Formulation and process optimisation of ethionamide 250 MGtablets using quality by design principles
- Authors: Isaacs, Nasreen
- Date: 2015
- Subjects: Pharmaceutical chemistry , Drugs -- Design , Pharmaceutical technology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3979 , vital:20497
- Description: The traditional approach of Quality by Testing (QbT) limits the assurance of product quality to in-process and post-production testing. To overcome these limitations, a more proactive and systematic means to product development and optimisation is required. Quality by Design (QbD) is an example of such an approach which focuses on understanding the product and its manufacturing process and emphasises that quality should be built into the product and not merely tested. The study aims to optimise ethionamide tablets, an immediate release oral solid dosage form using QbD.
- Full Text:
- Date Issued: 2015
Formulation and process optimisation of ethionamide 250 MGtablets using quality by design principles
- Authors: Isaacs, Nasreen
- Date: 2015
- Subjects: Pharmaceutical chemistry , Drugs -- Design , Pharmaceutical technology
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3979 , vital:20497
- Description: The traditional approach of Quality by Testing (QbT) limits the assurance of product quality to in-process and post-production testing. To overcome these limitations, a more proactive and systematic means to product development and optimisation is required. Quality by Design (QbD) is an example of such an approach which focuses on understanding the product and its manufacturing process and emphasises that quality should be built into the product and not merely tested. The study aims to optimise ethionamide tablets, an immediate release oral solid dosage form using QbD.
- Full Text:
- Date Issued: 2015
Gene expression analysis of Thaumatotibia leucotreta in response to the Cryptophlebia leucotreta granulovirus
- Authors: Ridgeway, Jaryd Antony
- Date: 2015
- Subjects: Gene expression , Insects -- Viruses , Tortricidae -- Viruses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5931 , http://hdl.handle.net/10962/d1017809
- Description: Gene expression studies provide baseline information on the interactions of insects with their environment. Despite the importance of this information, limited gene expression data are available for most insect pests, including the family Tortricidae (Lepidoptera), which includes Thaumatotibia leucotreta (Meyr), an important agricultural pest in Africa. Because T. leucotreta can be controlled successfully by a granulovirus, this system is a good model for exploring insect-virus susceptibility. The main aim of this study was to investigate gene expression of T. leucotreta in responce to virus infection. However, before pursuing this aim, two objectives required completion. First, the most suitable RNA extraction method for insects needed to be determined and second, the most suitable reference genes for qPCR for Tortricidae pests needed to be identified. Once these objectives were accomplished, the response of T. leucotreta to its granulovirus was evaluated at different temperatures and points after infection.Four RNA extraction methods, the RNeasy® Mini Kit, SV Total RNA isolation system, TRIzol® reagent, and a CTAB-based method, were compared using two beetle and two moth species, including T. leucotreta. The quality of extracted RNA was similar for all four species for all extraction methods. Based on several criteria, the best RNA extraction method was the SV Total RNA isolation system. Six candidate reference genes were evaluated for qPCR using different tissue types of T. leucotreta and two other Tortricidae pests. Additionally, reference genes were evaluated for T. leucotreta with and without its granulovirus at different temperatures. Reference gene stability was found to be dependent on species and tissue type. Overall the most suitable combination of reference genes for T. leucotreta were α-actin, arginine kinase and elongation factor 1-α.Gene expression of T. leucotreta in response to granulovirus infection at different temperatures and intervals after infection was evaluated by qPCR using 13 target genes associated with the infection process. Most genes were down-regulated after 24 and 48 h.p.i. However, after 72 h.p.i most genes were up-regulated. The same trend was observed at different temperatures, where most genes were down-regulated at 15°C and 25°C but up-regulated at 35°C. These results show that there is a dynamic gene expression response in T. leucotreta due to granulovirus infection under different conditions. Not only do these findings provide insight into the control of this tortricid pest, they also contribute further to our knowledge of insect-virus interactions.
- Full Text:
- Date Issued: 2015
- Authors: Ridgeway, Jaryd Antony
- Date: 2015
- Subjects: Gene expression , Insects -- Viruses , Tortricidae -- Viruses
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5931 , http://hdl.handle.net/10962/d1017809
- Description: Gene expression studies provide baseline information on the interactions of insects with their environment. Despite the importance of this information, limited gene expression data are available for most insect pests, including the family Tortricidae (Lepidoptera), which includes Thaumatotibia leucotreta (Meyr), an important agricultural pest in Africa. Because T. leucotreta can be controlled successfully by a granulovirus, this system is a good model for exploring insect-virus susceptibility. The main aim of this study was to investigate gene expression of T. leucotreta in responce to virus infection. However, before pursuing this aim, two objectives required completion. First, the most suitable RNA extraction method for insects needed to be determined and second, the most suitable reference genes for qPCR for Tortricidae pests needed to be identified. Once these objectives were accomplished, the response of T. leucotreta to its granulovirus was evaluated at different temperatures and points after infection.Four RNA extraction methods, the RNeasy® Mini Kit, SV Total RNA isolation system, TRIzol® reagent, and a CTAB-based method, were compared using two beetle and two moth species, including T. leucotreta. The quality of extracted RNA was similar for all four species for all extraction methods. Based on several criteria, the best RNA extraction method was the SV Total RNA isolation system. Six candidate reference genes were evaluated for qPCR using different tissue types of T. leucotreta and two other Tortricidae pests. Additionally, reference genes were evaluated for T. leucotreta with and without its granulovirus at different temperatures. Reference gene stability was found to be dependent on species and tissue type. Overall the most suitable combination of reference genes for T. leucotreta were α-actin, arginine kinase and elongation factor 1-α.Gene expression of T. leucotreta in response to granulovirus infection at different temperatures and intervals after infection was evaluated by qPCR using 13 target genes associated with the infection process. Most genes were down-regulated after 24 and 48 h.p.i. However, after 72 h.p.i most genes were up-regulated. The same trend was observed at different temperatures, where most genes were down-regulated at 15°C and 25°C but up-regulated at 35°C. These results show that there is a dynamic gene expression response in T. leucotreta due to granulovirus infection under different conditions. Not only do these findings provide insight into the control of this tortricid pest, they also contribute further to our knowledge of insect-virus interactions.
- Full Text:
- Date Issued: 2015
Generalizations of some fixed point theorems in banach and metric spaces
- Niyitegeka, Jean Marie Vianney
- Authors: Niyitegeka, Jean Marie Vianney
- Date: 2015
- Subjects: Fixed point theory , Banach spaces , Mappings (Mathematics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5265 , vital:20828
- Description: A fixed point of a mapping is an element in the domain of the mapping that is mapped into itself by the mapping. The study of fixed points has been a field of interests to mathematicians since the discovery of the Banach contraction theorem, i.e. if is a complete metric space and is a contraction mapping (i.e. there exists such that for all ), then has a unique fixed point. The Banach contraction theorem has found many applications in pure and applied mathematics. Due to fixed point theory being a mixture of analysis, geometry, algebra and topology, its applications to other fields such as physics, economics, game theory, chemistry, engineering and many others has become vital. The theory is nowadays a very active field of research in which many new theorems are published, some of them applied and many others generalized. Motivated by all of this, we give an exposition of some generalizations of fixed point theorems in metric fixed point theory, which is a branch of fixed point theory about results of fixed points of mappings between metric spaces, where certain properties of the mappings involved need not be preserved under equivalent metrics. For instance, the contractive property of mappings between metric spaces need not be preserved under equivalent metrics. Since metric fixed point theory is wide, we limit ourselves to fixed point theorems for self and non-self-mappings on Banach and metric spaces. We also take a look at some open problems on this topic of study. At the end of the dissertation, we suggest our own problems for future research.
- Full Text:
- Date Issued: 2015
- Authors: Niyitegeka, Jean Marie Vianney
- Date: 2015
- Subjects: Fixed point theory , Banach spaces , Mappings (Mathematics)
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/5265 , vital:20828
- Description: A fixed point of a mapping is an element in the domain of the mapping that is mapped into itself by the mapping. The study of fixed points has been a field of interests to mathematicians since the discovery of the Banach contraction theorem, i.e. if is a complete metric space and is a contraction mapping (i.e. there exists such that for all ), then has a unique fixed point. The Banach contraction theorem has found many applications in pure and applied mathematics. Due to fixed point theory being a mixture of analysis, geometry, algebra and topology, its applications to other fields such as physics, economics, game theory, chemistry, engineering and many others has become vital. The theory is nowadays a very active field of research in which many new theorems are published, some of them applied and many others generalized. Motivated by all of this, we give an exposition of some generalizations of fixed point theorems in metric fixed point theory, which is a branch of fixed point theory about results of fixed points of mappings between metric spaces, where certain properties of the mappings involved need not be preserved under equivalent metrics. For instance, the contractive property of mappings between metric spaces need not be preserved under equivalent metrics. Since metric fixed point theory is wide, we limit ourselves to fixed point theorems for self and non-self-mappings on Banach and metric spaces. We also take a look at some open problems on this topic of study. At the end of the dissertation, we suggest our own problems for future research.
