Understanding biotic interactions in invaded pond communities in the Sundays River irrigation network, South Africa
- Authors: Mofu, Lubabalo
- Date: 2020
- Subjects: Mozambique tilapia -- South Africa -- Sundays River (Eastern Cape) , Western mosquitofish -- South Africa -- Sundays River (Eastern Cape) , Gobiidae -- South Africa -- Sundays River (Eastern Cape) , Clupeidae -- South Africa -- Sundays River (Eastern Cape) , Reservoirs -- South Africa -- Sundays River (Eastern Cape) , Zooplankton -- South Africa -- Sundays River (Eastern Cape) , Freshwater ecology -- South Africa -- Sundays River (Eastern Cape) , Biotic communities -- South Africa -- Sundays River (Eastern Cape) , Fishes -- Effect of temperature on -- South Africa -- Sundays River (Eastern Cape) , Stable isotopes , Relative Impact Potential
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167089 , vital:41436
- Description: The Sundays River valley irrigation ponds provide a unique opportunity to investigate biotic interactions within a biological invasions context, as they contain both native and non-native fish species. This study focusses on two native species (Glossogobius callidus and Gilchristella aestuaria) and two non-native species (Oreochromis mossambicus and Gambusia affinis). The ecology of the ponds was driven by physico-chemical variables, mainly temperature, but the interactions between fishes were a complex interplay between temperature, pond community ecology and food web structure. Seasonal changes in temperature and subsequent fluctuations in water levels resulted in changes in zooplankton community. Chlorophyll-a, temperature, G. callidus and G. affinis were the drivers of the seasonal changes in macroinvertebrate composition. Stable isotope analysis identified substantial ontogenetic dietary shifts in all species, corresponding to changes in body size. Stable isotope analysis revealed that the niche space occupied by G. affinis was broad and overlapped with that of the other three focal species. Stable isotope metrics showed that G. affinis and O. mossambicus utilised a wide range of resources compared to G. callidus and G. aestuaria. Stomach content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, while G. aestuaria fed mainly plankton resources. Functional response experiments revealed that G. callidus and G. affinis both displayed Type II functional responses. In single fish trials, G. affinis had significantly higher functional responses than G. callidus. In heterospecific G. callidus-G. affinis combinations the functional response of G. callidus was reduced by the presence of G. affinis, whereas, this combination greatly enhanced G. affinis functional response magnitudes. The functional response of G. callidus, O. mossambicus and G. affinis under two temperature treatments along with fish abundance data was used to determine temporal differences in the ecological impacts of each fish species between seasons. The relative impact potential of O. mossambicus was consistently higher than that of G. callidus and G. affinis. This study demonstrates how seasonal temperature fluctuations affect the relative impact capacities of introduced species. Overall, this thesis showed that high temperature along with life-history traits contributes to the biotic interactions between native and non-native species in novel environments.
- Full Text:
- Date Issued: 2020
- Authors: Mofu, Lubabalo
- Date: 2020
- Subjects: Mozambique tilapia -- South Africa -- Sundays River (Eastern Cape) , Western mosquitofish -- South Africa -- Sundays River (Eastern Cape) , Gobiidae -- South Africa -- Sundays River (Eastern Cape) , Clupeidae -- South Africa -- Sundays River (Eastern Cape) , Reservoirs -- South Africa -- Sundays River (Eastern Cape) , Zooplankton -- South Africa -- Sundays River (Eastern Cape) , Freshwater ecology -- South Africa -- Sundays River (Eastern Cape) , Biotic communities -- South Africa -- Sundays River (Eastern Cape) , Fishes -- Effect of temperature on -- South Africa -- Sundays River (Eastern Cape) , Stable isotopes , Relative Impact Potential
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: http://hdl.handle.net/10962/167089 , vital:41436
- Description: The Sundays River valley irrigation ponds provide a unique opportunity to investigate biotic interactions within a biological invasions context, as they contain both native and non-native fish species. This study focusses on two native species (Glossogobius callidus and Gilchristella aestuaria) and two non-native species (Oreochromis mossambicus and Gambusia affinis). The ecology of the ponds was driven by physico-chemical variables, mainly temperature, but the interactions between fishes were a complex interplay between temperature, pond community ecology and food web structure. Seasonal changes in temperature and subsequent fluctuations in water levels resulted in changes in zooplankton community. Chlorophyll-a, temperature, G. callidus and G. affinis were the drivers of the seasonal changes in macroinvertebrate composition. Stable isotope analysis identified substantial ontogenetic dietary shifts in all species, corresponding to changes in body size. Stable isotope analysis revealed that the niche space occupied by G. affinis was broad and overlapped with that of the other three focal species. Stable isotope metrics showed that G. affinis and O. mossambicus utilised a wide range of resources compared to G. callidus and G. aestuaria. Stomach content analysis showed that G. callidus, O. mossambicus and G. affinis fed predominantly on benthic resources, while G. aestuaria fed mainly plankton resources. Functional response experiments revealed that G. callidus and G. affinis both displayed Type II functional responses. In single fish trials, G. affinis had significantly higher functional responses than G. callidus. In heterospecific G. callidus-G. affinis combinations the functional response of G. callidus was reduced by the presence of G. affinis, whereas, this combination greatly enhanced G. affinis functional response magnitudes. The functional response of G. callidus, O. mossambicus and G. affinis under two temperature treatments along with fish abundance data was used to determine temporal differences in the ecological impacts of each fish species between seasons. The relative impact potential of O. mossambicus was consistently higher than that of G. callidus and G. affinis. This study demonstrates how seasonal temperature fluctuations affect the relative impact capacities of introduced species. Overall, this thesis showed that high temperature along with life-history traits contributes to the biotic interactions between native and non-native species in novel environments.
