Phototransformation of pollutants using lutetium and zinc phthalocyanines anchored on electrospun polymer fibers
- Authors: Zugle, Ruphino
- Date: 2013
- Subjects: Electrospinning Phthalocyanines Lutetium Zinc Polymers Dysprosium Pollutants Air Pollution Photochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4286 , http://hdl.handle.net/10962/d1002962
- Description: Novel lanthanide phthalocyanines containing dysprosium, erbium and lutetium as central metals were synthesized using phthalonitrile:metal salt ratio of 4:1 or lower phthalonitrile content as well as using unmetallated phthalocyanine. They were characterized using various spectroscopic and elemental analyses. Dysprosium bis-phthalocyanine was obtained while monomers were obtained for erbium and lutetium phthalocyanines. Theopen-shelldysprosiumbis-phthalocyanine and the monomeric complex of the open-shell erbium were neither fluorescent nor showed the ability to generate singlet oxygen. The triplet states of all the lutetium phthalocyanines were found to be populated with high triplet quantum yields and corresponding high singlet oxygen quantum yields. The fluorescence quantum yields of the lutetium phthalocyanines were however found to be very low. The lutetium phthalocyanines together with unsubstituted zinc phthalocyanine and its derivatives were successfully incorporated into electrospun polymer fibers either by covalent linkage or sorption forces. Spectral characteristics of the functionalized electrospun polymer fibers indicated that the phthalocyanines were bound and their integrity maintained within the fiber matrices. Most importantly the fluorescence and photoactivity of the phthalocyanines were equally maintained within the electrospun fibers. The functionalized electrospun polymer fibers especially those containing the zinc phthalocyanines could qualitatively detect nitrogen dioxide, a known environmental air pollutant. Also all the functionalized electrospun polystyrene and polysulfone fibers containing lutetium and zinc phthalocyanines could be applied for the photoconversion of 4-chlorophenol, 4-nitrophenol and methyl orange. Those of polystyrene could be re-used. Polyacrylic acid and polyurethane functionalized electrospun fibers were found not to be suitable for photocatalytic applications in aqueous medium. 4-Chlorophenol was found to be more susceptible to photodegradation while methyl orange very difficult to degrade.
- Full Text:
- Date Issued: 2013
- Authors: Zugle, Ruphino
- Date: 2013
- Subjects: Electrospinning Phthalocyanines Lutetium Zinc Polymers Dysprosium Pollutants Air Pollution Photochemistry
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4286 , http://hdl.handle.net/10962/d1002962
- Description: Novel lanthanide phthalocyanines containing dysprosium, erbium and lutetium as central metals were synthesized using phthalonitrile:metal salt ratio of 4:1 or lower phthalonitrile content as well as using unmetallated phthalocyanine. They were characterized using various spectroscopic and elemental analyses. Dysprosium bis-phthalocyanine was obtained while monomers were obtained for erbium and lutetium phthalocyanines. Theopen-shelldysprosiumbis-phthalocyanine and the monomeric complex of the open-shell erbium were neither fluorescent nor showed the ability to generate singlet oxygen. The triplet states of all the lutetium phthalocyanines were found to be populated with high triplet quantum yields and corresponding high singlet oxygen quantum yields. The fluorescence quantum yields of the lutetium phthalocyanines were however found to be very low. The lutetium phthalocyanines together with unsubstituted zinc phthalocyanine and its derivatives were successfully incorporated into electrospun polymer fibers either by covalent linkage or sorption forces. Spectral characteristics of the functionalized electrospun polymer fibers indicated that the phthalocyanines were bound and their integrity maintained within the fiber matrices. Most importantly the fluorescence and photoactivity of the phthalocyanines were equally maintained within the electrospun fibers. The functionalized electrospun polymer fibers especially those containing the zinc phthalocyanines could qualitatively detect nitrogen dioxide, a known environmental air pollutant. Also all the functionalized electrospun polystyrene and polysulfone fibers containing lutetium and zinc phthalocyanines could be applied for the photoconversion of 4-chlorophenol, 4-nitrophenol and methyl orange. Those of polystyrene could be re-used. Polyacrylic acid and polyurethane functionalized electrospun fibers were found not to be suitable for photocatalytic applications in aqueous medium. 4-Chlorophenol was found to be more susceptible to photodegradation while methyl orange very difficult to degrade.
- Full Text:
- Date Issued: 2013
Neurocognitive effects of head and body collisions on club level rugby union players
- Authors: Zoccola, Diana
- Date: 2015
- Subjects: Head -- Wounds and injuries -- Psychology , Neuropsychological tests , Head -- Wounds and injuries , Sports injuries -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3257 , http://hdl.handle.net/10962/d1016397
- Description: The objective of the study was to investigate the cumulative neurocognitive effects of repetitive concussive and subconcussive events in club level Rugby Union (hereafter rugby) during the course of one rugby season, in a combined group and individualized case-based approach. Amateur adult club level rugby players (n = 20) were compared with a non-contact control group (n = 22) of equivalent age, years of education and estimated IQ (p = > .05, in all instances), although the two groups were clearly differentiated on the basis of a history of reported concussions (p = < .05). Video analyses documented the tackling maneuvers observed amongst the players during all matches across the rugby season revealing a sobering average of more than a thousand tackles per player, excluding any contact practice sessions. Five rugby players (n = 5) who were observed to have a head jarring event were also isolated for individualized postconcussive follow-up analysis of their neurocognitive profiles. Measures included the ImPACT Verbal and Visual Memory, Visual Motor Speed and Reaction Time composites and the Purdue Pegboard. Independent and dependent statistical analyses were employed to compare the rugby versus control group neurocognitive test profiles at and between the three test intervals. Correlational analyses explored the association between concussion, tackling and neurocognitive test outcomes. Descriptive comparisons of individual neurocognitive test scores with normative data were employed for the case analyses. Taken together, the results implicated vulnerability amongst club rugby players on the motor and speeded tasks, with less robust indications on the memory tasks. While limited in terms of its small sample size, it is considered that the outcome of the study was rendered more robust by virtue of being methodologically multifaceted with heuristic implications for future research studies in the area. The novel inclusion of tackling data as well as fine-tuned case analyses, were of particular relevance in that regard. The results add to a growing body of literature that implicates deleterious neurocognitive effects in participants of a sport such as rugby due to repetitive head jarring incidents that are intrinsic to the game.
- Full Text:
- Date Issued: 2015
- Authors: Zoccola, Diana
- Date: 2015
- Subjects: Head -- Wounds and injuries -- Psychology , Neuropsychological tests , Head -- Wounds and injuries , Sports injuries -- Psychological aspects
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3257 , http://hdl.handle.net/10962/d1016397
- Description: The objective of the study was to investigate the cumulative neurocognitive effects of repetitive concussive and subconcussive events in club level Rugby Union (hereafter rugby) during the course of one rugby season, in a combined group and individualized case-based approach. Amateur adult club level rugby players (n = 20) were compared with a non-contact control group (n = 22) of equivalent age, years of education and estimated IQ (p = > .05, in all instances), although the two groups were clearly differentiated on the basis of a history of reported concussions (p = < .05). Video analyses documented the tackling maneuvers observed amongst the players during all matches across the rugby season revealing a sobering average of more than a thousand tackles per player, excluding any contact practice sessions. Five rugby players (n = 5) who were observed to have a head jarring event were also isolated for individualized postconcussive follow-up analysis of their neurocognitive profiles. Measures included the ImPACT Verbal and Visual Memory, Visual Motor Speed and Reaction Time composites and the Purdue Pegboard. Independent and dependent statistical analyses were employed to compare the rugby versus control group neurocognitive test profiles at and between the three test intervals. Correlational analyses explored the association between concussion, tackling and neurocognitive test outcomes. Descriptive comparisons of individual neurocognitive test scores with normative data were employed for the case analyses. Taken together, the results implicated vulnerability amongst club rugby players on the motor and speeded tasks, with less robust indications on the memory tasks. While limited in terms of its small sample size, it is considered that the outcome of the study was rendered more robust by virtue of being methodologically multifaceted with heuristic implications for future research studies in the area. The novel inclusion of tackling data as well as fine-tuned case analyses, were of particular relevance in that regard. The results add to a growing body of literature that implicates deleterious neurocognitive effects in participants of a sport such as rugby due to repetitive head jarring incidents that are intrinsic to the game.
- Full Text:
- Date Issued: 2015
Information and propaganda in the federation of Rhodesia and Nyasaland with special reference to print and radio propaganda for Africans, 1953-1963
- Authors: Zimudzi, Tapiwa Brown
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6957 , vital:21204
- Description: This thesis contributes to the history of the information and propaganda policy and practice of the government of the Federation of Rhodesia and Nyasaland by examining this government's pro-Federation print and radio propaganda for Africans in the Federation. Using a multi-theoretical approach, it analyses the character of this propaganda, highlighting its main methods and themes as well as the policy considerations, plus political and economic circumstances that gave rise to it. It also discusses how Africans in the Federation reacted to this propaganda and assesses its effectiveness in gaining the support of these Africans for Federation and the policies of the Federal government. The thesis argues that Federal government propaganda aimed at gaining the support of Africans for Federation was predominantly panic-driven propaganda and was the product of an information panic that lay at the heart of the very idea of Federation itself. This information panic arose out of the Federal government's belated recognition of the strength of African opposition to Federation and of how this opposition seriously threatened the continued survival of the Federation. It is also argued that this panic-driven pro-Federation propaganda elicited largely hostile reactions from the majority of Africans in the Federation and failed to persuade them to support Federation.
- Full Text:
- Date Issued: 2017
- Authors: Zimudzi, Tapiwa Brown
- Date: 2017
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/6957 , vital:21204
- Description: This thesis contributes to the history of the information and propaganda policy and practice of the government of the Federation of Rhodesia and Nyasaland by examining this government's pro-Federation print and radio propaganda for Africans in the Federation. Using a multi-theoretical approach, it analyses the character of this propaganda, highlighting its main methods and themes as well as the policy considerations, plus political and economic circumstances that gave rise to it. It also discusses how Africans in the Federation reacted to this propaganda and assesses its effectiveness in gaining the support of these Africans for Federation and the policies of the Federal government. The thesis argues that Federal government propaganda aimed at gaining the support of Africans for Federation was predominantly panic-driven propaganda and was the product of an information panic that lay at the heart of the very idea of Federation itself. This information panic arose out of the Federal government's belated recognition of the strength of African opposition to Federation and of how this opposition seriously threatened the continued survival of the Federation. It is also argued that this panic-driven pro-Federation propaganda elicited largely hostile reactions from the majority of Africans in the Federation and failed to persuade them to support Federation.
- Full Text:
- Date Issued: 2017
The ecology and control of Opuntia Aurantiaca in South Africa in relation to the cochineal insect, Dactylopius Austrinus
- Authors: Zimmermann, Helmuth G
- Date: 1982
- Subjects: Cochineal insect -- South Africa Cactus -- South Africa Weeds -- Control -- South Africa Insect-plant relationships
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5612 , http://hdl.handle.net/10962/d1003061
- Description: The cochineal insect Dactylopius austrinus De Lotto, which was released on jointed cactus, Opuntia aurantiaca Lindley, in South Africa in 1932, failed to bring the weed under an acceptable level of control in spite of the encouraging results during the first few years after release. The reasons for this apparent failure were never clearly understood. In 1957 the State embarked on an intensive herbicidal control programme which is still in force today. This sustained and expensive programme has undoubtedly reduced the density of the weed in most areas but has failed to solve the problem and the plant continues to expand its range. The biological control of o. aurantiaca in South Africa has been fundamentally influenced by this chemical control campaign. The relationship between chemical and biological control methods is reported in this study.
- Full Text:
- Date Issued: 1982
- Authors: Zimmermann, Helmuth G
- Date: 1982
- Subjects: Cochineal insect -- South Africa Cactus -- South Africa Weeds -- Control -- South Africa Insect-plant relationships
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5612 , http://hdl.handle.net/10962/d1003061
- Description: The cochineal insect Dactylopius austrinus De Lotto, which was released on jointed cactus, Opuntia aurantiaca Lindley, in South Africa in 1932, failed to bring the weed under an acceptable level of control in spite of the encouraging results during the first few years after release. The reasons for this apparent failure were never clearly understood. In 1957 the State embarked on an intensive herbicidal control programme which is still in force today. This sustained and expensive programme has undoubtedly reduced the density of the weed in most areas but has failed to solve the problem and the plant continues to expand its range. The biological control of o. aurantiaca in South Africa has been fundamentally influenced by this chemical control campaign. The relationship between chemical and biological control methods is reported in this study.
- Full Text:
- Date Issued: 1982
Family diversity : a South African perspective focusing on Whites in Grahamstown
- Authors: Ziehl, Susan C
- Date: 1998
- Subjects: Families -- History -- Research Families -- South Africa -- Grahamstown Families Families -- Research -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3341 , http://hdl.handle.net/10962/d1004467
- Description: Drawing on developments in the field of family history and studies of families in contemporary settings, the study addresses the question of explaining variations in household patterns. Its empirical basis is a survey of White households in Grahamstown. The surveyed population was broken down in terms of class (occupation) and culture (language) and analyses conducted to determine if there are any statistically significant relationships between these variables and the tendency to reside in particular household structures. The question of 'family ideology' was also addressed as an attempt was made to uncover subjects' views on a variety of family-related issues. On the basis of the research results, a model of the relationship between class, culture and household structure was developed. Its application to a comparison of Black and White household structures in South Africa as well as the United States, is discussed. Finally, attempts at redefining the family are addressed and a new definition of the family proposed.
