Synthesis of coumarin based fluorescent chemosensors for the detection of metal ions.
- Authors: Hamukoshi, Simeon Shiweda
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Organic compounds--Synthesis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52041 , vital:43422
- Description: The study focused on the synthesis of three coumarin-based chemosensors; hydrazone fluorescent chemosensor , azo-benzothiazole dye and azo-quinoline dye. The hydrazone fluorescent chemosensor was synthesised through multiple reaction steps were the azide functionality at position 8 of the coumarin backbone was replaced with the hydrazone group in the last reaction step. The azo dyes were synthesised through a two step reaction process. The photophysical properties of all three chemosensors were investigated. The hydrazone chemosensor and azo-benzothiazole dye presented high absorption and emission, while the azo-quinoline only presented absorption properties. The chemosensing ability of the three products were investigated through absorption and emission. The hydrazone chemosensor was found to be highly selective towards Fe3+ in water and the dyes were found to be selective towards Hg2+. The mechanisms of interaction between the chemosensors and their selective metal ions were investigated via computational analysis and 1H NMR analysis. All of the chemosensors where characyerised using 1H NMR, Fourier Transform Infrared Spectrometer (FTIR) and the X Ray Chrystal structure for the hydrazone chemosensor was obtained via X ray Chrystallography. Finally, the electron density distribution of the all synthesised compounds their predicted stable metal ion complexes was determined using Density Functionaly Theory (DFT). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Hamukoshi, Simeon Shiweda
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Organic compounds--Synthesis
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52041 , vital:43422
- Description: The study focused on the synthesis of three coumarin-based chemosensors; hydrazone fluorescent chemosensor , azo-benzothiazole dye and azo-quinoline dye. The hydrazone fluorescent chemosensor was synthesised through multiple reaction steps were the azide functionality at position 8 of the coumarin backbone was replaced with the hydrazone group in the last reaction step. The azo dyes were synthesised through a two step reaction process. The photophysical properties of all three chemosensors were investigated. The hydrazone chemosensor and azo-benzothiazole dye presented high absorption and emission, while the azo-quinoline only presented absorption properties. The chemosensing ability of the three products were investigated through absorption and emission. The hydrazone chemosensor was found to be highly selective towards Fe3+ in water and the dyes were found to be selective towards Hg2+. The mechanisms of interaction between the chemosensors and their selective metal ions were investigated via computational analysis and 1H NMR analysis. All of the chemosensors where characyerised using 1H NMR, Fourier Transform Infrared Spectrometer (FTIR) and the X Ray Chrystal structure for the hydrazone chemosensor was obtained via X ray Chrystallography. Finally, the electron density distribution of the all synthesised compounds their predicted stable metal ion complexes was determined using Density Functionaly Theory (DFT). , Thesis (MSc) -- Faculty of Science, School of Biomolecular and Chemical Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
A systematic review of research into working capital management in South Africa
- Authors: Watson, Storm Brandon
- 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/10948/52995 , vital:44906
- Description: This study is set out to apply mixed methods approach to a systematic review of research into working capital management in South Africa. Research into working capital management has primarily focused on the effect it has on a business’s profitability, liquidity and performance. There is, however, limited research on the topic working capital management in South Africa and, as such, the primary objective of this study is to review research outputs on working capital management in South Africa. The purpose is to identify research gaps in the current body of knowledge by means of the development of a recommendation’s framework. , Thesis (MA) -- Faculty of Business and Economic Sciences, School of Management Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Watson, Storm Brandon
- 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/10948/52995 , vital:44906
- Description: This study is set out to apply mixed methods approach to a systematic review of research into working capital management in South Africa. Research into working capital management has primarily focused on the effect it has on a business’s profitability, liquidity and performance. There is, however, limited research on the topic working capital management in South Africa and, as such, the primary objective of this study is to review research outputs on working capital management in South Africa. The purpose is to identify research gaps in the current body of knowledge by means of the development of a recommendation’s framework. , Thesis (MA) -- Faculty of Business and Economic Sciences, School of Management Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
