Prediction of protein secondary structure using binary classificationtrees, naive Bayes classifiers and the Logistic Regression Classifier
- Eldud Omer, Ahmed Abdelkarim
- Authors: Eldud Omer, Ahmed Abdelkarim
- Date: 2016
- Subjects: Bayesian statistical decision theory , Logistic regression analysis , Biostatistics , Proteins -- Structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5581 , http://hdl.handle.net/10962/d1019985
- Description: The secondary structure of proteins is predicted using various binary classifiers. The data are adopted from the RS126 database. The original data consists of protein primary and secondary structure sequences. The original data is encoded using alphabetic letters. These data are encoded into unary vectors comprising ones and zeros only. Different binary classifiers, namely the naive Bayes, logistic regression and classification trees using hold-out and 5-fold cross validation are trained using the encoded data. For each of the classifiers three classification tasks are considered, namely helix against not helix (H/∼H), sheet against not sheet (S/∼S) and coil against not coil (C/∼C). The performance of these binary classifiers are compared using the overall accuracy in predicting the protein secondary structure for various window sizes. Our result indicate that hold-out cross validation achieved higher accuracy than 5-fold cross validation. The Naive Bayes classifier, using 5-fold cross validation achieved, the lowest accuracy for predicting helix against not helix. The classification tree classifiers, using 5-fold cross validation, achieved the lowest accuracies for both coil against not coil and sheet against not sheet classifications. The logistic regression classier accuracy is dependent on the window size; there is a positive relationship between the accuracy and window size. The logistic regression classier approach achieved the highest accuracy when compared to the classification tree and Naive Bayes classifiers for each classification task; predicting helix against not helix with accuracy 77.74 percent, for sheet against not sheet with accuracy 81.22 percent and for coil against not coil with accuracy 73.39 percent. It is noted that it is easier to compare classifiers if the classification process could be completely facilitated in R. Alternatively, it would be easier to assess these logistic regression classifiers if SPSS had a function to determine the accuracy of the logistic regression classifier.
- Full Text:
- Authors: Eldud Omer, Ahmed Abdelkarim
- Date: 2016
- Subjects: Bayesian statistical decision theory , Logistic regression analysis , Biostatistics , Proteins -- Structure
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5581 , http://hdl.handle.net/10962/d1019985
- Description: The secondary structure of proteins is predicted using various binary classifiers. The data are adopted from the RS126 database. The original data consists of protein primary and secondary structure sequences. The original data is encoded using alphabetic letters. These data are encoded into unary vectors comprising ones and zeros only. Different binary classifiers, namely the naive Bayes, logistic regression and classification trees using hold-out and 5-fold cross validation are trained using the encoded data. For each of the classifiers three classification tasks are considered, namely helix against not helix (H/∼H), sheet against not sheet (S/∼S) and coil against not coil (C/∼C). The performance of these binary classifiers are compared using the overall accuracy in predicting the protein secondary structure for various window sizes. Our result indicate that hold-out cross validation achieved higher accuracy than 5-fold cross validation. The Naive Bayes classifier, using 5-fold cross validation achieved, the lowest accuracy for predicting helix against not helix. The classification tree classifiers, using 5-fold cross validation, achieved the lowest accuracies for both coil against not coil and sheet against not sheet classifications. The logistic regression classier accuracy is dependent on the window size; there is a positive relationship between the accuracy and window size. The logistic regression classier approach achieved the highest accuracy when compared to the classification tree and Naive Bayes classifiers for each classification task; predicting helix against not helix with accuracy 77.74 percent, for sheet against not sheet with accuracy 81.22 percent and for coil against not coil with accuracy 73.39 percent. It is noted that it is easier to compare classifiers if the classification process could be completely facilitated in R. Alternatively, it would be easier to assess these logistic regression classifiers if SPSS had a function to determine the accuracy of the logistic regression classifier.
- Full Text:
Recombinant expression, purification and in vitro interaction analysis of HOP and RhoC
- Vaaltyn, Michaelone Chantelle
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64523 , vital:28555
- Description: Expected release date-May 2019
- Full Text:
- Authors: Vaaltyn, Michaelone Chantelle
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64523 , vital:28555
- Description: Expected release date-May 2019
- Full Text:
Reproductive biology of important invasive plants in the Eastern Cape Province of South Africa
- Authors: Thorne, Cara-Jayne
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3683 , vital:20535
- Description: Baker’s rule predicts species capable of uniparental reproduction are more likely to establish after long distance dispersal (or introduction in the case of invasive plants), thus the ability to undergo autonomous self-pollination should promote colonization. An investigation into the reproductive biology of eleven invasive species in the Eastern Cape Province of South Africa between 2012 and 2014 showed strong support for Baker’s law. Breeding system results showed evidence of self-compatibility in eight species, ten species were capable of autonomous self-pollination, and only three species showed evidence of varying levels of self-incompatibility. These results provide evdence that autonomous self-pollination occurs more frequently among invasive species, self-compatible species more frequently become invasive compared with self-incompatible species and that autogamous species should have a larger invasive range. Co-opting suitable local pollinators may be problematic for invasive plants, especially those with highly specialized pollination systems. The species investigated appear to be largely independent of pollinators, mostly setting seed in the absence of pollinators. Despite this, all eleven invasive plant species are regularly visited by a variety of generalist pollinators including Apis mellifera, Xylocopa bees and Allodapini species. Pollinators all carried substantial pollen loads, even managing to extract pollen from more specialized plants, such as the poricidal anthers of Solanum species, and frequently came into contact with both anthers and stigmas. Considering most of theses species are capable of autonomous self-pollination, their reliance on pollinators may be low. Even the most self-incompatible species, Passiflora caerulea, appears to have successfully co-opted local pollinators (honeybees and carpenter bees), ensuring successful pollination and seed set. The ability for cross-pollination by local pollinators allows for some degree of genetic variation within invasive plant populations, especially for self-incompatible species. Inadequate pollen deposition by unreliable or inefficient pollinators, or reduced resource availability, can result in pollen limitation. Invasive plant species may be especially susceptible, with three of the plant species investiagted showing possible pollen limitation at the level of seed set, while the remaining nine invasive plant species showed no evidence of pollen limitation in South Africa. The ability to utilize uniparental reproduction (as Baker’s law predicted), and co-opt local pollinators has allowed invasive plants in the Eastern Cape to successfully establish and persist after introduction. Hence, the inclusion of reproductive traits of plants should therefore be included in risk assessments for future plant invaders.
- Full Text:
- Authors: Thorne, Cara-Jayne
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3683 , vital:20535
- Description: Baker’s rule predicts species capable of uniparental reproduction are more likely to establish after long distance dispersal (or introduction in the case of invasive plants), thus the ability to undergo autonomous self-pollination should promote colonization. An investigation into the reproductive biology of eleven invasive species in the Eastern Cape Province of South Africa between 2012 and 2014 showed strong support for Baker’s law. Breeding system results showed evidence of self-compatibility in eight species, ten species were capable of autonomous self-pollination, and only three species showed evidence of varying levels of self-incompatibility. These results provide evdence that autonomous self-pollination occurs more frequently among invasive species, self-compatible species more frequently become invasive compared with self-incompatible species and that autogamous species should have a larger invasive range. Co-opting suitable local pollinators may be problematic for invasive plants, especially those with highly specialized pollination systems. The species investigated appear to be largely independent of pollinators, mostly setting seed in the absence of pollinators. Despite this, all eleven invasive plant species are regularly visited by a variety of generalist pollinators including Apis mellifera, Xylocopa bees and Allodapini species. Pollinators all carried substantial pollen loads, even managing to extract pollen from more specialized plants, such as the poricidal anthers of Solanum species, and frequently came into contact with both anthers and stigmas. Considering most of theses species are capable of autonomous self-pollination, their reliance on pollinators may be low. Even the most self-incompatible species, Passiflora caerulea, appears to have successfully co-opted local pollinators (honeybees and carpenter bees), ensuring successful pollination and seed set. The ability for cross-pollination by local pollinators allows for some degree of genetic variation within invasive plant populations, especially for self-incompatible species. Inadequate pollen deposition by unreliable or inefficient pollinators, or reduced resource availability, can result in pollen limitation. Invasive plant species may be especially susceptible, with three of the plant species investiagted showing possible pollen limitation at the level of seed set, while the remaining nine invasive plant species showed no evidence of pollen limitation in South Africa. The ability to utilize uniparental reproduction (as Baker’s law predicted), and co-opt local pollinators has allowed invasive plants in the Eastern Cape to successfully establish and persist after introduction. Hence, the inclusion of reproductive traits of plants should therefore be included in risk assessments for future plant invaders.
