Alternative dispute resolution in the best interests of the child
- Authors: Van Zyl, Lesbury
- Date: 1995
- Subjects: Divorce mediation -- South Africa , Dispute resolution (Law) -- South Africa , Custody of children -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3697 , http://hdl.handle.net/10962/d1003212 , Divorce mediation -- South Africa , Dispute resolution (Law) -- South Africa , Custody of children -- South Africa
- Description: The development of private divorce mediation appears to offer a friendly and informal alternative to the "hostile" adversarial divorce. A close analysis of its claims, however, shows them to be largely unproven. Urgent attention should therefore be given to the philosophical base of the movement. There is also a need for empirical research and for standardised training. Further unanswered questions relate to the part to be played by different professions, and to professional ethics. It is submitted that the appointment of Family Advocates is a step in the right direction but that the establishment of a full Family Court will best protect children's interests.
- Full Text:
- Date Issued: 1995
- Authors: Van Zyl, Lesbury
- Date: 1995
- Subjects: Divorce mediation -- South Africa , Dispute resolution (Law) -- South Africa , Custody of children -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3697 , http://hdl.handle.net/10962/d1003212 , Divorce mediation -- South Africa , Dispute resolution (Law) -- South Africa , Custody of children -- South Africa
- Description: The development of private divorce mediation appears to offer a friendly and informal alternative to the "hostile" adversarial divorce. A close analysis of its claims, however, shows them to be largely unproven. Urgent attention should therefore be given to the philosophical base of the movement. There is also a need for empirical research and for standardised training. Further unanswered questions relate to the part to be played by different professions, and to professional ethics. It is submitted that the appointment of Family Advocates is a step in the right direction but that the establishment of a full Family Court will best protect children's interests.
- Full Text:
- Date Issued: 1995
Bacterial interaction in hide biodeterioration with special reference to selected Clostridium species
- Authors: Thompson, Gillian Ann
- Date: 1995
- Subjects: Hides and skins -- Preservation Aerobic bacteria Pseudomonas aeruginosa Clostridium Halobacterium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4041 , http://hdl.handle.net/10962/d1004102
- Description: Animal hides are the basic raw material of the leather industry and they undergo rapid putrefaction unless "cured". This study investigated the role and interactive effects of three selected bacteria, Pseudomonas aeruginosa. Clostridium histoly ticum and Clostridium sporogenes in in-situ cattle hide degradation using a model system set up for the purpose. The system consisted of 3cm diameter hide pieces contained in sealed jars and sterilised by ethylene oxide to remove resident microbes and inactivate autolytic tissue enzymes. The inocula were prepared either as individual cultures or as combinations of two inocula or all three inocula. Degradative changes during storage at 30°C were measured for up to 8 days using ten different parameters. Initial trials confirmed that the selected inocula were readily isolated from raw hides and could outcompete resident populations to produce putrefactive decomposition. Growth rates and enzyme profiles of the organisms and the effects of nutrients and reductants on their relative denaturative effects were used to standardise the system. Trials on the effects of ethylene oxide indicated the suitability of the method for hide and collagen sterilisation. The findings of in-situ trials with the selected inocula confirmed previous studies of protein putrefaction in that a bacterial succession was evident involving aerobic proteolytic bacteria, micro-aerophilic proteolytic bacteria and strictly anaerobic amino acid degrading bacteria. However, this study showed that the micro-aerophilic collagenase producing C. histolyticum degraded hides at a far greater rate when inoculated on its own than when in the presence of either or both of the other two inocula. It also demonstrated a bacterial antagonism between the two clostridia in which C. sporogenes prevented degradative changes occurring for up to 4-6 days possibly due to cysteine production by C. sporogenes. These findings have implications for hide preservation since maintenance of aerobic conditions and suppression of spore outgrowth could be used to delay growth of collagenase producing clostridia. The use of C. sporogenes as a biocontrol agent is also postulated. The model system was also used to examine salted hides during storage and these studies indicated that Halobacteriaceae do not produce collagenase but that inadequately salted hides could possibly be subject to degradation by delsulfovibrios.
- Full Text:
- Date Issued: 1995
- Authors: Thompson, Gillian Ann
- Date: 1995
- Subjects: Hides and skins -- Preservation Aerobic bacteria Pseudomonas aeruginosa Clostridium Halobacterium
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4041 , http://hdl.handle.net/10962/d1004102
- Description: Animal hides are the basic raw material of the leather industry and they undergo rapid putrefaction unless "cured". This study investigated the role and interactive effects of three selected bacteria, Pseudomonas aeruginosa. Clostridium histoly ticum and Clostridium sporogenes in in-situ cattle hide degradation using a model system set up for the purpose. The system consisted of 3cm diameter hide pieces contained in sealed jars and sterilised by ethylene oxide to remove resident microbes and inactivate autolytic tissue enzymes. The inocula were prepared either as individual cultures or as combinations of two inocula or all three inocula. Degradative changes during storage at 30°C were measured for up to 8 days using ten different parameters. Initial trials confirmed that the selected inocula were readily isolated from raw hides and could outcompete resident populations to produce putrefactive decomposition. Growth rates and enzyme profiles of the organisms and the effects of nutrients and reductants on their relative denaturative effects were used to standardise the system. Trials on the effects of ethylene oxide indicated the suitability of the method for hide and collagen sterilisation. The findings of in-situ trials with the selected inocula confirmed previous studies of protein putrefaction in that a bacterial succession was evident involving aerobic proteolytic bacteria, micro-aerophilic proteolytic bacteria and strictly anaerobic amino acid degrading bacteria. However, this study showed that the micro-aerophilic collagenase producing C. histolyticum degraded hides at a far greater rate when inoculated on its own than when in the presence of either or both of the other two inocula. It also demonstrated a bacterial antagonism between the two clostridia in which C. sporogenes prevented degradative changes occurring for up to 4-6 days possibly due to cysteine production by C. sporogenes. These findings have implications for hide preservation since maintenance of aerobic conditions and suppression of spore outgrowth could be used to delay growth of collagenase producing clostridia. The use of C. sporogenes as a biocontrol agent is also postulated. The model system was also used to examine salted hides during storage and these studies indicated that Halobacteriaceae do not produce collagenase but that inadequately salted hides could possibly be subject to degradation by delsulfovibrios.
- Full Text:
- Date Issued: 1995
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
Comprehending strike action: the South African experience c.1950-1990 and the theoretical implications thereof
- Authors: Wood, Geoffrey Thomas
- Date: 1995
- Subjects: Strikes and lockouts -- South Africa -- History Industrial relations -- South Africa -- History Labor unions -- South Africa -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3319 , http://hdl.handle.net/10962/d1003107
- Description: Regular strike action has become a central characteristic of the South African industrial relations system. Whilst in the 1950s strikes were mostly isolated outbursts of relatively short duration, strikes in the 1980s were challenges of unprecedented duration and intensity. It is argued that despite this dramatic change, reflecting a series of discontinuities in both the political and economic arenas, strike action in South Africa does follow distinct patterns, and can be ascribed to a combination of identifiable causes. Principal causal factors include wage aspirations, past experiences and the subjective interpretation thereof, and the role of the union movement. Contingent factors include the prevailing political climate, industrial relations legislation, the amount of information opposing sides possess of their adversaries' intentions as well as spatial issues, such as the internal dynamics of individual communities. Partially as a result of South Africa's political transformation, the late 1980s and early 1990s saw further changes in the industrial relations environment. Reflecting these developments, it is argued that a new type of trade unionism has developed, "coterminous unionism" . This will have far-reaching implications for the nature of industrial conflict. However, it falls fully within the theoretical parameters outlined in this thesis. Despite significant developments in social theory in the 1980s and 1990s, there have been few attempts accordingly to update theories of strike action. One of the objectives of this thesis has been to attempt such an update. It is hoped that the constructs developed will shed light on a widely prevalent form of social conflict, assist in the analysis of future outbreaks, and enable the identification of those situations where a high propensity to engage in strike action may exist.
- Full Text:
- Date Issued: 1995
- Authors: Wood, Geoffrey Thomas
- Date: 1995
- Subjects: Strikes and lockouts -- South Africa -- History Industrial relations -- South Africa -- History Labor unions -- South Africa -- History
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3319 , http://hdl.handle.net/10962/d1003107
- Description: Regular strike action has become a central characteristic of the South African industrial relations system. Whilst in the 1950s strikes were mostly isolated outbursts of relatively short duration, strikes in the 1980s were challenges of unprecedented duration and intensity. It is argued that despite this dramatic change, reflecting a series of discontinuities in both the political and economic arenas, strike action in South Africa does follow distinct patterns, and can be ascribed to a combination of identifiable causes. Principal causal factors include wage aspirations, past experiences and the subjective interpretation thereof, and the role of the union movement. Contingent factors include the prevailing political climate, industrial relations legislation, the amount of information opposing sides possess of their adversaries' intentions as well as spatial issues, such as the internal dynamics of individual communities. Partially as a result of South Africa's political transformation, the late 1980s and early 1990s saw further changes in the industrial relations environment. Reflecting these developments, it is argued that a new type of trade unionism has developed, "coterminous unionism" . This will have far-reaching implications for the nature of industrial conflict. However, it falls fully within the theoretical parameters outlined in this thesis. Despite significant developments in social theory in the 1980s and 1990s, there have been few attempts accordingly to update theories of strike action. One of the objectives of this thesis has been to attempt such an update. It is hoped that the constructs developed will shed light on a widely prevalent form of social conflict, assist in the analysis of future outbreaks, and enable the identification of those situations where a high propensity to engage in strike action may exist.
- Full Text:
- Date Issued: 1995
Confrontation, cooptation and collaboration : the response and reaction of the Labour Party of South Africa to Government Policy, 1965-1984
- Authors: Du Pré, Roy Howard
- Date: 1995
- Subjects: South African Labour Party -- History Colored people (South Africa) -- Politics and government South Africa -- Politics and government -- 1948-1994
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2539 , http://hdl.handle.net/10962/d1002391
- Description: The Labour Party was a prominent political party amongst coloured people for more than twenty-five years. Formed in 1965 to contest elections for the Coloured Persons' Representative Council (CRC), the Labour Party at the outset adopted an anti-apartheid, anti-separate representation and anti-eRe stance. During the first five years of its existence, the party tried to muster coloured support for its policies. Its promise to cripple the CRC by refusing to occupy seats in the council became the rallying call. The Labour Party won a majority of the elected seats in the first CRC election in 1969 but the government nominated progovernment candidates to all the nominated seats, depriving the Labour Party of an overall majority. Thwarted in their bid to "wreck" the CRC, Labour Party members instead took their seats in the council, vowing to destroy it from within. For the next five years the Labour Party pursued a policy of "confrontation. " By using a "boycott" strategy, it not only hamstrung the effective working of the CRC but thwarted the government in other areas of its "coloured" policy. In the 1975 election the Labour Party won an outright victory, giving it the power to cripple the CRC. However, it did not seize this opportunity. Its decision to "govern" in the CRC constituted a decisive step in the change from confrontation to cooptation. The Labour Party's continued support of the CRC drew widespread criticism from supporters and opponents alike. Its leaders tried to hold together a disaffected party and eventually agreed to the dissolution of the CRC in 1980 in an effort to paper over the cracks in party unity, and to forestall growing coloured opposition to the CRC at the next election. In 1983, the Labour Party displayed a decisive shift in its anti-separate representation stance by lending support to the tricameral system. By doing so, it laid itself open to the same charge of collaboration it had levelled at the other CRC parties. This thesis will examine the history of the Labour Party from its formation in 1965 as an anti-government party, to one of cooperation with its erstwhile opponent by 1984.
