Evaluation of Lewis acid catalysed and other nitration strategies for the selective nitration of cresols
- Van Niekerk, Rudolf Jacob Francois
- Authors: Van Niekerk, Rudolf Jacob Francois
- Date: 2001
- Subjects: Nitration
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10957 , http://hdl.handle.net/10948/60 , Nitration
- Description: The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
- Full Text:
- Date Issued: 2001
- Authors: Van Niekerk, Rudolf Jacob Francois
- Date: 2001
- Subjects: Nitration
- Language: English
- Type: Thesis , Masters , MTech (Chemistry)
- Identifier: vital:10957 , http://hdl.handle.net/10948/60 , Nitration
- Description: The nitration of m- and p-cresol was investigated under mild reaction conditions in a number of solvents; the effects of certain nitration catalysts were also evaluated. These different reaction parameters were evaluated in terms of their effect on a number of important reaction responses. Other important factors that were investigated were the manipulation of the isomer ratios by changing reaction parameters, as well as important process chemistry information, such as product distribution, isolation and purification, identification of side products formed, and evaluation of the heat of reaction. Use was made of an experimental design system to evaluate the effect of reaction parameters on the chosen design responses. It was found that the ratio of para to ortho nitrocresol products could be influenced slightly by using low concentrations of nitric acid and low reaction temperatures. A different mechanism for the formation of 2-methyl-1,4-benzoquinone (from mcresol nitration) was proposed (compared with that previously reported), which could explain a “one mole nitric acid” pathway and the fact that only the pbenzoquinone isomer was observed. Reaction side products were identified and found to consist of dimers of cresol and nitrocresol, which were probably the result of oxidation of the cresol, subsequent formation of a quinomethide intermediate and reaction with either the product or the substrate. The heat of nitration was determined for various reaction systems and found to be governed by two factors, namely the actual nitration process and also an oxidation process, which is responsible for the formation of side products.
- Full Text:
- Date Issued: 2001
Expanding the capabilities of the DPS lonosonde system
- Authors: Magnus, Lindsay Gerald
- Date: 2001
- Subjects: Ionosondes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5560 , http://hdl.handle.net/10962/d1018243
- Description: The Digisonde Portable Sounder (DPS) is a low power pulse ionosonde capable of recording a wealth of scientific information about the ionosphere. The routine vertical incidence mode, that produces the scaled ionospheric parameters, only records limited Doppler and no precise angle of arrival (AoA) information. The drift mode produces precise scientific information but only limited range information. This thesis explains the operation of the DPS and then examines the drift data by first showing the Doppler velocities (V*) calculated for a fixed frequency ionogram as well as the velocities calculated from an interesting ionospheric disturbance measured with a stepped frequency ionogram and second by illustrating the presence of a variation in the AoA of ionospheric echoes at sunrise. The conclusion of the thesis is that a drift vertical incidence mode be developed to allow the simultaneous measurement of the scaled ionospheric parameters and the precise AoA and full Doppler spectrum information.
- Full Text:
- Date Issued: 2001
- Authors: Magnus, Lindsay Gerald
- Date: 2001
- Subjects: Ionosondes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5560 , http://hdl.handle.net/10962/d1018243
- Description: The Digisonde Portable Sounder (DPS) is a low power pulse ionosonde capable of recording a wealth of scientific information about the ionosphere. The routine vertical incidence mode, that produces the scaled ionospheric parameters, only records limited Doppler and no precise angle of arrival (AoA) information. The drift mode produces precise scientific information but only limited range information. This thesis explains the operation of the DPS and then examines the drift data by first showing the Doppler velocities (V*) calculated for a fixed frequency ionogram as well as the velocities calculated from an interesting ionospheric disturbance measured with a stepped frequency ionogram and second by illustrating the presence of a variation in the AoA of ionospheric echoes at sunrise. The conclusion of the thesis is that a drift vertical incidence mode be developed to allow the simultaneous measurement of the scaled ionospheric parameters and the precise AoA and full Doppler spectrum information.
- Full Text:
- Date Issued: 2001
Experiences in porting a virtual reality system to Java
- Authors: Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433157 , vital:72947 , https://doi.org/10.1145/513867.513875
- Description: Practical experience in porting a large virtual reality system from C/C++ to Java indicates that porting this type of real-time application is both feasible, and has several merits. The ability to transfer objects in space and time allows useful facilities such as distributed agent support and persistence to be added. Reflection and type comparisons allow flexible manipulations of objects of different types at run-time. Native calls and native code compilation reduce or remove the overhead of interpreting code.Problems encountered include difficulty in achieving cross-platform code portability, limitations of the networking libraries in Java, and clumsy coding practices forced by the language.
- Full Text:
- Date Issued: 2001
- Authors: Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433157 , vital:72947 , https://doi.org/10.1145/513867.513875
- Description: Practical experience in porting a large virtual reality system from C/C++ to Java indicates that porting this type of real-time application is both feasible, and has several merits. The ability to transfer objects in space and time allows useful facilities such as distributed agent support and persistence to be added. Reflection and type comparisons allow flexible manipulations of objects of different types at run-time. Native calls and native code compilation reduce or remove the overhead of interpreting code.Problems encountered include difficulty in achieving cross-platform code portability, limitations of the networking libraries in Java, and clumsy coding practices forced by the language.
- Full Text:
- Date Issued: 2001
Exploring job satisfaction amongst government social workers in East London
- Authors: Sela, Michelle
- Date: 2001
- Subjects: Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:705 , http://hdl.handle.net/10962/d1006499 , Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Description: During this research an attempt was made to gain an understanding of job satisfaction amongst government social workers. To achieve this, twenty social workers employed at the Department of Welfare in East London and Mdantsane were interviewed. South African literature on this topic is limited and it is believed that this study will present a valuable basis to pursue in further research. Literature that was consulted was found to be supportive of the theoretical notion that social work has long been recognised as being a stressful profession and that the nature of social work practice itself can be potentially stressful. The study found that there are many stressors and dissatisfactions which government social workers are currently experiencing. Some of the social workers have indicated a desire to leave the profession as a result of the dissatisfactions. The study findings suggest a need for combining oganisational with individual oriented initiatives to decrease the many stressors the social workers are experiencing. The thesis ends with recommendations of various strategies for addressing the concerns of the social workers in order to increase their job satisfaction
- Full Text:
- Date Issued: 2001
- Authors: Sela, Michelle
- Date: 2001
- Subjects: Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:705 , http://hdl.handle.net/10962/d1006499 , Social workers -- Supervision of , Social workers -- Professional ethics , Social workers -- South Africa -- Eastern Cape -- Attitudes , Social service -- Vocational guidance
- Description: During this research an attempt was made to gain an understanding of job satisfaction amongst government social workers. To achieve this, twenty social workers employed at the Department of Welfare in East London and Mdantsane were interviewed. South African literature on this topic is limited and it is believed that this study will present a valuable basis to pursue in further research. Literature that was consulted was found to be supportive of the theoretical notion that social work has long been recognised as being a stressful profession and that the nature of social work practice itself can be potentially stressful. The study found that there are many stressors and dissatisfactions which government social workers are currently experiencing. Some of the social workers have indicated a desire to leave the profession as a result of the dissatisfactions. The study findings suggest a need for combining oganisational with individual oriented initiatives to decrease the many stressors the social workers are experiencing. The thesis ends with recommendations of various strategies for addressing the concerns of the social workers in order to increase their job satisfaction
- Full Text:
- Date Issued: 2001
Extractives from six species of South African Marine Opisthobranch Molluscs
- Authors: McPhail, Kerry Lee
- Date: 2001
- Subjects: Mollusks -- Nutrition Mollusks -- Anatomy Marine fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4433 , http://hdl.handle.net/10962/d1007412
- Description: The natural product chemistry of six species of South African opisthobranch molluscs and some of their dietary marine invertebrates was investigated. Nineteen previously undescribed secondary metabolites and twelve known compounds were isolated and their structures determined by a combination of spectroscopic and chemical methods. The circumtropical sea hares Aplysia parvula and A. dactylomela were found to contain halogenated red algal metabolites. 3Z-bromofucin (120), the Z analogue of a known Laurencia CIS acetogenin, was isolated from A. parvula. A. dactylomela yielded a series of novel non-aromatic cuparanes, the algoanes (121-123), the novel tricyclic Iaurane ether ibhayinol (124) and three known chamigrane sesquiterpenes, prepacifenol epoxide (101), pacif-7-enediol (104) and nidificene (125). A variety of new octocoral sesquiterpenes were isolated from the endemic South African arminacean nudibranch Leminda millecra including algoafuran (150), cubebenone (151), 8-hydroxycalamenene (152) and a series of seven triprenylated toluquinones and toluquinols (153-159). L. millecra also yielded the known sesquiterpenes millecrones A (142) and B (143) and isofuranodiene (149). Twenty eight voucher specimens and eighteen crude extracts of South African octocorals collected by the Coral Reef Research Foundation were screened by GC and GC-MS and 142 was found in Alcyonium fauri, while 143, 151 and possibly 149 were present in Leptogorgia palma. An investigation of southern African chromodorids yielded the known macrocyc1e latrunculin B (220) and two new spongiane diterpenes (221) and (222) from Chromodoris hamiltoni, while the known spongiane diterpene (210) was isolated from the endemic nudibranch Glossodoris sp. 4. The endemic nudibranch Hypselodoris capensis contained the known furanosesquiterpenes nakafuran-8 (223) and -9 (224) and the known furanosesterterpenes variabilin (195), 22-deoxyvariabilin (225) and furospinosulin (227) together with the new variant 22-deoxy-23-hydroxymethylvariabilin (226). Compounds 223 and 224 were also found in a Dysidea sponge, while the furanosesterterpenes 195, and 225-227 were present in a Fasciospongia sponge upon which H capensis specimens were found. The Dysidea dietary sponge of H capensis also yielded a new aromatic sesquiterpene, tsitsikarnmafuran (266), whose structure was confirmed by the synthesis of two possible regioisomers.
