The synthesis and characterisation of Sn(IV) porphyrin derivatives and their potential application in anti-cancer and antimicrobial photodynamic therapy
- Authors: Dingiswayo, Somila
- Date: 2021-10
- Subjects: Porphyrins , Photochemotherapy , Cancer Photochemotherapy , Active oxygen Physiological effect , Aromaticity (Chemistry) , Tetrapyrroles , Magnetic circular dichroism , Corroles , Chlorins , Photodynamic antimicrobial chemotherapy (PACT)
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188843 , vital:44791
- Description: In photodynamic therapy (PDT), the activation of light-sensitive drugs in tumour cells produces reactive singlet oxygen species, which cause tumour destruction through a cascade of biochemical reactions. Over the years, the wavelength of activation has been shown to be a critical factor in the penetration of light. Hence the properties of photosensitiser dyes in this context shape their ability to treat deep-seated tumours. In this study, the synthesis, structural characterisation and photophysicochemical properties of a series of Sn(IV) porphyrins with meso-methylthiophenyl rings that have been prepared to study their PDT and photodynamic antimicrobial chemotherapy (PACT) activity properties are reported. The series of Sn(IV) complexes is comprised of a porphyrin (1-Sn), a corrole (2-Sn), a chlorin (3-Sn) and an N-confused porphyrin (4-Sn). Herein, the low symmetry Sn(IV) porphyrin derivatives are shown to have excellent singlet oxygen generation capabilities, and lifetimes of the triplet excited states were in the microsecond range. For example, 4-Sn had a singlet oxygen quantum yield (ФΔ) and an excited triplet state lifetime (τT) of 0.88 and 27 μs, respectively. The complexes were studied using UV-visible and magnetic circular dichroism (MCD) spectroscopies. Interestingly, the positive-to-negative sign sequences of the Faraday B0 terms of 2-Sn and 3-Sn reveal that the structural modifications involved break the degeneracy of the MOs derived from the 1eg* LUMO of the porphyrin 1-Sn. In contrast, a conventional negative-to-positive sign sequence is observed for 4-Sn, since the confusion of a pyrrole moiety also results in a large separation of the 1a1u and 1a2u MOs of the porphyrin 1-Sn that are derived from the HOMO of a C16H162−parent hydrocarbon perimeter. The trends in the electronic structures of the Sn(IV) complexes were further investigated through a series of time-dependent density functional theory calculations, so that the suitability of the different types of complex for use in singlet oxygen applications could be further explored. During in vitro photodynamic antimicrobial chemotherapy (PACT) studies, chlorin derivative 3-Sn had the highest activity towards S. aureus and E. coli with log10 reductions of 10.5 and 8.74, respectively. The unusually high activity of 3-Sn against E.coli suggests that the interaction of neutral photosensitisers with gram-negativebacteria is more complex than previously understood. Anti-cancer PDT studies demonstrated that the photosensitisers had negligible dark cytotoxicity. Upon photoirradiation, the Sn(IV) complexes consistently exhibited IC50 values lower than 15 μM against MCF-7 adenocarcinoma cells. An IC50 value of 1.4 μM for 4-Sn after activation at the deep-red region of the spectrum demonstrates that complexes of this type merit further in-depth investigation. The results provide evidence that the low-symmetry Sn(IV) chlorins and N-confused porphyrins merit further in-depth study for use in singlet oxygen applications. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
- Full Text:
- Date Issued: 2021-10
- Authors: Dingiswayo, Somila
- Date: 2021-10
- Subjects: Porphyrins , Photochemotherapy , Cancer Photochemotherapy , Active oxygen Physiological effect , Aromaticity (Chemistry) , Tetrapyrroles , Magnetic circular dichroism , Corroles , Chlorins , Photodynamic antimicrobial chemotherapy (PACT)
- Language: English
- Type: Masters theses , text
- Identifier: http://hdl.handle.net/10962/188843 , vital:44791