- Full Text:
- Date Issued: 1998
- Authors: Ziehl, Susan C
- Date: 1998
- Subjects: Families -- History -- Research Families -- South Africa -- Grahamstown Families Families -- Research -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3341 , http://hdl.handle.net/10962/d1004467
- Description: Drawing on developments in the field of family history and studies of families in contemporary settings, the study addresses the question of explaining variations in household patterns. Its empirical basis is a survey of White households in Grahamstown. The surveyed population was broken down in terms of class (occupation) and culture (language) and analyses conducted to determine if there are any statistically significant relationships between these variables and the tendency to reside in particular household structures. The question of 'family ideology' was also addressed as an attempt was made to uncover subjects' views on a variety of family-related issues. On the basis of the research results, a model of the relationship between class, culture and household structure was developed. Its application to a comparison of Black and White household structures in South Africa as well as the United States, is discussed. Finally, attempts at redefining the family are addressed and a new definition of the family proposed.
- Full Text:
- Date Issued: 1998
An adaptive approach for optimized opportunistic routing over Delay Tolerant Mobile Ad hoc Networks
- Authors: Zhao, Xiaogeng
- Date: 2008
- Subjects: Ad hoc networks (Computer networks) Computer network architectures Computer networks Routing protocols (Computer network protocols)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4588 , http://hdl.handle.net/10962/d1004822
- Description: This thesis presents a framework for investigating opportunistic routing in Delay Tolerant Mobile Ad hoc Networks (DTMANETs), and introduces the concept of an Opportunistic Confidence Index (OCI). The OCI enables multiple opportunistic routing protocols to be applied as an adaptive group to improve DTMANET routing reliability, performance, and efficiency. The DTMANET is a recently acknowledged networkarchitecture, which is designed to address the challenging and marginal environments created by adaptive, mobile, and unreliable network node presence. Because of its ad hoc and autonomic nature, routing in a DTMANET is a very challenging problem. The design of routing protocols in such environments, which ensure a high percentage delivery rate (reliability), achieve a reasonable delivery time (performance), and at the same time maintain an acceptable communication overhead (efficiency), is of fundamental consequence to the usefulness of DTMANETs. In recent years, a number of investigations into DTMANET routing have been conducted, resulting in the emergence of a class of routing known as opportunistic routing protocols. Current research into opportunistic routing has exposed opportunities for positive impacts on DTMANET routing. To date, most investigations have concentrated upon one or other of the quality metrics of reliability, performance, or efficiency, while some approaches have pursued a balance of these metrics through assumptions of a high level of global knowledge and/or uniform mobile device behaviours. No prior research that we are aware of has studied the connection between multiple opportunistic elements and their influences upon one another, and none has demonstrated the possibility of modelling and using multiple different opportunistic elements as an adaptive group to aid the routing process in a DTMANET. This thesis investigates OCI opportunities and their viability through the design of an extensible simulation environment, which makes use of methods and techniques such as abstract modelling, opportunistic element simplification and isolation, random attribute generation and assignment, localized knowledge sharing, automated scenario generation, intelligent weight assignment and/or opportunistic element permutation. These methods and techniques are incorporated at both data acquisition and analysis phases. Our results show a significant improvement in all three metric categories. In one of the most applicable scenarios tested, OCI yielded a 31.05% message delivery increase (reliability improvement), 22.18% message delivery time reduction (performance improvement), and 73.64% routing depth decrement (efficiency improvement). We are able to conclude that the OCI approach is feasible across a range of scenarios, and that the use of multiple opportunistic elements to aid decision-making processes in DTMANET environments has value.
- Full Text:
- Date Issued: 2008
- Authors: Zhao, Xiaogeng
- Date: 2008
- Subjects: Ad hoc networks (Computer networks) Computer network architectures Computer networks Routing protocols (Computer network protocols)
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4588 , http://hdl.handle.net/10962/d1004822
- Description: This thesis presents a framework for investigating opportunistic routing in Delay Tolerant Mobile Ad hoc Networks (DTMANETs), and introduces the concept of an Opportunistic Confidence Index (OCI). The OCI enables multiple opportunistic routing protocols to be applied as an adaptive group to improve DTMANET routing reliability, performance, and efficiency. The DTMANET is a recently acknowledged networkarchitecture, which is designed to address the challenging and marginal environments created by adaptive, mobile, and unreliable network node presence. Because of its ad hoc and autonomic nature, routing in a DTMANET is a very challenging problem. The design of routing protocols in such environments, which ensure a high percentage delivery rate (reliability), achieve a reasonable delivery time (performance), and at the same time maintain an acceptable communication overhead (efficiency), is of fundamental consequence to the usefulness of DTMANETs. In recent years, a number of investigations into DTMANET routing have been conducted, resulting in the emergence of a class of routing known as opportunistic routing protocols. Current research into opportunistic routing has exposed opportunities for positive impacts on DTMANET routing. To date, most investigations have concentrated upon one or other of the quality metrics of reliability, performance, or efficiency, while some approaches have pursued a balance of these metrics through assumptions of a high level of global knowledge and/or uniform mobile device behaviours. No prior research that we are aware of has studied the connection between multiple opportunistic elements and their influences upon one another, and none has demonstrated the possibility of modelling and using multiple different opportunistic elements as an adaptive group to aid the routing process in a DTMANET. This thesis investigates OCI opportunities and their viability through the design of an extensible simulation environment, which makes use of methods and techniques such as abstract modelling, opportunistic element simplification and isolation, random attribute generation and assignment, localized knowledge sharing, automated scenario generation, intelligent weight assignment and/or opportunistic element permutation. These methods and techniques are incorporated at both data acquisition and analysis phases. Our results show a significant improvement in all three metric categories. In one of the most applicable scenarios tested, OCI yielded a 31.05% message delivery increase (reliability improvement), 22.18% message delivery time reduction (performance improvement), and 73.64% routing depth decrement (efficiency improvement). We are able to conclude that the OCI approach is feasible across a range of scenarios, and that the use of multiple opportunistic elements to aid decision-making processes in DTMANET environments has value.
- Full Text:
- Date Issued: 2008
Removal and recovery of heavy metals from synthetic solutions and electroplating effluents using yeast and the water fern Azolla filiculoides
- Authors: Zhao, Ming
- Date: 1998
- Subjects: Heavy metals -- Environmental aspects Azolla filiculoides -- Biological control Aquatic weeds -- Biological control Yeast Metal ions Yeast fungi -- Biotechnology Cations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4001 , http://hdl.handle.net/10962/d1004061
- Description: The aims of the project were twofold. The initial objective of the study, based on previous results, was to develop an economically viable methodology for immobilizing yeast cells for the treatment of heavy metal-laden waste water. The non-viable yeast cross-linked by 13% (w/v) formaldehyde/1N HNO₃ exhibited satisfactory mechanical strength and rigidity in a continuous-flow column operation. No apparent disruption of the biomass after repeated use was observed. The cost of immobilizing 1kg dry yeast pellets was estimated at less than US$I. Zn uptake capacity of FA-cross-linked pellets, on batch trials, remained similar to that of raw yeast, reflecting that the immobilizing procedure did not hinder its metal removing capacity. In column studies, cation metals were effectively removed by the yeast pellets from aqueous solution at natural pHs, and then recovered completely by washing the pellets in situ with O.1M HCl. The recovered metals were concentrated in such small volumes that recycling or precipitation of them was facilitated. The metal uptake capacity of the regenerated biomass remained constant in comparison with cycle 1, indicating that reuse of the yeast would be possible. In the case of Cr⁶⁺, a gradual breakthrough curve of Cr in the column profile was noted, with a simultaneous reduction of Cr⁶⁺ to Cr³⁺. However, Cr⁶⁺ in the effluent can be markedly minimised either by accumulation onto the biomass or reduction to its trivalent form. Desorption of bound Cr⁶⁺ with either alkali or salt could not accomplish the regeneration of the biomass. A combination of reduction and desorption with FA/HNO₃ appeared promising in regeneration of the saturated biomass at 4°C. The metal sorption capacities of the yeast pellets, on a batch or a fixed-bed system are relatively lower than that of documented sorbents. Apparently more of the yeast pellets would be required for treating a certain volume of waste effluent, than with other sorbents. Therefore Azolla filiculoides was examined as a suitable sorbent for this purpose. This constitutes the second part of the project. Azolla filiculoides, a naturally-abundant water fern, was screened for its metal sorption and recovering capacities, mechanical stability, flow-permeability and reusability. The azolla biomass appeared to have fulfilled the required mechanical criteria during the repeated sorption-desorption column operations. It is water-insoluble and appears flexible under pressure when rinsed with water. These characters are of crucial importance in a continuous-flow system since a column can be operated at high flow rates without apparent compact of the biomass and pressure loss. Therefore, immobilization of the biomass can be avoided. The sorption isotherm data, obtained from batch removal of Cr⁶⁺, showed that the sorption process was effective, endothermic and highly pH dependent. Considerable amounts of Cr⁶⁺ were accumulated at the optimum pHs of 2-2.5. Column sorption of Cr⁶⁺ at a low flow rate and pH of 2.5 showed optimum performance with a total Cr uptake of 50.4mg/g at 60% saturation of the biomass. Removal of Cr⁶⁺ from an electroplating effluent using an azolla column was deemed reasonably satisfactory, although the uptake declined slightly. Desorption of bound Cr⁶⁺ with various desorbents was incomplete, which resulted in a low regeneration efficiency of about 50%. However, removal and recovery of Cr³⁺ using the azolla column was than that of Cr⁶⁺. Desorption of Cr³⁺ from the spent biomass column was accomplished with the recovery of 80% using O.5N H₂SO₄, The regeneration efficiencies for Cr³⁺ removal were up to 90% and demonstrated that the biomass is reusable. Cation metal uptake capacities of azolla, obtained either from batch or column experiments, are reasonably high in comparison with other sorbents. The uptake of Ni or Zn ions from solution is pH dependent showing the optimum pH of around 6 to 6.5, under the current experimental conditions. The sorption kinetics for cation metals was rapid with about 80% of the bound Ni ions being taken up in the first 10 min. The character of rapid binding is extremely important in a column sorption process, especially on a large scale since it favours an optimum uptake of metals at high flow rates. The Ni or Zn uptakes in column sorption were not markedly affected when the flow rates were increased from 80mllh up to 800ml/h for the 5g biomass used. The cation heavy metals removed from waste effluents were recovered in a concentrated solution of small volume. The desorption of bound Ni and Zn ions from the saturated biomass was accomplished with either O.2N HCl or H₂SO₄ that resulted in recoveries of more than 95%. The metals recovered, in the case of Ni and Zn, are identical to that of plating agents ego nickel sulphate or chloride, so that recycling of the metals is possible. An effluent-free, closed loop of Ni or Zn treatment system was proposed, whereby the Ni or Zn ions can be recycled to the plating bath whilst the purified water is fed back to the rinse tanks. Ca and Mg ions, commonly present in the electroplating effluents, appeared to affect sorption of heavy metals by azolla when metal concentrations were relatively low, presumedly through its competitive binding for the shared sites on surfaces of azolla. The data obtained from column sorption of Ni and Zn follows the BDST model well, enabling the application of the model to predicting design parameters for scale-up of the biosorption column system. It is interesting that the values of metal uptake, expressed in molar quantities, obtained on respective single-metal solutions and the multiple metal system, are similar, implying that the mechanisms involved in the sorption of all metal cations are similar and that the binding sites on surfaces of azolla are probably shared by all cation metals. The surface of the biomass provides sites for metal binding estimated in the range of 0.45-0.57mmol/g, based on the current experiments. The biomass has a surface area of 429 m²/g and water retention of 14.3 ml/g. The functional groups on the surface of azolla were partially identified using chemical modification and metal binding comparison. Among the functional groups examined, carboxyl groups, provided by amino acids and polysaccharides, appeared to play an important role in metal cation binding. The infrared spectra of the samples support this conclusion.