- Full Text:
- Date Issued: 2001
- Authors: McPhail, Kerry Lee
- Date: 2001
- Subjects: Mollusks -- Nutrition Mollusks -- Anatomy Marine fishes -- South Africa
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:4433 , http://hdl.handle.net/10962/d1007412
- Description: The natural product chemistry of six species of South African opisthobranch molluscs and some of their dietary marine invertebrates was investigated. Nineteen previously undescribed secondary metabolites and twelve known compounds were isolated and their structures determined by a combination of spectroscopic and chemical methods. The circumtropical sea hares Aplysia parvula and A. dactylomela were found to contain halogenated red algal metabolites. 3Z-bromofucin (120), the Z analogue of a known Laurencia CIS acetogenin, was isolated from A. parvula. A. dactylomela yielded a series of novel non-aromatic cuparanes, the algoanes (121-123), the novel tricyclic Iaurane ether ibhayinol (124) and three known chamigrane sesquiterpenes, prepacifenol epoxide (101), pacif-7-enediol (104) and nidificene (125). A variety of new octocoral sesquiterpenes were isolated from the endemic South African arminacean nudibranch Leminda millecra including algoafuran (150), cubebenone (151), 8-hydroxycalamenene (152) and a series of seven triprenylated toluquinones and toluquinols (153-159). L. millecra also yielded the known sesquiterpenes millecrones A (142) and B (143) and isofuranodiene (149). Twenty eight voucher specimens and eighteen crude extracts of South African octocorals collected by the Coral Reef Research Foundation were screened by GC and GC-MS and 142 was found in Alcyonium fauri, while 143, 151 and possibly 149 were present in Leptogorgia palma. An investigation of southern African chromodorids yielded the known macrocyc1e latrunculin B (220) and two new spongiane diterpenes (221) and (222) from Chromodoris hamiltoni, while the known spongiane diterpene (210) was isolated from the endemic nudibranch Glossodoris sp. 4. The endemic nudibranch Hypselodoris capensis contained the known furanosesquiterpenes nakafuran-8 (223) and -9 (224) and the known furanosesterterpenes variabilin (195), 22-deoxyvariabilin (225) and furospinosulin (227) together with the new variant 22-deoxy-23-hydroxymethylvariabilin (226). Compounds 223 and 224 were also found in a Dysidea sponge, while the furanosesterterpenes 195, and 225-227 were present in a Fasciospongia sponge upon which H capensis specimens were found. The Dysidea dietary sponge of H capensis also yielded a new aromatic sesquiterpene, tsitsikarnmafuran (266), whose structure was confirmed by the synthesis of two possible regioisomers.
- Full Text:
- Date Issued: 2001
Factors Influencing the Entrepreneurial Orientation of Students
- Amos, Trevor L, Louw, L, Baxter, Jeremy
- Authors: Amos, Trevor L , Louw, L , Baxter, Jeremy
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270879 , vital:54488 , xlink:href="https://scialert.net/abstract/?doi=jas.2001.329.334"
- Description: With entrepreneurship being an important catalyst in wealth creation, it is imperative that entrepreneurs be developed. The aim of this exploratory research is to contribute to our understanding of the development of entrepreneurs and to encourage further research in the area. This paper proposes a model of entrepreneurship and tests the influencing factors on this model. Based on the findings of this research, it appears that entrepreneurial activity of family members influences the development of entrepreneurship more than gender, race, age or education. With education being a logical site for the development of entrepreneurship within society, this finding raises more questions than it provides answers, highlighting the need for educators to critically review the educational process if entrepreneurship is to be a realistic outcome.
- Full Text:
- Date Issued: 2001
- Authors: Amos, Trevor L , Louw, L , Baxter, Jeremy
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/270879 , vital:54488 , xlink:href="https://scialert.net/abstract/?doi=jas.2001.329.334"
- Description: With entrepreneurship being an important catalyst in wealth creation, it is imperative that entrepreneurs be developed. The aim of this exploratory research is to contribute to our understanding of the development of entrepreneurs and to encourage further research in the area. This paper proposes a model of entrepreneurship and tests the influencing factors on this model. Based on the findings of this research, it appears that entrepreneurial activity of family members influences the development of entrepreneurship more than gender, race, age or education. With education being a logical site for the development of entrepreneurship within society, this finding raises more questions than it provides answers, highlighting the need for educators to critically review the educational process if entrepreneurship is to be a realistic outcome.
- Full Text:
- Date Issued: 2001
Failure rather than success : conflict management and resolution in the Democratic Republic of Congo, 1996-1999
- Authors: Munyae, Isaac Muinde
- Date: 2001
- Subjects: Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2856 , http://hdl.handle.net/10962/d1007427 , Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Description: History has proven time and time again that conflict is an inevitable aspect of any given society. The seemingly long-standing nature of conflicts in Africa has been changing over time and these conflicts have been either inter-state or intra-state. However, sometimes intrastate wars have escalated into regional conflicts. These scenarios can be seen in the Great Lakes region of Africa where you have the civil war of 1996-7 and the rebellion, which began in 1998 in the Democratic Republic of Congo (DRC). In the DRC there have been at least four stages of conflict. The first is against the Belgians and secondly, the civil strife of the early 1960s. Third, is the civil strife against Mobutu and fourthly, currently against Kabila. The expanding nature of conflict is characterised by power struggles, politicisation of ethnicity, and the impact of external forces. It is noted that the expanding nature of conflict calls for a change in the methods of conflict management and resolution. Initially conflicts were resolved through military intervention. but with the complexity of African wars it has become apparent that peaceful methods are more prudent. With reference to Africa it can be assumed that conflicts need to be increasingly resolved through political means, such as the use of the diplomatic process. The conflict in Chad between 1968 and 1984 is a good example in which military intervention was used but failed, giving way to mediation and negotiation through the use of diplomacy. Both the DRC and Chadian conflicts are similar because they witnessed the influence of external forces (neighbouring countries and non-African states such as France and the US) and African states attempting to find solutions to their own problems. The conflict in the DRC provides a unique example of the changing nature of intra-state conflict in Africa. Thus, the study aims to trace the characteristics of conflict in the DRC and attempts made at conflict management and resolution. The study uses the period bet ween 1996 and 1999 because it highlights this change in the nature and character of conflict.
