said space-time in vacuum. The area of the ingoing wave profile is varied and inferences are made about the different phenomena that arise in the curvature of space-time during the evolution. It is found that there exists a critical value of the wave’s area, ac, whereby taking the area below this value the system asymptotes to its initial state, and above the system diverges, indicating the presence of a singularity. Furthermore, we define an expansion parameter H to measure how the gravitational waves influence the accelerated expansion, generalising (numerically) results of Tsamis and Woodard. , Thesis (MSc) -- Faculty of Science, Mathematics, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Hakata, Jonathan
- Date: 2021-10
- Subjects: Gravitational waves , Space and time , Einstein field equations , de Sitter metric , Perturbed spacetime
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190248 , vital:44977
- Description: Unlike electromagnetic waves, gravitational waves self interact. This interaction is non-linear and can have very interesting properties which effect the curvature of space-time. A gravitational plane wave collider, implemented in the Python package COFFEE [20] that been developed in recent years by the Otago relativity group and implements the method of lines, can be reliably used to study this self-interaction. This was shown to work well numerically as profounded by Frauendiener, Stevens and Whale in 2014 [24]. For this reason, COFFEE will be used to study these gravitational wave propagations and subsequently collisions. The Einstein field equations are formulated as a well-posed initial boundary value problem (IBVP) in the Friedrich-Nagy gauge [26] and due to the large class of boundary conditions admitted by this framework, a variety of investigations into the propagation of plane gravitational waves could be carried out. This study focuses on the propagation of plane gravitational waves in the de Sitter (dS) space-time, which is the maximally symmetric solution of the Einstein’s vacuum field equations with a positive cosmological constant λ. There is substantial cosmological evidence that our universe is asymptotically de Sitter, yet no work, analytical nor numerical, has been done on gravitational plane waves propagating on such a space-time, mainly due to the increased complexity from the non-vanishing λ. Firstly, it is found analytically that with an arbitrary cosmological constant λ and a non-vanishing energy momentum tensor, the constraints will propagate. This means that we still have a wellposed IBVP, which is nontrivial since the Friedrich-Nagy gauge has only been shown to lead to a wellposed IBVP without matter [26]. Using this system, we consider one ingoing wave propagating on said space-time in vacuum. The area of the ingoing wave profile is varied and inferences are made about the different phenomena that arise in the curvature of space-time during the evolution. It is found that there exists a critical value of the wave’s area, ac, whereby taking the area below this value the system asymptotes to its initial state, and above the system diverges, indicating the presence of a singularity. Furthermore, we define an expansion parameter H to measure how the gravitational waves influence the accelerated expansion, generalising (numerically) results of Tsamis and Woodard. , Thesis (MSc) -- Faculty of Science, Mathematics, 2021
- Full Text:
- Date Issued: 2021-10
Phylogeography and reproductive isolation of the brown mussel, Perna perna, on the South African coastline
- Authors: Barker, Cassandra
- Date: 2021-10
- Subjects: Mexilhao mussel South Africa , Phylogeography South Africa , Mexilhao mussel Reproduction , Mexilhao mussel Genetics , Intertidal organisms South Africa , Mexilhao mussel Climatic factors South Africa , Cytochrome oxidase , Mitochondrial DNA , Haplotype network
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190041 , vital:44958
- Description: Maintenance of a species’ abundance and adaptive potential is partially dependent on its genetic diversity. Distinct genetic lineages within a species can differ significantly in their resistance and resilience to environmental pressure. An assessment of such differences is key to grasp the adaptive potential of a species. Physical environmental conditions are significant determinants of the distribution of species and their genetic lineages. Under climate change scenarios, the assessment of the temporal stability of the spatial distribution of genetic structure has important consequences for conservation as it offers key insights into the adaptive potential and evolutionary capacity of a species. This thesis investigated the phylogeography and reproductive isolation of Perna perna, the brown mussel. This species is an ecologically and economically important intertidal mussel on South Africa’s coastline. It was determined in 2007 that there were two distinct genetic lineages of P. perna present on South Africa’s coastline, the Eastern and Western lineage. This thesis compared mitochondrial DNA between samples collected in 2007 and samples collected in 2019 to determine differences in genetic structure of P. perna over time. This thesis further investigated the reproductive timing of the two lineages to determine if this contributes to the maintenance of the genetic structure of this species. The results show that there is a shift in the distribution of the Eastern lineage since 2007, an increase in the range of the overlap region, and there was a change in genetic diversity in the form of private haplotypes between 2007 and 2019. The lineages have unsynchronised spawning and reproductive patterns are more closely linked to changes in temperature. While the lineages have shown slight distributional changes over time, the influence of environmental conditions and the predicted changes in sea surface temperatures could see a change in future populations’ fitness and dispersal. Thus, changes in sea surface temperature could affect reproductive timing and the future genetic stability of the species. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Barker, Cassandra
- Date: 2021-10
- Subjects: Mexilhao mussel South Africa , Phylogeography South Africa , Mexilhao mussel Reproduction , Mexilhao mussel Genetics , Intertidal organisms South Africa , Mexilhao mussel Climatic factors South Africa , Cytochrome oxidase , Mitochondrial DNA , Haplotype network
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190041 , vital:44958
