Learning styles, availability, and utilization of instructional materials as correlates of grade 6 learners’ mathematics performance in Buffalo city
- Authors: Adu, Kemi Olajumoke
- Date: 2020
- Subjects: Learning ability
- Language: English
- Type: Thesis , Doctoral , PhD (Education)
- Identifier: http://hdl.handle.net/10353/11374 , vital:39066
- Description: Mathematics is the foundation for the economic and technological development of any nation. It has been asserted that Mathematics is expected to help in accelerating social, economic and technological progress of any society. Performance of this subject is very important and there are different types of learners; such auditory, visual, and kinesthetic. Auditory learners appreciate listening to the teachers and sit down close to the teachers in class. Visual learners like to see things physically during teaching. They learn by materials like charts, graphs, and pictures. Kinesthetic learners learn by doing. Students can prefer one, two, or three learning styles; all these are subject to the availability of instructional materials. The Primary school level is very important in any educational system and any lack at this level would permeate to other levels of the educational system. Hence, this thesis examines the Learning Styles, Availability, and Utilization of Instructional Materials as Correlates of Grade 6 Learners’ Mathematics Performance in Buffalo City. The study adopted the positivist paradigm and employed the quantitative approach in investigating the phenomenon. The thesis made use of correlational research design as it attempted to find out the effects of learning styles and instructional materials on learners’ performance in Mathematics. Stratified sampling was used to select participants. Stratified sampling is a process of dividing the sample frame into strata to obtain relatively homogenous subgroups; this gave us 1225 Grade 6 learners selected across 35 schools in Buffalo City as the sample of the study. Three instruments which are Students’ Learning Styles Scale (SLSS), Availability and Utilization of Instructional Materials Inventory (AUIMI), and Mathematics Achievement Test (MAT) whose reliability co-efficient are; 0.87, 0.78 and 0.89 respectively. The data collected were analysed using descriptive and inferential statistics. The findings of the study revealed among others; students learning style (visual, auditory, and kinesthetic) have a significant relationship on Grade 6 learners Mathematics performance (B=-.113, t=-3.886, p<0.05). Students learning style (∆R2=.012, ∆F (1, 1223) = 5.047, p < 0.05) emerged as the best predictor of Grade 6 learners Mathematics performance in Buffalo City, while the availability and utilization of instructional materials (∆R2 = .000), ∆F (1,223) = .018, P > 0.05), and gender (∆R2 = .000, ∆F (1,1223) = .036, p>0.05) emerged as better predictors. The study further iv revealed that, Grade six learners with visual learning style ( = 13.242, SD = 5.565) had the best performance in Mathematics at Buffalo City, followed by learners with auditory learning style ( = 12.996, SD = 3.883), and learners with Kinaesthetic learning style ( = 11.525, SD =3.800). The study concluded that one of the most fundamental issues to consider in improving Mathematics performance is the understanding of the learners’ learning styles and effective use of appropriate instructional materials for teaching Mathematics.
- Full Text:
- Date Issued: 2020
- Authors: Adu, Kemi Olajumoke
- Date: 2020
- Subjects: Learning ability
- Language: English
- Type: Thesis , Doctoral , PhD (Education)
- Identifier: http://hdl.handle.net/10353/11374 , vital:39066
- Description: Mathematics is the foundation for the economic and technological development of any nation. It has been asserted that Mathematics is expected to help in accelerating social, economic and technological progress of any society. Performance of this subject is very important and there are different types of learners; such auditory, visual, and kinesthetic. Auditory learners appreciate listening to the teachers and sit down close to the teachers in class. Visual learners like to see things physically during teaching. They learn by materials like charts, graphs, and pictures. Kinesthetic learners learn by doing. Students can prefer one, two, or three learning styles; all these are subject to the availability of instructional materials. The Primary school level is very important in any educational system and any lack at this level would permeate to other levels of the educational system. Hence, this thesis examines the Learning Styles, Availability, and Utilization of Instructional Materials as Correlates of Grade 6 Learners’ Mathematics Performance in Buffalo City. The study adopted the positivist paradigm and employed the quantitative approach in investigating the phenomenon. The thesis made use of correlational research design as it attempted to find out the effects of learning styles and instructional materials on learners’ performance in Mathematics. Stratified sampling was used to select participants. Stratified sampling is a process of dividing the sample frame into strata to obtain relatively homogenous subgroups; this gave us 1225 Grade 6 learners selected across 35 schools in Buffalo City as the sample of the study. Three instruments which are Students’ Learning Styles Scale (SLSS), Availability and Utilization of Instructional Materials Inventory (AUIMI), and Mathematics Achievement Test (MAT) whose reliability co-efficient are; 0.87, 0.78 and 0.89 respectively. The data collected were analysed using descriptive and inferential statistics. The findings of the study revealed among others; students learning style (visual, auditory, and kinesthetic) have a significant relationship on Grade 6 learners Mathematics performance (B=-.113, t=-3.886, p<0.05). Students learning style (∆R2=.012, ∆F (1, 1223) = 5.047, p < 0.05) emerged as the best predictor of Grade 6 learners Mathematics performance in Buffalo City, while the availability and utilization of instructional materials (∆R2 = .000), ∆F (1,223) = .018, P > 0.05), and gender (∆R2 = .000, ∆F (1,1223) = .036, p>0.05) emerged as better predictors. The study further iv revealed that, Grade six learners with visual learning style ( = 13.242, SD = 5.565) had the best performance in Mathematics at Buffalo City, followed by learners with auditory learning style ( = 12.996, SD = 3.883), and learners with Kinaesthetic learning style ( = 11.525, SD =3.800). The study concluded that one of the most fundamental issues to consider in improving Mathematics performance is the understanding of the learners’ learning styles and effective use of appropriate instructional materials for teaching Mathematics.
- Full Text:
- Date Issued: 2020
Chemical transformation and phytochemical studies of bioactive constituents from extract of callistemon citrinus (curtis) skeels
- Authors: Larayetan, Rotimi Abisoye
- Date: 2018
- Subjects: Callistemon Wild flowers
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9122 , vital:34272
- Description: Callistemon citrinus belongs to the family Myrtaceae and exhibits therapeutic activities. The aerial parts of this plant are used to treat different ailments, among them are parasitic infections. The leaves, flowers and stems of Callistemon citrinus were subjected to hydrodistillation. The oils collected were studied by GC-MS analysis for the essential constituents. The overall phenolic content of the leaves oil, radical scavenging, antibacterial action and antioxidant activities of the essential oils of Callistemon citrinus were determined using standard methods, with free radical DPPH or ABTS as reference antioxidants. Chemical transformation of the components was examined for a whole year. A relationship between the chemical change in the volatile oil constituents, antioxidant capacity, percentage yield of the oil of Callistemon citrinus and fluctuation in season has been established. Active phytochemicals present in both ethyl acetate and methanolic extracts of Callistemon citrinus were determined spectrophotometrically. The antimicrobial properties, time of kill, and antioxidant activity of the extracts were explored. The bioactive components were characterized by high level of fatty acids. Squalene, a triterpenoid synthesized in human liver was obtained in the two extracts at varying amounts. The ethyl acetate extract demonstrated strong activity against P. aeruginosa ACC (28.7 ± 1.2 mm), Listeria ACC (26.0 ± 2.0 mm) and Escherichia coli ATCC 35150 (24.0 ± 3.5 mm). Qualitative phytochemical screening revealed the presence of alkaloids, glycosides, saponins, steroids and triterpenoids, fats and oils, flavonoids, phenols and tannins in them. In the quantitative phytochemical determination (total tannin, total flavonoids and flavonols, total phenolic and total antioxidant capacity) were carried out. The minimum time needed to kill the tested bacterial strains totally ranged from 15 to 24 hours. The aqueous extracts used for biosynthesis of nanoparticles were obtained from the fresh aerial parts of the plant. The biosynthesized gold and silver nanoparticles (AuNPs and AgNPs) of the aqueous extracts of the seed, flower and leaf of the plant, which are active as reducing and capping agents, were characterized using UV-VIS spectrophotometry, XRD, SEM, EDS, TEM, and FT IR. The XRD analysis revealed that the AgNPs were crystalline and the TEM showed that the shapes were spherical with an average size of 29 nm. For AuNPs, an average particle size of about 37 nm was confirmed by the TEM while the morphology and composition of the AuNPs were ascertained by SEM and EDS micrographs; uneven spherical shaped nanoparticles were established by the SEM. Both SEM and EDS demonstrated triangular shaped materials made up of silver and oxygen only. Absorption spectra confirmed by UV-VIS signify the dispersed nature of the synthesized nanoparticles with absorption band observed at 280 nm for the leaf AgNPs. FT IR had absorption bands at about 1700 cm-1 establishing the C=O stretching due to the amide bond while the FT IR for the AuNPs showed an absorption peak at 230 cm-1 confirming the presence of gold nanoparticles. The phytochemical investigation, isolation and characterization of the bioactive compounds of various organic crude extracts like hexane, dichloromethane, methanol and ethyl acetate were as well carried out, and the compounds responsible for their medicinal actions were determined. The results from different experiments revealed that the leaves and flowers of Callistemon citrinus possessed phenolic compounds and cyclic ethers with a variety of pharmacological action. The ethyl acetate and methanol crude extracts were found to possess broad spectrum of antimicrobial activities and pharmaceutically essential bioactive components with striking antioxidant capacities that may be used in the synthesis of novel drugs for the management of different ailments. The AuNPs and AgNPs synthesized from the seed, flower and leaf extracts of Callistemon citrinus where found to have prominent antimalarial, antiplasmodial, and antibacterial activities. The biosynthesized nanoparticles inhibit all the bacterial strains used and they were not cytotoxic to Hela cells, confirming their prospect for use as an excellent source for naturally occurring drugs against malaria, cell cytotoxicity, trypanosomes, and microbial infection. Similarly the crude organic extracts and the fractions derived from them exhibited high antimalarial and antitrypanosomal activities, but they were toxic to Hela cells. This is an indication that they will not be safe for use as targeted drugs for mammalian organism.