- Full Text:
- Date Issued: 2020
A model of support for divorced professional nurses in the Eastern Cape, South Africa
- Authors: Murray, Daphne
- Date: 2018
- Subjects: Divorce counseling -- South Africa -- Eastern Cape Divorce -- Social aspects -- South Africa -- Eastern Cape Employees -- Counseling of -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , Nursing
- Identifier: http://hdl.handle.net/10353/10028 , vital:35293
- Description: The purpose of this research study was to develop a support model for divorced professional nurses in the health-care facilities of the Department of Health, Eastern Cape, with guidelines to operationalise the model. Divorce is a process with psychological as well as social implications, and with a series of economic causes it also has implications in terms of the society and culture in which individuals operate. The main causes for divorce are adultery and domestic violence, especially against women and children (Lurea, 2011:99). A need for support from managers in the health-care facilities of the Department of Health, Eastern Cape during the process of divorce was identified by divorced professional nurses, since a lack of support and all the negativity that encompasses divorce could lead to severe depression, which will later have a negative effect on work performance (Abdul Kadir & Bifulco, 2010:858). The literature in this field of study, along with experience, indicates that it is imperative for divorced professional nurses to be supported in the workplace to help them to cope emotionally with their work demands, as prescribed by the South African Nursing Council. An explorative, descriptive and contextual qualitative design with theory generation was used to achieve the purpose of the study. Snowball sampling was employed to select participants, namely divorced professional nurses who were unknown to the researcher. A sample of 21 divorced professional nurses who work in health-care facilities in the Buffalo City Metropolitan Municipality in the Eastern Cape participated in the study. Data was collected by means of individual face-face interviews with divorced professional nurses. The interviews continued until data saturation was reached. Field notes supplemented data that could not be portrayed by audio-taped interviews, such as non- verbal communication in observed interactions. Data analysis was done using Tesch’s approach to open coding in qualitative research. Themes, categories and sub-categories emerged from the data analysis and were fully discussed, becoming fundamental units in the development of the conceptual framework as well as in the model. The researcher did a thorough literature review to conceptualise the identified concepts on which the model was based. The description and evaluation of the model, along with guidelines to operationalise the model, were done in accordance with the method described by Chinn and Kramer (2011:197). The justification of the research, the limitations, and the recommendations for operationalisation of the model of support for divorced professional nurses working in the Buffalo City Metropolitan Municipality of the Department of Health, Eastern Cape Province, and South Africa were indicated accordingly.
- Full Text:
- Date Issued: 2018
- Authors: Murray, Daphne
- Date: 2018
- Subjects: Divorce counseling -- South Africa -- Eastern Cape Divorce -- Social aspects -- South Africa -- Eastern Cape Employees -- Counseling of -- South Africa -- Eastern Cape
- Language: English
- Type: Thesis , Doctoral , Nursing
- Identifier: http://hdl.handle.net/10353/10028 , vital:35293
- Description: The purpose of this research study was to develop a support model for divorced professional nurses in the health-care facilities of the Department of Health, Eastern Cape, with guidelines to operationalise the model. Divorce is a process with psychological as well as social implications, and with a series of economic causes it also has implications in terms of the society and culture in which individuals operate. The main causes for divorce are adultery and domestic violence, especially against women and children (Lurea, 2011:99). A need for support from managers in the health-care facilities of the Department of Health, Eastern Cape during the process of divorce was identified by divorced professional nurses, since a lack of support and all the negativity that encompasses divorce could lead to severe depression, which will later have a negative effect on work performance (Abdul Kadir & Bifulco, 2010:858). The literature in this field of study, along with experience, indicates that it is imperative for divorced professional nurses to be supported in the workplace to help them to cope emotionally with their work demands, as prescribed by the South African Nursing Council. An explorative, descriptive and contextual qualitative design with theory generation was used to achieve the purpose of the study. Snowball sampling was employed to select participants, namely divorced professional nurses who were unknown to the researcher. A sample of 21 divorced professional nurses who work in health-care facilities in the Buffalo City Metropolitan Municipality in the Eastern Cape participated in the study. Data was collected by means of individual face-face interviews with divorced professional nurses. The interviews continued until data saturation was reached. Field notes supplemented data that could not be portrayed by audio-taped interviews, such as non- verbal communication in observed interactions. Data analysis was done using Tesch’s approach to open coding in qualitative research. Themes, categories and sub-categories emerged from the data analysis and were fully discussed, becoming fundamental units in the development of the conceptual framework as well as in the model. The researcher did a thorough literature review to conceptualise the identified concepts on which the model was based. The description and evaluation of the model, along with guidelines to operationalise the model, were done in accordance with the method described by Chinn and Kramer (2011:197). The justification of the research, the limitations, and the recommendations for operationalisation of the model of support for divorced professional nurses working in the Buffalo City Metropolitan Municipality of the Department of Health, Eastern Cape Province, and South Africa were indicated accordingly.
