The thermal physiology of Stenopelmus rufinasus and Neohydronomus affinis (Coleoptera: Curculionidae), biological control agents for the invasive alien aquatic weeds Azolla filiculoides and Pistia stratiotes respectively
- Authors: Mvandaba, Sisanda F
- Date: 2018
- Subjects: Beetles -- South Africa , Curculionidae -- South Africa , Azolla filiculoides -- South Africa , Water lettuce -- South Africa , Aquatic weeds -- Biological control -- South Africa , Stenopelmus rufinasus , Neohydronomus affinis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62362 , vital:28158
- Description: Water lettuce, Pistia stratiotes L. (Araceae), and red water fern, Azolla filiculoides Lam. (Azollaceae), are floating aquatic macrophytes that have become problematic invaders in numerous South African waterbodies. Two weevils, Neohydronomus affinis Hustache 1926 (Coleoptera: Curculionidae) and Stenopelmus rufinasus Gyllenhal 1936 (Coleoptera: Curculionidae), are successful biological control agents of these two species, respectively, in South Africa. However, nothing is known about the thermal physiology of these two species Therefore, the aim of this study was to investigate the thermal physiologies of these two species to explain their establishment, distribution and impact in the field. Laboratory based thermal physiology trials showed that both weevils were widely tolerant of cold and warm temperatures. The CTmin of N. affinis was determined to be 5.5 ± 0.312°C and the CTmax was 44 ± 0.697°C, while the CTmin of S. rufinasus was 5.4 ± 0.333°C and the CTmax was 44.5 ± 0.168°C. In addition, the lower lethal temperatures were -9.8 ± 0.053°C and -7.2 ± 0.19°C, and the upper lethal temperatures were 42.8 ± 0.053°C and 41.9 ± 0.19°C respectively. These results suggest that both species should not be limited by cold winter temperatures, as previously thought. This is evident in the field, where S. rufinasus has established widely on A. filiculoides, despite local cold climates in some areas of the plant’s distribution. Even though N. affinis has a similar thermal range, and should therefore theoretically reflect a similar distribution to S. rufinasus throughout South Africa, its distribution is limited by the range of its host, which is restricted to the warmer regions of the country, as is its biocontrol agent. Using the reduced major axis regression method, the development for N. affinis was described using the formulay=12.976x+435.24, while the development of S. rufinasus was described by y=13.6x+222.45. These results showed that S. rufinasus develops much faster, in fact almost twice as quickly, than N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. This study showed that although the native range of these two species is warm temperate to tropical, they possess sufficient thermal plasticity to not only establish, but also damage their respective host plants in far cooler climates. Thus, in South Africa N. affinis and S. rufinasus are limited by the distribution of their target weeds and not climate.
- Full Text:
- Date Issued: 2018
- Authors: Mvandaba, Sisanda F
- Date: 2018
- Subjects: Beetles -- South Africa , Curculionidae -- South Africa , Azolla filiculoides -- South Africa , Water lettuce -- South Africa , Aquatic weeds -- Biological control -- South Africa , Stenopelmus rufinasus , Neohydronomus affinis
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62362 , vital:28158
- Description: Water lettuce, Pistia stratiotes L. (Araceae), and red water fern, Azolla filiculoides Lam. (Azollaceae), are floating aquatic macrophytes that have become problematic invaders in numerous South African waterbodies. Two weevils, Neohydronomus affinis Hustache 1926 (Coleoptera: Curculionidae) and Stenopelmus rufinasus Gyllenhal 1936 (Coleoptera: Curculionidae), are successful biological control agents of these two species, respectively, in South Africa. However, nothing is known about the thermal physiology of these two species Therefore, the aim of this study was to investigate the thermal physiologies of these two species to explain their establishment, distribution and impact in the field. Laboratory based thermal physiology trials showed that both weevils were widely tolerant of cold and warm temperatures. The CTmin of N. affinis was determined to be 5.5 ± 0.312°C and the CTmax was 44 ± 0.697°C, while the CTmin of S. rufinasus was 5.4 ± 0.333°C and the CTmax was 44.5 ± 0.168°C. In addition, the lower lethal temperatures were -9.8 ± 0.053°C and -7.2 ± 0.19°C, and the upper lethal temperatures were 42.8 ± 0.053°C and 41.9 ± 0.19°C respectively. These results suggest that both species should not be limited by cold winter temperatures, as previously thought. This is evident in the field, where S. rufinasus has established widely on A. filiculoides, despite local cold climates in some areas of the plant’s distribution. Even though N. affinis has a similar thermal range, and should therefore theoretically reflect a similar distribution to S. rufinasus throughout South Africa, its distribution is limited by the range of its host, which is restricted to the warmer regions of the country, as is its biocontrol agent. Using the reduced major axis regression method, the development for N. affinis was described using the formulay=12.976x+435.24, while the development of S. rufinasus was described by y=13.6x+222.45. These results showed that S. rufinasus develops much faster, in fact almost twice as quickly, than N. affinis. Using these formulae and temperature data obtained from the South African Weather Service, N. affinis was predicted to complete between 4 and 9 generations per year in South Africa, while S. rufinasus was predicted to complete between 5 and 14 generations per year around the country. This study showed that although the native range of these two species is warm temperate to tropical, they possess sufficient thermal plasticity to not only establish, but also damage their respective host plants in far cooler climates. Thus, in South Africa N. affinis and S. rufinasus are limited by the distribution of their target weeds and not climate.
- Full Text:
- Date Issued: 2018
The use of experimental design for the development and validation of an HPLC-ECD method for the quantitation of efavirenz
- Makoni, Pedzisai A, Khamanga, Sandile M, Kasongo, Kasongo W, Walker, Roderick B
- Authors: Makoni, Pedzisai A , Khamanga, Sandile M , Kasongo, Kasongo W , Walker, Roderick B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183556 , vital:44006 , xlink:href="https://doi.org/10.1691/ph.2018.8074"
- Description: A high performance liquid chromatography with electrochemical detection (HPLC-ECD) method for the quantitation of efavirenz (EFV) was developed, since traditional HPLC-UV methods may be inappropriate, given that EFV undergoes photolytic degradation following exposure to UV light. This work describes the use of response surface methodology (RSM) based on a central composite design (CCD) to develop a stability-indicating HPLC method with pulsed ECD in direct current (DC) mode at an applied potential difference and current of +1400 mV and 1.0 μA for the analysis of EFV. Separation of EFV and imipramine was achieved using a Nova-Pak®C18 cartridge column and a mobile phase of phosphate buffer (pH 4.5): acetonitrile (ACN) (55:45 v/v). Mobile phase pH, buffer molarity, ACN concentration and applied potential difference were investigated. The optimized method produced sharp well resolved peaks for imipramine and EFV with retention times of 3.70 and 8.89 minutes. The calibration curve was linear (R2 = 0.9979) over the range 5-70 μg/mL. Repeatability and intermediate precision ranged between 3.37 and 4.34 % RSD and 1.31 and 4.29 % RSD and accuracy between -0.80 and 4.71 % bias. The LOQ and LOD were 5.0 and 1.5 μg/mL. The method was specific for EFV and was used to analyse EFV in commercially available tablets. The HPLC-ECD method is more suitable for quantitative analysis of EFV than HPLC-UV.