- Full Text:
- Date Issued: 1998
- Authors: Zhao, Ming
- Date: 1998
- Subjects: Heavy metals -- Environmental aspects Azolla filiculoides -- Biological control Aquatic weeds -- Biological control Yeast Metal ions Yeast fungi -- Biotechnology Cations
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4001 , http://hdl.handle.net/10962/d1004061
- Description: The aims of the project were twofold. The initial objective of the study, based on previous results, was to develop an economically viable methodology for immobilizing yeast cells for the treatment of heavy metal-laden waste water. The non-viable yeast cross-linked by 13% (w/v) formaldehyde/1N HNO₃ exhibited satisfactory mechanical strength and rigidity in a continuous-flow column operation. No apparent disruption of the biomass after repeated use was observed. The cost of immobilizing 1kg dry yeast pellets was estimated at less than US$I. Zn uptake capacity of FA-cross-linked pellets, on batch trials, remained similar to that of raw yeast, reflecting that the immobilizing procedure did not hinder its metal removing capacity. In column studies, cation metals were effectively removed by the yeast pellets from aqueous solution at natural pHs, and then recovered completely by washing the pellets in situ with O.1M HCl. The recovered metals were concentrated in such small volumes that recycling or precipitation of them was facilitated. The metal uptake capacity of the regenerated biomass remained constant in comparison with cycle 1, indicating that reuse of the yeast would be possible. In the case of Cr⁶⁺, a gradual breakthrough curve of Cr in the column profile was noted, with a simultaneous reduction of Cr⁶⁺ to Cr³⁺. However, Cr⁶⁺ in the effluent can be markedly minimised either by accumulation onto the biomass or reduction to its trivalent form. Desorption of bound Cr⁶⁺ with either alkali or salt could not accomplish the regeneration of the biomass. A combination of reduction and desorption with FA/HNO₃ appeared promising in regeneration of the saturated biomass at 4°C. The metal sorption capacities of the yeast pellets, on a batch or a fixed-bed system are relatively lower than that of documented sorbents. Apparently more of the yeast pellets would be required for treating a certain volume of waste effluent, than with other sorbents. Therefore Azolla filiculoides was examined as a suitable sorbent for this purpose. This constitutes the second part of the project. Azolla filiculoides, a naturally-abundant water fern, was screened for its metal sorption and recovering capacities, mechanical stability, flow-permeability and reusability. The azolla biomass appeared to have fulfilled the required mechanical criteria during the repeated sorption-desorption column operations. It is water-insoluble and appears flexible under pressure when rinsed with water. These characters are of crucial importance in a continuous-flow system since a column can be operated at high flow rates without apparent compact of the biomass and pressure loss. Therefore, immobilization of the biomass can be avoided. The sorption isotherm data, obtained from batch removal of Cr⁶⁺, showed that the sorption process was effective, endothermic and highly pH dependent. Considerable amounts of Cr⁶⁺ were accumulated at the optimum pHs of 2-2.5. Column sorption of Cr⁶⁺ at a low flow rate and pH of 2.5 showed optimum performance with a total Cr uptake of 50.4mg/g at 60% saturation of the biomass. Removal of Cr⁶⁺ from an electroplating effluent using an azolla column was deemed reasonably satisfactory, although the uptake declined slightly. Desorption of bound Cr⁶⁺ with various desorbents was incomplete, which resulted in a low regeneration efficiency of about 50%. However, removal and recovery of Cr³⁺ using the azolla column was than that of Cr⁶⁺. Desorption of Cr³⁺ from the spent biomass column was accomplished with the recovery of 80% using O.5N H₂SO₄, The regeneration efficiencies for Cr³⁺ removal were up to 90% and demonstrated that the biomass is reusable. Cation metal uptake capacities of azolla, obtained either from batch or column experiments, are reasonably high in comparison with other sorbents. The uptake of Ni or Zn ions from solution is pH dependent showing the optimum pH of around 6 to 6.5, under the current experimental conditions. The sorption kinetics for cation metals was rapid with about 80% of the bound Ni ions being taken up in the first 10 min. The character of rapid binding is extremely important in a column sorption process, especially on a large scale since it favours an optimum uptake of metals at high flow rates. The Ni or Zn uptakes in column sorption were not markedly affected when the flow rates were increased from 80mllh up to 800ml/h for the 5g biomass used. The cation heavy metals removed from waste effluents were recovered in a concentrated solution of small volume. The desorption of bound Ni and Zn ions from the saturated biomass was accomplished with either O.2N HCl or H₂SO₄ that resulted in recoveries of more than 95%. The metals recovered, in the case of Ni and Zn, are identical to that of plating agents ego nickel sulphate or chloride, so that recycling of the metals is possible. An effluent-free, closed loop of Ni or Zn treatment system was proposed, whereby the Ni or Zn ions can be recycled to the plating bath whilst the purified water is fed back to the rinse tanks. Ca and Mg ions, commonly present in the electroplating effluents, appeared to affect sorption of heavy metals by azolla when metal concentrations were relatively low, presumedly through its competitive binding for the shared sites on surfaces of azolla. The data obtained from column sorption of Ni and Zn follows the BDST model well, enabling the application of the model to predicting design parameters for scale-up of the biosorption column system. It is interesting that the values of metal uptake, expressed in molar quantities, obtained on respective single-metal solutions and the multiple metal system, are similar, implying that the mechanisms involved in the sorption of all metal cations are similar and that the binding sites on surfaces of azolla are probably shared by all cation metals. The surface of the biomass provides sites for metal binding estimated in the range of 0.45-0.57mmol/g, based on the current experiments. The biomass has a surface area of 429 m²/g and water retention of 14.3 ml/g. The functional groups on the surface of azolla were partially identified using chemical modification and metal binding comparison. Among the functional groups examined, carboxyl groups, provided by amino acids and polysaccharides, appeared to play an important role in metal cation binding. The infrared spectra of the samples support this conclusion.
- Full Text:
- Date Issued: 1998
Representation and use of indigenous heritage constructs : implications for the quality and relevance of heritage education in post colonial southern Africa
- Authors: Zazu, Cryton
- Date: 2013
- Subjects: Albany Museum (Grahamstown, South Africa) Cultural property -- Conservation and restoration -- Research -- Africa, Southern Great Zimbabwe (Extinct city) Indigenous peoples -- Material culture -- Africa, Southern Anthropological museums and collections -- Management -- Research -- Africa, Southern Cultural property -- Management -- Research Ethnoscience -- Study and teaching -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1407 , http://hdl.handle.net/10962/d1002015
- Description: This study explores representation and use of indigenous heritage constructs with a view to identifying implications thereof for the quality and relevance of heritage education practices in post colonial southern Africa. Framed within a critical hermeneutic research paradigm under-laboured by critical realist ontology, the study was conducted using a multiple case study research design. The data collection protocol was three-phased, starting with a process of contextual profiling, within which insights were gained into discourses shaping the constitution and orientation of heritage education practices at the Albany Museum in South Africa, the Great Zimbabwe Monument in Zimbabwe and the Supa Ngwao Museum in Botswana. The second phase of data collection entailed modelling workshops in which educators engaged in discussion around the status of heritage education in post apartheid South Africa. This highlighted, through modelled lessons, some of the tensions, challenges and implications for working with notions of social transformation and inclusivity in heritage education. The third phase of data collection involved in-depth interviews. Twelve purposively selected research participants were interviewed between 2010 and 2011. Data generated across the study was processed and subjected to different levels of critical discourse analysis. Besides noting how heritage education in post colonial southern Africa is poorly framed and under-researched, this study revealed that current forms of representing indigenous heritage constructs are influenced more by socio-political discourses than the need to protect and conserve local heritage resources. The study also noted that the observed heritage education practices are oriented more towards addressing issues related to marginalisation and alienation of indigenous cultures and practices, than enhancing learners’ agency to manage and utilise local heritage resources in a more sustainable ways. Based on these findings the study recommends re-positioning heritage education within the framework of Education for Sustainable Development (ESD). ESD acknowledges both issues of social justice and the dialectical interplay between nature and culture; as such, it may allow for representation and use of indigenous heritage constructs in ways that expand current political orientations to include sustainability as an additional objective of heritage education. Given that little research focusing on heritage education has been undertaken within southern Africa, the findings of this study provide a basis upon which future research may emerge.
- Full Text:
- Date Issued: 2013
- Authors: Zazu, Cryton
- Date: 2013
- Subjects: Albany Museum (Grahamstown, South Africa) Cultural property -- Conservation and restoration -- Research -- Africa, Southern Great Zimbabwe (Extinct city) Indigenous peoples -- Material culture -- Africa, Southern Anthropological museums and collections -- Management -- Research -- Africa, Southern Cultural property -- Management -- Research Ethnoscience -- Study and teaching -- Africa, Southern
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1407 , http://hdl.handle.net/10962/d1002015
- Description: This study explores representation and use of indigenous heritage constructs with a view to identifying implications thereof for the quality and relevance of heritage education practices in post colonial southern Africa. Framed within a critical hermeneutic research paradigm under-laboured by critical realist ontology, the study was conducted using a multiple case study research design. The data collection protocol was three-phased, starting with a process of contextual profiling, within which insights were gained into discourses shaping the constitution and orientation of heritage education practices at the Albany Museum in South Africa, the Great Zimbabwe Monument in Zimbabwe and the Supa Ngwao Museum in Botswana. The second phase of data collection entailed modelling workshops in which educators engaged in discussion around the status of heritage education in post apartheid South Africa. This highlighted, through modelled lessons, some of the tensions, challenges and implications for working with notions of social transformation and inclusivity in heritage education. The third phase of data collection involved in-depth interviews. Twelve purposively selected research participants were interviewed between 2010 and 2011. Data generated across the study was processed and subjected to different levels of critical discourse analysis. Besides noting how heritage education in post colonial southern Africa is poorly framed and under-researched, this study revealed that current forms of representing indigenous heritage constructs are influenced more by socio-political discourses than the need to protect and conserve local heritage resources. The study also noted that the observed heritage education practices are oriented more towards addressing issues related to marginalisation and alienation of indigenous cultures and practices, than enhancing learners’ agency to manage and utilise local heritage resources in a more sustainable ways. Based on these findings the study recommends re-positioning heritage education within the framework of Education for Sustainable Development (ESD). ESD acknowledges both issues of social justice and the dialectical interplay between nature and culture; as such, it may allow for representation and use of indigenous heritage constructs in ways that expand current political orientations to include sustainability as an additional objective of heritage education. Given that little research focusing on heritage education has been undertaken within southern Africa, the findings of this study provide a basis upon which future research may emerge.
- Full Text:
- Date Issued: 2013
A genetic and ecophysiological comparison of co-occuring indigenous (Perna perna) and invasive (Mytilus galloprovincialis) intertidal mussels
- Authors: Zardi, G I
- Date: 2006
- Subjects: Perna -- South Africa Mytilus galloprovincialis -- South Africa Mussels -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5613 , http://hdl.handle.net/10962/d1003066
- Description: The Mediterranean mussel Mytilus galloprovincialis is the most successful marine invasive species in South Africa. Its presence has had significant ecological consequences on the intertidal communities of the west coast. On the south coast, M galloprovincialis co-exists and competes with the indigenous intertidal mussel Perna perna in the lower balanoid zone, where they show partial habitat segregation. The upper and the lower mussel zones are dominated by M. galloprovincialis and P. perna respectively while they co-occur in the mid zone. In this thesis M. galloprovincialis and P. perna are compared in terms of their population genetics and their ecophysiology. The success of an invader depends on its ability to react to new environmental factors, especially when compared to indigenous species. The distribution and diversity of intertidal species throughout the world are strongly influenced by periodic sand inundation and hydrodynamic stress. Occupying the lower intertidal zone, P. perna is more strongly influenced by sand (burial and sand in suspension) than M. galioprovincialis. Despite this, P. perna is more vulnerable to the effects of sand, showing higher mortality rates under experimental conditions in both the laboratory and the field. M. galioprovincialis has longer labial palps than P. perna, indicating a better ability to sort particles. This, and a higher tolerance to anoxia, explains its lower mortality rates when exposed to burial or suspended sand. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. The ability of a mussel to withstand wave-generated hydrodynamic stress depends mainly on its byssal attachment strength. The higher attachment strength of P. perna compared to M. galioprovincialis and of solitary mussels compared to mussels living within a bed (bed mussels) can be explained by more and thicker byssal threads. M galloprovincialis also has a wider shell, is subjected to higher hydrodynamic loads than P. perna and shows a higher theoretical probability of dislodgement, this is borne out under field conditions. The attachment strength of both species increased from higher to lower shore, in parallel to a gradient of a stronger wave action. Monthly measurements showed that P. perna is always more strongly attached than M. galloprovincialis and revealed seasonal fluctuations of attachment strength for both species in response to wave height. The gonad index of both species was negatively cross-correlated with attachment strength. The results are discussed in the context of the evolutionary strategy of the alien mussel, which directs most of its energy to fast growth and high reproductive output, apparently at the cost of reduced attachment strength. This raises the prediction that its invasive impact will be more pronounced at sites subjected to low or moderate wave action at heavily exposed sites. The potential of a species for invasion is also determined by the ability of the invader to disperse. Population genetics provide indirect information about dispersal through a direct measurement of gene flow. The low genetic divergence (measured as mtDNA) of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the population genetics structure of P. perna revealed strong divergence on the south-east coast, resulting in a western lineage (straddling the distributional gap of the Benguela System), and an eastern lineage, with an overlap region of the two on the south coast between Kenton-on-Sea and Haga Haga. This genetic disjunction may be caused by Agulhas Current acting as an oceanographic barrier to larval dispersal, or by different environmental selective forces acting on regional populations. Over the last ten years, M. galloprovincialis has shown a decrease or cessation of its spread to the east in exactly the region of the genetic disjunction in P. perna, again suggesting either an oceanographic barrier to larval dispersal, or increasing selection driven by sharp gradients in environmental conditions.