- Full Text:
- Date Issued: 1995
- Authors: Du Pré, Roy Howard
- Date: 1995
- Subjects: South African Labour Party -- History Colored people (South Africa) -- Politics and government South Africa -- Politics and government -- 1948-1994
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2539 , http://hdl.handle.net/10962/d1002391
- Description: The Labour Party was a prominent political party amongst coloured people for more than twenty-five years. Formed in 1965 to contest elections for the Coloured Persons' Representative Council (CRC), the Labour Party at the outset adopted an anti-apartheid, anti-separate representation and anti-eRe stance. During the first five years of its existence, the party tried to muster coloured support for its policies. Its promise to cripple the CRC by refusing to occupy seats in the council became the rallying call. The Labour Party won a majority of the elected seats in the first CRC election in 1969 but the government nominated progovernment candidates to all the nominated seats, depriving the Labour Party of an overall majority. Thwarted in their bid to "wreck" the CRC, Labour Party members instead took their seats in the council, vowing to destroy it from within. For the next five years the Labour Party pursued a policy of "confrontation. " By using a "boycott" strategy, it not only hamstrung the effective working of the CRC but thwarted the government in other areas of its "coloured" policy. In the 1975 election the Labour Party won an outright victory, giving it the power to cripple the CRC. However, it did not seize this opportunity. Its decision to "govern" in the CRC constituted a decisive step in the change from confrontation to cooptation. The Labour Party's continued support of the CRC drew widespread criticism from supporters and opponents alike. Its leaders tried to hold together a disaffected party and eventually agreed to the dissolution of the CRC in 1980 in an effort to paper over the cracks in party unity, and to forestall growing coloured opposition to the CRC at the next election. In 1983, the Labour Party displayed a decisive shift in its anti-separate representation stance by lending support to the tricameral system. By doing so, it laid itself open to the same charge of collaboration it had levelled at the other CRC parties. This thesis will examine the history of the Labour Party from its formation in 1965 as an anti-government party, to one of cooperation with its erstwhile opponent by 1984.
- Full Text:
- Date Issued: 1995
Constituent processes contributing to stress induced β-carotene accumulation in Dunaliella salina
- Authors: Phillips, Lesley Gail
- Date: 1995
- Subjects: Dunaliella Carotenes Plants -- Effect of stress on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5658 , http://hdl.handle.net/10962/d1005341
- Description: The alga Dunaliella salina possesses the unique ability to accumulate up to 14 % of it's dry weight as β-carotene in response to stress conditions. This hyper-accumulation of β-carotene has led to the commercial exploitation of this alga for the biotechnological production of this important carotenoid. In order to maximise β-carotene production, a dual-stage process which separates the distinctive growth phase from the β-carotene accumulating stress phase has recently been patented. Preliminary laboratory studies showed that although stress factors such as high salinity and nutrient limitation enhance β-carotene accumulation in D. salina (± 10 pg.cell⁻¹), high light intensity was the single most important factor contributing to the induction of β-carotene accumulation in this alga (± 20 pg.cell⁻¹). Moreover, it was demonstrated that β-carotene accumulation can be further stimulated by exposing the alga to a combination of high light intensity, salt and nutrient stresses (± 30-60 pg.cell⁻¹). The response of D. salina to stress was shown to occur in two phases. The first phase occurred within 24 hours and was characterized most importantly by higher rates of β-carotene accumulation for all the stresses investigated. In cells exposed to multiple stress factors in mass culture, the β-carotene accumulation rate was as much as 9.5 pg.cell⁻¹.day⁻¹ in the first phase compared to only 3 pg.cell·day⁻¹ in the second phase. Since the rate of β-carotene accumulation was higher within the first 24 hours after exposure to stress, the first phase was considered crucial for stress-induced β-carotene accumulation. Characterization of this phase revealed that the stress response was multifaceted. Transition of cells from the growth stage to stress conditions was characterized by the following: 1) Change in cell volume. Hypersalinity caused cell shrinkage while cells exposed to nutrient limitation and/or high light intensity caused cells to swell. Restoration of cell volume was shown to occur within 8 hours for all stresses investigated. 2) Altered photosynthesis. Inhibition of both carbon fixation and oxygen evolution was demonstrated in cells immediately after exposure to multiple stress factors. 3) Production of abscisic acid. Intracellular ABA levels increased within 6-8 hours after exposure to all stresses investigated. The rise in intracellular ABA levels coincided with an increase or return to starting cell volume. High intracellular ABA levels were however transient and within 24 hours ABA began to partition into the culture medium. 4) Change in pigment composition. Changes in xanthophyll cycle pigment content was demonstrated soon after exposure to stress conditions. In hypersalinity shocked cells, initial epoxidation of zeaxanthin to violaxanthin and subsequent de-epoxidation to zeaxanthin occurred, whereas exposure to high stress resulted in an immediate and continued decrease in the epoxidation state indicating accumulation of zeaxanthin. A rapid rate of chlorophyll depletion was also demonstrated. In addition to the above responses a rapid decrease in growth rate during this phase was also noted. An interrelationship between cell volume change, ABA production, maintenance of xanthophyll cycle operation and β-carotene accumulation therefore appeared to exist. ABA production was shown to be stoichiometrically related to changes in xanthophyll content with r² = 0.84 and slope of the curve = 0.91 being achieved for high light stressed cells. This study therefore presents strong circumstantial evidence in support of a carotenoid origin for ABA in Dunaliella. In addition, enhanced β-carotene content was achieved by the application of exogenous ABA and related compounds suggesting a role for ABA as a regulator of the overall stress response. Furthermore, zeaxanthin accumulation was shown to be positively correlated ( r²≥ 0.81) to β-carotene accumulation for all the stresses investigated. The second phase was characterized by a return to homoeostasis of the physiological processes mentioned above, indicating acclimation of the cell to prevailing conditions. This stage was characterised by continued β-carotene accumulation and a decreased epoxidation state of the xanthophyll cycle which together appeared to sustain photosynthesis, allowing this organism to tolerate stress conditions.
- Full Text:
- Date Issued: 1995
- Authors: Phillips, Lesley Gail
- Date: 1995
- Subjects: Dunaliella Carotenes Plants -- Effect of stress on
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5658 , http://hdl.handle.net/10962/d1005341
- Description: The alga Dunaliella salina possesses the unique ability to accumulate up to 14 % of it's dry weight as β-carotene in response to stress conditions. This hyper-accumulation of β-carotene has led to the commercial exploitation of this alga for the biotechnological production of this important carotenoid. In order to maximise β-carotene production, a dual-stage process which separates the distinctive growth phase from the β-carotene accumulating stress phase has recently been patented. Preliminary laboratory studies showed that although stress factors such as high salinity and nutrient limitation enhance β-carotene accumulation in D. salina (± 10 pg.cell⁻¹), high light intensity was the single most important factor contributing to the induction of β-carotene accumulation in this alga (± 20 pg.cell⁻¹). Moreover, it was demonstrated that β-carotene accumulation can be further stimulated by exposing the alga to a combination of high light intensity, salt and nutrient stresses (± 30-60 pg.cell⁻¹). The response of D. salina to stress was shown to occur in two phases. The first phase occurred within 24 hours and was characterized most importantly by higher rates of β-carotene accumulation for all the stresses investigated. In cells exposed to multiple stress factors in mass culture, the β-carotene accumulation rate was as much as 9.5 pg.cell⁻¹.day⁻¹ in the first phase compared to only 3 pg.cell·day⁻¹ in the second phase. Since the rate of β-carotene accumulation was higher within the first 24 hours after exposure to stress, the first phase was considered crucial for stress-induced β-carotene accumulation. Characterization of this phase revealed that the stress response was multifaceted. Transition of cells from the growth stage to stress conditions was characterized by the following: 1) Change in cell volume. Hypersalinity caused cell shrinkage while cells exposed to nutrient limitation and/or high light intensity caused cells to swell. Restoration of cell volume was shown to occur within 8 hours for all stresses investigated. 2) Altered photosynthesis. Inhibition of both carbon fixation and oxygen evolution was demonstrated in cells immediately after exposure to multiple stress factors. 3) Production of abscisic acid. Intracellular ABA levels increased within 6-8 hours after exposure to all stresses investigated. The rise in intracellular ABA levels coincided with an increase or return to starting cell volume. High intracellular ABA levels were however transient and within 24 hours ABA began to partition into the culture medium. 4) Change in pigment composition. Changes in xanthophyll cycle pigment content was demonstrated soon after exposure to stress conditions. In hypersalinity shocked cells, initial epoxidation of zeaxanthin to violaxanthin and subsequent de-epoxidation to zeaxanthin occurred, whereas exposure to high stress resulted in an immediate and continued decrease in the epoxidation state indicating accumulation of zeaxanthin. A rapid rate of chlorophyll depletion was also demonstrated. In addition to the above responses a rapid decrease in growth rate during this phase was also noted. An interrelationship between cell volume change, ABA production, maintenance of xanthophyll cycle operation and β-carotene accumulation therefore appeared to exist. ABA production was shown to be stoichiometrically related to changes in xanthophyll content with r² = 0.84 and slope of the curve = 0.91 being achieved for high light stressed cells. This study therefore presents strong circumstantial evidence in support of a carotenoid origin for ABA in Dunaliella. In addition, enhanced β-carotene content was achieved by the application of exogenous ABA and related compounds suggesting a role for ABA as a regulator of the overall stress response. Furthermore, zeaxanthin accumulation was shown to be positively correlated ( r²≥ 0.81) to β-carotene accumulation for all the stresses investigated. The second phase was characterized by a return to homoeostasis of the physiological processes mentioned above, indicating acclimation of the cell to prevailing conditions. This stage was characterised by continued β-carotene accumulation and a decreased epoxidation state of the xanthophyll cycle which together appeared to sustain photosynthesis, allowing this organism to tolerate stress conditions.