- Full Text:
- Date Issued: 2018
- Authors: Makoni, Pedzisai A , Khamanga, Sandile M , Kasongo, Kasongo W , Walker, Roderick B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183556 , vital:44006 , xlink:href="https://doi.org/10.1691/ph.2018.8074"
- Description: A high performance liquid chromatography with electrochemical detection (HPLC-ECD) method for the quantitation of efavirenz (EFV) was developed, since traditional HPLC-UV methods may be inappropriate, given that EFV undergoes photolytic degradation following exposure to UV light. This work describes the use of response surface methodology (RSM) based on a central composite design (CCD) to develop a stability-indicating HPLC method with pulsed ECD in direct current (DC) mode at an applied potential difference and current of +1400 mV and 1.0 μA for the analysis of EFV. Separation of EFV and imipramine was achieved using a Nova-Pak®C18 cartridge column and a mobile phase of phosphate buffer (pH 4.5): acetonitrile (ACN) (55:45 v/v). Mobile phase pH, buffer molarity, ACN concentration and applied potential difference were investigated. The optimized method produced sharp well resolved peaks for imipramine and EFV with retention times of 3.70 and 8.89 minutes. The calibration curve was linear (R2 = 0.9979) over the range 5-70 μg/mL. Repeatability and intermediate precision ranged between 3.37 and 4.34 % RSD and 1.31 and 4.29 % RSD and accuracy between -0.80 and 4.71 % bias. The LOQ and LOD were 5.0 and 1.5 μg/mL. The method was specific for EFV and was used to analyse EFV in commercially available tablets. The HPLC-ECD method is more suitable for quantitative analysis of EFV than HPLC-UV.
- Full Text:
- Date Issued: 2018
The uses of Chrysomya megacephala (Fabricius, 1794)(Diptera: Calliphoridae) in forensic entomology:
- Badenhorst, Rozane, Villet, Martin H
- Authors: Badenhorst, Rozane , Villet, Martin H
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140631 , vital:37905 , DOI: 10.1080/20961790.2018.1426136
- Description: Chrysomya megacephala (Fabricius, 1794) occurs on every continent and is closely associated with carrion and decaying material in human environments. Its abilities to find dead bodies and carry pathogens give it a prominence in human affairs that may involve prosecution or litigation, and therefore forensic entomologists. The identification, geographical distribution and biology of the species are reviewed to provide a background for approaches that four branches of forensic entomology (urban, stored-product, medico-criminal and environmental) might take to investigations involving this fly.
- Full Text:
- Date Issued: 2018
- Authors: Badenhorst, Rozane , Villet, Martin H
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/140631 , vital:37905 , DOI: 10.1080/20961790.2018.1426136
- Description: Chrysomya megacephala (Fabricius, 1794) occurs on every continent and is closely associated with carrion and decaying material in human environments. Its abilities to find dead bodies and carry pathogens give it a prominence in human affairs that may involve prosecution or litigation, and therefore forensic entomologists. The identification, geographical distribution and biology of the species are reviewed to provide a background for approaches that four branches of forensic entomology (urban, stored-product, medico-criminal and environmental) might take to investigations involving this fly.
- Full Text:
- Date Issued: 2018
The “Pleasure Streets” of exile: queer subjectivities and the body in Arthur Nortje’s London poems
- Authors: Thorpe, Andrea
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68432 , vital:29255 , https://doi.org/10.1080/02564718.2018.1447865
- Description: Publisher version , In this article, I aim to expand our understanding of Arthur Nortje as a poet of “exile” by exploring the dialectic between self-loathing and pleasure, as well as between engagement and isolation, which he portrays performatively through his London poetry. While critics have emphasised Nortje’s “marginality” or “liminality”, both as an “exile” and a “coloured” South African, I draw on the critical writing of Zoë Wicomb in order to extend readings of his poetry beyond this tragic paradigm. I furthermore take up Sarah Nuttall’s suggestion that Nortje’s London poetry describes a degree of immersion within the city and that this aspect of his work demands further study. After tracing Nortje’s playful use of literary influences and his reworking of the trope of flânerie, I provide a series of close readings of poems in which Nortje depicts an exploration of queer subjectivities, staged within the city. In his London poetry, Nortje subverts and eludes fixed racial, sexual, national and class identities. Nortje’s London poetry exemplifies how South African literature was developed in response to the alienating condition of exile, but also through engagement with the places where exile occurred.
- Full Text: false
- Date Issued: 2018
- Authors: Thorpe, Andrea
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/68432 , vital:29255 , https://doi.org/10.1080/02564718.2018.1447865
- Description: Publisher version , In this article, I aim to expand our understanding of Arthur Nortje as a poet of “exile” by exploring the dialectic between self-loathing and pleasure, as well as between engagement and isolation, which he portrays performatively through his London poetry. While critics have emphasised Nortje’s “marginality” or “liminality”, both as an “exile” and a “coloured” South African, I draw on the critical writing of Zoë Wicomb in order to extend readings of his poetry beyond this tragic paradigm. I furthermore take up Sarah Nuttall’s suggestion that Nortje’s London poetry describes a degree of immersion within the city and that this aspect of his work demands further study. After tracing Nortje’s playful use of literary influences and his reworking of the trope of flânerie, I provide a series of close readings of poems in which Nortje depicts an exploration of queer subjectivities, staged within the city. In his London poetry, Nortje subverts and eludes fixed racial, sexual, national and class identities. Nortje’s London poetry exemplifies how South African literature was developed in response to the alienating condition of exile, but also through engagement with the places where exile occurred.
- Full Text: false
- Date Issued: 2018
Themes in self-presentation on a gay male dating site: a content analysis of the profiles of a sample of online daters from the Eastern Cape Province
- Authors: Lelimo, Thabang Lucky
- Date: 2018
- Subjects: Online dating -- South Africa -- Eastern Cape , Gay men -- South Africa -- Eastern Cape , Gay men -- Identity , Self-presentation , Homophobia -- South Africa -- Eastern Cape , Gay men -- Sexual behavior -- South Africa -- Eastern Cape , Language and sex , Communication and sex
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/60233 , vital:27757
- Description: My thesis research explores themes in self-presentation in the dating profiles of gay men from the Eastern Cape Province on an online dating site for men only. Although there is a growing body of research on this topic, this research is generally located in Europe and North America. In South Africa, research on same-sex intimacies has a chequered history. In the apartheid past, gay men and lesbian women were largely ignored by psychologists and social scientists. And, when they did receive their attention, it was largely discriminatory. In the post-apartheid context, there is far more interest in queer sexualities. However, as this research focuses on HIV transmission and on discrimination and violent homophobia, it too has played a role in painting a gloomy picture of what it means to be queer in South Africa. This study both address a ‘gap in literature’ on gay male dating online by focusing on the South African context, and it addresses the crisis of representation by giving consideration to the ways in which gay men see and present themselves to others. This study takes the form of a content analysis of 200 dating profiles. Key themes in self-presentation emerging in the analysis are: Ethnicity; Age; Education; Geographic Location; Living Arrangements; Sexuality; Relationship Status; Lifestyle; Appearance; Political Outlook; Personality; Faith. I discuss important observations relating to these themes and the insights they provide on key issues shaping public debate on same-sex sexualities in the South African context.