- Full Text:
- Date Issued: 2001
- Authors: Munyae, Isaac Muinde
- Date: 2001
- Subjects: Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Language: English
- Type: Thesis , Masters , MA
- Identifier: vital:2856 , http://hdl.handle.net/10962/d1007427 , Conflict management -- Congo (Democratic Republic) , Dispute resolution (Law) -- Congo (Democratic Republic). , Congo (Democratic Republic) -- History -- 1997-
- Description: History has proven time and time again that conflict is an inevitable aspect of any given society. The seemingly long-standing nature of conflicts in Africa has been changing over time and these conflicts have been either inter-state or intra-state. However, sometimes intrastate wars have escalated into regional conflicts. These scenarios can be seen in the Great Lakes region of Africa where you have the civil war of 1996-7 and the rebellion, which began in 1998 in the Democratic Republic of Congo (DRC). In the DRC there have been at least four stages of conflict. The first is against the Belgians and secondly, the civil strife of the early 1960s. Third, is the civil strife against Mobutu and fourthly, currently against Kabila. The expanding nature of conflict is characterised by power struggles, politicisation of ethnicity, and the impact of external forces. It is noted that the expanding nature of conflict calls for a change in the methods of conflict management and resolution. Initially conflicts were resolved through military intervention. but with the complexity of African wars it has become apparent that peaceful methods are more prudent. With reference to Africa it can be assumed that conflicts need to be increasingly resolved through political means, such as the use of the diplomatic process. The conflict in Chad between 1968 and 1984 is a good example in which military intervention was used but failed, giving way to mediation and negotiation through the use of diplomacy. Both the DRC and Chadian conflicts are similar because they witnessed the influence of external forces (neighbouring countries and non-African states such as France and the US) and African states attempting to find solutions to their own problems. The conflict in the DRC provides a unique example of the changing nature of intra-state conflict in Africa. Thus, the study aims to trace the characteristics of conflict in the DRC and attempts made at conflict management and resolution. The study uses the period bet ween 1996 and 1999 because it highlights this change in the nature and character of conflict.
- Full Text:
- Date Issued: 2001
Feeding biology of common and blue duiker
- Authors: Kigozi, Frederick
- Date: 2001
- Subjects: Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5625 , http://hdl.handle.net/10962/d1004725 , Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Description: The blue duiker, Philantomba monticola and common or grey duiker, Sylvicapra grimmia represent two of the three duiker genera as well as two of the three species occurring in Southern Africa. The two species have not been adequately studied in their habitats within the Eastern Cape Province of South Africa, and this thesis centres around their biology with focus on diet and dental microwear. Faecal analysis was used to study the diet of blue duiker at Salem in the Albany district, and of common duiker on two farms, one a predominantly cattle farm at Kasouga and the other a farm for cultivation of chicory at Grants valley, both in the Bathurst district. The validity of faecal analysis was reviewed, and its applicability to blue and common duiker assessed. The method was appropriate for diet analysis of both species, as the common duiker is shy and secretive and the blue duiker is a rare and protected species which does not habituate readily. Results showed that the blue duiker was mainly folivorous with a seasonally stable diet of 79 percent dicot foliage and only 17 percent fruit. Common duiker diet at both study sites comprised mostly dicot foliage, with only two monocotyledonous plant species. Twenty-seven and nineteen plant species were identified in the diets of common duiker at Kasouga and Grants valley respectively and the annual percentage occurrences of dicot foliage in the diets were about 99 percent at both study sites. The predominantly browsing common duiker, therefore offered negligible competition for food resources to the grazing cattle on Kasouga farm. Both blue and common duiker fed selectively, with approximately one third of the total number of plant species identified in their diets providing at least 50 percent of the food eaten annually. Ehretia rigida was the most important plant species in the diets of both duiker species. Chicory, Chichorium intybus provided more than one third (35.6 percent) of the winter diet and a substantial proportion (14.4 percent) of the spring diet of common duiker at Grants valley, thereby confirming earlier reports of this species feeding on chicory and other cultivated crops. The diet of common duiker at Kasouga did not vary seasonally but that of common duiker at Grants valley did vary and this was attributed to utilisation of chicory. Results from the dental microwear analyses did not show any significant differences in dental microwear between blue and common duiker, but supported and confirmed that the two were browsing species, characterised by many pits and few scratches on their dental surfaces. A high incidence of pits was found on the dental surfaces of both duiker species, and was attributed to utilisation of fruit in the diet.
- Full Text:
- Date Issued: 2001
- Authors: Kigozi, Frederick
- Date: 2001
- Subjects: Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5625 , http://hdl.handle.net/10962/d1004725 , Duikers -- Nutrition -- South Africa -- Eastern Cape , Sylvicapra grimmia -- Nutrition -- South Africa -- Eastern Cape , Herbivores -- Nutrition , Folivores -- Nutrition , Teeth -- Abrasion
- Description: The blue duiker, Philantomba monticola and common or grey duiker, Sylvicapra grimmia represent two of the three duiker genera as well as two of the three species occurring in Southern Africa. The two species have not been adequately studied in their habitats within the Eastern Cape Province of South Africa, and this thesis centres around their biology with focus on diet and dental microwear. Faecal analysis was used to study the diet of blue duiker at Salem in the Albany district, and of common duiker on two farms, one a predominantly cattle farm at Kasouga and the other a farm for cultivation of chicory at Grants valley, both in the Bathurst district. The validity of faecal analysis was reviewed, and its applicability to blue and common duiker assessed. The method was appropriate for diet analysis of both species, as the common duiker is shy and secretive and the blue duiker is a rare and protected species which does not habituate readily. Results showed that the blue duiker was mainly folivorous with a seasonally stable diet of 79 percent dicot foliage and only 17 percent fruit. Common duiker diet at both study sites comprised mostly dicot foliage, with only two monocotyledonous plant species. Twenty-seven and nineteen plant species were identified in the diets of common duiker at Kasouga and Grants valley respectively and the annual percentage occurrences of dicot foliage in the diets were about 99 percent at both study sites. The predominantly browsing common duiker, therefore offered negligible competition for food resources to the grazing cattle on Kasouga farm. Both blue and common duiker fed selectively, with approximately one third of the total number of plant species identified in their diets providing at least 50 percent of the food eaten annually. Ehretia rigida was the most important plant species in the diets of both duiker species. Chicory, Chichorium intybus provided more than one third (35.6 percent) of the winter diet and a substantial proportion (14.4 percent) of the spring diet of common duiker at Grants valley, thereby confirming earlier reports of this species feeding on chicory and other cultivated crops. The diet of common duiker at Kasouga did not vary seasonally but that of common duiker at Grants valley did vary and this was attributed to utilisation of chicory. Results from the dental microwear analyses did not show any significant differences in dental microwear between blue and common duiker, but supported and confirmed that the two were browsing species, characterised by many pits and few scratches on their dental surfaces. A high incidence of pits was found on the dental surfaces of both duiker species, and was attributed to utilisation of fruit in the diet.