- Description: In photodynamic therapy (PDT), the activation of light-sensitive drugs in tumour cells produces reactive singlet oxygen species, which cause tumour destruction through a cascade of biochemical reactions. Over the years, the wavelength of activation has been shown to be a critical factor in the penetration of light. Hence the properties of photosensitiser dyes in this context shape their ability to treat deep-seated tumours. In this study, the synthesis, structural characterisation and photophysicochemical properties of a series of Sn(IV) porphyrins with meso-methylthiophenyl rings that have been prepared to study their PDT and photodynamic antimicrobial chemotherapy (PACT) activity properties are reported. The series of Sn(IV) complexes is comprised of a porphyrin (1-Sn), a corrole (2-Sn), a chlorin (3-Sn) and an N-confused porphyrin (4-Sn). Herein, the low symmetry Sn(IV) porphyrin derivatives are shown to have excellent singlet oxygen generation capabilities, and lifetimes of the triplet excited states were in the microsecond range. For example, 4-Sn had a singlet oxygen quantum yield (ФΔ) and an excited triplet state lifetime (τT) of 0.88 and 27 μs, respectively. The complexes were studied using UV-visible and magnetic circular dichroism (MCD) spectroscopies. Interestingly, the positive-to-negative sign sequences of the Faraday B0 terms of 2-Sn and 3-Sn reveal that the structural modifications involved break the degeneracy of the MOs derived from the 1eg* LUMO of the porphyrin 1-Sn. In contrast, a conventional negative-to-positive sign sequence is observed for 4-Sn, since the confusion of a pyrrole moiety also results in a large separation of the 1a1u and 1a2u MOs of the porphyrin 1-Sn that are derived from the HOMO of a C16H162−parent hydrocarbon perimeter. The trends in the electronic structures of the Sn(IV) complexes were further investigated through a series of time-dependent density functional theory calculations, so that the suitability of the different types of complex for use in singlet oxygen applications could be further explored. During in vitro photodynamic antimicrobial chemotherapy (PACT) studies, chlorin derivative 3-Sn had the highest activity towards S. aureus and E. coli with log10 reductions of 10.5 and 8.74, respectively. The unusually high activity of 3-Sn against E.coli suggests that the interaction of neutral photosensitisers with gram-negativebacteria is more complex than previously understood. Anti-cancer PDT studies demonstrated that the photosensitisers had negligible dark cytotoxicity. Upon photoirradiation, the Sn(IV) complexes consistently exhibited IC50 values lower than 15 μM against MCF-7 adenocarcinoma cells. An IC50 value of 1.4 μM for 4-Sn after activation at the deep-red region of the spectrum demonstrates that complexes of this type merit further in-depth investigation. The results provide evidence that the low-symmetry Sn(IV) chlorins and N-confused porphyrins merit further in-depth study for use in singlet oxygen applications. , Thesis (MSc) -- Faculty of Science, Chemistry, 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
The Anatomy of Microchaetus Saxatilis: with some notes on allied species
- Authors: Louw, M A
- Date: 1941
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193666 , vital:45382
- Description: Earthworms of the genus Microchaetus, Rapp.1849, are abundant in the Grahams town district. Microohaetus saxatilis, Rosa, 1S98,has been chosen as a subject for investigation as it is a valuable type for laboratory work, and it showed interesting characters which required detailed study. Members of the genus Micro chaet us are available in many regions of South Africa and are useful for work in South African schools and Universities. Micro chaetus saxatills is an 01igochaete worm belonging to the family Glossoseolecidae. These wonns were originally placed in the Lumbricina by Grube, (1850 p.345), but Rosa in 1887 (p.7) formed a separate family naming it the Geoscolecidae. He divided it into two sub-families :- (1) Geoscolecinae, and (B) Microchaetinae. Beddard was studying the classification of this family at the same time as Rosa. He spelt the name slightly differently, calling the family the Geoscolicidae, but he arrived independently at the same division into subfamilies (1888, pp. £43-278), although he suggests that perhaps an additional sub-family - the Homo gas. tridae - should be formed. Homo gas ter is undoubtedly an aberrant type, and it seems strange that Rosa who studied this genus should not have placed it in a separate sub-family. , Thesis (MSc) -- Faculty of Science, Zoology, 1941
- Full Text:
- Date Issued: 1941
- Authors: Louw, M A
- Date: 1941
- Subjects: Uncatalogued
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/193666 , vital:45382