- Full Text:
- Date Issued: 2006
- Authors: Zardi, G I
- Date: 2006
- Subjects: Perna -- South Africa Mytilus galloprovincialis -- South Africa Mussels -- South Africa Mytilidae -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5613 , http://hdl.handle.net/10962/d1003066
- Description: The Mediterranean mussel Mytilus galloprovincialis is the most successful marine invasive species in South Africa. Its presence has had significant ecological consequences on the intertidal communities of the west coast. On the south coast, M galloprovincialis co-exists and competes with the indigenous intertidal mussel Perna perna in the lower balanoid zone, where they show partial habitat segregation. The upper and the lower mussel zones are dominated by M. galloprovincialis and P. perna respectively while they co-occur in the mid zone. In this thesis M. galloprovincialis and P. perna are compared in terms of their population genetics and their ecophysiology. The success of an invader depends on its ability to react to new environmental factors, especially when compared to indigenous species. The distribution and diversity of intertidal species throughout the world are strongly influenced by periodic sand inundation and hydrodynamic stress. Occupying the lower intertidal zone, P. perna is more strongly influenced by sand (burial and sand in suspension) than M. galioprovincialis. Despite this, P. perna is more vulnerable to the effects of sand, showing higher mortality rates under experimental conditions in both the laboratory and the field. M. galioprovincialis has longer labial palps than P. perna, indicating a better ability to sort particles. This, and a higher tolerance to anoxia, explains its lower mortality rates when exposed to burial or suspended sand. Habitat segregation is often explained by physiological tolerances, but in this case, such explanations fail. The ability of a mussel to withstand wave-generated hydrodynamic stress depends mainly on its byssal attachment strength. The higher attachment strength of P. perna compared to M. galioprovincialis and of solitary mussels compared to mussels living within a bed (bed mussels) can be explained by more and thicker byssal threads. M galloprovincialis also has a wider shell, is subjected to higher hydrodynamic loads than P. perna and shows a higher theoretical probability of dislodgement, this is borne out under field conditions. The attachment strength of both species increased from higher to lower shore, in parallel to a gradient of a stronger wave action. Monthly measurements showed that P. perna is always more strongly attached than M. galloprovincialis and revealed seasonal fluctuations of attachment strength for both species in response to wave height. The gonad index of both species was negatively cross-correlated with attachment strength. The results are discussed in the context of the evolutionary strategy of the alien mussel, which directs most of its energy to fast growth and high reproductive output, apparently at the cost of reduced attachment strength. This raises the prediction that its invasive impact will be more pronounced at sites subjected to low or moderate wave action at heavily exposed sites. The potential of a species for invasion is also determined by the ability of the invader to disperse. Population genetics provide indirect information about dispersal through a direct measurement of gene flow. The low genetic divergence (measured as mtDNA) of M. galloprovincialis confirms its recent arrival in South Africa. In contrast, the population genetics structure of P. perna revealed strong divergence on the south-east coast, resulting in a western lineage (straddling the distributional gap of the Benguela System), and an eastern lineage, with an overlap region of the two on the south coast between Kenton-on-Sea and Haga Haga. This genetic disjunction may be caused by Agulhas Current acting as an oceanographic barrier to larval dispersal, or by different environmental selective forces acting on regional populations. Over the last ten years, M. galloprovincialis has shown a decrease or cessation of its spread to the east in exactly the region of the genetic disjunction in P. perna, again suggesting either an oceanographic barrier to larval dispersal, or increasing selection driven by sharp gradients in environmental conditions.
- Full Text:
- Date Issued: 2006
Complex interactions involving the Cape fig, Ficus sur Forsskål, and its associated insects
- Authors: Zachariades, Costas
- Date: 1995
- Subjects: Insect-plant relationships Mutualism (Biology) Fig -- South Africa Fig wasp -- South Africa Ants Homoptera
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5655 , http://hdl.handle.net/10962/d1005338
- Description: The inadequacy of arbitrarily classifying interactions between species as antagonistic, neutral or mutualistic has become clear in recent years. Both direct and indirect interactions between species can vary between mutualism and antagonism, depending on the intrinsic and extrinsic contexts of the interaction. This study investigated the characteristics of an ant-plant-homopteran interaction in southern Africa. The polyphagous homopteran Hilda patruelis (Tettigometridae) feeds primarily on the trunk-borne fruiting branches and figs of the Cape fig tree, Ficus sur, and produces honeydew which attracts tending ants. Ten of the sixteen ant species/species groups present on F. sur tended H. patruelis, with Pheidole megacephala the most frequent attendant. Ants attracted to F. sur by H. patruelis honeydew or other liquid food sources also preyed on insects on the tree, including adults of the small agaonid fig wasps whose larvae feed on the ovules in the developing figs. One fig wasp species (Ceratosolen capensis) is also the tree's only pollinator. No benefits to H. patruelis from being tended by ants were detected, either in terms of reduced parasitism, or predation by a lycaenid caterpillar. A P. megacephala colony foraging on a F. sur tree was found to receive a high proportion of its likely energy requirements from the tree, mainly in the form of H. patruelis honeydew, during periods when it was bearing fruit. It is probable that the H. patruelis-P. megacephala interaction constitutes a direct mutualism at times, but that benefits to the homopteran are intermittent or weak. Both H. patruelis and ants benefitted from F. sur, directly or indirectly, through the provision of food (and for some ants, nesting sites). The removal of phloem sap by H. patruelis did not detectably reduce the trees' reproductive output, either in terms of pollinator or viable seed production. The indirect effects of ant and H. patruelis presence on the F. sur trees were on average positive, as ants preyed disproportionately heavily on fig wasp species parasitic on or competing with the pollinator, thus increasing pollinator production. Effects of ant presence on seed production were not investigated, but have been demonstrated as beneficial elsewhere. However, there is great varatlon both in the composition of the wasp fauna arriving to oviposit at different crops, and in ant densities per fig, on several temporal and spatial scales. This results in high variability in the effects of ants on the pollinator and, through it, the tree, from positive to zero and potentially even negative. Despite this conditionality of beneficial outcomes for the tree, the mean effect of ants on the F. sur population studied was to increase pollinator production by up to nearly 20%. This study is among the few to have demonstrated an overall benefit to a plant of having homopteran-tending ants present on it.
- Full Text:
- Date Issued: 1995
- Authors: Zachariades, Costas
- Date: 1995
- Subjects: Insect-plant relationships Mutualism (Biology) Fig -- South Africa Fig wasp -- South Africa Ants Homoptera
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5655 , http://hdl.handle.net/10962/d1005338
- Description: The inadequacy of arbitrarily classifying interactions between species as antagonistic, neutral or mutualistic has become clear in recent years. Both direct and indirect interactions between species can vary between mutualism and antagonism, depending on the intrinsic and extrinsic contexts of the interaction. This study investigated the characteristics of an ant-plant-homopteran interaction in southern Africa. The polyphagous homopteran Hilda patruelis (Tettigometridae) feeds primarily on the trunk-borne fruiting branches and figs of the Cape fig tree, Ficus sur, and produces honeydew which attracts tending ants. Ten of the sixteen ant species/species groups present on F. sur tended H. patruelis, with Pheidole megacephala the most frequent attendant. Ants attracted to F. sur by H. patruelis honeydew or other liquid food sources also preyed on insects on the tree, including adults of the small agaonid fig wasps whose larvae feed on the ovules in the developing figs. One fig wasp species (Ceratosolen capensis) is also the tree's only pollinator. No benefits to H. patruelis from being tended by ants were detected, either in terms of reduced parasitism, or predation by a lycaenid caterpillar. A P. megacephala colony foraging on a F. sur tree was found to receive a high proportion of its likely energy requirements from the tree, mainly in the form of H. patruelis honeydew, during periods when it was bearing fruit. It is probable that the H. patruelis-P. megacephala interaction constitutes a direct mutualism at times, but that benefits to the homopteran are intermittent or weak. Both H. patruelis and ants benefitted from F. sur, directly or indirectly, through the provision of food (and for some ants, nesting sites). The removal of phloem sap by H. patruelis did not detectably reduce the trees' reproductive output, either in terms of pollinator or viable seed production. The indirect effects of ant and H. patruelis presence on the F. sur trees were on average positive, as ants preyed disproportionately heavily on fig wasp species parasitic on or competing with the pollinator, thus increasing pollinator production. Effects of ant presence on seed production were not investigated, but have been demonstrated as beneficial elsewhere. However, there is great varatlon both in the composition of the wasp fauna arriving to oviposit at different crops, and in ant densities per fig, on several temporal and spatial scales. This results in high variability in the effects of ants on the pollinator and, through it, the tree, from positive to zero and potentially even negative. Despite this conditionality of beneficial outcomes for the tree, the mean effect of ants on the F. sur population studied was to increase pollinator production by up to nearly 20%. This study is among the few to have demonstrated an overall benefit to a plant of having homopteran-tending ants present on it.
- Full Text:
- Date Issued: 1995
Some adaptations of myrmeleontid (Neuroptera) and rhagionid (Diptera) larvae to life in hot dry sand
- Authors: Youthed, Gayle Jean
- Date: 1974
- Subjects: Ant lions Rhagionidae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5818 , http://hdl.handle.net/10962/d1007228
- Description: From Introduction: Larvae of the families Myrmeleontidae, Neuroptera, (ant-lions) and Rhagionidae, Diptera, (worm-lions) all live in hot dry sand. Many of the ant-lion larvae and all the worm-lion larvae, construct small conical pits in the sand which are used for the capture of prey (Haub, 1942; Youthed and Horan, 1969a). Those ant-lion larvae which do not construct pits lie in wait for their prey just below the surface of the sand.
- Full Text:
- Date Issued: 1974
Some adaptations of myrmeleontid (Neuroptera) and rhagionid (Diptera) larvae to life in hot dry sand
- Authors: Youthed, Gayle Jean
- Date: 1974
- Subjects: Ant lions Rhagionidae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5818 , http://hdl.handle.net/10962/d1007228
- Description: From Introduction: Larvae of the families Myrmeleontidae, Neuroptera, (ant-lions) and Rhagionidae, Diptera, (worm-lions) all live in hot dry sand. Many of the ant-lion larvae and all the worm-lion larvae, construct small conical pits in the sand which are used for the capture of prey (Haub, 1942; Youthed and Horan, 1969a). Those ant-lion larvae which do not construct pits lie in wait for their prey just below the surface of the sand.
- Full Text:
- Date Issued: 1974
Synthetic and bioactivity studies of antiplasmodial and antibacterial marine natural products
- Authors: Young, Ryan Mark
- Date: 2012
- Subjects: Antibacterial agents Marine natural products Marine pharmacology Plasmodium falciparum Staphylococcus aureus Isocyanides Imidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4378 , http://hdl.handle.net/10962/d1005043
- Description: This thesis is divided into two parts, assessing marine and synthetic compounds active firstly against Plasmodium falciparum (Chapter 3 and 4) and secondly active against methicillin resistant Staphylococcus aureus (MRSA, Chapter 5). In Chapter 3 the synthesis of nine new tricyclic podocarpanes (3.203-3.207 and 3.209-3.212) from the diterpene (+)-manool is described. Initial SAR study of synthetic podocarpanes concluded that the most active compound was a C-13 phenyl substituted podocarpane (3.204, IC₅₀ 6.6 μM). By preparing analogues with varying halogenated substituents on the phenyl ring (3.209-3.212) the antiplasmodial activity was improved (IC₅₀ 1.4 μM), while simultaneously decreasing the haemolysis previously reported for this class of compounds. Inspired by the antiplasmodial activity of Wright and Wattanapiromsakul’s tricycle marine isonitriles (2.16-2.21 and 2.24-2.27) an unsuccessfully attempt was made to convert tertiary alcohol moieties to isonitrile functionalities in compounds 3.188, 3.204-3.207 and 3.209-3.212. Over a decade ago Wright et al. proposed a putative antiplasmodial mechanism of action for marine isonitriles (2.4, 2.9, 2.15, 2.19 and 2.35) and isothiocyanate (2.34) which involved interference in haem detoxification by P. falciparum thus inhibiting the growth of the parasite. In Chapter 4 we describe how we successfully managed to scale down Egan’s β-haematin inhibition assay for the analyses of small quantities of marine natural products as potential β-haematin inhibitors. Our modified assay revealed that the most active antiplasmodial marine isonitrile 2.9 (IC₅₀ 13 nM) showed total β-haematin inhibition while 2.15 (IC₅₀ 81 nM) and 2.19 (IC₅₀ 31 nM) showed partial inhibition at three equivalents relative to haem. Using contempary molecular modelling techniques the charge on the isonitrile functionality was more accurately describe and the modified charge data sets was used to explore docking of marine isonitriles to haem using AutoDock. In Chapter 5 we describe how a lead South African marine bisindole MRSA pyruvate kinase inhibitor (5.8) was discovered in collaboration with colleagues at the University of British Columbia (UBC) and how this discovery inspired us to design a synthetic route to the dibrominated bisindole, isobromotopsentin (5.20) in an attempt to increase the bioactivity displayed by 5.8. We devised a fast and high yielding synthetic route using microwave assited organic synthesis. We first tested this synthesis using simple aryl glyoxals (5.27-5.32) as precursors to synthesize biphenylimidazoles (5.21-5.26), which later allowed us to synthesize the ascidian natural product 5.111. This method was sucessfully extended to the synthesis of deoxytopsentin (5.33) from an N-Boc protected indole methyl ketone (5.89). We subsequently were able to effectively remove the carbamate protection via thermal decomposition by heating the protected bisindole imidazole (5.90) in a microwave reactor for 5 min under argon. The synthesis of 5.20 resulted in an inseparable mixture of monoprotected and totally deprotected topsentin products, and due to time constraints we were not able to optimise this synthesis. Nonetheless our synthesis of the marine natural product 5.33 which was faster and higher yielding than previously reported routes could be extended to the synthesis of other topsentin bisindoles (5.138-5.140). Work towards this goal continues in our laboratory.