- Full Text:
- Date Issued: 2001
Feeding ecology of Bathyclarias nyasensis (Siluroidei: Claridae) from Lake Malawi
- Kaunda, Emmanuel Kamlipe Watson Hawkins
- Authors: Kaunda, Emmanuel Kamlipe Watson Hawkins
- Date: 2001
- Subjects: Fishes -- Malawi Fishes -- Nyasa, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5282 , http://hdl.handle.net/10962/d1005126
- Description: In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
- Full Text:
- Date Issued: 2001
- Authors: Kaunda, Emmanuel Kamlipe Watson Hawkins
- Date: 2001
- Subjects: Fishes -- Malawi Fishes -- Nyasa, Lake
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:5282 , http://hdl.handle.net/10962/d1005126
- Description: In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.
- Full Text:
- Date Issued: 2001
Field Trip A1: Karoo dykes, sills and volcanics in the Eastern Cape
- Authors: Marsh, Julian S
- Date: 2001
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144835 , vital:38383
- Description: The Karoo Province (Fig. I I ) is one of the classic Mesozoic continental flood basalt provinces At present erosion levels it comprises numerous eroded remnants of extensive, thick, and largely volcanic sequence and a well-exposed subvolcanic intrusive complex of dykes and sheets.
- Full Text:
- Date Issued: 2001
- Authors: Marsh, Julian S
- Date: 2001
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/144835 , vital:38383
- Description: The Karoo Province (Fig. I I ) is one of the classic Mesozoic continental flood basalt provinces At present erosion levels it comprises numerous eroded remnants of extensive, thick, and largely volcanic sequence and a well-exposed subvolcanic intrusive complex of dykes and sheets.
- Full Text:
- Date Issued: 2001
Formulation and dissolution assessment of a novel repeat action tablet containing a decongestant and an antihistamine
- Authors: Verner, Jennifer Joan
- Date: 2001
- Subjects: Antihistamines , Tablets (Medicine) , Tableting , Ephedrine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3798 , http://hdl.handle.net/10962/d1003276 , Antihistamines , Tablets (Medicine) , Tableting , Ephedrine
- Description: Controlled and sustained release dosage forms are the focus of worldwide research. These dosage forms facilitate patient compliance by simplifying the dosage regimen, and decrease the risk of adverse effects by reducing large fluctuations in the plasma concentration of the drug. The objective of this study was to formulate a repeat-action tablet to provide a sustained release dose of pseudoephedrine sulfate (PSS), and an immediate release dose of both PSS and loratadine. The release profile was compared to that of a commercially available preparation, Clarityne-D®. This formulation developed presents a novel mechanism of sustaining the release of PSS. The prototype tablet consisted of a sustained release core coated with an ethylcellulose dispersion to introduce a lag phase into the release profile and a second outer film coat incorporating PSS and loratadine. The core comprised an ethylcellulose granulation of PSS compressed into a hydroxypropyl methylcellulose matrix. The release of PSS from prototypes was assessed using USP Apparatus 3, as this apparatus was more representative of in vivo conditions and discriminated more effectively between the different tablet compositions produced during development. All dissolution samples were analysed for PSS and loratadine using validated highperformance liquid chromatographic methods. The prototype sustained release cores were found to be more resistant than the reference product to elevated temperature and humidity (40°C/87% RH) with fewer observed changes to the release profiles following storage for up to six months. This study was a feasibility study to obtain proof of concept. The release profile obtained from the prototype tablets was similar (f₂ = 50.0) to that of the reference product. Further development and optimisation of this dosage form is necessary, including evaluation of the choice of hydrophobic polymer, the effect of compression force and tablet geometry and characterisation of the release mechanism from the coated matrix. Assessment of these factors is necessary in order to optimise the formulation with respect to the desired therapeutic objectives.
- Full Text:
- Date Issued: 2001
- Authors: Verner, Jennifer Joan
- Date: 2001
- Subjects: Antihistamines , Tablets (Medicine) , Tableting , Ephedrine
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3798 , http://hdl.handle.net/10962/d1003276 , Antihistamines , Tablets (Medicine) , Tableting , Ephedrine
- Description: Controlled and sustained release dosage forms are the focus of worldwide research. These dosage forms facilitate patient compliance by simplifying the dosage regimen, and decrease the risk of adverse effects by reducing large fluctuations in the plasma concentration of the drug. The objective of this study was to formulate a repeat-action tablet to provide a sustained release dose of pseudoephedrine sulfate (PSS), and an immediate release dose of both PSS and loratadine. The release profile was compared to that of a commercially available preparation, Clarityne-D®. This formulation developed presents a novel mechanism of sustaining the release of PSS. The prototype tablet consisted of a sustained release core coated with an ethylcellulose dispersion to introduce a lag phase into the release profile and a second outer film coat incorporating PSS and loratadine. The core comprised an ethylcellulose granulation of PSS compressed into a hydroxypropyl methylcellulose matrix. The release of PSS from prototypes was assessed using USP Apparatus 3, as this apparatus was more representative of in vivo conditions and discriminated more effectively between the different tablet compositions produced during development. All dissolution samples were analysed for PSS and loratadine using validated highperformance liquid chromatographic methods. The prototype sustained release cores were found to be more resistant than the reference product to elevated temperature and humidity (40°C/87% RH) with fewer observed changes to the release profiles following storage for up to six months. This study was a feasibility study to obtain proof of concept. The release profile obtained from the prototype tablets was similar (f₂ = 50.0) to that of the reference product. Further development and optimisation of this dosage form is necessary, including evaluation of the choice of hydrophobic polymer, the effect of compression force and tablet geometry and characterisation of the release mechanism from the coated matrix. Assessment of these factors is necessary in order to optimise the formulation with respect to the desired therapeutic objectives.
- Full Text:
- Date Issued: 2001
Guy Butler: 21 January 1918 - 26 April 2001
- Authors: Wright, Laurence
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:7053 , http://hdl.handle.net/10962/d1007413
- Description: [From Introduction]: For much of the last twenty-five years of his life, Butler’s thought and work were not perceived to be ‘current’ at all. His poetry was hardly read (what’s new there? – neither is anyone else’s); some of it lay in manuscript or obscure little publications until the Collected Poems appeared in 1999. The autobiographies attracted a loyal following amongst a small, educated reading public. His early dramas, though they met with initial success, were stifled by the poetic idiom to which they aspired, and by the racial claustrophobia against which they fought. (Demea, Butler’s South African reworking of the Medea, made it to the boards only in 1990 – the multi-racial cast, let alone the themes, kept it in hibernation until then.) The deluge of journalism and polemic suffered the usual fate of ephemera. Until resurrected by Stephen Watson in 1990, the essays and lectures remained buried in periodicals where they could not be assessed as a totality. His inspiring teaching was a gift to his students, hardly accessible to the wider society; and above all, much of his time was spent as homo commiticus, serving on the boards and sub-committees of numerous university institutions and other organizations, some of which he founded. In his autobiography, he observed wryly of his changed status following accession to the Chair of English at Rhodes in 1951: ‘Professors are not entirely themselves. Their interest as persons decreases because they are now public personages. Much of their time is spent on committees whose function is to pick the brains of individuals without giving them credit.’ Guy Butler gave generously of his brains in such circumstances.
- Full Text:
- Date Issued: 2001
- Authors: Wright, Laurence
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:7053 , http://hdl.handle.net/10962/d1007413
- Description: [From Introduction]: For much of the last twenty-five years of his life, Butler’s thought and work were not perceived to be ‘current’ at all. His poetry was hardly read (what’s new there? – neither is anyone else’s); some of it lay in manuscript or obscure little publications until the Collected Poems appeared in 1999. The autobiographies attracted a loyal following amongst a small, educated reading public. His early dramas, though they met with initial success, were stifled by the poetic idiom to which they aspired, and by the racial claustrophobia against which they fought. (Demea, Butler’s South African reworking of the Medea, made it to the boards only in 1990 – the multi-racial cast, let alone the themes, kept it in hibernation until then.) The deluge of journalism and polemic suffered the usual fate of ephemera. Until resurrected by Stephen Watson in 1990, the essays and lectures remained buried in periodicals where they could not be assessed as a totality. His inspiring teaching was a gift to his students, hardly accessible to the wider society; and above all, much of his time was spent as homo commiticus, serving on the boards and sub-committees of numerous university institutions and other organizations, some of which he founded. In his autobiography, he observed wryly of his changed status following accession to the Chair of English at Rhodes in 1951: ‘Professors are not entirely themselves. Their interest as persons decreases because they are now public personages. Much of their time is spent on committees whose function is to pick the brains of individuals without giving them credit.’ Guy Butler gave generously of his brains in such circumstances.