- Full Text:
- Date Issued: 2015
Geomorphic and ambient environmental impacts on lichen distribution on two inland Nunataks in western Dronning Maud Land, Antarctica
- Authors: Dwight, Rosemary Anne
- Date: 2015
- Subjects: Lichens -- Antarctica -- Queen Maud Land , Lichen communities -- Antarctica -- Queen Maud Land , Lichens -- Climatic factors -- Antarctica -- Queen Maud Land , Lichens -- Effect of environment on -- Antarctica -- Queen Maud Land , Biotic communities -- Antarctica -- Queen Maud Land , Biotic communities -- Climatic factors -- Antarctica -- Queen Maud Land , Biodiversity -- Climatic factors -- Antarctica -- Queen Maud Land
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4889 , http://hdl.handle.net/10962/d1018189
- Description: Feedbacks between abiotic variables and community structure in Antarctica are poorly understood. Research is, therefore, required to elucidate the patterns of biodiversity that exist and the factors that influence them, particularly under changing climates. Landscape processes affect environmental heterogeneity, which in turn affect patterns of biodiversity. Two inland Antarctic nunataks, Robertskollen and the Northern Buttress of Vesleskarvet, were selected for investigation to determine the potential impact of selected environmental factors on lichen distribution and abundance, at the intra- and inter-nunatak scales. Lichens were found to prefer rock faces with dips between 1° and 45°, and northern/southern aspects. Lichen colonisation was mostly in microtopographical features that result from rock weathering. The distribution of lichens was found to be regular at the intra- and inter-nunatak scale, whereas lichen abundance was found to be mostly influenced by temperature. On the Northern Buttress, rock hardness displays a similar pattern to lichen abundance, both of which are suggested to be a function of exposure time, which is dependent on deglaciation. The two nunataks serve as excellent laboratories that can potentially be used as proxies for investigating the possible impacts of climate change
- Full Text:
- Date Issued: 2015
- Authors: Dwight, Rosemary Anne
- Date: 2015
- Subjects: Lichens -- Antarctica -- Queen Maud Land , Lichen communities -- Antarctica -- Queen Maud Land , Lichens -- Climatic factors -- Antarctica -- Queen Maud Land , Lichens -- Effect of environment on -- Antarctica -- Queen Maud Land , Biotic communities -- Antarctica -- Queen Maud Land , Biotic communities -- Climatic factors -- Antarctica -- Queen Maud Land , Biodiversity -- Climatic factors -- Antarctica -- Queen Maud Land
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4889 , http://hdl.handle.net/10962/d1018189
- Description: Feedbacks between abiotic variables and community structure in Antarctica are poorly understood. Research is, therefore, required to elucidate the patterns of biodiversity that exist and the factors that influence them, particularly under changing climates. Landscape processes affect environmental heterogeneity, which in turn affect patterns of biodiversity. Two inland Antarctic nunataks, Robertskollen and the Northern Buttress of Vesleskarvet, were selected for investigation to determine the potential impact of selected environmental factors on lichen distribution and abundance, at the intra- and inter-nunatak scales. Lichens were found to prefer rock faces with dips between 1° and 45°, and northern/southern aspects. Lichen colonisation was mostly in microtopographical features that result from rock weathering. The distribution of lichens was found to be regular at the intra- and inter-nunatak scale, whereas lichen abundance was found to be mostly influenced by temperature. On the Northern Buttress, rock hardness displays a similar pattern to lichen abundance, both of which are suggested to be a function of exposure time, which is dependent on deglaciation. The two nunataks serve as excellent laboratories that can potentially be used as proxies for investigating the possible impacts of climate change
- Full Text:
- Date Issued: 2015
Glycolytic potential and meat quality from dorper and merino sheep slaughtered at a commercial abattoir
- Authors: Stempa, Thuthuzelwa
- Date: 2015
- Subjects: Slaughtering and slaughter-houses Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15310 , vital:40361
- Description: The objective of the study was to determine glycolytic potential and meat quality from Dorper and Merino sheep of both sexes slaughtered at a commercial abattoir. Dorper (n=52) and Merino (n= 48) breeds aged eight years, consisting of 50 intact rams and 50 non-pregnant ewes were used in the study. The sheep used in the study were reared, transported and lairised under identical conditions. Blood samples were collected at exsanguination for the measurement of glucose, lactate and cortisol levels. Samples were also collected from the Muscularis longmissius thoracis et lumborum (LTL) for the measurement glycogen, lactate levels, pH decline and colour. Correlations amongst blood stress indicators, muscle metabolites and meat quality attributes were also determined. Sex and breed had no effect on muscle glycolytic potential, glycogen and lactate levels from Dorper and Merino sheep of both sexes at the abattoir. Although sex and breed had an effect on pre-slaughter stress indicators (lactate and cortisol) collected at exsanguination. Ewes had higher levels of blood lactate (7.4 3 ± 0.49 mmol/L) and cortisol (293.92 ± 14.32 nmol/L) than the rams which had (5.19 ± 0.49 mmol/L) and (179.50 ± 14.32 nmol/L) lactate and cortisol levels, respectively. Furthermore, higher levels of lactate were observed in Dorper (7.54 ± 0.42 mmol/L) compared to the Merino sheep (4.97 ± 0.49 mmol/L). Meat pH decline and colour were also significantly affected by sex and breed. Ewes had higher levels of at pH45 minutes post slaughter (7.05 ± 0.04), pH3 hours (6.45 ± 0.04) , pH24 hours (6.00 ± 0.03), a* (14.31 ± 0.33) , b* (8.84 ± 0.29), H* (31.47 ± 0.73) and C* (16.75 ± 0.24) compared to the rams which had pH45 minutes (6.44 ± 0.04), pH3 hours (6.12 ± 0.04), pH24 hours (5.88 ± 0.03), a* (12.25 ± 0.33), b* (7.00 ± 0.29), H* (29.36 ± 0.73) and C* (14.15 ± 0.42) values. Moreover, Merino sheep had higher levels of L* (38.17 ± 0.48) and H* (31.59 ± 0.74) compared to the Dorper which had (36.39 ± 0.46) and (29.33 ± 0.71) L* and H* values, respectively. Blood cortisol was also positively correlated (P < 0.05) to glucose (r = 0.27), lactate (r = 0.37) but was negatively correlated (P < 0.001) to meat lightness (r = -0.44). Furthermore, blood cortisol was positively correlated (P < 0.001) to pH45 (r = 0.34), pH24 (r =0.22), meat yellowness (r = 0.24) and chroma (r = 0.37), but was negatively correlated to meat lightness (r = -0.47). Glycolytic potential was positively correlated (P < 0.001) to muscle glycogen levels (r = 0.66) and muscle lactate (r = 0.71).
- Full Text:
- Date Issued: 2015
- Authors: Stempa, Thuthuzelwa
- Date: 2015
- Subjects: Slaughtering and slaughter-houses Meat -- Quality
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/15310 , vital:40361
- Description: The objective of the study was to determine glycolytic potential and meat quality from Dorper and Merino sheep of both sexes slaughtered at a commercial abattoir. Dorper (n=52) and Merino (n= 48) breeds aged eight years, consisting of 50 intact rams and 50 non-pregnant ewes were used in the study. The sheep used in the study were reared, transported and lairised under identical conditions. Blood samples were collected at exsanguination for the measurement of glucose, lactate and cortisol levels. Samples were also collected from the Muscularis longmissius thoracis et lumborum (LTL) for the measurement glycogen, lactate levels, pH decline and colour. Correlations amongst blood stress indicators, muscle metabolites and meat quality attributes were also determined. Sex and breed had no effect on muscle glycolytic potential, glycogen and lactate levels from Dorper and Merino sheep of both sexes at the abattoir. Although sex and breed had an effect on pre-slaughter stress indicators (lactate and cortisol) collected at exsanguination. Ewes had higher levels of blood lactate (7.4 3 ± 0.49 mmol/L) and cortisol (293.92 ± 14.32 nmol/L) than the rams which had (5.19 ± 0.49 mmol/L) and (179.50 ± 14.32 nmol/L) lactate and cortisol levels, respectively. Furthermore, higher levels of lactate were observed in Dorper (7.54 ± 0.42 mmol/L) compared to the Merino sheep (4.97 ± 0.49 mmol/L). Meat pH decline and colour were also significantly affected by sex and breed. Ewes had higher levels of at pH45 minutes post slaughter (7.05 ± 0.04), pH3 hours (6.45 ± 0.04) , pH24 hours (6.00 ± 0.03), a* (14.31 ± 0.33) , b* (8.84 ± 0.29), H* (31.47 ± 0.73) and C* (16.75 ± 0.24) compared to the rams which had pH45 minutes (6.44 ± 0.04), pH3 hours (6.12 ± 0.04), pH24 hours (5.88 ± 0.03), a* (12.25 ± 0.33), b* (7.00 ± 0.29), H* (29.36 ± 0.73) and C* (14.15 ± 0.42) values. Moreover, Merino sheep had higher levels of L* (38.17 ± 0.48) and H* (31.59 ± 0.74) compared to the Dorper which had (36.39 ± 0.46) and (29.33 ± 0.71) L* and H* values, respectively. Blood cortisol was also positively correlated (P < 0.05) to glucose (r = 0.27), lactate (r = 0.37) but was negatively correlated (P < 0.001) to meat lightness (r = -0.44). Furthermore, blood cortisol was positively correlated (P < 0.001) to pH45 (r = 0.34), pH24 (r =0.22), meat yellowness (r = 0.24) and chroma (r = 0.37), but was negatively correlated to meat lightness (r = -0.47). Glycolytic potential was positively correlated (P < 0.001) to muscle glycogen levels (r = 0.66) and muscle lactate (r = 0.71).