- Full Text:
- Date Issued: 2018
- Authors: Lelimo, Thabang Lucky
- Date: 2018
- Subjects: Online dating -- South Africa -- Eastern Cape , Gay men -- South Africa -- Eastern Cape , Gay men -- Identity , Self-presentation , Homophobia -- South Africa -- Eastern Cape , Gay men -- Sexual behavior -- South Africa -- Eastern Cape , Language and sex , Communication and sex
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/60233 , vital:27757
- Description: My thesis research explores themes in self-presentation in the dating profiles of gay men from the Eastern Cape Province on an online dating site for men only. Although there is a growing body of research on this topic, this research is generally located in Europe and North America. In South Africa, research on same-sex intimacies has a chequered history. In the apartheid past, gay men and lesbian women were largely ignored by psychologists and social scientists. And, when they did receive their attention, it was largely discriminatory. In the post-apartheid context, there is far more interest in queer sexualities. However, as this research focuses on HIV transmission and on discrimination and violent homophobia, it too has played a role in painting a gloomy picture of what it means to be queer in South Africa. This study both address a ‘gap in literature’ on gay male dating online by focusing on the South African context, and it addresses the crisis of representation by giving consideration to the ways in which gay men see and present themselves to others. This study takes the form of a content analysis of 200 dating profiles. Key themes in self-presentation emerging in the analysis are: Ethnicity; Age; Education; Geographic Location; Living Arrangements; Sexuality; Relationship Status; Lifestyle; Appearance; Political Outlook; Personality; Faith. I discuss important observations relating to these themes and the insights they provide on key issues shaping public debate on same-sex sexualities in the South African context.
- Full Text:
- Date Issued: 2018
There’s another story here
- Authors: Nkosi, Lindokuhle
- Date: 2018
- Subjects: Creative writing (Higher education) -- South Africa , South African fiction (English) -- 21st century , Short stories, South African (English) -- 21st century
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/63065 , vital:28360
- Description: Written in fragments and combining fiction and narrative non-fiction, this novella explores how South Africa's history of violence and current violence against women affects and influences how women relate to each other. Based in the knowledge that our memories and behaviours are linked to the experiences of our ancestors via our bodies, I engage what our violent history and the disappearing myths that are still embedded in our bloodstream mean for life today. Drawing on the experiences of several generations of women in my family, current affairs and the lives of women close to me, my novella picks at the fragile things that hold us together. I take influence from the prose poetry in Claudia Rankine’s Citizen, and the use of fragmentation, myth and biography in Lydia Yuknavitch’s A Chronology of Water and Lily Hoang’s A Bestiary, and use an amalgam of genres to ask how we hold each other; how we breath, create, love and dream.
- Full Text:
- Date Issued: 2018
- Authors: Nkosi, Lindokuhle
- Date: 2018
- Subjects: Creative writing (Higher education) -- South Africa , South African fiction (English) -- 21st century , Short stories, South African (English) -- 21st century
- Language: English
- Type: text , Thesis , Masters , MA
- Identifier: http://hdl.handle.net/10962/63065 , vital:28360
- Description: Written in fragments and combining fiction and narrative non-fiction, this novella explores how South Africa's history of violence and current violence against women affects and influences how women relate to each other. Based in the knowledge that our memories and behaviours are linked to the experiences of our ancestors via our bodies, I engage what our violent history and the disappearing myths that are still embedded in our bloodstream mean for life today. Drawing on the experiences of several generations of women in my family, current affairs and the lives of women close to me, my novella picks at the fragile things that hold us together. I take influence from the prose poetry in Claudia Rankine’s Citizen, and the use of fragmentation, myth and biography in Lydia Yuknavitch’s A Chronology of Water and Lily Hoang’s A Bestiary, and use an amalgam of genres to ask how we hold each other; how we breath, create, love and dream.
- Full Text:
- Date Issued: 2018
Thermoluminescence of annealed synthetic quartz: the influence of annealing on kinetic parameters and thermal quenching
- Dawam, Robert R, Chithambo, Makaiko L
- Authors: Dawam, Robert R , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110050 , vital:33218 , https://doi.org/10.1016/j.radmeas.2018.06.004
- Description: The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 oCs−1 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 0.90±0.02eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 0.65±0.02eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 0.65±0.02eV, 0.82±0.02eV and 0.95±0.06eV. Evidently, annealing affects recombination processes in synthetic quartz.
- Full Text: false
- Date Issued: 2018
- Authors: Dawam, Robert R , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/110050 , vital:33218 , https://doi.org/10.1016/j.radmeas.2018.06.004
- Description: The thermoluminescence of synthetic quartz annealed at various temperatures up to 900 °C is reported. Glow curves measured at 1 oCs−1 following beta irradiation to 40 Gy from a sample annealed at 500 °C and from an unannealed one consist of a prominent peak at 70 °C and secondary peaks at 110, 180 and 310 °C. In comparison, the glow peak from the sample annealed at 900 °C consists of three peaks but with the main peak at 86 °C and other lower intensity peaks at 170 and 310 °C. Kinetic analysis was carried out on the main peak only in each case. The order of kinetics of this peak was determined to be first order using various methods. The activation energy was evaluated as an average of 0.90±0.02eV for the unannealed sample and the one annealed at 500 °C. However, when the synthetic quartz is annealed at 900 °C, the activation energy decreases to 0.65±0.02eV. The main point of interest however concerns thermal quenching. It was noted that for the sample annealed at 500 °C as well as the unannealed one, the maximum intensity of the main peak decreases with heating rate. This phenomenon is associated with thermal quenching. When the same experiment is carried out using quartz annealed at 900 °C and irradiated to the same dose, namely 40 Gy, the intensity increases with heating rate. This would imply that this sample is not affected by thermal quenching. Using the notion that the radiative and non-radiative recombination routes are competitive, we repeated the experiment using a low dose of 3 Gy. In this case, the intensity decreased with heating rate showing that the process can be tuned. The activation energy for thermal quenching for the samples annealed at 900 °C, 500 °C and unnannealed one was found as 0.65±0.02eV, 0.82±0.02eV and 0.95±0.06eV. Evidently, annealing affects recombination processes in synthetic quartz.