- Full Text:
- Date Issued: 2012
- Authors: Young, Ryan Mark
- Date: 2012
- Subjects: Antibacterial agents Marine natural products Marine pharmacology Plasmodium falciparum Staphylococcus aureus Isocyanides Imidazoles
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4378 , http://hdl.handle.net/10962/d1005043
- Description: This thesis is divided into two parts, assessing marine and synthetic compounds active firstly against Plasmodium falciparum (Chapter 3 and 4) and secondly active against methicillin resistant Staphylococcus aureus (MRSA, Chapter 5). In Chapter 3 the synthesis of nine new tricyclic podocarpanes (3.203-3.207 and 3.209-3.212) from the diterpene (+)-manool is described. Initial SAR study of synthetic podocarpanes concluded that the most active compound was a C-13 phenyl substituted podocarpane (3.204, IC₅₀ 6.6 μM). By preparing analogues with varying halogenated substituents on the phenyl ring (3.209-3.212) the antiplasmodial activity was improved (IC₅₀ 1.4 μM), while simultaneously decreasing the haemolysis previously reported for this class of compounds. Inspired by the antiplasmodial activity of Wright and Wattanapiromsakul’s tricycle marine isonitriles (2.16-2.21 and 2.24-2.27) an unsuccessfully attempt was made to convert tertiary alcohol moieties to isonitrile functionalities in compounds 3.188, 3.204-3.207 and 3.209-3.212. Over a decade ago Wright et al. proposed a putative antiplasmodial mechanism of action for marine isonitriles (2.4, 2.9, 2.15, 2.19 and 2.35) and isothiocyanate (2.34) which involved interference in haem detoxification by P. falciparum thus inhibiting the growth of the parasite. In Chapter 4 we describe how we successfully managed to scale down Egan’s β-haematin inhibition assay for the analyses of small quantities of marine natural products as potential β-haematin inhibitors. Our modified assay revealed that the most active antiplasmodial marine isonitrile 2.9 (IC₅₀ 13 nM) showed total β-haematin inhibition while 2.15 (IC₅₀ 81 nM) and 2.19 (IC₅₀ 31 nM) showed partial inhibition at three equivalents relative to haem. Using contempary molecular modelling techniques the charge on the isonitrile functionality was more accurately describe and the modified charge data sets was used to explore docking of marine isonitriles to haem using AutoDock. In Chapter 5 we describe how a lead South African marine bisindole MRSA pyruvate kinase inhibitor (5.8) was discovered in collaboration with colleagues at the University of British Columbia (UBC) and how this discovery inspired us to design a synthetic route to the dibrominated bisindole, isobromotopsentin (5.20) in an attempt to increase the bioactivity displayed by 5.8. We devised a fast and high yielding synthetic route using microwave assited organic synthesis. We first tested this synthesis using simple aryl glyoxals (5.27-5.32) as precursors to synthesize biphenylimidazoles (5.21-5.26), which later allowed us to synthesize the ascidian natural product 5.111. This method was sucessfully extended to the synthesis of deoxytopsentin (5.33) from an N-Boc protected indole methyl ketone (5.89). We subsequently were able to effectively remove the carbamate protection via thermal decomposition by heating the protected bisindole imidazole (5.90) in a microwave reactor for 5 min under argon. The synthesis of 5.20 resulted in an inseparable mixture of monoprotected and totally deprotected topsentin products, and due to time constraints we were not able to optimise this synthesis. Nonetheless our synthesis of the marine natural product 5.33 which was faster and higher yielding than previously reported routes could be extended to the synthesis of other topsentin bisindoles (5.138-5.140). Work towards this goal continues in our laboratory.
- Full Text:
- Date Issued: 2012
Aspects of condition in captive and free-ranging dolphins
- Authors: Young, Deborah Dione
- Date: 1999
- Subjects: Dolphins -- Physiology Dolphins -- Behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5799 , http://hdl.handle.net/10962/d1006117
- Description: Aspects of morphological and physiological condition of captive and net-caught dolphins were studied with respect to age, diet, reproduction and seasonal changes in environmental factors. These investigations aimed to provide base-line data on marine mammal physiological and morphological condition indices and to expand the knowledge of condition assessment of small cetaceans. By examining the interactive nature of animal condition and growth, diet and the environment, the study investigated the potential usefulness of animal condition indices to assess and monitor habitat quality. Base-line values for haematological and blood chemistry parameters were established for five captive bottlenose dolphins (Tursiops truncatus), using monthly blood samples, collected between 1992 and 1995, and corresponding measures of body weight and blubber thickness; feeding, dietary energy intake, water temperature and behavioural and medical records. Curves of best fit were used to interpret trends between leukocytic, haematological and blood chemistry parameters and morphology, diet and water temperature. WBC's and WBC differential cell types were related more distinctly to clinical changes in health, than to condition. RBC, HB and PCV were useful as short-term indicators of nutritional condition, with enhanced haematological status associated with greater food intake and improved diet quality. Weight was a more effective long-term indicator of nutritional status. The importance of blubber thickness measurements as a morphological index of condition was reinforced, with relationships between blubber thickness and haematology highlighting interactions between morphological and physiological condition. The complex interactions between haematology, diet, temperature and weight emphasised the need to account for all influential factors when considering haematological condition. The blood chemistry parameters of serum creatinine, BUN, BUN:creatinine and serum albumin provided the best indication of nutritional condition and diet quality in captive dolphins. Creatinine and BUN:creatinine also reflected changes in morphological condition. Reduced ALP was associated with nutritional stress but was more effectively used as an indication of metabolism and growth activity. LDH and CPK were highly variable and fluctuated with changing activity levels, limiting their use as condition indices. Serum sodium was an important indication of diet quality and hydration status. Many of these parameters effectively illustrated that physiological condition is compromised outside of the thermoneutral zone of the species. Bottlenose and common (Delphinus delphis) dolphins, incidentally caught in shark nets, were used to investigate the condition of free-ranging dolphins. Blood samples, taken as soon as possible after capture from drowned animals, were used to analyse physiological parameters. Dissections provided morphological data. Age and dietary status were assessed using growth layer groups in teeth and stomach content analyses, respectively. Morphological measures of net-caught dolphins reflected important interactions with diet, water temperature and reproductive status. Weight, girth and blubber thickness were valuable indicators of condition, although blubber thickness and proportional blubber weight were the best indicators of nutritional status. Condition of net-caught dolphins was difficult to assess in terms of leukocytic and haematological parameters. Stress- and post-mortem-associated changes, and variable data, reduced the usefulness of some parameters. WBC counts reflected on immunological status and served to emphasise changes in health, which may lead to deterioration in condition. WBC's showed potential as indicators of habitat quality, in terms of parasite load and/or pollution. Interactions between RBC, HB, PCV, MCV and dietary, morphological and environmental factors proved valuable in the short-term. Several haematological parameters were related to morphological condition, with weight, girth and blubber thickness, showing potential as non-invasive predictors of haematological status. Relationships between haematology and water temperature implied that dolphins have physiological and environmental "zones of comfort", within which condition is optimised. LDH and CPK were elevated by capture stress and post-mortem changes. Serum sodium and plasma glucose were good indicators of short-term nutritional status, but were altered by stress, which reduced their usefulness as condition indicators. BUN, albumin, globulin, albumin:globulin, total cholesterol and triglycerides appeared to be little affected by these changes and are potentially valuable indicators of condition in net-caught and/or free-ranging dolphins, particularly with respect to nutritional condition, and associated changes in morphology. Although data were limited, these parameters show the greatest potential as physiological indicators of animal condition and environmental health. The limitations of this study are recognised, however, results highlight the feasibility of using net-caught specimens to monitor the condition of free-ranging marine mammals, and the marine habitat as a whole. Relationships established in this study will be used to elucidate further on the interactive nature of marine mammal condition and aid in the development of a non-invasive condition assessment technique.
- Full Text:
- Date Issued: 1999
- Authors: Young, Deborah Dione
- Date: 1999
- Subjects: Dolphins -- Physiology Dolphins -- Behavior
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5799 , http://hdl.handle.net/10962/d1006117
- Description: Aspects of morphological and physiological condition of captive and net-caught dolphins were studied with respect to age, diet, reproduction and seasonal changes in environmental factors. These investigations aimed to provide base-line data on marine mammal physiological and morphological condition indices and to expand the knowledge of condition assessment of small cetaceans. By examining the interactive nature of animal condition and growth, diet and the environment, the study investigated the potential usefulness of animal condition indices to assess and monitor habitat quality. Base-line values for haematological and blood chemistry parameters were established for five captive bottlenose dolphins (Tursiops truncatus), using monthly blood samples, collected between 1992 and 1995, and corresponding measures of body weight and blubber thickness; feeding, dietary energy intake, water temperature and behavioural and medical records. Curves of best fit were used to interpret trends between leukocytic, haematological and blood chemistry parameters and morphology, diet and water temperature. WBC's and WBC differential cell types were related more distinctly to clinical changes in health, than to condition. RBC, HB and PCV were useful as short-term indicators of nutritional condition, with enhanced haematological status associated with greater food intake and improved diet quality. Weight was a more effective long-term indicator of nutritional status. The importance of blubber thickness measurements as a morphological index of condition was reinforced, with relationships between blubber thickness and haematology highlighting interactions between morphological and physiological condition. The complex interactions between haematology, diet, temperature and weight emphasised the need to account for all influential factors when considering haematological condition. The blood chemistry parameters of serum creatinine, BUN, BUN:creatinine and serum albumin provided the best indication of nutritional condition and diet quality in captive dolphins. Creatinine and BUN:creatinine also reflected changes in morphological condition. Reduced ALP was associated with nutritional stress but was more effectively used as an indication of metabolism and growth activity. LDH and CPK were highly variable and fluctuated with changing activity levels, limiting their use as condition indices. Serum sodium was an important indication of diet quality and hydration status. Many of these parameters effectively illustrated that physiological condition is compromised outside of the thermoneutral zone of the species. Bottlenose and common (Delphinus delphis) dolphins, incidentally caught in shark nets, were used to investigate the condition of free-ranging dolphins. Blood samples, taken as soon as possible after capture from drowned animals, were used to analyse physiological parameters. Dissections provided morphological data. Age and dietary status were assessed using growth layer groups in teeth and stomach content analyses, respectively. Morphological measures of net-caught dolphins reflected important interactions with diet, water temperature and reproductive status. Weight, girth and blubber thickness were valuable indicators of condition, although blubber thickness and proportional blubber weight were the best indicators of nutritional status. Condition of net-caught dolphins was difficult to assess in terms of leukocytic and haematological parameters. Stress- and post-mortem-associated changes, and variable data, reduced the usefulness of some parameters. WBC counts reflected on immunological status and served to emphasise changes in health, which may lead to deterioration in condition. WBC's showed potential as indicators of habitat quality, in terms of parasite load and/or pollution. Interactions between RBC, HB, PCV, MCV and dietary, morphological and environmental factors proved valuable in the short-term. Several haematological parameters were related to morphological condition, with weight, girth and blubber thickness, showing potential as non-invasive predictors of haematological status. Relationships between haematology and water temperature implied that dolphins have physiological and environmental "zones of comfort", within which condition is optimised. LDH and CPK were elevated by capture stress and post-mortem changes. Serum sodium and plasma glucose were good indicators of short-term nutritional status, but were altered by stress, which reduced their usefulness as condition indicators. BUN, albumin, globulin, albumin:globulin, total cholesterol and triglycerides appeared to be little affected by these changes and are potentially valuable indicators of condition in net-caught and/or free-ranging dolphins, particularly with respect to nutritional condition, and associated changes in morphology. Although data were limited, these parameters show the greatest potential as physiological indicators of animal condition and environmental health. The limitations of this study are recognised, however, results highlight the feasibility of using net-caught specimens to monitor the condition of free-ranging marine mammals, and the marine habitat as a whole. Relationships established in this study will be used to elucidate further on the interactive nature of marine mammal condition and aid in the development of a non-invasive condition assessment technique.