- Full Text:
- Date Issued: 2018
Management practices, milk quality, haemato-chemical biomarkers of free ranging pregnant goats from three genotypes and linear body measurements of their respective kids
- Idamokoro, Emrobowansan Monday
- Authors: Idamokoro, Emrobowansan Monday
- Date: 2016
- Subjects: Milk--Quality Biochemical markers Goat milk
- Language: English
- Type: Thesis , Doctoral , Animal Science
- Identifier: http://hdl.handle.net/10353/11548 , vital:39082
- Description: The broad objective of this study was to assess farmers’ perceptions on the welfare and management practices of pregnant goats and to determine the effect of genotypes and physiological status on doe’s performance (blood metabolites and milk quality) and their respective kid’s linear body measurements of goats reared in an extensive system of production. A survey was conducted among 153 goat farmers to assess their perception on goat mortality and management practices during and after gestation period. The results from the survey showed that 98.7percent of the farmers depended on pastures to feed their pregnant and lactating does. Majority of the farmers (59.9percent) did not vaccinate their dams against diseases before using them for breeding purposes. An aggregate of 77.8percent respondents allowed their does to mate freely on the veld. Most of the respondents (75.2percent) kept their pregnant goats together with other flocks in mud floor pen (kraals) fenced with tree branches. Farmers indicated that, poor diet (32percent), disease (24 percent) and predators (15percent) were some factors that cause mortality in pregnant does. About 66.7percent respondents perceived that, quality diet is a factor that can boost the reproductive performance of pregnant goats. The haemato-biochemical parameters of Nguni, Boer and Non-descript goats at late and early lactation revealed that, Nguni goat had higher (P ˂ 0.05) values of red cell counts (13.37 x1011/L), haemoglobin (9.07 g/dL) and creatine kinase (269.54 U/L) compared to Boer (9.96 x 1011/L, 7.94 g/ dL and 132.16 U/L) and Non-descript goats (12.98 x 1011 /L, 7.85 g/ dL and 143.50 U/L), respectively. The Nguni goats also had higher (P ˂ 0.05) mean values of glucose (3.38 mmol/L), sodium (141.66 mmol/L) and urea content (5.51 mmol/L) compared to Boer (2.96 mmol/L, 135.70 mmol/L and 4.45 mmol/L) and Non-descript goats (2.50 mmol/L, 141.31 mmol/L and 3.90 mmol/L), respectively. The results of blood metabolites also revealed that, there was significant difference (P < 0.05) in the physiological status of goats. The late stage of pregnancy had higher mean values of red cell counts (14.44 x 1011 /L), haemoglobin (8.57 g/dL), haematocrit (0.67 L/L), glucose (3.12 mmol/L), sodium (141.74 mmol/L) and calcium content (2.37 mmol/L) compared to the early stage of lactation (9.77 x 1011/ L, 8.00 g /dL, 0.55 L/L, 2.77 mmol/L, 137.37 mmol/L and 2.23 mmol/L), respectively. Furthermore, it was revealed that, Nguni goats produced (1.2±0.09, 1.3±0.11 and 1.2±0.07 litres per day) more milk (P ˂ 0.05) at early, mid and late stages of lactation than Boer (0.6±0.10, 1.0±0.17 and 0.6±0.09 litres per day) and Non-descript (0.3±0.10, 0.3±0.12 and 0.3±0.09 litres per day) goats. There was significant difference (P ˂ 0.05) of genotypes on milk fat, milk magnesium and sodium contents among Nguni, Boer and Non-descript goats. Lactation stages had a significant effect (P ˂ 0.05) on some milk compositions (fat, protein, lactose and solid non-fat) and mineral profiles (Ca, Mg, Na, K, and Fe) of Nguni goats. Lactation stages had a significant effect (P ˂ 0.05) on fat, protein, lactose and solid non-fat content and mineral profiles (Ca, Mg, Na, K, and Fe) of Nguni goats. Milk protein content of Nguni goat was positively correlated to milk fat but, not in Boer and Non-descript goats. Milk quality parameters from the three goat genotypes possessed relatively moderate milk compositions and mineral profiles which is comparable to some exotic goat breeds. Nguni kids had higher mean weights (7.36 kg, 11.85 kg and 13.72 kg) than the Boer kids (5.20 kg, 7.18 kg and 10.20 kg) and the Non-descript goat kids (5.23 kg, 6.19 kg and 8.01 kg) at weeks 4, 6 and 8 after parturition, respectively. In terms of height at withers, the Nguni kids had higher mean values in heights (41.92 cm, 44.71 cm, 49.38 cm and 55.75 cm) than the Boer kids (35.67 cm, 37.14 cm, 42.40 and 44.20 cm) and the Non-descript kids (36.38 cm, 40.20 cm, 41.14 cm and 43.50 cm) at week 2, 4, 6 and 8 after parturition, respectively. Conversely, there was a positive correlation (P ˂ 0.05) between body lengths and live weights of Nguni goats and not in Boer and Non-descript goats. It was concluded from this study that, the indigenous Nguni, Boer and Non-descript pregnant goats were managed in poor conditions by communal farmers and the perceived causes of mortality of pregnant goats among others include poor feed, diseases and predators. In addition, the Nguni goats had higher mean values in some haematological parameters (red cell counts and haemoglobin) and serum biochemical profiles (glucose, sodium, urea and creatine kinase) than Boer and Non-descript goats during the periods of investigation. Nguni goats also produced more milk at the early and late stages of lactation compared to the Boer and Non-descript goats. The Non-descript goats had a higher mean value of milk fat compared to Nguni and Boer goats. Likewise, the Boer goats were observed to have higher mean value of milk magnesium and sodium content compared to Nguni and Non-descript goats. In terms of body weights and linear body measurments, the Nguni goat kids were superior compared to Boer and Non-descript goats.
