Woman vulnerability to HIV/AIDS : an investigation into women's conceptions and experiences in negotiating sex and safe sex in Okalongo constituency, Omusati Region, Namibia
- Authors: Haipinge, Rauha
- Date: 2013
- Subjects: AIDS (Disease) in women -- Namibia -- Omusati AIDS (Disease) -- Social aspects -- Namibia -- Omusati HIV infections -- Social aspects -- Namibia -- Omusati Women -- Namibia -- Omusati -- Social conditions Women -- Sexual behavior -- Namibia -- Omusati Man-woman relationships -- Namibia -- Omusati Sex instruction -- Namibia -- Omusati Safe sex in AIDS prevention -- Namibia -- Omusati Sex role -- Namibia -- Omusati HIV-positive persons -- Sex differences -- Namibia -- Omusati Male domination (Social structure) -- Namibia -- Omusati Sex discrimination against women -- Namibia -- Omusati
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1839 , http://hdl.handle.net/10962/d1004337
- Description: This study emerged from the high prevalence rate of HIV and AIDS infection among women in Sub-Saharan Africa, which has no exception to Namibia. Women have been vulnerable to HIV and AIDS let alone on sex related issues since the epidemic emerged, but not research has been done specifically to Okalongo women. The way in which women vulnerable to HIV and AIDS infection were explored by examined social and cultural identities that affect women’s sexual relations in negotiating sex and safe sex. Qualitative study on a sample of fifteen women was conducted in Okalongo. The purpose of this study was to investigate the conceptions and experiences of women in negotiating sex and safe sex with their husband and partners. Feminist theory guided the methodology and analysis of data. I assumed that gender roles andsexuality are socially constructed, shaped by religion, social, political, and economic influences and modified throughout life. Feminist theory assisted in documentary the ways in which the female’s gender and sexuality in Okalongo is shaped by cultural influences and by institutions that disadvantage female and other oppressed groups by silencing their voices. The feminist further guided the discussion of the contradicting messages about women’s sexuality and their experiences, as women complied, conformed and even colluded with their oppression. To address the issue under study, the primary analysis of data from the focus group discussion and individual interview were utilised. The following themes were the heart of analysis: Women Positionality, Normalisation and Compliance, Women Agency and Male Dominance Power, Women Perceptions of Risk, Sex Education in and out of school among Women.In this study the data suggested that women in Okalongo are more vulnerable to their lack of assertiveness, as they have difficult in developing an authoritative voice, they tend to be humble about their achievements and knowledge and to only assertively when concerned about others. The findings supported the literature that women’s vulnerability is strongly influenced and tied by broader forces present in the society. Women’s vulnerability is real and needs to be tackled for any progress to occur in the fight against AIDS. Until factors that constraints and enabling women agency to negotiate sex and safe sex acknowledged and addressed, women will continue to succumb to the HIV pandemic.
- Full Text:
- Date Issued: 2013
- Authors: Haipinge, Rauha
- Date: 2013
- Subjects: AIDS (Disease) in women -- Namibia -- Omusati AIDS (Disease) -- Social aspects -- Namibia -- Omusati HIV infections -- Social aspects -- Namibia -- Omusati Women -- Namibia -- Omusati -- Social conditions Women -- Sexual behavior -- Namibia -- Omusati Man-woman relationships -- Namibia -- Omusati Sex instruction -- Namibia -- Omusati Safe sex in AIDS prevention -- Namibia -- Omusati Sex role -- Namibia -- Omusati HIV-positive persons -- Sex differences -- Namibia -- Omusati Male domination (Social structure) -- Namibia -- Omusati Sex discrimination against women -- Namibia -- Omusati
- Language: English
- Type: Thesis , Masters , MEd
- Identifier: vital:1839 , http://hdl.handle.net/10962/d1004337
- Description: This study emerged from the high prevalence rate of HIV and AIDS infection among women in Sub-Saharan Africa, which has no exception to Namibia. Women have been vulnerable to HIV and AIDS let alone on sex related issues since the epidemic emerged, but not research has been done specifically to Okalongo women. The way in which women vulnerable to HIV and AIDS infection were explored by examined social and cultural identities that affect women’s sexual relations in negotiating sex and safe sex. Qualitative study on a sample of fifteen women was conducted in Okalongo. The purpose of this study was to investigate the conceptions and experiences of women in negotiating sex and safe sex with their husband and partners. Feminist theory guided the methodology and analysis of data. I assumed that gender roles andsexuality are socially constructed, shaped by religion, social, political, and economic influences and modified throughout life. Feminist theory assisted in documentary the ways in which the female’s gender and sexuality in Okalongo is shaped by cultural influences and by institutions that disadvantage female and other oppressed groups by silencing their voices. The feminist further guided the discussion of the contradicting messages about women’s sexuality and their experiences, as women complied, conformed and even colluded with their oppression. To address the issue under study, the primary analysis of data from the focus group discussion and individual interview were utilised. The following themes were the heart of analysis: Women Positionality, Normalisation and Compliance, Women Agency and Male Dominance Power, Women Perceptions of Risk, Sex Education in and out of school among Women.In this study the data suggested that women in Okalongo are more vulnerable to their lack of assertiveness, as they have difficult in developing an authoritative voice, they tend to be humble about their achievements and knowledge and to only assertively when concerned about others. The findings supported the literature that women’s vulnerability is strongly influenced and tied by broader forces present in the society. Women’s vulnerability is real and needs to be tackled for any progress to occur in the fight against AIDS. Until factors that constraints and enabling women agency to negotiate sex and safe sex acknowledged and addressed, women will continue to succumb to the HIV pandemic.