- Description: Earthworms of the genus Microchaetus, Rapp.1849, are abundant in the Grahams town district. Microohaetus saxatilis, Rosa, 1S98,has been chosen as a subject for investigation as it is a valuable type for laboratory work, and it showed interesting characters which required detailed study. Members of the genus Micro chaet us are available in many regions of South Africa and are useful for work in South African schools and Universities. Micro chaetus saxatills is an 01igochaete worm belonging to the family Glossoseolecidae. These wonns were originally placed in the Lumbricina by Grube, (1850 p.345), but Rosa in 1887 (p.7) formed a separate family naming it the Geoscolecidae. He divided it into two sub-families :- (1) Geoscolecinae, and (B) Microchaetinae. Beddard was studying the classification of this family at the same time as Rosa. He spelt the name slightly differently, calling the family the Geoscolicidae, but he arrived independently at the same division into subfamilies (1888, pp. £43-278), although he suggests that perhaps an additional sub-family - the Homo gas. tridae - should be formed. Homo gas ter is undoubtedly an aberrant type, and it seems strange that Rosa who studied this genus should not have placed it in a separate sub-family. , Thesis (MSc) -- Faculty of Science, Zoology, 1941
- Full Text:
- Date Issued: 1941
Gray
- Authors: Fouché, James De Clerque
- Date: 2022-04-07
- Subjects: Creative writing (Higher education) South Africa , Diaries -- Authorship , Detective and mystery stories, South African (English) 21st century , South African fiction (English) 21st century , South African essays (English) 21st century , English fiction 20th century History and criticism , American fiction African American authors History and criticism , American fiction 20th century History and criticism
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/292715 , vital:57009
- Description: My thesis is a crime fiction novella. I’m moved by the idea of developing feasible, relatable characters with flaws – a staple of the crime fiction genre. I also appreciate how crime serves as a platform from which to launch into human drama, the way James Ellroy does in The Black Dahlia. While my protagonist endures trials on a near Jobian scale, the narrative meditates on the consequences of crime and conflict in a satirical way. Writers like Ross Macdonald, Raymond Chandler, Flannery O’Connor, China Miéville and Derek Raymond have inspired me with their sharp imagery and unconventional characterization techniques. These techniques accelerate the ease with which a reader can step into the shoes of any given narrator. Their writing is crisp, uncluttered and uncomplicated. , Thesis (MA) -- Faculty of Humanities, School of Languages and Literatures, 2022
- Full Text:
- Date Issued: 2022-04-07
- Authors: Fouché, James De Clerque
- Date: 2022-04-07
- Subjects: Creative writing (Higher education) South Africa , Diaries -- Authorship , Detective and mystery stories, South African (English) 21st century , South African fiction (English) 21st century , South African essays (English) 21st century , English fiction 20th century History and criticism , American fiction African American authors History and criticism , American fiction 20th century History and criticism
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/292715 , vital:57009
- Description: My thesis is a crime fiction novella. I’m moved by the idea of developing feasible, relatable characters with flaws – a staple of the crime fiction genre. I also appreciate how crime serves as a platform from which to launch into human drama, the way James Ellroy does in The Black Dahlia. While my protagonist endures trials on a near Jobian scale, the narrative meditates on the consequences of crime and conflict in a satirical way. Writers like Ross Macdonald, Raymond Chandler, Flannery O’Connor, China Miéville and Derek Raymond have inspired me with their sharp imagery and unconventional characterization techniques. These techniques accelerate the ease with which a reader can step into the shoes of any given narrator. Their writing is crisp, uncluttered and uncomplicated. , Thesis (MA) -- Faculty of Humanities, School of Languages and Literatures, 2022
- Full Text:
- Date Issued: 2022-04-07
Factors constraining and enabling the adoption of a disruptive technology by African small, micro, and medium enterprises for the Fourth Industrial Revolution: The case of mobile money
- Authors: Tarr, Dillon
- Date: 2022-10-14