- Full Text:
- Date Issued: 2018
- Authors: Larayetan, Rotimi Abisoye
- Date: 2018
- Subjects: Callistemon Wild flowers
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/9122 , vital:34272
- Description: Callistemon citrinus belongs to the family Myrtaceae and exhibits therapeutic activities. The aerial parts of this plant are used to treat different ailments, among them are parasitic infections. The leaves, flowers and stems of Callistemon citrinus were subjected to hydrodistillation. The oils collected were studied by GC-MS analysis for the essential constituents. The overall phenolic content of the leaves oil, radical scavenging, antibacterial action and antioxidant activities of the essential oils of Callistemon citrinus were determined using standard methods, with free radical DPPH or ABTS as reference antioxidants. Chemical transformation of the components was examined for a whole year. A relationship between the chemical change in the volatile oil constituents, antioxidant capacity, percentage yield of the oil of Callistemon citrinus and fluctuation in season has been established. Active phytochemicals present in both ethyl acetate and methanolic extracts of Callistemon citrinus were determined spectrophotometrically. The antimicrobial properties, time of kill, and antioxidant activity of the extracts were explored. The bioactive components were characterized by high level of fatty acids. Squalene, a triterpenoid synthesized in human liver was obtained in the two extracts at varying amounts. The ethyl acetate extract demonstrated strong activity against P. aeruginosa ACC (28.7 ± 1.2 mm), Listeria ACC (26.0 ± 2.0 mm) and Escherichia coli ATCC 35150 (24.0 ± 3.5 mm). Qualitative phytochemical screening revealed the presence of alkaloids, glycosides, saponins, steroids and triterpenoids, fats and oils, flavonoids, phenols and tannins in them. In the quantitative phytochemical determination (total tannin, total flavonoids and flavonols, total phenolic and total antioxidant capacity) were carried out. The minimum time needed to kill the tested bacterial strains totally ranged from 15 to 24 hours. The aqueous extracts used for biosynthesis of nanoparticles were obtained from the fresh aerial parts of the plant. The biosynthesized gold and silver nanoparticles (AuNPs and AgNPs) of the aqueous extracts of the seed, flower and leaf of the plant, which are active as reducing and capping agents, were characterized using UV-VIS spectrophotometry, XRD, SEM, EDS, TEM, and FT IR. The XRD analysis revealed that the AgNPs were crystalline and the TEM showed that the shapes were spherical with an average size of 29 nm. For AuNPs, an average particle size of about 37 nm was confirmed by the TEM while the morphology and composition of the AuNPs were ascertained by SEM and EDS micrographs; uneven spherical shaped nanoparticles were established by the SEM. Both SEM and EDS demonstrated triangular shaped materials made up of silver and oxygen only. Absorption spectra confirmed by UV-VIS signify the dispersed nature of the synthesized nanoparticles with absorption band observed at 280 nm for the leaf AgNPs. FT IR had absorption bands at about 1700 cm-1 establishing the C=O stretching due to the amide bond while the FT IR for the AuNPs showed an absorption peak at 230 cm-1 confirming the presence of gold nanoparticles. The phytochemical investigation, isolation and characterization of the bioactive compounds of various organic crude extracts like hexane, dichloromethane, methanol and ethyl acetate were as well carried out, and the compounds responsible for their medicinal actions were determined. The results from different experiments revealed that the leaves and flowers of Callistemon citrinus possessed phenolic compounds and cyclic ethers with a variety of pharmacological action. The ethyl acetate and methanol crude extracts were found to possess broad spectrum of antimicrobial activities and pharmaceutically essential bioactive components with striking antioxidant capacities that may be used in the synthesis of novel drugs for the management of different ailments. The AuNPs and AgNPs synthesized from the seed, flower and leaf extracts of Callistemon citrinus where found to have prominent antimalarial, antiplasmodial, and antibacterial activities. The biosynthesized nanoparticles inhibit all the bacterial strains used and they were not cytotoxic to Hela cells, confirming their prospect for use as an excellent source for naturally occurring drugs against malaria, cell cytotoxicity, trypanosomes, and microbial infection. Similarly the crude organic extracts and the fractions derived from them exhibited high antimalarial and antitrypanosomal activities, but they were toxic to Hela cells. This is an indication that they will not be safe for use as targeted drugs for mammalian organism.
- Full Text:
- Date Issued: 2018
Evaluating the contributions of selected drug rehabilitation centres in Gauteng : towards ameliorating the drug problem in South Africa
- Authors: Makuyana, Abigail
- Date: 2017
- Subjects: Rehabilitation centers -- South Africa -- Gauteng Substance abuse -- Rehabilitation Addicts -- Rehabilitation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8876 , vital:33703
- Description: This study aimed at evaluating the contributions of two (2) selected rehabilitation centres to the goal of ameliorating the substance abuse problem in Gauteng. The study utilized a methodological triangulation approach for data collection, but with greater emphasis on qualitative methods. The study collected its qualitative data from four focus groups conducted with 32 participants and six key informants who were subjected to in-depth interviews. The quantitative aspect of the study made use of a mini-survey in which one hundred (100) questionnaires were distributed amongst the primary caregivers of recovering drug and substance abusers. The major findings of the study pointed out that rehabilitation centres were unequivocally contributing to the goal of ameliorating substance abuse in Gauteng and, by extension, South Africa. Among some of the outstanding contributions of the rehabilitation centres was the provision of a non-judgmental and supportive therapeutic environment for clients to recover. It was also observed that rehabilitation centres were acting as character reformatories for substance abusers, and, thus, aiding their easy reintegration back into their families, societies and work places. The study also found out that the selected rehabilitation centres were providing ample admission periods and competent counselling services for their clients to navigate their way to recovery. The study unearthed new trends in the substance abuse landscape of Gauteng. Firstly, it was established that more educated people were falling into substance abuse usage. Secondly, the drugs which were rendering users more amenable to rehabilitation were noted to be highly potent. The high potency was noted to be responsible for extreme difficulties in withdrawal and rehabilitation. This was, therefore, noted to accentuate the imperativeness of the role and contributions of rehabilitation centres in helping drug users to achieve recovery in an environment that was supportive, nurturing and safe. It is, therefore, on the basis of these fundamental findings that this study concluded that the contributions of rehabilitation centres were not only important in the fight against drug and substance abuse, but were also a necessary precondition in this endeavour. Conversely, it was established that the contributions of the rehabilitation centres were being thwarted by exorbitant and extortionate treatment fees charged by the rehabilitation centres. More so, rehabilitation centres faced the dire challenge of poor visibility due to the poor marketing of services, as well as their location in affluent or remote areas which are mainly accessible only through private transport. This means that some people, especially the rural and the urban poor, were not equitably benefiting from the services of the rehabilitation centres. The study observed that women, girls and children in general were largely excluded from benefiting from the services of the rehabilitation centres. The research closed off by recommending to rehabilitation centres that they ought to address administrative gaps such as embracing and practising social, linguistic, dietary and gender sensitivity in their programmes to ensure that they remain relevant to their clients while also reflecting the diversity in South Africa. Recommendations were also made to the government to intervene and moderate the pricing of substance abuse treatment services, by making them reflect the country’s socioeconomic inequalities.
- Full Text:
- Date Issued: 2017
- Authors: Makuyana, Abigail
- Date: 2017
- Subjects: Rehabilitation centers -- South Africa -- Gauteng Substance abuse -- Rehabilitation Addicts -- Rehabilitation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10353/8876 , vital:33703
- Description: This study aimed at evaluating the contributions of two (2) selected rehabilitation centres to the goal of ameliorating the substance abuse problem in Gauteng. The study utilized a methodological triangulation approach for data collection, but with greater emphasis on qualitative methods. The study collected its qualitative data from four focus groups conducted with 32 participants and six key informants who were subjected to in-depth interviews. The quantitative aspect of the study made use of a mini-survey in which one hundred (100) questionnaires were distributed amongst the primary caregivers of recovering drug and substance abusers. The major findings of the study pointed out that rehabilitation centres were unequivocally contributing to the goal of ameliorating substance abuse in Gauteng and, by extension, South Africa. Among some of the outstanding contributions of the rehabilitation centres was the provision of a non-judgmental and supportive therapeutic environment for clients to recover. It was also observed that rehabilitation centres were acting as character reformatories for substance abusers, and, thus, aiding their easy reintegration back into their families, societies and work places. The study also found out that the selected rehabilitation centres were providing ample admission periods and competent counselling services for their clients to navigate their way to recovery. The study unearthed new trends in the substance abuse landscape of Gauteng. Firstly, it was established that more educated people were falling into substance abuse usage. Secondly, the drugs which were rendering users more amenable to rehabilitation were noted to be highly potent. The high potency was noted to be responsible for extreme difficulties in withdrawal and rehabilitation. This was, therefore, noted to accentuate the imperativeness of the role and contributions of rehabilitation centres in helping drug users to achieve recovery in an environment that was supportive, nurturing and safe. It is, therefore, on the basis of these fundamental findings that this study concluded that the contributions of rehabilitation centres were not only important in the fight against drug and substance abuse, but were also a necessary precondition in this endeavour. Conversely, it was established that the contributions of the rehabilitation centres were being thwarted by exorbitant and extortionate treatment fees charged by the rehabilitation centres. More so, rehabilitation centres faced the dire challenge of poor visibility due to the poor marketing of services, as well as their location in affluent or remote areas which are mainly accessible only through private transport. This means that some people, especially the rural and the urban poor, were not equitably benefiting from the services of the rehabilitation centres. The study observed that women, girls and children in general were largely excluded from benefiting from the services of the rehabilitation centres. The research closed off by recommending to rehabilitation centres that they ought to address administrative gaps such as embracing and practising social, linguistic, dietary and gender sensitivity in their programmes to ensure that they remain relevant to their clients while also reflecting the diversity in South Africa. Recommendations were also made to the government to intervene and moderate the pricing of substance abuse treatment services, by making them reflect the country’s socioeconomic inequalities.