- Full Text:
- Date Issued: 2013
Life-history and stock assessment of Clarias Gariepinus in the Okavango Delta, Botswana
- Authors: Bokhutlo, Thethela
- Date: 2012
- Subjects: Catfishes -- Botswana -- Okavango River Delta , Clarias gariepinus , Aquaculture -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5297 , http://hdl.handle.net/10962/d1005142 , Catfishes -- Botswana -- Okavango River Delta , Clarias gariepinus , Aquaculture -- Botswana -- Okavango River Delta
- Description: Large catfishes (Clarias gariepinus & Clarias ngamensis) are not exploited commercially in the Okavango Delta, Botswana. They however constitute a large proportion of the gill net fishery catch (23 %) albeit as by-catch, coming second after cichlids (70 %). Monthly experimetal gill net sampling over 8 years showed that C. gariepinus was the most abundant species in the Okavango Delta by mass making up 37 % of the catch composition by fresh weight. Despite the relatively high abundance of C. gariepinus in the Okavango Delta, its status has never been fully assessed. For this reason, this study aimed to assess the status of C. gariepinus in the Okavango Delta with the particular goal to determine if the species could support a directed commercial gill net fishery. Investigation of the effects of the flood pulse on abundance of C. gariepinus showed that variability in water levels was the major driver of population abundance for this species. Three biological variables: (1) catch per unit effort (CPUE); (2) % catch composition and (3) Shannon's diversity index (H') exhibited a negative and significant relationship with the flood index within a year. The variation in these variables was statistically significant between months. There was a weak positive relationship between water levels and the biological variables between years suggesting increase in productivity of the system at high water levels without a lag period. Age and growth were determined using sectioned otoliths. Edge analysis showed that growth zone deposition occurred during the drawdown period in summer when water temperature and day length were increasing. The maximum recorded age was 15 years. Growth of this species was best described by the linear models (y = 21.50x + 427.39 mm LT; r² = 0.35) for females and (y = 23.79x + 440.83 mm LT; r² = 0.38) for males. The von Bertalanffy growth model described growth as Lt = 10000(1- exp(-0.002(t + 18.07))) mm LT for combined sexes Lt = 10000(1- exp( -0.002(t + 18.50))) mm LT , for females and Lt =908(1-exp(-0.076(t+7.95)))mmLT for males. Age at 50 % maturity was attained in the first year of life. Spawning occurred throughout the year with an apparent peak between November and April. The mean total annual mortality rate (Z) was 0.25 per year. The mean annual natural mortality rate (M) was 0.20 per year and fishing mortality (F) was calculated at 0.05 per year. The life history strategy of C. gariepinus was in between the periodic and opportunistic strategies. Therefore management of this species should be aimed at maintaining a healthy adult population and age structure. Since a large portion of the Okavango Delta is already protected and most other parts are also inaccessible to fishers there are enough spatial refugia for the species and the status quo should be maintained. Under this scenario, there is no need for regulation of the current mesh sizes because the species is harvested after maturity and replenishment of exploited populations will always occur from other parts of the system. Per recruit analyses indicate that the current fishing mortality maintains spawner biomass at levels greater than 90 % of pristine levels. Therefore a commercial fishery may be established using mesh 93 mm to maximize yield with a rotational harvesting strategy. Close monitoring is essential to ensure that re-colonization of overexploited habitats does indeed occur. Recreational angling and commercial gill net fishing need to be separated on a spatial and temporal scale during the feeding run to minimize potential conflicts.
- Full Text:
- Date Issued: 2012
- Authors: Bokhutlo, Thethela
- Date: 2012
- Subjects: Catfishes -- Botswana -- Okavango River Delta , Clarias gariepinus , Aquaculture -- Botswana -- Okavango River Delta
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5297 , http://hdl.handle.net/10962/d1005142 , Catfishes -- Botswana -- Okavango River Delta , Clarias gariepinus , Aquaculture -- Botswana -- Okavango River Delta
- Description: Large catfishes (Clarias gariepinus & Clarias ngamensis) are not exploited commercially in the Okavango Delta, Botswana. They however constitute a large proportion of the gill net fishery catch (23 %) albeit as by-catch, coming second after cichlids (70 %). Monthly experimetal gill net sampling over 8 years showed that C. gariepinus was the most abundant species in the Okavango Delta by mass making up 37 % of the catch composition by fresh weight. Despite the relatively high abundance of C. gariepinus in the Okavango Delta, its status has never been fully assessed. For this reason, this study aimed to assess the status of C. gariepinus in the Okavango Delta with the particular goal to determine if the species could support a directed commercial gill net fishery. Investigation of the effects of the flood pulse on abundance of C. gariepinus showed that variability in water levels was the major driver of population abundance for this species. Three biological variables: (1) catch per unit effort (CPUE); (2) % catch composition and (3) Shannon's diversity index (H') exhibited a negative and significant relationship with the flood index within a year. The variation in these variables was statistically significant between months. There was a weak positive relationship between water levels and the biological variables between years suggesting increase in productivity of the system at high water levels without a lag period. Age and growth were determined using sectioned otoliths. Edge analysis showed that growth zone deposition occurred during the drawdown period in summer when water temperature and day length were increasing. The maximum recorded age was 15 years. Growth of this species was best described by the linear models (y = 21.50x + 427.39 mm LT; r² = 0.35) for females and (y = 23.79x + 440.83 mm LT; r² = 0.38) for males. The von Bertalanffy growth model described growth as Lt = 10000(1- exp(-0.002(t + 18.07))) mm LT for combined sexes Lt = 10000(1- exp( -0.002(t + 18.50))) mm LT , for females and Lt =908(1-exp(-0.076(t+7.95)))mmLT for males. Age at 50 % maturity was attained in the first year of life. Spawning occurred throughout the year with an apparent peak between November and April. The mean total annual mortality rate (Z) was 0.25 per year. The mean annual natural mortality rate (M) was 0.20 per year and fishing mortality (F) was calculated at 0.05 per year. The life history strategy of C. gariepinus was in between the periodic and opportunistic strategies. Therefore management of this species should be aimed at maintaining a healthy adult population and age structure. Since a large portion of the Okavango Delta is already protected and most other parts are also inaccessible to fishers there are enough spatial refugia for the species and the status quo should be maintained. Under this scenario, there is no need for regulation of the current mesh sizes because the species is harvested after maturity and replenishment of exploited populations will always occur from other parts of the system. Per recruit analyses indicate that the current fishing mortality maintains spawner biomass at levels greater than 90 % of pristine levels. Therefore a commercial fishery may be established using mesh 93 mm to maximize yield with a rotational harvesting strategy. Close monitoring is essential to ensure that re-colonization of overexploited habitats does indeed occur. Recreational angling and commercial gill net fishing need to be separated on a spatial and temporal scale during the feeding run to minimize potential conflicts.
