An evaluation of the Xenopus laevis liver slice model to study the toxic effects of microcystin
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
- Full Text:
- Date Issued: 2003
- Authors: Coates, Nadya
- Date: 2003
- Subjects: Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11069 , http://hdl.handle.net/10948/307 , Zenopus laevis , Microcystis aeruginosa -- Toxicology
- Description: Blooms of cyanobacteria have increased in occurrence in the past three decades and have been reported to cause severe problems for animals and humans, leading to death in extreme instances. The majority of poisonings that have taken place have been attributed to a hepatotoxin produced by the species Microcystis aeruginosa, namely microcystin. The appearance of a cyanobacterial bloom does not give any indication as to its toxicity and therefore, it is imperative that simple, yet sensitive, bioassays are developed to overcome this problem. This study was undertaken to evaluate the effects of microcystin-LR on the liver of Xenopus laevis both in vitro and in vivo. This animal provides an opportunity to study the long-term hepatotoxic effects of the toxin compared to in vitro studies performed with mice and rats. The use of the liver slice model system as a potential bioassay to study the effects of microcystin-LR on Xenopus laevis liver was evaluated. Liver slices were cultured in RPMI- 1640 culture medium for periods ranging from 30 hours to 10 days and the liver slices were exposed to toxin concentrations ranging from 1nM to 500nM. The use of frog liver slices to study the longer-term effects of low-dose exposure to microcystin-LR was evaluated by observing the ultrastructural changes within hepatocytes using transmission electron microscopy, the release of the enzymes alanine aminotransferase and lactate dehydrogenase into the surrounding culture medium, as well as using a 3-[4,5-dimethylthiazol-2yl]-2,5- diphenyl tetrazolium bromide assay to determine the viability of the liver slices in culture. The amount of lipid peroxidation in the liver slices after exposure to microcystin-LR was assessed using the Thiobarbituric Acid Test. Results showed the frog liver slice culture system to be an inadequate method to evaluate the hepatotoxic effects of microcystin-LR. An in vivo assessment of the effects of microcystin-LR on Xenopus laevis was carried out using a total of 9 frogs (3 groups of 3 frogs). Frogs received a single intraperitoneal dose of 120mg/kg of microcystin-LR and were sacrificed at 8 and 24 hours post exposure. Microcystin-LR caused no significant change in serum lactate dehydrogenase levels, hepatosomatic index (liver weight as a percentage body weight), glutathione peroxidase activity, glycogen or lipid peroxidation. There was, however, an increase in glutathione sii transferase activity in the liver. The presence of the toxin in the liver was confirmed by immunohistochemistry. This study suggests that Xenopus laevis has, in some way, adapted to detoxifying aquatic toxins in the environment.
- Full Text:
- Date Issued: 2003
An evaluation of UPLC technology for the simultaneous analysis of actives in a multi-active drug
- Authors: Bawjee, Janita
- Date: 2011
- Subjects: High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10384 , http://hdl.handle.net/10948/d1008407 , High performance liquid chromatography
- Description: The evaluation of the potential to use Ultra Performance Liquid Chromatography (UPLC) for the simultaneous quantification of all the actives in a multi-active tablet is described in this work. Part of the evaluation was to ensure that the necessary regulatory requirements were adhered to by ascertaining that an analytical method is suitable for a specific purpose through analytical method validation for the specific multi-active tablet. The UPLC method was also tested for the analysis of similar products, namely tablet formulations that contain similar active ingredients in the same proportions but with an additional active ingredient. A method for the simultaneous determination of paracetamol, caffeine and codeine phosphate was developed using UPLC technology. The UPLC developed method was more efficient than the existing in-house HPLC method. The UPLC method was then validated in accordance to ICH and USP guidelines. The application of this UPLC method for the analysis of similar products containing paracetamol, caffeine, codeine phosphate and one extra active ingredient was very challenging. The low concentration of the additional component, differences in sample matrix and differences in formulations added to the challenges. The direct application for the analysis of products Y and Z was not successful; however the method could be used as a platform for further research. A cost comparison between the UPLC and HPLC methods showed the UPLC method to be more cost effective. Thus, while maintenance costs are higher for the UPLC instrument, column costs are comparable to HPLC columns, but solvent and waste disposal charges decrease considerably due to lower solvent use. The reduction in instrument time dramatically improves the cost effectiveness of UPLC over HPLC due to a concurrent reduction in analyst time requirement. The results of this study show that the analytical costs associated with the analysis of multi-active drugs using HPLC procedures can be reduced substantially by the CONFIDENTIAL INTELLECTUAL PROPERTY OF ASPEN PHARMACARE implementation of UPLC technology. The hypothesis that the enhanced chromatographic power of UPLC can be leveraged to provide faster analysis times hence increased product throughput rates, and lower operating costs for the analysis of multi-active drugs was accepted. These advantages were achieved whilst meeting all regulatory requirements for analytical methods as required by regulatory bodies.
- Full Text:
- Date Issued: 2011
- Authors: Bawjee, Janita
- Date: 2011
- Subjects: High performance liquid chromatography
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: vital:10384 , http://hdl.handle.net/10948/d1008407 , High performance liquid chromatography
- Description: The evaluation of the potential to use Ultra Performance Liquid Chromatography (UPLC) for the simultaneous quantification of all the actives in a multi-active tablet is described in this work. Part of the evaluation was to ensure that the necessary regulatory requirements were adhered to by ascertaining that an analytical method is suitable for a specific purpose through analytical method validation for the specific multi-active tablet. The UPLC method was also tested for the analysis of similar products, namely tablet formulations that contain similar active ingredients in the same proportions but with an additional active ingredient. A method for the simultaneous determination of paracetamol, caffeine and codeine phosphate was developed using UPLC technology. The UPLC developed method was more efficient than the existing in-house HPLC method. The UPLC method was then validated in accordance to ICH and USP guidelines. The application of this UPLC method for the analysis of similar products containing paracetamol, caffeine, codeine phosphate and one extra active ingredient was very challenging. The low concentration of the additional component, differences in sample matrix and differences in formulations added to the challenges. The direct application for the analysis of products Y and Z was not successful; however the method could be used as a platform for further research. A cost comparison between the UPLC and HPLC methods showed the UPLC method to be more cost effective. Thus, while maintenance costs are higher for the UPLC instrument, column costs are comparable to HPLC columns, but solvent and waste disposal charges decrease considerably due to lower solvent use. The reduction in instrument time dramatically improves the cost effectiveness of UPLC over HPLC due to a concurrent reduction in analyst time requirement. The results of this study show that the analytical costs associated with the analysis of multi-active drugs using HPLC procedures can be reduced substantially by the CONFIDENTIAL INTELLECTUAL PROPERTY OF ASPEN PHARMACARE implementation of UPLC technology. The hypothesis that the enhanced chromatographic power of UPLC can be leveraged to provide faster analysis times hence increased product throughput rates, and lower operating costs for the analysis of multi-active drugs was accepted. These advantages were achieved whilst meeting all regulatory requirements for analytical methods as required by regulatory bodies.
- Full Text:
- Date Issued: 2011
An evolutionary algorithm approach to ecological optimal control problems
- Authors: Westcott, Amy-Rose
- Date: 2022-04
- Subjects: Mathematical optimization -- South africa , Evolutionary programming (Computer science)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55544 , vital:52812
- Description: There are several challenges associated with applying conventional (hereafter classic) optimal control (OC) methods to ecological optimal control problems (OCPs). Conditions required by these methods, including differentiability and convexity, for example, are not always met, and ecological problems do not always adhere to solvable OCP formulations. Moreover, mathematically optimal solutions do not always translate to optimal ecological strategies in practice. Despite this, alternative OC approaches are relatively under-explored. Evolutionary algorithms (EAs) circumvent many of the complex aspects of classic OC methods and have been successfully applied to diverse OCPs. Nevertheless, EAs have sel dom been applied to ecological OCPs. The viability of an EA approach to ecological OCPs was therefore investigated in the current study, facilitated by four case studies of increasing complexity and a genetic algorithm (GA) as a representative EA approach. To ascertain the accuracy of a GA approach, comparisons between a GA and classic OC methods were conducted in the first three case studies. The GA generated near-optima in these comparisons, comparable to the corresponding classical solutions, whilst avoiding non-trivial mathematical theory. Supported by these results, an unconventional OCP, that arguably cannot be solved using classic OC methods, was formulated in the fourth case study, and solved using a GA approach. The resulting solution was feasible and further conformed with strategies found to be successful in practice. Additionally, the GA approach was rela tively simple to apply in all case studies. These collective outcomes of demonstrated the viability of a GA as an OC method in eco logical OCPs, thereby supporting the use of an EA approach as an alternative to classic OC methods in ecological OCPs. The feasibility of an EA approach to atypical OCPs was further demonstrated, which may act to increase realism in OC applications. Further investigation in this regard is thus warranted by this study. , Thesis (MS) -- Faculty of Science, Mathematics and Applied Mathematics, 2022
- Full Text:
- Date Issued: 2022-04
- Authors: Westcott, Amy-Rose
- Date: 2022-04
- Subjects: Mathematical optimization -- South africa , Evolutionary programming (Computer science)
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10948/55544 , vital:52812
- Description: There are several challenges associated with applying conventional (hereafter classic) optimal control (OC) methods to ecological optimal control problems (OCPs). Conditions required by these methods, including differentiability and convexity, for example, are not always met, and ecological problems do not always adhere to solvable OCP formulations. Moreover, mathematically optimal solutions do not always translate to optimal ecological strategies in practice. Despite this, alternative OC approaches are relatively under-explored. Evolutionary algorithms (EAs) circumvent many of the complex aspects of classic OC methods and have been successfully applied to diverse OCPs. Nevertheless, EAs have sel dom been applied to ecological OCPs. The viability of an EA approach to ecological OCPs was therefore investigated in the current study, facilitated by four case studies of increasing complexity and a genetic algorithm (GA) as a representative EA approach. To ascertain the accuracy of a GA approach, comparisons between a GA and classic OC methods were conducted in the first three case studies. The GA generated near-optima in these comparisons, comparable to the corresponding classical solutions, whilst avoiding non-trivial mathematical theory. Supported by these results, an unconventional OCP, that arguably cannot be solved using classic OC methods, was formulated in the fourth case study, and solved using a GA approach. The resulting solution was feasible and further conformed with strategies found to be successful in practice. Additionally, the GA approach was rela tively simple to apply in all case studies. These collective outcomes of demonstrated the viability of a GA as an OC method in eco logical OCPs, thereby supporting the use of an EA approach as an alternative to classic OC methods in ecological OCPs. The feasibility of an EA approach to atypical OCPs was further demonstrated, which may act to increase realism in OC applications. Further investigation in this regard is thus warranted by this study. , Thesis (MS) -- Faculty of Science, Mathematics and Applied Mathematics, 2022