- Full Text:
- Date Issued: 2001
Happiness trends under democracy: where will the new South African set-level come to rest?
- Authors: Moller, Valerie
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:7111 , http://hdl.handle.net/10962/d1010743 , http://dx.doi.org/10.1023/A:1011557404822
- Description: Five years after South Africa’s first democratic elections in 1994, life satisfaction and happiness still reflect societal divides sowed by apartheid social engineering. The paper reports the indicators: life satisfaction, happiness and expectations for the future, from national surveys conducted between 1983 and 1999 for the South African Quality-of-Life Trends Project. Post-election euphoria, which saw all South Africans happy and satisfied with life for a brief moment in 1994, raises the question where the new set-level of subjective well-being will eventually come to rest. In 1999, in spite of some gains in living conditions, the level of life satisfaction of blacks has not risen above the mid-point and happiness is only slightly above the midpoint. Meanwhile, whites, who have forfeited their political dominance, continue to score above the mid-point on happiness and life satisfaction. The paper draws on the literature, particularly on quality-of-life trends in reunified Germany and paradoxical trends in African-American life satisfaction when discussing the dynamics underlying South African subjective well-being. It is argued that coping mechanisms may play an important role in determining levels of subjective well-being in the complex situation of South Africa.
- Full Text:
- Date Issued: 2001
- Authors: Moller, Valerie
- Date: 2001
- Language: English
- Type: Article
- Identifier: vital:7111 , http://hdl.handle.net/10962/d1010743 , http://dx.doi.org/10.1023/A:1011557404822
- Description: Five years after South Africa’s first democratic elections in 1994, life satisfaction and happiness still reflect societal divides sowed by apartheid social engineering. The paper reports the indicators: life satisfaction, happiness and expectations for the future, from national surveys conducted between 1983 and 1999 for the South African Quality-of-Life Trends Project. Post-election euphoria, which saw all South Africans happy and satisfied with life for a brief moment in 1994, raises the question where the new set-level of subjective well-being will eventually come to rest. In 1999, in spite of some gains in living conditions, the level of life satisfaction of blacks has not risen above the mid-point and happiness is only slightly above the midpoint. Meanwhile, whites, who have forfeited their political dominance, continue to score above the mid-point on happiness and life satisfaction. The paper draws on the literature, particularly on quality-of-life trends in reunified Germany and paradoxical trends in African-American life satisfaction when discussing the dynamics underlying South African subjective well-being. It is argued that coping mechanisms may play an important role in determining levels of subjective well-being in the complex situation of South Africa.
- Full Text:
- Date Issued: 2001
Heads and tales: the effect of mild head injuries of rugby players: cognitive deficit and postconcussive symptoms
- Authors: Border, Michael Anthony
- Date: 2001
- Subjects: Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2937 , http://hdl.handle.net/10962/d1002446 , Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Description: This study investigated the cumulative effect of mild head injuries on rugby players. A comprehensive battery of neuropsychological tests was administered and subjects completed a self-report postconcussive symptom questionnaire. Data were collected for the two rugby groups, Springbok rugby players (n = 26) and Under 21 rugby players (n = 19), and for the control group, national hockey players (n = 21). Group comparisons of the percentage of individuals with deficit or self-reported symptomatology were made between: (i) the contact sport groups and the control group; (ii) the forwards and the backs within each rugby group and the rugby forwards and the control group; and (iii) the Springbok and Under 21 rugby players. Broadly speaking, comparative results on the neuropsychological tests and the self-reported postconcussive symptoms clearly distinguished between contact sport players and non-contact sport players and indicated the presence of diffuse brain damage in the contact sport players. There was also clear evidence of positional variation within the rugby groups, with the forwards (more full contact positions) most susceptible to impairment. Neuropsychological test results revealed deficit in information processing speed, attention and concentration, mental flexibility, visual memory and verbal new learning. The most significant neuropsychiatric complaints were reported in the areas of memory, social contact, sensitivity to noise, lowered frustration tolerance, anxiety and worry, and depression. The most sensitive neuropsychological test used in the present study was the Digit Symbol Substitution test. This test clearly distinguished contact sport players from non-contact sport players, and forwards from backs.
- Full Text:
- Date Issued: 2001
- Authors: Border, Michael Anthony
- Date: 2001
- Subjects: Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:2937 , http://hdl.handle.net/10962/d1002446 , Rugby football injuries , Head -- Wounds and injuries -- Psychology , Head -- Wounds and injuries -- Complications , Brain damage
- Description: This study investigated the cumulative effect of mild head injuries on rugby players. A comprehensive battery of neuropsychological tests was administered and subjects completed a self-report postconcussive symptom questionnaire. Data were collected for the two rugby groups, Springbok rugby players (n = 26) and Under 21 rugby players (n = 19), and for the control group, national hockey players (n = 21). Group comparisons of the percentage of individuals with deficit or self-reported symptomatology were made between: (i) the contact sport groups and the control group; (ii) the forwards and the backs within each rugby group and the rugby forwards and the control group; and (iii) the Springbok and Under 21 rugby players. Broadly speaking, comparative results on the neuropsychological tests and the self-reported postconcussive symptoms clearly distinguished between contact sport players and non-contact sport players and indicated the presence of diffuse brain damage in the contact sport players. There was also clear evidence of positional variation within the rugby groups, with the forwards (more full contact positions) most susceptible to impairment. Neuropsychological test results revealed deficit in information processing speed, attention and concentration, mental flexibility, visual memory and verbal new learning. The most significant neuropsychiatric complaints were reported in the areas of memory, social contact, sensitivity to noise, lowered frustration tolerance, anxiety and worry, and depression. The most sensitive neuropsychological test used in the present study was the Digit Symbol Substitution test. This test clearly distinguished contact sport players from non-contact sport players, and forwards from backs.
- Full Text:
- Date Issued: 2001
How can cooperative learning be developed to enhance the teaching of biology at secondary school level?
- Authors: Pillay, Paramasivan
- Date: 2001
- Subjects: Biology -- Study and teaching (Secondary) Group work in education Group work in education -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1557 , http://hdl.handle.net/10962/d1003439
- Description: This research was undertaken by a group of practising teachers as a collaborative effort to develop a cooperative approach to the teaching of Biology at Secondary School level. The research focussed on Grade 10 learners at three different schools over a period of one full academic school-year. During this time, four complete cycles within an action research framework were completed and reflected upon. Learners were then surveyed by means of a questionnaire and follow-up interviews. The reflective sessions, together with the responses from the questionnaire and interviews, provided a wealth of information with regard to the development of a cooperative approach to teaching. The cooperative classroom is vastly different from the traditional one. Here, new roles are assumed by both teacher and learner. Learners are largely expected to take charge of their learning experience in the classroom. The teacher, while still responsible for facilitating this learning experience, delegates authority to the learners. It was the experience of the group that the relationship between teacher and learner, as well as between learner and learner, vastly improved in the cooperative class where the participants were more relaxed. Over time, learners became more accountable in terms of their work and learning. Learners’ self-esteem and self-confidence grew, and the majority of learners indicated that their understanding of the work improved. Furthermore, the cooperative structure encouraged and developed self-discipline in the learners. In the early stages of this research, the group did find certain behaviour to be inhibiting: excessive noise, laziness, too much tomfoolery, and absenteeism. These problems were easily addressed within the action research framework, and were nearly non-existent by the end of the research. The group also found that: (i) cooperative lessons required more time than traditional lessons, often at the expense (justifiably) of the syllabus, and that: (ii) cooperative lessons played a major role in reactivating learner interest towards the learning process both in and outside the classroom.