- Full Text:
- Date Issued: 2017
Evaluation of flocculating potentials and charecterization of bioflocculants produced by three bacterial isolates from Algoa Bay, South Africa
- Authors: Okaiyeto, Kunle
- Date: 2016
- Subjects: Flocculation Water -- Purification -- Flocculation Water quality management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2633 , vital:27947
- Description: Flocculation has been widely adopted as one of the most effective methods to remove colloidal particles in water or wastewater treatment. Synthetic flocculants are conventionally used because of their high flocculating efficiency and cost-effectiveness. However, they have been reported to have hazardous properties and implicated in some serious health problems including senile dementia and neuro-toxicity, as well as being recalcitrant in the environment. Consequently, efforts are being geared away from the use of synthetic flocculants in water and wastewater treatment. Hence, the need for safe and eco-friendly flocculants has become imperative. Compared with synthetic flocculants, bioflocculants have special advantages such as safety, biodegradability and harmlessness to the environment and humans; attributes which make them potential alternatives in water treatment, downstream as well as fermentation processes. In the current study, the potentials of bacterial isolates recovered from Algoa Bay in the Eastern Cape Province of South Africa for bioflocculant production were investigated. The bacterial isolates were identified by polymerase chain reaction (PCR) as belonging to the Bacillus genus. The analysis of 16S ribosomal deoxyribonucleic acid (rDNA) nucleotide sequence of isolate M72 showed 99 percent similarity to Bacillus toyonensis strain BCT-7112 and was deposited in the GenBank as Bacillus toyonensis strain AEMREG6 with accession number KP406731. Likewise, the 16S rDNA nucleotide sequences of isolates M69 and M67 showed 98 percent sequence similarity to Bacillus licheniformis strain W7 and Bacillus algicola strain QD43 respectively; and M67 isolate was subsequently deposited in the GenBank as Bacillus sp. AEMREG7 with accession number KF933697.1. The results of the nutritional requirements and fermentation conditions revealed that optimum inoculum size for REG-6 production was 4 percent (v/v), while 5 percent (v/v) and 3 percent (v/v) were most favourable for MBF-W7 and MBF-UFH production respectively. Glucose was the best carbon source for the production of bioflocculants (REG-6 and MBF-UFH) by Bacillus toyonensis AEMREG6 and Bacillus sp. AEMREG7 respectively, while maltose supported optimum bioflocculant (MBF-W7) production by Bacillus specie. Inorganic nitrogen (NH4NO3) was the favoured nitrogen source for both REG-6 and MBF-W7 production, while mixed nitrogen sources [yeast extract + urea + (NH4)2SO4] supported the maximum production of MBF-UFH. The initial medium pH for REG-6 was 5, while MBF-W7 and MBF-UFH were both maximally produced at the initial pH of 6. After a 96 h cultivation period under optimal culture conditions, 3.2 g of purified REG-6 with a maximum flocculating activity of 77 percent was recovered from 1 L fermented broth of Bacillus toyonensis AEMREG6. Yields of 3.8 g and 1.6 g pure bioflocculants with the respective highest flocculating activities of 94.9 percent and 83.2 percent were also obtained from 1 L, 72 h-fermented broths of Bacillus licheniformis and Bacillus sp. AEMREG7 respectively. Furthermore, all the three bioflocculants (REG-6, MBF-W7 and MBF-UFH), displayed thermal stability within the temperature range of 50 to 100 oC, with strong flocculating activities of over 80 percent against kaolin suspension over a wide range of pH range (3–11) and relatively low dosage requirements of 0.1-03 mg/ml in the presence of divalent cations in the treatment of kaolin clay suspension and Thyme River waters. Chemical composition analyses of the bioflocculants showed them to be glycoproteins with a predominantly polysaccharide backbones as shown by the following carbohydrate/protein (w/w) ratios: 77.8 percent:11.5 percent (REG-6); 73.7 percent:6.2 percent (MBF-W7) and 76 percent:14 percent (MBF-UFH).
- Full Text:
- Date Issued: 2016
- Authors: Okaiyeto, Kunle
- Date: 2016
- Subjects: Flocculation Water -- Purification -- Flocculation Water quality management
- Language: English
- Type: Thesis , Doctoral , DPhil
- Identifier: http://hdl.handle.net/10353/2633 , vital:27947
- Description: Flocculation has been widely adopted as one of the most effective methods to remove colloidal particles in water or wastewater treatment. Synthetic flocculants are conventionally used because of their high flocculating efficiency and cost-effectiveness. However, they have been reported to have hazardous properties and implicated in some serious health problems including senile dementia and neuro-toxicity, as well as being recalcitrant in the environment. Consequently, efforts are being geared away from the use of synthetic flocculants in water and wastewater treatment. Hence, the need for safe and eco-friendly flocculants has become imperative. Compared with synthetic flocculants, bioflocculants have special advantages such as safety, biodegradability and harmlessness to the environment and humans; attributes which make them potential alternatives in water treatment, downstream as well as fermentation processes. In the current study, the potentials of bacterial isolates recovered from Algoa Bay in the Eastern Cape Province of South Africa for bioflocculant production were investigated. The bacterial isolates were identified by polymerase chain reaction (PCR) as belonging to the Bacillus genus. The analysis of 16S ribosomal deoxyribonucleic acid (rDNA) nucleotide sequence of isolate M72 showed 99 percent similarity to Bacillus toyonensis strain BCT-7112 and was deposited in the GenBank as Bacillus toyonensis strain AEMREG6 with accession number KP406731. Likewise, the 16S rDNA nucleotide sequences of isolates M69 and M67 showed 98 percent sequence similarity to Bacillus licheniformis strain W7 and Bacillus algicola strain QD43 respectively; and M67 isolate was subsequently deposited in the GenBank as Bacillus sp. AEMREG7 with accession number KF933697.1. The results of the nutritional requirements and fermentation conditions revealed that optimum inoculum size for REG-6 production was 4 percent (v/v), while 5 percent (v/v) and 3 percent (v/v) were most favourable for MBF-W7 and MBF-UFH production respectively. Glucose was the best carbon source for the production of bioflocculants (REG-6 and MBF-UFH) by Bacillus toyonensis AEMREG6 and Bacillus sp. AEMREG7 respectively, while maltose supported optimum bioflocculant (MBF-W7) production by Bacillus specie. Inorganic nitrogen (NH4NO3) was the favoured nitrogen source for both REG-6 and MBF-W7 production, while mixed nitrogen sources [yeast extract + urea + (NH4)2SO4] supported the maximum production of MBF-UFH. The initial medium pH for REG-6 was 5, while MBF-W7 and MBF-UFH were both maximally produced at the initial pH of 6. After a 96 h cultivation period under optimal culture conditions, 3.2 g of purified REG-6 with a maximum flocculating activity of 77 percent was recovered from 1 L fermented broth of Bacillus toyonensis AEMREG6. Yields of 3.8 g and 1.6 g pure bioflocculants with the respective highest flocculating activities of 94.9 percent and 83.2 percent were also obtained from 1 L, 72 h-fermented broths of Bacillus licheniformis and Bacillus sp. AEMREG7 respectively. Furthermore, all the three bioflocculants (REG-6, MBF-W7 and MBF-UFH), displayed thermal stability within the temperature range of 50 to 100 oC, with strong flocculating activities of over 80 percent against kaolin suspension over a wide range of pH range (3–11) and relatively low dosage requirements of 0.1-03 mg/ml in the presence of divalent cations in the treatment of kaolin clay suspension and Thyme River waters. Chemical composition analyses of the bioflocculants showed them to be glycoproteins with a predominantly polysaccharide backbones as shown by the following carbohydrate/protein (w/w) ratios: 77.8 percent:11.5 percent (REG-6); 73.7 percent:6.2 percent (MBF-W7) and 76 percent:14 percent (MBF-UFH).