- Full Text:
Single station TEC modelling during storm conditions
- Authors: Uwamahoro, Jean Claude
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3812 , vital:20545
- Description: It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, mathematical equations were developed to estimate TEC over Sutherland (32.38oS, 20.81oE), during storm conditions, using the Empirical Orthogonal Function (EOF) analysis, combined with regression analysis. TEC was derived from GPS observations and a geomagnetic storm was defined for Dst ≤ -50 nT. The inputs for the model were chosen based on the factors that influence TEC variation, such as diurnal, seasonal, solar and geomagnetic activity variation, and these were represented by hour of the day, day number of the year, F10.7 and A index respectively. The EOF model was developed using GPS TEC data from 1999 to 2013 and tested on different storms. For the model validation (interpolation), three storms were chosen in 2000 (solar maximum period) and three others in 2006 (solar minimum period), while for extrapolation six storms including three in 2014 and three in 2015 were chosen. Before building the model, TEC values for the selected 2000 and 2006 storms were removed from the dataset used to construct the model in order to make the model validation independent on data. A comparison of the observed and modelled TEC showed that the EOF model works well for storms with non-significant ionospheric TEC response and storms that occurred during periods of low solar activity. High correlation coefficients between the observed and modelled TEC were obtained showing that the model covers most of the information contained in the observed TEC. Furthermore, it has been shown that the EOF model developed for a specific station may be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7o and 10.6o respectively. This is an important result as it reduces the data dimensionality problem for computational purposes. It may therefore not be necessary for regional storm-time TEC modelling to compute TEC data for all the closest GPS receiver stations since most of the needed information can be extracted from measurements at one location.
- Full Text:
- Authors: Uwamahoro, Jean Claude
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3812 , vital:20545
- Description: It has been shown in ionospheric research that modelling total electron content (TEC) during storm conditions is a big challenge. In this study, mathematical equations were developed to estimate TEC over Sutherland (32.38oS, 20.81oE), during storm conditions, using the Empirical Orthogonal Function (EOF) analysis, combined with regression analysis. TEC was derived from GPS observations and a geomagnetic storm was defined for Dst ≤ -50 nT. The inputs for the model were chosen based on the factors that influence TEC variation, such as diurnal, seasonal, solar and geomagnetic activity variation, and these were represented by hour of the day, day number of the year, F10.7 and A index respectively. The EOF model was developed using GPS TEC data from 1999 to 2013 and tested on different storms. For the model validation (interpolation), three storms were chosen in 2000 (solar maximum period) and three others in 2006 (solar minimum period), while for extrapolation six storms including three in 2014 and three in 2015 were chosen. Before building the model, TEC values for the selected 2000 and 2006 storms were removed from the dataset used to construct the model in order to make the model validation independent on data. A comparison of the observed and modelled TEC showed that the EOF model works well for storms with non-significant ionospheric TEC response and storms that occurred during periods of low solar activity. High correlation coefficients between the observed and modelled TEC were obtained showing that the model covers most of the information contained in the observed TEC. Furthermore, it has been shown that the EOF model developed for a specific station may be used to estimate TEC over other locations within a latitudinal and longitudinal coverage of 8.7o and 10.6o respectively. This is an important result as it reduces the data dimensionality problem for computational purposes. It may therefore not be necessary for regional storm-time TEC modelling to compute TEC data for all the closest GPS receiver stations since most of the needed information can be extracted from measurements at one location.
- Full Text:
Street tree composition, distribution and urban residents’ perceptions within and between Eastern Cape towns
- Authors: Gwedla, Nanamhla
- Date: 2016
- Subjects: Urbanization -- South Africa -- Eastern Cape , Urban ecology (Sociology) -- South Africa -- Eastern Cape , Tree planting -- South Africa -- Eastern Cape , Trees in cities -- Environmental aspects -- South Africa -- Eastern Cape , Urban forestry -- Law and legislation -- South Africa -- Eastern Cape , Low-income housing -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4702 , vital:20714
- Description: Promoting urban sustainability is vital in the face of rapid human and urban population growth. A core tenet of urban sustainability, urban forestry, is poised to “go global” with the intent of mitigating the negative environmental and social effects of urbanisation through green infrastructure, spaces and trees. Amongst these, the planting of street trees has become a major strategy. The public functions of street trees as demonstrated through the provision of ecosystem services are highly dependent on the structure, composition and diversity of tree species within the urban forest. The bulk of available literature on the composition, diversity and perceptions of residents regarding street trees has largely focused on the developed world, while the few in the developing world have been conducted at only one or two sites. The aim of this study was to investigate the composition, diversity and density of urban street trees in relation to the perceptions of local residents and horticulturists, across a range of ecological and social contexts. To do this, the species composition, diversity and dominance of street trees planted in 10 randomly selected Eastern Cape towns was assessed. Within each town ten replicate 200 m transects were located in three different suburbs. Perceptions and appreciation of street trees were assessed by 1 200 household questionnaires, as well as key informant interviews with personnel responsible for street tree planting and maintenance. Sixty-nine out of 300 sampled transects had street trees, with 888 trees enumerated, spanning ninety-seven species. Alien tree species accounted for 71 % of all the enumerated trees while indigenous trees species accounted for 12 %. The non-former homeland towns had a significantly higher (5.8±1.6 trees) mean street tree density per transect than the former homeland towns (0.6±03). There were no significant relationships between street tree density or richness to mean annual rainfall or the background biome in which the town was situated. However, density strongly was related to size of the town. RDP and township suburbs had fewer street trees and low species richness relative to the affluent suburbs. In selecting street trees, root system of the prospective tree, the eventual size or shape of the species, whether an alien or indigenous species, and the species’ adaptability to the climate of the respective town are considered before planting. The biggest identified threats to street trees were the deliberate vandalism of trees by people and animals, and lack of education and awareness regarding the importance of street trees among urban residents and municipal officials. More than half of the respondents prefer that trees be planted both on the street and in their yards while a few do not want trees at all. The majority of respondents with this preference do so because they want shade and abundant fruit, and to have beautiful yards and streets. Those who do not want trees at all do so because they just do not like trees, there is no space for trees, or they fear that criminals hide behind trees. The presence of trees in peoples’ yards correlated with a positive preference for trees in the street. The majority of respondents were neither satisfied with the general appearance of their street nor with the number of trees on their street. Residents from the RDP suburbs were the least satisfied with both the appearance and number of trees on their streets, while those from the affluent suburbs were the most satisfied. Street trees were seen as greatly important to have by the majority of people. The more educated people were more appreciative of the importance of street trees. Local municipalities were identified by the majority of respondents as the stakeholders responsible for the planting and maintenance of street trees, although a considerable proportion of respondents reported a willingness to volunteer to help plant and maintain trees on their streets. Municipalities were seen as doing very little to provide and maintain trees in the various suburbs by the majority of respondents. The majority of respondents also reported that they had never been consulted about tree planting activities in their suburbs before, and would like to have been consulted.
- Full Text:
- Authors: Gwedla, Nanamhla
- Date: 2016
- Subjects: Urbanization -- South Africa -- Eastern Cape , Urban ecology (Sociology) -- South Africa -- Eastern Cape , Tree planting -- South Africa -- Eastern Cape , Trees in cities -- Environmental aspects -- South Africa -- Eastern Cape , Urban forestry -- Law and legislation -- South Africa -- Eastern Cape , Low-income housing -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/4702 , vital:20714
- Description: Promoting urban sustainability is vital in the face of rapid human and urban population growth. A core tenet of urban sustainability, urban forestry, is poised to “go global” with the intent of mitigating the negative environmental and social effects of urbanisation through green infrastructure, spaces and trees. Amongst these, the planting of street trees has become a major strategy. The public functions of street trees as demonstrated through the provision of ecosystem services are highly dependent on the structure, composition and diversity of tree species within the urban forest. The bulk of available literature on the composition, diversity and perceptions of residents regarding street trees has largely focused on the developed world, while the few in the developing world have been conducted at only one or two sites. The aim of this study was to investigate the composition, diversity and density of urban street trees in relation to the perceptions of local residents and horticulturists, across a range of ecological and social contexts. To do this, the species composition, diversity and dominance of street trees planted in 10 randomly selected Eastern Cape towns was assessed. Within each town ten replicate 200 m transects were located in three different suburbs. Perceptions and appreciation of street trees were assessed by 1 200 household questionnaires, as well as key informant interviews with personnel responsible for street tree planting and maintenance. Sixty-nine out of 300 sampled transects had street trees, with 888 trees enumerated, spanning ninety-seven species. Alien tree species accounted for 71 % of all the enumerated trees while indigenous trees species accounted for 12 %. The non-former homeland towns had a significantly higher (5.8±1.6 trees) mean street tree density per transect than the former homeland towns (0.6±03). There were no significant relationships between street tree density or richness to mean annual rainfall or the background biome in which the town was situated. However, density strongly was related to size of the town. RDP and township suburbs had fewer street trees and low species richness relative to the affluent suburbs. In selecting street trees, root system of the prospective tree, the eventual size or shape of the species, whether an alien or indigenous species, and the species’ adaptability to the climate of the respective town are considered before planting. The biggest identified threats to street trees were the deliberate vandalism of trees by people and animals, and lack of education and awareness regarding the importance of street trees among urban residents and municipal officials. More than half of the respondents prefer that trees be planted both on the street and in their yards while a few do not want trees at all. The majority of respondents with this preference do so because they want shade and abundant fruit, and to have beautiful yards and streets. Those who do not want trees at all do so because they just do not like trees, there is no space for trees, or they fear that criminals hide behind trees. The presence of trees in peoples’ yards correlated with a positive preference for trees in the street. The majority of respondents were neither satisfied with the general appearance of their street nor with the number of trees on their street. Residents from the RDP suburbs were the least satisfied with both the appearance and number of trees on their streets, while those from the affluent suburbs were the most satisfied. Street trees were seen as greatly important to have by the majority of people. The more educated people were more appreciative of the importance of street trees. Local municipalities were identified by the majority of respondents as the stakeholders responsible for the planting and maintenance of street trees, although a considerable proportion of respondents reported a willingness to volunteer to help plant and maintain trees on their streets. Municipalities were seen as doing very little to provide and maintain trees in the various suburbs by the majority of respondents. The majority of respondents also reported that they had never been consulted about tree planting activities in their suburbs before, and would like to have been consulted.
- Full Text:
Study into the synthesis, characterisation and applications of Vanadium-based metal organic frameworks, using 1, 2, 4, 5-benzenetetracarboxylic acid
- Authors: Feldmann, Wesley
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/55245 , vital:26680
- Description: This study focussed on the synthesis, characterisation and catalytic application of synthesised vanadium-based Metal-Organic Frameworks using 1,2,4,5-benzenetetracarboxylic acid as a ligand. A number of synthetic methods were tested in multiple attempts to synthesise a V-MOF, these included; ambient, gel, reflux and solvothermal methods of synthesis. Two products of interest were identified, an ambient synthesis produced a vanadium-based complex with the empirical formula: V2O2(Na2H2B4C).6H2O (RU-V2) and a solvothermal synthesis produced a MOF with the empirical formula: V2O2(H2O)2(B4C) (RU-V1). Both products were characterised using elemental analysis, infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray powder diffraction. The catalytic activity of these products was tested, alongside the activity of the solid decavanadate ion, for the conversion of cyclohexene to cyclohexene oxide. The decavanadate ion was included to determine if the ion was catalytically active in the solid state, to potentially be used in the construction of a future MOF or V-complex. The reaction for the conversion of cyclohexene to cyclohexene oxide was chosen, as it has been previously conducted using a V-MOF and was found to be successful. The product of the reaction, the epoxide: cyclohexene oxide, is a very useful precursor for a number of reactions involved in the pharmaceutical industry, so developing catalysts which are able to convert cyclohexene to the epoxide with high yields and selectivities are well sought after in industry. The results of the catalytic reactions were varied, as the materials exhibited high yields and selectivities to the epoxide, but these results were only obtained when water was present in the reaction mixture. Water was able to bring about the cleavage of the bonds between the metal and ligand in a highly coordinated framework, at a faster rate than other solvents, such as decane. This ultimately leads to the structural decomposition of the entire complex or framework, depending upon the reaction time. The use of water was a double edged sword in that it was required to initiate the catalytic reaction, but was also the reason that the catalytic materials were noted to decompose over time. The solid decavanadate ion was only noted to exhibit homogeneous activity by dissolving into the small volume of water present in the reaction mixture. The study proved that using a multidentate ligand such as 1,2,4,5-benzenetetracarboxylic acid yielded products which were highly coordinated in nature and would therefore not have large open spaces associated with them, which is commonly observed with other MOFs. Instead the closed nature of the synthesised complexes and frameworks offered a different environment for catalytic reactions, where the small pores/channels had a controlling and inhibiting effect on the reaction. The conversion of cyclohexene to the epoxide is accompanied with a number of undesired side products, so when using the synthesised closed-natured MOF, it was found that there was a greater selectivity for the epoxide over other potential products. This indicates that close natured MOFs may find application in catalytic reactions which require high selectivities for a particular product.
- Full Text:
- Authors: Feldmann, Wesley
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/55245 , vital:26680
- Description: This study focussed on the synthesis, characterisation and catalytic application of synthesised vanadium-based Metal-Organic Frameworks using 1,2,4,5-benzenetetracarboxylic acid as a ligand. A number of synthetic methods were tested in multiple attempts to synthesise a V-MOF, these included; ambient, gel, reflux and solvothermal methods of synthesis. Two products of interest were identified, an ambient synthesis produced a vanadium-based complex with the empirical formula: V2O2(Na2H2B4C).6H2O (RU-V2) and a solvothermal synthesis produced a MOF with the empirical formula: V2O2(H2O)2(B4C) (RU-V1). Both products were characterised using elemental analysis, infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and X-ray powder diffraction. The catalytic activity of these products was tested, alongside the activity of the solid decavanadate ion, for the conversion of cyclohexene to cyclohexene oxide. The decavanadate ion was included to determine if the ion was catalytically active in the solid state, to potentially be used in the construction of a future MOF or V-complex. The reaction for the conversion of cyclohexene to cyclohexene oxide was chosen, as it has been previously conducted using a V-MOF and was found to be successful. The product of the reaction, the epoxide: cyclohexene oxide, is a very useful precursor for a number of reactions involved in the pharmaceutical industry, so developing catalysts which are able to convert cyclohexene to the epoxide with high yields and selectivities are well sought after in industry. The results of the catalytic reactions were varied, as the materials exhibited high yields and selectivities to the epoxide, but these results were only obtained when water was present in the reaction mixture. Water was able to bring about the cleavage of the bonds between the metal and ligand in a highly coordinated framework, at a faster rate than other solvents, such as decane. This ultimately leads to the structural decomposition of the entire complex or framework, depending upon the reaction time. The use of water was a double edged sword in that it was required to initiate the catalytic reaction, but was also the reason that the catalytic materials were noted to decompose over time. The solid decavanadate ion was only noted to exhibit homogeneous activity by dissolving into the small volume of water present in the reaction mixture. The study proved that using a multidentate ligand such as 1,2,4,5-benzenetetracarboxylic acid yielded products which were highly coordinated in nature and would therefore not have large open spaces associated with them, which is commonly observed with other MOFs. Instead the closed nature of the synthesised complexes and frameworks offered a different environment for catalytic reactions, where the small pores/channels had a controlling and inhibiting effect on the reaction. The conversion of cyclohexene to the epoxide is accompanied with a number of undesired side products, so when using the synthesised closed-natured MOF, it was found that there was a greater selectivity for the epoxide over other potential products. This indicates that close natured MOFs may find application in catalytic reactions which require high selectivities for a particular product.
- Full Text:
Surface characteristics of rock glaciers in the Jutulsessen, Dronning Maud Land, Antarctica
- Rudolph, Elizabeth Magdalena
- Authors: Rudolph, Elizabeth Magdalena
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2667 , vital:20314
- Description: Rock glaciers are landforms that present downslope movement of debris under the influence of ice and gravity. These landforms can be used as paleo-climate indicators as well as proxies for climate change. Rock glaciers have been investigated in a variety of climates and landscapes, however continental Antarctica, Dronning Maud Land specifically, remains understudied. This thesis aimed to investigate and classify five rock glaciers observed in the Jutulsessen, Dronning Maud Land. The surface characteristics and geomorphology were assessed and used as generic classifiers. Size, shape and landscape association was established by field surveying and GIS, whilst sediment and clast characteristics were determined from sampling. A surface temperature profile was created from short-term high frequency temperature measurements. All of the rock glaciers exhibit either undulating surfaces or patterned ground, or both, which suggests active-layer related processes. Sediment particle size analysis is inconclusive. The 137Cs-content and fabric analysis suggest movement regimes similar to other rock glaciers with higher activity at the head, and variable movement directions at the toe. Relative “activeness” is inferred from morphology: Grjotlia, Grjotøyra and Vassdalen were classified as lobate, spatulate and tongue-shaped respectively with Grjotlia the most stable. A new morphological classification of ‘crown-shaped’ is suggested for Brugdedalen and Jutuldalen, and they also appear most active. The control of local climate on rock glacier mechanics is emphasised by the findings, and thus climatic interpolation from a single weather stations is not useful. Increased spatial and temporal coverage of sediment profiles, surface topography and active-layer characteristics could be used to elucidate the processes and controls of these landforms in the Antarctic.
- Full Text:
- Authors: Rudolph, Elizabeth Magdalena
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2667 , vital:20314
- Description: Rock glaciers are landforms that present downslope movement of debris under the influence of ice and gravity. These landforms can be used as paleo-climate indicators as well as proxies for climate change. Rock glaciers have been investigated in a variety of climates and landscapes, however continental Antarctica, Dronning Maud Land specifically, remains understudied. This thesis aimed to investigate and classify five rock glaciers observed in the Jutulsessen, Dronning Maud Land. The surface characteristics and geomorphology were assessed and used as generic classifiers. Size, shape and landscape association was established by field surveying and GIS, whilst sediment and clast characteristics were determined from sampling. A surface temperature profile was created from short-term high frequency temperature measurements. All of the rock glaciers exhibit either undulating surfaces or patterned ground, or both, which suggests active-layer related processes. Sediment particle size analysis is inconclusive. The 137Cs-content and fabric analysis suggest movement regimes similar to other rock glaciers with higher activity at the head, and variable movement directions at the toe. Relative “activeness” is inferred from morphology: Grjotlia, Grjotøyra and Vassdalen were classified as lobate, spatulate and tongue-shaped respectively with Grjotlia the most stable. A new morphological classification of ‘crown-shaped’ is suggested for Brugdedalen and Jutuldalen, and they also appear most active. The control of local climate on rock glacier mechanics is emphasised by the findings, and thus climatic interpolation from a single weather stations is not useful. Increased spatial and temporal coverage of sediment profiles, surface topography and active-layer characteristics could be used to elucidate the processes and controls of these landforms in the Antarctic.
- Full Text:
Synthesis, spectroscopic and nonlinear optical properties of metal-free and nickel β substituted binuclear phthalocyanines
- Authors: Kabwe, Kapambwe Peter
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3013 , vital:20352
- Description: In this project, nickel and metal-free 4β-(4-tert-butylphenoxy) phthalocyanine, biphenyl bridged binuclear 4-tert-butylphenoxy phthalocyanine and naphthalene bridged binuclear 4-tert-butylphenoxy phthalocyanine have been synthesised. The Z-scan technique has been employed to comparatively study their second order nonlinear optical (NLO) properties. This work, shows that the presence of H-aggregation in binuclear Pcs of metal-free and nickel 4β-(4-tertbutylphenoxy) phthalocyanines do not have an effect on the magnitude of second order nonlinear absorption coefficient (β) as compared to monomeric Pcs. Density functional (DFT) calculations of dipolar/octupolar contributions were performed, in order to explain experimentally determined β values. Spectroscopic and photophysical properties of the synthesised compounds have been determined using a range of different spectroscopic techniques, including magnetic circular dichroism (MCD), time correlated single photon counting spectroscopy (TCSPC), UV-visible absorption spectroscopy, mass spectroscopy and IR Spectroscopy.
- Full Text:
- Authors: Kabwe, Kapambwe Peter
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3013 , vital:20352
- Description: In this project, nickel and metal-free 4β-(4-tert-butylphenoxy) phthalocyanine, biphenyl bridged binuclear 4-tert-butylphenoxy phthalocyanine and naphthalene bridged binuclear 4-tert-butylphenoxy phthalocyanine have been synthesised. The Z-scan technique has been employed to comparatively study their second order nonlinear optical (NLO) properties. This work, shows that the presence of H-aggregation in binuclear Pcs of metal-free and nickel 4β-(4-tertbutylphenoxy) phthalocyanines do not have an effect on the magnitude of second order nonlinear absorption coefficient (β) as compared to monomeric Pcs. Density functional (DFT) calculations of dipolar/octupolar contributions were performed, in order to explain experimentally determined β values. Spectroscopic and photophysical properties of the synthesised compounds have been determined using a range of different spectroscopic techniques, including magnetic circular dichroism (MCD), time correlated single photon counting spectroscopy (TCSPC), UV-visible absorption spectroscopy, mass spectroscopy and IR Spectroscopy.
- Full Text:
Testing the effectiveness and cost-efficiency of livestock guarding dogs in Botswana
- Authors: Horgan, Jane Elizabeth
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5951 , http://hdl.handle.net/10962/d1021300
- Description: Livestock guarding dogs (LSGDs) have been used for centuries to reduce depredation on livestock and more recently, to facilitate the conservation of threatened predator species. Conservation NGOs (non-government organisations) in southern Africa promote the use of Anatolian Shepherds as LSGDs. However, livestock farmers in Botswana have been using a variety of different breeds for this purpose, including the local mixed-breed “Tswana” dogs. Postal, telephonic and face-to-face interview questionnaires were administered to 108 livestock farmers in Botswana to gauge how their LSGDs were being used, in order to determine what factors contributed to the success and affordability of these dogs. Eighty-three percent of farmers had LSGDs which equaled or decreased livestock depredations on their farms, with an average reduction in livestock depredation of 75% per year. This equated to an average saving of US$2,017 annually per farm. The costs of purchasing (average US$27) and maintaining the 198 LSGDs in my study (average US$169/LSGD/year) were very low compared to other countries and helped contribute to the high profits obtained by farmers (average US$1,497/farm or US$789/LSGD). A unique investigation of different breeds was possible due to the diverse array of breeds in the sample (Anatolian Shepherds, Cross Breeds, Tswana dogs, Greyhounds and Pitbulls), with the crossbreed dogs (Crosses and Tswana LSGDs) performing the best. LSGDs that reduced depredation and had minimal behavioural problems were the most likely to incite positive changes in their owners in regards to attitudes towards predators. Sixtysix percent of farmers stated that they were more tolerant of predators since obtaining a LSGD, and 51% reported that they were less likely to kill predators since obtaining a LSGD. My results indicate that successful, well-behaved LSGDs are a cost-effective tool that has the ability to increase farm productivity and improve predator-farmer conflicts in Botswana. The methods recommended in my thesis, in particular the benefits of using local breeds of dog as LSGDs, can be implemented on farming practices the world over to assist farming productivity and to promote conservation efforts.
- Full Text:
- Authors: Horgan, Jane Elizabeth
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5951 , http://hdl.handle.net/10962/d1021300
- Description: Livestock guarding dogs (LSGDs) have been used for centuries to reduce depredation on livestock and more recently, to facilitate the conservation of threatened predator species. Conservation NGOs (non-government organisations) in southern Africa promote the use of Anatolian Shepherds as LSGDs. However, livestock farmers in Botswana have been using a variety of different breeds for this purpose, including the local mixed-breed “Tswana” dogs. Postal, telephonic and face-to-face interview questionnaires were administered to 108 livestock farmers in Botswana to gauge how their LSGDs were being used, in order to determine what factors contributed to the success and affordability of these dogs. Eighty-three percent of farmers had LSGDs which equaled or decreased livestock depredations on their farms, with an average reduction in livestock depredation of 75% per year. This equated to an average saving of US$2,017 annually per farm. The costs of purchasing (average US$27) and maintaining the 198 LSGDs in my study (average US$169/LSGD/year) were very low compared to other countries and helped contribute to the high profits obtained by farmers (average US$1,497/farm or US$789/LSGD). A unique investigation of different breeds was possible due to the diverse array of breeds in the sample (Anatolian Shepherds, Cross Breeds, Tswana dogs, Greyhounds and Pitbulls), with the crossbreed dogs (Crosses and Tswana LSGDs) performing the best. LSGDs that reduced depredation and had minimal behavioural problems were the most likely to incite positive changes in their owners in regards to attitudes towards predators. Sixtysix percent of farmers stated that they were more tolerant of predators since obtaining a LSGD, and 51% reported that they were less likely to kill predators since obtaining a LSGD. My results indicate that successful, well-behaved LSGDs are a cost-effective tool that has the ability to increase farm productivity and improve predator-farmer conflicts in Botswana. The methods recommended in my thesis, in particular the benefits of using local breeds of dog as LSGDs, can be implemented on farming practices the world over to assist farming productivity and to promote conservation efforts.
- Full Text:
The consumption and use of wild foods by children across a deforestation gradient in Zomba District, Malawi
- Authors: Maseko, Heather Nonhlanhla
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3212 , vital:20392
- Description: Despite consensus on their significant nutritional value, wild foods are continually excluded from both food security statistics and economic values of natural resources. Though largely unexplored, there is evidence on the use of wild foods by children to supplement their diets and as a source of income. Children have knowledge on the gathering and hunting of selected wild food species and sources thereof. Wetlands, agro-ecosystems, natural forests, human landscapes and river systems remain important sources of wild food resources. The provision of and access to these resources are significantly affected by the interference and disruption to natural ecosystems. In Malawi, interference has been largely due to deforestation and land use change caused by an interplay of pressures from population growth for development and agricultural expansion. Against this background, the implications of deforestation and vegetation cover on the availability of wild foods and their access and use by children is largely unexplored. Through a comprehensive analysis of data collected from 150 children and 50 elderly men and women, the integration of Participatory Rural Appraisal (PRA) exercises and Geographic Information System (GIS), in the four sites of Mpheta, Mtuluma, Kasonga and Makombe in Zomba district, wild foods availability was established and their contribution to the nutritional status of children and households’ food security assessed. Study sites were identified along the deforestation gradient of Lake Chilwa, Zomba Mountain and Shire River basin with an additional focus on varying landscapes. One hundred and twenty species of wild foods were identified with greatest availability in areas of high vegetation cover and the lowest in areas of low vegetation cover, but with meaningful differences per wild food category. There was considerable reduction in the availability of wild foods with increasing deforestation; mainly wild game and fruits species and, in turn, decreased access of these by children. Nevertheless, small game, insects, other wild fruits and wild vegetables thrive well in agro-ecosystems and therefore were minimally affected by deforestation but largely by management practices of those systems and can be possibly improved through the promotion of agro-ecological farming systems. The research reveals that wild foods form an important component of the starch based diets of households from agricultural communities in the various landscapes. Besides securing the household’s food base, all children largely supplemented their diets with wild foods but with increased dependence by children from poorer households who are highly vulnerable to food insecurity. Access and use of wild foods was largely dependent on children’s knowledge, perceptions of the wild food and ease of access, with considerable variations due to gender and socio-cultural norms. Besides contributing to the nutritional status and food security, commercialisation of wild foods was common among children, hence providing them with an alternative livelihood strategy and in some cases only viable source of income.
- Full Text:
- Authors: Maseko, Heather Nonhlanhla
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3212 , vital:20392
- Description: Despite consensus on their significant nutritional value, wild foods are continually excluded from both food security statistics and economic values of natural resources. Though largely unexplored, there is evidence on the use of wild foods by children to supplement their diets and as a source of income. Children have knowledge on the gathering and hunting of selected wild food species and sources thereof. Wetlands, agro-ecosystems, natural forests, human landscapes and river systems remain important sources of wild food resources. The provision of and access to these resources are significantly affected by the interference and disruption to natural ecosystems. In Malawi, interference has been largely due to deforestation and land use change caused by an interplay of pressures from population growth for development and agricultural expansion. Against this background, the implications of deforestation and vegetation cover on the availability of wild foods and their access and use by children is largely unexplored. Through a comprehensive analysis of data collected from 150 children and 50 elderly men and women, the integration of Participatory Rural Appraisal (PRA) exercises and Geographic Information System (GIS), in the four sites of Mpheta, Mtuluma, Kasonga and Makombe in Zomba district, wild foods availability was established and their contribution to the nutritional status of children and households’ food security assessed. Study sites were identified along the deforestation gradient of Lake Chilwa, Zomba Mountain and Shire River basin with an additional focus on varying landscapes. One hundred and twenty species of wild foods were identified with greatest availability in areas of high vegetation cover and the lowest in areas of low vegetation cover, but with meaningful differences per wild food category. There was considerable reduction in the availability of wild foods with increasing deforestation; mainly wild game and fruits species and, in turn, decreased access of these by children. Nevertheless, small game, insects, other wild fruits and wild vegetables thrive well in agro-ecosystems and therefore were minimally affected by deforestation but largely by management practices of those systems and can be possibly improved through the promotion of agro-ecological farming systems. The research reveals that wild foods form an important component of the starch based diets of households from agricultural communities in the various landscapes. Besides securing the household’s food base, all children largely supplemented their diets with wild foods but with increased dependence by children from poorer households who are highly vulnerable to food insecurity. Access and use of wild foods was largely dependent on children’s knowledge, perceptions of the wild food and ease of access, with considerable variations due to gender and socio-cultural norms. Besides contributing to the nutritional status and food security, commercialisation of wild foods was common among children, hence providing them with an alternative livelihood strategy and in some cases only viable source of income.
- Full Text:
The design, development and evaluation of cross-platform mobile applications and services supporting social accountability monitoring
- Authors: Reynell, Edward Robin
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3652 , vital:20533
- Description: Local government processes require meaningful and effective participation from both citizens and their governments in order to remain truly democratic. This project investigates the use of mobile phones as a tool for supporting this participation. MobiSAM, a system which aims to enhance the Social Accountability Monitoring (SAM) methodology at local government level, has been designed and implemented. The research presented in this thesis examines tools and techniques for the development of cross-platform client applications, allowing access to the MobiSAM service, across heterogeneous mobile platforms, handsets and interaction styles. Particular attention is paid to providing an easily navigated user interface (UI), as well as offering clear and concise visualisation capabilities. Depending on the host device, interactivity is also included within these visualisations, potentially helping provide further insight into the visualised data. Guided by the results obtained from a comprehensive baseline study of the Grahamstown area, steps are taken in an attempt to lower the barrier of entry to using the MobiSAM service, potentially maximising its market reach. These include extending client application support to all identified mobile platforms (including feature phones); providing multi-language UIs (in English, isiXhosa and Afrikaans); as well as ensuring client application data usage is kept to a minimum. The particular strengths of a given device are also leveraged, such as its camera capabilities and built-in Global Positioning System (GPS) module, potentially allowing for more effective engagement with local municipalities. Additionally, a Short Message Service (SMS) gateway is developed, allowing all Global System for Mobile Communications (GSM) compatible handsets access to the MobiSAM service via traditional SMS. Following an iterative, user-centred design process, a thorough evaluation of the client application is also performed, in an attempt to gather feedback relating to the navigation and visualisation capabilities. The results of which are used to further refine its design. A comparative usability evaluation using two different versions of the cross-platform client application is also undertaken, highlighting the perceived memorability, learnabilitv and satisfaction of each. Results from the evaluation reveals which version of the client application is to be deployed during future pilot studies.
- Full Text:
- Authors: Reynell, Edward Robin
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3652 , vital:20533
- Description: Local government processes require meaningful and effective participation from both citizens and their governments in order to remain truly democratic. This project investigates the use of mobile phones as a tool for supporting this participation. MobiSAM, a system which aims to enhance the Social Accountability Monitoring (SAM) methodology at local government level, has been designed and implemented. The research presented in this thesis examines tools and techniques for the development of cross-platform client applications, allowing access to the MobiSAM service, across heterogeneous mobile platforms, handsets and interaction styles. Particular attention is paid to providing an easily navigated user interface (UI), as well as offering clear and concise visualisation capabilities. Depending on the host device, interactivity is also included within these visualisations, potentially helping provide further insight into the visualised data. Guided by the results obtained from a comprehensive baseline study of the Grahamstown area, steps are taken in an attempt to lower the barrier of entry to using the MobiSAM service, potentially maximising its market reach. These include extending client application support to all identified mobile platforms (including feature phones); providing multi-language UIs (in English, isiXhosa and Afrikaans); as well as ensuring client application data usage is kept to a minimum. The particular strengths of a given device are also leveraged, such as its camera capabilities and built-in Global Positioning System (GPS) module, potentially allowing for more effective engagement with local municipalities. Additionally, a Short Message Service (SMS) gateway is developed, allowing all Global System for Mobile Communications (GSM) compatible handsets access to the MobiSAM service via traditional SMS. Following an iterative, user-centred design process, a thorough evaluation of the client application is also performed, in an attempt to gather feedback relating to the navigation and visualisation capabilities. The results of which are used to further refine its design. A comparative usability evaluation using two different versions of the cross-platform client application is also undertaken, highlighting the perceived memorability, learnabilitv and satisfaction of each. Results from the evaluation reveals which version of the client application is to be deployed during future pilot studies.
- Full Text:
The development of captopril pellets using the principles of quality by design
- Veerubhotla, Hari Mani Krishna
- Authors: Veerubhotla, Hari Mani Krishna
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64769 , vital:28599
- Description: Expected release date-May 2018
- Full Text:
- Authors: Veerubhotla, Hari Mani Krishna
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64769 , vital:28599
- Description: Expected release date-May 2018
- Full Text:
The effect of novel thiazole-derived small molecules on the neuronal differentiation of human neuroblastoma SH-SY5Y cells
- Authors: Joos-Vandewalle, Julia
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64507 , vital:28554
- Description: Expected release date-April 2020
- Full Text:
- Authors: Joos-Vandewalle, Julia
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/64507 , vital:28554
- Description: Expected release date-April 2020
- Full Text:
The efficacy of a community based eccentric hamstring strengthening program in peri-urban Black South African soccer players
- Authors: Ryan, Bennett
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3573 , vital:20526
- Description: Introduction: Hamstring injury prevalence in soccer remains a major concern. Research in this context has focused on Caucasian populations with little attention given to other ethnic groups. The compatibility and applicability of such research to the South African context, particularly at an amateur level, may be minimal due to fundamental differences in physical characteristics, as well as complexities with regards to implementation. The aim of this investigation was therefore twofold. 1) Identify the lower extremity strength and performance profile of Peri-urban Amateur South African Players, and 2) Assess the efficacy of a community based intervention through the use of the Nordic Hamstring Exercise. Methods: 19 Black male Eastern Cape amateur players participated in a 12 week randomly controlled trial (9 = Control, 10 = Intervention). All participants completed regular training, while the intervention group, in addition, performed the Nordic Hamstring exercise post warm up. The incremental program design was taken from Mjolsnes et al. (2004), with a progressive increase in both sets and repetitions. Compliance was defined as completion of the required exercises for that session. Isokinetic strength evaluations (at 60°.s-1 and 180°.s-1) including assessment of peak torque and total work, as well as performance measures of countermovement and squat jump, were completed pre and post intervention, with the profile of the Peri-urban player the combined responses of both groups at baseline. Additionally, both the functional ratio (Eccentric Hamstrings/Concentric Quadriceps) and eccentric utilization ratio (Countermovement Jump/Squat Jump) were calculated. Results: Concentric quadriceps peak torque at baseline reported values of 195 (±22) Nm and 141 (±21) Nm at 60°.s-1 and 180°.s-1. Values of 162 (±21) Nm were observed for peak torque of the eccentric hamstrings at 60°.s-1, while 157 (±18) Nm was indicated at 180°.s-1. Mean functional ratio responses were observed as 0.83 (±0.11) and 1.12 (±0.16) for 60°.s-1 and 180°.s-1 respectively. Additionally, the eccentric utilization ratio responses were recorded as 1.04 (±0.08). Regarding the intervention, concentric quadriceps total work of the dominant limb significantly improved over the time course of experimentation within the intervention group. Other quadriceps variables, concentric hamstrings, squat jump capability and performance measures all reported no significant changes (p>0.05) over the course of assessment when compared to the control. Eccentric hamstrings peak torque observed significant improvements (p<0.05) of between 5.72 and 12.82 % within the intervention group, while the countermovement jump indicated a significant 15.59 % increase (p<0.05). Additionally, the functional ratio and the eccentric utilization ratio both indicated no significant changes (p>0.05), with a 2.48-7.66 % and 5.33 % improvement noted following completion of assessment. Conclusion: Isokinetic responses at baseline observed decreased quadriceps strength, and increased hamstring strength when compared to both amateur and professional populations examined in previous studies, for both isokinetic testing speeds. Additionally, performance measures indicated similar responses to other amateur populations. Regarding the intervention, significant improvements in eccentric hamstring peak torque and countermovement jump indicate the partial success of the present intervention. Additionally, while the functional ratio and eccentric utilization ratio reported no significant changes, improvements were noted within the intervention group while the control noted no change. The Nordic hamstring lower therefore resulted in strength improvements within the eccentric hamstrings, reported as a significant factor for injury risk, however, such changes were not sufficient to significantly impact the functional ratio. It can be concluded that community based programs within South Africa have the potential to be effective; however, there are many barriers to implementation, including, language, ethnic and cultural differences, while a lack of resources and infrastructure play a significant role in a lack of development. More research of this nature is required to provide scientific support for structures and guidelines for the peri-urban community based South African player, to ensure the efficacy of internationally successful interventions such as the Nordic exercise.
- Full Text:
- Authors: Ryan, Bennett
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3573 , vital:20526
- Description: Introduction: Hamstring injury prevalence in soccer remains a major concern. Research in this context has focused on Caucasian populations with little attention given to other ethnic groups. The compatibility and applicability of such research to the South African context, particularly at an amateur level, may be minimal due to fundamental differences in physical characteristics, as well as complexities with regards to implementation. The aim of this investigation was therefore twofold. 1) Identify the lower extremity strength and performance profile of Peri-urban Amateur South African Players, and 2) Assess the efficacy of a community based intervention through the use of the Nordic Hamstring Exercise. Methods: 19 Black male Eastern Cape amateur players participated in a 12 week randomly controlled trial (9 = Control, 10 = Intervention). All participants completed regular training, while the intervention group, in addition, performed the Nordic Hamstring exercise post warm up. The incremental program design was taken from Mjolsnes et al. (2004), with a progressive increase in both sets and repetitions. Compliance was defined as completion of the required exercises for that session. Isokinetic strength evaluations (at 60°.s-1 and 180°.s-1) including assessment of peak torque and total work, as well as performance measures of countermovement and squat jump, were completed pre and post intervention, with the profile of the Peri-urban player the combined responses of both groups at baseline. Additionally, both the functional ratio (Eccentric Hamstrings/Concentric Quadriceps) and eccentric utilization ratio (Countermovement Jump/Squat Jump) were calculated. Results: Concentric quadriceps peak torque at baseline reported values of 195 (±22) Nm and 141 (±21) Nm at 60°.s-1 and 180°.s-1. Values of 162 (±21) Nm were observed for peak torque of the eccentric hamstrings at 60°.s-1, while 157 (±18) Nm was indicated at 180°.s-1. Mean functional ratio responses were observed as 0.83 (±0.11) and 1.12 (±0.16) for 60°.s-1 and 180°.s-1 respectively. Additionally, the eccentric utilization ratio responses were recorded as 1.04 (±0.08). Regarding the intervention, concentric quadriceps total work of the dominant limb significantly improved over the time course of experimentation within the intervention group. Other quadriceps variables, concentric hamstrings, squat jump capability and performance measures all reported no significant changes (p>0.05) over the course of assessment when compared to the control. Eccentric hamstrings peak torque observed significant improvements (p<0.05) of between 5.72 and 12.82 % within the intervention group, while the countermovement jump indicated a significant 15.59 % increase (p<0.05). Additionally, the functional ratio and the eccentric utilization ratio both indicated no significant changes (p>0.05), with a 2.48-7.66 % and 5.33 % improvement noted following completion of assessment. Conclusion: Isokinetic responses at baseline observed decreased quadriceps strength, and increased hamstring strength when compared to both amateur and professional populations examined in previous studies, for both isokinetic testing speeds. Additionally, performance measures indicated similar responses to other amateur populations. Regarding the intervention, significant improvements in eccentric hamstring peak torque and countermovement jump indicate the partial success of the present intervention. Additionally, while the functional ratio and eccentric utilization ratio reported no significant changes, improvements were noted within the intervention group while the control noted no change. The Nordic hamstring lower therefore resulted in strength improvements within the eccentric hamstrings, reported as a significant factor for injury risk, however, such changes were not sufficient to significantly impact the functional ratio. It can be concluded that community based programs within South Africa have the potential to be effective; however, there are many barriers to implementation, including, language, ethnic and cultural differences, while a lack of resources and infrastructure play a significant role in a lack of development. More research of this nature is required to provide scientific support for structures and guidelines for the peri-urban community based South African player, to ensure the efficacy of internationally successful interventions such as the Nordic exercise.
- Full Text:
The EPR paradox: back from the future
- Authors: Bryan, Kate Louise Halse
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2881 , vital:20338
- Description: The Einstein-Podolsky-Rosen (EPR) thought experiment produced a problem regarding the interpretation of quantum mechanics provided for entangled systems. Although the thought experiment was reformulated mathematically in Bell's Theorem, the conclusion regarding entanglement correlations is still debated today. In an attempt to provide an explanation of how entangled systems maintain their correlations, this thesis investigates the theory of post-state teleportation as a possible interpretation of how information moves between entangled systems without resorting to nonlocal action. Post-state teleportation describes a method of communicating to the past via a quantum information channel. The resulting picture of the EPR thought experiment relied on information propagating backward from a final boundary condition to ensure all correlations were maintained. Similarities were found between this resolution of the EPR paradox and the final state solution to the black hole information paradox and the closely related firewall problem. The latter refers to an apparent conflict between unitary evaporation of a black hole and the strong subadditivity condition. The use of observer complementarity allows this solution of the black hole problem to be shown to be the same as a seemingly different solution known as “ER=EPR", where ‘ER’ refers to an Einstein-Rosen bridge or wormhole.
- Full Text:
- Authors: Bryan, Kate Louise Halse
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/2881 , vital:20338
- Description: The Einstein-Podolsky-Rosen (EPR) thought experiment produced a problem regarding the interpretation of quantum mechanics provided for entangled systems. Although the thought experiment was reformulated mathematically in Bell's Theorem, the conclusion regarding entanglement correlations is still debated today. In an attempt to provide an explanation of how entangled systems maintain their correlations, this thesis investigates the theory of post-state teleportation as a possible interpretation of how information moves between entangled systems without resorting to nonlocal action. Post-state teleportation describes a method of communicating to the past via a quantum information channel. The resulting picture of the EPR thought experiment relied on information propagating backward from a final boundary condition to ensure all correlations were maintained. Similarities were found between this resolution of the EPR paradox and the final state solution to the black hole information paradox and the closely related firewall problem. The latter refers to an apparent conflict between unitary evaporation of a black hole and the strong subadditivity condition. The use of observer complementarity allows this solution of the black hole problem to be shown to be the same as a seemingly different solution known as “ER=EPR", where ‘ER’ refers to an Einstein-Rosen bridge or wormhole.
- Full Text:
The impact of three different footwear conditions on individual biomechanical, physiological and perceptual responses during running.
- Authors: McDougall, Justin John
- Date: 2016
- Subjects: Running -- Physiological aspects , Running shoes -- Physiological aspects , Running -- Health aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5177 , http://hdl.handle.net/10962/d1019988
- Description: Background: Despite the introduction of running footwear in the 1970’s, running injury rates continue to be unacceptably high. The subsequent revival of barefoot running and the introduction of minimalist footwear occurred, in an attempt to reduce injury rates and increase performance. There is much contention in the literature around the effectiveness of these footwear conditions. Furthermore individual responses have recently been proposed to provide more accurate and reflective conclusions than the use of mean data. Objectives: Twofold: a) to compare the biomechanical, physiological and perceptual responses between the shod, minimalist and barefoot footwear conditions and b) to assess and compare individual responses under these footwear conditions. Methods: 26 well-trained, male, habitually shod endurance runners, aged between 18 - 30 years completed three experimental sessions on an indoor runway and motorized treadmill. Each session was completed in either the shod, minimalist or barefoot condition, running at 15km.h-1. Variables assessed included stride rate, stride length, impact peak, vertical impact and average loading rate and strike time (biomechanical); heart rate, oxygen consumption and electromyography (physiological); and rating of perceived exertion and body discomfort (perceptual). Results: Biomechanics – Stride rate and stride length showed a significant (p<0.001) increase and decrease respectively when running in the minimalist or barefoot conditions versus shod. Running barefoot versus the minimalist and shod conditions resulted in a significantly (p<0.001) greater vertical impact loading rate. Strike time was significantly (p=0.008) reduced running in the minimalist and barefoot conditions versus shod. Physiology – Running barefoot versus shod resulted in a significantly (p=0.02) reduced heart rate and Tibialis Anterior activity (p=0.005). There was a large variability in individual responses for many variables, with responders and non-responders seen. Conclusion: The study suggests that there are significant differences between all three forms of running for some variables. It was further noted that there is support for the proposal that individual responses are highly variable and should be analysed accordingly
- Full Text:
- Authors: McDougall, Justin John
- Date: 2016
- Subjects: Running -- Physiological aspects , Running shoes -- Physiological aspects , Running -- Health aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5177 , http://hdl.handle.net/10962/d1019988
- Description: Background: Despite the introduction of running footwear in the 1970’s, running injury rates continue to be unacceptably high. The subsequent revival of barefoot running and the introduction of minimalist footwear occurred, in an attempt to reduce injury rates and increase performance. There is much contention in the literature around the effectiveness of these footwear conditions. Furthermore individual responses have recently been proposed to provide more accurate and reflective conclusions than the use of mean data. Objectives: Twofold: a) to compare the biomechanical, physiological and perceptual responses between the shod, minimalist and barefoot footwear conditions and b) to assess and compare individual responses under these footwear conditions. Methods: 26 well-trained, male, habitually shod endurance runners, aged between 18 - 30 years completed three experimental sessions on an indoor runway and motorized treadmill. Each session was completed in either the shod, minimalist or barefoot condition, running at 15km.h-1. Variables assessed included stride rate, stride length, impact peak, vertical impact and average loading rate and strike time (biomechanical); heart rate, oxygen consumption and electromyography (physiological); and rating of perceived exertion and body discomfort (perceptual). Results: Biomechanics – Stride rate and stride length showed a significant (p<0.001) increase and decrease respectively when running in the minimalist or barefoot conditions versus shod. Running barefoot versus the minimalist and shod conditions resulted in a significantly (p<0.001) greater vertical impact loading rate. Strike time was significantly (p=0.008) reduced running in the minimalist and barefoot conditions versus shod. Physiology – Running barefoot versus shod resulted in a significantly (p=0.02) reduced heart rate and Tibialis Anterior activity (p=0.005). There was a large variability in individual responses for many variables, with responders and non-responders seen. Conclusion: The study suggests that there are significant differences between all three forms of running for some variables. It was further noted that there is support for the proposal that individual responses are highly variable and should be analysed accordingly
- Full Text:
The phytogeography of Southern Mistbelt Forests of the Eastern Cape, South Africa
- Authors: Matiwane, Aviwe
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3224 , vital:20393
- Description: In the Eastern Cape, a moisture gradient (from west to east) exists along the Escarpment where patches of Southern Mistbelt Forests (SMF) occur. There is a notable profusion of plants in these forests, but the factors that drive plant species composition and abundance in these patches is poorly understood and such knowledge is critical if we are to address or mitigate the problems imposed by global change. Many of our ideas on plant community assembly are based on the premise that species differ in their environmental requirements for successful regeneration, especially when young. The aims of this study were to document the floristic diversity of poorly known patches of Southern Mistbelt Forests in the Eastern Cape and identify the environmental factors that influence plant community composition in these forest patches. Twenty six forest patches across the Eastern Cape were sampled. In each forest 400m2 circular plots were constructed. The diameter at breast height and stem counts for the tree species was taken and the % cover of the herbaceous species was recorded. General collections were also made to supplement the plot data in order to obtain a comprehensive flora for each forest patch. All sampling was done during the summer season of 2013 and 2014. Using plot data, Hierarchal Cluster Analysis and Multidimensional Scaling Analysis were done to compare similarities between patches. Plots from the same forest patch clustered which indicated that the species composition in each forest patch was unique. However, this pattern went down when only tree species were considered. Plant diversity also varied between patches; with those located in the east being generally more diverse than those in the west are. Clustering patterns in fragmented communities and differences in species diversity indicate evidence of species “nestedness”. Analysis of nestedness indicated that these forest patches were significantly nested. To identify which environmental variables might be correlated with both species diversity and nestedness, twelve environmental variables was selected for analysis using Canonical Correspondence Analysis and Principal Component Analysis. Results show that Mean Annual Precipitation, Mean Annual Potential Evapotranspiration, and percentage of Organic Matter of the soil were most strongly correlated with the patterns of diversity observed in these forest patches. Regression analysis indicated that Mean Annual Precipitation accounted for most of the variation in species diversity, especially for the herbaceous species. The herbaceous species thus show a greater sensitivity to “climate filtering” as a consequence of rainfall gradients. With the implementation of suitable monitoring programs, changes in abundance or even local extinction of these species can act as an early warning indicator of the possible long-term effects of climate change on forest communities.
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- Authors: Matiwane, Aviwe
- Date: 2016
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/3224 , vital:20393
- Description: In the Eastern Cape, a moisture gradient (from west to east) exists along the Escarpment where patches of Southern Mistbelt Forests (SMF) occur. There is a notable profusion of plants in these forests, but the factors that drive plant species composition and abundance in these patches is poorly understood and such knowledge is critical if we are to address or mitigate the problems imposed by global change. Many of our ideas on plant community assembly are based on the premise that species differ in their environmental requirements for successful regeneration, especially when young. The aims of this study were to document the floristic diversity of poorly known patches of Southern Mistbelt Forests in the Eastern Cape and identify the environmental factors that influence plant community composition in these forest patches. Twenty six forest patches across the Eastern Cape were sampled. In each forest 400m2 circular plots were constructed. The diameter at breast height and stem counts for the tree species was taken and the % cover of the herbaceous species was recorded. General collections were also made to supplement the plot data in order to obtain a comprehensive flora for each forest patch. All sampling was done during the summer season of 2013 and 2014. Using plot data, Hierarchal Cluster Analysis and Multidimensional Scaling Analysis were done to compare similarities between patches. Plots from the same forest patch clustered which indicated that the species composition in each forest patch was unique. However, this pattern went down when only tree species were considered. Plant diversity also varied between patches; with those located in the east being generally more diverse than those in the west are. Clustering patterns in fragmented communities and differences in species diversity indicate evidence of species “nestedness”. Analysis of nestedness indicated that these forest patches were significantly nested. To identify which environmental variables might be correlated with both species diversity and nestedness, twelve environmental variables was selected for analysis using Canonical Correspondence Analysis and Principal Component Analysis. Results show that Mean Annual Precipitation, Mean Annual Potential Evapotranspiration, and percentage of Organic Matter of the soil were most strongly correlated with the patterns of diversity observed in these forest patches. Regression analysis indicated that Mean Annual Precipitation accounted for most of the variation in species diversity, especially for the herbaceous species. The herbaceous species thus show a greater sensitivity to “climate filtering” as a consequence of rainfall gradients. With the implementation of suitable monitoring programs, changes in abundance or even local extinction of these species can act as an early warning indicator of the possible long-term effects of climate change on forest communities.
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The trophic and spatial ecology of juvenile porcupine rays Urogymnus asperrimus at the remote St. Joseph Atoll
- Authors: Elston, Chantel
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/965 , vital:20007
- Description: Little information exists for the widely occurring but rare porcupine ray Urogymnus asperrimus. This is a concern given that it is a vulnerable species and likely plays an important ecological role in tropical atoll ecosystems. The aims of this thesis were to investigate the trophic and spatial ecology of juvenile porcupine rays within the St. Joseph Atoll, which is hypothesized to be functioning as a nursery for this species. Specific objectives were to determine i) the dietary composition and resource selectivity displayed by juvenile porcupine rays, ii) residency to the atoll, space use, and seasonality in movements, and iii) whether environmental factors affect short-term movements. Gastric lavage was used to collect stomach contents from 55 juveniles and sediment samples were collected. Thirteen juveniles were implanted with acoustic transmitters and monitored for a year by an array of 88 acoustic receivers situated in and around the St. Joseph Atoll. Porcupine rays appeared to be generalist and opportunistic feeders, foraging predominantly on annelids with the highest environmental availability. Polychaetes of the family Capitellidae were the most important prey item (Index of Importance = 35%). Rays only fed on deep infaunal prey, likely because of their foraging behaviour, suggesting they may influence this community. There was a size-related shift in the crustacean families consumed. The tagged rays displayed high residency to the atoll (mean residency index of 64%) and restricted movements, with small core use and activity space areas (mean of 0.5km² and 3km² respectively) and the majority of detections were recorded within 1km of their tagging locations. The rays favoured the sand ats where 88% of detections occurred. Transient use of the lagoon and fringe reef peaked in the north-west monsoon season, indicating a seasonal usage of these habitats. The effects of temperature and water depth on movements were manifested as diel and tidal cyclical patterns in presence. Evidence illustrates that the St. Joseph Atoll constitutes an important nursery for this species, which has been declared a Marine Protected Area. A major determinant behind the dependence of this nursery habitat is related to predator avoidance. Thermoregulatory behaviours were identified, suggesting that this species is vulnerable to climate change.
- Full Text:
- Authors: Elston, Chantel
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/965 , vital:20007
- Description: Little information exists for the widely occurring but rare porcupine ray Urogymnus asperrimus. This is a concern given that it is a vulnerable species and likely plays an important ecological role in tropical atoll ecosystems. The aims of this thesis were to investigate the trophic and spatial ecology of juvenile porcupine rays within the St. Joseph Atoll, which is hypothesized to be functioning as a nursery for this species. Specific objectives were to determine i) the dietary composition and resource selectivity displayed by juvenile porcupine rays, ii) residency to the atoll, space use, and seasonality in movements, and iii) whether environmental factors affect short-term movements. Gastric lavage was used to collect stomach contents from 55 juveniles and sediment samples were collected. Thirteen juveniles were implanted with acoustic transmitters and monitored for a year by an array of 88 acoustic receivers situated in and around the St. Joseph Atoll. Porcupine rays appeared to be generalist and opportunistic feeders, foraging predominantly on annelids with the highest environmental availability. Polychaetes of the family Capitellidae were the most important prey item (Index of Importance = 35%). Rays only fed on deep infaunal prey, likely because of their foraging behaviour, suggesting they may influence this community. There was a size-related shift in the crustacean families consumed. The tagged rays displayed high residency to the atoll (mean residency index of 64%) and restricted movements, with small core use and activity space areas (mean of 0.5km² and 3km² respectively) and the majority of detections were recorded within 1km of their tagging locations. The rays favoured the sand ats where 88% of detections occurred. Transient use of the lagoon and fringe reef peaked in the north-west monsoon season, indicating a seasonal usage of these habitats. The effects of temperature and water depth on movements were manifested as diel and tidal cyclical patterns in presence. Evidence illustrates that the St. Joseph Atoll constitutes an important nursery for this species, which has been declared a Marine Protected Area. A major determinant behind the dependence of this nursery habitat is related to predator avoidance. Thermoregulatory behaviours were identified, suggesting that this species is vulnerable to climate change.
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The use of treated brewery effluent as a water and nutrient source in crop irrigation
- Authors: Taylor, Richard Peter
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5390 , http://hdl.handle.net/10962/d1021265
- Description: Brewery effluent (BE) needs to be treated before it can be released into the environment, reused or used in down-stream activities. Current technologies used to address this concern at the experimental wastewater treatment plant at Ibahyi Brewery (SAB Ltd) include anaerobic digestion (AD), primary facultative ponds (PFP), high rate algal ponds (HRAP) and constructed wetlands (CW). The aim of this work was to determine if BE treated in these systems might be suitable for crop irrigation. A test crop, cabbage (Brassica oleracea cv. Star 3301), grew best on post-AD and post-PFP BE compared to those irrigated with post-HRAP or post-CW effluent. However, the yield was 13% lower than cabbage plants irrigated with a commercial nutrient solution and fresh water. The relatively high conductivity (3019.05 ± 48.72 μs/cm2) of BE may be the main factor reducing the cabbage yields. Post-HRAP and post-CW BE were the least suitable for irrigated crop production due to the higher conductivity and lower nutrient content of these treated effluents. After three months, soils irrigated with post-AD and post-PFP BE had a significantly higher sodium content and sodium adsorption ratio (3919 ± 94.77 mg/kg & 8.18 ± 0.17) than soil irrigated with a commercial nutrient solution (920.58 ± 27.46 mg/kg & 2.20 ± 0.05; p<0.05). However, this was not accompanied by a deterioration in the soil’s hydro-physical properties, nor a change in the metabolic community structure of the soil (p>0.05). After prolonged irrigation with treated BE, sodium is likely to build up in the soil and this can be expected to be accompanied by a deterioration in the soil physical structure. However, crops species such as millet (Echinochloa esculenta), lucerne (Medicago sativa) and saltbush (Atriplex nummularia) reduced the build-up of sodium in the soil. The results suggest that sodium was mainly removed from the soil through plant-assisted leaching. Of the crops grown, lucerne showed the most promise because it improved the soil physical properties, is able to grow well in alkaline environments, is a popular fodder crop and can be harvested multiple times from a single stand. Brewery effluent is more suitable for soil production systems than hydroponic production systems because the soil was able to act as a buffer against the high pH of post-AD BE, whereas in a hydroponics systems the high pH reduced the availability of key minerals to plants. In conclusion brewery effluent contains sufficient plants nutrients to support the growth of cabbages, saltbush, lucerne and millet. However the sodium content of BE is a concern as it accumulates in the soil, and in the long-term it may lead to soil degradation. It is suggested that the brewery change the pH neutralising treatment of BE from sodium hydroxide to potassium hydroxide, or dolomitic lime (calcium and magnesium carbonate) because this would reduce the introduction of sodium into the system, and would increase the suitability of BE for crop production, given potassium and calcium are plant nutrients. The benefits of developing this nutrient and water resource could contribute to cost-reductions at the brewery, more efficient water, nutrient and energy management, create job opportunities with the potential of improving food security in the local community.
- Full Text:
- Authors: Taylor, Richard Peter
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5390 , http://hdl.handle.net/10962/d1021265
- Description: Brewery effluent (BE) needs to be treated before it can be released into the environment, reused or used in down-stream activities. Current technologies used to address this concern at the experimental wastewater treatment plant at Ibahyi Brewery (SAB Ltd) include anaerobic digestion (AD), primary facultative ponds (PFP), high rate algal ponds (HRAP) and constructed wetlands (CW). The aim of this work was to determine if BE treated in these systems might be suitable for crop irrigation. A test crop, cabbage (Brassica oleracea cv. Star 3301), grew best on post-AD and post-PFP BE compared to those irrigated with post-HRAP or post-CW effluent. However, the yield was 13% lower than cabbage plants irrigated with a commercial nutrient solution and fresh water. The relatively high conductivity (3019.05 ± 48.72 μs/cm2) of BE may be the main factor reducing the cabbage yields. Post-HRAP and post-CW BE were the least suitable for irrigated crop production due to the higher conductivity and lower nutrient content of these treated effluents. After three months, soils irrigated with post-AD and post-PFP BE had a significantly higher sodium content and sodium adsorption ratio (3919 ± 94.77 mg/kg & 8.18 ± 0.17) than soil irrigated with a commercial nutrient solution (920.58 ± 27.46 mg/kg & 2.20 ± 0.05; p<0.05). However, this was not accompanied by a deterioration in the soil’s hydro-physical properties, nor a change in the metabolic community structure of the soil (p>0.05). After prolonged irrigation with treated BE, sodium is likely to build up in the soil and this can be expected to be accompanied by a deterioration in the soil physical structure. However, crops species such as millet (Echinochloa esculenta), lucerne (Medicago sativa) and saltbush (Atriplex nummularia) reduced the build-up of sodium in the soil. The results suggest that sodium was mainly removed from the soil through plant-assisted leaching. Of the crops grown, lucerne showed the most promise because it improved the soil physical properties, is able to grow well in alkaline environments, is a popular fodder crop and can be harvested multiple times from a single stand. Brewery effluent is more suitable for soil production systems than hydroponic production systems because the soil was able to act as a buffer against the high pH of post-AD BE, whereas in a hydroponics systems the high pH reduced the availability of key minerals to plants. In conclusion brewery effluent contains sufficient plants nutrients to support the growth of cabbages, saltbush, lucerne and millet. However the sodium content of BE is a concern as it accumulates in the soil, and in the long-term it may lead to soil degradation. It is suggested that the brewery change the pH neutralising treatment of BE from sodium hydroxide to potassium hydroxide, or dolomitic lime (calcium and magnesium carbonate) because this would reduce the introduction of sodium into the system, and would increase the suitability of BE for crop production, given potassium and calcium are plant nutrients. The benefits of developing this nutrient and water resource could contribute to cost-reductions at the brewery, more efficient water, nutrient and energy management, create job opportunities with the potential of improving food security in the local community.
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Thermoluminescence of annealed synthetic quartz
- Atang, Elizabeth Fende Midiki
- Authors: Atang, Elizabeth Fende Midiki
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/420 , vital:19957
- Description: The kinetic and dosimetric features of the main thermoluminescent peak of synthetic quartz have been investigated in quartz ordinarily annealed at 500_C as well as quartz annealed at 500_C for 10 minutes. The main peak is found at 78 _C for the samples annealed at 500_C for 10 minutes irradiated to 10 Gy and heated at 1.0 _C/s. For the samples ordinarily annealed at 500_C the main peak is found at 106 _C after the sample has been irradiated to 30 Gy and heated at 5.0 _C/s. In these samples, the intensity of the main peak is enhanced with repetitive measurement whereas its maximum temperature is unaffected. The peak position of the main peak in the sample is independent of the irradiation dose and this, together with its fading characteristics, are consistent with first-order kinetics. For doses between 5 and 25 Gy, the dose response of the main peak of the annealed sample is superlinear. The half-life of the main TL peak of the annealed sample is about 1 h. The activation energy E of the main peak is around 0.90 eV. For a heating rate of 0.4 _C/s, its order of kinetics b derived from the whole curve method of analysis is 1.0. Following irradiation, preheating and illumination with 470 nm blue light, the main peak in the annealed sample is regenerated during heating. The resulting phototransferred peak occurs at the same temperature as the original peak and has similar kinetic and dosimetric features, with a half-life of about 1 h. For a preheat temperature of 200 _C, the intensity of the phototransferred peak in the sample increases with illumination time up to a maximum and decreases thereafter. At longer illumination times, no further decrease in the intensity of the phototransferred peak is observed. The traps associated with the 325 _C peak are the main source of the electrons responsible for the regenerated peak.
- Full Text:
- Authors: Atang, Elizabeth Fende Midiki
- Date: 2016
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/420 , vital:19957
- Description: The kinetic and dosimetric features of the main thermoluminescent peak of synthetic quartz have been investigated in quartz ordinarily annealed at 500_C as well as quartz annealed at 500_C for 10 minutes. The main peak is found at 78 _C for the samples annealed at 500_C for 10 minutes irradiated to 10 Gy and heated at 1.0 _C/s. For the samples ordinarily annealed at 500_C the main peak is found at 106 _C after the sample has been irradiated to 30 Gy and heated at 5.0 _C/s. In these samples, the intensity of the main peak is enhanced with repetitive measurement whereas its maximum temperature is unaffected. The peak position of the main peak in the sample is independent of the irradiation dose and this, together with its fading characteristics, are consistent with first-order kinetics. For doses between 5 and 25 Gy, the dose response of the main peak of the annealed sample is superlinear. The half-life of the main TL peak of the annealed sample is about 1 h. The activation energy E of the main peak is around 0.90 eV. For a heating rate of 0.4 _C/s, its order of kinetics b derived from the whole curve method of analysis is 1.0. Following irradiation, preheating and illumination with 470 nm blue light, the main peak in the annealed sample is regenerated during heating. The resulting phototransferred peak occurs at the same temperature as the original peak and has similar kinetic and dosimetric features, with a half-life of about 1 h. For a preheat temperature of 200 _C, the intensity of the phototransferred peak in the sample increases with illumination time up to a maximum and decreases thereafter. At longer illumination times, no further decrease in the intensity of the phototransferred peak is observed. The traps associated with the 325 _C peak are the main source of the electrons responsible for the regenerated peak.
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