- Full Text: false
- Date Issued: 2016
- Authors: Idamokoro, Emrobowansan Monday
- Date: 2016
- Subjects: Milk--Quality Biochemical markers Goat milk
- Language: English
- Type: Thesis , Doctoral , Animal Science
- Identifier: http://hdl.handle.net/10353/11548 , vital:39082
- Description: The broad objective of this study was to assess farmers’ perceptions on the welfare and management practices of pregnant goats and to determine the effect of genotypes and physiological status on doe’s performance (blood metabolites and milk quality) and their respective kid’s linear body measurements of goats reared in an extensive system of production. A survey was conducted among 153 goat farmers to assess their perception on goat mortality and management practices during and after gestation period. The results from the survey showed that 98.7percent of the farmers depended on pastures to feed their pregnant and lactating does. Majority of the farmers (59.9percent) did not vaccinate their dams against diseases before using them for breeding purposes. An aggregate of 77.8percent respondents allowed their does to mate freely on the veld. Most of the respondents (75.2percent) kept their pregnant goats together with other flocks in mud floor pen (kraals) fenced with tree branches. Farmers indicated that, poor diet (32percent), disease (24 percent) and predators (15percent) were some factors that cause mortality in pregnant does. About 66.7percent respondents perceived that, quality diet is a factor that can boost the reproductive performance of pregnant goats. The haemato-biochemical parameters of Nguni, Boer and Non-descript goats at late and early lactation revealed that, Nguni goat had higher (P ˂ 0.05) values of red cell counts (13.37 x1011/L), haemoglobin (9.07 g/dL) and creatine kinase (269.54 U/L) compared to Boer (9.96 x 1011/L, 7.94 g/ dL and 132.16 U/L) and Non-descript goats (12.98 x 1011 /L, 7.85 g/ dL and 143.50 U/L), respectively. The Nguni goats also had higher (P ˂ 0.05) mean values of glucose (3.38 mmol/L), sodium (141.66 mmol/L) and urea content (5.51 mmol/L) compared to Boer (2.96 mmol/L, 135.70 mmol/L and 4.45 mmol/L) and Non-descript goats (2.50 mmol/L, 141.31 mmol/L and 3.90 mmol/L), respectively. The results of blood metabolites also revealed that, there was significant difference (P < 0.05) in the physiological status of goats. The late stage of pregnancy had higher mean values of red cell counts (14.44 x 1011 /L), haemoglobin (8.57 g/dL), haematocrit (0.67 L/L), glucose (3.12 mmol/L), sodium (141.74 mmol/L) and calcium content (2.37 mmol/L) compared to the early stage of lactation (9.77 x 1011/ L, 8.00 g /dL, 0.55 L/L, 2.77 mmol/L, 137.37 mmol/L and 2.23 mmol/L), respectively. Furthermore, it was revealed that, Nguni goats produced (1.2±0.09, 1.3±0.11 and 1.2±0.07 litres per day) more milk (P ˂ 0.05) at early, mid and late stages of lactation than Boer (0.6±0.10, 1.0±0.17 and 0.6±0.09 litres per day) and Non-descript (0.3±0.10, 0.3±0.12 and 0.3±0.09 litres per day) goats. There was significant difference (P ˂ 0.05) of genotypes on milk fat, milk magnesium and sodium contents among Nguni, Boer and Non-descript goats. Lactation stages had a significant effect (P ˂ 0.05) on some milk compositions (fat, protein, lactose and solid non-fat) and mineral profiles (Ca, Mg, Na, K, and Fe) of Nguni goats. Lactation stages had a significant effect (P ˂ 0.05) on fat, protein, lactose and solid non-fat content and mineral profiles (Ca, Mg, Na, K, and Fe) of Nguni goats. Milk protein content of Nguni goat was positively correlated to milk fat but, not in Boer and Non-descript goats. Milk quality parameters from the three goat genotypes possessed relatively moderate milk compositions and mineral profiles which is comparable to some exotic goat breeds. Nguni kids had higher mean weights (7.36 kg, 11.85 kg and 13.72 kg) than the Boer kids (5.20 kg, 7.18 kg and 10.20 kg) and the Non-descript goat kids (5.23 kg, 6.19 kg and 8.01 kg) at weeks 4, 6 and 8 after parturition, respectively. In terms of height at withers, the Nguni kids had higher mean values in heights (41.92 cm, 44.71 cm, 49.38 cm and 55.75 cm) than the Boer kids (35.67 cm, 37.14 cm, 42.40 and 44.20 cm) and the Non-descript kids (36.38 cm, 40.20 cm, 41.14 cm and 43.50 cm) at week 2, 4, 6 and 8 after parturition, respectively. Conversely, there was a positive correlation (P ˂ 0.05) between body lengths and live weights of Nguni goats and not in Boer and Non-descript goats. It was concluded from this study that, the indigenous Nguni, Boer and Non-descript pregnant goats were managed in poor conditions by communal farmers and the perceived causes of mortality of pregnant goats among others include poor feed, diseases and predators. In addition, the Nguni goats had higher mean values in some haematological parameters (red cell counts and haemoglobin) and serum biochemical profiles (glucose, sodium, urea and creatine kinase) than Boer and Non-descript goats during the periods of investigation. Nguni goats also produced more milk at the early and late stages of lactation compared to the Boer and Non-descript goats. The Non-descript goats had a higher mean value of milk fat compared to Nguni and Boer goats. Likewise, the Boer goats were observed to have higher mean value of milk magnesium and sodium content compared to Nguni and Non-descript goats. In terms of body weights and linear body measurments, the Nguni goat kids were superior compared to Boer and Non-descript goats.