- Full Text:
- Date Issued: 2016
Climate variability and climate change in water resources management of the Zambezi River basin
- Authors: Tirivarombo, Sithabile
- Date: 2013
- Subjects: Water resources development -- Zambezi River Watershed Climatic changes -- Zambezi River Watershed Water-supply -- Zambezi River Watershed Water-supply -- Political aspects -- Africa, Southern Water rights -- Africa, Southern Water security -- Africa, Southern Rain and rainfall -- Africa, Southern Rainfall probabilities -- Africa, Southern Food security -- Africa, Southern Drought forecasting -- Africa, Southern Watersheds -- Africa, Southern Water supply -- Measurement -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6024 , http://hdl.handle.net/10962/d1002955
- Description: Water is recognised as a key driver for social and economic development in the Zambezi basin. The basin is riparian to eight southern African countries and the transboundary nature of the basin’s water resources can be viewed as an agent of cooperation between the basin countries. It is possible, however, that the same water resource can lead to conflicts between water users. The southern African Water Vision for ‘equitable and sustainable utilisation of water for social, environmental justice and economic benefits for the present and future generations’ calls for an integrated and efficient management of water resources within the basin. Ensuring water and food security in the Zambezi basin is, however, faced with challenges due to high variability in climate and the available water resources. Water resources are under continuous threat from pollution, increased population growth, development and urbanisation as well as global climate change. These factors increase the demand for freshwater resources and have resulted in water being one of the major driving forces for development. The basin is also vulnerable due to lack of adequate financial resources and appropriate water resources infrastructure to enable viable, equitable and sustainable distribution of the water resources. This is in addition to the fact that the basin’s economic mainstay and social well-being are largely dependent on rainfed agriculture. There is also competition among the different water users and this has the potential to generate conflicts, which further hinder the development of water resources in the basin. This thesis has focused on the Zambezi River basin emphasising climate variability and climate change. It is now considered common knowledge that the global climate is changing and that many of the impacts will be felt through water resources. If these predictions are correct then the Zambezi basin is most likely to suffer under such impacts since its economic mainstay is largely determined by the availability of rainfall. It is the belief of this study that in order to ascertain the impacts of climate change, there should be a basis against which this change is evaluated. If we do not know the historical patterns of variability it may be difficult to predict changes in the future climate and in the hydrological resources and it will certainly be difficult to develop appropriate management strategies. Reliable quantitative estimates of water availability are a prerequisite for successful water resource plans. However, such initiatives have been hindered by paucity in data especially in a basin where gauging networks are inadequate and some of them have deteriorated. This is further compounded by shortages in resources, both human and financial, to ensure adequate monitoring. To address the data problems, this study largely relied on global data sets and the CRU TS2.1 rainfall grids were used for a large part of this study. The study starts by assessing the historical variability of rainfall and streamflow in the Zambezi basin and the results are used to inform the prediction of change in the future. Various methods of assessing historical trends were employed and regional drought indices were generated and evaluated against the historical rainfall trends. The study clearly demonstrates that the basin has a high degree of temporal and spatial variability in rainfall and streamflow at inter-annual and multi-decadal scales. The Standardised Precipitation Index, a rainfall based drought index, is used to assess historical drought events in the basin and it is shown that most of the droughts that have occurred were influenced by climatic and hydrological variability. It is concluded, through the evaluation of agricultural maize yields, that the basin’s food security is mostly constrained by the availability of rainfall. Comparing the viability of using a rainfall based index to a soil moisture based index as an agricultural drought indicator, this study concluded that a soil moisture based index is a better indicator since all of the water balance components are considered in the generation of the index. This index presents the actual amount of water available for the plant unlike purely rainfall based indices, that do not account for other components of the water budget that cause water losses. A number of challenges were, however, faced in assessing the variability and historical drought conditions, mainly due to the fact that most parts of the Zambezi basin are ungauged and available data are sparse, short and not continuous (with missing gaps). Hydrological modelling is frequently used to bridge the data gap and to facilitate the quantification of a basin’s hydrology for both gauged and ungauged catchments. The trend has been to use various methods of regionalisation to transfer information from gauged basins, or from basins with adequate physical basin data, to ungauged basins. All this is done to ensure that water resources are accounted for and that the future can be well planned. A number of approaches leading to the evaluation of the basin’s hydrological response to future climate change scenarios are taken. The Pitman rainfall-runoff model has enjoyed wide use as a water resources estimation tool in southern Africa. The model has been calibrated for the Zambezi basin but it should be acknowledged that any hydrological modelling process is characterised by many uncertainties arising from limitations in input data and inherent model structural uncertainty. The calibration process is thus carried out in a manner that embraces some of the uncertainties. Initial ranges of parameter values (maximum and minimum) that incorporate the possible parameter uncertainties are assigned in relation to physical basin properties. These parameter sets are used as input to the uncertainty version of the model to generate behavioural parameter space which is then further modified through manual calibration. The use of parameter ranges initially guided by the basin physical properties generates streamflows that adequately represent the historically observed amounts. This study concludes that the uncertainty framework and the Pitman model perform quite well in the Zambezi basin. Based on assumptions of an intensifying hydrological cycle, climate changes are frequently expected to result in negative impacts on water resources. However, it is important that basin scale assessments are undertaken so that appropriate future management strategies can be developed. To assess the likely changes in the Zambezi basin, the calibrated Pitman model was forced with downscaled and bias corrected GCM data. Three GCMs were used for this study, namely; ECHAM, GFDL and IPSL. The general observation made in this study is that the near future (2046-2065) conditions of the Zambezi basin are expected to remain within the ranges of historically observed variability. The differences between the predictions for the three GCMs are an indication of the uncertainties in the future and it has not been possible to make any firm conclusions about directions of change. It is therefore recommended that future water resources management strategies account for historical patterns of variability, but also for increased uncertainty. Any management strategies that are able to satisfactorily deal with the large variability that is evident from the historical data should be robust enough to account for the near future patterns of water availability predicted by this study. However, the uncertainties in these predictions suggest that improved monitoring systems are required to provide additional data against which future model outputs can be assessed.
- Full Text:
- Date Issued: 2013
- Authors: Tirivarombo, Sithabile
- Date: 2013
- Subjects: Water resources development -- Zambezi River Watershed Climatic changes -- Zambezi River Watershed Water-supply -- Zambezi River Watershed Water-supply -- Political aspects -- Africa, Southern Water rights -- Africa, Southern Water security -- Africa, Southern Rain and rainfall -- Africa, Southern Rainfall probabilities -- Africa, Southern Food security -- Africa, Southern Drought forecasting -- Africa, Southern Watersheds -- Africa, Southern Water supply -- Measurement -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:6024 , http://hdl.handle.net/10962/d1002955
- Description: Water is recognised as a key driver for social and economic development in the Zambezi basin. The basin is riparian to eight southern African countries and the transboundary nature of the basin’s water resources can be viewed as an agent of cooperation between the basin countries. It is possible, however, that the same water resource can lead to conflicts between water users. The southern African Water Vision for ‘equitable and sustainable utilisation of water for social, environmental justice and economic benefits for the present and future generations’ calls for an integrated and efficient management of water resources within the basin. Ensuring water and food security in the Zambezi basin is, however, faced with challenges due to high variability in climate and the available water resources. Water resources are under continuous threat from pollution, increased population growth, development and urbanisation as well as global climate change. These factors increase the demand for freshwater resources and have resulted in water being one of the major driving forces for development. The basin is also vulnerable due to lack of adequate financial resources and appropriate water resources infrastructure to enable viable, equitable and sustainable distribution of the water resources. This is in addition to the fact that the basin’s economic mainstay and social well-being are largely dependent on rainfed agriculture. There is also competition among the different water users and this has the potential to generate conflicts, which further hinder the development of water resources in the basin. This thesis has focused on the Zambezi River basin emphasising climate variability and climate change. It is now considered common knowledge that the global climate is changing and that many of the impacts will be felt through water resources. If these predictions are correct then the Zambezi basin is most likely to suffer under such impacts since its economic mainstay is largely determined by the availability of rainfall. It is the belief of this study that in order to ascertain the impacts of climate change, there should be a basis against which this change is evaluated. If we do not know the historical patterns of variability it may be difficult to predict changes in the future climate and in the hydrological resources and it will certainly be difficult to develop appropriate management strategies. Reliable quantitative estimates of water availability are a prerequisite for successful water resource plans. However, such initiatives have been hindered by paucity in data especially in a basin where gauging networks are inadequate and some of them have deteriorated. This is further compounded by shortages in resources, both human and financial, to ensure adequate monitoring. To address the data problems, this study largely relied on global data sets and the CRU TS2.1 rainfall grids were used for a large part of this study. The study starts by assessing the historical variability of rainfall and streamflow in the Zambezi basin and the results are used to inform the prediction of change in the future. Various methods of assessing historical trends were employed and regional drought indices were generated and evaluated against the historical rainfall trends. The study clearly demonstrates that the basin has a high degree of temporal and spatial variability in rainfall and streamflow at inter-annual and multi-decadal scales. The Standardised Precipitation Index, a rainfall based drought index, is used to assess historical drought events in the basin and it is shown that most of the droughts that have occurred were influenced by climatic and hydrological variability. It is concluded, through the evaluation of agricultural maize yields, that the basin’s food security is mostly constrained by the availability of rainfall. Comparing the viability of using a rainfall based index to a soil moisture based index as an agricultural drought indicator, this study concluded that a soil moisture based index is a better indicator since all of the water balance components are considered in the generation of the index. This index presents the actual amount of water available for the plant unlike purely rainfall based indices, that do not account for other components of the water budget that cause water losses. A number of challenges were, however, faced in assessing the variability and historical drought conditions, mainly due to the fact that most parts of the Zambezi basin are ungauged and available data are sparse, short and not continuous (with missing gaps). Hydrological modelling is frequently used to bridge the data gap and to facilitate the quantification of a basin’s hydrology for both gauged and ungauged catchments. The trend has been to use various methods of regionalisation to transfer information from gauged basins, or from basins with adequate physical basin data, to ungauged basins. All this is done to ensure that water resources are accounted for and that the future can be well planned. A number of approaches leading to the evaluation of the basin’s hydrological response to future climate change scenarios are taken. The Pitman rainfall-runoff model has enjoyed wide use as a water resources estimation tool in southern Africa. The model has been calibrated for the Zambezi basin but it should be acknowledged that any hydrological modelling process is characterised by many uncertainties arising from limitations in input data and inherent model structural uncertainty. The calibration process is thus carried out in a manner that embraces some of the uncertainties. Initial ranges of parameter values (maximum and minimum) that incorporate the possible parameter uncertainties are assigned in relation to physical basin properties. These parameter sets are used as input to the uncertainty version of the model to generate behavioural parameter space which is then further modified through manual calibration. The use of parameter ranges initially guided by the basin physical properties generates streamflows that adequately represent the historically observed amounts. This study concludes that the uncertainty framework and the Pitman model perform quite well in the Zambezi basin. Based on assumptions of an intensifying hydrological cycle, climate changes are frequently expected to result in negative impacts on water resources. However, it is important that basin scale assessments are undertaken so that appropriate future management strategies can be developed. To assess the likely changes in the Zambezi basin, the calibrated Pitman model was forced with downscaled and bias corrected GCM data. Three GCMs were used for this study, namely; ECHAM, GFDL and IPSL. The general observation made in this study is that the near future (2046-2065) conditions of the Zambezi basin are expected to remain within the ranges of historically observed variability. The differences between the predictions for the three GCMs are an indication of the uncertainties in the future and it has not been possible to make any firm conclusions about directions of change. It is therefore recommended that future water resources management strategies account for historical patterns of variability, but also for increased uncertainty. Any management strategies that are able to satisfactorily deal with the large variability that is evident from the historical data should be robust enough to account for the near future patterns of water availability predicted by this study. However, the uncertainties in these predictions suggest that improved monitoring systems are required to provide additional data against which future model outputs can be assessed.