- Full Text: false
- Date Issued: 2018
Thermoluminescence of the persistent-luminescence phosphor, BaAl2O4: a stuffed tridymite
- Pandey, A, Chithambo, Makaiko L
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
- Full Text: false
- Date Issued: 2018
- Authors: Pandey, A , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/113048 , vital:33693 , hhttps://doi.org/10.1016/j.radmeas.2018.01.004
- Description: BaAl2O4 is a stuffed tridymite used as a long-lasting phosphor. The thermoluminescence of BaAl2O4 prepared by solution-combustion is reported. Analysis of the sample using X-ray diffraction shows that it formed as a single phase compound with a hexagonal structure following annealing at 1200 °C. A broad photoluminescence emission band between 300 and 650 nm was detected due to excitation at 248 nm. The phosphor showed a natural TL peak at 102 °C for measurement at 1 oCs−1 and, when beta irradiated to 100 Gy, two broad peaks at 123 and 318 °C also for heating at 1 oCs−1. The analysis of the main glow peak at 123 °C suggests that it is a combination of several collocated peaks, that is, peaks embedded within each other. We resolved four such components labelled peaks 1 to 4. The thermoluminescence decreases with heating rate in a way consistent with thermal quenching whose activation energy was determined as ∼0.65eV using peak 3. Interestingly, this value of the activation energy for thermal quenching for BaAl2O4, a stuffed derivative of silica, is similar to literature values for quartz (a silica), suggesting that the recombination centre in the two cases may be similar.
- Full Text: false
- Date Issued: 2018
Thermoluminescence of α-Al2O3: C, Mg annealed at 1200° C
- Kalita, Jitumani M, Chithambo, Makaiko L
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111030 , vital:33365 , https://doi.org/10.1016/j.nimb.2018.03.003
- Description: Stimulated luminescence in α-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 °C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of α-Al2O3:C,Mg annealed at 1200 °C. A glow curve measured at 1 °C/s from the samples annealed at 1200 °C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 °C. Kinetic analyses show that the peak at 54 °C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 1010–1014 s−1. The intensity of the peaks at 54, 80, 102 and 173 °C increase with heating rate whereas those of the peaks at 238 and 290 °C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 °C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 °C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 °C are (1.02 ± 0.16) eV and (1.33 ± 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 °C are sublinear within 1–10 Gy and the peak at 54 °C saturates above 6 Gy. In contrast, the response of the peak at 173 °C is sublinear with 1–4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.
- Full Text: false
- Date Issued: 2018
- Authors: Kalita, Jitumani M , Chithambo, Makaiko L
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/111030 , vital:33365 , https://doi.org/10.1016/j.nimb.2018.03.003
- Description: Stimulated luminescence in α-Al2O3:C,Mg has thus far been studied for samples annealed at temperature no higher than 900 °C as can be seen by an examination of the literature. We report the thermoluminescence (TL) features of α-Al2O3:C,Mg annealed at 1200 °C. A glow curve measured at 1 °C/s from the samples annealed at 1200 °C shows eight peaks at 54, 80, 102, 173, 238, 290, 330 and 387 °C. Kinetic analyses show that the peak at 54 °C follows general order kinetics (b = 1.3) whereas the rest follow first order kinetics. The values of the activation energy of the peaks are between 0.77 eV and 1.90 eV and the frequency factors are of the order of 1010–1014 s−1. The intensity of the peaks at 54, 80, 102 and 173 °C increase with heating rate whereas those of the peaks at 238 and 290 °C decrease with heating rate. The decrease of intensity of the peaks at 238 and 290 °C with heating rate is due to thermal quenching whereas the increase of intensity of the peaks with heating rate indicates an inverse thermal-quenching-like behaviour. Interestingly this behaviour is observed only after annealing at 1200 °C. The activation energy for thermal quenching as calculated using the peaks at 238 and 290 °C are (1.02 ± 0.16) eV and (1.33 ± 0.15) eV respectively. Regarding the dosimetric features, the dose response of the peaks at 54, 80 and 102 °C are sublinear within 1–10 Gy and the peak at 54 °C saturates above 6 Gy. In contrast, the response of the peak at 173 °C is sublinear with 1–4 Gy and superlinear between 4 and 10 Gy. The peaks are found to fade at different rates and the rate of fading is also affected by annealing.
- Full Text: false
- Date Issued: 2018
Think Piece on Amanzi for Food. Working with Critical Realism to Inform a Situated Learning Framework for Climate Change Education
- Authors: O'Donoghue, Rob B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/388136 , vital:68309 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/172215"
- Description: This study is developed as a think piece which deliberates the problem of transformative human agency in a curriculum setting. Using a critical realism perspective and schematic tools it examines the deliberative framing of an Amanzi for Food teaching garden as an education process for mediating the learning of rainwater harvesting. Working with Bhaskar’s Transformational Model of Social Activity and using expansions of his ‘four-planar social being’ schema and its resolution in his ‘social cube’ model, the study contemplates the framing for a curriculum for the mediation of co-engaged social learning in the contexts of practical work in an agricultural college curriculum setting. In this way the research process is developed as an under-labouring review of the emerging curriculum in search of theory to inform pedagogy for mediating situated processes of transformative social learning.
- Full Text:
- Date Issued: 2018
- Authors: O'Donoghue, Rob B
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/388136 , vital:68309 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/172215"
- Description: This study is developed as a think piece which deliberates the problem of transformative human agency in a curriculum setting. Using a critical realism perspective and schematic tools it examines the deliberative framing of an Amanzi for Food teaching garden as an education process for mediating the learning of rainwater harvesting. Working with Bhaskar’s Transformational Model of Social Activity and using expansions of his ‘four-planar social being’ schema and its resolution in his ‘social cube’ model, the study contemplates the framing for a curriculum for the mediation of co-engaged social learning in the contexts of practical work in an agricultural college curriculum setting. In this way the research process is developed as an under-labouring review of the emerging curriculum in search of theory to inform pedagogy for mediating situated processes of transformative social learning.
- Full Text:
- Date Issued: 2018
Think Piece. Intersectional Resonance and the Multiplicity of Being in a Polarised World
- Authors: Kulundu, Injairu
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/388037 , vital:68301 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/172212"
- Description: Understandings of collective learning and change agency often conjure up an image of a particular group or community identifying important concerns and finding the momentum to learn together to address them. In reality, gaining consensus around what issues need to be addressed is a complex process in polarised societies. It requires an attentiveness to different standpoints and experiences of the social dynamics at play, and the ways in which ecological, political, socio-economic and psychic experiences manifest themselves within different contexts, generating disparate and connected views on what is missing and what is needed to create a more just society. This paper asks questions about what it means to learn in-between and through complex and interrelated societal dynamics amongst a community of change drivers. By highlighting the individual, communal and collective learning of a diverse group of change drivers in a very polarised South Africa, we can begin to ask questions about the following: 1) how different embodied experiences or ‘a multiplicity of being’, as referred to in this paper, are essential in the pursuit of a sustainable society; and 2) why we need to learn in ways that can foster a sense of ‘intersectional resonance’ between and amongst change drivers in a polarised world.