- Full Text:
- Date Issued: 1995
Coping in two cultures: an ecological study of mentally ill people and their families in rural South Africa
- Authors: Cumes, Heide Ulrike
- Date: 1995
- Subjects: Mental illness -- South Africa Xhosa (African people) -- Psychology Xhosa (African people) -- Religion Xhosa (African people) -- Social life and customs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2958 , http://hdl.handle.net/10962/d1002467
- Description: This study explores severe mental illness in a South African ru~al district, moving, as with a zoom lens, from the macroperspectives of (i) Xhosa culture, and (ii) biomedicine, to the lived experience of the individual. Its methodology, predominantly qualitative, employed anthropological and psychological procedures. The fieldwork (1988-1989)encompassed a three month stay in the village of Msobomvu. Patients continued to be tracked informally until June, 1995. The empirical research has three parts. In part one, the person with a mental illness was contextualized within Xhosa cosmology and social attitudes. The cognitive and social ecologies were tapped through the narratives of high school and university students at different stages of a Western-biased education. Social attitudes regarding mental illness, and confidence in treatment by traditional healers and the hospital, were also evaluated. Traditional attitudes and supernatural beliefs of illness causation persisted in spite of Eurocentric education, with a concurrent increase in the acceptance of Western-type causal explanations commensurate with continued education. Part two considered the the patients in relation to (i) the biomedical framework (the mental and local hospitals), and (ii) their readjustment to the community after hospitalization. Data came from patient charts, interviews with medical staff, and follow-up visits in the villages. Socio-political and economic issues were salient. Part three case-studied people identified by the village residents as having a mental illness. Resources for treatment - traditional healers, mobile clinic, and village health workers - were the focus. The traditional healing system, and biomedicine, were compared for effectiveness, through the course of illness events. While biomedicine was more effective in containing acute psychotic episodes than treatment by the traditional healer, lack of appropriate resources within the biomedical setting had disastrous results for patient compliance and long-term management of the illness, particularly in people with obvious symptoms of bipolar disorder. The mental hospital emerged as an agent of control. While Xhosa culture provided a more tolerant setting for people with a mental illness, the course of severe mental illness was by no means benign, despite research suggesting a more positive outcome for such conditions in the developing world.
- Full Text:
- Date Issued: 1995
- Authors: Cumes, Heide Ulrike
- Date: 1995
- Subjects: Mental illness -- South Africa Xhosa (African people) -- Psychology Xhosa (African people) -- Religion Xhosa (African people) -- Social life and customs
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2958 , http://hdl.handle.net/10962/d1002467
- Description: This study explores severe mental illness in a South African ru~al district, moving, as with a zoom lens, from the macroperspectives of (i) Xhosa culture, and (ii) biomedicine, to the lived experience of the individual. Its methodology, predominantly qualitative, employed anthropological and psychological procedures. The fieldwork (1988-1989)encompassed a three month stay in the village of Msobomvu. Patients continued to be tracked informally until June, 1995. The empirical research has three parts. In part one, the person with a mental illness was contextualized within Xhosa cosmology and social attitudes. The cognitive and social ecologies were tapped through the narratives of high school and university students at different stages of a Western-biased education. Social attitudes regarding mental illness, and confidence in treatment by traditional healers and the hospital, were also evaluated. Traditional attitudes and supernatural beliefs of illness causation persisted in spite of Eurocentric education, with a concurrent increase in the acceptance of Western-type causal explanations commensurate with continued education. Part two considered the the patients in relation to (i) the biomedical framework (the mental and local hospitals), and (ii) their readjustment to the community after hospitalization. Data came from patient charts, interviews with medical staff, and follow-up visits in the villages. Socio-political and economic issues were salient. Part three case-studied people identified by the village residents as having a mental illness. Resources for treatment - traditional healers, mobile clinic, and village health workers - were the focus. The traditional healing system, and biomedicine, were compared for effectiveness, through the course of illness events. While biomedicine was more effective in containing acute psychotic episodes than treatment by the traditional healer, lack of appropriate resources within the biomedical setting had disastrous results for patient compliance and long-term management of the illness, particularly in people with obvious symptoms of bipolar disorder. The mental hospital emerged as an agent of control. While Xhosa culture provided a more tolerant setting for people with a mental illness, the course of severe mental illness was by no means benign, despite research suggesting a more positive outcome for such conditions in the developing world.
- Full Text:
- Date Issued: 1995
Dispersal, settlement and recruitment : their influence on the population dynamics of intertidal mussels
- Authors: Phillips, Tracey Elizabeth
- Date: 1995
- Subjects: Perna -- South Africa -- Eastern Cape -- Algoa bay Mytilus galloprovincialis -- South Africa -- Eastern Cape -- Algoa bay Mytilidae -- South Africa -- Eastern Cape -- Algoa bay
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5663 , http://hdl.handle.net/10962/d1005347
- Description: Recruitment of planktonic larvae into sedentary benthic populations regulates the population dynamics of marine invertebrates. The processes controlling recruitment, however, are poorly understood, and recruitment remains largely unpredictable, which complicates management of exploited shellfish resources. The mussels Perna perna, Choromytilus meridionalis and Mytilus galloprovincialis, found on the south coast of southern Africa, have planktonic larvae and sedentary adult stages. This thesis examines dispersal, settlement and early post-settlement growth and mortality, and their effect on recruitment and demography of intertidal mussel populations in the region of Algoa Bay on the south coast of southern Africa. Temporal and spatial variation in the body mass, density and size structure of mussels, the distribution of bivalve larvae on plankton grids in the nearshore zone and the distribution of a recently introduced invasive mussel, Mytilus galloprovincialis, were examined between 1989 and 1992. Furthermore, data on hourly or daily changes in wind strength and direction, air and sea surface temperatures and low and high tide levels in the study region, were obtained. There were 3-4 peaks in spawning (characterised by an abrupt decline in weight) and settlement activity annually. These peaks varied in exact timing, intensity and duration between sites and over time. However, at a site, spawning was followed by settlement 4-8 weeks later, and there was a significant (P < 0.05) direct correlation between spawning intensity prior to the appearance of a new cohort and the cohort density (settlement intensity). The stochastic spatial and temporal variation in breeding activity was superimposed on a more general pattern of a higher intensity of spawning and settlement in Algoa Bay than on the open coast, and a higher settlement intensity on coastal sandstone shores than on dune rock shores. Spawning was more frequent in winter and spring, and the probability of spawning and settlement peaked around the spring and autumn equinox, if temperature and wind conditions were suitable. Larval behaviour had little effect on their dispersal in the well-mixed nearshore region. Larvae were passively dispersed by currents, and their dispersal range and direction depended on prevailing winds and local topography. The sharp decline in density of recruit and adult M. galloprovincialis with increasing distance from the point of introduction, showed that some larvae were carried by wind generated currents over moderately long distances (-100 km). However, since most (76 %) M. galloprovincialis recruited within 4 km of the parent population, it is possible that larvae become trapped in small gullies and crevices around rocky shores, and have a limited dispersal range. This could explain the link between local patterns of spawning and settlement. The distribution and abundance of settlers on the shore was influenced by larval behaviour and the availability of settlement, substrata. Larvae preferred to settle primarily on foliose coralline algae and migrate to the adult mussel bed when they were larger (0.60-7 mm), but larvae also settled directly on adult mussels, possibly because the amount of coralline algae was limited. Both direct and secondary settlement were considered to be important in maintaining mussel populations since the rate of settlement was low(generally < 60 000.m-2). Cohort analyses showed that prior to maturity post-settlement growth (- 30 mm in 10 months) and mortality rates (60-100%) were high, but varied. When settlement intensity was low this variability uncoupled the relationship between spawning and recruitment intensity. Multiple regression analysis showed that together reproductive effort (gamete output), settlement intensity, growth and mortality prior to maturity, accounted for 76 % of the variance in recruitment into mature adult populations. The low settlement rate coupled with the short life span of mussels « 3 years), meant that populations underwent marked spatial and temporal variations in structure and abundance as settlement intensity varied, but there were consistent general differences between mussel populations on dune rock and sandstone shores in Algoa Bay and on the open coast. It was concluded from these results that, spawning intensity and post-settlement growth and mortality, rather than dispersal, regulated recruitment and the structure and abundance of intertidal P. perna and C. meridionalis populations along the south coast of southern Africa. On the basis of these results it is recommended that species with limited dispersal, variable recruitment and high natural mortality, such as P. perna, should be conserved by protecting a small part of the population in reserves, and controlling utilisation outside reserves to minimize disturbance to local brood stocks. Furthermore, since the potential for reseeding adjacent exploited areas is limited, several small reserves placed at regular intervals along the coast would be more effective than a single large reserve.
- Full Text:
- Date Issued: 1995
- Authors: Phillips, Tracey Elizabeth
- Date: 1995
- Subjects: Perna -- South Africa -- Eastern Cape -- Algoa bay Mytilus galloprovincialis -- South Africa -- Eastern Cape -- Algoa bay Mytilidae -- South Africa -- Eastern Cape -- Algoa bay
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5663 , http://hdl.handle.net/10962/d1005347
- Description: Recruitment of planktonic larvae into sedentary benthic populations regulates the population dynamics of marine invertebrates. The processes controlling recruitment, however, are poorly understood, and recruitment remains largely unpredictable, which complicates management of exploited shellfish resources. The mussels Perna perna, Choromytilus meridionalis and Mytilus galloprovincialis, found on the south coast of southern Africa, have planktonic larvae and sedentary adult stages. This thesis examines dispersal, settlement and early post-settlement growth and mortality, and their effect on recruitment and demography of intertidal mussel populations in the region of Algoa Bay on the south coast of southern Africa. Temporal and spatial variation in the body mass, density and size structure of mussels, the distribution of bivalve larvae on plankton grids in the nearshore zone and the distribution of a recently introduced invasive mussel, Mytilus galloprovincialis, were examined between 1989 and 1992. Furthermore, data on hourly or daily changes in wind strength and direction, air and sea surface temperatures and low and high tide levels in the study region, were obtained. There were 3-4 peaks in spawning (characterised by an abrupt decline in weight) and settlement activity annually. These peaks varied in exact timing, intensity and duration between sites and over time. However, at a site, spawning was followed by settlement 4-8 weeks later, and there was a significant (P < 0.05) direct correlation between spawning intensity prior to the appearance of a new cohort and the cohort density (settlement intensity). The stochastic spatial and temporal variation in breeding activity was superimposed on a more general pattern of a higher intensity of spawning and settlement in Algoa Bay than on the open coast, and a higher settlement intensity on coastal sandstone shores than on dune rock shores. Spawning was more frequent in winter and spring, and the probability of spawning and settlement peaked around the spring and autumn equinox, if temperature and wind conditions were suitable. Larval behaviour had little effect on their dispersal in the well-mixed nearshore region. Larvae were passively dispersed by currents, and their dispersal range and direction depended on prevailing winds and local topography. The sharp decline in density of recruit and adult M. galloprovincialis with increasing distance from the point of introduction, showed that some larvae were carried by wind generated currents over moderately long distances (-100 km). However, since most (76 %) M. galloprovincialis recruited within 4 km of the parent population, it is possible that larvae become trapped in small gullies and crevices around rocky shores, and have a limited dispersal range. This could explain the link between local patterns of spawning and settlement. The distribution and abundance of settlers on the shore was influenced by larval behaviour and the availability of settlement, substrata. Larvae preferred to settle primarily on foliose coralline algae and migrate to the adult mussel bed when they were larger (0.60-7 mm), but larvae also settled directly on adult mussels, possibly because the amount of coralline algae was limited. Both direct and secondary settlement were considered to be important in maintaining mussel populations since the rate of settlement was low(generally < 60 000.m-2). Cohort analyses showed that prior to maturity post-settlement growth (- 30 mm in 10 months) and mortality rates (60-100%) were high, but varied. When settlement intensity was low this variability uncoupled the relationship between spawning and recruitment intensity. Multiple regression analysis showed that together reproductive effort (gamete output), settlement intensity, growth and mortality prior to maturity, accounted for 76 % of the variance in recruitment into mature adult populations. The low settlement rate coupled with the short life span of mussels « 3 years), meant that populations underwent marked spatial and temporal variations in structure and abundance as settlement intensity varied, but there were consistent general differences between mussel populations on dune rock and sandstone shores in Algoa Bay and on the open coast. It was concluded from these results that, spawning intensity and post-settlement growth and mortality, rather than dispersal, regulated recruitment and the structure and abundance of intertidal P. perna and C. meridionalis populations along the south coast of southern Africa. On the basis of these results it is recommended that species with limited dispersal, variable recruitment and high natural mortality, such as P. perna, should be conserved by protecting a small part of the population in reserves, and controlling utilisation outside reserves to minimize disturbance to local brood stocks. Furthermore, since the potential for reseeding adjacent exploited areas is limited, several small reserves placed at regular intervals along the coast would be more effective than a single large reserve.
