An evaluation of synergistic interactions between feruloyl esterases and xylanases during the hydrolysis of various pre-treated agricultural residues
- Authors: Mkabayi, Lithalethu
- Date: 2021-04
- Subjects: Esterases , Xylanases , Hydrolysis , Agricultural wastes -- Recycling , Enzymes , Lignocellulose -- Biodegradation , Escherichia coli , Oligosaccharides , Hydroxycinnamic acids
- Language: English
- Type: thesis , text , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/178224 , vital:42922 , 10.21504/10962/178224
- Description: Agricultural residues are readily available and inexpensive renewable resources that can be used as raw materials for the production of value-added chemicals. The application of enzymes to facilitate the degradation of agricultural residues has long been considered the most environmentally friendly strategy for converting this material into good quality value-added chemicals. However, agricultural residues are typically lignocellulosic in composition and recalcitrant to enzymatic hydrolysis. Due to this recalcitrant nature, the complete degradation of biomass residues requires the synergistic action of a broad range of enzymes. The development and optimisation of synergistic enzyme cocktails is an effective approach for achieving high hydrolysis efficiency of lignocellulosic biomass. The aim of the current study was to evaluate the synergistic interactions between two termite metagenome-derived feruloyl esterases (FAE6 and FAE5) and endo-xylanases for the production of hydroxycinnamic acids and xylo-oligosaccharides (XOS) from model substrates, and untreated and pre-treated agricultural residues. Firstly, the two fae genes were heterologously expressed in Escherichia coli, and the recombinant enzymes were purified to homogeneity. The biochemical properties of the purified recombinant FAEs and xylanases (XT6 and Xyn11) were then assessed to determine the factors which influenced their activities and to select suitable operating conditions for synergy studies. An optimal protein loading ratio of xylanases to FAEs required to maximise the release of both reducing sugar and ferulic acid (FA) was established using 0.5% (w/v) insoluble wheat arabinoxylan (a model substrate). The enzyme combination of 66% xylanase and 33% FAE (on a protein loading basis) produced the highest amounts of reducing sugars and FA. The enzyme combination of XT6 (GH10 xylanase) and FAE5 or FAE6 liberated the highest amount of FA while a combination of Xyn11 (GH11 xylanase) and FAE5 or FAE6 produced the highest reducing sugar content. The synergistic interactions which were established between the xylanases and FAEs were further investigated using agricultural residues (corn cobs, rice straw and sugarcane bagasse). The three substrates were subjected to hydrothermal and dilute acid pre-treatment prior to synergy studies. It is generally known that, during pre-treatment, many compounds can be produced which may influence enzymatic hydrolysis. The effects of these by-products were assessed and it was found that lignin and its degradation products were the most inhibitory to the FAEs. The optimised enzyme cocktail was then applied to 1% (w/v) of untreated and pre-treated substrates for the efficient production of XOS and hydroxycinnamic acids. A significant improvement in xylanase substrate degradation was observed, especially with the combination of 66% Xyn11 and 33% FAE6 which displayed an improvement in reducing sugars of approximately 1.9-fold and 3.4-fold for hydrothermal and acid pre-treated corn cobs (compared to when Xyn11 was used alone), respectively. The study demonstrated that pre-treatment substantially enhanced the enzymatic hydrolysis of corn cobs and rice straw. Analysis of the hydrolysate product profiles revealed that the optimised enzyme cocktail displayed great potential for releasing XOS with a low degree of polymerisation. In conclusion, this study provided significant insights into the mechanism of synergistic interactions between xylanases and metagenome-derived FAEs during the hydrolysis of various substrates. The study also demonstrated that optimised enzyme cocktails combined with low severity pre-treatment can facilitate the potential use of xylan-rich lignocellulosic biomass for the production of valuable products in the future. , Thesis (PhD) -- Faculty of Science, Biochemistry and Microbiology, 2021
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- Date Issued: 2021-04
An exploration into an ESD-based teaching strategy to improve the critical thinking and problem-solving skills amongst development studies students at Nelson Mandela University
- Authors: Abrahams, Andre John
- Date: 2021-04
- Subjects: Sustainable development -- Study and teaching , Universities and colleges -- South Africa , Critical thinking
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/50906 , vital:43149
- Description: In recent years, Education for Sustainable Development (ESD) has been a significant focus for research pertaining to teacher education and transformative approaches to teaching and learning. However, there has been less specific focus on the implementation of ESD in the context of higher education. This study, therefore, explored the use of an ESD-based teaching and learning approach in an undergraduate Development Studies programme. The focus was on developing a teaching approach that was informed by the principles of ESD and which could assist Development Studies lecturers in creating a more transformative, student-centred environment. This study was a qualitative undertaking, conducted at the Nelson Mandela University’s (NMU) Development Studies undergraduate programme. The ESD-based approach was implemented by two participating lecturers who utilised the approach across four undergraduate classes. Qualitative data were generated through a systematic literature analysis (SLA), exploratory interviews, student exercises and assessments, focus group discussions, and reflective journal entries. The gathered data were then analysed using a framework analysis rubric adapted from the theoretical framework utilised in the study. In addition, the data were coded using the six coding techniques promoted by Saldaña (2013). The findings suggest that the ESD-based approach developed in the study could effectively contribute towards promoting ESD in the Development Studies programme. The findings also suggest that, when properly implemented, the ESD-based approach could assist lecturers in creating a more transformative learning environment where students have greater control over their learning experience. In addition, this study found that students in the selected Development Studies undergraduate programme could benefit from continued exposure to the teaching methods and techniques adopted in the approach. The implementation of the approach also uncovered some of the inhibiting factors that may prevent an ESD-based approach being mainstreamed into the context of higher education. , Thesis (DPhil) -- Faculty of Business and Economic Sciences, Development Studies, 2021
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- Date Issued: 2021-04
An exploratory investigation into an Integrated Vulnerability and Patch Management Framework
- Authors: Carstens, Duane
- Date: 2021-04