- Full Text:
- Date Issued: 2018
- Authors: Kulundu, Injairu
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/388037 , vital:68301 , xlink:href="https://www.ajol.info/index.php/sajee/article/view/172212"
- Description: Understandings of collective learning and change agency often conjure up an image of a particular group or community identifying important concerns and finding the momentum to learn together to address them. In reality, gaining consensus around what issues need to be addressed is a complex process in polarised societies. It requires an attentiveness to different standpoints and experiences of the social dynamics at play, and the ways in which ecological, political, socio-economic and psychic experiences manifest themselves within different contexts, generating disparate and connected views on what is missing and what is needed to create a more just society. This paper asks questions about what it means to learn in-between and through complex and interrelated societal dynamics amongst a community of change drivers. By highlighting the individual, communal and collective learning of a diverse group of change drivers in a very polarised South Africa, we can begin to ask questions about the following: 1) how different embodied experiences or ‘a multiplicity of being’, as referred to in this paper, are essential in the pursuit of a sustainable society; and 2) why we need to learn in ways that can foster a sense of ‘intersectional resonance’ between and amongst change drivers in a polarised world.
- Full Text:
- Date Issued: 2018
Think Piece: Pioneers as relational subjects? Probing relationality as phenomenon shaping collective learning and change agency formation
- Authors: Lotz-Sisitka, Heila
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182787 , vital:43874 , xlink:href="DOI 10.4314/sajee.v34i1.5"
- Description: This paper deliberates on how relationality is framed in collective learning and change agency formation processes, with an emphasis on green economy and renewable energy learning contexts. The paper is not focused on empirical analysis of relationality in collective learning, but rather probes the phenomenon in order to provide more carefully constituted theoretical and analytical tools for further empirical research. The paper uses references to South African and Danish cases (albeit in slightly different ways), and, through this, it sets out to provide tools for generative insights and research into a recent international policy and strategy process which is bringing national-level Green Economy Learning Assessments (GELA) into being, including one in South Africa. Central to these GELAs is the notion of participatory or relational competence, which appears to be a central feature of collective learning, although this is not empirically analysed in this paper. In case study work undertaken for the GELA in South Africa that focused on South Africa’s major renewable energy development, and in the Samsø Island renewable energy transition case in Denmark, this competence appeared to come into focus in praxis. Interestingly, however, it appeared to come into focus colloquially as a discourse on ‘pioneers’ or ‘champions’, a phenomenon noticed in both the South African and Danish contexts. This paper probes this phenomenon further, especially since it initially appears to be contradictory to the emphasis on participatory and relational competence in the GELA study framework. This is because the concept of ‘pioneer/champion’ appears to highlight individual capabilities rather than collective, relational competences. Yet, on closer inspection, it is indeed the relational competences of the pioneer/champion, who is constituted as a ‘relational subject’ with a key role to play in producing shared relational goods, that appears to be significant to the collective learning and action process. This, as argued in the paper, requires a differentiation of relationism and relational realism. This Think Piece, which thinks with both theory and praxis, therefore offers a possible framework for more detailed empirical studies on relationality in collective learning and change agency formation.
- Full Text:
- Date Issued: 2018
- Authors: Lotz-Sisitka, Heila
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182787 , vital:43874 , xlink:href="DOI 10.4314/sajee.v34i1.5"
- Description: This paper deliberates on how relationality is framed in collective learning and change agency formation processes, with an emphasis on green economy and renewable energy learning contexts. The paper is not focused on empirical analysis of relationality in collective learning, but rather probes the phenomenon in order to provide more carefully constituted theoretical and analytical tools for further empirical research. The paper uses references to South African and Danish cases (albeit in slightly different ways), and, through this, it sets out to provide tools for generative insights and research into a recent international policy and strategy process which is bringing national-level Green Economy Learning Assessments (GELA) into being, including one in South Africa. Central to these GELAs is the notion of participatory or relational competence, which appears to be a central feature of collective learning, although this is not empirically analysed in this paper. In case study work undertaken for the GELA in South Africa that focused on South Africa’s major renewable energy development, and in the Samsø Island renewable energy transition case in Denmark, this competence appeared to come into focus in praxis. Interestingly, however, it appeared to come into focus colloquially as a discourse on ‘pioneers’ or ‘champions’, a phenomenon noticed in both the South African and Danish contexts. This paper probes this phenomenon further, especially since it initially appears to be contradictory to the emphasis on participatory and relational competence in the GELA study framework. This is because the concept of ‘pioneer/champion’ appears to highlight individual capabilities rather than collective, relational competences. Yet, on closer inspection, it is indeed the relational competences of the pioneer/champion, who is constituted as a ‘relational subject’ with a key role to play in producing shared relational goods, that appears to be significant to the collective learning and action process. This, as argued in the paper, requires a differentiation of relationism and relational realism. This Think Piece, which thinks with both theory and praxis, therefore offers a possible framework for more detailed empirical studies on relationality in collective learning and change agency formation.
- Full Text:
- Date Issued: 2018
This is our story: iconography of carved doors and panels in Òyó Palace
- Authors: Fọlárànmí, Stephen
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145698 , vital:38459 , https://0-doi.org.wam.seals.ac.za/10.1162/afar_a_00402
- Description: This saying or prayer is one of the numerous expressions among the Yorùbá about the door and its significance, not only as a physical and important aspect of their architecture, but also in their language and culture. It also alludes to its pride of place as perhaps the most decorated element of Yorùbá architecture. From private homes, to the homes of the rich, shrines, and palaces, Yorùbá doors are usually imbued with a considerable array of images and icons that proclaims the owner's identity, religion, occupation. The Yorùbá are not unique in this respect. For example, among the Dogon, the door is as important as the house on which it is affixed. The granary, according to Willett (2002: 176), protects the the food stored inside it, while the door is seen or referred to as an element not only for physical protection, but also as a spiritual means of warding off unwanted spirits. It is reasonable, therefore, to expect the door to receive aesthetic attention by embellishment with an array of images.
- Full Text:
- Date Issued: 2018
- Authors: Fọlárànmí, Stephen
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/145698 , vital:38459 , https://0-doi.org.wam.seals.ac.za/10.1162/afar_a_00402
- Description: This saying or prayer is one of the numerous expressions among the Yorùbá about the door and its significance, not only as a physical and important aspect of their architecture, but also in their language and culture. It also alludes to its pride of place as perhaps the most decorated element of Yorùbá architecture. From private homes, to the homes of the rich, shrines, and palaces, Yorùbá doors are usually imbued with a considerable array of images and icons that proclaims the owner's identity, religion, occupation. The Yorùbá are not unique in this respect. For example, among the Dogon, the door is as important as the house on which it is affixed. The granary, according to Willett (2002: 176), protects the the food stored inside it, while the door is seen or referred to as an element not only for physical protection, but also as a spiritual means of warding off unwanted spirits. It is reasonable, therefore, to expect the door to receive aesthetic attention by embellishment with an array of images.