- Full Text:
- Date Issued: 1995
Environmental education and research in southern Africa: a landscape of shifting priorities
- Authors: Van Rensburg, Eureta Janse
- Date: 1995
- Subjects: Environmental education -- Research -- South Africa Environmental sciences -- Study and teaching (Higher) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1513 , http://hdl.handle.net/10962/d1003395
- Description: What has come to be labelled as 'the environment crisis' has roots in the structures and orientations of modern societies. True to our modernist ways we call on, or offer, education and research, experts and science, to address our socio-ecological concerns. This study set out to identify research priorities in environmental education from within the institutional setting of a university and within the context of environmental and political change in southern Africa and epistemological shifts in educational research traditions. The emergent research design allowed for a progressive clarification of theoretical vantage point: from an instrumental listing of priorities, through the participatory development of a critical and consensual framework for research, to a reflexive description of a landscape of shifting priorities. I collected data over a 3-year period, in inter alia 38 semi-structured interviews, workshops with some 150 participants, focus group discussions, documents and conferences. Participants' professional contexts included environmental education, natural resource management, social and biophysical sciences, development, formal and non-formal education, funding agencies, academic and non-academic settings. My engagement with the emerging discourses revealed patterns and inconsistencies in participants' views on research, environmental education, change and research priorities. I identified three orientations - Research for Management to Restore Order to Nature and Society, Research to Resolve Practitioners' and Communities' Problems, and Research for Radical Reconstruction - in the emerging landscape. These orientations were accompanied by change models and themes (discourses of difference and 'othering', instrumental views of education and research and accumulative knowledge, a conceptual theory-practice gap) which limited their potential for transformation towards sustainable living. They presented solutions cut from the same modernist cloth as the environment crisis. An emerging Reflexive perspective in and on environmental education research showed potential as a transitionary orientation outside modernist assumptions. I outline research priorities from this perspective. Reflexivity reveals the myths of expert-driven, instrumental and institutionalised research separated from environmental education and based upon rationalistic interpretations of science. It opens up possibilities for transformative knowledge emerging from 're-search' based versions of education as a process of, rather than a means to, social change.
- Full Text:
- Date Issued: 1995
- Authors: Van Rensburg, Eureta Janse
- Date: 1995
- Subjects: Environmental education -- Research -- South Africa Environmental sciences -- Study and teaching (Higher) -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1513 , http://hdl.handle.net/10962/d1003395
- Description: What has come to be labelled as 'the environment crisis' has roots in the structures and orientations of modern societies. True to our modernist ways we call on, or offer, education and research, experts and science, to address our socio-ecological concerns. This study set out to identify research priorities in environmental education from within the institutional setting of a university and within the context of environmental and political change in southern Africa and epistemological shifts in educational research traditions. The emergent research design allowed for a progressive clarification of theoretical vantage point: from an instrumental listing of priorities, through the participatory development of a critical and consensual framework for research, to a reflexive description of a landscape of shifting priorities. I collected data over a 3-year period, in inter alia 38 semi-structured interviews, workshops with some 150 participants, focus group discussions, documents and conferences. Participants' professional contexts included environmental education, natural resource management, social and biophysical sciences, development, formal and non-formal education, funding agencies, academic and non-academic settings. My engagement with the emerging discourses revealed patterns and inconsistencies in participants' views on research, environmental education, change and research priorities. I identified three orientations - Research for Management to Restore Order to Nature and Society, Research to Resolve Practitioners' and Communities' Problems, and Research for Radical Reconstruction - in the emerging landscape. These orientations were accompanied by change models and themes (discourses of difference and 'othering', instrumental views of education and research and accumulative knowledge, a conceptual theory-practice gap) which limited their potential for transformation towards sustainable living. They presented solutions cut from the same modernist cloth as the environment crisis. An emerging Reflexive perspective in and on environmental education research showed potential as a transitionary orientation outside modernist assumptions. I outline research priorities from this perspective. Reflexivity reveals the myths of expert-driven, instrumental and institutionalised research separated from environmental education and based upon rationalistic interpretations of science. It opens up possibilities for transformative knowledge emerging from 're-search' based versions of education as a process of, rather than a means to, social change.
- Full Text:
- Date Issued: 1995
Evaluation of Gratiana spadicea (Klug, 1829) and Metriona elatior (Klug, 1829) (Chrysomelidae: Cassidinae) for the biological control of sticky nightshade Solanum sisymbriifolium Lamarck (Solanaceae) in South Africa
- Authors: Hill, Martin Patrick
- Date: 1995
- Subjects: Solanaceae Solanaceae -- Biological control Chrysomelidae Chrysomelidae -- Host plants Cassida
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5688 , http://hdl.handle.net/10962/d1005374 , https://orcid.org/0000-0003-0579-5298
- Description: Solanum sisymbriifolium (sticky nightshade) is a shrubby weed of South American origin that was introduced to South Africa at the turn of the century. Despite being indicative of disturbed habitats, the weed was found to be invasive in conservation, agricultural recreational and suburban areas; this, coupled with the failure of both chemical and mechanical control attempts suggested that the weed was a good candidate for biological control. A biological control programme which followed a standard protocol was initiated. Observations suggested that S. sisymbriifolium dispersed primarily by seeds. Plants produced large quantities of fleshy fruit, favoured by frugivorous birds, which facilitated the rapid spread of the weed into new habitats. The seeds germinated quickly, especially in disturbed soil, often below the parent plant where they dropped from burst fruit, and along fences where birds roost. The pre-introductory survey of the weed revealed that S. sisymbriifolium was attacked by a relatively small number of, mainly polyphagous, herbivorous insects. These were localised and sporadic in incidence and inflicted very little observable damage. The herbivore fauna of S. sisymbriifolium was depauperate even in relation to two other exotic weeds, S. elaeaglllfolium and S. mauritianum, in South Africa. The paucity of native herbivores on S. sisymbriifoliwn was ascribed to a combination of the weed's taxonomic distinctness from South African Solanum species, and the dense covering of glandular trichomes on its leaves. Although it was shown that the exudate produced by these glandular trichomes of S. sisymbriifolium seriously impeded the movement and feeding of native herbivores, there was not enough evidence to suggest that the glandular trichomes, alone could have been responsible the lack of herbivores on the weed. Two leaf-feeding Cassidinae Gratiana spadicea and MetJ-iona elatior were screened as agents for the biological control of S. sisymbrilfolium. Favourable biological characteristics for both species included a high rate of increase, long-lived adults, many generations per year, and a high per capita feeding rate. Host range was investigated in larval survival tests and adult choice tests. The larvae of both species were reared through to the adult stage on several of the native Solanum species tested, and also on eggplant (S. melongena). However, the survival of G. spadicea on the majority of these species was very low, suggesting that the beetles would be unlikely to attack them in the field. This was supported by the adult choice tests, where G. spadicea females displayed, a strong oviposition preference for their natural host. In contrast, M. elatior larvae survived well on non-host plants, and the females selected several non-host species, including eggplant for oviposition. It was argued that the conflict of interests involving eggplant was overrated because eggplant is subjected to a stringent insecticide spray regime. Based on this evidence, permission for release was granted for G. spadicea. The impact of native parasitoid host range extensions to weed biological control agents in South Africa was investigated. Native parasitoids were recorded from nearly half of the agent species that had established on their target weed. The level of concealment and taxon influenced susceptibility of the agents to parasitoid attack Poorly concealed endophagous agents were most susceptible to attack, while exposed feeders were fairly free from attack. However, native parasitoids were reported not to strongly influence weed biological control agent populations and it was concluded that no agent should be rejected based only on its susceptibility to native parasitoid attack. Finally, several predictions are made as to the potential success of G. spadicea on S. sisymbriifolium and some of the challenges facing the biological control of weeds are discussed.