- Subjects: Computer security , Computer security -- Management , Computer networks -- Security measures , Patch Management , Integrated Vulnerability
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/177940 , vital:42892
- Description: In the rapidly changing world of cybersecurity, the constant increase of vulnerabilities continues to be a prevalent issue for many organisations. Malicious actors are aware that most organisations cannot timeously patch known vulnerabilities and are ill-prepared to protect against newly created vulnerabilities where a signature or an available patch has not yet been created. Consequently, information security personnel face ongoing challenges to mitigate these risks. In this research, the problem of remediation in a world of increasing vulnerabilities is considered. The current paradigm of vulnerability and patch management is reviewed using a pragmatic approach to all associated variables of these services / practices and, as a result, what is working and what is not working in terms of remediation is understood. In addition to the analysis, a taxonomy is created to provide a graphical representation of all associated variables to vulnerability and patch management based on existing literature. Frameworks currently being utilised in the industry to create an effective engagement model between vulnerability and patch management services are considered. The link between quantifying a threat, vulnerability and consequence; what Microsoft has available for patching; and the action plan for resulting vulnerabilities is explored. Furthermore, the processes and means of communication between each of these services are investigated to ensure there is effective remediation of vulnerabilities, ultimately improving the security risk posture of an organisation. In order to effectively measure the security risk posture, progress is measured between each of these services through a single averaged measurement metric. The outcome of the research highlights influencing factors that impact successful vulnerability management, in line with identified themes from the research taxonomy. These influencing factors are however significantly undermined due to resources within the same organisations not having a clear and consistent understanding of their role, organisational capabilities and objectives for effective vulnerability and patch management within their organisations. , Thesis (MSc) -- Faculty of Science, Computer Science, 2021
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- Date Issued: 2021-04
An investigation into the current state of web based cryptominers and cryptojacking
- Authors: Len, Robert
- Date: 2021-04
- Subjects: Cryptocurrencies , Malware (Computer software) , Computer networks -- Security measures , Computer networks -- Monitoring , Cryptomining , Coinhive , Cryptojacking
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178248 , vital:42924
- Description: The aim of this research was to conduct a review of the current state and extent of surreptitious crypto mining software and its prevalence as a means for income generation. Income is generated through the use of a viewer's browser to execute custom JavaScript code to mine cryptocurrencies such as Monero and Bitcoin. The research aimed to measure the prevalence of illicit mining scripts being utilised for “in-browser" cryptojacking while further analysing the ecosystems that support the cryptomining environment. The extent of the research covers aspects such as the content (or type) of the sites hosting malicious “in-browser" cryptomining software as well as the occurrences of currencies utilised in the cryptographic mining and the analysis of cryptographic mining code samples. This research aims to compare the results of previous work with the current state of affairs since the closure of Coinhive in March 2018. Coinhive were at the time the market leader in such web based mining services. Beyond the analysis of the prevalence of cryptomining on the web today, research into the methodologies and techniques used to detect and counteract cryptomining are also conducted. This includes the most recent developments in malicious JavaScript de-obfuscation as well as cryptomining signature creation and detection. Methodologies for heuristic JavaScript behaviour identification and subsequent identification of potential malicious out-liars are also included within the research of the countermeasure analysis. The research revealed that although no longer functional, Coinhive remained as the most prevalent script being used for “in-browser" cryptomining services. While remaining the most prevalent, there was however a significant decline in overall occurrences compared to when coinhive.com was operational. Analysis of the ecosystem hosting \in-browser" mining websites was found to be distributed both geographically as well as in terms of domain categorisations. , Thesis (MSc) -- Faculty of Science, Computer Science, 2021
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- Date Issued: 2021-04
An investigation into the effects of nano-carbons on the negative electrode morphology of lead acid batteries under high rate partial state of capacity cycling
- Authors: Bolo, Lukanyo
- Date: 2021-04
- Subjects: Port Elizabeth (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/53324 , vital:45132
- Description: New technological developments in the field of Hybrid Electric Vehicles (HEV’s), vehicle stop-start applications and electrical power utility devices have brought about new demands on the use of energy storage devices such as the Pb-acid battery. These applications require a new understanding and research into the material chemistry of the battery where it has to functionin a Partial State of Capacity Cycling (PSoCC) or High Rate Partial State of Capacity Cycling (HRPSoCC)duty. The Pb-acid battery is well known for its use in the automotive industry where it had worked for decades as a typical Starter, Lighting and Ignition (SLI) power source. However, the conventional Pb-acid battery is not suitable for the new types of vehicle demands and applications. When the Pb-lead acid battery is subjected to PSoCC conditions, very quickly excessive amount of non-conducting PbSO4crystals are formed on the negative plates of the battery that then drastically reduce its useful life in application. Over the years, researchers have shown that the small addition of certain carbon types to the negative plate active material (NAM) during battery manufacturing can reduce the sulfation effect thereby increasing its use the modern vehicle applications. This study investigated industrial manufactured cells that contained up to 0.5 % by weight two types of carbons in the NAM. These were compared to standard built cells in terms of their standard achievable capacities at various rates, their Cold Cranking Ability (CCA), their Dynamic Charge Acceptance (DCA) and a simplified PSoCC test. The carbons were classified as an activated carbon and a carbon nano-fiber and were included as a dry weight additive during the standard paste manufacturing process of the negative plate. Cells were built with a 9-plate configuration using standard expanded grid positive plates with a nominal rated capacity of 36 Ah. The cells were formed and subjected to a number of electrochemical tests, of which selected negative plates were then studied using Scanning Electron Microscopy (SEM) and Electrochemical in-situ Atomic Force Microscopy (EC-AFM). The microscopic study was then used to try and relate the observed material characteristics of the NAM with the carbons to the electrochemical results observed when testing a built cell. , Thesis (MA) --Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