- Full Text:
- Date Issued: 2001
- Authors: Pillay, Paramasivan
- Date: 2001
- Subjects: Biology -- Study and teaching (Secondary) Group work in education Group work in education -- Evaluation
- Language: English
- Type: Thesis , Doctoral , PhD
- Identifier: vital:1557 , http://hdl.handle.net/10962/d1003439
- Description: This research was undertaken by a group of practising teachers as a collaborative effort to develop a cooperative approach to the teaching of Biology at Secondary School level. The research focussed on Grade 10 learners at three different schools over a period of one full academic school-year. During this time, four complete cycles within an action research framework were completed and reflected upon. Learners were then surveyed by means of a questionnaire and follow-up interviews. The reflective sessions, together with the responses from the questionnaire and interviews, provided a wealth of information with regard to the development of a cooperative approach to teaching. The cooperative classroom is vastly different from the traditional one. Here, new roles are assumed by both teacher and learner. Learners are largely expected to take charge of their learning experience in the classroom. The teacher, while still responsible for facilitating this learning experience, delegates authority to the learners. It was the experience of the group that the relationship between teacher and learner, as well as between learner and learner, vastly improved in the cooperative class where the participants were more relaxed. Over time, learners became more accountable in terms of their work and learning. Learners’ self-esteem and self-confidence grew, and the majority of learners indicated that their understanding of the work improved. Furthermore, the cooperative structure encouraged and developed self-discipline in the learners. In the early stages of this research, the group did find certain behaviour to be inhibiting: excessive noise, laziness, too much tomfoolery, and absenteeism. These problems were easily addressed within the action research framework, and were nearly non-existent by the end of the research. The group also found that: (i) cooperative lessons required more time than traditional lessons, often at the expense (justifiably) of the syllabus, and that: (ii) cooperative lessons played a major role in reactivating learner interest towards the learning process both in and outside the classroom.
- Full Text:
- Date Issued: 2001
Ichthyofaunal characteristics of a typical temporarily open/closed estuary on the southeast coast of South Africa
- Cowley, Paul D, Heemstra, Phillip C
- Authors: Cowley, Paul D , Heemstra, Phillip C
- Date: 2001
- Subjects: Estuarine fishes -- Ecology -- Indian Ocean , Estuarine ecology -- South Africa , Fish communities -- South Africa , Fish communities -- Indian Ocean
- Language: English
- Type: Text
- Identifier: vital:15021 , http://hdl.handle.net/10962/d1019862 , ISSN 0073-4381 , Ichthyological Bulletin J.L.B. Smith Institute of Ichthyology; No. 71
- Description: The present study was undertaken to describe the species composition, size composition and distribution of the fish fauna associated with the temporarily open/closed East Kleinemonde Estuary on the southeast coast of South Africa. Data collected on the estuary mouth condition from March 1993 to August 1997 indicated that this system was predominantly closed, while open mouth conditions were unseasonal and prevailed for only a short duration following periods of high rainfall. Fishes were sampled throughout the estuary between April 1993 and January 1997 using seine and gill nets. A total of 30 species belonging to 17 families were recorded, including the critically endangered estuarine pipefish Syngnathus watermeyeri. Besides the estuarine pipefish, an additional five species capable of completing their life cycle within the estuary were recorded. The ichthyofaunal community was dominated by 18 marine-spawning species with varying degrees of dependence on estuaries as nursery areas. The marine species that are not dependent on estuaries as nursery areas were represented by three species, while the euryhaline freshwater species, obligate catadromous species and facultative catadromous species were each represented by one species. The dominant members of the estuarine-spawning group were well represented by all post-larval life-history stages, whereas the mean size of each marine-spawning species indicated that juvenile size classes dominated this group. Classification and ordination of both the small- and large-mesh seine net fish assemblages revealed a high degree of similarity throughout the estuary, with the exception of a distinct grouping associated with sandy substrata in the lower reaches of the system. Catch per unit effort (CPUE) data provided evidence of spatial segregation by several species as well as within some families (e.g. Gobiidae). , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 2001
- Authors: Cowley, Paul D , Heemstra, Phillip C
- Date: 2001
- Subjects: Estuarine fishes -- Ecology -- Indian Ocean , Estuarine ecology -- South Africa , Fish communities -- South Africa , Fish communities -- Indian Ocean
- Language: English
- Type: Text
- Identifier: vital:15021 , http://hdl.handle.net/10962/d1019862 , ISSN 0073-4381 , Ichthyological Bulletin J.L.B. Smith Institute of Ichthyology; No. 71
- Description: The present study was undertaken to describe the species composition, size composition and distribution of the fish fauna associated with the temporarily open/closed East Kleinemonde Estuary on the southeast coast of South Africa. Data collected on the estuary mouth condition from March 1993 to August 1997 indicated that this system was predominantly closed, while open mouth conditions were unseasonal and prevailed for only a short duration following periods of high rainfall. Fishes were sampled throughout the estuary between April 1993 and January 1997 using seine and gill nets. A total of 30 species belonging to 17 families were recorded, including the critically endangered estuarine pipefish Syngnathus watermeyeri. Besides the estuarine pipefish, an additional five species capable of completing their life cycle within the estuary were recorded. The ichthyofaunal community was dominated by 18 marine-spawning species with varying degrees of dependence on estuaries as nursery areas. The marine species that are not dependent on estuaries as nursery areas were represented by three species, while the euryhaline freshwater species, obligate catadromous species and facultative catadromous species were each represented by one species. The dominant members of the estuarine-spawning group were well represented by all post-larval life-history stages, whereas the mean size of each marine-spawning species indicated that juvenile size classes dominated this group. Classification and ordination of both the small- and large-mesh seine net fish assemblages revealed a high degree of similarity throughout the estuary, with the exception of a distinct grouping associated with sandy substrata in the lower reaches of the system. Catch per unit effort (CPUE) data provided evidence of spatial segregation by several species as well as within some families (e.g. Gobiidae). , Rhodes University Libraries (Digitisation)
- Full Text:
- Date Issued: 2001
Ichthyofaunal community structures in different types of Eastern Cape estuaries
- Authors: Vorwerk, Paul D
- Date: 2001
- Subjects: Estuarine fishes -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5377 , http://hdl.handle.net/10962/d1016241
- Description: This investigation had three major objectives; firstly to document the estuarine fishes from several poorly studied Eastern Cape estuaries, secondly, to identify similarities and differences in the fish communities from permanently open and intermittently open estuaries, and thirdly, to establish which physico-chemical or environmental variables are responsible for the structuring of these communities. The study area incorporated 10 estuaries along a 70 km long stretch of the Eastern Cape coastline between the towns of Seafield (33° 32' 42" S, 27° 03' 05" E) in the south-east and Hamburg (33° 16' 45" S, 27° 29' 50" E) in the north-west. The systems investigated included two permanently open estuaries and eight intermittently open systems of varying sizes. Overall fish abundance and species richness in the study area revealed no significant seasonal variation. A contrast between open and closed estuaries was evident in the dominance of species from different estuarine dependence categories. Open estuaries comprised mainly category Ib, lla and IIb species, with a high proportion of category IV species. Closed estuaries were dominated by category IIa species, with few category IV species represented. Clear longitudinal trends in relative abundance were demonstrated for individual species. Margalefs species richness index for seine net catches, and a combination of the seine and gill net data, were significantly correlated with catchment size, mean annual runoff, estuarine area and linear length. Fish assemblages in the permanently open and intermittently open estuaries were significantly different (p<0.001) when analysed on a community and density basis. Similarly, the communities in large and small intermittently open estuaries differed significantly on a community (p=0.01) and density basis (p<0.001). These differences where caused by changes in abundance of the dominant estuarine resident and marine migrant species. The environmental variable that was dominant in accounting for these differences was the estuary mouth status. Estuarine resident species had smaller overall body lengths when compared with the marine migrant species. In addition, the estuarine resident species had smaller modal size classes in the closed estuaries when compared with the open estuaries. These differences may be linked to the foraging strategies of the species, as well as food availability and different levels of predation in the different estuary types. The marine migrant species did not show any trends in this respect although the closed systems had the largest individuals for all four dominant marine species. This finding may be linked to the inability of these species to breed in closed estuaries, thus channelling reproductive energy resources into somatic growth. In addition, prolonged periods of mouth closure prevent the emigration of large individuals back to the sea. Otter trawling was conducted in fiye estuaries and captured mostly demersal species. The otter trawl data confirmed the seine net community analysis, with significantly different communities identified in the permanently open and intermittently open estuaries (p=0.02), as well as in the small and large intermittently open estuaries (p=0.03). The environmental variables responsible for these community differences were mouth status and variables associated with estuarine size. The identification of estuary mouth status by this study as the most influential environmental factor is compounded by this "ariable affecting or being indicative of numerous other physico-chemical features. The large differences in the fish communities in different estuary types indicate the importance of each estuary type to various species. This should be taken into account before allowing any form of commercial fishing in these important nursery areas.