- Subjects: Disruptive technologies , Mobile commerce , Industry 4.0 , Small business Africa, Sub-Saharan , Diffusion of innovations Africa, Sub-Saharan , Technological innovations Management
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/357709 , vital:64770
- Description: The Fourth Industrial Revolution (4IR) is set to disrupt existing economic and social structures through the use of cyber-physical systems that result from a fusion of the digital, biological, and physical spheres. The fifth and current long wave of innovation is going through such a digital revolution in the ongoing deployment period which is being driven by the generalpurpose technologies of Artificial Intelligence and the Internet of Things, among other cyberphysical systems. The impact of mobile money in the access of financial services has shown how disruptive incremental innovations in mobile and digital technologies can be. The transformational power of mobile money in financial access is due to its use as an accessible financial tool that utilizes mobile devices to send and/or receive money over great distances. With the 4IR looming, this thesis determines the factors that enable and constrain the adoption of a disruptive technology amongst Sub-Saharan African small, micro, and medium enterprises (SMMEs). Therefore, due to its impact on financial inclusion and the formalization of SMMEs, mobile money is used as an indicator for the adoption of 4IR disruptive digital technologies. The adoption of mobile money was evaluated using secondary data from a survey conducted by Research ICT Africa, which surveyed 4408 SMMEs in nine African countries. The Diffusion of Innovations (DOI) model and the Unified Theory of Acceptance and Use of Technology (UTAUT) model were used to identify the factors enabling and constraining the adoption of a disruptive technology, in this case mobile money. Factors included gender, vocational training, business skills training, tertiary education, services, performance expectancy, social media, location, and nine African countries (Kenya, Mozambique, Ghana, Nigeria, Rwanda, South Africa, Tanzania, Uganda, and Senegal). The factors were grouped into owner characteristics, firm attributes and country attributes. SMME owners with business skills (49%) showed the highest level of adoption in terms of owner characteristics, Kenyan SMMEs (21%) had the highest adoption between the countries surveyed, and social media (62%) showed the highest adoption in terms of firm attributes followed by the formal variable (47%). In general, only 29% of SMMEs surveyed adopted mobile money. The study found that women SMME owners were more likely to be affected by business formality when adopting a disruptive technology compared to male owned SMMEs. This is because informality often exacerbates other barriers/challenges women face such as lower access to finance, lower ability to exercise property, business, and labour rights, and lower visibility. The results also demonstrate that vocational training is more important than general tertiary education for the ii adoption of a disruptive technology such as mobile money. Furthermore, when using social media as a tool for business advice SMME owners were more likely to adopt the disruptive technology. The study suggests that to encourage African SMMEs to adequately adopt disruptive technologies of the 4IR, more women owned SMMEs need to enter the formal economy, and vocational training targeted at business skills must be promoted amongst all SMME owners. Eastern African SMMEs were found to be more likely to adopt mobile money compared to other African regions. The finding demonstrates the need for more African countries (particularly outside of the Eastern African region) to encourage innovation by addressing the four enablers of mobile connectivity (i.e. infrastructure, affordability, consumer readiness, and mobile services) which will in effect lead to economic growth and development. The study shows that to address country/regional differences, in addition to building the required infrastructure in terms of mobile internet connectivity, countries should increase the local relevancy of disruptive technologies between SMMEs. To achieve this the study suggests increasing mobile social media penetration rates. This is because when social media is used as a tool for business advice SMME owners are more likely to adopt a disruptive technology (as is the case with mobile money) due to the social influence of social media. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Tarr, Dillon