- Full Text:
- Date Issued: 2015
Green procurement for municipal construction projects
- Authors: Maboza, Luthando Sithembele
- Date: 2015
- Subjects: Sustainable construction , Construction industry -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3165 , vital:20407
- Description: The study is a qualitative investigation of the implementation of green procurement in the construction sector at Local Government level. The focus is on the Metropolitan Municipalities of EThekwini, Nelson Mandela Bay and City of Cape Town. For the purpose of realising an extended comparative perspective, an additional three smaller municipalities were also reviewed. Green procurement is the tool used by governments to source the supply of products and services that are environmentally friendly to counter the global problem of climate change. The study commences with the exposition of the aspects of green procurement from the basis of the enabling legal framework to the scholarly contribution from which the study can be predicated. It becomes apparent from this review of legislation that there is a scope within the existing body of legislation for the use of green procurement as an environmental tool. Scholarly work addresses adoption of green procurement and considers, inter alia, the Bottom-up Approach, the Top-down Approach, and the Procura + Milestones model. Literature indicates that development has a negative impact on the environment, which includes vegetation loss, illegal dumping, and greenhouse gas emissions. Further, the literature recommends green lifecycle design and production of construction projects to reduce the impact of construction on the environment. A systematic investigation of municipalities by means of interviews with relevant municipal officials involved with the procurement of products and services, infrastructure services and environmental affairs officials made it possible to identify factors that impact on the implementation of green procurement. The investigation finds that the major obstacles to green procurement are socio-economic challenges that confront municipalities, lack of policy, and lack of awareness. Recommendations include the proposal of initiatives that encourage and improve the implementation of green procurement. The study hopes to inspire innovation in the implementation of green procurement in the construction sector.
- Full Text:
- Date Issued: 2015
- Authors: Maboza, Luthando Sithembele
- Date: 2015
- Subjects: Sustainable construction , Construction industry -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/3165 , vital:20407
- Description: The study is a qualitative investigation of the implementation of green procurement in the construction sector at Local Government level. The focus is on the Metropolitan Municipalities of EThekwini, Nelson Mandela Bay and City of Cape Town. For the purpose of realising an extended comparative perspective, an additional three smaller municipalities were also reviewed. Green procurement is the tool used by governments to source the supply of products and services that are environmentally friendly to counter the global problem of climate change. The study commences with the exposition of the aspects of green procurement from the basis of the enabling legal framework to the scholarly contribution from which the study can be predicated. It becomes apparent from this review of legislation that there is a scope within the existing body of legislation for the use of green procurement as an environmental tool. Scholarly work addresses adoption of green procurement and considers, inter alia, the Bottom-up Approach, the Top-down Approach, and the Procura + Milestones model. Literature indicates that development has a negative impact on the environment, which includes vegetation loss, illegal dumping, and greenhouse gas emissions. Further, the literature recommends green lifecycle design and production of construction projects to reduce the impact of construction on the environment. A systematic investigation of municipalities by means of interviews with relevant municipal officials involved with the procurement of products and services, infrastructure services and environmental affairs officials made it possible to identify factors that impact on the implementation of green procurement. The investigation finds that the major obstacles to green procurement are socio-economic challenges that confront municipalities, lack of policy, and lack of awareness. Recommendations include the proposal of initiatives that encourage and improve the implementation of green procurement. The study hopes to inspire innovation in the implementation of green procurement in the construction sector.
- Full Text:
- Date Issued: 2015
Identification of novel SNPSTRs by 454 sequencing in Nguni and Sotho-Tswana populations
- Authors: Laurence, Jo-Anne Elizabeth
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/55885 , vital:26752
- Description: DNA profiling is currently performed by analysis of the electropherogram that results following the amplification of a panel of Short Tandem Repeat (STR) loci. A need has arisen, however, for the development of a typing method that generates results which are compatible and comparable with existing databases, but that have a higher discrimination power by supplying sequence data as well as repeat-number data. Recent studies that explore these alternative typing methodologies have revealed the existence of a number of STR variants. There is, however, little information about the exact nature and prevalence of these sub-alleles. There have also been limited population studies of the genetic profiles of sub-Saharan African populations, despite the fact that evidence suggests that there is greater genetic structure and genetic diversity in these populations. In this study, a processing protocol for the generation of 454 sequencing-ready amplicons of vWA, D2S441, D3S1358, D13S317, D21S11 and D7S820 loci was developed. This protocol was applied to buccal swabs collected from 144 individuals of the Nguni and Sotho-Tswana population groups. A total of 145 485 reads were obtained from the sequencing of these amplicons, of which 97 400 and 48 085 reads were obtained for the Nguni and Sotho-Tswana populations respectively. The proportional representation for each locus ranged from 8-20%, and the allele calls and observed frequencies of these alleles suggested a high degree of relatedness between population groups. The sequencing results, furthermore, enabled the identification of a number of previously undescribed STR variants and SNPSTRs; with allele 13´ for D13S317 representing a SNP that may be predictive of Nguni-ancestry. The results also demonstrated the usefulness of next generation sequencing for increasing the number of discernible alleles for STR profiling.
- Full Text:
- Date Issued: 2015
- Authors: Laurence, Jo-Anne Elizabeth
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/55885 , vital:26752
- Description: DNA profiling is currently performed by analysis of the electropherogram that results following the amplification of a panel of Short Tandem Repeat (STR) loci. A need has arisen, however, for the development of a typing method that generates results which are compatible and comparable with existing databases, but that have a higher discrimination power by supplying sequence data as well as repeat-number data. Recent studies that explore these alternative typing methodologies have revealed the existence of a number of STR variants. There is, however, little information about the exact nature and prevalence of these sub-alleles. There have also been limited population studies of the genetic profiles of sub-Saharan African populations, despite the fact that evidence suggests that there is greater genetic structure and genetic diversity in these populations. In this study, a processing protocol for the generation of 454 sequencing-ready amplicons of vWA, D2S441, D3S1358, D13S317, D21S11 and D7S820 loci was developed. This protocol was applied to buccal swabs collected from 144 individuals of the Nguni and Sotho-Tswana population groups. A total of 145 485 reads were obtained from the sequencing of these amplicons, of which 97 400 and 48 085 reads were obtained for the Nguni and Sotho-Tswana populations respectively. The proportional representation for each locus ranged from 8-20%, and the allele calls and observed frequencies of these alleles suggested a high degree of relatedness between population groups. The sequencing results, furthermore, enabled the identification of a number of previously undescribed STR variants and SNPSTRs; with allele 13´ for D13S317 representing a SNP that may be predictive of Nguni-ancestry. The results also demonstrated the usefulness of next generation sequencing for increasing the number of discernible alleles for STR profiling.
- Full Text:
- Date Issued: 2015
In silico analysis of human Hsp90 for the identification of novel anti-cancer drug target sites and natural compound inhibitors
- Authors: Penkler, David Lawrence
- Date: 2015
- Subjects: Heat shock proteins , Cancer -- Treatment , Molecular chaperones , Homeostasis , Carcinogenesis , Chemotherapy , Ligand binding (Biochemistry) , Protein-protein interactions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4162 , http://hdl.handle.net/10962/d1018938
- Description: The 90-KDa heat shock protein (Hsp90) is part of the molecular chaperone family, and as such it is involved in the regulation of protein homeostasis within cells. Specifically, Hsp90 aids in the folding of nascent proteins and re-folding of denatured proteins. It also plays an important role in the prevention of protein aggregation. Hsp90’s functionality is attributed to its several staged, multi-conformational ATPase cycle, in which associated client proteins are bound and released. Hsp90 is known to be associated with a wide array of client proteins, some of which are thought to be involved in multiple oncogenic processes. Indeed Hsp90 is known to be directly involved in perpetuating the stability and function of multiple mutated, chimeric and over-expressed signalling proteins that are known to promote the growth and survival of cancer cells. Hsp90 inhibitors are thus thought to be promising therapeutic agents for cancer treatment. A lack of a 3D structure of human Hsp90 however has restricted Hsp90 inhibitor development in large to in vivo investigations. This study, aims to investigate and calculate hypothetical homology models of the full human Hsp90 protein, and to probe these structural models for novel drug target sites using several in silico techniques. A multi-template homology modelling methodology was developed and in conjunction with protein-protein docking techniques, two functionally important human Hsp90 structural models were calculated; the nucleotide free “v-like” open and nucleotide bound closed conformations. Based on the conservation of ligand binding, virtual screening experiments conducted on both models using 316 natural compounds indigenous to South Africa, revealed three novel putative target sites. Two binding pockets in close association with important Hsp90-Hop interaction residues and a single binding pocket on the dimerization interface in the C-terminal domain. Targeted molecular docking experiments at these sites revealed two compounds (721395-11-5 and 264624-39-7) as putative inhibitors, both showing strong binding affinities for at least one of the three investigated target sites. Furthermore both compounds were found to only violate one Lipinski’s rules, suggesting their potential as candidates for further drug development. The combined work described here provides a putative platform for the development of next generation inhibitors of human Hsp90.