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- Date Issued: 2021-04
An investigation into the role of lesson study in developing teachers’ mathematics content and pedagogical content knowledge
- Authors: Kgothego, Naomi Ntsae
- Date: 2021-04
- Subjects: Mathematics -- Study and teaching (Elementary) -- South Africa -- Bojanala Platinum District Municipality , Pedagogical content knowledge , Lesson planning -- South Africa -- Bojanala Platinum District Municipality , Mathematics teachers -- Training of -- South Africa -- Bojanala Platinum District Municipality , South Africa. Department of Basic Education , Kokusai Kyōryoku Jigyōdan
- Language: English
- Type: thesis , text , Masters , MEd
- Identifier: http://hdl.handle.net/10962/178019 , vital:42899
- Description: Results of international assessments conducted with South African learners, both in primary and secondary schools, suggest that South African learners underperform in mathematics (Spaull, 2013). While there are numerous explanations for this, one of the key explanations is that teachers are deemed to have inadequate knowledge of both mathematics content and pedagogy. Poor content and pedagogical knowledge are indications that teachers are not adequately trained to teach mathematics (Green, 2011). To improve teachers' content and pedagogical knowledge, well-planned and researched professional development programmes need to be put in place. Current professional development opportunities that centre on workshops are not working as they provide little opportunity for teachers to connect the workshop content to the contexts in which they teach. Through a collaboration between the Department of Basic Education (DBE) and Japan International Corporation Agency (JICA), the Lesson Study approach is being introduced to support teachers' professional development. This research seeks to research this approach within the context of Foundation Phase mathematics education. The research asks: How does Lesson Study contribute to the development of teachers' mathematics content and pedagogical content knowledge? Two sub-questions were developed to support the main question: • What mathematics content knowledge do teachers develop as the engage in LS? • What pedagogical content knowledge do teachers develop as they engage in LS? Using a qualitative interpretivist case study approach, I worked collaboratively with four Grade 1 teachers from two schools. Data was generated through observations, semi-structured interviews and document analysis as we engaged in the Lesson Study process. The Mathematics Knowledge for Teaching (Ball, Thames & Phelps, 2008) and the Knowledge Quartet (Rowland, Turner, Thwaites & Huckstep, 2009) frameworks were used as analytic and explanatory tools in this research. This study's findings showed that participation in the interactive cycles of Lesson Study developed the teachers’ confidence, their pedagogical content knowledge and skills and provided them with the opportunity to collaborate and reflect on their knowledge. The study's findings suggest that lesson study can be used as a strategy for improving teacher professional development. , Thesis (MEd) -- Faculty of Education, Education, 2021
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- Date Issued: 2021-04
An investigation into the use of a consumer incentive to encourage recycling in South Africa
- Authors: Conway, John Charles
- Date: 2021-04
- Subjects: Recycling (Waste, etc.) -- Economic aspects , Consumption (Economics) -- South Africa , Consumer behavior
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/51096 , vital:43208
- Description: The focus of this study is the factors that influence recycling behaviours, particularly whether incentives are likely to change consumers’ recycling behaviours in South Africa. Africa is said to become the most polluted continent within a few decades. Three of the largest metropoles in South African are likely to run out of landfill space within the next ten years. Waste streams provide considerable opportunity if waste can be safely collected and either reused, recycled, or recovered, but extracting value from the waste streams is costly and difficult. Consumers need to separate waste at source to improve the efficacy of the recycling stream, yet South Africans do not separate waste at source as a norm. The question that arises then is would an incentive improve South Africans’ willingness to recycle? This study tried to determine if incentives are likely to change consumers’ recycling behaviours in South Africa. It explored the relationship between factors that influence recycling behaviours grounded in Taylor and Todd's (1995) extension of Ajzen's (1991) Theory Of Planned Behaviour. A quantitative survey design, using both online and face to face questionnaires, was used to collect data from a cross section of randomly selected consumers. The research determines that the call to address waste management infrastructure and facilities, is indeed correct. It further confirms previous research findings that an incentive alone is not enough to change recycling behaviours as it will not negate other environmental factors. Lower income groups are more conscientious about recycling and may be enticed to participate in the recycling industry through an incentive to improve their income. , Thesis (MBA) -- Faculty of Business and Economic Sciences, Business Administration, 2021
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- Date Issued: 2021-04
An investigation of support services available for black female owners of bed & breakfasts in Makhanda
- Authors: Mdluli, Lukhona Silubonile
- Date: 2021-04
- Subjects: Bed and breakfast accommodations -- South Africa -- Makhanda , Businesspeople, Black -- South Africa -- Makhanda , Business enterprises, Black -- South Africa -- Makhanda , Women-owned business enterprises -- South Africa -- Makhanda , Government aid to small business -- South Africa , Small business -- South Africa -- Makhanda , Racism -- South Africa -- Makhanda , Businesswomen -- South Africa -- Makhanda
- Language: English
- Type: thesis , text , Masters , MBA
- Identifier: http://hdl.handle.net/10962/177181 , vital:42797