- Full Text:
- Date Issued: 2012
Small mammal communities at high altitude within the Sneeuberg Mountain complex, Eastern Cape Province, South Africa
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
- Authors: Kok, Armand du Preez
- Date: 2012
- Subjects: Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5766 , http://hdl.handle.net/10962/d1005454 , Mountain animals -- Research -- South Africa -- Eastern Cape , Mammal populations -- Research -- South Africa -- Eastern Cape , Mammals -- Research -- South Africa -- Eastern Cape
- Description: Due to their widespread and specious nature, small mammals are ideal for biogeographical studies. Small mammals also effectively connect various trophic levels by being both consumers and prey items for other animals. The Great Escarpment is the dominant mountain landscape in South Africa. Yet, very little small mammal research has been conducted on the Great Escarpment outside of the Main Drakensberg Mountains. This is surprising given the importance of mountains in shaping regional ecology. In this study, I assessed the diversity and community composition of small mammals at three high altitude (>1700m) sites within the Sneeuberg Mountain Complex (SMC) from June 2009 to May 2010. I also tested the effectiveness of five different bait types for measuring small mammal diversity (i.e. number of individuals caught, species richness, Shannon diversity index and Simpson index of diversity). Out of a total of 423 captures, 292 individuals of 12 small mammal species (one shrew, one elephant shrew and 10 rodents) were recorded over 5280 trap nights. The species richness and diversity of small mammals captured at the three sites were similar and this homogeneity was probably related to the regional processes (e.g. climate and latitude) that govern species richness and diversity. The most effective bait type in terms of capture success, species richness and diversity measurements was peanut butter and oats. In addition, the use of richness estimators revealed that peanut butter and oats was the most effective bait for sampling the species richness of small mammals. The effectiveness of peanut butter and oats was related to this bait having a more attractive scent, when compared to the other bait types. Future studies should focus on researching the range of local and regional processes that drive small mammal diversity at high altitudes in South Africa. I also recommend the use of more than one bait type when planning to survey small mammal communities.
- Full Text:
- Date Issued: 2012
Nanostructures and metallophthalocyanines : applications in microbial fuel cells
- Authors: Edwards, Sean
- Date: 2011
- Subjects: Microbial fuel cells , Waste products as fuel , Nanostructured materials , Electrochemistry , Nanotubes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4107 , http://hdl.handle.net/10962/d1011742 , Microbial fuel cells , Waste products as fuel , Nanostructured materials , Electrochemistry , Nanotubes
- Description: Microbial fuel cells (MFCs) are a promising form of alternative energy capable of harnessing the potential energy stores in organic waste. The oxygen reduction reaction (ORR) forms an integral role in the generation of electricity in MFCs however it is also a potential obstacle in enhancing the performance of MFCs. Platinum, a commonly used catalyst for the ORR, is expensive and rare. Significant research has been conducted into developing alternative catalysts. Metallophthalocyanines (MPc) have garnered attention for use as catalysts. Iron phthalocyanine (FePc) has been shown to have catalytic activity towards the reduction of oxygen. Coupling of the catalyst to nanostructured carbon materials, such as multi-walled carbon nanotubes, has been observed to have several advantages as nanostructures have a high surface-to-volume ratio. In this study, we have attempted to assess the suitability of FePc, both its bulk and nanostructured form, as an oxygen reduction catalyst and acid functionalized multi-walled carbon nanotubes for use as a catalyst support using electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. We showed, for the first time, the catalytic nature of nanostructured FePc towards the ORR. Applying the data obtained from the electrochemical analyses, electrodes were modified using FePc and MWCNTs and applied to an Enterobacter cloacae-based MFC. Several operational parameters of the MFC, such as temperature and ionic strength, were optimized during the course of the study. We showed that optimized FePc:MWCNT-modified electrodes compared favourably to platinum-based electrodes in terms of power densities obtained in a microbial fuel cell.
- Full Text:
- Date Issued: 2011
- Authors: Edwards, Sean
- Date: 2011
- Subjects: Microbial fuel cells , Waste products as fuel , Nanostructured materials , Electrochemistry , Nanotubes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4107 , http://hdl.handle.net/10962/d1011742 , Microbial fuel cells , Waste products as fuel , Nanostructured materials , Electrochemistry , Nanotubes
- Description: Microbial fuel cells (MFCs) are a promising form of alternative energy capable of harnessing the potential energy stores in organic waste. The oxygen reduction reaction (ORR) forms an integral role in the generation of electricity in MFCs however it is also a potential obstacle in enhancing the performance of MFCs. Platinum, a commonly used catalyst for the ORR, is expensive and rare. Significant research has been conducted into developing alternative catalysts. Metallophthalocyanines (MPc) have garnered attention for use as catalysts. Iron phthalocyanine (FePc) has been shown to have catalytic activity towards the reduction of oxygen. Coupling of the catalyst to nanostructured carbon materials, such as multi-walled carbon nanotubes, has been observed to have several advantages as nanostructures have a high surface-to-volume ratio. In this study, we have attempted to assess the suitability of FePc, both its bulk and nanostructured form, as an oxygen reduction catalyst and acid functionalized multi-walled carbon nanotubes for use as a catalyst support using electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. We showed, for the first time, the catalytic nature of nanostructured FePc towards the ORR. Applying the data obtained from the electrochemical analyses, electrodes were modified using FePc and MWCNTs and applied to an Enterobacter cloacae-based MFC. Several operational parameters of the MFC, such as temperature and ionic strength, were optimized during the course of the study. We showed that optimized FePc:MWCNT-modified electrodes compared favourably to platinum-based electrodes in terms of power densities obtained in a microbial fuel cell.
- Full Text:
- Date Issued: 2011
Life history, population dynamics and conservation status of Oldenburgia grandis (Asteraceae), an endemic of the Eastern Cape of South Africa
- Authors: Swart, Carin
- Date: 2008
- Subjects: Compositae , Fynbos ecology -- South Africa -- Eastern Cape , Endemic plants -- South Africa -- Eastern Cape , Rare plants -- South Africa -- Eastern Cape , Plant populations -- South Africa -- Eastern Cape , Vegetation dynamics -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Endangered species -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4230 , http://hdl.handle.net/10962/d1003799 , Compositae , Fynbos ecology -- South Africa -- Eastern Cape , Endemic plants -- South Africa -- Eastern Cape , Rare plants -- South Africa -- Eastern Cape , Plant populations -- South Africa -- Eastern Cape , Vegetation dynamics -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Endangered species -- South Africa -- Eastern Cape
- Description: Oldenburgia grandis is a rare, long-lived woody paleoendemic of the Fynbos Biome of South Africa. Confined to quartzite outcrops, it has a small geographic range and narrow habitat specificity. O. grandis responds to its fire-prone environment by resprouting. Elasticity analysis of O. grandis reveals that growth and fecundity were traded off for persistence of adult, mature and sapling stages. Morphological adaptations such as a corky fire-resistant bark and the ability to resprout after fire are traits that O. grandis have evolved to persist in a frequently disturbed environment. Population growth rate for sites undisturbed by fire for a number of years (l = 1.01) and sites at various stages of recovery after fire (l = 1.00) were very similar. The highest variation in transition probabilities for all sites was seen in the persistence of the seedling stage and growth from seedling to sapling. Observed population structure and stable stage distribution determined by the matrix model show that sites recently undisturbed by fire had high abundances of the adult and sapling stages. A peak in sapling stages was seen for the stable stage distribution where similar peak in sapling numbers were seen for population structures of sites at various stages of recoveryafter fire. Favourable environmental conditions for the persistence of O. grandis populations include no fire with transition probabilities between the observed minimum and maximum and fire frequency at a 10 year interval where seedling protection from the fire is high and adult and mature mortalities during the fire are low. Stochastic environmental events that could put populations (particularly small populations) at an increased risk of extinction include high to moderate fire intensities where seedling protection from the fire is low and adult and mature mortalities are high as a result of the fire.