- Description: Maintenance of a species’ abundance and adaptive potential is partially dependent on its genetic diversity. Distinct genetic lineages within a species can differ significantly in their resistance and resilience to environmental pressure. An assessment of such differences is key to grasp the adaptive potential of a species. Physical environmental conditions are significant determinants of the distribution of species and their genetic lineages. Under climate change scenarios, the assessment of the temporal stability of the spatial distribution of genetic structure has important consequences for conservation as it offers key insights into the adaptive potential and evolutionary capacity of a species. This thesis investigated the phylogeography and reproductive isolation of Perna perna, the brown mussel. This species is an ecologically and economically important intertidal mussel on South Africa’s coastline. It was determined in 2007 that there were two distinct genetic lineages of P. perna present on South Africa’s coastline, the Eastern and Western lineage. This thesis compared mitochondrial DNA between samples collected in 2007 and samples collected in 2019 to determine differences in genetic structure of P. perna over time. This thesis further investigated the reproductive timing of the two lineages to determine if this contributes to the maintenance of the genetic structure of this species. The results show that there is a shift in the distribution of the Eastern lineage since 2007, an increase in the range of the overlap region, and there was a change in genetic diversity in the form of private haplotypes between 2007 and 2019. The lineages have unsynchronised spawning and reproductive patterns are more closely linked to changes in temperature. While the lineages have shown slight distributional changes over time, the influence of environmental conditions and the predicted changes in sea surface temperatures could see a change in future populations’ fitness and dispersal. Thus, changes in sea surface temperature could affect reproductive timing and the future genetic stability of the species. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-10
Scaffolding argumentative writing through Reading to Learn (RtL) pedagogy: a case study of three grade 11 English second language teachers in Namibia
- Authors: Matengu, Ernest Samubu
- Date: 2021-10
- Subjects: Rose, David, 1955- , Reading (Secondary) , Persuasion (Rhetoric) Study and teaching (Secondary) Namibia , English language Writing Study and teaching (Secondary) Namibia , English language Rhetoric Study and teaching (Secondary) Namibia , English language Study and teaching (Secondary) Foreign speakers Case studies , Reading to Learn , Scaffolding Interaction Cycle
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191148 , vital:45065
- Description: The central aim of this study was to investigate the positive impact of Reading to Learn (RtL) pedagogy in enhancing Grade 11 learners’ argumentative writing skills. This was a case study of one school in Otjozondjupa region in Namibia. The pedagogy, RtL, was designed to address learning inequalities with marginalised communities in Australia. Coupled with challenges in literacy development in learners, current methods have not successfully addressed the teaching and learning of argumentative writing amidst learning inequalities. This study employed the six stages of Scaffolding Interaction Cycle of RtL in order to teach argumentative writing. As is evidenced in recent research, the scaffolding cycle of RtL provides equal opportunities to learners from diverse backgrounds to attain epistemological access at the same pace. RtL’s theoretical and conceptual framework is derived from Bernstein’s theory of education as pedagogic discourse (a device for maintaining inequality in society), Vygotsky’s theory of learning as a social process and Halliday’s model of language as text in social context. The two research questions for this study were: (1) What role does Reading to Learn (RtL) pedagogy play in developing Grade 11 learners’ ability to write argumentative essays? And (2) How can the implementation of RtL pedagogy through scaffolding impact on/improve learners’ literacy skills development for argumentative essay writing? This qualitative case study generated data through observation of three teachers’ lessons, a Stimulated Recall Interview (SRI) conducted with the three teachers and learners’ pre and posttest of argumentative essays. The findings of this study revealed that teachers found RtL as a comprehensive pedagogy that makes teaching and learning of argumentative writing successful through systematic scaffolding of learning. Learners’ written pre and posttest also showed a narrowing of the gap between weak and strong learners in that weak learners recorded an upward trend similar to that of strong learners in their posttest. Given the design of RtL and studies conducted globally, the findings of this study can be comparable. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Matengu, Ernest Samubu
- Date: 2021-10
- Subjects: Rose, David, 1955- , Reading (Secondary) , Persuasion (Rhetoric) Study and teaching (Secondary) Namibia , English language Writing Study and teaching (Secondary) Namibia , English language Rhetoric Study and teaching (Secondary) Namibia , English language Study and teaching (Secondary) Foreign speakers Case studies , Reading to Learn , Scaffolding Interaction Cycle
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191148 , vital:45065
- Description: The central aim of this study was to investigate the positive impact of Reading to Learn (RtL) pedagogy in enhancing Grade 11 learners’ argumentative writing skills. This was a case study of one school in Otjozondjupa region in Namibia. The pedagogy, RtL, was designed to address learning inequalities with marginalised communities in Australia. Coupled with challenges in literacy development in learners, current methods have not successfully addressed the teaching and learning of argumentative writing amidst learning inequalities. This study employed the six stages of Scaffolding Interaction Cycle of RtL in order to teach argumentative writing. As is evidenced in recent research, the scaffolding cycle of RtL provides equal opportunities to learners from diverse backgrounds to attain epistemological access at the same pace. RtL’s theoretical and conceptual framework is derived from Bernstein’s theory of education as pedagogic discourse (a device for maintaining inequality in society), Vygotsky’s theory of learning as a social process and Halliday’s model of language as text in social context. The two research questions for this study were: (1) What role does Reading to Learn (RtL) pedagogy play in developing Grade 11 learners’ ability to write argumentative essays? And (2) How can the implementation of RtL pedagogy through scaffolding impact on/improve learners’ literacy skills development for argumentative essay writing? This qualitative case study generated data through observation of three teachers’ lessons, a Stimulated Recall Interview (SRI) conducted with the three teachers and learners’ pre and posttest of argumentative essays. The findings of this study revealed that teachers found RtL as a comprehensive pedagogy that makes teaching and learning of argumentative writing successful through systematic scaffolding of learning. Learners’ written pre and posttest also showed a narrowing of the gap between weak and strong learners in that weak learners recorded an upward trend similar to that of strong learners in their posttest. Given the design of RtL and studies conducted globally, the findings of this study can be comparable. , Thesis (MEd) -- Faculty of Education, Education, 2021
- Full Text:
- Date Issued: 2021-10
Self-inquiry: Comparing Plato and Patanjali
- Authors: Coughlan, Daniel Michael
- Date: 2021-10
- Subjects: Plato , Patañjali , Self , Identity (Philosophical concept) , Comparison (Philosophy) , Justification (Theory of knowledge)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190066 , vital:44960