- Full Text: false
- Date Issued: 2016
Nonlinear optical studies of phthalocyanines and their conjugates with nanomaterials
- Authors: Sanusi, Sikiru Olukayode
- Date: 2015
- Subjects: Phthalocyanines , Nonlinear optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4545 , http://hdl.handle.net/10962/d1017925
- Description: A number of metallophthalocyanines (MPcs) and metal-free phthalocyanines (H₂Pcs) have been synthesized and characterized using various characterization tools such as ¹H-NMR, TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and CHNS elemental analysis. Some of the MPcs were covalently linked to nanomaterials such as silica nanoparticles (SiNPs), single-walled carbon nanotubes (SWCNTs), magnetite nanoparticles (MNPs) and quantum dots (QDs), or embedded in polymer thin-films using poly(methyl methacrylate) (PMMA) and poly(acrylic acid) (PAA) as the polymer sources. The phthalocyanine-nanomaterial composites (Pc-NMCs) were characterized with FT-IR, UV-visible spectrophotometry, transmission electron microscopy (TEM), thermogravimetry analysis and X-ray diffractometry. The nonlinear optical (NLO) properties (using the open-aperture Z-scan technique) of the MPcs and the Pc-NMCs were investigated. In general, most of the investigated MPcs showed good optical limiting behaviors, except for a few, like the non-peripherally-substituted 2-pyridyloxy phthalocyanines, which showed inhibited NLO response as a result of the ring-strain effects. The absence of a metal center was found to greatly reduce the inherent high nonlinearities expected of some of the phthalocyanine complexes. The octaphenoxy derivatives (61a – 61e) were found to exhibit reverse saturable absorption (RSA) that depends on the singlet-singlet transitions, hence making them less reliable optical limiters. The optical limiting properties of the MPcs were improved in the presence of nanomaterials such as the QDs, MNPs and SWCNTs, with MPc-QDs showing the best optical limiting behavior of the three. SiNPs have no significant effect on the optical limiting behavior of the MPcs. The optical limiting properties of the MPcs were greatly enhanced in the presence of PMMA or PAA polymers. The PAA polymer showed better optical limiting behavior compared to PMMA
- Full Text:
- Date Issued: 2015
- Authors: Sanusi, Sikiru Olukayode
- Date: 2015
- Subjects: Phthalocyanines , Nonlinear optics
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4545 , http://hdl.handle.net/10962/d1017925
- Description: A number of metallophthalocyanines (MPcs) and metal-free phthalocyanines (H₂Pcs) have been synthesized and characterized using various characterization tools such as ¹H-NMR, TOF mass spectrometry, FT-IR, UV-visible spectrophotometry and CHNS elemental analysis. Some of the MPcs were covalently linked to nanomaterials such as silica nanoparticles (SiNPs), single-walled carbon nanotubes (SWCNTs), magnetite nanoparticles (MNPs) and quantum dots (QDs), or embedded in polymer thin-films using poly(methyl methacrylate) (PMMA) and poly(acrylic acid) (PAA) as the polymer sources. The phthalocyanine-nanomaterial composites (Pc-NMCs) were characterized with FT-IR, UV-visible spectrophotometry, transmission electron microscopy (TEM), thermogravimetry analysis and X-ray diffractometry. The nonlinear optical (NLO) properties (using the open-aperture Z-scan technique) of the MPcs and the Pc-NMCs were investigated. In general, most of the investigated MPcs showed good optical limiting behaviors, except for a few, like the non-peripherally-substituted 2-pyridyloxy phthalocyanines, which showed inhibited NLO response as a result of the ring-strain effects. The absence of a metal center was found to greatly reduce the inherent high nonlinearities expected of some of the phthalocyanine complexes. The octaphenoxy derivatives (61a – 61e) were found to exhibit reverse saturable absorption (RSA) that depends on the singlet-singlet transitions, hence making them less reliable optical limiters. The optical limiting properties of the MPcs were improved in the presence of nanomaterials such as the QDs, MNPs and SWCNTs, with MPc-QDs showing the best optical limiting behavior of the three. SiNPs have no significant effect on the optical limiting behavior of the MPcs. The optical limiting properties of the MPcs were greatly enhanced in the presence of PMMA or PAA polymers. The PAA polymer showed better optical limiting behavior compared to PMMA
- Full Text:
- Date Issued: 2015
Life history changes of two reef fish species in exploited and unexploited marine environments in South Africa
- Authors: Buxton, Colin David
- Date: 1988