- Full Text:
- Date Issued: 2015
- Authors: Penkler, David Lawrence
- Date: 2015
- Subjects: Heat shock proteins , Cancer -- Treatment , Molecular chaperones , Homeostasis , Carcinogenesis , Chemotherapy , Ligand binding (Biochemistry) , Protein-protein interactions
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4162 , http://hdl.handle.net/10962/d1018938
- Description: The 90-KDa heat shock protein (Hsp90) is part of the molecular chaperone family, and as such it is involved in the regulation of protein homeostasis within cells. Specifically, Hsp90 aids in the folding of nascent proteins and re-folding of denatured proteins. It also plays an important role in the prevention of protein aggregation. Hsp90’s functionality is attributed to its several staged, multi-conformational ATPase cycle, in which associated client proteins are bound and released. Hsp90 is known to be associated with a wide array of client proteins, some of which are thought to be involved in multiple oncogenic processes. Indeed Hsp90 is known to be directly involved in perpetuating the stability and function of multiple mutated, chimeric and over-expressed signalling proteins that are known to promote the growth and survival of cancer cells. Hsp90 inhibitors are thus thought to be promising therapeutic agents for cancer treatment. A lack of a 3D structure of human Hsp90 however has restricted Hsp90 inhibitor development in large to in vivo investigations. This study, aims to investigate and calculate hypothetical homology models of the full human Hsp90 protein, and to probe these structural models for novel drug target sites using several in silico techniques. A multi-template homology modelling methodology was developed and in conjunction with protein-protein docking techniques, two functionally important human Hsp90 structural models were calculated; the nucleotide free “v-like” open and nucleotide bound closed conformations. Based on the conservation of ligand binding, virtual screening experiments conducted on both models using 316 natural compounds indigenous to South Africa, revealed three novel putative target sites. Two binding pockets in close association with important Hsp90-Hop interaction residues and a single binding pocket on the dimerization interface in the C-terminal domain. Targeted molecular docking experiments at these sites revealed two compounds (721395-11-5 and 264624-39-7) as putative inhibitors, both showing strong binding affinities for at least one of the three investigated target sites. Furthermore both compounds were found to only violate one Lipinski’s rules, suggesting their potential as candidates for further drug development. The combined work described here provides a putative platform for the development of next generation inhibitors of human Hsp90.
- Full Text:
- Date Issued: 2015
In vivo and In vitro investigations to elucidate the associations of B-N-methylamino-L-alanine with proteins
- Authors: Van Onselen, Rianita
- Date: 2015
- Subjects: Cyanobacteria , Bioaccumulation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4923 , vital:20767
- Description: The cyanobacterially synthesized non-canonical amino acid β-N-methylamino-ʟ-alanine (BMAA) has been proposed to be a causative agent in the development of sporadic neurodegenerative diseases. This neurotoxin bioaccumulates and biomagnifies with increasing trophic levels in ecosystems by associating with proteins. It has been suggested that these associations with host proteins also serve as a reservoir from where BMAA is slowly released with normal protein catabolism, resulting in a continuous low level exposure. However, the nature of these associations remains poorly defined. The widely accepted hypothesis regarding the nature of these associations is that BMAA associates with proteins through primary incorporation into proteins with specific replacement of serine. In addition to excitotoxicity, BMAA misincorporation has been proposed as a potential mechanism of toxicity because of its link to protein tangle diseases. Interactions between BMAA and proteins that are not the result of misincorporation, have also been observed. However, the nature of these non-primary associations has not been investigated. This study focussed on establishing whether BMAA is misincorporated into host proteins with consequent toxicity, and on elucidating the nature of the BMAA-protein associations not linked to primary incorporation. In comparative studies between BMAA and canavanine, an arginine analogue known to misincorporate, exposure to BMAA did not result in any toxicity in prokaryotes or in an undifferentiated eukaryotic mammalian cell line, in contrast to what was observed upon canavanine exposure. Differentiation of the cell line with nerve growth factor to express glutamate receptors resulted in marked toxicity upon BMAA exposure, highlighting excitoxicity as the main mechanism of BMAA toxicity. Furthermore, it was demonstrated that BMAA interacts with free amino acids and proteins in the absence of de novo protein synthesis, causing enzyme inhibition and protein misfolding. It was concluded that BMAA does not interact with proteins through primary incorporation and that the observed associations are the result of an interaction between BMAA and amino acid side chains to form covalent bonds.
- Full Text:
- Date Issued: 2015
- Authors: Van Onselen, Rianita
- Date: 2015
- Subjects: Cyanobacteria , Bioaccumulation
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/4923 , vital:20767
- Description: The cyanobacterially synthesized non-canonical amino acid β-N-methylamino-ʟ-alanine (BMAA) has been proposed to be a causative agent in the development of sporadic neurodegenerative diseases. This neurotoxin bioaccumulates and biomagnifies with increasing trophic levels in ecosystems by associating with proteins. It has been suggested that these associations with host proteins also serve as a reservoir from where BMAA is slowly released with normal protein catabolism, resulting in a continuous low level exposure. However, the nature of these associations remains poorly defined. The widely accepted hypothesis regarding the nature of these associations is that BMAA associates with proteins through primary incorporation into proteins with specific replacement of serine. In addition to excitotoxicity, BMAA misincorporation has been proposed as a potential mechanism of toxicity because of its link to protein tangle diseases. Interactions between BMAA and proteins that are not the result of misincorporation, have also been observed. However, the nature of these non-primary associations has not been investigated. This study focussed on establishing whether BMAA is misincorporated into host proteins with consequent toxicity, and on elucidating the nature of the BMAA-protein associations not linked to primary incorporation. In comparative studies between BMAA and canavanine, an arginine analogue known to misincorporate, exposure to BMAA did not result in any toxicity in prokaryotes or in an undifferentiated eukaryotic mammalian cell line, in contrast to what was observed upon canavanine exposure. Differentiation of the cell line with nerve growth factor to express glutamate receptors resulted in marked toxicity upon BMAA exposure, highlighting excitoxicity as the main mechanism of BMAA toxicity. Furthermore, it was demonstrated that BMAA interacts with free amino acids and proteins in the absence of de novo protein synthesis, causing enzyme inhibition and protein misfolding. It was concluded that BMAA does not interact with proteins through primary incorporation and that the observed associations are the result of an interaction between BMAA and amino acid side chains to form covalent bonds.
- Full Text:
- Date Issued: 2015
Investigating integrated catchment management using a simple water quantity and quality model : a case study of the Crocodile River Catchment, South Africa
- Retief, Daniel Christoffel Hugo
- Authors: Retief, Daniel Christoffel Hugo
- Date: 2015
- Subjects: Watersheds -- South Africa -- Krokodilrivier (Mpumalanga) , Integrated water development -- South Africa -- Krokodilrivier (Mpumalanga) , Water quality management -- South Africa -- Krokodilrivier (Mpumalanga) , Water-supply -- South Africa -- Krokodilrivier (Mpumalanga) , Water quality -- Measurement
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6050 , http://hdl.handle.net/10962/d1017875
- Description: Internationally, water resources are facing increasing pressure due to over-exploitation and pollution. Integrated Water Resource Management (IWRM) has been accepted internationally as a paradigm for integrative and sustainable management of water resources. However, in practice, the implementation and success of IWRM policies has been hampered by the lack of availability of integrative decision support tools, especially within the context of limited resources and observed data. This is true for the Crocodile River Catchment (CRC), located within the Mpumalanga Province of South Africa. The catchment has been experiencing a decline in water quality as a result of the point source input of a cocktail of pollutants, which are discharged from industrial and municipal wastewater treatment plants, as well as diffuse source runoff and return flows from the extensive areas of irrigated agriculture and mining sites. The decline in water quality has profound implications for a range of stakeholders across the catchment including increased treatment costs and reduced crop yields. The combination of deteriorating water quality and the lack of understanding of the relationships between water quantity and quality for determining compliance/non-compliance in the CRC have resulted in collaboration between stakeholders, willing to work in a participatory and transparent manner to create an Integrated Water Quality Management Plan (IWQMP). This project aimed to model water quality, (combined water quality and quantity), to facilitate the IWQMP aiding in the understanding of the relationship between water quantity and quality in the CRC. A relatively simple water quality model (WQSAM) was used that receives inputs from established water quantity systems models, and was designed to be a water quality decision support tool for South African catchments. The model was applied to the CRC, achieving acceptable simulations of total dissolved solids (used as a surrogate for salinity) and nutrients (including orthophosphates, nitrates +nitrites and ammonium) for historical conditions. Validation results revealed that there is little consistency within the catchment, attributed to the non-stationary nature of water quality at many of the sites in the CRC. The analyses of the results using a number of representations including, seasonal load distributions, load duration curves and load flow plots, confirmed that the WQSAM model was able to capture the variability of relationships between water quantity and quality, provided that simulated hydrology was sufficiently accurate. The outputs produced by WQSAM was seen as useful for the CRC, with the Inkomati-Usuthu Catchment Management Agency (IUCMA) planning to operationalise the model in 2015. The ability of WQSAM to simulate water quality in data scarce catchments, with constituents that are appropriate for the needs of water resource management within South Africa, is highly beneficial.