- Full Text:
- Date Issued: 2022-04
An exploration of the Participatory Guarantee System (PGS) facilitating the growth and certification of small-scale organic farmers: Giyani, Garden Route and Overberg case studies
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
- Authors: Mashele,N’wa-Jama
- Date: 2023-04
- Subjects: Organic farming – Case studies --South Africa , Organic farming research
- Language: English
- Type: Doctoral theses , text
- Identifier: http://hdl.handle.net/10948/60741 , vital:66574
- Description: In this study, I evaluated the Participatory Guarantee System (PGS) as a framework to support the growth and certification of small-scale organic farmers. I used the interpretivism and constructivism lenses to understand the PGS from the perspective of members of three PGS groups. The research was qualitative, treating the three PGS groups as case studies. I collected data using focus groups, semi-structured interviews, questionnaires, field notes and observations. The theoretical frameworks that guided the research and data analysis were Socio-ecological Systems (SES) based principles and the Multi-Level-Perspective (MLP) framework. The data were analysed using Atlas.ti content analysis software. The key results were grouped into four themes: capacity; market and logistics; learning process; and disturbance, shock and stress. The theme of ‘capacity’ dealt with the functioning of a PGS, where three categories were identified: group composition and capacity; resource limitations and institutional support; marketing and consumer education. The more diversity in age, education and culture of PGS stakeholders, the better performance and chances of continuity and propagation. PGS has limited capacity partly due to its voluntary nature and infancy. It needs institutional support to grow and be useful for members. Department of Agriculture extension officers knew little about organic farming, thus limiting their engagement and assistance to such farmers. The theme of ‘market and logistics’ looked at the various factors that influence the farmers’ market reach. The perception from the members was that there was minimal consumer awareness about organic agriculture and the PGS. The marketing of organic produce relied largely on the individual farmer’s efforts and ability to search for and secure markets. The theme of the ‘learning process’ was categorised into learning and knowledge exchange. Members of the PGS groups highly regarded the invaluable knowledge shared through farm visits and online platforms, such as their WhatsApp groups. This knowledge improved and informed their farming techniques and led to the growth of v their skill base and experimentation. They viewed the way knowledge was exchanged as non-threatening and highly useful. The fourth theme of ‘disturbance, shock and stress’ dealt with the effects of COVID19. The three groups were all affected by lockdown restrictions (at the time of data collection) and were initially cut off from their usual markets. This led to a loss of income, loss of farm staff and a loss of the desired growth of the farms. The group’s diverse farming practices bolstered their resilience, enabling them to adapt and try alternative marketing strategies. , Thesis (MSc) -- Faculty of Science, School of Natural Resource Management, 2023
- Full Text:
- Date Issued: 2023-04
An exploration of the processes that encourage HIV and AIDS affected Basotho female adolescent resilience in Sedibeng West in the Vaal Triangle area of the Gauteng Province
- Authors: De Lange, Une
- Date: 2017
- Subjects: Resilience (Personality trait) in adolescence -- South Africa -- Gauteng Teenage girls -- South Africa -- Gauteng
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10948/22220 , vital:29875
- Description: This study aimed to explore processes encouraging resilience in HIV and AIDS affected Basotho female adolescents in Sedibeng West in the Vaal Triangle area of the Gauteng province; and to identify guidelines to help these individuals to get through their adversities in constructive ways. By using purposive sampling (a non-probability sampling method), 61 high risk, high resilient HIV and AIDS affected Basotho female adolescents in Sedibeng West were identified to participate in the research An extensive literature review revealed the following gaps with regard to the topic of this study: • Shortage of literature regarding the effects that HIV and AIDS have on Basotho female adolescents and how these adolescents cope with these challenges; • Lack of focus on resilience of specific cultural adolescent groups; • Lack of focus on processes that encourage resilience in adolescents; • Need for qualitative studies of resilience and visual qualitative studies in particular. Consequently, a qualitative, visual phenomenological study was done where data was collected by a multi-dimensional data gathering method consisting of open-ended questionnaires, drawings and semi-structured interviews. The findings revealed that HIV and AIDS affected all participants in a substantial way. The following three main processes encourage resilience in Basotho female adolescents: Benefitting from constructive bonds; Making meaning; and Acting constructively. Furthermore, Spiritual beings and Mothers were primarily identified as figures of strength and support during adolescents’ adversity. Based on the findings, the researcher recommends that: • The Department of Education include all aspects concerning HIV and AIDS, as well as aspects concerning Religion and Spirituality in the Life Skills curriculum without making any preference of religion; • a mother figure should be established in every child’s life at a very young age, preferably as early as birth; • young people be taught skills and strategies to build interpersonal relationships and attachment bonds to significant others; • families and schools empower individuals with skills to find meaning in adversity • parents and family members model constructive regulation of behaviour to adolescents.
- Full Text:
- Date Issued: 2017
- Authors: De Lange, Une
- Date: 2017
- Subjects: Resilience (Personality trait) in adolescence -- South Africa -- Gauteng Teenage girls -- South Africa -- Gauteng
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: http://hdl.handle.net/10948/22220 , vital:29875
- Description: This study aimed to explore processes encouraging resilience in HIV and AIDS affected Basotho female adolescents in Sedibeng West in the Vaal Triangle area of the Gauteng province; and to identify guidelines to help these individuals to get through their adversities in constructive ways. By using purposive sampling (a non-probability sampling method), 61 high risk, high resilient HIV and AIDS affected Basotho female adolescents in Sedibeng West were identified to participate in the research An extensive literature review revealed the following gaps with regard to the topic of this study: • Shortage of literature regarding the effects that HIV and AIDS have on Basotho female adolescents and how these adolescents cope with these challenges; • Lack of focus on resilience of specific cultural adolescent groups; • Lack of focus on processes that encourage resilience in adolescents; • Need for qualitative studies of resilience and visual qualitative studies in particular. Consequently, a qualitative, visual phenomenological study was done where data was collected by a multi-dimensional data gathering method consisting of open-ended questionnaires, drawings and semi-structured interviews. The findings revealed that HIV and AIDS affected all participants in a substantial way. The following three main processes encourage resilience in Basotho female adolescents: Benefitting from constructive bonds; Making meaning; and Acting constructively. Furthermore, Spiritual beings and Mothers were primarily identified as figures of strength and support during adolescents’ adversity. Based on the findings, the researcher recommends that: • The Department of Education include all aspects concerning HIV and AIDS, as well as aspects concerning Religion and Spirituality in the Life Skills curriculum without making any preference of religion; • a mother figure should be established in every child’s life at a very young age, preferably as early as birth; • young people be taught skills and strategies to build interpersonal relationships and attachment bonds to significant others; • families and schools empower individuals with skills to find meaning in adversity • parents and family members model constructive regulation of behaviour to adolescents.
- Full Text:
- Date Issued: 2017
An exposition of Hilbert C-modules
- Authors: Sokopo, Bulelani Joab
- Date: 2015
- Subjects: Mathematics Algebra , Functions, Continuous Mathematical analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50008 , vital:41974
- Description: In trying to prove that derivations of type I AW -algebras are inner, I. Kaplansky introduced and developed the basics of the concept of Hilbert C- modules. He sought to generalize the idea of a Hilbert space by replacing the field C of all complex numbers with a general (commutative and unital) C-algebra. Twenty years later, the concept was broadened and expanded to non-commutative C-algebras by W. L. Paschke and M. A. Rieffel in their papers on inner product modules over B-algebras and induced representations of C-algebras, respectively. Since then, the theory of Hilbert C-modules has grown rapidly. It was used by G. G. Kasparov as the framework for his bivariant K-theory. More recently, Hilbert C-modules have formed the technical basis for the C*-algebraic approach to quantum group theory. The aim of this dissertation is to provide as detailed an account as possible of the theory of Hilbert C-modules, as given in a book of E. C. Lance, up to and including the KSGNS construction. The KSGNS construction, named after Kasparov, Stinespring, Gelfand, Naimark and Segal, is a generalization to Hilbert C-modules of the familiar GNS construction for C-algebras. The result by Kaplansky that all derivations of a type I AW-algebra are inner is given as an application in the final chapter of the dissertation.
- Full Text:
- Date Issued: 2015
- Authors: Sokopo, Bulelani Joab
- Date: 2015
- Subjects: Mathematics Algebra , Functions, Continuous Mathematical analysis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50008 , vital:41974
- Description: In trying to prove that derivations of type I AW -algebras are inner, I. Kaplansky introduced and developed the basics of the concept of Hilbert C- modules. He sought to generalize the idea of a Hilbert space by replacing the field C of all complex numbers with a general (commutative and unital) C-algebra. Twenty years later, the concept was broadened and expanded to non-commutative C-algebras by W. L. Paschke and M. A. Rieffel in their papers on inner product modules over B-algebras and induced representations of C-algebras, respectively. Since then, the theory of Hilbert C-modules has grown rapidly. It was used by G. G. Kasparov as the framework for his bivariant K-theory. More recently, Hilbert C-modules have formed the technical basis for the C*-algebraic approach to quantum group theory. The aim of this dissertation is to provide as detailed an account as possible of the theory of Hilbert C-modules, as given in a book of E. C. Lance, up to and including the KSGNS construction. The KSGNS construction, named after Kasparov, Stinespring, Gelfand, Naimark and Segal, is a generalization to Hilbert C-modules of the familiar GNS construction for C-algebras. The result by Kaplansky that all derivations of a type I AW-algebra are inner is given as an application in the final chapter of the dissertation.