- Subjects: Reef fishes -- Africa, Southern Chrysoblephus laticeps Chrysoblephus cristiceps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5189 , http://hdl.handle.net/10962/d1001965
- Description: A detailed investigation into the life histories of Chrysoblephus laticeps and c. cristiceps in exploited and unexploited marine environments on the south-east coast of southern Africa is presented. The study provided information necessary for the evaluation of marine reserves as a management option for these and similar reef species. Visual underwater assessments showed a clear spatial separation between adults and juveniles of both species, suggesting a recruitment of juveniles into shallow water followed by a gradual outward migration into deeper water with age. Denslty estlmates of C. laticeps in the Noordhoek (0.0064 fish/m²) and Tsitslkamma (0.0254 fish/m²) areas were significantly different and were attributed to exploitation. Within area differences in density were also significantly correlated with temperature) depth and substratum relief. Similar comparisons for C. cristiceps were not possible because these fish shied away from divers. Habitat preferences were mirrored in the diets of both species which fed on a wide variety of reef associated benthic animals. Size of prey appeared to be gape limited, only larger fish being able to manipulate prey. Quantitative differences between the diets of fish sampled in different areas were a reflection of differences in available prey and not related to the relative density of predators. The dietary characteristics recorded in these fish were typical of search hunters. An age and growth study based on the examination of sectioned otoliths showed that both species were slow growing and long lived. Maximum recorded ages were 18 and 22 years for C. laticeps and C. cristiceps respectively. Growth rates in exploited and unexploited areas were not significantly different although there was an indication that growth was slower in the exploited areas for C. cristiceps. Several inconsistencies in otolith interpretation and terminology were evaluated. Contrary to other South African studies the results suggested that somatic growth was fastest just after spawning. This coincided with the winter months and was reflected by the deposition of a hyaline zone in the otolith. Two independent estimates, the Pauli derivation and visually assessed length frequency analysis, produced the same value for total mortality of C. laticeps in the Tsitsikamma area (0.2). This result, together with a significant difference in the rate of fishing mortality at different areas along the coast suggested that the populations sampled were discrete and supported the postulate that both species were sedentary. Further support was obtained from a mark-recapture study. Although sample numbers were low the results showed no evidence of large scale migratory patterns in these fish. An investigation of the reproductive biology of both fish showed that they were protogynous hermaphrodites, all males being derived from females with no evidence for polyandry. Males were shown to be capable of mating with a number of females and this, together with monandry, monochromatism and a small testis size, suggested a polygynous mating system in both species. Observations of the courtship behaviour in captive c. laticeps also supported polygyny. A significant difference in the mean size at sex reversal between unexploited and exploited populations supported the postulate that sex reversal was independent of the size or age of the animal. The size at which sex reversal occurred appeared to be dependent on sex ratio. A detailed yield per recruit analysis of the response of the population to different levels of fishing mortality and size at recruitment (t [subscript]r), showed that sex reversing species were particularly vulnerable to over fishing. This was due to a dramatic decline in the number of surviving individuals past t[subscript]r which resulted in a skewing of the sex ratio towards females. Evidence is presented to show that current legislation is inadequately protecting the spawner stock of both species. In conclusion it is shown that longevity, sex reversal, restricted movements and the occupation of a demersal habitat make these species particularly vulnerable to over exploitation in a size- selective fishery. The sustained yield in the linefishery is suggested to be a result of distant recruitment from relatively unexploited populations rather than the adequacy of current conservation measures. The need to protect the spawner stock is emphasised and the use of marine reserves as an additional protection for sedentary reef-dwelling species is therefore advocated.