- Full Text:
- Date Issued: 1995
- Authors: Hill, Martin Patrick
- Date: 1995
- Subjects: Solanaceae Solanaceae -- Biological control Chrysomelidae Chrysomelidae -- Host plants Cassida
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5688 , http://hdl.handle.net/10962/d1005374 , https://orcid.org/0000-0003-0579-5298
- Description: Solanum sisymbriifolium (sticky nightshade) is a shrubby weed of South American origin that was introduced to South Africa at the turn of the century. Despite being indicative of disturbed habitats, the weed was found to be invasive in conservation, agricultural recreational and suburban areas; this, coupled with the failure of both chemical and mechanical control attempts suggested that the weed was a good candidate for biological control. A biological control programme which followed a standard protocol was initiated. Observations suggested that S. sisymbriifolium dispersed primarily by seeds. Plants produced large quantities of fleshy fruit, favoured by frugivorous birds, which facilitated the rapid spread of the weed into new habitats. The seeds germinated quickly, especially in disturbed soil, often below the parent plant where they dropped from burst fruit, and along fences where birds roost. The pre-introductory survey of the weed revealed that S. sisymbriifolium was attacked by a relatively small number of, mainly polyphagous, herbivorous insects. These were localised and sporadic in incidence and inflicted very little observable damage. The herbivore fauna of S. sisymbriifolium was depauperate even in relation to two other exotic weeds, S. elaeaglllfolium and S. mauritianum, in South Africa. The paucity of native herbivores on S. sisymbriifoliwn was ascribed to a combination of the weed's taxonomic distinctness from South African Solanum species, and the dense covering of glandular trichomes on its leaves. Although it was shown that the exudate produced by these glandular trichomes of S. sisymbriifolium seriously impeded the movement and feeding of native herbivores, there was not enough evidence to suggest that the glandular trichomes, alone could have been responsible the lack of herbivores on the weed. Two leaf-feeding Cassidinae Gratiana spadicea and MetJ-iona elatior were screened as agents for the biological control of S. sisymbrilfolium. Favourable biological characteristics for both species included a high rate of increase, long-lived adults, many generations per year, and a high per capita feeding rate. Host range was investigated in larval survival tests and adult choice tests. The larvae of both species were reared through to the adult stage on several of the native Solanum species tested, and also on eggplant (S. melongena). However, the survival of G. spadicea on the majority of these species was very low, suggesting that the beetles would be unlikely to attack them in the field. This was supported by the adult choice tests, where G. spadicea females displayed, a strong oviposition preference for their natural host. In contrast, M. elatior larvae survived well on non-host plants, and the females selected several non-host species, including eggplant for oviposition. It was argued that the conflict of interests involving eggplant was overrated because eggplant is subjected to a stringent insecticide spray regime. Based on this evidence, permission for release was granted for G. spadicea. The impact of native parasitoid host range extensions to weed biological control agents in South Africa was investigated. Native parasitoids were recorded from nearly half of the agent species that had established on their target weed. The level of concealment and taxon influenced susceptibility of the agents to parasitoid attack Poorly concealed endophagous agents were most susceptible to attack, while exposed feeders were fairly free from attack. However, native parasitoids were reported not to strongly influence weed biological control agent populations and it was concluded that no agent should be rejected based only on its susceptibility to native parasitoid attack. Finally, several predictions are made as to the potential success of G. spadicea on S. sisymbriifolium and some of the challenges facing the biological control of weeds are discussed.
- Full Text:
- Date Issued: 1995
HPLC analysis and pharmacokinetics of cyclizine
- Authors: Walker, Roderick Bryan
- Date: 1995
- Subjects: High performance liquid chromatography Piperazine Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3801 , http://hdl.handle.net/10962/d1003279
- Description: The investigations detailed in this dissertation have been conducted to address the paucity of pharmacokinetic information, in published literature, pertaining to cyclizine. The areas of investigation have included the selective quantitation of both cyclizine and its demethylated metabolite, norcyclizine in serum and urine, assessment of stability of both compounds in stored biological samples, dosage form analysis, dissolution rate testing of tablets, and bioavailability and pharmacokinetics following administration of an intravenous solution, and tablets to humans. High-performance liquid chromatography (HPLC) was used as the main analytical technique throughout these studies. An original HPLC method employing ultraviolet detection with a limit of quantitation of 5μg/ℓ was developed for the determination of cyclizine in serum and both cyclizine and norcyclizine in urine, Solid-phase extraction using extraction columns packed with reversed-phase C18 material, and followed by a simple phase-separation step proved successful for the accurate and precise isolation of the compounds. The validated method was applied to the analysis of serum and urine samples from a pilot study in which a single volunteer was administered 50mg of cyclizine hydrochloride. Several samples collected during the pilot study revealed the presence of both drug and metabolite in concentrations below the limit of detection. In order to improve the selectivity and sensitivity of the analytical method an HPLC method with electrochemical detection operating in the "oxidative-screen" mode was developed. The solid-phase extraction procedure was modified slightly and the method found to be precise, accurate, selective and highly sensitive with a limit of quantitation of Iμg/g/l for both cyclizine and norcyclizine in both serum and urine. This method was applied to the determination of both compounds after intravenous and oral administration of cyclizine to humans. HPLC with electrochemical detection was used for the analysis of samples collected during dissolution studies on the batch of tablets used for pharmacokinetic studies. In addition, this method was used to assess content uniformity of the tablets and of samples from the batch of intravenous ampoules of cyclizine lactate. Dissolution studies showed that all tablets tested passed the compendial specifications for cyclizine. Content uniformity assessment revealed that within-batch uniformity existed for both the tablets and ampoules and, therefore, variations in pharmacokinetic parameters for the drug would more than likely be as a result of inter- and intra-individual variability within the subject population. Pharmacokinetic information for cyclizine was obtained following administration of an intravenous bolus dose of cyclizine lactate as a solution, oral administration of cyclizine hydrochloride as a single dose of 50mg and as fixed multiple doses of 50mg every 8 hours for five days. Further information was acquired following administration of single doses of 100mg and 150mg cyclizine hydrochloride. Data collected from these studies were evaluated using both compartmental and non-compartmental techniques. Cyclizine was rapidly absorbed following oral administration with mean kₐ = 1.54 hr⁻¹ and was found to have an absolute bioavailability (F) of 0.47. The presence of norcyclizine in serum following oral and not intravenous dosing suggests cyclizine is susceptible to "first-pass" metabolism in either the gut wall or the I iver. Mean ClTOT determined following the intravenous dose was 0.865 ℓ/hr/kg. The mean ClTOT of 0.823 ℓ/hr/kg calculated following oral dosing, using a unique value of F for each subject compared favourahly with that obtained following intravenous dosing. Renal clearance of cyclizine is negligihle indicating that non-renal routes of elimination account for the majority of removal of cyclizine form the body. Cyclizine is extensively distributed and the mean Vz following an intravenous dose was 16.70 ℓ/kg. This value is lower than that calculated from all oral studies from which the mean Vz was determined to be 25.74 ℓ/kg. Cyclizine is eliminated slowly with a mean elimination t½ = 20.11 hours. Cyclizine dose not appear to follow dosedependent kinetics and therefore, inability to predict steady state levels are more than likely due to accumulation as a result of frequent dosing rather than saturation of elimination mechanisms. Modelling of intravenous data to one-compartment (lBCM), two-compartment (2BCM) and threecompartment models indicated that the pharmacokinetics of cyclizine can be adequately described by a 3BCM. The drug is rapidly distributed into a "shallow" peripheral compartment (α = 9.44 hr⁻¹ , and k₂₁ = 2.09 hr⁻¹ ), and slowly distributed to the "deep" peripheral compartment (β = 0.451 hr⁻¹ and k₃₁ = 0.120 hr⁻¹ ). Modelling of all oral data indicated that a 2BCM best described the pharmacokinetics of the drug, however, distribution to the peripheral compartment is not as rapid as to the "shallow" peripheral compartment following the intravenous dose. Mean distribution parameters were α = 0.64 hr⁻¹1 and, k₂₁ = 0.39 hr⁻¹. Mean CITOT following intravenous dosing of 0.70 ℓ/hr/kg was similar to the mean CIToT of 0.73 ℓ/hr/kg determined after oral dosing. The mean distribution volume at steady state determined following intravenous dosing (17.78 ℓ/kg) was lower than that obtained from the oral studies (25.52 ℓ/kg). The mean terminal elimination half-lives calculated for cyclizine following fitting of intravenous and oral data was 25.09 hours. In general, mean pharmacokinetic parameters calculated following titting of data to a 2BCM after oral administration correlate closely with those calculated using non-compartmental techniques. However, the pharmacokinetics following intravenous dosing are better described by a 3BCM and a close correlation between parameters estimated using noncompartmental techniques and compartmental techniques is evident when a 3BCM model is used.
- Full Text:
- Date Issued: 1995
- Authors: Walker, Roderick Bryan
- Date: 1995
- Subjects: High performance liquid chromatography Piperazine Pharmacokinetics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3801 , http://hdl.handle.net/10962/d1003279
- Description: The investigations detailed in this dissertation have been conducted to address the paucity of pharmacokinetic information, in published literature, pertaining to cyclizine. The areas of investigation have included the selective quantitation of both cyclizine and its demethylated metabolite, norcyclizine in serum and urine, assessment of stability of both compounds in stored biological samples, dosage form analysis, dissolution rate testing of tablets, and bioavailability and pharmacokinetics following administration of an intravenous solution, and tablets to humans. High-performance liquid chromatography (HPLC) was used as the main analytical technique throughout these studies. An original HPLC method employing ultraviolet detection with a limit of quantitation of 5μg/ℓ was developed for the determination of cyclizine in serum and both cyclizine and norcyclizine in urine, Solid-phase extraction using extraction columns packed with reversed-phase C18 material, and followed by a simple phase-separation step proved successful for the accurate and precise isolation of the compounds. The validated method was applied to the analysis of serum and urine samples from a pilot study in which a single volunteer was administered 50mg of cyclizine hydrochloride. Several samples collected during the pilot study revealed the presence of both drug and metabolite in concentrations below the limit of detection. In order to improve the selectivity and sensitivity of the analytical method an HPLC method with electrochemical detection operating in the "oxidative-screen" mode was developed. The solid-phase extraction procedure was modified slightly and the method found to be precise, accurate, selective and highly sensitive with a limit of quantitation of Iμg/g/l for both cyclizine and norcyclizine in both serum and urine. This method was applied to the determination of both compounds after intravenous and oral administration of cyclizine to humans. HPLC with electrochemical detection was used for the analysis of samples collected during dissolution studies on the batch of tablets used for pharmacokinetic studies. In addition, this method was used to assess content uniformity of the tablets and of samples from the batch of intravenous ampoules of cyclizine lactate. Dissolution studies showed that all tablets tested passed the compendial specifications for cyclizine. Content uniformity assessment revealed that within-batch uniformity existed for both the tablets and ampoules and, therefore, variations in pharmacokinetic parameters for the drug would more than likely be as a result of inter- and intra-individual variability within the subject population. Pharmacokinetic information for cyclizine was obtained following administration of an intravenous bolus dose of cyclizine lactate as a solution, oral administration of cyclizine hydrochloride as a single dose of 50mg and as fixed multiple doses of 50mg every 8 hours for five days. Further information was acquired following administration of single doses of 100mg and 150mg cyclizine hydrochloride. Data collected from these studies were evaluated using both compartmental and non-compartmental techniques. Cyclizine was rapidly absorbed following oral administration with mean kₐ = 1.54 hr⁻¹ and was found to have an absolute bioavailability (F) of 0.47. The presence of norcyclizine in serum following oral and not intravenous dosing suggests cyclizine is susceptible to "first-pass" metabolism in either the gut wall or the I iver. Mean ClTOT determined following the intravenous dose was 0.865 ℓ/hr/kg. The mean ClTOT of 0.823 ℓ/hr/kg calculated following oral dosing, using a unique value of F for each subject compared favourahly with that obtained following intravenous dosing. Renal clearance of cyclizine is negligihle indicating that non-renal routes of elimination account for the majority of removal of cyclizine form the body. Cyclizine is extensively distributed and the mean Vz following an intravenous dose was 16.70 ℓ/kg. This value is lower than that calculated from all oral studies from which the mean Vz was determined to be 25.74 ℓ/kg. Cyclizine is eliminated slowly with a mean elimination t½ = 20.11 hours. Cyclizine dose not appear to follow dosedependent kinetics and therefore, inability to predict steady state levels are more than likely due to accumulation as a result of frequent dosing rather than saturation of elimination mechanisms. Modelling of intravenous data to one-compartment (lBCM), two-compartment (2BCM) and threecompartment models indicated that the pharmacokinetics of cyclizine can be adequately described by a 3BCM. The drug is rapidly distributed into a "shallow" peripheral compartment (α = 9.44 hr⁻¹ , and k₂₁ = 2.09 hr⁻¹ ), and slowly distributed to the "deep" peripheral compartment (β = 0.451 hr⁻¹ and k₃₁ = 0.120 hr⁻¹ ). Modelling of all oral data indicated that a 2BCM best described the pharmacokinetics of the drug, however, distribution to the peripheral compartment is not as rapid as to the "shallow" peripheral compartment following the intravenous dose. Mean distribution parameters were α = 0.64 hr⁻¹1 and, k₂₁ = 0.39 hr⁻¹. Mean CITOT following intravenous dosing of 0.70 ℓ/hr/kg was similar to the mean CIToT of 0.73 ℓ/hr/kg determined after oral dosing. The mean distribution volume at steady state determined following intravenous dosing (17.78 ℓ/kg) was lower than that obtained from the oral studies (25.52 ℓ/kg). The mean terminal elimination half-lives calculated for cyclizine following fitting of intravenous and oral data was 25.09 hours. In general, mean pharmacokinetic parameters calculated following titting of data to a 2BCM after oral administration correlate closely with those calculated using non-compartmental techniques. However, the pharmacokinetics following intravenous dosing are better described by a 3BCM and a close correlation between parameters estimated using noncompartmental techniques and compartmental techniques is evident when a 3BCM model is used.