- Full Text:
- Date Issued: 2015
An in vitro evaluation of anti-breast cancer activity of novel, heterocyclic aromatic compounds in combination with curcumin
- Authors: Pereira, Melanie Claire
- Date: 2017
- Subjects: Breast -- Cancer Heterocyclic compounds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20416 , vital:29284
- Description: Nearly two thirds of breast cancers are classified as estrogen receptor positive. Estrogen receptor (+) breast cancer is usually treated with anti-estrogen therapy, using Tamoxifen as the primary standard of treatment. Unfortunately, resistance to Tamoxifen is known to occur after 1 to 3 years of Tamoxifen therapy. For this reason, improved treatment strategies for ER (+) breast cancer are urgently needed. The general toxicity exerted by most anti-cancer drugs on proliferating cells, as well as some normal cells, restricts their therapeutic use. Novel cytotoxic agents developed with unique mechanisms of action have not been therapeutically suitable, since many of these compounds lack tumour selectivity. The adverse effects and the inefficacies of most chemotherapeutic therapies have motivated extensive investigations of alternatives. Numerous studies have demonstrated the advantages of using combination therapy with naturally-derived agents as an alternative, due to the higher therapeutic efficacy; with the added benefit of lower drug usage and reduction in drug-resistance development. An excellent example of a naturally derived and common dietary agent is curcumin, the active constituent of turmeric. Curcumin is known to modulate several signalling pathways in addition to displaying a diverse range of anti-tumour activities against a number of cancer cells. Several reports point to curcumin being beneficial if used in addition to chemotherapeutic drugs. In this study, synthetic aminonaphthoquinone derivatives (coded Rau 008, Rau 010, Rau 015 and Rau 018) were tested individually and in combination with curcumin for the potential as anti-breast cancer agents in different tumour cell lines. Notably, the aminonaphthoquinone class of compounds have shown potential as anti-cancer agents in various tumour cell lines. This study was thus aimed at screening the Rau compounds (and selected combinations with curcumin) for anti-cancer activity using a range of in vitro biological assays, and was not mechanistic in nature. The IC50 values of the individual and combined drugs were determined from dose-response curves using non-linear regression analyses. Synergistic, additive and antagonistic drug interactions were assessed using combination index and isobologram approaches. Based on these interactions, selected drug combinations were then further analysed for their potential anti-estrogenic, cytotoxic, anti-angiogenic and anti-metastatic effects against the ER(-) MDA-MB-231 and ER(+) MCF-7 breast cancer cell lines. The potential anti-cancer effects of the selected drug combinations on other estrogen-responsive models, such as the osteosarcoma (MG-63) and endometrial cancer (HEC-1A) cell lines, were also investigated. Overall, the findings of this study indicated that the sensitivity of the tumour cells to the various test compounds was significantly enhanced when combined with curcumin. For instance, in the presence of curcumin, Rau 008 or Rau 010 reduced the metastatic capability of ER(-) breast cancer cells significantly. The anti-proliferative effect of the Rau 015+curcumin combination was enhanced in ER(+) and ER(-) breast cancer, including oteosarcoma cells, while a combination of Rau 015 and curcumin induced a significant cytotoxic effect in ER(-) breast cancer and endometrial cancer-derived cells. A combination of Rau 018 and curcumin inhibited the proliferation of ER(+) breast cancer, and the combined effect was significantly more enhanced compared to individual treatment. A similar effect was noted in osteosarcoma-derived cells. Further, the Rau 018+curcumin combination exerted a marked cytotoxic and anti-angiogenic effect in ER(-) breast cancer, osteosarcoma and endometrial cancer in addition to inhibiting the attachment of ER(-) breast cancer cells to collagen. Notably, curcumin enhanced the anti-proliferative effect of Tamoxifen in breast cancer (MCF-7 and MDA-MB-231), osteosarcoma and endometrial cancer, and also induced a significant cytotoxic effect against ER(+) breast cancer and osteosarcoma, whilst also reducing the invasive potential of ER(-) breast cancer. A combination of 17β-estradiol and curcumin induced a marked anti-proliferative effect in ER(+) and ER(-) breast cancer, reduced the adhesion of ER(-) breast cancer to laminin, and elicited a significant cytotoxic and anti-angiogenic effect against endometrial cancer. Notably all the selected combinations (except Rau 018 and curcumin) inhibited bone mineralization. These findings point to the vital influence of curcumin in the responsiveness of ER(+) and ER(-) tumours towards the relative test agents. Further, among the Rau+curcumin combinations tested in this study, the anti-cancer activity of Rau 015+curcumin and Rau 018+curcumin appeared to be the most effective in the different cell lines tested. Nonetheless, it appears that a combination of 30 μM Rau 018 with 100 μM curcumin may be more promising as an anti-breast cancer agent against ER(+) and perhaps triple negative breast cancer, and warrants further investigation.
- Full Text:
- Date Issued: 2017
- Authors: Pereira, Melanie Claire
- Date: 2017
- Subjects: Breast -- Cancer Heterocyclic compounds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/20416 , vital:29284
- Description: Nearly two thirds of breast cancers are classified as estrogen receptor positive. Estrogen receptor (+) breast cancer is usually treated with anti-estrogen therapy, using Tamoxifen as the primary standard of treatment. Unfortunately, resistance to Tamoxifen is known to occur after 1 to 3 years of Tamoxifen therapy. For this reason, improved treatment strategies for ER (+) breast cancer are urgently needed. The general toxicity exerted by most anti-cancer drugs on proliferating cells, as well as some normal cells, restricts their therapeutic use. Novel cytotoxic agents developed with unique mechanisms of action have not been therapeutically suitable, since many of these compounds lack tumour selectivity. The adverse effects and the inefficacies of most chemotherapeutic therapies have motivated extensive investigations of alternatives. Numerous studies have demonstrated the advantages of using combination therapy with naturally-derived agents as an alternative, due to the higher therapeutic efficacy; with the added benefit of lower drug usage and reduction in drug-resistance development. An excellent example of a naturally derived and common dietary agent is curcumin, the active constituent of turmeric. Curcumin is known to modulate several signalling pathways in addition to displaying a diverse range of anti-tumour activities against a number of cancer cells. Several reports point to curcumin being beneficial if used in addition to chemotherapeutic drugs. In this study, synthetic aminonaphthoquinone derivatives (coded Rau 008, Rau 010, Rau 015 and Rau 018) were tested individually and in combination with curcumin for the potential as anti-breast cancer agents in different tumour cell lines. Notably, the aminonaphthoquinone class of compounds have shown potential as anti-cancer agents in various tumour cell lines. This study was thus aimed at screening the Rau compounds (and selected combinations with curcumin) for anti-cancer activity using a range of in vitro biological assays, and was not mechanistic in nature. The IC50 values of the individual and combined drugs were determined from dose-response curves using non-linear regression analyses. Synergistic, additive and antagonistic drug interactions were assessed using combination index and isobologram approaches. Based on these interactions, selected drug combinations were then further analysed for their potential anti-estrogenic, cytotoxic, anti-angiogenic and anti-metastatic effects against the ER(-) MDA-MB-231 and ER(+) MCF-7 breast cancer cell lines. The potential anti-cancer effects of the selected drug combinations on other estrogen-responsive models, such as the osteosarcoma (MG-63) and endometrial cancer (HEC-1A) cell lines, were also investigated. Overall, the findings of this study indicated that the sensitivity of the tumour cells to the various test compounds was significantly enhanced when combined with curcumin. For instance, in the presence of curcumin, Rau 008 or Rau 010 reduced the metastatic capability of ER(-) breast cancer cells significantly. The anti-proliferative effect of the Rau 015+curcumin combination was enhanced in ER(+) and ER(-) breast cancer, including oteosarcoma cells, while a combination of Rau 015 and curcumin induced a significant cytotoxic effect in ER(-) breast cancer and endometrial cancer-derived cells. A combination of Rau 018 and curcumin inhibited the proliferation of ER(+) breast cancer, and the combined effect was significantly more enhanced compared to individual treatment. A similar effect was noted in osteosarcoma-derived cells. Further, the Rau 018+curcumin combination exerted a marked cytotoxic and anti-angiogenic effect in ER(-) breast cancer, osteosarcoma and endometrial cancer in addition to inhibiting the attachment of ER(-) breast cancer cells to collagen. Notably, curcumin enhanced the anti-proliferative effect of Tamoxifen in breast cancer (MCF-7 and MDA-MB-231), osteosarcoma and endometrial cancer, and also induced a significant cytotoxic effect against ER(+) breast cancer and osteosarcoma, whilst also reducing the invasive potential of ER(-) breast cancer. A combination of 17β-estradiol and curcumin induced a marked anti-proliferative effect in ER(+) and ER(-) breast cancer, reduced the adhesion of ER(-) breast cancer to laminin, and elicited a significant cytotoxic and anti-angiogenic effect against endometrial cancer. Notably all the selected combinations (except Rau 018 and curcumin) inhibited bone mineralization. These findings point to the vital influence of curcumin in the responsiveness of ER(+) and ER(-) tumours towards the relative test agents. Further, among the Rau+curcumin combinations tested in this study, the anti-cancer activity of Rau 015+curcumin and Rau 018+curcumin appeared to be the most effective in the different cell lines tested. Nonetheless, it appears that a combination of 30 μM Rau 018 with 100 μM curcumin may be more promising as an anti-breast cancer agent against ER(+) and perhaps triple negative breast cancer, and warrants further investigation.
- Full Text:
- Date Issued: 2017
An information extraction model for recommending the most applied case
- Authors: Padayachy, Thashen
- Date: 2019
- Subjects: Information technology , Information storage and retrieval systems System design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43325 , vital:36794
- Description: The amount of information produced by different domains is constantly increasing. One domain that particularly produces large amounts of information is the legal domain, where information is mainly used for research purposes. However, too much time is spent by legal researchers on searching for useful information. Information is found by using special search engines or by consulting hard copies of legal literature. The main research question that this study addressed is “What techniques can be incorporated into a model that recommends the most applied case for a field of law?”. The Design Science Research (DSR) methodology was used to address the research objectives. The model developed is the theoretical contribution produced from following the DSR methodology. A case study organisation, called LexisNexis, was to help investigate the real-world problem. The initial investigation into the real-world problem revealed that too much time is spent on searching for the Most Applied Case (MAC) and no formal or automated processes were used. An analysis of an informal process followed by legal researchers enabled the identification of different concepts that could be combined to create a prescriptive model to recommend the MAC. A critical analysis of the literature was conducted to obtain a better understanding of the legal domain and the techniques that can be applied to assist with problems faced in this domain, related to information retrieval and extraction. This resulted in the creation of an IE Model based only on theory. Questionnaires were sent to experts to obtain a further understanding of the legal domain, highlight problems faced, and identify which attributes of a legal case can be used to help recommend the MAC. During the Design and Development activity of the DSR methodology, a prescriptive MAC Model for recommending the MAC was created based on findings from the literature review and questionnaires. The MAC Model consists of processes concerning: Information retrieval (IR); Information extraction (IE); Information storage; and Query-independent ranking. Analysis of IR and IE helped to identify problems experienced when processing text. Furthermore, appropriate techniques and algorithms were identified that can process legal documents and extract specific facts. The extracted facts were then further processed to allow for storage and processing by query-independent ranking algorithms. The processes incorporated into the model were then used to create a proof-of-concept prototype called the IE Prototype. The IE Prototype implements two processes called the IE process and the Database process. The IE process analyses different sections of a legal case to extract specific facts. The Database process then ensures that the extracted facts are stored in a document database for future querying purposes. The IE Prototype was evaluated using the technical risk and efficacy strategy from the Framework for Evaluation of Design Science. Both formative and summative evaluations were conducted. Formative evaluations were conducted to identify functional issues of the prototype whilst summative evaluations made use of real-world legal cases to test the prototype. Multiple experiments were conducted on legal cases, known as source cases, that resulted in facts from the source cases being extracted. For the purpose of the experiments, the term “source case” was used to distinguish between a legal case in its entirety and a legal case’s list of cases referred to. Two types of NoSQL databases were investigated for implementation namely, a graph database and a document database. Setting up the graph database required little time. However, development issues prevented the graph database from being successfully implemented in the proof-of-concept prototype. A document database was successfully implemented as an alternative for the proof-of-concept prototype. Analysis of the source cases used to evaluate the IE Prototype revealed that 96% of the source cases were categorised as being partially extracted. The results also revealed that the IE Prototype was capable of processing large amounts of source cases at a given time.