- Date: 2022-10-14
- Subjects: Disruptive technologies , Mobile commerce , Industry 4.0 , Small business Africa, Sub-Saharan , Diffusion of innovations Africa, Sub-Saharan , Technological innovations Management
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/357709 , vital:64770
- Description: The Fourth Industrial Revolution (4IR) is set to disrupt existing economic and social structures through the use of cyber-physical systems that result from a fusion of the digital, biological, and physical spheres. The fifth and current long wave of innovation is going through such a digital revolution in the ongoing deployment period which is being driven by the generalpurpose technologies of Artificial Intelligence and the Internet of Things, among other cyberphysical systems. The impact of mobile money in the access of financial services has shown how disruptive incremental innovations in mobile and digital technologies can be. The transformational power of mobile money in financial access is due to its use as an accessible financial tool that utilizes mobile devices to send and/or receive money over great distances. With the 4IR looming, this thesis determines the factors that enable and constrain the adoption of a disruptive technology amongst Sub-Saharan African small, micro, and medium enterprises (SMMEs). Therefore, due to its impact on financial inclusion and the formalization of SMMEs, mobile money is used as an indicator for the adoption of 4IR disruptive digital technologies. The adoption of mobile money was evaluated using secondary data from a survey conducted by Research ICT Africa, which surveyed 4408 SMMEs in nine African countries. The Diffusion of Innovations (DOI) model and the Unified Theory of Acceptance and Use of Technology (UTAUT) model were used to identify the factors enabling and constraining the adoption of a disruptive technology, in this case mobile money. Factors included gender, vocational training, business skills training, tertiary education, services, performance expectancy, social media, location, and nine African countries (Kenya, Mozambique, Ghana, Nigeria, Rwanda, South Africa, Tanzania, Uganda, and Senegal). The factors were grouped into owner characteristics, firm attributes and country attributes. SMME owners with business skills (49%) showed the highest level of adoption in terms of owner characteristics, Kenyan SMMEs (21%) had the highest adoption between the countries surveyed, and social media (62%) showed the highest adoption in terms of firm attributes followed by the formal variable (47%). In general, only 29% of SMMEs surveyed adopted mobile money. The study found that women SMME owners were more likely to be affected by business formality when adopting a disruptive technology compared to male owned SMMEs. This is because informality often exacerbates other barriers/challenges women face such as lower access to finance, lower ability to exercise property, business, and labour rights, and lower visibility. The results also demonstrate that vocational training is more important than general tertiary education for the ii adoption of a disruptive technology such as mobile money. Furthermore, when using social media as a tool for business advice SMME owners were more likely to adopt the disruptive technology. The study suggests that to encourage African SMMEs to adequately adopt disruptive technologies of the 4IR, more women owned SMMEs need to enter the formal economy, and vocational training targeted at business skills must be promoted amongst all SMME owners. Eastern African SMMEs were found to be more likely to adopt mobile money compared to other African regions. The finding demonstrates the need for more African countries (particularly outside of the Eastern African region) to encourage innovation by addressing the four enablers of mobile connectivity (i.e. infrastructure, affordability, consumer readiness, and mobile services) which will in effect lead to economic growth and development. The study shows that to address country/regional differences, in addition to building the required infrastructure in terms of mobile internet connectivity, countries should increase the local relevancy of disruptive technologies between SMMEs. To achieve this the study suggests increasing mobile social media penetration rates. This is because when social media is used as a tool for business advice SMME owners are more likely to adopt a disruptive technology (as is the case with mobile money) due to the social influence of social media. , Thesis (MCom) -- Faculty of Commerce, Economics and Economic History, 2022