- Description: Over the last 26 years, the South African government has committed to SMME development. To do this, policies and support institutions were put in place which would create a favourable environment for SMME development. This was particularly important as after 1994, when the South African economy was re-integrated into global markets after years of having sanctions imposed against the country as a result of the apartheid system. The tourism industry was identified as one of the key economic drivers which would strengthen the economy and assist in job creation, especially since South Africa would be able to attract international tourists. Further, it created the opportunity for new participants to enter the industry, including black entrepreneurs who previously could not enter the industry as a result of the apartheid laws. The opening up of the country to international markets and the focus on the tourism industry also presented the opportunity for new forms of tourism to be explored including township tourism, which gave rise to the black-owned bed & breakfast sector. Over time, it has become evident that black entrepreneurs in this sector are facing a number of challenges, in spite of the pro-SMME policies and support institutions that are in place. Because this study seeks to investigate the support services available for black female bed & breakfast owners in Makhanda, a qualitative research approach using the interpretative theoretical framework was applied. By using semi-structured interview questions, to establish what challenges do black female bed and breakfast owners face the researcher was able to respond to the following; what participants identify as their needs; and whether they are able to access the support services that are made available by the Government. Results indicated that the majority of entrepreneurs have difficulty accessing funding to develop their businesses. The seasonality of Grahamstown/ Makhanda tourism businesses has its pros and cons for tourism entrepreneurs. Despite efforts by government to transform the tourism industry, black female entrepreneurs in this industry still experience a myriad of challenges, including passive racism. Insufficient institutional support and inaccessible support services for women have made it difficult to manage in this this environment. Thus, a recommendation is put forward for female focused entrepreneurship policy, which is more responsive in terms of a judicial and legal system(s) aimed at addressing women’s particular needs and challenges. , Thesis (MBA) -- Faculty of Commerce, Rhodes Business School, 2021
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- Date Issued: 2021-04
Anisotropic copper oxide nanorods decorated with gold and palladium nanoparticles and their enzymatic properties
- Authors: Sicwetsha, Simbongile
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178547 , vital:42949
- Description: Access restricted until April 2023. , Thesis (MSc) -- Faculty of Science, Chemistry, 2021
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- Date Issued: 2021-04
Antibiotics combination therapy option for the control of antimicrobial-resistant non-cholera causing Vibrio species recovered from environmental niches of Eastern Cape, South Africa
- Authors: Ayodele, Oluwakemi Victoria
- Date: 2021-04
- Subjects: Drug resistance in microorganisms , Vibrio cholerae
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/20396 , vital:45661
- Description: Increased rate of antibiotic resistance (AR) poses a serious threat with a resultant notion of a possible end of the antibiotics era, making it a problem of concern to public health and a great implication on the world economy and human society. Despite many approaches developed to curb this menace, antibiotics resistance is still a challenge worldwide. This has made the use of combined therapy as one of the options in many cases. This study was conducted to assess antibiotics combination therapy as an option for the control of antimicrobial-resistant non-cholera causing Vibrio species that were recovered from the environment in the Eastern Cape, South Africa. Two hundred and twenty-eight Vibrio species were recovered from the environment in the Province, and these were deposited in the archive of AEMREG. PCR was used to identify target Vibrio species. Disc diffusion method was used to evaluate the antibiotic susceptibility profile of the confirmed isolates against 11 antibiotics commonly used against infections. MIC and MBC were determined using antibiotics (imipenem, tetracycline, and nalidixic acid) that high resistance was discovered. Checkerboard assay was used to carry out antibiotics combination assay, and the FICI was calculated. Rate of kill was also determined using ½ × MIC, 1 × MIC, and 2 × MIC concentrations of the combined antibiotics at 2 hr intervals. One hundred of the isolates were confirmed to be Vibrio parahaemolyticus, 82 were Vibrio vulnificus and 46 were Vibrio fluvialis. Twenty-two (22) percent of the Vibrio parahaemolyticus isolates showed resistance against tetracycline and their resistance against other antimicrobials is as follows; nalidixic acid (16 percent), ampicillin (14 percent), cefotaxime (14 percent), chloramphenicol (12 percent) and amikacin (11 percent). For Vibrio vulnificus, prevalence of resistance was as follows: imipenem (40 percent), tetracycline (22 percent), ampicillin (18 percent), meropenem (15 percent), and chloramphenicol (11 percent). Vibrio fluvialis showed the following resistance profile: nalidixic acid (28 percent), tetracycline (28percent), ampicillin (20 percent), chloramphenicol (15 percent), amikacin (11 percent) and cefotaxime (11 percent). About 38 multiple antibiotic resistance phenotypes (MARP) were recorded in all species that were evaluated. About 23 percent were resistant to over 3 antibiotics used. The multiple antibiotic resistant indices (MARI) ranged between 0.3 and 0.8. MIC and MBC were carried against isolates that were resistant to the two most common antibiotics tested. MIC and MBC were determined in the following order: tetracycline and nalidixic acid at concentrations ranging from 16 μg/ml to 1024 μg/ml for Vibrio parahaemolyticus and 32 μg/ml to 2048 μg/ml for Vibrio fluvialis. Also, the MIC and MBC of imipenem and tetracycline at concentrations ranging from 8 μg/ml to 256 μg/ml for Vibrio vulnificus were determined. Antibiotics combination therapy was carried out and synergistic activity was observed in 3 of the 16 resistant V. parahaemolyticus isolates, 3 of the16 resistant V. vulnificus isolates and 2 of the 13 resistant V. fluvialis isolates. Antagonism was not observed across all the drug combinations. Rate of kill was also determined and at 6 hr exposure time, the highest concentration (2 × MIC) exhibited bactericidal effect across all three Vibrio species. The result derived in this research, therefore, propose that combination therapy is a promising solution to antimicrobial resistance in Vibrio species. , Thesis (MSc) -- Faculty of Science and Agriculture, 2021
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- Date Issued: 2021-04
Antifungal activity of silver nanoparticles on Cryptococcus species
- Authors: Roman, Nasstasja
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Cryptococcus
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52089 , vital:43445