- Full Text:
- Date Issued: 1999
Navigating Blackness in the African Diaspora
- Authors: Yates, Sarah
- Date: 2020
- Subjects: Ellison, Ralph. Invisible man , Everett, Percival. Erasure , Wicomb, Zoe. Playing in the light , Bulawayo, NoViolet. We need new names , Africans in literature , Race in literature , African fiction (English) -- History and criticism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/145720 , vital:38461
- Description: This thesis offers a comparative reading of Ralph Ellison’s Invisible Man, Percival Everett’s Erasure, Zoë Wicomb’s Playing in the Light and NoViolet Bulawayo’s We Need New Names in order to explore the diversity of subjectivities included within the terms ‘African’ and ‘black’ and to argue for the necessity of renewed definitions of Africa(nness) and blackness which allow for diverse and fluid representations. The diverse historical and political contexts in which these novels are published, as well as the critical and theoretical discussions which surround them demonstrate an evolution in literary portrayals of identity politics. As the categories of race and nation become more fluid, so too do narrative forms. In particular, this thesis is interested in the textual strategies authors use to navigate the various ways in which depictions of blackness continue to be restricted by racism, stereotypes, and the dynamics of a global literary market. As portrayals and discussions of identity politics proliferate in popular culture, they become increasingly commodified, and therefore increasingly restricted by the market.
- Full Text:
- Date Issued: 2020
- Authors: Yates, Sarah
- Date: 2020
- Subjects: Ellison, Ralph. Invisible man , Everett, Percival. Erasure , Wicomb, Zoe. Playing in the light , Bulawayo, NoViolet. We need new names , Africans in literature , Race in literature , African fiction (English) -- History and criticism
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/145720 , vital:38461
- Description: This thesis offers a comparative reading of Ralph Ellison’s Invisible Man, Percival Everett’s Erasure, Zoë Wicomb’s Playing in the Light and NoViolet Bulawayo’s We Need New Names in order to explore the diversity of subjectivities included within the terms ‘African’ and ‘black’ and to argue for the necessity of renewed definitions of Africa(nness) and blackness which allow for diverse and fluid representations. The diverse historical and political contexts in which these novels are published, as well as the critical and theoretical discussions which surround them demonstrate an evolution in literary portrayals of identity politics. As the categories of race and nation become more fluid, so too do narrative forms. In particular, this thesis is interested in the textual strategies authors use to navigate the various ways in which depictions of blackness continue to be restricted by racism, stereotypes, and the dynamics of a global literary market. As portrayals and discussions of identity politics proliferate in popular culture, they become increasingly commodified, and therefore increasingly restricted by the market.
- Full Text:
- Date Issued: 2020
Access to land as a human right the payment of just and equitable compensation for dispossessed land in South Africa
- Authors: Yanou, Michael A
- Date: 2005
- Subjects: Human rights -- South Africa , Compensation (Law) -- South Africa , Right of property -- South Africa , Land reform -- South Africa , Land tenure -- South Africa , Constitutional history -- South Africa , Restitution -- South Africa , Land tenure -- Law and legislation -- South Africa , Land reform -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3699 , http://hdl.handle.net/10962/d1003214 , Human rights -- South Africa , Compensation (Law) -- South Africa , Right of property -- South Africa , Land reform -- South Africa , Land tenure -- South Africa , Constitutional history -- South Africa , Restitution -- South Africa , Land tenure -- Law and legislation -- South Africa , Land reform -- Law and legislation -- South Africa
- Description: This thesis deals with the conceptualization of access to land by the dispossessed as a human right and commences with an account of the struggle for land between the peoples of African and European extractions in South Africa. It is observed that the latter assumed sovereignty over the ancestral lands of the former. The thesis discusses the theoretical foundation of the study and situates the topic within its conceptual parameters. The writer examines the notions of justice and equity in the context of the post apartheid constitutional mandate to redress the skewed policy of the past. It is argued that the dispossession of Africans from lands that they had possessed for thousands of years on the assumption that the land was terra nullius was profoundly iniquitous and unjust. Although the study is technically limited to dispossessions occurring on or after the 13th June 1913, it covers a fairly extensive account of dispossession predating this date. This historical analysis is imperative for two reasons. Besides supporting the writer’s contention that the limitation of restitution to land dispossessed on or after 1913 was arbitrary, it also highlights both the material and non-material cost of the devastating wars of dispossessions. The candidate comments extensively on the post apartheid constitutional property structure which was conceived as a redress to the imbalance created by dispossession. This underlying objective explains why the state’s present land policy is geared towards facilitating access to land for the landless. The thesis investigates the extent to which the present property structure which defines access to land as a human right has succeeded in achieving the stated objective. It reviews the strengths and weaknesses of the land restitution process as well as the question of the payment of just and equitable compensation for land expropriated for restitution. The latter was carefully examined because it plays a crucial role in the success or otherwise of the restitution scheme. The writer argues that the courts have, on occasions, construed just and equitable compensation generously. This approach has failed to reflect the moral component inherent in the Aristotelian corrective justice. This, in the context of South Africa, requires compensation to reflect the fact that what is being paid for is land dispossessed from the forebears of indigenous inhabitants. It seems obvious that the scales of justice are tilted heavily in favour of the propertied class whose ancestors were responsible for this dispossession. This has a ripple effect on the pace of the restitution process. It also seems to have the effect of favouring the property class at the expense of the entire restitution process. The candidate also comments on the court’s differing approaches to the interpretation of the constitutional property clause. The candidate contends that the construction of the property clause and related pieces of legislation in a manner that stresses the maintenance of a balance between private property interest and land reform is flawed. This contention is supported by the fact that these values do not have proportional worth in the present property context of South Africa. The narrow definition of “past racially discriminatory law and practices” and labour tenant as used in the relevant post apartheid land reform laws is criticized for the same reason of its uncontextual approach. A comparative appraisal of similar developments relating to property law in other societies like India and Zimbabwe has been done. The writer has treated the post reform land evictions as a form of dispossession. The candidate notes that the country should guard against allowing the disastrous developments in Zimbabwe to influence events in the country and calls for an amendment of the property clause of the constitution in response to the practical difficulties which a decade of the operation of the current constitution has revealed.
- Full Text:
- Date Issued: 2005
- Authors: Yanou, Michael A
- Date: 2005
- Subjects: Human rights -- South Africa , Compensation (Law) -- South Africa , Right of property -- South Africa , Land reform -- South Africa , Land tenure -- South Africa , Constitutional history -- South Africa , Restitution -- South Africa , Land tenure -- Law and legislation -- South Africa , Land reform -- Law and legislation -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3699 , http://hdl.handle.net/10962/d1003214 , Human rights -- South Africa , Compensation (Law) -- South Africa , Right of property -- South Africa , Land reform -- South Africa , Land tenure -- South Africa , Constitutional history -- South Africa , Restitution -- South Africa , Land tenure -- Law and legislation -- South Africa , Land reform -- Law and legislation -- South Africa
- Description: This thesis deals with the conceptualization of access to land by the dispossessed as a human right and commences with an account of the struggle for land between the peoples of African and European extractions in South Africa. It is observed that the latter assumed sovereignty over the ancestral lands of the former. The thesis discusses the theoretical foundation of the study and situates the topic within its conceptual parameters. The writer examines the notions of justice and equity in the context of the post apartheid constitutional mandate to redress the skewed policy of the past. It is argued that the dispossession of Africans from lands that they had possessed for thousands of years on the assumption that the land was terra nullius was profoundly iniquitous and unjust. Although the study is technically limited to dispossessions occurring on or after the 13th June 1913, it covers a fairly extensive account of dispossession predating this date. This historical analysis is imperative for two reasons. Besides supporting the writer’s contention that the limitation of restitution to land dispossessed on or after 1913 was arbitrary, it also highlights both the material and non-material cost of the devastating wars of dispossessions. The candidate comments extensively on the post apartheid constitutional property structure which was conceived as a redress to the imbalance created by dispossession. This underlying objective explains why the state’s present land policy is geared towards facilitating access to land for the landless. The thesis investigates the extent to which the present property structure which defines access to land as a human right has succeeded in achieving the stated objective. It reviews the strengths and weaknesses of the land restitution process as well as the question of the payment of just and equitable compensation for land expropriated for restitution. The latter was carefully examined because it plays a crucial role in the success or otherwise of the restitution scheme. The writer argues that the courts have, on occasions, construed just and equitable compensation generously. This approach has failed to reflect the moral component inherent in the Aristotelian corrective justice. This, in the context of South Africa, requires compensation to reflect the fact that what is being paid for is land dispossessed from the forebears of indigenous inhabitants. It seems obvious that the scales of justice are tilted heavily in favour of the propertied class whose ancestors were responsible for this dispossession. This has a ripple effect on the pace of the restitution process. It also seems to have the effect of favouring the property class at the expense of the entire restitution process. The candidate also comments on the court’s differing approaches to the interpretation of the constitutional property clause. The candidate contends that the construction of the property clause and related pieces of legislation in a manner that stresses the maintenance of a balance between private property interest and land reform is flawed. This contention is supported by the fact that these values do not have proportional worth in the present property context of South Africa. The narrow definition of “past racially discriminatory law and practices” and labour tenant as used in the relevant post apartheid land reform laws is criticized for the same reason of its uncontextual approach. A comparative appraisal of similar developments relating to property law in other societies like India and Zimbabwe has been done. The writer has treated the post reform land evictions as a form of dispossession. The candidate notes that the country should guard against allowing the disastrous developments in Zimbabwe to influence events in the country and calls for an amendment of the property clause of the constitution in response to the practical difficulties which a decade of the operation of the current constitution has revealed.
- Full Text:
- Date Issued: 2005
Studies on mixed-species colonies of honeybees, Apis cerana and Apis mellifera
- Authors: Yang, Ming-Xian
- Date: 2010
- Subjects: Bees Apis cerana Honeybee Honeybee -- Behavior Bee culture Honeybee -- Physiology Insect societies Animal communication Bees -- Nests
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5779 , http://hdl.handle.net/10962/d1005467
- Description: The honeybees Apis cerana and Apis mellifera are derived from the same ancestral base about two million years ago. With speciation and evolution, they have acquired many advanced living skills in common, but have also evolved very different living strategies due to different distributions. This thesis is an intensive study of the biology of the mixed-species colonies of these species, the aims of which were to investigate their behavioural relationships and uncover the evolutionary conserved features of their behaviours subsequent to speciation. The results show that the two species can form a stable society to perform normal tasks. First, workers of both species in the mixed-colonies could form the typical retinue behaviour to hetero-species queens, thus indicating that queen pheromones could be spread to and by both species. Secondly, both species did not show significantly different ovarian activation under hetero-species queens, suggesting that the queen pheromones more likely play a role of "honest signal" rather than a "repression" substance in the honeybee colonies. Thirdly, both species could mutually decode each other‘s waggle dances, with unexpectedly low misunderstanding; revealing that the dance language in a dark environment is quite adaptive for cavity-nesting honeybees. Fourthly, workers of both species could cooperate with each other in comb construction, although the combs they built contain many irregular cells. Interestingly, A. cerana workers could be stimulated by A. mellifera workers to perform this task, thus confirming self-organization theory in the colony. Fifthly, A. mellifera workers behaved more "defectively" in thermoregulation, but perhaps because A. cerana workers are more sensitive to changes in hive temperature. Given these differences in strategy, A. mellifera workers‘ performance might in fact reduce conflicts. Lastly, when faced with threats of predatory wasps, both species engaged in aggressive defence. Although they did not learn from each other‘s responses, species-specific strategies were adopted by each of them so that the defence of the mixed-colonies is very effective. I conclude that the two species can adapt to each other‘s efforts and task allocation is reasonably organized allowing mixed-species colonies to reach stability. These results suggest that all of the social behaviours discussed here were highly conserved following speciation. This thesis could provide some clues for the study of honeybee evolution from open-nesting to the transition of cavity-nesting.
- Full Text:
- Date Issued: 2010
- Authors: Yang, Ming-Xian
- Date: 2010
- Subjects: Bees Apis cerana Honeybee Honeybee -- Behavior Bee culture Honeybee -- Physiology Insect societies Animal communication Bees -- Nests
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5779 , http://hdl.handle.net/10962/d1005467
- Description: The honeybees Apis cerana and Apis mellifera are derived from the same ancestral base about two million years ago. With speciation and evolution, they have acquired many advanced living skills in common, but have also evolved very different living strategies due to different distributions. This thesis is an intensive study of the biology of the mixed-species colonies of these species, the aims of which were to investigate their behavioural relationships and uncover the evolutionary conserved features of their behaviours subsequent to speciation. The results show that the two species can form a stable society to perform normal tasks. First, workers of both species in the mixed-colonies could form the typical retinue behaviour to hetero-species queens, thus indicating that queen pheromones could be spread to and by both species. Secondly, both species did not show significantly different ovarian activation under hetero-species queens, suggesting that the queen pheromones more likely play a role of "honest signal" rather than a "repression" substance in the honeybee colonies. Thirdly, both species could mutually decode each other‘s waggle dances, with unexpectedly low misunderstanding; revealing that the dance language in a dark environment is quite adaptive for cavity-nesting honeybees. Fourthly, workers of both species could cooperate with each other in comb construction, although the combs they built contain many irregular cells. Interestingly, A. cerana workers could be stimulated by A. mellifera workers to perform this task, thus confirming self-organization theory in the colony. Fifthly, A. mellifera workers behaved more "defectively" in thermoregulation, but perhaps because A. cerana workers are more sensitive to changes in hive temperature. Given these differences in strategy, A. mellifera workers‘ performance might in fact reduce conflicts. Lastly, when faced with threats of predatory wasps, both species engaged in aggressive defence. Although they did not learn from each other‘s responses, species-specific strategies were adopted by each of them so that the defence of the mixed-colonies is very effective. I conclude that the two species can adapt to each other‘s efforts and task allocation is reasonably organized allowing mixed-species colonies to reach stability. These results suggest that all of the social behaviours discussed here were highly conserved following speciation. This thesis could provide some clues for the study of honeybee evolution from open-nesting to the transition of cavity-nesting.