- Full Text:
- Date Issued: 2019
- Authors: Padayachy, Thashen
- Date: 2019
- Subjects: Information technology , Information storage and retrieval systems System design
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43325 , vital:36794
- Description: The amount of information produced by different domains is constantly increasing. One domain that particularly produces large amounts of information is the legal domain, where information is mainly used for research purposes. However, too much time is spent by legal researchers on searching for useful information. Information is found by using special search engines or by consulting hard copies of legal literature. The main research question that this study addressed is “What techniques can be incorporated into a model that recommends the most applied case for a field of law?”. The Design Science Research (DSR) methodology was used to address the research objectives. The model developed is the theoretical contribution produced from following the DSR methodology. A case study organisation, called LexisNexis, was to help investigate the real-world problem. The initial investigation into the real-world problem revealed that too much time is spent on searching for the Most Applied Case (MAC) and no formal or automated processes were used. An analysis of an informal process followed by legal researchers enabled the identification of different concepts that could be combined to create a prescriptive model to recommend the MAC. A critical analysis of the literature was conducted to obtain a better understanding of the legal domain and the techniques that can be applied to assist with problems faced in this domain, related to information retrieval and extraction. This resulted in the creation of an IE Model based only on theory. Questionnaires were sent to experts to obtain a further understanding of the legal domain, highlight problems faced, and identify which attributes of a legal case can be used to help recommend the MAC. During the Design and Development activity of the DSR methodology, a prescriptive MAC Model for recommending the MAC was created based on findings from the literature review and questionnaires. The MAC Model consists of processes concerning: Information retrieval (IR); Information extraction (IE); Information storage; and Query-independent ranking. Analysis of IR and IE helped to identify problems experienced when processing text. Furthermore, appropriate techniques and algorithms were identified that can process legal documents and extract specific facts. The extracted facts were then further processed to allow for storage and processing by query-independent ranking algorithms. The processes incorporated into the model were then used to create a proof-of-concept prototype called the IE Prototype. The IE Prototype implements two processes called the IE process and the Database process. The IE process analyses different sections of a legal case to extract specific facts. The Database process then ensures that the extracted facts are stored in a document database for future querying purposes. The IE Prototype was evaluated using the technical risk and efficacy strategy from the Framework for Evaluation of Design Science. Both formative and summative evaluations were conducted. Formative evaluations were conducted to identify functional issues of the prototype whilst summative evaluations made use of real-world legal cases to test the prototype. Multiple experiments were conducted on legal cases, known as source cases, that resulted in facts from the source cases being extracted. For the purpose of the experiments, the term “source case” was used to distinguish between a legal case in its entirety and a legal case’s list of cases referred to. Two types of NoSQL databases were investigated for implementation namely, a graph database and a document database. Setting up the graph database required little time. However, development issues prevented the graph database from being successfully implemented in the proof-of-concept prototype. A document database was successfully implemented as an alternative for the proof-of-concept prototype. Analysis of the source cases used to evaluate the IE Prototype revealed that 96% of the source cases were categorised as being partially extracted. The results also revealed that the IE Prototype was capable of processing large amounts of source cases at a given time.
- Full Text:
- Date Issued: 2019
An information services framework for commercial extension services
- Authors: Simpson, Antony Paul
- Date: 2014
- Subjects: Agricultural extension work , Business networks , Information resources management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8575 , vital:26408
- Description: The first of the eight United Nations Millennium Development Goals for 2015 is to “Eradicate Extreme Poverty and Hunger”. Achieving this goal would be aided by having an effective and productive agricultural community. Agricultural organisations assist producers to be more effective in their operation through Commercial Extension Services (CES). Through CES, producers are advised and educated about new agricultural practices, techniques and products. A key component of CES is the provision of relevant information to producers. The problem this research addressed was that producers experience difficulty in accessing the information they require in a timeous, relevant and personalised manner. No suitable framework was found for agricultural organisations to use when designing and implementing an Information Services Platform. The main research objective was to develop and evaluate an Information Services Framework (ISF) for organisations offering information as a CES. The research methodology used to achieve this objective was Design Science Research (DSR). DSR is an iterative methodology with three cycles, namely the relevance, the design and the rigor cycles. The relevance cycle was used to acquire the information required to inform the design cycle. The information was collected by using literature research and empirical studies. The first study, the Producer Information Requirements Survey (PIRS) sought to determine the information requirements of grain producers and was conducted by interviewing grain producers in the Swartland region of South Africa. The second study, the Internet and Mobile Device Usage Survey (IMDUS) investigated the use of the Internet and mobile devices amongst South African producers by means of a national on-line survey. The quantitative and qualitative results of the analysis were used during the design phase to develop the ISF. The design phase of DSR process led to the creation of an ISF for providing Information as a Service (IaaS) in CES. The framework allows for information services to be provided in a manner and form customised to an individual producer’s preferences. The foundation of the framework is that information can be sourced from various sources, internal or external to the organisation and distributed to producers by using a unified platform. During the research, an agricultural organisation, BKB GrainCo used the proposed ISF to develop an Information Services Platform (ISP) to provide information to its producers. BKB GrainCo’s development process included two evaluations. The first evaluation, the Information Preferences Prototype Survey, was intended to test a key component of the framework, the nformation Preferences Profile. The Information Preferences Profile was conceptualized following the PIRS. In the PIRS it was determined that individual producers would prefer to specify what information they would receive, when they required it and have it delivered by using a medium of their choice. The second evaluation of the design phase was a Usability Study. The Usability Study was intended to test the functionality of the system across various technologies. The rigor cycle, following the implementation of BKB GrainCo’s ISP, contained the main evaluation, the Information Services Platform Evaluation. The evaluation was used to test the impact of BKB GrainCo’s ISP on perception of received service. The evaluation used a standardised version of the standardised SERVQUAL instrument specifically adapted in this research to measure the provision of IaaS. The results obtained during the evaluation indicated that the BKB GrainCo’s Information Services Platform was found to be valued by producers and improved the communication services of agricultural organisations. It was inferred from the successful implementation of BKB GrainCo’s ISP and the positive response from producers, after the evaluations, that the developed ISF was suitable for an agricultural organisation to provide CES. The theoretical contributions included underpinning the concept of CES in terms of stakeholder theory. Its underpinning provides justification for agricultural organisations to improve CES – including the provision of information. A second theoretical contribution was the extension of SERVQUAL as an IS theory by developing and validating a dimension designed to test the provision of IaaS. Providing producers with accurate and reliable personalised information has the capacity to improve producers’ ability to make informed decisions. Informed decision making will contribute to having an effective and productive agricultural community; resulting in improvement of agricultural output and contributing to food security and job creation. Improved agricultural output, better food security and job creation are aspects which will contribute toward the attainment of the first of eight United Nations Millennium Development Goals for 2015, which is to “Eradicate Extreme Poverty and Hunger”.
- Full Text:
- Date Issued: 2014
- Authors: Simpson, Antony Paul
- Date: 2014
- Subjects: Agricultural extension work , Business networks , Information resources management
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10948/8575 , vital:26408
- Description: The first of the eight United Nations Millennium Development Goals for 2015 is to “Eradicate Extreme Poverty and Hunger”. Achieving this goal would be aided by having an effective and productive agricultural community. Agricultural organisations assist producers to be more effective in their operation through Commercial Extension Services (CES). Through CES, producers are advised and educated about new agricultural practices, techniques and products. A key component of CES is the provision of relevant information to producers. The problem this research addressed was that producers experience difficulty in accessing the information they require in a timeous, relevant and personalised manner. No suitable framework was found for agricultural organisations to use when designing and implementing an Information Services Platform. The main research objective was to develop and evaluate an Information Services Framework (ISF) for organisations offering information as a CES. The research methodology used to achieve this objective was Design Science Research (DSR). DSR is an iterative methodology with three cycles, namely the relevance, the design and the rigor cycles. The relevance cycle was used to acquire the information required to inform the design cycle. The information was collected by using literature research and empirical studies. The first study, the Producer Information Requirements Survey (PIRS) sought to determine the information requirements of grain producers and was conducted by interviewing grain producers in the Swartland region of South Africa. The second study, the Internet and Mobile Device Usage Survey (IMDUS) investigated the use of the Internet and mobile devices amongst South African producers by means of a national on-line survey. The quantitative and qualitative results of the analysis were used during the design phase to develop the ISF. The design phase of DSR process led to the creation of an ISF for providing Information as a Service (IaaS) in CES. The framework allows for information services to be provided in a manner and form customised to an individual producer’s preferences. The foundation of the framework is that information can be sourced from various sources, internal or external to the organisation and distributed to producers by using a unified platform. During the research, an agricultural organisation, BKB GrainCo used the proposed ISF to develop an Information Services Platform (ISP) to provide information to its producers. BKB GrainCo’s development process included two evaluations. The first evaluation, the Information Preferences Prototype Survey, was intended to test a key component of the framework, the nformation Preferences Profile. The Information Preferences Profile was conceptualized following the PIRS. In the PIRS it was determined that individual producers would prefer to specify what information they would receive, when they required it and have it delivered by using a medium of their choice. The second evaluation of the design phase was a Usability Study. The Usability Study was intended to test the functionality of the system across various technologies. The rigor cycle, following the implementation of BKB GrainCo’s ISP, contained the main evaluation, the Information Services Platform Evaluation. The evaluation was used to test the impact of BKB GrainCo’s ISP on perception of received service. The evaluation used a standardised version of the standardised SERVQUAL instrument specifically adapted in this research to measure the provision of IaaS. The results obtained during the evaluation indicated that the BKB GrainCo’s Information Services Platform was found to be valued by producers and improved the communication services of agricultural organisations. It was inferred from the successful implementation of BKB GrainCo’s ISP and the positive response from producers, after the evaluations, that the developed ISF was suitable for an agricultural organisation to provide CES. The theoretical contributions included underpinning the concept of CES in terms of stakeholder theory. Its underpinning provides justification for agricultural organisations to improve CES – including the provision of information. A second theoretical contribution was the extension of SERVQUAL as an IS theory by developing and validating a dimension designed to test the provision of IaaS. Providing producers with accurate and reliable personalised information has the capacity to improve producers’ ability to make informed decisions. Informed decision making will contribute to having an effective and productive agricultural community; resulting in improvement of agricultural output and contributing to food security and job creation. Improved agricultural output, better food security and job creation are aspects which will contribute toward the attainment of the first of eight United Nations Millennium Development Goals for 2015, which is to “Eradicate Extreme Poverty and Hunger”.