- Description: Cryptococcus neoformans is responsible for cryptococcal infections, which have become a great concern particularly in immunocompromised patients. This pulmonary disease causes damage to lung tissue and is presumed to be responsible for approximately 650,000 deaths annually. There is a major need for novel antimicrobial agents to avoid the emergence of resistant strains due to extended use of known antifungal drugs. Silver has become an important antimicrobial agent used in medical devices, cosmetics and even house-hold or clothing products. It is highly toxic and has a reduced risk of resistance. Silver nanoparticles have been broadly explored as an antimicrobial agent due to its high reactivity, large surface area and small size. They have been reported to display antimicrobial activity towards bacteria, viruses and fungi. C. neoformans is a pathogenic microorganism that possesses a number of virulence factors which increases the infectivity of the microorganism in immunocompromised individuals. Some of these include the presence of a polysaccharide capsule, melanin, urease and phospholipase production. Owing to limited availability of antifungal drugs and the possibility of drug resistance, this study focused on an alternative antimicrobial agent, namely silver nanoparticles, and the effects that silver nanoparticles had on fungal β-glucan, chitin and urease, phospholipase and melanin virulence factors. Results from our study show that silver nanoparticles inhibited the growth of C. neoformans at concentrations between 3.125 ƒM and 25 ƒM. Both 26.4 nm and 28.4 nm nanoparticles displayed growth inhibition, but were unable to kill the organism at concentrations of 200 ƒM and above. The silver nanoparticles caused a reduction in βglucan content. There was also an accumulation of intracellular ROS, and phospholipase activity, was reduced. In contrast, the organism displayed an increase in chitin content, melanin and urease activity upon exposure to the nanoparticles. This study shows that chemically synthesized silver nanoparticles are an effective antifungal alternative that greatly reduces or inhibits C. neoformans growth at very low concentrations (ƒM). For future studies it may be feasible to investigate the use of these nanoparticles in combination with known antifungal agents, to prevent the emergence of resistance and inhibit possible defense mechanisms displayed by the organism. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
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- Date Issued: 2021-04
Antiproliferative activity of novel rhenium complexes and medicinal plant extracts
- Authors: Oosthuizen, Kenneth Thomas , Venables, Luanne
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Medicinal plants -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52028 , vital:43441
- Description: Cancer is a complex, multifactorial disease that affects millions of individuals every year. The adverse side effects and escalating costs of current therapies coupled with the increased incidence of resistance to these therapies make it imperative that we explore novel treatments for the disease. This study investigated two avenues for novel drug design namely, novel synthetic compounds and medicinal plant extracts. The benzimidazole ring system has shown potential as a scaffold for designing novel anticancer agents. Conjugation of the metal rhenium to novel variants of this ring system open up the possibility of designing novel drugs that serve both a diagnostic and a therapeutic function. This study investigated the in vitro anticancer potential of ten such complexes against selected breast and cervical cancer cell lines. The selectivity of the complexes for cancer cells over normal cells was also investigated while the mechanism of action of effective complexes was determined by exploring cell cycle arrest, biochemical markers of apoptosis and mitochondrial membrane disruption. All ten complexes were screened against MCF7 breast and HeLa cervical cancer cell lines with four showing antiproliferative activity against both cancer cell lines and one showing cell line specific toxicity against MCF7 breast cancer cells. When looking at the SAR of the compounds it was noted that activity was higher in compounds which contain two potentially bidentate benzothiazole ligands, while compounds with potentially tridentate ligands show good activity, but only if the benzothiazole moiety is not involved in coordination. The complexes showed greater antiproliferative activity against the MCF7 breast cancer cells with IC50 values ranging from 3.2 to 7.0 µM versus a range of 7.6 to 24.4 µM being obtained on the HeLa cervical cancer cells. Antiproliferative complexes were tested against confluent and log phase Vero cells at their respective IC50 values to determine their effect on “normal” cells. Confluent Vero cells showed less cell death than those in log phase indicating that the complexes show preference for proliferating cells. The mechanism of action of the complexes was studied on both cancer cell lines via cell cycle analysis and apoptosis assays investigating phosphatidylserine translocation, caspase -3 and -8 activation and mitochondrial membrane potential with most complexes inducing cell cycle arrest followed by cell death via both the extrinsic and intrinsic pathways of apoptosis. Since 1940, 49% of all the available anticancer drugs approved for cancer treatment were natural products or directly derived from natural products. Plants are an excellent source of secondary metabolites, many of which are unique chemical compounds that cannot be synthesized in a laboratory. Ethnobotanical surveys conducted in conjunction with Traditional Health Practitioners of the Mkuranga and Same districts in Tanzania identified 25 plants that are used for the treatment of cancer. Four of these plants (A. mossambicensis, C. adenocaule, C. pseudopulchelusis and R. natalensis) with ethnobotanically reported anticancer usage showed cytotoxic activity against brine shrimp and were selected for further in vitro anticancer studies. All four plants were found to have antiproliferative activity against HeLa cervical cancer cells with IC50 values ranging from 3.4 to 50.8 µg/mL. This study was also tasked with investigating the mechanism of action of C. pseudopulchelus on HeLa cervical cancer cells by exploring cell cycle arrest, biochemical markers of apoptosis and mitochondrial membrane x disruption. C. pseudopulchelus caused early M phase arrest followed by slippage and subsequent cell death via the extrinsic pathway of apoptosis. In conclusion, this study showed that both novel complexes as well as medicinal plant extracts represent an interesting avenue for the development of novel anticancer drugs that are cheaper and produce less side effects than current therapies. , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
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- Date Issued: 2021-04
Assessing community engagement programmes to mitigate uncontrolled, deliberately ignited fires in forestry plantation-communal land interface, Kwazulu-Natal, South Africa
- Authors: Ramantswana, Nontethelelo
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Forest fires -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52008 , vital:43439
- Description: Forestry plantations in South Africa are surrounded by poor local communities that normally depend on the forestry resources for subsistence. This interface area is faced with human induced uncontrolled fires. There is a lack of understanding regarding the reasons for deliberate ignition of uncontrolled fires. There is also lack of information on the success of community engagement programs (CEPs) as fire protection intervention and / or their implementation barriers. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2021