- Description: At its most effective my research hopes to re-affirm the central value and importance of self-inquiry. That is, I hope to echo the familiar call of the wise to know thyself. Of the many mouths and temple walls that have lent authority to this precept there is perhaps no mouth more important than one’s own. To know thyself is the task and responsibility of the individual. In order to arrive at the point where I can re-affirm its value I explore the nature of self-inquiry with the help of Plato, Patanjali and a comparison between them. I propose two general senses in which we might understand self-inquiry and seek to bring out the core problems faced by each. We find an account of these two senses and the relationship between them in both Plato and Patanjali, so too, though less obviously, in the comparison between them. The comparison provides the opportunity for reflecting on the ground that it moves from and depends on, the common ground we assume between the two compared philosophers/ies. I contend that this ground is ultimately the comparer, one’s self. The consequence is that the comparative project and the project of self-inquiry both meet and are mutually beneficial. The three together; Plato, Patanjali, and the comparison between them help us account for nature of self-inquiry in helping us to better understand the relationship between the two senses in which we can come to understand and think about it. In the first sense, self-inquiry is cast as the examination of one’s life. In the second sense, we are invited to consider the possibility of an unmediated knowing of the examiner, an unmediated self-knowing. With a better understanding of what self-inquiry is I stand to conclude by re-affirming its value. , Thesis (MPhil) -- Faculty of Humanities, Philosophy, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Coughlan, Daniel Michael
- Date: 2021-10
- Subjects: Plato , Patañjali , Self , Identity (Philosophical concept) , Comparison (Philosophy) , Justification (Theory of knowledge)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190066 , vital:44960
- Description: At its most effective my research hopes to re-affirm the central value and importance of self-inquiry. That is, I hope to echo the familiar call of the wise to know thyself. Of the many mouths and temple walls that have lent authority to this precept there is perhaps no mouth more important than one’s own. To know thyself is the task and responsibility of the individual. In order to arrive at the point where I can re-affirm its value I explore the nature of self-inquiry with the help of Plato, Patanjali and a comparison between them. I propose two general senses in which we might understand self-inquiry and seek to bring out the core problems faced by each. We find an account of these two senses and the relationship between them in both Plato and Patanjali, so too, though less obviously, in the comparison between them. The comparison provides the opportunity for reflecting on the ground that it moves from and depends on, the common ground we assume between the two compared philosophers/ies. I contend that this ground is ultimately the comparer, one’s self. The consequence is that the comparative project and the project of self-inquiry both meet and are mutually beneficial. The three together; Plato, Patanjali, and the comparison between them help us account for nature of self-inquiry in helping us to better understand the relationship between the two senses in which we can come to understand and think about it. In the first sense, self-inquiry is cast as the examination of one’s life. In the second sense, we are invited to consider the possibility of an unmediated knowing of the examiner, an unmediated self-knowing. With a better understanding of what self-inquiry is I stand to conclude by re-affirming its value. , Thesis (MPhil) -- Faculty of Humanities, Philosophy, 2021
- Full Text:
- Date Issued: 2021-10
The impact of the BBB-EE policy instrument on wealth inequality : A case study on the banking sector of South Africa
- Moshikaro, Kei Kgaogelo Felia
- Authors: Moshikaro, Kei Kgaogelo Felia
- Date: 2021-10
- Subjects: Black Economic Empowerment (Program : South Africa) , Income distribution South Africa , South Africa Economic policy , South Africa Economic conditions 1991- , Banks and banking South Africa , South Africa. Financial Sector Regulation Act, 2017
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191035 , vital:45052
- Description: It has been recognised that, whether measured in terms of income or wealth, South Africa remains as one of the most unequal societies in the world. Reducing these high levels of inequalities has been an important area of focus through the formulation of policy instruments by South African policy makers. Within a specific focus on the South African banking sector, the objective of this research is to ascertaining the extent to which addressing inequalities was in fact achieved through the changing of wealth ownerships under the Broad Based Black Economic Empowerment policy instrument. To contextualise, the thesis surveys literature on two stylised economic hypotheses on both income and wealth to understand the potential causes of their respective inequalities. An exploration of both income, wealth measurements and their distributions in South Africa are presented, in addition to policy instruments designed to ameliorate income and wealth inequalities in South Africa. The thesis further presents brief case studies from the literature on Brazil’s success in reducing its high income inequality and the Malaysian National Economic Policy empowerment program to effect wealth economic transformation, as comparatives to the South African experience. The thesis findings indicate that contrary to the objectives of the BBB-EE instrument and wealth transfers, the program within the banking sector resulted in highly unequal wealth shares and equally high concentration levels. The richest top one per cent of individuals participating in the BEE transactions in the banking sector captured 79 per cent of the total wealth transfers, this providing indications of extremely high concentrations of wealth. Further, wealth meaningfully cumulates at only the 50 percentage level of the wealth distribution, this additionally suggesting that wealth transfers featured less in the bottom half of the wealth distribution. The banking BBB-EE wealth Gini coefficient of 0.88 is evidence of the extremely high levels of inequality that resulted from the BBB-EE program within the banking sector. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Moshikaro, Kei Kgaogelo Felia
- Date: 2021-10
- Subjects: Black Economic Empowerment (Program : South Africa) , Income distribution South Africa , South Africa Economic policy , South Africa Economic conditions 1991- , Banks and banking South Africa , South Africa. Financial Sector Regulation Act, 2017
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/191035 , vital:45052