- Full Text:
- Date Issued: 2015
- Authors: Retief, Daniel Christoffel Hugo
- Date: 2015
- Subjects: Watersheds -- South Africa -- Krokodilrivier (Mpumalanga) , Integrated water development -- South Africa -- Krokodilrivier (Mpumalanga) , Water quality management -- South Africa -- Krokodilrivier (Mpumalanga) , Water-supply -- South Africa -- Krokodilrivier (Mpumalanga) , Water quality -- Measurement
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6050 , http://hdl.handle.net/10962/d1017875
- Description: Internationally, water resources are facing increasing pressure due to over-exploitation and pollution. Integrated Water Resource Management (IWRM) has been accepted internationally as a paradigm for integrative and sustainable management of water resources. However, in practice, the implementation and success of IWRM policies has been hampered by the lack of availability of integrative decision support tools, especially within the context of limited resources and observed data. This is true for the Crocodile River Catchment (CRC), located within the Mpumalanga Province of South Africa. The catchment has been experiencing a decline in water quality as a result of the point source input of a cocktail of pollutants, which are discharged from industrial and municipal wastewater treatment plants, as well as diffuse source runoff and return flows from the extensive areas of irrigated agriculture and mining sites. The decline in water quality has profound implications for a range of stakeholders across the catchment including increased treatment costs and reduced crop yields. The combination of deteriorating water quality and the lack of understanding of the relationships between water quantity and quality for determining compliance/non-compliance in the CRC have resulted in collaboration between stakeholders, willing to work in a participatory and transparent manner to create an Integrated Water Quality Management Plan (IWQMP). This project aimed to model water quality, (combined water quality and quantity), to facilitate the IWQMP aiding in the understanding of the relationship between water quantity and quality in the CRC. A relatively simple water quality model (WQSAM) was used that receives inputs from established water quantity systems models, and was designed to be a water quality decision support tool for South African catchments. The model was applied to the CRC, achieving acceptable simulations of total dissolved solids (used as a surrogate for salinity) and nutrients (including orthophosphates, nitrates +nitrites and ammonium) for historical conditions. Validation results revealed that there is little consistency within the catchment, attributed to the non-stationary nature of water quality at many of the sites in the CRC. The analyses of the results using a number of representations including, seasonal load distributions, load duration curves and load flow plots, confirmed that the WQSAM model was able to capture the variability of relationships between water quantity and quality, provided that simulated hydrology was sufficiently accurate. The outputs produced by WQSAM was seen as useful for the CRC, with the Inkomati-Usuthu Catchment Management Agency (IUCMA) planning to operationalise the model in 2015. The ability of WQSAM to simulate water quality in data scarce catchments, with constituents that are appropriate for the needs of water resource management within South Africa, is highly beneficial.
- Full Text:
- Date Issued: 2015
Isolation and structure elucidation of halogenated metabolites from Portieria hornemannii and Portieria tripinnata
- Authors: Adam, Mohammed
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64674 , vital:28591
- Description: The red marine algal genus, Portieria, is known to produce a number of potent cytotoxic compounds with anticancer potential. The most important anticancer lead produced by this genus is the compound halomon. Unfortunately, the lack of sufficient quantities of this compound hampered its further development. Two Portieria species, Portieria hornemannii and Portieria tripinnata, are found along the South African coastline. Recent studies, based on DNA analysis, suggest that Portieria hornemannii may in fact be divided into several cryptic species. The current project is part of a larger study designed to investigate the use of secondary metabolites to identify new marine algal species. In this study 1H NMR profiles of the organic extracts of selected Portieria spp were compared in order to identify new species. Selected compounds were then isolated and characterised as potential chemotaxonomic markers. Four halogenated monoterpenes were isolated from Portieria hornemannii. Two of these were new compounds 4-(3-bromo-4-chloro-4-methylpentyl)-3-chlorofuran-2(5H)-one, which were isomers of each other. The two known compounds had been previously isolated from Portieria hornemannii samples off the Madagascar coast. These compounds could prove to be useful as chemotaxonomic marker compounds, as they have never been isolated from any other species of marine algae. Three known halogenated monoterpenes were isolated from Portieria tripinnata. These compounds had been previously isolated from different species of marine algae and therefore, could not serve as chemotaxonomic marker compounds for this species of marine alga. Further work needs to be done on Portieria tripinnata, with regards to its chemistry, as it is a species of marine algae that has not been previously researched.
- Full Text:
- Date Issued: 2015
- Authors: Adam, Mohammed
- Date: 2015
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64674 , vital:28591
- Description: The red marine algal genus, Portieria, is known to produce a number of potent cytotoxic compounds with anticancer potential. The most important anticancer lead produced by this genus is the compound halomon. Unfortunately, the lack of sufficient quantities of this compound hampered its further development. Two Portieria species, Portieria hornemannii and Portieria tripinnata, are found along the South African coastline. Recent studies, based on DNA analysis, suggest that Portieria hornemannii may in fact be divided into several cryptic species. The current project is part of a larger study designed to investigate the use of secondary metabolites to identify new marine algal species. In this study 1H NMR profiles of the organic extracts of selected Portieria spp were compared in order to identify new species. Selected compounds were then isolated and characterised as potential chemotaxonomic markers. Four halogenated monoterpenes were isolated from Portieria hornemannii. Two of these were new compounds 4-(3-bromo-4-chloro-4-methylpentyl)-3-chlorofuran-2(5H)-one, which were isomers of each other. The two known compounds had been previously isolated from Portieria hornemannii samples off the Madagascar coast. These compounds could prove to be useful as chemotaxonomic marker compounds, as they have never been isolated from any other species of marine algae. Three known halogenated monoterpenes were isolated from Portieria tripinnata. These compounds had been previously isolated from different species of marine algae and therefore, could not serve as chemotaxonomic marker compounds for this species of marine alga. Further work needs to be done on Portieria tripinnata, with regards to its chemistry, as it is a species of marine algae that has not been previously researched.
- Full Text:
- Date Issued: 2015
Link between ghost artefacts, source suppression and incomplete calibration sky models
- Authors: Nunhokee, Chuneeta Devi
- Date: 2015
- Subjects: Interferometry , Calibration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5556 , http://hdl.handle.net/10962/d1017900
- Description: Calibration is a fundamental step towards producing radio interferometric images. However, naive calibration produces calibration artefacts, in the guise of spurious emission, buried in the thermal noise. This work investigates these calibration artefacts, henceforth referred to as “ghosts”. A 21 cm observation with the Westerbork Synthesis Radio Telescope yielded similar ghost sources, and it was anticipated that they were due to calibrating with incomplete sky models. An analytical ghost distribution of a two-source scenario is derived to substantiate this theory and to seek answers to the related bewildering features (regular ghost pattern, points spread function-like sidelobes, independent of model flux). The theoretically predicted ghost distribution qualitatively matches with the observational ones and shows high dependence on the array geometry. The theory draws the conclusion that both the ghost phenomenon and suppression of the unmodelled flux have the same root cause. In addition, the suppression of the unmodelled flux is studied as functions of unmodelled flux, differential gain solution interval and the number of sources subjected to direction-dependent gains. These studies summarise that the suppression rate is constant irrespective of the degree of incompleteness of the calibration sky model. In the presence of a direction-dependent effect, the suppression drastically increases; however, this increase can be compensated for by using longer solution intervals.
- Full Text:
- Date Issued: 2015
- Authors: Nunhokee, Chuneeta Devi
- Date: 2015
- Subjects: Interferometry , Calibration
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5556 , http://hdl.handle.net/10962/d1017900
- Description: Calibration is a fundamental step towards producing radio interferometric images. However, naive calibration produces calibration artefacts, in the guise of spurious emission, buried in the thermal noise. This work investigates these calibration artefacts, henceforth referred to as “ghosts”. A 21 cm observation with the Westerbork Synthesis Radio Telescope yielded similar ghost sources, and it was anticipated that they were due to calibrating with incomplete sky models. An analytical ghost distribution of a two-source scenario is derived to substantiate this theory and to seek answers to the related bewildering features (regular ghost pattern, points spread function-like sidelobes, independent of model flux). The theoretically predicted ghost distribution qualitatively matches with the observational ones and shows high dependence on the array geometry. The theory draws the conclusion that both the ghost phenomenon and suppression of the unmodelled flux have the same root cause. In addition, the suppression of the unmodelled flux is studied as functions of unmodelled flux, differential gain solution interval and the number of sources subjected to direction-dependent gains. These studies summarise that the suppression rate is constant irrespective of the degree of incompleteness of the calibration sky model. In the presence of a direction-dependent effect, the suppression drastically increases; however, this increase can be compensated for by using longer solution intervals.
- Full Text:
- Date Issued: 2015
Long term effects of temperature and humidity on lignocellulosic fibres and composites
- Authors: Molaba, Tshepiso Princess
- Date: 2015
- Subjects: Lignocellulose Fibrous composites Textile fabrics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/10276 , vital:26648
- Description: The study deals with the chemical and flame retardant (FR) treatment of woven flax fabric and preparation and characterization of flax reinforced phenolic composites. Sheets of flax fabric were subjected to chemical treatments using NaOH and silane coupling agents. A phosphate-based flame retardant (DAP) was applied to decrease the flammability of the flax fabric. The effect of the chemical treatments and FR treatments on the thermal and flammability properties of the fabric and composites was investigated using thermogravimetric analysis (TGA), vertical flame resistance test and cone calorimeter. The mechanical properties of the flax fabric and composites, before and after environmental ageing, were investigated. Ageing studies were carried out by exposing the samples in an environmental chamber at specified conditions for two weeks. TGA results showed that the treatment of the fabric with FR shifts the decomposition temperature to lower level and increases the char residue. Vertical flame resistance testing showed that FR treatment of the flax fabric improved the flammability properties. There was no after flame and afterglow observed for FR treated flax fabric due to self-extinguishment after removal of the flame. Flax Fabric without FR burned completely and there was no result for the char length due to the complete destruction of the fabric. The FR treatment, however, seemed to have had a negative effect on the tensile strength of the flax fabric. This was further intensified upon exposure of FR treated flax fabric to high temperatures during ageing studies which drastically reduced the tensile strength by more than 90%, and the flax fabric were found to be brittle and darker in visual appearance. TGA results of flax/phenolic composites showed that for composites containing chemically treated and FR treated flax fabric the decomposition temperatures shifted to lower temperatures; however there was no significant difference in the amount of char residue. Untreated flax/phenolic composites exhibited the lowest char residue. Cone calorimeter results showed that the peak heat release rate (PHRR), smoke production rate (SPR) and carbon dioxide (CO2) emission rate was reduced for the flax/phenolic composite produced using FR treated flax fabric. The tensile strength of these composites was reduced while there was an increase in modulus value. Exposure of the FR treated composites to high temperatures further reduced the tensile strength and increased the E-modulus. Both FR treated and untreated composites changed in colour and the FR treated composites were found to be brittle after exposure to high temperatures.