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- Date Issued: 2021-04
Baculovirus synergism for improved management of false codling moth Thaumatotibia leucotreta Meyr. (Lepidoptera: Tortricidae)
- Authors: Taylor, David Graham
- Date: 2021-04
- Subjects: Baculoviruses , Cryptophlebia leucotreta , Cryptophlebia leucotreta -- Biological control , Biological pest control agents , Citrus -- Diseases and pests , Codling moth , Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV)
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/176942 , vital:42774
- Description: Baculoviruses are an environmentally friendly and effective agent for managing lepidopteran pests. This includes the management of Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), a serious pest of citrus in Southern Africa and a major threat to the South African citrus export industry. For more than 15 years, CrleGV-SA- based biopesticides have been used as part of an integrated pest management strategy for the control of T. leucotreta in citrus orchards in South Africa, under the names Cryptogran™ and Cryptex®. While these biopesticides have been effective during this period, there are some areas in which baculovirus use could potentially be improved. Baculoviruses are notoriously slow to kill in comparison to chemical-based pesticides, and lately, pest resistance to baculoviruses has become a major concern with the development of resistance by Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) to its granulovirus occurring in the field in Europe. The consistent use of CrleGV-SA for more than 15 years in the field has raised concern that T. leucotreta could develop resistance to this virus, and has made it necessary to alter baculovirus-based management strategies to prevent this from occurring. A second baculovirus, Cryptophlebia peltastica nucleopolyhedrovirus (CrpeNPV), has recently been isolated and was shown to be effective against T. leucotreta. However, the interactions between CrleGV-SA and CrpeNPV are not yet understood and so it is important to test these interactions before both viruses are applied on the same orchards. Not only is it important to know whether these viruses could negatively impact each other, but it is also important to test whether they could interact synergistically. A synergistic interaction could not only provide a potential tool for the management of resistance, but it could also be exploited to improve baculovirus-based management of T. leucotreta. In this study, a stock of CrleGV-SA was purified by glycerol gradient centrifugation from T. leucotreta cadavers, while a stock of CrpeNPV purified from Cryptophlebia peltastica (Meyrick) (Lepidoptera: Tortricidae) cadavers was provided by River Bioscience (Pty) Ltd. These stocks were screened for purity by a multiplex polymerase chain reaction (mPCR) protocol designed to detect CrleGV-SA and CrpeNPV. The occlusion body (OB) density was then calculated using darkfield microscopy and a counting chamber. Both stocks were shown to be pure within the limits of the mPCR protocol, and the CrleGV-SA and CrpeNPV stocks were calculated to contain 3.08 × 1011 OBs/mL and 1.92 × 1011 OBs/mL respectively The first aspect of the interaction between CrleGV-SA and CrpeNPV that was investigated was the dose mortality, in terms of lethal concentration. This was calculated using 7-day surface-dose biological assays for each virus and a 1:1 mixture of OBs of the two against T. leucotreta neonates. The lethal concentrations of each treatment required to kill 50 % of larvae (LC50) and 90 % of larvae (LC90) for each treatment were then calculated and compared using a probit regression. The mixed infection performed significantly better than either virus by itself, while each virus by itself did not differ significantly from the other. The LC50 for CrleGV-SA, CrpeNPV and the mixed infection were 1.53 × 104 OBs/mL, 1.15 × 104 OBs/mL and 4.38 × 103 OBs/mL respectively. The LC90 of CrleGV-SA, CrpeNPV and the mixed infection were calculated to be 4.10 × 105 OBs/mL, 1.05 × 105 OBs/mL, and 4.09 × 104 OBs/mL respectively. The second aspect of the interaction between CrleGV-SA and CrpeNPV that was investigated was the speed of kill. A time-response biological assay protocol was created that allowed for effective observation of the larvae. This was then used to generate time-mortality data that were analysed by a logit regression function to calculate and compare the treatments at the time of 50 % larval mortality (LT50) and the time of 90 % mortality (LT90). Each virus by itself did not differ significantly from the other, while the mixed infection took significantly longer to kill 50 % and 90 % of the larvae, suggesting that there is competition for resources between viruses during the secondary, systemic phase of infection. The LT50 for CrleGV-SA, CrpeNPV and the mixed infection were 117.5 hours, 113.5 hours and 139.0 hours respectively. The LT90 for CrleGV-SA, CrpeNPV and the mixed infection were 153.2 hours, 159.3, and 193.4 hours respectively. Finally, the composition of OBs recovered from the cadavers produced by the time-response biological assays were investigated by mPCR. A method for extracting gDNA from OBs in neonate-sized T. leucotreta larvae is described. The presence of CrpeNPV along with CrleGV-SA was noted in 4 out of 9 larvae inoculated with only CrleGV-SA. The presence of CrleGV-SA as well as CrpeNPV was noted in all but one larva inoculated with only CrpeNPV, and both CrleGV-SA and CrpeNPV were noted in all but one larva inoculated with a 1:1 mixture of the two, with one larva only being positive for CrleGV-SA. This suggests either stock contamination or the presence of covert infections of CrleGV-SA and CrpeNPV in the T. leucotreta population used in this study. This is the second study to report an improved lethal concentration of a mixed infection of CrleGV-SA and CrpeNPV against T. leucotreta neonates, and the first study to report the slower speed of kill of a mixed infection of CrleGV-SA and CrpeNPV against T. leucotreta neonates. While the improved lethal concentration of the mixed infection is a promising step in the future improvement of baculovirus-based biopesticides, it is at the cost of a slower speed of kill. , Thesis (MSc) -- Faculty of Science, Department of Zoology and Entomology, 2021
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- Date Issued: 2021-04
Barriers and reasons for exercise of rural and urban overweight and obese populations in Buffalo City Metropolitan Municipality, Eastern Cape
- Authors: Mrwebi, Thembani
- Date: 2021-04
- Subjects: Obesity--Prevention , Public health--Exercise
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10353/22522 , vital:52388