- Full Text:
- Date Issued: 2014
An intelligent multimodal interface for in-car communication systems
- Authors: Sielinou, Patrick Tchankue
- Date: 2011
- Subjects: Automotive telematics , Automobiles -- Electronic equipment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10461 , http://hdl.handle.net/10948/1495 , Automotive telematics , Automobiles -- Electronic equipment
- Description: In-car communication systems (ICCS) are becoming more frequently used by drivers. ICCS are used in order to minimise the driving distraction due to using a mobile phone while driving. Several usability studies of ICCS utilising speech user interfaces (SUIs) have identified usability issues that can affect the workload, performance, satisfaction and user experience of the driver. This is due to current speech technologies which can be a source of errors that may frustrate the driver and negatively affect the user experience. The aim of this research was to design a new multimodal interface that will manage the interaction between an ICCS and the driver. Unlike the current ICCS, it should make more voice input available, so as to support tasks (e.g. sending text messages; browsing the phone book, etc), which still require a cognitive workload from the driver. An adaptive multimodal interface was proposed in order to address current ICCS issues. The multimodal interface used both speech and manual input; however only the speech channel is used as output. This was done in order to minimise the visual distraction that graphical user interfaces or haptics devices can cause with current ICCS. The adaptive interface was designed to minimise the cognitive distraction of the driver. The adaptive interface ensures that whenever the distraction level of the driver is high, any information communication is postponed. After the design and the implementation of the first version of the prototype interface, called MIMI, a usability evaluation was conducted in order to identify any possible usability issues. Although voice dialling was found to be problematic, the results were encouraging in terms of performance, workload and user satisfaction. The suggestions received from the participants to improve the system usability were incorporated in the next implementation of MIMI. The adaptive module was then implemented to reduce driver distraction based on the driver‟s current context. The proposed architecture showed encouraging results in terms of usability and safety. The adaptive behaviour of MIMI significantly contributed to the reduction of cognitive distraction, because drivers received less information during difficult driving situations.
- Full Text:
- Date Issued: 2011
- Authors: Sielinou, Patrick Tchankue
- Date: 2011
- Subjects: Automotive telematics , Automobiles -- Electronic equipment
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10461 , http://hdl.handle.net/10948/1495 , Automotive telematics , Automobiles -- Electronic equipment
- Description: In-car communication systems (ICCS) are becoming more frequently used by drivers. ICCS are used in order to minimise the driving distraction due to using a mobile phone while driving. Several usability studies of ICCS utilising speech user interfaces (SUIs) have identified usability issues that can affect the workload, performance, satisfaction and user experience of the driver. This is due to current speech technologies which can be a source of errors that may frustrate the driver and negatively affect the user experience. The aim of this research was to design a new multimodal interface that will manage the interaction between an ICCS and the driver. Unlike the current ICCS, it should make more voice input available, so as to support tasks (e.g. sending text messages; browsing the phone book, etc), which still require a cognitive workload from the driver. An adaptive multimodal interface was proposed in order to address current ICCS issues. The multimodal interface used both speech and manual input; however only the speech channel is used as output. This was done in order to minimise the visual distraction that graphical user interfaces or haptics devices can cause with current ICCS. The adaptive interface was designed to minimise the cognitive distraction of the driver. The adaptive interface ensures that whenever the distraction level of the driver is high, any information communication is postponed. After the design and the implementation of the first version of the prototype interface, called MIMI, a usability evaluation was conducted in order to identify any possible usability issues. Although voice dialling was found to be problematic, the results were encouraging in terms of performance, workload and user satisfaction. The suggestions received from the participants to improve the system usability were incorporated in the next implementation of MIMI. The adaptive module was then implemented to reduce driver distraction based on the driver‟s current context. The proposed architecture showed encouraging results in terms of usability and safety. The adaptive behaviour of MIMI significantly contributed to the reduction of cognitive distraction, because drivers received less information during difficult driving situations.
- Full Text:
- Date Issued: 2011
An intelligent user interface model for contact centre operations
- Authors: Singh, Akash
- Date: 2007
- Subjects: User interfaces (Computer systems) , Human-computer interaction , Mobile computing , Customer services -- Management , Call centers -- Customer services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10475 , http://hdl.handle.net/10948/d1011399 , User interfaces (Computer systems) , Human-computer interaction , Mobile computing , Customer services -- Management , Call centers -- Customer services
- Description: Contact Centres (CCs) are at the forefront of interaction between an organisation and its customers. Currently, 17 percent of all inbound calls are not resolved on the first call by the first agent attending to that call. This is due to the inability of the contact centre agents (CCAs) to diagnose customer queries and find adequate solutions in an effective and efficient manner. The aim of this research is to develop an intelligent user interface (IUI) model to support and improve CC operations. A literature review of existing IUI architectures, modelbased design and existing CC software together with a field study of CCs has resulted in the design of an IUI model for CCs. The proposed IUI model is described in terms of its architecture, component-level design and interface design. An IUI prototype has been developed as a proof of concept of the proposed IUI model. The IUI prototype was evaluated in order to determine to what extent it supports problem identification and query resolution. User testing, incorporating the use of eye tracking and a post-test questionnaire, was used in order to determine the usability and usefulness of the prototype. The results of this evaluation show that the users were highly satisfied with the task support and query resolution assistance provided by the IUI prototype. This research resulted in the design of an IUI model for the domain of CCs. This model can be used to assist the development of CC applications incorporating IUIs. Use of the proposed IUI model is expected to support and enhance the effectiveness and efficiency of CC operations. Further research is needed to conduct a longitudinal study to determine the impact of IUIs in the CC domain.
- Full Text:
- Date Issued: 2007
- Authors: Singh, Akash
- Date: 2007
- Subjects: User interfaces (Computer systems) , Human-computer interaction , Mobile computing , Customer services -- Management , Call centers -- Customer services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10475 , http://hdl.handle.net/10948/d1011399 , User interfaces (Computer systems) , Human-computer interaction , Mobile computing , Customer services -- Management , Call centers -- Customer services
- Description: Contact Centres (CCs) are at the forefront of interaction between an organisation and its customers. Currently, 17 percent of all inbound calls are not resolved on the first call by the first agent attending to that call. This is due to the inability of the contact centre agents (CCAs) to diagnose customer queries and find adequate solutions in an effective and efficient manner. The aim of this research is to develop an intelligent user interface (IUI) model to support and improve CC operations. A literature review of existing IUI architectures, modelbased design and existing CC software together with a field study of CCs has resulted in the design of an IUI model for CCs. The proposed IUI model is described in terms of its architecture, component-level design and interface design. An IUI prototype has been developed as a proof of concept of the proposed IUI model. The IUI prototype was evaluated in order to determine to what extent it supports problem identification and query resolution. User testing, incorporating the use of eye tracking and a post-test questionnaire, was used in order to determine the usability and usefulness of the prototype. The results of this evaluation show that the users were highly satisfied with the task support and query resolution assistance provided by the IUI prototype. This research resulted in the design of an IUI model for the domain of CCs. This model can be used to assist the development of CC applications incorporating IUIs. Use of the proposed IUI model is expected to support and enhance the effectiveness and efficiency of CC operations. Further research is needed to conduct a longitudinal study to determine the impact of IUIs in the CC domain.
- Full Text:
- Date Issued: 2007
An intergrated continuous flow system for the manufacture of biodiesel from waste cooking oil using a heterogeneous acid catalyst and homogeneous base catalyst
- Authors: Mathe,Francis Matota
- Date: 2017
- Subjects: Biodiesel fuels industry , Catalysis , Vegetable oils as fuel
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44460 , vital:37837
- Description: The continuous flow production of biodiesel from waste cooking oil (WCO) was investigated in this study. Two different methods of biodiesel production were investigated. The first method involved the acid esterification of free fatty acids (FFAs). In the biodiesel community, the esterification of FFAs in WCO is usually regarded as the pre-treatment stage of biodiesel production using low-quality feedstock.The second method involved the transesterification of triglycerides in WCO. Homogeneous catalysts (NaOH or H2SO4) and heterogeneous catalysts (NaOH/ZnO, Sn/ZnO, Amberlyst-15, Amberlite-IRA 904, Fe/Bentonite and Amberlite IRN 78) were evaluated in the transesterification reaction. Catalyst screening was done using a batch reactor. NaOH gave a high úME content of 96.7% and was chosen as the optimum catalyst for the reaction.The main aim of the project was to make an integrated system that incorporates the esterification and transesterification reaction in the flow production of biodiesel using WCO. The system was developed using the conditions obtained from optimum studies of the separate reactions. Slight adjustments based on further experimental work were made to create an efficient system. The effect of excess methanol from the first step on the concentration of NaOH in the second phase was investigated. It was shown that the excess methanol decreases the concentration of the NaOH and this decreases the úMEs in the final mixture of biodiesel.
- Full Text:
- Date Issued: 2017
- Authors: Mathe,Francis Matota
- Date: 2017
- Subjects: Biodiesel fuels industry , Catalysis , Vegetable oils as fuel
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/44460 , vital:37837
- Description: The continuous flow production of biodiesel from waste cooking oil (WCO) was investigated in this study. Two different methods of biodiesel production were investigated. The first method involved the acid esterification of free fatty acids (FFAs). In the biodiesel community, the esterification of FFAs in WCO is usually regarded as the pre-treatment stage of biodiesel production using low-quality feedstock.The second method involved the transesterification of triglycerides in WCO. Homogeneous catalysts (NaOH or H2SO4) and heterogeneous catalysts (NaOH/ZnO, Sn/ZnO, Amberlyst-15, Amberlite-IRA 904, Fe/Bentonite and Amberlite IRN 78) were evaluated in the transesterification reaction. Catalyst screening was done using a batch reactor. NaOH gave a high úME content of 96.7% and was chosen as the optimum catalyst for the reaction.The main aim of the project was to make an integrated system that incorporates the esterification and transesterification reaction in the flow production of biodiesel using WCO. The system was developed using the conditions obtained from optimum studies of the separate reactions. Slight adjustments based on further experimental work were made to create an efficient system. The effect of excess methanol from the first step on the concentration of NaOH in the second phase was investigated. It was shown that the excess methanol decreases the concentration of the NaOH and this decreases the úMEs in the final mixture of biodiesel.