- Full Text:
- Date Issued: 1988
- Authors: Buxton, Colin David
- Date: 1988
- Subjects: Reef fishes -- Africa, Southern Chrysoblephus laticeps Chrysoblephus cristiceps
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5189 , http://hdl.handle.net/10962/d1001965
- Description: A detailed investigation into the life histories of Chrysoblephus laticeps and c. cristiceps in exploited and unexploited marine environments on the south-east coast of southern Africa is presented. The study provided information necessary for the evaluation of marine reserves as a management option for these and similar reef species. Visual underwater assessments showed a clear spatial separation between adults and juveniles of both species, suggesting a recruitment of juveniles into shallow water followed by a gradual outward migration into deeper water with age. Denslty estlmates of C. laticeps in the Noordhoek (0.0064 fish/m²) and Tsitslkamma (0.0254 fish/m²) areas were significantly different and were attributed to exploitation. Within area differences in density were also significantly correlated with temperature) depth and substratum relief. Similar comparisons for C. cristiceps were not possible because these fish shied away from divers. Habitat preferences were mirrored in the diets of both species which fed on a wide variety of reef associated benthic animals. Size of prey appeared to be gape limited, only larger fish being able to manipulate prey. Quantitative differences between the diets of fish sampled in different areas were a reflection of differences in available prey and not related to the relative density of predators. The dietary characteristics recorded in these fish were typical of search hunters. An age and growth study based on the examination of sectioned otoliths showed that both species were slow growing and long lived. Maximum recorded ages were 18 and 22 years for C. laticeps and C. cristiceps respectively. Growth rates in exploited and unexploited areas were not significantly different although there was an indication that growth was slower in the exploited areas for C. cristiceps. Several inconsistencies in otolith interpretation and terminology were evaluated. Contrary to other South African studies the results suggested that somatic growth was fastest just after spawning. This coincided with the winter months and was reflected by the deposition of a hyaline zone in the otolith. Two independent estimates, the Pauli derivation and visually assessed length frequency analysis, produced the same value for total mortality of C. laticeps in the Tsitsikamma area (0.2). This result, together with a significant difference in the rate of fishing mortality at different areas along the coast suggested that the populations sampled were discrete and supported the postulate that both species were sedentary. Further support was obtained from a mark-recapture study. Although sample numbers were low the results showed no evidence of large scale migratory patterns in these fish. An investigation of the reproductive biology of both fish showed that they were protogynous hermaphrodites, all males being derived from females with no evidence for polyandry. Males were shown to be capable of mating with a number of females and this, together with monandry, monochromatism and a small testis size, suggested a polygynous mating system in both species. Observations of the courtship behaviour in captive c. laticeps also supported polygyny. A significant difference in the mean size at sex reversal between unexploited and exploited populations supported the postulate that sex reversal was independent of the size or age of the animal. The size at which sex reversal occurred appeared to be dependent on sex ratio. A detailed yield per recruit analysis of the response of the population to different levels of fishing mortality and size at recruitment (t [subscript]r), showed that sex reversing species were particularly vulnerable to over fishing. This was due to a dramatic decline in the number of surviving individuals past t[subscript]r which resulted in a skewing of the sex ratio towards females. Evidence is presented to show that current legislation is inadequately protecting the spawner stock of both species. In conclusion it is shown that longevity, sex reversal, restricted movements and the occupation of a demersal habitat make these species particularly vulnerable to over exploitation in a size- selective fishery. The sustained yield in the linefishery is suggested to be a result of distant recruitment from relatively unexploited populations rather than the adequacy of current conservation measures. The need to protect the spawner stock is emphasised and the use of marine reserves as an additional protection for sedentary reef-dwelling species is therefore advocated.
- Full Text:
- Date Issued: 1988
Die metaroman : dekonstruksie-ondersoek
- Authors: Hambidge, Joan, 1956-
- Date: 1984
- Subjects: Fiction -- 20th century -- History and criticism Experimental fiction -- History and criticism
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3611 , http://hdl.handle.net/10962/d1005056
- Full Text:
- Date Issued: 1984
- Authors: Hambidge, Joan, 1956-
- Date: 1984
- Subjects: Fiction -- 20th century -- History and criticism Experimental fiction -- History and criticism
- Language: Afrikaans
- Type: Thesis , Doctoral , PhD
- Identifier: vital:3611 , http://hdl.handle.net/10962/d1005056
- Full Text:
- Date Issued: 1984
Synthesis of flavan-3, 4-diols, stereochemistry of novel biflavanols and new non-tannins from Acacia Mearnsii
- Authors: Saayman, Henry Martin
- Date: 1967
- Subjects: Tannins Acacia mearnsii Stereochemistry Wattles (Plants) Chemistry, Analytic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4444 , http://hdl.handle.net/10962/d1007704
- Description: From Summary: The structural elucidation of condensed tannins, which are considered to consist of C₁₅-flavan units, presents certain difficulties. These tannins occur in extremely complex mixtures, and their isolation is complicated by their susceptibility to oxidative denaturation. Limitations in the formation of significant degradation products add to these problems. Since condensed tannins of black wattle bark yield anthocyanidins on treatment with mineral acids, they are considered to be proanthocyanidin in character. For this reason the initial approach to the investigation of the structures of condensed tannins was by way of the synthesis of novel 7-hydroxyflavan-3,4-diols having a low degree of hydroxyl substitution. Submission of these to modern physical techniques such as nuclear magnetic resonance (n.m.r.) spectroscopy would yield valuable data regarding the chemical shifts and coupling constants of heterocyclic and benzenoid protons which may be used for subsequent work on more highly hydroxylated diols, biflavanols and finally the condensed tannins themselves.