- Description: It has been recognised that, whether measured in terms of income or wealth, South Africa remains as one of the most unequal societies in the world. Reducing these high levels of inequalities has been an important area of focus through the formulation of policy instruments by South African policy makers. Within a specific focus on the South African banking sector, the objective of this research is to ascertaining the extent to which addressing inequalities was in fact achieved through the changing of wealth ownerships under the Broad Based Black Economic Empowerment policy instrument. To contextualise, the thesis surveys literature on two stylised economic hypotheses on both income and wealth to understand the potential causes of their respective inequalities. An exploration of both income, wealth measurements and their distributions in South Africa are presented, in addition to policy instruments designed to ameliorate income and wealth inequalities in South Africa. The thesis further presents brief case studies from the literature on Brazil’s success in reducing its high income inequality and the Malaysian National Economic Policy empowerment program to effect wealth economic transformation, as comparatives to the South African experience. The thesis findings indicate that contrary to the objectives of the BBB-EE instrument and wealth transfers, the program within the banking sector resulted in highly unequal wealth shares and equally high concentration levels. The richest top one per cent of individuals participating in the BEE transactions in the banking sector captured 79 per cent of the total wealth transfers, this providing indications of extremely high concentrations of wealth. Further, wealth meaningfully cumulates at only the 50 percentage level of the wealth distribution, this additionally suggesting that wealth transfers featured less in the bottom half of the wealth distribution. The banking BBB-EE wealth Gini coefficient of 0.88 is evidence of the extremely high levels of inequality that resulted from the BBB-EE program within the banking sector. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2021
- Full Text:
- Date Issued: 2021-10
The physical activity status and the impact of lifestyle behaviours on workplace productivity and absenteeism of Transnet employees
- Authors: Zimmermann, Sharnae Vanessa
- Date: 2021-10
- Subjects: Transnet (Firm : South Africa) Employees , Absenteeism (Labor) South Africa Durban , Labor productivity South Africa Durban , Exercise , Sedentary behavior , Lifestyles
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190077 , vital:44961
- Description: Increased sitting time, insufficient physical activity and sub-optimal body composition are all contributing to the global disease burden. This is made evident by increases in obesity, type II diabetes, cardiovascular diseases (i.e. hypertension and strokes), cancer and other non-communicable diseases resulting in absenteeism and reduced productivity in the workplace. The global rise in sitting time and physical inactivity is caused, in part, by changes in transport convenience, work roles and technological advancements. Employees working in office environments or driving trains sit for prolonged periods; something which is evident in the industry that Transnet operates in. Sitting time and physical inactivity are independent risk factors for non-communicable diseases with poor nutrition, smoking, alcohol consumption and psychological wellbeing, being separate constructs. The purpose of the study is to determine the levels of sedentary behaviour, physical inactivity, obesity, nutrition, alcohol consumption, smoking, non-communicable disease risk, mental wellbeing and their association with productivity and absenteeism in office workers and train drivers at Transnet Freight Rail, Durban. A cross-sectional study was done with 40 participants, 20 office workers and 20 train drivers. Stature (175.80 ± 9.43 ±cm) and body mass (83.85 ± 20.31 kg) were measured; and body mass index calculated (26.98 ± 5.37 kg.m2). Physical activity levels, sedentary behaviour, body mass index and other lifestyle factors were explored using an amended version of The Health and Wellbeing survey, a self-report measure. The results revealed that there was a high prevalence of sedentary behaviour (train drivers = 7.85 ± 2.21 and office workers = 8.3 ± 1.03), particularly among office workers. Most of the participants had a relatively high body mass index, placing in the overweight and obese category, particularly among train drivers. The prevalence of physical inactivity was marginally higher for office workers compared to train drivers. There were significantly (p<0.05) higher levels of physical activity within train drivers with a moderate effect size. There were limited associations found between lifestyle factors and sickness absenteeism and worker productivity. Obesity had the most prominent relationship with noncommunicable diseases, followed by high levels of sedentary behaviour, not meeting physical activity guidelines, obesity, overweight, and prolonged sitting time at work. A significant and moderate correlation was found between obesity and absenteeism (train drivers: r = 0.32 and office workers: r= 0.46), however, no associations were found between sedentary behaviour, physical activity and fruit and vegetable intake and absenteeism. Lastly, the association between physical activity and productivity among the train drivers was low negative (r=-0.15) which was not significant (p>0.05). The associations between physical activity and productivity among office workers, however, was both significant (p<0.05) and moderate positive (r=0.39). The vegetable intake among the office workers showed a significant (p<0.05) moderate positive association with productivity (r=0.49). The association between vegetable intake and productivity among the train drivers was not significant (p>0.05) and low positive (r=0.16). There was a significant (p<0.05) and moderate positive association between fruit intake and productivity among both train drivers (r=0.43) and office workers (r=0.47). No significant associations between sedentary behaviour and obesity and productivity were found. The current study provided new insight into the risks associated with lifestyle factors of office workers and train drivers in the transportation sector. The poor lifestyle factors, together with the high prevalence of sedentary behaviour and physical inactivity, provide ideal opportunities for future interventions to focus on workers productivity and overall wellbeing. The job design of train drivers and office workers does not place significant importance on employee health and wellness. Essentially they are not “healthy” but they work productively, giving reason as to why employee wellness is not a priority for employers. The current findings of the study suggest that adopting regular physical activity, healthy dietary patterns and reduced sitting time should be promoted as key components of lifestyle interventions for the prevention of non-communicable diseases in office workers and train drivers. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Zimmermann, Sharnae Vanessa
- Date: 2021-10
- Subjects: Transnet (Firm : South Africa) Employees , Absenteeism (Labor) South Africa Durban , Labor productivity South Africa Durban , Exercise , Sedentary behavior , Lifestyles
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190077 , vital:44961