- Full Text:
- Date Issued: 2008
- Authors: Swart, Carin
- Date: 2008
- Subjects: Compositae , Fynbos ecology -- South Africa -- Eastern Cape , Endemic plants -- South Africa -- Eastern Cape , Rare plants -- South Africa -- Eastern Cape , Plant populations -- South Africa -- Eastern Cape , Vegetation dynamics -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Endangered species -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4230 , http://hdl.handle.net/10962/d1003799 , Compositae , Fynbos ecology -- South Africa -- Eastern Cape , Endemic plants -- South Africa -- Eastern Cape , Rare plants -- South Africa -- Eastern Cape , Plant populations -- South Africa -- Eastern Cape , Vegetation dynamics -- South Africa -- Eastern Cape , Plant conservation -- South Africa -- Eastern Cape , Endangered species -- South Africa -- Eastern Cape
- Description: Oldenburgia grandis is a rare, long-lived woody paleoendemic of the Fynbos Biome of South Africa. Confined to quartzite outcrops, it has a small geographic range and narrow habitat specificity. O. grandis responds to its fire-prone environment by resprouting. Elasticity analysis of O. grandis reveals that growth and fecundity were traded off for persistence of adult, mature and sapling stages. Morphological adaptations such as a corky fire-resistant bark and the ability to resprout after fire are traits that O. grandis have evolved to persist in a frequently disturbed environment. Population growth rate for sites undisturbed by fire for a number of years (l = 1.01) and sites at various stages of recovery after fire (l = 1.00) were very similar. The highest variation in transition probabilities for all sites was seen in the persistence of the seedling stage and growth from seedling to sapling. Observed population structure and stable stage distribution determined by the matrix model show that sites recently undisturbed by fire had high abundances of the adult and sapling stages. A peak in sapling stages was seen for the stable stage distribution where similar peak in sapling numbers were seen for population structures of sites at various stages of recoveryafter fire. Favourable environmental conditions for the persistence of O. grandis populations include no fire with transition probabilities between the observed minimum and maximum and fire frequency at a 10 year interval where seedling protection from the fire is high and adult and mature mortalities during the fire are low. Stochastic environmental events that could put populations (particularly small populations) at an increased risk of extinction include high to moderate fire intensities where seedling protection from the fire is low and adult and mature mortalities are high as a result of the fire.
- Full Text:
- Date Issued: 2008
The effects of selected reference toxicants on embryonic development of the freshwater shrimp caridina nilotica (Decapoda: Atyidae)
- Authors: Ketse, Noziphiwo
- Date: 2007
- Subjects: Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6025 , http://hdl.handle.net/10962/d1005367 , Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Description: Aquatic toxicity tests are increasingly being used in water resource management worldwide, and currently in South Africa, policy and legislation are being drafted to reflect this international trend. While standard toxicity test methods and test organisms are being considered to develop and set water quality guidelines and effluent discharge limits, it is not clear whether guidelines and discharge limits set using these standard test organisms will be sufficient to protect South Africa’s scarce water resources. As part of ongoing research to investigate the use of indigenous riverine organisms as toxicity test organisms a number of potential species have been identified, including the freshwater shrimp Caridina nilotica. For much of the history of aquatic toxicological data the bulk of the data has been generated by acute toxicity testing, based on short exposures and using mortality as the response end point. There are relatively few chronic, longterm tests with sub-lethal endpoints. However, it was recognized that information about longer exposure durations and non lethal response endpoints was needed, instead of mortality. Chronic tests can provide a more environmentally realistic measure of chemical toxicity than acute toxicity tests. Caridina nilotica has been identified as a potential standard toxicity test organism, as it is widely distributed, easy to find and it occurs in flowing waters. It is an indigenous species which can be easily cultured and maintained in the laboratory and is also ecologically important. Both adults and juveniles have been used successfully in acute toxicity tests at the Institute for Water Research (Rhodes University) and the ability to rear the organisms under laboratory conditions has allowed the development of chronic toxicity tests using C. nilotica. Chronic early life stage tests include continuous exposure of the early life stages, which are presumed to be the most sensitive for aquatic organisms. This study reports on the embryonic development of C. nilotica at the culture temperature of 24⁰C. Morphological developmental stages were monitored and measured and 7 developmental stages were identified. Based on the measurements of the features that were identified, toxicity tests using the reference chemicals sodium chloride (NaCl), sodium sulphate (Na₂SO₄) and cadmium chloride (CdCl₂) were undertaken to test the suitability of C. nilotica embryonic development for chronic toxicity tests for use in water resource management. The length, width, length:width ratios and area of the features decreased in size when exposed to the chemicals. The Lowest Observed Effect Concentration (LOEC) values were 2000mg/L for Na₂SO₄, 3000mg/L for NaCl and 0.31mg/L for CdCl₂. The No Observed Effect Concentration (NOEC) values were 1000mg/L for Na₂SO₄, 2000mg/L for NaCl and <0.31mg/L for CdCl₂. Further research on the teratogenic effects of single chemicals and industrial effluent on developing C. nilotica embryos needs to be undertaken in order to evaluate the described test protocol for use in water resource management.