- Full Text:
- Date Issued: 1995
Influence of macro- versus microcooling on the physiological and psychological performance of the human operator
- Authors: Heyns, Gerhardus Johannes
- Date: 1995
- Subjects: Cold -- Physiological effect , Temperature -- Physiological effect , Body temperature -- Regulation , Heat -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5167 , http://hdl.handle.net/10962/d1016247
- Description: This study evaluated the effect of a macro- versus a microcooling system on the cognitive, psychomotor and physiological performance of human operators. Male subjects (n = 24) were acclimatized for four days and then subjected to three different environmental conditions: hot ambient (40°C; 40% RH), microcooling and macrocooling. Each environmental condition was repeated twice; once under a rest condition and once while simulating a physical workload of 40 W. Four performance tests (reasoning, eye-hand coordination, memory, reaction time) were conducted once every hour for four hours. Five physiological measurements, viz rectal temperature, skin temperature, heart rate, total sweat loss and sweat rate, were taken. A significant difference existed between the physiological responses under the hot ambient condition and both cooling conditions. For all five physiological parameters he human operator benefitted substantially whatever the cooling condition. The psychological performance results indicated a greater benefit under the cooling conditions, though various external factors may have influenced responses. User perception showed that macrocooling was perceived to be the optimal method of cooling. The results showed that there was no difference in the extent to which both rectal temperature and heart rate (for rest and work conditions) decreased over the 4-hour study period with micro- and macrocooling. In the baseline hot environment both increase. Sweat rate was lowest when resting or working in a microcooled environment and at its highest in the hot baseline environment. Mean skin temperature was lowest (for rest and work conditions) with microcooling and highest in the hot baseline environment. Reaction time and memory/attention were the same under all three environmental conditions. Eye-hand coordination was better with cooling than without, but did not differ between the two cooling conditions. Reasoning ability was poorest under the hot baseline condition and best in the macrocooled environment. User perception showed that the subjects found macrocooling highly acceptable. Microcooling was found to be uncomfortable, particularly because cold air (18 - 21°C) entered the jacket at one point which caused numbness of the skin at that point. Jackets did not always fit subjects well and the umbilical cord restricted free movement.
- Full Text:
- Date Issued: 1995
- Authors: Heyns, Gerhardus Johannes
- Date: 1995
- Subjects: Cold -- Physiological effect , Temperature -- Physiological effect , Body temperature -- Regulation , Heat -- Physiological effect
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5167 , http://hdl.handle.net/10962/d1016247
- Description: This study evaluated the effect of a macro- versus a microcooling system on the cognitive, psychomotor and physiological performance of human operators. Male subjects (n = 24) were acclimatized for four days and then subjected to three different environmental conditions: hot ambient (40°C; 40% RH), microcooling and macrocooling. Each environmental condition was repeated twice; once under a rest condition and once while simulating a physical workload of 40 W. Four performance tests (reasoning, eye-hand coordination, memory, reaction time) were conducted once every hour for four hours. Five physiological measurements, viz rectal temperature, skin temperature, heart rate, total sweat loss and sweat rate, were taken. A significant difference existed between the physiological responses under the hot ambient condition and both cooling conditions. For all five physiological parameters he human operator benefitted substantially whatever the cooling condition. The psychological performance results indicated a greater benefit under the cooling conditions, though various external factors may have influenced responses. User perception showed that macrocooling was perceived to be the optimal method of cooling. The results showed that there was no difference in the extent to which both rectal temperature and heart rate (for rest and work conditions) decreased over the 4-hour study period with micro- and macrocooling. In the baseline hot environment both increase. Sweat rate was lowest when resting or working in a microcooled environment and at its highest in the hot baseline environment. Mean skin temperature was lowest (for rest and work conditions) with microcooling and highest in the hot baseline environment. Reaction time and memory/attention were the same under all three environmental conditions. Eye-hand coordination was better with cooling than without, but did not differ between the two cooling conditions. Reasoning ability was poorest under the hot baseline condition and best in the macrocooled environment. User perception showed that the subjects found macrocooling highly acceptable. Microcooling was found to be uncomfortable, particularly because cold air (18 - 21°C) entered the jacket at one point which caused numbness of the skin at that point. Jackets did not always fit subjects well and the umbilical cord restricted free movement.
- Full Text:
- Date Issued: 1995
Physiological signal transduction from the photosynthetic apparatus in the green alga Dunaliella salina
- Logie, Malcolme Ronald Ruxton
- Authors: Logie, Malcolme Ronald Ruxton
- Date: 1995
- Subjects: Cellular signal transduction Photosynthesis -- Research Green algae Dunaliella
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4035 , http://hdl.handle.net/10962/d1004095
- Description: The transduction of stress signals in plants is known to involve complex hysiological responses. In D. salina a range of stresses results in hyperaccumulation of ft-carotene and an understanding of stress responses in this organism has important biotechnological implications. In this thesis an attempt was made to elucidate the physiological components involved and establish a role for pH in response to high light stress. In order to achieve this the effect of high light stress on photosynthesis and cell productivity was measured. Results showed that photosynthetic carbon assimilation, oxygen evolution and cellular productivity was initially inhibited by exposure to high light intensities, but this inhibition was transient and was overcome by a rapid increase in all three parameters. The response of the carbon pool intermediates was also investigated. It was shown that on exposure to high light ft-carotene declined but then showed a rapid increase after about 4 hours of exposure. It was also demonstrated that the initial loss of ft-carotene was due to loss of this pigment from the photosynthetic pigment bed and that the hyper-accumulation of ft-carotene was due to accumulation of ft-carotene in lipoidal globules located in the chloroplast stroma. It was further demonstrated that there was mass movement of carbon in the xanthophyll cycle shortly after exposure to high light. This was characterized by the de-epoxidation of violaxanthin to antheraxanthin with a further de-epoxidation to zeaxanthin, thereby decreasing the epoxidation state of the cycle. Furthermore, it was shown that there was relocation of carbon from violaxanthin to the plant growth regulator abscisic acid. It was also shown for the first time in D. salina that the production of ft-carotene and operation of the epoxidation state of the xanthophyll cycle has a periodicity which is established after exposure to successive cycles of a light regime. Chlorophyll fluorescence was used together with well established ammonia stress responses to acquire a general overview of energy dissipation from the photosynthetic pigment bed. In conjunction with an understanding of xanthophyll cycle operation during exposure to high light stress it has been possible to establish a relationship between chlorophyll florescence, xanthophyll cycle operation and intracellular pH. It was also shown using chlorophyll fluorescence that after 4 hour exposure to high light a maximum fluorescence peak could no longer be induced indicating a transition at about this point from a state of reversibility to commitment of the full stress response. Nuclear magnetic resonance was used to follow intracellular pH fluxes during exposure to high light. A novel technique was developed for studying photosynthetically active organisms in the dark using nuclear magnetic resonance. These results showed that on exposure to high light stress there is rapid acidification of the chloroplast stroma and to a lesser degree of the acidic vacuole. The pH of these compartments is re-established after about 4 hours which is co-incident with the onset of fl-carotene hyper-accumulation and the loss of the induction of the chlorophyll fluorescence peak indicating an intimate relationship for fl-carotene, chlorophyll fluorescence, xanthophyll cycle operation and pH. The results from this study allow for the proposal of a general physiological stress transduction response mechanism for D. salina which is common for a range of different stresses and where intracellular pH plays a central role.
- Full Text:
- Date Issued: 1995
- Authors: Logie, Malcolme Ronald Ruxton
- Date: 1995
- Subjects: Cellular signal transduction Photosynthesis -- Research Green algae Dunaliella
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4035 , http://hdl.handle.net/10962/d1004095
- Description: The transduction of stress signals in plants is known to involve complex hysiological responses. In D. salina a range of stresses results in hyperaccumulation of ft-carotene and an understanding of stress responses in this organism has important biotechnological implications. In this thesis an attempt was made to elucidate the physiological components involved and establish a role for pH in response to high light stress. In order to achieve this the effect of high light stress on photosynthesis and cell productivity was measured. Results showed that photosynthetic carbon assimilation, oxygen evolution and cellular productivity was initially inhibited by exposure to high light intensities, but this inhibition was transient and was overcome by a rapid increase in all three parameters. The response of the carbon pool intermediates was also investigated. It was shown that on exposure to high light ft-carotene declined but then showed a rapid increase after about 4 hours of exposure. It was also demonstrated that the initial loss of ft-carotene was due to loss of this pigment from the photosynthetic pigment bed and that the hyper-accumulation of ft-carotene was due to accumulation of ft-carotene in lipoidal globules located in the chloroplast stroma. It was further demonstrated that there was mass movement of carbon in the xanthophyll cycle shortly after exposure to high light. This was characterized by the de-epoxidation of violaxanthin to antheraxanthin with a further de-epoxidation to zeaxanthin, thereby decreasing the epoxidation state of the cycle. Furthermore, it was shown that there was relocation of carbon from violaxanthin to the plant growth regulator abscisic acid. It was also shown for the first time in D. salina that the production of ft-carotene and operation of the epoxidation state of the xanthophyll cycle has a periodicity which is established after exposure to successive cycles of a light regime. Chlorophyll fluorescence was used together with well established ammonia stress responses to acquire a general overview of energy dissipation from the photosynthetic pigment bed. In conjunction with an understanding of xanthophyll cycle operation during exposure to high light stress it has been possible to establish a relationship between chlorophyll florescence, xanthophyll cycle operation and intracellular pH. It was also shown using chlorophyll fluorescence that after 4 hour exposure to high light a maximum fluorescence peak could no longer be induced indicating a transition at about this point from a state of reversibility to commitment of the full stress response. Nuclear magnetic resonance was used to follow intracellular pH fluxes during exposure to high light. A novel technique was developed for studying photosynthetically active organisms in the dark using nuclear magnetic resonance. These results showed that on exposure to high light stress there is rapid acidification of the chloroplast stroma and to a lesser degree of the acidic vacuole. The pH of these compartments is re-established after about 4 hours which is co-incident with the onset of fl-carotene hyper-accumulation and the loss of the induction of the chlorophyll fluorescence peak indicating an intimate relationship for fl-carotene, chlorophyll fluorescence, xanthophyll cycle operation and pH. The results from this study allow for the proposal of a general physiological stress transduction response mechanism for D. salina which is common for a range of different stresses and where intracellular pH plays a central role.