- Description: Increased sitting time, insufficient physical activity and sub-optimal body composition are all contributing to the global disease burden. This is made evident by increases in obesity, type II diabetes, cardiovascular diseases (i.e. hypertension and strokes), cancer and other non-communicable diseases resulting in absenteeism and reduced productivity in the workplace. The global rise in sitting time and physical inactivity is caused, in part, by changes in transport convenience, work roles and technological advancements. Employees working in office environments or driving trains sit for prolonged periods; something which is evident in the industry that Transnet operates in. Sitting time and physical inactivity are independent risk factors for non-communicable diseases with poor nutrition, smoking, alcohol consumption and psychological wellbeing, being separate constructs. The purpose of the study is to determine the levels of sedentary behaviour, physical inactivity, obesity, nutrition, alcohol consumption, smoking, non-communicable disease risk, mental wellbeing and their association with productivity and absenteeism in office workers and train drivers at Transnet Freight Rail, Durban. A cross-sectional study was done with 40 participants, 20 office workers and 20 train drivers. Stature (175.80 ± 9.43 ±cm) and body mass (83.85 ± 20.31 kg) were measured; and body mass index calculated (26.98 ± 5.37 kg.m2). Physical activity levels, sedentary behaviour, body mass index and other lifestyle factors were explored using an amended version of The Health and Wellbeing survey, a self-report measure. The results revealed that there was a high prevalence of sedentary behaviour (train drivers = 7.85 ± 2.21 and office workers = 8.3 ± 1.03), particularly among office workers. Most of the participants had a relatively high body mass index, placing in the overweight and obese category, particularly among train drivers. The prevalence of physical inactivity was marginally higher for office workers compared to train drivers. There were significantly (p<0.05) higher levels of physical activity within train drivers with a moderate effect size. There were limited associations found between lifestyle factors and sickness absenteeism and worker productivity. Obesity had the most prominent relationship with noncommunicable diseases, followed by high levels of sedentary behaviour, not meeting physical activity guidelines, obesity, overweight, and prolonged sitting time at work. A significant and moderate correlation was found between obesity and absenteeism (train drivers: r = 0.32 and office workers: r= 0.46), however, no associations were found between sedentary behaviour, physical activity and fruit and vegetable intake and absenteeism. Lastly, the association between physical activity and productivity among the train drivers was low negative (r=-0.15) which was not significant (p>0.05). The associations between physical activity and productivity among office workers, however, was both significant (p<0.05) and moderate positive (r=0.39). The vegetable intake among the office workers showed a significant (p<0.05) moderate positive association with productivity (r=0.49). The association between vegetable intake and productivity among the train drivers was not significant (p>0.05) and low positive (r=0.16). There was a significant (p<0.05) and moderate positive association between fruit intake and productivity among both train drivers (r=0.43) and office workers (r=0.47). No significant associations between sedentary behaviour and obesity and productivity were found. The current study provided new insight into the risks associated with lifestyle factors of office workers and train drivers in the transportation sector. The poor lifestyle factors, together with the high prevalence of sedentary behaviour and physical inactivity, provide ideal opportunities for future interventions to focus on workers productivity and overall wellbeing. The job design of train drivers and office workers does not place significant importance on employee health and wellness. Essentially they are not “healthy” but they work productively, giving reason as to why employee wellness is not a priority for employers. The current findings of the study suggest that adopting regular physical activity, healthy dietary patterns and reduced sitting time should be promoted as key components of lifestyle interventions for the prevention of non-communicable diseases in office workers and train drivers. , Thesis (MSc) -- Faculty of Science, Human Kinetics and Ergonomics, 2021
- Full Text:
- Date Issued: 2021-10
The tuber-feeding weevil Listronotus frontalis as a candidate biological control agent for the invasive semi-aquatic plant Sagittaria platyphylla within South Africa
- Authors: Rogers, Daniel James
- Date: 2021-10
- Subjects: Listronotus South Africa , Arrowhead (Plants) South Africa , Arrowhead (Plants) Biological control South Africa , Invasive plants Biological control South Africa , Insects as biological pest control agents South Africa , Plant populations South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190731 , vital:45023
- Description: Sagittaria platyphylla (Engelm.) J.G.Sm. (Alismataceae) is an invasive, aquatic macrophyte originating in the southern United States of America. In South Africa, the plant was first detected in Krantzkloof Nature Reserve, KwaZulu-Natal Province in 2008, and due to its known impact in other countries, it was listed as a Category 1a invader species under the National Environmental Management: Biodiversity Act 2004 (NEM:BA). This invasive plant has proved difficult to manage due to its varied growth forms and reproductive strategies, such as prolific seed and below ground tuber production. Due to the limitations of conventional control mechanisms, biological control is currently being considered as a potential control option. The tuber feeding weevil Listronotus frontalis LeConte (Coleoptera: Curculionidae) has been identified as a candidate biological control agent for this invasive species. The aims of this study were twofold; to firstly determine the importance of tubers to S. platyphylla populations growing in South Africa; and secondly, to determine the biology and suitability of L. frontalis, a tuber feeder, as a candidate biological control agent. Surveys of S. platyphylla populations in South Africa showed that tubers were found in all sampled sites, except for Krantzkloof Nature reserve in KwaZulu-Natal Province. The highest number of tubers was 97.75 ± 10.62 (SE) m-2 recorded at Jonkershoek in the Western Cape Province. Monthly sampling from two sites in the Eastern Cape Province, the Makana Botanical Gardens and Maden Dam showed that neither season nor water depth affected tuber production. However, the mean number of tubers as well as mass of tubers sampled, were consistently higher (F(1,179) = 20.9542, P < 0.0001) and heavier (F(1, 857) = 585.7293, P < 0.0001) at the Botanical Gardens than at Maden Dam, respectively. The study showed that tubers are an important life stage of S. platyphylla populations and may vary in size and abundance between and within sites. The tuber feeding weevil was shown to develop from egg to ovipositing adult within just over 40 days. Females were recorded to lay up to 48 eggs within a period of one week. Impact studies showed that adult feeding led to a reduction in all but one of the 11 measured plant growth and developmental measurements, including a reduction in the mean mass of the above-ground plant material (F(2,2743) = 12.05, P = 0.002) as well as a reduction in size and abundance of tubers (F(2,58.47) = 9.756, P = 0.0006) and stolons(F(14.943) = 8.7577, P = 0.003). These results are encouraging and suggest that if the insect is released in South Africa, it may prove to be a valuable biocontrol agent. It is concluded that, until suitable biological control options become available in South Africa, the chemical and mechanical control measures currently implemented should continue, however, controlling tubers should be considered during the planning and implementation of these strategies. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Rogers, Daniel James