- Full Text:
- Date Issued: 2010
The impact of land restitution and resettlement in the Eastern Cape, South Africa: restoring dignity without strengthening livelihoods?
- Authors: Xaba, Mzingaye Brilliant
- Date: 2019
- Subjects: Reparations for historic injustices -- South Africa , Land reform -- Law and legislation -- South Africa , Land reform -- South Africa -- Social aspects , Agricultural development projects -- South Africa -- Social aspects , Land tenure -- Law and legislation -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/96336 , vital:31264
- Description: Land reform in South Africa, which is comprised of land redistribution, land tenure reform, and land restitution, continues to be an emotive subject and has largely racially polarised South Africa. The slow pace of land reform, expropriation, the amount of land to be returned to black people, debates around the role of the Constitution in land reform, the market-based approach and the perceived negative attitude of white farmers have dominated the debates on land reform. There is, therefore, a huge chorus on the struggles for land acquisition and less on what happens when people are given land. A few studies on post-settlement livelihoods experience have managed to close this gap slightly in the literature by showing that land reform has contributed little or no material and livelihood benefits to beneficiaries and that many farms are lying idle after land reform, especially land restitution, projects. These studies on post-settlement livelihoods experiences of land reform beneficiaries have not managed to capture fully the “voices” of beneficiaries on land and livelihoods. This dissertation seeks to provide a sociological documentation of the post-settlement livelihood experiences of land restitution beneficiaries. It does this by primarily tracing the ability and/or the inability of land restitution beneficiaries of Macleantown, about 40 kilometres northwest of East London, in the Eastern Cape to reconstruct livelihoods after resettlement, bearing in mind that these land restitution beneficiaries have been resettled twice, during forced removals in the 1970s and after land restitution, post-1994. Therefore, the study engages with questions of whether or in what ways land compensated restitution beneficiaries have managed to reconstruct livelihoods after land transfer. To capture the livelihood experiences of land restitution beneficiaries fully, I also studied the Salem restitution case, which is 20km away from Grahamstown in the Eastern Cape. Because land restitution involves resettlement, I decided to use two resettlement theories, namely Thayer Scudder’s four stages model and Michael Cernea’s Impoverishment Risks and Reconstruction (IRR), to understand risks associated with resettlement. Additionally, since this dissertation seeks to understand and document livelihood reconstruction and poverty reduction within the context of restitution resettlement, I also utilised the Sustainable Livelihoods approach and Amartya Sen’s capabilities approach. This thesis is based on multiple research methods that include documentary study, focus group discussions, conversations, archival research, in-depth interviews, transect walks, participant observation and life histories. My findings show that land transfer under the land restitution programme has largely not enabled land beneficiaries in Macleantown and Salem to reconstruct land-based livelihoods after settlement. I also established that land restitution beneficiaries face risks that are identified by resettlement theorists such as lack of proper planning, resettling trauma, struggles in community reconstruction and poverty. Beneficiaries have not managed to reap any meaningful benefits from the land, meaning that restitution has not led to self-sufficiency for these beneficiaries because all land beneficiaries are heavily dependent on social grants. However, one needs to emphasize that land restitution has restored the dignity of beneficiaries because beneficiaries have accessed their forefathers’ land that they fought for. This is because beneficiaries believed that it was their duty to fight for their land on behalf of their ancestors. I reach the conclusion that the whole idea that restitution claimants who are scattered all over can be grouped into a Community Property Association (CPA) and farm collectively as a ‘community’ to improve livelihoods is a misleading romanticisation of the envisaged outcomes of the land restitution project. Time has passed after land dispossession and land claimants are different human beings to what they were before land dispossession, i.e. far from the agrarian society they were before land dispossession. Group dynamics, lack of adequate post-settlement support (PSS), land reform designs, lack of commercial agricultural skills, as well as entitlement syndrome, old age of beneficiaries, infighting and marginality of agricultural business has made it nearly impossible for restitution beneficiaries to reconstruct land-based livelihoods. Additionally, the government appears to be more interested in ‘correcting apartheid’ rather than creating viable farms. It is important to state that this thesis does not advocate for the erasure of the restitution programme or to belittle land beneficiaries but argues for the rethinking of the restitution model in the context of massive failures, as well as coming up with a new and flexible model of land restitution that will meet the modern needs of beneficiaries. This thesis contributes to an understanding of the risks and the challenges of livelihoods reconstruction faced by resettling communities through an investigation into the post-settlement livelihoods experiences of land restitution beneficiaries through ‘thick descriptions’.
- Full Text:
- Date Issued: 2019
- Authors: Xaba, Mzingaye Brilliant
- Date: 2019
- Subjects: Reparations for historic injustices -- South Africa , Land reform -- Law and legislation -- South Africa , Land reform -- South Africa -- Social aspects , Agricultural development projects -- South Africa -- Social aspects , Land tenure -- Law and legislation -- South Africa
- Language: English
- Type: text , Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/96336 , vital:31264
- Description: Land reform in South Africa, which is comprised of land redistribution, land tenure reform, and land restitution, continues to be an emotive subject and has largely racially polarised South Africa. The slow pace of land reform, expropriation, the amount of land to be returned to black people, debates around the role of the Constitution in land reform, the market-based approach and the perceived negative attitude of white farmers have dominated the debates on land reform. There is, therefore, a huge chorus on the struggles for land acquisition and less on what happens when people are given land. A few studies on post-settlement livelihoods experience have managed to close this gap slightly in the literature by showing that land reform has contributed little or no material and livelihood benefits to beneficiaries and that many farms are lying idle after land reform, especially land restitution, projects. These studies on post-settlement livelihoods experiences of land reform beneficiaries have not managed to capture fully the “voices” of beneficiaries on land and livelihoods. This dissertation seeks to provide a sociological documentation of the post-settlement livelihood experiences of land restitution beneficiaries. It does this by primarily tracing the ability and/or the inability of land restitution beneficiaries of Macleantown, about 40 kilometres northwest of East London, in the Eastern Cape to reconstruct livelihoods after resettlement, bearing in mind that these land restitution beneficiaries have been resettled twice, during forced removals in the 1970s and after land restitution, post-1994. Therefore, the study engages with questions of whether or in what ways land compensated restitution beneficiaries have managed to reconstruct livelihoods after land transfer. To capture the livelihood experiences of land restitution beneficiaries fully, I also studied the Salem restitution case, which is 20km away from Grahamstown in the Eastern Cape. Because land restitution involves resettlement, I decided to use two resettlement theories, namely Thayer Scudder’s four stages model and Michael Cernea’s Impoverishment Risks and Reconstruction (IRR), to understand risks associated with resettlement. Additionally, since this dissertation seeks to understand and document livelihood reconstruction and poverty reduction within the context of restitution resettlement, I also utilised the Sustainable Livelihoods approach and Amartya Sen’s capabilities approach. This thesis is based on multiple research methods that include documentary study, focus group discussions, conversations, archival research, in-depth interviews, transect walks, participant observation and life histories. My findings show that land transfer under the land restitution programme has largely not enabled land beneficiaries in Macleantown and Salem to reconstruct land-based livelihoods after settlement. I also established that land restitution beneficiaries face risks that are identified by resettlement theorists such as lack of proper planning, resettling trauma, struggles in community reconstruction and poverty. Beneficiaries have not managed to reap any meaningful benefits from the land, meaning that restitution has not led to self-sufficiency for these beneficiaries because all land beneficiaries are heavily dependent on social grants. However, one needs to emphasize that land restitution has restored the dignity of beneficiaries because beneficiaries have accessed their forefathers’ land that they fought for. This is because beneficiaries believed that it was their duty to fight for their land on behalf of their ancestors. I reach the conclusion that the whole idea that restitution claimants who are scattered all over can be grouped into a Community Property Association (CPA) and farm collectively as a ‘community’ to improve livelihoods is a misleading romanticisation of the envisaged outcomes of the land restitution project. Time has passed after land dispossession and land claimants are different human beings to what they were before land dispossession, i.e. far from the agrarian society they were before land dispossession. Group dynamics, lack of adequate post-settlement support (PSS), land reform designs, lack of commercial agricultural skills, as well as entitlement syndrome, old age of beneficiaries, infighting and marginality of agricultural business has made it nearly impossible for restitution beneficiaries to reconstruct land-based livelihoods. Additionally, the government appears to be more interested in ‘correcting apartheid’ rather than creating viable farms. It is important to state that this thesis does not advocate for the erasure of the restitution programme or to belittle land beneficiaries but argues for the rethinking of the restitution model in the context of massive failures, as well as coming up with a new and flexible model of land restitution that will meet the modern needs of beneficiaries. This thesis contributes to an understanding of the risks and the challenges of livelihoods reconstruction faced by resettling communities through an investigation into the post-settlement livelihoods experiences of land restitution beneficiaries through ‘thick descriptions’.
- Full Text:
- Date Issued: 2019
The archival turn: rereading the Guy Butler Collection in the National English Literary Museum
- Authors: Wyrill, Beth
- Date: 2020
- Subjects: National English Literary Museum (South Africa) , Butler, Guy, 1918-2001 , Archives -- South Africa , Archives -- Philosophy , Memory (Philosophy)
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10962/145746 , vital:38463
- Description: This thesis takes as its theoretical springboard the ‘archival turn’ in South African historical studies, a moment that arguably reached its culmination in 2002 with the publication of Refiguring the Archive. The archival turn posits that, rather than using it as an unproblematic source of original material, scholars might begin to investigate the archive itself, including its processes of construction and organisation. This theoretical model also proposes that the archive might reflect the cultural beliefs and epistemologies common to the era in which it was set up. It seems that the time is ripe for a reconsideration of the insights gleaned from this academic moment in South Africa, given the recent contestation over the meanings of history and our cultural markers of heritage in the public domain, largely grouped under the term ‘Fallism.’ As such, a fresh look at South African museums, which in this country are often rooted in colonial practices of knowledge production, seems apt. This work uses the case of Guy Butler, founder of many South African English cultural institutes and arts bodies, as a conduit and lens for thinking through these problematics. One of Butler’s institutional ‘offspring,’ born from his overarching work on behalf of the English cultural and literary cause in South Africa in the twentieth century, is the National English Literary Museum (NELM). Investigating the founding context and practices of NELM is a useful way of exploring the impact of Butler’s life’s work on literary heritage in South Africa. Issues such as the way in which NELM and Grahamstown continue to signify as loci of thought and practice in the contemporary South African literary landscape will be addressed. The study draws extensively on the Butler collection at NELM, and spends much time investigating Butler’s positioning in a South African literary historical context in the twentieth century, to better understand the forces at work during the time of NELM’s coming-into-being. Derrida’s seminal work on the function of archives, in Archive Fever, is mined for a theoretical basis for the study, as is Deleuze and Guattari’s thought on how bodies (taking the NELM institution here to represent a ‘body’) form, change, and interact, explicated in the work A Thousand Plateaus. The study offers some insights into how the NELM archive was formed, and which forces continue to shape its work in the South African spheres of English literature and heritage.
- Full Text:
- Date Issued: 2020
- Authors: Wyrill, Beth
- Date: 2020
- Subjects: National English Literary Museum (South Africa) , Butler, Guy, 1918-2001 , Archives -- South Africa , Archives -- Philosophy , Memory (Philosophy)
- Language: English
- Type: Thesis , Doctoral , PHD
- Identifier: http://hdl.handle.net/10962/145746 , vital:38463
- Description: This thesis takes as its theoretical springboard the ‘archival turn’ in South African historical studies, a moment that arguably reached its culmination in 2002 with the publication of Refiguring the Archive. The archival turn posits that, rather than using it as an unproblematic source of original material, scholars might begin to investigate the archive itself, including its processes of construction and organisation. This theoretical model also proposes that the archive might reflect the cultural beliefs and epistemologies common to the era in which it was set up. It seems that the time is ripe for a reconsideration of the insights gleaned from this academic moment in South Africa, given the recent contestation over the meanings of history and our cultural markers of heritage in the public domain, largely grouped under the term ‘Fallism.’ As such, a fresh look at South African museums, which in this country are often rooted in colonial practices of knowledge production, seems apt. This work uses the case of Guy Butler, founder of many South African English cultural institutes and arts bodies, as a conduit and lens for thinking through these problematics. One of Butler’s institutional ‘offspring,’ born from his overarching work on behalf of the English cultural and literary cause in South Africa in the twentieth century, is the National English Literary Museum (NELM). Investigating the founding context and practices of NELM is a useful way of exploring the impact of Butler’s life’s work on literary heritage in South Africa. Issues such as the way in which NELM and Grahamstown continue to signify as loci of thought and practice in the contemporary South African literary landscape will be addressed. The study draws extensively on the Butler collection at NELM, and spends much time investigating Butler’s positioning in a South African literary historical context in the twentieth century, to better understand the forces at work during the time of NELM’s coming-into-being. Derrida’s seminal work on the function of archives, in Archive Fever, is mined for a theoretical basis for the study, as is Deleuze and Guattari’s thought on how bodies (taking the NELM institution here to represent a ‘body’) form, change, and interact, explicated in the work A Thousand Plateaus. The study offers some insights into how the NELM archive was formed, and which forces continue to shape its work in the South African spheres of English literature and heritage.