- Full Text:
- Date Issued: 1995
Reactions of iron- and zinc-fuelled pyrotechnic systems
- Authors: Tribelhorn, Michael John
- Date: 1995
- Subjects: Detonators Peroxides Chemistry, Analytic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4341 , http://hdl.handle.net/10962/d1005003
- Description: A major industrial use of pyrotechnic compositions is as delay fuses in electric detonators. Suitable delay times may be achieved through (i) choice of chemical components (ii) adjustment of composition of the system chosen and, finally, (iii) adjustment of the length of fuse used. This study forms part of a survey of binary fuel/oxidant combinations in an attempt to provide some fundamental information on the first step above: (i) choice of chemical components. The complete survey has included studies of a single fuel in combination with one of a variety of oxidants, and studies of the oxidation of one of several different fuels separately by barium peroxide and strontium peroxide. This study is part of this second approach and the fuels chosen were iron and zinc powders, mainly for chemical reasons (including the potential for use of thermomagnetometry on the iron systems), but also for possible environmental advantages. The mixed oxide products of pyrotechnic combustion could also have some scientific and/or commercial value. The techniques used included thermal analyses of mixtures and their individual components, and measurements of temperature-time profiles during combustion. Thermodynamic and kinetic information was obtained under a variety of conditions and scanning electron microscopy and X-ray diffraction and microprobe analyses provided additional information. Possible mechanisms of reactions are discussed in detail. The practical conclusions were that any potential use which the Fe/peroxide systems may have as delay compositions, with burning-rates of from 3-30 mm s⁻¹, is offset by the susceptibility of the oxidants to reaction with water and CO₂ in the atmosphere. The Zn/BaO₂ and Zn/SrO₂ systems did not burn under compaction, and combustion of uncompacted powders was erratic. Zinc liquid (and probably zinc vapour) take part in the reaction and the gaseous nature of the combustion makes zinc-fuelled pyrotechnic systems unsuitable for delay applications. All the techniques used showed the heterogeneity of the solid residues of combustion. If these residues were to be of any value, they would need further conventional treatment involving grinding of the residue, possible adjustment of compositions, and calcining to produce uniform materials.
- Full Text:
- Date Issued: 1995
- Authors: Tribelhorn, Michael John
- Date: 1995
- Subjects: Detonators Peroxides Chemistry, Analytic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4341 , http://hdl.handle.net/10962/d1005003
- Description: A major industrial use of pyrotechnic compositions is as delay fuses in electric detonators. Suitable delay times may be achieved through (i) choice of chemical components (ii) adjustment of composition of the system chosen and, finally, (iii) adjustment of the length of fuse used. This study forms part of a survey of binary fuel/oxidant combinations in an attempt to provide some fundamental information on the first step above: (i) choice of chemical components. The complete survey has included studies of a single fuel in combination with one of a variety of oxidants, and studies of the oxidation of one of several different fuels separately by barium peroxide and strontium peroxide. This study is part of this second approach and the fuels chosen were iron and zinc powders, mainly for chemical reasons (including the potential for use of thermomagnetometry on the iron systems), but also for possible environmental advantages. The mixed oxide products of pyrotechnic combustion could also have some scientific and/or commercial value. The techniques used included thermal analyses of mixtures and their individual components, and measurements of temperature-time profiles during combustion. Thermodynamic and kinetic information was obtained under a variety of conditions and scanning electron microscopy and X-ray diffraction and microprobe analyses provided additional information. Possible mechanisms of reactions are discussed in detail. The practical conclusions were that any potential use which the Fe/peroxide systems may have as delay compositions, with burning-rates of from 3-30 mm s⁻¹, is offset by the susceptibility of the oxidants to reaction with water and CO₂ in the atmosphere. The Zn/BaO₂ and Zn/SrO₂ systems did not burn under compaction, and combustion of uncompacted powders was erratic. Zinc liquid (and probably zinc vapour) take part in the reaction and the gaseous nature of the combustion makes zinc-fuelled pyrotechnic systems unsuitable for delay applications. All the techniques used showed the heterogeneity of the solid residues of combustion. If these residues were to be of any value, they would need further conventional treatment involving grinding of the residue, possible adjustment of compositions, and calcining to produce uniform materials.
- Full Text:
- Date Issued: 1995
Structural studies on the capsular antigens of some Escherichia coli serotypes
- Authors: Leslie, Margaret Ruth
- Date: 1995
- Subjects: Escherichia Polysaccharides Antigens Enterobacteriaceae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3767 , http://hdl.handle.net/10962/d1003245
- Description: The research presented in this thesis forms part of an on-going collaborative programme concerned with the determination of the chemical structures of the surface antigens of bacteria belonging to genera within the family Enterobacteriaceae. Bacteria of this family are opportunistic pathogens and are frequently responsible for serious infections in animals and man. Surface antigens produced by virulent strains are largely polysaccharides and occur as lipopolysaccharides (the O-antigens) and capsular polysaccharides (the K-antigens) respectively. The extracellular polysaccharide antigens expressed by strains of the species Escherichia coli are of considerable . interest due to their effect on immunological processes and the relationship which exists between their chemical structure and virulence. To date, some seventy-four K-antigens have been distinguished serologically within the species E. coli and structures have been determined for most of these. The K-antigens of E. coli are structurally diverse and exhibit serological cross-reactivity with other pathogenic bacteria. The structures of five previously unstudied E. coli K-antigens, viz. those produced by serotypes 020:K1 01 :H-, 08:K45:H9, 08:K50:H-, 0101 :K1 03:H-, and 08:K43:H11, are presented in this thesis. A variety of chemical techniques has been employed in the structural analysis, and these are discussed. Two-dimensional NMR spectroscopic techniques proved invaluable for the structural elucidation of these complex carbohydrates, and high-field NMR spectroscopy alone was used in the analysis of the K43 antigen. Structural analysis of the K1 03 antigen was facilitated by specific enzymatic degradation, using a bacteriophage-borne endoglycanase. The K45 antigen was found to contain the unusual sugar 3-acetamido-3,6-dideoxygalactopyranose, while the K50 and K103 antigens join a minority group of polysaccharides which contain pyruvate as their only acidic component.
- Full Text:
- Date Issued: 1995
- Authors: Leslie, Margaret Ruth
- Date: 1995
- Subjects: Escherichia Polysaccharides Antigens Enterobacteriaceae
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3767 , http://hdl.handle.net/10962/d1003245
- Description: The research presented in this thesis forms part of an on-going collaborative programme concerned with the determination of the chemical structures of the surface antigens of bacteria belonging to genera within the family Enterobacteriaceae. Bacteria of this family are opportunistic pathogens and are frequently responsible for serious infections in animals and man. Surface antigens produced by virulent strains are largely polysaccharides and occur as lipopolysaccharides (the O-antigens) and capsular polysaccharides (the K-antigens) respectively. The extracellular polysaccharide antigens expressed by strains of the species Escherichia coli are of considerable . interest due to their effect on immunological processes and the relationship which exists between their chemical structure and virulence. To date, some seventy-four K-antigens have been distinguished serologically within the species E. coli and structures have been determined for most of these. The K-antigens of E. coli are structurally diverse and exhibit serological cross-reactivity with other pathogenic bacteria. The structures of five previously unstudied E. coli K-antigens, viz. those produced by serotypes 020:K1 01 :H-, 08:K45:H9, 08:K50:H-, 0101 :K1 03:H-, and 08:K43:H11, are presented in this thesis. A variety of chemical techniques has been employed in the structural analysis, and these are discussed. Two-dimensional NMR spectroscopic techniques proved invaluable for the structural elucidation of these complex carbohydrates, and high-field NMR spectroscopy alone was used in the analysis of the K43 antigen. Structural analysis of the K1 03 antigen was facilitated by specific enzymatic degradation, using a bacteriophage-borne endoglycanase. The K45 antigen was found to contain the unusual sugar 3-acetamido-3,6-dideoxygalactopyranose, while the K50 and K103 antigens join a minority group of polysaccharides which contain pyruvate as their only acidic component.
- Full Text:
- Date Issued: 1995
Synthetic and spectrometric studies of benzodioxepinone derivatives
- Authors: Gelebe, Aifheli Carlson
- Date: 1995
- Subjects: Benzodiazepines -- Research Flavonoids -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4382 , http://hdl.handle.net/10962/d1005047
- Description: An extensive range of oxygen and sulphur substituted benzodiazepine analogues has been synthesised via Baeyer-Villiger and Schmidt reactions of specially prepared flavanone and N-acetyl-4-quinolone precursors. Alternative, cyclisation routes have also been used to prepare some of these compounds. Ring-opening reactions of 1,5-benzodioxepinones have been investigated and a detailed kinetic-mechanistic study of the Baeyer-Villiger reaction of flavanones has been carried out using 1 H NMR spectroscopy to explain the observed regiochemistry of oxygen insertion. The electron-impact mass spectrometric fragmentation patterns of series of 4-aryl-l ,5-benzoxathiepinones, 3-aryl-4, I-benzoxathiepinones and 3-aryl-4,1-benzoxathiepines have been studied using a combination of low-resolution, highresolution and metastable-peak analyses. The 170 NMR spectroscopic properties of various oxygenated analogues have also been studied. The binding affinities of selected benzodiazepine analogues for rat brain benzodiazepine receptors have been evaluated using a radioreceptor assay technique; at certain concentrations, some of test compounds exhibited remarkable potentiation of diazepam binding, others the ability to displace diazepam from benzodiazepine receptors. A conformational analysis of the 7-membered ring systems has been undertaken, using lH NMR spectroscopic, computer modelling and x-ray crystallographic techniques, and certain conformational preferences have been identified.