- Full Text:
- Date Issued: 2007
- Authors: Ketse, Noziphiwo
- Date: 2007
- Subjects: Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:6025 , http://hdl.handle.net/10962/d1005367 , Toxicity testing -- South Africa , Shrimp fisheries -- South Africa , Decapoda , Caridina , Water quality management -- South Africa
- Description: Aquatic toxicity tests are increasingly being used in water resource management worldwide, and currently in South Africa, policy and legislation are being drafted to reflect this international trend. While standard toxicity test methods and test organisms are being considered to develop and set water quality guidelines and effluent discharge limits, it is not clear whether guidelines and discharge limits set using these standard test organisms will be sufficient to protect South Africa’s scarce water resources. As part of ongoing research to investigate the use of indigenous riverine organisms as toxicity test organisms a number of potential species have been identified, including the freshwater shrimp Caridina nilotica. For much of the history of aquatic toxicological data the bulk of the data has been generated by acute toxicity testing, based on short exposures and using mortality as the response end point. There are relatively few chronic, longterm tests with sub-lethal endpoints. However, it was recognized that information about longer exposure durations and non lethal response endpoints was needed, instead of mortality. Chronic tests can provide a more environmentally realistic measure of chemical toxicity than acute toxicity tests. Caridina nilotica has been identified as a potential standard toxicity test organism, as it is widely distributed, easy to find and it occurs in flowing waters. It is an indigenous species which can be easily cultured and maintained in the laboratory and is also ecologically important. Both adults and juveniles have been used successfully in acute toxicity tests at the Institute for Water Research (Rhodes University) and the ability to rear the organisms under laboratory conditions has allowed the development of chronic toxicity tests using C. nilotica. Chronic early life stage tests include continuous exposure of the early life stages, which are presumed to be the most sensitive for aquatic organisms. This study reports on the embryonic development of C. nilotica at the culture temperature of 24⁰C. Morphological developmental stages were monitored and measured and 7 developmental stages were identified. Based on the measurements of the features that were identified, toxicity tests using the reference chemicals sodium chloride (NaCl), sodium sulphate (Na₂SO₄) and cadmium chloride (CdCl₂) were undertaken to test the suitability of C. nilotica embryonic development for chronic toxicity tests for use in water resource management. The length, width, length:width ratios and area of the features decreased in size when exposed to the chemicals. The Lowest Observed Effect Concentration (LOEC) values were 2000mg/L for Na₂SO₄, 3000mg/L for NaCl and 0.31mg/L for CdCl₂. The No Observed Effect Concentration (NOEC) values were 1000mg/L for Na₂SO₄, 2000mg/L for NaCl and <0.31mg/L for CdCl₂. Further research on the teratogenic effects of single chemicals and industrial effluent on developing C. nilotica embryos needs to be undertaken in order to evaluate the described test protocol for use in water resource management.
- Full Text:
- Date Issued: 2007
A comparison of web-based technologies to serve images from an Oracle9i database
- Authors: Swales, Dylan
- Date: 2004 , 2013-06-18
- Subjects: Active server pages , Microsoft .NET , JavaServer pages , Oracle (Computer file) , Internet searching , Web site development--Computer programs , World Wide Web , Online information services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4583 , http://hdl.handle.net/10962/d1004380 , Active server pages , Microsoft .NET , JavaServer pages , Oracle (Computer file) , Internet searching , Web site development--Computer programs , World Wide Web , Online information services
- Description: The nature of Internet and Intranet Web applications has changed from a static content-distribution medium into an interactive, dynamic medium, often used to serve multimedia from back-end object-relational databases to Web-enabled clients. Consequently, developers need to make an informed technological choice for developing software that supports a Web-based application for distributing multimedia over networks. This decision is based on several factors. Among the factors are ease of programming, richness of features, scalability, and performance. The research focuses on these key factors when distributing images from an Oracle9i database using Java Servlets, JSP, ASP, and ASP.NET as the server-side development technologies. Prototype applications are developed and tested within each technology: one for single image serving and the other for multiple image serving. A matrix of recommendations is provided to distinguish which technology, or combination of technologies, provides the best performance and development platform for image serving within the studied envirorunent. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2004
- Authors: Swales, Dylan
- Date: 2004 , 2013-06-18
- Subjects: Active server pages , Microsoft .NET , JavaServer pages , Oracle (Computer file) , Internet searching , Web site development--Computer programs , World Wide Web , Online information services
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4583 , http://hdl.handle.net/10962/d1004380 , Active server pages , Microsoft .NET , JavaServer pages , Oracle (Computer file) , Internet searching , Web site development--Computer programs , World Wide Web , Online information services
- Description: The nature of Internet and Intranet Web applications has changed from a static content-distribution medium into an interactive, dynamic medium, often used to serve multimedia from back-end object-relational databases to Web-enabled clients. Consequently, developers need to make an informed technological choice for developing software that supports a Web-based application for distributing multimedia over networks. This decision is based on several factors. Among the factors are ease of programming, richness of features, scalability, and performance. The research focuses on these key factors when distributing images from an Oracle9i database using Java Servlets, JSP, ASP, and ASP.NET as the server-side development technologies. Prototype applications are developed and tested within each technology: one for single image serving and the other for multiple image serving. A matrix of recommendations is provided to distinguish which technology, or combination of technologies, provides the best performance and development platform for image serving within the studied envirorunent. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2004
Synthetic approaches to marine labdane diterpenes
- Authors: Wisch, Gregory Albert
- Date: 2002 , 2013-05-10
- Subjects: Diterpenes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4289 , http://hdl.handle.net/10962/d1003131 , Diterpenes