An assessment of the key factors that may impact the future demand for red meat in South Africa
- Authors: Pearce, Nathan
- 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/10948/53019 , vital:44887
- Description: The global human population is estimated to be in excess of nine billion by the year 2050, and the added population is expected to put further pressure on already over- extended resources such as food and water. Increased demand, positive growth and record high prices should be encouraging for the red meat industry. Despite all the positives such as the growth in the world population and the consumer’s ability to spend, the popularity of red meat around the world and in South Africa is continually declining in favour of white meat and other non-meat proteins. Although red meat will often be the most expensive component of any diet, the nutritional value that red meat offers as part of a healthy and balanced eating plan, should not be understated. This study intends to identify and assess factors that may impact on the future sustainable demand for red meat. Sixty-two adults were surveyed through an electronic questionnaire to assess their views on red meat consumption in South Africa. A set of 52 questions were deduced from the main focus and objectives. The data was analysed and conclusions derived from it. The results show that the demand for red meat is sustainable if outlets selling red meat are accessible and the preference for red meat remains, even with stiff competition from substitutes like pork, chicken and vegetables. , Thesis (MBA) -- Faculty of Business and Economic Sciences, NMU Business School, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Pearce, Nathan
- 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/10948/53019 , vital:44887
- Description: The global human population is estimated to be in excess of nine billion by the year 2050, and the added population is expected to put further pressure on already over- extended resources such as food and water. Increased demand, positive growth and record high prices should be encouraging for the red meat industry. Despite all the positives such as the growth in the world population and the consumer’s ability to spend, the popularity of red meat around the world and in South Africa is continually declining in favour of white meat and other non-meat proteins. Although red meat will often be the most expensive component of any diet, the nutritional value that red meat offers as part of a healthy and balanced eating plan, should not be understated. This study intends to identify and assess factors that may impact on the future sustainable demand for red meat. Sixty-two adults were surveyed through an electronic questionnaire to assess their views on red meat consumption in South Africa. A set of 52 questions were deduced from the main focus and objectives. The data was analysed and conclusions derived from it. The results show that the demand for red meat is sustainable if outlets selling red meat are accessible and the preference for red meat remains, even with stiff competition from substitutes like pork, chicken and vegetables. , Thesis (MBA) -- Faculty of Business and Economic Sciences, NMU Business School, 2021
- Full Text: false
- Date Issued: 2021-04
Strategies to sustain SMEs post the hard lockdown period: a multiple case study in Gauteng
- Rabohale, Mokabolane Innocent
- Authors: Rabohale, Mokabolane Innocent
- 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/10948/53015 , vital:44889
- Description: The outbreak of the Covid 19 pandemic and the lockdown restrictions imposed by the government in March 2020 exacerbated uncertain conditions of the weak South African business environment. This meant that SME owners and managers in different sectors had to implement strategies to manoeuvre the further weakened and unprecedented business environment. To investigate this, the research question asked was: what sustainable strategies will SME owners and managers craft and implement to use post the lockdown period? The study analysed strategies before, during, and post the hard lockdown period to provide insight into how SMEs adopted to the uncertain business environment. This study interviewed twenty (20) SMEs in different sectors in Gauteng to explore strategies that SME owners and managers used to sustain their businesses prior to, during, and post the level 5 and level 4 lockdown. The study revealed strategies employed by SME owners across five sectors. Furthermore, the study indicated that during the hard lockdown, owners used a “wait and see” strategy in different degrees. Post the level 5 and 4 lockdown, different sectors were innovating, cost cutting, and digitisation according to their level of comfortability and diversification. The study reveals that strategic planning was missing prior, during, and post the level 4 and 5 lockdowns, despite SME owners’ educational background. , Thesis (MBA) -- Faculty of Business and Economic Sciences, NMU Business School, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Rabohale, Mokabolane Innocent
- 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/10948/53015 , vital:44889