- Date: 2021-10
- Subjects: Listronotus South Africa , Arrowhead (Plants) South Africa , Arrowhead (Plants) Biological control South Africa , Invasive plants Biological control South Africa , Insects as biological pest control agents South Africa , Plant populations South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/190731 , vital:45023
- Description: Sagittaria platyphylla (Engelm.) J.G.Sm. (Alismataceae) is an invasive, aquatic macrophyte originating in the southern United States of America. In South Africa, the plant was first detected in Krantzkloof Nature Reserve, KwaZulu-Natal Province in 2008, and due to its known impact in other countries, it was listed as a Category 1a invader species under the National Environmental Management: Biodiversity Act 2004 (NEM:BA). This invasive plant has proved difficult to manage due to its varied growth forms and reproductive strategies, such as prolific seed and below ground tuber production. Due to the limitations of conventional control mechanisms, biological control is currently being considered as a potential control option. The tuber feeding weevil Listronotus frontalis LeConte (Coleoptera: Curculionidae) has been identified as a candidate biological control agent for this invasive species. The aims of this study were twofold; to firstly determine the importance of tubers to S. platyphylla populations growing in South Africa; and secondly, to determine the biology and suitability of L. frontalis, a tuber feeder, as a candidate biological control agent. Surveys of S. platyphylla populations in South Africa showed that tubers were found in all sampled sites, except for Krantzkloof Nature reserve in KwaZulu-Natal Province. The highest number of tubers was 97.75 ± 10.62 (SE) m-2 recorded at Jonkershoek in the Western Cape Province. Monthly sampling from two sites in the Eastern Cape Province, the Makana Botanical Gardens and Maden Dam showed that neither season nor water depth affected tuber production. However, the mean number of tubers as well as mass of tubers sampled, were consistently higher (F(1,179) = 20.9542, P < 0.0001) and heavier (F(1, 857) = 585.7293, P < 0.0001) at the Botanical Gardens than at Maden Dam, respectively. The study showed that tubers are an important life stage of S. platyphylla populations and may vary in size and abundance between and within sites. The tuber feeding weevil was shown to develop from egg to ovipositing adult within just over 40 days. Females were recorded to lay up to 48 eggs within a period of one week. Impact studies showed that adult feeding led to a reduction in all but one of the 11 measured plant growth and developmental measurements, including a reduction in the mean mass of the above-ground plant material (F(2,2743) = 12.05, P = 0.002) as well as a reduction in size and abundance of tubers (F(2,58.47) = 9.756, P = 0.0006) and stolons(F(14.943) = 8.7577, P = 0.003). These results are encouraging and suggest that if the insect is released in South Africa, it may prove to be a valuable biocontrol agent. It is concluded that, until suitable biological control options become available in South Africa, the chemical and mechanical control measures currently implemented should continue, however, controlling tubers should be considered during the planning and implementation of these strategies. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2021
- Full Text:
- Date Issued: 2021-10
Gender bias in the field of economics: an analysis of South African academia
- Authors: Hitchcock, Siobhan
- Date: 2020-10-30
- Subjects: Sexism South Africa , Sexism in higher education South Africa , Economics Study and teaching (Higher) South Africa , Economics teachers South Africa , Women in higher education South Africa
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/366275 , vital:65850
- Description: In recent years there has been a growing focus internationally on the low participation of females in Economics, both in academia and business. While female enrolment in higher education, including other maths-based subjects, has grown substantially, this has not been the case for Economics. Economics, particularly as one progresses through postgraduate studies to doctoral degrees now stands out as an outlier. A number of reasons have been advanced for this, including the nature of the subject, the type of people it attracts and the lack of female role models. Male and female enrolments in South African HEIs have grown between 2007 and 2017, but females have grown at a faster rate, thus increasing the female share of total enrolments to 59%. Female students are more successful and so make up an even greater proportion of South African graduates. Female enrolments and graduates are also higher than in the US. As in the US there is a significant drop off in female representation when progressing from undergraduate to postgraduate studies in South Africa. When looking at Economics in South Africa in comparison to the broad CESM categories, female enrolment in Economics Bachelor degrees is significantly lower than in Business and Humanities, but on a par with STEM subjects. At the Doctoral level, there are sharp drop offs in female enrolments for all categories. Business and Economics are the laggards at the Doctoral level, below STEM and Humanities. Furthermore, females make up a minority of academic staff in South African HEIs, with males dominating in especially the higher academic ranks. As one moves up the academic ladder, the female share decreases. This research analyses gender compositions of staff and students at South African HEIs. National data are obtained from government publications and data relating to four specific South African universities was obtained directly from the universities. Questionnaires were sent to a sample of academic staff and students who are in the field of economics to identify whether there is a role model effect for economics students and whether female academics experience the same forms of biases, discrimination, or treatment as that identified in international studies. It was concluded that while there are drop offs in the overall female representation of students at the Masters and Doctoral levels in South Africa, this share is gradually increasing. Additionally, Economics seems to perform better than what is depicted in the US, and in comparison to some STEM subjects in South Africa. Furthermore, the environment within the field of academic economics for both female students and staff seems to be more positive than what the international literature depicts for the US. But there are nonetheless different levels of satisfaction between male and female academic economists. While the student surveys revealed that female Economics students do not attach great importance to female role models, there is some evidence of correlation between the percentage of female professors and the percentage of female PhD students across a range of STEM subjects in South Africa. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2020
- Full Text:
- Date Issued: 2020-10-30
- Authors: Hitchcock, Siobhan
- Date: 2020-10-30
- Subjects: Sexism South Africa , Sexism in higher education South Africa , Economics Study and teaching (Higher) South Africa , Economics teachers South Africa , Women in higher education South Africa