- Full Text:
- Date Issued: 2017
An Internet of things model for field service automation
- Authors: Kapeso, Mando Mulabita
- Date: 2017
- Subjects: Internet of things Manufacturing processes -- Automation , Automation
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/18641 , vital:28698
- Description: Due to the competitive nature of the global economy, organisations are continuously seeking ways of cutting costs and increasing efficiency to gain a competitive advantage. Field service organisations that offer after sales support seek to gain a competitive advantage through downtime minimisation. Downtime is the time between service requests made by a customer or triggered by equipment failure and the completion of the service to rectify the problem by the field service team. Researchers have identified downtime as one of the key performance indicators for field service organisations. The lack of real-time access to information and inaccuracy of information are factors which contribute to the poor management of downtime. Various technology advancements have been adopted to address some of the challenges faced by field service organisations through automation. The emergence of an Internet of Things (IoT), has brought new enhancement possibilities to various industries, for instance, the manufacturing industry. The main research question that this study aims to address is “How can an Internet of Things be used to optimise field service automation?” The main research objective was to develop and evaluate a model for the optimisation of field services using an IoT’s features and technologies. The model aims at addressing challenges associated with the inaccuracy or/and lack of real-time access to information during downtime. The model developed is the theoretical artefact of the research methodology used in this study which is the Design Science Research Methodology (DSRM). The DSRM activities were adopted to fulfil the research objectives of this research. A literature review in the field services domain was conducted to establish the problems faced by field service organisations. Several interviews were held to verify the problems of FSM identified in literature and some potential solutions. During the design and development activity of the DSRM methodology, an IoT model for FSA was designed. The model consists of:The Four Layered Architecture; The Three Phase Data Flow Process; and Definition and descriptions of IoT-based elements and functions. The model was then used to drive the design, development, and evaluation of “proof of concept” prototype, the KapCha prototype. KapCha enables the optimisation of FSA using IoT techniques and features. The implementation of a sub-component of the KapCha system, in fulfilment of the research. The implementation of KapCha was applied to the context of a smart lighting environment in the case study. A two-phase evaluation was conducted to review both the theoretical model and the KapCha prototype. The model and KapCha prototype were evaluated using the Technical and Risk efficacy evaluation strategy from the Framework for Evaluation of Design Science (FEDS). The Technical Risk and Efficacy strategy made use of formative, artificial-summative and summative-naturalistic methods of evaluation. An artificial-summative evaluation was used to evaluate the design of the model. Iterative formative evaluations were conducted during the development of the KapCha. KapCha was then placed in a real-environment conditions and a summative-naturalistic evaluation was conducted. The summative-naturalistic evaluation was used to determine the performance of KapCha under real-world conditions to evaluate the extent it addresses FSA problems identified such as real-time communication and automated fault detection.
- Full Text:
- Date Issued: 2017
- Authors: Kapeso, Mando Mulabita
- Date: 2017
- Subjects: Internet of things Manufacturing processes -- Automation , Automation
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10948/18641 , vital:28698
- Description: Due to the competitive nature of the global economy, organisations are continuously seeking ways of cutting costs and increasing efficiency to gain a competitive advantage. Field service organisations that offer after sales support seek to gain a competitive advantage through downtime minimisation. Downtime is the time between service requests made by a customer or triggered by equipment failure and the completion of the service to rectify the problem by the field service team. Researchers have identified downtime as one of the key performance indicators for field service organisations. The lack of real-time access to information and inaccuracy of information are factors which contribute to the poor management of downtime. Various technology advancements have been adopted to address some of the challenges faced by field service organisations through automation. The emergence of an Internet of Things (IoT), has brought new enhancement possibilities to various industries, for instance, the manufacturing industry. The main research question that this study aims to address is “How can an Internet of Things be used to optimise field service automation?” The main research objective was to develop and evaluate a model for the optimisation of field services using an IoT’s features and technologies. The model aims at addressing challenges associated with the inaccuracy or/and lack of real-time access to information during downtime. The model developed is the theoretical artefact of the research methodology used in this study which is the Design Science Research Methodology (DSRM). The DSRM activities were adopted to fulfil the research objectives of this research. A literature review in the field services domain was conducted to establish the problems faced by field service organisations. Several interviews were held to verify the problems of FSM identified in literature and some potential solutions. During the design and development activity of the DSRM methodology, an IoT model for FSA was designed. The model consists of:The Four Layered Architecture; The Three Phase Data Flow Process; and Definition and descriptions of IoT-based elements and functions. The model was then used to drive the design, development, and evaluation of “proof of concept” prototype, the KapCha prototype. KapCha enables the optimisation of FSA using IoT techniques and features. The implementation of a sub-component of the KapCha system, in fulfilment of the research. The implementation of KapCha was applied to the context of a smart lighting environment in the case study. A two-phase evaluation was conducted to review both the theoretical model and the KapCha prototype. The model and KapCha prototype were evaluated using the Technical and Risk efficacy evaluation strategy from the Framework for Evaluation of Design Science (FEDS). The Technical Risk and Efficacy strategy made use of formative, artificial-summative and summative-naturalistic methods of evaluation. An artificial-summative evaluation was used to evaluate the design of the model. Iterative formative evaluations were conducted during the development of the KapCha. KapCha was then placed in a real-environment conditions and a summative-naturalistic evaluation was conducted. The summative-naturalistic evaluation was used to determine the performance of KapCha under real-world conditions to evaluate the extent it addresses FSA problems identified such as real-time communication and automated fault detection.
- Full Text:
- Date Issued: 2017
An investigation into a natural language interface for contact centers
- Authors: Sankar, Gopal Ravi
- Date: 2009
- Subjects: Call centers -- Management , Customer services -- Management , Telephone selling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10468 , http://hdl.handle.net/10948/890 , Call centers -- Management , Customer services -- Management , Telephone selling
- Description: Contact centres are the first point of contact between a company and a customer after the purchase of a product or service. These centres make use of contact centre agents to service customer queries. In the past contact centres hired as many agents as they could in order to service customers, which have led to an increase in personnel costs causing contact centres to become costly to run. Automation techniques were introduced to decrease personnel costs and one such technique is the Interactive Voice Response (IVR). The usability of IVR systems is, however, dismal. Customers would rather speak to a contact centre agent than navigate through the menu structure found in these systems. The menu structure has come under scrutiny because it is difficult to use and navigate, is often not aligned to caller usage patterns, and the menu options are long and vague. This research investigated whether a Natural Language Interface (NLI) could alleviate the problems inherent to IVR. NLIs, however, come with their own disadvantages of which the main ones are ambiguity and the loss of context of a conversation. Two prototypes were implemented, one of which resembled an IVR and the other an NLI (using ALICE concepts). An evaluation of two prototypes confirmed the advantages and disadvantages of these concepts in accordance to theory. A Hybrid prototype was proposed with the aid of two models. The model which proposed an NLI using a rule base was chosen for implementation. The Hybrid prototype was then evaluated against the NLI and IVR prototypes to deduce which prototype was the most effective, efficient and satisfying. The evaluation through the aid of descriptive and inferential statistics showed that the Hybrid prototype was the most usable prototype. The evaluation of the Hybrid prototype confirmed that a Hybrid approach could limit the shortcomings of IVR through the elimination of the menu structure found in these systems, thereby allowing users to state their queries in natural language. The incorporated rule base provided the Hybrid system with long term memory, eliminating one of the main disadvantages of NLIs.
- Full Text:
- Date Issued: 2009
- Authors: Sankar, Gopal Ravi
- Date: 2009
- Subjects: Call centers -- Management , Customer services -- Management , Telephone selling
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10468 , http://hdl.handle.net/10948/890 , Call centers -- Management , Customer services -- Management , Telephone selling
- Description: Contact centres are the first point of contact between a company and a customer after the purchase of a product or service. These centres make use of contact centre agents to service customer queries. In the past contact centres hired as many agents as they could in order to service customers, which have led to an increase in personnel costs causing contact centres to become costly to run. Automation techniques were introduced to decrease personnel costs and one such technique is the Interactive Voice Response (IVR). The usability of IVR systems is, however, dismal. Customers would rather speak to a contact centre agent than navigate through the menu structure found in these systems. The menu structure has come under scrutiny because it is difficult to use and navigate, is often not aligned to caller usage patterns, and the menu options are long and vague. This research investigated whether a Natural Language Interface (NLI) could alleviate the problems inherent to IVR. NLIs, however, come with their own disadvantages of which the main ones are ambiguity and the loss of context of a conversation. Two prototypes were implemented, one of which resembled an IVR and the other an NLI (using ALICE concepts). An evaluation of two prototypes confirmed the advantages and disadvantages of these concepts in accordance to theory. A Hybrid prototype was proposed with the aid of two models. The model which proposed an NLI using a rule base was chosen for implementation. The Hybrid prototype was then evaluated against the NLI and IVR prototypes to deduce which prototype was the most effective, efficient and satisfying. The evaluation through the aid of descriptive and inferential statistics showed that the Hybrid prototype was the most usable prototype. The evaluation of the Hybrid prototype confirmed that a Hybrid approach could limit the shortcomings of IVR through the elimination of the menu structure found in these systems, thereby allowing users to state their queries in natural language. The incorporated rule base provided the Hybrid system with long term memory, eliminating one of the main disadvantages of NLIs.
- Full Text:
- Date Issued: 2009
An investigation into bile formation of Wistar rats for excretion of injected gold nanoparticles
- Authors: Thole, Sagoleka Thabo
- Date: 2019
- Subjects: Nanoparticles , Nanomedicine Gold -- Immunology Bile acids -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43900 , vital:37082
- Description: There is an increase in the use of nanoparticles (NPs) throughout the world. Gold nanoparticles (AuNPs) are commonly used NPs in the field of biomedicine. NPs bigger than 8 nm are excreted via the hepatobiliary system. Bile acids (BAs) are regarded as the main components of bile. If there is a decreased or increased secretion of BAs, the composition of microbiota in the gut can change. Under normal physiological condition BAs fluctuates daily without causing any harm. Nevertheless, it is the long-term changes in bile acid secretion that can affect microbiota in the gut. If there is an increased excretion of AuNPs via hepatobiliary pathway it can alter bile formation. The aim of this study was to investigate whether the hepatobiliary excretion of AuNPs will alter the bile formation two weeks after intravenous administration of 14 nm AuNPs to Wistar rats. Rat liver samples of two previous experiments were used to investigate bile formation. The rats had been injected intravenously with a single dose of citrate capped and functionalised AuNPs. These rats were killed 14 days later. Small pieces of liver were stored in RNAlater. The mRNA of different enzymes and transporters in the hepatobiliary system were quantified in these samples and compared with suitable control. As a reference the mRNA of the same enzymes and transporters were extracted and quantified in rat liver that were killed one day after injection with one of the abovementioned functionalised AuNPs. The study shows down-regulation of genes responsible for conjugation of BAs whereas the rate-limiting enzymes were not significantly changed. This was the first study to investigate the formation of bile in relation to the use of AuNPs. The effect and consequences of AuNPs on the hepatobiliary system need further investigation.