- Description: The work presented in this thesis describes the synthesis of labd-13-en-8ß, 15-diol (46) a stable reduced derivative of an unstable marine natural product aldehyde [8ß-hydroxylabd-13E-en-15-al (6)] isolated by Cimino, et al. from the skin of a Notaspidean mollusc Pleurobranchaea meckelii. The rationale for the synthesis was to provide sufficient 46 for eventual mild oxidation to 6 and investigation of the biological activity of this latter compound. (-)-Sclareol (32), a common diterpene synthetic precursor, was the starting point for the ten step synthesis of 46 described in this thesis. A search of the literature revealed that only one non stereospecific synthesis of 46 had been previously reported. To provide the necessary background to the synthetic component of this thesis, both the occurrence of labdane and ent-labdane in the marine environment and the use of sclareol in the synthesis of marine natural products, was reviewed. The initial step in the synthesis of 46 was the potassium permanganate oxidation of sclareol to give a bisnorlabdane ketone. Reduction of this ketone with lithium aluminium hydride produced a mixture of diols which, through t-butyldimethysilyl triflate protection, afforded a quantitative route to protecting the C-13 ketone in an effort to prevent unwanted intramolecular cyclization reactions. Dehydration of the tertiary alcohol moiety at C-8 with phosphorous oxychloride yielded the Δ⁸·¹⁵ exocyclic alkene required for the next oxidation step. Ozonolysis succeeded in producing the desired C-8 ketone after much deliberation and research into alternative oxidation strategies. Methyl lithium methylation quantitatively afforded the desired a-methyl substitution at C-8, identified at the onset as the key step in the synthesis. Tetra-butylarnmonium fluoride deprotection yielded the 8ß,13-dihydoxylated product, which was in turn subjected to a Swern oxidition to give the desired 8ß-hydroxy-bisnorlabda-13-one. A modified Horner-Wadsworth-Emmons reaction allowed for elaboration at C-13 to yield a to Δ¹³ olefin with a terminal C-15 ethyl ester. Diisobutylaluminium hydride reduction of the ester produced the desired labd-13-en-8ß, 15-diol (46) in a low overall yield of 3.4%. Although opportunities for optimization of at least three steps in the synthesis exist, time constraints prevented both optimization of these steps and an investigation of the oxidation of 46 to 6. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2002
- Authors: Wisch, Gregory Albert
- Date: 2002 , 2013-05-10
- Subjects: Diterpenes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4289 , http://hdl.handle.net/10962/d1003131 , Diterpenes
- Description: The work presented in this thesis describes the synthesis of labd-13-en-8ß, 15-diol (46) a stable reduced derivative of an unstable marine natural product aldehyde [8ß-hydroxylabd-13E-en-15-al (6)] isolated by Cimino, et al. from the skin of a Notaspidean mollusc Pleurobranchaea meckelii. The rationale for the synthesis was to provide sufficient 46 for eventual mild oxidation to 6 and investigation of the biological activity of this latter compound. (-)-Sclareol (32), a common diterpene synthetic precursor, was the starting point for the ten step synthesis of 46 described in this thesis. A search of the literature revealed that only one non stereospecific synthesis of 46 had been previously reported. To provide the necessary background to the synthetic component of this thesis, both the occurrence of labdane and ent-labdane in the marine environment and the use of sclareol in the synthesis of marine natural products, was reviewed. The initial step in the synthesis of 46 was the potassium permanganate oxidation of sclareol to give a bisnorlabdane ketone. Reduction of this ketone with lithium aluminium hydride produced a mixture of diols which, through t-butyldimethysilyl triflate protection, afforded a quantitative route to protecting the C-13 ketone in an effort to prevent unwanted intramolecular cyclization reactions. Dehydration of the tertiary alcohol moiety at C-8 with phosphorous oxychloride yielded the Δ⁸·¹⁵ exocyclic alkene required for the next oxidation step. Ozonolysis succeeded in producing the desired C-8 ketone after much deliberation and research into alternative oxidation strategies. Methyl lithium methylation quantitatively afforded the desired a-methyl substitution at C-8, identified at the onset as the key step in the synthesis. Tetra-butylarnmonium fluoride deprotection yielded the 8ß,13-dihydoxylated product, which was in turn subjected to a Swern oxidition to give the desired 8ß-hydroxy-bisnorlabda-13-one. A modified Horner-Wadsworth-Emmons reaction allowed for elaboration at C-13 to yield a to Δ¹³ olefin with a terminal C-15 ethyl ester. Diisobutylaluminium hydride reduction of the ester produced the desired labd-13-en-8ß, 15-diol (46) in a low overall yield of 3.4%. Although opportunities for optimization of at least three steps in the synthesis exist, time constraints prevented both optimization of these steps and an investigation of the oxidation of 46 to 6. , KMBT_363 , Adobe Acrobat 9.54 Paper Capture Plug-in
- Full Text:
- Date Issued: 2002
The biological control of Hakea sericea Schrader by the Hakea seed-moth, Carposina autologa Meyrick, in South Africa
- Authors: Gordon, Antony John
- Date: 1993
- Subjects: Weeds -- Biological control -- South Africa , Moths , Carposinidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5648 , http://hdl.handle.net/10962/d1005330 , Weeds -- Biological control -- South Africa , Moths , Carposinidae
- Description: Hakea sericea Schrader was introduced to South Africa from Australia and has become a major problem in nearly all the coastal mountain ranges of the Cape Province. The hakea seed-moth, Carposina autologa Meyrick was released in South Africa for the biological control of H. sericea. The impact of the moth on the canopy-stored seeds of H. sericea was evaluated at two study sites in the south-western Cape over three years. The moth has reduced the accumulated seeds at the two study sites by 59.4% and 42.6%, respectively. The moth has shown a surprising ability to disperse and establish new colonies at low population levels. Factors contributing to the slow colonization of C. autologa in South Africa was investigated. The moths appear to be unable to distinguish between healthy and previously attacked fruits; 42.5% of the eggs were laid on attacked fruits. Only 13.1% of the healthy fruits with eggs yielded mature larvae. The high pre-penetration mortality found in the present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichum gloeosporioides (Penz.) Sacc., on both H. sericea and C. autologa was investigated. H. sericea trees and branches that die as a result of fungus cause the accumulated fruits on the affected trees or branches to dehisce. This seed loss occurs at a crucial stage during C. autologa larval development. Only 42.1% and 33.0% of the trees were found to be healthy at the two study sites, respectively. One seed crop will always be available for regeneration, since recruitment is linked to fires, and wild-fires occur at a stage when the latest seed crop has escaped attack by c. autologa. C. autologa was released at six sites in the south-western Cape by attaching egg-bearing follicles to healthy fruits in the field. Three release sites were evaluated the year following release to determine whether the moth established or not. The role of C. autologa in the H. sericea biological control programme is discussed. Although seed destruction by C. autologa is not severe, it is expected to contribute to the control of H. sericea.