- Description: The outbreak of the Covid 19 pandemic and the lockdown restrictions imposed by the government in March 2020 exacerbated uncertain conditions of the weak South African business environment. This meant that SME owners and managers in different sectors had to implement strategies to manoeuvre the further weakened and unprecedented business environment. To investigate this, the research question asked was: what sustainable strategies will SME owners and managers craft and implement to use post the lockdown period? The study analysed strategies before, during, and post the hard lockdown period to provide insight into how SMEs adopted to the uncertain business environment. This study interviewed twenty (20) SMEs in different sectors in Gauteng to explore strategies that SME owners and managers used to sustain their businesses prior to, during, and post the level 5 and level 4 lockdown. The study revealed strategies employed by SME owners across five sectors. Furthermore, the study indicated that during the hard lockdown, owners used a “wait and see” strategy in different degrees. Post the level 5 and 4 lockdown, different sectors were innovating, cost cutting, and digitisation according to their level of comfortability and diversification. The study reveals that strategic planning was missing prior, during, and post the level 4 and 5 lockdowns, despite SME owners’ educational background. , Thesis (MBA) -- Faculty of Business and Economic Sciences, NMU Business School, 2021
- Full Text: false
- Date Issued: 2021-04
Antiproliferative activity of novel rhenium complexes and medicinal plant extracts
- Oosthuizen, Kenneth Thomas, Venables, Luanne
- 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
- Full Text: false
- Date Issued: 2021-04
- 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
- Full Text: false
- Date Issued: 2021-04
Impact of feeding milk once-a-day on growth and development of jersey calves
- Authors: Myburgh, Albertus Petrus
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Calves -- Feeding and feeds
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52095 , vital:43438
- Description: In conventional calf rearing systems calves are fed milk twice a day. Calves are normally housed in a calf shed, kept in individual pens or in groups. The goal should be to limit mor-talities to less than 5% from birth to 30 days. This can be achieved by reducing animal stress, controlling diseases and feeding the animals properly. The immune function can be de-pressed by inadequate nutrition which will increase susceptibility to diseases. Key objective on a dairy farm should be to rear a healthy calf until the calf reaches the optimum mating weight. Digestive disorders and respiratory diseases are the main causes of mortalities of young calves. Jersey calves at Outeniqua Research Farm are kept in movable hutches out-side, for 8 weeks and whole milk is fed only once a day. Although it is common practice to feed milk to calves twice-a-day, Jersey calves are raised with great success by feeding whole milk once-a-day, but proven data was never collected to indicate that feeding whole milk to Jersey calves does not compromise growth or development of calves. Much research was done on feeding of milk to Holstein calves, but little was done on Jersey calves. Research also shows results on feeding of milk replacer rather than whole milk. This raised the question of can whole milk be fed once-a-day successfully to Jersey calves with-out compromising growth and development and what are the advantages of feeding whole milk once-a-day to Jersey calves? , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04
- Authors: Myburgh, Albertus Petrus
- Date: 2021-04
- Subjects: Gqeberha (South Africa) , Eastern Cape (South Africa) , Calves -- Feeding and feeds
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/52095 , vital:43438
- Description: In conventional calf rearing systems calves are fed milk twice a day. Calves are normally housed in a calf shed, kept in individual pens or in groups. The goal should be to limit mor-talities to less than 5% from birth to 30 days. This can be achieved by reducing animal stress, controlling diseases and feeding the animals properly. The immune function can be de-pressed by inadequate nutrition which will increase susceptibility to diseases. Key objective on a dairy farm should be to rear a healthy calf until the calf reaches the optimum mating weight. Digestive disorders and respiratory diseases are the main causes of mortalities of young calves. Jersey calves at Outeniqua Research Farm are kept in movable hutches out-side, for 8 weeks and whole milk is fed only once a day. Although it is common practice to feed milk to calves twice-a-day, Jersey calves are raised with great success by feeding whole milk once-a-day, but proven data was never collected to indicate that feeding whole milk to Jersey calves does not compromise growth or development of calves. Much research was done on feeding of milk to Holstein calves, but little was done on Jersey calves. Research also shows results on feeding of milk replacer rather than whole milk. This raised the question of can whole milk be fed once-a-day successfully to Jersey calves with-out compromising growth and development and what are the advantages of feeding whole milk once-a-day to Jersey calves? , Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 2021
- Full Text: false
- Date Issued: 2021-04