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/366275 , vital:65850
- Description: In recent years there has been a growing focus internationally on the low participation of females in Economics, both in academia and business. While female enrolment in higher education, including other maths-based subjects, has grown substantially, this has not been the case for Economics. Economics, particularly as one progresses through postgraduate studies to doctoral degrees now stands out as an outlier. A number of reasons have been advanced for this, including the nature of the subject, the type of people it attracts and the lack of female role models. Male and female enrolments in South African HEIs have grown between 2007 and 2017, but females have grown at a faster rate, thus increasing the female share of total enrolments to 59%. Female students are more successful and so make up an even greater proportion of South African graduates. Female enrolments and graduates are also higher than in the US. As in the US there is a significant drop off in female representation when progressing from undergraduate to postgraduate studies in South Africa. When looking at Economics in South Africa in comparison to the broad CESM categories, female enrolment in Economics Bachelor degrees is significantly lower than in Business and Humanities, but on a par with STEM subjects. At the Doctoral level, there are sharp drop offs in female enrolments for all categories. Business and Economics are the laggards at the Doctoral level, below STEM and Humanities. Furthermore, females make up a minority of academic staff in South African HEIs, with males dominating in especially the higher academic ranks. As one moves up the academic ladder, the female share decreases. This research analyses gender compositions of staff and students at South African HEIs. National data are obtained from government publications and data relating to four specific South African universities was obtained directly from the universities. Questionnaires were sent to a sample of academic staff and students who are in the field of economics to identify whether there is a role model effect for economics students and whether female academics experience the same forms of biases, discrimination, or treatment as that identified in international studies. It was concluded that while there are drop offs in the overall female representation of students at the Masters and Doctoral levels in South Africa, this share is gradually increasing. Additionally, Economics seems to perform better than what is depicted in the US, and in comparison to some STEM subjects in South Africa. Furthermore, the environment within the field of academic economics for both female students and staff seems to be more positive than what the international literature depicts for the US. But there are nonetheless different levels of satisfaction between male and female academic economists. While the student surveys revealed that female Economics students do not attach great importance to female role models, there is some evidence of correlation between the percentage of female professors and the percentage of female PhD students across a range of STEM subjects in South Africa. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2020
- Full Text:
- Date Issued: 2020-10-30
Determination of speaker configuration for an immersive audio content creation system
- Authors: Lebusa, Motebang
- Date: 2020
- Subjects: Loudspeakers , Surround-sound systems , Algorithms , Coordinates
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/163375 , vital:41034
- Description: Various spatialisation algorithms require the knowledge of speaker locations to accurately localise sound in 3D environments. The rendering process uses speaker coordinates to feed into their algorithms so that they can render the immersive audio content as intended by an artist. The need to measure the loudspeaker coordinates becomes necessary, especially in environments where the speaker layouts change frequently. Manually measuring the coordinates, however, tends to be a laborious task that is prone to errors. This research provides an automated solution to the problem of speaker coordinates measurement. The solution system, SDIAS, is a client-server system that uses the capabilities provided by the Ethernet Audio Video Bridging standard to measure the 3D loudspeaker coordinates for immersive sound systems. SDIAS deploys commodity hardware and readily available software to implement the solution. A server sends a short tone to each speaker in the speaker configuration, at equal intervals. A microphone attached to a mobile device picks up these transmitted tones on the client side, from different locations. The transmission and reception times from both components of the system are used to measure the time of flight for each tone sent to a loudspeaker. These are then used to determine the 3D coordinates of each loudspeaker in the available layout. Tests were performed to determine the accuracy of the determination algorithm for SDIAS, and were compared to the manually measured coordinates. , Thesis (MSc) -- Faculty of Science, Computer Science, 2020
- Full Text:
- Date Issued: 2020
- Authors: Lebusa, Motebang
- Date: 2020
- Subjects: Loudspeakers , Surround-sound systems , Algorithms , Coordinates
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/163375 , vital:41034
- Description: Various spatialisation algorithms require the knowledge of speaker locations to accurately localise sound in 3D environments. The rendering process uses speaker coordinates to feed into their algorithms so that they can render the immersive audio content as intended by an artist. The need to measure the loudspeaker coordinates becomes necessary, especially in environments where the speaker layouts change frequently. Manually measuring the coordinates, however, tends to be a laborious task that is prone to errors. This research provides an automated solution to the problem of speaker coordinates measurement. The solution system, SDIAS, is a client-server system that uses the capabilities provided by the Ethernet Audio Video Bridging standard to measure the 3D loudspeaker coordinates for immersive sound systems. SDIAS deploys commodity hardware and readily available software to implement the solution. A server sends a short tone to each speaker in the speaker configuration, at equal intervals. A microphone attached to a mobile device picks up these transmitted tones on the client side, from different locations. The transmission and reception times from both components of the system are used to measure the time of flight for each tone sent to a loudspeaker. These are then used to determine the 3D coordinates of each loudspeaker in the available layout. Tests were performed to determine the accuracy of the determination algorithm for SDIAS, and were compared to the manually measured coordinates. , Thesis (MSc) -- Faculty of Science, Computer Science, 2020
- Full Text:
- Date Issued: 2020
Investigating cannabinoids and endocannabinoid receptors as drug targets for pain and inflammation
- Authors: Marwarwa, Sinobomi Zamachi
- Date: 2020
- Subjects: Cannabinoids , Cannabinoids Receptors , Inflammation Alternative treatment , Pain Alternative treatment , Drug targeting
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/164468 , vital:41121