- Full Text:
- Date Issued: 1993
- Authors: Gordon, Antony John
- Date: 1993
- Subjects: Weeds -- Biological control -- South Africa , Moths , Carposinidae
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5648 , http://hdl.handle.net/10962/d1005330 , Weeds -- Biological control -- South Africa , Moths , Carposinidae
- Description: Hakea sericea Schrader was introduced to South Africa from Australia and has become a major problem in nearly all the coastal mountain ranges of the Cape Province. The hakea seed-moth, Carposina autologa Meyrick was released in South Africa for the biological control of H. sericea. The impact of the moth on the canopy-stored seeds of H. sericea was evaluated at two study sites in the south-western Cape over three years. The moth has reduced the accumulated seeds at the two study sites by 59.4% and 42.6%, respectively. The moth has shown a surprising ability to disperse and establish new colonies at low population levels. Factors contributing to the slow colonization of C. autologa in South Africa was investigated. The moths appear to be unable to distinguish between healthy and previously attacked fruits; 42.5% of the eggs were laid on attacked fruits. Only 13.1% of the healthy fruits with eggs yielded mature larvae. The high pre-penetration mortality found in the present study is similar to that found in Australia. The effect of the indigenous fungus, Colletotrichum gloeosporioides (Penz.) Sacc., on both H. sericea and C. autologa was investigated. H. sericea trees and branches that die as a result of fungus cause the accumulated fruits on the affected trees or branches to dehisce. This seed loss occurs at a crucial stage during C. autologa larval development. Only 42.1% and 33.0% of the trees were found to be healthy at the two study sites, respectively. One seed crop will always be available for regeneration, since recruitment is linked to fires, and wild-fires occur at a stage when the latest seed crop has escaped attack by c. autologa. C. autologa was released at six sites in the south-western Cape by attaching egg-bearing follicles to healthy fruits in the field. Three release sites were evaluated the year following release to determine whether the moth established or not. The role of C. autologa in the H. sericea biological control programme is discussed. Although seed destruction by C. autologa is not severe, it is expected to contribute to the control of H. sericea.
- Full Text:
- Date Issued: 1993
Gold mineralization in an archaean granite-greenstone remnant west of Melmoth, Natal ore genesis and implications for exploration
- Authors: Bullen, Warwick David
- Date: 1991
- Subjects: Gold ores -- Geology -- South Africa , Greenstone belts -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4967 , http://hdl.handle.net/10962/d1005579 , Gold ores -- Geology -- South Africa , Greenstone belts -- South Africa -- KwaZulu-Natal
- Description: The previously undifferentiated, "Melmoth Granite-Greenstone Remnant" (MGGR¹) crops out over an area of about 360 km² in northern Natal, South Africa. The greenstone sequence is comprised mainly of mafic metalavas with lesser serpentinite, talc schist, dacitic tuff, quartz-muscovite schist, quartzite and calc-silicate rocks. The greenstones are intruded by syntectonic trondhjemitic gneisses, late-tectonic granodioritic gneisses and post-tectonic granite dykes. Four phases of deformation and metamorphism are recognized. Epigenetic, disseminated and quartz vein-hosted gold mineralization is associated with D₂ shearing - a positive correlation existing between the intensity of the shearing, the thickness of the shear zone and the grade of ore it contains. Auriferous quartz veins are distinguished from an earlier generation of barren vein quartz on the basis of mineralogy, texture and relationship to the s-fabric. The mineralization occurs in zones of dilation associated with shear zone refraction. Associated wall rock alteration includes sericitization, argillization and chloritization. An ore genesis model based on the aforementioned parameters, is proposed. Finally, an exploration programme has been devised in order to locate undiscovered gold deposits in the MGGR. The programme could probably be applied, with minor modifications, to shear zone-hosted gold deposits in other granite-greenstone remnants in northern Natal. ¹- Name suggested by writer.
- Full Text:
- Date Issued: 1991
- Authors: Bullen, Warwick David
- Date: 1991
- Subjects: Gold ores -- Geology -- South Africa , Greenstone belts -- South Africa -- KwaZulu-Natal
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4967 , http://hdl.handle.net/10962/d1005579 , Gold ores -- Geology -- South Africa , Greenstone belts -- South Africa -- KwaZulu-Natal
- Description: The previously undifferentiated, "Melmoth Granite-Greenstone Remnant" (MGGR¹) crops out over an area of about 360 km² in northern Natal, South Africa. The greenstone sequence is comprised mainly of mafic metalavas with lesser serpentinite, talc schist, dacitic tuff, quartz-muscovite schist, quartzite and calc-silicate rocks. The greenstones are intruded by syntectonic trondhjemitic gneisses, late-tectonic granodioritic gneisses and post-tectonic granite dykes. Four phases of deformation and metamorphism are recognized. Epigenetic, disseminated and quartz vein-hosted gold mineralization is associated with D₂ shearing - a positive correlation existing between the intensity of the shearing, the thickness of the shear zone and the grade of ore it contains. Auriferous quartz veins are distinguished from an earlier generation of barren vein quartz on the basis of mineralogy, texture and relationship to the s-fabric. The mineralization occurs in zones of dilation associated with shear zone refraction. Associated wall rock alteration includes sericitization, argillization and chloritization. An ore genesis model based on the aforementioned parameters, is proposed. Finally, an exploration programme has been devised in order to locate undiscovered gold deposits in the MGGR. The programme could probably be applied, with minor modifications, to shear zone-hosted gold deposits in other granite-greenstone remnants in northern Natal. ¹- Name suggested by writer.