- Full Text:
- Date Issued: 2013
An investigation into the antidiabetic and catalytic properties of oxovanadium(IV) complexes
- Authors: Walmsley, Ryan Steven
- Date: 2012
- Subjects: Hypoglycemic agents Ligands (Biochemistry) Complex compounds Potentiometry Proton transfer reactions Stability Imidazoles Vanadium catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4320 , http://hdl.handle.net/10962/d1004978
- Description: In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.
- Full Text:
- Date Issued: 2012
- Authors: Walmsley, Ryan Steven
- Date: 2012
- Subjects: Hypoglycemic agents Ligands (Biochemistry) Complex compounds Potentiometry Proton transfer reactions Stability Imidazoles Vanadium catalysts
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4320 , http://hdl.handle.net/10962/d1004978
- Description: In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.
- Full Text:
- Date Issued: 2012
Comparative study of the feeding damage caused by the South African biotypes of the Russian wheat aphid (Diuraphis noxia Kurdjumov) on resistant and non-resistant lines of barley (Hordeum vulgare L.)
- Authors: Jimoh, Mahboob Adekilekun
- Date: 2011
- Subjects: Aphids Russian wheat aphid -- Research -- South Africa Barley -- Diseases and pests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4201 , http://hdl.handle.net/10962/d1003770
- Description: Cereal crop productivity is hampered when these plants are infested by phloem feeding aphids. A great deal of research has been carried out with the direct aim of a clearer understanding of the mechanism involved in the interaction between aphids and their host plants. Research has directly or indirectly been geared towards enhanced plant productivity and achieving sustainable agriculture. Barley (Hordeum vulgare L.) is an important small grain crop in South Africa, whose crop performance is negatively affected by fluctuations in weather patterns as well as by agricultural pests. One of the insect pests infesting barley is the Russian wheat aphid, Diuraphis noxia Kurdjumov (RWA), of which the two South African biotypes, codenamed RWASA1 and RWASA2, were studied in this thesis. During dry spells, RWA infestation becomes a more serious threat to barley productivity. Resistant plants have been used to combat RWA infestation of small grains. In South Africa, 27 RWA-resistant wheat cultivars are currently used in commercial cultivation, but no resistant barley lines have, unfortunately, been developed, in spite of this grain’s significant economic importance. This informed the study in this thesis, and this interest particularly focussed on three RWA-resistant lines developed by the USDA, testing their performance against South African RWA biotypes, for possible adaptation to South Africa. The aim was thus to examine the plant-aphid interactions, aphid breeding rates, plant damage and sustainability, evidence of resistance or tolerance and finally potential performance under elevated CO2 (a very real climate change threat). Two major avenues of research were undertaken. The first aspect involved examination of structural and functional damage caused by RWASA1 and RWASA2 on the three resistant and a non-resistant line. Aphid population growth and damage symptoms (chlorosis and leaf roll) of infestation by these aphid biotypes were evaluated. This was followed by a structural and functional approach in which the effects of feeding on the transport systems (phloem and xylem) of barley were investigated. Fluorescence microscopy techniques (using aniline blue fluorochrome, a specific stain for callose and 5,6-CFDA, a phloem-mobile probe) were applied to investigate the feeding-related damage caused by the aphids, through an examination of wound callose formation and related to this, the resultant reduction in phloem transport capacity. Transmission electron microscopy (TEM) techniques provided evidence of the extent of the feeding-related cell damage. The second aspect involved a study of the effect of changing CO2 concentrations ([CO2]) on the resistant and susceptible barley cultivars to feeding by the two RWA biotypes. Leaves of plants grown at ambient and two elevated levels of [CO2] were analysed to investigate the effect of changing [CO2] on biomass, leaf nitrogen content and C:N ratio of control (uninfested) and infested plants. The population growth studies showed that the populations of the two RWA biotypes as well as bird cherry-oat aphid (BCA, Rhopalosiphum padi L.) increased substantially on the four barley lines. BCA was included here, as it had been the subject of several previous studies. RWASA2 bred faster than RWASA1 on all lines. The breeding rates of the two RWA biotypes were both suppressed and at near-equivalent levels on the three resistant lines, compared to the non-resistant PUMA. This suggests that the resistant lines possessed an antibiosis resistance mechanism against the feeding aphids. Feeding by the aphids manifested in morphological damage symptoms of chlorosis and leaf roll. The two biotypes inflicted severe chlorosis and leaf roll on the non-resistant PUMA. In the resistant plants, leaf rolling was more severe because of RWASA2 feeding compared to RWASA1 feeding. In contrast, chlorosis symptoms were more severe during RWASA1 feeding than was the case with RWASA2 feeding. Investigation of the effect of aphid feeding on the plants showed that callose was deposited within 24h and that this increased with longer feeding exposure. Wound callose distribution is more extensive in the non-resistant PUMA than in the resistant plants. RWASA2 feeding on the resistant lines caused deposition of more callose than was evident with RWASA1 feeding. During long-term feeding, it was evident that variation in the intensity and amount of wound callose was visible in the longitudinal and transverse veins of the resistant plants. Of the three STARS plants, STARS-9301B had the least callose. Interestingly, wound callose occurred in both resistant and non-resistant plants, in sharp contrast to what has been reported on resistant wheat cultivars that were developed in South Africa. The relative reduction in the wound callose deposited in the resistant line, when compared to the non-resistant lines, suggests the presence of a mechanism in the resistant lines, which may prevent excessive callose formation. Alternatively, the mechanism may stimulate callose breakdown. RWASA2 feeding on the resistant lines deposited more wound callose than RWASA1 feeding. This evidence supports the hypothesis that RWASA2 is a resistance breaking and more aggressive feeder than RWASA1 is; and further underscores the urgent need for development of RWA-resistant barley cultivars. The ultrastructural investigation of the feeding damage showed that the two biotypes caused extensive vascular damage in non-resistant plants. There was extensive and severe cell disruption and often obliteration of cell structure of the vascular parenchyma, xylem and phloem elements. In sharp contrast, among the resistant plants, feeding-related cell damage appeared to be substantially reduced compared to the non-resistant PUMA. Low frequency of damaged cells indicated that majority of the cell components of the vascular tissues were intact and presumed functional. There was evidence of salivary material lining the secondary walls of the vascular tissue, which resulted in severe damage. Within xylem vessels, saliva material impregnated half-bordered pit pairs between the vessels and adjacent xylem parenchyma. This is believed to prevent solute exchange through this interface, thereby inducing leaf stress and vi leaf roll. A notable finding is that RWASA2 effectively induced more cell damage to vascular tissues in the resistant lines than did RWASA1. In general the experimental evidence (see Chapter 5) suggests that the resistant lines are possibly more tolerant (or able to cope with) to RWA feeding. Evidence for this is the reduction of wound callose and at the TEM level, a comparatively less obvious cell damage in the resistant lines, which suggests that they possess antibiosis and tolerance capacity. The apparent reduction of feeding-related cell damage from the TEM study confirmed the disruptive action of the feeding aphids in experiments using the phloem-mobile probe, 5,6-CF. Results showed that feeding by RWASA1 and RWASA2 reducedthe transport functionality of the phloem in all cases, but that RWASA2 feeding caused a more obvious reduction in the rate and distance that 5,6-carboxyfluorescein was transported, than did RWASA1. Investigation of the effect of changing [CO2] on the barley cultivars showed that in the absence of aphids and under elevated CO2 conditions, the plants grew more vigorously. In this series of experiments, the infested plants suffered significant reduction in biomass under ambient (as was expected) and under the two elevated CO2 regimes. Biomass loss was greater at elevated CO2 than under ambient [CO2]. The infested nonresistant PUMA plants showed a more significant biomass loss than did the resistant cultivars. Clearly, the benefits derived from elevated CO2 enrichment was thus redirected to the now-advantaged aphids. Uninfested vii plants showed an increase in leaf nitrogen under the experimental conditions. However, feeding aphids depleted leaf nitrogen content and this was more apparent on plants exposed to RWASA2 than was the case with RWASA1. The end result of this was that C:N ratio of infested plants were higher than uninfested plants. Clearly, the faster breeding rates of the aphids at elevated CO2 caused depletion of N and a resultant deficiency exacerbated chlorosis as well as leaf rolling due to the higher aphid population density under elevated CO2 than at ambient. By 28 days after infestation (DAI), majority of the plants exposed to enriched CO2 treatments had died. A major finding here was thus that although this study demonstrated that elevated CO2 resulted in an increase in biomass, this was detrimentally offset in plants infested by the aphids, with a decline in biomass and loss of functionality leading to plant death at 28DAI. The overriding conclusion from this study is a clear signal that the twin effects of CO2 enrichment (a feature of current climate change) and aphid infestations may precipitate potential grain shortages. A disastrous food security threat looms.