- Full Text:
- Date Issued: 2015
- Authors: Molaba, Tshepiso Princess
- Date: 2015
- Subjects: Lignocellulose Fibrous composites Textile fabrics
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/10276 , vital:26648
- Description: The study deals with the chemical and flame retardant (FR) treatment of woven flax fabric and preparation and characterization of flax reinforced phenolic composites. Sheets of flax fabric were subjected to chemical treatments using NaOH and silane coupling agents. A phosphate-based flame retardant (DAP) was applied to decrease the flammability of the flax fabric. The effect of the chemical treatments and FR treatments on the thermal and flammability properties of the fabric and composites was investigated using thermogravimetric analysis (TGA), vertical flame resistance test and cone calorimeter. The mechanical properties of the flax fabric and composites, before and after environmental ageing, were investigated. Ageing studies were carried out by exposing the samples in an environmental chamber at specified conditions for two weeks. TGA results showed that the treatment of the fabric with FR shifts the decomposition temperature to lower level and increases the char residue. Vertical flame resistance testing showed that FR treatment of the flax fabric improved the flammability properties. There was no after flame and afterglow observed for FR treated flax fabric due to self-extinguishment after removal of the flame. Flax Fabric without FR burned completely and there was no result for the char length due to the complete destruction of the fabric. The FR treatment, however, seemed to have had a negative effect on the tensile strength of the flax fabric. This was further intensified upon exposure of FR treated flax fabric to high temperatures during ageing studies which drastically reduced the tensile strength by more than 90%, and the flax fabric were found to be brittle and darker in visual appearance. TGA results of flax/phenolic composites showed that for composites containing chemically treated and FR treated flax fabric the decomposition temperatures shifted to lower temperatures; however there was no significant difference in the amount of char residue. Untreated flax/phenolic composites exhibited the lowest char residue. Cone calorimeter results showed that the peak heat release rate (PHRR), smoke production rate (SPR) and carbon dioxide (CO2) emission rate was reduced for the flax/phenolic composite produced using FR treated flax fabric. The tensile strength of these composites was reduced while there was an increase in modulus value. Exposure of the FR treated composites to high temperatures further reduced the tensile strength and increased the E-modulus. Both FR treated and untreated composites changed in colour and the FR treated composites were found to be brittle after exposure to high temperatures.
- Full Text:
- Date Issued: 2015
Mapping and prediction of archaeological sites of habitation by modern humans using GIS and expert mapping on the south coast of South Africa
- Authors: Kleyn, Philippa May
- Date: 2015
- Subjects: Geographic information systems -- South Africa , Archaeological sites , Kitchen-middens -- South Africa , Prehistoric peoples -- South Africa , Prehistoric peoples -- Dwellings -- South Africa , Geological mapping -- South Africa , Coastal archaeology -- South Africa , Archaeological significance -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4890 , http://hdl.handle.net/10962/d1018662
- Description: South Africa contains many archaeological resources including shell middens from the Middle Stone Age (MSA) and Later Stone Age (LSA). These shell middens give researchers insight into the behaviour of modern humans where the first fossil evidence appears in Africa around 200 000 years ago (Klein, 2008). Research into shell middens is therefore vital to understand the origin of human kind. This study investigates whether Geographical Information Systems (GIS) is a useful tool for predicting locations of unknown shell midden sites using the characteristics of known areas of modern human habitation. This was done using suitability analysis and expert mapping techniques. Ground truthing of the results of the desktop analysis revealed that GIS is not a useful tool for predicting sites of modern habitation as the characteristics that determine human habitation are too variable.
- Full Text:
- Date Issued: 2015
- Authors: Kleyn, Philippa May
- Date: 2015
- Subjects: Geographic information systems -- South Africa , Archaeological sites , Kitchen-middens -- South Africa , Prehistoric peoples -- South Africa , Prehistoric peoples -- Dwellings -- South Africa , Geological mapping -- South Africa , Coastal archaeology -- South Africa , Archaeological significance -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4890 , http://hdl.handle.net/10962/d1018662
- Description: South Africa contains many archaeological resources including shell middens from the Middle Stone Age (MSA) and Later Stone Age (LSA). These shell middens give researchers insight into the behaviour of modern humans where the first fossil evidence appears in Africa around 200 000 years ago (Klein, 2008). Research into shell middens is therefore vital to understand the origin of human kind. This study investigates whether Geographical Information Systems (GIS) is a useful tool for predicting locations of unknown shell midden sites using the characteristics of known areas of modern human habitation. This was done using suitability analysis and expert mapping techniques. Ground truthing of the results of the desktop analysis revealed that GIS is not a useful tool for predicting sites of modern habitation as the characteristics that determine human habitation are too variable.
- Full Text:
- Date Issued: 2015
Microbiological analyses of beef slaughtering process and meat safety knowledge of handlers at selected high and low thoughput abattoirs
- Authors: Nyamakwere, Faith
- Date: 2015
- Subjects: Slaughtering and slaughter-houses -- South Africa -- Eastern Cape Meat industry and trade -- Quality control Beef -- Quality -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2238 , vital:27712
- Description: The objective of the study was to evaluate meat hygiene practices among meat handlers and microbiological analysis of beef carcasses, slaughtermen hands, equipment and water from low throughput (LTA) and high throughput (HTA) abattoirs in the Eastern Cape Province of South Africa. In stage one of the study, the level of knowledge, practices and attitudes towards meat safety and personal hygiene of slaughtermen were assessed. Forty workers directly involve in beef cattle slaughtering process were surveyed. Data were collected using a structured questionnaire, it contained questions on some of the most important meat safety cues such as knowledge, attitudes, personal hygiene and handling practices. Cross tabulation and Chi-square Test of Association were performed to examine the relationships between the demographic information and the knowledge regarding meat safety using the Statistical Package for Social Sciences (SPSS) version 22. Overall, a significant adherence to basic hygiene practices and a satisfactory level of knowledge were observed. Workers from a HTA yielded comparatively better statistically significant scores. Moreover, knowledge and practices of respondents were significantly associated (P<0.05) due to educational level and professional training. The second stage of the study involved evaluating the level to which cattle carcass, equipment, slaughtermen hands and water were contaminated with Enterobacteriaceae, Salmonella, Escherichia coli and aerobic colony counts (ACC) at different stages during the slaughter process (skinning, evisceration, carcass slitting, inspection, washing and packing). Cattle carcasses were sampled at four sites (rump, neck, flank and brisket) from a LTA (n= 240) and HTA (n= 384) abattoirs. Using conventional biochemical tests, HTA yielded significantly (P<0.05) higher ACC (5.2 log CFU/cm2), E. coli (2.6 log CFU/cm2) and Enterobacteriaceae (2.9 log CFU/cm2) carcass mean scores than LTA after skinning and evisceration. Specific abattoir hygiene differences were noted from washed and chilled carcasses. Salmonella was not detected across all sampled slaughter process stages. In addition, the equipment had bacterial load ranging from 10 to 4 CFU/cm2 for LTA, whereas in HTA this was found to be 7 to 3 CFU/cm2. The bacterial counts for slaughtermen hands were estimated to be 15 to 8 CFU/cm2 in HTA and 10 to 5 CFU/cm2 in LTA. Overall, slaughtermen hands and equipment in the dirty area (skinning and evisceration) yielded more bacterial counts compared to those in the clean area (slitting, inspection, washing and packing) from both abattoirs. For all the sampled carcasses, equipment and slaughtermen hands, HTA yielded comparatively higher (P<0.05) bacterial counts than the LTA. Although the results showed a significant adherence to basic hygiene practices, some aspects such as routine medical examination, health certificates and professional training of slaughtermen still need to be improved. Therefore, these findings show that slaughtermen, equipment and water can be sources of contamination during the slaughter process.