- Description: It is documented that obesity is highly prevalent across rural and urban groups in industrialised and underdeveloped countries. This problem is an alarming issue as community members remain unsure about avoiding risking their health. Various health surveys reveal that obesity has increased among communities in the Buffalo City Metro Municipality in the Eastern Cape, and it has consequently made communities vulnerable to non-communicable diseases. The researcher explored factors and barriers of exercise for rural and urban obese populations in Buffalo City Metropolitan Municipality, Eastern Cape. This study was descriptive and explorative, utilising a questionnaire for gathering information. A purposive sample of 80 members from the two selected communities completed the questionnaire. A factor analysis was performed to identify factors that motivate physical activity and barriers to physical activity. It was discovered that all evaluated members were fully aware of the harmful repercussions of being overweight or obese. Nevertheless, only a tiny percentage of those who took part in the study decided to live a healthier lifestyle because of their obesity. Constructive motivating factors included increasing their self-image, enhancing their wellbeing, and getting highly involved in active and regular exercise. Negative motivators included finding it challenging to fit into old clothes and the worry of developing obesity-related diseases. Respondents noted the following impediments in regular exercises and physical activities; African cultural values, limited operational hours of physical activity facilities, insufficient time, and a lack of enthusiasm. , Thesis (MPhil) -- Faculty of Science and Agriculture, 2021
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- Date Issued: 2021-04
Bayesian tolerance intervals and their application to ballistic grouping consistency in competitive shooting
- Authors: Gardiner, Marcell
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Bayesian statistical decision theory -- South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52456 , vital:43662
- Description: Competitive shooting has become immensely popular since the first modern Games held in 1896. Competitive shooting remains the fastest growing segment in the firearm industry, catering to individuals of all ages. Elite shooters are capable of reaching extreme levels of precision and accuracy, despite many factors existing that affect performance in Olympic shooting. One such factor is speed variability, which is dependent on the mass of the bullet, how constant is the lead being used, and, how constant the gunpowder is. The study focusses on the Bayesian simulation method proposed by Wolfinger (1998) for determining three kinds of tolerance intervals when applied to competitive shooting data, particularly examining speed variability. These tolerance intervals included the (𝛼𝛼,𝛿𝛿) tolerance interval (where 𝛼𝛼 is the content and 𝛿𝛿 is the confidence), the 𝛼𝛼 - expectation tolerance interval (where 𝛼𝛼 is the expected coverage of the interval) and the fixed-in advance tolerance interval in which the interval is held fixed and the proportion of process measurements it contains, is estimated. Speed measurements of individual shots fired were measured with either an Oeler 35P or Magneto Speed V3 chronograph and the data was fitted to a one-way random effects model. , Thesis (MSc) -- Faculty of Science, School of Computer Science, Mathematics, Physics and Statistics, 2021
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- Date Issued: 2021-04
Benthic habitat mapping using marine geophysics and machine learning on the continental shelf of South Africa
- Authors: Pillay, Talicia
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Marine geophysics
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52061 , vital:43452
- Description: A method to map seafloor substrates using machine learning, based primarily on hydroacoustic data including multibeam bathymetry, backscatter, and side-scan sonar, has been developed. The aim was to produce a customdesigned benthic habitat classification method that digitally integrates marine geophysics and biological science data, with relevance to all elements of the local substrate, and this was the first time it was attempted in a South African context. The algorithm developed is able to produce bio-physical benthic habitat maps and this can be extended along the continental shelf of South Africa as new data setsare collected and the algorithm is supplemented. At the outset, this work has focused on broad categories of rock and detailed categories of sediment. Four study sites with varying substrate were selected to holistically build the algorithm that followed a tiered approach of machine learning: Table Bay, Clifton, Koeberg Harbour and Cape St Francis. Table Bay was used to develop a new method of physical seafloor classification, by comparing and contrasting a number of statistical algorithms and software programs. Clifton was used to test the developed clustering algorithm, and Koeberg which is 35 km to the north was used to validate the algorithm because sediment samples, along with drop camera footage, were integrated to better define the results. The resultant verified algorithm was tested at Cape St Francis, where Remotely Operated Vehicle (ROV) footage was acquired in addition to hydroacoustic data. In the first phase of the process towards developing an algorithm, a customised tool was created within ArcGIS using python scripting language to classify seafloor bathymetry, which can be applied to any area of seafloor whatsoever. The tool was based on pioneering work done by the National Oceanic and Atmospheric Administration (NOAA) on a benthic terrain modelling toolbox and adapted to include side-scan sonar data. In the second phase of work, multibeam bathymetry, backscatter and side-scan sonar data that were processed using Qimera, Fledermaus Geocoder Toolbox, and Navlog processing software, were classified using different machine learning techniques including Decision Trees, Random Forests, and k-means clustering computer algorithms. The results from these algorithms were compared to manually-digitised polygons which were created to classify the seafloor substrate distribution by identification of different textures. Integrating all results facilitated a quantitative comparison that illuminated advantages and disadvantages of each machine learning technique and ultimately the k-means clustering techniques were found to be the simplest to implement and understand and worked most efficiently based on their seafloor segmentation capabilities in Table Bay, against all three hydroacoustic data sets (multibeam bathymetry, backscatter and side-scan sonar). In the third phase of work, ground-truthed seafloor characterisation maps were produced for the two study areas of Clifton and Koeberg Harbour. This applied multibeam bathymetry and backscatter data that were collected and processed with machine learning clustering techniques. , Thesis (MSc) -- Faculty of Science, Ocean Sciences, 2021
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- Date Issued: 2021-04
Bioethical analysis of selected biomedical issues in South Africa and other countries
- Authors: Rusere, Jean
- Date: 2021-04
- Subjects: To be added
- Language: English
- Type: thesis , text , Masters , MPharm
- Identifier: http://hdl.handle.net/10962/178530 , vital:42948
- Description: Access restricted until April 2023. , Thesis (MPharm) -- Faculty of Pharmacy, Pharmacy, 2021
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- Date Issued: 2021-04
Biology, ecology and management of the Keurboom moth, Leto venus Cramer and the leafhopper Molopopterus sp. Jacobi in cultivated Honeybush (Cyclopia spp.)