- Full Text:
- Date Issued: 2019
- Authors: Thole, Sagoleka Thabo
- Date: 2019
- Subjects: Nanoparticles , Nanomedicine Gold -- Immunology Bile acids -- Physiological effect
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/43900 , vital:37082
- Description: There is an increase in the use of nanoparticles (NPs) throughout the world. Gold nanoparticles (AuNPs) are commonly used NPs in the field of biomedicine. NPs bigger than 8 nm are excreted via the hepatobiliary system. Bile acids (BAs) are regarded as the main components of bile. If there is a decreased or increased secretion of BAs, the composition of microbiota in the gut can change. Under normal physiological condition BAs fluctuates daily without causing any harm. Nevertheless, it is the long-term changes in bile acid secretion that can affect microbiota in the gut. If there is an increased excretion of AuNPs via hepatobiliary pathway it can alter bile formation. The aim of this study was to investigate whether the hepatobiliary excretion of AuNPs will alter the bile formation two weeks after intravenous administration of 14 nm AuNPs to Wistar rats. Rat liver samples of two previous experiments were used to investigate bile formation. The rats had been injected intravenously with a single dose of citrate capped and functionalised AuNPs. These rats were killed 14 days later. Small pieces of liver were stored in RNAlater. The mRNA of different enzymes and transporters in the hepatobiliary system were quantified in these samples and compared with suitable control. As a reference the mRNA of the same enzymes and transporters were extracted and quantified in rat liver that were killed one day after injection with one of the abovementioned functionalised AuNPs. The study shows down-regulation of genes responsible for conjugation of BAs whereas the rate-limiting enzymes were not significantly changed. This was the first study to investigate the formation of bile in relation to the use of AuNPs. The effect and consequences of AuNPs on the hepatobiliary system need further investigation.
- Full Text:
- Date Issued: 2019
An investigation into the effect of carbon type addictives on the negative electrode during the partial state of charge capacity cycling of lead acid batteries
- Authors: Snyders, Charmelle
- Date: 2011
- Subjects: Lead-acid batteries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10379 , http://hdl.handle.net/10948/1494 , Lead-acid batteries
- Description: It is well known that a conventional lead acid cell that is exposed to a partial state of charge capacity cycling (PSoCCC) would experience a build-up of irreversible PbSO4 on the negative electrode. This results into a damaged negative electrode due to excessive PbSO4 formation by the typical visual “Venetian Blinds” effect of the active material. This displays the loss of adhesion of the active material with the electrode’s grids thereby making large sections of the material ineffective and reducing the cells useful capacity during high current applications. The addition of certain graphites to the negative paste mix had proven to be successful to reduce this effect. In the first part of the study, the physical and chemical properties of the various additives that are added to the negative electrode paste mix were comparatively studied. This was done to investigate any significant differences between various suppliers that could possibly influence the electrochemical characteristics of the Pb-acid battery performance. This comparative study was done by using the following analytical techniques; BET surface area, laser diffraction particle size, PXRD, TGA-MS and SEM. The study showed that there were no significant differences between the additives supplied from different suppliers except for some anomalies in the usefulness of techniques such as N2 adsorption to study the BET surface area of BaSO4. In order to reduce the sulphation effect from occurring within the Pb-acid battery a number of adjustments are made to the electrode active material. For example, Pb-acid battery manufacturers make use of an inert polymer based material, known as Polymat, to cover the electrode surfaces as part of their continuous electrode pasting process. It is made from a non woven polyester fiber that is applied to the pasted electrodes during the continuous pasting process. In this study the Polymat pasted electrodes has demonstrated a better physical adhesion of the active material to the grid support thereby maintaining the active material’s physical integrity. This however did not reduce the sulphation effect due to the high rate partial state of capacity cycling (HRPSoCCC) test but reduced the physical damage due to the irreversible active material blistering effect. The study investigated what effect the Polymat on the electrodes has on the III battery’s Cold Cranking Ability (CCA) at -18 degree C, the HRPSoCCC cycling and its active material utilization. The study showed that there was little or no differences in the CCA and HRPSoCCC capabilities of cells made with the Polymat when compared to cells without the Polymat, with significant improvement in active material’s adhesion and integrity to the grid wire. This was confirmed by PXRD and SEM analysis. Negative electrodes were made with four types of graphites (natural, flake, expanded and nano fibre) added to the negative paste mixture in order to reduce the effect of sulphation. The study looked at using statistical design of experiment (DoE) principles to investigate the variables (additives) such as different graphites, BaSO4 and Vanisperse to the negative electrode paste mixture where upon measuring the responses (electrochemical tests) a set of controlled experiments were done to study the extent of the variables interaction, dependency and independency on the cells electrochemical properties. This was especially in relation to the improvement of the battery’s ability to work under HRPSoCCC. The statistical analysis showed that there was a notable significant influence of the amounts of vanisperse, BaSO4 and their respective interactions on a number of electrochemical responses, such as the Peukert constant (n), CCA discharge time, material utilization at different discharge rates and the ability to capacity cycle under the simulated HRPSoCCC testing. The study did not suggest an optimized concentration of the additives, but did give an indication that there was a statistical significant trend in certain electrochemical responses with an interaction between the amounts of the additives BaSO4 and Vanisperse. The study also showed that the addition of a small amount of Nano carbon can significantly change the observed crystal morphology of the negative active material and that an improvement in the number of capacity cycles can be achieved during the HRPSoCCC test when compared to the other types of graphite additives.
- Full Text:
- Date Issued: 2011
- Authors: Snyders, Charmelle
- Date: 2011
- Subjects: Lead-acid batteries
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10379 , http://hdl.handle.net/10948/1494 , Lead-acid batteries
- Description: It is well known that a conventional lead acid cell that is exposed to a partial state of charge capacity cycling (PSoCCC) would experience a build-up of irreversible PbSO4 on the negative electrode. This results into a damaged negative electrode due to excessive PbSO4 formation by the typical visual “Venetian Blinds” effect of the active material. This displays the loss of adhesion of the active material with the electrode’s grids thereby making large sections of the material ineffective and reducing the cells useful capacity during high current applications. The addition of certain graphites to the negative paste mix had proven to be successful to reduce this effect. In the first part of the study, the physical and chemical properties of the various additives that are added to the negative electrode paste mix were comparatively studied. This was done to investigate any significant differences between various suppliers that could possibly influence the electrochemical characteristics of the Pb-acid battery performance. This comparative study was done by using the following analytical techniques; BET surface area, laser diffraction particle size, PXRD, TGA-MS and SEM. The study showed that there were no significant differences between the additives supplied from different suppliers except for some anomalies in the usefulness of techniques such as N2 adsorption to study the BET surface area of BaSO4. In order to reduce the sulphation effect from occurring within the Pb-acid battery a number of adjustments are made to the electrode active material. For example, Pb-acid battery manufacturers make use of an inert polymer based material, known as Polymat, to cover the electrode surfaces as part of their continuous electrode pasting process. It is made from a non woven polyester fiber that is applied to the pasted electrodes during the continuous pasting process. In this study the Polymat pasted electrodes has demonstrated a better physical adhesion of the active material to the grid support thereby maintaining the active material’s physical integrity. This however did not reduce the sulphation effect due to the high rate partial state of capacity cycling (HRPSoCCC) test but reduced the physical damage due to the irreversible active material blistering effect. The study investigated what effect the Polymat on the electrodes has on the III battery’s Cold Cranking Ability (CCA) at -18 degree C, the HRPSoCCC cycling and its active material utilization. The study showed that there was little or no differences in the CCA and HRPSoCCC capabilities of cells made with the Polymat when compared to cells without the Polymat, with significant improvement in active material’s adhesion and integrity to the grid wire. This was confirmed by PXRD and SEM analysis. Negative electrodes were made with four types of graphites (natural, flake, expanded and nano fibre) added to the negative paste mixture in order to reduce the effect of sulphation. The study looked at using statistical design of experiment (DoE) principles to investigate the variables (additives) such as different graphites, BaSO4 and Vanisperse to the negative electrode paste mixture where upon measuring the responses (electrochemical tests) a set of controlled experiments were done to study the extent of the variables interaction, dependency and independency on the cells electrochemical properties. This was especially in relation to the improvement of the battery’s ability to work under HRPSoCCC. The statistical analysis showed that there was a notable significant influence of the amounts of vanisperse, BaSO4 and their respective interactions on a number of electrochemical responses, such as the Peukert constant (n), CCA discharge time, material utilization at different discharge rates and the ability to capacity cycle under the simulated HRPSoCCC testing. The study did not suggest an optimized concentration of the additives, but did give an indication that there was a statistical significant trend in certain electrochemical responses with an interaction between the amounts of the additives BaSO4 and Vanisperse. The study also showed that the addition of a small amount of Nano carbon can significantly change the observed crystal morphology of the negative active material and that an improvement in the number of capacity cycles can be achieved during the HRPSoCCC test when compared to the other types of graphite additives.
- Full Text:
- Date Issued: 2011
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
- Full Text:
- Date Issued: 2021-04
- 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
- Full Text:
- Date Issued: 2021-04
An investigation into the induction of oxidative stress and apoptosis by microcystin-LR in the CaCo2 cell line and intestinal tract of Balb/c mice
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
- Full Text:
- Date Issued: 2003
- Authors: Botha, Nicolette
- Date: 2003
- Subjects: Microcystis aeruginosa -- Toxicology , Apoptosis
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:11066 , http://hdl.handle.net/10948/349 , Microcystis aeruginosa -- Toxicology , Apoptosis
- Description: This study reports the findings on the effect of Microcystin-LR (MCLR) on the gastrointestinal tract cells of mice and on two different cell lines, Caco2 and MCF-7. The cyanobacterium Microcystis aeruginosa produces the potent toxin, MCLR. This toxin has been implicated in a number of cases of ill-health. It was decided to investigate whether microcystin-LR induced apoptosis in the gastrointestinal tract of mice and also which possible mechanisms were involved in the induction in vitro. Balb/c mice were given a 75% LD50 intraperitoneal dose of pure microcystin -LR and sacrificed at 8, 16, 24 and 32 hours post-exposure. The small intestinal sections were stained with haematoxylin and eosin and examined for apoptotic cells. There was a time-dependent increase in the number of apoptotic cells with most in the duodenum and the jejunum. No change in glycogen content was evident at 24 hours post exposure when PAS-stained sections were examined. To determine that microcystin was the agent responsible for the changes, fluoroscein isothiocyanate (FITC) immunostaining for the toxin was done on the sections. Apoptosis in vitro was investigated in Caco2, a cell line that behaves like normal enterocytes when the cells are differentiated at confluency, and MCF-7, a breast cancer cell line deficient in pro-caspase-3, cells by 3-[dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays and by staining with DAPI and Rhodamine 123. MCLR exposure induced apoptosis, as seen in decreased cell viability and increased leakage of LDH, as well as mitochondrial damage shown by Rhodamine staining. The MCF-7 cells, deficient in pro-caspase-3, and Caco2 cells did not show cleavage of poly(ADP)ribose polymerase (PARP) after exposure to 50μM MCLR after 72 hours exposure. Both micro- and milli-calpain activity was however significantly increased in both cell lines exposed to the toxin. There was a significant increase in H2O2, one of the key reactive oxygen species, production during the first 30 minutes that the cells were exposed to 50 mM MCLR.