- Full Text:
- Date Issued: 2015
- Authors: Nyamakwere, Faith
- Date: 2015
- Subjects: Slaughtering and slaughter-houses -- South Africa -- Eastern Cape Meat industry and trade -- Quality control Beef -- Quality -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/2238 , vital:27712
- Description: The objective of the study was to evaluate meat hygiene practices among meat handlers and microbiological analysis of beef carcasses, slaughtermen hands, equipment and water from low throughput (LTA) and high throughput (HTA) abattoirs in the Eastern Cape Province of South Africa. In stage one of the study, the level of knowledge, practices and attitudes towards meat safety and personal hygiene of slaughtermen were assessed. Forty workers directly involve in beef cattle slaughtering process were surveyed. Data were collected using a structured questionnaire, it contained questions on some of the most important meat safety cues such as knowledge, attitudes, personal hygiene and handling practices. Cross tabulation and Chi-square Test of Association were performed to examine the relationships between the demographic information and the knowledge regarding meat safety using the Statistical Package for Social Sciences (SPSS) version 22. Overall, a significant adherence to basic hygiene practices and a satisfactory level of knowledge were observed. Workers from a HTA yielded comparatively better statistically significant scores. Moreover, knowledge and practices of respondents were significantly associated (P<0.05) due to educational level and professional training. The second stage of the study involved evaluating the level to which cattle carcass, equipment, slaughtermen hands and water were contaminated with Enterobacteriaceae, Salmonella, Escherichia coli and aerobic colony counts (ACC) at different stages during the slaughter process (skinning, evisceration, carcass slitting, inspection, washing and packing). Cattle carcasses were sampled at four sites (rump, neck, flank and brisket) from a LTA (n= 240) and HTA (n= 384) abattoirs. Using conventional biochemical tests, HTA yielded significantly (P<0.05) higher ACC (5.2 log CFU/cm2), E. coli (2.6 log CFU/cm2) and Enterobacteriaceae (2.9 log CFU/cm2) carcass mean scores than LTA after skinning and evisceration. Specific abattoir hygiene differences were noted from washed and chilled carcasses. Salmonella was not detected across all sampled slaughter process stages. In addition, the equipment had bacterial load ranging from 10 to 4 CFU/cm2 for LTA, whereas in HTA this was found to be 7 to 3 CFU/cm2. The bacterial counts for slaughtermen hands were estimated to be 15 to 8 CFU/cm2 in HTA and 10 to 5 CFU/cm2 in LTA. Overall, slaughtermen hands and equipment in the dirty area (skinning and evisceration) yielded more bacterial counts compared to those in the clean area (slitting, inspection, washing and packing) from both abattoirs. For all the sampled carcasses, equipment and slaughtermen hands, HTA yielded comparatively higher (P<0.05) bacterial counts than the LTA. Although the results showed a significant adherence to basic hygiene practices, some aspects such as routine medical examination, health certificates and professional training of slaughtermen still need to be improved. Therefore, these findings show that slaughtermen, equipment and water can be sources of contamination during the slaughter process.
- Full Text:
- Date Issued: 2015
Montane Wetlands of the South African Great Escarpment : plant communities and environmental drivers
- Authors: Janks, Matthew Richard
- Date: 2015
- Subjects: Mountain plants -- South Africa -- Eastern Cape , Wetland plants -- South Africa -- Eastern Cape , Wetland plants -- Effect of altitude on -- South Africa -- Eastern Cape , Wetland ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4274 , http://hdl.handle.net/10962/d1018917
- Description: Wetlands provide a number of valuable functions to both the surrounding environment and society. The anaerobic conditions created by flooding in wetlands provide a habitat that supports unique assemblages of plant life. High altitude wetlands are amongst the most species-rich in South Africa. They house a number of rare species and play a vital role in the supply of water to lower lying areas. These are some of the reasons that mountain wetlands are of high conservation value. A phytosociological study was undertaken on the high altitude wetlands of the Great Escarpment with the aim of classifying the plant communities and identifying the environmental drivers of plant community patterns within these ecosystems. Data collection was focused in the Eastern Cape and was supplemented with data from existing studies to gain a more complete understanding of the wetlands of the Great Escarpment of South Africa. Using the Braun-Blanquet approach, Hierarchical Cluster Analysis and Indicator Species Analysis; five broad wetland groups were identified, comprised of 33 individual plant communities and 81 indicator species. Multivariate analysis, including Canonical Correspondence Analysis revealed that the effects of altitude, such as temperature and rainfall, are the most significant large-scale drivers of vegetation patterns. Smaller scale drivers include wetness and soil nutrients including nitrogen, phosphorus, electrical conductivity, sodium, and organic content. The identification of indicator species served to reveal potentially important wetland species across different areas of the Great Escarpment. The effects of altitude on plant community patterns highlights the susceptibility of the high altitude specific communities to upward temperature zone shifts resulting from global warming. Other threats include livestock trampling, water extraction, and land use change for agricultural purposes. The relative absence of alien species in these wetlands gives an indication of their pristine condition and therefore their importance as a reference from which they may be monitored. A large proportion of the wetlands studied here occur outside protected areas, and given the rate of wetland loss in South Africa, it is important that continued effective land management is practiced to ensure that these ecosystems are conserved in the future .
- Full Text:
- Date Issued: 2015
Montane Wetlands of the South African Great Escarpment : plant communities and environmental drivers
- Authors: Janks, Matthew Richard
- Date: 2015
- Subjects: Mountain plants -- South Africa -- Eastern Cape , Wetland plants -- South Africa -- Eastern Cape , Wetland plants -- Effect of altitude on -- South Africa -- Eastern Cape , Wetland ecology -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4274 , http://hdl.handle.net/10962/d1018917
- Description: Wetlands provide a number of valuable functions to both the surrounding environment and society. The anaerobic conditions created by flooding in wetlands provide a habitat that supports unique assemblages of plant life. High altitude wetlands are amongst the most species-rich in South Africa. They house a number of rare species and play a vital role in the supply of water to lower lying areas. These are some of the reasons that mountain wetlands are of high conservation value. A phytosociological study was undertaken on the high altitude wetlands of the Great Escarpment with the aim of classifying the plant communities and identifying the environmental drivers of plant community patterns within these ecosystems. Data collection was focused in the Eastern Cape and was supplemented with data from existing studies to gain a more complete understanding of the wetlands of the Great Escarpment of South Africa. Using the Braun-Blanquet approach, Hierarchical Cluster Analysis and Indicator Species Analysis; five broad wetland groups were identified, comprised of 33 individual plant communities and 81 indicator species. Multivariate analysis, including Canonical Correspondence Analysis revealed that the effects of altitude, such as temperature and rainfall, are the most significant large-scale drivers of vegetation patterns. Smaller scale drivers include wetness and soil nutrients including nitrogen, phosphorus, electrical conductivity, sodium, and organic content. The identification of indicator species served to reveal potentially important wetland species across different areas of the Great Escarpment. The effects of altitude on plant community patterns highlights the susceptibility of the high altitude specific communities to upward temperature zone shifts resulting from global warming. Other threats include livestock trampling, water extraction, and land use change for agricultural purposes. The relative absence of alien species in these wetlands gives an indication of their pristine condition and therefore their importance as a reference from which they may be monitored. A large proportion of the wetlands studied here occur outside protected areas, and given the rate of wetland loss in South Africa, it is important that continued effective land management is practiced to ensure that these ecosystems are conserved in the future .
- Full Text:
- Date Issued: 2015
Multi linear regression-based modeling and performance monitoring of flat plate solar collector outlet temperature in Alice, South Africa
- Authors: Ndlovu, Nothando
- Date: 2015
- Subjects: Solar collectors Solar water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12676 , vital:39298
- Description: In a period of rapidly increasing energy demand, the exploitation of abundantly available solar energy is imperative. Temperate climates like South Africa show good potential for utilizing solar-driven technologies such as solar water heaters. These systems offer an attractive alternative over conventional water geysers as a means to supply hot water for residential use. In South Africa, the solar water heater industry is growing rapidly as the government offers incentives manufactures and consumers. This necessitates the determination of performance of these systems through experimental analysis as well as performance prediction. This study evaluated the summer and winter performance of a flat plate, thermosyphon solar water heater under climatic conditions encountered in Alice, South Africa by considering the collector outlet temperature. The performance and weather data obtained were used to develop a multi linear regression (MLR) model for each season. MLR is a simple and easily applicable modelling approach which uses a set of input and output data to determine the model coefficients of a linear relation of two or more variables. The collector outlet temperature was correlated with solar radiation, ambient temperature, relative humidity, and collector inlet temperature since these variables have a direct impact on the collector temperature rise. Results from the performance showed that the collector performs well, attaining temperatures up to 87.2oC during the summer season and 70oC during winter season. The summer and winter percentage mean absolute error for the whole monitoring period were 4.07 percent and 6.2 percent respectively which indicate that MLR can be successfully applied to predict collector outlet temperatures in both seasons.
- Full Text:
- Date Issued: 2015
- Authors: Ndlovu, Nothando
- Date: 2015
- Subjects: Solar collectors Solar water heaters
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/12676 , vital:39298
- Description: In a period of rapidly increasing energy demand, the exploitation of abundantly available solar energy is imperative. Temperate climates like South Africa show good potential for utilizing solar-driven technologies such as solar water heaters. These systems offer an attractive alternative over conventional water geysers as a means to supply hot water for residential use. In South Africa, the solar water heater industry is growing rapidly as the government offers incentives manufactures and consumers. This necessitates the determination of performance of these systems through experimental analysis as well as performance prediction. This study evaluated the summer and winter performance of a flat plate, thermosyphon solar water heater under climatic conditions encountered in Alice, South Africa by considering the collector outlet temperature. The performance and weather data obtained were used to develop a multi linear regression (MLR) model for each season. MLR is a simple and easily applicable modelling approach which uses a set of input and output data to determine the model coefficients of a linear relation of two or more variables. The collector outlet temperature was correlated with solar radiation, ambient temperature, relative humidity, and collector inlet temperature since these variables have a direct impact on the collector temperature rise. Results from the performance showed that the collector performs well, attaining temperatures up to 87.2oC during the summer season and 70oC during winter season. The summer and winter percentage mean absolute error for the whole monitoring period were 4.07 percent and 6.2 percent respectively which indicate that MLR can be successfully applied to predict collector outlet temperatures in both seasons.