- Full Text:
- Date Issued: 2001
- Authors: Vorwerk, Paul D
- Date: 2001
- Subjects: Estuarine fishes -- South Africa -- Eastern Cape , Estuarine fishes -- South Africa
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:5377 , http://hdl.handle.net/10962/d1016241
- Description: This investigation had three major objectives; firstly to document the estuarine fishes from several poorly studied Eastern Cape estuaries, secondly, to identify similarities and differences in the fish communities from permanently open and intermittently open estuaries, and thirdly, to establish which physico-chemical or environmental variables are responsible for the structuring of these communities. The study area incorporated 10 estuaries along a 70 km long stretch of the Eastern Cape coastline between the towns of Seafield (33° 32' 42" S, 27° 03' 05" E) in the south-east and Hamburg (33° 16' 45" S, 27° 29' 50" E) in the north-west. The systems investigated included two permanently open estuaries and eight intermittently open systems of varying sizes. Overall fish abundance and species richness in the study area revealed no significant seasonal variation. A contrast between open and closed estuaries was evident in the dominance of species from different estuarine dependence categories. Open estuaries comprised mainly category Ib, lla and IIb species, with a high proportion of category IV species. Closed estuaries were dominated by category IIa species, with few category IV species represented. Clear longitudinal trends in relative abundance were demonstrated for individual species. Margalefs species richness index for seine net catches, and a combination of the seine and gill net data, were significantly correlated with catchment size, mean annual runoff, estuarine area and linear length. Fish assemblages in the permanently open and intermittently open estuaries were significantly different (p<0.001) when analysed on a community and density basis. Similarly, the communities in large and small intermittently open estuaries differed significantly on a community (p=0.01) and density basis (p<0.001). These differences where caused by changes in abundance of the dominant estuarine resident and marine migrant species. The environmental variable that was dominant in accounting for these differences was the estuary mouth status. Estuarine resident species had smaller overall body lengths when compared with the marine migrant species. In addition, the estuarine resident species had smaller modal size classes in the closed estuaries when compared with the open estuaries. These differences may be linked to the foraging strategies of the species, as well as food availability and different levels of predation in the different estuary types. The marine migrant species did not show any trends in this respect although the closed systems had the largest individuals for all four dominant marine species. This finding may be linked to the inability of these species to breed in closed estuaries, thus channelling reproductive energy resources into somatic growth. In addition, prolonged periods of mouth closure prevent the emigration of large individuals back to the sea. Otter trawling was conducted in fiye estuaries and captured mostly demersal species. The otter trawl data confirmed the seine net community analysis, with significantly different communities identified in the permanently open and intermittently open estuaries (p=0.02), as well as in the small and large intermittently open estuaries (p=0.03). The environmental variables responsible for these community differences were mouth status and variables associated with estuarine size. The identification of estuary mouth status by this study as the most influential environmental factor is compounded by this "ariable affecting or being indicative of numerous other physico-chemical features. The large differences in the fish communities in different estuary types indicate the importance of each estuary type to various species. This should be taken into account before allowing any form of commercial fishing in these important nursery areas.
- Full Text:
- Date Issued: 2001
Implementation and applications of the distortion operator
- Authors: Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433382 , vital:72966 , https://doi.org/10.1145/513867.513872
- Description: The distortion operator transforms 2D images in a manner similar to image warping or morphing, allowing source pixels to be mapped to any destination pixel. This operator can be implemented on current hardware, allowing at least one distortion per frame at interactive frame rates. Potential applications are numerous, but those described include re-mapping images for correct projection onto curved screens, correcting camera distortion from multiple sources simultaneously, and allowing constant time dynamic texturing and lighting of a static scene which is independent of geometric complexity.
- Full Text:
- Date Issued: 2001
- Authors: Bangay, Shaun D
- Date: 2001
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/433382 , vital:72966 , https://doi.org/10.1145/513867.513872
- Description: The distortion operator transforms 2D images in a manner similar to image warping or morphing, allowing source pixels to be mapped to any destination pixel. This operator can be implemented on current hardware, allowing at least one distortion per frame at interactive frame rates. Potential applications are numerous, but those described include re-mapping images for correct projection onto curved screens, correcting camera distortion from multiple sources simultaneously, and allowing constant time dynamic texturing and lighting of a static scene which is independent of geometric complexity.
- Full Text:
- Date Issued: 2001
In the gaze of God : aspects of the spiritual significance of Rublev's holy trinity
- Authors: Snyman, Desiree
- Date: 2001
- Subjects: Prayer , Spirituality
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1302 , http://hdl.handle.net/10962/d1016261
- Description: An icon is more than an image. It is a "sacramental form of presence" that makes present that which it signifies (Evdokimov 1976: 167). To come before an icon is to come before the presence of God. To gaze at an icon is to pray. Rublev's Holy Trinity icon (see frontispiece) is a theology in colour. Inspired by the story in Genesis 18, the icon depicts the three hypostases of the Trinity sitting around an altar with a chalice placed on top. The Biblical story is an account of the genuine hospitality that Abraham and Sarah shared with three pilgrims. This theme of hospitality is expressed by the three hypostases in the icon who invite the cosmos to share in their love-life. This research project investigates aspects of the spiritual significance that Rublev's icon has on our Christian living. To this end, an interpretation of the icon is offered in chapter two. Chapter three focuses on the relationship among the three hypostases in the icon. This chapter reflects on the meaning that trinitarian pericheresis could have on our spiritual living in the way we develop our relationships and the type of church and socio-political structures we adopt and support. The research project also explores the meaning that Rublev's icon could have for Methodists. The resource that Wesleyan spirituality offers to those who seek a deepened spirituality is the doctrine of Christian perfection. Perfection, in the Wesleyan model, is sought through the means of grace, nurtured through Christian koinonia and evidenced in social transformation. Christian perfection is discussed with reference to Rublev's icon in chapter four. Chapter five summarises aspects of the spirituality of the icon, postulates some implications that the icon has and unravels key issues arising out of this study.