- Full Text:
- Date Issued: 2022-10-14
Constraints on Cr-PGE Mineralisation Models: Geochemical and petrological studies in the Middle Group 1 and 3 Chromitites, Western Limb, Bushveld Complex, South Africa
- Authors: Arunachellan, Yogendran
- Date: 2022-10-14
- Subjects: Chromite South Africa Bushveld Complex , Mineralogy South Africa Bushveld Complex , Geochemical surveys South Africa Bushveld Complex
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362730 , vital:65357
- Description: The Bushveld Complex in South Africa has been of interest in various research groups for decades, along with diverse theories regarding its origin, formation, and emplacement. These theories include magma mixing, contamination, and changes in the chamber's ephemeral parameters. Of interest for our current study is the formation of the middle group chromitite layers in the Western Limb. In this research, we aimed to determine the emplacement mechanism of the MG group chromitites by scrutinising the MG 1 and MG 3 layers. In core KD 151, the focus was placed on the MG 3 and MG 1 chromitite layers and their associated silicate rocks; on these regions of the core, time was spent for detailed observations. The differences and similarities of these layers were explored as the study advanced. The objectives were to determine the in-situ or proximal crystallisation of the chromitite by evaluating mineral textures and compositions. This required that we determine the characteristics of the immediate HW (hanging wall) and FW (footwall) to these chromitites, with insights into the relationship that anorthositic zones may offer and examine the PGE profiles of the chromitites in contrasting lithological settings. The sampled borehole was in the Western Limb of the Bushveld Complex; the immediate HW, chromitite layers and FW were divided into sections (2.5 x 5 cm) along selected horizons for a microscale study. The preliminary results of a study on the sub-economic Middle Group (MG) layers within the Critical Zone (CZ), contrasting the MG 1 (Lower CZ) and MG 3 (Upper CZ) chromitite layers of the Rustenburg Layered Suite of the Bushveld Complex, South Africa were analysed. The MG 3 and 1 suites of silicate rocks show disequilibrium textures between the pyroxenes and plagioclase, forming discontinuous olivine rims. These reaction rims are interpreted as products of magmatic aqueous fluid-facilitated reactions with minerals in a sub-solidus state. Deformation of the plagioclase was also noted in MG 1; this fracturing indicates either the transportation of these minerals or compaction by an overlying crystal mush. The MG 3 package of plagioclase, pyroxene and chromite compositions range from An67-78, En71-86 and Cr# of 68-84, respectively. The MG 1 package of plagioclase, pyroxene and chromite compositions are An64-91, En79-88 and Cr# of 70-80, respectively. The Cu/Pd ratio decreases from the base of the FW as it approaches the base of the chromitite, then remains low within the chromitite layer and finally increases upwards in the HW. These trends are observed in both the MG 3 and 1 package, therefore not influenced by the sulphide control. There is a decrease in both IPGE and PPGE upwards as the HW progresses into the chromitite. The FW levels of Ir and Ru increase upwards immediately adjacent to the FW contact, while Pd and Rh concentrations decrease. The whole-rock Mg# indicates a decrease in the MG 3 with a uniform increase in the HW and an erratic upward increase observed in the FW. The chondrite normalised PGE plots show a bell-shaped curve which is evident for the En content of the pyroxenes and the content of plagioclase with the highest values in the chromitite layer itself. The Cr# of the chromite decreases upwards with the highest values along the FW. The Cu/Pd ratio for MG 1 indicates chromitite control rather than sulphide control of the PGE. The whole-rock Mg# decreases in MG 1 with higher uniform values observed in the HW and FW. The geochemical and petrological data from the MG group study revealed that in situ fractional crystallisation seems unlikely as the sole mechanism for their formation in the CZ. A model is suggested in which the migration and transport of a magmatic slurry type suspension with accompanying hydrous fluids would likely have resulted in the emplacement of these chromitite packages along with the PGE mineralisation of the chromitites. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