- Full Text:
- Date Issued: 2018
Three new pentacyclic triterpenoids from twigs of Manniophyton fulvum (Euphorbiaceae)
- Mbeunkeu, Ahri B D, Noundou, Xavier S, Krause, Rui W M, Teinkela, Jean E M, Laatsch, Hartmut, Azebaze, Anatole G B, Vardamides, Juliette C, Tala, Michel F
- Authors: Mbeunkeu, Ahri B D , Noundou, Xavier S , Krause, Rui W M , Teinkela, Jean E M , Laatsch, Hartmut , Azebaze, Anatole G B , Vardamides, Juliette C , Tala, Michel F
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126782 , vital:35922 , https://doi.org/10.1016/j.phytol.2018.06.019
- Description: Phytochemical investigation of the methanol extracts of the twigs of Manniophyton fulvum has led to the isolation and characterization of three new pentacyclic triterpenoids, designated as 3α,28-dihydroxyfriedelan-1-one (1), manniotaraxerol A (3) and manniotaraxerol B (4), along with fourteen known compounds, 3α-hydroxy-1-oxofriedelane (2), betulinic acid (5), friedelin (S1), taraxerol (S2), a mixture of stigmasterol (S3) and β-sitosterol (S4), herranone (S5), docosanoic acid (S6), ursolic acid (S7), nasutin B (S8), bergenin (S9), stigmasterol-3-O-β-Dglucopyranoside (S10), 1,2-di-O-palmitoyl-3-O-(6-sulfo-α-D-quinovopyranosyl)glycerol (S11), and aridanin (S12). The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR, EI and ESI-MS). 3α,28-Dihydroxyfriedelan-1-one (1), 3α-hydroxy-1-oxofriedelane (2), manniotaraxerol A (3), manniotaraxerol B (4), and betulinic acid (5) were evaluated against HeLa (human cervix adenocarcinoma) cancer cells. Manniotaraxerol A (3) showed weak in vitro cytotoxicity with a cell viability value of 49.3%. Betulinic acid (5) also showed significant cytotoxicity against HeLa cell with a cell viability value of 4.0%; the other compounds were inactive in this test.
- Full Text:
- Date Issued: 2018
- Authors: Mbeunkeu, Ahri B D , Noundou, Xavier S , Krause, Rui W M , Teinkela, Jean E M , Laatsch, Hartmut , Azebaze, Anatole G B , Vardamides, Juliette C , Tala, Michel F
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/126782 , vital:35922 , https://doi.org/10.1016/j.phytol.2018.06.019
- Description: Phytochemical investigation of the methanol extracts of the twigs of Manniophyton fulvum has led to the isolation and characterization of three new pentacyclic triterpenoids, designated as 3α,28-dihydroxyfriedelan-1-one (1), manniotaraxerol A (3) and manniotaraxerol B (4), along with fourteen known compounds, 3α-hydroxy-1-oxofriedelane (2), betulinic acid (5), friedelin (S1), taraxerol (S2), a mixture of stigmasterol (S3) and β-sitosterol (S4), herranone (S5), docosanoic acid (S6), ursolic acid (S7), nasutin B (S8), bergenin (S9), stigmasterol-3-O-β-Dglucopyranoside (S10), 1,2-di-O-palmitoyl-3-O-(6-sulfo-α-D-quinovopyranosyl)glycerol (S11), and aridanin (S12). The structures of all compounds were determined by comprehensive spectroscopic analyses (1D and 2D NMR, EI and ESI-MS). 3α,28-Dihydroxyfriedelan-1-one (1), 3α-hydroxy-1-oxofriedelane (2), manniotaraxerol A (3), manniotaraxerol B (4), and betulinic acid (5) were evaluated against HeLa (human cervix adenocarcinoma) cancer cells. Manniotaraxerol A (3) showed weak in vitro cytotoxicity with a cell viability value of 49.3%. Betulinic acid (5) also showed significant cytotoxicity against HeLa cell with a cell viability value of 4.0%; the other compounds were inactive in this test.
- Full Text:
- Date Issued: 2018
Ties that bind: the ambiguous role played by social capital in black working class first-generation South African students’ negotiation of university life
- Vincent, Louise, Hlatshwayo, M
- Authors: Vincent, Louise , Hlatshwayo, M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141722 , vital:37999 , DOI: 10.20853/32-3-2538
- Description: In this article we examine the ambiguous role that social capital plays in first generation Black working class South African students’ negotiation of entry into an elite higher education institutional environment. First generation student experiences have a particular relevance in South Africa where student enrolment increased by 193 000 between 1993 and 2004, with many of the new entrants first-generation students. South African research on first-generation working class Black students has focused on the low proportion of these students who reach university at all and among those who do enter university, the significant number who perform poorly or drop out before completing their degrees. The role played by social capital (social networks, close friends, associations, clubs and other affiliations) in these students’ experiences of negotiating their entry into university has been little explored.
- Full Text:
- Date Issued: 2018
- Authors: Vincent, Louise , Hlatshwayo, M
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/141722 , vital:37999 , DOI: 10.20853/32-3-2538
- Description: In this article we examine the ambiguous role that social capital plays in first generation Black working class South African students’ negotiation of entry into an elite higher education institutional environment. First generation student experiences have a particular relevance in South Africa where student enrolment increased by 193 000 between 1993 and 2004, with many of the new entrants first-generation students. South African research on first-generation working class Black students has focused on the low proportion of these students who reach university at all and among those who do enter university, the significant number who perform poorly or drop out before completing their degrees. The role played by social capital (social networks, close friends, associations, clubs and other affiliations) in these students’ experiences of negotiating their entry into university has been little explored.
- Full Text:
- Date Issued: 2018
Tomographic imaging of East African equatorial ionosphere and study of equatorial plasma bubbles
- Authors: Giday, Nigussie Mezgebe
- Date: 2018
- Subjects: Ionosphere -- Africa, Central , Tomography -- Africa, Central , Global Positioning System , Neural networks (Computer science) , Space environment , Multi-Instrument Data Analysis System (MIDAS) , Equatorial plasma bubbles
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63980 , vital:28516
- Description: In spite of the fact that the African ionospheric equatorial region has the largest ground footprint along the geomagnetic equator, it has not been well studied due to the absence of adequate ground-based instruments. This thesis presents research on both tomographic imaging of the African equatorial ionosphere and the study of the ionospheric irregularities/equatorial plasma bubbles (EPBs) under varying geomagnetic conditions. The Multi-Instrument Data Analysis System (MIDAS), an inversion algorithm, was investigated for its validity and ability as a tool to reconstruct multi-scaled ionospheric structures for different geomagnetic conditions. This was done for the narrow East African longitude sector with data from the available ground Global Positioning Sys-tem (GPS) receivers. The MIDAS results were compared to the results of two models, namely the IRI and GIM. MIDAS results compared more favourably with the observation vertical total electron content (VTEC), with a computed maximum correlation coefficient (r) of 0.99 and minimum root-mean-square error (RMSE) of 2.91 TECU, than did the results of the IRI-2012 and GIM models with maximum r of 0.93 and 0.99, and minimum RMSE of 13.03 TECU and 6.52 TECU, respectively, over all the test stations and validation days. The ability of MIDAS to reconstruct storm-time TEC was also compared with the results produced by the use of a Artificial Neural Net-work (ANN) for the African low- and mid-latitude regions. In terms of latitude, on average,MIDAS performed 13.44 % better than ANN in the African mid-latitudes, while MIDAS under performed in low-latitudes. This thesis also reports on the effects of moderate geomagnetic conditions on the evolution of EPBs and/or ionospheric irregularities during their season of occurrence using data from (or measurements by) space- and ground-based instruments for the east African equatorial sector. The study showed that the strength of daytime equatorial electrojet (EEJ), the steepness of the TEC peak-to-trough gradient and/or the meridional/transequatorial thermospheric winds sometimes have collective/interwoven effects, while at other times one mechanism dominates. In summary, this research offered tomographic results that outperform the results of the commonly used (“standard”) global models (i.e. IRI and GIM) for a longitude sector of importance to space weather, which has not been adequately studied due to a lack of sufficient instrumentation.
- Full Text:
- Date Issued: 2018
- Authors: Giday, Nigussie Mezgebe
- Date: 2018
- Subjects: Ionosphere -- Africa, Central , Tomography -- Africa, Central , Global Positioning System , Neural networks (Computer science) , Space environment , Multi-Instrument Data Analysis System (MIDAS) , Equatorial plasma bubbles
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/63980 , vital:28516
- Description: In spite of the fact that the African ionospheric equatorial region has the largest ground footprint along the geomagnetic equator, it has not been well studied due to the absence of adequate ground-based instruments. This thesis presents research on both tomographic imaging of the African equatorial ionosphere and the study of the ionospheric irregularities/equatorial plasma bubbles (EPBs) under varying geomagnetic conditions. The Multi-Instrument Data Analysis System (MIDAS), an inversion algorithm, was investigated for its validity and ability as a tool to reconstruct multi-scaled ionospheric structures for different geomagnetic conditions. This was done for the narrow East African longitude sector with data from the available ground Global Positioning Sys-tem (GPS) receivers. The MIDAS results were compared to the results of two models, namely the IRI and GIM. MIDAS results compared more favourably with the observation vertical total electron content (VTEC), with a computed maximum correlation coefficient (r) of 0.99 and minimum root-mean-square error (RMSE) of 2.91 TECU, than did the results of the IRI-2012 and GIM models with maximum r of 0.93 and 0.99, and minimum RMSE of 13.03 TECU and 6.52 TECU, respectively, over all the test stations and validation days. The ability of MIDAS to reconstruct storm-time TEC was also compared with the results produced by the use of a Artificial Neural Net-work (ANN) for the African low- and mid-latitude regions. In terms of latitude, on average,MIDAS performed 13.44 % better than ANN in the African mid-latitudes, while MIDAS under performed in low-latitudes. This thesis also reports on the effects of moderate geomagnetic conditions on the evolution of EPBs and/or ionospheric irregularities during their season of occurrence using data from (or measurements by) space- and ground-based instruments for the east African equatorial sector. The study showed that the strength of daytime equatorial electrojet (EEJ), the steepness of the TEC peak-to-trough gradient and/or the meridional/transequatorial thermospheric winds sometimes have collective/interwoven effects, while at other times one mechanism dominates. In summary, this research offered tomographic results that outperform the results of the commonly used (“standard”) global models (i.e. IRI and GIM) for a longitude sector of importance to space weather, which has not been adequately studied due to a lack of sufficient instrumentation.
- Full Text:
- Date Issued: 2018
Toward distributed key management for offline authentication
- Linklater, Gregory, Smith, Christian, Herbert, Alan, Irwin, Barry V W
- Authors: Linklater, Gregory , Smith, Christian , Herbert, Alan , Irwin, Barry V W
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430283 , vital:72680 , https://doi.org/10.1145/3278681.3278683
- Description: Self-sovereign identity promises prospective users greater control, security, privacy, portability and overall greater convenience; however the immaturity of current distributed key management solutions results in general disregard of security advisories in favour of convenience and accessibility. This research proposes the use of intermediate certificates as a distributed key management solution. Intermediate certificates will be shown to allow multiple keys to authenticate to a single self-sovereign identity. Keys may be freely added to an identity without requiring a distributed ledger, any other third-party service or sharing private keys between devices. This research will also show that key rotation is a superior alternative to existing key recovery and escrow systems in helping users recover when their keys are lost or compromised. These features will allow remote credentials to be used to issuer, present and appraise remote attestations, without relying on a constant Internet connection.
- Full Text:
- Date Issued: 2018
- Authors: Linklater, Gregory , Smith, Christian , Herbert, Alan , Irwin, Barry V W
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/430283 , vital:72680 , https://doi.org/10.1145/3278681.3278683
- Description: Self-sovereign identity promises prospective users greater control, security, privacy, portability and overall greater convenience; however the immaturity of current distributed key management solutions results in general disregard of security advisories in favour of convenience and accessibility. This research proposes the use of intermediate certificates as a distributed key management solution. Intermediate certificates will be shown to allow multiple keys to authenticate to a single self-sovereign identity. Keys may be freely added to an identity without requiring a distributed ledger, any other third-party service or sharing private keys between devices. This research will also show that key rotation is a superior alternative to existing key recovery and escrow systems in helping users recover when their keys are lost or compromised. These features will allow remote credentials to be used to issuer, present and appraise remote attestations, without relying on a constant Internet connection.
- Full Text:
- Date Issued: 2018
Towards a collection of cost-effective technologies in support of the NIST cybersecurity framework
- Shackleton, Bruce Michael Stuart
- Authors: Shackleton, Bruce Michael Stuart
- Date: 2018
- Subjects: National Institute of Standards and Technology (U.S.) , Computer security , Computer networks Security measures , Small business Information technology Cost effectiveness , Open source software
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62494 , vital:28199
- Description: The NIST Cybersecurity Framework (CSF) is a specific risk and cybersecurity framework. It provides guidance on controls that can be implemented to help improve an organisation’s cybersecurity risk posture. The CSF Functions consist of Identify, Protect, Detect, Respond, and Recover. Like most Information Technology (IT) frameworks, there are elements of people, processes, and technology. The same elements are required to successfully implement the NIST CSF. This research specifically focuses on the technology element. While there are many commercial technologies available for a small to medium sized business, the costs can be prohibitively expensive. Therefore, this research investigates cost-effective technologies and assesses their alignment to the NIST CSF. The assessment was made against the NIST CSF subcategories. Each subcategory was analysed to identify where a technology would likely be required. The framework provides a list of Informative References. These Informative References were used to create high- level technology categories, as well as identify the technical controls against which the technologies were measured. The technologies tested were either open source or proprietary. All open source technologies tested were free to use, or have a free community edition. Proprietary technologies would be free to use, or considered generally available to most organisations, such as components contained within Microsoft platforms. The results from the experimentation demonstrated that there are multiple cost-effective technologies that can support the NIST CSF. Once all technologies were tested, the NIST CSF was extended. Two new columns were added, namely high-level technology category, and tested technology. The columns were populated with output from the research. This extended framework begins an initial collection of cost-effective technologies in support of the NIST CSF.
- Full Text:
- Date Issued: 2018
- Authors: Shackleton, Bruce Michael Stuart
- Date: 2018
- Subjects: National Institute of Standards and Technology (U.S.) , Computer security , Computer networks Security measures , Small business Information technology Cost effectiveness , Open source software
- Language: English
- Type: text , Thesis , Masters , MSc
- Identifier: http://hdl.handle.net/10962/62494 , vital:28199
- Description: The NIST Cybersecurity Framework (CSF) is a specific risk and cybersecurity framework. It provides guidance on controls that can be implemented to help improve an organisation’s cybersecurity risk posture. The CSF Functions consist of Identify, Protect, Detect, Respond, and Recover. Like most Information Technology (IT) frameworks, there are elements of people, processes, and technology. The same elements are required to successfully implement the NIST CSF. This research specifically focuses on the technology element. While there are many commercial technologies available for a small to medium sized business, the costs can be prohibitively expensive. Therefore, this research investigates cost-effective technologies and assesses their alignment to the NIST CSF. The assessment was made against the NIST CSF subcategories. Each subcategory was analysed to identify where a technology would likely be required. The framework provides a list of Informative References. These Informative References were used to create high- level technology categories, as well as identify the technical controls against which the technologies were measured. The technologies tested were either open source or proprietary. All open source technologies tested were free to use, or have a free community edition. Proprietary technologies would be free to use, or considered generally available to most organisations, such as components contained within Microsoft platforms. The results from the experimentation demonstrated that there are multiple cost-effective technologies that can support the NIST CSF. Once all technologies were tested, the NIST CSF was extended. Two new columns were added, namely high-level technology category, and tested technology. The columns were populated with output from the research. This extended framework begins an initial collection of cost-effective technologies in support of the NIST CSF.
- Full Text:
- Date Issued: 2018
Towards a threat assessment framework for consumer health wearables
- Authors: Mnjama, Javan Joshua
- Date: 2018
- Subjects: Activity trackers (Wearable technology) , Computer networks -- Security measures , Data protection , Information storage and retrieval systems -- Security systems , Computer security -- Software , Consumer Health Wearable Threat Assessment Framework , Design Science Research
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/62649 , vital:28225
- Description: The collection of health data such as physical activity, consumption and physiological data through the use of consumer health wearables via fitness trackers are very beneficial for the promotion of physical wellness. However, consumer health wearables and their associated applications are known to have privacy and security concerns that can potentially make the collected personal health data vulnerable to hackers. These concerns are attributed to security theoretical frameworks not sufficiently addressing the entirety of privacy and security concerns relating to the diverse technological ecosystem of consumer health wearables. The objective of this research was therefore to develop a threat assessment framework that can be used to guide the detection of vulnerabilities which affect consumer health wearables and their associated applications. To meet this objective, the Design Science Research methodology was used to develop the desired artefact (Consumer Health Wearable Threat Assessment Framework). The framework is comprised of fourteen vulnerabilities classified according to Authentication, Authorization, Availability, Confidentiality, Non-Repudiation and Integrity. Through developing the artefact, the threat assessment framework was demonstrated on two fitness trackers and their associated applications. It was discovered, that the framework was able to identify how these vulnerabilities affected, these two test cases based on the classification categories of the framework. The framework was also evaluated by four security experts who assessed the quality, utility and efficacy of the framework. Experts, supported the use of the framework as a relevant and comprehensive framework to guide the detection of vulnerabilities towards consumer health wearables and their associated applications. The implication of this research study is that the framework can be used by developers to better identify the vulnerabilities of consumer health wearables and their associated applications. This will assist in creating a more securer environment for the storage and use of health data by consumer health wearables.
- Full Text:
- Date Issued: 2018
- Authors: Mnjama, Javan Joshua
- Date: 2018
- Subjects: Activity trackers (Wearable technology) , Computer networks -- Security measures , Data protection , Information storage and retrieval systems -- Security systems , Computer security -- Software , Consumer Health Wearable Threat Assessment Framework , Design Science Research
- Language: English
- Type: text , Thesis , Masters , MCom
- Identifier: http://hdl.handle.net/10962/62649 , vital:28225
- Description: The collection of health data such as physical activity, consumption and physiological data through the use of consumer health wearables via fitness trackers are very beneficial for the promotion of physical wellness. However, consumer health wearables and their associated applications are known to have privacy and security concerns that can potentially make the collected personal health data vulnerable to hackers. These concerns are attributed to security theoretical frameworks not sufficiently addressing the entirety of privacy and security concerns relating to the diverse technological ecosystem of consumer health wearables. The objective of this research was therefore to develop a threat assessment framework that can be used to guide the detection of vulnerabilities which affect consumer health wearables and their associated applications. To meet this objective, the Design Science Research methodology was used to develop the desired artefact (Consumer Health Wearable Threat Assessment Framework). The framework is comprised of fourteen vulnerabilities classified according to Authentication, Authorization, Availability, Confidentiality, Non-Repudiation and Integrity. Through developing the artefact, the threat assessment framework was demonstrated on two fitness trackers and their associated applications. It was discovered, that the framework was able to identify how these vulnerabilities affected, these two test cases based on the classification categories of the framework. The framework was also evaluated by four security experts who assessed the quality, utility and efficacy of the framework. Experts, supported the use of the framework as a relevant and comprehensive framework to guide the detection of vulnerabilities towards consumer health wearables and their associated applications. The implication of this research study is that the framework can be used by developers to better identify the vulnerabilities of consumer health wearables and their associated applications. This will assist in creating a more securer environment for the storage and use of health data by consumer health wearables.
- Full Text:
- Date Issued: 2018
Towards Enhanced Threat Intelligence Through NetFlow Distillation
- Herbert, Alan, Irwin, Barry V W
- Authors: Herbert, Alan , Irwin, Barry V W
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427699 , vital:72456 , https://www.researchgate.net/profile/Barry-Ir-win/publication/327624198_Towards_Enhanced_Threat_Intelligence_Through_NetFlow_Distillation/links/5b9a501fa6fdcc59bf8ee8ea/Towards-Enhanced-Threat-Intelligence-Through-NetFlow-Distillation.pdf
- Description: Bolvedere is a hardware-accelerated NetFlow analysis platform intended to discern and distribute NetFlow records in a requested format by a user. This functionality removes the need for a user to deal with the NetFlow protocol directly, and also reduces the requirement of CPU resources as data would be passed on to a host in the known requested format.
- Full Text:
- Date Issued: 2018
- Authors: Herbert, Alan , Irwin, Barry V W
- Date: 2018
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/427699 , vital:72456 , https://www.researchgate.net/profile/Barry-Ir-win/publication/327624198_Towards_Enhanced_Threat_Intelligence_Through_NetFlow_Distillation/links/5b9a501fa6fdcc59bf8ee8ea/Towards-Enhanced-Threat-Intelligence-Through-NetFlow-Distillation.pdf
- Description: Bolvedere is a hardware-accelerated NetFlow analysis platform intended to discern and distribute NetFlow records in a requested format by a user. This functionality removes the need for a user to deal with the NetFlow protocol directly, and also reduces the requirement of CPU resources as data would be passed on to a host in the known requested format.
- Full Text:
- Date Issued: 2018