- Full Text:
- Date Issued: 2011
- Authors: Jimoh, Mahboob Adekilekun
- Date: 2011
- Subjects: Aphids Russian wheat aphid -- Research -- South Africa Barley -- Diseases and pests -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4201 , http://hdl.handle.net/10962/d1003770
- Description: Cereal crop productivity is hampered when these plants are infested by phloem feeding aphids. A great deal of research has been carried out with the direct aim of a clearer understanding of the mechanism involved in the interaction between aphids and their host plants. Research has directly or indirectly been geared towards enhanced plant productivity and achieving sustainable agriculture. Barley (Hordeum vulgare L.) is an important small grain crop in South Africa, whose crop performance is negatively affected by fluctuations in weather patterns as well as by agricultural pests. One of the insect pests infesting barley is the Russian wheat aphid, Diuraphis noxia Kurdjumov (RWA), of which the two South African biotypes, codenamed RWASA1 and RWASA2, were studied in this thesis. During dry spells, RWA infestation becomes a more serious threat to barley productivity. Resistant plants have been used to combat RWA infestation of small grains. In South Africa, 27 RWA-resistant wheat cultivars are currently used in commercial cultivation, but no resistant barley lines have, unfortunately, been developed, in spite of this grain’s significant economic importance. This informed the study in this thesis, and this interest particularly focussed on three RWA-resistant lines developed by the USDA, testing their performance against South African RWA biotypes, for possible adaptation to South Africa. The aim was thus to examine the plant-aphid interactions, aphid breeding rates, plant damage and sustainability, evidence of resistance or tolerance and finally potential performance under elevated CO2 (a very real climate change threat). Two major avenues of research were undertaken. The first aspect involved examination of structural and functional damage caused by RWASA1 and RWASA2 on the three resistant and a non-resistant line. Aphid population growth and damage symptoms (chlorosis and leaf roll) of infestation by these aphid biotypes were evaluated. This was followed by a structural and functional approach in which the effects of feeding on the transport systems (phloem and xylem) of barley were investigated. Fluorescence microscopy techniques (using aniline blue fluorochrome, a specific stain for callose and 5,6-CFDA, a phloem-mobile probe) were applied to investigate the feeding-related damage caused by the aphids, through an examination of wound callose formation and related to this, the resultant reduction in phloem transport capacity. Transmission electron microscopy (TEM) techniques provided evidence of the extent of the feeding-related cell damage. The second aspect involved a study of the effect of changing CO2 concentrations ([CO2]) on the resistant and susceptible barley cultivars to feeding by the two RWA biotypes. Leaves of plants grown at ambient and two elevated levels of [CO2] were analysed to investigate the effect of changing [CO2] on biomass, leaf nitrogen content and C:N ratio of control (uninfested) and infested plants. The population growth studies showed that the populations of the two RWA biotypes as well as bird cherry-oat aphid (BCA, Rhopalosiphum padi L.) increased substantially on the four barley lines. BCA was included here, as it had been the subject of several previous studies. RWASA2 bred faster than RWASA1 on all lines. The breeding rates of the two RWA biotypes were both suppressed and at near-equivalent levels on the three resistant lines, compared to the non-resistant PUMA. This suggests that the resistant lines possessed an antibiosis resistance mechanism against the feeding aphids. Feeding by the aphids manifested in morphological damage symptoms of chlorosis and leaf roll. The two biotypes inflicted severe chlorosis and leaf roll on the non-resistant PUMA. In the resistant plants, leaf rolling was more severe because of RWASA2 feeding compared to RWASA1 feeding. In contrast, chlorosis symptoms were more severe during RWASA1 feeding than was the case with RWASA2 feeding. Investigation of the effect of aphid feeding on the plants showed that callose was deposited within 24h and that this increased with longer feeding exposure. Wound callose distribution is more extensive in the non-resistant PUMA than in the resistant plants. RWASA2 feeding on the resistant lines caused deposition of more callose than was evident with RWASA1 feeding. During long-term feeding, it was evident that variation in the intensity and amount of wound callose was visible in the longitudinal and transverse veins of the resistant plants. Of the three STARS plants, STARS-9301B had the least callose. Interestingly, wound callose occurred in both resistant and non-resistant plants, in sharp contrast to what has been reported on resistant wheat cultivars that were developed in South Africa. The relative reduction in the wound callose deposited in the resistant line, when compared to the non-resistant lines, suggests the presence of a mechanism in the resistant lines, which may prevent excessive callose formation. Alternatively, the mechanism may stimulate callose breakdown. RWASA2 feeding on the resistant lines deposited more wound callose than RWASA1 feeding. This evidence supports the hypothesis that RWASA2 is a resistance breaking and more aggressive feeder than RWASA1 is; and further underscores the urgent need for development of RWA-resistant barley cultivars. The ultrastructural investigation of the feeding damage showed that the two biotypes caused extensive vascular damage in non-resistant plants. There was extensive and severe cell disruption and often obliteration of cell structure of the vascular parenchyma, xylem and phloem elements. In sharp contrast, among the resistant plants, feeding-related cell damage appeared to be substantially reduced compared to the non-resistant PUMA. Low frequency of damaged cells indicated that majority of the cell components of the vascular tissues were intact and presumed functional. There was evidence of salivary material lining the secondary walls of the vascular tissue, which resulted in severe damage. Within xylem vessels, saliva material impregnated half-bordered pit pairs between the vessels and adjacent xylem parenchyma. This is believed to prevent solute exchange through this interface, thereby inducing leaf stress and vi leaf roll. A notable finding is that RWASA2 effectively induced more cell damage to vascular tissues in the resistant lines than did RWASA1. In general the experimental evidence (see Chapter 5) suggests that the resistant lines are possibly more tolerant (or able to cope with) to RWA feeding. Evidence for this is the reduction of wound callose and at the TEM level, a comparatively less obvious cell damage in the resistant lines, which suggests that they possess antibiosis and tolerance capacity. The apparent reduction of feeding-related cell damage from the TEM study confirmed the disruptive action of the feeding aphids in experiments using the phloem-mobile probe, 5,6-CF. Results showed that feeding by RWASA1 and RWASA2 reducedthe transport functionality of the phloem in all cases, but that RWASA2 feeding caused a more obvious reduction in the rate and distance that 5,6-carboxyfluorescein was transported, than did RWASA1. Investigation of the effect of changing [CO2] on the barley cultivars showed that in the absence of aphids and under elevated CO2 conditions, the plants grew more vigorously. In this series of experiments, the infested plants suffered significant reduction in biomass under ambient (as was expected) and under the two elevated CO2 regimes. Biomass loss was greater at elevated CO2 than under ambient [CO2]. The infested nonresistant PUMA plants showed a more significant biomass loss than did the resistant cultivars. Clearly, the benefits derived from elevated CO2 enrichment was thus redirected to the now-advantaged aphids. Uninfested vii plants showed an increase in leaf nitrogen under the experimental conditions. However, feeding aphids depleted leaf nitrogen content and this was more apparent on plants exposed to RWASA2 than was the case with RWASA1. The end result of this was that C:N ratio of infested plants were higher than uninfested plants. Clearly, the faster breeding rates of the aphids at elevated CO2 caused depletion of N and a resultant deficiency exacerbated chlorosis as well as leaf rolling due to the higher aphid population density under elevated CO2 than at ambient. By 28 days after infestation (DAI), majority of the plants exposed to enriched CO2 treatments had died. A major finding here was thus that although this study demonstrated that elevated CO2 resulted in an increase in biomass, this was detrimentally offset in plants infested by the aphids, with a decline in biomass and loss of functionality leading to plant death at 28DAI. The overriding conclusion from this study is a clear signal that the twin effects of CO2 enrichment (a feature of current climate change) and aphid infestations may precipitate potential grain shortages. A disastrous food security threat looms.