- Full Text:
- Date Issued: 2020
White writers and Shaka Zulu
- Authors: Wylie, Dan
- Date: 1996
- Subjects: Shaka, Zulu Chief, 1787?-1828 In literature Shaka, Zulu Chief, 1787?-1828 Zulu (African people) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2233 , http://hdl.handle.net/10962/d1002276
- Description: The figure of Shaka (c. 1780-1828) looms massively in the historical and symbolic landscapes of Southern Africa. He has been unquestioningly credited, in varying degrees, with creating the Zulu nation, murderous bloodlust, and military genius, so launching waves of violence across the subcontinent (the "mfecane"). The empirical evidence for this is slight and controversial. More importantly, however, Shaka has attained a mythical reputation on which not only Zulu self-conceptions, but to a significant degree white settler self-identifications have been built. This study describes as comprehensively as possible the genealogy of white Shakan literature, including eyewitness accounts, histories, fictions and poetry. The study argues that the vast majority of these works are characterised by a high degree of incestuous borrowing from one another, and by processes of mythologising catering primarily to the social-psychological needs of the writers. So coherent is this genealogy that the formation of an idealised notion of settler identity can be discerned, especially through the common use of particular textual "gestures". At the same time, while conforming largely to unquestioning modes of discourse such as popularised history and romance fiction, individual writers have attempted to adjust to socio-political circumstances; this study includes four close studies of individual texts. Such close stylistic attention serves to underline the textually-constructed nature of both the figure of Shaka and the "selves" of the writers. The study makes no attempt to reduce its explorations to a single Grand Unified Explanation, and takes eclectic theoretical positions, but it does seek throughout to explore the social-psychological meanings of textual productions of Shaka - in short, to explore the question, Why have white writers written about Shaka in these particular ways?
- Full Text:
- Date Issued: 1996
- Authors: Wylie, Dan
- Date: 1996
- Subjects: Shaka, Zulu Chief, 1787?-1828 In literature Shaka, Zulu Chief, 1787?-1828 Zulu (African people) -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2233 , http://hdl.handle.net/10962/d1002276
- Description: The figure of Shaka (c. 1780-1828) looms massively in the historical and symbolic landscapes of Southern Africa. He has been unquestioningly credited, in varying degrees, with creating the Zulu nation, murderous bloodlust, and military genius, so launching waves of violence across the subcontinent (the "mfecane"). The empirical evidence for this is slight and controversial. More importantly, however, Shaka has attained a mythical reputation on which not only Zulu self-conceptions, but to a significant degree white settler self-identifications have been built. This study describes as comprehensively as possible the genealogy of white Shakan literature, including eyewitness accounts, histories, fictions and poetry. The study argues that the vast majority of these works are characterised by a high degree of incestuous borrowing from one another, and by processes of mythologising catering primarily to the social-psychological needs of the writers. So coherent is this genealogy that the formation of an idealised notion of settler identity can be discerned, especially through the common use of particular textual "gestures". At the same time, while conforming largely to unquestioning modes of discourse such as popularised history and romance fiction, individual writers have attempted to adjust to socio-political circumstances; this study includes four close studies of individual texts. Such close stylistic attention serves to underline the textually-constructed nature of both the figure of Shaka and the "selves" of the writers. The study makes no attempt to reduce its explorations to a single Grand Unified Explanation, and takes eclectic theoretical positions, but it does seek throughout to explore the social-psychological meanings of textual productions of Shaka - in short, to explore the question, Why have white writers written about Shaka in these particular ways?
- Full Text:
- Date Issued: 1996
Development of a novel in situ CPRG-based biosensor and bioprobe for monitoring coliform β-D-Galactosidase in water polluted by faecal matter
- Authors: Wutor, Victor Collins
- Date: 2008
- Subjects: Biosensors Molecular probes Enterobacteriaceae Feces -- Microbiology Water -- Pollution -- Environmental aspects Environmental monitoring Chromogenic compounds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3944 , http://hdl.handle.net/10962/d1004003
- Description: The ultimate objective of this work was to develop a real-time method for detecting and monitoring β-D-galactosidase as a suitable indicator of the potential presence of total coliform bacteria in water environments. Preliminary comparison of the chromogenic substrate, chlorophenol red β-D-galactopyranoside and the fluorogenic substrate, MuGAL, revealed unreliable results with the fluorogenic technique due to interference from compounds commonly found in environmental water samples. Thus, the chromogenic assay was further explored. Hydrolysis of the chromogenic substrate chlorophenol red β-D-galactopyranoside by β-D-galactosidase to yield chlorophenol red was the basis of this assay. Fundamental studies with chlorophenol red β-Dgalactopyranoside showed that β-D-galactosidase occurs extracellularly and in low concentrations in the polluted water environment. A direct correlation between enzyme activity and an increase in environmental water sample volume, as well as enzyme activity with total coliform colony forming unit counts were observed. Spectrophotometric detection was achieved within a maximum period of 24 h with a limit of detection level of 1 colony forming unit 100 ml[superscript -1]. This enzyme also exhibited physical and kinetic properties different from those of the pure commercially available β-D-galactosidase. Cell permeabilisation was not required for releasing enzymes into the extracellular environment. PEG 20 000 offered the best option for concentrating β-D-galactosidase. The source of β-D-galactosidase in the polluted environmental water samples was confirmed as Escherichia coli through SDS-PAGE, tryptic mapping and MALDI-TOF, thus justifying the further use of this method for detecting and/or monitoring total coliforms. Several compounds and metal ions commonly found in environmental water samples (as well as those used in water treatment processes) did have an effect on β-D-galactosidase. All the divalent cations except Mg [superscript 2+], at the concentrations studied, inhibited the relative activity of β-D-galactosidase in both commercial β-D-galactosidase and environmental samples. Immobilisation of chlorophenol red β-D-galactopyranoside onto a solid support material for the development of a strip bioprobe was unsuccessful, even though the nylon support material yielded some positive results. A monthly (seasonal) variation in β-Dgalactosidase activity from the environmental water samples was observed, with the highest activity coinciding with the highest monthly temperatures. Electro-oxidative detection and/or monitoring of chlorophenol red was possible. Chlorophenol red detection was linear over a wide range of concentrations (0.001-0.01 μg ml[superscript -1]). Interference by chlorophenol red β-D-galactopyranoside in the reduction window affected analysis. A range of phthalocyanine metal complexes were studied in an attempt to reduce fouling and/or increase the sensitivity of the biosensor. The selected phthalocyanine metal complexes were generally sensitive to changes in pH with a reduction in sensitivity from acidic pH to alkaline pH. The tetrasulphonated phthalocyanine metal complex of copper was, however, more stable with a minimum change of sensitivity. The phthalocyanine metal complexes were generally stable to changes in temperature. While only two consecutive scans were possible with the unmodified glassy carbon electrode, 77 consecutive scans were performed successfully with the CuPc-modified glassy carbon electrode. Among the phthalocyanine metal complexes studied, the CuPc-modified glassy carbon electrode therefore provided excellent results for the development of a biosensor. The CuPc modified-glassy carbon electrode detected 1 colony forming unit 100 ml[superscript -1] in 15 minutes, while the plain unmodified glassy carbon electrode required 6 hours to detect the equivalent number of colony forming units. CoPc, ZnPc and CuTSPc required 2, 2.25 and 1.75 h, respectively, to detect the same numbers of colony forming units. The CuPcmodified glassy carbon electrode detected 40 colony forming units 100 ml[superscript -1] instantly. In general, a direct correlation between colony forming units and current generated in the sensor was observed (R2=0.92). A higher correlation coefficient of 0.99 for 0-30 coliform colony forming units 100 ml[superscript -1] was determined. Current was detected in some water samples which did not show any colony forming units on the media, probably due to the phenomenon of viable but non-culturable bacteria, which is the major disadvantage encountered in the use of media for detecting indicator microorganisms. This novel biosensor therefore presents a very robust and sensitive technique for the detection and/or monitoring of coliform bacterial activity in water.
- Full Text:
- Date Issued: 2008
- Authors: Wutor, Victor Collins
- Date: 2008
- Subjects: Biosensors Molecular probes Enterobacteriaceae Feces -- Microbiology Water -- Pollution -- Environmental aspects Environmental monitoring Chromogenic compounds
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3944 , http://hdl.handle.net/10962/d1004003
- Description: The ultimate objective of this work was to develop a real-time method for detecting and monitoring β-D-galactosidase as a suitable indicator of the potential presence of total coliform bacteria in water environments. Preliminary comparison of the chromogenic substrate, chlorophenol red β-D-galactopyranoside and the fluorogenic substrate, MuGAL, revealed unreliable results with the fluorogenic technique due to interference from compounds commonly found in environmental water samples. Thus, the chromogenic assay was further explored. Hydrolysis of the chromogenic substrate chlorophenol red β-D-galactopyranoside by β-D-galactosidase to yield chlorophenol red was the basis of this assay. Fundamental studies with chlorophenol red β-Dgalactopyranoside showed that β-D-galactosidase occurs extracellularly and in low concentrations in the polluted water environment. A direct correlation between enzyme activity and an increase in environmental water sample volume, as well as enzyme activity with total coliform colony forming unit counts were observed. Spectrophotometric detection was achieved within a maximum period of 24 h with a limit of detection level of 1 colony forming unit 100 ml[superscript -1]. This enzyme also exhibited physical and kinetic properties different from those of the pure commercially available β-D-galactosidase. Cell permeabilisation was not required for releasing enzymes into the extracellular environment. PEG 20 000 offered the best option for concentrating β-D-galactosidase. The source of β-D-galactosidase in the polluted environmental water samples was confirmed as Escherichia coli through SDS-PAGE, tryptic mapping and MALDI-TOF, thus justifying the further use of this method for detecting and/or monitoring total coliforms. Several compounds and metal ions commonly found in environmental water samples (as well as those used in water treatment processes) did have an effect on β-D-galactosidase. All the divalent cations except Mg [superscript 2+], at the concentrations studied, inhibited the relative activity of β-D-galactosidase in both commercial β-D-galactosidase and environmental samples. Immobilisation of chlorophenol red β-D-galactopyranoside onto a solid support material for the development of a strip bioprobe was unsuccessful, even though the nylon support material yielded some positive results. A monthly (seasonal) variation in β-Dgalactosidase activity from the environmental water samples was observed, with the highest activity coinciding with the highest monthly temperatures. Electro-oxidative detection and/or monitoring of chlorophenol red was possible. Chlorophenol red detection was linear over a wide range of concentrations (0.001-0.01 μg ml[superscript -1]). Interference by chlorophenol red β-D-galactopyranoside in the reduction window affected analysis. A range of phthalocyanine metal complexes were studied in an attempt to reduce fouling and/or increase the sensitivity of the biosensor. The selected phthalocyanine metal complexes were generally sensitive to changes in pH with a reduction in sensitivity from acidic pH to alkaline pH. The tetrasulphonated phthalocyanine metal complex of copper was, however, more stable with a minimum change of sensitivity. The phthalocyanine metal complexes were generally stable to changes in temperature. While only two consecutive scans were possible with the unmodified glassy carbon electrode, 77 consecutive scans were performed successfully with the CuPc-modified glassy carbon electrode. Among the phthalocyanine metal complexes studied, the CuPc-modified glassy carbon electrode therefore provided excellent results for the development of a biosensor. The CuPc modified-glassy carbon electrode detected 1 colony forming unit 100 ml[superscript -1] in 15 minutes, while the plain unmodified glassy carbon electrode required 6 hours to detect the equivalent number of colony forming units. CoPc, ZnPc and CuTSPc required 2, 2.25 and 1.75 h, respectively, to detect the same numbers of colony forming units. The CuPcmodified glassy carbon electrode detected 40 colony forming units 100 ml[superscript -1] instantly. In general, a direct correlation between colony forming units and current generated in the sensor was observed (R2=0.92). A higher correlation coefficient of 0.99 for 0-30 coliform colony forming units 100 ml[superscript -1] was determined. Current was detected in some water samples which did not show any colony forming units on the media, probably due to the phenomenon of viable but non-culturable bacteria, which is the major disadvantage encountered in the use of media for detecting indicator microorganisms. This novel biosensor therefore presents a very robust and sensitive technique for the detection and/or monitoring of coliform bacterial activity in water.
- Full Text:
- Date Issued: 2008