- Full Text:
- Date Issued: 1991
A structural study of the capsular antigens of escherichia coli K36 and klebiella K68
- Authors: Stanley, Shawn Mark Ross
- Date: 1987 , 2013-03-11
- Subjects: Enterobacteriaceae , Klebsiella , Escherichia , Antigens
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3814 , http://hdl.handle.net/10962/d1004613 , Enterobacteriaceae , Klebsiella , Escherichia , Antigens
- Description: From Introduction: Bacterial cells all have a cytoplasmic membrane (see Figure 1) which regulates the movement of ions and molecules into and out of the bacterium. Enclosing this membrane is a cell wall of which there are two general types, which are differentiated by the Gram stain(02) as being either gram positive or gram negative (depending upon whether they hold the gram stain after washing with ethanol). The cell wall provides the cell with shape and rigidity and is composed, in the case of gram positive types, of peptidoglycan, and in the case of gram negative bacteria, of a peptidoglycan and an outer membrane (see Figure 2). The peptidoglycan layer, common to both cell wall types, consists of a backbone of alternating units of N-acetylglucosamine and N-acetylmuramic acid to which peptides are attached by amide links. This heteropolymer is a highly cross linked mosaic and this gives it strength and rigidity. In gram positive bacteria, this layer also contains two carbohydr ate antigens, a simple polysaccharide and a teichoic acid; these are usually the type specific or major group antigens of the bacterium. Many of the bacteria also produce exopolysaccharides (see Figure 3) either as discrete capsules (for example, the Enterobacteriaceae K antigens) or unattached slime layers (for example, the Enterobacteriaceae M antigens). The vast majority of these polysaccharides are heteroglycans(03) composed of contiguous oligosaccharide repeating units. Their monosaccharide components are largely neutral hexoses, 6-deoxy hexoses and also amino sugars. (03) Pentose units are rare. (03) The capsular polysaccharides usually have a high content of acidic constituents such as uronic acids, phosphate groups, or pyruvate ketals. (01) , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1987
- Authors: Stanley, Shawn Mark Ross
- Date: 1987 , 2013-03-11
- Subjects: Enterobacteriaceae , Klebsiella , Escherichia , Antigens
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3814 , http://hdl.handle.net/10962/d1004613 , Enterobacteriaceae , Klebsiella , Escherichia , Antigens
- Description: From Introduction: Bacterial cells all have a cytoplasmic membrane (see Figure 1) which regulates the movement of ions and molecules into and out of the bacterium. Enclosing this membrane is a cell wall of which there are two general types, which are differentiated by the Gram stain(02) as being either gram positive or gram negative (depending upon whether they hold the gram stain after washing with ethanol). The cell wall provides the cell with shape and rigidity and is composed, in the case of gram positive types, of peptidoglycan, and in the case of gram negative bacteria, of a peptidoglycan and an outer membrane (see Figure 2). The peptidoglycan layer, common to both cell wall types, consists of a backbone of alternating units of N-acetylglucosamine and N-acetylmuramic acid to which peptides are attached by amide links. This heteropolymer is a highly cross linked mosaic and this gives it strength and rigidity. In gram positive bacteria, this layer also contains two carbohydr ate antigens, a simple polysaccharide and a teichoic acid; these are usually the type specific or major group antigens of the bacterium. Many of the bacteria also produce exopolysaccharides (see Figure 3) either as discrete capsules (for example, the Enterobacteriaceae K antigens) or unattached slime layers (for example, the Enterobacteriaceae M antigens). The vast majority of these polysaccharides are heteroglycans(03) composed of contiguous oligosaccharide repeating units. Their monosaccharide components are largely neutral hexoses, 6-deoxy hexoses and also amino sugars. (03) Pentose units are rare. (03) The capsular polysaccharides usually have a high content of acidic constituents such as uronic acids, phosphate groups, or pyruvate ketals. (01) , KMBT_363 , Adobe Acrobat 9.53 Paper Capture Plug-in
- Full Text:
- Date Issued: 1987
Community metabolism and phosphorus dynamics in a seasonally closed South African estuary
- Liptrot, Mark Robert Michael
- Authors: Liptrot, Mark Robert Michael
- Date: 1978
- Subjects: Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5810 , http://hdl.handle.net/10962/d1006966 , Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Description: The effects of seawater inflows and macrophyte beds on community metabolism and phosphorus dynamics in the seasonally-closed Swartvlei estuary were investigated. Metabolic rates were determined by diurnal oxygen curve analysis. Gross primary production ranged from 0,7 to 14,9 g 0₂ m⁻² day⁻¹, and respiration from 0,9 to 25,2 g 0₂ m⁻² day⁻¹. The highest production rates were recorded inside the dense beds of Zostera capens is Setchell (x- = 7,8 g 0₂ m⁻² day⁻¹ ). Metabolism was positively correlated to submersed macrophyte cover, and decreased upstream of the mouth region. No seasonal variation in gross production could be detected, and mouth closure had no detectable effect on metabolic rates. Growth of the green alga Enteromorpha sp. in winter, and the effect of decay of this alga on dissolved oxygen, total inorganic carbon and total dissolved phosphorus in the water column is discussed. High day-time respiration values, measured in a darkened polythene enclosure, indicate that photorespiration occurs in Zostera. Apparently the annual amount of oxygen respired throughout the estuary exceeded that produced by 2 7100 tonnes, i.e. the estuary was heterotrophic. This is discussed in relation to the effectiveness of the diurnal curve method as a way of measuring metabolic rates, and to the possibility of organic matter input via river inflows. There is a net gain of up to 17,4 kg of particulate phosphorus over mean tides. Diurnal phosphorus studies indicate that Zostera releases phosphate into the water column in the light. Enteromorpha takes up phosphate in the morning, which it appears to release over the rest of the day. The cycling of phosphorus between seawater, sediments, macrophytes and the water column is discussed.
- Full Text:
- Date Issued: 1978
- Authors: Liptrot, Mark Robert Michael
- Date: 1978
- Subjects: Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5810 , http://hdl.handle.net/10962/d1006966 , Estuarine ecology -- Research -- South Africa -- Swartvlei , Eelgrass -- Research -- South Africa , Enteromorpha -- Research -- South Africa
- Description: The effects of seawater inflows and macrophyte beds on community metabolism and phosphorus dynamics in the seasonally-closed Swartvlei estuary were investigated. Metabolic rates were determined by diurnal oxygen curve analysis. Gross primary production ranged from 0,7 to 14,9 g 0₂ m⁻² day⁻¹, and respiration from 0,9 to 25,2 g 0₂ m⁻² day⁻¹. The highest production rates were recorded inside the dense beds of Zostera capens is Setchell (x- = 7,8 g 0₂ m⁻² day⁻¹ ). Metabolism was positively correlated to submersed macrophyte cover, and decreased upstream of the mouth region. No seasonal variation in gross production could be detected, and mouth closure had no detectable effect on metabolic rates. Growth of the green alga Enteromorpha sp. in winter, and the effect of decay of this alga on dissolved oxygen, total inorganic carbon and total dissolved phosphorus in the water column is discussed. High day-time respiration values, measured in a darkened polythene enclosure, indicate that photorespiration occurs in Zostera. Apparently the annual amount of oxygen respired throughout the estuary exceeded that produced by 2 7100 tonnes, i.e. the estuary was heterotrophic. This is discussed in relation to the effectiveness of the diurnal curve method as a way of measuring metabolic rates, and to the possibility of organic matter input via river inflows. There is a net gain of up to 17,4 kg of particulate phosphorus over mean tides. Diurnal phosphorus studies indicate that Zostera releases phosphate into the water column in the light. Enteromorpha takes up phosphate in the morning, which it appears to release over the rest of the day. The cycling of phosphorus between seawater, sediments, macrophytes and the water column is discussed.
- Full Text:
- Date Issued: 1978
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