- Full Text:
- Date Issued: 2011
Petrographic and geochemical constraints on the origin and post-depositional history of the Hotazel iron-manganese deposits, Kalahari Manganese Field, South Africa
- Authors: Tsikos, Harilaos
- Date: 2000
- Subjects: Manganese ores -- South Africa Manganese ores -- Geology -- South Africa Iron ores -- Geology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4987 , http://hdl.handle.net/10962/d1005599
- Description: The giant Palaeoproterozoic manganese deposits of the Kalahari manganese field (KMF), Northern Cape Province, South Mrica, have been a world renowned resource of manganese ore for many decades. In recent years, the mineralogical composition, geochemistry and genesis of these deposits have been the objects of many geological investigations, yet their origin remains contentious up to the present day. A characteristic feature of the Kalahari deposits is the intimate association of manganese ore and iron-formation of the Superior-type, in the form of three discrete sedimentary cycles constituting the Hotazel Formation. This striking lithological association is an almost unique feature on a global scale. From that point of view, the present study is effectively the first attempt to shed light on the origin and post-depositional history of the Hotazel succession, using as prime focus the petrographic and geochemical characteristics ofthe host iron-formation. Petrographic and whole-rock geochemical information of iron-formation from the southern parts of the KMF, suggests that the Hotazel iron-formation is almost identical to other iron-formations of the world of similar age and petrological character. The rock exhibits essentially no high-grade metamorphic or low-temperature alteration effects. Mineralogically, it contains abundant chert, magnetite, subordinate amounts of silicate minerals (greenalite, minnesotaite, stilpnomelane) and appreciable concentrations of carbonate constituents in the form of coexisting calcite and ankerite. Such mineralogical composition is indicative of processes occurring in a diagenetic" to burial (up to very low-greenschist facies) metamorphic environment. Bulk-rock geochemical data point towards a simple composition with Si02, total Fe-oxide and CaO being the chief major oxide components. Whole-rock rare-earth element data suggest that the iron-formation precipitated from a water column with chemical signatures comparable to modern, shallow oceanic seawater. The virtual absence of positive Eu anomalies is a feature that compares well with similar data from Neoproterozoic, glaciogenic iron-formations of the Rapitan type, and suggests but only a dilute hydrothermal signal, poten!ially derived from distal submarine volcanic activity. Carbon and oxygen isotope data from iron-formation and Mn-bearing carbonates as well as overlying ferriferous limestone of the Mooidraai Formation, compare well with the literature. The former exhibit variable depletion relative to seawater in terms of both BC and 180, while the latter have signatures comparable to normal marine bicarbonate. Isotopic variations appear to be related to fluctuations in the amount of co-precipitated marine carbonate, in conjunction with processes of coupled organic matter oxidation - FelMn reduction in the diagenetic environment. Oxygen isotope data from quartz-magnetite-calcite triplets suggest that crystallisation took place under open-system conditions, with magnetite being the most susceptible phase in terms of fluid-rock isotopic exchange. Data also suggest that the calcite-magnetite pair may constitute a more reliable geothermometer than the quartz-magnetite one, mainly due to the interlinked diagenetic histories between calcite and magnetite. Iron-formation from the northern parts of the KMF can by categorised into three main classes, namely pristine, altered and oxidised. Pristine iron-formation is identical to the one seen in the southernmost parts of the field. Altered iron-formation corresponds to a carbonate-free derivative of intense oxidation and leaching processes at the expense ofpristine iron-formation, and contains almost exclusively binary quartz-hematite mixtures. The rock appears to have lost essentially its entire pre-existing carbonate-related components (i.e., Ca, Mg, Sr, most Mn and Ba) and displays residual enrichments in elements such as Cr, Th, V, Ni and Pb, which would have behaved as immobile constituents during low-temperature alteration. The low temperature origin of altered iron-formation is supported by oxygen isotope data from quartz-hematite pairs which indicate that isotopically light hematite would have derived from oxidation of magneftte and other ferroussilicate compounds in the presence of a low-temperature meteoric fluid, while quartz would have remained isotopically unchanged. Occasional occurrences of acmite-hematite assemblages suggest localised metasomatic processes related to the action ofNaCI-rich fluids at the expense of altered iron-formation. The conditions of acmite genesis are very poorly constrained due to the very broad stability limits of the mineral in environments ranging from magmatic to surface-related. Oxidised iron-formation constitutes a distinct rock-type and shares common attributes with both the pristine and the altered iron-formation. The rock contains hematite as an important constituent while the amount of magnetite is substantially reduced. With regard to carbonate nlinerals, calcite contents are clearly very low or absent, having being replaced in most instances by a single, Mgenriched, dolomite/ankerite:type species. Oxidised iron-formation contains somewhat higher amounts of iron and reduced amounts of Sr and Ba relative to pristine iron-formation, whereas enrichments in elements such as Ni, Th, Pb, Cr, and V are seen, similar to altered iron-formation. Oxidised iron-formation appears to have originated from processes of dissolution-mobilisationreprecipitation of solutes derived primarily from leaching that produced altered iron-formation. It is proposed that the Hotazel iron-formation and associated manganese deposits were formed as a result of episodic sea-level fluctuations in a stratified depositional environment that gradually evolved into a shallow carbonate platform. A critical parameter in the development of manganese sediment may include regional climatic patterns related to a glacial event (Makganyene diamictite) prior to deposition of the Hotazel strata. This suggestion draws parallels with processes that are believed to have led to the formation of worldwide iron-formations and associated manganese deposits subsequent to Neoproterozoic episodes of glaciation. Submarine volcanism related to the underlying Ongeluk lavas appears to have had very little (if any) metallogenic significance, while evidence for a sudden rise in the oxygen contents of the atmosphere and ambient waters is lacking. With regard to later alteration processes, combination of geological and geochemical data point towards the potential influence of surface weathering prior to deposition of rocks of the unconformably overlying Olifantshoek Supergroup, possibly coupled with fault- and/or thrustcontrolled fluid-flow and leaching of the Hotazel succession during post-Olifantshoek times.
- Full Text:
- Date Issued: 2000
- Authors: Tsikos, Harilaos
- Date: 2000
- Subjects: Manganese ores -- South Africa Manganese ores -- Geology -- South Africa Iron ores -- Geology -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4987 , http://hdl.handle.net/10962/d1005599
- Description: The giant Palaeoproterozoic manganese deposits of the Kalahari manganese field (KMF), Northern Cape Province, South Mrica, have been a world renowned resource of manganese ore for many decades. In recent years, the mineralogical composition, geochemistry and genesis of these deposits have been the objects of many geological investigations, yet their origin remains contentious up to the present day. A characteristic feature of the Kalahari deposits is the intimate association of manganese ore and iron-formation of the Superior-type, in the form of three discrete sedimentary cycles constituting the Hotazel Formation. This striking lithological association is an almost unique feature on a global scale. From that point of view, the present study is effectively the first attempt to shed light on the origin and post-depositional history of the Hotazel succession, using as prime focus the petrographic and geochemical characteristics ofthe host iron-formation. Petrographic and whole-rock geochemical information of iron-formation from the southern parts of the KMF, suggests that the Hotazel iron-formation is almost identical to other iron-formations of the world of similar age and petrological character. The rock exhibits essentially no high-grade metamorphic or low-temperature alteration effects. Mineralogically, it contains abundant chert, magnetite, subordinate amounts of silicate minerals (greenalite, minnesotaite, stilpnomelane) and appreciable concentrations of carbonate constituents in the form of coexisting calcite and ankerite. Such mineralogical composition is indicative of processes occurring in a diagenetic" to burial (up to very low-greenschist facies) metamorphic environment. Bulk-rock geochemical data point towards a simple composition with Si02, total Fe-oxide and CaO being the chief major oxide components. Whole-rock rare-earth element data suggest that the iron-formation precipitated from a water column with chemical signatures comparable to modern, shallow oceanic seawater. The virtual absence of positive Eu anomalies is a feature that compares well with similar data from Neoproterozoic, glaciogenic iron-formations of the Rapitan type, and suggests but only a dilute hydrothermal signal, poten!ially derived from distal submarine volcanic activity. Carbon and oxygen isotope data from iron-formation and Mn-bearing carbonates as well as overlying ferriferous limestone of the Mooidraai Formation, compare well with the literature. The former exhibit variable depletion relative to seawater in terms of both BC and 180, while the latter have signatures comparable to normal marine bicarbonate. Isotopic variations appear to be related to fluctuations in the amount of co-precipitated marine carbonate, in conjunction with processes of coupled organic matter oxidation - FelMn reduction in the diagenetic environment. Oxygen isotope data from quartz-magnetite-calcite triplets suggest that crystallisation took place under open-system conditions, with magnetite being the most susceptible phase in terms of fluid-rock isotopic exchange. Data also suggest that the calcite-magnetite pair may constitute a more reliable geothermometer than the quartz-magnetite one, mainly due to the interlinked diagenetic histories between calcite and magnetite. Iron-formation from the northern parts of the KMF can by categorised into three main classes, namely pristine, altered and oxidised. Pristine iron-formation is identical to the one seen in the southernmost parts of the field. Altered iron-formation corresponds to a carbonate-free derivative of intense oxidation and leaching processes at the expense ofpristine iron-formation, and contains almost exclusively binary quartz-hematite mixtures. The rock appears to have lost essentially its entire pre-existing carbonate-related components (i.e., Ca, Mg, Sr, most Mn and Ba) and displays residual enrichments in elements such as Cr, Th, V, Ni and Pb, which would have behaved as immobile constituents during low-temperature alteration. The low temperature origin of altered iron-formation is supported by oxygen isotope data from quartz-hematite pairs which indicate that isotopically light hematite would have derived from oxidation of magneftte and other ferroussilicate compounds in the presence of a low-temperature meteoric fluid, while quartz would have remained isotopically unchanged. Occasional occurrences of acmite-hematite assemblages suggest localised metasomatic processes related to the action ofNaCI-rich fluids at the expense of altered iron-formation. The conditions of acmite genesis are very poorly constrained due to the very broad stability limits of the mineral in environments ranging from magmatic to surface-related. Oxidised iron-formation constitutes a distinct rock-type and shares common attributes with both the pristine and the altered iron-formation. The rock contains hematite as an important constituent while the amount of magnetite is substantially reduced. With regard to carbonate nlinerals, calcite contents are clearly very low or absent, having being replaced in most instances by a single, Mgenriched, dolomite/ankerite:type species. Oxidised iron-formation contains somewhat higher amounts of iron and reduced amounts of Sr and Ba relative to pristine iron-formation, whereas enrichments in elements such as Ni, Th, Pb, Cr, and V are seen, similar to altered iron-formation. Oxidised iron-formation appears to have originated from processes of dissolution-mobilisationreprecipitation of solutes derived primarily from leaching that produced altered iron-formation. It is proposed that the Hotazel iron-formation and associated manganese deposits were formed as a result of episodic sea-level fluctuations in a stratified depositional environment that gradually evolved into a shallow carbonate platform. A critical parameter in the development of manganese sediment may include regional climatic patterns related to a glacial event (Makganyene diamictite) prior to deposition of the Hotazel strata. This suggestion draws parallels with processes that are believed to have led to the formation of worldwide iron-formations and associated manganese deposits subsequent to Neoproterozoic episodes of glaciation. Submarine volcanism related to the underlying Ongeluk lavas appears to have had very little (if any) metallogenic significance, while evidence for a sudden rise in the oxygen contents of the atmosphere and ambient waters is lacking. With regard to later alteration processes, combination of geological and geochemical data point towards the potential influence of surface weathering prior to deposition of rocks of the unconformably overlying Olifantshoek Supergroup, possibly coupled with fault- and/or thrustcontrolled fluid-flow and leaching of the Hotazel succession during post-Olifantshoek times.