- Authors: Mushore, Tapiwa Gift
- Date: 2021-04
- Subjects: Legumes , Legumes -- Diseases and pests , Hepialidae , Leafhoppers , Pests -- Biological control , Entomopathogenic fungi , Leafhoppers -- Biological control , Hepialidae -- Biological control , Keurboom moth (Leto venus Cramer) , Molopopterus sp. Jacobi , Honeybush (Cyclopia spp.)
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/177125 , vital:42792
- Description: Honeybush, Cyclopia spp. Vent (Fabaceae), farmers have raised pest concerns following commercial cultivation. The Keurboom moth Leto venus Cramer (Lepidoptera: Hepialidae) and the leafhopper Molopopterus sp. Jacobi (Hemiptera: Cicadellidae), are two of the major pests identified in cultivated Honeybush. Laboratory and field studies were conducted to gain an understanding of the biology of these two pests to inform future pest management solutions. Additionally, entomopathogenic fungi were isolated from Honeybush farms and screened for virulence against Molopopterus sp. as a possible management strategy. This study showed that the L. venus infestation on Honeybush was a product of four fixed effects; stem diameter, species of Cyclopia, Farm location and age of the plants. Cyclopia subternata, had the highest likelihood of infestation. Increase in age of the plants resulted in an increase in the stem diameter and therefore a higher probability of infestation. Stem diameter was also shown to be a significant predictor of infestation likelihood. Infestation severity, determined by the number of larvae per plant, was shown to be influenced by three fixed effects; stem diameter, plant species and Farm location. The results also showed that L. venus prefers to initiate penetration at, or just aboveground level. Laboratory studies showed that the leafhopper Molopopterus sp. undergoes five nymphal instars with an average egg incubation time of 20 days, development time from 1st instar to adult of 26 days and average generation time of 47 days. Laboratory experiments revealed variations in host preference by the leafhopper over a period of 15 days. Cyclopia longifolia was identified to be the most preferred species for feeding compared to the two other commonly cultivated species, C. subternata and C. maculata. The results were consistent with those obtained from the field survey which showed that leafhopper density was influenced by four fixed effects; plant species, age of the plant, Farm location and harvesting practices. There were significant differences in leafhopper density in different species with C. longifolia having the highest number of leafhoppers per plant. There were differences in leafhopper density in different farms as 57% of the sampled farms had leafhopper infestations, of these farms, Lodestone and Kurland had the highest leafhopper densities. Harvested plants were shown to have significantly higher leafhopper density than non-harvested plants. Age was also shown to influence leafhopper density, which reduced with an increase in the age of the plants. A total of 20 fungal isolates were recovered from 98 soil samples of which 70% were from Honeybush fields and 30% were from surrounding refugia. Fusarium oxysporum isolates comprised 20% of the recovered isolates, with Metarhizium anisopliae isolates making up the remainder. Laboratory bioassays against adults and nymphs of the leafhopper, Molopopterus sp., showed that F. oxysporum isolates induced 10 – 45% mortality and M. anisopliae isolates induce 30 – 80% mortality. Metarhizium anisopliae isolates J S1, KF S3, KF S11, KF S13, LS1 and LS2 were the most virulent and induced over 60% mortality in both Molopopterus sp. nymphs and adults. The results of this study showed pest preference towards different Cyclopia species. As such, they should be managed differently. Furthermore, L. venus was observed to occur in low densities, hence, it cannot be considered a major pest. However, Molopopterus sp. recorded high population densities making it a major pest in Honeybush production. Positive results indicated that some of the isolated fungal isolates have potential for control, an avenue worth investigating further. , Thesis (MSc) -- Faculty of Science, Department of Zoology and Entomology, 2021
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- Date Issued: 2021-04
Challenges faced by state owned entities and economic development in South Africa
- Authors: Willie, Ntsikelelo Mike Mncedi
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , South Africa
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52976 , vital:44907
- Description: Background: State Owned Enterprises (SOEs) play a vital role in government activities and the delivery of basic services to the people. The Government is active in the key sectors, such as, services, utilities, transportation and construction. Presumably, the distribution of basic resources and infrastructure development is to some extent dependent on SOEs. South Africa is inundated with challenges in SOE’s, such as, lack of service delivery, poor financial management, less growth, massive unemployment, corruption and low business confidence. These are a threat to economic and financial sustainability of a country. Twenty years into democracy, South Africa’s SOEs environment had many scandals in both private and public sectors. SOEs such as SABC, Eskom, and Transnet had their share of malpractice, fraud and corruption in management and at board level. These incidents call for interrogation at all levels as the impact undermines political, economic stability and growth prospects. One of today’s core challenges is to justify the existence of some of the SOEs in our economy. Looking at South Africa, most of the SOEs financial performances are severely deteriorating. Due to their financial constraints, they receive a bailout from government to enable them to continue to operate. Aim: This study identified specific governance challenges faced by SOEs and economic development in South Africa, over the period of 10 years (2014 - 2018). The study made recommendations to restore good governance in SOEs. Setting: This study reviewed articles and literature on the challenges faced by SOEs and economic development in South Africa. Primary sources for the document review took the form of newspapers, various official reports and ongoing records of SOEs activities, government departments, student transcripts, mission statements, annual reports, policy, manuals, student handbooks, and strategic plans, and press releases, theses from academic institutions, trade journals, business journals, government publications and business review publications. Secondary sources used were published books and journal articles. , Thesis (MA) -- Faculty of Business and Economic Sciences , School of Economics, Development and Tourism, 2021
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- Date Issued: 2021-04