- Full Text:
- Date Issued: 2015
Nanofiber immobilized cellulases and hemicellulases for fruit waste beneficiation
- Authors: Swart, Shanna
- Date: 2015
- Subjects: Agricultural wastes , Cellulase , Hemicellulose , Nanofibers , Electrospinning , Lignocellulose -- Biodegradation , Biomass conversion , Polysaccharides , Immobilized enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4153 , http://hdl.handle.net/10962/d1017914
- Full Text:
- Date Issued: 2015
- Authors: Swart, Shanna
- Date: 2015
- Subjects: Agricultural wastes , Cellulase , Hemicellulose , Nanofibers , Electrospinning , Lignocellulose -- Biodegradation , Biomass conversion , Polysaccharides , Immobilized enzymes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4153 , http://hdl.handle.net/10962/d1017914
- Full Text:
- Date Issued: 2015
Natural resource use as a coping and adaptation strategy to floods of vulnerable populations in the Eastern Cape
- Sachikonye, Mwazvita Tapiwa Beatrice
- Authors: Sachikonye, Mwazvita Tapiwa Beatrice
- Date: 2015
- Subjects: Flood damage prevention -- South Africa -- Eastern Cape , Natural resources -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Human ecology -- South Africa -- Eastern Cape , Nature -- Effect of human beings on -- South Africa -- Eastern Cape , Human beings -- Effect of environment on -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4786 , http://hdl.handle.net/10962/d1018194
- Description: Many of the anticipated increased occurances of natural hazards are not only a consequence of climate change, but rather of rapid and widespread land cover change and the subsequent loss of the buffering capacity provided by healthy ecosystems against natural hazards. Unplanned and unmanaged developments in informal settlements limit government’s ability to mitigate and manage, pointing towards natural resources as being integral for vulnerable communities in developing countries to cope with and mitigate flood disasters. There is a lack of understanding on how natural resources contribute to resilience of vulnerable populations in the Eastern Cape and how they are impacted by these populations before, during and after a flood shock. There also exists a gap in knowledge on how natural resources can mitigate the physical impacts of flooding in South Africa, more so in the Eastern Cape province. Using household questionnaires and GIS techniques, the strategies that households used to recover from the October 2012-February 2013 flood shocks were investigated in informal settlements of three towns (Grahamstown, Port Alfred and Port St Johns). Within the vulnerability paradigm and the sustainable livelihood framework, the study also quantified and evaluated the relative contribution of natural resources to recovery strategies, and lastly, the study investigated how patterns of land use, state of natural vegetation and household topographical location exacerbated or diminished the physical impacts of flooding. This study found that natural resources contributed up to 70 percent to recovery of households from the flood shock, most of this being to reconstruction of housing structures after the flood, less so to economic recovery. It was also found that at a settlement scale the buffering effect of vegetation, although variable amongst settlements, was significant. Settlements that were dominated by dense bush and small trees experienced up to 46 percent less impacts on their property than those surrounded by bare gravel and impervious roofs with degraded environments. The main findings of the research show that natural resources reduce the vulnerability of households in informal settlements to flooding in two significant ways; by physically mitigating against damage to shelters and by also providing an emergency-net function that substitutes financial capital in households. Their inclusion in disaster management has the potential to encourage the sustainable livelihoods of the urban poor in the Eastern Cape
- Full Text:
- Date Issued: 2015
- Authors: Sachikonye, Mwazvita Tapiwa Beatrice
- Date: 2015
- Subjects: Flood damage prevention -- South Africa -- Eastern Cape , Natural resources -- South Africa -- Eastern Cape , Land use -- South Africa -- Eastern Cape , Human ecology -- South Africa -- Eastern Cape , Nature -- Effect of human beings on -- South Africa -- Eastern Cape , Human beings -- Effect of environment on -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4786 , http://hdl.handle.net/10962/d1018194
- Description: Many of the anticipated increased occurances of natural hazards are not only a consequence of climate change, but rather of rapid and widespread land cover change and the subsequent loss of the buffering capacity provided by healthy ecosystems against natural hazards. Unplanned and unmanaged developments in informal settlements limit government’s ability to mitigate and manage, pointing towards natural resources as being integral for vulnerable communities in developing countries to cope with and mitigate flood disasters. There is a lack of understanding on how natural resources contribute to resilience of vulnerable populations in the Eastern Cape and how they are impacted by these populations before, during and after a flood shock. There also exists a gap in knowledge on how natural resources can mitigate the physical impacts of flooding in South Africa, more so in the Eastern Cape province. Using household questionnaires and GIS techniques, the strategies that households used to recover from the October 2012-February 2013 flood shocks were investigated in informal settlements of three towns (Grahamstown, Port Alfred and Port St Johns). Within the vulnerability paradigm and the sustainable livelihood framework, the study also quantified and evaluated the relative contribution of natural resources to recovery strategies, and lastly, the study investigated how patterns of land use, state of natural vegetation and household topographical location exacerbated or diminished the physical impacts of flooding. This study found that natural resources contributed up to 70 percent to recovery of households from the flood shock, most of this being to reconstruction of housing structures after the flood, less so to economic recovery. It was also found that at a settlement scale the buffering effect of vegetation, although variable amongst settlements, was significant. Settlements that were dominated by dense bush and small trees experienced up to 46 percent less impacts on their property than those surrounded by bare gravel and impervious roofs with degraded environments. The main findings of the research show that natural resources reduce the vulnerability of households in informal settlements to flooding in two significant ways; by physically mitigating against damage to shelters and by also providing an emergency-net function that substitutes financial capital in households. Their inclusion in disaster management has the potential to encourage the sustainable livelihoods of the urban poor in the Eastern Cape
- Full Text:
- Date Issued: 2015
Nonlinear optical studies of phthalocyanines and triazatetrabenzcorroles in solution and in thin films
- Authors: Mkhize, Nhlakanipho Colin
- Date: 2015
- Subjects: Phthalocyanines , Thin films , Nonlinear optics , Phosphorus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4542 , http://hdl.handle.net/10962/d1017922
- Description: This work presents photophysical and nonlinear optical properties of a novel Cd 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (CdOtBPPc) and compared with those of Pb 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (PbOtBPPc). For both the CdOtBPPc and PbOtBPPc, third order imaginary susceptibility and second order hyperpolarizability values were found to be within the limit set for good optical limiters. The Pcs were embedded in poly (methyl methacrylate) (PMMA) and poly(bisphenol A carbonate) (PBC) as thin films. The optical limiting values of the Pcs once embedded in film were found to be greatly improved and the limiting intensity of each film was well below the maximum threshold. Both PbOtBPPc and CdOtBPPc showed better optical limiting when embedded in PBC compared to PMMA. CdOtBPPc shows better nonlinear optical behaviour than PbOtBPPc in solution and as thin films, even though the former is aggregated in solution. Novel phosphorus triazatetrabenzcorroles (TBC) tetrasubstituted at the α- and β- and octa substituted at the β- positions of the peripheral fused benzene rings with t-butylphenoxy substituents were prepared and characterized. The effects of the substituents and the missing aza-nitrogen on the electronic structures and optical spectroscopy are investigated with TD-DFT calculations and MCD spectroscopy. The optical limiting properties were investigated to examine whether the lower symmetry that results from the direct pyrrole-pyrrole bond and hence the permanent dipole moment that is introduced result in higher safety thresholds, relative to the values that have been reported for phthalocyanines. The suitability of the compounds for singlet oxygen applications has also been examined. Novel phosphorus phthalocyanines, analogous to the triazatetrabenzcorroles were also investigated. Due to their high photodegradation quantum yield however, only the fluorescence quantum yields and lifetimes were able to be determined.
- Full Text:
- Date Issued: 2015
- Authors: Mkhize, Nhlakanipho Colin
- Date: 2015
- Subjects: Phthalocyanines , Thin films , Nonlinear optics , Phosphorus
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4542 , http://hdl.handle.net/10962/d1017922
- Description: This work presents photophysical and nonlinear optical properties of a novel Cd 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (CdOtBPPc) and compared with those of Pb 2,3-[octakis{4-tert-butylphenoxyphthalocyanine}] (PbOtBPPc). For both the CdOtBPPc and PbOtBPPc, third order imaginary susceptibility and second order hyperpolarizability values were found to be within the limit set for good optical limiters. The Pcs were embedded in poly (methyl methacrylate) (PMMA) and poly(bisphenol A carbonate) (PBC) as thin films. The optical limiting values of the Pcs once embedded in film were found to be greatly improved and the limiting intensity of each film was well below the maximum threshold. Both PbOtBPPc and CdOtBPPc showed better optical limiting when embedded in PBC compared to PMMA. CdOtBPPc shows better nonlinear optical behaviour than PbOtBPPc in solution and as thin films, even though the former is aggregated in solution. Novel phosphorus triazatetrabenzcorroles (TBC) tetrasubstituted at the α- and β- and octa substituted at the β- positions of the peripheral fused benzene rings with t-butylphenoxy substituents were prepared and characterized. The effects of the substituents and the missing aza-nitrogen on the electronic structures and optical spectroscopy are investigated with TD-DFT calculations and MCD spectroscopy. The optical limiting properties were investigated to examine whether the lower symmetry that results from the direct pyrrole-pyrrole bond and hence the permanent dipole moment that is introduced result in higher safety thresholds, relative to the values that have been reported for phthalocyanines. The suitability of the compounds for singlet oxygen applications has also been examined. Novel phosphorus phthalocyanines, analogous to the triazatetrabenzcorroles were also investigated. Due to their high photodegradation quantum yield however, only the fluorescence quantum yields and lifetimes were able to be determined.
- Full Text:
- Date Issued: 2015