- Full Text:
- Date Issued: 2000
Alternative mythical structures in the fiction of Patrick White
- Authors: Bosman, Brenda Evadne
- Date: 1990
- Subjects: White, Patrick, 1912-1990 , White, Patrick, 1912-1990 -- Criticism and interpretation , Myth in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2170 , http://hdl.handle.net/10962/d1001821
- Description: The texts in this study interrogate the dominant myths which have affected the constructs of identity and history in the white Australian socio-historical context. These myths are exposed by White as ideologically determined and as operating by processes of exclusion, repression and marginalisation. White challenges the autonomy of both European and Australian cultures, reveals the ideological complicity between them and adopts a critical approach to all Western cultural assumptions. As a post-colonial writer, White shares the need of both post-colonising and post-colonised groups for an identity established not in terms of the colonial power but in terms of themselves. As a dissident white male, he is a privileged member of the post- colonising group but one who rejects the dominant discourses as illegitimate and unlegitimating. He offers a re-writing of the myths underpinning colonial and post-colonising discourses which privileges their suppressed and repressed elements. His re-writings affect aboriginal men and women, white women and the 'privileged' white male whose subjection to social control is masked as unproblematic freedom. White's re-writing of myth enbraces the post-modern as well as the post- colonial. He not only deconstructs and demystifies the phallogocentric/ethnocentric order of things; he also attempts to avoid totalization by privileging indeterminacy, fragmentation, hybridization and those liminary states which defy articulation: the ecstatic, the abject, the unspeakable. He himself is denied authority in that his re-writings are presented as mere acts in the always provisional process of making interpretations. White acknowledges the problematics of both presentation and re-presentation - an unresolved tension between the post-colonial desire for self-definition and the post-modern decentring of all meaning and interpretation permeates his discourse. The close readings of the texts attempt, accordingly, to reflect varying oppositional strategies: those which seek to overturn hierarchies and expose power-relations and those which seek an idiom in which contemporary Australia may find its least distorted reflexion. Within this ideological context, the Lacanian thematics of the subject, and their re-writing by Kristeva, are linked with dialectical criticism in an attempt to reflect a strictly provisional process of (re) construction
- Full Text:
- Date Issued: 1990
- Authors: Bosman, Brenda Evadne
- Date: 1990
- Subjects: White, Patrick, 1912-1990 , White, Patrick, 1912-1990 -- Criticism and interpretation , Myth in literature
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2170 , http://hdl.handle.net/10962/d1001821
- Description: The texts in this study interrogate the dominant myths which have affected the constructs of identity and history in the white Australian socio-historical context. These myths are exposed by White as ideologically determined and as operating by processes of exclusion, repression and marginalisation. White challenges the autonomy of both European and Australian cultures, reveals the ideological complicity between them and adopts a critical approach to all Western cultural assumptions. As a post-colonial writer, White shares the need of both post-colonising and post-colonised groups for an identity established not in terms of the colonial power but in terms of themselves. As a dissident white male, he is a privileged member of the post- colonising group but one who rejects the dominant discourses as illegitimate and unlegitimating. He offers a re-writing of the myths underpinning colonial and post-colonising discourses which privileges their suppressed and repressed elements. His re-writings affect aboriginal men and women, white women and the 'privileged' white male whose subjection to social control is masked as unproblematic freedom. White's re-writing of myth enbraces the post-modern as well as the post- colonial. He not only deconstructs and demystifies the phallogocentric/ethnocentric order of things; he also attempts to avoid totalization by privileging indeterminacy, fragmentation, hybridization and those liminary states which defy articulation: the ecstatic, the abject, the unspeakable. He himself is denied authority in that his re-writings are presented as mere acts in the always provisional process of making interpretations. White acknowledges the problematics of both presentation and re-presentation - an unresolved tension between the post-colonial desire for self-definition and the post-modern decentring of all meaning and interpretation permeates his discourse. The close readings of the texts attempt, accordingly, to reflect varying oppositional strategies: those which seek to overturn hierarchies and expose power-relations and those which seek an idiom in which contemporary Australia may find its least distorted reflexion. Within this ideological context, the Lacanian thematics of the subject, and their re-writing by Kristeva, are linked with dialectical criticism in an attempt to reflect a strictly provisional process of (re) construction
- Full Text:
- Date Issued: 1990
Ethical issues in human movement research
- Authors: Olivier, Stephen Chris
- Date: 1989
- Subjects: Human mechanics , Human mechanics -- Research -- Moral and ethical aspects , Research -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5156 , http://hdl.handle.net/10962/d1015402
- Description: In acknowledging past abuses of humans in research contexts, and recognising the potential for malpractices in Human Movement Studies (HMS), this study evaluated the extent to which ethical issues are addressed in the discipline. The primary method consisted of the standard techniques of philosophic analysis, with empirical data complementing the conclusions. In general, the study contends that insufficient attention is paid to ethical issues in HMS research. In response to a set of specifically constructed, ethically problematic research proposals, only 1.8% of comments from senior researchers advocated rejection of the proposals on ethical grounds. Also, a journal search indicated that consideration of ethical issues in published research may largely be absent. Questionnaire responses revealed that South African HMS departments may be deficient in terms of accountability towards ethical guidelines. Whilst noting the existence of utilitarian ethics in HMS research, it is advocated that deontologic principles should take precedence. Further, only a sound educative effort will produce improvements. In conclusion, this study advocates a deontology-based approach to research ethics. This is consistent with the contention that the use of humans in research is a privilege, and that the rights of participants ought to outweigh the desire of researchers to conduct research.
- Full Text:
- Date Issued: 1989
- Authors: Olivier, Stephen Chris
- Date: 1989
- Subjects: Human mechanics , Human mechanics -- Research -- Moral and ethical aspects , Research -- Moral and ethical aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5156 , http://hdl.handle.net/10962/d1015402
- Description: In acknowledging past abuses of humans in research contexts, and recognising the potential for malpractices in Human Movement Studies (HMS), this study evaluated the extent to which ethical issues are addressed in the discipline. The primary method consisted of the standard techniques of philosophic analysis, with empirical data complementing the conclusions. In general, the study contends that insufficient attention is paid to ethical issues in HMS research. In response to a set of specifically constructed, ethically problematic research proposals, only 1.8% of comments from senior researchers advocated rejection of the proposals on ethical grounds. Also, a journal search indicated that consideration of ethical issues in published research may largely be absent. Questionnaire responses revealed that South African HMS departments may be deficient in terms of accountability towards ethical guidelines. Whilst noting the existence of utilitarian ethics in HMS research, it is advocated that deontologic principles should take precedence. Further, only a sound educative effort will produce improvements. In conclusion, this study advocates a deontology-based approach to research ethics. This is consistent with the contention that the use of humans in research is a privilege, and that the rights of participants ought to outweigh the desire of researchers to conduct research.
- Full Text:
- Date Issued: 1989
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