- Full Text:
- Date Issued: 2003
An investigation into the learnability of object-oriented case tools for computing education
- Authors: Scholtz, Brenda Mary
- Date: 2007
- Subjects: Computer science -- Study and teaching , Object-oriented programming (Computer science) , ACSES (Computer system)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10476 , http://hdl.handle.net/10948/694 , Computer science -- Study and teaching , Object-oriented programming (Computer science) , ACSES (Computer system)
- Description: The use of Computer Aided Software Engineering (CASE) tools for teaching object-oriented systems analysis and design (OOSAD) has many potential benefits, but there are also several problems associated with the usage of these tools. A large portion of these problems relate to the usability and learnability of these tools. Learnability is one of the most important attributes of usability and refers to the capability of the system to enable the user to learn its application. The main research question that this study aims to address is “How can the learnability of OO CASE tools for computing education in South Africa be evaluated?”. In order to answer this question several frameworks for evaluating CASE tool usability and learnability were investigated. One of these frameworks, as proposed by Senapathi, was selected as being the most appropriate for evaluating CASE tool learnability for computing education. This framework maintains that the learnability of a CASE tool is dependent on context of use factors such as the tool used, as well as user characteristics such as gender. The primary aim of this research was thus to validate Senapathi's framework for CASE tool learnability in a South African context. A secondary aim of the research was to extend the implementation of the framework in order to enable the comparison of two CASE tools and to support the inclusion of other user characteristics. An experiment was performed at the Nelson Mandela Metropolitan University (NMMU) in 2006. The participants recruited for this experiment were second year computing students at NMMU. During this experiment, the learnability of two OO CASE tools, namely IBM's Rational Software Modeller and Microsoft's Visio, was evaluated and compared. The quantitative and qualitative results supported Senapathi's results and showed that her framework could be used to evaluate CASE tool learnability and could be adapted to evaluate two CASE tools. The results also showed that the majority of the participants rated the learnability of Microsoft Visio higher for both tasks and that the main reasons participants preferred Visio was due to its simplicity, familiarity and recoverability.
- Full Text:
- Date Issued: 2007
- Authors: Scholtz, Brenda Mary
- Date: 2007
- Subjects: Computer science -- Study and teaching , Object-oriented programming (Computer science) , ACSES (Computer system)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10476 , http://hdl.handle.net/10948/694 , Computer science -- Study and teaching , Object-oriented programming (Computer science) , ACSES (Computer system)
- Description: The use of Computer Aided Software Engineering (CASE) tools for teaching object-oriented systems analysis and design (OOSAD) has many potential benefits, but there are also several problems associated with the usage of these tools. A large portion of these problems relate to the usability and learnability of these tools. Learnability is one of the most important attributes of usability and refers to the capability of the system to enable the user to learn its application. The main research question that this study aims to address is “How can the learnability of OO CASE tools for computing education in South Africa be evaluated?”. In order to answer this question several frameworks for evaluating CASE tool usability and learnability were investigated. One of these frameworks, as proposed by Senapathi, was selected as being the most appropriate for evaluating CASE tool learnability for computing education. This framework maintains that the learnability of a CASE tool is dependent on context of use factors such as the tool used, as well as user characteristics such as gender. The primary aim of this research was thus to validate Senapathi's framework for CASE tool learnability in a South African context. A secondary aim of the research was to extend the implementation of the framework in order to enable the comparison of two CASE tools and to support the inclusion of other user characteristics. An experiment was performed at the Nelson Mandela Metropolitan University (NMMU) in 2006. The participants recruited for this experiment were second year computing students at NMMU. During this experiment, the learnability of two OO CASE tools, namely IBM's Rational Software Modeller and Microsoft's Visio, was evaluated and compared. The quantitative and qualitative results supported Senapathi's results and showed that her framework could be used to evaluate CASE tool learnability and could be adapted to evaluate two CASE tools. The results also showed that the majority of the participants rated the learnability of Microsoft Visio higher for both tasks and that the main reasons participants preferred Visio was due to its simplicity, familiarity and recoverability.
- Full Text:
- Date Issued: 2007
An investigation into the localization of peptide-gold nanoparticles in an in vitro and in vivo colorectal cancer model
- Authors: Cairncross, Lynn
- Subjects: Colon (Anatomy) -- Cancer -- Treatment , Cancer -- Early detection
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10351 , http://hdl.handle.net/10948/d1020921
- Description: Background: Colorectal cancer is the third most common cancer and cause of related deaths worldwide. Early colorectal cancer diagnosis is vital in reducing incidence and mortality. There is a need for the development of non-invasive screening tools for enhancing the detection of the disease. Cancer specific peptides are useful cancer targeting agents that can be used to specifically improve early detection strategies. Several cancer targeting peptides have been identified. Previous work investigated the specific binding of three of these peptides (p.C, p.L and p.14) conjugated to quantum dots and were found to bind to colorectal cancer cell lines (HT-29 and Caco-2). However, their uptake, localization and biodistribution in an in vitro and in vivo colorectal cancer model have not been determined. This is essential in gaining an understanding for future diagnostic or therapeutic based applications. Primary Aim: The aim of this study was investigate the localization of three selected peptides p.C, p.L and p.14 conjugated to gold nanoparticles in an in vitro and in vivo colorectal cancer model using HRTEM. Methodology: The AuNP/peptide conjugates were characterized by HRTEM and DLS. For in vitro studies; HT-29, Caco-2 and C3A cells were exposed to the AuNP-p.C, AuNP-p.L and AuNP-p.14, collected and processed for HRTEM to assess targeting and localization. For in vivo studies; the establishment of a colorectal cancer model using the AOM/DSS model 1 and 2 was conducted. Wistar rats were assigned to 6 groups, five experimental and 1 control group. Group 1 received AOM/DSS method 1 and was treated with AuNP-p.L. Group 2 and 3 received AOM/DSS method 2 and were treated with AuNP-p.C and AuNP-p.14. Group 4 and 5 remained healthy and treated with AuNP-p.C and AuNP-p.14. Group 6 remained healthy receiving no nanoparticle treatment. After treatment, rats were sacrificed and tissue was processed for HRTEM. Tissue chosen for HRTEM analysis included: Group 1 (inflamed colon, rectum, pancreatic and kidney), Group 4 (kidney) and Group 5 (liver). Results: results obtained from nanoparticle characterization suggested that nanoparticles were conjugated to their respective peptides and were stable in dispersion. For in vitro studies, results suggested no AuNP targeting and localization in HT-29 cell lines. For in vivo studies, no colorectal cancer tumours were induced. TEM micrographs did not indicate the presence of nanoparticles in colon, rectum, pancreatic, kidney and liver tissue. However, AuNPs were found in the kidney tissue (group 4). Conclusion: Although the overall objectives were not met, this study provided insight into TEM cell preparation and optimization for future nanoparticle cell interaction research. This study also demonstrated the absence of AuNPs in healthy tissue and the presence of AuNPs in healthy kidney tissue through renal clearance, a favourable quality for diagnostic or therapeutic applications.
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- Authors: Cairncross, Lynn
- Subjects: Colon (Anatomy) -- Cancer -- Treatment , Cancer -- Early detection
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:10351 , http://hdl.handle.net/10948/d1020921
- Description: Background: Colorectal cancer is the third most common cancer and cause of related deaths worldwide. Early colorectal cancer diagnosis is vital in reducing incidence and mortality. There is a need for the development of non-invasive screening tools for enhancing the detection of the disease. Cancer specific peptides are useful cancer targeting agents that can be used to specifically improve early detection strategies. Several cancer targeting peptides have been identified. Previous work investigated the specific binding of three of these peptides (p.C, p.L and p.14) conjugated to quantum dots and were found to bind to colorectal cancer cell lines (HT-29 and Caco-2). However, their uptake, localization and biodistribution in an in vitro and in vivo colorectal cancer model have not been determined. This is essential in gaining an understanding for future diagnostic or therapeutic based applications. Primary Aim: The aim of this study was investigate the localization of three selected peptides p.C, p.L and p.14 conjugated to gold nanoparticles in an in vitro and in vivo colorectal cancer model using HRTEM. Methodology: The AuNP/peptide conjugates were characterized by HRTEM and DLS. For in vitro studies; HT-29, Caco-2 and C3A cells were exposed to the AuNP-p.C, AuNP-p.L and AuNP-p.14, collected and processed for HRTEM to assess targeting and localization. For in vivo studies; the establishment of a colorectal cancer model using the AOM/DSS model 1 and 2 was conducted. Wistar rats were assigned to 6 groups, five experimental and 1 control group. Group 1 received AOM/DSS method 1 and was treated with AuNP-p.L. Group 2 and 3 received AOM/DSS method 2 and were treated with AuNP-p.C and AuNP-p.14. Group 4 and 5 remained healthy and treated with AuNP-p.C and AuNP-p.14. Group 6 remained healthy receiving no nanoparticle treatment. After treatment, rats were sacrificed and tissue was processed for HRTEM. Tissue chosen for HRTEM analysis included: Group 1 (inflamed colon, rectum, pancreatic and kidney), Group 4 (kidney) and Group 5 (liver). Results: results obtained from nanoparticle characterization suggested that nanoparticles were conjugated to their respective peptides and were stable in dispersion. For in vitro studies, results suggested no AuNP targeting and localization in HT-29 cell lines. For in vivo studies, no colorectal cancer tumours were induced. TEM micrographs did not indicate the presence of nanoparticles in colon, rectum, pancreatic, kidney and liver tissue. However, AuNPs were found in the kidney tissue (group 4). Conclusion: Although the overall objectives were not met, this study provided insight into TEM cell preparation and optimization for future nanoparticle cell interaction research. This study also demonstrated the absence of AuNPs in healthy tissue and the presence of AuNPs in healthy kidney tissue through renal clearance, a favourable quality for diagnostic or therapeutic applications.
- Full Text: