Analysis of maximum power point tracking data for obtaining photovoltaic parameters
- Authors: Chitura, Anesu Godfrey
- Date: 2020
- Subjects: Photovoltaic power system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18576 , vital:42610
- Description: As a standard, photovoltaic (PV) modules are rated by the use of standard test conditions (STC). Such details entail current and voltage (I-V) measurements for modules under an irradiance of 1000 W/m2 an air mass ration of 1.5 global spectrum and 25˚C cell temperature. Outdoor weather conditions continuously vary with time and from one location to the other. This further offset the expected operational power outputs as outdoor conditions are generally characterized by high cell temperatures. The technology one uses will also complicate the power output prediction since different module technologies respond to these outdoor conditions differently. I-V tracers are able to measure the full I-V curve of the module thus can give the operational PV parameters at any given time. However, these tracers are sold at exorbitant prices and they require skilled personnel in order to operate them. Most if not all tracers require isolation of the module under test thereby disrupting the power production function of the module._________________________________________________________________________________________________________________________________________ In this study a method to obtain photovoltaic (PV) parameters using the maximum power point tracking (MPPT) data is presented and tested under natural outdoor conditions. The method features a customized data acquisition system (DAS) designed for the measurement and storage of meteorological and MPPT data. The DAS is capable of extracting parameters from any combination of modules with an open circuit voltage 〖(V〗_oc) less than or equal to 120 Volts and a short circuit current 〖(I〗_sc) of 100 Amps. The system used is capable of extracting MPPT data using a reliable, improved storage and a programmable data logger. In order to match the sampling operational speeds of internal charge controller switches a computer interfaced Peripheral Component Interconnect (PCI) card was also used. Data collection and characterization of the MPPT data was done in such a way that the power generation process remained uninterrupted throughout the whole process. The regression nonlinear least squares method was used to fit MPPT crests and obtain the knee part of the I-V curve. This was then extrapolated to obtain the full I-V curve, which then produces the operational PV parameters. The resultant parameters from the characterization process were logged and accessible at any time. The end result was a method that can be incorporated within a charge controller for quick, hands-free PV parameter extraction, using only the MPPT scanned data.
- Full Text:
- Date Issued: 2020
- Authors: Chitura, Anesu Godfrey
- Date: 2020
- Subjects: Photovoltaic power system
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10353/18576 , vital:42610
- Description: As a standard, photovoltaic (PV) modules are rated by the use of standard test conditions (STC). Such details entail current and voltage (I-V) measurements for modules under an irradiance of 1000 W/m2 an air mass ration of 1.5 global spectrum and 25˚C cell temperature. Outdoor weather conditions continuously vary with time and from one location to the other. This further offset the expected operational power outputs as outdoor conditions are generally characterized by high cell temperatures. The technology one uses will also complicate the power output prediction since different module technologies respond to these outdoor conditions differently. I-V tracers are able to measure the full I-V curve of the module thus can give the operational PV parameters at any given time. However, these tracers are sold at exorbitant prices and they require skilled personnel in order to operate them. Most if not all tracers require isolation of the module under test thereby disrupting the power production function of the module._________________________________________________________________________________________________________________________________________ In this study a method to obtain photovoltaic (PV) parameters using the maximum power point tracking (MPPT) data is presented and tested under natural outdoor conditions. The method features a customized data acquisition system (DAS) designed for the measurement and storage of meteorological and MPPT data. The DAS is capable of extracting parameters from any combination of modules with an open circuit voltage 〖(V〗_oc) less than or equal to 120 Volts and a short circuit current 〖(I〗_sc) of 100 Amps. The system used is capable of extracting MPPT data using a reliable, improved storage and a programmable data logger. In order to match the sampling operational speeds of internal charge controller switches a computer interfaced Peripheral Component Interconnect (PCI) card was also used. Data collection and characterization of the MPPT data was done in such a way that the power generation process remained uninterrupted throughout the whole process. The regression nonlinear least squares method was used to fit MPPT crests and obtain the knee part of the I-V curve. This was then extrapolated to obtain the full I-V curve, which then produces the operational PV parameters. The resultant parameters from the characterization process were logged and accessible at any time. The end result was a method that can be incorporated within a charge controller for quick, hands-free PV parameter extraction, using only the MPPT scanned data.
- Full Text:
- Date Issued: 2020
Knowledge of drowning risks amongst adolescents in the Nelson Mandela Metropole, Eastern Cape Province, South Africa
- Authors: Isaacs, Imeraan
- Date: 2020
- Subjects: Primary health care
- Language: English
- Type: Thesis , Masters , MPH
- Identifier: http://hdl.handle.net/10353/18422 , vital:42264
- Description: The purpose of this research study was to explore and describe the knowledge and the level of awareness of drowning risks amongst adolescents in the Nelson Mandela Metropole, Eastern Cape Province, and South Africa. Drowning is defined as the “process of experiencing respiratory impairment from either submersion or immersion into a water medium” (van Beeck et al 2005:853). Global statistics place drowning as being the third foremost cause of unintentional death worldwide (WHO 2013). The World Health Organization reports that more than 90% of the estimated 370 000 drowning fatalities recorded in 2012 occurred in low and middle income countries (WHO 2014). A qualitative descriptive explorative contextual design was employed in this research study. A non-probability convenience sampling method was used. Adolescents aged 10- 13 years old who attend a public primary school and model C primary school in Nelson Mandela Metropole area in the Eastern Cape Province were the target population who had the specific characteristics of interest and significance to the research phenomenon (Asiamah et al 2017). Four focus group interviews were conducted. The groups consisted of five to ten participants grouped together to discuss the matter. Field notes were also taken by the researcher on what was heard, observed, thought and experienced during the interview process (Streubert & Carpenter 2007). Ethical principles were maintained as well as the concepts of trustworthiness were applied throughout this study.Data analysis was done using Tesch’s approach to open coding in qualitative research. A total of six themes and seven sub-themes arose during the analysis of the data and were completely discussed. The findings suggest that most of the participants are quite aware and knowledgeable of the potential risks that predispose an individual to drowning. The consequences of what happens when a victim is exposed to drowning, however, requires more insight. The risk of being unsupervised as well as not being able to swim was echoed in most of the group interviews. vii A noteworthy finding was the fact that the participants who were involved with some form of water safety programme/s at school were very articulate in their responses to the questions. It was recommended that educational programmes ought to be aligned with current evidence which is reflective of the region’s demographics and dynamics. Even though all researchers do not share the sentiments that swim proficiencies heighten the safety of the individual in and around water, the need for ongoing research initiatives is a significant stimulus that will generate new evidence and inform current preventive strategies. Identification and awareness of drowning risks require a foundation of comprehension in order to better understand and interpret the consequences of these risks. Learn to swim or swim orientation initiatives could potentially assist at primary school level with the safety levels of learners.
- Full Text:
- Date Issued: 2020
- Authors: Isaacs, Imeraan
- Date: 2020
- Subjects: Primary health care
- Language: English
- Type: Thesis , Masters , MPH
- Identifier: http://hdl.handle.net/10353/18422 , vital:42264
- Description: The purpose of this research study was to explore and describe the knowledge and the level of awareness of drowning risks amongst adolescents in the Nelson Mandela Metropole, Eastern Cape Province, and South Africa. Drowning is defined as the “process of experiencing respiratory impairment from either submersion or immersion into a water medium” (van Beeck et al 2005:853). Global statistics place drowning as being the third foremost cause of unintentional death worldwide (WHO 2013). The World Health Organization reports that more than 90% of the estimated 370 000 drowning fatalities recorded in 2012 occurred in low and middle income countries (WHO 2014). A qualitative descriptive explorative contextual design was employed in this research study. A non-probability convenience sampling method was used. Adolescents aged 10- 13 years old who attend a public primary school and model C primary school in Nelson Mandela Metropole area in the Eastern Cape Province were the target population who had the specific characteristics of interest and significance to the research phenomenon (Asiamah et al 2017). Four focus group interviews were conducted. The groups consisted of five to ten participants grouped together to discuss the matter. Field notes were also taken by the researcher on what was heard, observed, thought and experienced during the interview process (Streubert & Carpenter 2007). Ethical principles were maintained as well as the concepts of trustworthiness were applied throughout this study.Data analysis was done using Tesch’s approach to open coding in qualitative research. A total of six themes and seven sub-themes arose during the analysis of the data and were completely discussed. The findings suggest that most of the participants are quite aware and knowledgeable of the potential risks that predispose an individual to drowning. The consequences of what happens when a victim is exposed to drowning, however, requires more insight. The risk of being unsupervised as well as not being able to swim was echoed in most of the group interviews. vii A noteworthy finding was the fact that the participants who were involved with some form of water safety programme/s at school were very articulate in their responses to the questions. It was recommended that educational programmes ought to be aligned with current evidence which is reflective of the region’s demographics and dynamics. Even though all researchers do not share the sentiments that swim proficiencies heighten the safety of the individual in and around water, the need for ongoing research initiatives is a significant stimulus that will generate new evidence and inform current preventive strategies. Identification and awareness of drowning risks require a foundation of comprehension in order to better understand and interpret the consequences of these risks. Learn to swim or swim orientation initiatives could potentially assist at primary school level with the safety levels of learners.
- Full Text:
- Date Issued: 2020
Synthesis, characterisation and electrocatalytic behaviour of three series of Metal Organic Frameworks
- Authors: Murinzi, Tafadzwa Wendy
- Date: 2020
- Subjects: Electrochemistry , Metal-organic frameworks , Polyoxometalates , Fourier transform infrared spectroscopy , Electrocatalysis , Cysteine
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167598 , vital:41495
- Description: Metal organic frameworks (MOFs) have received a lot of attention over the past few years due to their vast range of interesting properties and applications, such as catalysis, environmental sensing and storage. This wide range of potential applications is afforded by careful selection and manipulation of the components chosen in assembling of MOFs. In this study, three series of MOFs were synthesized from Co(II), Cu(II) and Mo(VI) polyoxometallates with either 1,3,5-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid or 2,6- pyridinedicarboxylic acid as the ligands. In series 1, the common 1,3,5- benzenetricarboxylic acid MOF, HKUST-1, and POM modified HKUST-1 compounds involving encapsulation and encorporation of the POM were utilised. In series 2, flexible cobalt(II) benzenepolycarboxylate MOFs which investigated the effect of varying the degree of carboxylate substituent were utilised. In series 3, flexibly reduced heterocyclic polycarboxylate MOFs using 2,6-pyridine dicarboxylate were utilised. Solvothermal and slow evaporation synthesis conditions were employed. Where single crystals of good quality were produced, single crystal X-ray diffraction (SC-XRD) was employed for structural elucidation. In the absence of such crystals, a combination of elemental analysis, inductively coupled plasma optical emission spectrometry (ICP-OES) and powder X-ray diffraction (PXRD) was used. Characterization of the MOFs was done by Fourier transform infrared spectrometry (FTIR) and thermal methods, namely thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The electrocatalytic potential of the compounds in the oxidation of L-cysteine was then investigated using a variety of techniques. Cyclic voltammetry was used for L-cysteine detection whilst chronoamperometry and differential pulse voltammetry were used to determine the nanoprobes’ sensitivity, rate constants and detection limits. Electrochemical impedence spectroscopy was used to investigate the charge transfer resistance (RCT) and electron transfer kinetics. Of the three, series 3 gave the best signals and sensitivities for electrocatalysis of L-cysteine followed by series 2 and lastly series 1. Series 2 showed the highest stability and series 1 required the least overpotential. The results highlight the effects of different metal centres and ligands on electrocatalysis. The application of MOFs in electrochemistry is a relatively new field making the findings of this study a significant addition to the body of knowledge.
- Full Text:
- Date Issued: 2020
- Authors: Murinzi, Tafadzwa Wendy
- Date: 2020
- Subjects: Electrochemistry , Metal-organic frameworks , Polyoxometalates , Fourier transform infrared spectroscopy , Electrocatalysis , Cysteine
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167598 , vital:41495
- Description: Metal organic frameworks (MOFs) have received a lot of attention over the past few years due to their vast range of interesting properties and applications, such as catalysis, environmental sensing and storage. This wide range of potential applications is afforded by careful selection and manipulation of the components chosen in assembling of MOFs. In this study, three series of MOFs were synthesized from Co(II), Cu(II) and Mo(VI) polyoxometallates with either 1,3,5-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid or 2,6- pyridinedicarboxylic acid as the ligands. In series 1, the common 1,3,5- benzenetricarboxylic acid MOF, HKUST-1, and POM modified HKUST-1 compounds involving encapsulation and encorporation of the POM were utilised. In series 2, flexible cobalt(II) benzenepolycarboxylate MOFs which investigated the effect of varying the degree of carboxylate substituent were utilised. In series 3, flexibly reduced heterocyclic polycarboxylate MOFs using 2,6-pyridine dicarboxylate were utilised. Solvothermal and slow evaporation synthesis conditions were employed. Where single crystals of good quality were produced, single crystal X-ray diffraction (SC-XRD) was employed for structural elucidation. In the absence of such crystals, a combination of elemental analysis, inductively coupled plasma optical emission spectrometry (ICP-OES) and powder X-ray diffraction (PXRD) was used. Characterization of the MOFs was done by Fourier transform infrared spectrometry (FTIR) and thermal methods, namely thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The electrocatalytic potential of the compounds in the oxidation of L-cysteine was then investigated using a variety of techniques. Cyclic voltammetry was used for L-cysteine detection whilst chronoamperometry and differential pulse voltammetry were used to determine the nanoprobes’ sensitivity, rate constants and detection limits. Electrochemical impedence spectroscopy was used to investigate the charge transfer resistance (RCT) and electron transfer kinetics. Of the three, series 3 gave the best signals and sensitivities for electrocatalysis of L-cysteine followed by series 2 and lastly series 1. Series 2 showed the highest stability and series 1 required the least overpotential. The results highlight the effects of different metal centres and ligands on electrocatalysis. The application of MOFs in electrochemistry is a relatively new field making the findings of this study a significant addition to the body of knowledge.
- Full Text:
- Date Issued: 2020
Development of MOVPE-grown InAsSb for barrier diode applications
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
- Authors: Dobson, Stephen R
- Date: 2020
- Subjects: Gallium arsenide semiconductors , Electronics
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10948/49071 , vital:41598
- Description: In this study, layers of GaSb, InAs and InAsSb are grown by metalorganic vapour phase epitaxy and characterised. Growth is conducted using the precursors of trimethylgallium, trimethylindium, trimethylantimony and tertiarybutylarsine. Focus is then placed on the characterisation of the materials, carried out by the techniques of X-ray diffraction, photoluminescence spectroscopy, Hall measurements and photocurrent spectroscopy. It is observed that V/III ratio plays a vital role in the growth of the GaSb and InAsSb layers. Epilayers of GaSb showed best crystalline quality when a V/III ratio of 1.2 was used at a growth temperature of 600 °C and a cell pressure of 600 Torr. Resultant Hall measurements indicated p-type GaSb. The Hall carrier concentrations of the p-type GaSb samples were analyzed considering electrical neutrality conditions and found to be highly compensated with evidence of band impurity conduction at low measurement temperatures. Both the donor and acceptor concentrations were determined to be of the order of 1016 cm−3 for all samples. For low temperature (< 150 K) a monovalent acceptor concentration is calculated to have an activation energy at approximately 20 meV. At high temperature (> 150 K) a divalent acceptor is extracted with an activation energy varying between samples based on compensation in a range of 90 meV to 70 meV. Photoluminescence measurements show four peaks with recombination mechanisms linked to the native acceptor identified in literature as either the gallium antisite and/or vacant gallium site. A fifth peak observed is attributed to the longitudinal phonon of the native acceptor. InAs and InAsSb epilayer are all grown at a temperature of 600 °C and cell pressure of 600 Torr. InAs is grown at a V/III ratio of 9.5 on GaAs substrate. Photoluminescence of the InAs layer shows two distinct peaks, one of which is an extrinsic band to band recombination. The other is attributed to free electron to acceptor or a donor-acceptor pair transition. An additional weak peak is also observed which is assigned to the longitudinal phonon of the band to band. InAsSb growth was conducted under a range of V/III ratios of 4.8 to 5, with a vapour phase composition of 0.4 to 0.435. Structural analysis via X-ray diffraction showed a 6 % to 12 % solid antimony content. Photoluminescence exhibited a single broad peak for all samples, with extended band tails. Temperature and power dependant analysis of luminescence indicated a convolution of extrinsic band to tail and band to band recombinations. Hall measurements indicated the InAsSb was n-type material with an apparent measured maximum mobility at 120 K of 9.5 × 103 cm2/V.s. and a room temperature apparent mobility of 7.5 × 103 cm2/V.s. Analysis of hall results using a two-layer model calculated a true bulk mobility of the epilayer at room temperature with an increased value of 15.4 × 103 cm2/V.s. The two-layer model details the effects of the surface conduction. From photoconductivity measurements and further analysis a resultant effective lifetime, at room temperature, was found to be on same order of magnitude as that of InAs materials. Application of a single Einstein oscillator extrapolated 0 K energy gaps for two samples of solid Sb contents of 6 % and 12 %, of 354 meV and 332 meV, respectively. Finally consideration was given to the growth of aluminium containing compounds, particularly AlGaSb. Multiple phases were observed under scanning electron microscope showing growth of GaSb regions surrounded by amorphous solid aluminium and/or aluminium oxide phases. The failure of the aluminium to incorporate into the desired crystal structure is speculated to be due to impure precursor introducing oxygen into the films. Additionally, the effectiveness of the gallium precursor compared to the aluminium precursor in helping the removal of the methyl groups at the growth surface, could also promote a preference for GaSb growth.
- Full Text:
- Date Issued: 2020
Effects of a resistance training intervention on the physical fitness of youth in a rural soccer development programme
- Authors: Greyling, Jacob Johannes
- Date: 2020
- Subjects: Physical fitness--Soccer
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/50795 , vital:42701
- Description: Background: Soccer is the most popular sport worldwide with an estimated 270 million people involved in the sport. Soccer is a fast-paced contact team sport that requires physical capabilities such as speed, agility, strength, power, aerobic and anaerobic fitness in addition to technical proficiency. Most goals are preceded by a linear sprint, jump or change of direction which is why the ability to perform fast powerful movements is important. Research has indicated that resistance training performed in combination with high intensity speed and plyometric training, improves athletic performance of soccer players. Aims and Objectives: This study investigated the effects of a resistance training intervention on the physical fitness of youth in a rural soccer development programme in Addo in the Eastern Cape province of South Africa. Methodology: This study employed a quantitative approach in the form of a quasi-experimental design with an experimental and control group. The sample was conveniently selected based on availability of players and on them meeting specific inclusion criteria. Local soccer clubs in the Nomathamsanqa township - an impoverished area in Addo, which forms part of the Addo Soccer Development Programme (ASDP) - were invited to participate in the study. The final sample for this study consisted of 12 participants. A 10-week soccer-based resistance training intervention, addressing the components of physical fitness with specific emphasis on resistance training, was implemented after completion of the baseline testing. The intervention was designed to be suitable for a rural setting. Results: Within group comparisons revealed significant improvements in the experimental group for power (p = 0.028), speed (p = 0.028) and overall performance (grouped physical fitness measures) (p = 0.018) whereas the control group improved significantly in speed (p = 0.043) and regressed significantly in cardiovascular endurance (p = 0.043). Between group comparisons revealed significant differences for overall performance improvement in the experimental group (p = 0.006) and a reduction in cardiovascular endurance in the control group (p = 0.028). The main finding of this study is therefore this: that the individual parameters did not show consistent improvement when viewed in isolation, however that the intervention had a positive effect on overall performance when all the physical fitness measures were computed as a collective result. Conclusion: The results of the study indicate that the intervention had a positive effect on overall performance however more research is required on soccer in rural and disadvantaged settings of South Africa to develop a convincing model for supplementary training other than conventional soccer practice to improve performance and to overcome the unique challenges faced in a rural setting.
- Full Text: false
- Date Issued: 2020
- Authors: Greyling, Jacob Johannes
- Date: 2020
- Subjects: Physical fitness--Soccer
- Language: English
- Type: Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10948/50795 , vital:42701
- Description: Background: Soccer is the most popular sport worldwide with an estimated 270 million people involved in the sport. Soccer is a fast-paced contact team sport that requires physical capabilities such as speed, agility, strength, power, aerobic and anaerobic fitness in addition to technical proficiency. Most goals are preceded by a linear sprint, jump or change of direction which is why the ability to perform fast powerful movements is important. Research has indicated that resistance training performed in combination with high intensity speed and plyometric training, improves athletic performance of soccer players. Aims and Objectives: This study investigated the effects of a resistance training intervention on the physical fitness of youth in a rural soccer development programme in Addo in the Eastern Cape province of South Africa. Methodology: This study employed a quantitative approach in the form of a quasi-experimental design with an experimental and control group. The sample was conveniently selected based on availability of players and on them meeting specific inclusion criteria. Local soccer clubs in the Nomathamsanqa township - an impoverished area in Addo, which forms part of the Addo Soccer Development Programme (ASDP) - were invited to participate in the study. The final sample for this study consisted of 12 participants. A 10-week soccer-based resistance training intervention, addressing the components of physical fitness with specific emphasis on resistance training, was implemented after completion of the baseline testing. The intervention was designed to be suitable for a rural setting. Results: Within group comparisons revealed significant improvements in the experimental group for power (p = 0.028), speed (p = 0.028) and overall performance (grouped physical fitness measures) (p = 0.018) whereas the control group improved significantly in speed (p = 0.043) and regressed significantly in cardiovascular endurance (p = 0.043). Between group comparisons revealed significant differences for overall performance improvement in the experimental group (p = 0.006) and a reduction in cardiovascular endurance in the control group (p = 0.028). The main finding of this study is therefore this: that the individual parameters did not show consistent improvement when viewed in isolation, however that the intervention had a positive effect on overall performance when all the physical fitness measures were computed as a collective result. Conclusion: The results of the study indicate that the intervention had a positive effect on overall performance however more research is required on soccer in rural and disadvantaged settings of South Africa to develop a convincing model for supplementary training other than conventional soccer practice to improve performance and to overcome the unique challenges faced in a rural setting.
- Full Text: false
- Date Issued: 2020
Photodynamic antimicrobial chemotherapy of a dimethylamino-functionalized asymmetric zinc (II) phthalocyanine and its quaternized derivative against Staphylococcus aureus when supported on asymmetric polystyrene polymer membranes:
- Mafukidze, Donovan Musizvinoda Chidyamurimi, Nyokong, Tebello
- Authors: Mafukidze, Donovan Musizvinoda Chidyamurimi , Nyokong, Tebello
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148595 , vital:38753 , https://doi.org/10.1016/j.reactfunctpolym.2020.104634
- Description: Membrane applications are hindered by fouling. Photoactive membranes (containing photosensitizers) show photodynamic antimicrobial chemotherapy (PACT) activity which reduces biological fouling. In this work we use phthalocyanines (Pcs) as photosensitizers. The Pcs used are: 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(dimethylamino) phthalocyaninato zinc(II) (1) and the quaternized 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(trimethylamino) phthalocyanine zinc(II) methyl sulfate (2). Complex 2 showed an enhanced singlet oxygen quantum yield (ΦΔ) of 0.76 compared to 0.53 for 1. Complex 2 showed enhanced PACT activity against Staphylococcus aureus giving a log reduction value of 9.4, while its precursor (complex 1) gave 0.08. The complexes were then conjugated to amine-functionalized polystyrene and embedded into polystyrene to form membranes resulting in ΦΔ values of 0.24 and 0.27 for complexes 1 and 2 respectively in water. The latter membrane showed better PACT activity.
- Full Text:
- Date Issued: 2020
- Authors: Mafukidze, Donovan Musizvinoda Chidyamurimi , Nyokong, Tebello
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/148595 , vital:38753 , https://doi.org/10.1016/j.reactfunctpolym.2020.104634
- Description: Membrane applications are hindered by fouling. Photoactive membranes (containing photosensitizers) show photodynamic antimicrobial chemotherapy (PACT) activity which reduces biological fouling. In this work we use phthalocyanines (Pcs) as photosensitizers. The Pcs used are: 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(dimethylamino) phthalocyaninato zinc(II) (1) and the quaternized 2-(4-carboxyphenoxy)-9(10), 16(17), 23(24)-tris(trimethylamino) phthalocyanine zinc(II) methyl sulfate (2). Complex 2 showed an enhanced singlet oxygen quantum yield (ΦΔ) of 0.76 compared to 0.53 for 1. Complex 2 showed enhanced PACT activity against Staphylococcus aureus giving a log reduction value of 9.4, while its precursor (complex 1) gave 0.08. The complexes were then conjugated to amine-functionalized polystyrene and embedded into polystyrene to form membranes resulting in ΦΔ values of 0.24 and 0.27 for complexes 1 and 2 respectively in water. The latter membrane showed better PACT activity.
- Full Text:
- Date Issued: 2020
The current nature of intra-regional trade in the proposed tripartite free trade area
- Authors: Chibuta, Chisengele
- Date: 2020
- Subjects: Customs unions -- Africa, Southern -- Economic integration , Africa, Southern -- Economic policy , Africa, Southern -- Economic integration , Africa, Southern -- Economic conditions , Tripartite Free Trade Area , Free trade -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/146744 , vital:38553
- Description: This thesis examines and analyses the current nature of intra-regional trade between member states of the proposed Tripartite Free Trade Area in order to contribute to an understanding of the potential for intra-regional trade within the region to increase. Trade Complementarity Indexes were used to determine how well the structures of the three founding blocs’ major imports and exports match. The results show that there is a high degree of trade complementarity in the trade of the top 5 major products traded between the regional groups. With the proposed TFTA in place, high trade complementarity could lead to increased trade between the regional groups. Trade Intensity Indexes were used to determine how intensively the three founding blocs trade with one another. Results from the indexes help determine the extent to which the blocs currently view each other as important trading partners and the implications of this for the proposed TFTA. Results show that EAC and SADC as well as EAC and COMESA viewed each other as significant trading partners while SADC and COMESA did not for the majority of the years from 2001 to 2018. With the TFTA in place, intra-regional trade could be strengthened among the members who currently trade intensively because tariffs between them would be progressively eliminated as required by the TFTA Agreement. Revealed Comparative Advantage Indexes were used to gain insights on whether member states have any comparative advantage in their top 5 exports. Results from the indexes were used to determine whether member states have comparative advantage in similar or dissimilar major exports and the implications of this for the proposed TFTA. Results show that member states have revealed comparative advantage in similar products and these products present opportunities for joint-production among member states as well as sectors for product development once the proposed TFTA is in place. Revealed Trade Barrier Indexes were used to gain insights into the extent of ease of market access into each regional bloc’s market. Results from the indexes indicate whether major products imported from each other receive possibly discriminatory or preferential treatment. The results indicate that the majority of the top 5 imports sourced from each region receive preferential treatment. This indicates that there is ease of market access for the top 5 imports sourced from each other and this could promote increased intra-regional trade among member states in these product categories because tariff and non-tariff barriers to trade will be progressively eliminated once the TFTA is in place.
- Full Text:
- Date Issued: 2020
- Authors: Chibuta, Chisengele
- Date: 2020
- Subjects: Customs unions -- Africa, Southern -- Economic integration , Africa, Southern -- Economic policy , Africa, Southern -- Economic integration , Africa, Southern -- Economic conditions , Tripartite Free Trade Area , Free trade -- Africa, Southern
- Language: English
- Type: Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/146744 , vital:38553
- Description: This thesis examines and analyses the current nature of intra-regional trade between member states of the proposed Tripartite Free Trade Area in order to contribute to an understanding of the potential for intra-regional trade within the region to increase. Trade Complementarity Indexes were used to determine how well the structures of the three founding blocs’ major imports and exports match. The results show that there is a high degree of trade complementarity in the trade of the top 5 major products traded between the regional groups. With the proposed TFTA in place, high trade complementarity could lead to increased trade between the regional groups. Trade Intensity Indexes were used to determine how intensively the three founding blocs trade with one another. Results from the indexes help determine the extent to which the blocs currently view each other as important trading partners and the implications of this for the proposed TFTA. Results show that EAC and SADC as well as EAC and COMESA viewed each other as significant trading partners while SADC and COMESA did not for the majority of the years from 2001 to 2018. With the TFTA in place, intra-regional trade could be strengthened among the members who currently trade intensively because tariffs between them would be progressively eliminated as required by the TFTA Agreement. Revealed Comparative Advantage Indexes were used to gain insights on whether member states have any comparative advantage in their top 5 exports. Results from the indexes were used to determine whether member states have comparative advantage in similar or dissimilar major exports and the implications of this for the proposed TFTA. Results show that member states have revealed comparative advantage in similar products and these products present opportunities for joint-production among member states as well as sectors for product development once the proposed TFTA is in place. Revealed Trade Barrier Indexes were used to gain insights into the extent of ease of market access into each regional bloc’s market. Results from the indexes indicate whether major products imported from each other receive possibly discriminatory or preferential treatment. The results indicate that the majority of the top 5 imports sourced from each region receive preferential treatment. This indicates that there is ease of market access for the top 5 imports sourced from each other and this could promote increased intra-regional trade among member states in these product categories because tariff and non-tariff barriers to trade will be progressively eliminated once the TFTA is in place.
- Full Text:
- Date Issued: 2020
Assessing factors that mitigate business risks in the operations of emerging black-owned businesses in Mthatha, Eastern Cape
- Authors: Bovungana, Afrika Khanyiso
- Date: 2020
- Subjects: Business enterprises, Black
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/47502 , vital:40121
- Description: The study sought to assessfactors that mitigate business risks in the operations of emerging black-owned businesses in Mthatha, Eastern Cape. Small businesses in the country are significant contributorsto the South African economy,as they provide employment and development opportunities to disadvantaged communities. Many of these businesses are operationalbut have no formal systems in place to operate effectively. The lack of proper operating procedures can result ininefficiencies that often lead to the collapse and eventual failure of these businesses. Van Vuuren,a professor at the University of Pretoria,mentionedin a round table dialogue that in South Africa the early stage entrepreneurial activity rate has been recorded as9.2% whereas in similar developing economies such as Brazil early stage entrepreneurialactivity isapproximately 40%. The study utilised a quantitative research design and employed a Likert scale questionnaire on a sample of 64 black-owned small, medium and micro enterprises (SMMEs) chosen by means of a random probability samplingmethod. QuestionPro was used to analyse the data and discuss the findings of the study.The various factors identified and highlighted indicate the integral challenges faced by the black-owned SMMEs remain prevalent. The success or failure is dependent on dynamic interventions that are taken into consideration and implemented for the improvement of the environment and business life cycle of black-owned businesses.
- Full Text:
- Date Issued: 2020
- Authors: Bovungana, Afrika Khanyiso
- Date: 2020
- Subjects: Business enterprises, Black
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/47502 , vital:40121
- Description: The study sought to assessfactors that mitigate business risks in the operations of emerging black-owned businesses in Mthatha, Eastern Cape. Small businesses in the country are significant contributorsto the South African economy,as they provide employment and development opportunities to disadvantaged communities. Many of these businesses are operationalbut have no formal systems in place to operate effectively. The lack of proper operating procedures can result ininefficiencies that often lead to the collapse and eventual failure of these businesses. Van Vuuren,a professor at the University of Pretoria,mentionedin a round table dialogue that in South Africa the early stage entrepreneurial activity rate has been recorded as9.2% whereas in similar developing economies such as Brazil early stage entrepreneurialactivity isapproximately 40%. The study utilised a quantitative research design and employed a Likert scale questionnaire on a sample of 64 black-owned small, medium and micro enterprises (SMMEs) chosen by means of a random probability samplingmethod. QuestionPro was used to analyse the data and discuss the findings of the study.The various factors identified and highlighted indicate the integral challenges faced by the black-owned SMMEs remain prevalent. The success or failure is dependent on dynamic interventions that are taken into consideration and implemented for the improvement of the environment and business life cycle of black-owned businesses.
- Full Text:
- Date Issued: 2020
An investigation into the application of Distributed Endpoint Processing to 3D Immersive Audio Rendering
- Authors: Devonport, Robin Sean
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163258 , vital:41022
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Computer Science, 2020.
- Full Text:
- Date Issued: 2020
- Authors: Devonport, Robin Sean
- Date: 2020
- Subjects: Uncatalogued
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/163258 , vital:41022
- Description: Thesis (MSc)--Rhodes University, Faculty of Science, Computer Science, 2020.
- Full Text:
- Date Issued: 2020
Traditional Dealerships’ Operational Capacity to Sell Electric Vehicles
- Authors: Knoetze, Alicia Jo-mari
- Date: 2020
- Subjects: Electric vehicle industry Automobile industry and trade
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/48686 , vital:41059
- Description: The global automotive industry faces an emerging turning point where an unceasing dependence on costly fossil fuels and a growing concern over global warming is driving the industry to form new possibilities. A major challenge for decision makers is to assure that the consumer market is informed about both the advantages and disadvantageous of electric vehicle technology. A significant amount of research has been done on both the operational ability of electric vehicles and consumer resistance and preferences towards new technology and the marketing of electric vehicles. Given the retail relationship between key industry stakeholders such as the Original Equipment Manufacturers, franchised dealership network and potential electric vehicle consumers, the transition towards new electric vehicle technology represents an important strategic realignment for dealerships in order to sell electric vehicles along with traditional internal combustion engine vehicles and questions their operational capacity to do so successfully. The primary data was collected from a sample of forty respondents by means of an online questionnaire. The questionnaire was designed from literature and using similar extracts from other electric vehicle consumer resistance studies questionnaires. An email containing a Universal Resource Link (URL) to the questionnaire was sent and by means of snowball sampling, a representative sample of forty-eight respondents participated in the study who fully completed all the sections of the questionnaire. Interviews were conducted with Senior Management of local dealerships in the Port Elizabeth area. The interviews were executed in the same method as a ‘walk-in’ potential customer. Participation therefore was based on the willingness, readiness and availability of management. Three dealerships who already sell electric vehicles as well as two dealership who still only sell traditional internal combustion engine vehicles participated in the interviews. In addition, the National Automobile Dealers Association (NADA) commented on the strategic realignment of the South African industry as a whole. The results indicated that the majority of respondents believed that electric vehicles were a suitable alternative to the traditional internal combustion engine vehicle and were willing to personally contribute to improved sustainable mobility. Uncertainty remained with consumers and there was unwillingness to purchase and electric vehicle within the next five years. Electric vehicles were also believed to perform better but there was uncertainty about the return that would be achieved from investment in an electric vehicle despite the reduction in their carbon footprint and the associated image boost with family and colleagues. Furthermore, there appeared to be an alignment amongst the interviewees that South Africa does not face and immediate threat in terms of electric vehicles as the anticipated tipping point is envisaged to be in the region of 2030 onwards, however NADA as a professional industry body still warns that this is not a set point in time and that market forces could change the outlook and adaption dramatically.
- Full Text:
- Date Issued: 2020
- Authors: Knoetze, Alicia Jo-mari
- Date: 2020
- Subjects: Electric vehicle industry Automobile industry and trade
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/48686 , vital:41059
- Description: The global automotive industry faces an emerging turning point where an unceasing dependence on costly fossil fuels and a growing concern over global warming is driving the industry to form new possibilities. A major challenge for decision makers is to assure that the consumer market is informed about both the advantages and disadvantageous of electric vehicle technology. A significant amount of research has been done on both the operational ability of electric vehicles and consumer resistance and preferences towards new technology and the marketing of electric vehicles. Given the retail relationship between key industry stakeholders such as the Original Equipment Manufacturers, franchised dealership network and potential electric vehicle consumers, the transition towards new electric vehicle technology represents an important strategic realignment for dealerships in order to sell electric vehicles along with traditional internal combustion engine vehicles and questions their operational capacity to do so successfully. The primary data was collected from a sample of forty respondents by means of an online questionnaire. The questionnaire was designed from literature and using similar extracts from other electric vehicle consumer resistance studies questionnaires. An email containing a Universal Resource Link (URL) to the questionnaire was sent and by means of snowball sampling, a representative sample of forty-eight respondents participated in the study who fully completed all the sections of the questionnaire. Interviews were conducted with Senior Management of local dealerships in the Port Elizabeth area. The interviews were executed in the same method as a ‘walk-in’ potential customer. Participation therefore was based on the willingness, readiness and availability of management. Three dealerships who already sell electric vehicles as well as two dealership who still only sell traditional internal combustion engine vehicles participated in the interviews. In addition, the National Automobile Dealers Association (NADA) commented on the strategic realignment of the South African industry as a whole. The results indicated that the majority of respondents believed that electric vehicles were a suitable alternative to the traditional internal combustion engine vehicle and were willing to personally contribute to improved sustainable mobility. Uncertainty remained with consumers and there was unwillingness to purchase and electric vehicle within the next five years. Electric vehicles were also believed to perform better but there was uncertainty about the return that would be achieved from investment in an electric vehicle despite the reduction in their carbon footprint and the associated image boost with family and colleagues. Furthermore, there appeared to be an alignment amongst the interviewees that South Africa does not face and immediate threat in terms of electric vehicles as the anticipated tipping point is envisaged to be in the region of 2030 onwards, however NADA as a professional industry body still warns that this is not a set point in time and that market forces could change the outlook and adaption dramatically.
- Full Text:
- Date Issued: 2020
Towards decolonizing a local university’s business school’s masters in business administration
- Authors: Du Preez, Daniella
- Date: 2020
- Subjects: Decolonization -- Education (Higher) -- Curricula
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/47735 , vital:40330
- Description: 2015 marked the year students went to great lengths to call on Higher Education institutions and their educators for a decolonised curriculum. This behaviour is attributable to the conditions that they had do study in. Buildings and campuses have colonial names, lectures mostly include White people’s intellectual contributions. Colonialism included colonial knowledge and denied African practices and existence. For centuries African philosophy was excluded and marginalised, which caused much pain and inhumanity. Higher education institutions remain detached from the developmental changes of African communities. Silence in academic disciplines was overwhelming Eurocentric / Westernised. Transformation of Higher Education curriculum in South Africa requires inclusion of African philosophy, and acknowledgement and respect for other cultures’ values, languages and knowledge. Educators play a pivotal role in transferring knowledge to students and producing the leaders for the future. Colonisation has ruled for decades and the effects thereof are still felt in various aspects of life. The education platform can break colonialism and if allowed, bring restoration to indigenous people. South African universities can contribute to society in transforming and decolonising curriculum and giving indigenous people and knowledge their rightful place. An education system free from colonialism positions students to add value to society as their worldviews are taken into consideration. This paper investigates the factors that could lead to a decolonised curriculum. Higher Education institutions have a role to play in ensuring a University free form colonial power and inequality. Decolonisation of the intellectual landscape will result in the decolonisation of the mind.
- Full Text:
- Date Issued: 2020
- Authors: Du Preez, Daniella
- Date: 2020
- Subjects: Decolonization -- Education (Higher) -- Curricula
- Language: English
- Type: Thesis , Masters , MBA
- Identifier: http://hdl.handle.net/10948/47735 , vital:40330
- Description: 2015 marked the year students went to great lengths to call on Higher Education institutions and their educators for a decolonised curriculum. This behaviour is attributable to the conditions that they had do study in. Buildings and campuses have colonial names, lectures mostly include White people’s intellectual contributions. Colonialism included colonial knowledge and denied African practices and existence. For centuries African philosophy was excluded and marginalised, which caused much pain and inhumanity. Higher education institutions remain detached from the developmental changes of African communities. Silence in academic disciplines was overwhelming Eurocentric / Westernised. Transformation of Higher Education curriculum in South Africa requires inclusion of African philosophy, and acknowledgement and respect for other cultures’ values, languages and knowledge. Educators play a pivotal role in transferring knowledge to students and producing the leaders for the future. Colonisation has ruled for decades and the effects thereof are still felt in various aspects of life. The education platform can break colonialism and if allowed, bring restoration to indigenous people. South African universities can contribute to society in transforming and decolonising curriculum and giving indigenous people and knowledge their rightful place. An education system free from colonialism positions students to add value to society as their worldviews are taken into consideration. This paper investigates the factors that could lead to a decolonised curriculum. Higher Education institutions have a role to play in ensuring a University free form colonial power and inequality. Decolonisation of the intellectual landscape will result in the decolonisation of the mind.
- Full Text:
- Date Issued: 2020
The effects of asymmetry in combination with reduced graphene oxide nanosheets on hydrazine electrocatalytic detection on cobalt phthalocyanines
- Mpeta, Lekhetho S, Sen, Pinar, Nyokong, Tebello
- Authors: Mpeta, Lekhetho S , Sen, Pinar , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186023 , vital:44456 , xlink:href="https://doi.org/10.1002/elan.202060094"
- Description: New symmetric {tetrakis [4-(4-(5-chloro-1Hbenzo[d]imidazol-2-yl) phenoxy phthalocyaninato] Co (II) (CoTPc)} and low symmetry {tris tert butyl phenoxy mono [4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl) phenoxy phthalocyaninato]} Co (II) (CoMPc) were successfully synthesised and combined with reduced graphene oxide nanosheets (rGONS) for electrocatalytic detection of hydrazine. Prior to electrocatalysis, the probes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy. Chronoamperometry was used to determine catalytic rate constant and the limit of detection (LOD). CoMPc-rGONS gave catalytic rate constant and LOD of 1.37×106 M 1 s 1 and 0.82 μM respectively, rendering it a more suitable probe for hydrazine, due to low symmetry.
- Full Text:
- Date Issued: 2020
- Authors: Mpeta, Lekhetho S , Sen, Pinar , Nyokong, Tebello
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186023 , vital:44456 , xlink:href="https://doi.org/10.1002/elan.202060094"
- Description: New symmetric {tetrakis [4-(4-(5-chloro-1Hbenzo[d]imidazol-2-yl) phenoxy phthalocyaninato] Co (II) (CoTPc)} and low symmetry {tris tert butyl phenoxy mono [4-(4-(5-chloro-1H-benzo[d]imidazol-2-yl) phenoxy phthalocyaninato]} Co (II) (CoMPc) were successfully synthesised and combined with reduced graphene oxide nanosheets (rGONS) for electrocatalytic detection of hydrazine. Prior to electrocatalysis, the probes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy. Chronoamperometry was used to determine catalytic rate constant and the limit of detection (LOD). CoMPc-rGONS gave catalytic rate constant and LOD of 1.37×106 M 1 s 1 and 0.82 μM respectively, rendering it a more suitable probe for hydrazine, due to low symmetry.
- Full Text:
- Date Issued: 2020
The exploration of ARF1 screening assays to determine the drug status of ARF1 in cancer and malaria
- Authors: Ntlantsana, Apelele
- Date: 2020
- Subjects: ADP ribosylation , Golgi apparatus , Guanosine triphosphatase , G proteins , Malariotherapy , Malaria -- Research , Cancer -- Chemotherapy , Malaria -- Chemotherpay
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167232 , vital:41458
- Description: ARF GTPases are key regulators of the secretory and endocytic pathways. ARF1 is involved in the secretory pathway. ARF1 has been implicated in the endoplasmic reticulum to Golgi transport, function of the Golgi apparatus and transport from the trans-Golgi network to endosomes. ARFs cycle between active GTP-bound and inactive GDP-bound conformations. GDP/GTP cycling is regulated by large families of guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). ARF GEFs facilitate the activation of ARFs by mediating the exchange of GDP for GTP, while ARF GAPs terminate ARF function by stimulating the hydrolysis of the terminal phosphate group of GTP. Based on existing evidence gained from gene manipulation and cell biological investigations, ARF1 has been shown to be fundamentally important for cancer cell proliferation and metastasis and may be a promising target for the development of anti-cancer drugs. Additionally, the conservation of ARFs in eukaryotic organisms leads to an interesting question of whether a single drug target can be used to target multiple diseases. In this case, can a human cancer drug employed for cancer therapy be used in anti-malarial drug therapies? To confirm the drug target status of ARFs using chemical validation experiments, novel inhibitory compounds are needed. This requires the development of complex in vitro protein- protein interaction assays that can be used to screen chemical libraries for ARF GTPase inhibitors. In this study, we developed a fluorescence resonance energy transfer (FRET) assay and a novel in vitro colorimetric plate-based assay to detect the activation status of truncated human and Plasmodium falciparum ARF1. In the case of the FRET assay, active (GTP-bound) and inactive (GDP-bound) ARF1 could be distinguished with Z-factor values >0.5, suggesting that further development of the assay format to identify GEF and GAP inhibitors may be feasible. In the case of the colorimetric assay, robust signals could be detected and the assay was useful for detecting the activation status of ARF1. However, although the activation of ARF1 by the Sec7 domains of the BIG1 and ARNO was detectable, signals were not robust enough to employ in screening campaigns.
- Full Text:
- Date Issued: 2020
- Authors: Ntlantsana, Apelele
- Date: 2020
- Subjects: ADP ribosylation , Golgi apparatus , Guanosine triphosphatase , G proteins , Malariotherapy , Malaria -- Research , Cancer -- Chemotherapy , Malaria -- Chemotherpay
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/167232 , vital:41458
- Description: ARF GTPases are key regulators of the secretory and endocytic pathways. ARF1 is involved in the secretory pathway. ARF1 has been implicated in the endoplasmic reticulum to Golgi transport, function of the Golgi apparatus and transport from the trans-Golgi network to endosomes. ARFs cycle between active GTP-bound and inactive GDP-bound conformations. GDP/GTP cycling is regulated by large families of guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs). ARF GEFs facilitate the activation of ARFs by mediating the exchange of GDP for GTP, while ARF GAPs terminate ARF function by stimulating the hydrolysis of the terminal phosphate group of GTP. Based on existing evidence gained from gene manipulation and cell biological investigations, ARF1 has been shown to be fundamentally important for cancer cell proliferation and metastasis and may be a promising target for the development of anti-cancer drugs. Additionally, the conservation of ARFs in eukaryotic organisms leads to an interesting question of whether a single drug target can be used to target multiple diseases. In this case, can a human cancer drug employed for cancer therapy be used in anti-malarial drug therapies? To confirm the drug target status of ARFs using chemical validation experiments, novel inhibitory compounds are needed. This requires the development of complex in vitro protein- protein interaction assays that can be used to screen chemical libraries for ARF GTPase inhibitors. In this study, we developed a fluorescence resonance energy transfer (FRET) assay and a novel in vitro colorimetric plate-based assay to detect the activation status of truncated human and Plasmodium falciparum ARF1. In the case of the FRET assay, active (GTP-bound) and inactive (GDP-bound) ARF1 could be distinguished with Z-factor values >0.5, suggesting that further development of the assay format to identify GEF and GAP inhibitors may be feasible. In the case of the colorimetric assay, robust signals could be detected and the assay was useful for detecting the activation status of ARF1. However, although the activation of ARF1 by the Sec7 domains of the BIG1 and ARNO was detectable, signals were not robust enough to employ in screening campaigns.
- Full Text:
- Date Issued: 2020
Chirema Chine Mazano Chinotamba Chakazendama Madziro
- Authors: Mapondera, Wallen
- Date: 2020
- Subjects: Art, Zimbabwean , Art -- Economic aspects -- Zimbabwe , Artists -- Zimbabwe , Takadiwa, Moffet , Nyandoro, Gareth , Clottey, Serge Attiku , Mapondera, Wallen -- Exhibitions
- Language: English
- Type: text , Thesis , Masters , MFA
- Identifier: http://hdl.handle.net/10962/147457 , vital:38638
- Description: This mini-thesis has developed as a practice-based supporting document to the exhibition Chirema Chine Mazano Chinotamba Chakazendama Madziro. The exhibition responds to how people become innovative in finding alternative means of survival and staying relevant in an economically depressed country. Zimbabwe is often the first country that comes to mind when people talk about hyperinflation; the situation was and still is intolerable, but somehow its citizens find means to pull through. Unemployment and poverty are the main causes of physical and mental problems for an individual. With this thesis, I highlight the innovations employed by Zimbabweans as a way of keeping themselves busy. I approach this through analysing the Zimbabwean general public’s creative reactions, and by tracing Zimbabwean visual artists’ use of found objects as a reaction to the country’s economic hardships. As people have been pushed to find alternative ways of survival, Zimbabwean artists in particular also shifted from using conventional art materials due to their unavailability. They began to redefine what art material is by employing objects in their artworks that previously had a non-art function. As such, there is a growing need to recognise, classify and document the shifts and establish platforms to generate growth of these innovations. In this minithesis I discuss my own practice, and I analyse the works of Moffat Takadiwa, Gareth Nyandoro and Serge Attiku Clottey.
- Full Text:
- Date Issued: 2020
- Authors: Mapondera, Wallen
- Date: 2020
- Subjects: Art, Zimbabwean , Art -- Economic aspects -- Zimbabwe , Artists -- Zimbabwe , Takadiwa, Moffet , Nyandoro, Gareth , Clottey, Serge Attiku , Mapondera, Wallen -- Exhibitions
- Language: English
- Type: text , Thesis , Masters , MFA
- Identifier: http://hdl.handle.net/10962/147457 , vital:38638
- Description: This mini-thesis has developed as a practice-based supporting document to the exhibition Chirema Chine Mazano Chinotamba Chakazendama Madziro. The exhibition responds to how people become innovative in finding alternative means of survival and staying relevant in an economically depressed country. Zimbabwe is often the first country that comes to mind when people talk about hyperinflation; the situation was and still is intolerable, but somehow its citizens find means to pull through. Unemployment and poverty are the main causes of physical and mental problems for an individual. With this thesis, I highlight the innovations employed by Zimbabweans as a way of keeping themselves busy. I approach this through analysing the Zimbabwean general public’s creative reactions, and by tracing Zimbabwean visual artists’ use of found objects as a reaction to the country’s economic hardships. As people have been pushed to find alternative ways of survival, Zimbabwean artists in particular also shifted from using conventional art materials due to their unavailability. They began to redefine what art material is by employing objects in their artworks that previously had a non-art function. As such, there is a growing need to recognise, classify and document the shifts and establish platforms to generate growth of these innovations. In this minithesis I discuss my own practice, and I analyse the works of Moffat Takadiwa, Gareth Nyandoro and Serge Attiku Clottey.
- Full Text:
- Date Issued: 2020
Cyber Security Responsibilization: an evaluation of the intervention approaches adopted by the Five Eyes Countries and China
- Renaud, Karen, Orgeron, Craig, Warkentin, Merrill, French, P Edward
- Authors: Renaud, Karen , Orgeron, Craig , Warkentin, Merrill , French, P Edward
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149806 , vital:38885 , https://0-doi.org.wam.seals.ac.za/10.1111/puar.13210
- Description: Governments can intervene to a greater or lesser extent in managing the risks that citizens face. They can adopt a maximal intervention approach (e .g. COVID‐19) or a hands‐off approach (e .g ., unemployment) , effectively “responsibilizing” their citizens. To manage the cyber risk, governments publish cyber‐related policies. This article examines the intervention stances the governments adopt in supporting individual citizens managing their personal cyber risk. The authors pinpoint the cyber‐related responsibilities that several governments espouse, applying a “responsibilization” analysis. Those applying to citizens are identified, thereby revealing the governments' cyber‐related intervention stance. The analysis reveals that most governments adopt a minimal cyber‐related intervention stance in supporting their citizens. Given the increasing number of successful cyber attacks on individuals, it seems time for the consequences of this stance to be acknowledged and reconsidered. The authors argue that governments should support individual citizens more effectively in dealing with cyber threats.
- Full Text:
- Date Issued: 2020
- Authors: Renaud, Karen , Orgeron, Craig , Warkentin, Merrill , French, P Edward
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149806 , vital:38885 , https://0-doi.org.wam.seals.ac.za/10.1111/puar.13210
- Description: Governments can intervene to a greater or lesser extent in managing the risks that citizens face. They can adopt a maximal intervention approach (e .g. COVID‐19) or a hands‐off approach (e .g ., unemployment) , effectively “responsibilizing” their citizens. To manage the cyber risk, governments publish cyber‐related policies. This article examines the intervention stances the governments adopt in supporting individual citizens managing their personal cyber risk. The authors pinpoint the cyber‐related responsibilities that several governments espouse, applying a “responsibilization” analysis. Those applying to citizens are identified, thereby revealing the governments' cyber‐related intervention stance. The analysis reveals that most governments adopt a minimal cyber‐related intervention stance in supporting their citizens. Given the increasing number of successful cyber attacks on individuals, it seems time for the consequences of this stance to be acknowledged and reconsidered. The authors argue that governments should support individual citizens more effectively in dealing with cyber threats.
- Full Text:
- Date Issued: 2020
Invalid submission of extension of time claims in the South African construction industry
- Authors: Neethling, Juan Pierre
- Date: 2020
- Subjects: Construction industry -- South Africa , Construction industry -- Management Project management Building -- Superintendence
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46805 , vital:39663
- Description: Most construction projects are delayed in the construction industry due to internal and/or external influences. Proving delay is not a simple task but rather a time-consuming process, as projects consist of numerous activities and a substantial amount of detail, and they interface with the many stakeholders. Several different methods can be used to prove a delay; however, these are academic and are mainly for simple projects. Proving a delay is often difficult for the contractor, who is consistently dealing with multiple project constraints. Therefore, to be effective with an extension of time claim, the contractor must establish causation and liability, and assist in demonstrating the extent of time-related damages experienced as a direct result of the delay events relied upon. The process of recording the delays is dynamic and requires solid knowledge of contract clauses, the ability to distinguish between different types of delays and the capability to identify what constitutes valid evidence. Therefore, a need arises to establish a framework that would assist contractors by standardising their submission. This would contribute to expediting the evaluation and approval process, thus limiting the negative impacts associated with prolonged delay claims. The research obtains a “lived” view from contractors who have participated with EOT claims, therefore, utilising the qualitative research method. The choice of data collection method was semi-structured one-on one face to face interviews. In deriving the findings of the research, the coding scheme techniques were used throughout the research process to manage both the secondary and primary data. The main factors which cause major problems in EOT claims are contractual knowledge, lack of supporting information, contractual compliance, employer inference and the different philosophies of contracts, which often leads to confusion and misinterpretation. There is a lack of awareness and knowledge of the analysis techniques and strategies which could assist in preparing EOT claims, even though there is a substantial amount of literature available. The concept that the industry needs a standardised submission process was welcomed by the participants; the existence of a common strategy would certainly resolve many problems in the submission process, including reducing the number of disputes. There was a consensus among all participants that there is no standard approach to submitting EOT claims in the South African construction industry and exploring a common approach was an idea that was viewed as reasonable and maybe offered a practical solution to address the submission challenges. There were several delimitations to this study. First, the sample only included individuals within the Eastern Cape region. Since the sample size was relatively small, the researcher was cautious when interpreting and generalising the results. Secondly, the targeted population for this research was selected using the purposive sampling method, as opposed to a random sampling, which means that the results of the study cannot be generally applied to a larger population. Lastly, the research was a qualitative study which relied on the interpretations of the researcher based on his understanding of the data collected.
- Full Text:
- Date Issued: 2020
- Authors: Neethling, Juan Pierre
- Date: 2020
- Subjects: Construction industry -- South Africa , Construction industry -- Management Project management Building -- Superintendence
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/46805 , vital:39663
- Description: Most construction projects are delayed in the construction industry due to internal and/or external influences. Proving delay is not a simple task but rather a time-consuming process, as projects consist of numerous activities and a substantial amount of detail, and they interface with the many stakeholders. Several different methods can be used to prove a delay; however, these are academic and are mainly for simple projects. Proving a delay is often difficult for the contractor, who is consistently dealing with multiple project constraints. Therefore, to be effective with an extension of time claim, the contractor must establish causation and liability, and assist in demonstrating the extent of time-related damages experienced as a direct result of the delay events relied upon. The process of recording the delays is dynamic and requires solid knowledge of contract clauses, the ability to distinguish between different types of delays and the capability to identify what constitutes valid evidence. Therefore, a need arises to establish a framework that would assist contractors by standardising their submission. This would contribute to expediting the evaluation and approval process, thus limiting the negative impacts associated with prolonged delay claims. The research obtains a “lived” view from contractors who have participated with EOT claims, therefore, utilising the qualitative research method. The choice of data collection method was semi-structured one-on one face to face interviews. In deriving the findings of the research, the coding scheme techniques were used throughout the research process to manage both the secondary and primary data. The main factors which cause major problems in EOT claims are contractual knowledge, lack of supporting information, contractual compliance, employer inference and the different philosophies of contracts, which often leads to confusion and misinterpretation. There is a lack of awareness and knowledge of the analysis techniques and strategies which could assist in preparing EOT claims, even though there is a substantial amount of literature available. The concept that the industry needs a standardised submission process was welcomed by the participants; the existence of a common strategy would certainly resolve many problems in the submission process, including reducing the number of disputes. There was a consensus among all participants that there is no standard approach to submitting EOT claims in the South African construction industry and exploring a common approach was an idea that was viewed as reasonable and maybe offered a practical solution to address the submission challenges. There were several delimitations to this study. First, the sample only included individuals within the Eastern Cape region. Since the sample size was relatively small, the researcher was cautious when interpreting and generalising the results. Secondly, the targeted population for this research was selected using the purposive sampling method, as opposed to a random sampling, which means that the results of the study cannot be generally applied to a larger population. Lastly, the research was a qualitative study which relied on the interpretations of the researcher based on his understanding of the data collected.
- Full Text:
- Date Issued: 2020
Low-frequency observations of the giant radio galaxy NGC 6251:
- Cantwell, T M, Bray, J D, Croston, J H, Scaife, A M M, Mulcahy, D D, Best, P N, Brüggen, M, Brunetti, G, Callingham, J R, Clarke, A O, Hardcastle, M J, Harwood, J J, Heald, G, Heesen, V, Iacobelli, M, Jamrozy, M, Morganti, R, Orru, E, O’Sullivan, S P, Riseley, C J, Röttgering, H J A, Shulevski, A, Sridhar, S S, Tasse, C, Van Eck, C L
- Authors: Cantwell, T M , Bray, J D , Croston, J H , Scaife, A M M , Mulcahy, D D , Best, P N , Brüggen, M , Brunetti, G , Callingham, J R , Clarke, A O , Hardcastle, M J , Harwood, J J , Heald, G , Heesen, V , Iacobelli, M , Jamrozy, M , Morganti, R , Orru, E , O’Sullivan, S P , Riseley, C J , Röttgering, H J A , Shulevski, A , Sridhar, S S , Tasse, C , Van Eck, C L
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149931 , vital:38913 , https://0-doi.org.wam.seals.ac.za/10.1093/mnras/staa1160
- Description: We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies.
- Full Text:
- Date Issued: 2020
- Authors: Cantwell, T M , Bray, J D , Croston, J H , Scaife, A M M , Mulcahy, D D , Best, P N , Brüggen, M , Brunetti, G , Callingham, J R , Clarke, A O , Hardcastle, M J , Harwood, J J , Heald, G , Heesen, V , Iacobelli, M , Jamrozy, M , Morganti, R , Orru, E , O’Sullivan, S P , Riseley, C J , Röttgering, H J A , Shulevski, A , Sridhar, S S , Tasse, C , Van Eck, C L
- Date: 2020
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/149931 , vital:38913 , https://0-doi.org.wam.seals.ac.za/10.1093/mnras/staa1160
- Description: We present LOFAR observations at 150 MHz of the borderline FRI/FRII giant radio galaxy NGC 6251. This paper presents the most sensitive and highest resolution images of NGC 6251 at these frequencies to date, revealing for the first time a low-surface-brightness extension to the northern lobe, and a possible backflow associated with the southern lobe. The integrated spectra of components of NGC 6251 are consistent with previous measurements at higher frequencies, similar to results from other LOFAR studies of nearby radio galaxies.
- Full Text:
- Date Issued: 2020
Using sound localization to gain depth perception for the visually impaired through sensory substitution
- Authors: De Klerk, James Carmichael
- Date: 2020
- Subjects: People with visual disabilities Directional hearing--Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50779 , vital:42674
- Description: The visually impaired do not have the visual ability to localize objects in three-dimensional space, rather, they rely on their other senses to gain depth perception. Sensory substitution is the concept of substituting one sense for another, normally substituting an impaired sense with a functioning sense. Visual-to-auditory sensory substitution substitutes an impaired visual sense with a functioning auditory sense. This research aimed to investigate and develop techniques for visualto-auditory sensory substitution – using sound localization as a sensory substitution for depth perception. The research started by investigating the characteristics of human audition with a particular focus on how humans localize sounds. It then looked at existing visual-to-auditory sensory substitution systems and the techniques they used. From the existing systems, a system known as MeloSee was chosen as a baseline for developing and evaluating further sensory substitution prototypes. The baseline prototype (𝑃0) was then implemented and a preliminary study performed. Based on the knowledge gained from the preliminary study, baseline implementation and the background research, a set of improvement recommendations were generated. The next iteration – Prototype 1 (𝑃1) – was then developed based on the recommendations. A comparative study between 𝑃0 and 𝑃1 was then performed. Based on the study, another set of improvement recommendations were generated. From the recommendations, a final prototype was developed – Prototype 2 (𝑃2). The last comparative study was then performed between 𝑃0 and 𝑃2, with a third set of recommendations being generated as a result. From the studies it was found that participants using 𝑃0 were able to identify when they were approaching large objects such as walls. 𝑃1 built on that, improving the ability to identify the quadrant of a nearby isolated object. 𝑃2 built on 𝑃0 and 𝑃1, achieving similar results to 𝑃1 for identifying the quadrant of nearby isolated objects, and improving on 𝑃0 and 𝑃1 with regard to depth discrimination – especially for navigation tasks where there were no obstacles. Based on the three sets of recommendations and what was learnt over the course of the research, a set of visual-to-auditory sensory substitution techniques were presented. The techniques aim to be useful for implementing visual-to-auditory sensory substitution systems, which would provide the visually impaired with the visual ability to localize objects in three-dimensional space through sound.
- Full Text:
- Date Issued: 2020
- Authors: De Klerk, James Carmichael
- Date: 2020
- Subjects: People with visual disabilities Directional hearing--Physiological aspects
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10948/50779 , vital:42674
- Description: The visually impaired do not have the visual ability to localize objects in three-dimensional space, rather, they rely on their other senses to gain depth perception. Sensory substitution is the concept of substituting one sense for another, normally substituting an impaired sense with a functioning sense. Visual-to-auditory sensory substitution substitutes an impaired visual sense with a functioning auditory sense. This research aimed to investigate and develop techniques for visualto-auditory sensory substitution – using sound localization as a sensory substitution for depth perception. The research started by investigating the characteristics of human audition with a particular focus on how humans localize sounds. It then looked at existing visual-to-auditory sensory substitution systems and the techniques they used. From the existing systems, a system known as MeloSee was chosen as a baseline for developing and evaluating further sensory substitution prototypes. The baseline prototype (𝑃0) was then implemented and a preliminary study performed. Based on the knowledge gained from the preliminary study, baseline implementation and the background research, a set of improvement recommendations were generated. The next iteration – Prototype 1 (𝑃1) – was then developed based on the recommendations. A comparative study between 𝑃0 and 𝑃1 was then performed. Based on the study, another set of improvement recommendations were generated. From the recommendations, a final prototype was developed – Prototype 2 (𝑃2). The last comparative study was then performed between 𝑃0 and 𝑃2, with a third set of recommendations being generated as a result. From the studies it was found that participants using 𝑃0 were able to identify when they were approaching large objects such as walls. 𝑃1 built on that, improving the ability to identify the quadrant of a nearby isolated object. 𝑃2 built on 𝑃0 and 𝑃1, achieving similar results to 𝑃1 for identifying the quadrant of nearby isolated objects, and improving on 𝑃0 and 𝑃1 with regard to depth discrimination – especially for navigation tasks where there were no obstacles. Based on the three sets of recommendations and what was learnt over the course of the research, a set of visual-to-auditory sensory substitution techniques were presented. The techniques aim to be useful for implementing visual-to-auditory sensory substitution systems, which would provide the visually impaired with the visual ability to localize objects in three-dimensional space through sound.
- Full Text:
- Date Issued: 2020
Sexual attraction and mating compatibility between Thaumatotibia leucotreta populations and implications for semiochemical dependent technologies
- Authors: Upfold, Jennifer Kate
- Date: 2020
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Reproduction , Citrus -- Disease and pests -- Control -- South Africa , Insect sterilization -- South Africa , Pheromones , Pheromone traps
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/148526 , vital:38747
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick), is the most important pest for the cultivation of citrus in South Africa. False codling moth is indigenous to southern Africa and is a regulated pest of many international markets for phytosanitary concerns. Considerable research efforts have been invested in the past decades to develop semiochemcial technologies, such as monitoring with sex pheromones, attract-and-kill, mating disruption and the sterile insect technique. One of the potential obstacles identified with semiochemical control is the differences in the ratio of the compounds comprising the sex pheromone at different geographical locations, resulting in what is known as regional attraction. This has been identified in FCM populations from three different countries, however, regional attraction within South African FCM populations was unknown. Therefore, the study assessed the genetic integrity of five laboratory-reared FCM populations originating from geographically isolated populations in South Africa using the AFLP technique in order to assess regional attractiveness within the country. The results found isolated populations from Addo, Citrusdal, Marble Hall, Nelspruit and a fifth group found to be closely related to Addo and Citrusdal called the ‘Old’ colony. These five genetically isolated populations as well as a population from Xsit (Pty) Ltd, used for the sterile insect technique (SIT), were used in regional attractiveness trials. Males were significantly (P = <0.05) more attracted to females originating from the same population. No significant attraction could be determined from the sterile males, as the recapture rates in the trap were too low. Furthermore, regional attractiveness was assessed through choice/ no-choice mating compatibility trials. Significant sexual isolation (ISI) occurred between mating combinations Addo × Nelspruit (ISI = 0,13; t2 = 6.23; p = 0.02), Addo × Marble Hall (ISI = 0,11; t2 = 4.72; p = 0.04), Citrusdal × Nelspruit (ISI = 0,11; t2 = 4.95; p = 0.04), and Citrusdal × Marble Hall (ISI = 0,12; t2 = 4.31; p = 0.04). In these combinations, Addo and Citrusdal males were found to have outcompeted Nelspruit and Marble Hall males for more mating events. Significant sexual isolation was also recorded for Sterile × Marble Hall (ISI = 0.12; t2 = 4.98; p =0.01) and Sterile × Citrusdal (ISI = 0.13; t2 = 3.96; p = 0.01) populations. The male relative performance index was significant in both combinations, indicating that non-sterile laboratory males outcompeted the sterile males in these two combinations. When given no choice, evaluated as spermatophore transfer/ female/ 48h, all males (including sterile) were successful in transferring spermatophores to all FCM populations, with no significant differences. These results indicate that there may be incipient pre-isolation mechanisms affected by local natural selection, resulting in localised sexual attraction via differences in the sex pheromone ratios. These findings provide important information for semiochemical technologies and the implication of these results with regard to monitoring with sex pheromones, attract-and-kill, mating disruption and sterile insect technique are discussed.
- Full Text:
- Date Issued: 2020
- Authors: Upfold, Jennifer Kate
- Date: 2020
- Subjects: Cryptophlebia leucotreta -- South Africa , Cryptophlebia leucotreta -- Reproduction , Citrus -- Disease and pests -- Control -- South Africa , Insect sterilization -- South Africa , Pheromones , Pheromone traps
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/148526 , vital:38747
- Description: False codling moth (FCM), Thaumatotibia leucotreta (Meyrick), is the most important pest for the cultivation of citrus in South Africa. False codling moth is indigenous to southern Africa and is a regulated pest of many international markets for phytosanitary concerns. Considerable research efforts have been invested in the past decades to develop semiochemcial technologies, such as monitoring with sex pheromones, attract-and-kill, mating disruption and the sterile insect technique. One of the potential obstacles identified with semiochemical control is the differences in the ratio of the compounds comprising the sex pheromone at different geographical locations, resulting in what is known as regional attraction. This has been identified in FCM populations from three different countries, however, regional attraction within South African FCM populations was unknown. Therefore, the study assessed the genetic integrity of five laboratory-reared FCM populations originating from geographically isolated populations in South Africa using the AFLP technique in order to assess regional attractiveness within the country. The results found isolated populations from Addo, Citrusdal, Marble Hall, Nelspruit and a fifth group found to be closely related to Addo and Citrusdal called the ‘Old’ colony. These five genetically isolated populations as well as a population from Xsit (Pty) Ltd, used for the sterile insect technique (SIT), were used in regional attractiveness trials. Males were significantly (P = <0.05) more attracted to females originating from the same population. No significant attraction could be determined from the sterile males, as the recapture rates in the trap were too low. Furthermore, regional attractiveness was assessed through choice/ no-choice mating compatibility trials. Significant sexual isolation (ISI) occurred between mating combinations Addo × Nelspruit (ISI = 0,13; t2 = 6.23; p = 0.02), Addo × Marble Hall (ISI = 0,11; t2 = 4.72; p = 0.04), Citrusdal × Nelspruit (ISI = 0,11; t2 = 4.95; p = 0.04), and Citrusdal × Marble Hall (ISI = 0,12; t2 = 4.31; p = 0.04). In these combinations, Addo and Citrusdal males were found to have outcompeted Nelspruit and Marble Hall males for more mating events. Significant sexual isolation was also recorded for Sterile × Marble Hall (ISI = 0.12; t2 = 4.98; p =0.01) and Sterile × Citrusdal (ISI = 0.13; t2 = 3.96; p = 0.01) populations. The male relative performance index was significant in both combinations, indicating that non-sterile laboratory males outcompeted the sterile males in these two combinations. When given no choice, evaluated as spermatophore transfer/ female/ 48h, all males (including sterile) were successful in transferring spermatophores to all FCM populations, with no significant differences. These results indicate that there may be incipient pre-isolation mechanisms affected by local natural selection, resulting in localised sexual attraction via differences in the sex pheromone ratios. These findings provide important information for semiochemical technologies and the implication of these results with regard to monitoring with sex pheromones, attract-and-kill, mating disruption and sterile insect technique are discussed.
- Full Text:
- Date Issued: 2020
Ethics and education as practices of freedom
- Authors: Tabensky, Pedro
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305672 , vital:58602 , xlink:href="https://doi.org/10.1080/00131857.2020.1791822"
- Description: On the one hand, according to Richard Rorty, Paulo Freire and others, education is the practice of freedom. On the other hand, according to Michael Foucault, Mary Midgley and others, ethics is the practice of freedom. How, then, are education and ethics related to one another and what do these authors mean by ‘the practice of freedom’? In this piece, I argue that education and ethics are two mutually constitutive aspects of the practice of freedom. Individuals who are able to engage in this practice can most properly be said to be the authors of their lives, that is, individuals who, to borrow from Neil MacGregor, are able to find their ‘place in things’. To find our ‘place in things’ is to do the necessary educative work required for becoming the authors of our lives, that is, for self-actualization (as Rorty and John Dewey have argued). To take on the authorial role is, moreover, to be able effectively to take control of our lives, to organize them into unities for which we are individually responsible. This, according to Midgley, is precisely what it is to be ethical. This work, moreover, requires ongoing development, that is, education, in Dewey’s sense. I further argue that professional education and skills training cannot be understood properly in isolation from these broader educational aims and I criticize mainstream educational practices for not paying sufficient attention to the intimate relationship between the vocational and non-vocational aspects of education.
- Full Text:
- Date Issued: 2020
- Authors: Tabensky, Pedro
- Date: 2020
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/305672 , vital:58602 , xlink:href="https://doi.org/10.1080/00131857.2020.1791822"
- Description: On the one hand, according to Richard Rorty, Paulo Freire and others, education is the practice of freedom. On the other hand, according to Michael Foucault, Mary Midgley and others, ethics is the practice of freedom. How, then, are education and ethics related to one another and what do these authors mean by ‘the practice of freedom’? In this piece, I argue that education and ethics are two mutually constitutive aspects of the practice of freedom. Individuals who are able to engage in this practice can most properly be said to be the authors of their lives, that is, individuals who, to borrow from Neil MacGregor, are able to find their ‘place in things’. To find our ‘place in things’ is to do the necessary educative work required for becoming the authors of our lives, that is, for self-actualization (as Rorty and John Dewey have argued). To take on the authorial role is, moreover, to be able effectively to take control of our lives, to organize them into unities for which we are individually responsible. This, according to Midgley, is precisely what it is to be ethical. This work, moreover, requires ongoing development, that is, education, in Dewey’s sense. I further argue that professional education and skills training cannot be understood properly in isolation from these broader educational aims and I criticize mainstream educational practices for not paying sufficient attention to the intimate relationship between the vocational and non-vocational aspects of education.
- Full Text:
- Date Issued: 2020