- Authors: Arunachellan, Yogendran
- Date: 2022-10-14
- Subjects: Chromite South Africa Bushveld Complex , Mineralogy South Africa Bushveld Complex , Geochemical surveys South Africa Bushveld Complex
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/362730 , vital:65357
- Description: The Bushveld Complex in South Africa has been of interest in various research groups for decades, along with diverse theories regarding its origin, formation, and emplacement. These theories include magma mixing, contamination, and changes in the chamber's ephemeral parameters. Of interest for our current study is the formation of the middle group chromitite layers in the Western Limb. In this research, we aimed to determine the emplacement mechanism of the MG group chromitites by scrutinising the MG 1 and MG 3 layers. In core KD 151, the focus was placed on the MG 3 and MG 1 chromitite layers and their associated silicate rocks; on these regions of the core, time was spent for detailed observations. The differences and similarities of these layers were explored as the study advanced. The objectives were to determine the in-situ or proximal crystallisation of the chromitite by evaluating mineral textures and compositions. This required that we determine the characteristics of the immediate HW (hanging wall) and FW (footwall) to these chromitites, with insights into the relationship that anorthositic zones may offer and examine the PGE profiles of the chromitites in contrasting lithological settings. The sampled borehole was in the Western Limb of the Bushveld Complex; the immediate HW, chromitite layers and FW were divided into sections (2.5 x 5 cm) along selected horizons for a microscale study. The preliminary results of a study on the sub-economic Middle Group (MG) layers within the Critical Zone (CZ), contrasting the MG 1 (Lower CZ) and MG 3 (Upper CZ) chromitite layers of the Rustenburg Layered Suite of the Bushveld Complex, South Africa were analysed. The MG 3 and 1 suites of silicate rocks show disequilibrium textures between the pyroxenes and plagioclase, forming discontinuous olivine rims. These reaction rims are interpreted as products of magmatic aqueous fluid-facilitated reactions with minerals in a sub-solidus state. Deformation of the plagioclase was also noted in MG 1; this fracturing indicates either the transportation of these minerals or compaction by an overlying crystal mush. The MG 3 package of plagioclase, pyroxene and chromite compositions range from An67-78, En71-86 and Cr# of 68-84, respectively. The MG 1 package of plagioclase, pyroxene and chromite compositions are An64-91, En79-88 and Cr# of 70-80, respectively. The Cu/Pd ratio decreases from the base of the FW as it approaches the base of the chromitite, then remains low within the chromitite layer and finally increases upwards in the HW. These trends are observed in both the MG 3 and 1 package, therefore not influenced by the sulphide control. There is a decrease in both IPGE and PPGE upwards as the HW progresses into the chromitite. The FW levels of Ir and Ru increase upwards immediately adjacent to the FW contact, while Pd and Rh concentrations decrease. The whole-rock Mg# indicates a decrease in the MG 3 with a uniform increase in the HW and an erratic upward increase observed in the FW. The chondrite normalised PGE plots show a bell-shaped curve which is evident for the En content of the pyroxenes and the content of plagioclase with the highest values in the chromitite layer itself. The Cr# of the chromite decreases upwards with the highest values along the FW. The Cu/Pd ratio for MG 1 indicates chromitite control rather than sulphide control of the PGE. The whole-rock Mg# decreases in MG 1 with higher uniform values observed in the HW and FW. The geochemical and petrological data from the MG group study revealed that in situ fractional crystallisation seems unlikely as the sole mechanism for their formation in the CZ. A model is suggested in which the migration and transport of a magmatic slurry type suspension with accompanying hydrous fluids would likely have resulted in the emplacement of these chromitite packages along with the PGE mineralisation of the chromitites. , Thesis (MSc) -- Faculty of Science, Geology, 2022
- Full Text:
- Date Issued: 2022-10-14
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