- Description: Cannabinoids and the endocannabinoid system have been studied in the past decades but have yet to be fully understood. An insight into interactions that occur between cannabinoid compounds and their receptors is important for understanding the cannabinoids and the endocannabinoid system. Cannabinoids are natural products found in some cannabis plants, and they have similar effects to endocannabinoids, which are chemicals in the body that are involved many aspects of health from appetite, memory, and movement to pain, inflammation and response to cancer. Cannabinoids have a high impact on the treatment of pain and inflammation, they show different antinociceptive mechanisms to existing drugs like opioids, also, they have antimigraine properties better than those achieved by aspirin. The CB1 and CB2 human receptors have been the most studied cannabinoid receptors. In this project, we used a combination of mass-spectrometry to generate plausible chemical fragments and computational techniques to assess the binding of these fragments to these two main CB receptors. CB1 was adapted from the protein data bank (PBD), file 5U09 and the CB2 model was predicted using the hierarchical protocol I-TASSER, starting from the amino acid sequence in UniProt (P34972 CNR2_HUMAN). The proposed active site for CB1 was reported in a publication accompanying the 5U09 PDB model, which was originally generated with a pre-existing ligand in the active site. However, CB2 had to be built from a homology model and the active site determined using a combination of I-TASSER, Maestro, and CASTp the more favourable binding energies were determined by CASTp, leading to the use of the CASTp coordinates as default for docking in the CB2 human receptor. The molecular docking of cannabinoids THC, CBD, CBDV, CBG and CBN on both the CB1 and CB2 proteins was performed to identify the amino acids that interact with these compounds at their active sites. This would provide a guide to a future fragment-based drug discovery (FBDD) synthesis project. The docking in this work showed adequate accuracy with binding energies between -8.23 kcal/mol and -9.97 kcal/mol for CB1 and between -6.78 kcal/mol and -7.74 kcal/mol for CB2. An observation made was that binding energies of the CB1 human receptor docking were higher than those of the CB2 human receptor, which could support the widely held belief that CB1 is more important in cannabinoid interactions. The cannabinoids were then subjected to collision-induced dissociation to produce fragment structures predicted in chapter 2. These hypothetical fragments were docked in the CB1 and CB2 human receptor, the general trend again being the binding energies for the CB1 receptor was again around 10% higher than those of the CB2 receptor. As expected, larger fragments tended to have better binding, with the fragment proposed from m/z 259 with binding energies -9.62 kcal/mol in CB1 and -6.26 kcal/mol. Those fragments with significant lipophilic side chains or some aromatic moiety also showed good binding or around -6.00 kcal/mol, similar to the intact cannabinoids. In our case, this fragment was proposed from m/z 223 with binding energies -7.71 kcal/mol in CB1 and -6.5 kcal/mol in CB2. The results from the fragment dockings were favourable in that they have binding affinities lower than -6.0 kcal/mol which is good enough for the structures to be leads in the creation of fragment libraries. The docking was performed with Autodock 1.5.6 and data visualization with a discovery studio. , Thesis (MSc) -- Faculty of Science, Chemistry, 2020
- Full Text:
- Date Issued: 2020
- Authors: Marwarwa, Sinobomi Zamachi
- Date: 2020
- Subjects: Cannabinoids , Cannabinoids Receptors , Inflammation Alternative treatment , Pain Alternative treatment , Drug targeting
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/164468 , vital:41121
- Description: Cannabinoids and the endocannabinoid system have been studied in the past decades but have yet to be fully understood. An insight into interactions that occur between cannabinoid compounds and their receptors is important for understanding the cannabinoids and the endocannabinoid system. Cannabinoids are natural products found in some cannabis plants, and they have similar effects to endocannabinoids, which are chemicals in the body that are involved many aspects of health from appetite, memory, and movement to pain, inflammation and response to cancer. Cannabinoids have a high impact on the treatment of pain and inflammation, they show different antinociceptive mechanisms to existing drugs like opioids, also, they have antimigraine properties better than those achieved by aspirin. The CB1 and CB2 human receptors have been the most studied cannabinoid receptors. In this project, we used a combination of mass-spectrometry to generate plausible chemical fragments and computational techniques to assess the binding of these fragments to these two main CB receptors. CB1 was adapted from the protein data bank (PBD), file 5U09 and the CB2 model was predicted using the hierarchical protocol I-TASSER, starting from the amino acid sequence in UniProt (P34972 CNR2_HUMAN). The proposed active site for CB1 was reported in a publication accompanying the 5U09 PDB model, which was originally generated with a pre-existing ligand in the active site. However, CB2 had to be built from a homology model and the active site determined using a combination of I-TASSER, Maestro, and CASTp the more favourable binding energies were determined by CASTp, leading to the use of the CASTp coordinates as default for docking in the CB2 human receptor. The molecular docking of cannabinoids THC, CBD, CBDV, CBG and CBN on both the CB1 and CB2 proteins was performed to identify the amino acids that interact with these compounds at their active sites. This would provide a guide to a future fragment-based drug discovery (FBDD) synthesis project. The docking in this work showed adequate accuracy with binding energies between -8.23 kcal/mol and -9.97 kcal/mol for CB1 and between -6.78 kcal/mol and -7.74 kcal/mol for CB2. An observation made was that binding energies of the CB1 human receptor docking were higher than those of the CB2 human receptor, which could support the widely held belief that CB1 is more important in cannabinoid interactions. The cannabinoids were then subjected to collision-induced dissociation to produce fragment structures predicted in chapter 2. These hypothetical fragments were docked in the CB1 and CB2 human receptor, the general trend again being the binding energies for the CB1 receptor was again around 10% higher than those of the CB2 receptor. As expected, larger fragments tended to have better binding, with the fragment proposed from m/z 259 with binding energies -9.62 kcal/mol in CB1 and -6.26 kcal/mol. Those fragments with significant lipophilic side chains or some aromatic moiety also showed good binding or around -6.00 kcal/mol, similar to the intact cannabinoids. In our case, this fragment was proposed from m/z 223 with binding energies -7.71 kcal/mol in CB1 and -6.5 kcal/mol in CB2. The results from the fragment dockings were favourable in that they have binding affinities lower than -6.0 kcal/mol which is good enough for the structures to be leads in the creation of fragment libraries. The docking was performed with Autodock 1.5.6 and data visualization with a discovery studio. , Thesis (MSc) -- Faculty of Science, Chemistry, 2020
- Full Text:
- Date Issued: 2020