- Full Text:
- Date Issued: 1967
- Authors: Saayman, Henry Martin
- Date: 1967
- Subjects: Tannins Acacia mearnsii Stereochemistry Wattles (Plants) Chemistry, Analytic
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4444 , http://hdl.handle.net/10962/d1007704
- Description: From Summary: The structural elucidation of condensed tannins, which are considered to consist of C₁₅-flavan units, presents certain difficulties. These tannins occur in extremely complex mixtures, and their isolation is complicated by their susceptibility to oxidative denaturation. Limitations in the formation of significant degradation products add to these problems. Since condensed tannins of black wattle bark yield anthocyanidins on treatment with mineral acids, they are considered to be proanthocyanidin in character. For this reason the initial approach to the investigation of the structures of condensed tannins was by way of the synthesis of novel 7-hydroxyflavan-3,4-diols having a low degree of hydroxyl substitution. Submission of these to modern physical techniques such as nuclear magnetic resonance (n.m.r.) spectroscopy would yield valuable data regarding the chemical shifts and coupling constants of heterocyclic and benzenoid protons which may be used for subsequent work on more highly hydroxylated diols, biflavanols and finally the condensed tannins themselves.
- Full Text:
- Date Issued: 1967
The preservation and standardisation of South African hides and skins
- Authors: Kritzinger, Carl Cronje
- Date: 1946
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21052 , http://hdl.handle.net/10962/6157
- Description: During the past fifty years the problems of the leather industry have been tackled from various aspects by scientific research workers all over the world, and "works control" today forms one of .the important foundation stones of efficiently run tanneries and footwear factories. The raw materials of the tanning industry, hides and skins, constitute the largest proportion of the cost of production, and it is ' only natural that the improvement of these valuable raw materials should be given primary attention by any leather scientist. Until only a few years ago, however, the South African hide and skin industry was at a serious ·disadvantage in that it had to base recommendations for improved production methods almost exclusively on overseas experience and practice. The importance of the differences existing between South Africa and European or American countries with regard to climate, slaughtering, hide and skin production in general, transport and sale, however, necessitates a different approach to our specific problems. The overseas hide and skin industry has had, since the beginning of this century, the support and particularly the guidance of scientific research; but it was not until 1935, when, through the support of the Hide and Skin advisory Board, Prof. W. F. Barker founded the original Tanning, Hides and Skins Research Department at Rhodes University College, Grahamstown, that science actively entered the field of hide and skin production in this country. Much of the work done had of course to be based on the results obtained by overseas research institutions, and the adaptation of such results to suit our own problems for some time formed a considerable part of the investigations undertaken. This thesis embodies the results of work undertaken by the writer since 1943 on specific problems of the South African hide and skin industry. Much of the work has already received publication through the Circulars and Journals of this Institute, but it is embodied here again in order to maintain the continuity. The attitude throughout has been to evolve methods of production suited to our own conditions, and the adoption of the recommendations contained in this thesis should lead to improvement in the quality of our hides and skins. Much still remains to be done, and it is the sincere hope of the writer that this work will stimulate and form the basis for subsequent investigations. For that reason more or less detailed descriptions are given of all experiments conducted, and the theory of curing in its relation to tanning is briefly discussed . The literature in each of the four Parts has been attached at the end of that Part to facilitate reference work. At the same time, however, the writer kept in mind the requirements of the trade itself, therefore much of the work is discussed in popular terms. It is hoped that the correct balance between the two extremes has been arrived at.
- Full Text:
- Date Issued: 1946
- Authors: Kritzinger, Carl Cronje
- Date: 1946
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:21052 , http://hdl.handle.net/10962/6157
- Description: During the past fifty years the problems of the leather industry have been tackled from various aspects by scientific research workers all over the world, and "works control" today forms one of .the important foundation stones of efficiently run tanneries and footwear factories. The raw materials of the tanning industry, hides and skins, constitute the largest proportion of the cost of production, and it is ' only natural that the improvement of these valuable raw materials should be given primary attention by any leather scientist. Until only a few years ago, however, the South African hide and skin industry was at a serious ·disadvantage in that it had to base recommendations for improved production methods almost exclusively on overseas experience and practice. The importance of the differences existing between South Africa and European or American countries with regard to climate, slaughtering, hide and skin production in general, transport and sale, however, necessitates a different approach to our specific problems. The overseas hide and skin industry has had, since the beginning of this century, the support and particularly the guidance of scientific research; but it was not until 1935, when, through the support of the Hide and Skin advisory Board, Prof. W. F. Barker founded the original Tanning, Hides and Skins Research Department at Rhodes University College, Grahamstown, that science actively entered the field of hide and skin production in this country. Much of the work done had of course to be based on the results obtained by overseas research institutions, and the adaptation of such results to suit our own problems for some time formed a considerable part of the investigations undertaken. This thesis embodies the results of work undertaken by the writer since 1943 on specific problems of the South African hide and skin industry. Much of the work has already received publication through the Circulars and Journals of this Institute, but it is embodied here again in order to maintain the continuity. The attitude throughout has been to evolve methods of production suited to our own conditions, and the adoption of the recommendations contained in this thesis should lead to improvement in the quality of our hides and skins. Much still remains to be done, and it is the sincere hope of the writer that this work will stimulate and form the basis for subsequent investigations. For that reason more or less detailed descriptions are given of all experiments conducted, and the theory of curing in its relation to tanning is briefly discussed . The literature in each of the four Parts has been attached at the end of that Part to facilitate reference work. At the same time, however, the writer kept in mind the requirements of the trade itself, therefore much of the work is discussed in popular terms. It is hoped that the correct balance between the two extremes has been arrived at.
- Full Text:
- Date Issued: 1946
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