- Full Text:
- Date Issued: 1995
- Authors: Gelebe, Aifheli Carlson
- Date: 1995
- Subjects: Benzodiazepines -- Research Flavonoids -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4382 , http://hdl.handle.net/10962/d1005047
- Description: An extensive range of oxygen and sulphur substituted benzodiazepine analogues has been synthesised via Baeyer-Villiger and Schmidt reactions of specially prepared flavanone and N-acetyl-4-quinolone precursors. Alternative, cyclisation routes have also been used to prepare some of these compounds. Ring-opening reactions of 1,5-benzodioxepinones have been investigated and a detailed kinetic-mechanistic study of the Baeyer-Villiger reaction of flavanones has been carried out using 1 H NMR spectroscopy to explain the observed regiochemistry of oxygen insertion. The electron-impact mass spectrometric fragmentation patterns of series of 4-aryl-l ,5-benzoxathiepinones, 3-aryl-4, I-benzoxathiepinones and 3-aryl-4,1-benzoxathiepines have been studied using a combination of low-resolution, highresolution and metastable-peak analyses. The 170 NMR spectroscopic properties of various oxygenated analogues have also been studied. The binding affinities of selected benzodiazepine analogues for rat brain benzodiazepine receptors have been evaluated using a radioreceptor assay technique; at certain concentrations, some of test compounds exhibited remarkable potentiation of diazepam binding, others the ability to displace diazepam from benzodiazepine receptors. A conformational analysis of the 7-membered ring systems has been undertaken, using lH NMR spectroscopic, computer modelling and x-ray crystallographic techniques, and certain conformational preferences have been identified.
- Full Text:
- Date Issued: 1995
The conflict between adaptation and constraint : the case of the Siphonariid limpets
- Authors: Chambers, Richard Jonathan
- Date: 1995
- Subjects: Siphonaria -- Adaptation Limpets -- Adaptation Pulmonata
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5657 , http://hdl.handle.net/10962/d1005340
- Description: The reproductive strategies of marine invertebrates have been related to various aspects of both their ecology, and their phylogenetic history. It has been the purpose of this thesis to try and separate these components among Siphonaria, a group of marine pulmonates. The taxonomy of these species is revised and I conclude that nine species are valid. All species deposit benthic egg masses and development may be either direct (S. anneae, S. compressa, S. dayi, S. nigerrima, S. serrata and S. tenuicostulata) or planktonic (S. capensis, S.concinna and S. oculus). Data on distribution and life-history relating to mode of larval development is then presented for 26 species of Siphonaria worldwide. Fifteen species are direct developers, nine are planktonic developers and a further two appear to have a dual developmental capacity, retaining both the velar swimming apparatus of a planktonic developer and the crawling foot of a direct developer. Direct developing species hatch from larger egg capsules, and generally occur higher on the shore than planktonic developers. Worldwide, planktonic developers are more widespread than direct developers, and individual planktonic species may have a greater latitudinal range. In most S~honaria subgenera, mode of larval development appears to be constant, although two subgenera (Patel/opsis and Sacculosiphonaria) include both developmental types. Locally, the intertidal zonation of three sympatric species (S. capensis, S. concinna and S. serrata) does not support a model which predicts direct development on the high shore and planktonic development on the low shore. However, distributions do correspond to particular intertidal microhabitats, and while there may be no, direct relationship between mode of larval development and intertidal height, the physical structure of egg masses, and the microhabitats used for spawning appear adaptive with regards to desiccation in the intertidal. S. concinna (planktonic development) and S. serrata (direct development) occur in similar microhabitats and are likely to be under similar selection pressures. In having different modes of larval development, there appears to be more than one optimal solution in a particular selective regime. In addition, both species seem to apportion similar amounts of energy to reproduction for each spawning episode, and also annually suggesting an optimum allocation of resources to reproduction. Genetic investigations using PolyAcrylamide Gel Electrophoresis (PAGE) confirm the status of the southern African species initially described, and indicate greater genetic variability associated with planktonic developing species than direct developing species. The systematic relationships revealed by DNA fingerprinting support the current classification systems, and also have implications with regards the evolution of larval development: direct development may be the plesiomorphic condition in, and among, some Siphonaria groups. There are both phylogenetic and adaptive explanations for the distribution of reproductive mode among benthic marine invertebrates. An evolutionary question, however, is not just a matter of either adaptation or constraint, it is a combination of these. Both contribute to the distribution of developmental mode among Siphonaria.
- Full Text:
- Date Issued: 1995
- Authors: Chambers, Richard Jonathan
- Date: 1995
- Subjects: Siphonaria -- Adaptation Limpets -- Adaptation Pulmonata
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5657 , http://hdl.handle.net/10962/d1005340
- Description: The reproductive strategies of marine invertebrates have been related to various aspects of both their ecology, and their phylogenetic history. It has been the purpose of this thesis to try and separate these components among Siphonaria, a group of marine pulmonates. The taxonomy of these species is revised and I conclude that nine species are valid. All species deposit benthic egg masses and development may be either direct (S. anneae, S. compressa, S. dayi, S. nigerrima, S. serrata and S. tenuicostulata) or planktonic (S. capensis, S.concinna and S. oculus). Data on distribution and life-history relating to mode of larval development is then presented for 26 species of Siphonaria worldwide. Fifteen species are direct developers, nine are planktonic developers and a further two appear to have a dual developmental capacity, retaining both the velar swimming apparatus of a planktonic developer and the crawling foot of a direct developer. Direct developing species hatch from larger egg capsules, and generally occur higher on the shore than planktonic developers. Worldwide, planktonic developers are more widespread than direct developers, and individual planktonic species may have a greater latitudinal range. In most S~honaria subgenera, mode of larval development appears to be constant, although two subgenera (Patel/opsis and Sacculosiphonaria) include both developmental types. Locally, the intertidal zonation of three sympatric species (S. capensis, S. concinna and S. serrata) does not support a model which predicts direct development on the high shore and planktonic development on the low shore. However, distributions do correspond to particular intertidal microhabitats, and while there may be no, direct relationship between mode of larval development and intertidal height, the physical structure of egg masses, and the microhabitats used for spawning appear adaptive with regards to desiccation in the intertidal. S. concinna (planktonic development) and S. serrata (direct development) occur in similar microhabitats and are likely to be under similar selection pressures. In having different modes of larval development, there appears to be more than one optimal solution in a particular selective regime. In addition, both species seem to apportion similar amounts of energy to reproduction for each spawning episode, and also annually suggesting an optimum allocation of resources to reproduction. Genetic investigations using PolyAcrylamide Gel Electrophoresis (PAGE) confirm the status of the southern African species initially described, and indicate greater genetic variability associated with planktonic developing species than direct developing species. The systematic relationships revealed by DNA fingerprinting support the current classification systems, and also have implications with regards the evolution of larval development: direct development may be the plesiomorphic condition in, and among, some Siphonaria groups. There are both phylogenetic and adaptive explanations for the distribution of reproductive mode among benthic marine invertebrates. An evolutionary question, however, is not just a matter of either adaptation or constraint, it is a combination of these. Both contribute to the distribution of developmental mode among Siphonaria.
- Full Text:
- Date Issued: 1995
The vocal works of Olivier Messiaen
- Authors: Donkin, Deborah Jean
- Date: 1995
- Subjects: Messiaen, Olivier, 1908-1992 Vocal music -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2634 , http://hdl.handle.net/10962/d1002299
- Description: Olivier Messiaen's compositions for voice, though less widely known than his instrumental works, span some forty years and comprise a fifth of his total output. They have hitherto not been subject to much attention. A study of the elements comprising the vocal lines and accompanying instrumentation from the piano-voice song set, Trois melodies (1930), to the vast orchestral-choral La Transfiguration de Notre Seigneur Jesus-Chlist (1969) reveals, amongst other characteristic and evolving features, the emergence of a unique, simulated, plainchant style and its subsequent transformation into incantation with suitably modified accompaniment. While wide-ranging, chromatic and rhythmically free vocal lines are typical of many twentieth century compositions, Messiaen's use of such features is found to be novel, by virtue of the peculiar modal and temporal ambits within which he operated. Vocal delivery is progressively expanded from conventional bel canto production to humming, howling,and eventually speech and percussive sounds and reaches an apotheosis in the virtuoso effects of Cinq Rechants (1949). This recedes somewhat in La Transfiguration, which displays instead a wealth of hybrid plainsong-type writing. Choral works are interesting in that the emphasis shifts from standard part-writing to monody or accompanied unison singing, with an attendant absence of characterised solo parts. By constantly varying the colour of the single melodic line with different permutations of voice types, timbre assumes a new importance, particularly in La Transfiguration. The study of the texts, most of which were conceived by the composer simultaneously with the music, contributes much to the understanding of each work. Biblical symbolism in the early lyrics is progressively enriched by references to numerological, mythological and nature symbolism, mixed in an increasingly Surrealistic manner. The gradual incorporation of emotive phonemes in the texts, culminates in the invented language of Cinq Rechants. The thesis thus reveals an evolving yet persistently idiosyncratic vocal style, which establishes Messiaen as one of the most original composers of his time. It further demonstrates that his vocal works are an important component of his total oeuvre and also a significant contribution to twentieth century vocal literature.
- Full Text:
- Date Issued: 1995
- Authors: Donkin, Deborah Jean
- Date: 1995
- Subjects: Messiaen, Olivier, 1908-1992 Vocal music -- Research
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:2634 , http://hdl.handle.net/10962/d1002299
- Description: Olivier Messiaen's compositions for voice, though less widely known than his instrumental works, span some forty years and comprise a fifth of his total output. They have hitherto not been subject to much attention. A study of the elements comprising the vocal lines and accompanying instrumentation from the piano-voice song set, Trois melodies (1930), to the vast orchestral-choral La Transfiguration de Notre Seigneur Jesus-Chlist (1969) reveals, amongst other characteristic and evolving features, the emergence of a unique, simulated, plainchant style and its subsequent transformation into incantation with suitably modified accompaniment. While wide-ranging, chromatic and rhythmically free vocal lines are typical of many twentieth century compositions, Messiaen's use of such features is found to be novel, by virtue of the peculiar modal and temporal ambits within which he operated. Vocal delivery is progressively expanded from conventional bel canto production to humming, howling,and eventually speech and percussive sounds and reaches an apotheosis in the virtuoso effects of Cinq Rechants (1949). This recedes somewhat in La Transfiguration, which displays instead a wealth of hybrid plainsong-type writing. Choral works are interesting in that the emphasis shifts from standard part-writing to monody or accompanied unison singing, with an attendant absence of characterised solo parts. By constantly varying the colour of the single melodic line with different permutations of voice types, timbre assumes a new importance, particularly in La Transfiguration. The study of the texts, most of which were conceived by the composer simultaneously with the music, contributes much to the understanding of each work. Biblical symbolism in the early lyrics is progressively enriched by references to numerological, mythological and nature symbolism, mixed in an increasingly Surrealistic manner. The gradual incorporation of emotive phonemes in the texts, culminates in the invented language of Cinq Rechants. The thesis thus reveals an evolving yet persistently idiosyncratic vocal style, which establishes Messiaen as one of the most original composers of his time. It further demonstrates that his vocal works are an important component of his total oeuvre and also a significant contribution to twentieth century vocal literature.
- Full Text:
- Date Issued: 1995
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