- Full Text:
- Date Issued: 2001
- Authors: Snyman, Desiree
- Date: 2001
- Subjects: Prayer , Spirituality
- Language: English
- Type: Thesis , Bachelor , BDiv
- Identifier: vital:1302 , http://hdl.handle.net/10962/d1016261
- Description: An icon is more than an image. It is a "sacramental form of presence" that makes present that which it signifies (Evdokimov 1976: 167). To come before an icon is to come before the presence of God. To gaze at an icon is to pray. Rublev's Holy Trinity icon (see frontispiece) is a theology in colour. Inspired by the story in Genesis 18, the icon depicts the three hypostases of the Trinity sitting around an altar with a chalice placed on top. The Biblical story is an account of the genuine hospitality that Abraham and Sarah shared with three pilgrims. This theme of hospitality is expressed by the three hypostases in the icon who invite the cosmos to share in their love-life. This research project investigates aspects of the spiritual significance that Rublev's icon has on our Christian living. To this end, an interpretation of the icon is offered in chapter two. Chapter three focuses on the relationship among the three hypostases in the icon. This chapter reflects on the meaning that trinitarian pericheresis could have on our spiritual living in the way we develop our relationships and the type of church and socio-political structures we adopt and support. The research project also explores the meaning that Rublev's icon could have for Methodists. The resource that Wesleyan spirituality offers to those who seek a deepened spirituality is the doctrine of Christian perfection. Perfection, in the Wesleyan model, is sought through the means of grace, nurtured through Christian koinonia and evidenced in social transformation. Christian perfection is discussed with reference to Rublev's icon in chapter four. Chapter five summarises aspects of the spirituality of the icon, postulates some implications that the icon has and unravels key issues arising out of this study.
- Full Text:
- Date Issued: 2001
In vitro passage of ibuprofen through synthetic and biological membranes
- Authors: Purdon, Carryn Hamilton
- Date: 2001
- Subjects: Ibuprofen , Diffusion processes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3786 , http://hdl.handle.net/10962/d1003264 , Ibuprofen , Diffusion processes
- Description: Ibuprofen is a non-steroidal anti-inflammatory drug with three major types of effect: anti-inflammatory, analgesic and antipyretic. Ibuprofen may be administered in a number of different forms via the oral as well as the topical route. Published evidence suggests that topical, unlike oral, non-steroidal anti-inflammatory drugs are associated with few systemic side effects as plasma concentrations are low compared to oral therapy. In some countries it is particularly difficult to obtain human skin for in vitro experimentation and it is therefore important to have alternate biological or synthetic membranes which mimic human skin for diffusion experiments. Synthetic membranes serve as predictive models for topical drug release and in South Africa, shed snake skin is easily obtainable from the many snake parks present in the country. The FDA guidelines were considered when choosing the apparatus to be used in the comparative diffusion study on proprietary ibuprofen-containing topical preparations from three countries and the verification of the usefulness, or otherwise, of shed snake skin as a biological membrane for the assessment of the permeation of ibuprofen. Two diffusion techniques were considered appropriate for the measurement of the amount of ibuprofen released from a topical formulation during in vitro testing. One was the Franz diffusion cell, as modified by Keshary and Chien (88,169) and the other was the European Pharmacopoeia diffusion cell (187). High performance liquid chromatography was used as the analytical technique for the analysis of ibuprofen in aqueous solution using ultraviolet detection at 222 nm. The validated method was applied to the determination of the diffusion of ibuprofen from topical ibuprofen-containing formulations (gels, creams and mousse) through synthetic silicone membrane and shed snake skin biological membrane from four different species. In a study of fifteen topical ibuprofen-containing formulations (gels, creams and mousse) from three countries (South Africa, United Kingdom and France) it was found that there was a trend of products from two countries consistently exhibiting superior diffusion characteristics as well as products from the same two countries consistently exhibiting the lowest diffusion of ibuprofen. Interpretation of the results of these studies demonstrated the importance of employing a combination of statistical analyses and peak integration values when drawing conclusions regarding comparative diffusion characteristics. Shed snake skin has been described as a 'model' membrane, i.e. a membrane which shows similar permeability to human stratum corneum. The results reported here show clearly that, for ibuprofen, the four species of snake produce shed skin with completely different diffusion characteristics when all other conditions are identical. It may well be that there is one particular species of snake which produces shed skin of identical permeability to human stratum corneum, but to describe shed snake skin in general as a model membrane seems incorrect. It is therefore important that if shed snake skin is used as a membrane, the species, skin site and orientation should be reported. The European Pharmacopoeia diffusion apparatus was judged to be the better of the two diffusion techniques assessed for the measurement of the amount of ibuprofen released from a topical formulation during in vitro testing using silicone membranes and for the measurement of the amount of ibuprofen diffusing across the ventral outside orientation of shed skin during in vitro testing, whereas the Franz diffusion apparatus was judged to be better for the measurement of the amount of ibuprofen diffusing across the dorsal outside orientation of shed skin during in vitro testing. However, the choice of this diffusion apparatus must be weighed against the relatively poor reproducibility as compared with the European Pharmacopoeia diffusion apparatus.
- Full Text:
- Date Issued: 2001
- Authors: Purdon, Carryn Hamilton
- Date: 2001
- Subjects: Ibuprofen , Diffusion processes
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3786 , http://hdl.handle.net/10962/d1003264 , Ibuprofen , Diffusion processes
- Description: Ibuprofen is a non-steroidal anti-inflammatory drug with three major types of effect: anti-inflammatory, analgesic and antipyretic. Ibuprofen may be administered in a number of different forms via the oral as well as the topical route. Published evidence suggests that topical, unlike oral, non-steroidal anti-inflammatory drugs are associated with few systemic side effects as plasma concentrations are low compared to oral therapy. In some countries it is particularly difficult to obtain human skin for in vitro experimentation and it is therefore important to have alternate biological or synthetic membranes which mimic human skin for diffusion experiments. Synthetic membranes serve as predictive models for topical drug release and in South Africa, shed snake skin is easily obtainable from the many snake parks present in the country. The FDA guidelines were considered when choosing the apparatus to be used in the comparative diffusion study on proprietary ibuprofen-containing topical preparations from three countries and the verification of the usefulness, or otherwise, of shed snake skin as a biological membrane for the assessment of the permeation of ibuprofen. Two diffusion techniques were considered appropriate for the measurement of the amount of ibuprofen released from a topical formulation during in vitro testing. One was the Franz diffusion cell, as modified by Keshary and Chien (88,169) and the other was the European Pharmacopoeia diffusion cell (187). High performance liquid chromatography was used as the analytical technique for the analysis of ibuprofen in aqueous solution using ultraviolet detection at 222 nm. The validated method was applied to the determination of the diffusion of ibuprofen from topical ibuprofen-containing formulations (gels, creams and mousse) through synthetic silicone membrane and shed snake skin biological membrane from four different species. In a study of fifteen topical ibuprofen-containing formulations (gels, creams and mousse) from three countries (South Africa, United Kingdom and France) it was found that there was a trend of products from two countries consistently exhibiting superior diffusion characteristics as well as products from the same two countries consistently exhibiting the lowest diffusion of ibuprofen. Interpretation of the results of these studies demonstrated the importance of employing a combination of statistical analyses and peak integration values when drawing conclusions regarding comparative diffusion characteristics. Shed snake skin has been described as a 'model' membrane, i.e. a membrane which shows similar permeability to human stratum corneum. The results reported here show clearly that, for ibuprofen, the four species of snake produce shed skin with completely different diffusion characteristics when all other conditions are identical. It may well be that there is one particular species of snake which produces shed skin of identical permeability to human stratum corneum, but to describe shed snake skin in general as a model membrane seems incorrect. It is therefore important that if shed snake skin is used as a membrane, the species, skin site and orientation should be reported. The European Pharmacopoeia diffusion apparatus was judged to be the better of the two diffusion techniques assessed for the measurement of the amount of ibuprofen released from a topical formulation during in vitro testing using silicone membranes and for the measurement of the amount of ibuprofen diffusing across the ventral outside orientation of shed skin during in vitro testing, whereas the Franz diffusion apparatus was judged to be better for the measurement of the amount of ibuprofen diffusing across the dorsal outside orientation of shed skin during in vitro testing. However, the choice of this diffusion apparatus must be weighed against the relatively poor reproducibility as compared with the European Pharmacopoeia diffusion apparatus.
- Full Text:
- Date Issued: 2001